# Patent

## Title
Method and apparatus for signal transmission in wireless communication system

## Abstract

Provided are a method and an apparatus for signal transmission in a wireless communication system. The apparatus comprises: an information processor for generating a first information sequence based on a first transmission symbol and a first resource index, and a second information sequence based on a second transmission symbol and a second resource index; a reference signal generator for generating a different reference signal depending upon whether a first resource block indicated by the first resource index and a second resource block indicated by the second resource index are the same; and an antenna for transmitting a signal generated based on the first information sequence, the second information sequence, and the reference signal sequence.

## Background
This application is the National Stage filing under 35 U.S.C. 371 of International Application No. PCT/KR2009/006696, filed on Nov. 13, 2009, which claims the benefit of U.S. Provisional Application Serial Nos. 61/118,473, filed on Nov. 27, 2008, 61/117,237, filed on Nov. 24, 2008, 61/116,298, filed on Nov. 20, 2008, 61/115,113, filed on Nov. 17, 2008, 61/114,481, filed on Nov. 14, 2008, and 61/114,479, filed on Nov. 14, 2008, the contents of all of which are incorporated by reference herein in their entirety.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for signal transmission in a wireless communication system.
2. Related Art
Wireless communication systems are widely spread all over the world to provide various types of communication services such as voice or data. The wireless communication system is designed for the purpose of providing reliable communication to a plurality of users irrespective of their locations and mobility. However, a wireless channel has an abnormal characteristic such as a fading phenomenon caused by a path loss, noise, and multipath, an inter-symbol interference (ISI), a Doppler effect caused by mobility of a user equipment, etc. Therefore, various techniques have been developed to overcome the abnormal characteristic of the wireless channel and to increase reliability of wireless communication.
A multiple input multiple output (MIMO) scheme is used as a technique for supporting a reliable high-speed data service. The MIMO scheme uses multiple transmit antennas and multiple receive antennas to improve data transmission/reception efficiency. Examples of the MIMO scheme include spatial multiplexing, transmit diversity, beamforming, etc. A MIMO channel matrix depending on the number of receive antennas and the number of transmit antennas can be decomposed into a plurality of independent channels. Each independent channel is referred to as a transmission layer or a stream. The number of transmission layers is referred to as a rank.
Meanwhile, there is an ongoing standardization effort for an international mobile telecommunication-advanced (IMT-A) system aiming at the support of an Internal protocol (IP)-based multimedia seamless service by using a high-speed data transfer rate of 1 gigabits per second (Gbps) in a downlink and 500 megabits per second (Mbps) in an uplink in the international telecommunication union (ITU) as a next generation (i.e., post 3rd generation) mobile communication system. A 3rd generation partnership project (3GPP) is considering a 3GPP long term evolution-advanced (LTE-A) system as a candidate technique for the IMT-A system. It is expected that the LTE-A system is developed to further complete an LTE system while maintaining backward compatibility with the LTE system. This is because the support of compatibility between the LTE-A system and the LTE system facilitates user convenience. In addition, the compatibility between the two systems is also advantageous from the perspective of service providers since the existing equipment can be reused.
A typical wireless communication system is a single-carrier system supporting one carrier. Since a data transfer rate is in proportion to a transmission bandwidth, the transmission bandwidth needs to increase to support a high-speed data transfer rate. However, except for some areas of the world, it is difficult to allocate frequencies of wide bandwidths. For the effective use of fragmented small bands, a spectrum aggregation technique, also referred to as bandwidth aggregation or carrier aggregation, is being developed. The spectrum aggregation technique is a technique for obtaining the same effect as when a band of a logically wide bandwidth is used by aggregating a plurality of physically non-contiguous bands in a frequency domain. By using the spectrum aggregation technique, multiple carriers can be supported in the wireless communication system. The wireless communication system supporting the multiple carriers is referred to as a multiple-carrier system. The multiple-carrier system is also referred to as a carrier aggregation system. The carrier may also be referred to as other terms, such as, a radio frequency (RF), a component carrier (CC), etc.
Time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), or the like can be used as a multiplexing scheme for communication between a base station and each of a plurality of user equipments. The CDM and/or the FDM may be used for simultaneous communication between the base station and each of the plurality of user equipments.
A resource for wireless communication is any one or more combinations of (1) time, (2) frequency, and (3) sequence according to a multiplexing scheme. However, to increase an amount of information that is transmitted concurrently, it may be necessary to allocate multiple resources to one user equipment (UE). When allocating the multiple resources, a problem may arise in a method of transmitting a signal such as an information signal and a reference signal by using the multiple resources.
Accordingly, there is a need for a method and apparatus for effective signal transmission.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for signal transmission in a wireless communication system.
In an aspect, a transmitter including an information processor configured for generating a first information sequence based on a first transmission symbol and a first resource index, and configured for generating a second information sequence based on a second transmission symbol and a second resource index, a reference signal generator configured for generating a different reference signal sequence depending upon whether a first resource block indicated by the first resource index is identical to a second resource block indicated by the second resource index, and an antenna for transmitting a signal generated based on the first information sequence, the second information sequence, and the reference signal sequence is provided.
In another aspect, a method for signal transmission performed by a transmitter in a wireless communication system is provided. The method include generating a first information sequence based on a first transmission symbol and a first resource index, and generating a second information sequence based on a second transmission symbol and a second resource index, generating a different reference signal sequence depending upon whether a first resource block indicated by the first resource index is identical to a second resource block indicated by the second resource index, and transmitting a signal generated based on the first information sequence, the second information sequence, and the reference signal sequence.
According to the present invention, an effective information transmission method and apparatus are provided in a wireless communication system. Therefore, an overall system performance can be improved.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a wireless communication system.
FIG. 2 is a diagram showing a radio protocol architecture for a user plane.
FIG. 3 is a diagram showing a radio protocol architecture for a control plane.
FIG. 4 shows a structure of a radio frame.
FIG. 5 shows an example of a resource grid for one UL slot.
FIG. 6 shows a structure of a DL subframe.
FIG. 7 shows an exemplary structure of a UL subframe.
FIG. 8 is a block diagram showing an exemplary structure of a transmitter. Herein, the transmitter may be a part of a UE or a BS.
FIG. 9 is a block diagram showing an exemplary structure of an information processor included in a transmitter.
FIG. 10 shows an example of PUCCH format 1/1a/1b transmission in case of a normal CP.
FIG. 11 shows an example of PUCCH format 1/1a/1b transmission in case of an extended CP.
FIG. 12 shows an example of PUCCH format 2 transmission when a normal CP is used.
FIG. 13 shows an example of PUCCH format 2 transmission when an extended CP is used.
FIG. 14 is a block diagram showing an exemplary structure of a transmitter including two antennas.
FIG. 15 is a block diagram showing an exemplary structure of a part of a transmitter including two antennas.
FIG. 16 is a block diagram showing an exemplary structure of a part of a transmitter including a single antenna.
FIG. 17 shows another example of a case where a 1st RB is different from a 2nd RB.
FIG. 18 shows an example in which a 1st RB is identical to a 2nd RB.
FIG. 19 is a block diagram showing another exemplary structure of a part of a transmitter including two antennas.
FIG. 20 is a block diagram showing wireless communication system to implement an embodiment of the present invention.



