JP2009044699A - Radio terminal, data transmission method, and data reception method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio terminal for flexibly handling channel equalization in time domain and in frequency domain. <P>SOLUTION: A subblock generation section 23 is provided. The subblock generation section 23 divides a transmission symbol into a prescribed number of information symbols. A symbol at the rear of the information symbol is added to the head of the prescribed number of information symbols as a cyclic prefix. When the symbol at the rear of the information symbol is added to the head of the prescribed number of information symbols as the cyclic prefix to compose a subblock, the continuity of symbols is maintained, thus reliably equalizing the channel in frequency domain. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless terminal, a data transmission method, and a data reception method, and particularly relates to a device that performs high-speed communication between a transmitter and a receiver using millimeter waves.

  Development of a wireless communication system of a millimeter wave WPAN (Wireless Personal Area Network) that uses millimeter waves to perform high-speed communication between wireless terminals is underway. In such a wireless communication system, an ultra wide band of 7 GHz to 9 GHz in the 60 GHz band is used, and ultra high speed communication of several Gbps is possible. Such a wireless communication system is expected to be used for transmission of uncompressed video signals and kiosk downloading type file transfer.

  As such a wireless communication system, there is one whose standardization is being studied as IEEE 802.15.3 (see Non-Patent Document 1). The wireless communication system will be described below.

  FIG. 12 shows the configuration of an IEEE 802.15.3 wireless communication system. In the IEEE 802.15.3 wireless communication system, a wireless terminal is called a device (DEV). Among the wireless terminals of these devices, one device is a control terminal called a piconet coordinator (PNC), and the other device (DEV) is a subordinate terminal. In FIG. 12, one control terminal (PNC) and four subordinate terminals (DEV) are shown. Note that the number of dependent terminals (DEV) is not limited to this. The control terminal (PNC) can also function as a subordinate terminal (DEV).

  When receiving a command from an upper layer, the control terminal (PNC) bundles the peripheral subordinate terminals (DEV) to form one piconet. A piconet is a network configured by connecting a plurality of slaves (here, subordinate terminals (DEV)) to one master (here, control terminal (PNC)). Here, the subordinate terminal (DEV) can freely join and leave the network.

  The control terminal (PNC) has a function of sending out a beacon and adjusting network timing. Each subordinate terminal (DEV) receives a beacon from a wireless terminal (PNC) and transmits / receives data at a designated timing.

  The control terminal (PNC) manages the time resources allocated to each subordinate terminal (DEV), thereby controlling the formation of the communication path of each subordinate terminal (DEV), and thereby, point-to-point between any devices The communication path is formed and data is transferred.

  FIG. 13 shows a superframe structure used in IEEE802.15.3. As shown in FIG. 13, one superframe is composed of three parts: a beacon period, a contention access period (CAP), and a channel time allocation period (CTAP).

  At the start of each super frame, there is a beacon period. During this beacon period, a beacon is broadcast from the control terminal (PNC). This beacon indicates the start of each superframe, and provides time allocation and management information from the control terminal (PNC) to each subordinate terminal (DEV).

  A contention access period (CAP) is allocated next to the beacon in the superframe. The contention access period (CAP) is a period in which all wireless terminals can access by CSMA / CA (Carrier Sense Multiple Access With Collision Avoidance). In this contention access period (CAP), time-independent data is transferred.

  The channel time allocation (CTPA) period is a period in which the control terminal (PNC) permits communication only to a specific subordinate terminal (DEV). The channel time allocation period (CTPA) is composed of management time slots (MCTA1, MCTA2) and several time slots (CTA1, CTA2,...). In this channel time allocation (CTPA) period, time-dependent data (isochronous data) is transferred.

  FIG. 14 shows the structure of an edgeless frame used in IEEE802.15.3. In each period (beacon period, contention access period (CAP), channel time allocation (CTPA) period), communication is performed using radio frames as shown in FIG.

  As shown in FIG. 14A, the radio frame is composed of a preamble part, a header part, and a payload part. As shown in FIG. 14B, the preamble part is further divided into a synchronization preamble (SYNC) for performing AGC, AFC, symbol synchronization, and frame synchronization, and a preamble (CE) for channel estimation. ing. The header includes attribute information of information data sent in a radio frame.

