KR20030066848A - Data block sending/receiving method for radio link control of general packet radio service - Google Patents

Abstract

PURPOSE: A data block transceiving method for an RNC(Radio Link Control) of a GPRS(General Packet Radio Service) system is provided to enable the RLC to easily recognize blocks actually received to a receiver and blocks failing in receiving and to retransmit unacknowledged data blocks, thereby minimizing data losses upon block transmission. CONSTITUTION: A MAC(Media Access Control) layer transmits a request to transmit reverse blocks to an RNC. If a mode is an operation mode in which both of an acknowledged response and a negative acknowledged response exist, a V(B) array is set as Pending_Ack and the negative acknowledged response block is sent. If a mode is not an operation mode in which both of an acknowledged response and a negative acknowledged response exist, whether window is installed is checked. If window is not stalled and no new data are transmitted, a Pending_Ack block is searched and sent, and then an absolute BSN(Block Sequence Number), a window_index, and a data_index are increased. If window is not stalled and no new data are transmitted, a Pending_Ack block is searched and sent, and if new data are transmitted, a search_index is set as a V(A) index, the new block is sent, a countdown value is increased and updated and a TFI(Transport Format Indicator) value is increased and updated.

Description

DATA BLOCK SENDING / RECEIVING METHOD FOR RADIO LINK CONTROL OF GENERAL PACKET RADIO SERVICE}

The present invention relates to a general packet radio service (GPRS) system, and more particularly, to a method of transmitting and receiving data blocks for radio link control (hereinafter referred to as RLC).

The Radio Link Control (RLC) layer is part of the RR sublayer in the General Packet Radio Service (GPRS) stack. The RLC layer is located below the LLC layer on the mobile station side and within the Broadcasting Satellite Service (BSS) on the network side. The mobile station and the network operate as transmitters and receivers depending on whether there is a reverse temporary block flow (TBF), a forward TBF, or both TBFs.

1 is a diagram illustrating an RLC position in a GPRS stack at a mobile station and a BSS.

Peer-to-pear interaction occurs between the RLC of the mobile station and the RLC of the BSS.

The main function of the RLC layer is to split the LLC PDU into RLC data blocks and then recombine the data blocks into LLC PDUs. After splitting into PDUs, the RLC sends these blocks to the Media Access Control (MAC) layer. In the approved transmission mode, the RLC waits from the network for acknowledgment for all data blocks it has transmitted. The RLC must retransmit both the unacknowledged data block or the data block waiting for acknowledgment. This is an important RLC function because retransmission of data blocks prevents data loss. The RLC continuously retransmits the data block until it receives an acknowledgment from the network so that it can receive all the data blocks transmitted from the network. However, if the block is outside the transfer window, the block transfer is aborted and the block state is changed to invalid in the V (B) array. RLC data block retransmission is only done in the approved mode of operation.

On both sides of the mobile station and the network, the RLC maintains an RLC Control Queue and an RLC Data Queue. All of the PDUs that the RLC receives from the LLC are divided into RLC data blocks. These blocks are stored in the RLC data queue and control messages are stored in the RLC control queue.

2 is a diagram illustrating an RLC data queue (reverse transmission) on the transmitting side.

3 is a diagram illustrating an RLC control queue (reverse transmission) on the transmitting side.

4 is a diagram illustrating an RLC receiver (forward reception), showing a combination of blocks received at a receiving end.

If there are RLC data blocks in the V (B) array that are not acknowledged (due to T3198 timer expiration) during transmission over TBF, the mobile station retransmits these blocks preferentially. Although there may be an RLC data block to be retransmitted with an acknowledgment status of PENDING_ACK, data blocks with an acknowledgment status of NACK are retransmitted. The blocks that are PENDING_ACK are not retransmitted. In particular, if the last data block to be transmitted is PENDING_ACK, there is a possibility of data loss, so it is not retransmitted.

Accordingly, an object of the present invention is to provide a method for preventing data loss during transmission or reception of an RLC block in a GPRS system.

