JP6868594B2 - Uplink control signaling in cellular telephone communication systems - Google Patents

Description

The present invention relates to the field of cellular radiotelephone communications, especially uplink signaling.

The communication system known as the evolved UMTS (Universal Mobile Phone Communication System) terrestrial radio access network (E-UTRAN, also called UTRAN-LTE or advanced long-term evolution LTE-A for its long-term evolution) is currently under development within 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 will be "single carrier FDMA" which is a kind of linearly pre-encoded OFDMA. It will be (SC-FDMA). Uplink system bandwidth uses the "Physical Uplink Control Channel" (PUCCH) to forward uplink control messages and the "Physical Uplink Shared Channel" (PUSCH) to send uplink user traffic. Has a structure that is Additional control messages can be sent within the resources initially assigned to the PUSCH. PUCCH carries uplink control information such as ACK / NACK messages, channel quality indicator (CQI), scheduling request indicator (SRI), channel rank indicator, downlink pre-encoded information, and the like.

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

According to another aspect of the present invention, the device specified in claim 14 is provided.

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

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

According to another aspect of the present invention, the device specified in claim 28 is provided.

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

Embodiments of the present invention are set forth in the dependent claims.

Embodiments of the present invention will be described below with reference to the accompanying drawings as a mere example.

It is a figure of the principle of cellular communication. It is a figure of the uplink system bandwidth structure in the latest UMTS system. It is a figure of the structure of the transmitter and the receiver for use in cellular communication. It is a figure of the current uplink signal structure in the latest UMTS. It is a flow chart which shows the process for carrying out the control message field assignment by embodiment of this invention. It is a figure of the effect of the control message field allocation by embodiment of this invention. It is a figure of the detailed processing for the control message field assignment by embodiment of this invention. It is a figure of the effect of the control message field allocation by FIG. 6A. It is a figure of the multiple stream transmission by embodiment of this invention.

The following embodiments are exemplary. The present specification may refer to "an", "one", or "partial" embodiments in several positions, wherein each such reference is to the same embodiment. Or does not necessarily mean that the feature applies only to a single embodiment. Single features of different embodiments can also be combined to result in other embodiments.

1A and 1B show 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 base station 100 provides wireless communication services from user terminals 110 to 122 in the range of cell 102. Base station 100 can belong to the long-term evolution (LTE) or advanced LTE (LTE-A) radio access network of UMTS (Universal Mobile Telephone Communication System) designated within 3GPP (3rd Generation Joint Project). Therefore, at least OFDMA and SC-FDMA can be supported as wireless access schemes for downlink and uplink respectively. A base station is a mobile controller (MME) that controls the movement of user terminals, one or more gateway nodes that pass when data is routed, and certain communication parameters known in the art. Connected to other parts of the cellular telephone communication system, such as operation and maintenance servers configured to control.

FIG. 1B shows the general structure of the uplink system bandwidth allocated to network operators to provide uplink communication services in accordance with LTE releases 8 and 9. The system bandwidth is such that the traffic channel, i.e. the physical uplink shared channel (PUSCH), is assigned to the center of the system bandwidth and the control channel, i.e. the physical uplink control channel (PUCCH), is located at both edges of the traffic channel bandwidth. Structured to be assigned. The size of the PUCCH can be set by the base station 100, and for certain network deployments, the base station 100 configures bandwidth utilization so that frequency resources at the edges of the system band are left blank. Can be done. In the current LTE system scenario, uplink L1 / L2 control signaling is 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. It is divided into two classes. The PUCCH is a shared frequency / time resource reserved exclusively for the user terminal that transmits only the L1 / L2 control signal. The present specification focuses on the PUSCH in which the PUSCH carries the uplink L1 / L2 control signal when the UE is scheduled for data transmission.

