JP5107337B2 - Base station and method used in mobile communication system - Google Patents

Description

  The present invention relates to a mobile communication system that applies orthogonal frequency division multiplexing (OFDM) in the downlink, and more particularly, to a base station apparatus and a communication control method.

  Long Term Evolution (LTE) has been studied by W-CDMA standardization organization 3GPP as a successor to W-CDMA and HSDPA, and as a radio access system, downlink is OFDM and uplink SC-FDMA (Single-Carrier Frequency Multiple Access) has been studied (see, for example, Non-Patent Document 1).

  OFDM is a method in which a frequency band is divided into a plurality of narrow frequency bands (subcarriers) and data is transmitted on each frequency band, and the subcarriers interfere with each other even though they partially overlap on the frequency. By arranging them closely, it is possible to achieve high-speed transmission and increase frequency utilization efficiency.

  SC-FDMA is a transmission method that can reduce interference between terminals by dividing a frequency band and performing transmission using different frequency bands among a plurality of terminals. Since SC-FDMA has a feature that fluctuations in transmission power are reduced, it is possible to realize low power consumption and wide coverage of a terminal.

  LTE is a system in which one or two or more physical channels are shared by a plurality of mobile stations for both uplink and downlink. The channel shared by the plurality of mobile stations is generally referred to as a shared channel, and in LTE, it is a Physical Uplink Shared Channel (PUSCH) in the uplink and a Physical Downlink Shared Channel (PDSCH) in the downlink. .

In a communication system using a shared channel as described above, signaling (notification) indicating to which mobile station the shared channel is allocated for each transmission time interval or subframe (TTI: Time Transmission Interval). There is a need to. The control channel (control signal) used for the signaling is called a downlink L1 / L2 control channel or a downlink L1 / L2 control signal in LTE. The DL L1 / L2 control channel information items include, for example, a DL L1 / L2 control channel format indicator (DL L1 / L2 Control Channel Format Indicator), a downlink scheduling grant (Downlink Scheduling Grant), an ACK / NACK, and an uplink scheduling grant. (UL Scheduling Grant), an overload indicator (Overload Indicator), a transmission power control command bit (TPC: Transmission Power Control Command Bit) may be included (these control information items are described in Non-Patent Document 2, for example) ing). The DL L1 / L2 Control Format Indicator described above is Physical
Also called Control Format Indicator Channel (PCFICH), the ACK / NACK is Physical Hybrid.
ARQ Indicator Channel
Also called (PHICH). The PCFICH and PHICH are not included in the PDCCH, but may be defined as different physical channels that have a parallel relationship with the PDCCH.

  In addition, the downlink scheduling grant includes, for example, downlink resource block (Resource Block) allocation information, UE ID, number of streams, information on precoding vector, data size, modulation scheme, and HARQ. Information etc. may be included. The downlink scheduling grant may be referred to as DL Assignment Information, DL Scheduling Grant, or DL Scheduling Information. The uplink scheduling grant includes, for example, uplink resource block (or resource unit) allocation information, UE ID, data size, modulation scheme, uplink transmission power information, and demodulation reference signal (Demodulation Reference Signal). Etc. may be included.

Here, the DL L1 / L2 control format indicator is information for notifying the format of the DL L1 / L2 control channel. Specifically, the DL L1 / L2 control format indicator indicates the DL L1 / L2 control channel format. The number of OFDM symbols to be mapped is notified. In LTE, the number of OFDM symbols mapped to the DL L1 / L2 control channel is one of 1, 2, and 3. Further, the DL L1 / L2 control channel is mapped from the first OFDM symbol in the TTI (Non-patent Document 3).
In general, in mobile communication, there is a pilot signal for use in channel estimation and measurement of radio quality, and this pilot signal is called a downlink reference signal (DL RS) in LTE. The DL RS is generally mapped to an OFDM symbol to which a DL L1 / L2 control channel may be mapped. The DL L1 / L2 control channel is generally mapped to the third OFDM symbol from the beginning of the TTI, and the DL RS is generally mapped to the OFDM symbol at the beginning of the TTI (Non-patent Document 3).

  The downlink reference signal in LTE is expressed by a two-dimensional sequence, and is composed of a two-dimensional orthogonal sequence and a two-dimensional pseudo-random sequence (Pseudo Random Sequence). The mapping (subcarrier number) of the reference signal to the physical resource is expressed by the following equation (Non-patent Document 3):

ここで、ｋはサブキャリア番号を示し、ｌはOFDMシンボル番号を示し、iはスロット番号を示す。ｍは次のような整数値をとる。

Here, k indicates a subcarrier number, l indicates an OFDM symbol number, and i indicates a slot number. m takes an integer value as follows.

