E. C. Foudriat

A carrier sensed multiple access protocol high data rate ring networks

This paper presents a significant extension of the CSMA network access protocol. The protocol is based on the facts that, at high data rates, networks can contain multiple messages simultaneously over their span, and that in a ring, nodes needs only to detect the presence of a message arriving from the immediate up stream neighbor. When an incoming signal is detected, the node truncates the message it is presently sending instead of aborting it. The system has been named Carrier Sensed Multiple Access Ring Network, CSMA/RN.Analytical studies using three performance factors, wait or access time, service time and response or end-to-end travel time are presented. The service time is basically a function of the network rate; it changes by a factor of 4 between no load and full load. Wait time, which is zero for no load, remains small for load factors up to 70% of full load. Response time, which adds travel time while on the network to wait and service time, is mainly a function of network length, especially for longer distance networks.Simulation results are shown for CSMA/RN where messages are removed at the destination. Destination removal on an average increases network load capacity by a factor of 2, i.e., a 1 Gbps network can handle a 2 Gbps load. A wide range of local and metropolitan area network parameters including variations in message size, network length and node count are studied. In all cases performance is excellent, and message fracture usually remains less than a factor of 4. Throughput, even at overload conditions, remains high for the protocol. The nominal network rate is 1 Gbps; however, performance remains good for data rates as low as 200 Mbps. Finally, a scaling factor based upon the ratio of message to network length demonstrates that the results of this paper, and hence, the CSMA/RN protocol, are applicable to wide area networks.

Wireless support for telemedicine in disaster management

Disaster response and recovery require timely interaction and coordination of public emergency services in order to save lives and property. An important role in this effort must be played by wireless telemedicine whose mandate is to bring to the scene of the disaster the experience and expertise of medical personnel that can direct and supervise paramedics in providing necessary life-support services. The main contribution of this work is to discuss a novel wireless architecture in support of a recently-proposed telemedicine architecture called WIRM incorporating leading-edge image compression technology, a robust interactive visualization tool, and a high-performance wireless multimedia network.

H3M - A Rapidly Deployable Architecture with QoS Provisioning for Wireless Networks

Future wireless networks will have to be based on highly mobile systems that are self-organizing, rapidly deployable, heterogeneous, and will not rely on expensive infrastructure. Since these networks will be called upon to support real-time interactive multimedia traffic, they must be able to provide their users with adequate quality of service (QoS) guarantees. In addition, we want to consider networks with highly dynamic resource requirements, such as QoS, by multiple,dynamically changing groups. The architecture and protocol is based upon a protocol called DRAMA.[4-8]. We have taken the kernel of DRAMA - operating CSMA/CD in a metropolitan area and multichannel load balancing ^O and created a new architecture suitable to a highly mobile environment. We refer to it as the Hierarchical Heterogeneous Highly Mobile network (H 3 M, for short). As the name short). As the name suggests, the H 3 M network consists of a hierarchy of heterogeneous hosts distributed over a geographical area and linked together in a wireless communication system. At the bottom level of the hierarchy we have a cluster architecture whose connectivity and management activities are assumed by a mobile base station (MBS). In turn, the MBSs are organized into a virtual network, essentially emulating a local area network like structure. The protocol for arbitrating as to who sends what on what frequency at what time is based on a combination of TDMA and CSMA/CD frames and frequency allocations to a cluster of nodes that allows for dynamic bandwidth allocation and which supports multicasting. Simulation and analysis have shown that H 3 M is robust, scales well and provides much higher throughput than other protocols, while supporting the same degree of host mobility. Importantly, H 3 M turns out to be well suited for handling on-demand multimedia communications in a heterogeneous, highly mobile environment. Multicasting is supported with minimal overhead.