FIG. 2 shows a very basic structure of SC-FDMA transmitters (blocks 200-212) and SC-FDMA receivers (blocks 214-226). Future releases of the LTE system will also consider using OFDM in the uplink direction. This structure is known to those skilled in the art of modern telephone communication systems and is therefore described below at a general level for FIG. In the SC-FDMA transmitter, the modulated symbols transmitted are first converted from series form to parallel form at block 200 and then into the frequency domain through the Discrete Fourier Transform (DFT) at 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 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. The inverse DFT is then calculated in block 206, the signal is converted from parallel to series in block 208, the circular prefix is added in block 210, the signal is converted to analog in block 212, and of the transmitter. It is transmitted through the radio frequency (RF) portion. At the receiver, at block 214, the radio signal is received through the antenna and the RF portion of the receiver, and the received signal is converted to the digital domain. The circular prefix is removed in block 216 and the serial to parallel transform is performed in block 218 before the DFT in block 220. Prior to the inverse DFT in block 224 and the parallel-to-series conversion in block 226, control symbols and traffic data symbols are extracted from these resource elements in block 222.

Future LTE versions are expected to support OFDM on the uplink as well. In such a case, it is simple to modify the structure of the SC-FDMA transmitter and receiver, and simply short-circuit the DFT block 202 in the transmitter and the inverse DFT block in the receiver to make the OFDM transmitter and receive. You get the opportunity. Accordingly, 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 the uplink transmission will be spatially multiplexed and higher. Data rate and better spectral efficiency are obtained. To this end, the transmitter and receiver structures of FIG. 2 include one signal branch for each transmit / receive antenna (FIG. 2 shows one branch) and selected multiple antenna transmit schemes. It will be modified to include a signal processor that performs signal processing according to. The signal processor can be installed virtually anywhere within the digital domain of the transmit / receive chain, which will be apparent to those skilled in the art. SU-MIMO transmission can be used with either OFDM transmission or SC-FDMA transmission.

Both the OFDM symbol and the SC-FDMA symbol are used for notational purposes and to distinguish the coded symbols mapped to each resource element from the OFDM symbols or SC-FDMA symbols that carry multiple coded symbols. It can be considered as a symbol block that carries multiple (modulated, channel-encoded) symbols as information elements.

FIG. 3 shows the current uplink PUSCH subframe structure and control messages to the PUSCH resource, i.e., the frequency resource block assigned to a given user terminal when the circular prefix appears to have a normal length. Shows field assignments. The time slot contains 7 SC-FDMA symbols and the subframe contains 2 time slots. In the extended circular prefix, the time slot contains 6 SC-FDMA symbols. The actual combinations of different L1 / L2 control signals and their size will vary from subframe to subframe. As will be described later, both the user terminal and the base station have information about the number of symbols reserved by the control portion. A reference signal (RS) is transmitted on all subcarriers of the symbol at the center of the time slot. An acknowledgment message (ACK / NACK) indicating correct (ACK) or incorrect (NACK) reception of the downlink data packet is located on the SC-FDMA symbol next to the RS transmitter, which is important. The reception quality of ACK / NACK messages is improved. The resource element assigned to the ACK / NACK message is located at one end of the SC-FDMA symbol. A rank indicator indicating the downlink channel rank can be assigned on the SC-FDMA symbol which is the same subcarrier as ACK / NACK but is adjacent to that of ACK / NAK. There are a maximum of two SC-FDMA symbols for each slot assigned to ACK / NACK signaling for each (virtual) subcarrier. The same applies to rank indicators. A channel quality indicator (CQI) message field is assigned to the other end of the resource element, and this field can be transmitted using a plurality of SC-FDMA symbols.

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

Since the DFT operation effectively spreads the contents 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 is suboptimal 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 susceptible to frequency selective fading. If the frequency of the subcarrier carrying the ACK / NACK message is significantly attenuated for fading reasons, the entire ACK / NACK message is likely to be lost. In addition or as an alternative, the SU-MIMO transmission method should be effectively utilized in order 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 process can be performed within the transmitter or receiver, i.e., within the user terminal or base station. Processing begins at block 400. At block 402, the uplink transmission method in the user terminal is selected. In block 404, the PUSCH resource in the user terminal is determined. In block 406, the PUSCH resource determined in block 404 is assigned a control message field according to the transmission method selected in block 402.