The present invention for achieving the above object is a data block transmission and reception method for a radio link control of a general-purpose packet radio service system, the media access control layer transmits a predetermined request to transmit a reverse block to the radio link control, The first process of setting the V (B) array to Pending_Ack and transmitting a negative block if the operation mode includes both the positive and negative blocks, and if not the operation mode in which both the positive and negative blocks exist. A second process of checking whether the processor is stalled, and a third process of finding and sending a Pending_Ack if not stalled in the second process and transmitting new data, and then increasing an absolute value BSN, a window_index, and a data_index. And, if it was not stalled in the second process and no new data was transmitted, the Pending_Ack is found and transmitted. If the data is transmitted, a fourth process of setting the search_index to the V (A) index, transmitting the new block, increasing and updating the countdown value, and increasing and updating the tfi value, is characterized by the above-mentioned.

1 illustrates the RLC position in a GPRS stack at a mobile station and a BSS;

2 is a diagram illustrating an RLC data queue (reverse transmission) of a transmitting side according to the present invention.

3 is a diagram illustrating an RLC control queue (reverse transmission) on a transmitting side;

4 is a diagram illustrating an RLC receiver (forward reception), showing a combination of blocks received at a receiving end.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals have the same reference numerals as much as possible even if displayed on different drawings. In the following description, numerous specific details such as components of specific circuits are shown, which are provided to help a more general understanding of the present invention, and it is understood that the present invention may be practiced without these specific details. It will be self-evident to those of ordinary knowledge. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

According to the present invention, RLC data block retransmission is performed to prevent data loss during transmission. When the RLC sends data to the receiver in unauthorized mode, it is not known whether the transmitted data is actually received on the network. Therefore, in the acknowledgment mode, the RLC waits for acknowledgment of all data blocks transmitted. In addition, if the receiver does not properly receive the data block, the RLC does not receive acknowledgment for blocks that failed to receive. In this case, the RLC retransmits the blocks and waits for another acknowledgment. This ensures that the network receives all the blocks normally and consequently prevents data loss.

The RLC data block retransmission will be described in detail as follows.

On the transmitter side, the RLC maintains a V (B) array. It also has a V (A) index, a V (S) index, and a search_index. The V (B) array is only maintained when the RLC is operating in grant mode.

Wherein the V (B) index is an array of elements of a Sequence Number Space (hereinafter referred to as SNS) window size (hereinafter referred to as WS) containing the acknowledge status of previous RLC data blocks.

V (A) points to the index of the oldest block on the V (B) array that was not approved as an admission status variable. V (A) ranges from 0 to SNS-1. The V (A) value is updated with the corresponding value in the received packet reverse acknowledgment / negative message block bitmap.

The V (S) index indicates the serial number of the next RLC data block to be transmitted. The value ranges from 0 to SNS-1.

After transmitting a data block whose block sequence number (BSN) is V (S), the BSN is increased by one.

WS is the window size, 64 in GPRS.

SNS represents a serial number space in an RLC transmitter and an RLC receiver, which is 128 in GPRS.

The BSN is a block serial number and is an SNS as an absolute BSN module of each RLC data block in the TBF. The BSN is used to recombine the data blocks received at the receiver side.

The states of these blocks in the V (B) array are as follows.

A: approved

P: pending response (pending_Ack)

N: disapproval or negative response and invalid

The RLC reports and receives the reception status of blocks transmitted through a packet reverse acknowledgment / negative response message. This message contains a receive block bitmap indicating the reception status of the 64 blocks.

If the block is successfully received by the network, the value in the bitmap is set to 1, otherwise it is set to 0.

Upon receiving the bitmap, RLC determines the reception status of the V (B) array according to the bits of the bitmap.

If the bit is zero, the receive status is acknowledged in the V (B) array, and if it is zero, it is disapproved.

When the MAC requests the RLC to send a block of data, the RLC first examines the V (B) array to find the oldest data block whose state is negative. If such a block exists, it is sent to the network and its block state is set to Pending_Ack in the V (B) array.

