Uplink Control Signaling in a Cellular Telephone Communication System

Abstract

To provide a method, apparatus, and computer program for controlling allocation of control message fields in uplink transmission in a cellular telecommunication system.SOLUTION: Uplink control message fields are allocated 406 to resources of a physical uplink shared traffic channel according to an uplink transmission scheme selected 402 for a user terminal. The control message fields are allocated so that transmission performance of the control messages is optimized for the selected uplink transmission scheme.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to the field of cellular radio telephone communication, and more particularly to uplink signaling.

Background Art

[0002] A communication system known as an evolved UMTS (Universal Mobile Telecommunications System) terrestrial radio access network (E-UTRAN, also referred to as UTRAN-LTE or advanced long term evolution LTE-A for reasons of its long term evolution) is currently under development within the 3GPP scope. In this system, the downlink radio access technology will be OFDMA (Orthogonal Frequency Division Multiple Access), and the uplink radio access technology will be "Single Carrier FDMA" (SC-FDMA), which is a type of linearly pre-coded OFDMA. The uplink system bandwidth has a structure in which a "Physical Uplink Control Channel" (PUCCH) is used to transfer uplink control messages and a "Physical Uplink Shared Channel" (PUSCH) is used for the transmission of uplink user traffic. Additional control messages can be transmitted within the resources initially allocated to the PUSCH. The PUCCH carries uplink control information such as ACK / NACK messages, Channel Quality Indicators (CQI), Scheduling Request Indicators (SRI), Channel Rank Indicators, and downlink pre-coding information.

Summary of the Invention

Means for Solving the Problems

[0003] An aspect of the present invention provides the method specified in claim 1.

[0004] Another aspect of the present invention provides the apparatus specified in claim 14.

[0005] Another aspect of the present invention provides a base station of a cellular telephone communication system as defined in claim 26.

[0006] According to another aspect of the present invention, there is provided a user terminal of the cellular telephone communication system defined in claim 27.

[0007] According to another aspect of the present invention, there is provided the apparatus specified in claim 28.

[0008] According to still another aspect of the present invention, there is provided a computer program product embodied on a computer-readable distribution medium specified in claim 29.

[0009] Embodiments of the present invention are defined in the dependent claims.

[0010] Embodiments of the present invention will be described below with reference to the accompanying drawings by way of example only.

Brief Description of the Drawings

[0011]

Figure 1A

Figure 1B

Figure 2

Figure 3

Figure 4

Figure 5A - B

Figure 6A

Figure 6B

Figure 7

Mode for Carrying Out the Invention

[0012] The following embodiments are illustrative. This specification may refer to "an", "one", or "some" embodiments at several places, but this does not necessarily mean that each such reference is to the same embodiment or that the feature applies only to a single embodiment. The single features of different embodiments can also be combined to bring about other embodiments.

[0013] Figures 1A and 1B show a general architecture of a cellular telephone communication system that provides voice and data transfer services to a mobile terminal. Figure 1A shows a general scenario of cellular communication where base station 100 provides wireless communication services within the range of cell 102 from user terminal 110 to 122. The base station 100 can belong to a radio access network of UMTS (Universal Mobile Telecommunications System) Long Term Evolution (LTE) or Advanced LTE (LTE-A) specified within 3GPP (3rd Generation Partnership Project), and thus can support at least OFDMA and SC-FDMA as radio access schemes for each of the downlink and uplink. The base station is connected to other parts of a cellular telephone communication system such as a Mobility Management Entity (MME) that controls the movement of user terminals, one or more gateway nodes through which data passes when being routed, and an operation and maintenance server configured to control certain communication parameters known in the art.

[0014] Figure 1B shows a general structure of an uplink system bandwidth allocated to a network operator to provide an uplink communication service according to LTE Releases 8 and 9. The system bandwidth is structured such that a traffic channel, i.e., a Physical Uplink Shared Channel (PUSCH), is allocated in the center of the system bandwidth, and a control channel, i.e., a Physical Uplink Control Channel (PUCCH), is allocated at both edges of the traffic channel bandwidth. The size of the PUCCH is configurable by the base station 100, and in certain network deployments, the base station 100 can configure the utilization of the bandwidth such that the frequency resources at the edges of the system bandwidth remain blank. In the current scenario of the LTE system, uplink L1 / L2 control signaling is divided into two classes within the LTE system: control signaling in the absence of UL data that occurs on the PUCCH, and control signaling in the presence of UL data that occurs on the PUSCH. The PUCCH is a shared frequency / time resource reserved exclusively for user terminals that transmit only L1 / L2 control signals. This specification focuses on the PUSCH that carries uplink L1 / L2 control signals when the UE is scheduled for data transmission.

