KR20050098995A - Method of controlling data packet retransmission in mobile packet communication system - Google Patents

Abstract

The present invention relates to a data packet retransmission control method in a wireless packet communication system. A data packet retransmission control method according to the present invention comprises: receiving a data packet transmitted from a terminal in a wireless packet communication system; Determining whether a transmission error exists in the data packet; Determining a channel condition when there is a transmission error in the data packet; And packet retransmission control information which is information on whether to allow or prohibit retransmission of the data packet to a signal (NACK) requesting retransmission of the data packet to the terminal due to a transmission error of the data packet according to the channel condition. And additionally transmitting. When the scheduling method of the uplink retransmission packet proposed by the present invention is applied to 3GPP WCDMA E-DCH transmission, a problem that may occur when scheduling of the retransmission packet is not performed (congestion, lack of radio resources, etc.) or As a result, the overall system efficiency can be increased.

Description

Method of controlling data packet retransmission in a wireless packet communication system

The present invention relates to a data packet retransmission control method in a wireless packet communication system. More specifically, in the wireless packet communication system, the receiving side determines whether to allow retransmission of packets in consideration of the channel situation and informs the transmitting side to alleviate problems such as unnecessary congestion or lack of resources in the channel. The present invention relates to a data packet retransmission control method in a wireless packet communication system capable of improving the efficiency of the system.

Recently, in the wireless mobile communication system, there is an active discussion on a high-speed packet communication method in uplink for transmitting data from a terminal to a base station in response to a demand for uplink speed and capacity increase. A representative example is the Enhanced Uplink Dedicated CHannel (E-DCH) technology, which is being discussed in the 3GPP WCDMA wireless mobile communication system. In the E-DCH technology, uplink packet scheduling by a base station (Node B) and HARQ (Hybrid ARQ) in the physical layer are introduced into an existing 3GPP WCDMA uplink dedicated channel (DCH) to improve efficiency of uplink. I'm trying.

In the ARQ technique, the receiving side checks the quality of the data packet transmitted from the transmitting side, and if there is a defect, requests the transmitting side to retransmit the data packet, and the transmitting side retransmits an error packet. An error detection code method that checks whether there is an error in the data transmitted from the receiver. A parity check method that determines whether an error exists by using an extra bit of 1 bit as a check bit and a cycle of adding a CRC code in units of blocks. Cyclic Redundancy Check.

In general, ARQ discards an error packet and decodes only the retransmitted packet.However, when HARQ technology is applied, an error packet is stored in a reception buffer. Since decoding is performed after combining the packet with various methods, it is possible to improve packet decoding performance during retransmission.

In a system using the High Speed Downlink Packet Access (HSDPA) method of UMTS, which is a European IMT-2000 standard, a UE may transmit a downlink data packet of a Node B. The 1-bit uplink response information (ACK / NACK) signal is transmitted.

As one of the E-DCH technologies applied to 3GPP WCDMA uplink, there is currently proposed base station scheduling (Node B scheduling). In the base station scheduling method, when the scheduler of the base station specifies a transmission rate, a transmission time, and the like for a packet transmitted from the terminal, the terminal transmits the packet accordingly. Rate scheduling is performed according to the content of the scheduling command transmitted by the base station to the terminal. Scheduling and time and rate scheduling have been proposed.

In the rate scheduling scheme, a base station controls a transmission rate of a packet for all terminals in a cell. The scheduling command used at this time may instruct to increase (UP), decrease (DOWN), or keep (KEEP) the transmission rate by a predetermined size. However, in general, it is not preferable to send a scheduling command including unnecessary information in terms of downlink resource efficiency because the setting values such as transmission power and transmission rate for a transmission packet use the same values as those applied to the first transmission. It may not.

The time and rate scheduling method controls the transmission time and the transmission speed of the packet for the terminals in the cell, so that only specific terminals can retransmit the packet at a specific rate at a specific time. The scheduling command may be sent in various ways (eg, periodical, event-triggered, random).

In addition, the base station scheduling method is divided into two methods according to whether or not to schedule the retransmission packet.

First, a Node B directly controls a retransmission packet using a scheduling command (SA), and the terminal transmits the retransmission packet according to the scheduling command. Scheduled retransmission. 1 is a view for explaining a conventional method (schedule retransmission method) for scheduling a retransmission packet. In this case, even if it is determined by the base station or RNC (Radio Network Controller) that the transmission or retransmission is no longer possible due to a congestion situation at the time of retransmission, the retransmission is started by the existing scheduling command at this time without special protocol for retransmission. Done. In this case, since there is no way to control retransmission at the physical layer (Layer 1) quickly, there is a problem in that coping with a congestion situation is delayed and the load on the system is increased.

The second method is a method in which the UE UE initiates retransmission by autonomous determination regardless of whether the Node B gives a scheduling command to the UE for the retransmission packet (autonomous retransmission). FIG. 2 is a diagram for describing autonomous retransmission. In this case, it is also assumed that the retransmission packet uses the set value (transmission power, TFCS, data rate, etc.) used for the first transmission. In this method, there is a problem that efficient resource management is difficult because retransmission occurs arbitrarily regardless of scheduling of the Node B scheduler.

In the first method (scheduled retransmission), the scheduling command may be designed to cope with the sudden system instability such as uplink congestion, noise increase, resource shortage, and the like. That is, it is possible by designing the scheduling command to include a function corresponding to the transmission permission / prohibition information proposed in the present invention.