If there is no block with a negative acknowledgment and the window is not stationary, ie 'V (S) <V (A) + WS modulo SNS', then the RLC sends a block with a BSN of V (S). The state of this block is set to Pending_Ack in the V (B) array. Increment the reverse window index and BSN count.

The V (S) count value is set to the next block to be transmitted.

If all new data blocks have been transferred and no block is waiting for transmission, RLC searches for the oldest block with Pending_Ack, retransmits the block, and then processes the next oldest block with Pending_Ack.

If there is no Pending_Ack block, the packet reverse dummy control block is transmitted to the network.

If the window is stationary, ie 'V (S) = V (A) + WS', the RLC does not send any new blocks to the network and only performs retransmissions.

RLC retrieves the oldest block with the state Pending_Ack. If no such block exists, this means that a retransmission index must be reset due to an error. The retransmission index is set to the same value as the V (A) index, and the block indicated by this V (A) index is transmitted. The state of this block in the V (B) array is Pending_Ack.

If a block with a status of Pending_Ack is found in the V (B) array, the block is transmitted.

Once all blocks with a status of Pending_Ack have been transmitted, retransmissions occur from the oldest block.

Retransmission of blocks that are NACKED or Pending_Ack lasts indefinitely. If a block falls out of the transmission window, the block state is set to invalid in the V (B) array and this block is not sent again.

The following is the RLC block transmission and reception control algorithm described above.

If op_mode = ACKED and NACKED _BLOCK present

{

set status in V (B) array to Pending_Ack

send the NACKED block

}

else

{

check if window is stalled

if window stalled = false and no new data to transmit

{

search for Pending_Acked block and send

}

else if window is not stalled but new data is available for transmission

{

set the search_index to vs_index and transmit the new block

add and update countdown value

add and update tfi value

}

increment absolute BSN

increase window_index

advance data_index

}

else

{if (op_mode = ACKED)

{

if (stalled = true)

{

find Pending_Ack data block

send the block

if Pending_Ack not found

{

set retransmission index to va_index

transmit the block

}

}

else (stalled = false)

{

find data block with status Pending_Ack

if (Pending_Ack not found)

{

send Packet Uplink Dummy Control block

}

else

{

send Pending_Ack block

}

increase window_index

}

}

}

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 defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention allows the RLC to easily know the blocks actually received and blocks that have not been received by the receiver. The RLC also retransmits unauthorized data blocks to minimize data loss during transmission. In addition, the RLC serves to determine the order of blocks to be transmitted to the MAC according to the state in the V (B) array to maintain the order of block transmission to facilitate the combination of these blocks.

Claims (2)

A data block transmission and reception method for radio link control of a general purpose packet radio service system, The medium access control layer sends a predetermined request to transmit a reverse block to radio link control, A first process of setting a V (B) array to Pending_Ack and transmitting a negative response block when the operation mode in which both the positive and negative response blocks exist exists; A second step of checking whether the window is stalled if the operation mode in which both the positive and negative blocks exist is present; A third step of finding and transmitting Pending_Ack if not stalled in the second process and not transmitting new data, and then increasing an absolute value BSN, a window_index, and a data_index; If not stalled in the second process and no new data is transmitted, Pending_Ack is found and transmitted.If new data is transmitted, the search_index is set to the V (A) index, the new block is transmitted, and the countdown value is set. Increasing and updating, and increasing and updating a tfi value. A data block transmission and reception method for radio link control of a general purpose packet radio service system, The medium access control layer sends a predetermined request to transmit a reverse block to radio link control, If the operation mode is affirmative and the window is stalled, find and transmit a Pending_Ack data block; if no Pending_Ack is found, set the retransmission index to the V (A) index and transmit the block; If the operation mode is affirmative and the window is not stalled, the data block with the Pending_Ack state is searched and the packet reverse dummy control block is transmitted if it is not found. Otherwise, the Pending_Ack block is transmitted and the window index is increased. How to feature.