WO2010005037A1 - 通信装置、通信システム、受信方法及び通信方法 - Google Patents
通信装置、通信システム、受信方法及び通信方法 Download PDFInfo
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- WO2010005037A1 WO2010005037A1 PCT/JP2009/062475 JP2009062475W WO2010005037A1 WO 2010005037 A1 WO2010005037 A1 WO 2010005037A1 JP 2009062475 W JP2009062475 W JP 2009062475W WO 2010005037 A1 WO2010005037 A1 WO 2010005037A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0023—Interference mitigation or co-ordination
- H04J11/0026—Interference mitigation or co-ordination of multi-user interference
- H04J11/0036—Interference mitigation or co-ordination of multi-user interference at the receiver
- H04J11/004—Interference mitigation or co-ordination of multi-user interference at the receiver using regenerative subtractive interference cancellation
- H04J11/0043—Interference mitigation or co-ordination of multi-user interference at the receiver using regenerative subtractive interference cancellation by grouping or ordering the users
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0045—Arrangements at the receiver end
- H04L1/0047—Decoding adapted to other signal detection operation
- H04L1/0048—Decoding adapted to other signal detection operation in conjunction with detection of multiuser or interfering signals, e.g. iteration between CDMA or MIMO detector and FEC decoder
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
- H04L1/0056—Systems characterized by the type of code used
- H04L1/0067—Rate matching
- H04L1/0068—Rate matching by puncturing
- H04L1/0069—Puncturing patterns
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1812—Hybrid protocols; Hybrid automatic repeat request [HARQ]
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1829—Arrangements specially adapted for the receiver end
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
- H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
- H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
- H04L1/1867—Arrangements specially adapted for the transmitter end
- H04L1/1893—Physical mapping arrangements
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/004—Orthogonal
- H04J13/0044—OVSF [orthogonal variable spreading factor]
Definitions
- the present invention relates to a communication device, a communication system, a reception method and a communication method, and more particularly to a communication device, a communication system, a reception method and a communication method to which automatic retransmission control is applied.
- hybrid automatic retransmission HARQ As an error control technique in a communication system, for example, hybrid automatic retransmission HARQ (ARQ: Automatic Repeat reQuest (ARQ) described in Non-Patent Document 1 and Non-Patent Document 2) and error correction coding such as turbo coding are combined.
- Hybrid-ARQ is a technique in which when a receiver detects an error in a received signal, it requests retransmission to the transmitter, and performs a decoding process on a combined signal of the signal received again and the signal already received.
- chase combining CC
- IR Incremental ⁇ Redundancy
- the hybrid automatic retransmission HARQ using the chase combining CC when an error is detected in the received packet, the retransmission of the same packet is requested. By combining these two received packets, the reception quality can be improved. Further, in the hybrid automatic retransmission HARQ using the increased redundancy IR, the redundant bits are divided and sequentially retransmitted little by little. Therefore, the coding rate can be lowered as the number of retransmissions increases, and the error correction capability can be enhanced.
- MC-CDM Multi Carrier Coded Multiplexing: Code Division Multiplexing
- OFDM Orthogonal Frequency Division Multiplexing
- CDM Code Division Multiplexing
- methods such as multi-carrier code division multiplexing
- Spread-OFDM Orthogonal Frequency and Division Multiplexing
- the successive interference canceller SIC disclosed in Non-Patent Document 3 and Non-Patent Document 4 includes the received signal power of each code channel or the received signal power versus interference power and noise among the code-multiplexed received signals.
- the signal is detected by despreading, demodulating, and decoding in order from the channel signal with the largest power ratio (SINR: Signal to Interference plus Noise power Ratio, hereafter referred to as “SINR”) to obtain a determination signal of an information symbol.
- SINR Signal to Interference plus Noise power Ratio
- an interference signal replica (undesired signal replica) created using the determination result is subtracted from the received signal.
- the successive interference canceller SIC when used on the reception side, the desired signal that becomes an interference signal with the received signal power of each code channel or the received signal SINR. Determining the order in which signals other than the code channels are removed may not be optimal. That is, the probability that the above removal order determination does not coincide with the code channel signal order with few errors increases. As a result, the number of times that retransmission is repeated increases, such as detecting an error in the result of decoding processing on the combined signal of the signal received again and the signal already received, and requesting retransmission again. There is a problem that the delay may become large.
- the present invention has been made in view of such circumstances, and an object of the present invention is to provide a communication device, a communication system, a reception method, and a communication method that prevent repetition of retransmission and increase in delay.
- the present invention has been made to solve the above-described problems.
- the communication device is a communication device that performs hybrid automatic retransmission that requests retransmission to a transmission source when an error is detected in a received signal. And a retransmission signal for any one of the signals, a reception unit that receives the multiplexed signal of the initial transmission signal and the retransmission signal, and the initial signal included in the signal received by the reception unit
- a detection order determining unit that determines an order in which the initial transmission signal and the retransmission signal are detected from signals received by the reception unit according to the number of retransmissions of the transmission signal and the retransmission signal; and the detection order determination unit In accordance with the order determined by the apparatus, using the detected signal related to the initial transmission signal and the detected signal related to the retransmission signal to cause interference from the signal received by the receiving unit.
- a signal detection unit that detects the initial transmission signal and the retransmission signal from the signal received by the reception unit, wherein the signal detection unit includes the detected retransmission signal and the previous retransmission signal.
- a synthesizing unit that synthesizes a signal detected from a received signal including at least one of the received related signals.
- the communication apparatus of the present invention is the communication apparatus described above, wherein the detection order determination unit determines the detection order so that the order of the retransmission signals comes before the initial transmission signal. .
- the communication apparatus of the present invention is the communication apparatus described above, wherein the detection order determination unit determines the detection order so as to detect in order from a signal having a large number of retransmissions.
- the communication apparatus is the communication apparatus described above, wherein the detection order determination unit is represented by a reception signal power and a reception signal to interference noise power ratio among the initial transmission signal and the retransmission signal. The order is determined based on the reception level.
- the communication apparatus is the communication apparatus described above, wherein the initial transmission signal and the retransmission signal are signals that have been error correction encoded at a transmission source, and the signal detection unit detects the signal.
- the signal detection unit detects the signal.
- a replica signal of an interference component for a signal to be detected is generated using a signal obtained by performing error correction decoding processing on the signal detected by the device using the error correction code, and the signal received by the receiving unit is generated from the signal received by the receiving unit.
- the replica signal is removed.
- the communication device of the present invention is the communication device described above, wherein the signal detection unit, when the signal received by the reception unit includes a retransmission signal, the related signal received before the retransmission signal In accordance with the detection order determined again by the detection order determination unit for the received signal including at least one of the received signal, the detected signal is used to remove interference components from the received signal, and the received signal is A signal is detected.
- the communication device of the present invention is the communication device described above, wherein the signal received by the receiving unit is code-multiplexed by multiplying the initial transmission signal and the retransmission signal by a unique spreading code sequence.
- the signal detection unit removes the interference component from the signal received by the reception unit, and then multiplies the signal from which the interference component is removed by the spreading code specific to the signal to be detected. , Detecting a signal as the detection target.
- the communication apparatus is the communication apparatus described above, and the signal received by the reception unit is a signal obtained by spatially multiplexing the initial transmission signal and the retransmission signal transmitted from different antennas.
- the signal detection unit detects the signal to be detected from the signal from which the interference component is removed based on the propagation path estimation value for each antenna after removing the interference component from the signal received by the reception unit. It is characterized by doing.
- the communication device of the present invention is the communication device described above, wherein the signal detection unit detects the initial transmission signal and the retransmission signal according to the order determined by the detection order determination unit for each signal. It is characterized by being performed once.
- the communication apparatus is the communication apparatus described above, wherein the signal detection unit repeats the detection of the initial transmission signal and the retransmission signal a plurality of times according to the order determined by the detection order determination unit. It is characterized by that.
- the communication system of the present invention includes a first communication device and a second communication device.
- the second communication device detects the first communication device.
- the second communication device is a signal that includes an initial transmission signal and a retransmission signal for any one of the signals
- a reception unit that receives a signal in which the retransmission signal is multiplexed, and a signal that is received by the reception unit according to the number of retransmissions of the initial transmission signal and the retransmission signal that are included in the signal received by the reception unit From the detection order determination unit for determining the order in which the initial transmission signal and the retransmission signal are detected, and the signal detected by the device according to the order determined by the detection order determination unit, the initial transmission signal Detected signal for And a signal detection unit that detects an initial transmission signal and the retransmission signal by removing an interference component from the signal received by the
- the communication system is the communication system described above, wherein the initial transmission signal and the retransmission signal are error-corrected encoded signals, and the signal detection unit detects the signal.
- the communication system of the present invention is the communication system described above, wherein the first communication device includes a retransmission control unit that determines transmission power for transmitting the initial transmission signal and the retransmission signal based on the number of retransmissions. And a transmission power control unit that controls to transmit the initial transmission signal and the retransmission signal with the transmission power determined by the retransmission control unit.
- the communication system of the present invention is the communication system described above, wherein the first communication device determines a spreading code sequence to be multiplied by the initial transmission signal and the retransmission signal based on the number of retransmissions. And a spreading unit that multiplies the initial transmission signal and the retransmission signal by the spreading code sequence determined by the retransmission control unit, and the signal detection unit of the second communication device receives the signal received by the receiving unit. After the interference component is removed from the signal, the signal from which the interference component has been removed is multiplied by the spreading code obtained by multiplying the signal to be detected by the spreading unit and the signal to be detected is detected. To do.
- the communication system of the present invention is the communication system described above, wherein the retransmission control unit is configured such that a spread code sequence that multiplies a signal with a large number of retransmissions and a spread code sequence that is more resistant to a loss of orthogonality. It is characterized by doing.
- the communication system of the present invention is the communication system described above, wherein the spreading code sequence is an orthogonal variable spreading factor code.
- the reception method of the present invention is a reception method in a communication apparatus that performs hybrid automatic retransmission that requests retransmission to a transmission source when an error is detected in a received signal.
- the communication device detects signals detected by the communication device according to the order determined in the second process, the detected signal related to the initial transmission signal and the detected signal related to the retransmission signal.
- the communication method of the present invention includes a first communication device and a second communication device.
- the second communication device detects the error in the first communication device.
- the first communication device transmits a first transmission signal and a retransmission signal for any one of the signals
- a second process in which the second communication device receives a signal including an initial transmission signal and a retransmission signal for any one signal, wherein the initial transmission signal and the retransmission signal are multiplexed; From the signal received in the second process, the second communication device according to the number of retransmissions of the initial transmission signal and the retransmission signal included in the signal received in the second process, Detect the initial transmission signal and the retransmission signal
- a third process for determining an order and a signal detected by the second communication apparatus in accordance with the order determined by the second communication apparatus in the third process, wherein the second communication
- the detection order determining unit determines the order of detecting signals that interfere with each other according to the number of retransmissions, and the signal detecting unit uses the detected signal in accordance with the order to receive the receiving unit. Removes the interference component from the received signal and detects the initial transmission signal and the retransmission signal. For this reason, the higher the number of retransmissions, the faster the detection order, so that the signal removal order can be determined in order from the code channel signal with less error with higher accuracy. Therefore, signal detection is performed with high accuracy and the number of retransmissions is reduced. It becomes possible. Therefore, it is possible to prevent the number of signal retransmissions from increasing and the delay from increasing.
- FIG. 6 is a diagram illustrating a code-multiplexed signal when packets P1 ′′, P2 ′, P3, and P4 are transmitted on code channels CH1 to CH4 in the same embodiment.
- FIG. 2 is a schematic block diagram showing a configuration of a code channel replica generation unit 705-1 in the same embodiment. It is a figure which shows the example of a synthetic
- FIG. 2 is a schematic block diagram showing a configuration of a symbol replica generation unit 1204-1 in the same embodiment. It is a flowchart explaining the reception operation
- a packet transmission device 100 (first communication device) and a packet reception device 200 (second communication device) are provided, and an MC-CDM (Multi Carrier-Code Division Multiplexing) method is used.
- a packet communication system communication system
- the packet transmission device 100 (first communication device)
- a packet including a successive interference canceller (SIC) that uses a repetitive process to transmit a signal that is code-multiplexed with a retransmission packet related to any initial transmission packet before the initial transmission packet.
- SIC successive interference canceller
- Receiving device 200 receives the signal packet transmission device 100 transmits, among the signals that are code-multiplexed, with priority signal for the retransmission packet, sequentially signal detection.
- the interference signal is an interference signal due to inter-code interference, and means another signal that is code-multiplexed. That is, for example, if signals P 1 and P 2 are code-multiplexed, is a signal P 2 is an interference signal to the signal P 1, the signal P 1 is an interference signal for the signal P 2, i.e. the signal P 1 It has a signal interfering with each other by being encoded multiplexed signal P 2 and. Signal detection is to obtain an information bit for propagation path distortion correction, despreading, and demodulation after reproducing an interference signal for the signal to be detected and performing interference cancellation processing for removing the reproduced signal (replica) from the received signal.
- the replica of the signal P 1 is removed from the received signal, and then the signal P 2 is code-separated (reversely processed).
- the received signal is code-separated (despread) without performing interference cancellation processing for the first signal detection. ) To detect the signal.
- FIG. 1 is a schematic block diagram showing a configuration of a packet transmission device 100 according to an embodiment of the present invention.
- the packet transmission device 100 is included in a downlink base station and an uplink mobile station in a mobile radio communication system.
- the relay station apparatus is provided in the downlink between the relay station and the mobile station.
- the packet transmission apparatus 100 includes code channel signal generation units 101-1 to 101-N (N is the number of code multiplexing), a code multiplexing unit 102, an IFFT unit 103, a multiplexing unit 104, a GI insertion unit 105, a transmission unit 106, a pilot signal.
- a generation unit 107, a retransmission control signal generation unit 108, a restoration unit 109, a reception unit 110, and an antenna unit 120 are provided.
- the code channel signal generation units 101-1 to 101-N have a function of generating a signal to be code-multiplexed from an information bit sequence constituting an input packet of each code channel.
- FIG. 2 is a schematic block diagram showing the configuration of the encoding unit 111.
- the encoding unit 111 has a function of adding redundant bits to the information bit sequence constituting the input packet so that the packet receiving apparatus 200 can perform error detection and error correction.
- a correction encoding unit 122, an encoded bit storage unit 123, and a puncturing unit 124 are provided.
