JP2006115164A - Method for controlling transmission/reception boundary in tdd communication and communication appratus using the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a TDD transmission/reception boundary by which high throughput can be obtained even if the variation of traffic is violent, and a communication apparatus using the method. <P>SOLUTION: The communication apparatus comprises means for controlling a transmission/reception boundary for setting the transmission/reception boundary to a prescribed position in a TDD frame when the transmission buffer using quantity of the communication apparatus itself is a first threshold or less and the transmission buffer using quantity of an opposite communication apparatus which is informed by the opposite communication apparatus is a second threshold or less, and in the other cases, determining the transmission/reception boundary of the TDD frame so that the ratio of the transmission time of the apparatus itself to a receiving time reaches a value corresponding to the ratio of the transmission buffer using quantity of the apparatus itself to the transmission buffer using quantity of the opposite apparatus. The opposite apparatus is informed of the determined transmission/reception boundary and the transmission and the reception of signals are switched on the determined transmission/reception boundary. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for controlling a signal direction switching timing (transmission / reception boundary) in a TDD frame in one-to-one TDD (Time Division Duplex) communication, and a communication apparatus using the method. .

  Communication systems can be classified into FDD (Frequency Division Duplex) and TDD depending on the difference in the method of separating the transmission signal and the reception signal. FDD is a system that separates a transmission signal and a reception signal by setting the frequency bands of the transmission signal and the reception signal to different frequency bands. Usually, since it is difficult to assume in advance a difference in traffic volume between a transmission signal and a reception signal, the same frequency bandwidth is allocated to the transmission signal and the reception signal. For this reason, the use efficiency of frequency resources is deteriorated for traffic that is asymmetric and has burstiness like Internet traffic.

  On the other hand, TDD is a system that uses the same frequency band for a transmission signal and a reception signal, but separates the transmission signal and the reception signal by alternately switching the transmission signal and the reception signal on the time axis. This is a communication method that can efficiently use frequency resources even for asymmetric traffic and traffic having burstiness by allocating a lot of time in a direction with a lot of traffic.

  In order to indicate the signal direction in TDD communication, for example, two opposing communication devices are provided with a parent-child (upper and lower) relationship, and the slave station (lower) device direction from the parent station (upper) device to the downstream direction In general, the expression in which the downlink is called a downlink, the reverse direction is called an uplink, and the uplink is called an uplink.

  In communication using TDD, efficient use of frequency resources can be achieved by appropriately controlling transmission / reception switching timing (hereinafter referred to as a transmission / reception boundary) in a TDD frame. Conventionally, studies have been made mainly on circuit-switched TDD radio communication systems. For example, a method has been proposed in which time slot allocation for efficiently accommodating voice calls and data calls is performed, and as a result, a transmission / reception boundary is set (see Non-Patent Document 1 and Non-Patent Document 2).

  For packet systems, the uplink / downlink traffic ratio is monitored so that the ratio of uplink and downlink transmission time is the same as the traffic ratio, that is, the transmission / reception boundary is proportionally distributed. Proposals have been made on how to determine this.

L. Chen et al “A Dynamic Timeslot Assignment Algorithm for Asymmetric Traffic in Multimedia TDMA / TDD Mobile Radio”, IEICE English Journal A, Vol.E81-A, no7, pp1358-1365, 1998 S. Park et al “An Enhanced Adaptive Time Slot Assignment using Access Statistics in TD / CDMA TDD System” Proceeding of 53rd IEEE VTC, vol.1, pp511-516, 2001 Kobayashi et al. “Radio resource management method for accommodating asymmetric traffic in CDMA / shared-TDD cellular packet system”, IEICE, RC2003-260, ppp97-102, January 2004

  For example, assuming that the number of time slots in a 1TDD frame is 10, the downlink traffic volume is a data volume that can be transmitted in 1/5 hours of a 1TDD frame, and the uplink traffic volume is data that can be transmitted in 1/45 hours of a 1TDD frame It is assumed that the transmission / reception boundary is determined by proportional distribution of the traffic amount.

  In this case, since the downlink to uplink traffic ratio is 9: 1, a position where the downlink / uplink is a 9/1 time slot is a transmission / reception boundary. However, when both the downlink / uplink traffic amount at the moment when the transmission / reception boundary is applied is the amount of data that can be transmitted in 1/5 hour of one TDD frame, that is, the amount that can be transmitted in two time slots, the uplink direction Since only one time slot is allocated to, half of the data cannot be transmitted even though there are remaining downlink time slots.

  As described above, in the method of setting the transmission / reception boundary by proportional distribution of the traffic amount, when the traffic asymmetry varies greatly, the traffic amount is monitored and the transmission / reception boundary based on the monitored value is applied. Due to this time difference, there is a problem that the throughput does not increase even though there are sufficient radio resources for the traffic volume.