DESCRIPTION OF EXEMPLARY EMBODIMENTS
Techniques described below can be used in various multiple access schemes such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. The SC-FDMA is a scheme in which inverse fast Fourier transform (IFFT) is performed on complex-valued symbols subjected to discrete Fourier transform (DFT) spreading, and is also referred to as DFT spreading-orthogonal frequency division multiplexing (DFTS-OFDM). In addition, the techniques described below can also be used in a multiple access scheme modified from the SC-FDMA, for example, clustered SC-FDMA, N×SC-FDMA, etc. The clustered SC-FDMA is a scheme in which complex-valued symbols subjected to DFT spreading are divided into a plurality of sub-blocks and the plurality of sub-blocks are distributed in a frequency domain and are mapped to subcarriers. The clustered SC-FDMA is also referred to as clustered DFTS-OFDM. The N×SC-FDMA is a scheme in which a code block is divided into a plurality of chunks and DFT and IFFT are performed on a chunk basis. The N×SC-FDMA is also referred to as chunk specific DFTS-OFDM.
The CDMA may be implemented as a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. The TDMA may be implemented as a radio technology such as a global system for mobile communications (GSM)/general packet radio service (GPRS)/enhanced data rates for GSM evolution (EDGE). The OFDMA may be implemented by a radio technology such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-UTRA (Evolved UTRA), and the like. The UTRA is part of a universal mobile telecommunications system (UMTS). 3GPP (3rd Generation, Partnership Project) LTE (Long Term Evolution) is part of an evolved UMTS (E-UMTS) using the E-UTRA, which employs the OFDMA in downlink and the SC-FDMA in uplink. LTE-A (Advanced) is an evolution of 3GPP LTE.
Hereinafter, for clarification, 3GPP LTE/LTE-A will be largely described, but the technical concept of the present invention is not meant to be limited thereto.
FIG. 1 shows a wireless communication system.
Referring to FIG. 1, a wireless communication system 10 includes at least one base station (BS) 11. Respective BSs 11 provide communication services to specific geographical regions (generally referred to as cells) 15a, 15b, and 15c. The cell can be divided into a plurality of regions (referred to as sectors). A user equipment (UE) 12 may be fixed or mobile, and may be referred to as another terminology, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem, a handheld device, etc. The BS 11 is generally a fixed station that communicates with the UE 12 and may be referred to as another terminology, such as an evolved node-B (eNB), a base transceiver system (BTS), an access point, etc.
Hereinafter, a downlink (DL) implies communication from the BS to the UE, and an uplink (UL) implies communication from the UE to the BS. In the DL, a transmitter may be a part of the BS, and a receiver may be a part of the UE. In the UL, the transmitter may be a part of the UE, and the receiver may be a part of the BS.
A heterogeneous network implies a network in which a relay station, a femto cell and/or a pico cell, and the like are deployed. In the heterogeneous network, the DL may imply communication from the BS to the relay station, the femto cell, or the pico cell. Further, the DL may also imply communication from the relay station to the UE. Furthermore, in case of multi-hop relay, the DL may imply communication from a first relay station to a second relay station. In the heterogeneous network, the UL may imply communication from the relay station, the femto cell, or the pico cell to the BS. Further, the UL may also imply communication from the UE to the relay station. Furthermore, in case of multi-hop relay, the UL may imply communication from the second relay station to the first relay station.
The wireless communication system can support multiple antennas. The transmitter may use a plurality of transmit (Tx) antennas, and the receiver may use a plurality of receive (Rx) antennas. The Tx antenna denotes a physical or logical antenna used for transmission of one signal or stream. The Rx antenna denotes a physical or logical antenna used for reception of one signal or stream. When the transmitter and the receiver use a plurality of antennas, the wireless communication system may be referred to as a multiple input multiple output (MIMO) system.
The wireless communication system can support UL and/or DL hybrid automatic repeat request (HARQ). In addition, a channel quality indicator (CQI) can be used for link adaptation.
A wireless communication process is preferably implemented with a plurality of independent hierarchical layers rather than one single layer. A structure of a plurality of hierarchical layers is referred to as a protocol stack. The protocol stack may refer to an open system interconnection (OSI) model which is a widely known protocol for communication systems.
FIG. 2 is a diagram showing a radio protocol architecture for a user plane. FIG. 3 is a diagram showing a radio protocol architecture for a control plane. The user plane is a protocol stack for user data transmission. The control plane is a protocol stack for control signal transmission.
Referring to FIGS. 2 and 3, between different physical (PHY) layers (i.e., a PHY layer of a transmitter and a PHY layer of a receiver), data is transferred through a physical channel. The PHY layer is also referred to as a layer 1 (L1). The PHY layer is coupled with a medium access control (MAC) layer, i.e., an upper layer of the PHY layer, through a transport channel. Between the MAC layer and the PHY layer, data is transferred through the transport channel. The PHY layer provides the MAC layer and an upper layer with an information transfer service through the transport channel.
The MAC layer provides services to a radio link control (RLC) layer, i.e., an upper layer of the MAC layer, through a logical channel. The RLC layer supports reliable data transmission. A packet data convergence protocol (PDCP) layer performs a header compression function to reduce a header size of an Internet protocol (IP) packet. The MAC layer, the RLC layer, and the PDCP layer are also referred to as a layer 2 (L2).
A radio resource control (RRC) layer is defined only in the control plane. The RRC layer is also referred to as a layer 3 (L3). The RRC layer controls radio resources between a UE and a network. For this, in the RRC layer, RRC messages are exchanged between the UE and the network. The RRC layer serves to control the logical channel, the transport channel, and the physical channel in association with configuration, reconfiguration and release of radio bearers. The radio bearer represents a logical path provided by the L1 and the L2 for data transmission between the UE and the network. Configuration of the radio bearer implies a process for defining characteristics of a radio protocol layer and channel to provide a specific service, and for configuring respective specific parameters and operation mechanisms. The radio bearer can be classified into a signaling radio bearer (SRB) and a data radio bearer (DRB). The SRB is used as a path for transmitting an RRC message in the control plane, and the DRB is used as a path for transmitting user data in the user plane. When an RRC connection is established between an RRC layer of the UE and an RRC layer of the network, it is called that the UE is in an RRC connected mode. When the RRC connection is not established yet, it is called that the UE is in an RRC idle mode.
A non-access stratum (NAS) layer belongs to an upper layer of the RRC layer and serves to perform session management, mobility management, or the like.
FIG. 4 shows a structure of a radio frame.
Referring to FIG. 4, the radio frame consists of 10 subframes. One subframe consists of two slots. Slots included in the radio frame are numbered with slot numbers #0 to #19. A time required to transmit one subframe is defined as a transmission time interval (TTI). The TTI may be a scheduling unit for data transmission. For example, one radio frame may have a length of 10 milliseconds (ms), one subframe may have a length of 1 ms, and one slot may have a length of 0.5 ms.
The radio frame of FIG. 4 is shown for exemplary purposes only. Thus, the number of subframes included in the radio frame or the number of slots included in the subframe may change variously.
FIG. 5 shows an example of a resource grid for one UL slot.
Referring to FIG. 5, the UL slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in a time domain and includes N(UL) resource blocks (RBs) in a frequency domain. The OFDM symbol represents one symbol period, and may also be referred to as other terms such as an OFDMA symbol, an SC-FDMA symbol, or the like according to a multiple access scheme. The number N(UL) of RBs included in the UL slot depends on a UL transmission bandwidth determined in a cell. One RB includes a plurality of subcarriers in the frequency domain.
Each element on the resource grid is referred to as a resource element (RE). The RE on the resource grid can be identified by an index pair (k, I) in a slot. Herein, k(k=0, . . . , N(UL)×12−1) denotes a subcarrier index in the frequency domain, and I(I=0, . . . , 6) denotes a symbol index in the time domain.
Although it is described herein that one RB includes 7×12 resource elements consisting of 7 OFDM symbols in the time domain and 12 subcarriers in the frequency domain for example, the number of OFDM symbols and the number of subcarriers in the RB are not limited thereto. Thus, the number of OFDM symbols and the number of subcarriers may change variously depending on a cyclic prefix (CP) length, a frequency spacing, etc. For example, when using a normal CP, the number of OFDM symbols is 7, and when using an extended CP, the number of OFDM symbols is 6.
The resource grid for one UL slot of FIG. 5 can also be applied to a resource grid for a DL slot.
FIG. 6 shows a structure of a DL subframe.
Referring to FIG. 6, the DL subframe includes two consecutive slots. First 3 OFDM symbols of a 1st slot included in the DL subframe correspond to a control region, and the remaining OFDM symbols correspond to a data region. Herein, the control region includes 3 OFDM symbols for exemplary purposes only.
A physical downlink shared channel (PDSCH) may be allocated to the data region. DL data is transmitted through the PDSCH. The DL data may be a transport block which is a data block for a downlink shared channel (DL-SCH), i.e., a transport channel transmitted during TTI. A BS may transmit the DL data to a UE through one antenna or multiple antennas. In 3GPP LTE, the BS may transmit one codeword to the UE through one antenna or multiple antennas, or may transmit two codewords through multiple antennas. The 3GPP LTE supports up to 2 codewords. The codewords are encoded bits in which channel coding is performed on an information bit corresponding to information. Modulation can be performed for each codeword.
A control channel may be allocated to the control region. Examples of the control channel include a physical control format indicator channel (PCFICH), a physical hybrid automatic repeat request (HARQ) indicator channel (PHICH), a physical downlink control channel (PDCCH), etc.
The PCFICH carries information indicating the number of OFDM symbols used for transmission of PDCCHs in a subframe to the UE. The number of OFDM symbols used for PDCCH transmission may change in every subframe. In the subframe, the number of OFDM symbols used for PDCCH transmission may be any one value among 1, 2, and 3. If a DL transmission bandwidth is less than a specific threshold, the number of OFDM symbols used for PDCCH transmission in the subframe may be any one value among 2, 3, and 4.
The PHICH carries HARQ acknowledgement (ACK)/negative acknowledgement (NACK) for UL data.
The control region consists of a set of a plurality of control channel elements (CCEs). If a total number of CCEs constituting a CCE set is N(CCE) in the DL subframe, the CCEs are indexed from 0 to N(CCE)-1. The CCEs correspond to a plurality of resource elements groups. The resource element group is used to define mapping of the control channel to a resource element. One resource element group consists of a plurality of resource elements. A PDCCH is transmitted through an aggregation of one or several contiguous CCEs. A plurality of PDCCHs may be transmitted in the control region. A PDCCH format and the number of available PDCCH bits are determined according to the number of CCEs constituting the CCE aggregation. Hereinafter, the number of CCEs used for PDCCH transmission is referred to as a CCE aggregation level. The CCE aggregation level is a CCE unit for searching for the PDCCH. A size of the CCE aggregation level is defined by the number of contiguous CCEs. For example, the CCE aggregation level may be an element of {1, 2, 4, 8}.
The PDCCH carries DL control information. Examples of the DL control information include DL scheduling information, UL scheduling information, a UL power control command, etc. The DL scheduling information is also referred to as a DL grant. The UL scheduling information is also referred to as a UL grant.
The BS does not provide the UE with information indicating where a PDCCH of the UE is located in the subframe. In general, in a state where the UE does not know a location of the PDCCH of the UE in the subframe, the UE finds the PDCCH of the UE by monitoring a set of PDCCH candidates in every subframe. Monitoring implies that the UE attempts to perform decoding for each of the PDCCH candidates according to all possible DCI formats. This is referred to as blind decoding or blind detection.
For example, when the BS transmits the DL data to the UE through a PDSCH within a subframe, the BS carries a DL grant used for scheduling of the PDSCH through a PDCCH within the subframe. The UE can first detect the PDCCH for transmitting the DL grant through blind decoding. The UE can read the DL data transmitted through the PDSCH based on the DL grant.
FIG. 7 shows an exemplary structure of a UL subframe.
Referring to FIG. 7, the UL subframe can be divided into a control region and a data region. A physical uplink control channel (PUCCH) for carrying UL control information is allocated to the control region. A physical uplink shared channel (PUSCH) for carrying user data is allocated to the data region. In 3GPP LTE (Release 8), resource blocks allocated to one UE are contiguous in a frequency domain to maintain a single-carrier property. One UE cannot transmit the PUCCH and the PUSCH concurrently. Concurrent transmission of the PUCCH and the PUSCH is under consideration In LTE-A (Release 10).
The PUCCH for one UE is allocated in a resource block (RB) pair in the subframe. RBs belonging to the RB pair occupy different subcarriers in each of 1st and 2nd slots. A frequency occupied by the RBs belonging to the RB pair to be allocated to the PUCCH is changed on a slot boundary basis. That is, RBs allocated to the PUCCH are hopped in a slot level. Hereinafter, hopping of the RB in the slot level is called frequency hopping. A frequency diversity gain is obtained when the UE transmits UL control information through a frequency located at different positions over time. In FIG. 7, m is a location index indicating a frequency-domain location of the RB pair allocated to the PUCCH within the subframe.
The PUSCH is mapped to an uplink shared channel (UL-SCH) which is a transport channel. Examples of UL control information transmitted through the PUCCH include HARQ ACK/NACK, a channel quality indicator (CQI) indicating a DL channel state, a scheduling request (SR) as a request for UL radio resource allocation, etc. Hereinafter, the CQI is the concept including a precoding matrix indicator (PMI) and a rank indicator (RI) in addition to the CQI.
Time division multiplexing (TDM), frequency division multiplexing (FDM), code division multiplexing (CDM), or the like can be used as a multiplexing scheme for communication between a BS and each of a plurality of UEs. The CDM and/or the FDM may be used for simultaneous communication between the BS and each of the plurality of UEs.
Multiplexing schemes based on an orthogonal sequence or a quasi-orthogonal sequence are collectively referred to as the CDM. That is, sequences used for the CDM are not necessarily orthogonal to each other. Sequences having a low correlation may also be used for the CDM.
Hereinafter, a method and apparatus for information transmission will be described when CDM and/or FDM are used as a multiplexing scheme.
When the CDM and/or the FDM are used as the multiplexing scheme, a resource used for information transmission is a sequence and/or a frequency resource. For example, when only the CDM is used as the multiplexing scheme, the resource is the sequence, and when the CDM and the FDM are used together, the resource is the sequence and the frequency resource. Hereinafter, the frequency resource and the sequence will be described in detail.
(1) Frequency Resource
The aforementioned resource block is an example of the frequency resource. This is because the frequency resource differs when the resource block differs within the same time period. Hereinafter, for convenience of explanation, the resource block is used in the concept of a normal frequency resource.
(2) Sequence
The sequence is not particularly limited, and thus may be any sequence.
For example, the sequence may be selected from a sequence set having a plurality of sequences as its elements. The plurality of sequences included in the sequence set may be orthogonal to each other, or may have a low correlation with each other. For convenience of explanation, it is assumed that the plurality of sequences included in the sequence set are orthogonal to each other. Hereinafter, the sequence set is an orthogonal sequence set consisting of orthogonal sequences. Each of the orthogonal sequences belonging to the orthogonal sequence set corresponds to one orthogonal sequence index in a one-to-one manner.
The orthogonal sequence set having length-4 orthogonal sequences as its elements may use a Walsh-Hadamard matrix. Table 1 below shows an example of an orthogonal sequence set consisting of an orthogonal sequence w(k, Ios) having a length of K=4 (Ios denotes an orthogonal sequence index and k denotes an element index of the orthogonal sequence, where 0≦k≦K−1).










TABLE 1







Orthogonal sequence index
[w(0), w(1), w(2), w(3)]









0
[+1 +1 +1 +1]



1
[+1 −1 +1 −1]



2
[+1 +1 −1 −1]



3
[+1 −1 −1 +1]










The orthogonal sequence set may consist of only some orthogonal sequences of Table 1 above. In 3GPP LTE, three orthogonal sequences are used except for [+1, +1, −1, −1].
Table 2 below shows an example of an orthogonal sequence set consisting of an orthogonal sequence w(k, Ios) having a length of K=3 (Ios denotes an orthogonal sequence index and k denotes an element index of the orthogonal sequence, where 0≦k≦K−1).










TABLE 2







Orthogonal sequence index
[w(0), w(1), w(2)]









0
[1 1 1]



1
[1 ej2π/3 ej4π/3]



2
[1 ej4π/3 3j2π/3]










Table 3 below shows an example of an orthogonal sequence set consisting of an orthogonal sequence w(k, Ios) having a length of K=2 (Ios denotes an orthogonal sequence index and k denotes an element index of the orthogonal sequence, where 0≦k≦K−1).