ここで、ｐはアンテナポート番号を示し、１アンテナしか使用しない場合はｐ＝０であるが、４アンテナ使用可能な場合は、ｐ＝０，１，２，３の値をとり得る。

Here, p represents an antenna port number. When only one antenna is used, p = 0. When four antennas can be used, p = 0, 1, 2, 3 can be taken.

  In the above formula, the value of ν is determined as follows:

ここで、f_hop(j)はセル固有の整数の系列であり、下りリファレンス信号のサブフレーム毎に又はスロット毎に変わるホッピングパターンを表す。すなわち、セル毎にf_hop(j)を変更することで、下りリファレンス信号をセル毎に異なるサブキャリアにマッピングすることが可能になる。

Here, f _hop (j) is a series of integers unique to the cell, and represents a hopping pattern that changes for each subframe of the downlink reference signal or for each slot. That is, by changing f _hop (j) for each cell, the downlink reference signal can be mapped to different subcarriers for each cell.

Note that f _hop (j) may be a fixed value that does not depend on time. When such a fixed value is set for each cell, the downlink reference signal has a mapping shifted by a fixed value that is different for each cell.

FIG. 1 shows an example of reference signal mapping. Mapping to the physical resource when the antenna port number is 0 (p = 0) and f _hop (j) is always 0 (left side), and the antenna port number is 0 (p = 0) In addition, mapping to the physical resource (right side) when f _hop (j) is always 2 is shown. As shown in the figure, in the former case, in the first OFDM symbol (l = 0), a downlink reference signal is mapped to k = 6 × j (j: integer of 0 or more) th subcarrier. However, in the latter case, k = 6 × j + 2 in the first OFDM symbol (l = 0)
A downlink reference signal is mapped to the (j: integer greater than or equal to 0) th subcarrier. In this way, the downlink reference signal in LTE is mapped to different subcarriers for each cell by appropriately setting f _hop (j).
3GPP TR 25.814 (V7.0.0), “Physical Layer Aspects for Evolved UTRA,” June 2006 R1-070103, DownlinkL1 / L2 Control Signaling Channel Structure: Coding 3GPP TR 36.211 (V0.3.1), “Physical Channels and Modulation,” November 2006

  As described above, the reference signal and the L1 / L2 control signal are mapped to a specific subcarrier of a specific OFDM symbol. Since the reference signal is the basis for channel estimation on the receiving side (typically, a user apparatus), the mapping position greatly affects the channel estimation accuracy. Therefore, as described above, the L1 / L2 control signal needs to be appropriately mapped according to the mapping position of the reference signal shifted in the frequency direction or hopped in the time axis direction. However, such mapping methods do not appear to be well studied so far.

  An object of the present invention is to use a base station, a user apparatus, and a base station for appropriately mapping an L1 / L2 control signal in a next-generation mobile communication system in which a mapping position of a reference signal changes in a frequency direction and a time direction. Is to provide a method.

  In the present invention, a base station that uses the OFDM scheme in the downlink is used. The base station includes means for generating a transmission signal using OFDM symbols including the first signal and the second signal, and transmission means for transmitting the transmission signal to the mobile station. The subcarrier to which the second signal is mapped is determined based on the position of the subcarrier to which the first signal is mapped.

More specifically, the subcarrier number X to which the reference signal is mapped is expressed by a first equidistant sequence having a predetermined first number n _shift as a first term and a predetermined second number as a tolerance. Of the control information included in the OFDM symbol including the reference signal, the subcarrier number to which the predetermined control information is mapped has a third number obtained by adding a predetermined number to the first number n _shift as a first term and has a predetermined number of subcarrier numbers. It is represented by a second series of differential numbers with a tolerance of 4 numbers.

  According to the present invention, in the next generation mobile communication system in which the mapping position of the reference signal changes in the frequency direction and the time direction, mapping of the L1 / L2 control signal can be performed appropriately.

It is a figure which shows the example of a mapping of a downlink reference signal. It is a block diagram which shows the structure of the mobile communication system concerning the Example of this invention. It is explanatory drawing which shows the structure of TTI. It is a figure which shows a mode that a L1 / L2 control channel is mapped by OFDM symbol # 1 and # 2. It is a figure which shows the correspondence of a resource block and a resource block group. It is a figure which shows another correspondence of a resource block and a resource block group. It is a partial block diagram which shows the base station apparatus which concerns on one Example of this invention. It is a block diagram which shows the baseband part of the base station apparatus which concerns on one Example of this invention. It is a figure which shows the subcarrier of the downlink L1 / L2 control channel format indicator. It is a figure which shows the subcarrier of UL-ACK / NACK. It is a figure which shows the subcarrier of an overload indicator. It is a figure which shows the subcarrier of a TPC control bit. It is a partial block diagram which shows the mobile station which concerns on one Example of this invention.

