JP2007049406A - Transmission method and apparatus, reception method and apparatus, and communication system utilizing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmission technique or a reception technique for performing transmission using a packet signal configured so as to improve utilization efficiency. <P>SOLUTION: A control unit 30 generates a packet signal including a control signal arranged in the pre-stage of a data signal having a variable length, the control signal including values of a plurality of bits indicating the length of the data signal. A radio unit 20 etc. transmits the generated packet signal. The control unit 30 divides the plurality of bits and correlates each of the bits with each of the control signals to be formed with a plurality of symbols, and reduces the number of the symbols of the control signal while maintaining the correlation when the length of the data signal reduces. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a transmission technique and a reception technique, and more particularly to a transmission method and apparatus for transmitting or receiving a packet signal including a control signal, a reception method and apparatus, and a communication system using them.

  An OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, which is one of the multicarrier schemes, is a communication scheme that enables high-speed data transmission and is strong in a multipath environment. This OFDM modulation scheme is applied to IEEE802.11a, g and HIPERLAN / 2, which are standardized standards for wireless LAN (Local Area Network). A packet signal in such a wireless LAN is generally transmitted via a transmission path environment that fluctuates with time, and is affected by frequency selective fading. Therefore, a receiver generally performs transmission path estimation dynamically. Execute.

In order for the receiving apparatus to perform transmission path estimation, two types of known signals are provided in the packet signal. One is a known signal provided for all carriers at the beginning of the packet signal, which is a so-called preamble or training signal. The other is a known signal provided for a part of carriers in the data section of the packet signal, which is called a so-called pilot signal (see Non-Patent Document 1, for example).
Sine Coleri, Mustafa Ergen, Anuj Puri, and Ahmad Bahai, “Channel Estimate Techniques Based on Pilot Arrangement in OFDM Systems”, IbnEnts. 48, no. 3, pp. 223-229, Sept. 2002.

  One technique for effectively using frequency resources in wireless communication is an adaptive array antenna technique. The adaptive array antenna technology controls the directivity pattern of an antenna by controlling the amplitude and phase of a signal to be processed in each of a plurality of antennas. There is a MIMO (Multiple Input Multiple Output) system as a technique for increasing the data rate by using such adaptive array antenna technology. In the MIMO system, each of a transmission apparatus and a reception apparatus includes a plurality of antennas and sets packet signals to be transmitted in parallel (hereinafter, each piece of data to be transmitted in parallel in the packet signal is referred to as a “sequence”). . That is, the data rate is improved by setting a sequence up to the maximum number of antennas for communication between the transmission device and the reception device.

  Furthermore, when such an MIMO system is combined with an OFDM modulation scheme, the data rate is further increased. In a packet signal in such a MIMO system, a control signal is arranged at the head portion. The control signal specifies a data rate, a data length, the number of antennas, and the like. In order to improve the utilization efficiency of the packet signal, it is desirable that the number of bits included in the control signal is small. In particular, since the signal increases in OFDM symbol units in the OFDM modulation scheme, the number of bits included in the control signal should be determined so as to be an integral multiple of the number of bits included in the OFDM symbol. In general, the number of bits of information for designating a data length is determined according to the longest data length. Therefore, when the data length is short, bits that are not necessarily required are also transmitted. Further, when the data length is shortened, the ratio of the information to the packet signal is increased, so that the utilization efficiency of the packet signal is lowered. On the other hand, when the length of the control signal is variably controlled, information for indicating the length of the control signal needs to be added to the packet signal. For this reason, the use efficiency of the packet signal is lowered, and there is a case where one OFDM symbol must be further added.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a transmission technique or a reception technique in which communication is performed using packet signals configured to improve utilization efficiency.

  In order to solve the above-described problem, a transmitting apparatus according to an aspect of the present invention includes a control signal arranged in a preceding stage of a variable-length data signal and includes a multi-bit value indicating the length of the data signal. A generating unit that generates a packet signal including the received control signal, and a transmitting unit that transmits the packet signal generated by the generating unit. The generation unit associates each of the control signals to be formed with a plurality of symbols while dividing a plurality of bits, and when the length of the data signal decreases, the number of control signal symbols is maintained while maintaining the correspondence. Also reduce.

  According to this aspect, when the control signal to be formed with a plurality of symbols is divided and associated with a plurality of bits and the length of the data signal is reduced, the number of control signal symbols is also maintained while maintaining the correspondence. Therefore, the length of the data signal can be specified according to the number of symbols of the control signal.

  The generation unit associates the lower bits of the plurality of bits with the front symbols of the plurality of symbols, and may remove the rear symbols when the number of symbols of the control signal decreases. . When the number of symbols in the control signal is one, the generation unit may arrange the same lower bits as in the case where the number of symbols in the control signal is plural. In this case, even if the number of symbols of the control signal changes, the information included in the symbols ahead of the control signal can be configured in the same format, so that the processing can be simplified.

  The generation unit may associate the upper bits of the plurality of bits with the front symbols of the plurality of symbols, and may remove the rear symbols when the number of control signal symbols decreases. . When the number of symbols of the control signal is one, the generation unit arranges the lower bits of the plurality of bits with the same number of bits as when the number of symbols of the control signal is plural. May be. In this case, the approximate length of the data signal can be notified to a receiving apparatus that can receive only one symbol as a control signal, even when the length of the data signal is designated by two symbols.

  Another aspect of the present invention is a receiving device. This apparatus receives a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a control signal including a plurality of bits indicating the length of the data signal. And, in the packet signal received by the receiving unit, based on a value of a plurality of bits included in the control signal, a specifying unit for specifying the length of the data signal, and a length of the data signal specified by the specifying unit A processing unit for processing a data signal is provided. A plurality of bits are associated with each of a plurality of symbols that should form a control signal received by the receiving unit, and when the length of the data signal decreases, the control signal symbols are maintained while maintaining the correspondence. The number is also reduced, and the specifying unit specifies the length of the data by extracting the bit value from the symbols forming the control signal received by the receiving unit and combining the extracted bit values.

  “By combining the extracted bit values” means, in addition to combining the bit values extracted from a plurality of symbols, the bit value extracted from one symbol and a predetermined value. This includes the case of synthesis. Furthermore, even when the synthesis is not actually performed, the case where the length of the data is specified from the bit value extracted from one symbol is included.

  According to this aspect, a plurality of bits are divided and associated with each of the control signals to be formed with a plurality of symbols, and when the length of the data signal is reduced, the number of control signal symbols is maintained while maintaining the correspondence. Therefore, the length of the data signal corresponding to the number of symbols of the control signal can be acquired.

  When the lower bits of the plurality of bits are associated with the forward symbols of the plurality of symbols that should form the control signal received by the receiving unit, and the number of symbols of the control signal decreases, The rear symbols are removed, and the specifying unit may specify the length of the data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. When the number of control signal symbols received by the receiving unit is one, the same low-order bits are arranged for that symbol as when there are a plurality of control signal symbols. The data length may be specified from the bit value. In this case, even if the number of symbols of the control signal changes, the information included in the symbols ahead of the control signal is configured in the same format, so that the processing can be simplified.

  When a higher order bit of a plurality of bits is associated with a front symbol of a plurality of symbols that should form a control signal received by the receiving unit, and the number of symbols of the control signal decreases, The rear symbols are removed, and the specifying unit may specify the length of the data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. In this case, when only one symbol can be received as a control signal, an approximate length of the data signal can be acquired even if the length of the data signal is specified by two symbols.