[0015] Figure 2 shows a very basic structure of an SC-FDMA transmitter (blocks 200 through 212) and an SC-FDMA receiver (blocks 214 through 226). Future releases of the LTE system are considering using OFDM also in the uplink direction. This structure is known to those skilled in the art of modern telecommunication systems, and thus will be described at a general level below with respect to Figure 2. In the SC-FDMA transmitter, the modulated symbols to be transmitted are first converted from serial form to parallel form in block 200 and then converted to the frequency domain through a discrete Fourier transform (DFT) in block 202. In the resource element mapping block 204, control symbols and traffic data symbols are assigned to the corresponding frequency resource elements according to a predetermined criterion. The resource element can be a subcarrier or a virtual subcarrier, which are terms widely used in the context of SC-FDMA transmission. Next, an inverse DFT is calculated in block 206, the signal is converted from parallel form to serial form in block 208, a cyclic prefix is added in block 210, the signal is converted to analog form in block 212, and is transmitted through the radio frequency (RF) part of the transmitter. In the receiver, a radio signal is received in block 214 through the antenna and the RF part of the receiver, and the received signal is converted to the digital domain. The cyclic prefix is removed in block 216, and a serial-to-parallel conversion is performed in block 218 prior to the DFT in block 220. Control symbols and traffic data symbols are extracted from these resource elements in block 222 prior to the inverse DFT in block 224 and the parallel-to-serial conversion in block 226.

[0016] Future LTE versions are considered to support OFDM also in the uplink. In such a case, it is simple to modify the structure of the SC-FDMA transmitter and receiver, and an OFDM transmitter and receiver can be obtained by simply short-circuiting the DFT block 202 in the transmitter and the inverse DFT block in the receiver. Accordingly, the transmitter can include a controller that controls the short-circuiting of the DFT block 202, and the receiver can include a corresponding controller that controls the short-circuiting of the inverse DFT block 224. Further, future user terminals will be equipped with a function to support single-user multiple-input multiple-output transmission (SU-MIMO) in the uplink, and uplink transmission can be spatially multiplexed to obtain higher data rates and better spectral efficiency. For this purpose, the structure of the transmitter and receiver in FIG. 2 is modified to include one signal branch (FIG. 2 shows one branch) at each transmit / receive antenna and a signal processor that performs signal processing according to the selected multiple antenna transmission scheme. The signal processor can be installed at virtually any position within the digital region of the transmit / receive chain, which is obvious to those skilled in the art. SU-MIMO transmission can be utilized together with either OFDM transmission or SC-FDMA transmission.

[0017] For notation purposes and to distinguish OFDM symbols or SC-FDMA symbols carrying multiple coded symbols from the coded symbols mapped to each resource element, both OFDM symbols and SC-FDMA symbols can be regarded as symbol blocks that carry multiple (modulated and channel-coded) symbols as information elements.

[0018] Figure 3 shows the current uplink PUSCH subframe structure and the PUSCH resources, i.e., the allocation of the control message field to the frequency resource blocks assigned to a given user terminal when the cyclic prefix is considered to have a normal length. The time slot contains seven SC-FDMA symbols, and the subframe contains two time slots. In the case of an extended cyclic prefix, the time slot contains six SC-FDMA symbols. The actual combination and their sizes of different L1 / L2 control signals vary from subframe to subframe. As will be described later, both the user terminal and the base station have information regarding the number of symbols reserved by the control part. On all subcarriers of the symbol at the very center of the time slot, a reference signal (RS) is transmitted. On the SC-FDMA symbol adjacent to the one transmitting the RS, an acknowledgement response message (ACK / NACK) indicating the correct (ACK) or incorrect (NACK) reception of the downlink data packet is located, thereby improving the reception quality of the important ACK / NACK message. The resource elements assigned to the ACK / NACK message are located at one end of the SC-FDMA symbol. On the SC-FDMA symbol that is on the same subcarrier as the ACK / NACK but adjacent to the one of the ACK / NAK, a rank indicator indicating the downlink channel rank can be assigned. There are at most two SC-FDMA symbols per slot assigned to ACK / NACK signaling per (virtual) subcarrier. The same also applies to the rank indicator. At the other end of the resource element, a channel quality indicator (CQI) message field is assigned, and this field can be transmitted using a plurality of SC-FDMA symbols.

[0019] At this stage, it should be noted that the term "subcarrier" refers to the subcarriers operated in block 204, but it may not be optimal in the sense that the transmitted radio signal does not have the form of a multi-carrier signal. Therefore, the term "virtual subcarrier" is also used in the context of SC-FDMA transmission.