In the second method (autonomous retransmission), since the UE determines the retransmission itself, it is difficult to correctly deal with abnormal situations such as uplink traffic congestion. That is, the attempt of autonomous retransmission of the terminal causes an unexpected RoT (Rise over Thermal) in the base station, thereby reducing the efficiency of resource management of the base station scheduler (scheduler). In order to strictly manage the noise rise to not exceed the threshold, it is possible only if there is little unexpected interference as mentioned above or the noise rise margin is very large. Therefore, there is a problem that the base station scheduler gain is reduced without proper management of retransmission.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above, and an object of the present invention is to determine whether to allow retransmission of packets in consideration of channel conditions at a receiving side in a wireless packet communication system employing a HARQ scheme. The present invention provides a method of controlling data packet retransmission in a wireless packet communication system that can improve efficiency of the entire system by mitigating a problem such as occurrence of unnecessary congestion in a channel or lack of resources by determining and informing a transmitting side. In particular, the present invention relates to a data packet retransmission control method in a wireless packet communication system using autonomous retransmission as a retransmission control method.

Summary of the Invention

A data packet retransmission control method according to the present invention comprises: receiving a data packet transmitted from a terminal in a wireless packet communication system; Determining whether a transmission error exists in the data packet; Determining a channel condition when there is a transmission error in the data packet; And packet retransmission control information which is information on whether to allow or prohibit retransmission of the data packet to a signal (NACK) requesting retransmission of the data packet to the terminal due to a transmission error of the data packet according to the channel condition. And additionally transmitting.

In the present invention, the packet retransmission control information is transmitted in addition to a signal (NACK) for requesting retransmission of a data packet, and the channel condition is determined based on Rise over Thermal (RoT) relative to thermal noise power. It is characterized by.

Example

Hereinafter, exemplary embodiments of data packet retransmission control methods in a wireless packet communication system according to the present invention will be described with reference to the accompanying drawings. Although the preferred embodiment of the present invention has been described with reference to Enhanced Uplink Dedicated CHannel (E-DCH), which is discussed in the 3rd Generation Partnership Project (3GPP) WCDMA system, the present invention is an arbitrary scheme using Node B scheduler and HARQ scheme. The present invention may also be applicable to a wireless packet communication system.

Figure 3 is a flow chart of the procedure of one preferred embodiment according to the present invention. The base station Node B receives the data packet transmitted by the terminal UE through the E-DCH [S31]. The base station Node B decodes the received data packet [S32] to determine whether there is a transmission error in the data packet [S33]. If there is no transmission error in the received data packet, the terminal transmits a data packet acknowledgment signal (ACK) to the terminal [S34] and returns to a reception wait state of the next data packet to be transmitted.

If there is a transmission error in the received data packet, the channel status at the present time is determined [S35]. In this case, the channel condition refers to determining whether a situation in which the UE is difficult to retransmit the data packet occurs in the E-DCH channel due to a lack of radio resources or an increase in access terminal.

The channel situation may be determined in various ways. One of them is rise over thermal (RoT). RoT is the received signal power compared to the thermal noise power at the base station. Specifically, RoT means a ratio of the total received power received from the antenna at the base station receiving end to the self thermal noise power of the base station system. Therefore, the channel state can be determined according to whether the RoT is above or below a predetermined threshold. In addition to the RoT, the channel state may be determined based on the total reception strength or power strength of the signal received at the base station.

According to the channel state determination result, information on whether to allow or prohibit retransmission of the packet (hereinafter referred to as "retransmission packet control information") is transmitted to the terminal [S36]. In other words, when it is determined that the packet has a negative effect on the system such as blocking, lowering throughput, lowering transmission rate, increasing error, and increasing retransmission due to retransmission of the packet (when RoT is above a threshold value), information that prohibits retransmission of the packet Is transmitted to the terminal, otherwise (in case RoT is less than the threshold value), information in the sense of allowing retransmission of the packet is transmitted.

As a specific method of transmitting the retransmission packet control information to the terminal, various methods can be considered. In the present invention, the base station is autonomous retransmission when the base station autonomously retransmits regardless of whether the base station schedules the retransmission packet. In the present invention, a method for transmitting packet retransmission control information is added to a signal (NACK) for requesting retransmission of a packet to a terminal. 4 is a diagram for explaining this.

In FIG. 4, since the UE UE autonomously determines retransmission regardless of whether the base station Node B schedules the retransmission packet, a signal for requesting retransmission to the terminal due to a reception error of a data packet ( NACK) is added to the retransmission packet control information and transmitted.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

When the scheduling method of the uplink retransmission packet proposed by the present invention is applied to 3GPP WCDMA E-DCH transmission, problems that may occur when scheduling of the retransmission packet is not performed (congestion, noise increase, resource shortage, etc.) It can be supplemented or solved, resulting in an increase in overall system efficiency.

1 is a diagram for explaining a conventional method (schedule retransmission method) for scheduling a retransmission packet.

2 is a diagram for explaining a conventional method (autonomous retransmission method) that does not schedule retransmission.

3 is a process flow diagram of one preferred embodiment according to the present invention.

4 is an explanatory diagram of a preferred embodiment according to the present invention.

Claims (4)

In a wireless packet communication system, Receiving a data packet transmitted from a terminal; Determining whether a transmission error exists in the data packet; Determining a channel condition when there is a transmission error in the data packet; And According to the channel condition, packet retransmission control information, which is information on whether to allow or prohibit retransmission of the data packet, is added to a signal (NACK) requesting retransmission of the data packet to the terminal due to a transmission error of the data packet. Retransmission control method comprising the step of transmitting the data packet. The method of claim 1, The channel condition is a data packet retransmission control method characterized in that it is determined based on the received signal power (RoT: Rise over Thermal) relative to the thermal noise power. The method of claim 2, And transmitting control information for prohibiting packet retransmission when the RoT is equal to or greater than a predetermined threshold, and transmitting control information for prohibiting packet retransmission when the RoT is less than the predetermined threshold. According to the first, And the channel is Enhanced Uplink Dedicated CHannel (E-DCH).