  When the number of control signal symbols received by the receiving unit is one, the same number of bits as in the case where there are a plurality of control signal symbols for that symbol, the lower bits of the plurality of bits are The specifying unit may specify the length of the data from the value of the lower bits. In this case, when the number of symbols is one, the data length corresponding to the number of symbols can be specified.

  Yet another embodiment of the present invention is a communication system. This communication system transmits a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a control signal including a multi-bit value indicating the length of the data signal. And a reception device that processes a data signal by specifying a length of the data signal based on a value of a plurality of bits included in the control signal after receiving the packet signal transmitted by the transmission device With. The transmission apparatus associates each control signal to be formed with a plurality of symbols while dividing a plurality of bits. When the length of the data signal is reduced, the number of control signal symbols is maintained while maintaining the correspondence. The receiving apparatus extracts the bit value from the symbol forming the received control signal, and synthesizes the extracted bit value to specify the length of the data.

  According to this aspect, when the control signal to be formed with a plurality of symbols is divided and associated with a plurality of bits and the length of the data signal is reduced, the number of control signal symbols is also maintained while maintaining the correspondence. Therefore, the length of the data signal can be specified according to the number of symbols of the control signal.

  Yet another embodiment of the present invention is a transmission method. This method is a transmission method for transmitting a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a multi-bit value indicating the length of the data signal. In this case, a plurality of bits are associated with each control signal to be formed by a plurality of symbols, and when the length of the data signal is reduced, the number of control signal symbols is maintained while maintaining the correspondence. Also reduce.

  Yet another embodiment of the present invention is also a transmission method. The method includes a step of generating a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a plurality of bits indicating the length of the data signal. And a step of transmitting the generated packet signal. The generating step associates each of the control signals to be formed with a plurality of symbols while dividing a plurality of bits. When the length of the data signal decreases, the control signal symbols are maintained while maintaining the correspondence. Also reduce the number.

  The generating step associates the lower bits of the plurality of bits with the front symbols of the plurality of symbols, and if the number of control signal symbols decreases, the rear symbols are removed. Good. In the generating step, when the number of symbols in the control signal is one, the same lower bits as in the case where the number of symbols in the control signal is plural may be arranged for the symbol.

  The generating step associates the upper bits of the plurality of bits with the front symbols of the plurality of symbols, and when the number of control signal symbols decreases, the rear symbols are removed. Good. In the generation step, when the number of symbols of the control signal is one, the lower bits of the plurality of bits are arranged with the same number of bits as when the number of symbols of the control signal is plural. May be.

  Yet another embodiment of the present invention is a reception method. This method is based on receiving a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a multi-bit value indicating the length of the data signal. A reception method for processing a data signal by specifying the length of the data signal based on a value of a plurality of bits included in the control signal, and a plurality of symbols to form the received control signal When a plurality of bits are associated with each other and the length of the data signal is reduced, the number of control signal symbols is also reduced while maintaining the correspondence. The bit value is extracted from the symbols that form, and the length of the data is specified by combining the extracted bit values.

  Yet another embodiment of the present invention is also a reception method. The method includes a step of receiving a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a multi-bit value indicating the length of the data signal; In the received packet signal, the step of identifying the length of the data signal based on the value of the plurality of bits included in the control signal and the processing of the data signal based on the length of the identified data signal And a step of performing. In the receiving step, a plurality of bits are associated with each of a plurality of symbols to form a control signal to be received, and when the length of the data signal decreases, the control signal of the control signal is maintained while maintaining the correspondence. The number of symbols is also reduced, and the identifying step identifies the length of the data by extracting bit values from the symbols forming the received control signal and combining the extracted bit values.

  When a lower bit of a plurality of bits is associated with a front symbol of a plurality of symbols to form a control signal received in the receiving step, and the number of control signal symbols decreases. The backward symbol is removed, and the specifying step may specify the length of data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. When the number of control signal symbols received in the receiving step is one, the same low-order bits as in the case where the number of control signal symbols is plural are arranged for the symbol, and the step of specifying The data length may be specified from the value of the lower bit.

  When the upper bits of the plurality of bits are associated with the front symbols of the plurality of symbols to form the control signal received in the receiving step, and the number of control signal symbols decreases The backward symbol is removed, and the specifying step may specify the length of data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. When the number of control signal symbols received in the step of receiving is one, the lower bit of the plurality of bits with the same number of bits as that when there are a plurality of control signal symbols for that symbol In the specifying step, the length of data may be specified from the value of the lower bits.

  It should be noted that any combination of the above-described constituent elements and a conversion of the expression of the present invention between a method, an apparatus, a system, a recording medium, a computer program, etc. are also effective as an aspect of the present invention.

  According to the present invention, communication can be performed using a packet signal configured to improve utilization efficiency.

  Before describing the present invention in detail, an outline will be described. Embodiments of the present invention relate to a MIMO system composed of at least two wireless devices. One of the wireless devices corresponds to a transmitting device, and the other corresponds to a receiving device. Packet signals are used for communication in a MIMO system. In general, a control signal (hereinafter, a control signal for the MIMO system is referred to as “HT-SIG”) is arranged at the head portion of the packet signal, and a data signal is arranged following the control signal. The HT-SIG includes information on the length of the data signal, information on the data rate in the data signal (hereinafter, information on the length of the data signal is referred to as “LENGTH”), and the like. The above information can be said to be information related to the MIMO system. Furthermore, in order to maintain compatibility with a communication system that is not a MIMO system (hereinafter referred to as “conventional system”), a control signal (hereinafter referred to as “L-SIG”) corresponding to the conventional system is provided before the HT-SIG. Be placed. The L-SIG includes information on the data rate in the HT-SIG (hereinafter referred to as “RATE”) and the like.

  Since information included in HT-SIG exists in addition to the information described above, the total amount of bits increases the amount of data. However, as described above, it is desirable that the amount of data is small in consideration of the packet signal utilization efficiency. On the other hand, when the length of the data signal is short, the length is specified by a part of the number of bits defined for LENGTH. Therefore, the other bits can be said to be signals that are not necessarily required. The transmission apparatus according to the embodiment of the present invention defines HT-SIG configured by two OFDM symbols (hereinafter, HT-SIG arranged in the previous stage is referred to as “HT-SIG1” and arranged in the subsequent stage. HT-SIG is referred to as “HT-SIG2”). Further, the transmission apparatus divides a plurality of bits for LENGTH into two, and arranges them in HT-SIG1 and HT-SIG2, respectively. At that time, the lower bits are arranged in HT-SIG1. Under such circumstances, when the length of the data signal is short, the transmission apparatus deletes HT-SIG2 and transmits HT-SIG1 after including it in the packet signal. That is, the transmission apparatus specifies the length of the data signal by the lower bits of LENGTH included in HT-SIG. In this way, the utilization efficiency of the packet signal is improved when the length of the data signal is short.

  When the number of OFDM symbols used for HT-SIG is changed, the transmitting apparatus notifies the receiving apparatus of the number of OFDM symbols in the previous stage of HT-SIG. Therefore, L-SIG is required to include information on the number of OFDM symbols of HT-SIG, but the amount of L-SIG data increases. In particular, when the data structure of L-SIG has already been determined, it is difficult to add new information. The transmission apparatus according to the embodiment of the present invention shares information regarding the number of symbols of HT-SIG with RATE of L-SIG. Specifically, when RATE indicates 6 Mbps, the number of OFDM symbols of HT-SIG is associated with “2”, and when RATE indicates 9 Mbps, the number of OFDM symbols of HT-SIG is set to “1”. Associate. As a result, it is possible to avoid adding new information to the L-SIG.

