tailieunhanh - Nhiều giao thức truy cập đối với truyền thông di động P7

MD PRMA WITH LOAD-BASED ACCESS CONTROL Chapter 5 provided descriptions of channel and traffic models used for investigations on the MD PRMA protocol, which was defined in detail in Chapter 6. Starting with this chapter, and continuing in Chapters 8 and 9, the outcomes of our research efforts on MD PRMA will be discussed. In this chapter, the focus is on load-based access control (for MD PRMA), a technique adopted to protect reservation-mode users from multiple access interference generated by contending users. Only voice traffic is considered. | 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 7 MD PRMA WITH LOAD-BASED ACCESS CONTROL Chapter 5 provided descriptions of channel and traffic models used for investigations on the MD PRMA protocol which was defined in detail in Chapter 6. Starting with this chapter and continuing in Chapters 8 and 9 the outcomes of our research efforts on MD PRMA will be discussed. In this chapter the focus is on load-based access control for MD PRMA a technique adopted to protect reservation-mode users from multiple access interference generated by contending users. Only voice traffic is considered. We are investigating an interferencelimited scenario where code-slots are not distinguished and random coding is assumed instead such that classical code-collisions cannot occur. However users may still suffer collisions due to excessive MAI which will cause packet erasure. With access control the overall packet-loss probability Ploss is composed of the packet-dropping ratio Pdrop and the packet-erasure rate Ppe. Load-based access control is applied to trade off packet dropping against packet erasure in a manner which minimises Ploss. To assess the benefits of load-based access control through so-called channel access functions CAFs several benchmarks are introduced. After a section defining the system considered both analytical and simulation results for the first benchmark a random access protocol are presented. The analysis is expanded to underpin some of the comments made in the introductory chapter of this book on multiplexing efficiency. Other benchmarks include one used as a reference to assess multiplexing efficiency and an ideal backlog-based access control scheme. Following considerations on channel access functions used for load-based access control performances of the different schemes considered are compared for various scenarios. .