AAL2分組話音系統(tǒng)信元裝配時(shí)延的研究
Study on the cell assembly delay in the AAL2 packet voice system
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摘要: 該文研究將AAL2分組填入ATM信元載荷域時(shí)的信元裝配時(shí)延。得出結(jié)論:ATM信元裝配時(shí)延由話音源編碼速率、分組占用時(shí)長(zhǎng)以及接入AAL2分組話音復(fù)接器中的話音源個(gè)數(shù)確定。當(dāng)話音源編碼速率較低,接入AAL2分組話音復(fù)接器中的話音源數(shù)較小時(shí),信元裝配時(shí)延可能很大,需要設(shè)置定時(shí)器以限制信元裝配時(shí)延,例如當(dāng)話音源編碼速率為8kb/s時(shí),可令定時(shí)器的取值為3ms;當(dāng)話音源編碼速率為32kb/s時(shí),若分組占用時(shí)長(zhǎng)為5ms,一般無(wú)需使用定時(shí)器。
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關(guān)鍵詞:
- 分組話音; ATM; AAL2; 服務(wù)質(zhì)量
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. -
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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