Explanation of symbols

50 cells 100 ₁ , 100 ₂ , 100 ₃ , 100 _n mobile station 102 transmission / reception antenna 104 amplifier unit 106 transmission / reception unit 108 baseband processing unit 110 call processing unit 112 application unit 200 base station device 202 transmission / reception antenna 204 amplifier unit 206 transmission / reception unit 208 Baseband processing section 210 Call processing section 212 Transmission path interface 2081 Layer 1 processing section 2082 MAC processing section 2083 RLC processing section 2084 Subcarrier mapping determination section 2085 DL L1 / L2 Control CH transmission power control section 300 Access gateway apparatus 400 Core network

  Next, the best mode for carrying out the present invention will be described based on the following embodiments with reference to the drawings. In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

  A mobile communication system to which a base station apparatus according to an embodiment of the present invention is applied will be described with reference to FIG.

The mobile communication system 1000 is a system to which, for example, Evolved UTRA and UTRAN (also known as Long Term Evolution or Super 3G) is applied, and includes a base station apparatus (eNB: eNode B) 200 and a plurality of mobile stations (UE: User). Equipment) 100 _n (100 ₁ , 100 ₂ , 100 ₃ ,... 100 _n , n is an integer of n> 0). Base station apparatus 200 is connected to an upper station, for example, access gateway apparatus 300, and access gateway apparatus 300 is connected to core network 400. Here, the mobile station 100 _n communicates with the base station apparatus 200 in the cell 50 using Evolved UTRA and UTRAN.

  The mobile communication system 1000 can operate with a plurality of variable bandwidths. As an example, such variable bandwidths are provided such as 5 MHz, 10 MHz and 20 MHz. An operator operates one or more of the variable bandwidths as a system band, and a user in the system has one or more resource blocks (for example, 25 resource blocks are prepared in a system band of 5 MHz). Can be used for communication.

Hereinafter, since the mobile station 100 _n (100 ₁ , 100 ₂ , 100 ₃ ,... 100 _n ) has the same configuration, function, and state, the following description will be given as the mobile station 100 _n unless otherwise specified. To proceed. Note that the mobile station may be referred to as a user apparatus.

  The mobile communication system 1000 uses OFDM (Orthogonal Frequency Division Multiple Access) for the downlink and SC-FDMA (Single Carrier-Frequency Division Multiple Access) for the uplink as radio access schemes. As described above, OFDM is a scheme in which a frequency band is divided into a plurality of narrow frequency bands (subcarriers) and data is transmitted on each frequency band. SC-FDMA is a transmission method that can reduce interference between terminals by dividing a frequency band and performing transmission using different frequency bands among a plurality of terminals.

As described above, for the downlink, the downlink shared physical channel (PDSCH) shared by each mobile station 100 _n and the downlink control channel Physical for LTE are used.
Downlink Control Channel (PDCCH) is used. The downlink control channel for LTE is called a downlink L1 / L2 control channel or a downlink L1 / L2 control signal (DL L1 / L2 Control Channel).

For the uplink, an uplink shared physical channel (PUSCH) shared by each mobile station 100 _n and an uplink control channel for LTE are used. There are two types of uplink control channels: channels that are time-multiplexed to the uplink shared physical channel and channels that are frequency-multiplexed. The latter is transmitted in a dedicated band separately from the uplink shared physical channel.

  In the uplink, downlink quality information (CQI: Channel Quality Indicator) and downlink shared physical channel delivery confirmation information (HARQ ACK information) are transmitted by the uplink control channel for LTE. The downlink quality information (CQI) is used to determine the resource allocation (scheduling) of the shared physical channel in the downlink and the Modulation and Coding Scheme (MCS) level of Adaptive Modulation and Coding (AMC). Also used.

  In downlink transmission, as illustrated in FIG. 3, 1 TTI is, for example, 1 ms, and, for example, 14 OFDM symbols are included in 1 TTI. 1TTI may be referred to as 1Sub-frame. The DL L1 / L2 control channel is mapped to some OFDM symbols from the beginning of 1 TTI. The maximum number of OFDM symbols to which the DL L1 / L2 control channel is mapped is 3. The DL L1 / L2 control channel is mapped to OFDM symbol # 1, mapped to OFDM symbols # 1 and # 2, and mapped to OFDM symbols # 1, # 2 and # 3. To be mapped. In FIG. 3, the DL L1 / L2 control channel is mapped to the first two OFDM symbols (# 1, # 2) of 1TTI. A data signal, a shared data channel (SCH), a broadcast channel (BCH), and the like are transmitted in the OFDM symbol to which the DL L1 / L2 control channel is not mapped. Also, M resource blocks (RBs) are prepared in the frequency direction. As an example, the frequency band per resource block is 180 kHz, and there are 12 subcarriers in one resource block. For convenience of explanation, a resource occupying a band of one subcarrier and a period of one OFDM symbol is called a “resource element”. The number M of resource blocks is 25 when the system bandwidth is 5 MHz, 50 when the system bandwidth is 10 MHz, and 100 when the system bandwidth is 20 MHz.

