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Characteristics of Network Delay and Delay Jitter and its Effect on Voice over IP. Li Zheng, Liren Zhang, Dong Xu Communications, 2001. ICC 2001. IEEE International Conference. Outline. Introduction System Model Analysis Numerical Results Conclusion. Introduction.
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Characteristics of Network Delay and Delay Jitter and its Effect on Voice over IP Li Zheng, Liren Zhang, Dong Xu Communications, 2001. ICC 2001. IEEE International Conference Chin-Kai Wu, CS, NTHU
Outline • Introduction • System Model • Analysis • Numerical Results • Conclusion Chin-Kai Wu, CS, NTHU
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. Chin-Kai Wu, CS, NTHU
T-stream B-stream IP Router ( Non-blocking Switching ) 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 ] Chin-Kai Wu, CS, NTHU
α Generate a packet at a rate of λ per time slot ON OFF β Fraction of time in ON state System Model (Cont’d) • Background traffic (B-stream) • N independent Interrupt Bernoulli Process (IBP) • Each source is described by a two state Markov chain Average packet arrival rate from a single source Chin-Kai Wu, CS, NTHU
Analysis Queueing length at the end of k-th slot before the n-th packet from T-stream With condition that ik 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 Chin-Kai Wu, CS, NTHU
Analysis (Cont’d) Chin-Kai Wu, CS, NTHU
Analysis (Cont’d) • Delay jitter is defined as the variation in delay between the two consecutive packets Chin-Kai Wu, CS, NTHU
Analysis (Cont’d) Chin-Kai Wu, CS, NTHU
Results • Effect of traffic load Chin-Kai Wu, CS, NTHU
Results • Effect of traffic burstiness • Burstiness is defined as the ratio of peak rate and mean rate Chin-Kai Wu, CS, NTHU
Result • Effect of burst length Chin-Kai Wu, CS, NTHU
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. Chin-Kai Wu, CS, NTHU