JP2007312060A - Radio apparatus, program and communication method for adaptively changing pilot signal arrangement - Google Patents

Abstract

A radio apparatus and the like capable of adaptively changing a modulation scheme and a coding rate and capable of improving transmission efficiency by adaptively changing a pilot signal arrangement.
A modulation scheme and coding adaptively changed with reference to a pilot signal allocation table and a pilot signal allocation table in which pilot signal allocation information is associated with each set of modulation scheme and coding rate. A pilot signal arrangement selection section 117 that selects pilot signal arrangement information corresponding to the set of rates, and a pilot signal insertion section 103 that inserts a pilot signal based on the pilot signal arrangement information. In the pilot signal arrangement table, the pilot signal interval is larger as the coding rate is higher and the coding rate is larger, and the pilot signal interval is smaller as the coding rate is lower and the coding rate is lower.
[Selection] Figure 7

Description

  The present invention relates to a radio apparatus, a program, and a communication method for adaptively changing a pilot signal arrangement.

  Conventionally, for mobile communication systems, there is an “adaptive modulation scheme” technique for realizing high-quality and high-speed transmission even in a fading environment. The adaptive modulation scheme can adaptively select modulation parameters (modulation scheme and encoding scheme) according to transmission quality. When the transmission quality is poor, a low transmission rate modulation method is adopted to improve the transmission quality. When transmission quality is good, a high transmission rate modulation method is adopted. The adaptive modulation method is used in IEEE802.11a which is a wireless LAN standard, HSDPA (High Speed Downlink Packet Access), and the like.

  In the adaptive modulation system, a set of combinations of a modulation system and a coding rate is usually prepared. A plurality of prepared modulation schemes have different transmission rates and error tolerances. This set is called an MCS (Modulation and Coding Scheme) set.

  In order to realize high-speed wireless transmission, an OFDM (Orthogonal Frequency Division Multiplexing) scheme that is strong against frequency selective fading and has high frequency use efficiency has been adopted. For example, IEEE802.11a of the wireless LAN also adopts the OFDM system.

  According to the OFDM scheme, the receiving apparatus needs to estimate transmission path characteristics and correct transmission distortion. In correcting transmission distortion, the accuracy of estimation of transmission path characteristics is very important. Usually, the transmission apparatus transmits a “pilot signal”, which is information for estimating transmission path characteristics, at an appropriate timing. The receiving apparatus estimates transmission path characteristics using the distortion of the pilot signals.

JP 2005-252745 A JP 2004-207958 A

  According to the prior art, pilot signals are always arranged at constant time intervals and frequency intervals. Therefore, the pilot signal is always inserted with the same arrangement regardless of the transmission quality, that is, any MCS set. Usually, the pilot signal arrangement is determined assuming normal transmission quality that can be handled by the system (stationary arrangement method). Therefore, when the transmission quality is good, since more pilot signals than necessary are inserted, the transmission efficiency is forcibly impaired. On the other hand, when the transmission quality is poor, pilot signal insertion is insufficient, and the estimation accuracy of the transmission path characteristics is poor.

  Therefore, the present invention provides a radio apparatus, a program, and a communication method that can adaptively change a modulation scheme and a coding rate and can improve transmission efficiency by adaptively changing a pilot signal arrangement. For the purpose.

According to the present invention, in a radio apparatus capable of adaptively changing a modulation scheme and a coding rate,
A pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate, and
Pilot signal arrangement selection means for selecting pilot signal arrangement information corresponding to a set of adaptively changed modulation scheme and coding rate with reference to the pilot signal arrangement table;
And pilot signal insertion means for inserting a pilot signal based on the pilot signal arrangement information.

  According to another embodiment of the radio apparatus of the present invention, the pilot signal arrangement information in the pilot signal arrangement table is a high-speed modulation scheme and the higher the coding rate, the larger the pilot signal interval and the lower the modulation rate. It is also preferable that the pilot signal interval is smaller as the scheme is smaller and the coding rate is smaller.

According to another embodiment of the wireless device of the present invention,
Adaptive modulation information transmitting means for transmitting the modulation scheme, coding rate and pilot signal arrangement information to the counterparty radio device;
It is also preferable to further include adaptive modulation information receiving means for receiving the modulation scheme, coding rate, and pilot signal arrangement information from the counterparty radio apparatus.

