Method for dynamic interpretation of transport block size

A system and method is provided which allows for the dynamic interpretation of a transport block size field in a Layer 1/Layer 2 (L1/L2) control channel, such that for any first H-ARQ transmission, the transport block size indication field will indicate the size of the transport block. For any retransmission, the transport block size indication bits can be transformed into dedicated bits for indicating the RV used as it relates to circular buffering. A robust bit field for indicating new data transmission (e,g, new data indication (NDI)) is therefore introduced, and from a UE perspective it is possible to determine how to interpret the transport block size field.

FIELD OF THE INVENTION

The present invention relates generally to radio communications. More particularly, the present invention relates to efficient signaling through the definition of downlink control channels in accordance with Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standardization.

BACKGROUND OF THE INVENTION

The Universal Mobile Telecommunications System (UMTS) is a third generation (3G) mobile communication system which provides a variety of multimedia services. The UMTS Terrestrial Radio Access Network (UTRAN) is a part of a UMTS network which includes one or more radio network controllers (RNCs) and one or more nodes. The 3GPP is a collaboration of several independent standardization organizations that is focused on the development of globally applicable 3G mobile phone system specifications. The Technical Specification Group Radio Access Network (TSG RAN) is responsible for the definition of the functions, requirements and interfaces of the universal terrestrial radio access (UTRA) network in its two modes, frequency division duplex (FDD) and time division duplex (TDD). Evolved UTRAN (E-UTRAN), which is also known as Long Term Evolution or LTE, provides new physical layer concepts and protocol architectures for UMTS.

LTE is currently part of a work item phase within the 3GPP. One of the central elements of the system is a downlink control channel, which will carry all of the control information needed to assign resources for the downlink as well as the uplink data channels, where downlink and uplink conventionally refer to transmission paths to and from a mobile station and, for example, a base transceiver station. The elements for the control channel carrying allocation for the downlink channel, following the 3GPP 25.814 specification, can comprise at least: a resource allocation map describing the allocation map for physical resource blocks (PRBs); a modulation scheme/technique; a transport block size or payload size; Hybrid Automatic Repeat-reQuest (H-ARQ) information; multiple-input multiple-output (MIMO) information; and/or a duration of assignment.

3GPP Release 5 (Rel-5) introduced a new high speed downlink shared channel (HS-DSCH). In HS-DSCH transmission utilizing a H-ARQ system (a N-process stop-and-wait system), due to fact that different H-ARQ processes may require a different number of retransmissions, the medium access layer (MAC-hs) packet data units (PDUs) are not necessarily received in order by a desiring MAC-hs receiver. For example, two packets, packet1and packet2, can be sent in consecutive transmission time intervals (TTIs). In this situation, it is possible that when packet2is received correctly by layer 1, the packet1may need further transmissions before it is correctly received and delivered to the MAC-hs layer of a user equipment (UE) receiver, thus leading to packet2getting to the MAC-hs before packet1during in-sequence delivery.

A physical downlink shared channel (PDSCH) can be used to carry the DSCH. In terms of considering PDSCH resource allocations, decisions in the 3GPP have gravitated towards using a circular buffer to implement rate matching between a turbo coded transport block and the amount of available physical resources. An issue related to the circular buffer technique has been described in a 3GPP contribution, R1-072273, entitled “Way Forward on LTE Rate Matching.” In this contribution, it was identified that in order to have good performance using the circular buffer technique, certain restrictions would be necessary, e.g., high redundancy version (RV) signaling granularity or limitations on the variability of the amounts of physical channel resources given to a single user for H-ARQ retransmissions. Therefore, both approaches can create additional problems in the form of either increased overhead or limited flexibility.

