| 摘要 |
Real-time media or multimedia services in 3GPP GSM/EDGE-compliant mobile radio networks call for reducing the actual latency of transmissions. Resources are assigned by the network to set up or reconfigure a TBF associated to the uplink/downlink transmission of radio blocks from/to an MS. A 5-bit "Coding" field is configured in the header of the involved RLC/MAC messages to select the transmitting/receiving window size. An additional signalling bit, also called scaling bit, is asserted/negated according to two opportunities offered by the new MAC protocol to properly select the window size. Thanks to the introduction of the scaling bit a subdivision of the time windows for type of services is made possible. Non real-time services, e.g. file transfer, avail of standard window sizes for MSs with multislot capability, as reported in 3GPP TS 44.060, V7.3.0 (2006-01), Release 7, subclause 9.1.9, for EGPRS TBFs. Delay-sensitive services, e.g. media or multimedia real-time transmissions, avail of new window sizes with scaled down values remapped to start from 1 to (maximum) 64 RLC/MAC blocks. The scaling bit is asserted or negated by BSC accordingly. Both peer entities comprised in a TBF are receiving the RLC/MAC messages with the proper setting of the scaling bit and the 5-bit coding IF; these entities decode the scaling bit and behave accordingly. The behaviour consists of either assuming the standard window size or scaled window size addressed by the same predetermined 5-bit "coding" information element (fig.3). |