  FIG. 4 shows an example of subcarrier mapping for OFDM symbols # 1 and # 2 in the case of the TTI configuration of FIG. In FIG. 4, the total number of subcarriers in one OFDM symbol is L, and subcarriers # 1, # 2,..., #L are numbered from the lowest frequency. When the system bandwidth is 5 MHz, L = 300, when the system bandwidth is 10 MHz, L = 600, and when the system bandwidth is 20 MHz, L = 1200. As shown in the figure, a downlink reference signal (DL RS) and a DL L1 / L2 control channel are mapped to subcarriers of OFDM symbol # 1. DL RS is transmitted at a rate of one for every six subcarriers. In FIG. 4, DL RS is mapped to the subcarrier whose subcarrier number is 6 × m + 1 (where m: 0, 1, 2,...). The configuration of OFDM symbol # 3 when the number of OFDM symbols mapped to the DL L1 / L2 control channel is 3 is basically the same as the configuration of OFDM symbol # 2 in FIG.

  The following outlines the information items that may be included in the DL L1 / L2 control channel.

The DL L1 / L2 control channel may include a DL L1 / L2 control channel format indicator, control information for downlink communication, and / or control information for uplink communication. The DL L1 / L2 control channel format indicator is Physical
It may also be referred to as Control Format Indicator Channel (PCFICH). The control information for downlink communication may be referred to as Downlink Scheduling Information, Downlink Scheduling Grant, or Downlink Assignment Information. The control information for uplink communication may be called Uplink Scheduling Grant.

  The DL L1 / L2 control channel format indicator indicates how many symbols the downlink L1 / L2 control channel occupies in one subframe. In LTE, it is one of 1, 2, 3 OFDM symbols and is represented by 2 bits. As an example, this indicator is represented by (0, 0) when it occupies 1 OFDM symbol, is represented by (0, 1) when it occupies 2 OFDM symbol, and is represented by (1, 0) when it occupies 3 OFDM symbol. Is done.

  The control information for downlink communication may include downlink resource allocation information, downlink MIMO information, transmission format information, retransmission control information, and user identification information.

  The downlink resource allocation information expresses which resource block is used for transmission of the downlink data signal. Many resource blocks included in the system band are grouped into several groups. Each group includes a predetermined number of resource blocks.

  FIG. 5 shows that the system bandwidth is 5 MHz, and all 25 resource blocks are grouped into 10 groups (RB group # 0 to # 9). The groups including only one resource block are two groups # 0 and # 9. Groups including two resource blocks are three groups # 1, # 4, and # 8. Groups including three resource blocks are # 2, # 3, and # 6. Two groups including four resource blocks are # 5 and # 7. For each of these groups, permission / inhibition of use is expressed in a bitmap format. In other words, in the illustrated example, the resource allocation information is represented by 10 bits, and each bit indicates whether or not the resource block of the corresponding group may be used. The correspondence relationship between the resource block and the group number may be different for each cell as well as for each system bandwidth. For example, grouping as shown in FIG. 6 may be performed instead of the grouping shown in FIG.

  The downlink MIMO information includes information on the number of streams, precoding vectors, and the like when multi-input multi-output communication or multi-antenna communication is performed.

  The transmission format information specifies what the combination of the data modulation scheme and the channel coding scheme is. As an example, the data modulation scheme may be selected from QPSK, 16QAM, and 64QAM. The channel coding scheme may be determined from the data modulation scheme and payload data size. Alternatively, not the channel coding scheme but the payload size itself may be included in the transmission format information.

  Retransmission control information (HARQ: Hybrid Automatic Repeat reQuest) represents information when hybrid ARQ is performed. The retransmission control information may include a process number, a new data indicator, the number of retransmission sequences, and the like.

  User identification information (UE ID) is identification information of a mobile station. User identification information may be managed for each cell. Further, the user identification information may include provisional identification information used in RACH, or may include a user group ID specified by a paging indicator.

  Control information for uplink communication includes uplink resource allocation information, transmission format information, demodulation reference signal information, transmission power control information, user identification information, uplink acknowledgment information (ACK / NACK), overload indicator, A transmission power control command bit may be included.

  The uplink resource allocation information indicates which resource block can be used for uplink data transmission. Since the single carrier scheme is used in the uplink, one or more resource blocks to be allocated are continuously specified. In other words, the start point and end point of the allocated resource block are designated.

