JP5738377B2 - Uplink control signaling in cellular telephone communication systems - Google Patents

Description

  The present invention relates to the field of cellular radiotelephone communications, and in particular to uplink signaling.

  A communication system known as the evolved UMTS (Universal Mobile Telephone Communication System) Terrestrial Radio Access Network (E-UTRAN, also known as UTRAN-LTE or Advanced Long-Term Evolution LTE-A for its long-term evolution) is currently being developed in the 3GPP range Below. In this system, the downlink radio access technology will be OFDMA (Orthogonal Frequency Division Multiple Access), and the uplink radio access technology is “single carrier FDMA” which is a kind of linearly pre-coded OFDMA. (SC-FDMA). Uplink system bandwidth uses "Physical Uplink Control Channel" (PUCCH) to transport uplink control messages and "Physical Uplink Shared Channel" (PUSCH) to transmit uplink user traffic Has a structure. Additional control messages can be sent in the resources initially assigned to the PUSCH. The PUCCH carries uplink control information such as an ACK / NACK message, a channel quality indicator (CQI), a scheduling request indicator (SRI), a channel rank indicator, downlink precoding information, and so on.

  According to an aspect of the invention, a method as specified in claim 1 is provided.

  According to another aspect of the present invention there is provided an apparatus as specified in claim 14.

  According to another aspect of the present invention, a base station of a cellular telephone communication system as defined in claim 26 is provided.

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

  According to another aspect of the present invention there is provided an apparatus as specified in claim 28.

  According to yet another aspect of the present invention there is provided a computer program product embodied on a computer readable distribution medium as specified in claim 29.

  Embodiments of the invention are defined in the dependent claims.

  Embodiments of the present invention are described below by way of example only with reference to the accompanying drawings.

It is a figure of the principle of cellular communication. FIG. 2 is a diagram of an uplink system bandwidth structure in a modern UMTS system. FIG. 2 is a diagram of the structure of a transmitter and receiver for use in cellular communication. FIG. 3 is a diagram of the current uplink signal structure in the latest UMTS. 5 is a flowchart illustrating a process for performing control message field assignment according to an embodiment of the present invention. FIG. 6 is a diagram of the effect of control message field assignment according to an embodiment of the present invention. FIG. 7 is a detailed process diagram for control message field allocation according to an embodiment of the present invention; 6B is a diagram of the effect of control message field assignment according to FIG. 6A. FIG. 4 is a diagram of multiple stream transmission according to an embodiment of the present invention.

  The following embodiments are exemplary. This specification may refer to “an”, “one”, or “part” embodiments in several places, as each such reference is to the same embodiment. It does not necessarily mean that the feature applies only to a single embodiment. Single features of different embodiments can also be combined to yield other embodiments.

  1A and 1B illustrate the general architecture of a cellular telephone communication system that provides voice and data transfer services to mobile terminals. FIG. 1A shows a general scenario of cellular communication in which the base station 100 provides user terminals 110 to 122 with a wireless communication service in the range of the cell 102. The base station 100 can belong to a long-term evolution (LTE) or advanced LTE (LTE-A) radio access network of UMTS (Universal Mobile Telecommunications System) designated within 3GPP (3rd Generation Joint Project), Accordingly, at least OFDMA and SC-FDMA can be supported as radio access schemes for the downlink and uplink, respectively. The base station is a mobility manager (MME) that controls the movement of user terminals, one or more gateway nodes through which data is routed, and certain communication parameters known in the art. Connected to other parts of the cellular telephone communication system, such as an operation and maintenance server configured to control.

  FIG. 1B shows the general structure of the uplink system bandwidth allocated to network operators to provide uplink communication services according to LTE releases 8 and 9. The system band is a traffic channel, i.e. a physical uplink shared channel (PUSCH), allocated in the middle of the system band, and a control channel, i.e. Structured to be assigned. The size of the PUCCH is configurable by the base station 100, and in certain network deployments, the base station 100 configures band usage so that frequency resources at the edge of the system band are left blank. Can do. In the current scenario of the LTE system, the uplink L1 / L2 control signaling is within the LTE system: control signaling in the absence of UL data occurring on the PUCCH and control signaling in the presence of UL data occurring on the PUSCH. It is divided into two classes. 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 the uplink L1 / L2 control signal when the UE is scheduled for data transmission.