A preamble (CE) for channel estimation is used for channel equalization in the time domain and frequency domain. Non-patent document 2 discloses a technique for equalizing a communication system that has been conventionally known to have a poor propagation path environment.
IEEE 802.15, Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specifications for Wireless Personal Area Networks (WPAN) Amendment 1: MAC Sublayer, IEEE Std. 802.15.3b, 2005 D. Falconer, et al., "Frequency domain equalization for single-carrier broadband wireless access," IEEE Communications Magazine, vol.40, no.4, pp.58-66, April 2002.

  As described above, in such a radio communication system, channel equalization due to the influence of multipath is performed using a preamble (CE) for channel estimation of radio frames. Channel equalization includes time domain equalization and frequency domain equalization. In order to deal with a wide range of propagation environments, it is desired to be able to flexibly cope with equalization in the time domain and equalization in the frequency domain.

  In such a wireless communication system, multipath signals such as reflected waves passing through a plurality of paths are interfered and arrive. In such an environment, when performing equalization in the frequency domain, a delayed signal is received via multipath. At this time, if there is a discontinuous portion in the signal component delayed by the multipath, a different frequency component is generated from this portion, and equalization of the frequency domain is not performed correctly.

  It is also conceivable to add symbols for frequency domain equalization. However, when a long symbol is inserted for frequency domain equalization, there arises a problem that transmission efficiency deteriorates.

  In view of the above-described problems, an object of the present invention is to provide a wireless terminal, a data transmission method, and a data reception method that can flexibly cope with equalization in a time domain and equalization in a frequency domain.

  In order to solve the above problems, a wireless terminal of the present invention forms a network from a control terminal and a plurality of subordinate terminals, and transmits a superframe from a beacon period, a contention access period, and a channel time allocation period. A transmission symbol transmitted in a radio frame in a radio terminal of a radio communication system that transmits and receives data using a radio frame composed of a synchronization and channel estimation preamble, a header, and a payload in each period of a super frame Is divided into a predetermined number of information symbols, and a sub-block generating means for forming a sub-block by adding a predetermined symbol pattern as a cyclic prefix to the predetermined number of information symbols. Features.

  In the wireless terminal of the present invention, preferably, a prefix length setting means for controlling the length of the cyclic prefix according to the multipath information is further provided.

  The radio terminal of the present invention preferably further includes channel equalization means for performing channel equalization in the frequency domain, and the symbol division means transmits with the number of symbols corresponding to the input of the channel equalization means in the frequency domain. The symbol is divided.

  Preferably, the radio terminal of the present invention further includes correlation detection means for detecting a correlation between the received symbol and the predetermined pattern, and detecting the reference position of the sub-block from the correlation detection value from the correlation detection means. Features.

  In the wireless terminal according to the present invention, preferably, the reference position is detected from the position of the window where the total power is maximum by detecting the total power of the correlation detection value using a window having a predetermined width.

  In the radio terminal according to the present invention, preferably, the reference position is detected based on a comparison output between the correlation detection value and the predetermined threshold value by comparing the correlation detection value with the predetermined threshold value.

  In the data transmission method of the present invention, a control terminal and a plurality of subordinate terminals form a network, a superframe is formed from a beacon period, a contention access period, and a channel time allocation period. In a data transmission method of a wireless communication system that transmits and receives data using a radio frame composed of a synchronization and channel estimation preamble, a header, and a payload, the transmission symbols transmitted in the radio frame are converted into a predetermined number of information symbols. And a step of adding a predetermined symbol pattern as a cyclic prefix to a predetermined number of information symbols to form a sub-block.

  In the data transmission method of the present invention, preferably, the length of the cyclic prefix is further controlled according to the multipath information.

  In the data transmission method of the present invention, it is preferable that the transmission symbols are further divided by the number of symbols corresponding to the channel equalization input in the frequency domain on the reception side.

  In the data reception method of the present invention, a control terminal and a plurality of subordinate terminals constitute a network, a superframe is formed from a beacon period, a contention access period, and a channel time allocation period. And detecting a correlation between a received symbol and a predetermined pattern in a data reception method of a wireless communication system that transmits and receives data using a radio frame including a synchronization and channel estimation preamble, a header, and a payload; And a step of detecting a reference position of the sub-block from the correlation detection value from the correlation detection means.

  In the data reception method, preferably, the reference position is detected from the position of the window where the total power is maximum by detecting the total power of the correlation detection value using a window having a predetermined width.

