WO2012147377A1 - 受信機及び受信方法 - Google Patents

受信機及び受信方法 Download PDF

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Publication number
WO2012147377A1
WO2012147377A1 PCT/JP2012/050919 JP2012050919W WO2012147377A1 WO 2012147377 A1 WO2012147377 A1 WO 2012147377A1 JP 2012050919 W JP2012050919 W JP 2012050919W WO 2012147377 A1 WO2012147377 A1 WO 2012147377A1
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Prior art keywords
signal
stbc
dstbc
receiver
frequency
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PCT/JP2012/050919
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English (en)
French (fr)
Japanese (ja)
Inventor
小林　岳彦
弘幸 芥川
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Kokusai Denki Electric Inc
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Hitachi Kokusai Electric Inc
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0667—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal
    • H04B7/0669—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of delayed versions of same signal using different channel coding between antennas
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/08—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station
    • H04B7/0891—Space-time diversity
    • 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
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H04L1/0631—Receiver arrangements
    • 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
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H04L1/0618—Space-time coding
    • H04L1/0637—Properties of the code
    • H04L1/0643—Properties of the code block codes

Definitions

  • the present invention relates to a receiver and a reception method that perform communication using a space-time block coding (STBC) method or a differential space-time block coding (DSTBC) method.
  • STBC space-time block coding
  • DTBC differential space-time block coding
  • a transmission diversity method using STBC which is one of MIMO (Multi Input Multi Output) techniques, as a means for improving communication quality by enhancing fading resistance.
  • STBC Multi Input Multi Output
  • the transmitter side preliminarily transmits channel state information (CSI: Channel State Information) needs to be known.
  • CSI specifically means response characteristics between the transmission antenna and the reception antenna.
  • CSI is necessary when performing STBC decoding as in other MIMO schemes.
  • known signals called pilots with predetermined patterns are periodically arranged. The method is generally taken. An appropriate arrangement period of pilots is determined by the speed of time fluctuation of a propagation path to be handled, that is, a fading frequency, and it is necessary to shorten the arrangement period as the fading frequency increases. That is, in the case of high-speed fading, information transmission efficiency may be significantly impaired. Therefore, a transmission diversity method using DSTBC has been proposed as a method that does not require CSI on the receiver side.
  • the DSTBC system has the disadvantage of sacrificing noise resistance due to differential conversion (delay detection) on the receiver side, but has the advantage of not requiring a pilot or the like and being easily compatible with high-speed fading. is there.
  • AFC automatic frequency control
  • CSI is observed multiple times at a certain time interval, and the frequency deviation is obtained from the phase change of CSI under the assumption that the fluctuation of CSI due to fading is sufficiently gradual. Is generally done.
  • OFDM Orthogonal Frequency Domain Multiplex
  • the system to which the STBC scheme is applied is often based on OFDM transmission. Similar to other MIMO schemes, when transmitting pilots to observe CSI from individual transmission antennas, the transmission from other transmission antennas is performed. In order not to interfere with the pilot of the transmission, it is transmitted separately on the frequency axis or the time axis. In the case of single carrier transmission, separation on the frequency axis is impossible, and in order to separate on the time axis, two symbol times are required to transmit one pilot, and transmission efficiency decreases. . That is, in single carrier transmission, there are currently few frequency deviation detection methods suitable for the STBC method or the DSTBC method.
  • the present invention has been made in view of such a conventional situation, and proposes a technique for effectively detecting a frequency deviation by a receiver in a communication system using the STBC method or the DSTBC method.
  • the purpose is to do.
  • the receiver when a signal including a predetermined synchronization signal is encoded by the STBC method or the DSTBC method and received by the receiver, the receiver stores in advance data corresponding to the synchronization signal in the received signal.
  • the channel response is estimated by comparing with the encoded data representing the synchronization signal. That is, in a receiver that receives a signal encoded by the STBC method or the DSTBC method, a storage unit that stores data representing a predetermined synchronization signal encoded by the STBC method or the DSTBC method, and the above-described signal in the received signal Data corresponding to the synchronization signal is input, and estimation means for comparing the input data with data stored in the storage means to estimate a propagation path response is provided.