TABLE 3







Orthogonal sequence index
[w(0), w(1)]









0
[1 1]



1
[1 −1]










For another example, a cyclically shifted sequence may be used as the sequence. The cyclically shifted sequence can be generated by cyclically shifting a base sequence by a specific cyclic shift (CS) amount. Various types of sequences can be used as the base sequence. For example, a well-known sequence such as a pseudo noise (PN) sequence and a Zadoff-Chu (ZC) sequence can be used as the base sequence. Alternatively, a computer generated constant amplitude zero auto-correlation (CAZAC) sequence may be used. Equation 1 below shows an example of the base sequence.

ri(n)=ejb(n)π/4  [Equation 1]

Herein, iε{0, 1, . . . , 29} denotes a root index, and n denotes a component index in the range of 0≦n≦N−1, where N is a sequence length. i can be determined by a cell identifier (ID), a slot number in a radio frame, etc. When one resource block includes 12 subcarriers, N can be set to 12. A different base sequence is defined according to a different root index. When N=12, b(n) can be defined by Table 4 below.








TABLE 4





i
b(0), . . . , b(11)



























0
−1
1
3
−3
3
3
1
1
3
1
−3
3


1
1
1
3
3
3
−1
1
−3
−3
1
−3
3


2
1
1
−3
−3
−3
−1
−3
−3
1
−3
1
−1


3
−1
1
1
1
1
−1
−3
−3
1
−3
3
−1


4
−1
3
1
−1
1
−1
−3
−1
1
−1
1
3


5
1
−3
3
−1
−1
1
1
−1
−1
3
−3
1


6
−1
3
−3
−3
−3
3
1
−1
3
3
−3
1


7
−3
−1
−1
−1
1
−3
3
−1
1
−3
3
1


8
1
−3
3
1
−1
−1
−1
1
1
3
−1
1


9
1
−3
−1
3
3
−1
−3
1
1
1
1
1


10
−1
3
−1
1
1
−3
−3
−1
−3
−3
3
−1


11
3
1
−1
−1
3
3
−3
1
3
1
3
3


12
1
−3
1
1
−3
1
1
1
−3
−3
−3
1


13
3
3
−3
3
−3
1
1
3
−1
−3
3
3


14
−3
1
−1
−3
−1
3
1
3
3
3
−1
1


15
3
−1
1
−3
−1
−1
1
1
3
1
−1
−3


16
1
3
1
−1
1
3
3
3
−1
−1
3
−1


17
−3
1
1
3
−3
3
−3
−3
3
1
3
−1


18
−3
3
1
1
−3
1
−3
−3
−1
−1
1
−3


19
−1
3
1
3
1
−1
−1
3
−3
−1
−3
−1


20
−1
−3
1
1
1
1
3
1
−1
1
−3
−1


21
−1
3
−1
1
−3
−3
−3
−3
−3
1
−1
−3


22
1
1
−3
−3
−3
−3
−1
3
−3
1
−3
3


23
1
1
−1
−3
−1
−3
1
−1
1
3
−1
1


24
1
1
3
1
3
3
−1
1
−1
−3
−3
1


25
1
−3
3
3
1
3
3
1
−3
−1
−1
3


26
1
3
−3
−3
3
−3
1
−1
−1
3
−1
−3


27
−3
−1
−3
−1
−3
3
1
−1
1
3
−3
−3


28
−1
3
−3
3
−1
3
3
−3
3
3
−1
−1


29
3
−3
−3
−1
−1
−3
−1
3
−3
3
1
−1









The base sequence r(n) can be cyclically shifted according to Equation 2 below to generate a cyclically shifted sequence r(n, Ics).




  
    
      
        
          
            r
            ⁡
            
              (
              
                n
                ,
                
                  I
                  cs
                
              
              )
            
          
          =
          
            
              r
              ⁡
              
                (
                n
                )
              
            
            ·
            
              exp
              ⁡
              
                (
                
                  
                    j2π
                    ⁢
                    
                      
                    
                    ⁢
                    
                      I
                      cs
                    
                    ⁢
                    n
                  
                  N
                
                )
              
            
          
        
        ,
        
          

        
        ⁢
        
          0
          ≤
          
            I
            cs
          
          ≤
          
            N
            -
            1
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          2
        
        ]
      
    
  




In Equation 2, Ics denotes a CS index indicating a CS amount (0≦Ics≦N−1, where Ics is an integer).
Hereinafter, an available CS index of the base sequence denotes a CS index that can be derived from the base sequence according to a CS interval. For example, if a length of the base sequence is 12 and the CS interval is 1, a total number of available CS indices of the base sequence is 12. Alternatively, if a length of the base sequence is 12 and the CS interval is 2 a total number of available CS indices of the base sequence is 6. The CS interval can be determined by considering a delay spread.
FIG. 8 is a block diagram showing an exemplary structure of a transmitter. Herein, the transmitter may be a part of a UE or a BS.
Referring to FIG. 8, a transmitter 100 includes an information processor 110, a reference signal generator 120, a resource block mapper 130, an OFDM signal generator 140, a radio frequency (RF) unit 150, and an antenna 190.
The information processor 110 and the reference signal generator 120 are connected to the resource block mapper 130. The resource block mapper 130 is connected to the OFDM signal generator 140. The OFDM signal generator 140 is connected to the RF unit 150. The RF unit 150 is connected to the antenna 190.
Information is input to the information processor 110. Examples of the information include user data, control information, mixed information of several pieces of control information, multiplexed information of the control information and the user data, etc. The information may have a bit or bit-stream format. The transmitter 100 can be implemented in a physical layer. In this case, the information may be derived from a higher layer such as a MAC layer.
The information processor 110 is configured to generate an information sequence based on information or a sequence. The information sequence consists of a plurality of information sequence elements. The information sequence can also be referred to as an information signal.
FIG. 9 is a block diagram showing an exemplary structure of an information processor included in a transmitter.
Referring to FIG. 9, an information processor 110 includes a channel coding unit 111, a modulator 112, and an information sequence generator 113.
An information bit corresponding to information to be transmitted by the transmitter is input to the channel coding unit 111. The channel coding unit 111 performs channel coding on the information bit to generate an encoded bit. There is no restriction on a channel coding scheme. Examples of the channel coding scheme include turbo coding, convolution coding, block coding, etc. The block code may be a Reed-Muller code family. A size of the encoded bit output from the channel coding unit 111 may be various.
The modulator 112 maps an encoded bit to a symbol that expresses a position on a signal constellation to generate a modulation symbol. There is no restriction on a modulation scheme. Examples of the modulation scheme include m-phase shift keying (m-PSK), m-quadrature amplitude modulation (m-QAM), etc. The number of modulation symbols output from the modulator 112 may be various according to the size of the encoded bit input to the modulator 112 and the modulation scheme.
The information processor 110 may (or may not) perform discrete Fourier transform (DFT) on the modulation symbol. When performing DFT, the information processor 110 may further include a DFT unit (not shown) for outputting a complex-valued symbol by performing DFT on the modulation symbol. It is assumed herein that the modulation symbol is directly input to the information sequence generator 113 without performing DFT. Hereinafter, the modulation symbol input to the information sequence generator 113 implies a complex-valued symbol corresponding to information to be transmitted by the transmitter 100.
The information sequence generator 113 generates an information sequence based on an information symbol or sequence. The information sequence may be a one-dimensional spread sequence or a two-dimensional spread sequence.
(1) One-Dimensional Spread Sequence
The one-dimensional spread sequence is generated based on a modulation symbol and a 1st sequence. One modulation symbol or each of a plurality of modulation symbols may be multiplied by the 1st sequence to generate the one-dimensional spread sequence.
Equation 3 below shows an example of generating K one-dimensional spread sequences s(n) based on modulation symbols d(0), . . . , d(K−1) and a 1st sequence x(n) with a length N (K and N are natural numbers, and n is an element index of the 1st sequence, where 0≦n≦N−1).

s(n)=d(k)x(n),0≦k≦K−1  [Equation 3]

In Equation 3, the modulation symbols d(0), . . . , d(K−1) may be K modulation symbols. Alternatively, one modulation symbol d(0) may be repetitively used K times.
The one-dimensional spread sequence s(n) is mapped to a time domain or a frequency domain. When it is mapped to the time domain, the one-dimensional spread sequence s(n) may be mapped to time samples, chips, or OFDM symbols. When it is mapped to the frequency domain, the one-dimensional spread sequence s(n) may be mapped to subcarriers.
Hereinafter, when the one-dimensional spread sequence s(n) is mapped to the time domain, the 1st sequence x(n) is called a time-domain sequence. When the one-dimensional spread sequence s(n) is mapped to the frequency domain, the 1st sequence x(n) is called a frequency-domain sequence.
(2) Two-Dimensional Spread Sequence
The two-dimensional spread sequence is generated based on the one-dimensional spread sequence and a 2nd sequence. That is, the two-dimensional spread sequence is generated based on the modulation symbol, the 1st sequence, and the 2nd sequence. The one-dimensional spread sequence may be spread to the 2nd sequence to generate the two-dimensional spread sequence.
Equation 4 below shows an example of generating a two-dimensional spread sequence z(n,k) by spreading K one-dimensional spread sequences s(n) to a 2nd sequence y(k) (k is an element index of the 2nd sequence, where 0≦k≦K−1).

z(n,k)=w(k)y(n)=w(k)d(k)x(n)  [Equation 4]

The two-dimensional spread sequence z(n,k) is mapped to the time domain or the frequency domain. For example, n may correspond to a subcarrier index, and k may correspond to a symbol index. Alternatively, n may correspond to a symbol index, and k may correspond to a subcarrier index.
Referring back to FIG. 8 again, the reference signal generator 120 generates a reference signal sequence. The reference signal sequence consists of a plurality of reference signal elements. The reference signal sequence can also be referred to as a reference signal (RS). The RS is a signal which is known to both a transmitter and a receiver. The RS can be used for information demodulation in the receiver. Any sequence can be used as the RS sequence without a particular restriction.
An RS sequence may be generated similarly to generation of an information sequence. When the information sequence is the one-dimensional spread sequence, the 1st sequence for an RS may be used as the RS sequence. If the information sequence is the two-dimensional spread sequence, the RS sequence may be generated based on the 1st sequence for the RS and the 2nd sequence for the RS.
The resource block mapper 130 is configured to map the information sequence and the RS sequence to a resource block allocated for information transmission. One information sequence element or one RS sequence element can be mapped to one resource element. Since CDM is used, multiplexing can be achieved to the same resource block. Of course, FDM can be used together with the CDM, and thus multiplexing can be achieved by different resource blocks.
One or more resource blocks may be used for information transmission. The resource block includes an information part and an RS part. The information sequence is mapped to the information part, and the RS sequence is mapped to the RS part.
The RS part and the information part may use different OFDM symbols within a resource block. Alternatively, the RS part and the information part may use different subcarriers within an OFDM symbol.
For convenience of explanation, it is assumed hereinafter that the RS part and the information part use different OFDM symbols within the resource block. One or more OFDM symbols within the resource block may be the RS part. When a plurality of OFDM symbols within the resource block correspond to the RS part, the plurality of OFDM symbols may be contiguous to each other or may be non-contiguous to each other. The position and number of OFDM symbols used as the RS part within the resource block may vary without a particular restriction. An OFDM symbol within the resource block except for the RS part may be used as the information part.
For example, it is assumed that the transmitter is a part of a UE, and transmits information through a PUCCH. The resource block mapper 130 maps the information sequence and the RS sequence to a resource block pair (see FIG. 7) within a subframe allocated for PUCCH transmission.
The OFDM signal generator 140 is configured to generate a time-continuous OFDM signal in every OFDM symbol within the resource block. The time-continuous OFDM signal is also referred to as an OFDM baseband signal. The OFDM signal generator 140 can generate an OFDM signal by performing an inverse fast Fourier transform (IFFT) operation, CP insertion, or the like for each OFDM symbol.
The RF unit 150 converts the OFDM baseband signal to a radio signal. The OFDM baseband signal can be converted to the radio signal by being up-converted to a carrier frequency. The carrier frequency is also referred to as a center frequency.
The radio signal is transmitted through the antenna 190.
As such, to perform information transmission, the transmitter 100 has to determine a resource used for information transmission. The resource may consist of at least one of (1) the 1st sequence, (2) the 2nd sequence, and (3) resource blocks. For example, the 1st sequence may be a cyclic shifted sequence, and the 2nd sequence may be an orthogonal sequence.
A resource index identifies the resource used for information transmission. Therefore, the resource is determined from the resource index. Each of sequences used to generate the information sequence and the RS sequence is determined from the resource index. In addition, a resource block to which the information sequence and the RS sequence are mapped can be determined from the resource index.
Therefore, the transmitter 100 has to obtain the resource index to perform information transmission. When the transmitter is a part of a BS, the transmitter may determine the resource index through scheduling.
When the transmitter is a part of a UE, a method of obtaining the resource index of the UE is problematic. The BS may report the resource index to the UE explicitly or implicitly. In addition, the resource index may change semi-statically or dynamically.
For example, the resource index may be determined by higher layer signaling. The higher layer may be an RRC layer. In this case, the resource index changes semi-statically. Information to be transmitted by the UE may be SR, semi-persistent scheduling (SPS) ACK/NACK, CQI, etc. The SPS ACK/NACK is HARQ ACK/NACK for DL data transmitted through semi-static scheduling. When the DL data is transmitted through a PDSCH, a PDCCH corresponding to the PDSCH may not exist.
For another example, the UE may obtain the resource index from a radio resource by which a control channel for receiving the DL data is transmitted. In this case, information transmitted by the UE may be dynamic ACK/NACK. The dynamic ACK/NACK is ACK/NACK for DL data transmitted through dynamic scheduling. In the dynamic scheduling, the BS transmits a DL grant to the UE every time through a PDCCH whenever DL data is transmitted through the PDSCH.
Equation 5 below shows an example of determining a resource index R for dynamic ACK/NACK transmission.

