Patent Description:
Orthogonal Frequency Division Multiplexing (OFDM) is a technique for transmitting data using multiple carriers, i.e. a multi-carrier transmission scheme, which converts a serial symbol stream to parallel symbol sets that are transmitted on the orthogonal multiple carriers.

The OFDM technique began in the late <NUM>'s with the Frequency Division Multiplexing (FDM) for military communication purposes, and OFDM using orthogonal overlapping multiple subcarriers was later developed but initially was not widely used due to the difficulty of implementing orthogonal modulations between multiple carriers. However, with the introduction in <NUM> of the use of a Discrete Fourier Transform (DFT) for implementation of the generation and reception of OFDM signals, by Weinstein, the OFDM technology has rapidly developed. Additionally, the introduction of a guard interval at the start of each symbol and use of cyclic prefix (CP) overcomes the negative effects caused by multipath signals and delay spread.

Due to these technical advances, the OFDM technology is now applied in various digital communications fields such as Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB), Wireless Local Area Network (WLAN), and Wireless Asynchronous Transfer Mode (WATM), based on the introduction of various digital signal processing technologies such as Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT).

OFDM is similar to FDM but is much more spectrally efficient for achieving high- speed data transmission by orthogonally overlapping multiple subcarriers. Due to the spectral efficiency and robustness to the multipath fading, OFDM has been considered as a prominent solution for improved broadband data communication systems. Other advantages of OFDM are to control the Inter-Symbol Interference (ISI) using the guard interval and reduce the equalizer complexity in view of hardware as well as spectral efficiency and robustness to the frequency selective fading and multipath fading. OFDM is also robust to noise impulses and thus may be employed in various communication systems.

In OFDM, modulation signals are located in two-dimensional time-frequency resources, which are divided into different OFDM symbols and are orthogonal with each other. Resources on the frequency domain are divided into different tones, and are also orthogonal with each other. That is, the OFDM scheme defines one minimum unit resource by designating a particular OFDM symbol on the time domain and a particular tone on the frequency domain, and the unit resource is called a Resource Element (RE). Since different REs are orthogonal with each other, signals transmitted on different REs can be received without causing interference to each other.

A physical channel is defined on the physical layer for transmitting modulation symbols obtained by modulating one or more coded bit sequences. In an Orthogonal Frequency Division Multiple Access (OFDMA) system, a plurality of physical channels can be transmitted depending on the usage of the information sequence or receiver. The transmitter and receiver negotiate the RE on which a physical channel is transmitted, which is a process called mapping.

High-speed, high-quality wireless data services are generally hindered by the channel environment, which suffers from frequent changes due to additive white Gaussian noise (AWGN) and power variation of received signals, caused by such instances as a fading phenomenon, shadowing, a Doppler effect from terminal movement and a frequent change in terminal velocity, and interference by other users or multipath signals. Therefore, in order to support high-speed, high-quality wireless data services, there is a need to efficiently overcome the above channel quality degradation factors.

<CIT> discloses an option in which the DL subframe grant is transmitted in the flexible subframe when it is dynamically chosen as a DL subframe. The UL subframe grant, PHICH and PUCCH are transmitted in the protected or fixed subframes of the example embodiment.

Aspects of the invention are defined by the independent claims.

The objects, features and advantages of the present invention will be more apparent from the following detailed description in conjunction with the accompanying drawings, in which:.

Embodiments of the present invention are described with reference to the accompanying drawings in detail. Detailed descriptions of well-known functions and structures incorporated herein may be omitted for the sake of clarity and conciseness.

Although the following description is directed to Long Term Evolution (LTE) and LTE-Advanced (LTE-A) systems, the present invention can be applied to other TDD-based radio communication systems operating with base station scheduling without addition or subtraction.

The LTE system is a representative system adopting OFDM in the downlink and Single Carrier-Frequency Division Multiple Access (SC-FDMA) in the uplink. An LTE system can be configured to operate in FDD mode in which one of two frequency bands is used for downlink transmission and the other for uplink or TDD mode in which one frequency band is time division duplexed into one channel for downlink transmission and the other for uplink transmission.