  The transmission format information specifies a combination of a data modulation scheme and a channel coding scheme used for uplink communication.

  The information of the reference signal for demodulation indicates what signal is used for the reference signal.

  The transmission power control information indicates how much the transmission power of the uplink shared data channel should differ from the transmission power of the sounding reference signal. In LTE, a reference signal (sounding reference signal) is periodically transmitted to a base station with a bandwidth over the entire system band. The base station controls the transmission power of the sounding reference signal according to the reception level or reception quality of the sounding reference signal. This control is performed by increasing or decreasing the next uplink transmission power by the transmission power control command bit.

  User identification information (UE ID) is identification information of a mobile station. User identification information may be managed for each cell. Further, the user identification information may include provisional identification information used in RACH, or may include a user group ID specified by a paging indicator.

  The acknowledgment information (ACK / NACK) regarding the uplink indicates whether data transmitted from the user apparatus in the past in the uplink has been properly received by the base station.

  The overload indicator is notified to neighboring cells when the other cell interference caused by the user equipment in another cell exceeds a predetermined value, and the notification is a signal for the user equipment in the other cell to reduce the transmission power. is there.

  The transmission power control command bit indicates that the next transmission power of the sounding reference signal periodically transmitted from the user apparatus should be increased or decreased from the current value. The transmission power of the sounding reference signal is the basis for determining the transmission power of the uplink L1 / L2 control channel and the uplink data channel. These are determined by adding the offset power specified by the base station to the transmission power of the sounding reference signal. In some cases, an overload indicator may be taken into account.

  A base station apparatus 200 according to an embodiment of the present invention will be described with reference to FIG.

  The base station apparatus 200 according to the present embodiment includes a transmission / reception antenna 202, an amplifier unit 204, a transmission / reception unit 206, a baseband signal processing unit 208, a call processing unit 210, and a transmission path interface 212.

Packet data to be transmitted from the base station apparatus 200 to the mobile station 100 _n via the downlink is baseband signal processing from the upper station located above the base station apparatus 200, for example, the access gateway apparatus 300 via the transmission path interface 212. Input to the unit 208.

  The baseband signal processing unit 208 performs processing in the PDLC layer, packet data division processing, combining processing, RLC (Radio Link Control) retransmission control transmission processing such as RLC layer transmission processing, MAC retransmission control processing, etc. The processed signal is transferred to the transmission / reception unit 206. The processing in the baseband signal processing unit 208 includes, for example, HARQ transmission processing, scheduling, transmission format selection, channel encoding, inverse fast Fourier transform (IFFT) processing, and the like. As will be described later, the baseband signal processing unit 208 determines the number of OFDM symbols to which the DL L1 / L2 control channel is mapped for each TTI, maps the DL L1 / L2 control channel to subcarriers, DL L1 / L2 Transmission power control and the like regarding the L2 control channel are performed.

  The transmission / reception unit 206 performs frequency conversion processing for converting the baseband signal output from the baseband signal processing unit 208 into a radio frequency band, and then is amplified by the amplifier unit 204 and transmitted from the transmission / reception antenna 202.

On the other hand, for data transmitted from the mobile station 100 _n to the base station apparatus 200 via the uplink, a radio frequency signal received by the transmission / reception antenna 202 is amplified by the amplifier unit 204, and frequency-converted by the transmission / reception unit 206. The signal is converted into a signal and input to the baseband signal processing unit 208.

  In the baseband signal processing unit 208, the input baseband signal is subjected to FFT processing, IDFT processing, error correction decoding, MAC retransmission control reception processing, RLC layer reception processing, PDCP layer processing, and the like. It is transferred to the access gateway device 300 via the route interface 212.

  The call processing unit 210 performs state management of the radio base station 200 and resource allocation.

  The configuration of the baseband signal processing unit 208 will be described with reference to FIG.

  The baseband signal processing unit 208 includes a layer 1 processing unit 2081, a MAC (Medium Access Control) processing unit 2082, an RLC processing unit 2083, a subcarrier mapping determination unit 2084, and a DL L1 / L2 control CH transmission power control unit 2085. Is provided.

  In the baseband signal processing unit 208, the layer 1 processing unit 2081, the MAC processing unit 2082, the RLC processing unit 2083, the subcarrier mapping determination unit 2084, the DL L1 / L2 control CH transmission power control unit 2085, and the call processing unit 210 are mutually connected. It is connected.

