JP2011087305A - Radio communication apparatus, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid a modulation class from being set higher than needed in the case where user data to be transmitted to a communication destination apparatus are not present or user data to be transmitted are extremely little. <P>SOLUTION: The radio communication method, which is used for the radio communication apparatus for selecting a modulation class in accordance with propagation path quality, includes the steps of: detecting a data amount of user data to be transmitted to a communication destination apparatus (S11A, S11B); determining whether the detected data amount is less than or equal to a predetermined data amount (S12A, S12B); and selecting a modulation class corresponding to the predetermined data amount if it is determined that the detected data amount is less than or equal to the predetermined data amount (S13A, S13B). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a radio communication apparatus and a radio communication method for selecting a modulation class indicating a data amount that can be transmitted to the communication destination apparatus in accordance with a propagation path quality that is a quality of a radio propagation path with the communication destination apparatus. .

  Conventionally, adaptive modulation is known as a technique for improving a data rate in a wireless communication system. In a wireless communication system that uses adaptive modulation, the wireless communication device can transmit data to the communication destination device as the quality of the wireless propagation channel with the communication destination device (hereinafter, “propagation channel quality”) is better. Communication is performed with a communication destination device using a modulation class having a large amount (data rate).

  Further, transmission power control is known as a technique for realizing stable communication in a wireless communication system. In a wireless communication system using adaptive modulation and transmission power control, when a modulation class is set by adaptive modulation, transmission power control is generally performed to maintain the modulation class (for example, Patent Document 1). reference.).

JP 2006-295736 A (pages 29-30, FIGS. 11-12)

  By the way, the amount of user data transmitted in a wireless communication system is often biased to either the downlink (downward) or the uplink (upward). For example, when content data (user data) is downloaded in a wireless terminal, the amount of data in the uplink is only control data for maintaining the wireless link with the wireless base station.

  However, conventionally, even when there is no user data to be transmitted to the communication destination device or when there is very little user data to be transmitted, the modulation class in the wireless communication device is maintained, so the modulation class is higher than necessary. Will be set.

  Therefore, when the modulation class is set higher than necessary and transmission power control is performed so as to maintain the modulation class, there is a problem that power consumption in the radio communication device and interference given to adjacent cells increase.

  In view of the above problems, in the wireless communication system using adaptive modulation, when the user data to be transmitted by the wireless communication apparatus does not exist or the user data to be transmitted is extremely small, the modulation class is higher than necessary. An object of the present invention is to provide a wireless communication apparatus and a wireless communication method that can avoid the setting.

  In order to achieve the above object, a first feature of the present invention is that the communication is performed according to a propagation path quality (for example, CNR) that is a quality of a wireless propagation path with a communication destination apparatus (for example, the wireless terminal 200). A radio communication apparatus (for example, the radio base station 100) that selects a modulation class indicating the amount of data that can be transmitted to a destination apparatus, and among the modulation classes that can be used in the propagation path quality, the transmittable data amount is A modulation class selection unit (control unit 108) that selects the modulation class that is the maximum, a data amount detection unit (data amount detection unit 106) that detects the amount of user data to be transmitted to the communication destination device, and the data amount A data amount determination unit (data amount determination unit 107) for determining whether or not the data amount detected by the detection unit is equal to or less than a predetermined data amount, wherein the modulation class selection unit includes the data class determination unit; If the data amount by the amount determination unit determines that the is equal to or less than the predetermined amount of data, and summarized in that selects a modulation class corresponding to said predetermined amount of data.

  According to such a feature, the modulation class selection unit selects a modulation class having the maximum transmittable data amount (data rate) from among usable modulation classes. Therefore, when the amount of user data to be transmitted to the communication destination device is large, the user data throughput is improved by selecting a larger modulation class.

  The modulation class selection unit selects a modulation class corresponding to the predetermined data amount when the data amount of the user data transmitted to the communication destination apparatus is equal to or less than the predetermined data amount. Therefore, when there is no user data to be transmitted to the communication destination device or when there is very little user data to be transmitted, it is possible to appropriately set the modulation class to reduce power consumption in the wireless communication device and interference given to adjacent cells. it can.

  A second feature of the present invention relates to the first feature of the present invention, wherein the modulation class selection unit determines that the data amount is equal to or less than the predetermined data amount by the data amount determination unit. The gist is to select a modulation class (BPSK) having a minimum amount of transmittable data from the usable modulation classes.