In TDD mode, the uplink and downlink are switched according to a rule, and the LTE defines total <NUM> TDD radio frame configurations among which one is selected and then maintained virtually the same. In TDD mode, if the cells are set with different configurations, they are likely to have failed transmission/reception due to inter-cell interference. Thus, all of the cells deployed within a certain area must be set with the same TDD configuration to acquire synchronization for uplink and downlink transmissions.

A subframe of the LTE system has a length of <NUM> in a time domain and the entire LTE transmission bandwidth in frequency domain and can be divided into two time slots. The LTE transmission bandwidth consists of a plurality of Resource Blocks (RBs), each of which being a basic unit of resource allocation. Each RB consists of <NUM> consecutive tones in the frequency domain and <NUM> consecutive OFDM symbols in the time domain. The subframe can include a control channel region for transmitting control channels and/or a data channel region for transmitting data channels. The control and/or data channel regions carry Reference Signals (RSs) for use in channel estimation.

Meanwhile, the control channel region for a legacy UE is arranged at the beginning of the subframe in the time domain. That is, the control channel region can be composed of L OFDM symbols at the beginning of the subframe, where L can be set to <NUM>, <NUM>, or <NUM>. When using Multi-Media Broadcast over a Single Frequency Network (MBSFN) subframe for carrying broadcast information, L is <NUM>. Regarding the MBSFN subframe, the UE can receive the control channel region of the corresponding subframe but not the data channel region.

Research has recently been focused on LTE-A, which has evolved from LTE. The LTE-A system operating in TDD mode cannot meet the variation of data traffic dynamically once the TDD radio frame configuration has been determined as described above. This is because the downlink subframe cannot be used for uplink transmission even when there is no downlink traffic while the uplink traffic increases. Extensive research is being conducted to solve this problem, which is likely to occur in the hierarchical cellular environment.

<FIG> illustrates a conceptual architecture of a wireless communication system to which the present invention is applied. As shown in <FIG>, the macro cells and picocells are deployed hierarchically in the same area.

Referring to <FIG>, reference number <NUM> denotes macrocells, and reference number <NUM> denotes picocells. Typically, the picocell operates at low transmit power as compared to the macrocell and is deployed at an area with high traffic density within the macrocell. The high traffic density area indicates a region where the data traffic to be processed varies in time.

For example, when a plurality of users receive downlink data and communicate through Voice over IP (VoIP), the UE is transmitting data in the uplink while receiving a large amount of data in the downlink. In this case, it is preferred for the system to configure the TDD radio frame with a relatively large number of subframes for downlink transmission while reducing the number of subframes for uplink transmission. With the conventional system configuration, however, it is difficult to meet the situation in which it is necessary to increase the uplink transmission resource for handling the abrupt increase of the data or VoIP signal to be transmitted in uplink.

<FIG> illustrates the structure of a frame for use in a conventional TDD system.

Referring to <FIG>, a radio frame <NUM> spans <NUM> and consists of two half-radio frames <NUM>. Each half-frame <NUM> consists of <NUM> subframes <NUM>. The radio frame consists of <NUM> subframes, and each subframe has a length of 1msec. The <NUM> subframes <NUM> can be set respectively according to one of a total <NUM> TDD configurations as shown in Table <NUM>. In configuration <NUM> of Table <NUM>, the <NUM>th and <NUM>th subframes are marked with "D" for indicating the downlink subframe, the <NUM>nd , <NUM>rd, <NUM>th, <NUM>th , and <NUM>th subframes are marked with "U" for indicating the uplink subframe, and <NUM>st and <NUM>th are marked with "S" for indicating a special subframe <NUM>.

The special subframe <NUM> consists of a downlink part (DwPTS), a Guard Period (GP), and an uplink part (UpPTS). The DwPTS is for transmitting downlink control and data channel, the GP is not a carrier, and UpPTS is for transmitting an uplink signal. Since the special subframe <NUM> has a small uplink region, it is used for PRACH and SRS transmission but not as a data and control channel. The GP is configured to secure the time necessary for switching from downlink transmission to uplink reception.

Referring to all of the TDD configuration information, there are subframes <NUM> configured for transmission in one direction fixedly regardless of the TDD configuration. The <NUM>th, <NUM>st, <NUM>th, and <NUM>th subframes are maintained in transmission direction regardless of the TDD configuration. The remaining subframes can be changed in transmission direction according to the TDD configuration. In the MBSFN subframe, the <NUM>nd, <NUM>rd, <NUM>th, <NUM>th, <NUM>th, and <NUM>th subframes can be used with the exception of the aforementioned <NUM>th, <NUM>st, <NUM>th, and <NUM>th subframes since the excluded subframes are used to transmit a synchronization signal such as Physical Broadcast CHannel (PBCH), Primary Synchronization Signal (PSS), and Secondary Synchronization Signal (SSS).