  The layer 1 processing unit 2081 performs channel coding and IFFT processing of data transmitted in the downlink, channel decoding, IDFT processing, FFT processing, and the like of data transmitted in the uplink. The layer processing unit 2081 maps the DL L1 / L2 control channel information to the subcarriers based on the subcarrier information notified from the subcarrier mapping determination unit 2084. In the OFDM symbol in which the DL RS is transmitted, the DL RS is mapped to a predetermined subcarrier. Also, the layer 1 processing unit 2081, based on the transmission power information notified from the DL L1 / L2 control CH transmission power control unit 2085, transmits the transmission power (per unit band) of the subcarrier to which the DL L1 / L2 control channel is mapped. Transmission power density or power density per subcarrier). Further, the layer 1 processing unit 2081 sets the transmission power of the subcarrier to which the DL RS is mapped. Here, the transmission power of the subcarrier to which the DL RS is mapped may be set by, for example, signaling from an upper node, or a value held as a parameter in the device of the base station device 200 May be set by referring to.

  The MAC processing unit 2082 performs downlink data MAC retransmission control, for example, HARQ transmission processing, scheduling, transmission format selection, frequency resource allocation, and the like. Here, the scheduling refers to a process of selecting a mobile station that transmits a data signal using a shared channel in the TTI. For example, round robin or proportional fairness is used as an algorithm for the selection. Also good. The selection of a transmission format refers to determining a modulation scheme, a coding rate, and a data size regarding a data signal to be transmitted to a mobile station selected in scheduling. The modulation scheme, coding rate, and data size are determined based on, for example, CQI reported from the mobile station in the uplink. Furthermore, the frequency resource allocation refers to a process of determining a resource block (RB) used for transmission of a data signal to be transmitted to a mobile station selected in scheduling. The resource block is determined based on, for example, CQI reported from the mobile station in the uplink.

  Also, the MAC processing unit 2082 performs reception processing and scheduling of uplink data MAC retransmission control, selection of a transmission format, allocation of frequency resources, and the like.

  In the RLC processing unit 2083, RLC layer transmission processing such as division / combination and transmission processing of RLC retransmission control for downlink packet data, RLC processing such as division / combination for uplink data, reception processing of RLC retransmission control, etc. Layer reception processing is performed. The RLC processing unit 2083 may further perform PDCP layer processing.

  The subcarrier mapping determination unit 2084 determines the number of OFDM symbols to which the DL L1 / L2 control channel is mapped and the subcarrier to which the DL L1 / L2 control channel is mapped for each TTI. The determined subcarrier number to which the DL L1 / L2 control channel is mapped is notified to the layer 1 processing unit 2081 as subcarrier information. Also, the subcarrier mapping determination unit 2084 notifies the layer 1 processing unit 2081 of the number of OFDM symbols to which the DL L1 / L2 control channel is mapped. For example, the subcarrier mapping determination unit 2084 determines the number of OFDM symbols to which the DL L1 / L2 control channel is mapped based on the number of downlink scheduling grants and uplink scheduling grants transmitted by the DL L1 / L2 control channel in the TTI. You may decide.

  The subcarrier mapping determination unit 2084 determines a subcarrier to which the DL L1 / L2 control channel is mapped based on the number of OFDM symbols to which the DL L1 / L2 control channel is mapped.

  Next, how the reference signal and the L1 / L2 control signal are mapped will be described in more detail.

In general, in an OFDM symbol to which a reference signal is mapped, the reference signal is mapped at a rate of one for every six subcarriers. If the subcarrier number to which the reference signal is mapped is X, X is
X = 6m + n _shift
It can be expressed as m is an integer of 0 or more. n _shift is an amount set for each cell, and 0, 1,. . . , 5 takes any value. More generally, n _shift is expressed by [ν + f _hop (j)] mod 6 (j is the maximum number among integers not exceeding i / 2) as described in “Background Art”. The

  The L1 / L2 control channel is mapped to subcarriers other than the subcarrier to which the reference signal is mapped. For convenience of explanation, a subcarrier number to which a downlink L1 / L2 control channel format indicator, an uplink ACK / NACK, an overload indicator, and a transmission power control command are mapped will be described. Other information items (downlink and uplink scheduling grants) of the L1 / L2 control channel are mapped to other subcarriers.

  The downlink L1 / L2 control channel format indicator is expressed by 2 bits as described above, and specifies whether the number of OFDM symbols occupied by the L1 / L2 control channel in the TTI is 1, 2 or 3. Two bits representing the downlink L1 / L2 control channel format indicator are encoded at a coding rate of 1/4 and converted to 8 bits. These 8 bits are modulated by the QPSK system, converted into four data symbols (QPSK symbols), and notified to the user apparatus. These four data symbols are mapped to the first OFDM symbol of 1 TTI.

  FIG. 9 shows subcarrier numbers to which four QPSK symbols are mapped for each variable frequency band (system band).

For system bandwidth of 5MHz,
66q + 52 + n _shift , (q = 0, 1, 2, 3)
Four data symbols are mapped to the subcarrier numbers expressed by the arithmetic sequence.

