Time Division Multiple Access (TDMA) is an attractive technique for digital portable communications systems.However,the inherent delay associated with TDMA frame duration may require the use of echo cancelers and is a concern in the early introduction of voice services in the loop environment.A low-delay TDMA frame structure is proposed to support low-delay speech coders in a 2-wire loop environment without requiring echo cancelers.When incorporated into a superframe structure,the low-delay TDMA architecture can support medium-delay speech codecs and also lends flexibility to the system.The performance of a code for joint burst synchronization and error detection to support the shorter burst is analyzed.Guard time considerations and portable transmitter and receiver timing are also investigated for the shorter burst.The proposed frame structure is consistent with the advantages of TDMA technology.Avoiding echo cancelers makes TDMA even more acceptable for early deployment in the loop plant.
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