FIG. 1illustrates an example of the circular buffer technique combined with H-ARQ using constant size resource allocation for H-ARQ retransmissions. According toFIG. 1, a transport block100is channel coded at102(omitting certain details such as cyclical redundancy check (CRC), tail bits, etc.). This provides, for example, three times the amount of bits, e.g., systematic bits104, parity 1 bits106, and parity 2 bits108. The systematic bits104are interleaved at110, resulting in interleaved systematic bits114, while the parity 1 and parity 2 bits are parity bit interleaved at112resulting in interleaved parity 1 and parity 2 bits116. According to the conventional circular buffer technique, the most important bits are taken for a first transmission118, e.g., the systematic bits114and a first portion of the interleaved parity 1 and parity 2 bits116. If reception of this first transmission118fails, a second transmission120is requested. For optimum operation of the conventional circular buffer technique, the second transmission120should take the coded bits that have not yet been transmitted, e.g., another portion of the interleaved parity 1 and parity 2 bits. Lastly, for a third transmission122, the remaining non-transmitted bits are sent, and if excess capacity exists on the physical channel, additional systematic bits from the interleaved systematic bits114are transmitted (hence the circular buffer terminology). Therefore, as retransmissions are performed, the effective puncturing (omission of, for example, bits) is gradually reduced, such that after a given number of retransmissions, all the systematic and parity bits have been transferred for optimum decoder performance.

The example of transmission with circular buffering shown inFIG. 1only illustrates a situation where the amount of physical resources is the same for each transmission attempt. With the need for frequency domain multi-user packet scheduling in LTE, a scenario will likely arise where H-ARQ retransmissions may not have access to the same amount of physical resources. Such a scenario is illustrated inFIG. 2, where the amount of physical resources for the second transmission is reduced, thus providing fewer parity bits for this particular H-ARQ retransmission.

LikeFIG. 1,FIG. 2shows a transport block100that is channel coded at102into systematic bits104, parity 1 bits106, and parity 2 bits108. Interleaving of these bits occurs at110and112, resulting in interleaved systematic bits114and interleaved parity 1 and parity 2 bits116. The most important bits are taken for transmission at118.

However, a problem arises when a second transmission120is lost in the receiver and the third transmission122is to take place. One possibility is to continue transmissions assuming that the physical resources are the same for each retransmission. This will cause “holes” in the received bit sequence, though, as shown inFIG. 2, where the third transmission122fails to transmit a certain portion(s) of the interleaved parity 1 and parity 2 bits. This effectively negates the “circular” property of circular buffering and penalizes H-ARQ performance (as compared to the conventional and idealized circular buffering scenario illustrated inFIG. 1). Alternatively, sufficient information could be provided at the starting point of the retransmitted data as shown by third transmission124. However, this would require a high number of control channel bits for indicating this value.

Thus, in the presence of unequal resource allocation for retransmissions or an asynchronous H-ARQ protocol, a “signaled resource block (RB)” approach is required (either explicit or implicit), as is the case for 3GPP Rel-5 rate matching. While redundancy versions can be defined for circular buffer rate matching, it should be noted that doing so incurs the cost of losing the “circular” property of circular buffering, making circular buffering and Rel-5 (or Rel-5+Dithering) proposals equivalent from an H-ARQ perspective. That is, the circular buffer technique has not been utilized in previous 3GPP releases, and conventional signaling methods have only been designed for 3GPP Release '99 rate matching with RVs, level indicators, etc.

SUMMARY OF THE INVENTION

Various embodiments of the present invention allow for the dynamic interpretation of the transport block size field in the Layer 1/Layer 2 (L1/L2) control channel, such that for any first H-ARQ transmission, the transport block size indication field will indicate the size of the transport block. For any retransmission, the transport block size indication bits can be transformed into dedicated bits for indicating the RV used as it relates to circular buffering. A robust bit field for indicating new data transmission (e,g, new data indication (NDI)) is therefore introduced and from a UE perspective, it is possible to determine how to interpret the transport block size field.