According to the present invention, in a program for causing a computer mounted on a wireless device capable of adaptively changing a modulation scheme and a coding rate,
A pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate, and
Pilot signal arrangement selection means for selecting pilot signal arrangement information corresponding to a set of adaptively changed modulation scheme and coding rate with reference to the pilot signal arrangement table;
The computer is caused to function as pilot signal insertion means for inserting a pilot signal based on pilot signal arrangement information.

According to another embodiment of the program of the present invention,
The pilot signal arrangement information in the pilot signal arrangement table indicates that the pilot signal interval is larger and the pilot signal interval is larger, the pilot signal interval is larger and the coding rate is lower and the coding rate is lower. It is also preferable to make the computer function so that the signal interval is small.

According to another embodiment of the program of the present invention,
Adaptive modulation information transmitting means for transmitting the modulation scheme, coding rate and pilot signal arrangement information to the counterparty radio device;
It is also preferable to further cause the computer to function as adaptive modulation information receiving means for receiving the modulation scheme, coding rate, and pilot signal arrangement information from the counterparty radio apparatus.

According to the present invention, in an uplink communication method in a system having a base station and a mobile station that communicates with the base station via a radio link,
The mobile station has in advance a pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate,
A first step in which a base station transmits a training signal to a mobile station;
A second step in which the mobile station measures the transmission quality of the received training signal and selects a set of modulation scheme and coding rate based on the transmission quality;
A third step in which the mobile station refers to the pilot signal arrangement table and selects pilot signal arrangement information corresponding to a set of modulation scheme and coding rate;
A fourth step in which the mobile station transmits the modulation scheme, coding rate and pilot signal arrangement information to the base station;
And a fifth step of inserting a pilot signal based on the pilot signal arrangement information.

According to the present invention, in a downlink communication method in a system having a base station and a mobile station that communicates with the base station via a radio link,
The base station has in advance a pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate,
A first step in which a base station transmits a training signal to a mobile station;
A second step in which the mobile station measures the transmission quality of the received training signal and transmits the transmission quality information to the base station;
A third step in which the base station selects a set of modulation scheme and coding rate based on the received transmission quality information;
A fourth step in which the base station refers to the pilot signal arrangement table and selects pilot signal arrangement information corresponding to the set of the selected modulation scheme and coding rate;
A fifth step in which the base station transmits the modulation scheme, coding rate and pilot signal arrangement information to the mobile station;
The base station has a sixth step of inserting a pilot signal based on the pilot signal arrangement information.

  According to the radio apparatus, the program, and the communication method of the present invention, the modulation scheme and the coding rate can be adaptively changed, and the transmission efficiency can be improved by adaptively changing the pilot signal arrangement. If the transmission quality is good, the transmission efficiency can be increased by reducing the number of inserted pilot signals. Also, if the transmission quality is poor, the estimation accuracy of the transmission path characteristics can be increased by increasing the number of pilot signals to be inserted.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

Table 1 is an example of an MCS set used in IEEE 802.11a.

  According to Table 1, the modulation scheme includes BPSK (Binary Phase Shift Keying), QPSK (Quadrature Phase Shift Keying), and 16QAM (16-Quadrature Amplitude Modulation). ) And 64QAM (64-Quadrature Amplitude Modulation).

  The coding rate includes 1/2, 2/3, and 3/4. “Encoding rate” refers to a ratio between original information input to an encoder and encoded information output from the encoder.

  Based on the transmission quality measured before transmitting data, the optimum MCS is selected from the MCS set in Table 1. For example, for the uplink, the mobile station measures the transmission quality of the received signal from the base station, for example, SIR (Signal to Interference Ratio), and selects the optimum MCS based on the transmission quality. To do.

  FIG. 1 is a frame configuration diagram showing a first pilot signal arrangement.

According to FIG. 1, the vertical direction is the frequency direction and the horizontal direction is the time direction. The frequency direction is represented for each subcarrier, and pilot signals are arranged at intervals of Nf = 4. The time direction is expressed in the order of the training signal, SIGNAL, and data portion. The training signal is a PLCP (Physical Layer Convergence Protocol) preamble, and is a fixed waveform signal necessary for reception synchronization processing. SIGNAL includes the transmission rate of the subsequent data part (that is, the information of the selected MCS set) and the data length.
Yes.