  In the data reception method, preferably, the reference position is detected based on a comparison output between the correlation detection value and the predetermined threshold value by comparing the correlation detection value with the predetermined threshold value.

  According to the radio terminal of the present invention, a control terminal and a plurality of subordinate terminals constitute a network, and a superframe is formed from a beacon period, a contention access period, and a channel time allocation period. In a radio terminal of a radio communication system that transmits and receives data using a radio frame composed of a preamble for synchronization and channel estimation, a header, and a payload during a period, a transmission symbol transmitted in the radio frame is converted into a predetermined number of information symbols. Since symbol dividing means for dividing and sub-block generating means for forming a sub-block by adding a predetermined symbol pattern on the back side to a predetermined number of information symbols as a cyclic prefix are provided. Can keep sex. For this reason, even when channel equalization in the frequency domain is performed, information symbol boundaries do not become discontinuous, and different frequency components do not occur from that portion. Thereby, it is possible to flexibly cope with equalization in the time domain and equalization in the frequency domain.

  Further, according to the radio terminal of the present invention, since the prefix length setting means for controlling the length of the cyclic prefix according to the multipath information is provided, the cyclic prefix according to the size of the multipath is provided. By setting the length, the data usage efficiency can be increased.

  The radio terminal according to the present invention further includes channel equalization means for performing channel equalization in the frequency domain, and the symbol division means has the number of symbols corresponding to the input of the channel equalization means in the frequency domain. Since the transmission symbols are divided, channel equalization in the frequency domain can be reliably performed.

  The radio terminal according to the present invention further includes correlation detection means for detecting a correlation between the received symbol and the predetermined pattern, and detects the reference position of the sub-block from the correlation detection value from the correlation detection means. Therefore, it is possible to perform channel equalization reliably by cutting out the information symbol portion of the sub-block from the received signal via the optimum path.

  Further, according to the wireless terminal of the present invention, the reference position is detected from the position of the window where the total power is the maximum by detecting the total power of the correlation detection value using a window of a predetermined width, so that the optimum route is selected. It is possible to reliably detect the reference position of the received signal.

  Further, according to the wireless terminal of the present invention, the reference position is detected based on a comparison output between the correlation detection value and the predetermined threshold value by comparing the correlation detection value with the predetermined threshold value. It is possible to reliably detect the reference position of the received signal via the simple path.

  According to the data transmission method of the present invention, a network is configured by a control terminal and a plurality of subordinate terminals, a superframe is formed from a beacon period, a contention access period, and a channel time allocation period. In a data transmission method of a wireless communication system in which data is transmitted and received using a radio frame including a preamble for synchronization and channel estimation, a header, and a payload in each period, a predetermined number of pieces of information are transmitted symbols transmitted in the radio frame. A step of dividing into symbols and a step of adding a predetermined rear symbol pattern as a cyclic prefix to a predetermined number of information symbols to form sub-blocks, so that continuity of symbols is maintained be able to. For this reason, even when channel equalization in the frequency domain is performed, information symbol boundaries do not become discontinuous, and different frequency components do not occur from that portion. Thereby, it is possible to flexibly cope with equalization in the time domain and equalization in the frequency domain.

  Further, according to the data transmission method of the present invention, since the length of the cyclic prefix is controlled according to the multipath information, the length of the cyclic prefix is set according to the size of the multipath. Thus, the data use efficiency can be improved.

  Further, according to the data transmission method of the present invention, since the transmission symbol is further divided by the number of symbols corresponding to the channel equalization input in the frequency domain on the reception side, the frequency domain channel on the reception side. Equalization can be performed reliably.

  According to the data receiving method of the present invention, a control terminal and a plurality of subordinate terminals form a network, and a superframe is formed from a beacon period, a contention access period, and a channel time allocation period. A step of detecting a correlation between a received symbol and a predetermined pattern in a data reception method of a wireless communication system in which data is transmitted and received using a radio frame including a synchronization and channel estimation preamble, a header, and a payload in each period And a step of detecting the reference position of the sub-block from the correlation detection value from the correlation detection means, so that the information symbol part of the sub-block is cut out from the received signal through the optimum path. Channel equalization can be performed reliably.

  Further, according to the data receiving method of the present invention, the reference position is detected from the position of the window where the total power is maximum by detecting the total power of the correlation detection value using a window having a predetermined width, so that the optimum route is obtained. The information symbol portion of the sub-block can be cut out from the received signal that has passed through.