  • the data portion corresponding to the synchronization signal in the received signal and the reference signal (stored in the storage unit) (Data) has a certain relationship, and the propagation path response can be estimated using this.
  • Data data portion corresponding to the synchronization signal in the received signal and the reference signal (stored in the storage unit)
  • the frequency deviation can be effectively detected by the receiver.
  • FIG. 1 shows a configuration example of an STBC transmission system which is a communication system using the STBC scheme.
  • QPSK Quadrature Phase Shift Keying
  • the STBC method is a method for calculating two symbols as one processing unit for time-series data to be transmitted and recombining and transmitting signals from two antennas in the time domain and the spatial domain. Two types of orthogonal sequences are output.
  • the STBC transmission system of the present example includes a transmitter that encodes and transmits time-series data to be transmitted by the STBC method, and receives and decodes a signal encoded by the STBC method, and transmits the time-series data to be transmitted. Having a receiver to get.
  • the transmitter of this example includes an input unit 101, a serial-parallel converter 102, a symbol mapper 103, an STBC encoder 104, transmission baseband units 105-1 and 105-2, transmission RF units 106-1 and 106-2, A frequency oscillator 107 and transmission antennas 108-1 and 108-2 are provided.
  • the receiver of this example includes a reception antenna 121, a reception RF unit 122, a frequency oscillator 123, a reception baseband unit 124, a serial-parallel converter 125, an STBC decoder 126, a symbol demapper 127, a parallel-serial converter 128, An output unit 129 is provided, and a frequency deviation detector 130 and a frequency control unit 131 are further provided.
  • the transmitter of this example generally performs the following processing. That is, when a bit string (transmission bit string) of time-series data to be transmitted is given to the input unit 101, the serial-parallel converter 102 bundles the transmission bit string input from the input unit 101 every 4 bits to form a symbol mapper. To 103. The symbol mapper 103 performs symbol mapping by QPSK modulation every 2 bits for the 4-bit transmission bit string input from the serial-parallel converter 102, and collects 2 symbols (1 symbol: 2 bits) at a time. The set is output to the STBC encoder 104. The STBC encoder 104 performs STBC encoding on the input symbol set, and outputs the result to the transmission baseband units 105-1 and 105-2.
  • the STBC encoder 104 is an alamouti encoder, and when the input symbol set is s 1 , s 2 , symbols in the order of s 1 , -s 2 * with respect to the transmission baseband unit 105-1. The sequence is output, and a symbol sequence in the order of s 2 and s 1 * is output to the transmission baseband unit 105-2.
  • x * is a conjugate complex of x.
  • the transmission baseband unit 105-1 performs processing such as waveform shaping on the symbol series input from the STBC encoder 104, generates a baseband signal, and outputs the baseband signal to the transmission RF unit 106-1.
  • Transmission RF section 106-1 performs processing such as frequency conversion and power amplification on the baseband signal input from transmission baseband section 105-1, and outputs the result to transmission antenna 108-1.
  • the transmission antenna 108-1 transmits the signal input from the transmission RF unit 106-1 to the receiver by radio.
  • the transmission baseband unit 105-2 performs processing such as waveform shaping on the symbol sequence input from the STBC encoder 104, generates a baseband signal, and outputs the baseband signal to the transmission RF unit 106-2.
  • the transmission RF unit 106-2 performs processing such as frequency conversion and power amplification on the baseband signal input from the transmission baseband unit 105-2, and outputs the result to the transmission antenna 108-2.
  • the transmission antenna 108-2 wirelessly transmits the signal input from the transmission RF unit 106-2 to the receiver.
  • the frequency conversion by the transmission RF units 106-1 and 106-2 is performed based on the signal of the frequency f TX that is the output of the frequency oscillator (local oscillator) 107.
  • Transmission frequency of the RF signal which is a result of the frequency conversion are those identical in transmission RF section 106-1 and 106-2, which is referred to as F TX.
  • the receiver of this example generally performs the following processing. That is, when the signal transmitted from the transmitter is received via the reception antenna 121, the reception RF unit 122 performs processing such as amplification, frequency conversion, and band limitation on the signal received by the reception antenna 121.
  • the baseband signal is generated and output to the reception baseband unit 124.