  FIG. 1 shows a spectrum of a multicarrier signal according to an embodiment of the present invention. In particular, FIG. 1 shows the spectrum of a signal in the OFDM modulation scheme. One of a plurality of carriers in the OFDM modulation system is generally called a subcarrier, but here, one subcarrier is designated by a “subcarrier number”. In the MIMO system, 56 subcarriers from subcarrier numbers “−28” to “28” are defined. The subcarrier number “0” is set to null in order to reduce the influence of the DC component in the baseband signal. On the other hand, in the conventional system, 52 subcarriers from subcarrier numbers “−26” to “26” are defined. An example of a conventional system is a wireless LAN compliant with the IEEE802.11a standard. Further, one signal unit composed of a plurality of subcarriers and one signal unit in the time domain is referred to as an “OFDM symbol”.

  Each subcarrier is modulated by a variably set modulation method. As a modulation method, any one of BPSK (Binary Phase Shift Keying), QSPK (Quadrature Phase Shift Keying), 16QAM (Quadrature Amplitude Modulation), and 64QAM is used.

  Also, convolutional coding is applied to these signals as an error correction method. The coding rate of convolutional coding is set to 1/2, 3/4, and the like. Furthermore, the number of data to be transmitted in parallel is set variably. Note that data is transmitted as packet signals, and each of the packet signals transmitted in parallel is referred to as a “sequence”. As a result, the data rate is also variably set by variably setting the modulation scheme, coding rate, and number of sequences. The “data rate” may be determined by any combination of these, or may be determined by one of them. In the conventional system, when the modulation method is BPSK and the coding rate is 1/2, the data rate is 6 Mbps. On the other hand, when the modulation method is BPSK and the coding rate is 3/4, the data rate is 9 Mbps.

  FIG. 2 shows a configuration of the communication system 100 according to the embodiment of the present invention. The communication system 100 includes a first wireless device 10a and a second wireless device 10b collectively referred to as a wireless device 10. The first radio apparatus 10a includes a first antenna 12a, a second antenna 12b, a third antenna 12c, and a fourth antenna 12d, which are collectively referred to as an antenna 12, and the second radio apparatus 10b is collectively referred to as an antenna 14. A first antenna 14a, a second antenna 14b, a third antenna 14c, and a fourth antenna 14d are included. Here, the first radio apparatus 10a corresponds to a transmission apparatus, and the second radio apparatus 10b corresponds to a reception apparatus.

  Before describing the configuration of the communication system 100, an outline of a MIMO system will be described. It is assumed that data is transmitted from the first radio apparatus 10a to the second radio apparatus 10b. The first radio apparatus 10a transmits a plurality of series of data from each of the first antenna 12a to the fourth antenna 12d. As a result, the data rate is increased. The second radio apparatus 10b receives a plurality of series of data by the first antenna 14a to the fourth antenna 14d. Furthermore, the second radio apparatus 10b separates the received data by adaptive array signal processing and independently demodulates a plurality of series of data.

  Here, since the number of antennas 12 is “4” and the number of antennas 14 is also “4”, the combination of transmission paths between the antennas 12 and 14 is “16”. A transmission path characteristic between the i-th antenna 12i and the j-th antenna 14j is denoted by hij. In the figure, the transmission path characteristic between the first antenna 12a and the first antenna 14a is h11, the transmission path characteristic between the first antenna 12a and the second antenna 14b is h12, the second antenna 12b and the first antenna. 14a, the transmission path characteristic between the second antenna 12b and the second antenna 14b is h22, and the transmission path characteristic between the fourth antenna 12d and the fourth antenna 14d is h44. Has been. Note that transmission lines other than these are omitted for clarity of illustration.

  The first radio apparatus 10a includes an HT-SIG that is arranged in front of a variable-length data signal and includes a LENGTH that is a multi-bit value indicating the length of the data signal. Send packet signal. LENGTH is a 12-bit value. In addition, the first radio apparatus 10a is an L-SIG arranged in the preceding stage of the HT-SIG and includes a packet signal including the L-SIG including the RATE that is information on the data rate in the HT-SIG. Send. Under such circumstances, the first radio apparatus 10a associates LENGTH with each of HT-SIGs to be formed by a plurality of OFDM symbols while dividing LENGTH.

  For example, among the 12 bits of LENGTH, the lower 8 bits are associated with HT-SIG1, and the upper 4 bits are associated with HT-SIG2. Further, when the length of the data signal is reduced, the number of HT-SIG symbols is reduced while maintaining the correspondence. That is, only HT-SIG1 is transmitted, and at that time, only 8 bits of LENGTH are transmitted. On the other hand, the first radio apparatus 10a identifies the number of HT-SIG OFDM symbols in the RATE by associating the data rate corresponding to the RATE included in the L-SIG with the number of OFDM symbols in the HT-SIG. To do.

  The second radio apparatus 10b receives the packet signal, and specifies the number of HT-SIG OFDM symbols while specifying the data rate from the RATE included in the L-SIG. Further, the second radio apparatus 10b processes the data signal by specifying the length of the data signal based on LENGTH included in HT-SIG. At that time, the second radio apparatus 10b extracts the bit value from the OFDM symbol forming the HT-SIG, and synthesizes the extracted bit value, thereby specifying the data length. The first radio apparatus 10a and the second radio apparatus 10b may be reversed.

  FIGS. 3A and 3B are diagrams illustrating packet formats in the communication system 100. FIG. FIG. 3A corresponds to the case where there is one HT-SIG, and FIG. 3B corresponds to the case where there are two HT-SIGs. In FIG. 3A, it is assumed that data included in the four sequences is to be transmitted, and packet formats corresponding to the first to fourth sequences are shown in order from the top to the bottom. In the packet signal corresponding to the first stream, “L-STF”, “HT-LTF”, and the like are arranged as preamble signals. “L-STF”, “L-LTF”, “L-SIG”, “HT-SIG” are known signals for timing estimation, known signals for transmission path estimation, control signals, MIMO systems corresponding to conventional systems Correspond to the control signals corresponding to. “HT-STF” and “HT-LTF” correspond to a known signal for timing estimation and a known signal for channel estimation corresponding to the MIMO system. On the other hand, “data 1” is a data signal.

  Further, in the packet signal corresponding to the second stream, “L-STF-50 ns”, “HT-LTF-400 ns”, and the like are arranged as preamble signals. In the packet signal corresponding to the third stream, “L-STF-100 ns”, “HT-LTF-200 ns”, and the like are arranged as preamble signals. In the packet signal corresponding to the fourth stream, “L-STF-150 ns”, “LTF-600 ns”, and the like are arranged as preamble signals. Here, “400 ns” or the like indicates a shift amount in CDD (Cyclic Delay Diversity). CDD is a process in which a waveform in the time domain is shifted backward by a shift amount in a predetermined section, and a waveform pushed out from the last part of the predetermined section is cyclically arranged at the head portion of the predetermined section. That is, “L-STF (50 ns)” is cyclically shifted with respect to “L-STF” with a delay amount of 50 ns.

