Heterogeneous Base Stations Research Articles

Design and operation of energy efficient heterogeneous mobile networks

During the last two decades we have witnessed a rapid growth in wireless communication services, which has dramatically increased the number of necessary radio access components to provide the adequate capacity and acceptable quality of service. The power cost for operating this huge number of radio Base Stations (BSs) is under serious consideration by the mobile communication industry and recent research efforts have focused on energy efficient design and optimization of the radio access network in order to alleviate the energy consumption and mobile network operators OPEX. In this work, we consider a deployment of heterogeneous BSs to serve a given geographical area and propose two energy-aware algorithms to optimally determine the operational mode of those BSs under various traffic load conditions. Performance evaluation results show that the proposed algorithms can provide near optimal solutions and achieve substantial network energy consumption reduction without compromising the efficient operation of the mobile network. We further benefit from the outcome of this formulation framework and propose BS activation schemes that yield proper BS activation profiles for continuous-time operation in the same network deployment. Various traffic loads are investigated in several simulation campaigns and our proposed schemes yield quite satisfactory energy saving gains compared to fully operational topology networks in all scenarios of interest examined.

Delay‐sensitive user scheduling and power control in heterogeneous networks

Delay-sensitive traffic services, such as live streaming video, voice over IP and multimedia teleconferencing, requires low end-to-end delay in order to maintain its interactive and streaming nature. In recent years, the popularity of delay-sensitive applications has been rapidly growing. In this study, the authors consider the delay-sensitive user scheduling and power control design for heterogeneous networks (HetNets). They model the problem as an infinite-horizon average cost Markov decision process MDP. Based on the dynamics of channel state information (CSI) and queue state information (QSI), they focus on finding an adaptive user scheduling and power control policy to minimise the average delay of network subjected to the power constraints of heterogeneous base stations. In order to reduce the computational complexity and facilitate the distributive implementation, the authors derive a distributive stochastic learning algorithm which only requires local CSI and local QSI to determine the optimal user scheduling and power control policy. The simulation results confirm that significant delay performance gain can be achieved compared with various baseline schemes.

Efficient eNB deployment strategy for heterogeneous cells in 4G LTE systems

Base station deployment is an important issue in cellular communication systems because it determines the cost to construct and maintain a system and also the service quality to users. Conventional 2G and 3G systems assume that base stations are identical in the sense that they have the similar coverage range. For 4G systems, LTE introduces the concept of heterogeneous base stations (also called eNBs), which supports different sizes of coverage range. Given the user distribution and demands in a service area, the problem of deploying heterogeneous eNBs is NP-hard. Therefore, we propose a four-stage eNB deployment strategy to efficiently solve the problem. Our strategy first employs a geometric approach to provide the basic coverage to the service area. Then, it adaptively adjusts the cell range to satisfy the user demands under the power and bandwidth constraints on each eNB. Simulation results verify that the proposed strategy not only significantly saves the system cost, but also reduces the power consumption while balances the traffic loads of eNBs.

Multi-cell cooperation based on time reversal in heterogeneous wireless networks

Cooperation among heterogeneous base stations can improve spectrum efficiency through interference avoidance. This paper introduces a time reversal (TR) technique in multi-cell cooperation to mitigate interference and efficiently allocate spectrum resources. Exploiting its inherent power concentration feature, TR can effectively tackle the problem of edge effect. We present analysis and simulation results to demonstrate that proper use of TR significantly improves the spectrum efficiency of heterogeneous networks.

Performance Analysis and Energy Efficiency of Random Network Coding in LTE-Advanced

Recent trends witness the shift of the 3GPP Long Term Evolution - Advanced (LTE-A) radio access network (RAN) architecture from a traditional macro-cellular layout towards smaller base stations moving closer to end users. The evolved LTE-A RAN offers rich environment for multi-point and multi-hop cooperation and coordination resulting in increased capacity and more predictable channel conditions between heterogeneous base stations and end users. While these opportunities are recently well investigated at the physical layer through various cooperative multi-point (CoMP) schemes, upper layer protocols preserve the design proposed for macro-cellular single-hop data delivery. In this paper, we address this issue by proposing and investigating in detail a cooperative RAN-wide MAC layer protocol based on random network coding (RNC) that is designed specifically for reliable and flexible data delivery over the evolved LTE-A RAN. The proposed RNC-based MAC protocol (MAC-RNC) is evaluated and compared with the existing HARQ-based (MAC-HARQ) protocol in various LTE-A RAN layouts using a customized packet-based link-level simulator based on Finite-State Markov Chain (FSMC) channel models. Our results show that the MAC-RNC protocol introduces simplicity and flexibility required for future LTE-A RANs, while preserving or improving the performance of the MAC-HARQ protocol in traditional single-point single-hop macro-cellular scenarios.

Fundamentals of Inter-Cell Overhead Signaling in Heterogeneous Cellular Networks

Heterogeneous base stations (e.g., picocells, microcells, femtocells, and distributed antennas) will become increasingly essential for cellular network capacity and coverage. Up until now, little basic research has been done on the fundamentals of managing so much infrastructure-much of it unplanned-together with the carefully planned macro-cellular network. Inter-cell coordination is in principle an effective way of ensuring different infrastructure components behave in a way that increases, rather than decreases, the key quality of service (QoS) metrics. The success of such coordination depends heavily on how the overhead is shared, and the rate and delay of the overhead sharing. We develop a novel framework to quantify overhead signaling for inter-cell coordination, which is usually ignored in traditional 1-tier networks, and assumes even more importance in multi-tier heterogeneous cellular networks (HCNs). We derive the overhead quality contour for general -tier HCNs-the achievable set of overhead packet rate, size, delay, and outage probability-in closed-form expressions or computable integrals under general assumptions on overhead arrivals and different overhead signaling methods (backhaul and/or wireless). The overhead quality contour is further simplified for two widely used models of overhead arrivals: Poisson and deterministic arrival process. This framework can be used in the design and evaluation of any inter-cell coordination scheme. It also provides design insights on backhaul and wireless overhead channels to handle specific overhead signaling requirements.

Traffic analysis of heterogeneous mobile cellular networks using “wrap-up” cell structure

In this paper, we develop a tool for evaluating performance of a heterogeneous mobile network under different traffic conditions. The traffic condition is specified in a cluster of seven heterogeneous base stations, and "wrap-up" cell structure is applied to account for the traffic that crosses the boundary of the cluster. The performance of the network is specified in metrics which can be computed using the algorithm developed. These metrics relate to call rejection, i.e. the blocking of new calls, and the termination of handoff calls, as well as the carried traffic i.e. the expected number of ongoing calls in a station. These metrics are either measured for a single base station in a cluster, or measured for the average over the whole cluster. We apply the algorithm to some hypothetical data and present the numerical results. We also consider approximating a heterogeneous model with a simpler homogeneous model. Through some numerical results, we demonstrate the magnitude of errors that could result in the approximation.