A packet radio network (for example, wireless LAN, mobile tactical network) consists of a number of nodes, each equipped with a transceiver, exchanging data packets via radio channels. In this paper we identify and discuss issues related to the process of forming a network in an automatic and distributed manner. During network initialisation and reconfiguration, the time to complete the network formation process is an important performance parameter. We define two measures which can be used for computing the network formation time. Also, we present a comparative evaluation of two channel-scanning schemes (synchronous and asynchronous) for multiple frequency operations using a broadcast access scheme based on CSMA. Our study of networks with different spatial distributions of nodes shows that the asynchronous scanning scheme performs better when the ratio of the number of 1-hop neighbours to the number of available channels is high. Its performance is somewhat worse than that of the synchronous scheme for sparse networks. It is also sensitive to changes in the channel dwell time of the receivers, compared with the synchronous case.

A comparison of channel scanning schemes for distributed formation and reconfiguration

A new class of time division multiple access (TDMA) protocols is developed for multihop packet radio networks, using the group testing paradigm that improves the performance of TDMA when collisions are not likely. Several strategies for implementing group testing in radio networks are investigated. These include a variable-length group testing protocol and two distributed group testing protocols. They are implemented in a detailed simulation and the delay performance results of each are presented. Simulation results indicate that group testing can improve the performance of TDMA when the probability of collisions is low. The best overall results are obtained by a distributed protocol called TDMA with interleaved slot testing. >

Strategies for group testing in multihop radio networks

The Naval Ocean Systems Center (NOSC) is tasked to design multiple access protocols for the Improved Link-ll program. Link-ll is an existing tactical data network that has been operational in the United States Navy for many years. The objectives of this project are to design and field improved multiple access protocols which will remedy the shortcomings of the present system. The multiple access protocols examined were TDMA (Time Division Multiple Access) and an adaptive TDMA scheme, developed at NOSC, known as HAMA (Handoff Assigned Multiple Access). Simulations of these two protocols were conducted using the Network Architecture Simulated Test and Evaluation Environment (NASTEE). Example results of these protocol simulations are presented in this paper.

Modeling and Evaluation of Multiple Access Protocols

A methodology to test and evaluate local area networks (LANs) prior to procurement and installation is discussed. Characteristics of the specific network architecture under study, HYPE Rbus, a Network Systems Corporation (NSC) product, are given. The methodology is based upon the use of the Network Architecture Simulated Test and Evaluation Environment (NASTEE), developed at the Naval Ocean Systems Center (NOSC). NASTEE comprises three program packages: a Configurer supports interactive specification of experiments to load and test the network; a Testbed executes user-specified experiments n batch mode; a Graphics Package (not yet complete) will display results. Protocols written by the user are linked to the Testbed and supply the intelligence to network nodes for all message processing.

Modeling and Evaluation of Local Area Networks

: This report describes a new architecture for mobile, narrowband, broadcast radio networks, which is called the Multichannel Architecture (MCA). We compare the performance limits of an MCA network to a single-channel architecture based on an Ideal Handoff Assigned Multiple Access (IHAMA) protocol. Both architectures have been proposed for Naval intratask force communications with HF and line-of-sight UHF radio. Formulas for the network load capacity for each architecture are derived for several important cases, and simulation results are presented for those cases where analytical results are not available. Based on equivalent equipment, the load capacity of MCA is shown to exceed that of IHAMA. MCA also out-performed IHAMA in other performance areas such as delay, the ability to handle voice and virtual circuits, and jam resistance. Networking, Mobile networks, H.F., High frequency communication.

A Multichannel Architecture for Naval Task Force Communication

The Handoff Assigned Multiple Access (HAMA) protocol has been designed to meet the performane requirements of the Tactical Intra-task Force Network, a hypothetical mobile Navy broadcast radio network. This packet switched network will facilitate the transmission and reception of target track data and various command and control messages between Navy platforms (ships) in a dynamic, tactical environment. The unique characteristics and requirement of the TACNET resulted in the development of the HAMA multiple access protocol. The protocol is based on Time Division Multiple Access, in which the communication channel is divided into time frames, which are further subdivided into time slots. Each network node (ship) is assigned a particular slot, with exactly one slot for each node. With HAMA each node is allowed to handoff its slot to other network nodes. Thus, a node which has no use for its slot can dynamically hand it off to another node which does need it. Analysis of the protocol, both analytical and by simulation, indicates it performs remarkably well, much better than Time Division Multiple Access (TDMA) even at very high throughputs. Of particular importance to military networks, the analysis results indicate the protocol is very robust, and performs well under a variety of tactical conditions.

Handoff Assigned Multiple Access (HAMA): A New Multiple Access Protocol for Computer Communication Networks

: This document describes the design concept of the Network Design Tool. The Network Design Tool (NDT) is a collection of analytical techniques, algorithms and simulation methods that may be used to characterize the performance of a computer communication network. Much work has been done over the past several years in network performance analysis and many techniques have been developed or proposed. Each of these methods applies to a particular aspect of the network design and is based on a particular modeling point of view. We define the computer communication network and then describe the different ways the network may be modeled. Each network model is related to the particular design problem being addressed. The various analytical approaches are briefly described and their relationship to the network models discussed. Chapter 2 is a survey of the major approaches to specific network design problems while Chapters 3 and 4 discuss two fairly well defined areas of network analysis: topological design/optimization and protocol validation. Chapter 5 is a survey of network design tools presently available locally or on the Advanced Research Projects Agency Network (ARPANET). Finally, Chapter 6 presents an outline of the NDT specification.

Gary J. Brown

Papers

Handoff Assigned Multiple Access (HAMA): A New Multiple Access Protocol for Computer Communication Networks

Modeling and Evaluation of Multiple Access Protocols

Network Design Tool for EHF Satellite Communications Networks