Average Area Spectral Efficiency Research Articles

Delivering Extended Cellular Coverage and Capacity Using High-Altitude Platforms

Interest in delivering cellular communication using a high-altitude platform (HAP) is increasing partly due to its wide coverage capability. In this paper, we formulate analytical expressions for estimating the area of a HAP beam footprint, average per-user capacity per cell, average spectral efficiency (SE) and average area spectral efficiency (ASE), which are relevant for radio network planning, especially within the context of HAP extended contiguous cellular coverage and capacity. To understand the practical implications, we propose an enhanced and validated recursive HAP antenna beam-pointing algorithm, which forms HAP cells over an extended service area while considering beam broadening and the degree of overlap between neighbouring beams. The performance of the extended contiguous cellular structure resulting from the algorithm is compared with other alternative schemes using the carrier-to-noise ratio (CNR) and carrier-to-interference-plus-noise ratio (CINR). Results show that there is a steep reduction in average ASE at the edge of coverage. The achievable coverage is limited by the minimum acceptable average ASE at the edge, among other factors. In addition, the results highlight that efficient beam management can be achieved using the enhanced and validated algorithm, which significantly improves user CNR, CINR, and coverage area compared with other benchmark schemes. A simulated annealing comparison verifies that such an algorithm is close to optimal.

Network Densification and Path-Loss Models Versus UDN Performance—A Unified Approach

Ultra-dense network (UDN) is one of the most important techniques to support massive number of different types of user equipments (UEs). It is essential to understand the impact of densification on various system performance metrics in future cellular networks. Two contradictory conclusions were made from the existing research works. Some works indicated that the network densification has reached its upper limit and deploying more UEs may only reduce UDN performance; whereas the others claimed that more UEs can still be supported by deploying more small cell base stations (SBSs). The existence of above different conclusions is due mainly to the difficulties to find an effective means to take into account different path loss models in UDNs. In this paper, we aim to propose a unified analytical approach, which is effective to simplify UDN performance analysis based on different path loss models with a low computation complexity. Using the proposed approach with idle mode of SBSs enabled, we can identify the impact of the densities of SBSs and UEs on various performance metrics, i.e., coverage probability and average area spectral efficiency (ASE). The conclusions will be supported by the analytical and simulation results verifying the effectiveness of the proposed unified analytical approach.

Performance Analysis and Power Allocation Strategy for Downlink NOMA Systems in Large-Scale Cellular Networks

In this paper, downlink non-orthogonal multiple access (NOMA) systems in large-scale cellular networks are considered and an analytical framework to evaluate the outage performance is developed. Different from the previous work where the users' distribution is assumed to be completely independent of the Base Station (BS) locations, the deployment of the BSs and the location of NOMA-user pair are modeled as Poisson Cluster Process so that the relation between system throughput and the density of BSs could be effectively formulated and clearly revealed. Under the proposed system model, the closed-form expressions of outage probabilities are derived for 2-user downlink NOMA systems. Furthermore, the power allocation strategy is proposed for minimizing the maximal outage probability among NOMA users. And the average area spectral efficiency is also defined and derived to evaluate the throughput of the network. The accuracy of the theoretical results is verified by the simulations.

A Unified Asymptotic Analysis of Area Spectral Efficiency in Ultradense Cellular Networks

This paper studies the asymptotic properties of average area spectral efficiency (ASE) of a downlink cellular network in the limit of very dense base station (BS) and user densities. This asymptotic analysis relies on three assumptions: 1) interference is treated as noise; 2) the BS locations are drawn from a Poisson point process; and 3) the path loss function is bounded above satisfying mild regularity conditions. We consider three possible definitions of the average ASE, all of which give units of bits per second per unit bandwidth per unit area. When there is no constraint on the minimum operational signal-to-interference-plus-noise ratio (SINR) and instantaneous full channel state information (CSI) is available at the transmitter, the average ASE is proven to saturate to a constant, which we derive in a closed form. For the other two ASE definitions, wherein either a minimum SINR is enforced or CSI is not available, the average ASE is instead shown to collapse to zero at high BS density. We provide several familiar case studies for the class of considered path loss models, and demonstrate that our results cover most previous models and results on ultradense networks as special cases.

Joint Interference Cancellation in Cache- and SIC-Enabled Networks

We consider a cache- and SIC-enabled wireless network, where the locations of the base stations (BSs) and users are modeled by the Poisson point process and Poisson cluster process, respectively. The BS serves two users simultaneously by transmitting a superimposed signal, and each user employs a joint scheme of cache-assisted interference cancellation (CAIC) and successive interference cancellation (SIC). Each user is classified as a caching or non-caching user depending on whether or not it caches data sent to its interferer in the same cell. The receiver operation of each user is classified into three possible cases: CAIC only, both CAIC and SIC, and SIC only. Then, the successful packet transmission probabilities of the caching and non-caching users are derived, based on which the average spectral efficiency (SE) and the average area SE (ASE) are obtained. The average SE and ASE are further optimized. Moreover, extensions to the scenario where the superimposed transmissions are within a finite radius around the BS are provided. Finally, the result for the general scenario of the BS serving multiple users simultaneously is obtained. The optimization problem of the general scenario is solved by converting it to the convex or the difference of convex problems in different subregions. Simulation results verify the analytical accuracy and the advantages of the proposed schemes.

In preparation towards future cellular networks: the detailed analysis of macro and micro site densification and sector densification

The next generation of cellular networks is expected to provide huge capacity, and site densification is one of the possible solution to increase the network capacity. The target of this paper is to show the impact of macro/micro site densification and higher order sectorization on signal strength, signal quality and throughput in LTE network. It also highlights the impact of site and sector densification on the cell overlapping and cell border areas. A detailed techno-economical analysis along with area power consumption and area spectral efficiency is also provided in this paper. In site densification, the intersite distance (ISD) between the base station sites is decreased, which results in strong inter cell interference. The results presented in this paper show that the spectral efficiency of the cell decreases with the site densification. However, the average area spectral efficiency increases due to a larger number of cells in the densified network. At the same time the number of cell border users overlapped by multiple servers also increases with the site and sector densification. It is shown that in one square kilometer, increasing the number of cells from 14 (3-sector site with 500 m ISD) to 693 (6-sector site with 100 m ISD) relatively improves the area spectral efficiency by 24.5 times at the cost of 49.5 times more number of cells. Almost identical power efficiency is provided with 3-, and 6-sector site. However, a higher order sectored site was found to be more cost efficient.

Spectral efficiency of adaptive coded modulation in urban microcellular networks

This tutorial paper describes a general adaptive coded modulation scheme for airlinks in urban wireless networks. Each airlink is degraded by shadowed Nakagami multipath fading, interference from other airlinks, and signal path loss. An instance of the adaptive coding scheme utilizes a set of trellis codes originally designed for additive white Gaussian noise channels. A model of the worst and best case interference configurations of a fully loaded network is developed to approximate the average link spectral efficiency (ALSE) of an arbitrary instance of the coding scheme. It is then shown why the ALSE of the adaptive coding scheme is larger than the fixed link spectral efficiency of a traditional nonadaptive coding scheme. Moreover, the ALSE approximation is modified to approximate the average area spectral efficiency (AASE) of the network, and how the cellular layout influences the AASE is shown.