  Further, according to the data receiving method of the present invention, the reference position is detected based on the comparison output between the correlation detection value and the predetermined threshold value by comparing the correlation detection value with the predetermined threshold value. The information symbol portion of the sub-block can be cut out from the received signal through the optimum path.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a wireless terminal to which the present invention is applied. The embodiment of the present invention can be used as a control terminal (PNC) and a subordinate terminal (DEV) in a wireless communication system proposed in IEEE 802.15.3.

  As shown in FIG. 1, a wireless terminal 1 according to an embodiment of the present invention mainly includes a MAC (Media Access Controller) unit 11, a baseband processing unit 12, and an RF (Radio Frequency) front end unit 13. ing.

  The MAC unit 11 performs processing of the MAC layer. The MAC layer process controls how terminals on the network transmit and receive data. In the embodiment of the present invention, data is transmitted and received using a superframe including a beacon period, a contention access period (CAP), and a channel time allocation period (CTAP).

  The baseband processing unit 12 performs processing of a baseband signal of data to be transmitted and a received baseband signal. The transmission-side baseband processing unit 12 includes an error correction coding unit 21, a baseband modulation unit 22, a sub-block generation unit 23, a radio frame generation unit 24, and a spectrum spreading unit 25.

  The error correction encoding unit 21 performs error correction encoding of transmission data. As the error correction code, a block code or a convolutional code can be used, and any error correction process may be performed.

  The baseband modulation unit 22 modulates transmission data, and uses any modulation method such as BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and multilevel QAM (Quadrature Amplitude Modulation). Also good.

  The sub-block generating unit 23 divides the transmission symbol into a predetermined number of information symbols and adds a cyclic prefix to the head of the predetermined number of information symbols to generate a sub-block.

  The cyclic prefix maintains the continuity of transmission symbols and is a symbol corresponding to the rear side of information symbols to be transmitted. In this way, by adding a symbol corresponding to the rear side of the information symbol to the beginning of the predetermined number of information symbols as a cyclic prefix, appropriate estimation can be performed when performing frequency domain channel estimation at the time of reception. . Note that the length of a symbol added as a cyclic prefix is set according to the multipath state. This will be described later.

  The radio frame generation unit 24 adds a preamble of a predetermined symbol and a header to transmission data (payload) to form a radio frame. The preamble includes an AGC, AFC, symbol synchronization and frame synchronization preamble (SYNC), and a channel estimation preamble (CE).

  The spread spectrum unit 25 performs spread spectrum of the transmission symbol using a random code sequence. Here, DS-CDMA (Direct Sequence Code Division Multiple Access) is performed by the spectrum spreading unit 24, but OFDM (Orthogonal Frequency Division Multiplex) and MB-OFDM (Multiband Orthogonal Frequency Division Multiplex) may also be used. Good.

  The receiving side of the baseband processing unit 12 includes a spectrum despreading unit 31, an AGC (Automatic Gain Control) / AFC (Automatic Frequency Control) unit 32, a channel equalization unit 33, a sub-block decomposition unit 34, A band demodulation unit 35, an error correction processing unit 36, and a synchronization acquisition unit 37 are included.

  The spectrum despreading unit 31 performs spectrum despreading using a random code sequence. The spectrum despreading is performed using the same random code as that at the time of transmission.

  The AGC / AFC unit 32 performs amplitude control and frequency deviation control using a preamble pattern. The amplitude control is performed by controlling the amplitude of the synchronization preamble (SYNC) to be a predetermined value. The control of the frequency deviation is performed by detecting the frequency deviation from the phase rotation amount of the synchronization preamble (SYNC).

  In addition, the synchronization acquisition unit 37 forms a symbol synchronization clock from the preamble (SYNC) for synchronization of the received signal. The symbol synchronization clock is sent to each unit, and symbol synchronization processing is performed.

  The channel equalization unit 33 performs channel estimation using a preamble (CE) for channel estimation, and performs processing for removing code interference due to multipath components using the channel estimation.

  As described above, in the embodiment of the present invention, a transmission symbol is divided into a predetermined number of information symbols, and a symbol pattern on the back side of the information symbol is added as a cyclic prefix to the head of the predetermined number of information symbols. Is a sub-block. For this reason, when performing channel estimation of the frequency domain, appropriate estimation can be performed.

  The sub-block decomposition unit 34 decomposes the sub-block and removes the cyclic prefix portion added to the sub-block.