Selection of transmission method can include selection between OFDM transmission and SC-FDMA transmission, and between single stream transmission and multiple stream transmission. The selection can be performed by selecting a channel rank that can automatically determine the multiple antenna transmission method and the multiple access method (or uplink waveform). The selection of the uplink transmission method can be performed by the base station, and this transmission method can be signaled to the user terminal in downlink signaling. The choice between the single-antenna transmission method and the multiple-antenna transmission method can be based on the channel rank indicator transmitted from the user terminal. The channel rank indicates the number of spatial MIMO channels available. Correspondingly, block 402 includes selection of an uplink transmission method when processing is performed in the base station and instruction of this transmission method to the user terminal. Similarly, block 404 bases to schedule the uplink PUSCH resource to the user terminal, signal the allocated PUSCH resource to the user terminal, and receive the uplink transmission of the user terminal from the allocated PUSCH resource. Includes the steps to configure the receiver of the station. Block 406 includes determining patterns in data and control message fields within the allocated PUSCH resource, and configuring the receiver to receive data and control messages accordingly.

When implemented within the user terminal, block 402 includes an uplink transmission deduction from the control message received from the base station, and block 404 is assigned to the user terminal from the control message received from the base station. Containing the deduction of the uplink PUSCH resource, block 406 determines the pattern in the data and control message fields in the allocated PUSCH resource and configures the transmitter to transmit the data and control message accordingly. Including the stage to do.

When the selected uplink transmission method is SC-FDMA, the control message field can be assigned by the conventional method as illustrated in FIG. In other words, the subcarrier mapping of the control message field can be performed so that the control message field is localized with respect to the allocated PUSCH resource. The DFT then spreads the subcarriers over the allocated frequency resources. On the other hand, when the selected uplink transmission method is OFDM, the symbols in each control message field are distributed across the PUSCH frequency resources of the user terminal. Accordingly, each control message field will be allocated along the frequency spectrum assigned to the user terminal, thereby frequency-selective fading compared to those using the structure of FIG. 3 in OFDM transmission. Better tolerance for.

Generally, the transmission method is selected by the base station. First, the base station applies a multiple antenna transmission scheme, namely spatial multiplexing through multiple spatially parallel transmit streams, or beam formation or transmit diversity transmission through a single stream (single input, multiple outputs, SIMO) can be selected. The selection can be made based on the uplink channel rank, i.e., the number of uncorrelated uplink space subchannels. If the base station chooses spatial multiplexing as the multiplex antenna transmission scheme, the base station also chooses the number of spatially parallel uplink subsystems. Next, selection between OFDM and SC-FDMA based on the selected multiple antenna transmission method, that is, selection of OFDM for spatial multiplexing, single stream beam formation or SC-FDMA for SIMO. Can be done. However, the embodiments of the present invention described below are not limited to this type of transmission method selection, and SC-FDMA (or OFDM) can be used in all multiple antenna transmission methods. In the user terminal, the transmission method (multiple antenna method and multiple access method) is determined by the dynamic scheduling allowable information signaled from the base station to the user terminal in downlink signaling, for example, downlink control information (DCI) format 0). can do. Signaling can be specified by using at least one signaling bit that indicates whether to use spatial multiplexing. Next, the user terminal performs either spatial multiplexing by OFDM or beam formation by SC-FDMA. Alternatively, the base station can implicitly signal the transmission scheme 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 formation by SC-FDMA. In yet another embodiment, the transmission scheme can 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 method, no specified signaling is required, and the transmission method is applied according to the function of the user terminal.

5A and 5B show two examples of the allocation of control message fields across frequency resources. In both FIGS. 5A and 5B, control message fields are evenly distributed (or "interleaved" across subcarriers; "interleaved", a term commonly used in this situation in OFDM transmissions). .. In other words, the control symbols in the control message fields are mapped to subcarriers by the frequency spacing between these control symbols, and this spacing is some other than the control symbols in the control message field between the control symbols in the control message field. To determine the symbol of, it is determined by the iteration coefficient selected for each control message field. The frequency spacing between the control symbols in the same control message field can be equal for all control symbols in the control message field of interest. FIG. 5A shows a mapping with an iteration factor of 2, i.e., the symbols in the control message field are mapped for each second subcarrier. FIG. 5B shows a mapping with an iteration factor of 4, i.e., the symbols in the control message field are mapped for each fourth subcarrier. Different iteration coefficients can be determined according to the size of the resource block assigned 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 limit iteration factor that makes 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 the first step in measuring the size of the control message field, then the step of determining the iteration factor and the start position subcarrier index, and then the control message. It can include the step of mapping the symbol to the corresponding subcarrier. This is illustrated in FIG. 6, which shows an embodiment of block 404. The flow diagram of FIG. 6 shows the mapping of control message fields to allocated PUSCH resources. The process of FIG. 6 illustrates the mapping of two control channel fields (CQI and ACK / NACK), but as is clear from the description below, this process is intended to target other control message fields. Can be easily extended to. In block 502, the number of symbols assigned to each control channel field (Nx) is determined according to the following equation.