R=n(CCE)+N(PUCCH)  [Equation 5]

In Equation 5, n(CCE) denotes a 1st CCE index used for PDCCH transmission with respect to a PDSCH, and N(PUCCH) denotes the number of resource indices allocated for SR and SPS ACK/NACK. N(PUCCH) is a cell-specific parameter, and can be determined by a higher layer such as an RRC layer.
Therefore, the BS can regulate a resource for ACK/NACK transmission by controlling the 1st CCE index used for PDCCH transmission.
As an example of an information transmission method based on CDM and FDM, there is a method transmitting UL control information through a PUCCH. Hereinafter, the method of transmitting the UL control information through the PUCCH will be described.
The PUCCH can support multiple formats. That is, it is possible to transmit the UL control signal whose number of bits per subframe differs according to the modulation scheme. Table 5 below shows an example of a modulation scheme and the number of bits per subframe based on a PUCCH format.











TABLE 5







PUCCH
Modulation
Number of bits per



format
scheme
subframe









1
N/A
N/A



1a
BPSK
1



1b
QPSK
2



2
QPSK
20



2a
QPSK + BPSK
21



2b
QPSK + QPSK
22










The PUCCH format 1 is used to transmit the SR. The PUCCH format 1a/1b is used to transmit the HARQ ACK/NACK signal. The PUCCH format 2 is used to transmit the CQI. The PUCCH format 2a/2b is used to transmit the CQI and the HARQ ACK/NACK signal.
In any subframe, if the HARQ ACK/NACK signal is transmitted alone, the PUCCH format 1a/1b is used, and if the SR is transmitted alone, the PUCCH format 1 is used. The UE can transmit the HARQ ACK/NACK signal and the SR simultaneously in the same subframe. For positive SR transmission, the UE transmits the HARQ ACK/NACK signal by using a PUCCH allocated for the SR. For negative SR transmission, the UE transmits the HARQ ACK/NACK signal by using a PUCCH resource allocated for the ACK/NACK.
In case of the PUCCH format 1a, an ACK/NACK bit (one bit) is output from a channel coding unit. For example, each ACK may be coded to a binary ‘1’, and each NACK may be coded to a binary ‘0’. In case of the PUCCH format 1b, ACK/NACK bits (two bits) b(0) and b(1) may be output from the channel coding unit. b(0) may correspond to an ACK/NACK bit for a 1st codeword, and b(1) may correspond to an ACK/NACK bit for a 2nd codeword. That is, the PUCCH format 1a is for HARQ ACK/NACK information for the 1st codeword, and the PUCCH format 1b is for HARQ ACK/NACK information of the 2nd codeword.
Each of the PUCCH formats 1, 1a, and 1b uses one complex-valued symbol d(0). The BS can detect an SR by only determining whether there is PUCCH format 1 transmission from the UE. That is, an on-off keying (OOK) modulation scheme can be used in SR transmission. Therefore, any complex value can be used as a value of the modulation symbol d(0) for the PUCCH format 1. For example, d(0)=1 may be used. The modulation symbol d(0) for the PUCCH format 1a is a modulation symbol generated when an encoded bit (1 bit) is modulated by using binary phase shift keying (BPSK). The complex-valued symbol d(0) for the PUCCH format 1b is a modulation symbol generated when encoded bits (2 bits) are modulated by using quadrature phase shift keying (QPSK).
Table 6 below shows an example of a modulation symbol to which an ACK/NACK bit is mapped according to a modulation scheme.









TABLE 6





Modulation scheme
Bit(s)
d(0)

















BPSK
0
1



1
−1


QPSK
00
1



01
−j



10
j



11
−1









FIG. 10 shows an example of PUCCH format 1/1a/1b transmission in case of a normal CP. Although it is expressed herein that resource blocks belonging to a resource block pair occupy the same frequency band in a 1st slot and a 2nd slot, the resource blocks can be hopped in a slot level as described with reference to FIG. 7.
Referring to FIG. 10, the 1st slot and the 2nd slot each include 7 OFDM symbols. Among the 7 OFDM symbols included in each slot, 3 OFDM symbols correspond to an RS part to which an RS sequence is mapped, and the remaining 4 OFDM symbols correspond to an information part to which an information sequence is mapped. The RS part corresponds to 3 contiguous OFDM symbols located in the middle of each slot. The position and number of OFDM symbols used as the RS part in each slot may vary, and thus the position and number of OFDM symbols used as the information part may also vary.
In the information part, an information sequence is generated based on a modulation symbol d(0), a cyclically shifted sequence r(n,Ics), and an orthogonal sequence w(k, Ios). The cyclically shifted sequence r(n,Ics) may also be referred to as a 1st sequence, and the orthogonal sequence w(k, Ios) may also be referred to as a 2nd sequence. Therefore, the information sequence is a two-dimensional spread sequence. By spreading information to a time-space domain, UE multiplexing capacity can be increased. The UE multiplexing capacity is the number of UEs that can be multiplexed to the same resource block.
The cyclically shifted sequence r(n,Ics) is generated from a base sequence for each OFDM symbol used as the information part within the subframe. The base sequence is identical within one slot. The 1st slot and the 2nd slot may have identical or different base sequences within the subframe. The cyclically shifted index Ics is determined from a resource index. The cyclically shifted index Ics can be CS-hopped in a symbol level. Hereinafter, hopping of a CS index in the symbol level is called CS hopping. The CS hopping can be performed according to a slot number n(s) within a radio frame and a symbol index I within a slot. Therefore, the CS index Ics can be expressed by Ics(n(s),I). CS hopping can be performed in a cell-specific manner to randomize inter-cell interference. In FIG. 10, the value Ics for each OFDM symbol in the information part is for exemplary purposes only.
A 1st sequence s(n) spread in a frequency domain is generated for each OFDM symbol of the information part on the basis of the modulation symbol d(0) and the cyclically shifted sequence r(n,Ics). The 1st sequence s(n) can be generated by multiplying the modulation symbol d(0) by the cyclically shifted sequence r(n,Ics) according to Equation 6 below.

s(n)=d(0)r(n,Ics)  [Equation 6]

An information sequence spread to a time-frequency domain is generated on the basis of the 1st sequence s(n) generated for each OFDM symbol of the information part and the orthogonal sequence w(k, Ios) having a length of K=4. The 1st sequence may be spread in a block type by using the orthogonal sequence w(k, Ios) to generate the information sequence. Elements constituting the orthogonal sequence correspond to OFDM symbols of the information part sequentially in a one-to-one manner. Each of the elements constituting the orthogonal sequence is multiplied by the 1st sequence s(0) mapped to its corresponding OFDM symbol to generate the information sequence.
The information sequence is mapped to a resource block pair allocated to a PUCCH within the subframe. The resource block pair is determined from the resource index. After the information sequence is mapped to the resource block pair, IFFT is performed on each OFDM symbol of the subframe to output a time-domain signal. Although the orthogonal sequence is multiplied before IFFT is performed in this case, the same result can also be obtained when the 1st sequence s(n) is mapped to the resource block pair and thereafter the orthogonal sequence is multiplied.
When a sounding reference signal (SRS) and the PUCCH formats 1/1a/1b are concurrently transmitted in one subframe, one OFDM symbol on the PUCCH is punctured. For example, a last OFDM symbol of the subframe may be punctured. In this case, in the 1st slot of the subframe, the control information consists of 4 OFDM symbols. In the 2nd slot of the subframe, the control information consists of 3 OFDM symbols. Therefore, the orthogonal sequence having the spreading factor K=4 is used for the 1st slot, and the orthogonal sequence having the spreading factor K=3 is used for the 2nd slot.
An orthogonal sequence Ios is determined from the resource index. The orthogonal sequence index Ios may be hopped in a slot level. Hereinafter, hopping of the orthogonal sequence index in the slot level is referred to as orthogonal sequence (OS) remapping. The OS remapping can be performed according to the slot number ns within the radio frame. Therefore, the orthogonal sequence index Ios can be expressed by Ios(ns). The OS remapping may be performed to randomize inter-cell interference.
In the RS part, the RS sequence is generated on the basis of the cyclically shifted sequence r(n,I′cs) and the orthogonal sequence w(k, I′os) having a length of K=3. I′cs denotes a CS index for the RS, and I′os denotes an orthogonal sequence index for the RS. I′cs and I′os are determined from respective resource indices. A cyclically shifted sequence is a frequency-domain sequence, and an orthogonal sequence is a time-domain sequence. Therefore, the RS sequence is a sequence which is spread to a time-frequency domain similarly to the information sequence.
In the RS part, the base sequence for generating the cyclically shifted sequence may be identical to the base sequence of the information part. The CS index Ics of the information part and the CS index I′cs of the RS part are both determined from the resource index. However, a method of determining the CS index from the resource index may be identical or different between the information part and the RS part.
FIG. 11 shows an example of PUCCH format 1/1a/1b transmission in case of an extended CP. Although it is expressed herein that resource blocks belonging to a resource block pair occupy the same frequency band in a 1st slot and a 2nd slot, the resource blocks can be hopped in a slot level as described with reference to FIG. 7.
Referring to FIG. 11, the 1st slot and the 2nd slot each include 6 OFDM symbols. Among the 6 OFDM symbols included in each slot, 2 OFDM symbols correspond to an RS part, and the remaining 4 OFDM symbols correspond to an information part. Other than that, the example of FIG. 10 in which the normal CP is used is applied directly. However, in the RS part, an RS sequence is generated on the basis of the cyclically shifted sequence and an orthogonal sequence having a length of K=2.
As described above, in both cases of the normal CP and the extended CP, a resource used for PUCCH format 1/1a/1b transmission has to be identified by a resource index. A resource block for transmitting information, a CS index Ics and an orthogonal sequence index Ios for generation of an information sequence, and a CS index I′cs and an orthogonal sequence index I′os for generation of the RS sequence are determined from the resource index.
For example, when a CS interval is 2 in the extended CP, the UE multiplexing capacity is as follows. Since the number of CS indices Ics and the number of orthogonal sequence indices Ios for the control information are respectively 6 and 3, 18 UEs can be multiplexed per one RB. However, the number of CS indices I′cs and the number of orthogonal sequence indices I′os for generation of the RS sequence are respectively 6 and 2, 12 UEs can be multiplexed per one resource block. Therefore, the UE multiplexing capacity is limited by the RS part rather than the information part.
FIG. 12 shows an example of PUCCH format 2 transmission when a normal CP is used. Although it is shown herein that resource blocks belonging to a resource block pair occupy the same frequency band in a 1st slot and a 2nd slot, the resource blocks may be hopped in a slot level as described in FIG. 7.
Referring to FIG. 12, among the 7 OFDM symbols included in each slot, 2 OFDM symbols correspond to an RS part to which an RS sequence is mapped, and the remaining 5 OFDM symbols correspond to an information part to which an information sequence is mapped. The position and number of OFDM symbols used as the RS part in each slot may vary, and thus the position and number of OFDM symbols used as the information part may also vary.
A UE generates an encoded CQI bit by performing channel coding on a CQI information bit. In this case, a block code may be used. In 3GPP LTE, a block code (20, A) is used, where A is a size of the CQI information bit. That is, in the 3GPP LTE, encoded bits (20 bits) are generated always irrespective of the size of the CQI information bit.
Table 7 below shows an example of 13 basis sequences for the block code (20, A).




















