JP2008288736A - Transmission apparatus, receiving apparatus, and communication system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a transmission apparatus which attains an efficient data transmission by applicably changing the number of pilot symbols or the like in a packet. <P>SOLUTION: The transmission apparatus includes: a format determination part (14) for estimating whether the channel estimation accuracy of a packet newly received by a receiving side apparatus on the basis of a past channel estimation value can be improved or not; and a transmission signal construction part (15) for generating a packet of which the number of packet symbols is smaller than that of a packet to be generated when no improvement is judged when judging that the improvement of estimation accuracy can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for efficiently transmitting a multicarrier signal in wireless communication.

  In recent years, multi-carrier transmission schemes such as OFDM (Orthogonal Frequency Division Multiplexing) or OFDMA (Orthogonal Frequency Division Multiplexing Access) have been used for various purposes such as wireless LAN, digital broadcasting, and mobile communication in wireless communication.

  In general, in wireless communication, propagation loss, received interference power, and the like during communication vary greatly depending on the positional relationship between the transceivers. In general, a receiver first performs channel estimation using a pilot signal (pilot symbol) included in a transmission signal to grasp a propagation path state. Thereafter, a data signal is demodulated and decoded using the channel estimation result, thereby receiving a data signal. At this time, unless good channel estimation accuracy is obtained, data demodulation / decoding processing cannot be performed well, and reception errors frequently occur. Therefore, maintaining good channel estimation accuracy is important in wireless communication.

  Until now, in the wireless communication standard, pilot signals are fixedly arranged in a frame. For example, in the standard described in Non-Patent Document 1 below, each packet uses the same pilot signal arrangement, and even when a packet is transmitted using a continuous time frame or a plurality of continuous bands, the pilot signal arrangement is used. Does not change. Regardless of the number of antennas of the receiver, the arrangement of pilot signals during packet transmission is constant. Further, when a packet reception error occurs in the receiver, retransmission is performed without changing the frame configuration and pilot signal arrangement.

  The technique described in Patent Document 1 below shows a method of changing the pilot / data arrangement format according to the reception quality state when transmitting an OFDM signal. In this method, a transmitter that transmits an OFDM signal determines pilot data arrangement of the OFDM signal based on feedback information of reception quality measured by the receiver. As a result, it is shown that good channel estimation accuracy can be maintained even on a transmission path with poor reception quality, and a situation in which communication is disabled can be avoided.

JP 2005-27294 A “IEEE802.16e (IEEE standard for local and metropolitan area networks Part 16: air interface for fixed and mobile broadband wireless access systems, in IEEE Std802.16e”, Feb.2006

  In the conventional method of adaptively changing the frame configuration, it is necessary to perform a process of measuring reception quality on the reception side and feeding back the information to the transmission side. However, there is a demand for a system that can perform efficient signal transmission using an adaptive frame configuration without performing feedback.

  Further, in recent wireless communication, packets are often transmitted by being assigned to continuous time frames or frequency bands, but each packet uses the same frame configuration. However, while the receiver needs to perform channel estimation using the pilot symbol in the first packet, the subsequent packet uses a part of the channel estimation result in the previously transmitted packet. it can. Therefore, the conditions for the number of necessary pilot signals differ depending on the transmission state of the packet. Considering this point, it is an important issue to improve the efficiency to transmit by changing the frame configuration adaptively so that the number of pilot symbols meets the necessity.

  Further, regarding the measurement of interference power, when continuous packet transmission is performed, it is possible that transmission efficiency can be improved by using an adaptive frame configuration in consideration of the fact that a part of the measurement result of the previous transmission packet can be used. Therefore, it is desired to realize a technique for adaptively changing the frame configuration so that highly efficient signal transmission can be simultaneously performed while realizing highly accurate interference power measurement.

  In packet transmission, control information such as terminal ID, modulation scheme / coding rate (MCS), transmission power level, and data amount may be added to the packet. The packet can use a part of the control information of the first packet. Therefore, provision of a technique for adaptively changing the form of control information according to the continuous packet transmission state is an important issue in improving transmission efficiency.

  In recent wireless communication, signal transmission is performed using the same frame configuration for initial transmission and retransmission in retransmission control. However, there are cases where the transmission efficiency can be improved by changing the frame configuration of the retransmission packet according to the transmission state, and it is desired to realize a technique for adaptively selecting the frame configuration and transmitting the retransmission packet.

  Recently, there are many environments in which a receiver receives signals using a plurality of antennas. However, in an adaptive array antenna, the number of pilot symbols necessary for obtaining an optimum combined weight differs depending on the number of reception antennas. Therefore, it is desired to realize a frame configuration in consideration of the number of receiver antennas.

  The present invention has been made in view of the above, and does not require feedback information from the receiving side, and appropriately changes the frame configuration in accordance with the packet transmission state, transmission purpose, device configuration, and the like. An object of the present invention is to obtain a transmission device, a reception device, and a communication system that efficiently perform data transmission.

  In order to solve the above-described problems and achieve the object, the present invention generates a packet including a pilot symbol in a multicarrier communication system that performs channel estimation using a pilot symbol included in a received packet. A transmission device that uses one or more of the packets, and when a packet is transmitted to the same destination a plurality of times, the reception side device that is the destination newly receives a packet based on the past channel estimation value This is generated when it is determined that the channel estimation accuracy cannot be improved when the estimation unit estimates whether the channel estimation accuracy can be improved and the estimation unit determines that the channel estimation accuracy can be improved. Packet generating means for generating a packet having a smaller number of pilot symbols than the packet. And features.

  According to the present invention, the transmission side determines the number of pilot symbols for each transmission signal (packet) in consideration of the number of pilot symbols necessary for channel estimation on the reception side. Can be adaptively changed to improve the data transmission efficiency.

  Hereinafter, embodiments of a transmission device, a reception device, and a communication system according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a communication system including a transmission device according to the present invention. This communication system includes a communication device on the transmission side and a communication device on the reception side. In FIG. 1, in order to clearly show the roles of the transmission side and the reception side, the transmission device 1 included in the communication device on the transmission side and the reception device 2 included in the communication measure on the reception side are illustrated. Usually, both the communication device on the transmission side and the reception side are provided with the transmission device 1 and the reception device 2.

  The transmission apparatus 1 includes a data symbol generation unit 11, a pilot symbol generation unit 12, a null symbol generation unit 13, a format determination unit 14, a transmission signal construction unit 15, an information storage unit 16, and a control information reception unit 17. And comprising. In addition, the reception device 2 includes a reception signal separation unit 21, a data symbol detection unit 22, a reception control unit 23, a format identification unit 24, an information storage unit 25, and a control information reception unit 26.

  In the transmission apparatus 1, the data symbol generation unit 11 generates a data symbol using the input transmission data. The pilot symbol generator 12 and the null symbol generator 13 generate a pilot symbol and a null symbol, respectively, according to the designation from the format determination unit 14.

  The format determining unit 14 (estimating means) determines the signal format of the transmission signal based on the information held in the information storage unit 16, and executes an operation for generating a transmission signal according to the determined content. Instructions are given to the data symbol generator 11, the pilot symbol generator 12, the null symbol generator 13, and the transmission signal construction unit 15.

  The transmission signal construction unit 15 (packet generation means) receives the data symbol received from the data symbol generation unit 11, the pilot symbol received from the pilot symbol generation unit 12, and the null symbol generation unit in accordance with the designation from the format determination unit 14. Null symbols are arranged in a frame to construct a transmission signal (packet).

  The information storage unit 16 holds the information received from the control information receiving unit 17. The control information receiving unit 17 (information acquisition unit) receives control information transmitted from the opposite communication device on the receiving side.

  Moreover, in the receiving device 2, the received signal separating unit 21 separates the data symbol and the pilot symbol from the received signal. The data symbol detection unit 22 (reception unit) performs reception processing on the data symbols received from the reception signal separation unit 21 in accordance with an instruction from the reception control unit 23. The reception control unit 23 determines a channel estimation method suitable for the signal format of the received signal notified from the format identification unit 24, a signal synthesis method between antennas, and the like.

  The format identification unit 24 identifies the signal format of the received signal based on the information held by the information storage unit 25. The information storage unit 25 holds information such as a packet transmission state and the number of reception antennas. The control information receiving unit 26 receives control information transmitted from a communication device on the opposite transmission side.

  FIGS. 2-1 and 2-2 are diagrams illustrating an example of a signal format (pilot symbol arrangement) used in the present embodiment, and a data symbol in which data (Data) is added to a guard interval (GI). It consists of a pilot symbol. A shaded portion indicates a pilot symbol. Hereinafter, in this embodiment, the format shown in FIG. 2-1 is referred to as format A, and the format shown in FIG.

  3 and 4 are diagrams illustrating an example of a signal format selection pattern (selection result) by the transmission apparatus 1 according to the present embodiment. FIG. 5 and FIG. 6 are respectively a flowchart showing an operation example of the transmission apparatus (base station) and an operation example of the reception apparatus (terminal) when this embodiment is applied to the cellular system downlink. FIG. 7 and FIG. 8 are a flowchart showing an operation example of a transmission apparatus (terminal) and a reception apparatus (base station), respectively, when this embodiment is applied to a cellular system uplink. FIGS. 9A and 9B are diagrams illustrating configuration examples of control signals used in the present embodiment.

  Hereinafter, the signal transmission procedure of the present embodiment will be described with reference to FIGS. In recent wireless communication, a multicarrier transmission method is widely used, and a method of adaptively selecting a subcarrier group (hereinafter referred to as a subband) for signal transmission in a unit of a certain time (for example, 1 ms) is conceivable. ing. This method has an advantage that signal transmission can be performed satisfactorily by selecting a subband having a good propagation state and transmitting the signal. Such a technique is known as frequency scheduling. In this transmission method, a subband used for signal transmission between a specific transmission device and a reception device may vary depending on a time frame, or the same subband may be continuously used in a continuous time frame.

  In the present embodiment, first, when transmitting apparatus 1 transmits a multicarrier signal, the signal format of the packet is adaptively determined according to the continuous transmission state of the packet. Specifically, format A in which a lot of pilot symbols shown in FIG. 2-1 are arranged (high density) and format B in which the density of pilot symbols shown in FIG. 2-2 is low are prepared and transmitted. The format to be used is adaptively selected according to the packet transmission state.

  FIG. 3 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus 1, and illustrates a signal format selection pattern when packets are continuously transmitted in the same subband. As shown in FIG. 3, in the transmission apparatus 1 according to the present invention, a packet is transmitted using a format A having a high density of pilot symbols in the first time frame in which packet transmission is started. On the other hand, in subsequent (second and subsequent) packets transmitted continuously in time in the same subband, the packet is transmitted using format B having a low pilot symbol density. In the first packet, it is necessary for the receiving side (receiving apparatus 2) to perform channel estimation using only pilot symbols present in the packet, and many pilot symbols are required to perform channel estimation with high accuracy. Because it becomes. On the other hand, in a packet that is continuously transmitted after that, since there is a correlation between the time when the first packet is transmitted and the channel (propagation path) state, a part of the channel estimation result in the first packet is obtained. Can be used to improve channel estimation accuracy. As a specific example, the estimation accuracy can be improved by appropriately weighted averaging the channel coefficient estimated in the first packet and the channel coefficient estimated in the second packet.

  Therefore, in order to obtain the desired channel estimation accuracy by using a part of the channel estimation result performed in the packet transmitted before the second and subsequent packets continuously transmitted in the same subband. The required number of pilot symbols can be made smaller than that of the first packet. If the number of pilot symbols is reduced, the number of symbols used for data transmission can be increased correspondingly, and efficient signal transmission is possible. Thus, the data transmission efficiency can be improved by adaptively selecting the signal format (number of pilot symbols) when the transmission apparatus 1 transmits a signal according to the transmission state of the packet.

  FIG. 4 is a diagram showing an example of a signal format selection pattern by the transmission apparatus 1, and shows a selection pattern different from that shown in FIG. FIG. 4 shows that the transmission apparatus 1 transmits three packets in a continuous time frame of one subband (subband # 2), and transmits two packets in a continuous time frame of different subbands (subband #N). An example of transmission is shown. In this case, since it is necessary to perform channel estimation only in the first packet that is continuously transmitted in subband #N, format A having a high pilot symbol density is selected. In the subsequent (second) packet, format B having a low pilot symbol density is selected.