  In the first stream, HT-LTFs are arranged in the order of “HT-LTF”, “−HT-LTF”, “HT-LFT”, and “−HT-LTF” from the top. Here, these are sequentially referred to as “first component”, “second component”, “third component”, and “fourth component” in all series. If the calculation of the first component-second component + third component-fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the first series. Further, if the calculation of the first component + second component + third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the second series. Further, if the calculation of the first component-second component-third component + fourth component is performed on all series of received signals, the receiving apparatus extracts a desired signal for the third series. Also, if the calculation of the first component + second component−third component−fourth component is performed on the received signals of all sequences, the desired signal for the fourth sequence is extracted in the receiving apparatus. The addition / subtraction process is executed by vector calculation.

  The parts from “L-LTF” to “HT-SIG1” use “52” subcarriers as in the conventional system. Of the “52” subcarriers, “4” subcarriers correspond to pilot signals. On the other hand, “56” subcarriers are used in the subsequent parts such as “HT-LTF”. In FIG. 3B, “HT-SIG2” is arranged after “HT-SIG1”. Other than that, it is the same as FIG. In particular, in relation to the present embodiment, “L-STF” includes “RATE”, and “HT-SIG1” and “HT-SIG2” include “LENGTH”.

  FIG. 4 shows the configuration of the first radio apparatus 10a. The first radio apparatus 10a includes a first radio unit 20a, a second radio unit 20b, a fourth radio unit 20d, a baseband processing unit 22, a modem unit 24, an IF unit 26, and a control unit 30, which are collectively referred to as a radio unit 20. Including. Further, as signals, a first time domain signal 200a, a second time domain signal 200b, a fourth time domain signal 200d, which are collectively referred to as a time domain signal 200, a first frequency domain signal 202a, which is collectively referred to as a frequency domain signal 202, and a second time domain signal 200b. A frequency domain signal 202b and a fourth frequency domain signal 202d are included. The second radio apparatus 10b is configured in the same manner as the first radio apparatus 10a.

  As a reception operation, the radio unit 20 performs frequency conversion on a radio frequency signal received by the antenna 12 and derives a baseband signal. The radio unit 20 outputs the baseband signal to the baseband processing unit 22 as a time domain signal 200. In general, baseband signals are formed by in-phase and quadrature components, so they should be transmitted by two signal lines. Here, for clarity of illustration, only one signal line is used. Shall be shown. An AGC (Automatic Gain Control) and an A / D conversion unit are also included.

  As a transmission operation, the radio unit 20 performs frequency conversion on the baseband signal from the baseband processing unit 22 and derives a radio frequency signal. Here, a baseband signal from the baseband processing unit 22 is also shown as a time domain signal 200. The radio unit 20 outputs a radio frequency signal to the antenna 12. Further, a PA (Power Amplifier) and a D / A converter are also included. The time domain signal 200 is a multicarrier signal converted into the time domain, and is a digital signal.

  As a reception operation, the baseband processing unit 22 converts each of the plurality of time domain signals 200 into the frequency domain, and performs adaptive array signal processing on the frequency domain signal. The baseband processing unit 22 outputs the result of adaptive array signal processing as the frequency domain signal 202. One frequency domain signal 202 corresponds to each of a plurality of sequences transmitted from the second radio apparatus 10b (not shown). Further, as a transmission operation, the baseband processing unit 22 receives the frequency domain signal 202 as a frequency domain signal from the modulation / demodulation unit 24, converts the frequency domain signal into the time domain, The time domain signal 200 is output while being associated.

  It is assumed that the number of antennas 12 to be used in the transmission process is specified by the control unit 30. Here, the frequency domain signal 202, which is a frequency domain signal, includes a plurality of subcarrier components as shown in FIG. For the sake of clarity, it is assumed that the frequency domain signals are arranged in the order of subcarrier numbers to form a serial signal.

  FIG. 5 shows the structure of a signal in the frequency domain. Here, one combination of subcarrier numbers “−28” to “28” shown in FIG. 1 is referred to as an “OFDM symbol”. In the “i” th OFDM symbol, subcarrier components are arranged in the order of subcarrier numbers “1” to “28” and subcarrier numbers “−28” to “−1”. Also, the “i−1” th OFDM symbol is arranged before the “i” th OFDM symbol, and the “i + 1” th OFDM symbol is arranged after the “i” th OFDM symbol. And In the portion such as “L-SIG” in FIG. 3, a combination of subcarrier numbers “−26” to “26” is used for one “OFDM symbol”.

ここで、δは、シフト量を示し、ｌは、サブキャリア番号を示している。さらに、行列Ｃと系列との乗算は、サブキャリアを単位にして実行される。すなわち、ベースバンド処理部２２は、Ｌ−ＳＴＦ等内での循環的なタイムシフトを系列単位に実行する。また、シフト量は、図３（ａ）−（ｂ）に対応するように、系列を単位にして異なった値に設定される。 Returning to FIG. Further, the baseband processing unit 22 executes CDD in order to generate a packet signal corresponding to the packet format shown in FIGS. CDD is performed as matrix C as follows.

Here, δ indicates a shift amount, and l indicates a subcarrier number. Further, the multiplication of the matrix C and the sequence is executed in units of subcarriers. That is, the baseband processing unit 22 performs a cyclic time shift within the L-STF or the like for each sequence. Further, the shift amount is set to a different value for each series so as to correspond to FIGS. 3 (a) to 3 (b).

  The modem unit 24 performs demodulation and deinterleaving on the frequency domain signal 202 from the baseband processing unit 22 as reception processing. Note that demodulation is performed in units of subcarriers. The modem unit 24 outputs the demodulated signal to the IF unit 26. Further, the modem unit 24 performs interleaving and modulation as transmission processing. The modem unit 24 outputs the modulated signal to the baseband processing unit 22 as the frequency domain signal 202. It is assumed that the modulation scheme is specified by the control unit 30 during the transmission process.

  The IF unit 26 combines signals from the plurality of modulation / demodulation units 24 as a reception process to form one data stream. In addition, one data scream is decrypted. The IF unit 26 outputs the decoded data stream. In addition, the IF unit 26 receives and encodes one data stream as transmission processing, and then separates it. Further, the IF unit 26 outputs the separated data to the plurality of modulation / demodulation units 24. It is assumed that the coding rate is specified by the control unit 30 during the transmission process. Here, an example of encoding is convolutional encoding, and an example of decoding is Viterbi decoding.

  The control unit 30 controls the timing of the first radio apparatus 10a. First, transmission processing by the control unit 30 will be described. The control unit 30 is an HT-SIG arranged in the preceding stage of the variable length data signal, for example, “data 1” in FIG. 3A, along with the IF unit 26, the modem unit 24, and the baseband processing unit 22. And a packet signal including HT-SIG including LENGTH. As described above, LENGTH is defined by 12 bits.

  FIG. 6 shows the data structure of a table relating to the data length stored in the control unit 30. As shown, a bit value column 90 and a data length column 92 are included. In the bit value column 90, the LENGTH value designated by 12 bits is shown in decimal. The data length column 92 shows the length of the data signal specified by LENGTH. Here, the length of the data signal is indicated by “L255” or the like, but this corresponds to a specific number of OFDM symbols or the number of bits. Further, it is assumed that the data signal becomes longer as the number after “L” increases. When the value of LENGTH is “255”, the lower 8 bits of LENGTH are “1”, and the upper 4 bits are “0”. Therefore, when the value of LENGTH is “255” or less, such a value is indicated by the lower 8 bits of LENGTH. Returning to FIG.

