JP4068881B2 - Base station apparatus and packet transmission method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a base station apparatus and a packet transmission method that perform downlink high-speed packet transmission.
[0002]
[Prior art]
A downlink high-speed packet transmission method (such as HSDPA) has been developed in which a plurality of communication terminal apparatuses share a high-speed and large-capacity downlink channel and perform high-speed packet transmission. In this transmission method, scheduling technology and adaptive modulation technology are used to increase transmission efficiency.
[0003]
The scheduling technique is a technique in which a base station apparatus sets a communication terminal apparatus (hereinafter referred to as “transmission destination apparatus”) that is a transmission destination of a downlink high-speed packet for each time slot, and allocates a packet to be transmitted to the transmission destination apparatus. . The adaptive modulation technique is a technique for adaptively determining a data modulation scheme or error correction coding scheme in accordance with the state of a propagation path of a communication terminal apparatus that transmits packets.
[0004]
The base station apparatus predicts the channel quality of each communication terminal apparatus for each time slot for one frame, and assigns a packet to the transmission destination apparatus to each time slot, with the communication terminal apparatus having the best line quality as the transmission destination apparatus. . Then, the base station apparatus performs error correction coding and modulation on the packet using information indicating the scheduling result and a method determined by the scheduling, and transmits the packet to the transmission destination apparatus.
[0005]
Each communication terminal apparatus performs demodulation in a time slot to which a packet addressed to itself is allocated based on information indicating the received scheduling result, performs CRC detection, etc., and can correctly demodulate packet data. An ACK signal indicating this is transmitted to the base station apparatus, and when packet data cannot be demodulated correctly, a NACK signal indicating this is transmitted to the base station apparatus.
[0006]
When receiving the NACK signal, the base station apparatus retransmits the previously transmitted packet in the time slot allocated by scheduling. However, when the number of retransmissions reaches the maximum number of retransmissions preset in the system, the packet is discarded and a new packet is transmitted.
[0007]
Here, in the conventional packet transmission method, the modulation scheme and coding rate for the predicted channel quality are uniquely determined by the service class of the transport channel.
[0008]
In addition, in the conventional packet transmission method, a data string is divided into blocks for each transport channel, CRC bit addition and error correction encoding processing are performed, and a plurality of blocks are connected to match the number of bits of the physical channel. Rate matching is performed, modulation is performed, and mapping to the physical channel is performed. That is, there is one type of modulation scheme that can be assigned to each physical channel.
[0009]
Therefore, in the conventional packet transmission method, data of a plurality of transport channels having the same modulation method can be allocated to one physical channel after being multiplexed.
[0010]
[Problems to be solved by the invention]
However, in the conventional packet transmission method, data of transport channels having different modulation schemes cannot be allocated to one physical channel, and finite channel resources cannot be effectively used.
[0011]
The present invention has been made in view of such a point, and even when the data modulation method of each channel selected based on channel quality is different, a base station apparatus that can be allocated to one physical channel and An object is to provide a packet transmission method.
[0012]
[Means for Solving the Problems]
The base station apparatus of the present invention determines a communication terminal apparatus as a packet transmission destination based on the report value indicating the propagation path status from the received signal, and based on the report value and the service class. Transmission destination determining means for determining a coding rate and a modulation method, and the transmission destination determination means adjusts the modulation method of each data when transmitting a packet by multiplexing data of a plurality of service classes. The structure to control is adopted.
[0013]
The transmission destination determination means in the base station apparatus of the present invention adopts a configuration in which the data modulation scheme of each service class is matched to the one with the lowest multi-value number.
[0014]
With these configurations, when a plurality of data with different service classes are transmitted in a multiplexed manner, if the modulation scheme capable of obtaining the desired quality differs between the service classes, it can be transmitted with one physical channel, Limited channel resources can be used effectively.
[0015]
The transmission destination determination means in the base station apparatus of the present invention adopts a configuration for controlling the coding rate of the service class that matches the modulation scheme with the one with the lowest multi-value number so that the transmission rate is maintained.
[0016]
With this configuration, data of a plurality of service classes can be transmitted using one physical channel, finite channel resources can be used effectively, and a decrease in transmission efficiency can be prevented.
[0017]
The transmission destination determination means in the base station apparatus of the present invention adopts a configuration in which a physical channel different from the data with the lowest multi-value number is assigned to data whose transmission rate cannot be maintained even if the coding rate is controlled.