Dynamic allocation of bandwidth in multichannel metropolitan area networks

Abstract Techniques are presented that integrate synchronous traffic (real time voice or video) and asynchronous traffic (e.g., file transfers, mail messages) and extend the size of local area networks to distances much greater than 2 km without loss in speed and capacity. The system, Dynamic Resource Allocation in Metropolitan Areas (DRAMA), is based on broadband technology and allows for allocation of bandwidth among clusters of nodes in the total network. DRAMA incorporates both channel allocation and traffic placement protocols. Its channel allocation algorithm is shown to be fair, stable and responsive to dynamic load conditions and reallocates resources in a near optimal manner. The suggested traffic placement protocol is based upon CSMA/CD access; it provides effective integration of synchronous and asynchronous traffic, handles diverse loads and momentary traffic overloads, varying numbers of nodes and modifications to the network structure. With DRAMA, we have extended the advantage off CSMA/CD from low load and medium speed (10 Mbps to high load and high speed networks (> 100 Mbps). These properties are demonstrated through simulation studies.

Traffic placement policies for multi-band network

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.

Media access using dynamic bandwidth system to improve satellite network uplink performance

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

An architecture for robust QoS provisioning for mobile tactical communications

We propose a rapidly deployable, heterogeneous network that is well suited for both multimedia and datagram traffic. The main motivation for our work was the recognition of the fact that in military and emergency type networks the stations may have diverse communication capabilities. While some stations have strong transmitters and their own power supply, some others are energy-constrained and have weaker signals which can only reach stations within their immediate vicinity. We refer to our system as the Hierarchical Heterogeneous Highly Mobile network (H3M). As the name suggests, the N3M consists of a hierarchy of heterogeneous stations distributed over a geographical area, linked together in a wireless communication system. The lowest level in the hierarchy is the cluster served by a mobile base station (MBS). In turn, the MBSs are organized into a virtual structure whose actual implementation is adaptive to the availability of assets in the network. Simulation and analysis revealed that H3M is robust, inherently supports multicast, scales well and is well suited for QoS provisioning in high-mobility environments, typical of tactical networks.

Modeling and analysis of high speed parallel token ring networks

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.<<ETX>>

Parallel Networking Improving Capacity and Multi-traffic Performance Together

The research reported in this paper show that parallel token ring networks are more effective in handling multiple traffic conditions than equivalent capacity single or bridged networks. This is in addition to the generic capacity increase obtained by added links. This capability is obtained because parallel networks can use message load distribution and joint token control policies not available to or effective for single link networks. The improvement is as much as a 7 fold decrease in message wait time for high priority (real-time and access time critical) traffic at high network loads. At the same time, regular message traffic is supported equally, if not better, for parallel ring networks are more suitable for handling multiple traffic (combination of synchronous and asynchronous) conditions. Further, this performance increase is attained without augmenting the token ring media access protocol by adding separate access mechanisms for synchronous and asynchronous traffic. The paper presents data on the two ring parallel network performance for a number of message distribution and token control policies. It then compares them for the best policies against single and bridged network performance. Finally, data is presented for a range of policy and network operational parameters in order to demonstrate that performance gains for parallel networks occur over a wide range of conditions.

High Performance Interconnection Between High Data Rate Networks

The bridge/gateway system needed to interconnect a wide range of computer networks to support a wide range of user quality-of-service requirements is discussed. The bridge/gateway must handle a wide range of message types including synchronous and asynchronous traffic, large, bursty messages, short, self-contained messages, time critical messages, etc. It is shown that messages can be classified into three basic classes, synchronous and large and small asynchronous messages. The first two require call setup so that packet identification, buffer handling, etc. can be supported in the bridge/gateway. Identification enables resequences in packet size. The third class is for messages which do not require call setup. Resequencing hardware based to handle two types of resequencing problems is presented. The first is for a virtual parallel circuit which can scramble channel bytes. The second system is effective in handling both synchronous and asynchronous traffic between networks with highly differing packet sizes and data rates. The two other major needs for the bridge/gateway are congestion and error control. A dynamic, lossless congestion control scheme which can easily support effective error correction is presented. Results indicate that the congestion control scheme provides close to optimal capacity under congested conditions. Under conditions where error may develop due to intervening networks which are not lossless, intermediate error recovery and correction takes 1/3 less time than equivalent end-to-end error correction under similar conditions.