here,

Represents a rounding operation to the nearest supporting integer in the direction of plus infinity, where O is the number of bits transmitted, eg, the CQI word length.

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

Is the number of multiple carrier symbols (OFDM symbols) (received from the base station on the PDCCH) that carry the PUSCH for each subframe.

Is the total number of bits transmitted on the PUSCH. The term "offset" is a quality offset that defines the desired reception quality of traffic data and the offset between the control data transferred within the control message field. The offset can be different for different control message fields, but can be created to depend on the transmission method selected. For example, if spatial multiplexing is selected as the transmission method, the "offset" can be set to have a higher value than for single stream beam forming transmissions or spatial transmission diversity, in this case. In essence, higher transmission reliability is obtained. The quality of transmission of traffic data is determined according to the service format of the data being transferred, and the modulation and coding scheme, as well as other parameters of PUSCH, are set to meet these requirements. In practice, the modulation scheme can be the same for all symbols transmitted over the PUSCH, similar to that in the current LTE-A specification, but the channel coding scheme for the control message field is , Can be selected based on "offset". In general, certain control messages, such as ACK / NACK messages, are less tolerant of errors and require higher receive quality, for example with respect to block error rate (BLER), and PUSCH parameters are these requirements. Is not automatically satisfied. In equation (1), the term "offset" guarantees the desired high reception quality for the modulation and coding scheme selected for the control message field, and the actual value of "offset" is the quality of the traffic data. It is used to ensure that the judgment is made according to the difference between (BLER) and the required quality (BLER) of the control message format. These values of "offset" are generally pre-determined and stored as dependent on the uplink transmission method selected. The higher the "offset" value, that is, 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. Applies to control message fields and vice versa. Therefore, the calculation of equation (1) is performed before the modulation and channel coding of the control message bits. 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, which 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, the iteration factor RPF is calculated for the CQI message field according to the following equation.

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

Is a truncation operation, that is, rounding to the nearest integer in the direction of minus infinity. The calculation and utilization of the iteration coefficients ensures that the CQI will be distributed (or interleaved) over the assigned frequency spectrum. Next, for the ACK / NACK message field, the iteration coefficient RPF is calculated according to the following equation.

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 decremented from the total number of resource elements, the iteration 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 dividing 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 iteration coefficient for yet another control message field (rank indicator, pre-encoded matrix indicator, etc.). At block 508, different start position resource elements are selected for different control message fields so that the resource element mapping starts from different resource elements by using the assigned iteration coefficients. The iteration factor can vary between 0 and RPF-1. In block 510, the control symbols in the control message field are the start position selected in block 508, the iteration factor calculated for CQI in block 504, and the iteration coefficient calculated for ACK / NACK in block 506. Is mapped to a resource element using.

FIG. 6 shows the results of the processing of FIG. 5 when N = 36, N _CQI = 7, and N _{AN = 4.} In response, the repetition factor R _CQI will become 5 according to equation (2) (36/7 = 5.143~5), R AN 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 (subcarrier index). In this case, the CQI symbol is mapped for each fifth subcarrier starting from subcarrier 0, and the ACK / NACK symbol is mapped for each 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. After all, it is difficult to find iteration coefficients that never overlap, and this technique ensures that ACK / NACK avoids predominantly crushing previously mapped CQI symbols. In the case of impairment of a data symbol that may be crushed, ACK / NACK may also crush the CQI symbol, as the reliable transmission of the ACK / NACK message takes precedence over the transmission of the CQI message. In general, any subsequent control message symbol will not be mapped to the same subcarrier as the previously mapped control symbol, which excludes the mapped resource element from yet another 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 mapping is correctly performed.

