Future microcellular systems will require distributed network control. A packet-switched network is particularly suitable for this requirement. Moreover, packet switching naturally accommodates speech activity detection to improve Vation-ALOHA protocol for packet speech transmission from wireless terminals to a base station. Because PRMA is a statistical multiplexer, the channel becomes congested when to0 many terminals are active. Voice packets require prompt delivery, and therefore PRMA responds to congestion by dropping packets ooint analvsis is used to evaluate system behavior. We derive the A * System Goodman et al. proposed packet reservation multiple access (PRMA) for packet voice terminals in cellular systems nals Since conversational speech produces multipacket messages during talkspurts. The present paper presents an analysis of PRMA, a modification of R-ALOHA for indoor microcellular applications. This particular application implies that cation implies that delayed Packets are dropped. These modi-capacity. Packet reservation multiple access (PRMA) is a Reser-14i. A reservation protocol is appropriate for speech termidelayed beyond a specified time limit. In this paper, equilibrium the are The speech appliprobability of packet dropping given the number of simultaneous conversations. We also establish conditions for system stability and efficiency. Numerical calculations based on the theory show close agreement with computer simulations. They also provide valuable guides to system design. For a particular example we find that speech activity detection permits 37 speech terminals to share a PRMA channel with 20 slots per frame, with a packet dropping probability of less than 1%.

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We propose a technique to measure channel quality in terms of signal-to-interference plus noise ratio (SINR) for the transmission of signals over fading channels. The Euclidean distance (ED) metric, associated with the decoded information sequence or a suitable modification thereof, is used as a channel quality measure. Simulations show that the filtered or averaged metric is a reliable channel quality measure which remains consistent across different coded modulation schemes and at different mobile speeds. The average scaled ED metric can be mapped to the SINR per symbol. We propose the use of this SINR estimate for data rate adaptation, in addition to mobile assisted handoff (MAHO) and power control. We particularly focus on data rate adaptation and propose a set of coded modulation schemes which utilize the SINR estimate to adapt between modulations, thus improving data throughput. Simulation results show that the proposed metric works well across the entire range of Dopplers to provide near-optimal rate adaptation to average SINR. This method of adaptation averages out short-term variations due to Rayleigh fading and adapts to the long-term effects such as shadowing. At low Dopplers, the metric can track Rayleigh fading and match the rate to a short-term average of the SINR, thus further increasing throughput.

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