  Therefore, an object of the present invention is to provide a transmission / reception boundary control method and a communication apparatus using the method, which can obtain a higher throughput than the conventional method even when the traffic fluctuation is severe.

According to the communication device of the present invention,
When the transmission buffer usage of the own device is less than or equal to the first threshold and the transmission buffer usage of the opposite device notified from the opposite device is less than or equal to the second threshold, the transmission / reception boundary is set in the TDD frame. In other cases, the TDD is set so that the ratio between the transmission time and the reception time of the own device becomes a value corresponding to the ratio of the transmission buffer usage of the own device and the transmission buffer usage of the opposite device. A transmission / reception boundary control means for determining a transmission / reception boundary of a frame is provided, the determined transmission / reception boundary is notified to an opposite apparatus, and transmission and reception of a signal are switched at the determined transmission / reception boundary.

According to another embodiment of the communication device of the present invention,
The first threshold is a data amount that can be transmitted in the transmission time of the own device when a predetermined position in the TDD frame is a transmission / reception boundary, and the second threshold is a predetermined amount in the TDD frame. When the position is a transmission / reception boundary, the amount of data that can be transmitted in the transmission time of the opposite device is also preferable.

According to another embodiment of the communication device of the present invention,
The predetermined position in the TDD frame is preferably the center of the TDD frame.

According to the transmission / reception boundary control method of the present invention,
In TDD communication, when the transmission buffer usage of the own device is less than or equal to the first threshold and the transmission buffer usage of the opposite device notified from the opposite device is less than or equal to the second threshold, the transmission / reception boundary is set. In other cases, the ratio between the transmission time and the reception time of the own device is a value corresponding to the ratio of the transmission buffer usage of the own device and the transmission buffer usage of the opposite device. Thus, the transmission / reception boundary of the TDD frame is determined.

  When the amount of traffic is small, by fixing the transmission / reception boundary, a high throughput can be ensured even when the traffic fluctuation is severe.

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

  FIG. 1 is a functional block diagram of a communication apparatus 1 that implements the transmission / reception boundary control method of the present invention. It is assumed that the opposite device communicating with the communication device 1 is dependent on the transmission / reception boundary determined by the communication device 1, that is, switches between transmission and reception according to the transmission / reception boundary notified from the communication device 1.

  FIG. 1 shows only functional blocks necessary for explaining the present invention. According to FIG. 1, the communication device 1 includes a transmission buffer 2, a transmission unit 3, a transmission / reception boundary control unit 4, a reception unit 5, and a reception buffer 6.

  In communication using TDD, the transmission signal from the communication device 1 is bursty, so that data to be transmitted is temporarily stored in the transmission buffer 2. The transmission unit 3 reads data from the transmission buffer 2 so that the transmission signal can be modulated and transmitted during a period in which the local station can transmit. Similarly, the reception signal received in bursts is demodulated by the reception unit 5, and the demodulated reception data is temporarily stored in the reception buffer 6 and read out at a constant speed.

  The transmission / reception boundary control unit 4 determines a transmission / reception boundary by a method to be described later, and notifies the transmission unit 3 and the reception unit 4 of the determined transmission / reception boundary by a transmission / reception boundary control signal. The transmission unit 3 and the reception unit 4 transmit and receive signals in bursts based on the notification. Furthermore, in order to notify the determined transmission / reception boundary to the opposite device that operates depending on the transmission / reception boundary determined by the communication device 1, the transmission unit 3 multiplexes the transmission / reception boundary with the transmission signal and transmits it.

The transmission / reception boundary control unit 4 determines the transmission / reception boundary B (t) by using the buffer usage amount Q _M (t) of the transmission buffer 2 of the own device and the buffer usage amount Q _S (t) of the transmission buffer of the opposite device. If, with the transmission of the information transmission rate _R M of the apparatus (t), and the information transmission rate of transmission of the opposite apparatus _R S (t), a time slot the total number N of the TDD frame, and TDD frame time P, the threshold value Th1, A threshold Th2 and a predetermined position b in the TDD frame and a constant K are used.

Since the transmission / reception boundary, the buffer usage amount, and the transmission speed vary with time, it becomes a function of the frame number t, and B (t), Q _M (t), Q _S (t), R _M (t), R _S (t ) Represents a value in the t-th frame.

  The transmission / reception boundary B (t) indicates the number of time slots of the TDD frame that the communication device 1 can use for transmission. FIG. 2 shows the relationship between the transmission / reception boundary B (t) and the TDD frame as viewed from the communication apparatus 1.

The transmission / reception boundary control unit 4 acquires the buffer usage amount Q _M (t) of the transmission buffer 2 of the own device from the transmission buffer 2. The opposite device monitors the transmission buffer of the opposite device, multiplexes the acquired buffer usage Q _S (t) with the transmission signal, and transmits the multiplexed signal to the communication device 1. The receiving unit 5 extracts the transmission buffer amount Q _S (t) of the opposing device multiplexed in the received signal and notifies the transmission / reception boundary control unit 4.