- the error detection encoding unit 121 performs error detection encoding such as CRC (Cyclic Redundancy Check) so that the packet receiving apparatus 200 that receives the packet can detect whether or not there is an error.
- CRC Cyclic Redundancy Check
- the error correction coding unit 122 performs error correction coding such as a turbo code, a convolutional code, and an LDPC (Low Density Parity Check) code on the output bit sequence from the error detection coding unit 121. .
- error correction coding such as a turbo code, a convolutional code, and an LDPC (Low Density Parity Check) code on the output bit sequence from the error detection coding unit 121.
- all bits constituting the packet are transmitted on the same code channel, and the error detection encoding unit 121 and the error correction encoding unit 122 perform processing for each packet.
- the coded bit storage unit 123 stores the coded bit sequence generated by the error correction coding unit 122. In addition, when a retransmission packet is generated, the stored encoded bit sequence is output to puncturing section 124.
- the puncturing unit 124 performs error correction coding according to the puncture pattern determined based on the response signal (acknowledgment ACK / non-acknowledgment NACK) of the packet reception device 200 received by the restoration unit 109 and the number of packet retransmissions calculated from the response signal.
- the encoded bit sequence output from the unit 122 or the encoded bit sequence output from the encoded bit storage unit 123 is punctured.
- the puncturing unit 124 when generating the initial transmission packet (when receiving a reception notification ACK as a response signal to the previous packet), the puncturing unit 124 applies the new encoded bit sequence output from the error correction encoding unit 122.
- the puncture process is performed and a retransmission packet is generated (when a non-acknowledgment notification NACK is received as a response signal)
- the puncture process is performed on the encoded bit sequence stored in the encoded bit storage unit 123.
- the puncturing unit 124 may perform rate matching such as bit padding (bit insertion) or bit repetition (bit repetition) in addition to the puncturing process.
- the error correction encoding unit 122 includes inner encoders 3001 and 3002 and an inner interleaving unit 3003. When the error detection encoded information bit sequence from the error detection encoding unit 121 is input, error correction encoding is performed.
- the unit 122 outputs three types of information bit sequences of systematic bits x, parity bits z, and parity bits z ′.
- the systematic bit x is the bit sequence itself input from the error detection encoding unit 121.
- the parity bit z is an output result of the internal encoder 3001 encoding the bit sequence from the error detection encoding unit 121.
- the parity bit z ′ is an output result obtained by first interleaving the bit sequence from the error detection coding unit 121 by the internal interleaving unit 3003 and coding the result of the interleaving process by the internal encoder 3002. .
- the inner encoder 3001 and the inner encoder 3002 may be the same encoder that performs the encoding of the same encoding method, or may be different encoders.
- a recursive convolutional encoder is used for both the inner encoder 3001 and the inner encoder 3002.
- the error correction encoding unit 122 will be described using a turbo code with the configuration shown in FIG.
- x is an information bit (including redundant bits added for error detection) input by the error detection encoding unit 121 to the error correction encoding unit 122, and this information bit is output as it is. Yes (also called systematic bits).
- z and z ′ indicate two types of redundant bits (parity bits) generated by the error correction encoding unit 122 from the information bits.
- the puncture unit 124 has a bit position of “1” in the puncture pattern shown in FIG. 4 among x, z, and z ′ output from the error correction encoding unit 122 or the encoded bit storage unit 123. Output bits.
- the chase combining CC is applied as the hybrid automatic retransmission HARQ
- the puncturing unit 124 performs puncturing processing according to pattern 1 in FIG.
- a signal obtained by performing the puncturing process with pattern 1 of FIG. 3 is output.
- the interleave unit 112 rearranges the bit arrangement of the encoded bit sequence that is the output from the encoding unit 111.
- the modulation unit 113 performs data modulation such as QPSK (Quadrature Phase Shift Keying: 4-level phase shift keying), 16QAM (16 Quadrature Amplitude Modulation: 16-level quadrature amplitude modulation) on the output from the interleave unit 112, and performs modulation. Generate a symbol.
- Spreading section 114 multiplies the modulation symbol generated by modulation section 113 by a unique spreading code sequence for each of code channel signal generation sections 101-1 to 101-N. For example, an orthogonal code such as a Walsh-Hadamard code is used as the spreading code sequence.
- the code channel signal generation units 101-1 to 101-N have the above-described functions, and in accordance with the retransmission request from the packet receiving apparatus 200, the code channel signal composed of the initial transmission packet or the retransmission packet. Generate.
- the code multiplexing unit 102 code-multiplexes the output signals from the respective code channel signal generation units 101-1 to 101-N. That is, in order to be transmitted from the antenna unit 120, the signal output from the code multiplexing unit 102 is code-multiplexed by multiplying the initial transmission signal and the retransmission signal transmitted through each code channel by a unique spreading code sequence. Signal.
- an output signal from the code multiplexing unit 102 assigned to the k-th subcarrier at the input to the IFFT unit 103 is S (k), it can be expressed as Expression (1).
- N indicates the number of multiplexed codes in the code multiplexing unit 102
- SF indicates the spreading factor of the spreading code multiplied by the spreading unit 114.
- c u v represents the value of the v th element of the spreading code sequence of the u th code channel
- a mod b represents the remainder obtained by dividing a by b.
- d u indicates a modulation symbol of the u-th code channel that is data-modulated by the modulation unit 113.
- N sub represents the total number of subcarriers.
- the IFFT unit 103 performs frequency-time conversion on the signal code-multiplexed by the code multiplexing unit 102 by inverse fast Fourier transform IFFT (Inverse Fast Fourier Transform) or the like to generate a time-domain signal.
- Multiplexing section 104 multiplexes the time domain signal output from IFFT section 103, the retransmission control signal output from retransmission control signal generation section 108, and the pilot signal output from pilot signal generation section 107.
- the multiplexing method in the multiplexing unit 104 may be any of time multiplexing, frequency multiplexing, code multiplexing, and the like.
- the pilot signal generation unit 107 generates a pilot signal used for propagation path estimation.
- the retransmission control signal generation unit 108 generates a signal (retransmission control signal) for notifying the packet reception device 200 of how many retransmissions the packet signal transmitted on each code channel is.
- the retransmission control signal may include information related to a transmission signal such as a coding rate, a modulation multi-level number, a spreading factor, and a spreading code.
- the GI insertion unit 105 inserts a guard interval GI (Guard Interval) into the signal output from the multiplexing unit 104 and inputs the signal to the transmission unit 106.
- the transmission unit 106 converts the output signal from the GI insertion unit 105 into an analog signal (Digital / Analogue conversion), performs a filtering process for band limitation, further converts to a transmittable frequency band, and outputs the signal. .
- the antenna unit 120 transmits the output signal of the transmission unit 106 to the packet reception device 200. Alternatively, a signal including a response signal transmitted from the packet reception device 200 is received.
- the reception unit 110 converts the signal received from the antenna unit 120 from the packet reception device 200 into a frequency band that can be restored (signal detection processing), filtering processing for band limitation, and converts an analog signal into a digital signal ( (A / D conversion).
- the restoration unit 109 performs reception signal restoration processing such as data demodulation and error correction decoding on the digital signal output from the reception unit 110 and extracts a response signal included in the signal from the packet reception device 200.
- the restoration unit 109 outputs the extracted response signal to the retransmission control signal generation unit 108 and the encoding unit 111.
- the restoration unit 109 has a function capable of processing a received signal based on a transmission method of the received signal.
- the response signal is a signal that confirms transmission and includes information on whether or not to request retransmission. For example, if there is a reception notification ACK (ACKnowledge) / non-acknowledgement notification NACK (Negative ACKnowledge) signal, and the reception side cannot correctly receive a packet transmitted from the transmission side, the reception side will not accept the transmission side. If the notification NACK signal is sent back and the signal is successfully received, the receiving side sends back a reception notification ACK signal. Note that if the transmission side does not receive a response signal within a predetermined time, the reception side can also determine that the packet has not been received correctly.
- ACK reception notification ACK
- NACK Negative ACKnowledge
- FIG. 5 is a schematic block diagram illustrating the configuration of the packet reception device 200 according to the present embodiment.
- the packet reception device 200 is included in a mobile station device in the downlink and a base station device in the uplink by the mobile radio communication system. Further, it is provided in a relay station apparatus in the downlink between the base station and the relay station.
- the packet reception device 200 includes an antenna unit 201, a reception unit 202, a propagation path estimation unit 203, a GI removal unit 204, an FFT unit 205, a reception packet management unit 206, a detection order determination unit 207, an interference cancellation unit 208, and a reception signal storage unit. 209, a response signal generation unit 210, and a transmission unit 211.
- the reception unit 202 receives a signal from the packet transmission device 100 via the antenna unit 201, performs conversion to a frequency band capable of signal processing such as signal detection processing, and filtering processing for band limitation, and then converts the analog signal into a digital signal. (Analogue / Digital conversion).
- the signal received by the receiving unit 202 is a signal including an initial transmission packet (initial transmission signal) and a retransmission packet (retransmission signal) for a packet transmitted in the past. Signals that interfere with each other.
- the propagation path estimation unit 203 estimates a propagation path (impulse response, transfer function, etc.) through which the reception signal has passed, using a pilot signal included in the reception signal converted into a digital signal by the reception unit 202. Instead of the pilot signal, other signals that can estimate the propagation path, such as a control channel and a preamble, may be used.
- the received packet management unit 206 determines from the retransmission control signal included in the received signal converted into the digital signal by the receiving unit 202 how many times the retransmitted packet signal is the signal of each code channel included in the received signal (also the initial transmission packet).
- Information that is, information indicating the number of retransmissions is extracted.
- a packet whose number of retransmissions is 0 is an initial transmission packet.
- the packet with the number of retransmissions of 1 is a retransmission packet transmitted next to the initial transmission packet.
- the detection order determination unit 207 determines the order of the code channels from which signals are detected by the interference cancellation unit 208 and notifies the interference cancellation unit 208 of the order.
- the detection order determination unit 207 determines whether the reception unit 202 receives a signal from the signal received by the reception unit 202 according to the number of retransmissions of the initial transmission packet (initial transmission signal) and the retransmission packet (retransmission signal) included in the signal received by the reception unit 202. The order in which the initial transmission packet and the retransmission packet are detected is determined. Details of order determination by the detection order determination unit 207 will be described later.
- the GI removal unit 204 removes a guard interval GI (Guard Interval) from the data signal included in the reception signal converted by the reception unit 202 into a digital signal.
- the FFT unit 205 converts the output signal of the GI removing unit 204 into a frequency domain signal by performing a fast Fourier transform FFT process.
- the interference cancellation unit 208 (signal detection unit) refers to the propagation path estimated value output from the propagation path estimation unit 203 according to the detection order determined by the detection order determination unit 207, and from the signal output from the FFT unit 205.
- An encoded bit LLR (Log Likelihood Ratio) of the information bit sequence is detected, and the detected encoded bit LLR and an information bit sequence that is a hard decision result of the encoded bit LLR are output. Error detection is performed on the bit LLR and an error detection result is output. Details of the operation of the interference cancellation unit 208 will be described later.
- the coded bit LLR is a logarithm of the ratio between the probability that the coded bit for each coded bit is “1” and the probability that it is “0”.
- the received signal storage unit 209 stores the soft decision value for the information bit sequence obtained by the demodulation processing for the received signal in the interference cancellation unit 208.
- the soft decision value for example, there is a coded bit LLR.
- the reception signal storage unit 209 detects at least one soft decision value for a packet received before this retransmission packet, the interference cancellation unit 208 (more specifically, Is output to a combining unit 711) described later.
- the reception signal storage unit 209 may output the encoded bit LLR of the first reception packet (initial transmission packet).
- the encoded bit LLR of the received packet for the (p-1) th time may be output.
- the response signal generation unit 210 receives the error detection result output from the interference cancellation unit 208, generates a data sequence including control data indicating the presence / absence of a packet error in accordance with the error detection result, and performs error correction coding and data modulation.
- a response signal is generated by performing signal processing such as.
- the transmission unit 211 converts the response signal into an analog signal (D / A conversion), converts the response signal into a transmittable frequency band (radio frequency band), and transmits from the antenna unit 201.
- the response signal communication method by the response signal generation unit 210 is OFDM, single carrier modulation method, or the like as long as the original response signal can be restored (demodulated and decoded) in the packet transmission device 100 that has received this response signal.
- the response signal generation unit 210 responds to the packet transmission device 100 that reception has been correctly completed.
- a reception notification ACK is generated as a signal.
- a non-acknowledgment notification NACK is generated as a response signal for requesting retransmission of the packet to the packet transmitting apparatus 100.
- the interference canceling unit 208 of the packet receiving apparatus 200 receives the received signal with respect to each packet using the detected signal according to the order determined by the detection order determining unit 207 based on the information indicating the number of retransmissions.
- An operation of removing each interference component from the code-multiplexed signal and detecting each packet will be described.
- the code multiplexing number N 4
- each of the code channel signal generation units 101-1 to 101-4 of the packet transmission device 100 outputs a signal of one packet among the packets P1 ′′, P2 ′, P3, and P4. It is assumed that the packet transmission apparatus 100 generates and transmits a signal obtained by code-multiplexing these signals as shown in Fig. 6.
- FIG. 6 shows packets P1 ", P2 ', P3 in code channels CH1 to CH4.
- FIG. 4 is a diagram illustrating a code-multiplexed signal when P4 is transmitted.
- the packet transmitting apparatus 100 transmits a retransmission control signal indicating the number of retransmissions of the packets P1 ′′, P2 ′, P3, and P4 together with the signals of these packets.
- the packet P3 is transmitted using the code channel CH2 multiplied by the spreading code C2.
- the receiving unit 202 of the packet receiving device 200 receives the signal transmitted by the packet transmitting device 100 via the antenna unit 201.
- the received packet management unit 206 acquires information indicating the number of retransmissions of the code-multiplexed packet of each signal from the retransmission control signal included in the received signal.
- the received packet management unit 206 receives the packets P3 and P4 0 times (initial transmission packet).
- the information indicating that the packet P2 ′ is once (retransmission packet) and the packet P1 ′′ is twice (retransmission packet) is obtained from the retransmission control signal.
- the detection order determination unit 207 determines the detection order (detection order) based on the information indicating the number of retransmissions so that the detection is performed in order from the code channel signal composed of packets with a large number of retransmissions.
- the code channel CH1 of the retransmission packet P1 ′′ having the highest number of retransmissions among the retransmission packets is first detected, then the code channel CH2 of the retransmission packet P2 ′ having the highest number of retransmissions is detected, and finally the retransmission is performed.
