Scheduling Transmissions in a multicast Packet When Call Splitting is Allowed

Multicast packet switching has recently received considerable attention [1, 2, 4, 5]. A multicast packet is one that has a set of destinations; hence, it has applications in multiparty communication (e.g. voice conference calls, video conferencing, and video distribution). The switch considered has N inputs and N outputs, as shown in Figure 1, and transports packets at the inputs that are destined for the outputs. Time is assumed to be slotted and packets at inputs are transmitted at slot boundaries. Packets transmitted in a given slot arrive at all their destinations in the same slot. The switch has the call splitting ability. This means that a multicast packet can be duplicated at an input so the destinations of the copies form a partition of the destinations of the original packet. The copies can then be transmitted at different times. The call splitting operation is assumed to require negligible time. Call splitting allows higher throughput. In fact, it has been shown experimentally that it provides near optimal throughput [4]. We consider the problem of finding a schedule of transmissions that delivers a set of multicast packets (or their copies) to their destinations in the minimum number of time slots.