  When the HT-SIG modulation scheme is BPSK and the coding rate is 1/2, 24-bit information is transmitted in one OFDM symbol. In addition to LENGTH, 5-bit “data rate information”, 4-bit “CRC bit”, 6-bit “tail bit”, and 1-bit “reserved bit” should be included in HT-SIG. is there. Therefore, only one OFDM symbol is insufficient as HT-SIG, and two OFDM symbols are basically used as HT-SIG.

  The control unit 30 associates each of HT-SIGs to be formed with a plurality of symbols, that is, HT-SIG1 and HT-SIG2 of FIG. Specifically, the lower 8 bits of LENGTH are associated with HT-SIG1, and the upper 4 bits are associated with HT-SIG2. FIG. 7 shows the division of LENGTH by the control unit 30. The upper part shows the arrangement of HT-SIG1 and HT-SIG2, and is the same as the corresponding part in FIG. As shown in the drawing, HT-SIG2 is arranged at the subsequent stage of HT-SIG1. The lower part shows LENGTH composed of 12 bits. Since the left side of the figure corresponds to the LSB and the right side of the figure corresponds to the MSB, the left side of the figure corresponds to the lower bits and the right side of the figure corresponds to the upper bits. The lower 8 bits of LENGTH are arranged in the front HT-SIG1, and the upper 4 bits are arranged in HT-SIG2. Returning to FIG.

  When the length of the data signal decreases, the control unit 30 also decreases the number of HT-SIG OFDM symbols while maintaining the correspondence. Specifically, the control unit 30 removes the rear HT-SIG2 when the length of the data signal is equal to or less than “L255” in FIG. 6. At that time, the lower 8 bits of LENGTH are associated with HT-SIG1, and the above-described correspondence is maintained. That is, when transmitting only HT-SIG1, control unit 30 places the same lower 8 bits in HT-SIG1 as when HT-SIG2 is also transmitted. When the length of the data signal is shortened, the 12 bits of LENGTH are not required to indicate the length, and therefore the control unit 30 uses only the lower 8 bits.

  Under such circumstances, in order to notify the number of OFDM symbols of HT-SIG while avoiding the addition of new information, the control unit 30 executes the following process. As described above, the control unit 30 arranges the L-SIG in front of the HT-SIG as shown in FIGS. 3A to 3B, and the L-SIG relates to the data rate in the HT-SIG. Information, i.e., "RATE" is included. RATE is determined by at least a modulation method and a coding rate. For example, the modulation scheme “BPSK” and the coding rate “1/2” correspond to “6 Mbps”. Further, the control unit 30 associates the RATE value with the number of HT-SIG OFDM symbols to identify the number of HT-SIG OFDM symbols based on the RATE value.

  FIG. 8 shows a data structure of a table related to the data rate stored in the control unit 30. As shown, a RATE column 40, a modulation scheme column 42, a coding rate column 44, and a symbol number column 46 are included. In the RATE column 40, a 4-bit value defined in the RATE is shown. The modulation method column 42 and the coding rate column 44 show the modulation method and coding rate corresponding to the RATE value. For example, RATE “1101” corresponds to modulation scheme “BPSK” and coding rate “1/2”, and corresponds to “6 Mbps” as described above. The symbol number column 46 indicates the number of OFDM symbols of HT-SIG. That is, when RATE is “1101”, the number of OFDM symbols of HT-SIG is “2”. At that time, HT-SIG1 and HT-SIG2 are used. On the other hand, when RATE is “1111”, the number of OFDM symbols of HT-SIG is “1”. At that time, HT-SIG1 is used.

  When HT-SIG uses one OFDM symbol, the coding rate is made larger than when two OFDM symbols are used, so that the amount of data that can be transmitted per OFDM symbol increases. Further, as described above, when RATE is set to a different value in order to notify the number of HT-SIG symbols, the control unit 30 changes the coding rate value while fixing the RATE to a constant modulation scheme. . That is, the control unit 30 uses BPSK as the modulation scheme and uses “1/2” or “3/4” as the coding rate. In order to explain the reason, constellations in L-SIG and HT-SIG are used.

  FIGS. 9A to 9B show constellations in L-SIG and HT-SIG. FIG. 9A shows a constellation defined for L-SIG. The horizontal axis represents the in-phase axis (hereinafter referred to as “I axis”), and the vertical axis represents the orthogonal axis (hereinafter referred to as “Q axis”). As shown in the figure, a signal point is arranged at “+1” or “−1” on the I axis. FIG. 9B shows a constellation defined for HT-SIG. As shown in the figure, signal points are arranged at “+1” or “−1” on the Q axis, and this arrangement is orthogonal to the signal point arrangement defined for L-SIG. Yes. This arrangement is defined in order for the receiving apparatus to automatically detect HT-SIG.

  That is, when the packet signal to be received by the receiving apparatus is compatible with the MIMO system, HT-SIG is arranged after the L-SIG, but when the packet signal is compatible with the conventional system, HT-SIG is not arranged in the latter stage of L-SIG. Therefore, the receiving apparatus specifies whether HT-SIG is arranged after L-SIG from the change in the constellation of BPSK. As a result, only “BPSK” can be used as the modulation scheme for HT-SIG. In order to specify the number of OFDM symbols of HT-SIG, the coding rate is associated.

  Another reason is as follows. Generally, in a wireless device compatible with a conventional system (hereinafter referred to as “conventional device”), when the destination of a received packet signal is not itself, the LENGTH included in the L-SIG is confirmed, and the corresponding LENGTH is determined. The reception process is executed for the period, and the transmission process is not executed. Further, in order to avoid collision of packet signals with the conventional system, it is desired that the conventional apparatus stop transmission for as long as possible. Therefore, in order to stop transmission by the conventional apparatus, the radio apparatus 10 should enter a data length value as long as LENGTH included in the L-SIG and a data rate value as low as RATE. As a result, in order to lengthen the HT-SIG period, a combination of modulation scheme BPSK and coding rate 1/2 is desirable. On the other hand, if the data length is shortened, only HT-SIG1 is sufficient, and the period during which the conventional apparatus stops transmission tends to be shortened. Therefore, in order to shorten the period of HT-SIG1, the modulation scheme BPSK and the coding rate 3/4 are desirable. Finally, the control unit 30 causes the generated packet signal to be transmitted from the IF unit 26, the modem unit 24, and the baseband processing unit 22.

  Subsequently, a reception process by the control unit 30 will be described. The control unit 30 receives the packet signal via the radio unit 20, the baseband processing unit 22, the modem unit 24, and the IF unit 26. In the packet signal, as shown in FIGS. 3A to 3B, an L-SIG is arranged in front of the HT-SIG, and the RATE is included in the L-SIG. Further, as described above, RATE is associated with the number of OFDM symbols of HT-SIG. Moreover, LENGTH is included in HT-SIG, and LENGTH is associated with HT-SIG1 and HT-SIG2 while being divided. In particular, the lower 8 bits of LENGTH are associated with HT-SIG1, and when the length of the data signal is short, HT-SIG2 is removed, thereby lowering the lower bits of LENGTH. 8 bits are transmitted. That is, when the length of the data signal is reduced, the number of HT-SIG symbols is also reduced while maintaining the correspondence.

  The control part 30 specifies the data rate with respect to HT-SIG based on the RATE included in L-SIG among the received packet signals. The data rate is specified by specifying the modulation method and the coding rate. When the received packet signal does not correspond to the MIMO system but corresponds to the conventional system, the data signal is arranged at the subsequent stage of the L-SIG, and the RATE at that time indicates the data rate for the data signal. Further, the control unit 30 detects whether the packet signal corresponds to the MIMO system or the conventional system. Since such detection may be performed by a known technique, description thereof is omitted here. The control unit 30 specifies the number of HT-SIG OFDM symbols to be processed according to the value of RATE. That is, the control unit 30 specifies that the number of OFDM symbols of the HT-SIG is “2” when the RATE is “1101”, and determines the OFDM symbol of the HT-SIG when the RATE is “1111”. The number is specified as “1”.

