VCAT synchroniser - reduction of buffer size in VCAT enabled next generation SDH networks

Abstract

Next generation synchronous digital hierarchy is a popular transport technology for integrated voice and data communication. It typically uses virtual concatenation (VCAT) for dynamic bandwidth management. This paper discusses different issues related to VCAT. Paper mainly focuses on the differential delay that occurs as all the VCAT members traverse through different path to reach the destination. These streams do not reach the destination at the same time and thus incur differential delay. Buffers are provided at the receiver to compensate for differential delay. The larger the differential delay, the larger is the buffer requirement at the receiver. Differential delay/buffer size can be reduced by proper routing of the traffic. In the existing receiver circuits, all incoming streams are allocated the same buffer space, specifying the maximum differential delay it can compensate. This results in a large buffer requirement. To overcome this limitation, this paper proposes a novel scheme of allocating buffers dynamically to all the streams. To achieve this, differential delay between the streams is computed by extracting the multiframe indicator and then as per the delay, each stream is allocated buffer space from a common buffer pool. The common buffer pool consists of a number of buffer modules. The size of each module is equal to the frame size for the specific virtual channel, and the size of the common buffer pool is architecture dependent. Sixty per cent reduction in the buffer requirement is predicted using this scheme, at the receiver. For functional verification of the concept, a hardware circuit is designed. Copyright © 2011 John Wiley & Sons, Ltd.