  FIG. 2 shows the very basic structure of an SC-FDMA transmitter (blocks 200 to 212) and an SC-FDMA receiver (blocks 214 to 226). Future releases of the LTE system will consider using OFDM also in the uplink direction. This structure is well known to those skilled in the art of modern telephony systems, and is therefore described below at a general level for FIG. In an SC-FDMA transmitter, the transmitted modulation symbols are first converted from serial to parallel form at block 200 and converted to the frequency domain through a discrete Fourier transform (DFT) at block 202. In resource element mapping block 204, control symbols and traffic data symbols are assigned to corresponding frequency resource elements according to predetermined criteria. The resource element can be a subcarrier or a virtual subcarrier, which is a term widely used in the context of SC-FDMA transmission. Next, the inverse DFT is calculated at block 206, the signal is converted from parallel form to serial form at block 208, a cyclic prefix is added at block 210, the signal is converted to analog form at block 212, and the transmitter's Sent over the radio frequency (RF) portion. At the receiver, a wireless signal is received at block 214 through the antenna and the RF portion of the receiver, and the received signal is converted to the digital domain. At block 216, the cyclic prefix is removed and a serial to parallel conversion is performed at block 218 prior to the DFT at block 220. Control symbols and traffic data symbols are extracted from these resource elements at block 222 prior to inverse DFT at block 224 and parallel to serial conversion at block 226.

  Future LTE versions are expected 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, simply short-circuiting the DFT block 202 at the transmitter and the inverse DFT block at the receiver, and the OFDM transmitter and receiver. A machine is obtained. In response, the transmitter can include a controller that controls the short circuit of the DFT block 202 and the receiver can include a corresponding controller that controls the short circuit of the inverse DFT block 224. Furthermore, 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 is spatially multiplexed to be higher Data rates and better spectral efficiency are obtained. For this purpose, the transmitter and receiver structure of FIG. 2 includes one signal branch (FIG. 2 shows one branch) at each transmit / receive antenna, and a selected multi-antenna transmission scheme. Will be modified to include a signal processor that performs signal processing according to The signal processor can be installed in virtually any location within the digital domain of the transmit / receive chain, as will be apparent to those skilled in the art. SU-MIMO transmission can be utilized with either OFDM transmission or SC-FDMA transmission.

  For notation purposes and to distinguish the encoding symbols mapped to each resource element from OFDM symbols or SC-FDMA symbols carrying multiple encoding symbols, both OFDM symbols and SC-FDMA symbols are: It can be regarded as a symbol block carrying a plurality of (modulated and channel encoded) symbols as information elements.

  FIG. 3 shows the current uplink PUSCH subframe structure and the control message to the PUSCH resource, ie the frequency resource block assigned to a given user terminal when the cyclic prefix is considered to have a normal length Indicates field assignment. A time slot includes seven SC-FDMA symbols, and a subframe includes two time slots. In the extended cyclic prefix, the time slot contains 6 SC-FDMA symbols. The actual combinations of different L1 / L2 control signals and their sizes vary from subframe to subframe. As will be explained later, both the user terminal and the base station have information about the number of symbols reserved by the control part. A reference signal (RS) is transmitted on all subcarriers of the most central symbol of the time slot. An acknowledgment message (ACK / NACK) indicating correct (ACK) reception or incorrect (NACK) reception of a downlink data packet is located on the SC-FDMA symbol next to the one carrying the RS, thereby The reception quality of the ACK / NACK message is improved. The resource element assigned to the ACK / NACK message is located at one end of the SC-FDMA symbol. On the SC-FDMA symbol that is the same subcarrier as ACK / NACK but adjacent to ACK / NAK, a rank indicator indicating the downlink channel rank can be assigned. There are a maximum of two SC-FDMA symbols per slot allocated for ACK / NACK signaling per (virtual) subcarrier. The same applies to the rank indicator. The other end of the resource element is assigned a channel quality indicator (CQI) message field, which can be transmitted using multiple SC-FDMA symbols.

  At this stage it should be noted that the term “subcarrier” refers to the subcarrier operated at block 204, but may not be optimal in the sense that the transmitted radio signal does not have the form of a multicarrier signal. . Therefore, the term “virtual subcarrier” is also used in the situation of SC-FDMA transmission.

  Since the DFT operation effectively spreads the contents of each subcarrier across the frequency domain, the structure illustrated in FIG. 3 is suitable for SC-FDMA transmission. However, for OFDM transmission, DFT operation is omitted, so that the structure of FIG. 3 is sub-optimal due to the location of the fixed and localized control message field. In practice, this means that the subcarriers are not spread across the frequency resource block and are susceptible to frequency selective fading. If the frequency of the subcarrier carrying the ACK / NACK message is greatly attenuated due to fading, the entire ACK / NACK message is likely to 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.

  FIG. 4 shows a process for using a PUSCH resource to transmit a control message according to an embodiment of the present invention. As will be described in more detail below, the processing can be performed in a transmitter or receiver, ie, in a user terminal or base station. Processing begins 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, the control message field is assigned to the PUSCH resource determined at block 404 according to the transmission scheme selected at block 402.