The actual mapping can be performed in several ways. The same mapping pattern can be repeated for all OFDM symbols, i.e., 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 start positions are selected for successive OFDM symbol mappings to obtain staggered mappings of control message fields in successive OFDM symbols. Thereby, the control message field occupies different frequency positions in different OFDM symbols, thus improving frequency diversity between consecutive OFDM symbols. Alternatively, interleaving can be performed across all subcarriers and multiple OFDM symbols, eg, across symbols within a time slot or subframe. At this time, when mapping a predetermined control message field, the subcarrier of the previous OFDM symbol that was last mapped is taken into account 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 iteration factor is 6, and it 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 consecutive OFDM symbols, based on the number of subcarriers and the iteration factor.

In yet another embodiment, interleaving can be performed across different spatial streams. As described above, it is expected that the user terminal will be equipped with a function that supports SU-MIMO, and in this case, a plurality of spatial transmission streams can be assigned to the user terminal. In such cases, the transmission can be multiplexed into a plurality of spatially parallel signal streams. In this case, the interleave can be extended to multiple streams. Interleaving can be performed, for example, by first mapping the control symbol to a subframe of the first stream, and then continuing this mapping for the second stream, and so on. The continuation of the mapping is between consecutive OFDM symbols so that different control message fields can occupy different subcarriers in the spatially parallel stream, based on the number of subcarriers and the iteration factor. It can be implemented in a similar manner. Alternatively, subsequent spatial stream mappings can be initialized to correspond to the first spatial stream mapping so that the starting position is the same for both streams. When calculating equation (1) and the iteration factor, it is clearly possible to deal with the number of additional symbols available due to the use of the additional signal stream. Equation (1) can be modified to accept the use of spatial multiplexing, as described below.

In the embodiment, the data symbol can be mapped to the resource element before ACK / NACK is mapped so that ACK / NACK will crush the data symbol. In this embodiment, the interleaving pattern for each control message field is determined by first calculating equation (1), repetition factor, and start position for each control message field. The CQI symbol and rank indicator symbol are then first mapped to the resource element according to the process of FIG. You can then map the data symbols to the remaining resource elements. The ACK / NACK symbol can then be assigned to its determined position so that the ACK / NACK symbol crushes the data symbol, i.e. replaces the data symbol. The reason why ACK / NACK crushes data is that if the user terminal misses the reception of the downlink data packet, it does not recognize the existence of the ACK / NACK message field in the uplink subframe and schedules accordingly. It is not possible to send the ACK / NACK message. Alternatively, the user terminal transmits the data in these resource elements.

In yet another embodiment, a predetermined number of subcarriers can be excluded from the control symbol mapping at the edges of the frequency resource block. In general, subcarriers at the edge of the frequency resource are more susceptible to interference, and therefore important control data can preferably be mapped to subcarriers near the center frequency of the frequency resource. In practice, this can be done by setting the start position high enough and omitting the mapping of subcarriers with indexes higher than the determined threshold (mapping jumps to the next symbol). .. If the mapping continues from the subcarrier whose mapping was completed in the previous OFDM symbol to the subsequent OFDM symbol, the mapping of the subcarrier having an index lower than another threshold value can be omitted.

Since resource elements do not spread over the frequency spectrum as in SC-FDMA, the use of OFDM allows the allocation of different transmit power values to different resource elements. In some embodiments, different transmit power offset values are assigned to the resource element carrying the control message field and the resource element carrying the data traffic field within the OFDM symbol. Higher transmission power can be allocated to these control message fields in the transmitter to ensure correct reception of at least some of the control message fields in the receiver. Of course, different control message fields can be assigned different additional transmit power offsets based on how important these control message fields carry important signaling information. Higher transmission power can be assigned to more important control messages. The additional transmit power assigned to the control message field can 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 in use, the more interference-tolerant modulation and coding schemes are likely to compensate for the demand for stronger transmit power. The transmit power offset assigned to is small.