[0020] Since the DFT operation effectively spreads the content of each subcarrier over the frequency domain, the structure illustrated in FIG. 3 is suitable for SC-FDMA transmission. However, in OFDM transmission, the DFT operation is omitted, and as a result, the structure of FIG. 3 becomes quasi-optimal due to the position of the fixed and localized control message field. In practice, this means that the subcarriers are not spread over the frequency resource blocks and are more susceptible to frequency-selective fading. When the frequency of the subcarrier carrying the ACK / NACK message is significantly attenuated due to fading, there is a high likelihood that the entire ACK / NACK message will be lost. Additionally or alternatively, the SU-MIMO transmission scheme should be effectively utilized to improve the transmission performance of important control messages in uplink transmission.

[0021] FIG. 4 shows a process for using PUSCH resources to transmit a control message according to an embodiment of the present invention. As will be described in more detail below, the process can be implemented within a transmitter or a receiver, i.e., within a user terminal or a base station. The process starts at block 400. At block 402, an uplink transmission scheme at the user terminal is selected. At block 404, PUSCH resources at the user terminal are determined. At block 406, a control message field is assigned to the PUSCH resources determined at block 404 according to the transmission scheme selected at block 402.

[0022] The selection of the transmission mode can include a selection between OFDM transmission and SC-FDMA transmission, and between single-stream transmission and multi-stream transmission. The selection can be carried out by the selection of a channel rank that can automatically determine the multi-antenna transmission method and the multiple access method (or uplink waveform). The selection of the uplink transmission mode can be carried out by the base station, and this transmission mode can be signaled to the user terminal in downlink signaling. The selection between the single-antenna transmission mode and the multi-antenna transmission mode can be based on a channel rank indicator transmitted from the user terminal. The channel rank indicates the number of available spatial MIMO channels. Accordingly, block 402 includes the selection of the uplink transmission mode when the processing is carried out within the base station and the indication of this transmission mode to the user terminal. Similarly, block 404 includes the stage of scheduling the uplink PUSCH resources for the user terminal, the stage of signaling the allocated PUSCH resources to the user terminal, and the stage of configuring the receiver of the base station to receive the uplink transmission from the user terminal on the allocated PUSCH resources. Block 406 includes the stage of determining the pattern in the data field and the control message field within the allocated PUSCH resources, and the stage of configuring the receiver to receive the data and the control message accordingly.

[0023] When implemented within the user terminal, block 402 includes the deduction of the uplink transmission mode from the control message received from the base station, block 404 includes the deduction of the uplink PUSCH resources allocated to the user terminal from the control message received from the base station, and block 406 includes the stage of determining the pattern in the data field and the control message field within the allocated PUSCH resources and configuring the transmitter to transmit the data and the control message accordingly.

[0024] When the selected uplink transmission scheme is SC-FDMA, as illustrated in FIG. 3, the control message field can be allocated in the conventional manner. In other words, the subcarrier mapping of the control message field can be performed such that the control message field is localized with respect to the allocated PUSCH resource. Next, the DFT spreads the subcarriers over the allocated frequency resources. On the other hand, when the selected uplink transmission scheme is OFDM, the symbols of each control message field are distributed over the PUSCH frequency resources of the user terminal. Accordingly, each control message field will be distributed along the frequency spectrum allocated to the user terminal, thereby providing a better tolerance to frequency selective fading compared to using the structure of FIG. 3 in OFDM transmission.

[0025] Generally, the transmission mode is selected by the base station. First, the base station can select the multiple antenna transmission mode to be applied, that is, spatial multiplexing through a plurality of spatially parallel transmission streams, or beamforming or transmit diversity transmission (single input multiple output, SIMO) through a single stream. The selection can be made based on the uplink channel rank, that is, the number of uncorrelated uplink spatial subchannels. When the base station selects spatial multiplexing as the multiple antenna transmission mode, the base station also selects the number of spatially parallel uplink substreams. Next, a selection between OFDM and SC-FDMA can be made based on the selected multiple antenna transmission mode, that is, OFDM for spatial multiplexing, or SC-FDMA for single stream beamforming or SIMO. However, the embodiments of the present invention described below are not limited to this kind of selection of the transmission mode, and SC-FDMA (or OFDM) can be used in all multiple antenna transmission modes. At the user terminal, the transmission mode (multiple antenna mode and multiple access mode) can be determined by dynamic scheduling permission information signaled from the base station to the user terminal in downlink signaling, for example, downlink control information (DCI) format 0). The signaling can be specifically implemented by using at least one signaling bit indicating whether to use spatial multiplexing. Next, the user terminal performs either spatial multiplexing by OFDM or beamforming by SC-FDMA. Alternatively, the base station can implicitly signal the transmission mode by transmitting an uplink rank indicator. When the rank indicator indicates a channel rank greater than 1, the user terminal performs any spatial multiplexing by OFDM. Otherwise, the user terminal performs beamforming by SC-FDMA. In yet another embodiment, the transmission mode can be signaled as a user terminal specific or cell specific parameter through higher layer (L3) signaling. When the user terminal supports only a fixed transmission mode, no specific signaling is required and the transmission mode is applied according to the function of the user terminal.