  Transmission scheme selection may include selection between OFDM transmission and SC-FDMA transmission and between single-stream transmission and multi-stream transmission. The selection can be performed by channel rank selection that can automatically define multiple antenna transmission methods and multiple access schemes (or uplink waveforms). The selection of the uplink transmission scheme can be performed by the base station, and this transmission scheme can be signaled to the user terminal in downlink signaling. The selection between the single antenna transmission scheme and the multiple antenna transmission scheme may 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 an uplink transmission scheme when processing is performed in the base station and an indication of this transmission scheme for the user terminal. Similarly, block 404 includes scheduling a uplink PUSCH resource to the user terminal, signaling the allocated PUSCH resource to the user terminal, and receiving a user terminal uplink transmission from the allocated PUSCH resource. Configuring the station receiver. Block 406 includes determining patterns in the data and control message fields in the assigned PUSCH resource and configuring the receiver to receive data and control messages accordingly.

  When implemented in a user terminal, block 402 includes deduction of uplink transmission schemes from control messages received from the base station, and block 404 assigns to user terminals from control messages received from the base station. Block 406 determines a pattern in the data field and control message field within the allocated PUSCH resource and configures the transmitter to transmit the data and control message accordingly. Including the steps of:

  When the selected uplink transmission scheme is SC-FDMA, as illustrated in FIG. 3, the control message field can be allocated in a conventional manner. In other words, the subcarrier mapping of the control message field can be implemented such that the control message field is localized with respect to the assigned PUSCH resource. The DFT then 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 assigned to the user terminal, thereby frequency selective fading compared to using the structure of FIG. 3 in OFDM transmission. Results in a better tolerance for.

  In general, the transmission scheme is selected by the base station. Initially, the base station applies the applied multi-antenna transmission scheme, ie, spatial multiplexing through multiple spatially parallel transmit streams, or beamforming or transmit diversity transmission through a single stream (single input multiple output, SIMO) can be selected. The selection can be made based on the uplink channel rank, ie, the number of uncorrelated uplink spatial subchannels. When the base station selects spatial multiplexing as the multi-antenna transmission scheme, the base station also selects the number of spatially parallel uplink substreams. Next, select between OFDM and SC-FDMA based on the selected multi-antenna transmission scheme, ie, select for OFDM for spatial multiplexing, SC-FDMA for single stream beamforming or SIMO. Can do. However, embodiments of the present invention described below are not limited to this type of transmission scheme selection, and SC-FDMA (or OFDM) can be used in all multi-antenna transmission schemes. In the user terminal, the transmission scheme (multi-antenna scheme and multiple access scheme) is determined by dynamic scheduling allowance information signaled from the base station to the user terminal in downlink signaling, eg, downlink control information (DCI) format 0). can do. Signaling can be performed selectively by using at least one signaling bit that indicates whether to use spatial multiplexing. Next, the user terminal performs either spatial multiplexing with OFDM or beamforming with SC-FDMA. Alternatively, the base station can signal the transmission scheme suggestively by transmitting an uplink rank indicator. If the rank indicator indicates a channel rank greater than 1, the user terminal performs any spatial multiplexing with OFDM. Otherwise, the user terminal performs beam forming by SC-FDMA. In yet another embodiment, the transmission scheme may be signaled as a user terminal specific or cell specific parameter through higher layer (L3) signaling. If the user terminal supports only the fixed transmission scheme, no specific signaling is required and the transmission scheme is applied according to the function of the user terminal.

  5A and 5B show two examples of control message field allocation across frequency resources. In both FIG. 5A and FIG. 5B, the control message fields are evenly distributed (or “interleaved” across the subcarriers. “Interleaving” is a term commonly used in this situation in OFDM transmission. ). In other words, the control symbols in the control message field are mapped to subcarriers by the frequency interval between these control symbols, and this interval may be between some control symbols in the control message field. Is defined by the repetition factor selected for each control message field. The frequency interval between control symbols of the same control message field can be equal for all control symbols of the control message field of interest. FIG. 5A shows a mapping with a repetition factor of 2, i.e. the symbols of the control message field are mapped for every second subcarrier. FIG. 5B shows a mapping with a repetition factor of 4, i.e. 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 allocated to the user terminal, the size of the control field, and the like. Of course, the symbols in the control message field are mapped with a repetition factor that is limited so that there are no more control symbols to be mapped.