The information transmission speeds R _M (t) and R _S (t) of transmission / reception, the total number of time slots N of the TDD frame, and the TDD frame time P are information inherently possessed by the device for communication, The transmission / reception boundary control unit 4 obtains by a method according to each TDD system, such as notification from the control unit of the communication device 1 as a whole not shown or notification by control information from the opposite station multiplexed in the received signal.

  The threshold Th1, the threshold Th2, and the predetermined position b and the constant K in the TDD frame are stored in the transmission / reception boundary control unit 4 in advance.

  From the above information, the transmission / reception boundary control unit 4 determines the transmission / reception boundary B (t) by, for example, the following equation (1).

The basic idea of this control method is to measure the buffer usage that correlates with the traffic volume, and that the transmission buffer usage Q _M (t) of its own device is equal to or less than the first threshold value and is notified from the opposite device. If the transmission buffer usage Q _S (t) of the opposite device is equal to or smaller than the second threshold, the transmission / reception boundary is set to a predetermined position b in the TDD frame regardless of the ratio of the two buffer usages, In other cases, the ratio between the transmission time and the reception time is a value corresponding to the ratio between the transmission buffer usage amount Q _M (t) of the own device and the transmission buffer usage amount Q _S (t) of the opposite device. Thus, the transmission / reception boundary of the TDD frame is determined.

  For this reason, the buffer usage correlated with the traffic volume is monitored by the communication device 1 and the opposite device, and the opposite device notifies the communication device 1 of the monitored buffer usage, and is transmitted and received by both buffer amounts and two thresholds. Determine the boundary. The processing can be performed in units of frames or in units of several frames.

  When all the data accumulated in the transmission buffer in both directions can be transmitted in one TDD frame with respect to the transmission / reception boundary position b, it is meaningless to change the transmission / reception boundary according to the traffic ratio. This causes a decrease in throughput due to a rapid change in the traffic ratio after the change. Therefore, the threshold value Th1 is a data amount that can be transmitted in the transmission time of the own device, that is, the communication device 1, when a predetermined position b in the TDD frame is a transmission / reception boundary, and the threshold value Th2 is a predetermined value in the TDD frame. When the position b is a transmission / reception boundary, the amount of data that can be transmitted in the transmission time of the opposite apparatus is preferable.

  Furthermore, since it is difficult to grasp in advance a difference in the amount of data to be transmitted and received, it is also preferable to set the predetermined position b in the TDD frame to N / 2, which is the center of the TDD frame. In this case, the threshold values Th1 and Th2 both mean “the amount of data accumulated in the transmission buffer can be transmitted in half the time of one TDD frame”. More specifically, Th1 and Th2 in formula (1) are both 0.5.

  The constant K is for securing the transmission time of the minimum K time slots even when the buffer amount is 0, and can take a value of 0 or more.

It is a functional block diagram of the communication apparatus which implement | achieves the transmission / reception boundary control method in the TDD system of this invention. It is a figure which shows the relationship between transmission / reception boundary B (t) and a TDD frame.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Communication apparatus 2 Transmission buffer 3 Transmission part 4 Transmission / reception boundary control part 5 Reception part 6 Reception buffer

Claims (4)

When the transmission buffer usage of the own device is less than or equal to the first threshold and the transmission buffer usage of the opposite device notified from the opposite device is less than or equal to the second threshold, the transmission / reception boundary is set in the TDD frame. In other cases, the TDD is set so that the ratio between the transmission time and the reception time of the own device becomes a value corresponding to the ratio of the transmission buffer usage of the own device and the transmission buffer usage of the opposite device. A transmission / reception boundary control means for determining a transmission / reception boundary of the frame;
A communication device that notifies the opposite device of the determined transmission / reception boundary and switches between transmission and reception of a signal at the determined transmission / reception boundary. The first threshold is an amount of data that can be transmitted in the transmission time of the own device when a predetermined position in the TDD frame is a transmission / reception boundary.
2. The communication apparatus according to claim 1, wherein the second threshold is a data amount that can be transmitted in a transmission time of the opposite apparatus when a predetermined position in the TDD frame is a transmission / reception boundary.   The communication apparatus according to claim 2, wherein the predetermined position in the TDD frame is a center of the TDD frame. In TDD communication,
When the transmission buffer usage of the own device is less than or equal to the first threshold and the transmission buffer usage of the opposite device notified from the opposite device is less than or equal to the second threshold, the transmission / reception boundary is set in the TDD frame. In other cases, the TDD is set so that the ratio between the transmission time and the reception time of the own device becomes a value corresponding to the ratio of the transmission buffer usage of the own device and the transmission buffer usage of the opposite device. A TDD transmission / reception boundary control method, comprising: determining a transmission / reception boundary of a frame.

Images