<FIG> illustrates a structure of the flexible subframe for use in the dynamic TDD data channel transmission method to which the present invention is applied.

Referring to <FIG>, once the TDD radio subframe is configured in the legacy LTE system, it is not changed by the data traffic amount. In the legacy LTE system, it takes more than 80msec to change the configuration even though there is TDD interference from neighbor cells. In order to switch between uplink and downlink subframes dynamically, although a method for use of a certain uplink or downlink subframe may be used, these methods may cause significant system problems.

When switching from a certain uplink subframe <NUM> to a downlink subframe <NUM>, following problems may take place. First, in the real communication environment, the switching occurs from downlink to uplink for processing a large amount of downlink traffic and sporadic uplink burst traffic. However, the switching from uplink to downlink is not appropriate for the real communication environment since it is necessary to configure a TDD radio frame having a large amount of uplink resource.

Second, the uplink subframe is associated with an uplink transmission process of the UE such that a specific downlink control channel is linked to the uplink subframe to transmit the control channel for the uplink data channel and an acknowledgement channel. Accordingly, if a certain uplink subframe disappears, the UE loses uplink data process and it is impossible to change a certain uplink subframe for a downlink subframe until the UE's uplink retransmission is completed. Accordingly, it is difficult to dynamically meet the traffic variation. Further, in order for the UE to check the subframe for use in the downlink, it is necessary to receive scheduling information such that when there is a false alarm in which the UE misinterprets scheduling information, this causes collision with the UE receiving a signal in the downlink, resulting in transmission/reception failure.

When using a certain downlink subframe <NUM> for uplink transmission as denoted by reference number <NUM>, the following problems may occur. First, all of the UEs receive a channel using reference signals received on the downlink region carrying the common reference signals. Thus, if a certain downlink subframe is used for uplink transmission, all of the UEs in the cell may not estimate the reference signal accurately and may lose the link between the UE and the eNB.

Second, similar to when the uplink subframe is used as downlink subframe, the uplink subframe is associated with an uplink transmission process of the UE such that a specific downlink control channel is linked to the uplink subframe to transmit the control channel for the uplink data channel and an acknowledgement channel. Accordingly, if a certain downlink subframe disappears, the UE loses the uplink data process such that, until the UE's uplink retransmission ends completely, a certain uplink subframe for a downlink subframe cannot be changed.

There is therefore a need of a method for switching between the uplink and downlink in adaptation to the traffic variation without compromising the UE's reference signal measurement as well as the UE's transmission/reception process.

<FIG> illustrates a structure of an adaptive TDD radio frame for use in the dynamic TDD data channel according to an embodiment of the present invention.

Referring to <FIG>, the system checks the static region <NUM> by referencing the TDD radio frame configuration information and determines the proposed dynamic data region by referencing the MBSFN subframe configuration information. In this case, the <NUM>nd, <NUM>rd, <NUM>th, <NUM>th, <NUM>th, and <NUM>th subframes are candidate subframes that can be configured, when used for downlink transmission, as flexible subframes for dynamic data transmission. The candidate subframes can appear contiguously or discretely. The system transmits the information on the dynamic data channel actually available for the dynamic data transmission among the candidate subframes, and the UE uses the corresponding region for dynamic data transmission.

If there is no dynamic data channel information, all of the MBSFN subframes can be used as dynamic data channel with the notification on whether the dynamic data channel is used in the system information. The dynamic data channel information includes the transmission/reception timing information on the control channel and acknowledgement channel for the uplink and downlink processes related to the dynamic data channel, and this information can be retained by the UE rather than signaled by the system. The candidate subframe for dynamic transmission is divided into a semi-static control region <NUM> and a dynamic data region <NUM>. The semi-static control region is for transmitting control channel from the eNB to the UE and can be changed semi-statically based on the MBSFN configuration information and dynamic data channel information.

