KR20020069991A - Apparatus and method for communicating radio link protocol in mobile communication system - Google Patents

Abstract

PURPOSE: An RLP(Radio Link Protocol) communication apparatus and method in a mobile communication system is provided to quickly guide the expiration of a timer and minimize the delay of data transmitted to an upper layer by increasing a retransmission timer when an eraser frame is received while the retransmission timer is driven. CONSTITUTION: If a frame is received(601), an RLP controller checks whether a retransmission timer is set(603). If the retransmission timer is set, the RLP controller checks whether a current retransmission round is a last retransmission round(605). If the current retransmission round is not the last retransmission round, the RLP controller judges a kind of the received RLP frame(607). The RLP controller checks whether the received frame is one among an eraser frame, an idle frame, and a data frame(609). If the received frame is one among the eraser frame, the idle frame, and the data frame, the RLP controller increases the retransmission timer(611) and checks whether the increased retransmission timer expires(613). If the increased retransmission timer expires, the RLP controller increases the counter of the retransmission round(615) and resets the retransmission timer for performing a next retransmission round(617).

Description

Radio link protocol communication apparatus and method in mobile communication system {APPARATUS AND METHOD FOR COMMUNICATING RADIO LINK PROTOCOL IN MOBILE COMMUNICATION SYSTEM}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a code division multiple access (hereinafter referred to as CDMA) mobile communication system. In particular, a radio link supporting a discontinuous transmission mode for efficient transmission of data in a wireless environment. Protocol (Radio Link Protocol; RLP) communication apparatus and method.

In general, the code division multiple access mobile communication system has evolved from the IS-95 standard, which mainly focuses on voice, to the cdma2000 standard, which enables high-speed data transmission as well as voice. According to the cdma2000 standard, services such as high quality voice, moving picture, and internet search are possible. Since the existing CDMA mobile communication system is mainly for voice service, the maximum data transfer rate was only 9.6 kbps or 14.4 kbps. However, in the cdma2000 standard, a maximum data rate of up to 2 Mbps is possible, so that 138 times as much data as a conventional CDMA mobile communication system can be transmitted at once.

In the CDMA mobile communication system, the data corruption in the wireless environment is solved using a radio link protocol. The radio link protocol is based on a frame having a length of 20 ms at a transmission rate of 9.6 kbps or 14.4 kbps or less.

On the other hand, the radio link protocol uses NAK based on the Automatic Repeat Request (ARQ) method to recover an error occurring on the air channel. The NAK frame requesting retransmission of the frame is transmitted to the transmitting RLP, and the receiving RLP transmits the requested frame. Here, the receiving end drives the retransmission timer waiting for reception of the frame after transmitting the NAK. This retransmission timer is set to a value obtained by adding a predetermined excess to a transmission delay (RTD: Round Trip Delay) obtained during the initialization of the RLP. This is the time it takes for the retransmission frame to be received after transmitting the NAK and must be at least greater than or equal to the RTD. Otherwise, the timer expires before the corresponding retransmission frame is received, and may perform another operation, resulting in the failure to receive the retransmission frame. On the contrary, if the timer value is set too large, it takes too much time until the timer expires, which requires a large amount of buffer, and delays the data transferred to the upper level, thereby slowing down the processing speed of the upper application. Let's go. In other words, finding the appropriate timer value is important. Hereinafter, the RLP operation according to the prior art will be described.

First, when the receiving end RLP finds a frame that has not been received, it immediately sends a NAK and starts a retransmission timer. The retransmission timer is incremented when an idle frame, data frame is received. The control frame, the retransmission frame, and the erasure frame are not incremented when received. If the retransmission frame is broken on the air channel, it is classified as an erasure frame, even though the retransmission timer is not increased. This case is illustrated in FIG. 2. As shown, the retransmission timer stops without increasing when an erasure frame generated by noise in the air channel is received. In this case, it is necessary to request retransmission to the transmitting RLP so that the retransmission frame can be received and transmitted to a higher layer in a faster time. In addition, since the erasure frame does not increase the retransmission timer upon reception, the retransmission timer is not only delayed. This caused a delay in the data delivered to the upper layers. This has the problem of lowering the processing speed of the application.

Accordingly, an object of the present invention is to provide a radio link protocol communication apparatus and method for increasing a timer even when an erasure frame is received while driving a retransmission timer to solve the above problem.

According to the first aspect of the present invention for achieving the above object, the radio link protocol communication method in the mobile communication system, the step of driving the retransmission timer after requesting the retransmission to the transmitting end RLP, and the type of the frame received when receiving the frame And determining the retransmission timer if the type of the received frame is an erasure frame.

According to a second aspect of the present invention, a radio link protocol communication method of a mobile communication system includes a step of driving a retransmission timer after requesting retransmission to a transmitting end RLP, and checking whether a retransmission round currently being performed is the last retransmission round when a frame is received. Increasing the retransmission timer when the erasure frame is received, if not in the last retransmission round, and not increasing the retransmission timer when the erasure frame is received in the last retransmission round. It characterized in that it comprises a process.