[0026] Figures 5A and 5B show two examples of the distribution of control message fields across frequency resources. In both Figure 5A and Figure 5B, the control message fields are evenly distributed (or "interleaved", where "interleaved" is a term commonly used in this context in OFDM transmission) across the subcarriers. In other words, the control symbols of the control message fields are mapped to the subcarriers by the frequency spacing between these control symbols, which is determined by the repetition factor selected for each control message field to define several symbols other than the control symbols of the control message field between the control symbols of the control message field. The frequency spacing between the control symbols of the same control message field can be assumed to be equal for all control symbols of the control message field under consideration. Figure 5A shows a mapping with a repetition factor of 2, that is, the symbols of the control message field are mapped every second subcarrier. Figure 5B shows a mapping with a repetition factor of 4, that is, the symbols of the control message field are mapped every fourth subcarrier. Different repetition factors can be determined according to the size of the resource block assigned to the user terminal, the size of the control field, etc. Of course, the symbols of the control message field are mapped using a repetition factor up to the limit where there are no more control symbols to be mapped.

[0027] The distribution of a predetermined control message field to the allocated resources can include a stage of first sizing the control message field, then a stage of determining the repetition factor and the start position subcarrier index, and then a stage of mapping the symbols of the control message to the corresponding subcarriers. This is illustrated in FIG. 6 showing an embodiment of block 404. The flowchart of FIG. 6 shows the mapping of the control message field to the allocated PUSCH resources. The process of FIG. 6 describes the mapping of two control channel fields (CQI and ACK / NACK), but as will be apparent from the following description, this process can be easily extended to target other control message fields. At block 502, the number of symbols allocated to each control channel field (Nx) is determined according to the following formula. JPEG0007695329000001.jpg13170where JPEG0007695329000002.jpg1313 represents a rounding operation to the nearest supporting integer in the positive infinity direction, O is the number of bits to be transmitted, for example, the CQI word length, JPEG0007695329000003.jpg1332 is the number of subcarriers (received on the PDCCH, which is the physical downlink control channel from the base station) that carry the PUSCH within the allocated frequency resources, JPEG0007695329000004.jpg1532 is the number of multi-carrier symbols (OFDM symbols) that carry the PUSCH per subframe (received on the PDCCH from the base station), JPEG0007695329000005.jpg1330 is the total number of bits transmitted on the PUSCH. The term "offset" is a quality offset that defines the offset between the desired reception quality of traffic data and the control data transferred within the control message field. The offset can be different in different control message fields, but can be created to depend on the selected transmission method. For example, when spatial multiplexing is selected as the transmission method, the "offset" can be set to have a larger value than in the case of single-stream beamforming transmission or spatial transmission diversity. In this case, essentially, higher transmission reliability can be obtained. The quality of the transmission of traffic data is judged according to the service format of the data transferred, and the modulation and coding methods, as well as other parameters of the PUSCH, are set to meet these requirements. In practice, the modulation method can be the same for all symbols transmitted on the PUSCH, similar to that in the current specifications of LTE-A, but the channel coding method of the control message field can be selected based on the "offset". Generally, certain control messages such as ACK / NACK messages are less tolerant to errors and require higher reception quality, for example, with respect to the block error rate (BLER), and the PUSCH parameters do not automatically meet these requirements. In Equation (1), the term "offset" is used to ensure that the selected modulation and coding method for the control message field guarantees a desired high reception quality, and that the actual value of the "offset" is determined according to the difference between the quality (BLER) of the traffic data and the required quality (BLER) of the control message format. These values of the "offset" are generally determined in advance and stored as being dependent on the selected uplink transmission method. The larger the value of the "offset", that is, the larger the difference between the required quality of the traffic data and the required quality of the control data, the more symbols are allocated to the control message field and the more robust channel coding is applied to the control message field (and vice versa).Therefore, the calculation of Equation (1) is performed before the modulation of the control message bits and the channel coding. As described above, Equation (1) is calculated for each control message format (CQI and ACK / NACK in this example). In fact, Equation (1) is a modification of the equation defined in the current 3GPP specification, and this modification is the term "offset".