TABLE 7





i
M(i, 0)
M(i, 1)
M(i, 2)
M(i, 3)
M(i, 4)
M(i, 5)
M(i, 6)
M(i, 7)
M(i, 8)
M(i, 9)
M(i, 10)
M(i, 11)
M(i, 12)




























0
1
1
0
0
0
0
0
0
0
0
1
1
0


1
1
1
1
0
0
0
0
0
0
1
1
1
0


2
1
0
0
1
0
0
1
0
1
1
1
1
1


3
1
0
1
1
0
0
0
0
1
0
1
1
1


4
1
1
1
1
0
0
0
1
0
0
1
1
1


5
1
1
0
0
1
0
1
1
1
0
1
1
1


6
1
0
1
0
1
0
1
0
1
1
1
1
1


7
1
0
0
1
1
0
0
1
1
0
1
1
1


8
1
1
0
1
1
0
0
1
0
1
1
1
1


9
1
0
1
1
1
0
1
0
0
1
1
1
1


10
1
0
1
0
0
1
1
1
0
1
1
1
1


11
1
1
1
0
0
1
1
0
1
0
1
1
1


12
1
0
0
1
0
1
0
1
1
1
1
1
1


13
1
1
0
1
0
1
0
1
0
1
1
1
1


14
1
0
0
0
1
1
0
1
0
0
1
0
1


15
1
1
0
0
1
1
1
1
0
1
1
0
1


16
1
1
1
0
1
1
1
0
0
1
0
1
1


17
1
0
0
1
1
1
0
0
1
0
0
1
1


18
1
1
0
1
1
1
1
1
0
0
0
0
0


19
1
0
0
0
0
1
1
0
0
0
0
0
0









In Table 7, Mi,n denotes a basis sequence (where 0≦n≦12, n is an integer). The encoded bit is generated by linear combination of the 13 basis sequences. Equation 7 below shows an example of the encoded bit b, (0≦i≦19, where i is an integer).




  
    
      
        
          b
          ⁡
          
            (
            i
            )
          
        
        =
        
          
            ∑
            
              n
              =
              0
            
            
              A
              -
              1
            
          
          ⁢
          
            
          
          ⁢
          
            
              {
              
                
                  a
                  ⁡
                  
                    (
                    n
                    )
                  
                
                ·
                
                  M
                  ⁡
                  
                    (
                    
                      i
                      ,
                      n
                    
                    )
                  
                
              
              }
            
            ⁢
            mod
            ⁢
            
              
            
            ⁢
            2
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          7
        
        ]
      
    
  




In Equation 7, a0, a1, . . . , aA-1 denotes an information bit, and A denotes the size of the information bit (where A is a natural number).
The encoded bits (20 bits) are mapped to 10 modulation symbols d(0), . . . , d(9) by using QPSK modulation. In the PUCCH format 2a, 1-bit HARQ ACK/NACK information is mapped to one modulation symbol d(10) by using BPSK modulation. In the PUCCH format 2b, 2-bit HARQ ACK/NACK information is mapped to one modulation symbol d(10) by using QPSK modulation. That is, in the PUCCH format 2a, the CQI and the 1-bit HARQ ACK/NACK information are concurrently transmitted, and in the PUCCH format 2b, the CQI and the 2-bit HARQ ACK/NACK information are concurrently transmitted. Herein, d(10) is used for generation of an RS. d(10) corresponds to one OFDM symbol between two OFDM symbols on which the RS is carried in each slot. In other words, according to d(10), phase modulation is performed on the RS carried on one OFDM symbol in each slot. The PUCCH formats 2a/2b can be supported only for the normal CP. As such, in each of the PUCCH formats 2a and 2b, one modulation symbol is used for generation of the RS.
In the information part, an information sequence is generated based on modulation symbols d(0), . . . , d(9) and a cyclically shifted sequence r(n,Ics). Each modulation symbol can be multiplied to the cyclic shifted sequence r(n,Ics). The information sequence is a one-dimensional spread sequence. Unlike the PUCCH formats 1/1a/1b, an orthogonal sequence is not used in the PUCCH formats 2/2a/2b.
The cyclically shifted sequence r(n,Ics) is generated from a base sequence for each OFDM symbol used as the information part within the subframe. The base sequence is identical within one slot. The 1st slot and the 2nd slot may have identical or different base sequences within the subframe. The cyclically shifted index Ics is determined from a resource index. The cyclically shifted index Ics can be CS-hopped in a symbol level. The CS hopping can be performed according to a slot number n(s) within a radio frame and a symbol index I within a slot. Therefore, the CS index Ics can be expressed by Ics(n(s),I). In FIG. 13, a value Ics for each OFDM symbol in the information part is for exemplary purposes only.
In the RS part, the cyclically shifted sequence r(n,I′cs) can be used as the RS sequence. I′cs is a CS index for the RS. I′cs is determined from the resource index.
In the RS part, the base sequence for generating the cyclically shifted sequence may be identical to the base sequence of the information part. The CS index Ics of the information part and the CS index I′cs of the RS part are both determined from the resource index. However, a method of determining the CS index from the resource index may be identical or different between the information part and the RS part.
In the PUCCH format 2a/2b, d(10) corresponds to one OFDM symbol of the RS part. That is, an RS sequence in which d(10) and the cyclically shifted sequence are multiplied is mapped to one OFDM symbol of the RS part within each slot.
FIG. 13 shows an example of PUCCH format 2 transmission when an extended CP is used. Although it is shown herein that resource blocks belonging to a resource block pair occupy the same frequency band in a 1st slot and a 2nd slot, the resource blocks may be hopped in a slot level as described in FIG. 7.
Referring to FIG. 13, each of the 1st slot and the 2nd slot includes 6 OFDM symbols. Among the 6 OFDM symbols included in each slot, one OFDM symbol corresponds to an RS part, and the remaining 5 OFDM symbols correspond to an information part. Other than that, the normal CP case of FIG. 11 is applied directly.
As described above, in both cases of the normal CP and the extended CP, a resource used for PUCCH format 2/2a/2b transmission has to be identified by a resource index. A resource block for transmitting information, a CS index Ics for generation of an information sequence, and a CS index I′cs for generation of an RS sequence are determined from the resource index. If a CS interval is 1, the number of CS indices Ics is 12 and the number of CS indices I′cs is 12. Thus, 12 UEs can be multiplexed per one resource block. If the CS interval is 2, the number of CS indices Ics is 6 and the number of CS indices I′cs is 6. Thus, 6 UEs can be multiplexed per one resource block.
As such, information can be transmitted by using code division multiplexing (CDM) and/or frequency division multiplexing (FDM) as a multiplexing scheme. Only one resource index is used in the information transmission method described up to now. However, to increase an amount of information that is transmitted concurrently, it may be necessary to allocate multiple resources to one UE. When allocating the multiple resources, there may be a problem in a method of transmitting a signal generated from information and a reference signal by using the multiple resources. Hereinafter, a method of transmitting a signal by using multiple resources will be described.
FIG. 14 is a block diagram showing an exemplary structure of a transmitter including two antennas. Herein, the transmitter may be a part of a UE or a part of a BS.
Referring to FIG. 14, a transmitter 200 includes an information processor 210, a reference signal generator 220, 1st and 2nd resource block mappers 230-1 and 230-2, 1st and 2nd OFDM signal generators 240-1 and 240-2, 1st and 2nd RF units 250-1 and 250-2, and two antennas 290-1 and 290-2.
The 1st and 2nd resource block mappers 230-1 and 230-2 are respectively coupled to the 1st and 2nd OFDM signal generators 240-1 and 240-2. The 1st and 2nd OFDM signal generators 240-1 and 240-2 are respectively coupled to the 1st and 2nd RF units 250-1 and 250-2. The 1st and 2nd RF units 250-1 and 250-2 are respectively coupled to the two antennas 290-1 and 290-2. That is, an nth resource block mapper 230-n is coupled to an nth OFDM symbol generator 240-n, the nth OFDM signal generator 240-n is coupled to an nth RF unit 250-n, and the nth RF unit is coupled to an nth antenna 290-n. In case of multiple-antenna transmission, there may be one resource grid defined for each antenna.
Two resource indices are allocated to the transmitter 200. The information processor 210 generates information sequences based on the two resource indices. Other than that, the description on the information transmission method of FIG. 8 to FIG. 13 can also be applied to a method and apparatus for information transmission through a plurality of Tx antennas.
Hereinafter, a method of generating information sequences based on two resource indices in the information processor 210 will be described.
FIG. 15 is a block diagram showing an exemplary structure of a part of a transmitter including two antennas.
Referring to FIG. 15, the information processor 210 includes a channel coding unit 211, a modulator 212, and 1st and 2nd information sequence generators 213-1 and 213-2. The 1st information sequence generator 213-1 is coupled to a 1st resource block mapper 230-1, and the 2nd information sequence generator 213-2 is coupled to a 2nd resource block mapper 230-2.
The information processor 210 can generate information sequences by using orthogonal space resource transmit diversity (OSRTD) or orthogonal space resource spatial multiplexing (OSRSM).
1. OSRTD
It is assumed that s(1) is a complex-valued signal corresponding to information to be transmitted by the transmitter 200. Herein, the complex-valued signal may be any signal, one or more modulation symbols, or a spread sequence.
The modulator 212 outputs s(1). Then, s(1) is input to each of the 1st information sequence generator 213-1 and the 2nd information sequence generator 213-2.
The 1st information sequence generator 213-1 generates a 1st information sequence based on s(1) and a 1st resource index. The 2nd information sequence generator 213-2 generates a 2nd information sequence based on s(1) and a 2nd resource index. The 1st information sequence is transmitted through the 1st antenna 290-1, and the 2nd information sequence is transmitted through the 2nd antenna 290-2. When the 1st resource index and the 2nd resource index are allocated differently, orthogonality can be maintained between antennas.
In order to perform channel estimation for each antenna, an RS has to be generated for each antenna. For this, each resource index may be mapped to each antenna in a one-to-one manner. Therefore, an RS for the 1st antenna may be generated based on the 1st resource index, and an RS for the 2nd antenna may be generated based on the 2nd resource index.
As such, the OSRTD is a method in which a resource index is allocated for each antenna and the same information is repetitively transmitted in an orthogonal manner for each antenna. By repetitively transmitting the same information through a plurality of antennas, a diversity gain can be obtained, and reliability of wireless communication can be increased.
If it is assumed that 18 UEs can be multiplexed per one resource block in case of single-antenna transmission, 9 UEs can be multiplexed per one resource block when using OSRTD for two antennas. In case of the PUCCH format 1/1a/1b, the same information is transmitted in a 1st slot and a 2nd slot. A resource block allocated to the PUCCH is hopped in a slot level. That is, by transmitting information through different subcarriers over time, a frequency diversity gain can be obtained. However, if a sufficient diversity gain can be obtained by using the OSRTD, the same control information as that of the 1st slot is not necessarily transmitted in the 1st slot. Therefore, different information can be transmitted in the 1st slot and the 2nd slot. In this case, UE multiplexing capacity of the OSRTD for the two antennas may be maintained to be the same as UE multiplexing capacity of single-antenna transmission. For example, in case of the single-antenna transmission, if 18 UEs are multiplexed per one resource block, 18 UEs can also be multiplexed per one resource block even in the OSRTD for the two antennas.
The 2nd information sequence generator 213-2 may generate the 2nd information sequence by modifying the complex-valued signal s(1). For example, the 2nd information sequence can be generated based on s(1)* and the 2nd resource index. Herein, (•)* denotes a complex conjugate. Alternately, a modified complex-valued signal s(2) processed by the 2nd information sequence generator can be expressed by Equation 8 below.

s(2)=s(1)·exp(jθ) or a·s(1)  [Equation 8]

In Equation 8, ‘a’ denotes a complex-valued scaling factor of the 2nd information sequence generator.
A Tx signal matrix can be expressed by Equation 9 below.




