On the Impact of Control Channel Reliability on Coordinated Multi-Point Transmission

In the heterogeneous networks (HetNets), co-channel interference is a serious problem. Coordinated multi-point (CoMP) transmission has emerged as a powerful technique to mitigate co-channel interference. However, all CoMP techniques rely on information exchange through reliable control channels, which are unlikely to be available in HetNets. In this paper, we study the effect of unreliable control channels, consisting of the access links and backhaul links, on the performance of CoMP. A control channel model is introduced by assigning link failure probability (LFP) to backhaul and access links for the cooperative clusters. Three CoMP architectures, namely the centralized, semi-distributed and fully distributed are analyzed. We investigate the probability of deficient control channels reducing quality of service, and impeding transmission. General closed-form expressions are derived for the probability of a cooperative transmission node staying silent in a resource slot due to unreliable control links. By evaluating the average sum rate of users within a CoMP cluster, we show that the performance gains offered by CoMP quickly diminish, as the unreliability of the control links grows

HAPS for 6G Networks: Potential Use Cases, Open Challenges, and Possible Solutions

High altitude platform station (HAPS), which is deployed in the stratosphere at an altitude of 20-50 kilometres, has attracted much attention in recent years due to their large footprint, line-of-sight links, and fixed position relative to the Earth. Compared with existing network infrastructure, HAPS has a much larger coverage area than terrestrial base stations and is much closer than satellites to the ground users. Besides small-cells and macro-cells, a HAPS can offer one mega-cell, which can complement legacy networks in 6G and beyond wireless systems. This paper explores potential use cases and discusses relevant open challenges of integrating HAPS into legacy networks, while also suggesting some solutions to these challenges. The cumulative density functions of spectral efficiency of the integrated network and cell-edge users are studied and compared with terrestrial network. The results show the capacity gains achieved by the integrated network are beneficial to cell-edge users. Furthermore, the advantages of a HAPS for backhauling aerial base stations are demonstrated by the simulation results

Green Cellular Networks: A Survey, Some Research Issues and Challenges

Energy efficiency in cellular networks is a growing concern for cellular operators to not only maintain profitability, but also to reduce the overall environment effects. This emerging trend of achieving energy efficiency in cellular networks is motivating the standardization authorities and network operators to continuously explore future technologies in order to bring improvements in the entire network infrastructure. In this article, we present a brief survey of methods to improve the power efficiency of cellular networks, explore some research issues and challenges and suggest some techniques to enable an energy efficient or "green" cellular network. Since base stations consume a maximum portion of the total energy used in a cellular system, we will first provide a comprehensive survey on techniques to obtain energy savings in base stations. Next, we discuss how heterogeneous network deployment based on micro, pico and femto-cells can be used to achieve this goal. Since cognitive radio and cooperative relaying are undisputed future technologies in this regard, we propose a research vision to make these technologies more energy efficient. Lastly, we explore some broader perspectives in realizing a "green" cellular network technologyComment: 16 pages, 5 figures, 2 table

Powerline communication and demand side management for microgrids

Motivation: The greatest challenge for microgrid deployment is making energy affordable, especially in remote low-income communities. This thesis answers the following research question: Can digital communication reduce the price of electricity for an islanded low voltage microgrid and if so, can broadband powerline communications meet microgrid control requirements? Approach: This study conducts a cost-benefit analysis of the addition of a field area network to a microgrid. Broadband powerline communication is selected as a candidate technology and tested on various microgrid networks to determine its suitability. Results: The main contributions of this study are: A demand-side management strategy and unsubsidised cost reflective tariff structure for rural microgrids in the developing world. A cost-benefit analysis that shows the addition of a low bit rate, medium latency communication system (1 kbps per customer, 100 ms) may reduce the levelized cost of energy by 32%. A performance evaluation of broadband HomePlug powerline communications for microgrids which shows the Homeplug AV2 has a range of 600 m and functions well on complex radial distribution networks. Conclusion: Investment in a minimally capable communication system has significant economic benefit to both customer and utility by enabling smart grid services such as automatic meter reading and demand side management. Since communication technologies share similar bit rate and latency capabilities and are similarly priced, the technology choice is driven more by microgrid geography, complexity, availability and reliability. Powerline communications require no additional cable, but boast reliability similar to dedicated cable solutions. The HomePlug AV meets bit rate and latency requirements, is affordable, reliable, simple and widely available around the world. This study concludes it is a solid candidate for low voltage islanded microgrids. The material presented in this thesis has been published or submitted for publication in an abbreviated format in the following publications: D. Neal et al, "Demand side energy management and customer behavioral response in a rural islanded microgrid," in IEEE PES/IAS PowerAfrica, 2020. D. Neal, D. Rogers and M. McCulloch, "A Techno-Economic Analysis of Communication in Islanded Microgrids," unpublished. Submitted Oct 2023 to Elsevier Renewable and Sustainable Energy Reviews. D. Neal, D. Rogers and M. McCulloch, "Broadband Powerline Communication for Low-Voltage Microgrids," unpublished. Submitted Oct 2023 to IEEE Transactions on Power Delivery