- the order is determined so as to detect the code channel CH3 of the initial transmission packet P3 whose number of times is 0 and the code channel CH4 of the initial transmission packet P4.
- the interference cancellation unit 208 performs signal detection processing preferentially from a packet with a large number of retransmissions, and removes an interference replica generated from the detection signal of the retransmission packet, which is the signal detection processing result, from the received signal. Then, a signal detection process is performed for a packet having the next highest number of retransmissions.
- a packet with a large number of retransmissions is a packet in which many received packets related to this retransmission packet are stored in the reception signal storage unit 209. The more signals that can be combined and the more signals that can be combined, the more the interference cancellation unit 208 The signal detection accuracy at is good.
- the signal detection of the packet with poor signal detection accuracy (packet with a small number of retransmissions) is performed. As a result, it is possible to improve the detection accuracy of the signal of the packet with inferior signal detection accuracy.
- retransmission packets having the same number of retransmissions may have any detection order.
- the detection order may be detected simultaneously, or the detection order may be determined using other criteria such as a spread code sequence, SINR (SignalSigntoInterference plus Noise Ratio).
- FIG. 7 is a schematic block diagram illustrating a configuration example of the interference canceling unit 208 that performs sequential-type repetitive interference cancellation.
- the interference canceling unit 208 sets code channel parameters such as spreading codes in each part of the interference canceling unit 208 so as to detect code channel signals in the order determined by the detection order determining unit 207.
- the interference cancellation unit 208 includes propagation path compensation units 701-1 to 701-N, code separation units 703-1 to 703-N, MCI replica generation units 704-1 to 704-N, and code channel replica generation units 705-1 to 705-1. 705-N and subtraction units 706-1 to 706-N.
- N indicates the maximum value of the number of multiplexed codes that can be received.
- Each of the code demultiplexing units 703-1 to 703-N includes a despreading unit 707, a demodulating unit 708, a deinterleaving unit 709, a depuncturing unit 710, a combining unit 711, and a decoding unit 712.
- a series of processing in the interference cancellation unit 208 is repeatedly executed by a predetermined number of repetitions. That is, when receiving the signal of the number N of multiplexed codes, the interference cancellation unit 208 performs interference cancellation and propagation path compensation by any of the subtraction units 706-1 to 706-N for each of the 1st to Nth code channels.
- Propagation path compensation by any one of the units 701-1 to 701-N, code channel separation by any of the code separation units 703-1 to 703-N, and any of the code channel replica generation units 705-1 to 705-N A series of processes for generating the code channel replica by the above and the generation of the interference replica by the MCI replica generation units 704-1 to 704-N are repeated repeatedly.
- the code channel replica generation unit 705-1 sets the C 1 is a spreading code sequence of the code channel CH1, the code separation unit 703-2, the code channel replica generation unit 705-2, the code channel CH2 spreading of the spreading code is set to C 2 is a sequence encoding the separation unit 703-3, the code channel replica generation unit 705-3, the code channel CH3 No.
- Set C 3 is a sequence
- the code separation unit 703-4, the code channel replica generation unit 705-4 sets the C 4 is a spreading code sequence of the code channel CH4.
- puncture pattern The puncture pattern of the corresponding code channel is set based on the detection order, and details of each part of the interference cancellation unit 208 will be described later.
- FIG. 8 is a schematic block diagram showing the configuration of the code channel replica generation unit 705-1.
- the code channel replica generation unit 705-1 includes a puncturing unit 721, an interleaving unit 722, a modulation symbol replica generation unit 723, and a spreading unit 724.
- the spreading code C 1 Based on the detection order determined by the detection order determining unit 207, the spreading code C 1 .
- N a code channel replica corresponding to the spreading code input to the spreading unit 724 is generated.
- the code channel replica generation unit 705-1 uses the code channel signal corresponding to the spreading code input to the despreading unit 707 among the spreading codes C 1 to C N by the code separation unit 703-1 in FIG. A code channel replica is generated based on the encoded bit LLR output each time detection is performed. Similarly, code channel replica generation units 705-2 to 705 -N generate code channel replicas based on coded bits LLR output from code separation units 703-2 to 703 -N, respectively.
- the encoded bit LLR is a log likelihood ratio LLR of each bit encoded by the error correction code of the encoding unit 111.
- the puncturing unit 721 performs, for each code channel (packet), the puncturing unit 124 of the packet transmission device 100 that is a packet transmission source with respect to the log likelihood ratio LLR of the encoded bit that is an output signal from the decoding unit 711. Puncturing processing is performed using the same pattern as the punctured pattern based on the detection order determined by the detection order determination unit 207.
- the interleave unit 722 performs a bit arrangement rearrangement process on the output signal from the puncture unit 721 using the same pattern as the interleave pattern applied by the interleave unit 112 of the packet transmission device 100 for each code channel (packet).
- Modulation symbol replica generation section 723 modulates the output signal from interleaving section 722 with the same modulation scheme as modulation section 113 such as QPSK modulation and 16QAM modulation, and generates a modulation symbol replica.
- the processing of the modulation symbol replica generation unit 723 will be described by taking QPSK modulation as an example.
- the modulation symbol replica generation unit 723 generates a QPSK modulation symbol replica by Equation (2). To do.
- j represents an imaginary unit.
- the modulation symbol replica output from the modulation symbol replica generation unit 723 duplicates only the spreading factor of the spread codes C 1 ... C N, among the spread codes C 1 ... C N, to the spreading portion 724
- the code channel replica (data signal replica) is generated by multiplying the code code of the code channel replica to be generated by the spreading code in the code channel.
- the receiving unit 202 receives the signal shown in FIG. 6, and the code channels in the order of the code channels CH1, CH2, CH3, and CH4 according to the detection order determined by the detection order determining unit 207.
- the operations of the MCI replica generation units 704-1 to 704-N, the subtraction unit 706, the propagation path compensation unit 701, and the code separation units 703-1 to 703-N when detecting and eliminating interference will be described in order.
- the MCI replica generation unit (interference replica generation unit) 704-1 detects the code channel CH1 detected first in the code separation unit 703-1 in the i-th repetition of the iterative processing in the interference cancellation unit 208.
- S ⁇ i-1,2 to S ⁇ i-1,4 which are replica signals of the code channels CH2 to CH4 generated by the code channel replica generation units 705-2 to 705-N in the i-1th iteration. are further multiplexed and multiplied by the propagation path estimation value calculated by the propagation path estimation unit 203, thereby generating an MCI replica that is a replica of a component that causes interference with the signal of the code channel CH1.
- the replica signals S a and b indicate that the detection order generated in the a-th iteration of the iterative process is the replica signal of the b-th code channel.
- subtracting section 706-1 subtracts the MCI replica for code channel CH1 generated by MCI replica generating section 704-1 from the output signal from FFT section 205.
- propagation path compensation section 701-1 multiplies the subtraction result of subtraction section 706-1 by a weighting factor that compensates for propagation path distortion calculated using the propagation path estimation value calculated by propagation path estimation section 203.
- MMSE Minimum Mean Square Error
- ORC Orthogonal Restoration Combi
- MRC Maximum Ratio Combining: maximum ratio combining
- the despreading unit 707 of the code demultiplexing unit 703-1 adds a spread code C1 specific to the code channel CH1 to the output signal from the propagation path compensation unit 701-1 based on the detection order determined by the detection order determination unit 207. Multiplication and despreading processing are performed to detect the signal of the code channel CH1. Thereafter, the demodulation unit 708 performs demodulation processing on the output signal from the despreading unit 707 in the same modulation scheme as the transmission side such as QPSK, 16QAM, and the result of the soft decision of the coded bits, for example, each coded bit An encoded bit LLR that is a log likelihood ratio of is calculated.
- the demodulating process of the demodulating unit 708 will be described by taking as an example a case where the modulation method is QPSK and the coded bit LLR is calculated as a soft decision result.
- the QPSK symbol transmitted on the transmission side that is, the modulation result by the modulation unit 113 in FIG. 1 is X
- the symbol after despreading on the reception side that is, the result of despreading by the despreading unit 707 is used as the modulation result estimation value Xc.
- the modulation result X can be expressed by Expression (3).
- j represents an imaginary unit.
- Re () represents the real part of a complex number.
- ⁇ is the equivalent amplitude after propagation path compensation.
- the propagation path estimation value in the k-th subcarrier is H (k) and the multiplied MMSE-based propagation path compensation weight W (k)
- ⁇ is W ( k) H (k).
- ⁇ (b 1 ) may be obtained by replacing the real part and the imaginary part of ⁇ (b 0 ) (in Expression (4), Re () is replaced with Im (), where Im () is a complex imaginary part. Represents). Note that the calculation can be performed based on the same principle even in the case of other modulation schemes such as 16QAM instead of QPSK. Further, the demodulation unit 608 may calculate a hard decision result instead of the soft decision result.
- the deinterleaving unit 709 rearranges the bit arrangement so as to perform the reverse operation of the interleaving performed by the interleaving unit 112 of the source packet transmitting apparatus 100.
- the depuncturing unit 710 uses the puncture pattern for the second retransmission packet, which is the number of retransmissions of the packet P1 ′′ of the code channel CH1, in accordance with the detection order determined by the detection order determination unit 207, and the deinterleaving unit 709 performs bit arrangement. Depuncture processing is performed on the rearranged encoded bits LLR, and the result is output to the synthesis unit 711 and the reception signal storage unit 209.
- the encoded bit sequence output from the error correction encoding unit 122 of the packet transmitting apparatus 100 is expressed as “x1, z1, z1 ′, x2, z2, z2 ′, x3, z3, z3 ′, x4, z4, z4 ′.
- X5, z5, z5 ′, x6, z6, z6 ′ the puncturing unit 124 performs puncturing processing for thinning out the bits in the pattern 1 of FIG. 4 to generate the encoded bit sequence“ x1, z1, x2, x3 ”.
- the encoded bit LLR that is output from the deinterleave unit 709 corresponding to the encoded bit sequence output from the puncture unit 124 and transmitted by the packet transmitting apparatus 100 is expressed as “x r2 1, z r2 1, x r2 2, xr2 3, xr2 4, zr2 4 ′, xr2 5, xr2 6 ”.
- the depuncture unit 710 transmits to the coded bits LLR “x r2 1, z r2 1, x r2 2, x r2 3, x r2 4, z r2 4 ′, x r2 5, x r2 6”.
- Virtual values are inserted into bit positions corresponding to z1 ′, z2, z2 ′, z3, z3 ′, z4, z5, z5 ′, z6, and z6 ′ thinned out by the original puncture unit 124.
- the encoded bit LLR output from the depuncture unit 710 is “x r2 1, z r2 1,0, x r2 2,0,0”. , X r2 3,0,0, x r2 4,0, z r2 4 ′, x r2 5,0,0, x r2 6,0,0 ”.
- the combining unit 711 combines the output signal of the depuncture unit 710 and the already received packet from the received signal storage unit 209.
- retransmission packet P1 ′′ is the second retransmission packet
- combining section 711 has already received the output signal of depuncturing section 710, that is, the signal of detected retransmission packet P1 ′′, and received signal storage section 209.
- the signal output to the decoding unit 712 is a detected signal related to the retransmission packet P1 ′′ used for removing the interference component by the interference cancellation unit 208.
- the related packet (related signal) of the retransmission packet meanss the initial transmission packet of the retransmission packet or the retransmission packet of the initial transmission packet of the retransmission packet excluding the retransmission packet itself.
- FIG. 9 is a diagram illustrating an example of a synthesis process performed by the synthesis unit 711.
- the depuncture output (third stage from the top in FIG. 9) of the retransmission packet P1 ′′ output from the depuncture unit 710 and the initial transmission of the retransmission packet P1 ′′ stored in the reception signal storage unit 209 An operation of the combining unit 711 when the depuncture output of the signal P1 (first stage from the top) and the depuncture output of the first retransmission signal P1′P (second stage from the top) is combined is shown.
- the encoded bit LLR “x r0 1, z r0 1, 0, x r0 2, 0, 0 ,...” which is the depuncture output of the initial transmission signal P1, and the retransmission packet P1 ′
- the depuncture unit 710 depunctures with the pattern 1, and for the retransmission packet P1 ′, the depuncture unit 710 performs the depuncture with the pattern 2.
- the combining unit 210 outputs the encoded bit LLR as it is.
- the decoding unit 712 performs error correction decoding processing corresponding to error correction coding such as turbo coding and convolution coding performed by the error correction coding unit 122 of the source packet transmission apparatus 100. Is performed on the encoded bit LLR output from the synthesizing unit 711, and the error-corrected encoded bit LLR is output.
- the code separation unit 703-1 separates the code channel CH1
- the code channel replica generation unit 705-1 performs coding bits of the code channel CH1 from the decoding unit 711 of the code separation unit 703-1.
- a replica signal of the code channel CH1 is generated using the LLR.
- the decoding unit 712 performs error detection processing on the packet by using an error detection code such as CRC (Cyclic Redundancy Check) performed on each packet by the error detection encoding unit 121 of the source packet transmission apparatus 100.
- the error detection result is input to the response signal generation unit 210.
- the error detection result is input to the decoding unit 712 of the code separation unit 703-N that performs signal detection of the last code channel. Receiving these inputs, the decoding unit 712 of the code separation unit 703-N repeats the iterative process that the decoding unit 712 counts whether all error detection processing results including the decoding unit 712 are error-free.
- the repetition process ends (output to the code channel replica generation unit 705-N is stopped).
- the decoding unit 712 whose error detection processing result has no error is an error from the bit sequence that generated the packet that is the hard decision result of the encoded bit LLR of the error correction decoding result by the decoding unit 712. An information bit sequence excluding redundant bits for detection is output.
- the interference cancellation unit 208 performs signal detection of the code channels CH2, CH3, and CH4 in the order of the code channels CH2, after detecting the signals of the code channels CH1 in the order determined by the detection order determination unit 207. This is performed using a replica generated from the code channel signal (detected signal) that has been detected.
- the code channel replica input to the MCI replica generation unit 704 is different from the MCI replica generation process for the code channel CH1.
- the MCI replica generation unit 704-2 When the code separation unit 703-2 detects the signal of the code channel CH2 in the i-th iteration of the iterative process in the interference cancellation unit 208, the MCI replica generation unit 704-2 generates the code channel generated in the i-th iteration.