  
    
      
        [
        
          
            
              
                s
                ⁡
                
                  (
                  1
                  )
                
              
            
            
              0
            
          
          
            
              0
            
            
              
                s
                ⁡
                
                  (
                  1
                  )
                
              
            
          
        
        ]
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          9
        
        ]
      
    
  




In Equation 9, a row and/or column of the Tx signal matrix may correspond to a Tx antenna, a resource index, etc. For example, rows of the Tx signal matrix may correspond to respective resource indices, and columns thereof may correspond to respective Tx antennas.
y(1) denotes a 1st Rx signal for the 1st information sequence generated based on the 1st resource index. y(2) denotes a 2nd Rx signal for the 2nd information sequence generated based on the 2nd resource index. An actual Rx signal y is a combination of the 1st Rx signal y1 and the 2nd Rx signal y2, i.e., y=y(1)+y(2). However, it is assumed that the Rx signal y can be split into the 1st Rx signal y1 and the 2nd Rx signal y2 by using a de-spreading operation. For convenience of explanation, it is assumed that a receiver has one Rx antenna.
An Rx signal matrix can be expressed by Equation 10 below.




  
    
      
        
          [
          
            
              
                
                  y
                  ⁡
                  
                    (
                    1
                    )
                  
                
              
            
            
              
                
                  y
                  ⁡
                  
                    (
                    2
                    )
                  
                
              
            
          
          ]
        
        =
        
          
            
              [
              
                
                  
                    
                      s
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                  
                    0
                  
                
                
                  
                    0
                  
                  
                    
                      s
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                
              
              ]
            
            ⁡
            
              [
              
                
                  
                    
                      h
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                
                
                  
                    
                      h
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
              
              ]
            
          
          +
          
            [
            
              
                
                  
                    n
                    ⁡
                    
                      (
                      1
                      )
                    
                  
                
              
              
                
                  
                    n
                    ⁡
                    
                      (
                      2
                      )
                    
                  
                
              
            
            ]
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          10
        
        ]
      
    
  




In Equation 10, h(1) denotes a channel for the 1st antenna 290-1, h(2) denotes a channel for the 2nd antenna 290-1, n(1) denotes noise of the 1st Rx signal, and n(2) denotes noise of the 2nd Rx signal. Herein, the noise may be additive white Gaussian noise (AWGN).
In general, if Tx power is limited, a normalization factor corresponding to the number of Tx antennas can be used. Equation 11 below shows an example of the normalization factor.




  
    
      
        1
        
          
            Ntx
            ×
            Nc
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          11
        
        ]
      
    
  




In Equation 11, Ntx denotes the number of Tx antennas, and Nc denotes the number of resources per antenna. However, for convenience of explanation, the normalization factor is omitted in the following description.
When de-spreading is performed on each resource index from the Rx signal, a diversity gain can be obtained as expressed by Equation 12 below.

|h(1)|2+|h(2)|2  [Equation 12]

The diversity gain is similar to maximal ratio coding (MRC) which is optimal combining. The MRC scheme is one of signal combining schemes for estimating a Tx signal from an Rx signal received through a plurality of Rx antennas.
Although it is described herein that the number of Tx antennas is 2 for convenience of explanation, the number of Tx antennas is not limited thereto.
When the transmitter includes M antennas (where M is a natural number), M resource indices can be allocated. The M antennas can be one-to-one mapped to the M resource indices, respectively. If the number of Tx antennas is 3 or more, OSRTD can be used in combination with other Tx diversity schemes such as cyclic delay diversity (CDD) or precoding vector switching (PVS). For example, when using 4 Tx antennas, the 4Tx antennas can be divided by two, and thus can be grouped into two antenna groups. The OSRTD is applied to each of the two antenna groups, and the CDD or the PVS can be applied between the groups.
2. OSRSM
It is assumed that s(1) and s(2) are complex-valued signals corresponding to information to be transmitted by the transmitter 200.
The 1st information sequence generator 213-1 generates the 1st information sequence based on the 1st information symbols s(1) and the 1st resource index. The 2nd information sequence generator 213-2 generates the 2nd information sequence based on the 2nd information symbol s(2) and the 2nd resource index. The 1st information sequence is transmitted through the 1st antenna 290-1, and the 2nd information sequence is transmitted through the 2nd antenna 290-2. When the 1st resource index and the 2nd resource index are allocated differently, orthogonality can be maintained between antennas.
In order to perform channel estimation for each antenna, an RS has to be generated for each antenna. For this, each resource index may be mapped to each antenna in a one-to-one manner. Therefore, an RS for the 1st antenna may be generated based on the 1st resource index, and an RS for the 2nd antenna may be generated based on the 2nd resource index.
Although it is described herein that the number of Tx antennas is 2 for convenience of explanation, the number of Tx antennas is not limited thereto.
When the transmitter includes M antennas (where M is a natural number), the transmitter can transmit M symbols. M resource indices can be allocated to the transmitter. The M antennas can be one-to-one mapped to the M resource indices, respectively. Different symbols can be transmitted through the respective M antennas. As such, an information transmission method having a spatial multiplexing rate of M is called OSRSM.
The encoded bit which is bit-level information output from the channel coding unit 211 can be permutated before being modulated by the modulator 212.
It is assumed that 1st encoded bits (2 bits) a(0) and a(1) and 2nd encoded bits (2 bits) b(0) and b(1) are input to the modulator 212. For example, the 1st encoded bit may be bit-level information of 1st ACK/NACK for 1st data transmitted through a 1st DL carrier, and the 2nd encoded bit may be bit-level information of 2nd ACK/NACK for 2nd data transmitted through a 2nd DL carrier.
The modulator 212 may generate a 1st modulation symbol d(0) by performing QPSK modulation on the 1st encoded bit, and may generate a 2nd modulation symbol e(0) by performing QPSK modulation on the 2nd encoded bit.
Alternatively, the modulator 212 may replace the 1st encoded bit and the 2nd encoded bit and then modulate the bits after replacement. For example, the modulator 212 may replace the bits by swapping the 1st bits a(0) and b(0) of the 1st and 2nd encoded bits. The modulator may generate the 1st modulation symbol d(0) by modulating the bits b(0) and a(1), and may generate the 2nd modulation symbol e(0) by modulating the bits a(0) and b(1).
The modulation symbols output from the modulator 212 are input to a splitter (not shown). The splitter splits the modulation symbol into the 1st information symbol s(1) and the 2nd information symbol s(2) by using the 1st modulation symbol d(0) and the 2nd modulation symbol e(0). For one example, the 1st modulation symbol may correspond to the 1st information symbol, and the 2nd modulation symbol may correspond to the 2nd information symbol. For another example, the 1st modulation symbol and the 2nd modulation symbol may be replaced and/or mixed and then may be split into the 1st information symbol and the 2nd information symbol.
Equation 13 below shows examples of the 1st modulation symbol d(0) and the 2nd modulation symbol e(0) which are replaced and/or mixed and then are split into the 1st information symbol s(1) and the 2nd information symbol s(2).

s(1)=d(0)+e(0),s(2)=d(0)−e(0)

s(1)=d(0)−e(0),s(2)=e(0)+d(0)*  [Equation 13]

Alternatively, as expressed by Equation 14 below, the 1st modulation symbol d(0) and the 2nd modulation symbol e(0) may be rotated by any phase, be replaced and/or mixed, and then be split into the 1st information symbol s(1) and the 2nd information symbol s(2).

s(1)=d(0)+e(0)eja,s(2)=d(0)−e(0)ejb 

s(1)=d(0)−e(0)*eja,s(2)=e(0)+d(0)*ejb  [Equation 14]