  • the reception baseband unit 124 performs processing such as waveform shaping including band limitation on the baseband signal input from the reception RF unit 122, and then converts the signal into a serial-parallel converter 125 as a complex discrete signal having a symbol period. Output to.
  • the serial-parallel converter 125 collects the signals input from the reception baseband unit 124 two symbols at a time and outputs them to the STBC decoder 126.
  • the STBC decoder 126 performs a decoding process corresponding to STBC coding on the signal of each two symbols input from the serial-parallel converter 125 and outputs the result to the symbol demapper 127.
  • the decoding process is performed using (Equation 1), and the signal q 1 of the decoding result is obtained.
  • Q 2 are output to the symbol demapper 127.
  • h 1 is the propagation path response for the propagation path from the transmission antenna 108-1 to the reception antenna 121
  • h 2 is the propagation path from the transmission antenna 108-2 to the reception antenna 121.
  • a propagation path response estimator (not shown) using a pilot, a synchronization word, or the like.
  • the symbol demapper 127 performs bit determination corresponding to QPSK modulation on the signals q 1 and q 2 input from the STBC decoder 126, and collectively outputs 4-bit signals to the parallel-serial converter 128. To do.
  • the parallel-serial converter 128 serially converts the 4-bit signal input from the symbol demapper 127 and outputs it to the output unit 129.
  • the frequency conversion performed by the reception RF unit 122 is performed based on the signal of the frequency f RX output from the frequency oscillator (local oscillator) 123.
  • the reception frequency of the RF signal which is a result of the frequency conversion to F RX.
  • the reception frequency F RX needs to match the transmission frequency F TX , or the difference must be within a certain tolerance.
  • the output of the serial-parallel converter 125 is input to the frequency deviation detector 130 to obtain an estimated frequency deviation, and the result is subjected to frequency control. To the unit 131.
  • the frequency control unit 131 based on the estimated frequency deviation is input from the frequency deviation detector 130, a frequency as (the error (deviation) between the transmission frequency F TX and the reception frequency F RX) becomes smaller frequency deviation
  • the output frequency f RX of the oscillator 123 is controlled.
  • the configuration of the frequency deviation detector 130 will be described.
  • a frame having a structure illustrated in FIG. 4 is used. That is, it is assumed that a signal string 502 of a synchronous word (SW) that is a known symbol sequence is inserted into one frame 501 as an example of a predetermined synchronization signal for 10 symbols.
  • the frame 501 of this example has a structure in which a data signal sequence, a synchronization word signal sequence 502, and a data signal sequence are arranged in this order, and the entire frame including the synchronization word is STBC encoded.
  • the synchronization word is a fixed bit pattern common to the transmitter and receiver to be synchronized.
  • a frame format is used in which a synchronization word is arranged at a position other than the beginning of the frame (a place after the beginning).
  • a frame format in which a synchronization word is arranged at the beginning of the frame may be used.
  • the signal sequence 502 of the synchronization word is represented by a (2n), a (2n + 1)
  • STBC The output 503 of the synchronization word part on the transmission antenna 108-1 side obtained by encoding is a (2n), -a (2n + 1) *
  • the output of the synchronization word part on the transmission antenna 108-2 side obtained by STBC encoding 504 becomes a (2n + 1), a (2n) *
  • the signal sequence 505 corresponding to the synchronization word in the signal received by the receiving antenna 121 is assumed to be r (2n) and r (2n + 1).
  • FIG. 2 shows a configuration example of the frequency deviation detector 130.
  • the frequency deviation detector 130 of this example includes a channel response calculator 151, a reference signal memory 152, frequency deviation calculators 153-1 and 153-2, and a selector 154.
  • the signal sequence 505 corresponding to the synchronization word 502 in the signal output from the serial-parallel converter 125 is input by two symbols.
  • the reference signal memory 152 stores (stores) data representing a known synchronization word 502 encoded with STBC as a reference signal.
  • the signal sequence after the STBC encoding is performed on the signal sequence 502 (a (2n), a (2n + 1)) of the synchronization word as a reference signal in the reference signal memory 152, that is, the STBC code
  • data representing the output 504 (a (2n + 1), a (2n) * ) of the word part is stored.
  • a combination of a (2n) and a (2n + 1) may be defined as a state, and each state may be stored with identification information such as a state number.