When spatial multiplexing is used as the transmission method, interleaving patterns can be addressed in the additional signal stream, as described above. The control message fields can be evenly distributed across different spatial streams, or the control message fields can be sized 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, and thus different spatial numbers with different bit numbers. Can be sent in a stream. Generally this is enabled when different SU-MIMO spatial streams are encoded with different spreading (or scrambled) codes. Otherwise, the same modulation and coding scheme is used for all streams and equal amounts 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 scrambled) code.

SU-MIMO uplink transmission improves the data rate by spatial multiplexing or improves the reliability of transmission by beam-forming transmission when the transmitted signal is brought to a spatial channel that provides the best signal-to-noise characteristics. Can be used for. In addition, spatial multiplexing can be combined with beam formation. Another variant is to use open-loop transmit diversity transmission when essentially 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), repetition coefficient, and subcarrier mapping in the case of OFDM transmission has 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 mentioned above in the previous paragraph, control message fields can be evenly distributed among different spatial streams, or the size of the control message fields for each spatial stream based on the modulation and encoding 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 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 beam forming 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 address spatial multiplexing when different ranks are determined for the control message format and traffic data. Equation (1) can be modified by adding the _{uplink rank specific parameter ΔR DC} , which determines 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 ACK / NACK message rank is 1 (beam formation or transmit diversity), ΔRD-C is 2 (2/1), and the equation. (1) has the form of the following equation after this modification.

Without modification, the control message field would not be assigned the correct number of symbols or subcarriers for different rank reasons. To take advantage of beam formation or transmit diversity for a control message field, preferably the same subcarrier occupies the same subcarrier in all spatial streams, so that the same subcarrier occupies the same subcarrier in all spatial streams. Assigned to the control message field of. The signal processor that performs beam formation 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 the symbol, a reverse operation is performed in the receiver, i.e. the signal processor performing beam formation in the receiver has a coefficient determined based on the determined spatial weighting. , The signal streams received from multiple antennas are multiplied and the symbols transmitted on the same subcarrier of different streams are combined.

FIG. 7 shows the above embodiment in which a ACK / NACK message is transmitted from a transmitter to a receiver through a single spatial transmit stream by using beam forming techniques to direct the stream to the desired spatial channel. There is. 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 made within the receiver so that the received signal is weighted so that ACK / NACK primarily amplifies the received spatial direction. To obtain higher data rates, data traffic is transmitted by using spatial multiplexing, and different data is transmitted / received through different transmit / receive branches and antennas. In transmitters and receivers, multiplex 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 beam formation, transmission diversity, and spatial multiplexing can be made at the subcarrier level. In such cases, it is preferred that the same symbol be mapped to the same carrier within each transmit branch within the transmitter, as described above. When the uplink transmission scheme is SC-FDMA, the choice between beam formation and transmission diversity and spatial multiplexing can be made on the SC-FDMA symbol level, as each subcarrier occupies the entire frequency spectrum. it can. The resolution of choices between beam formation and transmission diversity and spatial multiplexing can be made for each SC-FDMA symbol or for multiple SC-FDMA symbols at once, such as time slots or subframes. .. If the SC-FDMA symbol carries a control message that requires high reliability, the SC-FDMA symbol can be transmitted by using beam forming or transmission diversity, and the same data can be obtained in the transmitter. It is transmitted from all antenna branches of, and is received through all antenna branches in the receiver. Next, the interleave pattern determination and the mapping of symbols to the subcarriers are performed evenly 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. carrying different information. Multiple SC-FDMA symbols can be transmitted simultaneously through different spatial streams.

The use of beam formation in the transmission of control messages generally requires feedback information from the receiver regarding channel characteristics. When feedback information is not available, embodiments of the present invention include open-loop multiple antenna transmission diversity schemes, such as space-time block coding, to improve the reliability of transmission of critical control information. Transmit at least part of the control message field by using pre-coded vector switching, frequency selective transmission diversity, or cyclic retardation diversity that uses large or small retardation. Implementation of the open-loop transmission diversity schemes listed above is apparent to those of skill in the art and does not require substantial modifications to the embodiments described above. To send data traffic faster, data traffic can be sent by using spatial multiplexing.