- CH1 replica signals S ⁇ i, 1 and S ⁇ i-1,3 , S ⁇ i-1,4 which are replica signals of the code channels CH3 and CH4 generated in the i-1th iteration are code-multiplexed, Further, an MCI replica that causes interference with the code channel CH2 is generated by multiplying the estimated channel value.
- the code separation unit 703-3 and the code channel CH3 is the signal detection, MCI replica generation unit 704-3, the replica signal S ⁇ i, 1 of the code channel CH1 and CH2 generated in the i th iteration,
- the code channel CH3 is code-multiplexed with S ⁇ i-1,4 which is a replica signal of the code channel CH4 generated in the repetition of S ⁇ i, 2 and the (i-1) th iteration, and further multiplied by the propagation path estimation value.
- An MCI replica that causes interference is generated.
- the MCI replica generation unit 704-4 When the code separation unit 703-4 detects the signal of the code channel CH4, the MCI replica generation unit 704-4 generates the replica signals S ⁇ i, 1 ⁇ S ⁇ i of the code channels CH1 to CH3 generated in the i-th iteration. 3 is then multiplexed and further multiplied by the propagation path estimation value to generate an MCI replica that interferes with the code channel CH4.
- the code channel replica generation unit corresponding to the code channel whose signal is detected The MCI replica generation unit generates (updates) the code channel replica using the generated (updated) code channel replica, and uses the generated (updated) code channel replica.
- the MCI replica generation unit 704 -u uses the MCI replica R ⁇ i, u used for the interference cancellation process when detecting the u-th code channel detected by the detection order determination unit 207. Calculated by the following equation (5).
- H is a propagation path estimated value and N is the number of multiplexed code channels.
- the deinterleaving unit 709 and the depuncturing unit 710 perform processing according to the pattern corresponding to each code channel set according to the detection order by the detection order determining unit 207.
- Despreading section 707 multiplies the spreading code sequence set in accordance with the detection order by detection order determination section 207 and multiplied at the time of transmission specific to each code channel.
- interference cancellation is sequentially performed for each code channel based on the number of retransmissions of a packet constituting the code channel (code channel signal detection).
- the channels may be grouped and interference cancellation may be performed in order for each group.
- the code channel may be grouped according to the initial transmission packet or the retransmission packet.
- FIG. 10 is a flowchart for explaining the operation of the packet receiving apparatus 200.
- the packet receiving apparatus 200 receives the code multiplexed signal (S101)
- the received packet management unit 206 of the packet receiving apparatus 200 acquires the number of retransmissions of the packets constituting each code channel from the retransmission control signal included in the received signal. (S102).
- the detection order determination unit 207 determines the signal detection order (interference signal removal order) of the packet (code channel) for canceling the interference and detecting the signal from the retransmission number information acquired by the received packet management unit 206 (S103). .
- the interference cancellation unit 208 performs packet (code channel) cancellation processing and signal detection processing such as MCI replica subtraction, despreading, and demodulation processing according to the signal detection order determined in step S103 (S104).
- the decoding unit 712 performs a decoding process on the output signal from the synthesis unit 711 (S107), further determines whether or not the signal detected packet has an error (S108), and determines that there is no error
- the response signal generation unit 210 returns a response signal indicating that there is no error to the packet transmission device 100 (S110). If the decoding unit 712 determines in step S108 that there is an error in the packet, it determines whether or not the repetition processing of the interference cancellation unit 208 is repeated up to a predetermined number of repetitions (S109), and repeats up to the number of repetitions. When it is determined that it is not, the decoding unit 712 outputs the encoded bit LLR, and the interference cancellation unit 208 returns to step S104 and repeats again.
- the response signal generation unit 210 returns a response signal for requesting retransmission to the packet transmission device 100 (S111), and returns to step S101. The next signal is received.
- steps S104 to S108 have described only processing for a specific packet by the interference cancellation unit 208.
- the interference cancellation unit 208 processes steps S104 to S107 for each packet according to the detection order determined by the detection order determination unit 207, and the decoding unit 712 determines that there is no error in step S108 for all packets.
- the response signal generator 210 returns a response signal indicating that there is no error for all packets to the packet transmitter 100 (S110).
- the response signal generation unit 210 detects no error in step S108.
- a response signal indicating that there is no error is returned to the packet transmitting apparatus 100, and for the packet in which the error is detected, a response signal indicating that retransmission is requested is returned to the packet transmitting apparatus 100 (S111).
- the interference cancellation unit 208 has been described as performing the iterative process of repeatedly detecting the signal of the code-multiplexed code channel a plurality of times for each code channel signal. Only the first processing in the processing, that is, the detection of the signal of each code channel may be performed once for each code channel.
- the detection order determination unit 207 of the packet reception device 200 determines the signal detection order so that detection is performed from a packet with a large number of retransmissions among the code-multiplexed packets, and the interference cancellation unit 208 In accordance with the signal detection order, a signal is detected from a packet with a large number of retransmissions, an interference component due to the signal of the detected packet is removed from a received signal, and then a signal detection of a packet with the next largest number of retransmissions is performed in order. Do.
- a packet having a large number of retransmissions and a signal that can be combined that is, a packet signal with good signal detection accuracy in the interference cancellation unit 208 is detected first, and an interference replica generated from the detected packet signal is received.
- the signal detection of the packet with a small number of retransmissions is performed, so the detection accuracy of the packet signal with inferior signal detection accuracy can be improved because the number of retransmissions is small and the number of signals to be combined is small. It becomes. Therefore, it is possible to prevent the number of retransmissions of a specific packet from increasing and delay from increasing.
- the interference signal means another spatially multiplexed signal. That is, for example, if signals P 1 and P 2 are spatially multiplexed, a signal P 2 is an interference for the signal P 1, the signal P 1 is an interference for the signal P 2.
- the interference cancellation process is a process for removing interfering signals reproduced signal (replica) from the received signal, for example, when detecting a signal P 2 is used to remove a replica of the signal P 1 from the received signal the signal .
- FIG. 11 is a schematic block diagram illustrating the configuration of the packet transmission device 300 according to the present embodiment.
- the packet transmission device 300 is included in a downlink base station and an uplink mobile station in a wireless communication system. In addition, it is provided in a relay station on the downlink between the relay station and the mobile station.
- the packet transmission device 300 includes stream signal generation units 301-1 to 301-Ns (where Ns is the number of streams), antenna units 302-1 to 302-Ns, a retransmission control signal generation unit 311, a restoration unit 312, and a reception unit 313. Ns stream signals generated from different information bit sequences constituting each packet are transmitted one by one from each of the antenna units 302-1 to 302-Ns. Further, the packet transmission device 300 restores a signal including a response signal from the packet reception device 400.
- the receiving unit 313 converts the signal received from the packet receiving device 400 via the antenna unit 302-1 into a frequency band that can be restored (detected), performs band limitation by filtering, and converts the analog signal into a digital signal. (Analogue / Digital conversion).
- the restoration unit 312 performs reception signal restoration processing such as data demodulation and error correction decoding on the digital signal output from the reception unit 313, extracts a response signal included in the signal from the packet reception device 400, and the response signal is The packet reception success / failure information shown is notified to encoding section 303 and retransmission control signal generation section 311 in stream generation sections 301-1 to 301-Ns.
- the restoration unit 312 has a function capable of receiving signal processing based on a transmission method of the received signal.
- the receiving unit 313 is described as receiving via the antenna unit 302-1; however, the receiving unit 313 may receive via any of the antenna units 302-2 to 302-Ns, You may make it receive from a dedicated antenna.
- Stream signal generation sections 301-1 to 301-Ns generate transmission data signals for each stream from information bits constituting each input packet, and encode section 303, interleave section 304, modulation section 305, and IFFT section 306.
- the encoding unit 303 has a function of adding redundant bits to the information bit sequence of the input packet so that the packet receiving apparatus 400 can perform error detection and error correction.
- the encoding unit 303 encodes or retransmits the encoded bit of the initial transmission packet or the retransmission according to the response signal from the packet receiving apparatus 400 to the signal (packet signal) of each stream output from each of the stream signal generation units 301-1 to 301-Ns. Output the encoded bits of the packet.
- a packet is generated for each stream, and error detection coding and error correction coding are performed for each packet (each stream). That is, a signal of a certain packet is not distributed and transmitted in a plurality of streams, but is transmitted in the same stream.
- the interleaving unit 304 rearranges the bit arrangement of the encoded bits output from the encoding unit 303 according to a predetermined pattern.
- Modulation section 305 performs data modulation on the coded bits whose bit arrangement is rearranged by interleaving section 304 using a modulation scheme such as QPSK or 16QAM, and generates modulation symbols. Note that the data modulation method may be different for each stream.
- the IFFT unit 306 assigns the modulation symbol from the modulation unit 305 to each subcarrier, and performs frequency-time conversion by IFFT (Inverse Fast Fourier Transform) or the like to generate a time-domain signal.
- IFFT Inverse Fast Fourier Transform
- the multiplexing unit 307 multiplexes the time domain signal generated by the IFFT unit 306, the pilot signal generated by the pilot signal generation unit 310, and the retransmission control signal generated by the retransmission control signal generation unit 311.
- the retransmission control signal is multiplexed only by the multiplexing unit 306 included in the stream signal generation unit 301-1, and the multiplexing units 307 included in the other stream signal generation units 301-2 to 301-Ns are described above.
- the time domain signal and the pilot signal are multiplexed.
- the pilot signal generation unit 310 generates a pilot signal used for propagation path estimation of each stream signal on the reception side. Preferably, an orthogonal pilot signal is generated for each stream.
- the retransmission control signal generation unit 311 determines the number of retransmissions of a packet to be transmitted in each stream based on the success / failure information of each packet reception from the restoration unit 312, and notifies the packet reception device 400 of the determined number of retransmissions. Generate a control signal. In other words, when receiving success / failure information indicating packet reception failure, retransmission control signal generating section 311 generates a retransmission control signal with the number of retransmissions of the packet increased by one, and receiving success / failure information indicating successful packet reception. A retransmission control signal indicating the initial transmission packet is generated by setting the number of retransmissions of the next packet to be transmitted using the same successful stream to “0”.
- retransmission control signal generation section 311 is connected to multiplexing section 307 included in stream signal generation section 301-1, and retransmission control signal generated by retransmission control signal generation section 311 is generated by stream signal generation section 302-1.
- the retransmission control signal generation unit 311 is connected to one of the multiplexing portions 307 of the other stream signal generation units 302-2 to 302-N so that the stream signal is multiplexed to other stream (s). You may make it the structure multiplexed with the stream which a production
- retransmission control signal generation section 311 may generate a retransmission control signal including transmission parameters such as a data modulation scheme, coding rate, and spatial multiplexing number (MIMO rank information).
- MIMO rank information is MIMO multiplexing information defined by the transmission antenna and the reception antenna.
- the GI insertion unit 308 inserts a guard interval GI (Guard Interval) into the output signal of the multiplexing unit 307, and the transmission unit 309 converts the output signal from the GI insertion unit 308 into an analog signal (D / A Conversion), band limitation by filtering processing, and conversion to a frequency band that can be transmitted.
- the same processing is performed in the stream signal generation units 302-2 to 302-Ns other than the stream signal generation unit 301-1, and the output signals from the respective stream signal generation units 302-1 to 302-Ns correspond respectively.
- the transmitting apparatus 300 transmits a signal in which the initial transmission packet or the retransmission packet is spatially multiplexed by being transmitted by the antenna units 301-2 to Ns. Signals transmitted from antenna units 302-1 to 302-Ns are referred to as stream 1 to stream Ns.
- the retransmission packet is described as being transmitted from the same stream and the same antenna as the initial transmission packet, but may be transmitted from a different antenna for each number of retransmissions.
- the retransmission packet is transmitted from the same stream and the same antenna as the initial transmission packet.
- FIG. 12 is a schematic block diagram illustrating the configuration of the packet reception device 400 according to the present embodiment.
- the packet receiver 400 is provided in a mobile station in the downlink and a base station in the uplink by the wireless communication system. Also, it is provided in a relay station on the downlink between the base station and the relay station.
- the packet reception device 400 includes antenna units 401-1 to 401-M (where M is the number of reception antennas), signal processing units for each antenna 402-1 to 402-M, a received packet management unit 403, a detection order determination unit 404, It has an interference cancellation unit 405, a received signal storage unit 406, a response signal generation unit 409, and a transmission unit 410.
- the per-antenna reception processing units 402-1 to 402-M receive and process signals received via the corresponding antenna units 401-1 to 401-M, and receive the reception unit 411, GI removal unit 412, and FFT unit 413. , A propagation path estimation unit 414 is provided.
- the per-antenna reception processing unit 402-1 will be described, but the other per-antenna reception processing units 402-2 to 402-M also have corresponding antenna units 401-2 to 401-M, respectively.
- the configuration is the same as the reception processing unit for each antenna 402-1 except that no signal is output to the reception packet management unit 403.
- the reception unit 411 converts the signal from the packet transmission device 300 received via the antenna unit 401-1 into a frequency band that can be processed by a signal detection process or the like, limits the band by a filtering process, and converts the analog signal into a digital signal (Analogue / Digital conversion).
- the propagation path estimation unit 414 compares the pilot signal included in the digital signal converted by the reception unit 411 with the known pilot signal at the time of transmission in the unit, and compares each of the antenna units 301-1 to 301 of the packet transmission device 300. -Estimates the propagation path characteristics between Ns and the antenna unit 401-1 of the packet reception device 400, and outputs propagation path estimation values (transfer function, impulse response, etc.). In addition, you may make it use the other signal which can estimate a propagation path, such as a control channel and a preamble.
- the GI removal unit 412 removes the guard interval GI included in the digital signal converted by the reception unit 411.
- the FFT unit 413 performs fast Fourier transform FFT processing on the signal from which the GI removal unit 412 has removed the guard interval GI, thereby converting the signal into a frequency domain signal. The same processing is performed in the other antenna-specific reception processing units 402-2 to 402-M. Note that the retransmission control signal may be received from any of the antenna units 402-1 to 402-M and output to the received packet management unit 403.
- the signal R (k) in the k-th subcarrier of the spatially multiplexed signal received by the packet reception device 400 can be expressed by Equation (6).
- H (k) is a propagation path characteristic between the transmission antenna and the reception antenna
- S (k) is a transmission signal for each transmission antenna. That is, N elements S 1 (k),..., S N (k) constituting S (k) are transmitted from the antennas 302-1,. Is the signal of the k-th subcarrier of the stream signal.
- N (k) is noise for each receiving antenna
- T represents a transposed matrix.