[0018]
With this configuration, it is possible to effectively utilize limited channel resources for the entire system while maintaining the data transmission rate of each service class.
[0019]
The packet transmission method of the present invention determines a packet transmission destination communication terminal apparatus based on a report value indicating a propagation path condition, and multiplexes data of a plurality of service classes and transmits a packet. The coding rate and the modulation scheme are determined based on the report value and the service class so as to match the lowest multi-value number.
[0020]
By this method, when a plurality of data with different service classes are multiplexed and transmitted, and the modulation scheme capable of obtaining the desired quality differs between service classes, the modulation scheme of each service class has the most multi-value number. By adjusting to a low one, it is possible to transmit with one physical channel, and it is possible to effectively utilize finite channel resources.
[0021]
The packet transmission method of the present invention employs a method of controlling the coding rate of the service class that matches the modulation scheme with the one with the lowest multi-value number so that the transmission rate is maintained.
[0022]
By this method, data of a plurality of service classes can be transmitted with one physical channel, finite channel resources can be effectively used, and a decrease in transmission efficiency can be prevented.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The essence of the present invention is that when a plurality of data having different service classes are transmitted in a multiplexed manner, when the modulation scheme capable of obtaining a desired quality is different between service classes, the modulation scheme of each service class is the most multi-valued. It is to control to match the low number.
[0024]
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0025]
(Embodiment 1)
FIG. 1 is a block diagram showing a configuration of a base station apparatus according to Embodiment 1 of the present invention. 1, the base station apparatus includes an antenna 101, a duplexer 102, a reception RF unit 103, a demodulation unit 104, an error correction decoding unit 105, a separation unit 106, and an ARQ control unit 107. . Furthermore, the base station apparatus includes a user determination unit 151, a service type determination unit 152, an MCS (Modulation Coding Scheme: combination of modulation scheme and error correction code) selection unit 153, an MCS selection table 154, and a transmission queue (queue). ) 155, a multiplexing unit 156, an error correction coding unit 157, a modulation unit 158, and a transmission RF unit 159.
[0026]
The duplexer 102 outputs the signal received by the antenna 101 to the reception RF unit 103. Further, the duplexer 102 wirelessly transmits the signal output from the transmission RF unit 159 from the antenna 101.
[0027]
The reception RF unit 103 converts the radio frequency reception signal output from the duplexer 102 into a baseband digital signal and outputs it to the demodulation unit 104.
[0028]
Demodulation sections 104 are prepared for the number of communication terminal apparatuses that perform wireless communication, perform demodulation processing on the received baseband signal, and output to error correction decoding section 105. Error correction decoding sections 105 are prepared as many as the number of communication terminal apparatuses that perform wireless communication, perform decoding processing for error correction such as Viterbi decoding on the demodulated signal, and output the result to demultiplexing section 106.
[0029]
Separators 106 are prepared as many as the number of communication terminal apparatuses that perform radio communication, and separates an ACK signal or NACK signal from the decoded signal and outputs the result to ARQ controller 107. Separation section 106 also separates the report value from the decoded signal and outputs it to MCS selection section 153. The ACK signal is a signal indicating that the high-speed packet transmitted from the base station apparatus can be correctly demodulated in the communication terminal apparatus. On the other hand, the NACK signal is a signal indicating that the high-speed packet transmitted from the base station apparatus cannot be correctly demodulated in the communication terminal apparatus. In addition, the report value measured in the communication terminal apparatus is a value indicating a propagation path condition between each communication terminal apparatus and the base station apparatus, and in the case of the maximum C / I method, the CIR (Carrier to Interference Ratio: Carrier-to-interference ratio).
[0030]
The ARQ control unit 107 instructs the transmission queue 155 to transmit new data when an ACK signal is input. On the other hand, when the NRQ signal is input, the ARQ control unit 107 instructs the transmission queue 155 to retransmit the previously transmitted data.
[0031]
The user determination unit 151 determines to which user (communication terminal device) the transmission data is based on user information included in the header of the transmission data of each communication terminal device, and the determination result is the MCS selection unit 153. Output to.