In Equation 14, ‘a’ and ‘b’ may be identical or different from each other.
In both of the OSRTD and OSRSM schemes, a plurality of antennas can be mapped to a plurality of resource indices in a one-to-one manner. Therefore, one resource index is used for each antenna to generate and transmit an information sequence and an RS sequence.
FIG. 16 is a block diagram showing an exemplary structure of a part of a transmitter including a single antenna. Herein, the transmitter may be the transmitter 100 of FIG. 8.
Referring to FIG. 16, an information processor 110 includes a channel coding unit 111, a modulator 112, and 1st and 2nd information sequence generators 113-1 and 113-2. The 1st and 2nd information sequence generators 113-1 and 113-2 are coupled to a resource block mapper 130.
The modulator 112 outputs a 1st complex-valued signal s(1) and a 2nd complex-valued signal s(2). Each of the signals s(1) and s(2) is a complex-valued signal corresponding to information to be transmitted by the transmitter 100. Herein, the complex-valued signal may be any signal, one or more modulation symbols, or a spread sequence.
The 1st complex-valued signal may correspond to 1st information for a 1st DL carrier. The 2nd complex-valued signal may correspond to 2nd information for a 2nd DL carrier. The 1st information and the 2nd information may be transmitted through the same carrier. The 1st information may be 1st ACK/NACK for 1st data received by the UE through the 1st DL carrier. The 2nd information may be 2nd ACK/NACK for 2nd data received by the UE through the 2nd DL carrier. Alternatively, the 1st information may be 1st CQI for the 1st DL carrier, and the 2nd information may be 2nd CQI for the 2nd DL carrier. That is, a 1st resource index may be allocated to the 1st DL carrier, and a 2nd resource index may be allocated to the 2nd DL carrier. In this case, information for each of the 1st DL carrier and the 2nd DL carrier may be transmitted through one UL carrier. Therefore, the transmitter of FIG. 14 can be used in an asymmetric multi-carrier system in which the number of DL carriers is greater than the number of UL carriers. For example, it may be used in a multi-carrier system in which the ratio of the number of DL carriers to the number UL carriers is 2:1.
Alternatively, each of the 1st information and the 2nd information may be representative information. The representative information is one piece of information representing a plurality of pieces of information. Representing the plurality of pieces of information into one piece of representative information is called information bundling. Examples of the representative information include representative CQI, representative ACK/NACK, representative PMI, etc. The representative CQI may be one CQI for a plurality of DL carriers. For example, the representative CQI may be an average CQI for respective CQIs for a plurality of DL carriers. Alternatively, the representative CQI may be one CQI representing the respective CQIs for a plurality of codewords. The representative ACK/NACK may be one HARQ ACK/NACK for each data transmitted through the plurality of DL carriers. For example, if decoding of each data transmitted through the plurality of DL carriers is completely successful, the representative ACK/NACK is ACK, and otherwise the representative ACK/NACK is NACK. Alternatively, the representative ACK/NACK may be one HARQ ACK/NACK representing each ACK/NACK for a plurality of codewords.
For one example, the 1st information may be 1st representative information for a 1st DL carrier and a 2nd DL carrier, and the 2nd information may be 2nd representative information for a 3rd DL carrier and a 4th DL carrier. For another example, the 1st information may be 1st representative information for a plurality of codewords, and the 2nd information may be 2nd representative information for other codewords.
The 1st complex-valued signal s(1) is input to the 1st information sequence generator 113-1, and the 2nd complex-valued signal s(2) is input to the 2nd information sequence generator 113-2.
The 1st information sequence generator 113-1 generates a 1st information sequence based on the s(1) and a 1st resource index. The 2nd information sequence generator 113-2 generates a 2nd information sequence based on the s(2) and a 2nd resource index.
Each of the 1st information sequence and the 2nd information sequence is input to the resource block mapper 130. In this case, the 1st information sequence and/or the 2nd information sequence may be subjected to phase shift. This is to prevent the 1st information sequence and the 2nd information sequence from being offset when the two sequences are combined.
A 1st resource block (RB) is determined from the 1st resource index, and a 2nd RB is determined from the 2nd resource index. In this case, the 1st RB and the 2nd RB may be identical to each other or different from each other.
FIG. 17 shows another example of a case where a 1st RB is different from a 2nd RB.
Referring to FIG. 17, a resource block mapper 130 maps a 1st information sequence to an information part of the 1st RB, and maps a 2nd information sequence to an information part of the 2nd RB.
In this case, an RS sequence mapped to an RS part of the 1st RB is generated based on a 1st resource index. An RS sequence mapped to an RS part of the 2nd RB is generated based on a 2nd resource index.
If the 1st RB indicated by the 1st resource index is different from the 2nd RB indicated by the 2nd resource index, an information sequence and an RS sequence are both generated based on the two resource indices.
FIG. 18 shows an example in which a 1st RB is identical to a 2nd RB.
Referring to FIG. 18, a resource block mapper 130 adds a 1st information sequence and a 2nd information sequence and maps the added sequences to an information part of the RBs. In this case, the 1st information sequence and the 2nd information sequence may be added, or the 1st information sequence and/or the 2nd information sequence may be subjected to phase shift and then be added.
An RS sequence mapped to an RS part of an RB is generated based on one resource index among a 1st resource index and a 2nd resource index. Since channel estimation is possible by using only the RS sequence generated based on one resource index among the two resource indices, the RS sequence shall be generated based on one of the two resource indices.
There is no particular restriction on a resource index based on which the RS sequence is generated between the 1st resource index and the 2nd resource index. However, a receiver has to know the resource index based on which the RS sequence is generated for channel estimation. Therefore, a method of selecting a resource index for generating the RS sequence may be determined in advance by a protocol. For example, the RS sequence may be generated based on a smaller resource index between the two resource indices. Alternatively, the resource index based on which the RS sequence is generated may be reported through signaling.
As such, if the 1st RB indicated by the 1st resource index is identical to the 2nd RB indicated by the 2nd resource index, two information sequences are generated based on the two resource indices, whereas the RS sequence is generated based on one of the two resource indices.
FIG. 19 is a block diagram showing another exemplary structure of a part of a transmitter including two antennas.
Referring to FIG. 19, an information processor 210 includes a channel coding unit 211, a modulator 212, and a space-code block code (SCBC) processor 214. The SCBC processor 214 is coupled to 1st and 2nd resource mappers 230-1 and 230-2.
It is assumed that a 1st complex-valued signal s(1) and a 2nd complex-valued signal s(2) are complex-valued signals corresponding to information to be transmitted by the transmitter 200.
The SCBC processor 214 generates a 1st Tx vector and a 2nd Tx vector based on an Alamouti code from the 1st complex-valued signal s(1) and the 2nd complex-valued signal s(2). The 1st Tx vector is transmitted through the 1st antenna 290-1, and the 2nd Tx vector is transmitted through the 2nd antenna 290-2.
The 1st Tx vector consists of a 1st Tx symbol and a 2nd Tx symbol. The 2nd Tx vector consists of a 3rd Tx symbol and a 4th Tx symbol.
(1) 1st Tx Vector
A 1st information sequence is generated based on the 1st Tx symbol and a 1st resource index.
A 2nd information sequence is generated based on the 2nd Tx symbol and a 2nd resource index.
The 1st information sequence and the 2nd information sequence are input to the 1st resource block mapper 230-1.
(2) 2nd Tx Vector
A 3rd information sequence is generated based on the 3rd Tx symbol and the 1st resource index.
A 4th information sequence is generated based on the 4th Tx symbol and the 2nd resource index.
The 3rd information sequence and the 4th information sequence are input to the 2nd resource block mapper 230-2.
Therefore, the 1st information sequence and the 2nd information sequence may be combined and transmitted through the 1st antenna. The 2nd information sequence and the 4th information sequence may be combined and transmitted through the 2nd antenna. To decrease a cubic metric (CM), a phase of at least one information sequence may change when combining one information sequence to another information sequence. Alternatively, a phase of a Tx symbol may change before the information sequence is generated. For example, the 2nd information sequence may be added to the 1st information sequence by phase-shifting the 2nd information sequence by a specific phase. In addition, the 4th information sequence may be added to the 3rd information sequence by phase-shifting the 4th information sequence by a specific phase. In case of BPSK, the specific phase may be 90 degrees. In case of QPSK, the specific phase may be 45 degrees.
As such, when CDM/FDM is used as a multiplexing scheme, information can be transmitted by using a resource according to SCBC. The transmitter can perform smart repetition by using an antenna and a resource, thereby being able to obtain a diversity gain and to increase reliability of wireless communication. Hereinafter, such an information transmission method is called an SCBC information transmission method.
In the SCBC information transmission method, a resource index allocated to an information part is not mapped to an antenna in a one-to-one manner. However, an RS has to be generated for each antenna in order to perform channel estimation for each antenna. For this, each resource index can be mapped to each antenna in a one-to-one manner. Therefore, an RS for the 1st antenna can be generated based on the 1st resource index, and an RS for the 2nd antenna can be generated based on the 2nd resource index.
For SCBC information transmission, it is described above that the 2nd resource index is further allocated to the transmitter in addition to the 1st resource index. However, if different information has already been allocated by using a different resource index, the 2nd resource index is not necessarily allocated additionally.
If it is assumed that 18 UEs can be multiplexed per one resource block in case of single-antenna transmission, 9 UEs can be multiplexed per one resource block when applying an SCBC transmission method using two antennas. In case of the PUCCH format 1/1a/1b, the same information is transmitted in a 1st slot and a 2nd slot. A resource block allocated to the PUCCH is hopped in a slot level. That is, by transmitting information through different subcarriers over time, a frequency diversity gain can be obtained. However, if a sufficient diversity gain can be obtained by using the SCBC transmission method, the same control information as that of the 1st slot is not necessarily transmitted in the 2nd slot. Therefore, different information can be transmitted in the 1st slot and the 2nd slot. In this case, UE multiplexing capacity of the SCBC transmission method for the two antennas may be maintained to be the same as UE multiplexing capacity of single-antenna transmission. For example, in case of the single-antenna transmission, if 18 UEs are multiplexed per one resource block, 18 UEs can also be multiplexed per one resource block even in the SCBC transmission method for the two antennas.
Hereinafter, a Tx signal matrix is defined as a 2×2 matrix of which a 1st column is the 1st Tx vector and a 2nd column is the 2nd Tx vector. An element of an ith row and a jth column of the Tx matrix is expressed by (i,j) (where i=1, 2 and j=1,2). (1, 1) and (2, 1) respectively denote the 1st Tx symbol and the 2nd Tx symbol of the 1st Tx vector. (1, 2) and (2, 2) respectively denote the 3rd Tx symbol and the 4th Tx symbol of the 2nd Tx vector.
A Tx signal matrix can be expressed by Equation 15 below.




  
    
      
        [
        
          
            
              
                s
                ⁡
                
                  (
                  1
                  )
                
              
            
            
              
                s
                ⁡
                
                  (
                  2
                  )
                
              
            
          
          
            
              
                -
                
                  
                    s
                    ⁡
                    
                      (
                      2
                      )
                    
                  
                  *
                
              
            
            
              
                
                  s
                  ⁡
                  
                    (
                    1
                    )
                  
                
                *
              
            
          
        
        ]
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          15
        
        ]
      
    
  




In Equation 15, a row and/or column of the Tx signal matrix may correspond to a Tx antenna, a resource index, etc. For example, rows of the Tx signal matrix may correspond to respective resource indices, and columns thereof may correspond to respective Tx antennas.
The Tx signal matrix expressed in Equation 15 above is for exemplary purposes only, and is not for restricting a format of the Tx signal matrix. The Tx signal matrix includes all possible unitary transforms of the matrix of Equation 15 above. In this case, the unitary transform includes not only a transform for the 1st information symbol s(1) and the 2nd information symbol s(2) but also a transform in a state where s(1) and s(2) are separated into a real part and an imaginary part.
y(1) denotes a 1st Rx signal for the 1st information sequence generated based on the 1st resource index. y(2) denotes a 2nd Rx signal for the 2nd information sequence generated based on the 2nd resource index. An actual Rx signal y is a combination of the 1st Rx signal y1 and the 2nd Rx signal y2, i.e., y=y(1)+y(2). However, it is assumed that the Rx signal y can be split into the 1st Rx signal y1 and the 2nd Rx signal y2 by using a de-spreading operation. For convenience of explanation, it is assumed that a receiver has one Rx antenna.
An Rx signal matrix can be expressed by Equation 16 below.




  
    
      
        
          [
          
            
              
                
                  y
                  ⁡
                  
                    (
                    1
                    )
                  
                
              
            
            
              
                
                  y
                  ⁡
                  
                    (
                    2
                    )
                  
                
              
            
          
          ]
        
        =
        
          
            
              [
              
                
                  
                    
                      s
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                  
                    
                      s
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
                
                  
                    
                      -
                      
                        
                          s
                          ⁡
                          
                            (
                            2
                            )
                          
                        
                        *
                      
                    
                  
                  
                    
                      
                        s
                        ⁡
                        
                          (
                          1
                          )
                        
                      
                      *
                    
                  
                
              
              ]
            
            ⁡
            
              [
              
                
                  
                    
                      h
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                
                
                  
                    
                      h
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
              
              ]
            
          
          +
          
            [
            
              
                
                  
                    n
                    ⁡
                    
                      (
                      1
                      )
                    
                  
                
              
              
                
                  
                    n
                    ⁡
                    
                      (
                      2
                      )
                    
                  
                
              
            
            ]
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          16
        
        ]
      
    
  




In Equation 16, h(1) denotes a channel for the 1st antenna 290-1, h(2) denotes a channel for the 2nd antenna 290-1, n(1) denotes noise of the 1st Rx signal, and n(2) denotes noise of the 2nd Rx signal. Herein, the noise may be AWGN.
In general, if Tx power is limited, a normalization factor corresponding to the number of Tx antennas can be used. For convenience of explanation, the normalization factor is omitted in the following description.
Equation 16 above can be equivalently expressed by Equation 17 below.