ここで、

は、プラスの無限大の方向の最も近いサポートする整数への四捨五入演算を表し、Ｏは、送信されるビット数、例えば、ＣＱＩワード長であり、

は、割り当てられた周波数リソース内にＰＵＳＣＨを搬送する副搬送波（基地局から物理ダウンリンク制御チャンネルであるＰＤＣＣＨ上で受信した）の数であり、

は、サブフレーム毎にＰＵＳＣＨを搬送する多重搬送波記号（ＯＦＤＭ記号）（基地局からＰＤＣＣＨ上で受信した）の数であり、

は、ＰＵＳＣＨ上で送信されたビットの合計数である。「オフセット」という用語は、トラフィックデータの望ましい受信品質と、制御メッセージフィールド内で転送される制御データの間のオフセットを定める品質オフセットである。オフセットは、異なる制御メッセージフィールドにおいて異なるとすることができるが、選択された送信方式に依存するように作成することができる。例えば、送信方式として空間多重化が選択された場合には、「オフセット」は、単一ストリームビーム形成送信又は空間送信ダイバーシティの場合よりも大きい値を有するように設定することができ、この場合、本質的に、より高い送信信頼性が得られる。トラフィックデータの送信の品質は、転送されるデータのサービス形式に従って判断され、変調及び符号化の方式、並びにＰＵＳＣＨの他のパラメータは、これらの要件を満たすように設定される。実際には、変調方式は、ＬＴＥ−Ａの現在の仕様におけるものと同様に、ＰＵＳＣＨ上で送信される全ての記号に対して同じとすることができるが、制御メッセージフィールドのチャンネル符号化方式は、「オフセット」を基準にして選択することができる。一般的に、ＡＣＫ／ＮＡＣＫメッセージのようなある一定の制御メッセージは、エラーに対して耐性が低く、例えば、ブロックエラー率（ＢＬＥＲ）に関してより高い受信品質を必要とし、ＰＵＳＣＨパラメータは、これらの要求を自動的には満たさない。式（１）では、「オフセット」という用語は、制御メッセージフィールドに対して選択された変調及び符号化の方式が望ましい高い受信品質を保証し、「オフセット」の実際の値が、トラフィックデータの品質（ＢＬＥＲ）と制御メッセージ形式の要求品質（ＢＬＥＲ）の間の差分に従って判断することを保証するように使用される。「オフセット」のこれらの値は、一般的に事前に判断され、選択されたアップリンク送信方式に依存するものとして記憶される。「オフセット」の値が大きくなる程、すなわち、トラフィックデータの要求品質と制御データの要求品質の間の差分が大きい程、より多くの記号が制御メッセージフィールドに割り当てられ、より堅固なチャンネル符号化が制御メッセージフィールドに適用される（その逆も同様である）。したがって、式（１）の計算は、制御メッセージビットの変調及びチャンネル符号化の前に実施される。上述のように、式（１）は、各制御メッセージ形式（この例ではＣＱＩ及びＡＣＫ／ＮＡＣＫ）に対して計算される。実際には式（１）は、現在の３ＧＰＰ仕様に定められた式の修正であり、この修正は、「オフセット」という用語である。 The allocation of a given control message field to the allocated resources is performed by first measuring the size of the control message field, then determining the repetition factor and the starting position subcarrier index, and then the control message field. Mapping symbols to corresponding subcarriers can be included. This is illustrated in FIG. 6 which shows an embodiment of block 404. The flowchart of FIG. 6 shows the mapping of control message fields to assigned 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 description below, this process is intended to cover other control message fields. Can be easily extended. At block 502, the number of symbols assigned to each control channel field (Nx) is determined according to:

here,

Represents the rounding operation to the nearest supported integer in the direction of plus infinity, O is the number of bits to be transmitted, eg, the CQI word length,

Is the number of subcarriers (received on the PDCCH which is the physical downlink control channel from the base station) carrying the PUSCH within the allocated frequency resource,

Is the number of multi-carrier symbols (OFDM symbols) (received on the PDCCH from the base station) that carry the PUSCH per subframe,

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 the traffic data and the control data transferred in the control message field. The offset can be different in different control message fields, but can be created to depend on the selected transmission scheme. For example, if spatial multiplexing is selected as the transmission scheme, the “offset” can be set to have a larger value than in the case of single stream beamforming transmission or spatial transmission diversity, In essence, higher transmission reliability is obtained. The quality of the traffic data transmission is determined according to the service type of the data to be transferred, and the modulation and coding scheme, and other parameters of the PUSCH are set to meet these requirements. In practice, the modulation scheme can be the same for all symbols transmitted on PUSCH, as in the current specification of LTE-A, but the channel coding scheme of the control message field is , “Offset” can be selected as a reference. In general, certain control messages, such as ACK / NACK messages, are less resistant to errors, eg, require higher reception quality with respect to block error rate (BLER), and PUSCH parameters are used for these requests. Is not automatically met. In Equation (1), the term “offset” ensures high reception quality where the modulation and coding scheme selected for the control message field is desirable, and the actual value of “offset” is the quality of the traffic data. Used to ensure that the decision is made according to the difference between (BLER) and the required quality of the control message format (BLER). These values of “offset” are generally determined in advance and stored as dependent on the selected uplink transmission scheme. The larger the “offset” value, ie, the greater the difference between the required quality of traffic data and the required quality of control data, the more symbols are assigned to the control message field and the more robust the channel coding is. Applies to control message fields (and vice versa). Thus, the calculation of equation (1) is performed prior to modulation of control message bits and channel coding. As described above, equation (1) is calculated for each control message format (CQI and ACK / NACK in this example). In practice, equation (1) is a modification of the equation defined in the current 3GPP specification, and this modification is the term “offset”.