  For example, according to IEEE802.11a, the number of subcarriers in the frequency direction is a total of 52 subcarriers, 48 subcarriers used for information transmission and 4 pilot signal subcarriers. The subcarrier number of the center frequency is set to 0, and four subcarriers of subcarrier numbers -21, -7, +7, and +21 are used for pilot signal transmission.

Table 2 shows a downlink frame configuration transmitted from the base station to the mobile station. “P” represents a pilot signal.

Table 3 shows an uplink frame configuration transmitted from the mobile station to the base station.

  FIG. 2 is a frame configuration diagram showing a second pilot signal arrangement. Pilot signals are arranged at intervals of Nt = 6 in the time direction.

  FIG. 3 is a frame configuration diagram showing a third pilot signal arrangement. Pilot signals are arranged at intervals of Nf = 2 in the frequency direction and at intervals of Nt = 2 in the time direction.

  FIG. 4 is a frame configuration diagram showing a fourth pilot signal arrangement. Pilot signals are arranged at intervals of Nf = 2 in the frequency direction and at intervals of Nt = 3 in the time direction.

  FIG. 5 is a frame configuration diagram showing a fifth pilot signal arrangement. Pilot signals are arranged at intervals of Nf = 3 in the frequency direction and at intervals of Nt = 3 in the time direction.

  FIG. 6 is a frame configuration diagram showing a sixth pilot signal arrangement. Pilot signals are arranged at intervals of Nf = 4 in the frequency direction and at intervals of Nt = 3 in the time direction.

Table 4 is an MCPS (Modulation, Coding and Pilot Scheme) table in which pilot signal arrangement is associated with each MCS set.

  In the pilot signal arrangement information, the pilot signal interval is larger as the modulation rate is higher and the coding rate is larger, and the pilot signal interval is smaller as the pilot rate is lower and the coding rate is lower.

  In order to improve the accuracy of transmission estimation, it is preferable to reduce the frequency direction interval Nf and the time direction interval Nt. However, if more pilot signals are inserted than necessary, the transmission efficiency is impaired. The time direction interval Nt affects the speed of the temporal change in the transmission path characteristics. This is determined by the maximum Doppler frequency. Further, the frequency direction interval Nf affects the maximum delay spread of transmission.

  FIG. 7 is a functional configuration diagram of the transmission apparatus according to the present invention.

  According to FIG. 7, the transmission apparatus 1 includes an encoding unit 101, an interleaving unit 102, a pilot signal insertion unit 103, a serial / parallel conversion unit 104, a subcarrier modulation unit 105, an inverse Fourier transform unit 106, Parallel serial converter 107, guard interval adder 108, D / A converter 109, quadrature modulator 110, radio transmitter 111, antenna 112, radio receiver 113, transmission quality detector 114, Have These functional units have a general configuration of the OFDM scheme.

  In order to cope with the adaptive modulation scheme, an encoding control section 115 that controls the encoding section 101 and a modulation scheme control section 116 that controls the subcarrier modulation section are included. An MCPS selection unit 117 and an MCPS table 118 are further provided to instruct the encoding control unit 115 and the modulation scheme control unit 116 to specify a modulation scheme and a coding rate. In addition, an MCPS transmission unit 119 and an MCPS reception unit 120 are also included. These functional units can also be realized by a program that causes a computer installed in the transmission apparatus to be executed.

  The encoding unit 101 performs an encoding process based on the encoding rate notified from the encoding control unit 115. The interleaving unit 102 performs processing to change the order of the encoded transmission bits in order to enhance the error correction effect. Pilot signal insertion section 103 inserts a pilot signal based on the pilot signal arrangement notified from MCPS selection section 117.

  The serial / parallel converter 104 divides the data string to be transmitted according to the number of subcarriers. The subcarrier modulation unit 105 arbitrarily modulates each subcarrier. Further, the modulation scheme can be adaptively changed based on the modulation scheme notified from the modulation scheme control unit 116. According to IEEE802.11a, all subcarrier modulation sections 104 use the same modulation scheme.

  The inverse Fourier transform unit 106 transforms the plurality of subcarrier modulation signals into the time domain. The parallel-serial conversion unit 107 converts a plurality of carrier signals into a serial data string. A guard interval (GI) adding unit 108 adds a guard interval that is a redundant time inserted to reduce interference. Thereby, interference of multipath delay waves can be avoided.