  FIG. 5 is a flowchart showing an example of a signal format selection procedure when the transmitting apparatus 1 according to the present invention transmits a signal, and a control procedure in the transmitting apparatus 1 (corresponding to a base station) applied to the cellular system downlink. Is shown.

  First, in the transmission device 1 (base station), the format determination unit 14 determines a subband (not limited to one) used for packet transmission to each terminal (reception device 2) (step S11). Next, one of the determined subbands is selected as a processing target (step S12), and it is confirmed whether or not the selected subband (target subband) has been used for transmission to the same terminal even in the immediately preceding time frame. (Step S13). The base station stores the subband information packet-transmitted to each terminal in the immediately preceding time frame in the information storage unit 16, and the format determination unit 14 refers to the information and performs the determination in step S13. Then, when the target subband is used for transmission to the same terminal even in the immediately preceding time frame (step S13, Yes), a format B having a low pilot symbol density is selected (step S14). On the other hand, if it is not used for transmission to the same terminal in the immediately preceding time frame (No in step S13), format A having a high pilot symbol density is selected (step S15). Next, whether there are other subbands to be used for packet transmission, that is, whether there are subbands that have not yet been selected for the signal format to be used among the subbands determined in step S11. Are confirmed (step S16). If there is a subband that has not been selected (step S16, Yes), one of them is selected again as a processing target (step S17), and the above-described processing is executed (step S13 → step S14). Or step S13-> step S15). Thereafter, the processing is continued until the signal format is selected for all the subbands determined in step S11. When the signal format selection is completed for all the subbands determined in step S11 (No in step S16), the signal format selection procedure is ended. Through the above processing, the base station can realize adaptive format selection as shown in FIGS.

  FIG. 6 is a diagram illustrating an example of a processing procedure for appropriately receiving a signal transmitted by the transmission apparatus 1 according to the present invention on the reception side, and the reception apparatus 2 (corresponding to a terminal) applied to the cellular system downlink. The control procedure in is shown.

  First, in the receiving device 2 (terminal), the format identifying unit 24 (pilot symbol specifying means) recognizes a subband that receives a packet from the control information acquired through the control information receiving unit 26 (step S21). Next, the format identifying unit 24 identifies the format of the signal transmitted in the current time frame from the use subband state in the immediately preceding time frame and the current time frame (step S22). The terminal stores the subband information used in the immediately preceding time frame in the information storage unit 25, and by referring to the information, packets received in the current time frame are continuously transmitted (the immediately preceding time frame). It is determined whether the packet is transmitted in the same subband as the frame. In the case of continuously transmitted packets, it is determined that they are transmitted in format B, and in other cases, it is determined that they are transmitted in format A. When the format is recognized, the received signal separation unit 21 separates the data symbol and the pilot symbol according to the recognition result. Then, using the pilot symbols, the reception control unit 23 determines a channel estimation method suitable for the format of the received signal (step S23), and the data symbol detection unit 22 performs an operation according to the determination result in the reception control unit 23. The data packet is received by executing (step S24). In the case where the receiving apparatus 2 is configured to include a plurality of antennas, the reception control unit 23 also determines a signal synthesis method between the antennas in step S23.

  FIGS. 9A and 9B illustrate an example of control information notified from the transmission apparatus 1 to the reception apparatus 2. In the example illustrated in FIG. 9A, subbands used in the next time frame. Information (subband number (1), subband number (2),...) Is sent to the receiving device 2 to be notified together with the receiver ID. From the receiver ID and the subband number indicated by the control information, the receiving device 2 grasps the subband used in the next time frame and the receiving device of the transmission destination. In the example shown in FIG. 9-2, in addition to the subband information (subband number (1), subband number (2),...) Used in the next time frame, signal format information ( Format (1), format (2),... As shown in FIG. 9B, when the signal format information is included in the control information, the receiving device 2 can immediately recognize the signal format from the received control information, and thus the processing in step S22 described above can be omitted.

  FIG. 7 is a flowchart showing an example of a signal format selection procedure when the transmission apparatus 1 according to the present invention transmits a signal, and shows a control procedure in the transmission apparatus (corresponding to a terminal) applied to the cellular system uplink. ing.

  First, the transmitting device 1 (terminal) receives an instruction of a subband used for packet transmission from the base station (receiving device 2) via the control information receiving unit 17 (step S31). Next, one of the designated use subbands is selected as a processing target (step S32), and it is confirmed whether or not the selected subband (target subband) has been used for transmission even in the immediately preceding time frame (step S32). S33). The terminal stores the subband information used for transmission in the immediately preceding time frame in the information storage unit 16, and the format determination unit 14 performs the determination in step S33 with reference to the information. When the target subband is used for transmission even in the immediately preceding time frame (step S33, Yes), the format B having a low pilot symbol density is selected (step S34). On the other hand, if it is not used for transmission in the immediately preceding time frame (No at step S33), format A having a high pilot symbol density is selected (step S35). Next, whether there are other subbands to be used for packet transmission, that is, among the used subbands instructed in step S31, there is one for which the signal format to be used has not yet been selected. (Step S36). If there is a subband that has not been selected (step S36, Yes), one of them is selected again as a processing target (step S37), and the above-described processing is executed (step S33 → step S34). Or step S33-> step S35). Thereafter, the processing is continued until signal formats are selected for all the used subbands designated in step S31. When the signal format selection is completed for all the used subbands designated in step S31 (No in step S36), the signal format selection procedure is ended. Through the above processing, the terminal can realize adaptive format selection as shown in FIGS.

  FIG. 8 is a diagram illustrating an example of a processing procedure for appropriately receiving a signal transmitted by the transmission apparatus 1 according to the present invention on the reception side, and is a reception apparatus 2 (corresponding to a base station) applied to a cellular system uplink. ) Shows the control procedure.

  First, in the receiving apparatus 2 (base station), the format identifying unit 24 recognizes a subband that receives a packet from the control information acquired via the control information receiving unit 26 (step S41). When the scheduling information notified to the terminal by the base station is stored in the information storage unit 25 or the like, the subband that receives the packet may be recognized from the stored scheduling information. Good.

  Next, the format identifying unit 24 identifies the format of the signal transmitted in the current time frame from the use subband state in the immediately preceding time frame and the current time frame (step S42). The base station stores the subband information used in the previous time frame in the information storage unit 25, and by referring to the information, packets received in the current time frame are continuously transmitted (the previous time frame). It is determined whether the packet is transmitted in the same subband as the frame. In the case of continuously transmitted packets, it is determined that they are transmitted in format B, and in other cases, it is determined that they are transmitted in format A. When the format is recognized, the received signal separation unit 21 separates the data symbol and the pilot symbol according to the recognition result. Then, using pilot symbols, the reception control unit 23 determines a channel estimation method suitable for the format of the received signal (step S43), and the data symbol detection unit 22 performs an operation according to the determination result in the reception control unit 23. By executing, a data packet is received (step S44).

  Through the above processing, the transmission apparatus can transmit a packet in an appropriate format according to the continuous transmission state of the packet. As a result, the number of pilot symbols can be reduced in continuous packet transmission in which sufficient channel estimation accuracy can be obtained by using the immediately preceding channel estimation result, and the data transmission efficiency can be improved. Here, as an example of selecting an appropriate format, the case of changing the number of pilot symbols has been described. However, the format can be changed by various methods such as a null symbol and a control information format as described later in the embodiment. Is possible. Therefore, changing the number of pilot symbols is only an example of changing the signal transmission format. In the above description, the case where two types of formats are selected has been described. However, it is also possible to select from three or more types in consideration of the correlation with the immediately preceding channel estimation result.

  As shown in FIGS. 5 to 8, this embodiment can be applied to both the uplink and downlink of the cellular system. In addition, the present embodiment can be applied to any wireless transmission system that uses multicarrier transmission other than the cellular system. In the present embodiment, the case where the present invention is applied to a wireless system that performs frequency scheduling has been described as an example. However, the present embodiment can be applied to any wireless system that performs continuous packet transmission. For example, the present invention can also be applied to the case where there is only one subband in the entire system band.

  In addition, here, for convenience of explanation, the term “packet transmission in continuous time” is used. However, if a part of information included in a packet transmitted in the past (channel estimation result in this embodiment) can be used, Even if it is not completely continuous in time (even if it is not adjacent in the time domain), the same effect as described above can be obtained. Therefore, if there is a correlation between channel states of a plurality of time frames in which packet transmission is performed, the present embodiment can be similarly applied even when there are time intervals in the plurality of time frames. For example, when the current channel state is correlated with the channel state of the previous time frame, it is not necessary to transmit to the same destination in the same subband of the immediately previous (previous) time frame. If the same subband is used in the previous time frame, it is possible to select a format with a low pilot symbol density.For example, there is a correlation between the current channel state and the channel state when transmitting a close packet. I just need it. The same applies to the embodiments described later.

  Further, the signal format selection control operation of the present embodiment is also applicable to a MIMO (Multi-Input Multi-Output) system in which a transmission device and a reception device use a plurality of antennas. In a MIMO system, a transmitting apparatus may transmit a plurality of signals from a plurality of antennas or transmission beams at the same time. In this case, by performing selection control for each antenna or transmission beam, a signal transmission format can be smoothly set. Can be selected.

  FIG. 10 is a diagram illustrating an operation example when the above-described signal format selection control is applied to a MIMO system that performs spatial multiplexing transmission. Here, for simplicity, the number of subbands in the transmission band in each spatial multiplexing transmission is set to 1. In this MIMO system, it is also possible for the transmission apparatus to spatially multiplex a plurality of signals. When continuously transmitting packets in each transmission beam, a format A having a high pilot symbol density is used for the first packet, and Format B, which has a low pilot symbol density, is used in subsequent packets transmitted automatically. This control can be realized by executing the control shown in FIGS. 5 to 8 individually for each transmission beam. As described above, the signal format selection control shown in the present embodiment can also be applied to the case of spatial multiplexing transmission in the MIMO channel. Further, FIG. 10 shows a configuration in which the number of subbands is 1. However, the present invention can be similarly applied to a case where signals are transmitted in a plurality of subbands from each transmission beam.

  Thus, in the present embodiment, for each transmission signal (data packet), the format (pilot symbol arrangement in the packet) is selected from a plurality of formats to generate a transmission signal. In addition, when selecting the format, confirm the state of the subband used for packet transmission in the previous time frame, and as a result of confirmation, channel estimation using the channel estimation result in the previous time frame is possible. When judged, a format with a low pilot symbol density was selected. As a result, the number of data symbols transmitted per frame increases, and the data transmission efficiency can be improved.

Embodiment 2. FIG.
Next, the second embodiment will be described. In the present embodiment, a transmission device that improves the efficiency of data transmission by using channel estimation results in other subbands when transmitting signals using a plurality of subbands will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) are the same as those in the first embodiment described above (see FIG. 1).

  FIG. 11 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to the second embodiment. FIG. 12 and FIG. 13 are a flowchart showing an example of operation of a transmitting apparatus (base station) and an example of operation of a receiving apparatus (terminal) when this embodiment is applied to a cellular system downlink.

  Hereinafter, the signal transmission procedure of the present embodiment will be described with reference to FIGS. In recent multicarrier transmission systems, a method of adaptively selecting subbands for signal transmission has been considered. When this selection method is used, there are many cases in which signal transmission is performed by selecting a plurality of consecutive subbands. However, since adjacent subbands have similar channel states, channels are correlated using mutual correlation. The estimation accuracy can be improved.

  For example, as shown in FIG. 11, when signal transmission is performed using subbands # 1 to # 4 continuous in the frequency axis direction, packet transmission is also performed in subbands # 2 and # 3 in adjacent subbands. Therefore, in subbands # 2 and # 3, channel estimation accuracy can be improved using channel estimation results in adjacent subbands on both sides. Specifically, first, channel estimation is performed independently for each subband, and channel estimation results in adjacent subbands and appropriate weighted averaging can be performed to improve estimation accuracy. On the other hand, in subbands # 1 and # 4 located at both ends of a subband group (in this example, continuous subbands # 1 to # 4), only channel estimation results in one side subband are used in channel estimation. It is disadvantageous because it cannot be done (estimation accuracy is lower than when estimation results on both sides are available). Accordingly, more pilot symbols are required in both subbands # 1 and # 4 in order to maintain the same channel estimation accuracy as in subbands # 2 and # 3.

