Raphael Rom

Message-based priority functions in local multiaccess communication systems

Abstract The proliferation of computer networks has brought about a wealth of applications that impose disparate requirements upon the communication channels they use. In particular, the traffic requirements differ to such a degree that optimization of access schemes for one pattern is often detrimental to all rest. Message priority offers a solution to the problem. It provides a means of administering channel usage to meet these requirements while maintaining high total utilization. This paper proposes priority schemes appropriate for introduction into different architectures of local multiaccess communication systems to achieve these desired results.

Carrier sense access in an enviornment of two interfering channels

Abstract Interference problems in radio networks are investigated. A general model is developed for the case of two interfering channels. The model is used to analyzed the performance of a two-station packet radio network and a CSMA network with hidden terminals. Performance evaluations for both slotted and unslotted systems are presented.

Ordering subscribers on cable networks

Recent years have brought about a variety of distributed-control access schemes to cable-based local area networks, each with different performance characteristics. Cable networks share one feature in common-the ordering of subscribers along the cables. Only few networks, however, have taken advantage of this feature [3, 7, 8, 9] although it is intuitively clear that performance will increase if access control is passed among subscribers in an order related to their physical ordering along the cable. A large class of access schemes, the round robin schemes {e.g., BRAM [1] and MSAP [4] and others), would benefit not only from the order but also from knowledge of the total number of operational subscribers since there is typically an overhead associated with each potential subscriber. Some access schemes [6] even require subscriber ordering for normal operation. Manually updating all nodes is an unacceptable (and unreliable) procedure. This paper describes a distributed algorithm allowing cable subscribers to learn their order along the cable. As a side effect, this algorithm can be used to compute the number of subscribers in the network.