  The baseband demodulation unit 35 demodulates the baseband signal by performing demodulation processing such as BPSK, QPSK, and QAM.

  The error correction processing unit 36 performs error correction processing using a block code or a convolutional code.

  The RF front end unit 13 up-converts transmission data to a millimeter wave band (for example, 60 GHz) at the time of transmission, and amplifies the power for transmission. In reception, the received signal is amplified and the received data is down-converted.

  The RF front end unit 13 on the transmission side includes an orthogonal modulation circuit 41 and a power amplification circuit 42. The reception-side RF front end unit 13 includes an LNA (Low Noise Amplifier) 43 and an orthogonal demodulation circuit 44.

  As described above, in the wireless terminal according to the first embodiment of the present invention, the sub-block generating unit 23 is provided, and the sub-block generating unit 23 divides the transmission symbol into a predetermined number of information symbols, and this predetermined number The symbol behind this information symbol is added as a cyclic prefix to the head of the information symbol.

  FIG. 2 is an example of the sub-block generation unit 23. In FIG. 2, a transmission symbol is input to the symbol division unit 51. The symbol division unit 51 divides the input transmission symbol into a predetermined number L of information symbols.

  If a transmission symbol as shown in FIG. 3A is input to the symbol division unit 51, the transmission symbol is converted into a predetermined number L of information symbols by the symbol division unit 51 as shown in FIG. The data is divided and stored in the memory 52.

  Note that the number L of information symbols to be divided is set according to the number of inputs of the FFT 67 (see FIG. 7) when performing frequency domain channel estimation described later.

  Of the predetermined number L of information symbols stored in the memory 52, the rear M symbol is cut out as shown in FIG. 3C, and the rear M symbol of the information symbol is a cyclic prefix storage unit. 53 and stored as a cyclic prefix.

  A cyclic prefix length setting unit 55 is provided for the cyclic prefix storage unit 53. The cyclic prefix length setting unit 55 optimizes the cyclic prefix length M in accordance with the multipath length. Multipath information is input to the cyclic prefix length setting unit 55. The setting of the cyclic prefix length will be described later.

  In FIG. 2, the information symbols are read from the memory 52 and sent to the cyclic prefix insertion unit 54. Further, the M symbol on the rear side of the information symbol is read from the cyclic prefix storage unit 53 as a cyclic prefix and sent to the cyclic prefix insertion unit 54.

  As shown in FIG. 3D, the cyclic prefix insertion unit 54 adds the M symbols on the back side of the predetermined number L of information symbols as a cyclic prefix to one sub-block. Is generated.

  FIG. 4 is another example of the sub-block generation unit 23. In FIG. 4, the transmission symbol is input to the symbol division unit 71. The symbol division unit 71 divides the input transmission symbol into a predetermined number (LM) of information symbols.

  If a transmission symbol as shown in FIG. 5A is input to the symbol division unit 71, the transmission symbol is divided into a predetermined number (LM) of information symbols by the symbol division unit 71, and the memory 72 Accumulated in.

  The predetermined number L is set in accordance with the number of inputs of the FFT 67 (see FIG. 7) when performing frequency domain channel estimation described later.

  For a predetermined number (LM) of information symbols stored in the memory 72, a known symbol pattern of M symbols is generated as shown in FIG.

  A known cyclic prefix length setting unit 73 is provided for the known cyclic prefix generation unit 75. The known cyclic prefix length setting unit 73 optimizes the cyclic prefix length M in accordance with the multipath length. Multipath information is input to the known cyclic prefix length setting unit 73. The setting of the known cyclic prefix length will be described later.

  In FIG. 4, the information symbol is read from the memory 72 and sent to the known cyclic prefix insertion unit 74. Also, a known symbol pattern of M symbols is read from the known cyclic prefix generation unit 75 and sent to the known cyclic prefix insertion unit 74.

  As shown in FIGS. 5 (C) and 5 (D), the known cyclic prefix insertion unit 74 cyclically places known symbol patterns of M symbols at the beginning and rear of a predetermined number (LM) of information symbols. Added as a prefix, one sub-block is generated.

  In this way, one sub-block is configured by adding a predetermined M symbol as a cyclic prefix to a predetermined number of information symbols. When such a sub-block is used, the continuity of symbols is maintained.

