JP2005341498A - Radio base station - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a turn-around time and to improve throughput of a higher layer by performing scheduling processing while also considering a status of the higher layer. <P>SOLUTION: A schedule processing section receives data rate control information indicative of an instructed data rate receivable for each terminal (602), sets a coefficient indicating presence/non-presence of packet terminal information (603-605) by discriminating presence/non-presence of a packet containing the packet terminal information among packets received from terminals, computes the ratio of the data rate control information weighted with the coefficient for each terminal in average throughput transmitted to each terminal (606), and transmits a packet (607) while preferentially allocating a time slot to a terminal having the maximum ratio. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radio base station, and more particularly to a radio base station in which a plurality of radio terminals share a radio channel in a time-sharing manner and control time slot allocation according to radio conditions of each terminal.

  In recent years, due to data communication, demand for data communication is increasing even in wireless communication. However, since frequency resources are limited, frequency utilization efficiency is an important factor in a wireless communication system. In recent years, a system called 1xEV-DO (1x evolution data only) has been proposed in which frequency utilization efficiency is improved several times as compared with conventional techniques by specializing in packet communication. The specification of 1xEV-DO is described in Non-Patent Document 1.

  In 1xEV-DO, the downlink radio channel is time-shared by all terminals in the sector. Each terminal measures radio conditions at regular intervals, and transmits an instruction data rate that can be currently received to a radio base station through a DRC (Data Rate Control) channel. On the other hand, a packet transmitted to each terminal is divided into fixed-length physical layer packets by the control station and stored in the radio base station. The radio base station determines time slot allocation based on rate information (for example, whether data exists) of each terminal, and transmits a physical layer packet with a preamble representing a destination. This time slot allocation algorithm is called a scheduling algorithm. By devising this algorithm, 1xEV-DO realizes high frequency utilization efficiency, that is, high throughput.

  As an example of the scheduling algorithm, there is an algorithm called proportional fairness. This algorithm is an algorithm for calculating the ratio between the instantaneous DRC information of each terminal and the average throughput transmitted to each terminal and allocating a time slot to the terminal having the maximum ratio. This proportional fairness algorithm is introduced in Non-Patent Document 2 and the like. Since the time slot is more easily assigned as the data rate is higher, the throughput of the entire sector as viewed in the physical layer is increased as a result.

Conventional scheduling algorithms focus on improving throughput in the physical layer, and do not consider the influence of scheduling on the throughput of higher layers.
3GPP2 C.S0024 Version 3.0 cdma2000 High Rate Packet Data AirInterface Specification, December 5, 2001 Forward link packet allocation scheduler method for packet data: Proceedings of 2001 IEICE General Conference: B-5-193: KDD R & D Laboratories Inc: Yamaguchi

  Since a wireless channel may have a relatively high error rate, it is essential to use an ACK (acknowledgement) type or NAK (non-acknowledgement) type retransmission algorithm in combination. In the CDMA radio system and 1xEV-DO, a TCP / IP (transmission control protocol / internet protocol) protocol is implemented in an upper layer, and an error rate is reduced by a TCP ACK-type retransmission protocol. In TCP, the transmission side has a mechanism that does not transmit the next data until it receives an ACK indicating that a certain amount (window size) of packets has been received from the reception side. In a wireless communication system, there is a delay due to an interleaver or decoder to reduce the error rate in the wireless line, so the turnaround time from when a packet is transmitted to when an ACK is received is much longer than that of a wired system. . Therefore, even if the throughput of the radio channel is high, there is a problem that the throughput of the upper layer is limited by the turnaround time.

  In particular, in 1xEV-DO, the throughput of the physical layer is improved by adopting a scheduling algorithm or the like. However, since there is a delay due to scheduling processing at the same time, the delay amount of the entire system may become larger. The challenges will be greater.

  The present invention has been made in view of the above-described problems, and has an object to shorten turnaround time and improve upper layer throughput by performing scheduling processing that also considers upper layer conditions. .

  In order to achieve the above object, it is determined whether or not the physical layer packet includes an end of the upper layer packet, and a process of preferentially transmitting the physical layer packet including the end of the upper layer packet in the scheduling process is added. As a result, the scheduling delay time seen in the upper layer is shortened.

According to the solution of the present invention, a plurality of radio terminals share a radio line in a time-sharing manner, and time slot assignment is controlled according to the radio situation of each terminal, and data divided into a plurality of parts is transmitted via the radio line. In the radio base station for
A schedule processing unit for determining the allocation of time slots according to the rate information of each terminal for the divided packets and transmitting the packets;
The schedule processing unit
Receive data rate control information indicating the instruction data rate that each terminal can receive,
By determining whether or not there is a packet including the packet end information in the packet received from each terminal, a coefficient indicating the presence or absence of the packet end information is set,
Calculating the ratio of the data rate control information of each terminal weighted by the coefficient and the average throughput being transmitted to each terminal;
The radio base station is provided that transmits a packet by preferentially assigning a time slot to a terminal having the maximum ratio.

  According to the present invention, since the scheduling delay in the radio base station is reduced, the throughput of the higher layer can be improved.