  Therefore, in the present embodiment, when packet transmission is performed in a plurality of continuous subbands as in the example shown in FIG. 11, a signal transmission format is adaptively selected according to the usage status of adjacent subbands. For example, as shown in FIG. 11, transmission using the format A having a high pilot symbol density is performed in the subbands (subbands # 1 and # 4) at both ends of the subband group, and the others (subbands # 2 and # 4) In # 3), transmission is performed using format B having a low pilot symbol density. In this way, by reducing the pilot symbol density in the subbands (subbands # 2 and # 3) that are not located at both ends of the subband group, it is possible to transmit more data symbols within that frame, Data transmission efficiency can be improved.

  FIG. 12 is a flowchart showing an example of a signal format selection procedure when the transmission apparatus 1 according to the second embodiment transmits a signal, and control in the transmission apparatus 1 (corresponding to a base station) applied to the cellular system downlink. The procedure is shown. In addition, about the same process as the signal format selection procedure (refer FIG. 5) by the base station of Embodiment 1, the same step number is attached | subjected and the description is abbreviate | omitted.

  The format determination unit 14 of the transmission device 1 (base station) executes steps S11 and S12 to determine a subband to be used for packet transmission and to select a processing target for format selection. And it is confirmed whether it transmits to the same terminal using the subband of the both sides of the selected subband (target subband) (step S13a). The base station stores information on subbands used for transmission to each terminal in the information storage unit 16, and the format determination unit 14 performs the determination in step S13a with reference to the information. When transmitting to the same terminal using the subbands on both sides (step S13a, Yes), format B having a low pilot symbol density is selected (step S14). In other cases (step S13a, No), format A having a high pilot symbol density is selected (step S15). By executing the above processing for all the subbands determined in step S11, the base station can realize adaptive format selection as shown in FIG.

  On the other hand, the receiving device 2 (terminal) can recognize the subband in which the packet is transmitted from the control signal, and can identify the signal format of the subband used for transmission from the subband information. Since this control procedure can be executed by the same procedure as in FIG. 6 if the time frame information is replaced with the subband information in FIG. 6 described in the first embodiment, detailed description is omitted.

  FIG. 13 is a flowchart showing an example of a signal format selection procedure when the transmission apparatus 1 according to the present invention transmits a signal, and shows a control procedure in the transmission apparatus (corresponding to a terminal) applied to the cellular system uplink. ing. In addition, about the same process as the signal format selection procedure (refer FIG. 7) by the terminal of Embodiment 1, the same step number is attached | subjected and the description is abbreviate | omitted.

  The format determination unit 14 of the transmission apparatus 1 (terminal) executes steps S31 and S32 to determine a subband to be used for packet transmission and to select a processing target for format selection. Then, it is confirmed whether or not subbands on both sides of the selected subband (target subband) are used for transmission (step S33a). The terminal stores information on subbands used for transmission in the information storage unit 36, and the format determination unit 34 refers to the information and performs the determination in step S33a. When the subbands on both sides are used for transmission (step S33a, Yes), format B having a low pilot symbol density is selected (step S34). In other cases (step S33a, No), format A having a high pilot symbol density is selected (step S35). By executing the above processing for all the subbands determined in step S31, the terminal can realize adaptive format selection as shown in FIG.

  On the other hand, the receiving apparatus 2 (base station) can recognize the subband in which the packet is transmitted from the control signal, and can identify the signal format of the subband used for transmission from the subband information. Since this control procedure can be executed by the same procedure as in FIG. 6 if the time frame information is replaced with the subband information in FIG. 8 described in the first embodiment, detailed description is omitted.

  As described above, when signal transmission is performed in continuous subbands, data transmission efficiency can be improved by changing the pilot symbol density according to the subbands used.

  For convenience of explanation, the term “packet transmission in consecutive subbands” is used here. However, a part of information included in a packet transmitted in the past or at the same time (channel estimation result in this embodiment) is used. If it can be used, the same effect as described above can be obtained even if it is not completely continuous in time. Therefore, the present embodiment can be similarly applied to a case where there is a frequency interval enough to maintain the channel state between a plurality of subbands that perform packet transmission.

  Further, in this embodiment, even when a transmission apparatus transmits a plurality of signals simultaneously from a plurality of antennas or transmission beams in a MIMO system, by performing selection control for each antenna or transmission beam smoothly, The signal format can be selected.

  As described above, in this embodiment, when selecting the format of the transmission signal, the use state of the adjacent subbands is confirmed, and if it is determined that the subbands on both sides are also used as a result of the confirmation, the pilot symbols A format with low density was selected. As a result, the number of data symbols transmitted per frame increases, and the data transmission efficiency can be improved.

Embodiment 3 FIG.
Next, Embodiment 3 will be described. In the second embodiment, when transmission is performed using continuous subbands, the same pilot symbol arrangement format is used for the subbands at both ends of the subband group (see FIG. 11). It is also possible to use the same pilot symbol density. In this embodiment, a case where different formats are used in the subbands at both ends will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) are the same as those in the first embodiment described above (see FIG. 1).

  FIG. 14 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to the third embodiment. FIGS. 15A to 15D are diagrams illustrating an example of a signal format used in the present embodiment, and shaded portions indicate pilot symbols. Hereinafter, in the present embodiment, the formats shown in FIGS. 15-1 to 15-4 are referred to as format A0, format A1, format A2, and format A3, respectively. FIG. 16 is a flowchart showing an operation example of the transmission apparatus (base station) when the present embodiment is applied to the cellular system downlink.

  Hereinafter, the signal transmission procedure of the present embodiment will be described with reference to FIGS. As described in Embodiment 2, the channel estimation accuracy becomes a problem in the subbands at both ends of the subband group. If this is observed more carefully, it can be said that the channel estimation accuracy becomes a problem among the subbands at both ends (subcarrier portions on the side where the adjacent subband is not used). This is because only channel estimation information on one adjacent subcarrier can be used, which is conditionally disadvantageous compared to other subcarriers that can use channel estimation information on both subcarriers.

  Considering this point, the formats A1 and A2 are used so that the subbands at both ends have a large pilot symbol density in the subcarriers close to the frequency positions at both ends as shown in FIG. Thereby, deterioration of channel estimation accuracy can be prevented. Here, as shown in FIGS. 15-1 to 15-4, in formats A1 and A2, when a subcarrier group is divided in half within a subband, one subcarrier group has more pilots than the other subcarrier group. Set to have symbol density. By introducing such a format and increasing the pilot symbol density in the vicinity of the subcarriers at both ends in FIG. 14, stable channel estimation can be performed for all subcarriers.

  FIG. 16 is a flowchart illustrating an example of a signal format selection procedure when the transmission apparatus 1 according to the third embodiment transmits a signal, and control in the transmission apparatus 1 (corresponding to a base station) applied to the cellular system downlink. The procedure is shown. In addition, about the same process as the signal format selection procedure (refer FIG. 5) by the base station of Embodiment 1, the same step number is attached | subjected and the description is abbreviate | omitted.

  The format determination unit 14 of the transmission device 1 (base station) executes steps S11 and S12 to determine a subband to be used for packet transmission and to select a processing target for format selection. Then, it is determined whether or not to transmit to the same terminal even in an adjacent subband having a higher frequency than the selected subband (target subband) (step S13b). Step S51), otherwise, “i = 0” is set (Step S13b, No, Step S52). Furthermore, it is determined whether or not transmission is performed to the same terminal even in an adjacent subband having a frequency lower than that of the target subband (step S53), and in the case of transmission, “j = 1” is set (step S53, Yes, step S54). Otherwise, “j = 0” is set (step S53, No, step S55).

  Thereafter, a format corresponding to the states of “i” and “j” is selected (step S56). In this example, if “i = 0, j = 0”, the format A0 is selected, and if “i = 1, j = 0”, the format A1 is selected. When “i = 0, j = 1” and “i = 1, j = 1”, format A2 and format B are selected, respectively.

  Next, whether there are other subbands to be used for packet transmission, that is, whether there are subbands that have not yet been selected for the signal format to be used among the subbands determined in step S11. Are confirmed (step S16). If there is a subband that has not been selected (step S16, Yes), one of them is selected again as a processing target (step S17), and the above-described processing is executed. Thereafter, the processing is continued until the signal format is selected for all the subbands determined in step S11. When the signal format selection is completed for all the subbands determined in step S11 (No in step S16), the signal format selection procedure is ended. Through the above processing, the base station can realize adaptive format selection as shown in FIG.

  In addition, although the transmission apparatus (base station) applied to the cellular system downlink was shown here as an example, the operation of the corresponding receiving apparatus (terminal), the transmission apparatus (terminal) and the receiving apparatus (applied to the cellular system uplink) ( The operation of the base station) can be easily inferred from the combination of FIG. 16 and FIGS. 6 to 8 of the first embodiment, and the description thereof will be omitted.

  As described above, in this embodiment, when selecting the format of the transmission signal, if the usage state of adjacent subbands is confirmed, and it is determined that the subbands on both sides are simultaneously used as a result of the confirmation, the pilot symbol density We decided to select a format with a low. In addition, at both ends of the subband group, a format in which the subcarrier density in a region closer to the outer side (end side) is increased is selected. As a result, the number of data symbols transmitted per frame increases, and the data transmission efficiency can be further improved as compared with the case of the second embodiment described above.

Embodiment 4 FIG.
Next, the fourth embodiment will be described. In the first to third embodiments described above, the transmission apparatus that adaptively selects a signal format from a plurality of signal formats in which the pilot symbol density is changed has been described. In contrast, in the present embodiment, a transmission apparatus that adaptively selects a signal format from a plurality of signal formats in which pilot symbol power is changed will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) are the same as those in the first embodiment described above (see FIG. 1).

  In Embodiments 1 to 3, adjustment of pilot symbol density (selection of signal format) was performed in order to perform channel estimation smoothly. However, good channel estimation accuracy can be maintained even by using high pilot symbol power. This is because if the pilot symbol power is large, the ratio of the pilot symbol power and the interference noise power at the receiving apparatus becomes large, and good channel estimation accuracy can be obtained.

  Therefore, in this embodiment, as shown in FIGS. 17-1 to 17-4, formats A0, A1, A2, and B in which the transmission power difference (power offset) between the pilot symbol and the data signal is changed are defined, and the packet Select the format according to the continuous transmission status. As a result, pilot symbols are transmitted with the power required to perform appropriate channel estimation for each subband. In the example shown in FIGS. 17-1 to 17-4, the power offset is 3 dB, but the offset value is not limited to this. The same applies to the offset values used in the embodiments described later.

  Further, in FIGS. 17-1 to 17-4, the power offset of the pilot symbol is set as a fixed value, but can be freely set on the transmission side according to the state. FIG. 18 is a diagram illustrating an example of a control signal from the transmission apparatus 1 to the reception apparatus 2 that is necessary when the variable power offset is used. This control signal includes a receiver ID, format information, and a power offset amount α of the pilot signal (symbol). The transmission apparatus 1 can further increase the transmission power of pilot symbols by α [dB] based on the formats of FIGS. 17-1 to 17-4, and this control signal notifies the reception apparatus 2 of the transmission state. To do. The receiving device 2 grasps the transmission state from this control signal and performs channel estimation. Further, the transmission apparatus 1 may set the power offset α based on the reception state fed back from the reception apparatus 2.

  As described above, in this embodiment, by using a frame configuration that can adaptively change the transmission power of pilot symbols, only the transmission power of pilot symbols necessary for channel estimation is increased and transmitted. Thereby, unnecessary pilot symbols are also transmitted in the conventional fixed frame configuration, but more efficient signal transmission can be performed using this configuration.