ここで、Ｎは、サブフレーム内のユーザ端末に割り当てられた副搬送波の合計数であり、Ｎ_CQIは、サブフレーム内の送信されるＣＱＩ記号の数である。

は、切り捨て演算、すなわち、マイナス無限大の方向の最も近い整数への四捨五入である。反復係数の計算及び利用は、ＣＱＩが、割り当てられた周波数スペクトルにわたって配分される（又はインターリーブされる）ことになることを保証する。次に、ＡＣＫ／ＮＡＣＫメッセージフィールドに対して、反復係数ＲＰＦが次式に従って計算される。

ここで、Ｎ_ANは、サブフレーム内の送信されるＡＣＫ／ＮＡＣＫ記号の数である。送信されるＣＱＩリソース要素（又は記号）の数は、リソース要素の合計数から減らされるので、反復係数ＲＰＦ_ANは、ＣＱＩの後に論理的に利用可能なリソース要素に対処することによって計算される。このようにして、着目している特定の制御メッセージフィールドに対して使用するべき記号又はリソース要素の数による割算の前に、リソース要素Ｎの合計数から、割り当てられたリソース要素の数を低減することにより、更に別の制御メッセージフィールド（ランクインジケータ、事前符号化行列インジケータ等）に対する反復係数を計算することができる。ブロック５０８では、リソース要素マッピングが、割り当てられた反復係数を使用することによって異なるリソース要素から開始されるように、異なる制御メッセージフィールドに対して異なる開始位置リソース要素が選択される。反復係数は、０とＲＰＦ−１との間で変化することができる。ブロック５１０では、制御メッセージフィールドの制御記号が、ブロック５０８おいて選択された開始位置、ブロック５０４においてＣＱＩに対して計算された反復係数、及びブロック５０６においてＡＣＫ／ＮＡＣＫに対して計算された反復係数を用いてリソース要素にマップされる。 In block 504, for the CQI message field, the repetition factor RPF is calculated according to the following equation:

Here, N is the total number of subcarriers allocated to the user terminals in the subframe, and N _CQI is the number of CQI symbols transmitted in the subframe.

Is the truncation operation, ie rounding to the nearest integer in the direction of minus infinity. Calculation and utilization of the repetition factor ensures that the CQI will be distributed (or interleaved) across the assigned frequency spectrum. Next, the repetition factor RPF is calculated according to the following equation for the ACK / NACK message field.

Here, N _AN is the number of ACK / NACK symbols transmitted in the subframe. Since the number of CQI resource elements (or symbols) transmitted is subtracted from the total number of resource elements, the repetition factor RPF _AN is calculated by addressing the resource elements that are logically available after the CQI. In this way, the number of allocated resource elements is reduced from the total number of resource elements N before division by the number of symbols or resource elements to be used for the particular control message field of interest. By doing so, it is possible to calculate the repetition factor for further control message fields (rank indicator, precoding matrix indicator, etc.). At block 508, different starting position resource elements are selected for different control message fields such that resource element mapping is started from different resource elements by using the assigned repetition factor. The repetition factor can vary between 0 and RPF-1. At block 510, the control message field control symbols are the starting position selected at block 508, the repetition factor calculated for CQI at block 504, and the repetition factor calculated for ACK / NACK at block 506. Is mapped to a resource element using

FIG. 6 shows the result of the process of FIG. 5 when N = 36, N _CQI = 7, and N _AN = 4. Accordingly, the repetition factor R _CQI becomes 5 (36/7 = 5.143-5) and R _AN becomes 7 ((36−7) /4=7.25-7) according to equation (2). ). The start position of CQI is selected to be 0, and the start position of ACK / NACK is selected to be 2 (subcarrier index). In this case, CQI symbols are mapped for every fifth subcarrier starting from subcarrier 0, and ACK / NACK symbols are mapped for every seventh non-CQI subcarrier starting from subcarrier 2. The number of CQI symbols is excluded in equation (3), so these symbols are excluded when performing the actual mapping. Eventually, it is difficult to find repetition factors that will never overlap, and this approach ensures that ACK / NACK will mainly avoid crushing previously mapped CQI symbols. In the case of impairment of data symbols that may be corrupted, ACK / NACK may also collapse CQI symbols because reliable transmission of ACK / NACK messages takes precedence over transmission of CQI messages. In general, any subsequently mapped control message symbol will not be mapped to the same subcarrier as the previously mapped control symbol, which excludes the mapped resource element from further mapping. This is because that. 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 unmapping is performed correctly.

