In this study, the authors investigate the downlink area spectral efficiency (ASE) of infrastructure relay enhanced cellular systems. ASE for cellular systems is defined as the maximum achievable data rate per unit bandwidth per unit area supported by a base station. In relay enhanced systems, ASE can serve as an attractive performance metric by capturing the benefit of the relatively smaller spatial footprint of relay transmission and the resulting lower co‐channel interference. In this study, by applying a moment generating function based approach, the authors first derive the general closed‐form statistics of the total interference from dominant co‐channel cells over Rayleigh fading channels. These interference statistics are readily applied to the calculation of the resulting ASE. The authors also propose a novel in‐cell frequency reuse scheme to further exploit the smaller transmission power of relay stations (RSs). Through selected numerical examples, the authors show that in relay enhanced systems, the cell size, transmission power and RS positions should be properly selected to gain better ASE performance than the conventional systems without relays.

Area spectral efficiency (ASE) was introduced as a metric to quantify the spectral utilization efficiency of cellular systems. Unlike other performance metrics, ASE takes into account the spatial property of cellular systems. In this paper, we generalize the concept of ASE to study arbitrary wireless transmissions. Specifically, we introduce the notion of affected area to characterize the spatial property of arbitrary wireless transmissions. Based on the definition of affected area, we define the performance metric, generalized area spectral efficiency (GASE), to quantify the spatial spectral utilization efficiency as well as the greenness of wireless transmissions. After illustrating its evaluation for point-to-point transmission, we analyze the GASE performance of several different transmission scenarios, including dual-hop relay transmission, three-node cooperative relay transmission and underlay cognitive radio transmission. We derive closed-form expressions for the GASE metric of each transmission scenario under Rayleigh fading environment whenever possible. Through mathematical analysis and numerical examples, we show that the GASE metric provides a new perspective on the design and optimization of wireless transmissions, especially on the transmitting power selection. We also show that introducing relay nodes can greatly improve the spatial utilization efficiency of wireless systems. We illustrate that the GASE metric can help optimize the deployment of underlay cognitive radio systems.

Area spectral efficiency (ASE) was introduced as a metric to quantify the spectral efficiency of cellular systems. Unlike other performance metrics, ASE takes into account the spatial property of cellular wireless system. In this paper, we generalize the ASE metric for arbitrary wireless transmission. Specifically, we introduce the concept of affected area, based on which we evaluate the spectral and power efficiency of three different transmission scenarios, namely single user point-to-point transmission, two-user X channel transmission and two-hop relay transmission. We derive the closed-form expressions of resulting generalized ASE (GASE) metric for each transmission scenario over Rayleigh fading environment. We show through mathematical analysis and numerical examples that there is an optimal choice of transmitting power value in terms of maximizing the area spectrum efficiency.

Poisson point process has been widely adopted in the analysis of co-channel interference in dense frequency reuse systems. With the decaying power law, the aggregate co-channel interference in Poisson field can be viewed as the output of a shot noise process. In this paper, we first consider the wireless transmission of a single transmitter- receiver pair with a guard zone centered at the receiver. Other interfering transmitters are randomly distributed outside the guard zone according to a spatial Poisson process. We derive the generic closed-form moment generating function (MGF) of the aggregate interference over Rayleigh fading channels. Then we show that the ergodic capacity of wireless transmission in Poisson field over Rayleigh fading channels can be expressed as function of the MGF of the aggregate interference. Through numerical examples, we examine the accuracy of the Gaussian approximation on the aggregate interference in terms of ergodic capacity calculation. Finally we introduce the Matern point process to model the spatial distribution of multiple transmitter-receiver pairs with guard zones centered at respective receivers.

Cognitive radio is a promising technology to improve the spectrum utilization by allowing the unlicensed (secondary) user share a frequency bandwidth with the licensed (primary) owner under the condition that no harmful interference is imposed on the licensee. In this paper, we analyze the spatial spectrum utilization efficiency of underlay cognitive radio transmission. In particular, we apply the performance metric, generalized area spectral efficiency (GASE), to the performance evaluation and design of underlay cognitive radio transmission. Closed-form expressions are given on the ergodic capacity of the primary and secondary user in underlay cognitive radio transmission over Rayleigh fading channels, which are then utilized to evaluate GASE metric. Mathematical analysis and numerical examples show the asymptotic GASE performance of the underlay cognitive radio transmission with respect to the interference constraint on the primary receiver. We show that GASE performance metric provides a new perspective to the design of underlay cognitive radio transmission.

In this paper, we investigate the area spectral efficiency (ASE) in a three-node cooperative network with opportunistic relaying. On one hand, in conventional cellular network, ASE is defined to be the average data rate per unit bandwidth per unit area supported by a base station. On the other hand, in cooperative network, since there is no such a central base station, we redefine ASE to be the average data rate per unit bandwidth within a particular area, in which simultaneous transmissions are not allowed. In addition, to maximize the instantaneous capacity between the source and the destination, we apply a transmission mode selection criterion to determine whether the direct transmission or the multi-hop relay transmission is utilized. We derive the mathematical expression of ASE with the consideration of the relay node location and the impact of path-loss and fading effects. We show through selected numerical examples the effect of relay node position on the performance metric of ASE.