Embodiment 5. FIG.
Next, the fifth embodiment will be described. In the first and second embodiments described above, the transmitting apparatus that adaptively selects the signal format at the time of packet transmission using continuous time or continuous subband has been described. However, these are continuously transmitted in a two-dimensional region of time frequency. It can be expanded when transmission is performed. In this embodiment, a transmission apparatus that adaptively selects a signal format when packet transmission is continuously performed in a two-dimensional region of time frequency will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) are the same as those in the first embodiment described above (see FIG. 1).

  FIG. 19 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to the fifth embodiment. FIG. 20 is a flowchart showing an operation example of the transmission apparatus (base station) when the present embodiment is applied to the cellular system downlink.

  Hereinafter, the signal transmission procedure of the present embodiment will be described with reference to FIGS. As described in the first and second embodiments, the channel estimation accuracy becomes a problem because the packets transmitted in the subbands at both ends of the subband group and the transmission in the case of continuous transmission using the same subband. This is the start packet (the first packet to be transmitted). Therefore, when performing continuous transmission of packets in a two-dimensional area of time frequency, it is required to transmit signals using a transmission format having a high pilot symbol density in the subbands at both ends at the start of transmission. Considering this point, as shown in FIG. 19, by using format A having a large pilot symbol density in the subbands at both ends at the start of transmission, it is possible to prevent deterioration in channel estimation accuracy. The format A shown in FIG. 19 is the format shown in FIG. 2-1, and the format B is the format shown in FIG.

  FIG. 20 is a flowchart illustrating an example of a signal format selection procedure when the transmission apparatus 1 according to the fifth embodiment transmits a signal, and control in the transmission apparatus 1 (corresponding to a base station) applied to the cellular system downlink. The procedure is shown. In addition, about the same process as the signal format selection procedure (refer FIG. 5) by the base station of Embodiment 1, the same step number is attached | subjected and the description is abbreviate | omitted.

  The format determination unit 14 of the transmission device 1 (base station) executes steps S11 and S12 to determine a subband to be used for packet transmission and to select a processing target for format selection. And it is confirmed whether it transmits to the same terminal using the subband of the both sides of the selected subband (target subband) (step S13b). Then, when transmitting to the same terminal using the subbands on both sides (step S13b, Yes), format B having a low pilot symbol density is selected (step S14). On the other hand, when the subbands on both sides are not used (step S13a, No), it is further confirmed whether or not the target subband is used for transmission to the same terminal even in the immediately preceding time frame (step S61). Then, when the target subband is used for transmission to the same terminal even in the immediately preceding time frame (step S61, Yes), a format B having a low pilot symbol density is selected (step S14). On the other hand, if it is not used for transmission to the same terminal in the immediately preceding time frame (No in step S61), format A having a high pilot symbol density is selected (step S15). By executing the above processing for all the subbands determined in step S11, the base station can realize adaptive format selection as shown in FIG.

  In addition, although the transmission apparatus (base station) applied to the cellular system downlink was shown here as an example, the operation of the corresponding receiving apparatus (terminal), the transmission apparatus (terminal) and the receiving apparatus (applied to the cellular system uplink) ( The operation of the base station) can be easily inferred from the combination of FIG. 20 and FIG. 6 to FIG.

  Here, the two formats A and B (see FIGS. 2-1 and 2-2) used in the first and second embodiments are used, but the formats shown in the third and fourth embodiments (FIG. 2) are used. 15-2, FIG. 15-3, FIG. 17-2, and FIG. 17-3) can also be applied to this embodiment.

  As described above, in the present embodiment, when continuously transmitting packets in a two-dimensional region of time frequency, a format having a low pilot symbol density is selected except for packets at both ends of the subband group and at the start of transmission. did. As a result, the number of data symbols transmitted per frame increases, and the data transmission efficiency can be improved.

Embodiment 6 FIG.
Next, the transmission apparatus according to the sixth embodiment will be described. In the present embodiment, an example different from the above-described fourth embodiment will be described regarding the transmission power setting of pilot symbols. The configuration of the transmitting device and the configuration of the communication partner (receiving device) are the same as those in the first embodiment.

  In this embodiment, instead of FIG. 17-1 used in Embodiment 4, as shown in FIG. 21-1 or FIG. 21-2, transmission is performed near both ends of the subcarrier and the packet transmission start time and end time. A frame configuration with high power is used as format A0. This is because it is easy to perform good channel estimation using pilot symbols in the vicinity of pilot symbols with a power offset of 0 dB, but the available pilot symbols are limited at positions of pilot symbols with a power offset of 3 dB. is there.

  21A and 21B can be applied not only to continuous packet transmission but also to single packet transmission. In conventional frames, pilot symbols are transmitted with a single transmission power, but in this frame configuration, pilot symbols required for channel estimation are reduced by reducing the power of pilot symbols in the time-frequency domain for transmitting packets. Send power only. As a result, transmission power of unnecessary pilot symbols can be reduced, and transmission efficiency can be improved by reducing interference with peripheral devices.

  Although an example in which the pilot symbol power is reduced in the time-frequency domain for transmitting a packet has been described here, a method of reducing the pilot symbol density is also possible.

Embodiment 7 FIG.
Next, Embodiment 7 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In the first to sixth embodiments, the frame configuration for maintaining a good channel estimation at the time of packet reception has been described, but interference power measurement is also important in the receiving apparatus. The interference power measurement result is mainly used when decoding a signal or determining a signal combining weight with a plurality of antennas.

  Interference power measurement can be performed using pilot symbols, but as another effective method, a null symbol that does not transmit a signal (null symbol, a symbol with zero transmission power) is inserted into the packet, and interference from the surroundings can be easily performed. There is also a method of measuring power. FIG. 22-1 and FIG. 22-2 are diagrams illustrating an example of a signal format in which a null symbol is inserted. For example, in FIG. 22-1, “0” represents the position of the null symbol where the transmission power is 0, and the null symbol is randomly arranged in the time frequency domain of the packet. The receiving apparatus can easily measure the interference power from the surroundings by recognizing the arrangement of the null symbols from the information on the signal format and observing the power received at the null symbol position.

  Typically, when packets are transmitted using the same subband in consecutive subbands or continuous time frames, the interference power level is also correlated, and some of the interference power measured in adjacent subbands or time frames Can be used to improve the measurement accuracy of the interference power in the target packet. For example, the measurement accuracy can be improved by appropriately weighting and adding the interference power measurement value measured in the adjacent subband or time frame and the interference power measurement value uniquely measured in the target packet.

  Therefore, at the time of continuous packet transmission, the null symbol is adaptively set in the same manner as the signal transmission procedure in which the pilot symbol density or power offset is adaptively selected from the formats described in the first to fifth embodiments. By using the format, efficient signal transmission becomes possible. Note that the format identifying unit 24 provided in the receiving apparatus of the present embodiment corresponds to null symbol specifying means.

  FIGS. 22-1 and 22-2 are diagrams showing specific examples. Two formats A and B having different null symbol densities are prepared, and the format selection procedure described in the first, second, and fifth embodiments is as follows. By selecting an appropriate format using a similar algorithm, high signal transmission efficiency can be achieved while maintaining good interference power measurement.

  Thus, in this embodiment, null symbols are randomly inserted into the data symbol area, and data transmission is performed by adaptively using a plurality of signal formats having different null symbol densities. Thereby, high signal transmission efficiency can be achieved while maintaining interference power measurement accuracy.

Embodiment 8 FIG.
Next, an eighth embodiment will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In the first to seventh embodiments, the transmission apparatus that adaptively selects a signal format from a plurality of signal formats having different states of pilot symbols and null symbols and changes the format for each packet has been described. There are various forms of format changes. In this embodiment, a method for reducing the amount of control information during continuous packet transmission and selection of a packet transmission format associated with the reduction of control information will be described.

  In recent wireless communication, a multi-carrier transmission method is widely used, and a method such as scheduling for adaptively selecting a subband having a good propagation state in units of a certain time (for example, 1 ms) is considered. Yes. When using this method in the downlink, the base station selects a subband for each terminal and performs packet transmission. At this time, the base station notifies the terminal of the usage subband information, and there are various notification methods.

  As one method of notifying the usage subband information, the control information is described in the header of the packet transmitted in the subband, and the terminal detects the terminal ID included in the control information of each packet and detects its own terminal ID. There is a method of receiving a packet when Such a method is described, for example, in the document “Hara, Kawabata, Dan, Sekiguchi,“ Study on Frame Configuration and Control Method in Frequency Scheduling MC-CDM ”, RCS2002-130, July, 2002.”.

  In the case of using the method described in the above document, the packet has a configuration as shown in FIG. In this packet, a control information part (control information field) including a receiver ID and MCS is inserted in the preamble part. The control information part is fixedly set in the packet.

  The receiving apparatus checks the receiver ID included in the packet, and receives the packet (data) if it matches the own ID. Thus, by checking the receiver ID in the control information section, it is possible to determine and receive a packet addressed to itself. Conventionally, this control information part is fixedly set in each packet, but in this embodiment, a control information part having a variable number of symbols is set according to the transmission state of the packet.

  FIG. 24 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus 1 according to the present embodiment, and packet transmission is performed using continuous time frames. An example of the case is shown. As shown in FIG. 24, format A having a high pilot symbol density is used for the first packet to start transmission. This leading packet is a control information section including detailed control information required for the start of transmission (duration frame identification bit, receiver ID, MCS information, data amount, duration frame number, packet serial number, etc. ) Is included. Here, the continuation time frame identification bit is “0” in the first packet at the start of transmission, and is “1” in subsequent packets when packets are transmitted using a continuous time frame. Also, each control information is arranged in a region other than the pilot symbol. Data symbols are arranged in the remaining area after all control information is arranged.

  On the other hand, each packet transmitted following the first packet uses format B having a low pilot symbol density. The control information part included in these packets includes a duration frame identification bit and difference control information (indicated as “MCS difference” in the example of FIG. 24). Since each packet is not the head packet, the duration frame identification bit is “1”. The difference control information is a signal representing a difference from the control information used in the previous time frame. For example, “+1” when the MCS level increases by 1, “−1” when it decreases by one. It becomes.

  Although many levels of MCS are prepared, since the channel state is similar to the previous time frame during continuous packet transmission, the MCS is transmitted at a similar MCS level. Therefore, it can be notified as control information with a small number of bits by expressing it as difference control information. In FIG. 24, only the MCS difference information is shown as difference control information, but various control information such as transmission power level difference information can be transmitted.

  FIG. 25 is a flowchart illustrating an example of a procedure in which the transmission apparatus 1 according to the present embodiment constructs a packet. First, the transmitting apparatus 1 selects a format according to whether or not the packet is a transmission start packet as in the method described in the first embodiment. That is, the format determination unit 14 executes the procedure shown in FIG. The result is notified to the transmission signal construction unit 15, and the transmission signal construction unit 15 executes the procedure shown in FIG. 25 based on the notification content from the format determination unit 14 to construct a packet. The operation of the transmission signal construction unit 15 at this time will be described below.

  The transmission signal construction unit 15 that has started the packet construction operation confirms the notification content from the format determination unit 14, and determines whether the packet to be constructed is a format A packet (step S71). When constructing a format A packet (that is, a transmission start packet) (step S71, Yes), the duration frame identification bit constituting the control information section is set to “0” (step S72). Next, initial control information (duration frame identification bit, receiver ID, MCS information, data amount, duration frame number, etc.) is described (step S73), and the format of the packet to be constructed (format A in this case) Then, a data symbol is added to generate a packet (step S74). On the other hand, when constructing a packet other than format A (step S71, No), the duration frame identification bit constituting the control information part is set to “1” (step S75). Next, difference information for the control information (MCS information) of the packet positioned immediately before in the time domain with respect to the packet being constructed is described in the control information section (step S76), and the format of the packet to be constructed (in this case) A packet is generated by inserting data symbols in accordance with format B) (step S77). By repeating the above processing, a continuous data packet is constructed in the time domain. Although the number of control information bits is different between formats A and B, there is no practical problem because variable bits can be identified on the receiving side by performing the receiving operation according to the procedure shown in FIG.