[0032]
The service type determination unit 152 determines a service class from service information included in the header of transmission data of each communication terminal apparatus, and outputs the determination result to the MCS selection unit 153 in association with the communication terminal apparatus. At this time, if there are a plurality of service classes, all the service classes are output to the MCS selection unit 153. The service class is described in the IP header of the frame format. For example, it is described in the “service type” field in IPv4, and in the “traffic class” field in IPv6.
[0033]
The MCS selection unit 153 determines a communication terminal device (hereinafter referred to as “destination device”) that transmits a packet based on a report value from each communication terminal device, and transmits the packet by referring to the determination result of the user determination unit 151 Information indicating the destination device is output to the transmission queue 155. For example, in the case of the maximum C / I method, the MCS selection unit 153 determines a communication terminal apparatus having the maximum CIR as a transmission destination apparatus.
[0034]
Further, the MCS selection unit 153 selects an appropriate modulation scheme and coding rate from the MCS selection table 154 based on the report value of the transmission destination apparatus. At this time, when the transmission destination apparatus requests data of a plurality of service classes, the MCS selection unit 153 matches the modulation method of the data of each service class with the modulation method having the lowest multi-level number. Then, the MCS selection unit 153 outputs information indicating the selected modulation scheme and coding rate to the multiplexing unit 156, the error correction coding unit 157, and the modulation unit 158.
[0035]
Details of the contents stored in the MCS selection table 154 and the coding rate and modulation method of the MCS selection unit 153 will be described later.
[0036]
The transmission queue 155 selects data for the transmission destination apparatus instructed by the MCS selection unit 153. At that time, when receiving an instruction to transmit new data from the ARQ control unit 107, the transmission queue 155 deletes the stored data and outputs and stores new data to the multiplexing unit 156. On the other hand, when receiving an instruction to retransmit data from the ARQ control unit 107, the transmission queue 155 outputs the stored data to the multiplexing unit 156.
[0037]
The multiplexing unit 156 multiplexes the data output from the transmission queue 155 with the information indicating the modulation scheme and coding rate output from the MCS selection unit 153.
[0038]
The error correction coding unit 157 adds CRC bits to the output signal of the multiplexing unit 156 by dividing the data string into blocks for each transport channel, and adds the CRC bits according to the coding rate method selected by the MCS selection unit 153. Error correction coding processing is performed, a plurality of blocks are connected, rate matching is performed in order to match the number of bits of the physical channel, and output to the modulation unit 158.
[0039]
Modulation section 158 modulates the output signal of error correction coding section 157 using the modulation method selected by MCS selection section 153 and outputs the result to transmission RF section 159.
[0040]
The transmission RF unit 159 converts the baseband digital signal output from the modulation unit 158 into a radio frequency signal and outputs the signal to the duplexer 102.
[0041]
Next, the contents stored in the MCS selection table 154 and the coding rate and modulation scheme determination method of the MCS selection unit 153 will be described in detail.
[0042]
FIG. 2 is a diagram illustrating an example of contents stored in the MCS selection table 154. As shown in FIG. 2, the MCS selection table 154 stores the correspondence between the modulation scheme, coding rate, and transmission rate for the CIR for each service class.
[0043]
In general, there is a relationship that the higher the CIR, the higher the transmission rate.
[0044]
In the case where the content stored in the MCS selection table 154 is FIG. 2, for example, the CIR of the report value from the transmission destination device is “7 dB”, and this transmission destination device stores data of a plurality of service classes A and B. Suppose that it was what you requested. In this case, the MCS selection unit 153 first selects “16QAM, R = 1/3, 4800 bps” for the service class A, and selects “QPSK, R = 1/2, 3600 bps” for the service class B. However, since the modulation method is different between service class A and service class B, the MCS selection unit 153 uses the service class A to match the data modulation method of each service class with the one with the lowest multi-value number (QPSK). Is changed to “QPSK, R = 1/2, 3600 bps”.
[0045]
Then, the MCS selection unit 153 outputs information indicating the finally selected modulation scheme and coding rate to the multiplexing unit 156, the error correction coding unit 157, and the modulation unit 158.
[0046]
As described above, when a plurality of data having different service classes are multiplexed and transmitted, and the modulation scheme capable of obtaining the desired quality is different between the service classes, the modulation scheme of each service class has the most multi-value number. By adjusting to a low one, it is possible to transmit with one physical channel, and it is possible to effectively utilize finite channel resources.