  That is, as shown in FIG. 6A, it is assumed that a predetermined number L of the same information symbols (S1 to SL) are continuously arranged, and the continuous codes are cut at Q1 and Q2. In this case, as shown in FIG. 6B, the pattern of the cut symbol is the M symbol (S on the back side of the information symbol of the L symbol at the head of the information symbol (S1 to SL) of the L symbol. (L−M + 1) to SL) are the same as those added as cyclic prefixes. Therefore, if the sub-block is configured by adding the M symbols on the rear side of the information symbol as a cyclic prefix to the head of the predetermined number L of information symbols, the continuity of the symbols is maintained.

  FIG. 7 shows an example of the channel equalizer 33. As described above, the channel equalization unit 33 performs channel estimation using a channel estimation preamble (CE).

  The received channel estimation preamble (CE) is extracted by the preamble extraction unit 61 and sent to the correlation detection unit 62. A pattern similar to the channel estimation preamble (CE) is generated from the pattern generation unit 63 and sent to the correlation detection unit 62. The correlation detection unit 62 detects the correlation value between the received channel estimation preamble (CE) and the pattern from the pattern generation unit 63. The correlation detection unit 62 can be configured by a matched filter, for example.

  The correlation detection value from the correlation detection unit 62 is sent to the channel estimation unit 64. The channel estimation unit 64 converts the received channel estimation preamble (CE) into the frequency domain, and performs channel estimation in the frequency domain.

  Further, the correlation detection value from the correlation detection unit 62 is sent to the reference position setting unit 65. The reference position setting unit 65 uses the correlation value from the correlation detection unit 62 to set a reference position for extracting a sub-block.

  The reference position is set, for example, as shown in FIG. 8A, in which a detection window W is provided, and the detection window W is scanned to set the place where the maximum power is obtained as the reference position. . In other words, the correlation detection unit 62 outputs a correlation value as shown in FIG. A detection window W is provided for this correlation value, and the total power of the correlation value that falls within this detection window W is calculated. The detection window W is scanned, and the position where the total power of the correlation values entering the detection window W is maximized is obtained. The position where the total power of the correlation values entering the detection window W is the maximum is set as the reference position.

  In addition, as shown in FIG. 8B, the reference position is set by setting a predetermined threshold value for the correlation value, and a portion of the correlation value that first exceeds the threshold value is set as the reference position. Also good.

  In FIG. 7, the sub-block extracting unit 66 extracts symbols of each sub-block from the received symbols based on the reference position from the reference position setting unit 65. The symbols of each sub block are sent to an FFT (Fast Fourier Transform) 67.

  As described above, the sub-block is configured by adding the M symbol on the rear side of the information symbol as a cyclic prefix to the head of the predetermined number L of information symbols. At this time, a predetermined number L of information symbol portions are input to the FFT 67.

  The FFT 67 converts the symbol in the time domain into the frequency domain. The output of the FFT 67 is sent to the channel equalization filter 68. A channel equalization signal in the frequency domain is sent from the channel estimation unit 64 to the channel equalization filter 68. The channel equalization filter 68 performs channel equalization in the frequency domain.

  As channel equalization in the frequency domain, zero forcing equalization, minimum mean square error equalization, or similar equalization can be used.

  The output of the channel equalization filter 68 is sent to an IFFT (inverse Fast Fourier Transform) 69, converted back to a symbol in the time domain, and output.

  In the above example, the frequency domain equalization has been described. However, not only the frequency domain equalization but also the time domain equalization may be performed. As the equalization of the time domain, determination period equalization, maximum likelihood sequence estimation, and equalization equivalent thereto can be used. Further, time domain equalization and frequency domain equalization may be appropriately combined in accordance with the propagation path environment.

  As described above, in the embodiment of the present invention, the FFT 67 converts the time domain symbol into the frequency domain, and the channel equalization filter 68 performs channel equalization in the frequency domain. As described above, in the embodiment of the present invention, a transmission symbol is divided into a predetermined number L of information symbols, and the M symbol behind the information symbol is added as a cyclic prefix to the head of the predetermined number L of information symbols. Thus, sub-blocks are configured. When such a sub-block is used, the continuity of symbols is maintained, so that appropriate estimation can be performed when performing channel estimation in the frequency domain as described above.