For system bandwidth of 10MHz,
2 × (66q + 52) + n _shift , (q = 0, 1, 2, 3)
Four data symbols are mapped to the subcarrier numbers expressed by the arithmetic sequence.

For system bandwidth of 20MHz,
4 × (66q + 52) + n _shift , (q = 0, 1, 2, 3)
Four data symbols are mapped to the subcarrier numbers expressed by the arithmetic sequence.

  In the illustrated example, the tolerance of an arithmetic sequence in one variable bandwidth (for example, 10 MHz, 20 MHz) is an integral multiple (66 × 2, 66 × 4) of the tolerance of the arithmetic sequence in another variable bandwidth (5 MHz). It is.

  The uplink acknowledgment information (ACK / NACK) is spread with a different spreading factor depending on the system bandwidth and mapped to a predetermined subcarrier in the OFDM symbol. For example, when the system bandwidth is 5 MHz, 10 MHz, and 20 MHz, the spreading factor is determined as 8, 16, 32, respectively. Since ACK / NACK itself can be expressed by 1 bit, the number of bits after spreading is 8, 16, and 32 bits, respectively. These bits after spreading are mapped to all OFDM symbols.

  FIG. 10 shows the subcarrier numbers to which the spread bits are mapped for each variable frequency band (system band).

For system bandwidth of 5MHz,
33q + 17 + n _shift , (q = 0, 1,..., 7)
Eight bits are mapped to the subcarrier number represented by the arithmetic sequence.

For the system bandwidth of 10 MHz,
33q + 17 + n _shift , (q = 0, 1,..., 15)
16 bits are mapped to the subcarrier number represented by the arithmetic sequence.

For the system bandwidth of 20MHz,
33q + 17 + n _shift , (q = 0, 1,..., 31)
Thirty-one bits are mapped to the subcarrier number expressed by the arithmetic sequence.

  In the illustrated example, the subcarrier number to which the bit after spreading is mapped for any variable bandwidth is represented by the same arithmetic sequence.

  The overload indicator is also expressed by a different number of bits for each system band, and is mapped to a predetermined subcarrier in all OFDM symbols. For example, when the system bandwidth is 5 MHz, 10 MHz, and 20 MHz, they may be expressed by 4, 8, and 16 bits, respectively.

  FIG. 11 shows a subcarrier number to which a bit representing an overload indicator is mapped for each variable frequency band (system band).

For system bandwidth of 5MHz,
66q + 16 + n _shift , (q = 0, 1, 2, 3)
Four bits are mapped to the subcarrier number represented by the arithmetic sequence.

For system bandwidth of 10MHz,
66q + 16 + n _shift , (q = 0, 1, 2,..., 7)
Eight bits are mapped to the subcarrier number represented by the arithmetic sequence.

For system bandwidth of 10MHz,
66q + 16 + n _shift , (q = 0, 1, 2,..., 15)
16 bits are mapped to the subcarrier number represented by the arithmetic sequence.

  In the illustrated example, the subcarrier number to which the bit after spreading is mapped for any variable bandwidth is represented by the same arithmetic sequence.

  The transmission power control command is used to increase or decrease the transmission power of the sounding reference signal. The transmission power control command is spread with a different spreading factor depending on the system bandwidth, and is mapped to a predetermined subcarrier in the OFDM symbol. For example, when the system bandwidth is 5 MHz, 10 MHz, and 20 MHz, the spreading factor is determined as 8, 16, 32, respectively. Since the transmission power control command itself can be expressed by 1 bit, the number of bits after spreading is 8, 16, and 32 bits, respectively. These bits after spreading are mapped to all OFDM symbols.

  FIG. 12 shows subcarrier numbers to which the bits after spreading are mapped for each variable frequency band (system band).

For system bandwidth of 5MHz,
33q + 23 + n _shift , (q = 0, 1,..., 7)
Eight bits are mapped to the subcarrier number represented by the arithmetic sequence.

For system bandwidth of 10MHz,
33q + 23 + n _shift , (q = 0, 1,..., 15)
16 bits are mapped to the subcarrier number represented by the arithmetic sequence.

For system bandwidth of 20MHz,
33q + 23 + n _shift , (q = 0, 1, ..., 31)
32 bits are mapped to the subcarrier number represented by the arithmetic sequence.

  In the illustrated example, the subcarrier number to which the bit after spreading is mapped for any variable bandwidth is represented by the same arithmetic sequence.

  A mobile station 100n according to an embodiment of the present invention will be described with reference to FIG.

In FIG. 13, the mobile station 100 _n includes a transmission / reception antenna 102, an amplifier unit 104, a transmission / reception unit 106, a baseband signal processing unit 108, a call processing unit 110, and an application unit 112.