[0028] In block 504, for the CQI message field, the repetition factor RPF is calculated according to the following equation. JPEG0007695329000006.jpg11170Here, N is the total number of subcarriers allocated to the user terminal within the subframe, and N CQI is the number of CQI symbols transmitted within the subframe. JPEG0007695329000007.jpg1313 is the floor operation, that is, rounding to the nearest integer in the direction of negative infinity. The calculation and utilization of the repetition factor ensure that the CQI is distributed (or interleaved) over the allocated frequency spectrum. Next, for the ACK / NACK message field, the repetition factor RPF is calculated according to the following equation. JPEG0007695329000008.jpg10170Here, N AN is the number of ACK / NACK symbols transmitted within the subframe. Since the number of transmitted CQI resource elements (or symbols) is reduced from the total number of resource elements, the repetition factor RPF ANis calculated by dealing with the resource elements that are logically available after the CQI. In this way, before division by the number of symbols or resource elements to be used for a particular control message field of interest, the number of allocated resource elements is reduced from the total number of resource elements N, so that the repetition factor for another control message field (such as the rank indicator, the precoding matrix indicator, etc.) can be calculated. In block 508, different starting position resource elements are selected for different control message fields so that the resource element mapping starts from different resource elements by using the allocated repetition factor. The repetition factor can vary between 0 and RPF - 1. In block 510, the control symbols of the control message field are mapped to the resource elements by using the starting position selected in block 508, the repetition factor calculated for the CQI in block 504, and the repetition factor calculated for the ACK / NACK in block 506.

[0029] Figure 6 shows the result of the processing of Figure 5 for the case of N = 36, N CQI = 7, and N AN = 4. Accordingly, the repetition factor R CQI becomes 5 according to Equation (2) (36 / 7 = 5.143 ~ 5), R ANIt becomes 7 ((36 - 7) / 4 = 7.25 ~ 7). The start position of CQI is selected to be 0, and the start position of ACK / NACK is selected to be 2 (sub - carrier index). In this case, CQI symbols are mapped every fifth sub - carrier starting from sub - carrier 0, and ACK / NACK symbols are mapped every seventh non - CQI sub - carrier starting from sub - carrier 2. The number of CQI symbols is excluded in formula (3), and thus these symbols are excluded when actually performing the mapping. Ultimately, it is difficult to obtain a repetition factor that never overlaps, and this method guarantees that ACK / NACK mainly avoids overriding previously mapped CQI symbols. In the case of impairment of data symbols that may be overridden, since the reliable transmission of ACK / NACK messages is prioritized over the transmission of CQI messages, ACK / NACK may also override CQI symbols. Generally, any control message symbols mapped later will not be mapped to the same sub - carrier as previously mapped control symbols, because the mapped resource elements are further excluded from another mapping. The mapping can be performed in the resource element mapping block 204 of the transmitter, and a similar operation is performed in the resource element mapping removal block 222 of the receiver so that the demapping is correctly performed.

[0030] The actual mapping can be implemented in several ways. The same mapping pattern can be repeated for all OFDM symbols, i.e., the same control field can occupy the same subcarriers from one OFDM symbol to another. The size of a given control message field and the overall size of the control message field can be made variable for each symbol. In another embodiment, different starting positions are selected for successive OFDM symbol mappings so as to obtain a shifted mapping of the control message field in successive OFDM symbols. Thereby, since the control message field occupies different frequency positions in different OFDM symbols, the frequency diversity between successive OFDM symbols is improved. Alternatively, interleaving can be performed over all subcarriers and a plurality of OFDM symbols, e.g., over the symbols in a time slot or a subframe. At this time, when mapping a given control message field, when starting to map the subcarriers of the subsequent symbol, the subcarriers of the previous OFDM symbol that were last mapped are taken into account. For example, as shown in FIG. 6, when the number of subcarriers is 36, the index of the subcarrier that was last mapped is 34, the repetition factor is 6, and the first subcarrier to be mapped in the subsequent OFDM symbol has an index of 4. In this case, different control message fields can occupy different subcarriers in successive OFDM symbols based on the number of subcarriers and the repetition factor.

[0031] In yet another embodiment, interleaving can be implemented across different spatial streams. As described above, it is expected that the user terminal is equipped with a function to support SU-MIMO, in which case a plurality of spatial transmission streams can be allocated to the user terminal. In such a case, the transmission can be multiplexed into a plurality of spatially parallel signal streams. In this case, the interleaving can be extended to multiple streams. The interleaving can be implemented, for example, by first mapping the control symbols to the subframe of the first stream, and then continuing this mapping for the second stream and subsequent ones. Based on the subcarrier frequency and the repetition factor, the continuation of the mapping can be implemented in a manner similar to that between consecutive OFDM symbols so that different control message fields can occupy different subcarriers within the spatially parallel streams. Alternatively, the mapping of the subsequent spatial streams can be initialized to correspond to the mapping of the first spatial stream such that the start positions are the same in both streams. When calculating Equation (1) and the repetition factor, it is clearly possible to handle the number of additional symbols available due to the use of additional signal streams. Equation (1) can be modified to accept the use of spatial multiplexing as will be described later.

