tailieunhanh - Nhiều giao thức truy cập đối với truyền thông di động P8

MD PRMA ON CODE-TIME-SLOTS This chapter is concerned with MD PRMA on perfect-collision code-time-slot channels. The simple and abstract channel model used, representative for a blocking-limited system, allows one to consider an arbitrary number of code-slots E per time-slot, without having to worry about the spreading factor required to meet a certain packet erasure performance. In this framework, the scope of investigations can conveniently be extended to two extreme cases, namely only one code-slot per time-slot, but numerous time-slots N per TDMA frame, and only one time-slot per frame carrying numerous code-slots | Multiple Access Protocols for Mobile Communications GPRS UMTS and Beyond Alex Brand Hamid Aghvami Copyright 2002 John Wiley Sons Ltd ISBNs 0-471-49877-7 Hardback 0-470-84622-4 Electronic 8 MD PRMA ON CODE-TIME-SLOTS This chapter is concerned with MD PRMA on perfect-collision code-time-slot channels. The simple and abstract channel model used representative for a blocking-limited system allows one to consider an arbitrary number of code-slots E per time-slot without having to worry about the spreading factor required to meet a certain packet erasure performance. In this framework the scope of investigations can conveniently be extended to two extreme cases namely only one code-slot per time-slot but numerous time-slots N per TDMA frame and only one time-slot per frame carrying numerous code-slots. In the first case the CDMA feature is relinquished and MD PRMA degenerates to pure PRMA. In the second case the TDMA feature is relinquished. While this configuration and in fact also PRMA itself can simply be viewed as a special case of MD PRMA it actually corresponds to the Reservation-Code Multiple Access RCMA protocol proposed in Reference 35 . As in Chapter 7 only voice-traffic will be considered. However the focus shifts from load-based access control to fixed permission probabilities and backlog-based access control the latter in the shape of Bayesian broadcast . The performances of pure PRMA MD PRMA and RCMA will be compared all with the same number of resource units U N E. For MD PRMA with N 8 and E 8 . the original UTRA TD CDMA parameters the impact of acknowledgement delays and TDD operation on voice dropping performance is also studied. Furthermore the code-time-slot channel model is enhanced to account for multiple access interference MAI . In this scenario unlike the perfectcollision case load-based access control can make sense. Therefore on top of conventional Bayesian broadcast a scheme combining Bayesian broadcast with a channel access function is .