  The actual mapping can be implemented in several ways. The same mapping pattern can be repeated for all OFDM symbols, ie, the same control field can occupy the same subcarrier from one OFDM symbol to another. The size of the predetermined 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 control message fields in successive OFDM symbols. Thereby, the control message field occupies different frequency positions in different OFDM symbols, thus improving the frequency diversity between successive OFDM symbols. Alternatively, interleaving can be performed across all subcarriers and multiple OFDM symbols, eg, over symbols in a time slot or subframe. At this time, when mapping a predetermined control message field, the subcarrier of the previous OFDM symbol mapped last is considered when starting to map the subcarrier of the subsequent symbol. For example, as shown in FIG. 6, if the number of subcarriers is 36, the index of the last mapped subcarrier is 34, the repetition factor is 6, and is mapped in the subsequent OFDM symbol. The first subcarrier 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 repetition factor.

  In yet another embodiment, interleaving can be performed across different spatial streams. As described above, it is expected that the user terminal is equipped with a function for supporting SU-MIMO. In this case, a plurality of spatial transmission streams can be allocated to the user terminal. In such cases, the transmission can be multiplexed into multiple spatially parallel signal streams. In this case, interleaving can be extended to multiple streams. Interleaving can be performed, for example, by first mapping control symbols to the subframes of the first stream, and then continuing this mapping for the second stream and further thereafter. Based on the number of subcarriers and the repetition factor, the continuation of the mapping is as between consecutive OFDM symbols so that different control message fields can occupy different subcarriers in a spatially parallel stream. A similar scheme can be implemented. Alternatively, the subsequent spatial stream mapping can be initialized to correspond to the first spatial stream mapping so that the starting position is the same for both streams. Obviously, when calculating equation (1) and the repetition factor, the number of additional symbols available due to the use of additional signal streams can be addressed. Equation (1) can be modified to accept the use of spatial multiplexing, as will be described later.

  In an embodiment, data symbols may be mapped to resource elements prior to mapping ACK / NACK so that ACK / NACK will crush data symbols. In this embodiment, the interleave pattern for each control message field is determined by first calculating equation (1), repetition factor, and starting position for each control message field. Next, CQI symbols and rank indicator symbols are first mapped to resource elements according to the process of FIG. Thereafter, data symbols can be mapped to the remaining resource elements. The ACK / NACK symbol can then be assigned to its determined location such that the ACK / NACK symbol collapses the data symbol, ie replaces the data symbol. The reason for ACK / NACK crushing data is that if the user terminal misses the reception of the downlink data packet, it does not recognize the presence of the ACK / NACK message field in the uplink subframe and schedules it accordingly. The transmitted ACK / NACK message cannot be transmitted. Alternatively, the user terminal transmits data in these resource elements.

  In yet another embodiment, a predetermined number of subcarriers may be excluded from the control symbol mapping at the edge of the frequency resource block. In general, the sub-carriers at the edge of the frequency resource are more susceptible to interference, and thus important control data can preferably be mapped to sub-carriers near the center frequency of the frequency resource. In practice, this can be done by setting the starting position high enough and omitting mapping of subcarriers with an index higher than the determined threshold (mapping skips to the next symbol). . If the mapping continues in a subsequent OFDM symbol from a subcarrier that has been mapped in the previous OFDM symbol, the mapping of subcarriers with an index lower than another threshold may be omitted.

  Since resource elements will not spread across the frequency spectrum as in SC-FDMA, the use of OFDM allows for the assignment of different transmit power values for different resource elements. In some embodiments, different transmit power offset values are assigned to resource elements that carry control message fields and resource elements that carry data traffic fields within an OFDM symbol. In order to ensure correct reception of at least some control message fields at the receiver, higher transmission power can be allocated to these control message fields at the transmitter. Of course, different additional transmission power offsets can be assigned to different control message fields based on how important these control message fields carry signaling information. More important control messages can be assigned higher transmission power. The additional transmit power assigned to the control message field may depend on the modulation and coding scheme currently in use on the PUSCH. The lower the modulation order, and the more robust the coding scheme being used, the more robust the modulation and coding schemes that are resistant to interference will compensate for the requirement for stronger transmission power, so the control message field. The transmission power offset assigned to is small.

  When spatial multiplexing is used as a transmission scheme, as described above, an interleave pattern can be dealt with in an additional signal stream. The control message field can be evenly distributed across different spatial streams, or the size of the control message field can be defined separately for each spatial stream. This depends on the CQI instruction from the user terminal. If the user terminal transmits a separate CQI for each spatial stream, the base station can define different modulation and coding schemes for different spatial streams, thus different numbers of bits for different spatial streams. Can be sent in a stream. Generally this is enabled 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 assigned to different spatial streams. Generally this is enabled when different SU-MIMO spatial streams are encoded with the same spreading (or scrambling) code.