  A third feature of the present invention relates to the second feature of the present invention, wherein the modulation class selection unit determines that the data amount is equal to or less than the predetermined data amount by the data amount determination unit. The gist of the invention is to fix the modulation class applied to communication with the communication destination device to the modulation class that minimizes the amount of data that can be transmitted.

  According to a fourth aspect of the present invention, there is provided a wireless communication method for selecting a modulation class indicating a data amount that can be transmitted to the communication destination device in accordance with a propagation path quality that is a quality of a wireless propagation path with the communication destination device. The step of selecting the modulation class having the maximum transmittable data amount from the modulation classes that can be used in the propagation path quality (step S14A, step S14B), and transmitting to the communication destination device A step of detecting the amount of user data (step S11A, step S11B) and a step of determining whether the amount of data detected in the step of detecting is equal to or less than a predetermined amount of data (step S12A, step S12B); In the selecting step, the data amount is less than or equal to the predetermined data amount in the determining step If it is determined that that the selecting a modulation class corresponding to a predetermined data amount (step S13A, step S13B) It is summarized as.

  According to the features of the present invention, in a wireless communication system using adaptive modulation, when there is no user data to be transmitted by the wireless communication apparatus or when there is very little user data to be transmitted, the modulation class is set higher than necessary. It is possible to provide a wireless communication apparatus and a wireless communication method that can avoid this.

1 is a schematic configuration diagram of a radio communication system according to an embodiment of the present invention. It is a functional block diagram which shows the structure of the wireless base station which concerns on embodiment of this invention. It is a functional block diagram which shows the structure of the radio | wireless terminal which concerns on embodiment of this invention. It is a figure which shows the modulation class information memorize | stored in the wireless base station and wireless terminal which concern on embodiment of this invention. 5 is a flowchart illustrating an operation of selecting an operation mode before starting data communication in the radio base station and the radio terminal according to the embodiment of the present invention. 6 is a timing chart showing an operation of selecting an operation mode during data communication in the radio base station and the radio terminal according to the embodiment of the present invention (No. 1). FIG. 6 is a timing chart showing an operation of selecting an operation mode during data communication in the radio base station and the radio terminal according to the embodiment of the present invention (No. 2).

  Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Configuration of Radio Communication System First, the configuration of the radio communication system according to the present embodiment will be described.

(1.1) Overall Schematic Configuration FIG. 1 is a schematic configuration diagram of a radio communication system according to the present embodiment. As shown in FIG. 1, the radio communication system includes a radio base station 100 and a radio terminal 200. In the present embodiment, the radio base station 100 and the radio terminal 200 perform radio communication using a time division multiple access-time division duplex (TDMA-TDD) scheme.

  Specifically, the radio base station 100 and the radio terminal 200 perform radio communication based on iBurst (registered trademark) (for the iBurst standard, “High Capacity-Spatial Division Multiple Access (HC-SDMA)”, WTSC − 2005-032, see ATIS / ANSI).

  In iBurst, adaptive modulation (link adaptation) for selecting a modulation scheme and a coding scheme according to channel quality is introduced for the purpose of increasing the communication rate. Below, the case where a carrier-to-noise ratio (CNR) is used as propagation path quality is demonstrated.

(1.2) Configuration of Radio Base Station FIG. 2 is a functional block diagram showing the configuration of the radio base station 100.

  As shown in FIG. 2, the radio base station 100 includes an antenna 101, a radio processing unit 102, a signal processing unit 103, a buffer unit 104, an upper layer processing unit 105, a data amount detection unit 106, a data amount determination unit 107, and a control unit. 108.

  The wireless processing unit 102 transmits or receives a wireless signal (RF signal) using the antenna 101. The wireless processing unit 102 includes a reception system (LNA, down converter and A / D converter), a transmission system (D / A converter, up converter and power amplifier), and the like.

  The wireless processing unit 102 converts the baseband signal from the signal processing unit 103 into an analog signal at the time of signal transmission. The wireless processing unit 102 up-converts and amplifies the analog signal to generate a wireless signal, and transmits the generated wireless signal from the antenna 101. Further, the radio processing unit 102 controls the transmission power of the radio signal in accordance with an instruction from the control unit 108.

  The radio processing unit 102 converts the radio signal into a baseband signal by amplifying, down-converting, and A / D converting the radio signal from the antenna 101 at the time of signal reception. The baseband signal is input to the signal processing unit 103.

  The signal processing unit 103 demodulates user data from the baseband signal and performs error correction decoding at the time of signal reception. The signal processing unit 103 modulates user data and performs error correction coding using a modulation class instructed by the control unit 108 during signal transmission.