  Subsequently, a procedure for the reception device 2 of the present embodiment to receive a signal from the transmission device 1 will be described with reference to FIG. FIG. 26 is a flowchart illustrating an example of a signal reception procedure performed by the reception device 2 according to the eighth embodiment. First, the format identifying section 24 (format identifying means, judging means) of the receiving apparatus 2 detects a duration frame identifying bit included in the control information section of the received packet (step S81), and whether this identifying bit is “1”. Whether or not is confirmed (step S82). When the identification bit is “0” (No at Step S82), it is confirmed whether or not the address of the receiver ID matches the own ID (Step S83). As a result of the confirmation, if it matches the self ID (step S83, Yes), the data symbol detection unit 22 uses the initial control information included in the packet (target packet for reception processing) to set the target packet ( (Data included in the target packet) is received (step S84). On the other hand, when the receiver ID and the self ID do not match (No in step S83), the target packet is not received (step S86).

  On the other hand, if the duration frame identification bit is “1” (step S82, Yes), whether the packet in the previous time frame is addressed to itself, that is, whether the packet addressed to itself is received in the immediately preceding time frame. Is confirmed (step S85). When the packet in the previous time frame is addressed to itself (step S85, Yes), the data symbol detection unit 22 uses the control information used when receiving the packet in the previous time frame and the difference control information in the target packet. The target packet is received using (Step S87). Specifically, the difference control information in the target packet is confirmed, the control information used in the previous time frame is updated as necessary, and the target packet is received using the updated control information. When the control information is updated, it is retained for subsequent reception processing. On the other hand, when the packet in the previous time frame is not addressed to itself (No in step S85), the target packet is not received (step S86).

  Through such a series of procedures, the receiving device 2 can identify whether or not the target packet is a packet addressed to itself, and can recognize the control information and receive data. Although the number of bits of the control information differs between formats A and B, it can be received without any problem based on the above-described procedure. In addition, in packets continuously transmitted using the same subband, the control information can be recognized as difference information with a small number of bits using the format B. As a result, more data symbols can be transmitted in the format B packet than in the format A packet. Further, although the receiver ID is not included in the format B packet, the receiver can recognize the destination of the packet by expressing that the destination is the same as the packet transmitted in the previous time frame by a small number of bits. .

  As described above, in this embodiment, the control information is adaptively configured while adaptively changing the density of pilot symbols according to the transmission state of the packet. In comparison, packet transmission can be performed with higher transmission efficiency.

  In the above description, an example in which control for adaptively configuring control information and control for adaptively changing the pilot symbol density has been described. However, the pilot symbol power in Embodiment 4 is adaptively changed. You may combine with control. Further, the control may be combined with the control for adaptively changing the null symbol density according to the seventh embodiment.

Embodiment 9 FIG.
Subsequently, Embodiment 9 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In the present embodiment, a method for reducing the amount of control information during continuous packet transmission and selection of a packet transmission format accompanying the reduction in control information, which are performed using a procedure different from that in the above-described eighth embodiment, will be described.

  In the eighth embodiment, the procedure for adaptively configuring control information has been described by taking the case of transmitting packets in continuous time frames as an example. However, the control information is also adaptively transmitted when signals are transmitted using continuous subbands. The amount of control information can be reduced.

  FIG. 27 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus 1 according to the present embodiment, and an example in which packet transmission is performed in continuous subbands. Is shown. As shown in FIG. 27, a format A0 having a high pilot symbol density is used in a packet that exists at a position where the frequency is highest (or lower) among consecutive subbands. A packet of format A0 includes detailed control information necessary for packet transmission (control information section including continuation subband identification bits, receiver ID, MCS information, data amount, number of continuation subbands, packet serial number, etc. ) Is included. Here, the continuation subband identification bit is “0” in the packet existing at the highest (or lowest) position of the frequency, indicating that it is the first packet in the frequency domain. For packets other than the first packet, the continuation subband identification bit is “1”. Also, each control information is arranged in a region other than the pilot symbol. Data symbols are arranged in the remaining area after all control information is arranged.

  On the other hand, format B having a low pilot symbol density is used for each packet transmitted following the first packet in the frequency domain. The control information part included in these packets includes a continuation subband identification bit and difference control information (MCS difference information). Since each packet is not the head packet in the frequency domain, the continuation subband identification bit is “1”. The difference control information is a signal representing a difference from the control information used in the previous packet. For example, when the MCS level is increased by 1, “+1” is obtained, and when the MCS level is lowered, “−1” is obtained. Become.

  Although many levels of MCS are prepared, since continuous channel transmission is similar in channel state to adjacent subbands during continuous packet transmission on the frequency, continuous packets are transmitted at similar MCS levels. Therefore, it can be notified as control information with a small number of bits by expressing it as difference control information. In FIG. 27, only the MCS difference information is shown as difference control information, but various control information such as transmission power level difference information can be transmitted.

  Further, the format A1 is used for a packet (a packet having the lowest frequency in the same time frame) located at the other end of the top packet on the frequency domain. This format A1 includes a high pilot symbol density like the format A0. On the other hand, as with the format B, the control information includes the continuation subband identification bit “1” and the difference control information.

  FIG. 28 is a flowchart illustrating an example of a procedure in which the transmission device 1 according to the present embodiment constructs a packet. First, the transmitting apparatus 1 selects a format according to whether or not the packet is a transmission start packet as in the method described in the second embodiment. That is, the format determination unit 14 executes the procedure shown in FIG. The result is notified to the transmission signal construction unit 15, and the transmission signal construction unit 15 executes the procedure shown in FIG. 28 based on the notification content from the format determination unit 14 to construct a packet. The operation of the transmission signal construction unit 15 at this time will be described below.

  The transmission signal construction unit 15 that has started the packet construction operation confirms the notification content from the format determination unit 14, and determines whether the packet to be constructed is a packet of the format A0 (step S91). When constructing a packet of format A0 (that is, a head packet in the frequency domain) (step S91, Yes), the continuation subband identification bit constituting the control information section is set to “0” (step S92). Next, initial control information (continuation subband identification bit, receiver ID, MCS information, data amount, duration frame number, etc.) is described (step S93), and the format of the packet to be constructed (in this case, format A0) Then, a data symbol is added to generate a packet (step S94). On the other hand, when constructing a packet other than the format A0 (step S91, No), the continuation subband identification bit constituting the control information section is set to “1” (step S95). Next, the difference information with respect to the control information (MCS information) of the generated adjacent packet is described in the control information section (step S96), and further, a data symbol is inserted according to the format of the packet to be constructed (in this case, format B or A1) Then, a packet is generated (step S97). By repeating the above processing, a continuous data packet in the frequency domain is constructed. Although the number of control information bits is different between format A0 and other formats (A1, B), it is practically problematic because variable bits can be identified on the receiving side by performing the receiving operation according to the procedure shown in FIG. Absent.

  Next, a procedure for the reception device 2 of the present embodiment to receive a signal from the transmission device 1 will be described with reference to FIG. FIG. 29 is a flowchart illustrating an example of a signal reception procedure by the reception device 2 according to the ninth embodiment. First, the receiving apparatus 2 selects a packet having a high (or low) frequency as a processing target (step S101), and confirms whether or not the continuous subband identification bit included in the control information part is “1” (step S102). . When the identification bit is “0” (step S102, No), it is confirmed whether or not the address of the receiver ID matches the own ID (step S103). As a result of the confirmation, if it matches the own ID (step S103, Yes), the target packet (data included in the target packet) using the initial control information included in the packet (target packet for reception processing) ) Is received (step S104). On the other hand, when the receiver ID does not match the own ID (No at Step S103), the target packet is not received (Step S105).

  On the other hand, if the continuation subband identification bit is “1” (step S102, Yes), whether or not the packet of the adjacent subband confirmed before is addressed to itself, that is, the packet addressed to itself in the adjacent subband is It is checked whether or not it has been received (step S106). If the packet of the adjacent subband is addressed to itself (step S106, Yes), the target packet is determined using the control information used when the packet is received in the adjacent subband and the difference control information in the target packet. Receive (step S107). Specifically, the difference control information in the target packet is confirmed, the control information used when receiving the packet in the adjacent subband is updated as necessary, and the target packet is updated using the updated control information. Receive. When the control information is updated, it is retained for subsequent reception processing. On the other hand, when the packet in the previous time frame is not addressed to itself (No in step S106), the target packet is not received (step S106). Such a series of procedures is performed for all subbands in the order of higher frequency (or lower order) (steps S108 and S109). The order is such that the packet of format A0 is processed first. When the process is executed for all the subbands (Yes in step S108), the operation is terminated.

  Through such a series of procedures, the receiving device 2 can identify whether or not the target packet is a packet addressed to itself, and can recognize the control information and receive data. Although the number of bits of the control information differs between the format A0 and other formats, it can be received without any problem based on the procedure described above. In addition, control information can be recognized as difference information with a small number of bits in continuously transmitted packets. As a result, more data symbols can be transmitted than the first packet (format A0 packet). A packet other than format A does not include a receiver ID, but the receiving apparatus can recognize the destination of the packet by indicating that it is the same destination as the packet transmitted in the adjacent subband.

  As described above, in this embodiment, the control information is adaptively configured while adaptively changing the density of pilot symbols in accordance with the transmission state of the packet. In comparison, packet transmission can be performed with higher transmission efficiency.

  In the above description, an example in which control for adaptively configuring control information and control for adaptively changing the pilot symbol density has been described. However, the pilot symbol power in Embodiment 4 is adaptively changed. You may combine with control. Further, the control may be combined with the control for adaptively changing the null symbol density according to the seventh embodiment.

Embodiment 10 FIG.
Subsequently, Embodiment 10 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In the ninth embodiment, the initial control information is notified to the receiving side in the case of the leading packet, and the differential control information is notified to the receiving side in the case of continuous transmission packets (packets other than the leading packet). That is, the control information to be notified is determined depending on whether or not it is the head packet. However, it is also possible to adaptively switch between the initial control information and the difference control information independently of the packet state (whether it is the leading packet).

  30-1 and 30-2 are diagrams illustrating a configuration example of control information used in the tenth embodiment. As shown in the figure, in this embodiment, a “control information format identification bit” is added instead of the duration frame identification bit used in the eighth embodiment and the continuous subband identification bit used in the tenth embodiment. Control information of the configured configuration is used. This control information format identification bit is a bit for identifying the initial control information and the difference control information. If this bit is “0”, it represents initial control information, and control information that operates even with a single packet is described in the subsequent area. If it is “1”, it represents differential control information, and differential information for the control information of other packets is described. In the difference control information, the control amount can be reduced by notifying only the relative difference as a bit.

  As described above, if the formats of FIGS. 30-1 and 30-2 are used, the change of the control information format can be selected independently of the head or continuous packet transmission. For example, even in the continuous packet transmission state, when the control information is largely changed, the initial control information can be transmitted even with a packet other than the head packet. As another example, even if the channel state has no correlation with the past packet, the control information may have a large correlation with the past packet. In this case, the channel estimation is handled as the head packet, but the control information can be expressed as difference information with respect to the past packet, so that the control amount can be reduced.

  As described above, in the present invention, the format necessary for obtaining the accompanying information of the current packet is obtained using the correlation with the accompanying information (channel estimation value, interference power, control information, etc.) of the packet transmitted in the past. decide. That is, “continuous transmission” described in the above-described embodiment and the embodiment described later corresponds to a “state in which accompanying information has a correlation with a past packet” in a broad sense.

  Accordingly, in each embodiment, multi-carrier transmission in a wireless communication environment has been described. However, even in packet transmission in wired communication, control information is adaptively set to an absolute value or relative value according to the correlation with a previous packet. The amount of control information can be reduced by expressing the value (difference value).

Embodiment 11 FIG.
Next, Embodiment 11 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In the present embodiment, a method for reducing the amount of control information during continuous packet transmission and selection of a packet transmission format that accompanies the reduction in control information, which are performed using procedures different from those in the eighth and ninth embodiments, will be described.

  In the seventh and eighth embodiments, the procedure for adaptively configuring the control information has been described taking the case of transmitting packets in continuous time frames or continuous subbands as an example. However, packets are continuously transmitted in a two-dimensional region of time frequency. Even in this case, it is possible to adaptively configure the control information and reduce the amount of control information.