The dynamic data region <NUM> is for transmitting actual data and can be used as a downlink data channel for transmitting a large amount of downlink traffic or an uplink data channel for transmitting increased uplink data transmission according to the traffic variation in the cell. Whether to configure the dynamic data region <NUM> for downlink transmission is determined depending on the existence of the downlink control channel received in the semi-static region of the same MBSFN subframe. When transmitting the downlink control channel for the UE in the semi-static control region <NUM>, the eNB transmits the data channel scheduled in the corresponding region.

Since the corresponding region is the MBSFN subframe and carries a common reference signal, the data channel is transmitted using DMRS. In order to use the dynamic data region for uplink transmission, the eNB transmits uplink scheduling received in a certain linked downlink control channel region. Upon receipt of the uplink scheduling in the linked downlink control channel region, the linked dynamic data region <NUM> is used for uplink transmission, and the eNB stops transmission to receive the signal from the UE. This frame structure overcomes the shortcoming of the method described with reference to <FIG>.

<FIG> illustrates the transmission-reception relationship of the dynamic TDD data channel of the dynamic TDD data channel transmission method according to an embodiment of the present invention. <FIG> illustrates how to overcome the shortcoming of the scheduling and reference signal measurement using the semi-static control region and dynamic data region disclosed in the present invention.

<FIG> relates to a technique for guaranteeing control channel transmission of the eNB regardless of the change in data region. The semi-static region <NUM> and <NUM> can be used for transmitting uplink scheduling information, downlink scheduling information, and an acknowledgement channel. Since the acknowledgement channel <NUM> and <NUM> corresponding to the uplink transmission linked to the corresponding dynamic data channel can always be transmitted regardless of the downlink transmission <NUM> of the dynamic data channel and the uplink grant <NUM>, it is possible to use the dynamic data region even when the UE's transmission process is terminated.

Since MBSFN is available only in the downlink and the disclosed technique is for using the downlink resource for uplink transmission, it can be applied to the system having a downlink-dominant traffic pattern with sporadic uplink burst traffic. Since the MBSFN subframe carries the common reference signal only in the control channel with a blank data region, it is not used for common reference signal-based channel estimation such that, even though the corresponding region is used for uplink transmission, it does not influence the reference signal measurement. Thus, the UE's reception performance is not affected.

Although it is assumed that the UE has received the uplink scheduling control channel <NUM>, the eNB can transmit the downlink control channel again in the control channel region <NUM> regardless of a false alarm so as to reduce the false alarm probability. If it is assumed that the false alarm occurs at a probability of p (p<<NUM>) as usual, the false alarm probability becomes p*p when using the disclosed method, thereby overcoming the false alarm problem.

<FIG> illustrates relationship among control, acknowledgement, and data channels when the dynamic subframe is used for uplink transmission according to an embodiment of the present invention.

Referring to <FIG>, when the system instructs one TDD radio frame configuration to all of the UEs, the UEs transmit and receive the data can controls channels at transmission/reception timings. This is applied to both the uplink and downlink data transmission. For example, if the system is configured with the configuration <NUM><NUM>, the UEs can have up to <NUM> uplink data processes based on the timings <NUM> and <NUM>. If it is required to instantly allocate further uplink resources, the eNB can use a certain downlink resource that can be configured for MBSFN based on two methods.

One method is to configure the subframes changed by applying a flexible subframe as shown in Table <NUM>, and the other method is to configure the subframes according to a configuration not shown in Table <NUM>. When using the configurations shown in Table <NUM>, e.g. the fourth subframe <NUM> is used, the configuration is identical with the TDD radio frame configuration <NUM> in Table <NUM> from the reference point of the timing available for entire uplink transmission. In this case, since the UE knows the transmission-reception configuration of the channels as shown in Table <NUM>, it recognizes that other configurations in Table <NUM> can be applied such that the UE can use the transmission/reception timing of configuration <NUM> of Table <NUM>.

If the dynamic subframe is applied to change the configuration for another configuration of Table <NUM>, it can be possible to change only the process linked to the changed uplink subframe, and the other method can be of changing the process linked to the uplink subframe for a new configuration. It is also possible to add a <NUM>-bit field to the control channel to indicate the configuration among normal the TDD radio frame structure or a temporarily applied TDD radio frame configuration.