  SU-MIMO uplink transmission improves data rate by spatial multiplexing or improves transmission reliability by beamforming transmission when the transmitted signal is brought into a spatial channel that provides the best signal-to-noise characteristics. Can be used for Furthermore, spatial multiplexing can be combined with beamforming. Another variation is to use open-loop transmit diversity transmissions where essentially the same data is transmitted from all antennas with 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), repetition factor, and subcarrier mapping in the case of OFDM transmission has been described above. For SC-FDMA transmission, the current SC-FDMA PUSCH structure illustrated in FIG. 3 can be used for all spatial streams. As described above in the previous paragraph, the control message field can be evenly distributed among different spatial streams, or the size of the control message field for each spatial stream based on the modulation and coding scheme in use. Can be determined separately. The number of symbols to be used for a given control message field is calculated using equation (1), and the subcarrier mapping is performed according to the pattern illustrated in FIG.

修正なしでは、異なるランクの理由から、制御メッセージフィールドには正しい数の記号又は副搬送波が割り当てられないことになる。制御メッセージフィールドに対してビーム形成又は送信ダイバーシティを利用するためには、同じ制御メッセージ記号が、全ての空間ストリーム内で同じ副搬送波を占有するように、好ましくは、同じ副搬送波が、空間ストリーム内の制御メッセージフィールドに割り当てられる。次に、送信機内でビーム形成を実施する信号プロセッサは、ビームの望ましい方向に基づいて判断された係数で記号を乗算する。当然ながら、記号の受信を可能にするために、受信機内で逆作動が実施される、すなわち、受信機内でビーム形成を実施する信号プロセッサは、判断された空間重み付けに基づいて判断された係数により、複数のアンテナから受信した信号ストリームを乗算し、異なるストリームの同じ副搬送波上で送信された記号が組み合わされる。 According to embodiments of the present invention, at least a portion of the control data, eg, ACK / NACK messages, can be transmitted by using beamforming or transmit diversity transmission, while data traffic uses spatial multiplexing. Can be sent. In fact, this means that ACK / NACK is transmitted on the assumption that the channel rank is 1, and 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 control message format and traffic data. Equation (1) can be modified by adding an uplink rank specific parameter ΔR _DC that defines the ratio between the number of ranks of traffic data and the control message field of interest. For example, if the traffic data rank is 2 (two spatial streams), the rank of the ACK / NACK message is 1 (beamforming or transmit diversity), ΔRD-C is 2 (2/1), (1) has the form of the following equation after this modification.

Without modification, the control message field will not be assigned the correct number of symbols or subcarriers for different rank reasons. In order to utilize beamforming or transmit diversity for the control message field, preferably the same subcarriers are in the spatial stream so that the same control message symbols occupy the same subcarriers in all spatial streams. Assigned to the control message field. The signal processor that performs beamforming in the transmitter then multiplies the symbol by a factor determined based on the desired direction of the beam. Of course, in order to enable the reception of symbols, the reverse operation is performed in the receiver, i.e., the signal processor performing beamforming in the receiver is based on the determined coefficient based on the determined spatial weighting. Multiply the signal streams received from multiple antennas and combine the symbols transmitted on the same subcarrier in different streams.

  FIG. 7 shows the above 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 to direct the stream to the desired spatial channel. Yes. In other words, the same ACK / NACK message is transmitted from both antenna elements of the transmitter, and the direction is controlled by phasing signals transmitted from different antennas, as is known in the art. Corresponding phase adjustments are implemented in the receiver to weight the received signal and thereby amplify the spatial direction in which the ACK / NACK was mainly received. In order to obtain higher data rates, data traffic is transmitted using spatial multiplexing and different data is transmitted / received through different transmit / receive branches and antennas. At the transmitter and receiver, multi-antenna transmission is controlled by digital signal processors 700 and 702 designed for control purposes.

  When the uplink transmission scheme is OFDM, the choice between beamforming, transmit diversity, and spatial multiplexing can be made at the subcarrier level. In such cases, as described above, the same symbol is preferably mapped to the same carrier in each transmit branch in the transmitter. When the uplink transmission scheme is SC-FDMA, each subcarrier occupies the entire frequency spectrum, so the choice between beamforming, transmit diversity and spatial multiplexing can be made on the SC-FDMA symbol level. it can. The resolution of the choice between beamforming, transmit diversity and spatial multiplexing can be done for each SC-FDMA symbol or for multiple SC-FDMA symbols, eg time slots or subframes at a time. . If the 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 within the transmitter. Are received from all antenna branches in the receiver. Next, interleaving pattern determination and symbol mapping to subcarriers are performed equally for all transmit / receive branches. On the other hand, if the SC-FDMA symbol carries information that does not require high reliability, the SC-FDMA symbol can be transmitted by using spatial multiplexing, i.e., carry different information. Multiple SC-FDMA symbols can be sent simultaneously through different spatial streams.