  
    
      
        
          [
          
            
              
                
                  y
                  ⁡
                  
                    (
                    1
                    )
                  
                
              
            
            
              
                
                  
                    y
                    ⁡
                    
                      (
                      2
                      )
                    
                  
                  *
                
              
            
          
          ]
        
        =
        
          
            
              [
              
                
                  
                    
                      h
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                  
                    
                      h
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
                
                  
                    
                      
                        h
                        ⁡
                        
                          (
                          2
                          )
                        
                      
                      *
                    
                  
                  
                    
                      -
                      
                        
                          h
                          ⁡
                          
                            (
                            1
                            )
                          
                        
                        *
                      
                    
                  
                
              
              ]
            
            ⁡
            
              [
              
                
                  
                    
                      s
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                
                
                  
                    
                      s
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
              
              ]
            
          
          +
          
            [
            
              
                
                  
                    n
                    ⁡
                    
                      (
                      1
                      )
                    
                  
                
              
              
                
                  
                    
                      n
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                    *
                  
                
              
            
            ]
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          17
        
        ]
      
    
  




Equation 17 above can be modified to Equation 18 below.




  
    
      
        
          
            
              [
              
                
                  
                    
                      h
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                  
                    
                      h
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                  
                
                
                  
                    
                      
                        h
                        ⁡
                        
                          (
                          2
                          )
                        
                      
                      *
                    
                  
                  
                    
                      -
                      
                        
                          h
                          ⁡
                          
                            (
                            1
                            )
                          
                        
                        *
                      
                    
                  
                
              
              ]
            
            H
          
          ⁡
          
            [
            
              
                
                  
                    y
                    ⁡
                    
                      (
                      1
                      )
                    
                  
                
              
              
                
                  
                    
                      y
                      ⁡
                      
                        (
                        2
                        )
                      
                    
                    *
                  
                
              
            
            ]
          
        
        =
        
          
            
              
                
                  
                    [
                    
                      
                        
                          
                            h
                            ⁡
                            
                              (
                              1
                              )
                            
                          
                        
                        
                          
                            h
                            ⁡
                            
                              (
                              2
                              )
                            
                          
                        
                      
                      
                        
                          
                            
                              h
                              ⁡
                              
                                (
                                2
                                )
                              
                            
                            *
                          
                        
                        
                          
                            -
                            
                              
                                h
                                ⁡
                                
                                  (
                                  1
                                  )
                                
                              
                              *
                            
                          
                        
                      
                    
                    ]
                  
                  H
                
                ⁡
                
                  [
                  
                    
                      
                        
                          h
                          ⁡
                          
                            (
                            1
                            )
                          
                        
                      
                      
                        
                          h
                          ⁡
                          
                            (
                            2
                            )
                          
                        
                      
                    
                    
                      
                        
                          
                            h
                            ⁡
                            
                              (
                              2
                              )
                            
                          
                          *
                        
                      
                      
                        
                          -
                          
                            
                              h
                              ⁡
                              
                                (
                                1
                                )
                              
                            
                            *
                          
                        
                      
                    
                  
                  ]
                
              
              ⁡
              
                [
                
                  
                    
                      
                        s
                        ⁡
                        
                          (
                          1
                          )
                        
                      
                    
                  
                  
                    
                      
                        s
                        ⁡
                        
                          (
                          2
                          )
                        
                      
                    
                  
                
                ]
              
            
            +
            
              
                
                  [
                  
                    
                      
                        
                          h
                          ⁡
                          
                            (
                            1
                            )
                          
                        
                      
                      
                        
                          h
                          ⁡
                          
                            (
                            2
                            )
                          
                        
                      
                    
                    
                      
                        
                          
                            h
                            ⁡
                            
                              (
                              2
                              )
                            
                          
                          *
                        
                      
                      
                        
                          -
                          
                            
                              h
                              ⁡
                              
                                (
                                1
                                )
                              
                            
                            *
                          
                        
                      
                    
                  
                  ]
                
                H
              
              [
              
                
              
              ⁢
              
                
                  
                    
                      n
                      ⁡
                      
                        (
                        1
                        )
                      
                    
                  
                
                
                  
                    
                      
                        n
                        ⁡
                        
                          (
                          2
                          )
                        
                      
                      *
                    
                  
                
              
              ]
            
          
          =
          
             
            
              
                
                  [
                  
                    
                      
                        
                          
                            
                              
                              
                                h
                                ⁡
                                
                                  (
                                  1
                                  )
                                
                              
                              
                            
                            2
                          
                          +
                          
                            
                              
                              
                                h
                                ⁡
                                
                                  (
                                  2
                                  )
                                
                              
                              
                            
                            2
                          
                        
                      
                      
                        0
                      
                    
                    
                      
                        0
                      
                      
                        
                          
                            
                              
                              
                                h
                                ⁡
                                
                                  (
                                  1
                                  )
                                
                              
                              
                            
                            2
                          
                          +
                          
                            
                              
                              
                                h
                                ⁡
                                
                                  (
                                  2
                                  )
                                
                              
                              
                            
                            2
                          
                        
                      
                    
                  
                  ]
                
                ⁡
                
                  [
                  
                    
                      
                        
                          s
                          ⁡
                          
                            (
                            1
                            )
                          
                        
                      
                    
                    
                      
                        
                          s
                          ⁡
                          
                            (
                            2
                            )
                          
                        
                      
                    
                  
                  ]
                
              
              +
              
                [
                
                  
                    
                      
                        
                          n
                          ′
                        
                        ⁡
                        
                          (
                          1
                          )
                        
                      
                    
                  
                  
                    
                      
                        
                          n
                          ′
                        
                        ⁡
                        
                          (
                          2
                          )
                        
                      
                    
                  
                
                ]
              
            
          
        
      
    
    
      
        [
        
          Equation
          ⁢
          
            
          
          ⁢
          18
        
        ]
      
    
  




In Equation 18, (•)H denotes a Hermitian matrix. The 1st symbol s1 and the 2nd symbol s2 are orthogonally separated. The receiver can obtain a diversity gain expressed by Equation 12. This is the same diversity gain as the MRC which is the optimal combination.
Although it is described herein that the number of Tx antennas is 2 for convenience of explanation, the number of Tx antennas is not limited thereto.
When the transmitter includes M antennas (where M is a natural number), M resource indices can be allocated. The M antennas can be one-to-one mapped to the M resource indices, respectively. If the number of Tx antennas is 3 or more, the SCBC information transmission method can be used in combination with other Tx diversity schemes such as cyclic delay diversity (CDD) or precoding vector switching (PVS). For example, when using 4 Tx antennas, the 4Tx antennas can be divided by two, and thus can be grouped into two antenna groups. The SCBC information transmission method is applied to each of the two antenna groups, and the CDD or the PVS can be applied between the groups.
The transmitter of FIG. 16 and the transmitter of FIG. 19 have a common point in that two resource indices are allocated per antenna for an information part. That is, in the information part, an antenna and a resource index are not mapped in a one-to-one manner. However, in an RS part, the antenna and the resource index can be mapped in a one-to-one manner so that channel estimation is possible for each antenna. Therefore, if a plurality of resource indices is allocated to one antenna, an RS for an antenna may be generated in a different manner from generation of an information sequence.
The information transmission method described up to now is applicable to all CDM/FDM-type information transmission methods based on PUCCH format 1/1a/1b, format 2/2a/2b, etc.
FIG. 20 is a block diagram showing wireless communication system to implement an embodiment of the present invention. A BS 50 may include a processor 51, a memory 52 and a radio frequency (RF) unit 53. The processor 51 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 51. The memory 52 is operatively coupled with the processor 51 and stores a variety of information to operate the processor 51. The RF unit 53 is operatively coupled with the processor 11, and transmits and/or receives a radio signal. A UE 60 may include a processor 61, a memory 62 and a RF unit 63. The processor 61 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor 51. The memory 62 is operatively coupled with the processor 61 and stores a variety of information to operate the processor 61. The RF unit 63 is operatively coupled with the processor 61, and transmits and/or receives a radio signal.
The processors 51, 61 may include application-specific integrated circuit (ASIC), other chipset, logic circuit and/or data processing device. The memories 52, 62 may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and/or other storage device. The RF units 53, 63 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in memories 52, 62 and executed by processors 51, 61. The memories 52, 62 can be implemented within the processors 51, 61 or external to the processors 51, 61 in which case those can be communicatively coupled to the processors 51, 61 via various means as is known in the art.
As such, a method and apparatus for effective signal transmission in a wireless communication system can be provided. When multiple resources are allocated, an ambiguity problem of an information sequence generation method and a reference signal sequence generation method can be solved by using the multiple resources. Accordingly, reliability of wireless communication can be increased, and overall system performance can be improved.
Additional advantages, objectives, and features of the present invention will become more apparent to those of ordinary skill in the art upon implementation of the present invention based on the aforementioned descriptions or explanation. Moreover, other unexpected advantages may be found as those ordinary skilled in the art implement the present invention based on the aforementioned explanations.
Although a series of steps or blocks of a flowchart are described in a particular order when performing methods in the aforementioned exemplary system, the steps of the present invention are not limited thereto. Thus, some of these steps may be performed in a different order or may be concurrently performed. Those skilled in the art will understand that these steps of the flowchart are not exclusive, and that another step can be included therein or one or more steps can be omitted without having an effect on the scope of the present invention.
Various modifications may be made in the aforementioned embodiments. Although all possible combinations of the various modifications of the embodiments cannot be described, those ordinary skilled in that art will understand possibility of other combinations. For example, those ordinary skilled in the art will be able to implement the invention by combining respective structures described in the aforementioned embodiments. Therefore, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

## Claims

1. A transmitter comprising:
an information processor configured to generate
a first information sequence, for a first antenna, based on a first transmission symbol and a first resource index, and
a second information sequence, for a second antenna, based on a second transmission symbol and a second resource index different from the first resource index,

wherein the first resource index indicates a first resource block and the second resource index indicates a second resource block, which is different from the first resource block;
a reference signal generator operatively coupled to the information processor and configured to generate
a first reference signal sequence, for the first antenna, based on the first resource index, and
a second reference signal sequence, for the second antenna, based on the second resource index; and

the first antenna and the second antenna which are respectively configured to simultaneously transmit a first signal generated based on the first information sequence and the first reference signal sequence, and a second signal based on the second information sequence, and the second reference signal sequence.

2. The transmitter of claim 1,
wherein the first information sequence is mapped to an information part of the first resource block, and the first reference signal sequence is mapped to a reference signal part of the first resource block, and
wherein the second information sequence is mapped to an information part of the second resource block, and the second reference signal sequence is mapped to a reference signal part of the second resource block.

3. The transmitter of claim 1, wherein a resource block indicated by a resource index includes M orthogonal frequency division multiplexing (OFDM) symbols (where M is a natural number greater than or equal to 2), N OFDM symbols out of the M OFDM symbols correspond to an information part to which an information sequence is mapped, and the remaining (M-N) OFDM symbols correspond to a reference signal part to which a reference signal sequence is mapped.

4. The transmitter of claim 1,
wherein a sequence and a resource block are determined from a resource index,
wherein a spread information sequence is generated based on information and the sequence, and
wherein the spread information sequence is mapped to the resource block.

5. The transmitter of claim 4, wherein the sequence is a cyclically shifted sequence.

6. The transmitter of claim 1,
wherein a first sequence, a second sequence, and a resource block are determined from a resource index,
wherein a two-dimensional spread information sequence is generated based on information, the first sequence and the second sequence, and
wherein the two-dimensional spread information sequence is mapped to the resource block.

7. The transmitter of claim 6, wherein the first sequence is a cyclically shifted shift, and the second sequence is an orthogonal sequence.

8. A method for signal transmission performed by a transmitter in a wireless communication system, the method comprising:
generating a first information sequence, for a first antenna of the transmitter, based on a first transmission symbol and a first resource index, and generating a second information sequence, for a second antenna of the transmitter, based on a second transmission symbol and a second resource index different from the first resource index,
wherein the first resource index indicates a first resource block and the second resource index indicates a second resource block, which is different from the first resource block;
generating a first reference signal sequence, for the first antenna, based on the first resource index and a second reference signal sequence, for the second antenna, based on the second resource index; and
simultaneously transmitting a first signal, generated based on the first information sequence and the first reference signal sequence, through the first antenna, and a second signal, generated based on the second information sequence and the second reference signal sequence, through the second antenna.