The configuration with change of the dynamic subframe may not be included in Table <NUM>, such as when the ninth subframe <NUM> is used as the dynamic subframe. In this case, a rule is applied such that the control channel is transmitted at the subframe appearing first after four subframes since the dynamic subframe in the downlink control channel appears first before <NUM> dynamic subframes in consideration of the receipt of the control channel.

<FIG> illustrates a structure of a subframe configured for actual data transmission in the dynamic data region in the dynamic TDD data transmission method according to an embodiment of the present invention.

Referring to <FIG>, reference numeral <NUM> denotes the timing at which the dynamic data region is used for downlink transmission. Reference numeral <NUM> denotes the semi-static region for transmitting a control channel with the common reference signal. Reference numeral <NUM> denotes the region that is originally blank or carries a broadcast channel and, in the present invention, used for downlink data channel transmission with the Dedicated Modulation Reference Signal (DM-RS). Reference numeral <NUM> denotes the timing at which the dynamic data channel is used for uplink data channel transmission.

Even at the uplink data transmission timing, the first one or two symbols are used for downlink transmission as denoted by the reference numeral <NUM>, and this region is used for the UE to transmit the control channel using the common reference signal. Afterward, in order to switch to the uplink, the eNB stops transmission and the UE transmits the signal as denoted by reference numeral <NUM> in consideration of the UE's link switching timing <NUM> and the eNB's reception synchronization timing <NUM>. When the first two symbols are used for control channel transmission, a total <NUM> symbols can be used for uplink data channel as denoted by reference numeral <NUM> and, for this purpose, it is necessary to change the position of the reference signal.

The present invention discloses a subframe structure in which the <NUM>th and <NUM>th symbols are used for the reference signal with a total <NUM> symbols for data transmission. In this case, the number of available symbols in the dynamic data region is <NUM> and is used at the uplink channel interleaver. This is identical to when the Sounding Reference Signal (SRS) is transmitted in the subframe with an extended Cyclic Prefix (CP), and the column set of the channel interleaver for rank information is {<NUM>, <NUM>, <NUM>, <NUM>}. The column set for Hybrid Automatic Repeat ReQuest ACKnowledgement (HARQ-ACK is {<NUM>, <NUM>, <NUM>, <NUM>} and, in this case, the structure is identical with the case of transmission SRS in the subframe with extended CP. When the dynamic data channel is used as the uplink data channel, the UE's acknowledgement channel is not transmitted and, since the entire band is used for the data channel so as to compensate for the loss of the downlink control channel in a few symbols at the beginning, the system performance is not degraded.

<FIG> illustrates an eNB procedure of the dynamic TDD data channel transmission method according to an embodiment of the present invention.

Referring to <FIG>, the eNB transmits the system information including the TDD radio frame configuration information and the cell's MBSFN subframe configuration information to the UE at step <NUM>. Next, the eNB generates a dynamic TDD data region information for use of the dynamic data channel in the MBSFN subframe and transmits the data region information to the UE through higher layer signaling at step <NUM>. The eNB determines whether the dynamic data region of the mth subframe as MBSFN subframe is used for uplink transmission at step <NUM>.

If it is determined that the dynamic data region of the mth subframe is used for uplink transmission at step <NUM>, the eNB transmits uplink scheduling control channel at the control channel region of the (m-k)th subframe at step <NUM>. Here, k denotes the time interval defined according to the configurations listed in Table <NUM>, and any case which is not included in Table <NUM> indicates the subframe of which index (m-k) is greater than <NUM> and which is a downlink subframe. Accordingly, the eNB transmits the control channel at the mth subframe at step <NUM> and then switches to the reception mode at step <NUM>. At this time, the eNB can transmit the channel allocation information for the data channel of the mth subframe, and the channel allocation information for the data channel of the uplink subframe linked to the mth subframe. Next, the eNB receives the UE's Physical Uplink Shared Channel (PUSCH) data channel in the shortened format based on the scheduling result at step <NUM>. At this time, the eNB can receive the data channel using the uplink reference signal in the <NUM>th and <NUM>th symbols among <NUM>th to <NUM>th symbols of mth subframe.

