100Mbps Ethernet data transmission over SDH networks using Cross Virtual Concatenation

Cross Virtual Concatenation is the new technique proposed for bandwidth efficient transmission of data over SDH networks. SDH networks came into existence for reliable voice transmission. As the demand of data traffic grew in wide area networks, new technologies were developed and standardized by ITU for data transmission over SDH networks. The technologies used namely GFP (generic framing procedure), VCAT (virtual concatenation) and LCAS (link capacity adjustment scheme) enable network operator to provide integrated voice and data services over their legacy SDH infrastructure. Data packets are encapsulated using framing protocols GFP. VCAT is a process of distributing the GFP framed data payload in number of virtual channels of same capacity forming a Virtually Concatenated Group (VCG). LCAS is used for dynamic bandwidth allocation. LCAS enhances the VCAT scheme with hitless in service addition and removal of VCpsilas to/from the VCG. VCAT combines homogeneous virtual containers(VCpsilas) together which in some cases limits the performance of VCAT. This paper describes the implementation of new concatenation technology named cross virtual concatenation (CVC), which combines heterogeneous VCpsilas together to utilize the SDH bandwidth more efficiently. CVC implementation requires only end node equipments to be upgraded as VCG members travel through the link similar to the conventional VCAT. In this paper transmitter and receiver circuits are designed to transmit and receive 100Mbps Ethernet data using CVC, where two types of VCpsilas namely VC-3 and VC-12 are used for data transmission. The functionality of the circuit is tested using Modelsim Simulator using VHDL. Total Transmission delay is calculated as 125us and proved that, there is no complexity added at the receiver side due to this delay. The receiver is designed for 32ms differential delay compensation which can be increased up to maximum 256ms by increasing the buffer size at the receiver.