  FIG. 31 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus 1 according to the eleventh embodiment, and performs continuous packet transmission in a two-dimensional area of time frequency. An example of the case is shown. As shown in FIG. 31, the format A0 having a high pilot symbol density is used for a packet that is present at the earliest in time and the highest (or lower) frequency among the continuously transmitted packets. The packet of the format A0 includes detailed control information required for packet transmission (duration frame identification bit, continuation subband identification bit, receiver ID, MCS information, data amount, number of continuation subbands, packet serial number, etc. Control information section). Here, the continuation time frame identification bit is “0” in the first packet at the start of transmission, and is “1” in subsequent packets when packets are transmitted using a continuous time frame. Further, the continuation subband identification bit is “0” in the packet existing at the highest (or lowest) frequency, indicating that it is the first packet in the frequency domain. For packets other than the head packet in the frequency domain, the continuation subband identification bit is “1”. Also, each control information is arranged in a region other than the pilot symbol. Data symbols are arranged in the remaining area after all control information is arranged.

  On the other hand, format B having a low pilot symbol density is used for each packet transmitted following the first packet in the frequency domain. The control information part included in these packets includes a duration frame identification bit, a continuation subband identification bit, and difference control information (MCS difference information). In a packet on the same time frame as the first packet having the format A0, the duration frame identification bit is “0” and the duration subband identification bit is “1”. The difference control information is a signal representing a difference from the control information used in the previous packet. For example, when the MCS level is increased by 1, “+1” is obtained, and when the MCS level is lowered, “−1” is obtained. It becomes. Thus, all packets in the packet transmission start time frame (packets on the same time frame as the first packet) have a duration frame identification bit and a duration subband identification bit.

  Next, in a packet that is continuously transmitted in subsequent time frames, the control information portion has a duration frame identification bit “1” and no continuation subband identification bit. This is because there is continuity in packet transmission in the time frame, and the processing proceeds based on the control information of the packet in the previous time frame, so continuity in the subband is not particularly required as information.

  FIG. 32 is a flowchart illustrating an example of a procedure in which the transmission device 1 according to the eleventh embodiment constructs a packet. First, the transmitting apparatus 1 selects a format according to whether or not the packet is a transmission start packet as in the method described in the second embodiment. That is, the format determination unit 14 executes the procedure shown in FIG. The result is notified to the transmission signal construction unit 15, and the transmission signal construction unit 15 executes the procedure shown in FIG. 32 based on the notification content from the format determination unit 14 to construct a packet. The operation of the transmission signal construction unit 15 at this time will be described below.

  The transmission signal construction unit 15 that has started the packet construction operation confirms the notification content from the format determination unit 14 and determines whether the packet to be constructed is a packet of the format A0 (step S111). When constructing a packet of the format A0 (that is, the first packet existing at the highest (or lowest) position in the first time frame) (step S111, Yes), the duration frame identification bit and the continuation sub constituting the control information section Both band identification bits are set to “0” (step S112). Next, initial control information (continuation subband identification bit, receiver ID, MCS information, data amount, number of duration frames, etc.) is described (step S113), and the format of the packet to be constructed (in this case, format A0) Then, a data symbol is added to generate a packet (step S114).

  On the other hand, when a packet other than the format A0 is constructed (step S111, No), it is further determined whether the packet to be constructed is a packet of the format B0 or A1 (step S115). If a packet of format A1 or B0 (that is, a packet other than the first packet on the first time frame) is constructed (step S115, Yes), the duration frame identification bit is set to “0” and the continuation subband identification bit is set to “0”. 1 "(step S116). Next, the difference information with respect to the control information (MCS information) of the generated adjacent packet is described in the control information section (step S117), and a data symbol is added according to the format of the packet to be constructed (format B0 or A1). A packet is generated (step S118).

  When constructing a packet other than the format B0 or A1 (step S115, No), the duration frame identification bit is set to “1” (step S119). Next, difference information for the control information (MCS information) of the packet located immediately before in the time domain with respect to the packet being constructed is described in the control information section (step S120), and the format of the packet to be constructed Then, a data symbol is added to generate a packet (step S121). With this procedure, the transmission apparatus 1 can describe control information according to the format. By repeating the above processing, a continuous data packet is constructed in the time-frequency domain.

  Subsequently, a procedure for the reception device 2 of the present embodiment to receive a signal from the transmission device 1 will be described with reference to FIG. FIG. 33 is a flowchart illustrating an example of a signal reception procedure by the reception device 2 according to the eleventh embodiment. Note that the same step number is assigned to the same process as the signal format selection procedure (see FIG. 29) by the base station of the ninth embodiment, and the description thereof is omitted.

  First, the receiving device 2 selects a packet having a high frequency (or low frequency) as a processing target (step S101), and checks whether or not the duration frame identification bit included in the control information part is “1” (step S131). . When the identification bit is “0” (step S131, No), it is further confirmed whether or not the continuous subband identification bit is “1” (step S102). Steps S103 to S107 are the same as the processing of the same step number shown in FIG. 29 of the ninth embodiment.

  On the other hand, if it is determined in step S131 that the duration time frame identification bit is “1” (step S131, Yes), whether or not the packet in the previous time frame is addressed to itself, that is, addressed to itself in the immediately previous time frame. It is confirmed whether or not a packet has been received (step S132). When the packet in the previous time frame is addressed to itself (step S132, Yes), the target packet is received using the control information used when the packet is received in the previous time frame and the difference control information in the target packet. (Step S133). On the other hand, if the packet in the previous time frame is not addressed to itself (No in step S132), the target packet is not received (step S105). Note that the processes in steps S132 and S133 are the same processes as steps S85 and S87 shown in FIG. 26 of the eighth embodiment, respectively.

  When the above-described series of procedures is executed for all subbands in the order of high frequency (or low order) (step S108, Yes), the operation ends.

  Through such a series of procedures, the receiving device 2 can identify whether or not the target packet is a packet addressed to itself, and can recognize the control information and receive data. Although the number of bits of the control information differs between the format A0 and other formats, it can be received without any problem based on the procedure described above. Also, control information can be recognized as difference information with a small number of bits in a packet that is continuously transmitted in the time or frequency domain. As a result, more data symbols can be transmitted than the first packet (format A0 packet). Thus, by adaptively configuring the control information according to the packet transmission state, packet transmission can be performed with high transmission efficiency.

  In the present embodiment, since the control information is adaptively configured while adaptively changing the density of pilot symbols in accordance with the transmission state of the packet, compared with the above-described fifth embodiment, Packet transmission can be performed with high transmission efficiency.

  Note that all the adaptive format selections described in the first to eleventh embodiments have an advantage that feedback information from the receiving apparatus to the transmitting apparatus is not required.

Embodiment 12 FIG.
Next, the twelfth embodiment will be described. In this embodiment, in addition to the adaptive format selection described in Embodiments 1 to 11, an operation in the case of performing format selection by feeding back reception quality information from the receiving apparatus will be described.

  FIG. 34 is a diagram illustrating a configuration example of a transmission device and a reception device according to the twelfth embodiment. In the present embodiment, the reception apparatus measures reception quality and feeds back reception quality information to the transmission apparatus. The reception quality information may be measured using pilot symbols, or may be measured based on the reception status of packets transmitted in the past. The transmission apparatus selects an appropriate format in consideration of both the received reception quality information and the continuous transmission state of packets. Specifically, even in the subsequent packets at the time of continuous packet transmission, if the reception quality information is poor, a format having a higher pilot symbol density than the standard format of the subsequent packets is used. When the reception quality information is sufficiently good, a format having a pilot symbol density lower than the standard format of the subsequent packet is used. Further, the transmission device notifies the reception device of the format information. The receiving device recognizes the format information and receives the packet according to the recognized format.

  As described above, in this embodiment, since the format selection is performed using the reception quality information from the receiving apparatus in addition to the continuous packet transmission state, a more appropriate format is selected according to the reception state. be able to.

Embodiment 13 FIG.
Next, Embodiment 13 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) in the present embodiment are the same as those in the first embodiment.

  In this embodiment, a retransmission control method when changing the signal transmission format according to the packet transmission state will be described. In the first to eleventh embodiments, the transmission format and control information to be used are adaptively constructed according to the packet transmission state. As a result, the number of data symbols that can be transmitted varies depending on the format to be used. The transmitting device generates a packet by dividing all data to be transmitted according to the number of data symbols of each format, and transmits the packet as a plurality of packets. At this time, the first packet may not be accurately received by the receiving device, and an error may occur. In this case, in wireless communication, the transmission apparatus performs packet transmission again according to retransmission control, but the packet format at the time of retransmission is not necessarily the same as the packet format at the time of initial transmission. Therefore, there are cases where the number of usable data symbols differs between the initial transmission and the retransmission packet. This embodiment shows a retransmission control method in a format having such different numbers of data symbols.

  FIG. 35 is a diagram illustrating an example of a retransmission control operation in the thirteenth embodiment. In the example shown in FIG. 35, in the initial transmission operation, the transmission apparatus transmits Q1 data symbols (data packets including Q1 data symbols) according to the adaptively selected packet format. When a packet reception error occurs in the receiving device, a NACK signal is returned to the transmitting device. When the transmitting apparatus receives the NACK signal, the transmitting apparatus transmits data again using the Q2 data symbol. At this time, in this embodiment, since the format of the packet is adaptively changed according to the packet transmission state, Q1 and Q2 are not necessarily the same number. However, by performing transmission using a kind of hybrid ARQ (Hybrid ARQ) as described below, it is possible to perform retransmission control corresponding to different numbers of data symbols.

  FIG. 36 is a diagram showing a signal generation process in the transmission apparatus showing the retransmission control in Embodiment 13, and the information source is assumed to be composed of J bits. In the initial transmission, the encoder performs encoding at the encoding rate r1, and obtains J / r1 bits after encoding. Next, bits are mapped to an I (Inphase) phase and a Q (Quadrature) phase in accordance with the determined modulation method to obtain a modulated Q1 symbol. Here, the coding rate r1, the modulation scheme, and the information source J bit are appropriately set so that the Q1 symbol is obtained after modulation.

  When the initial transmission packet cannot be accurately received by the receiving apparatus and an error occurs, the transmission apparatus inputs the same information source J bit as that of the initial transmission to the encoder when constructing the retransmission packet, and the coding rate r2 To obtain J / r2 bits after encoding. Next, the bits are mapped to the I phase and the Q phase according to the determined modulation method to obtain a modulated Q2 symbol. Here, the coding rate r2 and the modulation scheme are appropriately set so that the Q2 symbol is obtained after the modulation.

  However, if a coding rate r2 and modulation scheme that completely match the Q2 symbol with the Q1 symbol at the time of initial transmission cannot be found, conversion to a data symbol slightly smaller than the Q2 symbol may be performed. In this case, unused symbols of the Q2 symbols are blanked (no transmission) during transmission. Thus, by appropriately setting the coding rate r2 and the modulation scheme, the information source can be retransmitted as a Q2 symbol.

  The combination of r2 and the modulation scheme is determined by the relationship between Q1 and Q2, but these may be determined in advance so as to be uniquely set for Q1 and Q2. In this case, if the values of Q1 and Q2 are given, the receiving apparatus can uniquely recognize the retransmission packet coding rate R2 and modulation scheme. As another method, the coding rate R2 and the modulation method may be transmitted as a control signal from the transmission apparatus to the reception apparatus.

FIG. 37 is a diagram illustrating a signal reception process in the reception device in the retransmission control according to the thirteenth embodiment. Note that the reception process of the initial transmission packet is not shown because it is the same as general processing. When receiving the retransmission packet, the receiving apparatus recognizes the modulation scheme, performs IQ demapping based on the recognition, and converts it into a J / r2 symbol. Similarly, the data symbols of the initial transmission packet are converted to J / r1 symbols by QI demapping at the initial transmission and stored in the memory. The receiver calls the first transmission J / r1 symbol stored in the memory, connects it to the retransmitted J / r2 symbol, and inputs it to the decoder with the coding rate (r1 ^-1 + r2 ^-1 ) ^-1 for decoding. To obtain the J bit. At this time, the receiving apparatus can decode the signal at a low coding rate, and can receive the signal with high success probability by hybrid ARQ in which the initial transmission and the retransmission are combined. Finally, an error check based on CRC is performed according to a general method, and it is determined whether or not the packet has been received without error. If the packet can be received without error, an ACK signal is fed back to the transmitting apparatus to notify the reception success. If an error occurs in packet reception, a NACK signal is transmitted to request retransmission.

