1,001 research outputs found
Energy-efficient multihop cooperative MISO transmission with optimal hop distance in wireless ad hoc networks
In this paper, we investigate the hop distance optimization problem in ad hoc networks where cooperative multiinput- single-output (MISO) is adopted to improve the energy efficiency of the network. We first establish the energy model of multihop cooperative MISO transmission. Based on the model, the energy consumption per bit of the network with high node density is minimized numerically by finding an optimal hop distance, and, to get the global minimum energy consumption, both hop distance and the number of cooperating nodes around each relay node for multihop transmission are jointly optimized. We also compare the performance between multihop cooperative MISO transmission and single-input-single-output (SISO) transmission, under the same network condition (high node density). We show that cooperative MISO transmission could be energyinefficient compared with SISO transmission when the path-loss exponent becomes high. We then extend our investigation to the networks with varied node densities and show the effectiveness of the joint optimization method in this scenario using simulation results. It is shown that the optimal results depend on network conditions such as node density and path-loss exponent, and the simulation results are closely matched to those obtained using the numerical models for high node density cases
Cross-layer schemes for performance optimization in wireless networks
Wireless networks are undergoing rapid progress and inspiring numerous applications. As the application of wireless networks becomes broader, they are expected to not only provide ubiquitous connectivity, but also support end users with certain service guarantees.
End-to-end delay is an important Quality of Service (QoS) metric in multihop wireless networks. This dissertation addresses how to minimize end-to-end delay through joint optimization of network layer routing and link layer scheduling. Two cross-layer schemes, a loosely coupled cross-layer scheme and a tightly coupled cross-layer scheme, are proposed. The two cross-layer schemes involve interference modeling in multihop wireless networks with omnidirectional antenna. In addition, based on the interference model, multicast schedules are optimized to minimize the total end-to-end delay.
Throughput is another important QoS metric in wireless networks. This dissertation addresses how to leverage the spatial multiplexing function of MIMO links to improve wireless network throughput. Wireless interference modeling of a half-duplex MIMO node is presented. Based on the interference model, routing, spatial multiplexing, and scheduling are jointly considered in one optimization model. The throughput optimization problem is first addressed in constant bit rate networks and then in variable bit rate networks. In a variable data rate network, transmitters can use adaptive coding and modulation schemes to change their data rates so that the data rates are supported by the Signal to Noise and Interference Ratio (SINR). The problem of achieving maximum throughput in a millimeter-wave wireless personal area network is studied --Abstract, page iv
An Energy-Based Comparison of Long-Hop and Short-Hop Routing in MIMO Networks
This paper considers the problem of selecting either routes that consist of
long hops or routes that consist of short hops in a network of multiple-antenna
nodes, where each transmitting node employs spatial multiplexing. This
distance-dependent route selection problem is approached from the viewpoint of
energy efficiency, where a route is selected with the objective of minimizing
the transmission energy consumed while satisfying a target outage criterion at
the final destination. Deterministic line networks and two-dimensional random
networks are considered. It is shown that when 1) the number of hops traversed
between the source and destination grows large or 2) when the target success
probability approaches one or 3) when the number of transmit and/or receive
antennas grows large, short-hop routing requires less energy than long-hop
routing. It is also shown that if both routing strategies are subject to the
same delay constraint, long-hop routing requires less energy than short-hop
routing as the target success probability approaches one. In addition,
numerical analysis indicates that given loose outage constraints, only a small
number of transmit antennas are needed for short-hop routing to have its
maximum advantage over long-hop routing, while given stringent outage
constraints, the advantage of short-hop over long-hop routing always increases
with additional transmit antennas.Comment: 27 pages, 12 figures, submitted to IEEE Transactions on Vehicular
Technology in March 2009, revised in July 200
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