[0032] In an embodiment, before mapping ACK / NACK so that ACK / NACK will overwrite data symbols, data symbols can be mapped to resource elements. In this embodiment, first, for each control message field, by calculating the formula (1), the interleaving factor, and the start position, an interleaving pattern for each control message field is determined. Next, according to the process of FIG. 5, CQI symbols and rank indicator symbols are first mapped to resource elements. Thereafter, data symbols can be mapped to the remaining resource elements. Next, ACK / NACK can be assigned to the determined position so that the ACK / NACK symbol overwrites, i.e., replaces, the data symbol. The reason why ACK / NACK overwrites data is that when the user terminal misses the reception of a downlink data packet, it cannot recognize the presence of the ACK / NACK message field in the uplink subframe and accordingly cannot transmit the scheduled ACK / NACK message. Alternatively, the user terminal transmits data within these resource elements.

[0033] In yet another embodiment, a predetermined number of subcarriers at the edge of the frequency resource block can be excluded from the mapping of control symbols. Generally, subcarriers at the edge of the frequency resource are more susceptible to interference, and thus, preferably, important control data can be mapped to subcarriers near the center frequency of the frequency resource. In practice, this can be implemented by setting the start position high enough and omitting the mapping of subcarriers having an index higher than the determined threshold (the mapping jumps to the next symbol). If the mapping continues from the subcarriers where the mapping ended in the previous OFDM symbol to the subsequent OFDM symbol, the mapping of subcarriers having an index lower than another threshold can be omitted.

[0034] Since the resource elements do not spread across the frequency spectrum as in SC-FDMA, the use of OFDM allows for the assignment of different transmit power values to different resource elements. In some embodiments, different transmit power offset values are assigned to the resource elements that carry the control message field and the resource elements that carry the data traffic field within the OFDM symbol. To ensure the correct reception of at least some of the control message fields at the receiver, higher transmit power can be assigned to these control message fields at the transmitter. Naturally, different additional transmit power offsets can be assigned to different control message fields based on how important signaling information these control message fields carry. Higher transmit power can be assigned to more important control messages. The additional transmit power assigned to the control message field can be made dependent on the modulation and coding scheme currently in use on the PUSCH. The lower the modulation order and the more robust the coding scheme in use, the smaller the transmit power offset assigned to the control message field, as a modulation and coding scheme that is more resistant to interference is considered to compensate for the stronger requirement for transmit power.

[0035] When using spatial multiplexing as a transmission method, as described above, it is possible to handle the interleaving pattern in the additional signal stream. The control message field can be evenly distributed among different spatial streams, or the size of the control message field can be determined separately for each spatial stream. This depends on the CQI indication from the user terminal. When the user terminal transmits separate CQIs for each spatial stream, the base station can determine different modulation and coding schemes for different spatial streams, and thus can transmit different numbers of bits within different spatial streams. Generally, this is effective when different SU-MIMO spatial streams are encoded with different spreading (or scrambling) codes. Otherwise, the same modulation and coding scheme is used for all streams, and an equal amount of control data can be allocated to different spatial streams. Generally, this is effective when different SU-MIMO spatial streams are encoded with the same spreading (or scrambling) code.

[0036] SU-MIMO uplink transmission can be used to improve the data rate by spatial multiplexing or the transmission reliability by beamforming transmission when the transmitted signal is brought to a spatial channel that gives the best signal-to-noise characteristics. Further, spatial multiplexing can be combined with beamforming. Another variation is to use open-loop transmit diversity transmission when basically the same data is transmitted from all antennas by any precoding. As described above, SU-MIMO transmission can be applied to both OFDM transmission and SC-FDMA transmission, and the application of Equation (1), the repetition factor, and subcarrier mapping in the case of OFDM transmission have been described above. In the case of SC-FDMA transmission, the current SC-FDMA PUSCH structure illustrated in FIG. 3 can be used for all spatial streams. As described in the previous paragraph, the control message field can be evenly distributed among different spatial streams, or the size of the control message field can be determined separately for each spatial stream based on the modulation and coding scheme in use. The number of symbols to be used for a given control message field is calculated using Equation (1), and subcarrier mapping is performed according to the pattern illustrated in FIG. 3.

[0037] According to an embodiment of the present invention, at least a part of control data, for example, an ACK / NACK message can be transmitted by using beamforming or transmit diversity transmission, while data traffic can be transmitted by using spatial multiplexing. In fact, this means that the ACK / NACK is transmitted on the assumption that the channel rank is 1, and the data traffic is transmitted on the assumption that the channel rank is higher than 1. Equation (1) can be modified to handle spatial multiplexing when different ranks are determined for the control message format and traffic data. Equation (1) defines an uplink rank-specific parameter ΔR that determines the ratio between the rank number of traffic data and the control message field of interest D-CIt can be corrected by adding. For example, when the rank of traffic data is 2 (two spatial streams), the rank of the ACK / NACK message is 1 (beamforming or transmit diversity), ΔRD-C is 2 (2 / 1), and Equation (1) has the following form after this correction. JPEG0007695329000009.jpgWithout correction, due to different ranks, the correct number of symbols or subcarriers cannot be assigned to the control message field. To utilize beamforming or transmit diversity for the control message field, preferably, the same control message symbol occupies the same subcarrier within all spatial streams, i.e., the same subcarrier is assigned to the control message field within the spatial stream. Next, the signal processor that performs beamforming in the transmitter multiplies the symbols by coefficients determined based on the desired direction of the beam. Naturally, for enabling symbol reception, inverse operations are performed in the receiver, i.e., the signal processor that performs beamforming in the receiver multiplies the signal streams received from multiple antennas by coefficients determined based on the determined spatial weighting, and the symbols transmitted on the same subcarrier of different streams are combined.