  According to this series of processing, in this embodiment, retransmission control can be performed while adjusting the coding rate r2 and the modulation scheme even when the number of data symbols Q1 and Q2 of the initial transmission and retransmission packets are different. In this control, the modulation schemes for initial transmission and retransmission are not necessarily the same, and retransmission can be performed using different modulation schemes. In this case as well, it is possible to realize good reception performance by performing decoding by collectively receiving the first transmission signal and the retransmission signal after mapping by IQ.

  As described above, retransmission control can be performed smoothly by appropriately setting the coding rate r2 and the modulation scheme at the time of retransmission while using an adaptive frame configuration.

Embodiment 14 FIG.
Subsequently, Embodiment 14 will be described. The configuration of the transmission device and the configuration of the communication partner (reception device) of the present embodiment are the same as those of the above-described first embodiment except for the antenna configuration.

  In the present embodiment, a signal transmission method will be described in the case where the packet transmission format is changed according to the number of antennas of the receiving apparatus. The present embodiment can also be applied to single packet transmission and does not have to be continuous packet transmission.

  In recent wireless communication, an array antenna technique is widely used in which a receiving apparatus receives signals using a plurality of antennas and performs signal synthesis between the plurality of antennas to improve reception quality. As a typical signal synthesis method, a MMSE (Minimum Mean Square Error) synthesis method is known. In this synthesis method, a desired signal can be synthesized with high quality while removing interference.

  Usually, in the MMSE combining method, a combined weight is calculated using a received signal existing at the position of a pilot symbol. For example, a received signal at a receiving device including an M antenna is represented as M × 1 received vector x (p) = hs (p) + z (p). Here, z (p) represents an M × 1 interference noise vector, h represents an M × 1 channel response vector, and s (p) represents a pilot symbol or a data signal. In the MMSE synthesis method, M × 1 weight v is calculated by the following equation (1) using the pilot symbol part of s (p).

Here, p ₀ represents the number of pilot symbols, H represents a transposed conjugate, and * represents a complex conjugate. The receiving apparatus performs weight multiplication on the received signal to obtain a combined output y (p) = v ^H x (p).

The ideal synthesis weight is given by p ₀ → ∞, but in practice it is necessary to use a finite number of pilot symbols p ₀ . If the average SINR (Signal to Interference plus Noise Ratio) at the combined output obtained when using the ideal weight is Γ, and the average SINR at the combined output obtained when using the actual weight is Γ ₀ , weight convergence is achieved by Γ ₀ / Γ. You can check the degree. Details of this weight convergence can be found in, for example, the document “Y. Hara,“ Weight convergence analysis of adaptive array antennas based on SMI algorithm ”, IEEE Trans. On Wireless Commun., Vol.2, issue 4, pp. 749--757, July. 2003. ", etc., and as the number of antennas basically increases, the weight convergence becomes slower. In order to understand this situation, the relationship between Γ ₀ / Γ and the number of pilot symbols p ₀ when the number of receiving device antennas is M = 2, 4, 6, 8, and Γ ₀ = 15 is calculated by simulation in FIG. Results are shown. As an approximation, it is said that the number of pilot symbols about 3 to 5 times the number of antennas M is necessary to realize Γ ₀ / Γ = −1 dB. Thus, in the receiving apparatus, the number of pilot symbols required for the composite weight calculation changes according to the number of receiving antennas.

  Therefore, the transmission apparatus according to the present embodiment adaptively determines the number of pilot symbols to be transmitted in the packet according to the number M of antennas of the reception apparatus. Specifically, as shown in FIG. 39-1, when the number of antennas is small, format B having a low pilot symbol density is selected. Also, as shown in FIG. 39-2, when the number of antennas is large, format A having a high pilot symbol density is selected. For example, formats A and B shown in FIGS. 2-1, 2-2, 15-1 to 15-4 can be used. Also, the larger the pilot symbol power, the better the weight convergence. Therefore, a format for changing the pilot symbol power as shown in FIGS. 17-1 to 17-4 may be used.

  Also, the literature “Y. Hara, C. Fujita, Y. Kamio,“ Initial weight computation method with rapid convergence for adaptive array antennas ”, IEEE Trans. On Wireless Commun., Vol.3, no.6, pp.1902- -1905, Nov. 2004. ", it is possible to speed up the weight convergence by using a received signal at a position where a desired signal does not exist. Therefore, weight convergence can also be improved by including many null symbols (symbols with zero transmission power) in the packet. Therefore, by using formats A and B having different numbers of null symbols as shown in FIGS. 22-1 and 22-2, it is possible to cope with different weight convergence depending on the number M of antennas. Also, as shown in FIGS. 40-1 and 40-2, a format in which both the pilot symbol density and the null symbol density are changed may be used.

  FIG. 41 is a flowchart illustrating an example of a signal transmission procedure by the transmission apparatus according to the fourteenth embodiment. The transmission device confirms the number M of antennas of the reception device from the control signal received from the reception device (step S141). This process is usually performed before the start of communication. Next, at the time of packet transmission, the transmission apparatus selects a format suitable for the number of reception antennas according to the number M of reception antennas on the reception side (step S142). Then, the transmission device generates and transmits a transmission signal according to the selected format (step S143).

  FIG. 42 is a flowchart illustrating an example of a signal reception procedure by the receiving apparatus according to the fourteenth embodiment. The receiving apparatus identifies the format to be transmitted from the number of antennas M or the control information received from the base station (step S151). Next, in accordance with the identified format, a combined weight is calculated using a received signal in which a pilot symbol exists, and a signal is combined between antennas to receive a signal (step S152). According to such a processing procedure, an appropriate format can be selected according to the number of antennas M and signal transmission can be performed.

  In the first to thirteenth embodiments, signals are transmitted in a fixed format regardless of the number M of receiving device antennas. In this case, the number of pilot symbols required when the number M of antennas is large is insufficient. Thus, there is a problem that the weight convergence cannot be obtained sufficiently and the received signal quality is deteriorated. In addition, when the number of antennas M is small, the number of pilot symbols becomes excessive, resulting in a problem that data transmission efficiency is lowered. On the other hand, the data transmission efficiency can be improved by adaptively selecting the transmission format according to the number of antennas M as shown in the present embodiment. Moreover, you may combine Embodiment 1-13 mentioned above and this Embodiment. Thereby, the data transmission efficiency can be further improved.

  As described above, the transmission apparatus according to the present invention is useful for a communication system, and in particular, for a communication apparatus on the transmission side of a communication system that performs channel estimation and interference power measurement using pilot symbols included in a received signal. Is suitable.

It is a figure which shows the structural example of Embodiment 1 of the communication system containing the transmitter concerning this invention. 6 is a diagram illustrating an example of a signal format used in Embodiment 1. FIG. It is a figure which shows an example of the signal format used by this Embodiment. 6 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to Embodiment 1. FIG. 5 is a flowchart illustrating an operation example of a transmission apparatus (base station) when Embodiment 1 is applied to a cellular system downlink. 5 is a flowchart illustrating an operation example of a receiving apparatus (terminal) when the first embodiment is applied to a cellular system downlink. The flowchart which shows the operation example of the transmitter (terminal) at the time of applying Embodiment 1 to a cellular system uplink. 6 is a flowchart showing an operation example of a receiving apparatus (base station) when the first embodiment is applied to a cellular system uplink. 6 is a diagram illustrating a configuration example of a control signal used in Embodiment 1. FIG. 6 is a diagram illustrating a configuration example of a control signal used in Embodiment 1. FIG. It is a figure which shows the operation example at the time of applying the signal format selection control of Embodiment 1 with respect to the MIMO system which performs spatial multiplexing transmission. 10 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to Embodiment 2. FIG. 10 is a flowchart illustrating an operation example of a transmission apparatus (base station) when Embodiment 2 is applied to a cellular system downlink. 10 is a flowchart illustrating an operation example of a receiving apparatus (terminal) when the second embodiment is applied to a cellular system downlink. FIG. 11 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to the third embodiment. 10 is a diagram illustrating an example of a signal format used in Embodiment 3. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 3. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 3. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 3. FIG. 10 is a flowchart illustrating an operation example of a transmission apparatus (base station) when Embodiment 3 is applied to a cellular system downlink. 10 is a diagram illustrating an example of a signal format used in Embodiment 4. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 4. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 4. FIG. 10 is a diagram illustrating an example of a signal format used in Embodiment 4. FIG. It is a figure which shows an example of the control signal transmitted from a transmitter to a receiver when using variable power offset. FIG. 10 is a diagram illustrating an example of a signal format selection pattern by the transmission apparatus according to the fifth embodiment. 10 is a flowchart illustrating an operation example of a transmission apparatus (base station) when Embodiment 5 is applied to a cellular system downlink. FIG. 20 is a diagram illustrating an example of a signal format used in the sixth embodiment. FIG. 20 is a diagram illustrating an example of a signal format used in the sixth embodiment. FIG. 20 is a diagram illustrating an example of a signal format used in the seventh embodiment. FIG. 20 is a diagram illustrating an example of a signal format used in the seventh embodiment. 218 is a diagram illustrating a configuration example of a packet transmitted by a transmission device in Embodiment 8. [FIG. FIG. 25 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus according to the eighth embodiment. 29 is a flowchart illustrating an example of a procedure by which the transmission device according to the eighth embodiment constructs a packet. 29 is a flowchart illustrating an example of a signal reception procedure by the receiving apparatus according to the eighth embodiment. FIG. 38 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus according to the ninth embodiment. 41 is a flowchart illustrating an example of a procedure by which the transmission device according to the ninth embodiment constructs a packet. 30 is a flowchart illustrating an example of a signal reception procedure by the reception device according to the ninth embodiment. FIG. 38 is a diagram illustrating a configuration example of control information used in the tenth embodiment. FIG. 38 is a diagram illustrating a configuration example of control information used in Embodiment 10. FIG. 38 is a diagram illustrating an example of a signal format selection pattern, a signal format, and control information arranged in a packet by the transmission apparatus according to the eleventh embodiment. 32 is a flowchart illustrating an example of a procedure by which the transmission device according to the eleventh embodiment constructs a packet. 32 is a flowchart illustrating an example of a signal reception procedure by the reception device in the eleventh embodiment. 218 is a diagram illustrating a configuration example of a transmission device and a reception device in Embodiment 12. [FIG. 218 is a diagram illustrating an example of a retransmission control operation in Embodiment 13. [FIG. 218 is a diagram illustrating a signal generation process in a transmission device illustrating retransmission control in Embodiment 13. [FIG. 218 is a diagram illustrating a signal reception process in a reception device in retransmission control according to Embodiment 13. [FIG. It is a figure for demonstrating the relationship between the number of antennas of a receiver, and weight convergence. 218 is a diagram illustrating an example of signal format selection operation by a transmission device in Embodiment 14. [FIG. 218 is a diagram illustrating an example of signal format selection operation by a transmission device in Embodiment 14. [FIG. 218 is a diagram illustrating an example of a signal format used in Embodiment 14. [FIG. 218 is a diagram illustrating an example of a signal format used in Embodiment 14. [FIG. 218 is a flowchart illustrating an example of a signal transmission procedure by the transmission device in the fourteenth embodiment. 40 is a flowchart illustrating an example of a signal reception procedure by the reception device in the fourteenth embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Reception apparatus 11 Data symbol generation part 12 Pilot symbol generation part 13 Null symbol generation part 14 Format determination part 15 Transmission signal construction part 16, 25 Information storage part 17, 26 Control information reception part 21 Reception signal separation part 22 Data Symbol detection unit 23 Reception control unit 24 Format identification unit

Claims (42)