[0047]
(Embodiment 2)
In Embodiment 1 described above, there remains dissatisfaction in that the transmission rate of the service class in which the modulation scheme is changed in order to match the modulation scheme with the lowest multilevel number is lowered.
[0048]
In the second embodiment of the present invention, a case will be described in which a decrease in the transmission rate of a service class in which the modulation scheme is changed in order to match the modulation scheme with the lowest multilevel number.
[0049]
FIG.3 is a block diagram showing the configuration of the base station apparatus according to Embodiment 2 of the present invention. In the base station apparatus shown in FIG. 3, the same components as those in FIG.
[0050]
In the base station apparatus shown in FIG. 3, the operation of the MCS selection unit 301 is different from that of the MCS selection unit 153 of FIG. 1, and the storage content of the MCS selection table 302 is different from that of the MCS selection table 154. 3 employs a configuration in which a multiplexing unit 303, an error correction coding unit 304, a modulation unit 305, and a multiplexing unit 306 are added to FIG.
[0051]
Hereinafter, the contents stored in the MCS selection table 302 and the coding rate and modulation method determination method of the MCS selection unit 301 will be described in detail.
[0052]
FIG. 4 is a diagram illustrating an example of contents stored in the MCS selection table 302 of the base station apparatus according to Embodiment 2 of the present invention.
[0053]
As shown in FIG. 4, in the MCS selection table 302, the correspondence relationship between the modulation scheme, coding rate, and transmission rate for the CIR is stored for each service class, and in order to obtain the same transmission rate, a plurality of types of modulation schemes, There is a coding rate.
[0054]
In the case where the content stored in the MCS selection table 302 is FIG. 4, for example, the CIR of the report value from the transmission destination device is “7 dB”, and this transmission destination device stores data of a plurality of service classes A and B. Suppose that it was what you requested. In this case, the MCS selection unit 301 first selects “16QAM, R = 1/3, 4800 bps” for the service class A, and selects “QPSK, R = 1/2, 3600 bps” for the service class B. After that, the MCS selection unit 301 sets the service class A to “QPSK, R = 2/3” in order to adjust the modulation scheme of each service class to the one with the lowest multi-value number (QPSK) and to maintain the transmission rate. 4800 bps ".
[0055]
Then, the MCS selection unit 301 outputs information indicating the finally selected modulation scheme and coding rate to the multiplexing unit 156, the error correction coding unit 157, and the modulation unit 158.
[0056]
In this way, when the modulation scheme of each service class is set to the lowest multi-level number, data of a plurality of service classes is transmitted by one physical channel by selecting a coding rate that maintains the transmission rate. Therefore, it is possible to effectively use finite channel resources and to prevent a decrease in transmission efficiency.
[0057]
Next, a case where the coding rate and the modulation method are determined differently from the above-described MCS selection unit 301 will be described in detail.
[0058]
FIG. 5 is a diagram showing an example of contents stored in the MCS selection table 302 of the base station apparatus according to Embodiment 2 of the present invention, and shows a case different from FIG. In the case where the content stored in the MCS selection table 302 is FIG. 5, for example, the CIR of the report value from the transmission destination device is “7 dB”, and this transmission destination device stores data of a plurality of service classes C and B. Suppose that it was what you requested. In this case, the MCS selection unit 301 first selects “16QAM, R = 7/12, 8400 bps” for the service class C, and selects “QPSK, R = 1/2, 3600 bps” for the service class B. After that, the MCS selection unit 301 adjusts the modulation scheme of each service class to the one with the lowest multilevel number (QPSK). However, in the case of FIG. 5, since the maximum transmission rate in QPSK is 7200 bps, if the modulation method of service class C is set to QPSK, the transmission rate is lowered.
[0059]
In this case, the MCS selection unit 301 selects the first “16QAM, R = 7/12, 8400 bps” for the service class C, and allocates a transport channel to each physical channel.
[0060]
Then, the MCS selection unit 301 outputs information indicating the transmission destination device to the transmission queue 155 for each service class, and transmits information indicating the finally selected modulation scheme and coding rate to the multiplexing unit 156, the multiplexing unit 303, the error The data is output to the correction encoder 157, the error correction encoder 304, the modulator 158, and the modulator 305.
[0061]
The transmission queue 155 selects data for the transmission destination apparatus instructed by the MCS selection unit 301 and outputs the data to the multiplexing unit 156 or the multiplexing unit 303. For example, in the case of FIG. 5, the transmission queue 155 outputs service class C data to the multiplexing unit 156 and outputs service class B data to the multiplexing unit 303.
