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Chapter 4Simulation and analytical modelling pConsidering the above limitation, the formulation of an accurate analytical modelbecomes highly complex. Despite the high level of complexity associated with theproduction of an analytical model, a form of validation process is essential, even of thebasic functionality of the DVB/DAVIC protocol in order to verify correctness of thesimulation model.The analytical model formalised in Sections 4.4.1 to 4.4.3, address some questions thatconcern performance evaluation of a new protocol, (i.e. the knowledge of packet accessdelays and maximum system throughput achieved per stations). This is one of the firstissues that participant vendors and cable network manufacturers have to address, asthere is a significant delay associated with transmissions in the upstream channel thathas to do with the CRGC, even where there are not contending users in the cablenetwork. The analytical model presented in Section 4.4.1 and Section 4.4.2 is based inthe following reasonable assumptions:• The bandwidth of the F-channel for fixed-rate access is not considered. This is anadvanced functionality included in the second version of EuroModems [36].• In accordance with the DVB/PDAVIC protocol, at least one MCI frame should betransmitted in the 3 ms period. We consider that the DVB/DAVIC transmits 4 MCIframes per 3 ms period. Thus the number of slots described per MCI frames is of 9slots, with a 6.17 Mbps upstream channel.The following formulation addresses issues of mean packet access delay and maximumsystem throughput achieved for a single upstream channel. The quantities andabbreviations that will be used throughout the analysis have been defined in Table 4.1.4-17