Abstract
Owing to the dramatic increase in the smart devices' users in quest of high link capacity, the design of the next generation of wireless networks will necessarily have to consider spectral and energy effciency as the key pillars. The future wireless heterogeneous cellular networks (HCNs), featuring planned base stations (BSs), overlaid with unplanned micro, pico and femto BSs, can provide substantial gains in throughput and user experience as compared to the conventional homogeneous networks. My research is focusing on developing analytical models for HCNs employing spectrum and energy efficient techinques using tools from stochastic geometry.The first work is motivated to jointly support energy sustainability and high throughput performance by integrating simultaneous information and wireless power transfer (SWIPT) with HCNs. In this work, a tractable model for joint uplink (UL) and downlink (DL) transmission in a K-tier HCN with SWIPT is developed where the mobile users (MUs) decode information as well as harvest energy in the DL. The harvested energy is then utilized for UL information transmission. The analytical expressions for the DL average received power, the DL and UL outage probabilities and average ergodic rates are derived for the system design. The UL performance of a MU is shown to be improved by increasing the fraction of the DL received power for energy harvesting in the network, whereas the energy eciency is shown to be improved with the increase in SBSs density.
The second work proposed a K-tier HCNs wherein the macrocell tier comprises half duplex (HD) BSs and the small cell tiers consist of full duplex (FD) BSs. In theory, FD data transmission is capable of doubling the spectral eciency with the same amount of energy compared to that of half-duplex (HD) system. The FD communication is considered at the small cell BSs only due to their low-powered nature and ease of deployment. The performance of the proposed HCNs is evaluated in terms of the DL and UL average ergodic rates which is shown to be improved as compared to the conventional HCNs where all tiers operate in HD mode.
An important challenge in HCNs with FD small cells is the decrease in coverage due to the increased interference from simultaneous DL and UL operations on the same band in FD mode. This motivates to consider massive multiuser multiple-input multiple-output (MIMO) at the macrocells, which is a promising wireless communication technology for improved coverage and cell edge performance. In the third work, HCNs with massive MIMO antennas at the macrocell BSs and FD small cell is studied. Since, UL power control further improves the coverage performance of the cell edge MUs and eciently utilize their battery, distance proportional fractional power control has been considered as well. It is shown that the link reliability and area spectral eciency of the network can be signi cantly leveraged by taking advantage of FD small cell BSs density and the number of antennas at the macrocell BSs.
At the end, according to the overall picture of the research conducted, the main conclusions together with some directions for the future work are presented.
| Date of Award | 2018 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Vasilis Friderikos (Supervisor) & Arumugam Nallanathan (Supervisor) |