As described above, the embodiment 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 corresponding device included in the user terminal or base station. The processor is configured to allocate control message fields to PUSCH resources according to the selected uplink transmission method so as to optimize the transmission performance of the control message in the selected uplink transmission method. The device can be the processors 700, 702 illustrated in FIG. If no multiple antenna transmission is used in the uplink transmission, the processor 700 of the user terminal is simplified in the sense that it does not perform multiple antenna signal processing. The processor can be a logical component implemented by multiple physical signal processing units. The term "processor" means a device capable of processing data. Processors can include electronic circuits that perform the required functions and / or microprocessors that run computer programs that perform the required functions. When designing an implementation, one of ordinary skill in the art will consider, for example, device size and power consumption, required processing functions, manufacturing costs, and requirements for production volume. Processors can include logical components, standard integrated circuits, microprocessors, and / or application specific integrated circuits (ASICs).

The microprocessor implements the function of a central processing unit (CPU) on an integrated circuit. The CPU is a logical machine that executes a computer program including program instructions. Program instructions can be encoded as computer programs that use high-level programming words such as C, Java®, or programming languages that can be low-level programming languages 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 multiple microinstructions for basic operations. The implementation of microinstruction can be different depending on the CPU design. The microprocessor can have an operating system (a dedicated operating system for embedded systems, or a real-time operating system) that can provide computer programs with 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, the specifications of mobile telephone communication systems, these network elements, and subscriber terminals are evolving rapidly. Such developments may require additional changes to the embodiments described. Therefore, all terms and expressions should be construed in a broad sense and are intended to exemplify rather than limit 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 various ways as technology advances. The present invention and embodiments thereof are not limited to the above-described examples, and can be modified within the scope of the claims.

400 Start 402 Uplink transmission method selection 406 Control message field assignment

Claims (24)

