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Chapter 6Optimisation of CRA using adaptive CSAs pStation 25 transmits successfully and then waits until the headend grants its request,which is at MCI 11. This is because the headend, at this point, was serving requestsfrom other stations not shown. Station 8 collides two more times at MCI 3 (with station1) and MCI 8 (with station 11). In MCI 16, station 8 transmits a successful request,which is granted in MCI 20. Station 43 transmits successfully at MCI 4 and its requestis served in MCI 13. This algorithm required 16 signalling frames (48 ms) to resolve acollision among three stations.Lets us now analyse the case when the splitting tree algorithm is utilised. At MCI 1,there are also three stations that collide (stations 28, 11 and 4). At MCI 3, the headendallocates one more CS (in the first position of the MCI), which is used only among thecollided stations. So, all stations transmit again after two MCIs once the collision hasbeen detected. At this moment, station 4 transmits a successful request using the firstminislot of this additional CS (scheduled for MCI 12). Station 11 and 28 collide againusing the third minislot. It is at MCI 5 when they transmit successfully and servedcompletely at MCI 15.Generally, the splitting tree algorithm is much more efficient because when a collisionhappens (e.g. between two or even three stations), it takes on average from 2 to 5 MCIcycles to resolve, whilst the exponential backoff algorithm takes from 2 to 16 (and sometimes longer). Another advantage of the splitting tree algorithm is that it requires fewercontention slots than the exponential backoff algorithm in order to transmit successfulrequests. From Figure 6.20, we can appreciate that the number of contention slots usedby the splitting tree algorithm ranged from 2 to 3 CSs, in comparison to 3 to 7 CSsrequired by the exponential backoff algorithm in each MCI cycle.The same performance analysis and a comparison between these two contentionresolutions algorithms, for an upstream channel of 6.176 Mbps, has been reported in[86] and summarised in Figure E.1 of Appendix E.6-28