1. Basic configuration of wireless communication system
FIG. 1 shows a “wireless communication system configuration diagram” relating to the present embodiment.
The control station 101 is connected to the IP network 106 and the wireless base station 102 via a wired or wireless line. The radio base station 102 communicates with a radio terminal A 103 and a radio terminal B 104 that exist in the service area 105.

FIG. 2 shows an internal configuration diagram of the radio base station. FIG. 3 is a diagram showing packet division by the control station.
The control station 101 connected to the radio base station 102 performs upper layer processing such as call processing, and particularly in the downlink, as shown in the physical layer packet input to the radio base station, as shown in FIG. Then, control information such as destination information 302 and data length information 304 is added to the IP packet 301 received from the IP network 106 and divided into physical layer packets 216. In addition, the control station 101 has a role of removing control information from the physical layer packet 216 output from the radio base station 102 on the uplink and combining it to transmit to the IP network 106. Actually, the function of the control station 101 may be divided into a plurality of devices, or some functions may be integrated with the radio base station 102.

  Here, it is assumed that the wireless terminal A 103 and the wireless terminal B 104 communicating with the wireless base station 102 make a reception request to the wireless base station 102. At this time, the uplink information transmitted from the wireless terminals A 103 and B 104 includes rate information DRCk 201. The radio base station 102 receives the uplink signal with the antenna ANT202. The received signal is further demodulated by a DEM unit 209 constituted by an FPGA and a DSP (Digital Signal Processor) after being subjected to baseband processing 206 through an LNA (Low Noise Amp) 204 of an RF (Radio Frequency) unit 205. A signal is output toward the control station 101 through the call processing unit 214 and the I / F unit 215. On the other hand, the DRCk information 207 demodulated from the DEM unit 209 is transmitted to the scheduling processing unit 213 and used as a parameter of the scheduling processing unit 213.

  Downlink information for the wireless terminals A 103 and B 104 is input from the control station 101 as a physical layer packet 216 and input to the MOD unit 210 configured by the FPGA and the DSP via the I / F unit 215 and the call processing unit 214. And stored in the terminal B data queue 211 and the terminal A data queue 212, respectively.

  These stored data are scheduled by the scheduling processing unit 213, and the scheduling processing unit 213 receives the wireless terminal A.1. The terminal 208 is set to a data rate to be selected and transmitted by the selector 208 in accordance with the DRCk 201 transmitted from 103, B 104. Further, the signal is amplified by the HPA 203 of the RF unit 205 via the baseband processing unit 206 and transmitted to the wireless terminals A 103 and B 104 by the ANT 202.

2. Outline of Scheduling Process A scheduling process related to the present embodiment will be described below.
FIG. 4 is a flowchart of related scheduling processing. When the scheduling process is started (401), the radio base station 102 receives DRCk 201 from the radio terminals A 103 and B 104 in the service area 105 in the downlink (402). Next, based on this information, the scheduling unit 213 in the MOD unit 210 performs processing shown in the processing example of the related scheduling processing unit as shown in the figure, and assigns (schedules) time slots according to radio conditions. (403). In this example, a ratio Rk between the instantaneous DRC information of each terminal and the average throughput transmitted to each terminal is calculated, and a time slot is allocated to the terminal having the maximum ratio. The radio base station 102 transmits a packet to the terminal having the largest Rk (404), and further updates Tk using DRCk (405).

  At this time, the time from when the packet is transmitted until the ACK is received by the upper TCP layer, and the turnaround time are shown in the turnaround time by the related conventional scheduling process of FIG. In this figure, symbols A and B represent the names of wireless terminals to be transmitted, and the subsequent numbers indicate the order of packets. Scheduling processing is performed on the transmission packet candidates 501 in the data queues 211 and 212, and transmitted to the wireless terminals A103 and B104 by the time division multiplexing method.

  In FIG. 5, the time slot 506 (1) is allocated to the wireless terminal A having a high RK 512 value during the scheduling process, and the next time slot 506 (2) is allocated to the wireless terminal B for the same reason. Is shown. In this example, since the A-2 packet 511 having the packet end information 303 is allocated to the time slot 506 (5) by giving priority to the physical throughput (because it waits from (2) to (4)), There is a time delay until the terminal transmits the higher layer Ack. For this reason, the turnaround time 505 becomes longer, and a transmission information empty slot 510 is generated.

  In other words, in this process, the physical throughput of the downlink can be improved because a line is preferentially allocated to a radio terminal having a good communication state. However, the turnaround time can be improved by a scheduling process or a higher layer TCP retransmission protocol. Increases, the throughput per wireless terminal viewed from the upper layer is limited by this turnaround time.

3. Therefore, in this embodiment, when the radio base station 102 finds the packet end information 303 in the physical layer packet 216 to be transmitted to the radio terminal stations A 103 and B 104, the scheduling process for increasing the physical throughput is performed. In addition to processing, processing for preferentially allocating time slots to packets including termination information is performed.