  The use of beamforming in the transmission of control messages generally requires feedback information from the receiver regarding channel characteristics. If feedback information is not available, embodiments of the present invention may use an open-loop multi-antenna transmit diversity scheme, eg, space-time block coding, to improve the reliability of transmission of critical control information. Transmit at least a portion of the control message field by using pre-encoded vector switching, frequency selective transmit diversity, or cyclic retardation diversity using large or small retardation. Implementation of the open loop transmit diversity schemes listed above will be apparent to those skilled in the art and does not require substantial modifications to the above-described embodiments. In order to transmit data traffic at higher speed, data traffic can be transmitted by using spatial multiplexing.

  As described above, the embodiments of the present invention can be implemented in a transmitter (user terminal) and a receiver (base station). Indeed, these embodiments are typically implemented by a processor or corresponding device included in a user terminal or base station. The processor is configured to assign control message fields to PUSCH resources according to the selected uplink transmission scheme so as to optimize transmission performance of the control message in the selected uplink transmission scheme. The apparatus can be the processor 700, 702 illustrated in FIG. If no multi-antenna transmission is utilized in the uplink transmission, the user terminal processor 700 is simplified in the sense that it does not perform multi-antenna signal processing. A processor can be a logical component implemented by multiple physical signal processing units. The term “processor” means a device capable of processing data. The processor may include an electronic circuit that performs the required function and / or a microprocessor that runs a computer program that performs the required function. When designing an implementation, those skilled in the art will consider requirements settings regarding, for example, device size and power consumption, required processing capabilities, manufacturing costs, and manufacturing volumes. The processor can include logic components, standard integrated circuits, microprocessors, and / or application specific integrated circuits (ASICs).

  The microprocessor implements the functions of a central processing unit (CPU) on the integrated circuit. The CPU is a logical machine that executes a computer program including 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, Java, 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 microinstructions can vary depending on the CPU design. The microprocessor can have an operating system (a dedicated operating system of an embedded system or a real-time operating system) that can provide a computer program having system services.

  The present invention is applicable to the cellular or mobile telephone communication systems defined above, but is also applicable to other suitable telephone communication systems. The protocols used, mobile telephone communication system specifications, these network elements, and subscriber terminals are rapidly evolving. Such development may require additional changes to the described embodiments. Accordingly, all terms and expressions are to be interpreted broadly and are intended to be illustrative rather than limiting the embodiments described above. It will be apparent to those skilled in the art that the concepts of the present invention can be implemented in a variety of ways as technology advances. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.

400 Start 402 Select uplink transmission method 406 Assign control message field

Claims (6)

A method for use in a user terminal of a cellular telephone communication system, comprising:
Receiving an indication of an uplink transmission scheme for use by a user terminal;
Determining physical uplink shared traffic channel resources of the user terminal;
In order to optimize the transmission performance of the control message prior Kia Uplink transmission scheme, and allocating the control message field to the resources of the physical uplink shared traffic channel according to 該A Uplink transmission scheme,
Including
Before when Kia Uplink transmission scheme utilizing a spatial multiplexing transmission in the uplink, transmitted by using a single stream beamforming multiple antennas transmit or transmit diversity multiple antenna transmitting at least one control message field, and method characterized by further including that step to send by using multiple streams spatial multiplexing at least data traffic field. If the previous Kia Uplink transmission scheme utilizing a spatial multiplexing transmission in the uplink, transmitted by using at least one control message field open loop multiple antenna transmit diversity, and multiple stream space at least data traffic field The method of claim 1, further comprising transmitting by using multiplexing. If before Kia Uplink transmission scheme is single carrier frequency division multiple access, wherein the control message field and wherein that you are the station localization at the edge of the physical uplink shared traffic channel resources of the user terminal The method according to claim 1 or 2. The method according to claim 3, characterized that you same localization of said control message field in a plurality of different spatial streams are applied. A user terminal of a cellular telephone communication system,
Means for receiving an indication of an uplink transmission scheme for use by a user terminal;
Means for determining a physical uplink shared traffic channel resource of the user terminal;
In order to optimize the transmission performance of the control message prior Kia Uplink transmission method, means for assigning the control message field to the resources of the physical uplink shared traffic channel according to 該A Uplink transmission scheme,
Including
Before when Kia Uplink transmission scheme utilizing a spatial multiplexing transmission in the uplink, transmitted by using a single stream beamforming multiple antennas transmit or transmit diversity multiple antenna transmitting at least one control message field, and user terminal, characterized by further comprising means you send by using multiple streams spatial multiplexing at least data traffic field. A computer program,
Embodied on a computer-readable distribution medium,
Comprising program instructions for performing the method of any of claims 1 to 4 when loaded into a device;
A computer program characterized by the above.

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