Link layer retransmission schemes for circuit-mode data over the CDMA physical channel |
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Authors: | Mooi Choo Chuah Bharat Doshi Subra Dravida Richard Ejzak Sanjiv Nanda |
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Institution: | (1) Bell Labs, Lucent Technologies, Holmdel, NJ 07733-3030, USA |
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Abstract: | In the last few years, wide-area data services over North American digital (TDMA and CDMA) cellular networks have been standardized.
The standards were developed under three primary constraints: (i) compatibility with existing land-line standards and systems,
(ii) compatibility with existing cellular physical layer standards that are optimized for voice, and (iii) market demands
for quick solutions. In particular, the IS-95 CDMA air interface standard permits multiplexing of primary traffic (e.g., voice or circuit data) and secondary traffic (e.g., packet data) or in-band signaling within the
same physical layer burst. In this paper, we describe two radio link protocols for circuit-mode data over IS-95. The first
protocol, Protocol S, relies on a single level of recovery and uses a flexible segmentation and recovery (FSAR) sublayer to efficiently pack data frames into multiplexed physical layer bursts. We next describe Protocol T, that consists of two levels of recovery. Protocol T has been standardized
for CDMA circuit-mode data as IS-99 (Telecommunications Industry Association, 1994). We provide performance comparisons of
the two protocols in terms of throughput, delay and recovery from fades. We find that the complexity of the two level recovery
mechanism can buy higher throughput through the reduced retransmission data unit size. However, the choice of TCP (and its
associated congestion control mechanism) as the upper layer of recovery on the link layer, leads to long fade recovery times
for Protocol T. The two approaches also have significant differences with respect to procedures and performance at handoff
and connection establishment.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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