  • the channel response estimator 151 includes a signal sequence 505 (r (2n), r (2n + 1)) input from the serial-parallel converter 125 and a reference signal (synchronization word signal sequence 502) held in the reference signal memory 152. Based on the signal sequence 503 (a (2n), -a (2n + 1) * ) and the signal sequence 504 (a (2n + 1), a (2n) * )) after STBC encoding is performed on channel response using a 2) (estimate of the channel response) h 1 (2n), calculating the h 2 (2n), the frequency estimate h 1 (2n) of the channel responses of the transmit antennas 108-1 side Output to deviation calculator 153-1 and output channel response estimated value h 2 (2n) on transmitting antenna 108-2 side to frequency deviation calculator 153-2.
  • (Expression 2) since the amplitude component of the propagation path response is discarded later for the scalar part, it can be omitted and set to “1”.
  • a (2n) * , -a (2n + 1) is a conjugate complex of the signal sequence 503 (a (2n), -a (2n + 1) * ), and a (2n + 1) *
  • a ( 2n) is a conjugate complex of the signal sequence 504 (a (2n + 1), a (2n) * ), and is obtained by calculation from the reference signal held in the reference signal memory 152 and substituted into (Equation 2).
  • (Expression 2) means that an estimated value of the propagation path response can be obtained by removing the code components (modulation components) by the synchronization word signal sequences 503 and 504 from the received signal sequence 505 and averaging them. .
  • the STBC-coded known synchronization word (reference signal) to be included in the signal transmitted from the transmitter and the synchronization word in the actually transmitted signal are supported.
  • a part having a certain relationship with respect to the propagation path response (a relation in which the propagation path response can be estimated by (Equation 2) based on the reference signal and the synchronization word part of the received signal)
  • the estimated value of the response can be obtained.
  • the reference signal memory 152 a combination of a (2n) and a (2n + 1) is stored as a reference signal as a unit of state, which is given to the channel response estimator 151, and the channel response estimator 151 is stored.
  • each conjugate complex may be obtained.
  • data representing the conjugate complex of the signal sequences 503 and 504 after the STBC encoding is performed on the signal sequence 502 of the synchronization word may be stored and directly substituted into (Equation 2). .
  • the frequency deviation calculator 153-1 receives the channel response estimation values h 1 (0), h 1 (2), h 1 (4), h on the transmission antenna 108-1 side input from the channel response estimator 151.
  • the phase is obtained using 1 (6) and h 1 (8), and the frequency deviation ⁇ f 1 is calculated from the amount of phase change and output to the selector 154.
  • the frequency deviation calculator 153-2 receives the channel response estimation values h 2 (0), h 2 (2), h 2 (4), h on the transmission antenna 108-2 side input from the channel response estimator 151.
  • 2 (6), h 2 (8) is used to determine the phase, and the frequency deviation ⁇ f 2 is calculated from the phase change amount and output to the selector 154.
  • the frequency deviations ⁇ f 1 and ⁇ f 2 obtained by the frequency deviation calculators 153-1 and 153-2 are essentially the same, but in the receiver of this example, the selector 154 has a higher accuracy. Is output to the frequency control unit 131.
  • the selector 154 calculates the channel response powers p 1 and p 1 by (Equation 3) based on the frequency deviations ⁇ f 1 and ⁇ f 2 input from the frequency deviation calculators 153-1 and 153-2, for example. and, the p 1 ⁇ p 1 if ⁇ f 1, to select the ⁇ f 1 if otherwise. Note that this selection criterion is an example, and a method of selecting according to another selection criterion may be adopted.
  • FIG. 3 shows a configuration example of the frequency deviation calculators 153-1 and 153-2.
  • the frequency deviation calculators 153-1 and 153-2 of this example have a function of calculating the phase of the estimated value of the input channel response and calculating the frequency deviation from the phase change amount.
  • a delay memory 162, a complex conjugate acquisition unit 163, a phase calculator 164, an integrator 165 composed of an adder 166 and a delay memory 167, and a frequency deviation calculation unit 168 are provided.