  The control unit 30 specifies the length of the data signal based on LENGTH included in HT-SIG. When the number of OFDM symbols of HT-SIG is “2”, the control unit 30 extracts the lower 8 bits of LENGTH from HT-SIG1, extracts the upper 4 bits of LENGTH from HT-SIG2, and combines them. As a result, 12-bit LENGTH is generated. Further, the control unit 30 specifies the length of the data signal from the generated 12-bit LENGTH.

  On the other hand, when the number of OFDM symbols of HT-SIG is “1”, control unit 30 extracts the lower 8 bits of LENGTH from HT-SIG1. However, since HT-SIG2 is not transmitted, the control unit 30 does not acquire the upper 4 bits. Instead, the control unit 30 generates a 12-bit LENGTH by combining the lower 4 bits of LENGTH with the upper 4 bits of “0000”. That is, the control unit 3 fills the upper 4 bits with all 0s. In this way, the control unit 30 adjusts the number of bits to be acquired according to the number of OFDM symbols of HT-SIG. The control unit 30 causes the radio unit 20, the baseband processing unit 22, the modem unit 24, and the IF unit 26 to process the data signal based on the specified length of the data signal.

  This configuration can be realized in terms of hardware by a CPU, memory, or other LSI of any computer, and in terms of software, it is realized by a program having a communication function loaded in the memory. Describes functional blocks realized by collaboration. Accordingly, those skilled in the art will understand that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof.

  FIG. 10 shows the configuration of the baseband processing unit 22. The baseband processing unit 22 includes a reception processing unit 50 and a transmission processing unit 52. The reception processing unit 50 executes a part corresponding to the reception operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 performs adaptive array signal processing on the time domain signal 200, and for that purpose, derivation of the weight vector of the time domain signal 200 is performed. Further, the reception processing unit 50 outputs the result of array synthesis as the frequency domain signal 202.

  The transmission processing unit 52 executes a part corresponding to the transmission operation among the operations in the baseband processing unit 22. That is, the reception processing unit 50 generates the time domain signal 200 by converting the frequency domain signal 202. In addition, the transmission processing unit 52 associates a plurality of sequences with the plurality of antennas 12, respectively. Further, the transmission processing unit 52 executes CDD as shown in FIGS. Note that the transmission processing unit 52 finally outputs the time domain signal 200.

  FIG. 11 shows the configuration of the reception processing unit 50. The reception processing unit 50 includes an FFT unit 74, a weight vector deriving unit 76, a first combining unit 80a, a second combining unit 80b, a third combining unit 80c, and a fourth combining unit 80d, which are collectively referred to as a combining unit 80.

  The FFT unit 74 converts the time domain signal 200 into a frequency domain value by performing FFT on the time domain signal 200. Here, it is assumed that the frequency domain values are configured as shown in FIG. That is, the frequency domain value for one time domain signal 200 is output on one signal line.

  The weight vector deriving unit 76 derives a weight vector for each subcarrier from the value in the frequency domain. The weight vector is derived so as to correspond to each of a plurality of sequences, and the weight vector for one sequence has an element corresponding to the number of antennas 12 for each subcarrier. Further, HT-LTF or the like is used for deriving the weight vector corresponding to each of the plurality of sequences. In order to derive the weight vector, an adaptive algorithm may be used, or transmission path characteristics may be used. However, since a known technique may be used for these processes, here, The description is omitted. Note that the weight vector deriving unit 76 calculates the first component−the second component + the third component−the fourth component as described above when deriving the weight. Finally, as described above, weights are derived in units of subcarriers, antennas 12 and sequences.

  The synthesizing unit 80 performs synthesis by using the frequency domain value converted by the FFT unit 78 and the weight vector from the weight vector deriving unit 76. For example, among the weight vectors from the weight vector deriving unit 76, a weight vector corresponding to one subcarrier and corresponding to the first series is selected as one multiplication target. The selected weight has a value corresponding to each of the antennas 12.

  As another multiplication target, a value corresponding to one subcarrier is selected from the frequency domain values converted by the FFT unit 78. The selected value has a value corresponding to each of the antennas 12. Note that the selected weight and the selected value correspond to the same subcarrier. While being associated with each of the antennas 12, the selected weight and the selected value are respectively multiplied, and the multiplication result is added, whereby a value corresponding to one subcarrier in the first sequence is obtained. Derived. In the first synthesizing unit 80a, the above processing is also performed for other subcarriers, and the first sequence is derived. In the second synthesizing unit 80b to the fourth synthesizing unit 80d, the fourth sequence is derived from the second sequence by the same process. The derived first to fourth sequences are output as the first frequency domain signal 202a to the fourth frequency domain signal 202d, respectively.

  FIG. 12 shows the configuration of the transmission processing unit 52. The transmission processing unit 52 includes a distribution unit 66 and an IFFT unit 68. The IFFT unit 68 performs IFFT on the frequency domain signal 202 and outputs a time domain signal. As a result, the IFFT unit 68 outputs a time domain signal corresponding to each of the sequences.

  The distribution unit 66 associates the series from the IFFT unit 68 with the antenna 12. Here, since the number of antennas 12 used and the number of series are the same, one series is associated with one antenna 12 as it is. Furthermore, the distribution unit 66 performs CDD on “L-SIG” or the like in each of the sequences to be transmitted, that is, packet signals.

  FIG. 13 is a flowchart showing the procedure of the transmission process in the first radio apparatus 10a. The control unit 30 acquires the data length as a bit value, that is, acquires 12-bit LENGTH (S10). If the data length indicated by LEGNTH is longer than the threshold (Y in S12), the control unit 30 sets HT-SIG to 2 OFDM symbols (S14). Here, the threshold value is defined as “255” or “L255” in FIG. Further, the control unit 30 sets RATE to “1101” (S16), and divides LENGTH (S18). As a result, the control unit 30 determines the contents of L-SIG, HT-SIG1, and HT-SIG2 (S20).

  On the other hand, if the data length indicated by LEGNTH is not longer than the threshold (N in S12), the control unit 30 sets HT-SIG to one OFDM symbol (S22). Further, the control unit 30 sets RATE to “1111” (S24), and extracts the lower 8 bits of LENGTH (S26). As a result, the control unit 30 determines the contents of L-SIG and HT-SIG1 (S28). Finally, the control unit 30 generates a packet signal with the determined content (S30).

  FIG. 14 is a flowchart illustrating a procedure of reception processing in the first radio apparatus 10a. The control unit 30 receives the packet signal via the radio unit 20, the baseband processing unit 22, the modem unit 24, and the IF unit 26 (S50). If the RATE included in the L-SIG is “1101” (Y in S52) and the HT-SIG is Q-BPSK (Y in S54), the control unit 30 specifies the data rate as 6 Mbps (S56). ). Here, Q-BPSK corresponds to the constellation shown in FIG. That is, the modulation scheme is specified as BPSK, and the coding rate is specified as 1/2. In addition, the control unit 30 specifies HT-SIG as 2 OFDM symbols (S58). The control unit 30 synthesizes LENGTH included in each of HT-SIG1 and HT-SIG2 (S60), and specifies the data length (S62).

