AAL2分组话音系统信元装配时延的研究
Study on the cell assembly delay in the AAL2 packet voice system
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摘要: 该文研究将AAL2分组填入ATM信元载荷域时的信元装配时延。得出结论:ATM信元装配时延由话音源编码速率、分组占用时长以及接入AAL2分组话音复接器中的话音源个数确定。当话音源编码速率较低,接入AAL2分组话音复接器中的话音源数较小时,信元装配时延可能很大,需要设置定时器以限制信元装配时延,例如当话音源编码速率为8kb/s时,可令定时器的取值为3ms;当话音源编码速率为32kb/s时,若分组占用时长为5ms,一般无需使用定时器。Abstract: This paper investigates the issues related to the cell assembly delay induced by filling AAL2 packets from different users into the payloads of ATM cells. A conclusion is drawn that the cell assembly delay is affected by the voice coding rate, voice packetization interval and the number of voice sources multiplexed. When the number of voice sources multiplexed is small and voice is compressed to a low bit rate, a timer is needed to limit the cell assembly delay. Timer can be set at 3ms if voice is compressed using 8kb/s G.729. When voice is compressed using 32kb/s G.726 with a voice packetization interval of 5ms, it is unnecessary to use the timer.
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K. Sriram, T. G. Lyons, Y. T. Wang, Anomalies due to delay and loss in AAL2 packet voice systems: Performance models and methods of mitigation, IEEE J. on Selected Areas in Communications, 1999, 17(1), 4-17.[2]K. Sriram, Y. T. Wang, Voice over ATM using AAL2 and bit dropping: Performance and call admission control, IEEE J. on Selected Areas in Communications, 1999, 17(1), 18-28.[3]G. Eneroth, et al., Applying ATM/AAL2 as switching technology in third-generation mobile access networks, IEEE Communications Magazine, 1999, 37(6), 112-122.[4]af-vtoa-0113.000, ATM trunking using AAL2 for narrowband services, Feb. 1999.[5]ITU-T Recommendation I.363.2, B-ISDN ATM adaptation layer type 2 specification, Feb. 1997. -
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