1 is a diagram illustrating an interface structure between a lion link protocol and a physical channel / multiplexer.

2 shows a diagram of a retransmission round according to the prior art.

3 shows a diagram of a retransmission round in accordance with the present invention.

4 is a view showing an error that may occur when the retransmission timer is increased for an erasure frame while the retransmission timer is being driven.

5 shows a diagram of a retransmission round that eliminates the error of FIG. 4 in accordance with the present invention.

6 is a diagram illustrating a processing procedure in a receiving end RLP according to an embodiment of the present invention.

7 is a diagram illustrating a processing procedure in a receiving end RLP according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, the present invention increases the timer even when the receiving end RLP transmits the NAK and receives an erasure frame when driving the retransmission timer in the radio link protocol. We will discuss ways to minimize delays. Basically, the following description takes the example of "three retransmission rounds". The "three retransmission rounds" means waiting to receive a retransmission frame until the retransmission timer expires three times.

1 illustrates an interface structure between a general Lion Link protocol and a physical channel / multiplexer. Referring to FIG. 2, two radio link protocols 211 and 212 exist on each side, and each radio link protocol exchanges RLP frames with respective physical channels and multiplexing devices 221 and 222. The physical channel / multiplexing apparatus 221 collects RLP frames when the RLP frames come from the upper radio link protocol 211 to form one physical channel frame, and transmits the created physical channel frame to the other side. The opposite physical channel / multiplexer 222 receives the transmitted physical channel frame, divides it into RLP frames, and forwards it to the higher radio link protocol 212. Transmitting the RLP frame from the higher radio link protocol to the opposite radio link protocol also goes through the same process.

First, the types of the frames described below are shown in Table 1 below.

frame meaning CONTROL frame The SYNC, SYNC / ACK, ACK, and NAK frames are included. Here, the SYNC, SYNC / ACK, and ACK frames are used for RLP initialization, and the NAK frame is a frame requiring retransmission. Data frames In the RLP, data of a higher layer is transmitted. The data frame includes a NEW data frame and a retransmission frame. Idle frame If there is no data of upper layer to transmit, this frame is transmitted. Eraser frame The frame is broken due to noise on the air channel.

3 shows a diagram of a retransmission round in accordance with the present invention. In the drawing, "D" represents a new data frame, "R" represents a retransmission frame, "R '" represents a retransmission frame to which data other than the retransmission requested data is transmitted, and "N" represents a NAK frame. , "R-Timer" indicates a retransmission timer.

As shown in FIG. 3, even when the retransmission frame R is broken on the air channel and an erasure frame is received, the retransmission timer of the receiving end RLP is increased to prevent the expiration of the timer. However, when performing RLP communication as shown in FIG. 3, if the erasure frame received at the receiving end RLP is a broken NAK frame or another retransmitting frame transmitted at the transmitting end RLP (see FIG. 4), the retransmission timer is increased at the receiving end RLP. It is not possible to receive the retransmission frame without transmitting another NAK. In this case, the retransmission timer is increased, which causes unnecessary processing to send the NAK again, and in the worst case, the retransmission round is terminated without receiving the requested retransmission frame. It may be.

However, as shown in the simulation results of Table 2 below, only 8.5% of NAK frames or retransmission frames are transmitted. Here, the probability is further reduced except for the case of the retransmission frame. In addition, since the retransmission timer value is implemented by adding an extra value to the RTD when the RLP is implemented, the probability of occurrence of the situation as shown in FIG. 4 is further reduced. Therefore, the retransmission round as shown in FIG. 3 may be driven without considering such a situation.

Test conditions FER = 2% Mux option = 0x905 (FCH 9.6 kbps, SCH 19.2 kbps) Test time = 10,000 time slot Test result Number of transmitted NAK frames = 509 Number of NEW DATA frames transmitted = 9147 Number of retransmitted frames transmitted = 341 * probability that a NAK frame or retransmission frame will be sent = 8.5%

FIG. 5 shows a diagram of a retransmission round to eliminate possible errors as in FIG. 4 above. As shown, the last retransmission round does not increment the retransmission timer when this laser frame is received. This minimizes the delay in data passing to the upper layers and eliminates possible errors.

6 illustrates a processing procedure in a receiving end RLP according to an embodiment of the present invention.

Referring to FIG. 6, when a frame is received in step 611, the receiving RLP controller (hereinafter referred to as RLP controller) checks whether the retransmission timer is set in step 603. If the retransmission timer is set, the RLP controller proceeds to step 605. Otherwise, the RLP controller performs a corresponding function.

In step 605, the RLP controller checks whether the current retransmission round is the last retransmission round. If 3 retransmission rounds are used, the last retransmission round is the third round. Here, if the current retransmission round is the last round, the flow proceeds to step 701 of FIG. 7, and if not, the flow proceeds to step 607. The processing procedure performed in the last round will be described in detail later in the description of FIG.