Otherwise, if it is determined that the dynamic data region of mth subframe is used for downlink transmission at step <NUM>, the eNB transmits downlink scheduling information at the control channel region of mth subframe at step <NUM>. Next, the eNB transmits the control channel in the mth subframe at step <NUM>. At this time, the eNB can transmit the channel allocation information for the data channel in the mth subframe. Afterward, the eNB transmits the data channel UE-specific reference signal at step <NUM>. The UE specific reference signal is a Dedicated Modulation Reference Signal (DMRS).

That is, the eNB divides an MBSFN subframe into a semi-static region and a dynamic region among a plurality of subframes multiplexed in a radio frame temporally. The eNB transmits a control signal in the semi-static region and receives uplink data or transmits downlink data in the dynamic region. At this time, the eNB can receive the uplink data or transmit the downlink data in the dynamic region according to the control signal in the semi-static region. The eNB also can receive the uplink data or transmit the downlink data in the dynamic region of the MBSFN subframe according to the control signal of the static subframe linked with the MBSFN subframe among the subframes. The eNB can also receive the uplink data in the static uplink subframe linked with the MBSFN subframe among the subframes according to the control signal in the semi-static region.

<FIG> illustrates a UE procedure of the dynamic TDD data channel transmission method according to an embodiment of the present invention.

Referring to <FIG>, the UE acquires the TDD radio frame configuration information and the MBSFN configuration information in the system information transmitted by the eNB at step <NUM>. Next, the UE receives the dynamic TDD data region configuration information at step <NUM>. If the uplink scheduling control channel is received successfully in the (m-k)th subframe at step <NUM>, the UE receives the control channel in the mth subframe at step <NUM>. If the downlink control channel is received successfully in the mth subframe at step <NUM>, the UE receives data in the dynamic data channel using the DMRS at step <NUM>.

Otherwise, if the downlink scheduling control channel is not received at step <NUM>, the UE switches to the transmission mode at step <NUM> and transmits the Physical Uplink Shared Channel (PUSCH) data channel in shortened format at step <NUM>.

If the uplink control channel is not received in (m-k)th subframe at step <NUM> and if the downlink control channel is received successfully in the mth subframe at step <NUM>, the UE receives the downlink data channel at step <NUM>. Otherwise, if it fails to receive the downlink control channel in the mth subframe at step <NUM>, the UE terminates reception session without receipt of any data.

That is, the UE checks the semi-static region and the dynamic region of the MBSFN subframes among a plurality of subframes multiplexed temporally in a radio frame. The UE receives the control signal in the semi-static region and transmits uplink data or receives downlink data in the dynamic region. At this time, the UE can transmit the uplink data or receive the downlink data in the dynamic region according to the control signal received in the semi-static region. The UE also can transmit the uplink data or receive the downlink data in the dynamic region of the MBSFN subframe according to the control signal carried in a static subframe linked to the MBSFN subframe among the subframes. The UE also can transmit the uplink data in the static uplink subframe linked to the MBSFN subframe among the subframes according to the control signal received in the semi-static region.

<FIG> illustrates a configuration of the eNB according to an embodiment of the present invention.

Referring to <FIG>, the eNB includes a Time Division Duplex Radio Frequency (TDD RF) unit <NUM>, a dynamic TDD converter <NUM>, a CRS generator <NUM>, a control channel generator <NUM>, a Dedicated Modulation Reference Signal (DMRS) generator <NUM>, a data channel generator <NUM>, mappers <NUM> and <NUM>, an uplink data receiver <NUM>, a channel estimator <NUM>, and a controller <NUM>.

The TDD RF unit <NUM> is responsible for transmitting and receiving signal in time-divided manner. The dynamic TDD converter <NUM> determines when the TDD RF unit <NUM> is used for downlink transmission and uplink reception under the control of the controller <NUM>. The Cell-specific Reference Signal (CRS) generator <NUM> and the control channel generator <NUM> configure a control channel, and the DMRS generator <NUM> and the data channel generator <NUM> configure a downlink data channel. The mappers <NUM> and <NUM> map the control and data channels in to the subframe.

The channel estimator <NUM> estimates uplink data channel according to the uplink reference signal, and the uplink data receiver <NUM> receives uplink data. That is, when the eNB is configured to transmit the control channel in the semi-static region and the downlink data in the dynamic region according to the present invention, the dynamic TDD converter <NUM> transmits the control channel and downlink data. If the dynamic data channel is used for uplink transmission, the dynamic TDD converter <NUM> receives the uplink data.

