GPRS for Mobile Internet
This book helps you understand how the GPRS system is used as a major technology building block for the emerging mobile Internet; the book
also provides you with detailed coverage of a wide range of important topics.
TABLE OF CONTENTS GPRS for Mobile Internet
5.6: RLC
5.6 RLC
The RLC layer provides a reliable link between the BSS and the MS, allowing transmission of RLC blocks in acknowledged or unacknowledged mode during an uplink or downlink TBF. The RLC layer is responsible for the segmentation of LLC frames into RLC data blocks. Before being transmitted on the radio interface, these blocks are numbered by the transmitter so that the receiver is able to detect undecoded data blocks and request their selective retransmission. When all the RLC data blocks belonging to one LLC frame have been received, the RLC layer at the receiver side ensures the reassembly of the LLC frame.
The RLC layer also provides a similar mechanism for the transmission of RLC/MAC control messages from the BSS to the mobile.
5.6.1 Transmission Modes
The RLC automatic repeat request (ARQ) functions support two modes of operation:
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RLC acknowledged mode;
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RLC unacknowledged mode.
In RLC acknowledged mode, the RLC ensures the selective retransmission of RLC data blocks that have not been correctly decoded by the receiver. This mode is used to achieve a high reliability in LLC PDU sending. In RLC unacknowledged mode, RLC data blocks that have not been correctly decoded are not retransmitted by the sending entity. This mode is used for applications that are tolerant of error and that request a constant throughput, such as streaming applications (video or audio streaming).
In uplink, the requested RLC mode is indicated in the PACKET RESOURCE REQUEST message in case of two-phase access and is by...
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