  • the propagation path response estimated value h (2n) input from the channel response calculator 151 and the propagation path delayed by one timing by the delay memory 162
  • the estimated value h (2 (n ⁇ 1)) of the response is multiplied by the conjugate complex value h (2 (n ⁇ 1)) * obtained by the complex conjugate acquisition unit 163 by the multiplier 161, and the phase ⁇ (2n ) Is calculated by the phase calculator 164.
  • the output (phase ⁇ (2n)) by the phase calculator 164 can be expressed by (Expression 4).
  • arg (x) is the phase of the complex number x, and the unit is [rad].
  • an integrator 165 including an adder 166 and a delay memory 167 calculates a phase change amount ⁇ (2n).
  • the output (phase change amount ⁇ (2n)) by the integrator 165 can be expressed by (Expression 5).
  • This phase change amount ⁇ (2n) that is, the inclination with respect to the passage of time, corresponds to the magnitude of the frequency deviation under the condition that the time change of the propagation path response h is sufficiently gentle.
  • the frequency deviation calculation unit 168 can calculate the frequency deviation using (Equation 6).
  • F b is a symbol transmission rate (frequency).
  • the frequency deviation calculators 153-1 and 153-2 can directly obtain the slope of the input channel response estimation value, but in this case, the phase of the channel response estimation value is wrapped (wrapping). ) Must be noted.
  • the present invention is applied to the STBC system, but the present invention is also effective for the DSTBC system.
  • a pilot or the like is originally inserted into a signal in order to perform channel response estimation, and the present invention is not necessarily effective.
  • the DSTBC system it is not originally assumed that channel response estimation is performed, and therefore, a pilot or the like is not inserted into the signal. Therefore, in the present invention, a channel response can be estimated using a DSTBC-encoded synchronization word inserted for the purpose of frame synchronization and the like, and a frequency deviation is detected from the estimated value of the channel response. ing.
  • FIG. 5 shows a configuration example of a DSTBC transmission system that is a communication system using the DSTBC scheme.
  • the transmitter of this example is obtained by replacing the STBC encoder 104 in the transmitter illustrated in FIG. 1 with a DSTBC encoder 201.
  • the receiver of this example is obtained by replacing the STBC decoder 126 in the receiver illustrated in FIG. 1 with a DSTBC decoder 202. That is, the transmitter and the receiver of this example are configured to use the DSTBC system instead of the STBC system.
  • Other configurations and operations are generally the same as the contents described for the STBC method, and thus description thereof is omitted.
  • the above problem is solved by using a technique for fixing the result of DSTBC encoding of the bit string immediately before the synchronization word.
  • the fixation of the result of DSTBC encoding of the bit string immediately before the synchronization word is roughly realized by using the following technique for a transmitter that transmits a signal by the DSTBC method. That is, a frame in which a synchronization word is arranged at a predetermined location after the head is used.
  • the initial value control means has a fixed signal point corresponding to immediately before the synchronization word in the DSTBC encoder that processes the transmission target based on the value before the synchronization word from the beginning of the frame.
  • the initial value of differential encoding when the frame is processed by the DSTBC encoder that processes the transmission target is set.
  • the mapping arrangement of the synchronization word can be a fixed mapping pattern, and between the transmitter and the receiver, Communication can be efficiently performed by the DSTBC method.
  • various frames may be used.
  • a frame in which changeable data such as voice to be transmitted is arranged before the synchronization word from the head is used.
  • various points may be used as the fixed point, for example, preset. .
  • the following configuration is used as an example of the configuration of the initial value control means of the transmitter related to the fixing. That is, the S / P conversion means performs serial / parallel conversion on the value before the synchronization word from the beginning of the frame, the symbol mapping means performs symbol mapping on the serial / parallel conversion result, and the differential encoding means Difference when the frame is processed by the DSTBC encoder that performs differential encoding on the symbol mapping result using a predetermined initial value and the initial value updating means processes the transmission target based on the differential encoding result. Update and set the initial value of dynamic encoding.
  • first differential encoding means for performing differential encoding on a value immediately before a synchronization word from the beginning of a frame using a predetermined initial value
  • An initial value setting means for setting an initial value based on a differential encoding result immediately before a synchronization word by one differential encoding means, and the frame to be transmitted using the initial value set by the initial value setting means
  • Second differential encoding means for performing differential encoding as described above.