FIG. 6 is a flowchart of the scheduling process according to this embodiment. This figure is a processing example of the scheduling processing unit 213.
When starting the scheduling process (601), the scheduling processing unit 213 receives the rate information DRCk of all terminals (602), and determines whether there is a physical layer packet including higher layer packet termination information in the queue (603). . Here, the DRCk is transmitted between the terminal and the base station periodically or by an instruction from the base station to the terminal. When packet end information is included (YES), αk = X (> 1) is set. On the other hand, when packet end information is not included (NO), αk = 1 is set. Here, X is a predetermined value and is appropriately set (1.5 in this example).

  Next, the scheduling processing unit calculates the ratio of the average throughput Tk and DRCk of each terminal (Rk = αk · DRCk / Tk) (606), and transmits the packet to the terminal having the largest Rk (607).

The average throughput information Tk may be obtained by measurement by the radio base station, may be obtained using information from the terminal or the control station, or may be obtained as appropriate.
Thereafter, the scheduling processing unit 213 updates Tk using DRCk (608). Each value of Rk, αk, DRCk, Tk, etc. can be written into or read out from the scheduling processing unit 213 appropriately or in the MOD unit 210 or other memory.

  As an example, the packet termination information 303 used in this method uses the upper layer packet boundary included in the lower layer. However, the packet termination information 303 is not limited to this, and padding (dummy data for packet length adjustment) is included in the upper layer packet. In this case, even when packet termination information or padding is included in a lower layer packet, these can be regarded as packet termination information 303 and processed in step S603 or the like as described above.

FIG. 7 shows the turnaround time according to the scheduling process of the present embodiment.
In the embodiment of the present invention, after the time slot 706 (1) is allocated to the wireless terminal A103 by newly considering the value of the coefficient (αk) 709 indicating the presence / absence of the packet end information 303, the packet end information 303 is included. The A-2 packet 711 is allocated and transmitted to the time slot 706 (2) (prior to the next slot). The wireless terminal A 103 that has received the packet termination information 303 returns an ACK 704 to the wireless base station 102. Further, the wireless base station 102 can transmit the next packet A-3 712, A-4 713 to the wireless terminal A 103 from the transmission packet candidates 708 in the data queue by receiving the ACK 704. It becomes.

  FIG. 7 shows a state in which, as a result of the turnaround time 705 being shortened, the empty slot 510 of the transmission information shown in FIG. Therefore, by performing the scheduling process of the present embodiment as shown here, the turnaround time can be reduced and the throughput viewed from the upper layer can be improved.

It is a block diagram of a radio system. It is the figure which showed the process in a radio base station. It is the figure which showed the packet division | segmentation by a control station. It is a flowchart of the related scheduling process. It is the figure which showed the turnaround time by related scheduling. It is a flowchart of the scheduling process of this Embodiment. It is the figure which showed the turnaround time by the scheduling of this Embodiment.

Explanation of symbols

101: Control station 102: Wireless base station 103: Wireless terminal A
104: Wireless terminal B
201: DRCk
202: ANT
203: HPA
204: LNA
205: RF unit 206: Baseband processing 207: DRCk information 208: Selector 209: DEM unit 210: MOD unit 211: Data queue for terminal B 212: Data queue for terminal A 213: Scheduling processing unit 214: Call processing unit 215: I / F unit 216: physical layer packet 217, 218: Data

Claims (7)

In a radio base station for time-sharing sharing a radio line with a plurality of radio terminals, controlling the allocation of time slots according to the radio status of each terminal, and transmitting data divided into a plurality over the radio line,
A schedule processing unit for determining the allocation of time slots according to the rate information of each terminal for the divided packets and transmitting the packets;
The schedule processing unit
Receive data rate control information indicating the instruction data rate that each terminal can receive,
By determining whether or not there is a packet including the packet end information in the packet received from each terminal, a coefficient indicating the presence or absence of the packet end information is set,
Calculating the ratio of the data rate control information of each terminal weighted by the coefficient and the average throughput being transmitted to each terminal;
The radio base station configured to preferentially assign a time slot to a terminal having the maximum ratio and transmit a packet. In the radio base station according to claim 1,
The schedule processing unit is a radio base station that further updates an average throughput for a terminal that has transmitted a packet. In the radio base station according to claim 1 or 2,
The radio base station, wherein the packet end information is information indicating the end of a divided packet, dummy data for packet adjustment, or padding. In the radio base station according to any one of claims 1 to 3,
The radio base station, wherein the packet termination information is information indicating a packet boundary of an upper layer included in a lower layer or information indicating a packet boundary of a lower layer. In the radio base station according to any one of claims 1 to 4,
A radio base station, in which an ACK-type retransmission protocol is implemented in an upper layer, and when the packet is transmitted through a radio channel, the upper layer packet is divided into a plurality of lower layer packets and transmitted. In the radio base station according to any one of claims 1 to 5,
A radio base station that performs time slot allocation control based on both a boundary of an upper layer packet included in a lower layer packet and a radio status. In the radio base station according to any one of claims 1 to 6,
A demodulator that extracts data rate control information from the received signal received from each terminal and outputs the information to the scheduling processing unit;
A plurality of data buffers for storing downlink information for each terminal;
A radio base station further comprising a selector for selecting one of the plurality of data buffers and transmitting a packet based on an instruction from the scheduling processing unit.

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