Coexistence of legacy GPRS/EGPRS radio blocks and reduced transmit time interval (RTTI) radio blocks

摘要

RTTI (reduced transmit time interval) radio blocks (10 ms) and standard (legacy) RLC/MAC radio blocks (20 ms) currently used by the GSM/EDGE compliant mobile radio networks will have to live together soon. The proposed method allows the coexistence of RTTI and legacy GPRS/EGPRS radio blocks on the shared resources allocated for sustaining temporary block flows (TBF). Accordingly, the transmitting entity, either BTS or MS, sets the configuration of standard stealing flags usable for selecting a corresponding coding scheme (CS) foreseen for either GMSK or 8-PSK modulated radio blocks. Then it sets the logical values of a predetermined number of additional stealing flags from payload, shared among the bursts composing a RTTI radio block to be transmitted, in order to obtain a configuration of flags univocally associated to the format of said RTTI radio block. The receiving entity, either MS or BTS, decodes the configuration of the additional stealing flags for detecting the format of the actual RTTI radio block. The method is valid for GPRS CS1-4 (GMSK), EGPRS MCS1-4 (GMSK), and EGPRS MCS5-9 (8-PSK). In a variant valid for the EGPRS MCS1-4 only, the four extra stealing flags already standardized can be negated to discriminate the RTTI block. RTTI blocks are provided in "2-burst format" (1 TS of 2 TDMA frames) and "4-burst format" (2 TS of 2 TDMA frames). The method also accounts for the USF scheduling of RTTI radio blocks multiplexed with standard radio blocks (fig.3).