Performance of an enhanced multiplexer with imperfect access lines in an ATM network

Multiplexers are used in communications networks to increase link efficiency. A multiplexer receives traffic from many sources on access lines and sends it to its destination on a trunk line. This technique results in a great savings when the traffic of the sources is bursty. A problem arises, however, if the access lines are imperfect, in the sense that they may introduce errors in the traffic they carry. A normal multiplexer unknowingly transmits the erroneous traffic to the destination. The destination, with the help of an error-detection routine, detects the errors and discards that traffic, but of course after it has wasted much needed bandwidth on the trunk. This paper proposes an enhanced multiplexer, which is just a normal multiplexer with an error-detection routine similar to that of the destination. The function of this routine is to discard the erroneous traffic right at the multiplexer, thus saving the bandwidth of the trunk for only the error-free traffic. A discrete queueing theoretic model is developed in this paper for the enhanced multiplexer. By analyzing the model, using the generating function approach, it is shown that the enhanced multiplexer is superior in performance to its normal counterpart. For conciseness, it is assumed that the multiplexer is hooked to an asynchronous transfer mode (ATM) network. However the model presented can be easily modified to suit other network standards.