Wireless Ad Hoc and Sensor Networks

Congestion Control in ATM Networks and the Internet 135TABLE 3.6Comparison of TQ with New-Reno TCPCase III TQ New-Reno TCPPacket loss ratio 0 0.42%Transmission delay 0.6587 0.6643System power 6.9984 6.968scheme actively controls the packets by using packet losses and end-toenddelay while ensuring minimal retransmissions, which in turn, couldreduce delay and the system power. On the contrary, the New-Reno TCPdoes not limit losses and causes higher retransmission of packets. Resultscomparing TQ and New-Reno TCP are shown in Table 3.6.Example 3.6.4: FairnessHere we use 2 Data traffic sources (elastic traffic), 1 VBR traffic source,and 3 CBR traffic sources (inelastic). Elastic source rates are adjusted usingthe feedback, uk ( ), and fair share equation 3.20. The bottleneck buffer sizeis taken as 10 packets. For results presented in Figure 3.27 throughFigure 3.29, congestion was created by reducing the bandwidth of Link0as follows:Bandwidth of Link0 = 10 Mbps,0≤ t < 3sec;= 8 Mbps,3≤ t < 6sec;= 4 Mbps,6≤ t < 24sec;= 8 Mbps,= 10 Mbps,24 ≤ t < 27 sec;27 ≤ t.From Figure 3.31 and Figure 3.32, we can see that the PLR obtainedusing the TQ congestion control scheme is much better than the New-Reno TCP. In particular, from Figure 3.30, we can see that the throughputobtained using the TQ scheme is smoother than the New-Reno TCP. Thecomparison is given in Table 3.7. The transmission time for individualtraffic sources are shown in Table 3.8. From this table, we can say thatTCP cannot guarantee fair share to all the users, whereas TQ scheme canachieve fair share for the users by adjusting the elastic traffics rate (becausethese traffics can tolerate a wide range in delay and throughput) while