  The D / A converter 109 converts the digital signal into an analog signal. The quadrature modulation unit 110 converts the baseband signal represented by a complex number into a radio signal having an intermediate frequency. The wireless transmission unit 111 amplifies the wireless signal and transmits it to the antenna 112.

  The wireless receiving unit 113 receives a wireless signal from the antenna 112. The transmission quality detection unit 114 detects the transmission quality of the reception signal in the wireless reception unit 113. The transmission quality is, for example, BER (Bit Error Rate).

  The MCPS table 118 stores the table of Table 4 described above. The MCPS selection unit 117 selects a modulation scheme and a coding rate set according to transmission quality. If the transmission quality is good, a high-speed modulation scheme and a large coding rate are selected. If the transmission quality is poor, a low-speed modulation scheme and a small coding rate are selected.

  The MCPS selection unit 117 derives pilot signal arrangement information corresponding to the selected modulation scheme and coding rate set. The pilot signal arrangement information indicates that the pilot signal interval (Nf and Nt) is larger as the coding rate is higher and the coding rate is higher, and the pilot rate is lower as the coding rate is lower and the coding rate is lower. The signal interval is small. The modulation scheme is notified to modulation scheme control section 116, the coding rate is notified to coding control section 115, and the pilot signal arrangement information is notified to pilot signal insertion section 103.

  The MCPS transmission unit 119 transmits information on the set of modulation scheme and coding rate selected by the MCPS selection unit 117 to the counterpart radio apparatus. The MCPS receiving unit 120 receives information on a set of modulation scheme and coding rate from the counterparty radio apparatus, and notifies the MCPS selection unit 117 of the information.

  FIG. 8 is a sequence diagram between a base station and a mobile station in the present invention.

The uplink (S801) base station transmits a frame including a training signal to the mobile station.
(S802) The mobile station detects an SINR of transmission quality from the received signal.
(S803) The mobile station selects MCPS (a set of modulation scheme, coding rate and pilot signal arrangement information) from the transmission quality SINR.
(S804) The mobile station transmits the selected MCPS information to the base station.
(S805) The mobile station sets a modulation scheme, a coding rate, and a pilot signal arrangement based on the selected MCPS.
(S806) The base station sets the modulation scheme, coding rate, and pilot signal arrangement based on the MCPS received from the mobile station.
(S807) The mobile station generates a SIGNAL and arranges a pilot signal in the data part.
(S808) The mobile station transmits a data frame to the base station.

The downlink (S811) base station transmits a frame including a training signal to the mobile station.
(S812) The mobile station detects the SINR of the transmission quality from the received signal.
(S813) The mobile station transmits SINR information of transmission quality to the base station.
(S814) The base station selects MCPS from the received transmission quality SINR.
(S815) The base station transmits the selected MCPS information to the mobile station.
(S816) The base station sets a modulation scheme, a coding rate, and a pilot signal arrangement based on the selected MCPS.
(S817) The mobile station sets the modulation scheme, coding rate, and pilot signal arrangement based on the MCPS received from the base station.
(S818) The base station generates a SIGNAL and arranges a pilot signal in the data part.
(S819) The base station transmits a data frame to the mobile station.

  As described above in detail, according to the radio apparatus, program, and communication method of the present invention, the modulation scheme and coding rate can be adaptively changed, and the pilot signal arrangement can be adaptively changed. Transmission efficiency can be increased. If the transmission quality is good, the transmission efficiency can be increased by reducing the number of inserted pilot signals. Also, if the transmission quality is poor, the estimation accuracy of the transmission path characteristics can be increased by increasing the number of pilot signals to be inserted.

  According to the various embodiments of the present invention described above, those skilled in the art can easily make various changes, modifications and omissions within the scope of the technical idea and the viewpoint of the present invention. The above description is merely an example, and is not intended to be restrictive. The invention is limited only as defined in the following claims and the equivalents thereto.