In addition, various embodiments of the present invention use a signaling method for the NDI that is different than the signalling method conventionally utilized for transmitting L1/L2 control channel data. As a result, the L1/L2 control channel size can be reduced such that the performance of the L1/L2 control channel is improved. Furthermore, H-ARQ performance can be improved, while the “holes” or omissions described above that result from applying the conventional circular buffer rate matching approach can be avoided.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the present invention allow for the dynamic interpretation of the transport block size field in the Layer 1/Layer 2 (L1/L2) control channel, such that for any first H-ARQ transmission (e.g., all initial transmissions), the transport block size indication field will indicate the size of the transport block (e.g., the user data payload). It should be noted that the L1/L2 control channel can be, for example, a downlink shared control channel or a physical downlink control channel (PDCCH). For any retransmission, the transport block size indication bits can be transformed into dedicated bits for indicating the RV used—in terms of the circular buffer technique. It should be noted that the term “RV” can refer to an offset. In order to achieve this dynamic interpretation, a robust bit field for indicating new data transmission (e,g, new data indication (NDI)) is introduced. Therefore, from a UE perspective it is possible to determine how to interpret the transport block size field.

As noted above, interpretation of the transport block size field depends on the NDI. That is, the various embodiments of the present invention define a signaling method for a UE via a control channel table, where the same transport block size field can be used to indicate both the transport block size in a first H-ARQ transmission and the RV (e.g., the starting point of the Nth transmission in circular buffer rate matching) in subsequent retransmissions. Table 1 below is an example of such a control channel table. It should be noted, however, that other variations/iterations of a control channel table can be defined in accordance with the various embodiments of the present invention.

It should be noted that the various embodiments of the present invention are implemented in accordance/associated with signal transmission rate matching between a transmitter and a receiver, e.g., mobile device UEs or a UE and a UMTS-equivalent base transceiver station (Node B). As described above, an exemplary communication system can utilize turbo coding of signals where a message to be transmitted by a transmitter is encoded so that the ratio of input bits representative of the message to output bits representative of the coded signal is, for example, ⅓. That is, the output signal has three times the number of bits as compared to the input, where each input bit is output as a corresponding systematic bit and after further encoding/interleaving, the input bits are also used to generate first and second parity bits. Communication systems, e.g., UMTS, can operate using a plurality of different coding rates, hence the utilization of rate matching where a transmitter can covert the original coding rate of an output from its encoder into another coding rate by either repetition or puncturing. Repetition occurs when, for example, the original coding rate is higher than the coding rate to which it is to be converted, while puncturing occurs when, for example, the original coding rate is lower than the coding rate to which it is to be converted.

As also described above, downlink and uplink data channels refer to transmission paths between, for example, a mobile device UE and a UMTS Node B. Additionally, the UMTS base transceiver station can be embodied by an evolved Node B (eNode B). In accordance with the various embodiments of the present invention, the Node B/eNode B will know that a UE has decoded the L1/L2 control channel correctly by receiving a negative acknowledgement (NACK). That is, the UE can act as a receiver that receives a signal, e.g., data packet, representative of the rate matched output described above, whereas signals which have not been decoded correctly are stored for future decoding in accordance with H-ARQ. It can be assumed that the UE knows or can determine the user information payload size (i.e., the transport block size) for any retransmission as long as the NDI is utilized and provided that the L1/L2 control channel information for the first H-ARQ transmission was decoded correctly. In other words, it is not necessary to implement another separate bit field for indicating H-ARQ retransmission information. Additionally, in light of the above assumption, transmitting such H-ARQ retransmissions information would result in wasted capacity.

It should be noted that various embodiments of the present invention can be implemented by utilizing a filed other than a new data indication/indicator field. For example, a retransmission sequence number (RSN) can be utilized to indicate a new data transmission/first transmission. Moreover, a field other than the transport block size field can be utilized to carry the transport block size, RV, etc. That is any field that goes unchanged for retransmissions can be utilized, as can some newly defined field that also does not change for retransmission purposes.