  Further, the signal processing unit 103 measures the uplink UL CNR at the time of signal reception. The control unit 108 notifies the radio terminal 200 of the measured uplink UL CNR.

  The buffer unit 104 temporarily stores user data in order to control the order of received user data at the time of signal reception. The buffer unit 104 temporarily stores the user data at the time of signal transmission until the transmission of the user data is completed.

  The upper layer processing unit 105 generates user data. For example, the upper layer processing unit 105 executes a communication protocol such as RTP (Transport Protocol for Real-Time Applications: RFC 1889) / UDP (User Datagram Protocol: RFC 768) / IP (Internet Protocol: RFC 791).

  The data amount detection unit 106 detects the amount of user data (user data amount) to be transmitted to the wireless terminal 200. Either of the following (a) or (b) is used as a method for detecting the amount of user data.

(A) Method of Referencing User Data Amount Stored in Buffer Unit The data amount detection unit 106 detects the amount of user data to be transmitted to the wireless terminal 200 by referring to the buffer unit 104. For example, when the transmission queue of the buffer unit 104 is full, the data amount detection unit 106 determines that the downlink DL traffic is very large. On the other hand, when there is no user data in the transmission queue, the data amount detection unit 106 determines that the user data amount of the downlink DL is zero.

(B) Method of Referencing Packet Header Information The data amount detection unit 106 receives packet header information from the higher layer processing unit 105 and determines the type of communication according to the header information. For example, when a voice call based on VoIP (Voice over Internet Protocol) is being performed, the data amount detection unit 106 determines that the amount of user data to be transmitted to the wireless terminal 200 is small. When the content data is being downloaded in the wireless terminal 200, the data amount detection unit 106 determines that the amount of user data to be transmitted to the wireless terminal 200 is large.

  The data amount determination unit 107 compares the user data amount detected by the data amount detection unit 106 with a threshold value. The threshold value may be zero or may be a predetermined data amount. In the present embodiment, the threshold is set to a data amount (data rate) that can be transmitted using BPSK.

  The data amount determination unit 107 determines whether the user data amount detected by the data amount detection unit 106 is equal to or less than a threshold value, and notifies the control unit 108 of the determination result.

  The control unit 108 selects a modulation class to be applied to downlink DL communication based on the downlink DL CNR notified by the radio terminal 200 (see FIG. 4). Further, the control unit 108 sets the operation mode of the radio base station 100 according to the determination result by the data amount determination unit 107. As the operation mode, “BPSK fixed mode” for fixing the modulation class to BPSK and “adaptive modulation mode” for selecting the maximum modulation class satisfying the required CNR are used.

  Note that the control unit 108 also performs automatic retransmission control (ARQ), error detection using CRC, and the like in communication with the wireless terminal 200. Hereinafter, information (ACK and sequence number) used in ARQ, CRC, and the like are referred to as “control data”.

(1.3) Configuration of Radio Terminal FIG. 3 is a functional block diagram showing the configuration of the radio terminal 200. As illustrated in FIG. 3, the radio base station 100 includes an antenna 201, a radio processing unit 202, a signal processing unit 203, a buffer unit 204, an upper layer processing unit 205, a data amount detection unit 206, a data amount determination unit 207, and a control unit. 208. As described above, the radio terminal 200 has the same configuration as the radio base station 100.

(2) Modulation class information Next, modulation class information stored in advance in the radio base station 100 and the radio terminal 200 will be described. The control unit 108 of the radio base station 100 and the control unit 208 of the radio terminal 200 store modulation class information as shown in FIG. 4 in advance.

  As shown in FIG. 4, the modulation class information associates the modulation class, the required CNR of the modulation class, and the data rate (three-slot total value) of the modulation class. In the present embodiment, a total of 11 modulation classes of Mod 0 to Mod 10 can be used.

  Even in BPSK, which is the modulation class with the lowest data rate, a data rate of 6.4 kbps is secured in the uplink UL (1 slot) and 35.2 kbps is secured in the downlink DL (1 slot). Transmission is possible.

  In the present embodiment, when the amount of user data transmitted from the radio base station 100 to the radio terminal 200 is equal to or less than the threshold, the modulation class is set to BPSK (BPSK fixed mode), and the required CNR of the radio terminal 200 can be secured. The transmission power of the radio base station 100 can be lowered.

  Similarly, when the amount of user data transmitted from the radio terminal 200 to the radio base station 100 is equal to or less than the threshold value, the modulation class is set to BPSK (BPSK fixed mode), and the radio base station 100 can secure the required CNR until the required CNR is secured. The transmission power of terminal 200 can be reduced.