The controller <NUM> discriminates between the semi-static region and the dynamic region of the MBSFN subframes in each radio frame. The controller <NUM> then transmits the control signal in the semi-static region and receives the uplink data or transmits the downlink data in the dynamic region. The controller <NUM> can control to transmit the downlink data in the dynamic region with DMRS. The controller <NUM> also can control to receive the uplink data using the uplink reference signals carried in the <NUM>th and <NUM>th symbols among the <NUM>th to <NUM>th symbols in the dynamic region.

The control signal can be included in the channel allocation information for uplink or downlink data in the dynamic region. The control signal also can be included in the channel allocation information for uplink data of the uplink subframe as static region linked to the MBSFN subframe among the subframes. The channel allocation information in the dynamic region can be transmitted through the control signal of another subframe as a static region linked to the MBSFN subframe among the subframes.

<FIG> illustrates a configuration of the UE according to an embodiment of the present invention.

Referring to <FIG>, the UE includes an RF unit <NUM>, a dynamic TDD converter <NUM>, demappers <NUM> and <NUM>, a CRS receiver <NUM>, a channel estimator <NUM>, a control channel receiver <NUM>, a DMRS receiver <NUM>, a channel estimator <NUM>, a Physical Downlink Shared Channel (PDSCH) data channel receiver <NUM>, a data channel generator <NUM>, and a controller <NUM>.

The RF unit <NUM> is configured as a single device responsible for both the signal transmission and reception. The dynamic TDD converter <NUM> determines the timings of uplink transmission and downlink reception of the RF unit <NUM> under the control of the controller <NUM>. The demappers <NUM> and <NUM> receive the control channel and the downlink data channel. The CRS receiver <NUM> receives the common reference signal, the channel estimator <NUM> estimates control channel using the common reference signal, and the control channel receiver <NUM> receives the control channel.

The DMRS receiver <NUM> receives the common reference signal, the channel estimator <NUM> estimates the downlink data channel using the common reference signal, and the data channel receiver <NUM> receives the downlink data channel. The data channel generator <NUM> generates the uplink data channel. That is, when the dynamic data region is used for downlink transmission, the UE switches to the reception mode to receive the control channel transmitted by the eNB. The UE receives the downlink data channel transmitted by the eNB. When the dynamic data region is used for uplink transmission, the UE generates uplink data channel through the transmission chain <NUM> and transmits the uplink data channel to the eNB.

The controller <NUM> discriminates between the semi-static region and the dynamic region of the MBSFN subframe in the radio frame. The controller <NUM> controls to receive the control signal in the semi-static region and transmit the uplink data or receive the downlink data in the dynamic region. The controller <NUM> can control to estimate the channel using the DMRS received in the dynamic region to receive the downlink data.

The controller <NUM> can control to transmit the uplink data with the uplink reference signals of the <NUM>th and <NUM>th symbols among the <NUM>th to <NUM>th symbols in the dynamic region. The control signal can include the channel allocation information for uplink data or downlink data in the dynamic region. The control signal can include the channel information for the uplink data of the uplink subframe as static subframe linked to the MBSFN subframe among the subframes. The channel allocation information of the dynamic region can be transmitted through the control information of other subframe as the static region linked to the MBSFN subframe among the subframes.

As described above, the dynamic TDD data channel transmission method and apparatus of the present invention enables the eNB to switch the resource between uplink and downlink in the dynamic data region in adaptation to the variation of data traffic without compromising channel estimation accuracy. Also, the dynamic TDD data channel transmission method and apparatus of the present invention is capable of minimizing resource waste, at the UE, caused by changing the resource in the semi-static region.

Claim 1:
A method by a terminal in a communication system, the method comprising:
receiving (<NUM>) system information including a time division duplex, TDD, configuration, wherein the TDD configuration is one of a predetermined set of TDD configurations;
receiving (<NUM>) configuration information including information associated with a subframe via higher layer signaling;
receiving (<NUM>), on a control channel, control information based on the subframe ; and
identifying an uplink or downlink configuration based on the control information,
wherein the identified uplink or downlink configuration is included in a changed TDD configuration that is one of a subset of the predetermined set of TDD configurations, and
wherein a radio frame includes a plurality of subframes, and a type of each of the plurality of subframes is identified based on the TDD configuration or the changed TDD configuration.