2001/11/29Chin-Kai Wu, CS, NTHU1 Characteristics of Network Delay and Delay Jitter and its Effect on Voice over IP Li Zheng, Liren Zhang, Dong Xu Communications, ICC IEEE International Conference

2001/11/29Chin-Kai Wu, CS, NTHU2 Outline Introduction System Model Analysis Numerical Results Conclusion

2001/11/29Chin-Kai Wu, CS, NTHU3 Introduction The queueing delay occurs due to multiplexing of packets. The goal of this paper is to study the statistics of delay and delay jitter by means of queueing transient solution. The main objective of this paper is to examine the relationship between the jitter and the characteristics of the background traffic, such as burstness, traffic load and bursty length.

2001/11/29Chin-Kai Wu, CS, NTHU4 System Model Non-blocking switch Designed traffic stream (T-stream) Inter-arrival time between two consecutive packets is independent Probability density f(k) = P[ inter-arrival time = k slots ] IP Router ( Non-blocking Switching ) T-stream B-stream

2001/11/29Chin-Kai Wu, CS, NTHU5 System Model (Cont’d) Background traffic (B-stream) N independent Interrupt Bernoulli Process (IBP) Each source is described by a two state Markov chain ONOFF α β Generate a packet at a rate of λ per time slot Fraction of time in ON state Average packet arrival rate from a single source

2001/11/29Chin-Kai Wu, CS, NTHU6 Analysis Queueing length at the end of k-th slot before the n-th packet from T-stream With condition that i k IBP processes in ON state at k-th slot from B-stream Number of packets from B-stream arrive at k-th slot together with (n+1)-th packet from T-stream, but served before it

2001/11/29Chin-Kai Wu, CS, NTHU7 Analysis (Cont’d)

2001/11/29Chin-Kai Wu, CS, NTHU8 Analysis (Cont’d) Delay jitter is defined as the variation in delay between the two consecutive packets

2001/11/29Chin-Kai Wu, CS, NTHU9 Analysis (Cont’d)

2001/11/29Chin-Kai Wu, CS, NTHU10 Results Effect of traffic load

2001/11/29Chin-Kai Wu, CS, NTHU11 Results Effect of traffic burstiness Burstiness is defined as the ratio of peak rate and mean rate

2001/11/29Chin-Kai Wu, CS, NTHU12 Result Effect of burst length

2001/11/29Chin-Kai Wu, CS, NTHU13 Conclusion A sequence of negative jitter (clustering) can result in packet loss, while positive jitter (dispersion) results in experiencing excessive delay. The jitter pdf provide information of individual jitters. For a given background traffic, when packet from a stream up to a large number, the transient queueing solution will close to steady state solution. To solve the jitter problem, a buffer of size much greater than one speech sample interval is needed at the receiver to remove the delay jitter.