It should be noted that the various embodiments of the present invention use a signaling method for the NDI that is different than the signalling method conventionally utilized for transmitting L1/L2 control channel data. Conventional signaling methods utilize a state change, where the same level is utilized for all transmissions within a single H-ARQ process and the level is changed when a new transmission is initiated. In addition, the complexity associated with decoding the L1/L2 control channel is increased slightly. However, such issues are outweighed by the advantages provided by the various embodiments of the present invention, e.g., a reduction in L1/L2 control channel size, such that the performance of the L1/L2 control channel will be improved. Furthermore, besides better L1/L2 control channel performance, H-ARQ performance can be improved as well, and the “holes” or omissions described above that are present when applying the conventional circular buffer rate matching approach can be avoided.

Various embodiments of the present invention discussed herein have been described in relation to downlink data transmission. However, various embodiments can be effectuated which utilize uplink data transmission as well. For example, in LTE, uplink data parameters can be sent in the downlink PDCCH and interpreted by a UE, but can also be used for transmitting data in the uplink. That is, for downlink data, as in High-Speed Downlink Packet Access (HSDPA), both control information and data are sent in the downlink direction and received by the UE. For uplink data, control information and data are sent from the UE to an eNode B, for example.

FIG. 3shows a system10in which the present invention can be utilized, comprising multiple communication devices that can communicate through a network. The system10may comprise any combination of wired or wireless networks including, but not limited to, a mobile telephone network, a wireless Local Area Network (LAN), a Bluetooth personal area network, an Ethernet LAN, a token ring LAN, a wide area network, the Internet, etc. The system10may include both wired and wireless communication devices.

For exemplification, the system10shown inFIG. 3includes a mobile telephone network11and the Internet28. Connectivity to the Internet28may include, but is not limited to, long range wireless connections, short range wireless connections, and various wired connections including, but not limited to, telephone lines, cable lines, power lines, and the like.

The exemplary communication devices of the system10may include, but are not limited to, a mobile device12, a combination PDA and mobile telephone14, a PDA16, an integrated messaging device (IMD)18, a desktop computer20, and a notebook computer22. The communication devices may be stationary or mobile as when carried by an individual who is moving. The communication devices may also be located in a mode of transportation including, but not limited to, an automobile, a truck, a taxi, a bus, a boat, an airplane, a bicycle, a motorcycle, etc. Some or all of the communication devices may send and receive calls and messages and communicate with service providers through a wireless connection25to a base station24. The base station24may be connected to a network server26that allows communication between the mobile telephone network11and the Internet28. The system10may include additional communication devices and communication devices of different types.

The communication devices may communicate using various transmission technologies including, but not limited to, Code Division Multiple Access (CDMA), Global System for Mobile Communications (GSM), Universal Mobile Telecommunications System (UMTS), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Transmission Control Protocol/Internet Protocol (TCP/IP), Short Messaging Service (SMS), Multimedia Messaging Service (MMS), e-mail, Instant Messaging Service (IMS), Bluetooth, IEEE 802.11, etc. A communication device may communicate using various media including, but not limited to, radio, infrared, laser, cable connection, and the like.

FIGS. 4 and 5show one representative mobile device12within which the present invention may be implemented. It should be understood, however, that the present invention is not intended to be limited to one particular type of electronic device. The mobile device12ofFIGS. 2 and 3includes a housing30, a display32in the form of a liquid crystal display, a keypad34, a microphone36, an ear-piece38, a battery40, an infrared port42, an antenna44, a smart card46in the form of a UICC according to one embodiment of the invention, a card reader48, radio interface circuitry52, codec circuitry54, a controller56and a memory58. Individual circuits and elements are all of a type well known in the art, for example in the Nokia range of mobile telephones.

Software and web implementations of the present invention could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various database searching steps, correlation steps, comparison steps and decision steps. It should also be noted that the words “component” and “module,” as used herein and in the claims, is intended to encompass implementations using one or more lines of software code, and/or hardware implementations, and/or equipment for receiving manual inputs.