It is a frame block diagram showing 1st pilot signal arrangement | positioning. It is a frame block diagram showing 2nd pilot signal arrangement | positioning. It is a frame block diagram showing a 3rd pilot signal arrangement | positioning. It is a frame block diagram showing 4th pilot signal arrangement | positioning. It is a frame block diagram showing 5th pilot signal arrangement | positioning. It is a frame block diagram showing 6th pilot signal arrangement | positioning. It is a function block diagram of the transmitter in this invention. It is a sequence diagram between the base station and mobile station in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 101 Coding part 102 Interleaving part 103 Pilot signal insertion part 104 Serial / parallel conversion part 105 Subcarrier modulation part 106 Inverse Fourier transform part 107 Parallel serial conversion part 108 Guard interval addition part 109 Digital / analog conversion part 110 Orthogonal modulation part DESCRIPTION OF SYMBOLS 111 Radio transmission part 112 Antenna 113 Wireless reception part 114 Transmission quality detection part 115 Coding control part 116 Modulation system control part 117 MCPS selection part 118 MCPS table 119 MCPS transmission part 120 MCPS reception part

Claims (8)

In a radio apparatus capable of adaptively changing a modulation scheme and a coding rate,
A pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate, and
Pilot signal arrangement selection means for referring to the pilot signal arrangement table and selecting pilot signal arrangement information corresponding to the set of modulation schemes and coding rates adaptively changed;
A radio apparatus comprising pilot signal insertion means for inserting a pilot signal based on the pilot signal arrangement information.   The pilot signal arrangement information of the pilot signal arrangement table indicates that the higher the modulation scheme and the higher the coding rate, the larger the pilot signal interval and the lower the modulation scheme and the smaller the coding rate. The radio apparatus according to claim 1, wherein the pilot signal interval is small. Adaptive modulation information transmitting means for transmitting the modulation scheme, the coding rate, and the pilot signal arrangement information to a counterparty radio device;
The radio apparatus according to claim 1, further comprising: an adaptive modulation information receiving unit that receives the modulation scheme, the coding rate, and the pilot signal arrangement information from the counterpart radio apparatus. In a program for causing a computer mounted on a wireless device capable of adaptively changing a modulation scheme and a coding rate to function,
A pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate, and
Pilot signal arrangement selection means for referring to the pilot signal arrangement table and selecting pilot signal arrangement information corresponding to the set of modulation schemes and coding rates adaptively changed;
A program causing a computer to function as pilot signal insertion means for inserting a pilot signal based on the pilot signal arrangement information.   The pilot signal arrangement information of the pilot signal arrangement table indicates that the higher the modulation scheme and the higher the coding rate, the larger the pilot signal interval and the lower the modulation scheme and the smaller the coding rate. The program according to claim 4, wherein the computer is caused to function so that the pilot signal interval is small. Adaptive modulation information transmitting means for transmitting the modulation scheme, the coding rate, and the pilot signal arrangement information to a counterparty radio device;
The program according to claim 4 or 5, further causing a computer to function as adaptive modulation information receiving means for receiving the modulation scheme, the coding rate, and the pilot signal arrangement information from the counterparty radio apparatus. In an uplink communication method in a system having a base station and a mobile station that communicates with the base station via a radio link,
The mobile station has in advance a pilot signal arrangement table in which pilot signal arrangement information is associated with each set of modulation scheme and coding rate,
A first step in which the base station transmits a training signal to the mobile station;
A second step in which the mobile station measures the transmission quality of the received training signal and selects a set of modulation scheme and coding rate based on the transmission quality;
A third step in which the mobile station refers to the pilot signal arrangement table and selects pilot signal arrangement information corresponding to the set of modulation scheme and coding rate;
A fourth step in which the mobile station transmits the modulation scheme, the coding rate, and the pilot signal arrangement information to the base station;
And a fifth step of inserting a pilot signal based on the pilot signal arrangement information. In a downlink communication method in a system having a base station and a mobile station that communicates with the base station via a radio link,
The base station has in advance a pilot signal arrangement table that associates pilot signal arrangement information for each set of modulation scheme and coding rate,
A first step in which the base station transmits a training signal to the mobile station;
A second step in which the mobile station measures the transmission quality of the received training signal and transmits the transmission quality information to the base station;
A third step in which the base station selects a set of modulation scheme and coding rate based on the received transmission quality information;
A fourth step in which the base station refers to the pilot signal allocation table and selects pilot signal allocation information corresponding to the selected modulation scheme and coding rate set;
A fifth step in which the base station transmits the modulation scheme, the coding rate, and the pilot signal arrangement information to the mobile station;
A downlink communication method, wherein the base station includes a sixth step of inserting a pilot signal based on the pilot signal arrangement information.

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