  That is, since the received signal is a multipath signal via a plurality of paths, multipath received data via a plurality of paths is sent to the FFT 67 as shown in FIG. A sub-block is extracted based on the reference position from the reference position setting unit 65 and, as shown in FIG. 9A, a portion R1 that is an information symbol is input to the FFT 67 from the received signal through the original path. And At this time, as shown in FIGS. 9B to 9D, the signals that have passed through the delay path are delayed by T1 to T3, respectively, so that the portions R2 to R4 are input to the FFT 67. become. As shown in FIGS. 9B to 9D, the cyclic prefix portion is included in the portions R2 to R4 that are input after being delayed through the delay path.

  At this time, if the code is discontinuous at the information symbol boundary, a different frequency component is generated from that portion, which affects the frequency characteristics. On the other hand, in the embodiment of the present invention, the M symbol behind the information symbol is a cyclic prefix. As described above, the use of such a sub-block maintains the continuity of the symbol. If the continuity of symbols is maintained, the frequency characteristics are not affected even if a cyclic prefix portion is included. That is, this means that the start position of the data input to the FFT 67, that is, the phase has changed, and the frequency is not affected. Therefore, the correlation characteristics can be maintained without affecting the frequency characteristics.

  Next, the setting of the length of the cyclic prefix portion added to the information symbol will be described.

  As described above, in the embodiment of the present invention, the M symbols on the rear side of the predetermined number L of information symbols are added as cyclic prefixes to maintain the continuity of the symbols, and in the frequency domain. The channel estimation in can be performed appropriately. In consideration of the effects of multipath, it is advantageous to increase the length of this cyclic prefix. However, if the length of the cyclic prefix is increased, the transmission efficiency deteriorates.

  Therefore, in this embodiment, as shown in FIG. 2, a cyclic prefix length setting unit 55 is provided for the cyclic prefix storage unit 53 to optimize the length of the cyclic prefix. . FIG. 10 is a flowchart showing the processing in the cyclic prefix length setting unit 55.

  In FIG. 10, when multipath information is input (step S11). It is determined whether the length of the multipath is longer than a predetermined value (step S12). The multipath information can be acquired from the detection output of the correlation detection unit 62 of the channel equalization unit shown in FIG. Further, multipath information may be exchanged with the other party's subordinate terminal (DEV) or control terminal (PNC). If the multipath length is longer than the predetermined value, as shown in FIG. 11A, the length M of the cyclic prefix is increased (for example, M = m1), and the multipath length is a predetermined value. If it is shorter, the length M of the cyclic prefix is shortened (for example, M = m2) as shown in FIG. Note that m1 is longer than the delay time of the multipath maximum path of the transmission path at that time, and m2 is a length satisfying (m1> m2).

  Thus, when the multipath is large, the cyclic prefix length is lengthened, and when the multipath is small, the cyclic prefix length is shortened, and the cyclic prefix length is changed according to the multipath length. If the length is optimized, the transmission efficiency can be prevented from deteriorating.

  In this example, the length of the cyclic prefix is set in two stages according to the length of the multipath, but the length of the cyclic prefix is made finer according to the length of the cyclic prefix. It may be set.

  Note that the present invention can be configured by digital signal processing hardware, or by software using a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), or the like.

  The present invention is not limited to the above-described embodiments, and various modifications and applications can be made without departing from the gist of the present invention.

  In particular, the present invention. It is suitable for use in a millimeter-wave WPAN wireless communication system in which millimeter-wave is used to perform high-speed communication between wireless terminals.