  • the initial value setting means is adapted to perform initial encoding in accordance with a differential encoding result immediately before the synchronization word that can be obtained when differential encoding is performed on a value immediately before the synchronization word from the beginning of the frame.
  • the immobilization uses the following characteristics of the DSTBC method. 1) In the DSTBC method, the encoding result obtained by differentially encoding a signal value by a predetermined arithmetic expression using a predetermined initial value is limited to a finite number regardless of the bit string signal value. being classified. That is, since every signal value is classified as a finite number of states, the signal values can be represented by these finite number of signal values. 2) Then, if an initial value in which the encoding result obtained by differentially encoding the finite number of signal values by the same predetermined arithmetic expression as described above becomes a predetermined target value is known, the encoding result is determined for an arbitrary signal value. Therefore, the target encoding result can be obtained by DSTBC encoding.
  • the initial value associated with the encoding result in advance. Is determined by referring to the table, and the specified initial value is used as the initial value in the second-stage encoding to perform the entire frame encoding process, thereby obtaining a predetermined encoding result as a target for the synchronization word portion of the frame. Obtainable.
  • the DSTBC-encoded known synchronization word (reference signal) scheduled to be included in the signal transmitted from the transmitter and the STBC method described above By utilizing the fact that the part corresponding to the synchronization signal in the actually transmitted signal has a certain relationship (the relationship of (Equation 2)) with respect to the channel response, the channel response without using a pilot or the like The estimated value of can be obtained.
  • the reference signal memory 152 for storing the synchronization word, and the propagation path response from the received signal and the reference signal corresponding to the synchronization word are obtained.
  • Channel response calculator 151 for calculating, two frequency deviation calculators 153-1 and 153-2 for detecting a frequency deviation from a series of propagation path calculated values, and selection for selecting one of the two detected frequency values
  • a frequency deviation detector 130 having a transmitter 154, and each of the frequency deviation calculators 153-1 and 153-2 propagates using a synchronization word string encoded by the STBC method or the DSTBC method. The road response was calculated.
  • the first advantage is that the orthogonality for separating the synchronization words transmitted from the two transmitters is ensured in the receiver.
  • the synchronization word transmissions respectively transmitted from the two transmitters need to be provided with means that do not interfere with each other so that they can be separated at the receiver.
  • the method in which one transmitter stops transmitting at the time when one transmitter is transmitting a synchronization word, or in the case of OFDM transmission one transmitter transmits the synchronization word.
  • the other transmitter may take a method of stopping transmission. The above method has a difficulty in the use efficiency of transmission time or frequency (subcarrier) necessary for transmitting the synchronization word.
  • each transmitter transmits each synchronization word string at the same time.
  • the STBC or DSTBC coding method of the synchronization word used in the present invention it is guaranteed that the two synchronization word signals transmitted from the respective transmitters as the coded output are orthogonal to each other by the STBC coding. Therefore, it is not necessary to take the above measures.
  • the second advantage relates particularly to DSTBC coding. Since DSTBC is a method of transmitting 4 bits of transmission information using a signal one time before as a reference signal, for example, when the operation of the encoder is temporarily interrupted at the beginning of a frame, the first 4 bits cannot be decoded. In a general frame configuration, there is no problem because a bit string that does not need to be decoded such as a preamble is arranged at the head. However, if a synchronization word string is arranged in the frame and the operation of the DSTBC encoder is interrupted here, the 4 bits immediately after the synchronization word cannot be decoded. The encoding of the synchronization word used in the present invention avoids such a situation and contributes to the transmission efficiency in that a so-called redundant bit is not required.
  • the configuration of the system and apparatus according to the present invention is not necessarily limited to the configuration described above, and various configurations may be used.
  • the present invention can also be provided as, for example, a method or method for executing the processing according to the present invention, a program for realizing such a method or method, or a recording medium for recording the program. It is also possible to provide various systems and devices.
  • the application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
  • a hardware resource including a processor, a memory, etc.
  • a processor is read by a ROM (Read A configuration controlled by executing a control program stored in (Only Memory) may be used.
  • each functional unit for executing the processing may be configured as an independent hardware circuit.
  • the present invention can be grasped as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, or the program (itself).
  • the processing according to the present invention can be performed by inputting the program from the recording medium to the computer and causing the processor to execute the program.

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