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Chapter 8Final conclusions pApplications with QoS 80-200High priority applications 201-255In this research, most of the analysis focused on 3 Mbps and 6 Mbps upstream channels.An interesting issue is to analyse the performance when applications that demand higherbandwidth requirements are delivered using a 12 Mbps channel.Another important topic that needs to be addressed as future work is quality of servicein the downstream direction. The mapping of up to eight upstream channels onto asingle downstream channel raises the issue of congestion in the downstream too. For thetransmission of traffic that does not originate in the CATV network, for example trafficcoming from either the Internet, PSTN or other CATV network via the router/ATMswitch attached to the INA, an efficient scheduler will be required in order to prioritiseand police traffic as well as maintain maximum link utilisation in the downstreamchannel.Finally, the work presented in this dissertation is highly relevant to emerging fixed,mobile and satellite architectures [20]. Fixed wireless architectures have the sameaccess topology as CATV networks. Figure 8.2 presents three different configurationsof CATV networks with satellite, terrestrial or HFC architectures. The spectrum isdivided into different unidirectional channels for the upstream and downstreamdirection. The major difference is the physical interface. In wireless architectures, thesignals propagate through the air while in CATV networks either coax or optic fibrelinks or a combination of both is used for transmissions. The physical interface wouldbe significantly different but the MAC would be identical.CATV networks have been considered as the ideal backbone network architecture forPersonal Communications Service (PCS), as illustrated in Figure 8.2c, [50]. Thebroadcast nature of CATV networks significantly simplifies the hand-off mechanism ofmobile stations thus reducing cost and complexity at both the base station and thetelecom switch.8-20