(3) Operation of Radio Communication System Next, the operation of the radio communication system according to the present embodiment will be described.

  Hereinafter, (3.1) an operation for selecting an operation mode before starting data communication and (3.2) an operation for selecting an operation mode during data communication will be described.

(3.1) Operation for selecting operation mode before starting data communication FIG. 5 is a flowchart showing an operation for selecting an operation mode before starting data communication in the radio base station 100 and the radio terminal 200. Note that, since the radio base station 100 and the radio terminal 200 perform similar operations, only the operation of the radio base station 100 will be described.

  In step S11A, the radio base station 100 detects the amount of user data to be transmitted to the radio terminal 200.

  In step S12A, the radio base station 100 determines whether or not the user data amount detected in step S11A is equal to or less than a threshold value. If the user data amount detected in step S11A is equal to or less than the threshold value, the process proceeds to step S13A. On the other hand, when the amount of user data detected in step S11A exceeds the threshold, the process proceeds to step S14A.

  In step S13A, the radio base station 100 sets the operation mode to the BPSK fixed mode.

  In step S14A, the radio base station 100 sets the operation mode to the adaptive modulation mode.

  In step S15, the radio base station 100 starts data communication with the radio terminal 200.

(3.2) Operation for selecting operation mode during data communication Next, an operation for selecting an operation mode during data communication will be described. Hereinafter, (3.2.1) operations of the radio base station and the radio terminal in downlink communication and (3.2.2) operations of the radio base station and the radio terminal in uplink communication will be described in this order. . A case will be described in which the radio base station 100 selects a modulation class to be applied to downlink DL and uplink UL communication.

(3.2.1) Operations of Radio Base Station and Radio Terminal in Downlink Communication FIG. 6 is a timing chart showing operations of the radio base station 100 and the radio terminal 200 in downlink DL communication. Here, a case where the amount of user data transmitted from the radio base station 100 to the radio terminal 200 is zero will be described.

  In step S101, the radio base station 100 detects the amount of user data transmitted to the radio terminal 200, and selects a modulation class to be applied to downlink DL communication according to the detected user data amount. Here, since the amount of user data is zero, BPSK is selected as a modulation class to be applied to downlink DL communication.

  In step S102, the radio base station 100 controls the transmission power of the downlink DL according to the CNR of the downlink DL notified by the radio terminal 200.

  In step S103, the radio terminal 200 measures the CNR of the downlink DL based on the radio signal received from the radio base station 100. The measured CNR is notified to the radio base station 100 in the next frame (frame 2).

  In step S104, the radio base station 100 sets a modulation class to be applied to downlink DL communication using the modulation class selected in step S101.

  In step S105, the downlink DL transmission power is controlled according to the downlink DL CNR notified by the radio terminal 200. Here, since BPSK is applied to downlink DL communication, it is possible to reduce downlink DL transmission power.

  In step S106, the radio terminal 200 measures the CNR of the radio signal received from the radio base station 100. The measured CNR is notified to the radio base station 100 in the next frame (frame 3).

(3.2.2) Operations of Radio Base Station and Radio Terminal in Uplink Communication FIG. 7 is a timing chart showing operations of the radio base station 100 and the radio terminal 200 in uplink UL communication. Here, a case where the amount of user data transmitted from radio terminal 200 to radio base station 100 is zero will be described.

  In step S201, the radio base station 100 receives the radio signal transmitted by the radio terminal 200, and measures the uplink UL CNR based on the received radio signal. Further, the radio terminal 200 notifies the radio base station 100 of the uplink UL user data amount.

  In step S202, the radio base station 100 selects a modulation class to be applied to uplink UL communication according to the amount of user data notified by the radio terminal 200. Here, since the amount of user data is zero, BPSK is selected as the modulation class applied to uplink UL communication.

  In step S203, the radio base station 100 controls the transmission power of the uplink UL according to the CNR measured in step S201.

  In step S204, the radio terminal 200 sets a modulation class to be applied to uplink UL communication using the modulation class selected in step S202. Also, the radio terminal 200 detects the amount of user data of the uplink UL. The detected user data amount is notified to the radio base station 100 in the next frame (frame 3).

  In step S205, the radio base station 100 receives the radio signal transmitted by the radio terminal 200, and measures the uplink UL CNR based on the received radio signal.

