This paper shows how cognitive radio (CR) can help to optimize system power consumption of multiple input multiple output (MIMO) communication systems. Leveraging results from information theory and capabilities of a CR (e.g., the awareness of the component capabilities and characteristics), a theoretical framework is developed to minimize the system power consumption of MIMO systems while still considering radiated power. This paper mathematically formulates the system power consumption minimization problem under a sum rate constraint for MIMO systems. The impact of channel correlation and partial channel state information at the transmitter is considered. Numerical algorithms are developed to solve the constrained optimization problem. The simulation results show that significant power savings (e.g., up to 75% for a 4 x 4 MIMO system with Class A power amplifiers) can be achieved compared to conventional power allocation schemes. The results also show that the more computationally efficient suboptimal heuristic algorithms can achieve power savings comparable to the exhaustive search algorithm.

In this paper, we show how cognitive radio can help minimize energy consumption of a wireless mobile communication device. We propose an energy optimization framework using cognitive radio for a given quality of service requirement based on the channel and the radio capabilities. The cognitive radio not only adjusts modulation, coding, and radiated power, as with conventional adaptive modulation, but also adjusts component characteristics (e.g., power amplifier characteristics) so that the radio operates with the highest energy efficient possible way. Simulation results show that significant energy savings (up to 75%) can be achieved compared to conventional adaptive modulation. This framework also can be applied to optimize radio operations to achieve additional goals.

This paper investigates the impact of multiple-input multiple-output (MIMO) implementations on both capacity and coverage of reverse link direct spread / code division multiple access (DS/CDMA) cellular systems. For the analytical analysis of the impact on the system, signal-to-interference ratio (SIR) of the reverse link DS/CDMA cellular systems with MIMO implementations is derived, and the outage probability is evaluated based on the derived formula.

This paper investigates the efficacy of MIMO implementations with adaptive spatial diversity in the uplink of direct spread/code division multiple access (DS/CDMA) cellular systems. Analytical framework to analyze both system capacity and coverage is developed based on the evaluation of outage probability of signal-to-interference ratio (SIR). It is shown that MIMO implementations can significantly improves the system performances; however, transmit diversity and receive diversity shows different system performances contrary to their link level bit error rate (BER) performances.

Abstract This work describes the Site‐Specific System Simulator for Wireless System Design (S4W), a problem‐solving environment (PSE) that integrates visualization and computational tools with a high‐level graphical user interface. S4W improves the ability of wireless system engineers to design an indoor wireless system by encouraging them to think in terms of designing the system for optimal performance. Issues of computation management, data management, and location of resources are hidden from the user. The complex nature of data sets in the domain of wireless simulations calls for a customized set of visualization tools. Therefore, a number ofad hocvisualizations were developed for S4W. A study comparing the integrated system with an earlier, unintegrated version is presented. This helps to demonstrate the productivity gains that a PSE provides. Copyright © 2007 John Wiley & Sons, Ltd.

This paper presents an analytical framework for evaluating the performance of a threshold-based generalized selection combining (GSC) scheme in equally correlated Nakagami-m fading channels. The framework extends previously published results by allowing arbitrary fading index values (mges0.5) in the analytical solution. Also, we exploit a second method which is computationally more efficient than the first approach, when fading index m is a positive integer

Using analytical approach, we investigate the impact of spatial diversity on the Erlang capacity of reverse link direct sequence code division multiple access (DS/CDMA) system. Several parameters which can affect the capacity are considered: transmit diversity order, spatial receive diversity order, the number of multipaths, fade distribution and arbitrary multipath intensity profile, maximum transmit power, soft-handoff, and traffic distribution with call admission control scheme.

The article presents an analytical framework for evaluating the performance of an equally correlated multi-branch predetection equal gain combining (EGC) diversity receiver in Nakagami-m fading channels. Specifically, the characteristic function (CHF) of the EGC output signal-to-noise ratio (SNR) with L correlated inputs is derived. Selected numerical examples are provided to illustrate the effects of branch correlation and fade distribution on the average error rate and outage probability of EGC receivers.

This article investigates the impact of antenna diversity implementation at both mobile handsets and basestations on the reverse link DS/CDMA capacity in a myriad of fading environments. Our numerical results reveal that transmit diversity implementation at mobile handsets is most beneficial in indoor propagation channels (since only a few significant resolvable multipaths are available) with low order antenna diversity at the base-station and in harsh fading environments.

A global optimization technique is applied to solve the optimal transmitter placement problem for indoor wireless systems. An efficient pattern search algorithm - DIviding RECTangles (DIRECT) of Jones et al.- has been connected to a parallel three-dimensional radio propagation ray tracing modeler running on a 200-node Beowulf cluster of Linux workstations. Surrogate functions for a parallel wideband code-division multiple-access (WCDMA) simulator were used to estimate the system performance for the global optimization algorithm. Power coverage and bit-error rate are considered as two different criteria for optimizing locations of a specified number of transmitters across the feasible region of the design space. This paper briefly describes the underlying radio propagation and WCDMA simulations and focuses on the design issues of the optimization loop.

This paper presents comparisons between STTD (transmit diversity in WCDMA), downlink beamforming, and a system which combines both transmit diversity and beamforming.