It is a block diagram which shows the structure of the radio | wireless terminal of embodiment of this invention. It is a block diagram which shows the structure of an example of the subblock production | generation part in the radio | wireless terminal of embodiment of this invention. It is explanatory drawing of an example of the subblock in embodiment of this invention. It is a block diagram which shows the structure of the other example of the subblock production | generation part in the radio | wireless terminal of embodiment of this invention. It is explanatory drawing of the other example of the subblock in embodiment of this invention. It is explanatory drawing of the subblock in embodiment of this invention. It is a block diagram which shows the structure of an example of the channel equalization part in the radio | wireless terminal of embodiment of this invention. It is explanatory drawing of the setting of the reference position in embodiment of this invention. It is explanatory drawing of the input of the information symbol via multipath. It is a flowchart used for description of control of the cyclic prefix length in embodiment of this invention. It is explanatory drawing of control of the cyclic prefix length in embodiment of this invention. It is explanatory drawing of the radio | wireless communications system of IEEE802.15.3. It is explanatory drawing of the super frame in the radio | wireless communications system of IEEE802.15.3. It is explanatory drawing of the radio | wireless frame in the radio | wireless communications system of IEEE802.15.3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 MAC part 12 Baseband process part 13 Front end part 21 Error correction encoding part 22 Baseband modulation part 23 Sub block generation part 24 Spectrum spread part 24 Radio frame generation part 25 Spectrum spread part 31 Spectrum despread part 32 AGC / AFC Unit 33 channel equalization unit 34 sub-block decomposition unit 35 baseband demodulation unit 36 error correction processing unit 37 synchronization acquisition unit 41 orthogonal modulation circuit 42 power amplification circuit 44 orthogonal demodulation circuit 51 symbol division unit 52 memory 53 cyclic prefix storage unit 54 Cyclic prefix insertion unit 55 Cyclic prefix length setting unit 61 Preamble extraction unit 62 Correlation detection unit 63 Pattern generation unit 64 Channel estimation unit 65 Reference position setting unit 67 FFT
66 Sub-block extraction unit 68 Channel equalization filter 69 IFFT
71 Symbol division unit 72 Memory 73 Known cyclic prefix length setting unit 74 Known cyclic prefix insertion unit 75 Known cyclic prefix generation unit

Claims (12)

A network is composed of a control terminal and a plurality of subordinate terminals, and a superframe is formed from a beacon period, a contention access period, and a channel time allocation period, and synchronization and channel estimation are performed in each period of the superframe. In a wireless terminal of a wireless communication system that transmits and receives data using a wireless frame composed of a preamble, a header, and a payload,
Symbol dividing means for dividing a transmission symbol transmitted in the radio frame into a predetermined number of information symbols;
Sub-block generating means for forming a sub-block by adding a predetermined symbol pattern as a cyclic prefix to the predetermined number of information symbols;
A wireless terminal characterized by comprising:   The wireless terminal according to claim 1, further comprising: a prefix length setting unit that controls the length of the cyclic prefix according to multipath information. Furthermore, channel equalization means for performing channel equalization in the frequency domain is provided,
The radio terminal according to claim 1 or 2, wherein the symbol division means divides the transmission symbol by the number of symbols corresponding to the input of the channel equalization means in the frequency domain.   4. The apparatus according to claim 1, further comprising correlation detection means for detecting a correlation between a received symbol and a predetermined pattern, wherein the reference position of the sub-block is detected from a correlation detection value from the correlation detection means. A wireless terminal according to any one of the above.   The wireless terminal according to claim 4, wherein the reference position is detected from a position of a window where the total power of the correlation detection value is detected by a window having a predetermined width and the total power is maximized.   The wireless terminal according to claim 4, wherein the reference position is detected based on a comparison output between the correlation detection value and a predetermined threshold value by comparing the correlation detection value with a predetermined threshold value. . A network is composed of a control terminal and a plurality of subordinate terminals, and a superframe is formed from a beacon period, a contention access period, and a channel time allocation period, and synchronization and channel estimation are performed in each period of the superframe. In a data transmission method of a wireless communication system that transmits and receives data using a wireless frame composed of a preamble, a header, and a payload,
Dividing a transmission symbol to be transmitted in the radio frame into a predetermined number of information symbols;
Adding a predetermined symbol pattern as a cyclic prefix to the beginning of the predetermined number of information symbols to form a sub-block;
A data transmission method characterized by comprising:   The data transmission method according to claim 7, further comprising controlling the length of the cyclic prefix according to multipath information.   9. The data transmission method according to claim 7, further comprising dividing the transmission symbols by the number of symbols corresponding to an input of channel equalization in a frequency domain on a reception side. A network is composed of a control terminal and a plurality of subordinate terminals, and a superframe is formed from a beacon period, a contention access period, and a channel time allocation period, and synchronization and channel estimation are performed in each period of the superframe. In a data reception method of a wireless communication system that transmits and receives data using a wireless frame composed of a preamble, a header, and a payload,
Detecting a correlation between a received symbol and a predetermined pattern;
And a step of detecting a reference position of the sub-block from a correlation detection value from the correlation detection means.   11. The data receiving method according to claim 10, wherein the reference position is detected from a window position where the total power is maximized by detecting the total power of the correlation detection value using a window having a predetermined width. 11. The data reception according to claim 10, wherein the reference position is detected based on a comparison output between the correlation detection value and a predetermined threshold value by comparing the correlation detection value with a predetermined threshold value. Method.

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