In a method of multiple input multiple output (MIMO) uplink transmission performed by a user terminal, the method is:
Sending the first plurality of symbols through the first spatial stream,
as well as,
Sending a second plurality of symbols through a second spatial stream,
Including
The first plurality of symbols correspond to the first plurality of control message fields, and the first plurality of control message fields as a whole correspond to the modulation and coding method in use for the first spatial stream. Have a size based on before modulation and encoding ,
The second plurality of symbols correspond to the second plurality of control message fields, and the second plurality of control message fields as a whole correspond to the modulation and coding method in use for the second spatial stream. Have a size based on before modulation and encoding ,
The modulation and coding method of the first spatial stream is different from the modulation and coding method of the second spatial stream, and the overall size of the first plurality of control message fields is different from that of the second plurality of control message fields. Unlike the overall size of the control message field
Each of the first and second control message fields is at least an acknowledgment (ACK / NACK) message, a rank indicator (RI), a pre-encoded matrix indicator (PMI), or a channel quality indicator (CQI) message. A method comprising one. The method of claim 1, further comprising transmitting the first and second spatial streams through at least two antennas. A claim in which at least one of the first or second control message fields includes an acknowledgment (ACK / NACK), a rank indicator (RI), a pre-encoded matrix indicator (PMI), and a channel quality indicator (CQI). Item 1. The method according to item 1. The method of claim 1, wherein the first and second plurality of control message fields are transmitted via a physical uplink shared channel (PUSCH). The method of claim 4, further comprising transmitting data traffic via the PUSCH. The method of claim 5, wherein at least a portion of the first and second plurality of control message fields is transmitted using transmit diversity and at least a portion of the data traffic is simultaneously transmitted using spatial multiplexing. .. Sending the first and second plurality of symbols includes allocating each control message field of the first and second plurality of control message fields to one or more resource elements, and the first and second plurality of symbols are transmitted. The method of claim 1, wherein the second plurality of symbols are assigned to one or more resource elements. The method of claim 1, further comprising receiving from a base station instructions on the modulation and coding scheme in use for each of the spatial streams. A user terminal capable of multiple input and multiple output (MIMO) uplink transmission, and the user terminal is
Sending the first plurality of symbols via the first spatial stream,
as well as,
It comprises a transmitter configured to transmit a second plurality of symbols over a second spatial stream.
The first plurality of symbols correspond to the first plurality of control message fields, and the first plurality of control message fields as a whole correspond to the modulation and coding method in use for the first spatial stream. Have a size based on before modulation and encoding ,
The second plurality of symbols correspond to the second plurality of control message fields, and the second plurality of control message fields as a whole correspond to the modulation and coding method in use for the second spatial stream. Have a size based on before modulation and encoding ,
The modulation and coding method of the first spatial stream is different from the modulation and coding method of the second spatial stream, and the overall size of the first plurality of control message fields is different from that of the second plurality of control message fields. Unlike the overall size of the control message field
The plurality of control message fields are characterized by comprising at least one of an acknowledgment (ACK / NACK) message, a rank indicator (RI), a pre-encoded matrix indicator (PMI), or a channel quality indicator (CQI) message. User terminal to do. In the user terminal according to claim 9.
With at least two additional antennas
The transmitter is a user terminal further configured to transmit the first and second spatial streams through the at least two antennas. In the user terminal according to claim 9, at least one of the first or second plurality of control message fields is an acknowledgment (ACK / NACK), a rank indicator (RI), a pre-encoded matrix indicator (PMI), and the like. And user terminals that include a channel quality indicator (CQI). The user terminal according to claim 9, wherein the first and second plurality of control message fields are transmitted via a physical uplink shared channel (PUSCH). The user terminal according to claim 12, wherein the transmitter is further configured to transmit data traffic via the PUSCH. In the user terminal according to claim 13, at least a part of the first and second plurality of control message fields is transmitted using transmission diversity, and at least a part of the data traffic is simultaneously using spatial multiplexing. User terminal to be transmitted. In the user terminal according to claim 9, each control message field of the first and second plurality of control message fields is assigned to one or more resource elements, and the first and second plurality of symbols are assigned. A user terminal assigned to one or more resource elements. The user terminal according to claim 9, further comprising a receiver configured to receive an instruction of a modulation and coding method in use for each of the spatial streams from a base station. On the computer
Procedure for transmitting the first plurality of symbols via the first spatial stream,
as well as,
Procedure for transmitting a second plurality of symbols via a second spatial stream,
A computer-readable recording medium on which a program for executing a program is recorded.
The first plurality of symbols correspond to the first plurality of control message fields, and the first plurality of control message fields as a whole correspond to the modulation and coding method in use for the first spatial stream. Have a size based on before modulation and encoding ,
The second plurality of symbols correspond to the second plurality of control message fields, and the second plurality of control message fields as a whole correspond to the modulation and coding method in use for the second spatial stream. Have a size based on before modulation and encoding ,
The modulation and coding method of the first spatial stream is different from the modulation and coding method of the second spatial stream, and the overall size of the first plurality of control message fields is different from that of the second plurality of control message fields. Unlike the overall size of the control message field
A recording medium in which the plurality of control message fields include at least one of an acknowledgment (ACK / NACK) message, a rank indicator (RI), a pre-encoded matrix indicator (PMI), or a channel quality indicator (CQI) message. In the recording medium of claim 17, the program further comprises a procedure of transmitting the first and second spatial streams through the at least two antennas. In the recording medium according to claim 17, at least one of the first or second plurality of control message fields is an acknowledgment (ACK / NACK), a rank indicator (RI), a pre-encoded matrix indicator (PMI), and the like. And a recording medium containing a channel quality indicator (CQI). The recording medium according to claim 17, wherein the first and second plurality of control message fields are transmitted via a physical uplink shared channel (PUSCH). The recording medium according to claim 20, wherein the program further comprises a procedure for transmitting data traffic via the PUSCH. In the recording medium of claim 21, at least a portion of the first and second plurality of control message fields is transmitted using transmit diversity, and at least a portion of the data traffic is simultaneously using spatial multiplexing. Recording medium to be transmitted. In the recording medium according to claim 17, the procedure for transmitting the first and second plurality of symbols sets each control message field of the first and second plurality of control message fields into one or more resource elements. A recording medium in which the first and second plurality of symbols are assigned to one or more resource elements, including a procedure for assigning to one or more resource elements. The recording medium according to claim 17, wherein the program further includes a procedure for receiving an instruction of a modulation and coding method in use for each of the spatial streams from a base station.

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