DL UL DL UL Initial packet a=0, a=0, Uniform Uniform arrival (ms) b=20 b=20 Packet arrival time Exponential Exponential (ms) Packet size Bimodal Normal (Byte) Normal Evaluation metrics MAC throughput Latency VoIP Traffic Model VoIP service uses the internet protocols to delivery real-time voice packets across networks. The VoIP traffic comprises periods of active talking and silence, as shown in Figure 1. It can be considered as a simple 2-state noice activity Markov model as shown in Figure 2. Figure 1: VoIP traffic profile Figure 2: Two-state voice activeity model For VoIP traffic, the VoIP user will always be in either the silence state (State 0) or active talking state (State 1), assuming that the probability of transitioning from state 0 to state 1 is and the reciprocal transition from state 1 a, to state 0 is Hence, the probability of staying in state 0 is 1-a and in state 1 is 1-b. The state update is assumed b. to be done at the speech encoder frame rate where is the encoder frame duration whose typical value is R=1/T, T 20ms for active talking state and 160ms for silence state, respectively. VoIP packets are generated at time intervals where is the network packet arrival delay jitter, and is the encoder frame index. During the iT+τ, i τ active state, voice packets with fixed size are generated at these time intervals, while the model is updated at regular frame intervals [1]. The detailed parameters of the VoIP traffic model are specified in Table 1. The rate of voice source assumes 12.2 kbps with a 50% voice activity factor. The payload size of active talking state and silence state are 33 byte and 7
DL UL DL UL Initial packet arrival (ms) Uniform Uniform a=0, b=20 a=0, b=20 Packet arrival time (ms) Exponential Exponential Packet size (Byte) Bimodal Normal Normal Evaluation metrics MAC throughput Latency VoIP Traffic Model VoIP service uses the internet protocols to delivery real-time voice packets across networks. The VoIP traffic comprises periods of active talking and silence, as shown in Figure 1. It can be considered as a simple 2-state noice activity Markov model as shown in Figure 2. Figure 1: VoIP traffic profile Figure 2: Two-state voice activeity model For VoIP traffic, the VoIP user will always be in either the silence state (State 0) or active talking state (State 1), assuming that the probability of transitioning from state 0 to state 1 is a, and the reciprocal transition from state 1 to state 0 is b. Hence, the probability of staying in state 0 is 1-a and in state 1 is 1-b. The state update is assumed to be done at the speech encoder frame rate R=1/T, where T is the encoder frame duration whose typical value is 20ms for active talking state and 160ms for silence state, respectively. VoIP packets are generated at time intervals iT+τ, where τ is the network packet arrival delay jitter, and i is the encoder frame index. During the active state, voice packets with fixed size are generated at these time intervals, while the model is updated at regular frame intervals [1]. The detailed parameters of the VoIP traffic model are specified in Table 1. The rate of voice source assumes 12.2 kbps with a 50% voice activity factor. The payload size of active talking state and silence state are 33 byte and 7
11-14-0571-06-00ax-evaluation-methodology.docx