[0038] FIG. 7 shows the above-described embodiment in which an ACK / NACK message is transmitted from a transmitter to a receiver through a single spatial transmission stream by using beamforming techniques so as to direct the stream to a desired spatial channel. In other words, the same ACK / NACK message is transmitted from both antenna elements of the transmitter, and the direction is controlled by phase-adjusting the signals transmitted from different antennas, as is known in the art. Corresponding phase adjustments are implemented in the receiver to weight the received signals so as to amplify the spatial direction in which the ACK / NACK is mainly received. To obtain higher data rates, data traffic is transmitted by using spatial multiplexing, and different data are transmitted / received through different transmit / receive branches and antennas. In the transmitter and receiver, multi-antenna transmission is controlled by digital signal processors 700 and 702 designed for control purposes.

[0039] When the uplink transmission scheme is OFDM, the selection between beamforming, transmit diversity, and spatial multiplexing can be made at the subcarrier level. In such a case, as described above, it is preferable that the same symbol be mapped to the same carrier within each transmit branch in the transmitter. When the uplink transmission scheme is SC-FDMA, since each subcarrier occupies the entire frequency spectrum, the selection between beamforming, transmit diversity, and spatial multiplexing can be made at the SC-FDMA symbol level. The resolution of the selection between beamforming, transmit diversity, and spatial multiplexing can be made for each SC-FDMA symbol, or for a plurality of SC-FDMA symbols at a time, for example, for a time slot or a subframe. When an SC-FDMA symbol carries a control message that requires high reliability, the SC-FDMA symbol can be transmitted by using beamforming or transmit diversity, and the same data is transmitted from all antenna branches in the transmitter and received through all antenna branches in the receiver. Next, the interleaving pattern determination and the mapping of symbols to subcarriers are performed equally for all transmit / receive branches. On the other hand, when an SC-FDMA symbol carries information that does not require high reliability, the SC-FDMA symbol can be transmitted by using spatial multiplexing, that is, a plurality of SC-FDMA symbols carrying different information can be transmitted simultaneously through different spatial streams.

[0040] The use of beamforming in the transmission of control messages generally requires feedback information from the receiver regarding channel characteristics. If the feedback information is not available, embodiments of the present invention use an open-loop multiple antenna transmission diversity scheme, such as space-time block coding, pre-coding vector switching, frequency-selective transmission diversity, or cyclic delay diversity using large or small delays, to transmit at least a portion of the control message field in order to improve the reliability of the transmission of important control information. The implementation of the open-loop transmission diversity schemes listed above is apparent to those skilled in the art and does not require substantial modification to the embodiments described above. To transmit data traffic at a higher speed, the data traffic can be transmitted by using spatial multiplexing.

[0041] As described above, embodiments of the present invention can be implemented in a transmitter (user terminal) and a receiver (base station). In fact, these embodiments are generally implemented by a processor or a corresponding device included in a user terminal or a base station. The processor is configured to allocate a control message field to a PUSCH resource according to a selected uplink transmission scheme so as to optimize the transmission performance of a control message in the selected uplink transmission scheme. The device can be the processors 700 and 702 illustrated in FIG. 7. When no multi-antenna transmission is used in uplink transmission, the processor 700 of the user terminal is simplified in the sense that it does not perform multi-antenna signal processing. The processor can be a logical component implemented by a plurality of physical signal processing units. The term "processor" means a device capable of processing data. The processor can include an electronic circuit that implements the required functions and / or a microprocessor that operates a computer program that implements the required functions. When designing an implementation, those skilled in the art will consider requirements settings regarding, for example, the size and power consumption of the device, the required processing functions, the manufacturing cost, and the production volume. The processor can include a logical component, a standard integrated circuit, a microprocessor, and / or an application-specific integrated circuit (ASIC).

[0042] A microprocessor implements the functions of a central processing unit (CPU) on an integrated circuit. The CPU is a logical machine that executes a computer program containing program instructions. The program instructions can be encoded as a computer program using a programming language that can be a high-level programming language such as C or Java (registered trademark), or a low-level programming language such as machine language or assembler. The CPU can include a set of registers, an arithmetic logic unit (ALU), and a control unit. The control unit is controlled by a series of program instructions transferred from the program memory to the CPU. The control unit can include a plurality of microinstructions for basic operations. The implementation of the microinstructions can be different depending on the CPU design. The microprocessor can have an operating system (a dedicated operating system for an embedded system or a real-time operating system) that can provide a computer program with system services.