On the other hand, if it is not the last retransmission round, the RLP controller determines the type of the received RLP frame in step 607. As shown in Table 1, there are a control frame, an idle frame, a data frame (including a retransmission frame) and an erasure frame. After determining the type of the received RLP frame, the RLP controller checks whether the received frame is one of an erasure frame, an idle frame and a data frame in step 609. If it is one of the three frames, the RLP controller proceeds to step 611 and, if otherwise, proceeds to step 619 to check whether the received frame is one of a control frame and a retransmission frame. If the control frame is one of the retransmission frames, the algorithm is terminated. Otherwise, the process returns to step 607 again to determine the type of the received frame and performs the following steps again.

If the received frame is one of an erasure, idle, and data frame, the RLP controller increments the retransmission timer in step 611 and checks whether the increased retransmission timer expires in step 613. If the retransmission timer expires, the RLP controller proceeds to step 615 to increment the counter of the retransmission round, and otherwise returns to step 601 to wait for reception of a frame.

The RL controller P increments the retransmission round counter, resets the retransmission timer for performing the next retransmission round in step 617, and terminates the algorithm. Strictly, after resetting the retransmission round, the RLP controller waits to receive a frame.

6 is a procedure performed in the retransmission round except the last round, and shows that the retransmission timer is increased when the erasure frame is received. As described above, the present invention can be implemented without considering the procedure of performing the last retransmission round (FIG. 7). Therefore, the last retransmission round may also be performed as shown in FIG. This is because the probability of receiving an erasure frame in which the NAK frame and the other retransmission frame are broken during the retransmission timer is very small.

7 is a flowchart illustrating a processing procedure of a receiver RLP according to an embodiment of the present invention. In particular, Figure 7 shows the procedure of performing the last retransmission round to eliminate even the small probability but possible errors described above.

Referring to FIG. 7, the RLP controller determines the type of the received RLP frame in step 701. As shown in Table 1, there are a control frame, an idle frame, a data frame (including a retransmission frame) and an erasure frame. After determining the type of the received RLP frame, the RLP controller checks whether the received frame is one of an idle frame and a data frame in step 703. If it is one of the two frames, the RLP controller proceeds to step 705, otherwise proceeds to step 711 to check whether the received frame is one of an erasure frame, a control frame and a retransmission frame. If the one of the three frames is one, the algorithm is terminated. Otherwise, the process returns to step 701 to determine the type of the received frame and performs the following steps again.

If the received frame is one of an idle frame and a data frame, the RLP controller increments the retransmission timer in step 7045 and checks whether the increased retransmission timer expires in step 707. If the retransmission timer expires, the RLP controller proceeds to step 709 where the current retransmission round is the last retransmission round and completely releases the retransmission timer and ends the present algorithm.

7 is a procedure performed in the last retransmission round, and shows that the retransmission timer is not increased when an erasure frame is received.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

As described above, the present invention can minimize the delay of data transmitted to the upper layer by effectively operating the retransmission timer in the RLP communication device. That is, even if an erasure frame is received during the operation of the retransmission timer at the RLP receiver, the retransmission timer is increased to quickly induce the expiration of the timer, thereby minimizing the delay of data transmitted to the upper layer. This has the advantage of improving the processing speed of the application.

Claims (8)

A radio link protocol communication apparatus in a mobile communication system, A retransmission timer driven after NAk frame transmission requesting retransmission to a transmitter RLP; And an RLP controller for increasing the retransmission timer when an erasure frame is received while the retransmission timer is being driven. The method of claim 1, And the RLP controller increments the retransmission timer when the received frame is one of an idle frame and a data frame. The method of claim 1, The RLP controller does not increment the retransmission timer if the received frame is one of a control frame and a retransmission frame. A radio link protocol communication apparatus in a mobile communication system, A retransmission timer driven after the transmission of the NAK frame requesting retransmission to the transmitter RLP; And an RLP controller for increasing the retransmission timer upon receiving the erasure frame during the retransmission round except for the last retransmission round. In the radio link protocol communication method in a mobile communication system, Driving a retransmission timer after requesting retransmission to a transmitter RLP; Determining the type of the received frame upon receiving the frame; Increasing the retransmission timer when the type of the received frame is an erasure frame. The method of claim 5, Increasing the retransmission round counter when the retransmission timer expires, and resetting the retransmission timer to wait for reception of a frame. The method of claim 5, Incrementing the retransmission timer if the received frame is one of an idle frame and a data frame; If the received frame is one of a control frame and a retransmission frame, further comprising not increasing the retransmission timer. In the radio link protocol communication method of a mobile communication system, Driving a retransmission timer after requesting retransmission to a transmitter RLP; Checking whether a retransmission round currently being executed is the last retransmission round when a frame is received; Increasing the retransmission timer when the erasure frame is received, if not in the last retransmission round; And in the case of the last retransmission round, not increasing the retransmission timer when receiving the erasure frame.