[0062]
Multiplexer 156 and multiplexer 303 multiplex the data output from transmission queue 155 with the information indicating the modulation scheme and coding rate output from MCS selector 301.
[0063]
The error correction coding unit 157 and the error correction coding unit 304 respectively perform error correction coding processing on the output signal of the multiplexing unit 156 or the multiplexing unit 303 by the coding rate method selected by the MCS selection unit 301. And output to modulation section 158 or modulation section 305. For example, in the case of FIG. 5, the error correction coding unit 157 performs error correction coding processing on the service class C data at a coding rate of 7/12, and the error correction coding unit 304 converts the service class B data. Error correction coding processing is performed at a coding rate of 1/2.
[0064]
Modulation section 158 and modulation section 305 modulate the output signal of error correction coding section 157 or error correction coding section 304 according to the modulation scheme selected by MCS selection section 301 and output the result to multiplexing section 306. For example, in the case of FIG. 5, the modulation unit 158 performs 16QAM modulation on the service class C data, and the modulation unit 305 performs QPSK modulation on the service class A data.
[0065]
The multiplexing unit 306 multiplexes the output signals of the modulation unit 158 and the modulation unit 305 and outputs the multiplexed signal to the transmission RF unit 159. The transmission RF unit 159 converts the baseband digital signal output from the multiplexing unit 306 into a radio frequency signal and outputs the signal to the duplexer 102.
[0066]
Thus, a physical channel different from the data with the lowest multi-level number can be assigned to the service class data that cannot maintain the transmission rate when the modulation scheme is adjusted to the one with the lowest multi-level number. This is particularly effective when it is desired to maintain the transmission rate, and such a case is considered rare in the system, so that the entire system can effectively use finite channel resources. .
[0067]
【The invention's effect】
As described above, according to the present invention, when a plurality of data having different service classes are multiplexed and transmitted, when the modulation scheme capable of obtaining a desired quality differs between service classes, By matching the modulation scheme to the one with the lowest multi-level number, it is possible to effectively utilize finite channel resources.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a base station apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing an example of contents stored in an MCS selection table of the base station apparatus according to the embodiment. FIG. 3 is a block diagram showing a configuration of a base station apparatus according to Embodiment 2 of the present invention. FIG. 4 is a diagram showing an example of contents stored in an MCS selection table of the base station apparatus according to the embodiment. FIG. 5 is a diagram showing an example of contents stored in the MCS selection table of the base station apparatus according to the above embodiment.
106 Separation unit 107 ARQ control unit 151 User determination unit 152 Service type determination unit 153, 301 MCS selection unit 154, 302 MCS selection table 155 Transmission queue 156, 303, 306 Multiplexing unit 157, 304 Error correction encoding unit 158, 305 Modulation Part

Claims (6)

Separating means for separating a report value indicating a propagation path condition from a received signal, a communication terminal device of a packet transmission destination is determined based on the report value, and a coding rate and a modulation scheme are determined based on the report value and a service class. A transmission destination determination means for determining,
The base station apparatus according to claim 1, wherein the transmission destination determining means controls to match the modulation scheme of each data when transmitting a packet by multiplexing data of a plurality of service classes. 2. The base station apparatus according to claim 1, wherein the transmission destination determining means matches the data modulation method of each service class with the one having the lowest multi-value number. 3. The base station apparatus according to claim 2, wherein the transmission destination determination means controls the coding rate of the service class that matches the modulation scheme with the one with the lowest multi-value number so that the transmission rate is maintained. 4. The base station apparatus according to claim 3, wherein the transmission destination determining unit assigns a physical channel different from the data having the lowest multi-value number to data whose transmission rate cannot be maintained even if the coding rate is controlled. . When the packet transmission destination communication terminal device is determined based on the report value indicating the propagation path status and the packet is transmitted by multiplexing the data of a plurality of service classes, the modulation method for each data has the lowest multi-value number A packet transmission method, wherein a coding rate and the modulation scheme are determined based on the report value and the service class. 6. The packet transmission method according to claim 5, wherein the coding rate of the service class is adjusted so that the transmission rate is maintained by adjusting the modulation method to the one with the lowest multi-value number.

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