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Chapter 1Introduction pthat such solutions could not be applicable for the approximation of networks with afinite number of nodes. Therefore, infinite model results have limited relevance to finitesystems like the ones studies in this text.Particularly, the CATV protocols require approximations of both exponential backoffand splitting tree algorithms, which cannot be accurately modelled using these existinganalytical models due to the variable bandwidth assigned to the contention andreservation access regions from cycle to cycle. Therefore, the high degree ofcomplexity and the need for accurate results indicate the use of simulation techniquesfor the performance evaluation and optimisation of CATV protocols.1.2.3.3 Simulation modelling of CATV protocolsA number of papers reviewed in the literature have focused on simulation techniques toanalyse specific characteristics and performance issues of the IEEE 802.14 and DOCSISprotocols based on HFC networks in general, and as such might not be directlyapplicable to the DVB/DAVIC protocol. The issues addressed include ContentionResolution Algorithms (CRA), Contention Slot Allocators (CSA), scheduling andprioritised mechanisms, performance comparison of CATV protocols, registration afterpower up and performance evaluation and comparison of CATV protocols. Below is areview of the research performed in each field. Special attention is paid to issuesregarding CRAs, CSAs and prioritised mechanisms.a) Contention Resolution Algorithms (CRA): the research carried out in this field dealswith how best to optimise the time to resolve collisions between reservation requesttransmissions. Citta et al. [18], Sala et al. [95], [97] and Golmie et al. [40], [41]analysed and compared the performance of two CRAs (p-persistence and splittingtree algorithm), for the IEEE 802.14 protocol.The p-persistence algorithm resolves collisions by restricting the contending users totransmit in the next contention minislot with probability p. Thus, when a collisionoccurs only a portion of the users involved in the collision transmits in the nextcontention minislot and eventually the collision is resolved.1-9