- Reception packet management section 403 determines the number of retransmission packet signals each stream transmitted from antenna sections 301-1 to 301-Ns of transmitting apparatus 300 from the retransmission control signal included in the received signal (also includes the initial transmission packet). Data including the number of retransmissions, data modulation scheme, coding rate, spatial multiplexing number (MIMO rank information), and other data related to transmission parameters are extracted.
- the detection order determination unit 404 determines the order in which signals are detected by the interference cancellation unit 405 based on information indicating the number of retransmissions extracted by the received packet management unit 403 and notifies the interference cancellation unit 405 of the order. Details of the order determination by the detection order determination unit 404 will be described later.
- the interference cancellation unit 405 (signal detection unit) transmits the channel estimation value output from the channel estimation unit 414 and the transmission of each packet output from the received packet management unit 403. Based on the data relating to the parameters, transmission is performed from each of the antenna units 301-1 to 301-N of the packet transmission device 300 from the data signal in the frequency domain output from the FFT unit 413 of each of the reception processing units 402-1 to 402-M for each antenna.
- the encoded bit LLR and the encoded bit LLR information bit sequence and the error detection result are output. Details of the operation of the interference cancellation unit 405 will be described later.
- the reception signal storage unit 406 has a function similar to that of the reception signal storage unit 209 of the first embodiment shown in FIG. 5 and stores Ns number of streams, but the reception in the first embodiment Since the signal storage unit 209 stores a signal for each code channel, both embodiments differ in this respect.
- the response signal generation unit 409 and the transmission unit 410 also have the same functions as the response signal generation unit 210 and the transmission unit 211 in the first embodiment.
- the detection order determination unit 404 determines the order in which a spatially multiplexed signal is detected using MIMO based on information indicating the number of retransmissions.
- the packet transmitting apparatus 300 receives the stream 1 composed of the retransmission packet P1 ′′ from the antenna unit 302-1 and the stream 2 composed of the retransmission packet P2 ′ from the antenna unit 302-2. -3 to stream 3 including the initial transmission packet P3 and the stream 4 including initial transmission packet P4 from the antenna unit 302-4 to the antenna units 402-1 to 402-4 of the packet reception device 400 simultaneously.
- the element S 1 (k) of the vector S (k) is the signal of the k-th subcarrier of the retransmission packet P1 ′′
- the element S 2 (k) is the retransmission packet.
- element S 3 (k) is the k-th subcarrier signal of retransmission packet P3, and element S 4 (k) Is a signal of the k-th subcarrier of the retransmission packet P4.
- the packet receiving apparatus 400 receives signals obtained by spatially multiplexing these streams 1 to 4 using the antenna units 402-1 to 402-4.
- the packets P1 ′′ and P2 ′ are the second and first retransmission packets for the initial transmission packets P1 and P2, respectively.
- Received packet management section 403 of packet receiving apparatus 400 obtains the number of retransmissions of packets transmitted by each stream from the retransmission control signal included in the signal received by antenna-specific signal processing section 402-1 via antenna section 401-1. To do.
- packets P1 ′′, P2 ′, P3, and P4 are transmitted in streams 1 to 4, respectively, and the received packet management unit 403 receives the packets P3 and P4 0 times (initially Information indicating that the packet P2 ′ is once (retransmitted packet) and the packet P1 ′′ is twice (retransmitted packet) from the retransmission control signal.
- the detection order determination unit 404 determines the detection order based on the information indicating the number of retransmissions acquired by the received packet management unit 403 so that a packet with a large number of retransmissions is detected first from the stream being transmitted.
- the stream 1 including the retransmission packet P1 ′′ having the highest number of retransmissions among the retransmission packets is detected first, and then the stream 2 including the retransmission packet P2 ′ having the next highest number of retransmissions is detected.
- the detection order is determined so as to detect stream 1 and stream 2 including initial transmission packets P1 and P2 whose number of retransmissions is zero.
- the interference cancellation unit 405 preferentially detects a signal from a stream that transmits a packet with a large number of retransmissions according to the detection order determined by the detection order determination unit 404, and generates the detection signal of the packet with a large number of retransmissions.
- the interference replica is removed from the received signal, and the signal detection of the stream that is transmitting the retransmission packet with the next highest number of retransmissions is performed.
- a packet with a large number of retransmissions is a packet in which many received packets related to this retransmission packet are stored in the reception signal storage unit 406. The more signals that can be combined and the more signals that can be combined, the interference cancellation unit 405 The signal detection accuracy at is good.
- the signal detection of the packet with poor signal detection accuracy (packet with a small number of retransmissions) is performed. As a result, it is possible to improve the detection accuracy of the signal of the packet having a low signal detection accuracy.
- the detection order determining unit 404 determines the detection order based on the number of retransmissions of the packets constituting the stream, and the signal to interference plus noise power ratio (SINR) between packets having the same number of retransmissions.
- the detection order may be determined based on the reception level such as the signal-to-interference noise power ratio SINR, such as detecting the larger one first.
- SINR signal-to-interference noise power ratio
- the streams may be grouped based on the number of packet retransmissions, and the order may be determined so that the packets of each stream are detected in order for each group.
- the order may be determined so that the packets of each stream are detected in order for each group.
- FIG. 14 is a schematic block diagram showing a configuration of an interference cancellation unit 405 that performs successive-type repeated interference cancellation on a spatially multiplexed signal.
- the interference cancellation unit 405 includes a stream 1 in which the packet transmission device 300 as illustrated in FIG. 13 transmits the packet P1 ′′ from the antenna unit 302-1 and a stream 2 in which the packet P2 ′ is transmitted from the antenna unit 302-2.
- the stream 1 to the stream 4 determined by the detection order determination unit 404 from the spatially multiplexed signal composed of the stream 3 transmitted from the antenna unit 302-3 and the stream 4 transmitted from the antenna unit 302-4 to the packet P4.
- These streams are sequentially detected in order based on the detection order of the stream 1.
- a series of processing (detection processing of stream 1 to stream 4) in the interference cancellation unit 405 is performed except that all information bits can be detected without error in the middle. The process is repeatedly executed a predetermined number of times.
- the interference cancellation unit 405 includes stream detection units 1201-1 to 1201-Ns, reception replica generation units 1202-1 to 1202-Ns, symbol replica generation units 1204-1 to 1204-Ns, and a signal processing unit 402 for each antenna.
- the replica of the interference signal is removed from the data signal in the frequency domain output from the FFT unit 413 of ⁇ 1 to 402-M, and the spatially multiplexed stream is separated, and each stream is demodulated, combined, and decoded.
- the stream detection unit 1201-1 detects the signal of the stream 1 with the first detection order
- the stream detection unit 1201-2 detects the signal of the stream 2 with the second detection order
- the stream detection unit 1201 -3 detects the signal of the stream 3 whose detection order is the third
- the symbol replica generation unit 1204-1 generates a symbol replica of the signal constituting the stream 1
- the symbol replica generation unit 1204-2 generates a symbol replica of the signal constituting the stream 2
- the symbol replica generation unit 1204- 3 generates a symbol replica of a signal constituting the stream 3
- Each of the stream detection units 1201-1 to 1201-Ns includes a subtraction unit 1203, a MIMO separation unit 1205 (stream separation unit), a demodulation unit 1207, a deinterleave unit 1208, a depuncture unit 1209, a synthesis unit 1210, and a decoding unit 1211.
- the subtraction unit 1203 subtracts the interference replica (stream replica) generated by the reception replica generation unit 1202 from the output signal of the FFT unit 413 of the per-antenna signal processing units 402-1 to 402-M.
- output signals R 1 to n, i, M (k) for the signal processing unit 402-M for each antenna of the subtraction unit 1203 of the stream detection unit 1201-n are expressed by the following equation (7).
- R M (k) is a frequency domain signal of the k-th subcarrier output from the FFT unit 413 of the per-antenna signal processing unit 402-M
- R ⁇ n, i, M (k) is a received replica generating unit 1202-
- the interference replica of the k-th subcarrier for the stream n received by the antenna unit 401-M in the i-th iterative process generated by n, and k indicates a subcarrier index.
- Reception replica generation sections 1202-1 to 1202-Ns use the symbol replica generated by symbol replica generation sections 1204-1 to 1204-Ns and the propagation path estimation value generated by propagation path estimation section 414 to generate an interference replica (reception Signal replica).
- an interference replica reception Signal replica
- the stream 1 to the stream (n ⁇ 1) and symbol replicas of stream (n + 1) to stream Ns are multiplied by the propagation path estimation value to generate an interference replica.
- the stream 1 to stream (n ⁇ 1) symbol replicas generated in the i-th iteration and the streams generated in the i-1-th iteration ( n + 1) to symbol N of stream Ns and a propagation path estimation value are used to generate a replica of an interference signal that is an interference component of the received signal.
- the replica R ⁇ n, i, M (k) of the interference signal output from the reception replica generation unit 1202-n for the stream n received by the antenna unit 401-M during the i-th iterative process is expressed by the following equation (8). It becomes.
- H u, M (k) is the channel estimation value of the stream u received by the antenna unit 401-M
- S u u, i (k) is the symbol replica generation unit 1204-u in the i-th iteration.
- a symbol replica of the generated stream u is shown.
- the subtraction unit 1203 of the stream detection unit 1201-n applies the signals received by all the antenna units 401-1 to 401-M, that is, the outputs of the FFT units 413 of the signal processing units 402-1 to 402-M for each antenna.
- the above-described interference cancellation processing is performed and output to the MIMO separation unit 1205.
- MIMO separation section 1205 performs stream separation and propagation path compensation of the spatially multiplexed (MIMO) signal on the output of subtraction section 1203 based on the propagation path estimation value that is the output of propagation path estimation section 414, and A stream modulation symbol sequence is generated. Specifically, the stream signal is reproduced by maximum likelihood estimation. Alternatively, a separation method such as calculating a ZF (Zero Factor) weight or an MMSE (Minimum Mean Square Error) weight for the output of the subtraction unit 1203 and multiplying the output of the subtraction unit 1203 by the calculated weight is used.
- ZF Zero Factor
- MMSE Minimum Mean Square Error
- the weighting factors W ZF, n (k), W MMSE, n (k) based on the ZF standard and MMSE standard of the MIMO separation unit 1205 belonging to the stream detection unit 1201-n are expressed by the following equations (9), (10 ).
- H is a complex conjugate transpose of a matrix
- ⁇ 1 is an inverse matrix
- ⁇ 2 is noise power
- I N is an N ⁇ N unit matrix.
- H n (k) is Equation (12).
- Demodulation section 1207 performs demodulation processing on the modulation symbol sequence that is the output signal from MIMO separation section 1205, and extracts a signal for each encoded bit.
- the log likelihood ratio (LLR) for each coded bit is output, similar to the demodulator 708 of the first embodiment shown in FIG.
- Deinterleaving section 1208 performs deinterleaving processing on the signal for each encoded bit output from demodulation section 1207. This deinterleaving process is a rearrangement for returning the order rearranged by the interleaving process in the interleaver unit 304 of the packet transmitting apparatus 300 to the original order.
- the depuncture unit 1209 performs the reverse process to the puncture (bit removal) process performed in the puncture unit 124 in the packet transmission device 300 by the same operation as the depuncture unit 710 of the first embodiment. Is output to the received signal storage unit 406 and the combining unit 1210. That is, a depuncture process for inserting a predetermined virtual value is performed on the bits removed by the puncture process.
- the synthesizing unit 1210 synthesizes the output signal of the depuncture unit 1209 and the already received packet from the received signal storage unit 406 by the same operation as the synthesizing unit 711 of the first embodiment.
- the decoding unit 1211 softens the output signal of the combining unit 1210 by error correction decoding processing for error correction coding such as turbo coding and convolutional coding performed by the error correction coding unit 122 of the packet transmission device 300.
- the log likelihood ratio LLR of the coded bit as the determination result is output.
- Symbol replica generation sections 1204-1 to 1204-Ns generate a symbol replica of each stream using the log likelihood ratio LLR of the encoded bits generated by decoding section 1211.
- the decoding unit 1211 performs error detection processing on the packet by error detection such as cyclic redundancy check CRC performed by the error detection coding unit 121 of the packet transmission device 300, and sends error detection information to the response signal generation unit 409. Output. Also, when outputting no error in the error detection information, the decoding unit 1211 removes redundant bits for error detection from the bit sequence that generated the packet that is the hard decision result of the encoded bit LLR of the error correction decoding result Output information bit sequence.
- error detection such as cyclic redundancy check CRC performed by the error detection coding unit 121 of the packet transmission device 300
- the decoding unit 1211 removes redundant bits for error detection from the bit sequence that generated the packet that is the hard decision result of the encoded bit LLR of the error correction decoding result Output information bit sequence.
- FIG. 15 is a schematic block diagram showing the configuration of the symbol replica generation unit 1204-1.
- the other symbol replica generation units 1204-2 to 1204-Ns have the same configuration.
- the symbol replica generation unit 1204-1 generates a symbol replica based on the encoded bit LLR output every time signal detection of the signal corresponding to the stream 1 is completed by the stream separation unit 1201-1, and interleaves with the puncture unit 1212 And a modulation symbol replica generation unit 1214.
- the puncturing unit 1212 has the same pattern as the LLR of the coded bit that is the output signal of the decoding unit 1211 for each stream (packet) by the puncturing unit 124 of the packet transmitting apparatus 300. Puncture processing is performed using a pattern (puncture pattern in FIG. 4). Similarly to the interleave unit 722 shown in FIG. 8, the interleave unit 1213 uses the same pattern as the pattern applied to the output signal from the puncture unit 1212 for each stream (packet) by the interleave unit 304 of the packet transmission device 300. Perform rearrangement processing.
- modulation symbol replica generation section 1214 modulates the output signal of interleaving section 1213 in the same manner as modulation section 305 of packet transmission apparatus 300 shown in FIG. 11, such as QPSK modulation and 16QAM modulation. Modulation is performed by a method to generate a modulation symbol replica. Modulation symbol replica generation section 1213, that is, symbol replica generation section 1204-1 inputs the generated symbol replicas to reception replica generation sections 1202-2 to 1202-Ns that generate replicas of interference signals for stream 2 to stream Ns. .
- FIG. 16 is a flowchart for explaining the reception operation of the packet reception device 400.
- the received packet management unit 403 acquires the retransmission count information of the packets constituting each stream from the retransmission control signal included in the received signal (S202).
- the detection order determination unit 404 determines the order in which packets are detected (the order in which streams are detected) from the retransmission count information acquired in step S202 (S203).