  On the other hand, if the RATE included in the L-SIG is not “1101” (N in S52), “1111” (Y in S64), and HT-SIG is Q-BPSK (Y in S66), the control is performed. The unit 30 specifies the data rate as 9 Mbps (S68). That is, the modulation scheme is specified as BPSK, and the coding rate is specified as 3/4. In addition, the control unit 30 specifies HT-SIG as one OFDM symbol (S70). The control unit 30 specifies the data length from LENGTH included in HT-SIG1 (S72). Finally, the control unit 30 causes the baseband processing unit 22, the modem unit 24, and the IF unit 26 to perform demodulation at the specified data rate and data length (S76).

  If RATE is not “1111” (N in S64) or HT-SIG is not Q-BPSK (N in S54, N in S66), the wireless device 10 is assumed to be in the conventional system mode (S74). The process corresponding to the conventional system is executed. Since the processing corresponding to the conventional system is realized by a known technique, the description thereof is omitted.

  According to the embodiment of the present invention, since the RATE included in the L-SIG is associated with the number of OFDM symbols of the HT-SIG, information indicating the number of OFDM symbols of the HT-SIG is added to the L-SIG. Even if not, the number of OFDM symbols can be specified. Moreover, since new information is not added to L-SIG, reduction in utilization efficiency can be suppressed. Even if the L-SIG format has already been determined, the number of HT-SIG OFDM symbols can be specified. In addition, when the number of OFDM symbols is reduced, by associating a high-speed data rate, it is possible to suppress a decrease in the amount of data that can be transmitted due to a decrease in OFDM symbols. In addition, when the RATE is set to a different value, the modulation method is fixed, so that the processing for the modulation can be reduced.

  Moreover, even if it is prescribed | regulated that BPSK with respect to L-SIG and BPSK with respect to HT-SIG will become the constellation which mutually orthogonally crossed, it can respond. BPSK for L-SIG and BPSK for HT-SIG are defined to be constellations that are orthogonal to each other, and it is possible to cope with the case where the receiving apparatus automatically detects the format of the packet signal using this rule. . Further, since the RATE included in the L-SIG and the number of OFDM symbols of the HT-SIG are associated with each other, information indicating the number of OFDM symbols of the HT-SIG is not added to the L-SIG. The receiving apparatus can specify the number of OFDM symbols.

  Also, LENGTH is divided and associated with each of the HT-SIGs to be formed by two OFDM symbols, and when the length of the data signal decreases, the HT-SIG OFDM symbol is maintained while maintaining the correspondence. Since the number is also reduced, the length of the data signal according to the number of OFDM symbols of HT-SIG can be designated. Further, since the number of LENGTH bits included in one HT-SIG is reduced, the number of LENGTH bits to be transmitted can be reduced when the HT-SIG is one OFDM symbol. Further, since the number of LENGTH bits to be transmitted is reduced, other information can be added to one HT-SIG. Further, even when the number of OFDM symbols of HT-SIG changes, information included in OFDM symbols ahead of HT-SIG can be configured in the same format, so that transmission processing for HT-SIG can be simplified. . Moreover, since the information included in the OFDM symbol ahead of HT-SIG is configured in the same format, additional information can be transmitted by adding an additional OFDM symbol.

  Further, when LENGTH is divided and associated with each of the HT-SIGs to be formed by two OFDM symbols and the length of the data signal decreases, the number of OFDM symbols of HT-SIG while maintaining the correspondence. Therefore, the receiving apparatus can acquire the length of the data signal corresponding to the number of OFDM symbols of HT-SIG. Even if the number of OFDM symbols in HT-SIG changes, LENGTH included in the OFDM symbol in front of HT-SIG is configured in the same format, so that reception processing for HT-SIG is simplified. it can.

  In the above, this invention was demonstrated based on the Example. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to the combination of each component and each processing process, and such modifications are also within the scope of the present invention. .

  In the embodiment of the present invention, the control unit 30 associates the lower bits of LENGTH with HT-SIG1 and associates the upper bits of LENGTH with HT-SIG2. However, the present invention is not limited to this. For example, the control unit 30 may associate the upper 8 bits of LENGTH with HT-SIG1 and associate the lower 4 bits of LENGTH with HT-SIG2. That is, the control unit 30 may associate the upper bits of the plurality of bits that should form LENGTH with the forward OFDM symbol of the plurality of OFDM symbols. At that time, when the number of OFDM symbols of HT-SIG decreases, control unit 30 removes the rear OFDM symbol, that is, HT-SIG2. According to this modification, even when LENGTH is included in two OFDM symbols, the approximate length of the data signal can be notified to a receiving apparatus that can receive only one OFDM symbol as HT-SIG. . As described above, if the data length is long, HT-SIG of 2 OFDM symbols is required. However, if reception of HT-SIG2 is an option, there may be a wireless device that cannot detect HT-SIG2. Therefore, if an upper bit is arranged in HT-SIG1, an approximate data length can be detected even by the wireless device as described above.

  In addition, when the number of OFDM symbols of HT-SIG1 is one, the control unit 30 uses the same number of bits “8” as the number of OFDM symbols of HT-SIG for the OFDM symbol. , LENGTH may be arranged with the lower 8 bits of the plurality of bits to be formed. That is, according to the number of OFDM symbols, another part of the plurality of bits that should form LENGTH may be arranged in HT-SIG1. FIGS. 15A and 15B show division of LENGTH according to the modification. 15 (a)-(b) corresponds to FIG. FIG. 15A shows a case where the upper 8 bits of LENGTH are arranged in HT-SIG1, and the lower 4 bits are arranged in HT-SIG2. FIG. 15B shows the arrangement of LENGTH when the number of OFDM symbols of HT-SIG becomes “1”. As shown in the figure, when the number of OFDM symbols of HT-SIG becomes “1”, the lower 8 bits are arranged in HT-SIG1 instead of the upper 8 bits of LENGTH. According to this modification, the length of the data signal can be specified by one OFDM symbol.

  On the other hand, regarding the reception process, the control unit 30 specifies the length of data while adjusting the number of bits to be acquired in LENGTH according to the number of OFDM symbols of HT-SIG. That is, when the number of OFDM symbols of HT-SIG is “1”, the data length can be specified from the value of LENGTH of the upper 8 bits. According to this modification, when only one OFDM symbol can be received as HT-SIG, the approximate length of the data signal can be acquired even if the length of the data signal is specified by two OFDM symbols. .

  In addition, when the number of OFDM symbols of HT-SIG is one, the same number of bits “8” as that when there are a plurality of OFDM symbols of HT-SIG for the OFDM symbol, When the lower 8 bits are arranged, the control unit 30 may specify the data length from the lower 8 bits. According to this modification, when the number of OFDM symbols is one, the data length corresponding to the number can be specified. That is, it is only necessary that a plurality of bits that constitute LENGTH are divided and associated with a plurality of OFDM symbols.

  In the Example of this invention, the control part 30 has set the data rate of HT-SIG to another value according to the value of RATE included in L-SIG. However, the present invention is not limited to this. For example, even when the control unit 30 sets the RATE value included in the L-SIG to a different value, the data rate for the HT-SIG may be fixed to a constant value. Good. Specifically, regardless of whether RATE is “1111” or “1101”, the control unit 30 sets 6 Mbps, that is, the modulation scheme to BPSK and the coding rate to ½. On the other hand, for the reception process, the control unit 30 sets the data rate for the HT-SIG to be processed to a constant value even when the RATE value included in the L-SIG is set to a different value. It may be fixed. According to this modification, since a predetermined value is used as the actual data rate, the number of OFDM symbols can be specified by RATE instead of the data rate for HT-SIG. That is, it is only necessary that the number of OFDM symbols can be specified by RATE.