In a multicarrier communication system that performs channel estimation using pilot symbols included in a received packet, a transmission apparatus that generates a packet including pilot symbols and transmits using one or more of the subbands,
Guess to infer whether or not the receiving side device as the destination can improve the channel estimation accuracy of the newly received packet based on the past channel estimation value when the packet is transmitted to the same destination multiple times Means,
A packet generation unit that generates a packet having a smaller number of pilot symbols than a packet generated when the estimation unit determines that the channel estimation accuracy can be improved;
A transmission device comprising: When continuously sending packets to the same destination using the same subband,
The transmission device according to claim 1, wherein the estimation unit estimates that the channel estimation accuracy cannot be improved for a packet to be transmitted first. When sending packets in parallel to the same destination using multiple adjacent subbands,
The transmission apparatus according to claim 1, wherein the estimation unit estimates that the channel estimation accuracy cannot be improved for a packet transmitted in a subband having the highest frequency and a subband having the lowest frequency. . The packet generation means includes
When generating a packet to be transmitted in a subband having the highest frequency, more pilot symbols are arranged on subcarriers having a higher frequency among the subcarriers constituting the subband,
In addition, when generating a packet to be transmitted in a subband having the lowest frequency, more pilot symbols are arranged on subcarriers having a lower frequency among the subcarriers constituting the subband. Item 4. The transmission device according to Item 3. When continuously sending packets to the same destination using the same subband and sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation means estimates that channel estimation accuracy cannot be improved for a packet transmitted first in a subband having the highest frequency and a packet transmitted first in a subband having the lowest frequency and transmitted first. The transmitter according to claim 1, wherein The packet generation means includes
When generating a packet to be transmitted in the subband having the highest frequency and transmitting first, more pilot symbols are arranged on subcarriers having a higher frequency among the subcarriers constituting the subband,
In addition, when generating a packet to be transmitted in the subband having the lowest frequency and transmitting first, more pilot symbols are allocated to subcarriers having a lower frequency among the subcarriers constituting the subband. The transmission device according to claim 5. When the reception quality of the packet sent by the device is fed back,
The transmission device according to claim 1, wherein the estimation unit estimates whether the channel estimation accuracy can be improved based on the reception quality.   When performing retransmission control, the packet generation means generates a retransmission packet using the number of pilot symbols, coding rate, and modulation method determined to be the same packet size as the initial transmission or smaller than the initial transmission. The transmission device according to claim 1, wherein the transmission device is a transmission device. In a multicarrier communication system that performs channel estimation using a pilot symbol included in a received packet, a transmission apparatus that generates a packet including a pilot symbol and transmits the packet using one or more of subbands,
Guess to infer whether or not the receiving side device as the destination can improve the channel estimation accuracy of the newly received packet based on the past channel estimation value when the packet is transmitted to the same destination multiple times Means,
When it is determined that the estimation means can improve the channel estimation accuracy, a packet including a pilot symbol having a transmission power lower than that of a pilot symbol included in a packet generated when it is determined that the channel estimation accuracy cannot be improved is generated. Packet generating means for
A transmission device comprising: When continuously sending packets to the same destination using the same subband,
10. The transmission apparatus according to claim 9, wherein the estimation means estimates that channel estimation accuracy cannot be improved for a packet to be transmitted first. When sending packets in parallel to the same destination using multiple adjacent subbands,
10. The transmission apparatus according to claim 9, wherein the estimation unit estimates that channel estimation accuracy cannot be improved for a packet transmitted in a subband having the highest frequency and a subband having the lowest frequency. . The packet generation means includes
A function of arranging a first pilot symbol as a pilot symbol and a second pilot symbol having lower transmission power than the first pilot symbol in the same packet;
Further, when generating a packet to be transmitted in the subband having the highest frequency, the first pilot symbol is arranged on the subcarrier side having the higher frequency among the subcarriers constituting the subband and the other side. And the second pilot symbol is arranged in
In addition, when generating a packet to be transmitted in a subband having the lowest frequency, the first pilot symbol is arranged on the subcarrier side having the lower frequency among the subcarriers constituting the subband and the other side. 12. The transmission apparatus according to claim 11, wherein the second pilot symbol is arranged in the area. When continuously sending packets to the same destination using the same subband and sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation means estimates that channel estimation accuracy cannot be improved for a packet transmitted first in a subband having the highest frequency and a packet transmitted first in a subband having the lowest frequency and transmitted first. The transmitter according to claim 9, wherein The packet generation means includes
A function of arranging a first pilot symbol as a pilot symbol and a second pilot symbol having lower transmission power than the first pilot symbol in the same packet;
Further, when generating a packet to be transmitted in the subband with the highest frequency and transmitting first, the first pilot symbol is arranged on the subcarrier side with the higher frequency among the subcarriers constituting the subband. And placing the second pilot symbol on the other side,
In addition, when a packet to be transmitted first and transmitted first in the subband having the lowest frequency is generated, the first pilot symbol is arranged on the subcarrier side having the lower frequency among the subcarriers constituting the subband. The transmitting apparatus according to claim 13, wherein the second pilot symbol is arranged on the other side. When the reception quality of the packet sent by the device is fed back,
The transmission apparatus according to claim 9, wherein the estimation unit estimates whether the channel estimation accuracy can be improved based on the reception quality.   When performing retransmission control, the packet generator generates a packet using a pilot symbol transmission power, a coding rate, and a modulation scheme determined to be the same packet size as the initial transmission or smaller than the initial transmission. The transmission device according to any one of claims 9 to 15, wherein: In a multicarrier communication system that performs interference power measurement using a null symbol included in a received packet, a transmitter that generates a packet including a null symbol and transmits the packet using one or more of the subbands,
When a packet is transmitted to the same destination multiple times, it is estimated whether the receiving side device as the destination can improve the interference power measurement accuracy of the newly received packet based on the past interference power measurement value. Guessing means to
A packet generating unit that generates a packet with a smaller number of null symbols than a packet generated when it is determined that the estimation unit can improve the interference power measurement accuracy, and it is determined that the interference power measurement accuracy cannot be improved;
A transmission device comprising: When continuously sending packets to the same destination using the same subband,
The transmission device according to claim 17, wherein the estimation means estimates that the interference power measurement accuracy cannot be improved for the interference power measurement of a packet to be transmitted first. When sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation means estimates that interference power measurement accuracy cannot be improved for interference power measurement of a packet transmitted in a subband having the highest frequency and a packet transmitted in a subband having the lowest frequency. The transmission device according to claim 17. The packet generation means includes
When generating a packet to be transmitted in a subband having the highest frequency, more null symbols are arranged on subcarriers having a higher frequency among the subcarriers constituting the subband.
In addition, when generating a packet to be transmitted in a subband having the lowest frequency, more null symbols are arranged in subcarriers having a lower frequency among the subcarriers constituting the subband. 19. The transmission device according to 19. When continuously sending packets to the same destination using the same subband and sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation means cannot improve interference power measurement accuracy for a packet transmitted first in a subband having the highest frequency and a packet transmitted first in a subband having the lowest frequency and transmitted first. The transmission apparatus according to claim 17, wherein the transmission apparatus estimates. The packet generation means includes
When transmitting in the highest frequency subband and generating a packet to be transmitted first, more null symbols are arranged on the higher frequency subcarriers among the subcarriers constituting the subband,
Also, when generating a packet to be transmitted first in the subband with the lowest frequency and transmitting first, it is necessary to arrange more null symbols on subcarriers with lower frequency among the subcarriers constituting the subband. The transmission device according to claim 21, wherein: When the reception quality of the packet sent by the device is fed back,
The transmission device according to any one of claims 17 to 22, wherein the estimation unit estimates whether or not the interference power measurement accuracy can be improved based on the reception quality.   The packet generation means, when performing retransmission control, generates a packet using the number of null symbols, the coding rate, and the modulation method determined to be the same size as the initial transmission or smaller than the initial transmission. The transmission device according to any one of claims 17 to 23. In a multicarrier communication system, a transmission device that generates a packet including control information and transmits using one or more of subbands,
Whether or not the receiver side device that is the destination can recognize the processing to be performed on the newly received packet based on the control information of the packet received in the past when sending the packet to the same destination multiple times , Guessing means to guess,
A packet generation unit that generates a packet including difference information with respect to the control information as a packet to be newly transmitted when it is estimated that the estimation unit can recognize;
A transmission device comprising: When continuously sending packets to the same destination using the same subband,
26. The transmission according to claim 25, wherein the estimation unit estimates that processing to be performed on a packet to be transmitted first cannot be recognized based on control information of a packet received in the past. apparatus. When sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation unit estimates that a process to be performed on a packet transmitted in a subband having the highest frequency cannot be recognized based on control information of a packet received in the past. 26. The transmission device according to 25. When continuously sending packets to the same destination using the same subband and sending packets in parallel to the same destination using multiple adjacent subbands,
The estimation means estimates that the process to be performed on the first transmitted packet transmitted in the subband having the highest frequency cannot be recognized based on the control information of the packet received in the past. The transmission device according to claim 25, characterized in that: When the reception quality of the packet sent by the device is fed back,
29. The method according to claim 25, wherein the estimation means estimates whether or not processing to be performed on the newly received packet can be recognized based on the reception quality. The transmitting device according to 1. In a multicarrier communication system that performs channel estimation using pilot symbols included in a received packet, a transmission apparatus that transmits a packet including pilot symbols,
Information acquisition means for acquiring information on the number of reception antennas from the reception side device;
Packet generating means for generating a packet including the number of pilot symbols determined based on the number of receiving antennas information;
A transmission device comprising:   31. The transmission apparatus according to claim 30, wherein the packet generation means generates a packet such that a larger number of pilot symbols is included as the number of reception antennas of the reception side apparatus increases. In a multicarrier communication system that performs interference power measurement using a null symbol included in a received packet, a transmission device that transmits a packet including a null symbol,
Information acquisition means for acquiring information on the number of reception antennas from the reception side device;
Packet generating means for generating a packet including a number of null symbols determined based on the number of receiving antennas information;
A transmission device comprising:   The transmission apparatus according to claim 32, wherein the packet generation unit generates a packet such that the number of null symbols is included as the number of reception antennas of the reception-side apparatus increases. Transmission in which a packet including pilot symbols and null symbols is transmitted in a multicarrier communication system that performs channel estimation using pilot symbols included in received packets and further measures interference power using null symbols included in received packets A device,
Information acquisition means for acquiring information on the number of reception antennas from the reception side device;
Packet generating means for generating a packet including a number of pilot symbols and null symbols determined based on the number of reception antennas information;
A transmission device comprising:   35. The transmission apparatus according to claim 34, wherein the packet generation unit generates a packet such that a larger number of reception antennas on a reception side includes more pilot symbols and null symbols. A reception device that constitutes a multicarrier communication system together with the transmission device according to claim 1,
Pilot symbol specifying means for specifying the pilot symbols arranged in the received packet based on the past packet reception results;
Receiving means for receiving data symbols included in the received packet based on the identified pilot symbols;
A receiving apparatus comprising: A receiving device that constitutes a multicarrier communication system together with the transmitting device according to claims 17 to 24,
A null symbol specifying means for specifying a null symbol arranged in a received packet based on a past packet reception result;
Receiving means for receiving data symbols included in the received packet using the specified null symbol;
A receiving apparatus comprising: A receiver that constitutes a multicarrier communication system together with the transmitter according to claims 25-29,
A format specifying means for specifying the format of the control information included in the received packet based on the past packet reception results;
Determining means for determining whether to use the control information used in the past reception processing based on the specifying result by the format specifying means;
With
If the determination means determines to use the control information used in the past reception process, the data included in the received packet based on the control information used in the past reception process and the control information included in the received packet Perform symbol reception processing,
On the other hand, when the determination unit determines not to use the control information used in the past reception processing, the reception processing of the data symbol included in the reception packet is performed based only on the control information included in the reception packet. A receiving apparatus. The transmission device according to any one of claims 1 to 16,
A receiving device according to claim 36;
A communication system comprising: The transmission device according to any one of claims 17 to 24;
A receiving device according to claim 37;
A communication system comprising: A transmission device according to any one of claims 25 to 29;
A receiving device according to claim 38;
A communication system comprising: A transmission device according to any one of claims 30 to 35;
A receiving apparatus that performs reception processing according to the state of pilot symbols and null symbols included in the signal transmitted from the transmitting apparatus;
A communication system comprising:

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