- the interference cancellation unit 405 sequentially performs signal detection such as interference cancellation processing, MIMO separation, and demodulation processing of the stream of the corresponding packet in accordance with the order of detecting the packets determined in step S203 (S204).
- the decoding unit 1211 performs a decoding process on the output signal from the synthesizing unit (S207), further determines whether there is an error in the signal detected packet (S208), and determines that there is no error in the packet Returns a reception notification ACK, which is a response signal indicating that there is no error, to the packet transmitting apparatus 300 (S210), and ends the process.
- step S208 determines whether or not the number of repetitions of interference cancellation processing and signal detection of these series of streams has reached a predetermined number of repetitions. (S209). If not reached, the process returns to step S204, and the stream interference cancellation process and signal detection are performed again. If it is determined in step S209 that the number of repetitions has been reached, a non-acknowledgment notification NACK that is a response signal requesting retransmission is returned to the packet transmitting apparatus 300 (S211), and the process returns to step S201. The next signal is received.
- the interference cancellation unit 405 which is a successive interference canceller SIC, is used for detection of signals spatially multiplexed by MIMO.
- V-BLAST Very-Bell Laboratories-Layered
- -Space-Time or another separation method that detects the stream in order may be used.
- the embodiment in which the present invention is applied when a spatially multiplexed signal is received by MIMO is shown, but the same applies when a code multiplexed and spatially multiplexed signal is received.
- the detection of the code-multiplexed signal of the first embodiment and the detection of the spatially-multiplexed signal of the present embodiment are applied in combination.
- the detection order determination unit 404 of the packet reception device 400 determines the signal detection order so that detection is performed from packets with a large number of retransmissions among the spatially multiplexed packets, and the interference cancellation unit 405.
- the signal detection order a signal is detected from a packet with a large number of retransmissions, an interference component due to the signal of the detected packet is removed from a received signal, and then a signal detection of a packet with the next largest number of retransmissions is performed in order.
- a signal having a large number of retransmissions and a signal with many signals that can be combined that is, a packet signal with good signal detection accuracy in the interference cancellation unit 405 is detected first, and an interference replica generated from the signal of the detected packet is received.
- the signal detection of the packet with a small number of retransmissions is performed, so the detection accuracy of the packet signal with inferior signal detection accuracy can be improved because the number of retransmissions is small and the number of signals to be combined is small. It becomes. Therefore, even when the received signal is spatially multiplexed as in this embodiment, it is possible to prevent the number of retransmissions of a specific packet from increasing and delay from increasing.
- the stream signal generation units 301-1 to 301-N of the packet transmission device 300 more packets are assigned by allocating such that signals are transmitted from antennas whose channel eigenvalues in MIMO transmission increase as the number of packets with a smaller number of retransmissions increases.
- the interference canceling unit 405 of the receiving apparatus 400 can accurately detect signals of packets with a small number of retransmissions and initial transmission packets.
- the channel eigenvalue is an index indicating the quality of each stream obtained by performing singular value decomposition on a matrix whose elements are propagation path responses of the streams transmitted from the antenna units 302-1 to 302-Ns of the packet transmission device 300. One indicates that the larger the stream, the higher the quality of the stream that can be transmitted.
- the accuracy of removing interference components from the retransmission packet signal based on the initial transmission packet signal is improved, and the signal detection of the retransmission packet can be improved. Also, when detecting a retransmission packet, detection processing is performed on a signal from which an interference component due to a retransmission packet having a smaller number of retransmissions than the detected retransmission packet is removed, and detection accuracy of a signal having a large number of retransmissions is improved. It becomes possible to improve.
- the present invention is applied to the case where the initial transmission packet and the retransmission packet of the hybrid automatic retransmission HARQ are code-multiplexed by the spreading code sequence, and the inter-code interference MCI is repeatedly removed by the successive interference canceller SIC.
- a communication system including a packet transmission device 500 and a packet reception device 600 different from the first embodiment will be described.
- the spreading code sequence in the present embodiment is an orthogonal variable spreading factor code (OVSF).
- FIG. 17 is a schematic block diagram showing the configuration of the packet transmission device 500 according to the present embodiment.
- Packet transmission apparatus 500 includes code channel signal generation units 501-1 to 501-N, code multiplexing unit 102, IFFT unit 103, multiplexing unit 104, GI insertion unit 105, transmission unit 106, pilot signal generation unit 107, retransmission control signal.
- a generation unit 108, a restoration unit 109, a reception unit 110, an antenna unit 120, and a retransmission control unit 1601 are included.
- Each of code channel signal generation units 501-1 to 501-N includes an encoding unit 111, an interleaving unit 112, a modulation unit 113, a spreading unit 114, and a power control unit 1602.
- the packet transmission device 500 is different from the packet transmission device 100 of the first embodiment in that a retransmission control unit 1601 and a power control unit 1602 are added, and the spreading unit 114 obtains control information from the full retransmission control unit 1602. Is different. Since the other units (reference numerals 102 to 114 and 120) have the same functions, the following description will be made on parts different from the packet transmitting apparatus 100.
- the retransmission control unit 1601 calculates the number of retransmissions of the packet of each code channel based on the response signal (acceptance notification ACK / non-acknowledgment notification NACK) of the packet reception device 600 received from the restoration unit 109, and based on the calculated number of retransmissions
- the spreading code sequence to be multiplied by the spreading section 114 corresponding to each code channel (each packet) is determined, and the determined spreading code sequence is notified to the corresponding spreading section 114. Details of the method of selecting the spreading code sequence will be described later.
- retransmission control section 1601 calculates the number of retransmissions of the packet of each code channel based on the response signal (acknowledgment ACK / non-acknowledgement NACK) of packet reception apparatus 600 received from restoration section 109, and the calculated number of retransmissions Based on the above, the transmission power for transmitting each code channel (each packet) is determined, and the determined transmission power is notified to the corresponding power control section 1602. Details of the transmission power determination method will be described later.
- the spreading unit 114 multiplies the output signal from the modulation unit 113 by the spreading code sequence according to the notification information from the retransmission control unit 1601.
- the power control unit 1602 controls the power of the output signal from the spreading unit 114 according to the notification information of the retransmission control unit 1601, that is, by changing the amplitude, the transmission power determined by the retransmission control unit 1601 is used for each code channel ( Each packet) is controlled to be transmitted. Note that the power control unit 1602 may not be provided, and the spreading unit 114 may change the amplitude of the output signal in accordance with the notification information of the retransmission control unit 1601.
- the retransmission control unit 1601 calculates the number of retransmissions of a packet to be transmitted on each code channel from the response signal of the packet reception device 600 received by the restoration unit 109, and the spreading code sequence to be multiplied by the code channel with a larger number of retransmissions is orthogonal. It is assumed that the spread code sequence is resistant to the collapse of.
- three code channels CH1, CH2, and CH3 are code-multiplexed and transmitted, the code channels CH1 and CH2 transmit a packet with the number of retransmissions of 0 (initial transmission packet), and the code channel CH3 has a number of retransmissions of 1
- the retransmission control unit 1601 assigns a spreading code sequence that is resistant to the loss of orthogonality in the code channel CH3, that is, the orthogonality is not easily lost.
- OVSF Orthogonal Variable Spreading Factor
- C4.3 is a spreading code sequence generated from the spreading code sequence C2.2, and there is no spreading code sequence in which the parent code C2.2 is common among the spreading code sequences to be used. High tolerance. In other words, spreading code sequences with different parent codes, in other words, the more the spreading code sequences having a common parent code among the spreading code sequences used, the more resistant to the loss of orthogonality.
- Retransmission control section 1601 determines transmission power for each code channel (each packet) and performs power control.
- Retransmission control section 1602 calculates the number of retransmissions for each code channel from the response signal of packet reception apparatus 600 received by restoration section 109, and gives a larger transmission power to a code channel with a large number of retransmissions than a code channel with a small number of retransmissions.
- retransmission control section 1601 holds a power level table for the number of retransmissions shown in FIG. 19, and determines the transmission power of each code channel according to the power level table.
- the power level table is a table in which the power level, the number of retransmissions, and the power value are stored in association with each other as in the example of FIG. 19. For example, the power level “ 1 ”, the number of retransmissions“ 0 ”and the power value“ 0 dB ”are stored in association with each other, and the power level“ 2 ”, the number of retransmissions“ 1 to 3 ”and the power value“ 1.5 dB ”are stored in association with each other. ing.
- the power value in FIG. 19 indicates an increase in transmission power with respect to the power level “1”.
- retransmission control section 1601 refers to the power level table, assigns transmission power of power level 2 (1.5 dB) to code channel CH3 having a large number of retransmissions, and is CH1 which is the initial transmission packet.
- CH2 is assigned transmission power of power level 1 (0 dB).
- the 20 exemplifies signal power when the code multiplexing unit 102 multiplexes the output of the power control unit 1602 when transmission power is assigned to the code channels CH1 to CH3 based on the power level table shown in FIG.
- the code channel CH3 having a large number of retransmissions is “1.5 dB”, which is a power value larger than “0 dB” of the code channels CH1 and CH2.
- FIG. 21 is a schematic block diagram showing the configuration of the packet reception device 600 according to this embodiment.
- the packet reception device 600 includes an antenna unit 201, a reception unit 202, a propagation path estimation unit 203, a GI removal unit 204, an FFT unit 205, a reception packet management unit 206, a detection order determination unit 207, a reception signal storage unit 1801, and an interference cancellation unit. 1802, a received signal storage unit 209, a response signal generation unit 210, and a transmission unit 211.
- the packet reception device 600 is different from the packet reception device 200 of the first embodiment in that a reception signal storage unit 1801 is added and an interference cancellation unit 1802 uses a signal from the reception signal storage unit 1801 as an input signal. Since the other units (reference numerals 201 to 207 and 209 to 211) have the same functions, the following description will be made on parts different from the packet receiving apparatus 200.
- Received signal storage section 1801 stores the output signals from FFT section 205 and propagation path estimation section 203 in association with each other.
- the reception signal storage unit 1801 outputs the output signal of the FFT unit 205 including at least one related packet received before this retransmission packet.
- the propagation path estimation value when the related packet is received are output to the interference cancellation unit 1802.
- the received signal storage unit 1801 includes an FFT including at least one of the initial transmission packet and the first retransmission packet for the stored second retransmission packet.
- the output signal of unit 205 and the propagation path estimation value when the packet is received are output to interference cancellation unit 1802.
- FIG. 22 is a schematic block diagram showing the configuration of the interference cancellation unit 1802 of the packet reception device 600 according to this embodiment.
- the inputs to the subtraction units 706-1 to 706-N are the output of the FFT unit 205 and the output of the reception signal storage unit 1801
- the MCI replica generation units 704-1 to 704- N and the inputs to the propagation path compensation units 701-1 to 701-N are the output of the propagation path estimation unit 203 and the output of the received signal storage unit 1801.
- the interference cancellation unit 1802 receives a signal received by the reception unit 202, that is, from the FFT unit 205.
- a signal received by the reception unit 202 that is, from the FFT unit 205.
- an output signal (an already received signal) of the FFT unit 205 including at least one of the related packets received before this retransmission packet, and when the related packet is received The propagation path estimated value is acquired from the received signal storage unit 1801, and according to the detection order determined again by the detection order determining unit 207 for the received signal, the interference component is removed from the received signal using the detected packet, Packets are also detected from already received signals.
- the related packet (related signal) of the retransmission packet (retransmission signal, number of retransmissions q1 is q1> 0) is the initial transmission packet of the retransmission packet or the initial packet of the retransmission packet excluding the retransmission packet itself.
- This is a retransmission packet of the transmission packet (the number of retransmissions q2 is q1> q2> 0).
- the detected packet is a packet detected from the signal received by the receiving unit 202 and a packet detected from the received signal when the received signal is received. Note that the packet detected from the received signal is the one stored in the received signal storage unit 209.
- FIG. 23 is a diagram illustrating the operation of the packet reception device 600 according to the present embodiment.
- the packet reception device 600 receives a second frame in which packet 3, packet 2, and packet 4 are code-multiplexed.
- the packet 3 is the second retransmission packet
- the initial transmission is transmitted in a past frame (not shown), and the first retransmission is performed in the first frame transmitted before the second frame.
- Packet 2 is the first retransmission packet, and the first transmission is transmitted in the first frame.
- Packet 4 is an initial transmission packet.
- the reception packet management unit 206 acquires information on the number of retransmissions of each packet from the retransmission control signal for the second frame, and the detection order determination unit 207 The detection order is determined in descending order. Since the information on the number of retransmissions of the packet 1 has already been acquired, the detection order determined by the detection order determination unit 207 is packet 1, packet 3, packet 2, and packet 4 in this case. Here, since the packet 1 has already been acquired as a correct signal without error when the second frame is received, the detection order is the first so as to be detected first regardless of the number of retransmissions.
- the output signal of the FFT unit 205 of the signal obtained by code-multiplexing the second frame, that is, the packet 2, the packet 3, and the packet 4 is stored in the received signal storage unit 1801.
- the initial transmission and the first retransmission signal of packet 3 and the initial transmission signal of packet 2 are stored in reception signal storage section 1801.
- the signal of the second frame is input to the interference cancellation unit 1802, the MCI cancellation processing by the subtraction unit 706, the despreading processing by the despreading unit 707, the demodulation processing by the demodulation unit 708, the deinterleaving by the deinterleaving unit 709,
- the detection process including the depuncture process by the depuncture unit 710 and the decoding process by the decoding unit 712 are repeated a predetermined number of times, and the output of the depuncture unit 710 after the predetermined number of times is stored in the received signal storage unit 209.
- the received signal storage unit 209 also stores the output of the depuncture unit 710 for packets already received before the second frame. Further, in the signal detection process and the decoding process of the second frame described above, the order of the packets to be subjected to the detection process and the decoding process may be any. Also, in the above-described second frame signal detection process and decoding process, the synthesis process by the synthesis unit 711 is not performed.
- the interference cancellation unit 1802 codes the packet 1, packet 2 and packet 3 of the first frame from the received signal storage unit 1801.
- the multiplexed signal is acquired, and signal detection processing and decoding processing are performed on the signal of the first frame.
- the detection order is packet 1, packet 3, and packet 2 with a large number of retransmissions (however, for packet 1, only the interference cancellation process for other packets is performed using the detected correct signal stored in the received signal storage unit 209) I do).