  In the embodiment of the present invention, the IF unit 26 performs convolutional encoding for each OFDM symbol of HT-SIG. That is, a tail bit is added to each OFDM symbol. However, the present invention is not limited to this. For example, when the HT-SIG is formed with a plurality of OFDM symbols, the IF unit 26 may execute integral convolutional coding on the plurality of OFDM symbols. In this case, a common tail bit is added to a plurality of OFDM symbols. Note that encoding other than convolutional encoding, such as block encoding, may be performed, and in this case, parity bits and the like are added. The same applies when CRC is applied. According to this modification, the number of redundant bits can be reduced by executing integral error correction coding on a plurality of OFDM symbols, so that the utilization efficiency can be improved.

  In an embodiment of the present invention, HT-SIG specifies that there are a maximum of 2 OFDM symbols. However, the present invention is not limited to this, and HT-SIG may be a maximum of 2 OFDM symbols or more. In this case, the bits obtained by dividing LENGTH may be arranged in all of the plurality of OFDM symbols or may be arranged in a part of the plurality of OFDM symbols. According to this modification, the number of OFDM symbols of HT-SIG can be increased.

It is a figure which shows the spectrum of the multicarrier signal which concerns on the Example of this invention. It is a figure which shows the structure of the communication system which concerns on the Example of this invention. FIGS. 3A and 3B are diagrams showing packet formats in the communication system of FIG. It is a figure which shows the structure of the 1st radio | wireless apparatus of FIG. It is a figure which shows the structure of the signal of the frequency domain in FIG. It is a figure which shows the data structure of the table regarding the data length memorize | stored in the control part of FIG. It is a figure which shows the division | segmentation of LENGTH by the control part of FIG. It is a figure which shows the data structure of the table regarding the data rate memorize | stored in the control part of FIG. FIGS. 9A to 9B are diagrams showing constellations of L-SIG and HT-SIG in FIGS. 3A and 3B. It is a figure which shows the structure of the baseband process part of FIG. It is a figure which shows the structure of the process part for reception of FIG. It is a figure which shows the structure of the process part for transmission of FIG. 6 is a flowchart showing a procedure of transmission processing in the first wireless device in FIG. 4. 5 is a flowchart showing a procedure of reception processing in the first wireless device of FIG. 4. FIGS. 15A to 15B are diagrams illustrating division of LENGTH according to the modification.

Explanation of symbols

  10 wireless devices, 12 antennas, 14 antennas, 20 wireless units, 22 baseband processing units, 24 modulation / demodulation units, 26 IF units, 30 control units, 50 reception processing units, 52 transmission processing units, 100 communication systems.

Claims (13)

A generation unit that generates a packet signal including a control signal that is a control signal arranged in a preceding stage of a variable-length data signal and includes a multi-bit value indicating the length of the data signal;
A transmission unit for transmitting the packet signal generated in the generation unit,
The generation unit associates each control signal to be formed with a plurality of symbols while dividing a plurality of bits, and when the length of the data signal is reduced, the control signal symbol is maintained while maintaining the correspondence. A transmission apparatus characterized in that the number is also reduced.   The generation unit associates a lower bit of the plurality of bits with a front symbol of the plurality of symbols, and removes the rear symbol when the number of control signal symbols decreases. The transmission device according to claim 1, wherein   3. The generation unit according to claim 2, wherein when the number of symbols of the control signal is one, the lower order bits that are the same as when the number of symbols of the control signal is plural are arranged for the symbol. The transmitting device described.   The generation unit associates upper bits of a plurality of bits with a front symbol of the plurality of symbols, and removes a rear symbol when the number of control signal symbols decreases. The transmission device according to claim 1, wherein   When the number of symbols of the control signal is one, the generation unit arranges the lower bits of the plurality of bits with the same number of bits as when the number of symbols of the control signal is plural. The transmission device according to claim 4, wherein: A receiving unit that receives a packet signal including a control signal that is a control signal arranged in a preceding stage of a variable-length data signal and includes a multi-bit value indicating the length of the data signal;
Of the packet signal received by the receiving unit, based on the value of a plurality of bits included in the control signal, a specifying unit for specifying the length of the data signal,
A processing unit for processing the data signal based on the length of the data signal specified by the specifying unit;
A plurality of bits are associated with each of a plurality of symbols to form a control signal received by the reception unit, and when the length of the data signal is reduced, the control signal of the control signal is maintained while maintaining the correspondence. The number of symbols is also reduced,
The specifying unit extracts a bit value from a symbol forming a control signal received by the receiving unit, and specifies a data length by combining the extracted bit values. apparatus. When a lower bit of a plurality of bits is associated with a front symbol of a plurality of symbols that should form a control signal received by the receiving unit, and the number of control signal symbols decreases , The backward symbol is removed,
The receiving device according to claim 6, wherein the specifying unit specifies the length of data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. When the number of control signal symbols received by the receiving unit is one, the same low-order bits as in the case where the number of control signal symbols is plural are arranged for the symbol,
The receiving device according to claim 7, wherein the specifying unit specifies a data length from a value of a lower bit. When a higher order bit of a plurality of bits is associated with a front symbol of a plurality of symbols that should form a control signal received by the receiving unit, and the number of control signal symbols decreases , The backward symbol is removed,
The receiving device according to claim 6, wherein the specifying unit specifies the length of data while adjusting the number of bits to be acquired according to the number of symbols of the control signal. When the number of control signal symbols received by the receiving unit is one, the lower bit of the plurality of bits with the same number of bits as the control signal when there are a plurality of control signal symbols. Is placed,
The receiving apparatus according to claim 9, wherein the specifying unit specifies a data length from a value of a lower bit. A transmission device that transmits a packet signal including a control signal that is a control signal arranged in a preceding stage of a variable-length data signal and includes a value of a plurality of bits indicating the length of the data signal;
A receiving device that processes a data signal by identifying a length of the data signal based on a value of a plurality of bits included in the control signal after receiving the packet signal transmitted by the transmitting device; Prepared,
The transmission device associates each control signal to be formed with a plurality of symbols while dividing a plurality of bits, and when the length of the data signal is reduced, the control signal symbols are maintained while maintaining the correspondence. Reduce the number,
A communication system characterized in that the receiving device extracts a bit value from a symbol forming a received control signal, and synthesizes the extracted bit value, thereby specifying a data length. A transmission method for transmitting a packet signal including a control signal arranged in a preceding stage of a variable-length data signal and including a multi-bit value indicating the length of the data signal,
Multiple bits are associated with each control signal to be formed with multiple symbols, and when the data signal length is reduced, the number of control signal symbols is also reduced while maintaining the correspondence. A transmission method characterized by the above. After receiving a packet signal including a control signal arranged in the preceding stage of a variable-length data signal and including a multi-bit value indicating the length of the data signal, the control signal is A reception method for processing a data signal by specifying the length of the data signal based on a value of a plurality of bits included,
When multiple bits are divided and associated with each of a plurality of symbols to form a received control signal and the length of the data signal is reduced, the number of control signal symbols is also reduced while maintaining the correspondence. A receiving method characterized by extracting a bit value from a symbol forming a received control signal and specifying the length of the data by synthesizing the extracted bit value .

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