  In step S206, the radio base station 100 controls the uplink UL transmission power. Here, since BPSK is applied to uplink UL communication in the next frame (frame 3), the radio base station 100 can reduce the transmission power of the radio base station 100.

(4) Operation / Effect As described above, according to the present embodiment, the radio base station 100 and the radio terminal 200 operate in the adaptive modulation mode when it is determined that the amount of user data to be transmitted exceeds the threshold. . Therefore, when the amount of user data to be transmitted to the communication destination apparatus is large, the user data throughput can be improved by selecting a larger modulation class.

  The radio base station 100 and the radio terminal 200 operate in the BPSK fixed mode when it is determined that the amount of user data to be transmitted is equal to or less than the threshold value. Therefore, when there is no user data to be transmitted to the communication destination device or when there is very little user data to be transmitted, the power consumption in the wireless communication device and the interference given to the adjacent cell are reduced by setting the modulation class to BPSK. be able to.

  In addition, it is possible to omit complex adaptive modulation processing based on CNR by fixing the modulation class to BPSK in the period from when the amount of user data to be transmitted falls below the threshold to when the amount of user data to be transmitted exceeds the threshold. Therefore, the processing load on the radio base station 100 and the radio terminal 200 can be reduced.

[Other Embodiments]
As mentioned above, although this invention was described by embodiment and the example of a change, it should not be understood that the statement and drawing which form a part of this indication limit this invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the above-described embodiment, the wireless communication system based on the iBurst standard has been described as an example. However, the wireless communication system using adaptive modulation is not limited to the wireless communication system based on the iBurst standard. Such a wireless communication method can be applied.

  In the above-described embodiment, CNR is used as channel quality, but reception field strength (RSSI), bit error rate (BER), frame error rate (FER), or the like may be used instead of CNR. .

  In the embodiment described above, when the amount of user data to be transmitted is equal to or less than the threshold, the modulation class is fixed to BPSK. However, the modulation class is not limited to BPSK, and may be BPSK + or QPSK.

  Thus, it should be understood that the present invention includes various embodiments and the like not described herein. Therefore, the present invention is limited only by the invention specifying matters in the scope of claims reasonable from this disclosure.

  DESCRIPTION OF SYMBOLS 100 ... Wireless base station, 101 ... Antenna, 102 ... Radio processing part, 103 ... Signal processing part, 104 ... Buffer part, 105 ... Upper layer processing part, 106 ... Data amount detection part, 107 ... Data amount determination part, 108 ... Control unit, 200 ... wireless terminal, 201 ... antenna, 202 ... radio processing unit, 203 ... signal processing unit, 204 ... buffer unit, 205 ... upper layer processing unit, 206 ... data amount detection unit, 207 ... data amount determination unit, 208 ... Control unit

Claims (4)

A wireless communication device that selects a modulation class indicating a data amount that can be transmitted to the communication destination device according to a propagation path quality that is a quality of a wireless propagation channel with the communication destination device,
A modulation class selection unit that selects a modulation class having the maximum amount of data that can be transmitted from among modulation classes that can be used in the propagation path quality;
A data amount detection unit for detecting a data amount of user data transmitted to the communication destination device;
A data amount determination unit that determines whether or not the data amount detected by the data amount detection unit is equal to or less than a predetermined data amount;
The modulation class selection unit is a wireless communication apparatus that selects a modulation class corresponding to the predetermined data amount when the data amount determination unit determines that the data amount is equal to or less than the predetermined data amount.   When the data amount determination unit determines that the data amount is equal to or less than the predetermined data amount, the modulation class selection unit has the smallest transmittable data amount out of the usable modulation classes. The wireless communication apparatus according to claim 1, wherein a certain modulation class is selected.   The modulation class selection unit can transmit a modulation class applied to communication with the communication destination device when the data amount determination unit determines that the data amount is equal to or less than the predetermined data amount. The wireless communication apparatus according to claim 2, wherein the wireless communication apparatus is fixed to a modulation class having a minimum data amount. A wireless communication method for selecting a modulation class indicating a data amount that can be transmitted to the communication destination device according to a propagation path quality that is a quality of a wireless propagation channel with the communication destination device,
Selecting a modulation class that maximizes the amount of transmittable data from among modulation classes that can be used in the channel quality;
Detecting a data amount of user data to be transmitted to the communication destination device;
Determining whether the data amount detected in the detecting step is equal to or less than a predetermined data amount,
In the selecting step, the wireless communication method of selecting a modulation class corresponding to the predetermined data amount when it is determined in the determining step that the data amount is equal to or less than the predetermined data amount.

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