- signal detection processing for packet 3 is performed as follows. First, the MCI replica generated by the MCI replica generation unit 704-2 from the code channel replica of the packet 1 and the packet 2 and the propagation path estimation value at the time of reception of the first frame from the reception signal storage unit 1801 by the subtraction unit 706-2. After the signal is subtracted from the signal of the first frame, the despreading unit 707 performs despreading processing, the demodulation unit 708 performs demodulation processing, the deinterleaving unit 709 performs deinterleaving processing, and the depuncture unit 710 performs depuncturing processing, and is depunctured. The first retransmission signal of packet 3 is obtained.
- the combining unit 711 combines the first retransmission signal of the packet 3 after the depuncture processing with the second retransmission signal and the first transmission signal of the packet 3 stored in the reception signal storage unit 209. Then, decoding section 712 performs decoding processing on the output signal of combining section 711, and then outputs the encoded bit LLR of packet 3 to code channel replica generation section 705-2, where code channel replica generation section 705- 2 generates a code channel replica of packet 3 from the coded bit LLR.
- the decoding unit 712 performs a decoding process on the output signal of the synthesis unit 711, and then outputs the encoded bit LLR of the packet 2 to the code channel replica generation unit 705-3. After the above interference cancellation, signal detection processing, synthesis processing, and decoding processing are repeated a predetermined number of times, error detection is performed.
- the packet reception device 600 when the packet reception device 600 receives the signal of the second frame in which the initial transmission packet and the retransmission packet are code-multiplexed, the packet reception device 600 is a related packet of the retransmission packet and the retransmission packet. Using a combination of the received related packets, signal detection for the first frame signal including the related packets is performed again in order from the packet having the highest number of retransmissions when the second frame is received. For this reason, after detecting the signal from the packet signal with many signals that can be combined with good signal detection accuracy in the interference cancellation unit 1802 and removing the interference replica generated from the signal of the detected packet from the received signal, the signal detection accuracy is improved.
- the spreading code sequence that is resistant to the loss of orthogonality is preferentially assigned from the packet with the large number of retransmissions, so that the signal detection accuracy of the packet with the large number of retransmissions is further improved. Can do.
- the packet receiving apparatus 600 by performing signal detection preferentially from a packet with a large number of retransmissions, it is possible to improve the signal detection accuracy of a packet with a low number of retransmissions with a poor signal detection accuracy.
- the packet transmission device 500 allocates a larger transmission power to a packet having a large number of retransmissions, the signal detection accuracy of the packet having a large number of retransmissions can be further improved.
- the packet receiving apparatus 600 by performing signal detection preferentially from a packet with a large number of retransmissions, it is possible to improve the signal detection accuracy of a packet with a low number of retransmissions with a poor signal detection accuracy.
- the packet transmission apparatus 500 may include only one of spreading code sequence allocation and power control based on the number of retransmissions of the code channel described above.
- the transmission power control described above is performed on code-multiplexed code channels.
- the present invention can also be applied to other multiplexed signals such as spatial multiplexing in the second embodiment. is there.
- the packet reception device 600 of the present embodiment can also receive a signal transmitted by the packet transmission device 100 of the first embodiment.
- the spreading code sequence having a spreading factor of “4” has been described.
- other spreading factors may be used.
- the orthogonal variable spreading factor OVSF code has been described as being used, other codes may be used.
- the spread code sequences to be used need only have a low correlation so that a desired signal can be detected by despreading, and do not necessarily have to be orthogonal.
- a spreading code sequence having a low correlation with spreading code sequences used for other code channels may be used as a spreading code sequence resistant to the loss of orthogonality, that is, a code channel with a large number of retransmissions.
- a spreading code sequence having a low correlation with spreading code sequences used for other code channels may be used.
- multi-carrier transmission such as OFDM, MC-CDMA (Multi Carrier-Code Division Multiple Access), but SC-FDMA (Single Carrier-Frequency Division).
- SC-FDMA Single Carrier-Frequency Division
- Single carrier transmission such as Multiple Access (Multiple Access), DS-CDMA (Direct Spread-Code Division Multiple Access), etc.
- SIC Successive Interference Canceler
- code channel signal generation units 101-1 to 101-N code multiplexing unit 102, IFFT unit 103, multiplexing unit 104, GI insertion unit 105, pilot signal generation unit 107, retransmission control signal generation unit 108 in FIG.
- Restoration unit 109, retransmission control unit 1601, and propagation path estimation unit 203, GI removal unit 204, FFT unit 205, received packet management unit 206, detection order determination unit 207, interference cancellation unit 208, response signal generation unit 210 in FIG. May be realized by dedicated hardware, and a program for realizing the functions of these units is recorded on a computer-readable recording medium, and the program recorded on the recording medium is recorded on the computer.
- the processing of each unit may be performed by reading it into the system and executing it.
- the “computer system” includes an OS and hardware such as peripheral devices.
- the “computer-readable recording medium” means a storage device such as a flexible disk, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case is also used to hold a program for a certain period of time.
- the program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.
- the present invention is suitable for use in a mobile phone system that transmits a packet from a mobile phone terminal to a base station apparatus, but is not limited thereto.
- DESCRIPTION OF SYMBOLS 100 Packet transmission apparatus 101-1 to 101-N ... Code channel signal generation part 102 ... Code multiplexing part 103 ... IFFT part 104 ... Multiplexing part 105 ... GI insertion part 106 ... Transmission part 107 ... Pilot signal generation part 108 ... Retransmission control Signal generation unit 109 ... restoration unit 110 ... reception unit 111 ... encoding unit 112 ... interleaving unit 113 ... modulation unit 114 ... spreading unit 120 ... antenna unit 121 ... error detection encoding unit 122 ... error correction encoding unit 123 ... encoding Bit storage unit 124 ... Puncture unit 200 ... Packet receiver 201 ...
- Antenna unit 202 ... Receiver unit 203 ... Propagation path estimation unit 204 ... GI removal unit 205 ... FFT unit 206 ... Received packet management unit 207 ... Detection order determination unit 208 ... Interference Cancellation unit 209 ... reception signal storage unit 210 ... response signal generation unit 21 DESCRIPTION OF SYMBOLS 1 ... Transmission part 701-1 to 701-N ... Propagation path compensation part 703-1 to 703-N ... Code separation part 704-1 to 704-N ... MCI replica generation part 705-1 to 705-N ...
- Retransmission control signal generation unit 312 ... Restoration unit 313 ... Reception unit 400 ... Packet reception device 401-1 to 401-M ... Antenna unit 402-1 to 402-M ... Signal processing unit for each antenna 403 ... Received packet Management unit 404 ... detection order determination unit 405 ... interference cancellation unit 406 ... received signal storage unit 409 ... response signal generation unit 410 ... transmission unit 411 ... reception unit 412 ... GI removal unit 413 ... FFT unit 414 ... propagation path estimation unit 500 ... Packet transmitters 501-1 to 501-N ... code channel signal generator 600 ... Packet receivers 1201-1 to 1201-Ns ... stream detectors 1202-1 to 1202-Ns ...
- received replica generator 1203 ... subtractor 1204- 1 to 1204-Ns ... symbol replica generation unit 1205 ... MIMO separation unit 120 ... demodulation unit 1208 ... deinterleave unit 1209 ... depuncture unit 1210 ... combination unit 1211 ... decoding unit 1212 ... puncture unit 1213 ... interleave unit 1214 ... modulation symbol replica generation unit 1601 ... retransmission control unit 1602 ... power control unit 1801 ... received signal storage Unit 1802 ... interference canceling unit 3001, 3002 ... inner encoder 3003 ... inner interleaving unit
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Abstract
Description
本願は、2008年07月09日に、日本に出願された特願2008-179111号に基づき優先権を主張し、その内容をここに援用する。
以下、図面を参照して、本発明の第1の実施形態について説明する。本実施形態では、パケット送信装置100(第1の通信装置)とパケット受信装置200(第2の通信装置)とを備え、MC-CDM(Multi Carrier-Code Division Multiplexing:マルチキャリア符号分割多重)方式、および、受信した信号に誤りを検出すると送信元に再送を要求するハイブリッド自動再送HARQを適用したパケット通信システム(通信システム)において、パケット送信装置100(第1の通信装置)が、初送パケットと該初送パケットより以前のいずれかの初送パケットに関する再送パケットとをコード多重した信号を送信し、繰り返し処理を用いた逐次型干渉キャンセラ(SIC:Successive Interference Canceller)を具備したパケット受信装置200(第2の通信装置)が、パケット送信装置100が送信した信号を受信し、コード多重されている信号のうち、再送パケットの信号を優先して、順に信号検出する。