  As for downlink data, a radio frequency signal received by the transmission / reception antenna 102 is amplified by the amplifier unit 104, frequency-converted by the transmission / reception unit 106 and converted into a baseband signal. This baseband signal is subjected to FFT processing, error correction decoding, retransmission control reception processing, and the like in the baseband signal processing unit 108 and then transferred to the application unit 112.

  On the other hand, uplink packet data is input from the application unit 112 to the baseband signal processing unit 108. The baseband signal processing unit 108 performs retransmission control (HARQ) transmission processing, transmission format selection, channel coding, DFT processing, IFFT processing, and the like, and transfers them to the transmission / reception unit 106.

  The transmission / reception unit 106 performs frequency conversion processing for converting the baseband signal output from the baseband signal processing unit 108 into a radio frequency band, and then is amplified by the amplifier unit 104 and transmitted from the transmission / reception antenna 102.

Further, the baseband signal processing unit 108 performs a process of demodulating and decoding the DL L1 / L2 control channel and acquiring information on the DL L1 / L2 control channel. Here, the information on which subcarrier the DL L1 / L2 control channel information is mapped to is acquired in advance by the mobile station 100 _n , and the subcarrier in which the DL L1 / L2 control channel information is assigned to Based on the information indicating whether mapping is performed, processing for acquiring information on the DL L1 / L2 control channel is performed.

  The call processing unit 110 manages communication with the base station 200, and the application unit 112 performs processing related to a layer higher than the physical layer and the MAC layer.

  In the above-described embodiments, an example in a system to which Evolved UTRA and UTRAN (also known as Long Term Evolution, or Super 3G) is applied has been described. It can be applied to all systems that use the OFDM scheme in the link.

    Although the present invention has been described above with reference to specific embodiments, each embodiment is merely illustrative, and those skilled in the art will appreciate various variations, modifications, alternatives, substitutions, and the like. Let's go. Although specific numerical examples have been described in order to facilitate understanding of the invention, these numerical values are merely examples and any appropriate values may be used unless otherwise specified. The division of each embodiment is not essential to the present invention, and two or more embodiments may be used as necessary. For convenience of explanation, an apparatus according to an embodiment of the present invention has been described using a functional block diagram. However, such an apparatus may be implemented by hardware, software, or a combination thereof. The present invention is not limited to the above embodiments, and various modifications, modifications, alternatives, substitutions, and the like are included in the present invention without departing from the spirit of the present invention.

  This international application claims priority based on Japanese Patent Application No. 2007-50838 filed on Feb. 28, 2007, the entire contents of which are incorporated herein by reference.

Claims (5)

A base station in a mobile communication system using an orthogonal frequency division multiplexing (OFDM) scheme in the downlink,
Means for mapping the reference signal and the L1L2 control signal to subcarriers to generate an OFDM symbol;
Means for generating a transmission signal including the OFDM symbol;
Means for transmitting the transmission signal to a mobile station;
And the subcarrier number X to which the reference signal is mapped is represented by a first arithmetic sequence having a predetermined first number n _shift as a first term and a predetermined second number as a tolerance,
Of the control information included in the OFDM symbol including the reference signal, the subcarrier number to which the predetermined control information is mapped has a third number obtained by adding a predetermined number to the first number n _shift as a first term and has a predetermined number of subcarrier numbers. A base station characterized in that it is expressed by a second equidistant sequence having a tolerance of 4 numbers. The mobile communication system is operable with a plurality of variable bandwidths;
The control information, the base station according to claim 1, characterized in that it is provided separately for each of the variable bandwidth. The tolerance of the second arithmetic sequence for a given control information in a variable bandwidth is
The base station according to claim 2 , wherein the base station is an integral multiple of a tolerance of the second arithmetic sequence for the control information in another variable bandwidth. The base station according to claim 3 , wherein subcarrier numbers to which predetermined control information is mapped for any variable bandwidth are expressed by the same arithmetic sequence. A method used in a base station in a mobile communication system that uses an orthogonal frequency division multiplexing (OFDM) scheme for the downlink,
Mapping reference signals and L1L2 control signals to subcarriers to generate OFDM symbols;
Generating a transmission signal including the OFDM symbol;
Transmitting the transmission signal to a mobile station;
And the subcarrier number X to which the reference signal is mapped is represented by a first arithmetic sequence having a predetermined first number n _shift as a first term and a predetermined second number as a tolerance,
Of the control information included in the OFDM symbol including the reference signal, the subcarrier number to which the predetermined control information is mapped has a third number obtained by adding a predetermined number to the first number n _shift as a first term and has a predetermined number of subcarrier numbers. The method is represented by a second series of differential numbers with a tolerance of 4 numbers.

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