[0043] The present invention is applicable to the cellular or mobile phone communication system defined above, but is also applicable to other suitable telephone communication systems. The protocols used, the specifications of the mobile phone communication system, these network elements, and the subscriber terminals are evolving rapidly. Such developments may require additional changes to the described embodiments. Therefore, all terms and expressions should be interpreted broadly and are considered to illustrate rather than limit the above-described embodiments. It will be apparent to those skilled in the art that the concept of the present invention can be implemented in various ways as technology advances. The present invention and its embodiments are not limited to the above-described examples and can be changed within the scope of the claims.

Explanation of Signs

[0044] 400 Start 402 Selection of uplink transmission method 406 Assignment of control message field

Claims

1. A method for supporting reception of uplink control information, operating a telephone communication system including at least one base station connected to at least one other telephone communication system node, including operating a base station among the at least one base station, operating the base station includes, the base station receiving first encoded control information from a user terminal via a first transmission and simultaneously receiving second encoded control information via a second transmission, wherein the first transmission and the second transmission use single carrier frequency division multiple access (SC-FDMA), the first transmission is from a different antenna than the second transmission, the first encoded control information is generated from control information spread by a first spreading code, and the second encoded control information is generated from the control information spread by a second spreading code different from the first spreading code, and, the base station generating the control information using a procedure reverse to that used when spreading the control information with the first spreading code to generate the first encoded control information, the base station generating the control information using a procedure reverse to that used when spreading the control information with the second spreading code to generate the second encoded control information, the base station transmitting a subsequent downlink transmission to the user terminal based on the control information, comprising, a method characterized by this.

2. The method according to claim 1, wherein the first encoded control information is scrambled by a first scrambling code and the second encoded control information is scrambled by a second scrambling code.

3. The method according to claim 1, wherein the control information is acknowledgement (ACK) / negative acknowledgement (NACK) information.

4. The method according to claim 1, wherein the control information is rank indicator information.

5. The method according to claim 1, wherein the first encoded control information and the second encoded control information scramble data.

6. The method according to claim 1, wherein the receiving further includes receiving the first encoded control information and the second encoded control information via a physical uplink shared channel (PUSCH).

7. The method according to claim 6, further including receiving data from the user terminal via the PUSCH.

8. The method according to claim 7, wherein at least a part of the first encoded control information and at least a part of the second encoded control information are received using transmit diversity and simultaneously with at least a part of the data.

9. The method according to claim 1, wherein the at least one other telephone communication system node includes another base station, a mobility management entity, a gateway node, an operation and maintenance server, and any combination thereof.

10. A telephone communication system operated by a network operator and configured to support reception of uplink control information, the telephone communication system comprising: a base station configured by the network operator; at least one other telephone communication system node; and the base station is: A receiver that receives first encoded control information via a first transmission and simultaneously receives second encoded control information via a second transmission from a user terminal, wherein the first transmission and the second transmission use single-carrier frequency-division multiple access (SC-FDMA), the first transmission is from a different antenna than the second transmission, the first encoded control information is generated from control information spread by a first spreading code, and the second encoded control information is generated from the control information spread by a second spreading code different from the first spreading code, and a receiver, Generate the control information using a procedure opposite to that used when spreading the control information with the first spreading code to generate the first encoded control information, Generate the control information using a procedure opposite to that used when spreading the control information with the second spreading code to generate the second encoded control information. A processor configured as described above, A transmitter configured to transmit a subsequent downlink transmission to the user terminal based on the control information, A telephone communication system, characterized by comprising:

11. The first encoded control information is scrambled by a first scrambling code, and the second encoded control information is scrambled by a second scrambling code. The telephone communication system according to claim 10.

12. The control information is acknowledgment (ACK) / negative acknowledgment (NACK) information. The telephone communication system according to claim 10.

13. The control information is rank indicator information. The telephone communication system according to claim 10.

14. The first encoded control information and the second encoded control information crush data. The telephone communication system according to claim 10.

15. The receiver of the base station is operable to receive the first encoded control information and the second encoded control information via a physical uplink shared channel (PUSCH). The telephone communication system according to claim 10.

16. The receiver of the base station is further operable to receive data from the user terminal via the PUSCH. The telephone communication system according to claim 15.

17. At least a part of the first encoded control information and at least a part of the second encoded control information use transmit diversity and are received simultaneously with at least a part of the data. The telephone communication system according to claim 16.

18. The at least one other telephone communication system node includes another base station, a mobility management entity, a gateway node, an operation and maintenance server, and any combination thereof. The telephone communication system according to claim 10.

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