誤り訂正符号化部122は、内部符号器3001、3002、内部インターリーブ部3003を具備し、誤り検出符号化部121からの誤り検出符号化された情報ビット系列が入力されると、誤り訂正符号化部122は、システマティックビットx、パリティビットz、パリティビットz’の3種類の情報ビット系列を出力する。ここで、システマティックビットxは、誤り検出符号化部121から入力されたビット系列そのものである。パリティビットzは誤り検出符号化部121からのビット系列を内部符号器3001が符号化処理を行った出力結果である。パリティビットz’は誤り検出符号化部121からのビット系列をまず内部インターリーブ部3003がインターリーブ処理し、このインターリーブ処理した結果を入力された内部符号器3002が符号化処理を行った出力結果である。ここで、内部符号器3001と内部符号器3002は同じ符号化方式の符号化を行う同様の符号器でもよいし、異なる符号器であっても良い。好ましくは、内部符号器3001、内部符号器3002ともに再帰的畳み込み符号器を用いる。以降では、誤り訂正符号化部122は、図3に示す構成でターボ符号を用いた場合で説明する。
IFFT部103への入力において、第k番目サブキャリアに割り当てるコード多重部102からの出力信号をS(k)とおくと、式(1)のように表すことができる。
拡散部724は、変調シンボルレプリカ生成部723から出力された変調シンボルレプリカを、拡散符号C1…CNの拡散率分だけ複製し、拡散符号C1…CNのうち、当該拡散部724にて生成するコードチャネルレプリカのコードチャネルにおける拡散符号を乗算して、コードチャネルレプリカ(データ信号レプリカ)を生成する。
まず、MCIレプリカ生成部(干渉レプリカ生成部)704-1は、干渉キャンセル部208における繰り返し処理の第i回目の繰り返しにおいて、最初に検出するコードチャネルCH1をコード分離部703-1において信号検出するので、第i-1回目の繰り返しにおいてコードチャネルレプリカ生成部705-2~705-Nが生成したコードチャネルCH2~CH4のレプリカ信号であるS^i-1,2~S^i-1,4をコード多重し、さらに伝搬路推定部203が算出した伝搬路推定値を乗算することでコードチャネルCH1の信号に対して干渉となる成分のレプリカであるMCIレプリカを生成する。
次に、減算部706-1は、FFT部205からの出力信号から、MCIレプリカ生成部704-1が生成したコードチャネルCH1に対するMCIレプリカを減算する。
以下に説明する、コードチャネルCH2、CH3、CH4に対するMCIレプリカの生成処理では、コードチャネルCH1に対するMCIレプリカの生成処理とは、MCIレプリカ生成部704に入力されるコードチャネルレプリカが異なる。
なお、逐次型の繰り返し干渉キャンセラである上述の干渉キャンセル部208において、i=1の場合、第i-1回目コードチャネルレプリカS^i-1,n=S^0,nは生成できないため、MCIレプリカ生成部704-1~704-Nは、生成可能なi=1のコードチャネルレプリカのみでMCIレプリカを生成する。
また、デインターリーブ部709、デパンクチャ部710は、検出順決定部207による検出順に従って設定された、各々のコードチャネルに対応したパターンに従って処理が行われる。逆拡散部707は、検出順決定部207による検出順に従って設定された、各々のコードチャネル固有の送信時に乗算された拡散符号系列を乗算する。
一方、ステップS109にて、繰り返し数まで繰り返していると判定したときは、応答信号生成部210は、再送要求する旨の応答信号をパケット送信装置100に返信し(S111)、ステップS101に戻って、次の信号を受信する。
第1の実施形態では、ハイブリッド自動再送HARQの初送パケットと再送パケットとが拡散符号によってコード多重され、コード間干渉MCIを繰り返し遂次型干渉キャンセラ(SIC)によって除去する場合について説明した。第2の実施形態では、パケット送信装置300とパケット受信装置400とを備える通信システムであって、パケット送信装置300が送信した初送パケットと再送パケットとがMIMO(Multi Input Multi Output:マルチ入力マルチ出力)を用いて空間多重され、パケット受信装置400は、他ストリームの信号を繰り返し逐次型干渉キャンセラ(SIC)によって除去する通信システムについて説明する。本実施形態では、パケットの伝送方式として、OFDM方式(Orthogonal Frequency Division Multiplexing:直交周波数分割多重)方式を適用した場合で説明する。
パケット送信装置300は、ストリーム信号生成部301-1~301-Ns(ただし、Nsはストリーム数)、アンテナ部302-1~302-Ns、再送制御信号生成部311、復元部312、受信部313を有し、各パケットを構成する異なる情報ビット系列から生成したNs個のストリーム信号を、各アンテナ部302-1~302-Nsから1つずつ送信する。また、パケット送信装置300は、パケット受信装置400からの応答信号を含む信号を復元する。
パケット受信装置400は、アンテナ部401-1~401-M(ただし、Mは受信アンテナ数)、アンテナ毎信号処理部402-1~402-M、受信パケット管理部403、検出順決定部404、干渉キャンセル部405、受信信号記憶部406、応答信号生成部409、送信部410を有する。
なお、検出順決定部404は、各ストリームを構成するパケットの再送回数に基づいて、1ストリームずつ順に各ストリームのパケットを検出(ストリームの干渉キャンセルとMIMOの空間多重を分離)する順番を決定してもよいし、パケットの再送回数に基づいてストリームをグループ分けし、グループ毎に、順に各ストリームのパケットを検出するように順番を決定してもよい。グループ毎に決定する場合の例としては、ストリームを構成しているパケットが初送パケットか、再送パケットかでグループ分けするなどがある。
復号部1211は、合成部1210の出力信号に対して、パケット送信装置300の誤り訂正符号化部122が行ったターボ符号化、畳み込み符号化などの誤り訂正符号化に対する誤り訂正復号処理により、軟判定結果である符号化ビットの対数尤度比LLRを出力する。シンボルレプリカ生成部1204-1~1204-Nsは、復号部1211が生成した符号化ビットの対数尤度比LLRを用いて各ストリームのシンボルレプリカを生成する。
また、本実施形態では、MIMOで空間多重された信号を受信した場合に、本発明を適用した実施形態を示しているが、コード多重および空間多重された信号を受信した場合においても、同様に適用可能で有り、その際には、第1の実施形態のコード多重された信号の検出と本実施形態の空間多重された信号の検出を組み合わせて適用する。
第3の実施形態では、ハイブリッド自動再送HARQの初送パケットと再送パケットとが拡散符号系列によってコード多重され、コード間干渉MCIを繰り返し遂次型干渉キャンセラSICによって除去する場合について、本発明を適用した通信システムであって、第1の実施形態とは別のパケット送信装置500とパケット受信装置600を備える通信システムについて説明する。なお、本実施形態における拡散符号系列は、直交可変拡散率符号(Orthogonal Variable Spreading Factor;OVSF)である。
たとえば、3つのコードチャネルCH1、CH2、CH3がコード多重されて送信され、コードチャネルCH1、CH2が再送回数0回のパケット(初送パケット)を送信し、コードチャネルCH3が再送回数1回のパケット(再送パケット)を送信する場合、再送制御部1601は、コードチャネルCH3に直交性の崩れへの耐性がある、すなわち直交性が崩れ難い拡散符号系列を割り当てる。
たとえば、再送制御部1601は、図19に示す再送回数に対する電力レベルテーブルを保持しており、該電力レベルテーブルに従い、各コードチャネルの送信電力を決定する。電力レベルテーブルは、図19の例のように、電力レベルと再送回数と電力値とを対応させて格納したテーブルであり、再送回数が多いほど送信電力が大きくなるように、例えば、電力レベル「1」と再送回数「0」と電力値「0dB」とを対応させて格納し、電力レベル「2」と再送回数「1から3」と電力値「1.5dB」とを対応させて格納している。図19の電力値は、電力レベル「1」に対する送信電力の増分を示す。
たとえば、パケット3、パケット2、パケット4がコード多重された第2のフレームをパケット受信装置600が受信したとする。ここで、パケット3は2回目の再送パケットで過去のフレーム(不図示)で初送を送信し、第2のフレームの前に送信された第1のフレームで1回目の再送を行っている。パケット2は1回目の再送パケットで、第1のフレームで初送を送信している。パケット4は初送パケットである。
次に、干渉キャンセル部1802に第2のフレームの信号が入力され、減算部706によるMCIキャンセル処理、逆拡散部707による逆拡散処理、復調部708による復調処理、デインターリーブ部709によるデインターリーブ、デパンクチャ部710によるデパンクチャ処理を含む検出処理と、復号部712による復号処理とを所定回数繰り返し行い、所定回数後のデパンクチャ部710の出力を受信信号記憶部209に記憶する。
また、パケット送信装置500は、前述のコードチャネルの再送回数に基づく拡散符号系列の割り当て、および電力制御のどちらか一方だけ備えていてもよい。
また、本実施形態では、上述の送信電力制御をコード多重されたコードチャネルに対して行っているが、第2の実施形態における空間多重など他の多重信号に対しても適用することが可能である。
なお、本実施形態のパケット受信装置600は、第1の実施形態のパケット送信装置100が送信した信号を受信することも可能である。
101-1~101-N…コードチャネル信号生成部
102…コード多重部
103…IFFT部
104…多重部
105…GI挿入部
106…送信部
107…パイロット信号生成部
108…再送制御信号生成部
109…復元部
110…受信部
111…符号化部
112…インターリーブ部
113…変調部
114…拡散部
120…アンテナ部
121…誤り検出符号化部
122…誤り訂正符号化部
123…符号化ビット記憶部
124…パンクチャ部
200…パケット受信装置
201…アンテナ部
202…受信部
203…伝搬路推定部
204…GI除去部
205…FFT部
206…受信パケット管理部
207…検出順決定部
208…干渉キャンセル部
209…受信信号記憶部
210…応答信号生成部
211…送信部
701-1~701-N…伝搬路補償部
703-1~703-N…コード分離部
704-1~704-N…MCIレプリカ生成部
705-1~705-N…コードチャネルレプリカ生成部
706-1~706-N…減算部
707…逆拡散部
708…復調部
709…デインターリーブ部
710…デパンクチャ部
711…合成部
712…復号部
721…パンクチャ部
722…インターリーブ部
723…変調シンボルレプリカ生成部
724…拡散部
300…パケット送信装置
301-1~301-Ns…ストリーム信号生成部
302-1~302-Ns…アンテナ部
303…符号化部
304…インターリーブ部
305…変調部
306…IFFT部
307…多重部
308…GI挿入部
309…送信部
310…パイロット信号生成部
311…再送制御信号生成部
312…復元部
313…受信部
400…パケット受信装置
401-1~401-M…アンテナ部
402-1~402-M…アンテナ毎信号処理部
403…受信パケット管理部
404…検出順決定部
405…干渉キャンセル部
406…受信信号記憶部
409…応答信号生成部
410…送信部
411…受信部
412…GI除去部
413…FFT部
414…伝搬路推定部
500…パケット送信装置
501-1~501-N…コードチャネル信号生成部
600…パケット受信装置
1201-1~1201-Ns…ストリーム検出部
1202-1~1202-Ns…受信レプリカ生成部
1203…減算部
1204-1~1204-Ns…シンボルレプリカ生成部
1205…MIMO分離部
1207…復調部
1208…デインターリーブ部
1209…デパンクチャ部
1210…合成部
1211…復号部
1212…パンクチャ部
1213…インターリーブ部
1214…変調シンボルレプリカ生成部
1601…再送制御部
1602…電力制御部
1801…受信信号記憶部
1802…干渉キャンセル部
3001、3002…内部符号器
3003…内部インターリーブ部
Claims (18)
- 受信した信号に誤りを検出すると送信元に再送を要求するハイブリッド自動再送を行う通信装置において、
初送信号といずれかの信号に対する再送信号とを含む信号であって、前記初送信号と前記再送信号とが多重化された信号を受信する受信部と、
前記受信部が受信した信号に含まれる前記初送信号と前記再送信号との再送回数に応じて、前記受信部が受信した信号から、前記初送信号と前記再送信号とを検出する順番を決定する検出順決定部と、
前記検出順決定部が決定した順番に従い、当該装置により検出済の信号であって、前記初送信号に関する検出済の信号および前記再送信号に関する検出済の信号を用いて、前記受信部が受信した信号から干渉成分を除去して、前記受信部が受信した信号から前記初送信号および前記再送信号を検出する信号検出部と
を具備し、
前記信号検出部は、検出した前記再送信号と、前記再送信号以前に受信した関連信号の少なくとも一つが含まれている既受信信号から検出した信号とを合成する合成部を具備すること
を特徴とする通信装置。 - 前記検出順決定部は、前記再送信号の順番が前記初送信号より先になるように検出順を決定することを特徴とする請求項1に記載の通信装置。
- 前記検出順決定部は、再送回数が多い信号から順番に検出するように検出する順番を決定することを特徴とする請求項1に記載の通信装置。
- 前記検出順決定部は、前記初送信号および前記再送信号のうち、受信信号電力、受信信号対干渉雑音電力比により代表される受信レベルを基準として順番を決定することを特徴とする請求項2または請求項3に記載の通信装置。
- 前記初送信号および前記再送信号は、送信元において誤り訂正符号化された信号であり、
前記信号検出部は、前記信号を検出する際に、当該装置により検出済の信号を前記誤り訂正符号により誤り訂正復号処理した信号を用いて検出対象としている信号に対する干渉成分のレプリカ信号を生成し、前記受信部が受信した信号から該レプリカ信号を除去することを特徴とする請求項1に記載の通信装置。 - 前記信号検出部は、前記受信部が受信した信号に再送信号が含まれているときは、該再送信号以前に受信した関連信号の少なくとも一つが含まれている既受信信号について前記検出順決定部が再度決定した検出順に従い、検出済の信号を用いて、前記既受信信号から干渉成分を除去して、前記既受信信号から信号を検出すること
を特徴とする請求項1に記載の通信装置。 - 前記受信部が受信する信号は、前記初送信号と前記再送信号とに各々に固有の拡散符号系列が乗算されたコード多重された信号であり、
前記信号検出部は、前記受信部が受信した信号から干渉成分を除去した後、該干渉成分を除去した信号に、検出対象としている信号に固有の前記拡散符号を乗算して、前記検出対象としている信号を検出することを特徴とする請求項1に記載の通信装置。 - 前記受信部が受信する信号は、前記初送信号と前記再送信号とが各々異なるアンテナから送信されて空間多重された信号であり、
前記信号検出部は、前記受信部が受信した信号から干渉成分を除去した後、前記アンテナ毎の伝搬路推定値に基づいて、該干渉成分を除去した信号から前記検出対象としている信号を検出することを特徴とする請求項1に記載の通信装置。 - 前記信号検出部は、前記検出順決定部が決定した順番に従った前記初送信号および前記再送信号の検出を、各信号について1回ずつ行うことを特徴とする請求項1に記載の通信装置。
- 前記信号検出部は、前記検出順決定部が決定した順番に従った前記初送信号および前記再送信号の検出を、複数回繰り返すことを特徴とする請求項1に記載の通信装置。
- 第1の通信装置と第2の通信装置とを具備し、前記第1の通信装置から受信した信号に誤りを検出すると、前記第2の通信装置が前記第1の通信装置に再送を要求するハイブリッド自動再送を行う通信システムにおいて、
前記第2の通信装置は、
初送信号といずれかの信号に対する再送信号とを含む信号であって、前記初送信号と前記再送信号とが多重化された信号を受信する受信部と、
前記受信部が受信した信号に含まれる前記初送信号と前記再送信号との再送回数に応じて、前記受信部が受信した信号から、前記初送信号と前記再送信号とを検出する順番を決定する検出順決定部と、
前記検出順決定部が決定した順番に従い、当該装置により検出済の信号であって、前記初送信号に関する検出済の信号および前記再送信号に関する検出済の信号を用いて、前記受信部が受信した信号から干渉成分を除去して、前記初送信号および前記再送信号を検出する信号検出部と
を具備し、
前記信号検出部は、検出した前記再送信号と、前記再送信号以前に受信した関連信号の少なくとも一つが含まれている既受信信号から検出した信号とを合成する合成部を具備すること
を特徴とする通信システム。 - 前記初送信号および前記再送信号は、誤り訂正符号化された信号であり、
前記信号検出部は、前記信号を検出する際に、当該装置により検出済の信号を前記誤り訂正符号により誤り訂正復号処理した信号を用いて検出対象としている信号に対する干渉成分のレプリカ信号を生成し、前記受信部が受信した信号から該レプリカ信号を除去すること
を特徴とする請求項11に記載の通信システム。 - 前記第1の通信装置は、
再送回数に基づいて、前記初送信号および再送信号を送信する送信電力を決定する再送制御部と、
前記再送制御部が決定した送信電力で、前記初送信号および再送信号を送信するように制御する送信電力制御部と
を具備することを特徴とする請求項11に記載の通信システム。 - 前記第1の通信装置は、
再送回数に基づいて、前記初送信号および再送信号に乗算する拡散符号系列を決定する再送制御部と、
前記初送信号および再送信号に、前記再送制御部が決定した拡散符号系列を乗算する拡散部と
を具備し、
前記第2の通信装置の信号検出部は、前記受信部が受信した信号から干渉成分を除去した後、該干渉成分を除去した信号に、検出対象としている信号に前記拡散部が乗算した前記拡散符号を乗算して、前記検出対象としている信号を検出すること
を特徴とする請求項11に記載の通信システム。 - 前記再送制御部は、再送回数が多い信号に乗算する拡散符号系列ほど、直交性の崩れに対して耐性がある拡散符号系列とすることを特徴とする請求項14に記載の通信システム。
- 前記拡散符号系列は、直交可変拡散率符号であることを特徴とする請求項14に記載の通信システム。
- 受信した信号に誤りを検出すると送信元に再送を要求するハイブリッド自動再送を行う通信装置における受信方法において、
前記通信装置が、初送信号といずれかの信号に対する再送信号とを含む信号であって、前記初送信号と前記再送信号とが多重化された信号を受信する第1の過程と、
前記通信装置が、前記第1の過程にて受信した信号に含まれる前記初送信号と前記再送信号との再送回数に応じて、前記第1の過程にて受信した信号から、前記初送信号と前記再送信号とを検出する順番を決定する第2の過程と、
前記通信装置が、前記第2の過程にて決定した順番に従い、前記通信装置により検出済の信号であって、前記初送信号に関する検出済の信号および前記再送信号に関する検出済の信号を用いて、前記第1の過程にて受信した信号から干渉成分を除去して、前記初送信号および前記再送信号を検出する第3の過程と
を有し、
前記第3の過程において、前記通信装置は、検出した前記再送信号と、前記再送信号以前に受信した関連信号の少なくとも一つが含まれている既受信信号から検出した信号とを合成すること
を特徴とする受信方法。 - 第1の通信装置と第2の通信装置とを具備し、前記第1の通信装置から受信した信号に誤りを検出すると、前記第2の通信装置が前記第1の通信装置に再送を要求するハイブリッド自動再送を行う通信システムにおける通信方法において、
前記第1の通信装置が、初送信号といずれかの信号に対する再送信号とを送信する第1の過程と、
前記第2の通信装置が、初送信号といずれかの信号に対する再送信号とを含む信号であって、前記初送信号と前記再送信号とが多重化された信号を受信する第2の過程と、
前記第2の通信装置が、前記第2の過程にて受信した信号に含まれる前記初送信号と前記再送信号との再送回数に応じて、前記第2の過程にて受信した信号から、前記初送信号と前記再送信号とを検出する順番を決定する第3の過程と、
前記第2の通信装置が、前記第3の過程にて決定した順番に従い、前記第2の通信装置により検出済の信号であって、前記初送信号に関する検出済の信号および前記再送信号に関する検出済の信号を用いて、前記第2の過程にて受信した信号から干渉成分を除去して、前記初送信号および前記再送信号を検出する第4の過程と
を有し、
前記第4の過程において、前記第2の通信装置は、検出した前記再送信号と、前記再送信号以前に受信した関連信号の少なくとも一つが含まれている既受信信号から検出した信号とを合成すること
を特徴とする通信方法。
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EA201071414A1 (ru) | 2011-08-30 |
EP2299602A1 (en) | 2011-03-23 |
CN102084599A (zh) | 2011-06-01 |
US20110126072A1 (en) | 2011-05-26 |
JPWO2010005037A1 (ja) | 2012-01-05 |
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