Photonic Network Communications, 1:2, 111±124 (1999)
# 1999 Kluwer Academic Publishers, Boston. Manufactured in The Netherlands.
The Advantages of Partitioning Multicast Transmissions in a
Single-Hop Optical WDM Network*
Jason P. Jue
Department of Computer Science, University of California, Davis, CA 95616, E-mail: email@example.com
Department of Computer Science, University of California, Davis, CA 95616, E-mail: firstname.lastname@example.org
Received Febuary 20, 1999; Revised April 14, 1999
Abstract. In a single-hop WDM optical network, a straightforward approach to implementing multicasting is to schedule a single transmission
to multiple destinations so that all of the destinations may receive the same transmission by tuning their receivers to the same channel at the
same time. Although scheduling a single transmission in this manner reduces the amount of transmitter and channel resources being used, it may
also place a burden on the receivers in the network. If all receivers do not become available at the same time, then some receivers may have to
wait (and be idle) for signi®cantly long periods of time before receiving the message. In this paper, we investigate methods for partitioning a
multicast group into a number of smaller subgroups and for scheduling a separate transmission for each of these subgroups. We show that this
approach more effectively conserves and balances the usage of transmitter and receiver resources in the network and may lead to signi®cantly
improved system performance over the conventional single-transmission multicast approach.
Keywords: WDM, broadcast network, multicasting, partitioning
In modern networks, the demand for bandwidth and
high quality of service requires the ef®cient utilization
of network resources such as transmitters, receivers,
and channel bandwidth. One method for conserving
these resources is to employ ef®cient implementations
of multicasting wherever possible.
Traditionally, networks have supported unicast
transmissions in which a single source may transmit
data to a single destination. However, if a message is
intended for multiple destinations, sending a separate
transmission to each destination may result in an
inef®cient use of resources. Using multicasting, a
source sending a message to multiple destinations
may schedule a single transmission which can then be
broadcast to multiple destinations or forwarded from
one destination to another, thus conserving transmitter
resources and channel bandwidth.
Methods for implementing multicasting in net-
works have been gaining much attention in recent
years. Many previous efforts in multicasting have
focused on the multihop multicasting problem. The
multihop multicasting problem is to construct a
minimal cost tree which is rooted at the source node
and spans all of the destination nodes. The cost of the
tree is determined by the amount of network resources
consumed, such as the number of links in the tree.
This problem has traditionally been formulated as the
Steiner Minimal Tree problem and has been studied in
a number of previous works [1,2].
A problem that has received less attention is the
single-hop multicasting problem. Since single-hop
optical networks are based on a broadcast medium
(Fig. 1), multiple destinations may receive the same
transmission simultaneously, thereby reducing the
number of times that a message is transmitted.
However, in a single-hop network with multiple
channels, each destination may have its receiver tuned
to a different channel. Thus, we have the additional
problem of coordinating the source node and the
*This work has been supported in part by the Defense Advanced Research Projects Agency (DARPA) Contract No. DAAH04-95-1-0487. A
shorter version of this paper was presented at ICC '97, Montreal, June 1997.