Ad hoc wireless networks can be quickly deployed to provide wireless communication services in areas without pre-established infrastructure of base stations. Since delivering signals between sources and destinations is a primary function of ad hoc networks, the design and analysis of ad hoc networks are also a task of signal processing. In this paper, we review some of the major results on maximum throughput of ad hoc networks. Both single-hop ad hoc networks and multi-hop ad hoc networks are considered. In particular, we show examples of how to maximize the throughput of a large ad hoc network through a closed-loop analysis of two medium access control (MAC) schemes: synchronous array method (SAM) and asynchronous array method (AAM). Both omni-directional antennas and directional antennas are examined. This study illustrates an importance of the interplays between signal processing, information theory and networking protocols.

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Maximizing the throughput of large ad hoc wireless networks

In this paper, an optimum packet based transmission scheme for WSN (Wireless Sensor Network) where packet size is varied depending on the node density and channel condition is discussed. A WSN based on a square grid topology is investigated. This optimum size packet yields highest energy efficiency for a particular network condition. Optimum packet length is evaluated under several network conditions in presence of shadowing. Impact of severity of shadowing on optimal packet size is also investigated. Energy expenditure for optimum packet based scheme is compared with that of an arbitrary fixed packet size based transmission. Further impact of severity of fading on energy consumption is also studied. An infinite ARQ (Automatic Repeat reQuest) scheme between adjacent nodes has been considered to successfully deliver a file. Optimal transmit power is also derived for the above network. Optimal transmit power is the minimum transmit power used by all nodes to guarantee network connectivity with a prefixed BER (Bit Error Rate) threshold. Further impacts of lognormal shadowing on optimal transmit power, route BER and energy efficiency are studied for such WSN.

Optimal transmit power and packet size in wireless sensor networks in lognormal shadowed environment

: Recent developments in communication systems technology promise to greatly improve the performance of point-to-point communications for both commercial and tactical networks. These developments include the use of electronically steerable antenna arrays, space-time multiple input multiple output (MIMO) signal processing techniques, and improved techniques for error correction. In this project we will address the challenging question of how these technological developments can best be exploited in a tactical networking context, where signal interference and channel uncertainty issues have a tremendous impact on end-to-end system performance. Tactical applications pose unique requirements for the network, including decentralized control to eliminate single points-of-failure, vulnerability to jamming and electronic warfare, and mission critical latency bounds for end-to-end data delivery. Moreover, a tactical network is generally composed of mobile nodes and the routing protocols must deal with a range of node mobilities and time varying channel conditions. Consequently this project is focused on the design of ad hoc networking architectures that utilize MIMO transmitters and receivers at each node. The goal of this program is to define the best way to utilize multiple transmit and receive antennas at each node to improve the robustness, capacity, and quality of service of the network.

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Space-Time Processing for Tactical Mobile Ad Hoc Networks

The throughput of a large network of wireless routers critically depends on the design of distributed medium access control (MAC). In this paper, a distributed MAC scheme called opportunistic synchronous array method (SAM) is presented and analyzed. The opportunistic SAM combines multiuser diversity and interference suppression in a distributed fashion. Depending on the choice of two control parameters, the opportunistic SAM may reduce to three specializations: multiuser SAM, switching SAM or deterministic SAM. The network throughput of the opportunistic SAM is analyzed, and its throughput gain over its specializations is illustrated.

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A distributed medium access control scheme for a large network of wireless routers

This paper evaluates energy level performance of three packet delivery schemes in a Wireless Sensor Networks (WSN) in presence of Rayleigh fading. Three different information delivery mechanisms are investigated using regenerative relays with or without error correction capability. Energy consumption for successful delivery of a data packet for each mechanism is evaluated and compared under several conditions of node density, bit rate, transmit power etc. Energy efficiency of different retransmission schemes are evaluated. Further an optimal packet length based on energy efficiency is derived.

Energy Level Performance of Packet Delivery Schemes in Wireless Sensor Networks in Presence of Rayleigh Fading Channel

Capacity analysis of sensor networks or wireless ad hoc networks has attracted a great attention in the past years. But the research in this area has primarily focused on scaling laws of arbitrary or random network instead of the exact capacity of given topologies. While the insight into how the capacity of an arbitrary or random network scales with the number of nodes in a given area is important, the exact capacity of a network depends on the network topology and can be more desirable in practice. In this paper, we compare the throughput of a large network with three possible topologies: square (rectangular), hexagonal and triangular. With a given topology, the network throughput also depends on the choice of routing protocols. We follow a synchronous array method (SAM) that is known so far to yield the highest throughout of a network on a rectangular grid

Kezhu Hong

Papers

Throughput of Large Wireless Networks on Square, Hexagonal and Triangular Grids