Abstract The paper describes a media access system for satellite network uplinks. The media access protocol is designed to support a range of low‐level protocols using a dual‐framing system, that is, there is a synchronous traffic subframe in which registered station requests are assigned fixed blocks or slots and an asynchronous traffic subframe for unregistered station random access on a contention basis. Slots for the registered stations are assigned through request to the satellite; the remaining frame time is assigned to unregistered stations. Capacity waste through contention resulting in collisions is minimized. The system uses dynamic bandwidth (bit rate) allocation for each channel, that is, the base frequency and bandwidth are changed for each channel at frame boundaries. The total bandwidth for the sum of all uplink channels is fixed. Channels that have low load based upon their request in a prior uplink frame are assigned lower bandwidth, while those with higher loading are provided larger bandwidth. By sharing bandwidth over channels at frame boundaries, overall network efficiency and fairness are significantly enhanced. Bandwidth allocation is decided in the satellite. It allocates sufficient bandwidth for all synchronous traffic and then commits the remaining bandwidth to asynchronous traffic. Here, the allocation for asynchronous traffic provides each channel with sufficient slots so that equal probability of success for stations sharing the channel can be expected. The combination of traffic assignment and bandwidth allocation provides significant improvement in overall network efficiency and fairness for all traffic types. The hardware implementation of media access for variable bandwidth sharing between channels use the concepts of Digital Software Radio. Copyright © 2003 John Wiley & Sons, Ltd.

Four factors in parallel token ring systems which can improve network performance are identified. An analytical model is developed to predict the performance of these systems. The predictions obtained with the analytical model are compared with simulation results. While the current model accurately predicts the performance of networks with 16 or more rings, it is not so accurate at lower numbers of rings. The short/long cycle behavior of the token interarrival times is identified as one cause of the inaccuracies. The benefits and limitations of parallel token ring networks for gigabit speeds are discussed.>

The paper describes the operation and performance of an integrated traffic network using separate media access protocols to support different traffic types on a single unidirectional ring or bus. One protocol, based upon local carrier sensing (CSMA/RN) provides access for asynchronous traffic; the other, a 'train like' protocol called the circulating reservations packets (CRPs), provides access for synchronous voice and video traffic. Other media access protocols like slotted ring or QPSX are equally applicable for use as the asynchronous protocol.>

Recently protocols have been introduced that enable the integration of synchronous traffic (voice or video) and asynchronous traffic (data) and extend the size of local area networks without loss in speed or capacity. One of these is DRAMA, a multiband protocol based on broadband technology. It provides dynamic allocation of bandwidth among clusters of nodes in the total network. In this paper, we propose and evaluate a number of traffic placement policies for such networks. Metrics used for performance evaluation include average network access delay, degree of fairness of access among the nodes, and network throughput. The feasibility of the DRAMA protocol is established through simulation studies. DRAMA provides effective integration of synchronous and asynchronous traffic due to its ability to separate traffic types. Under the suggested traffic placement policies, the DRAMA protocol is shown to handle diverse loads, mixes of traffic types, and numbers of nodes, as well as modifications to the network structure and momentary traffic overloads.