Optimising energy efficiency and spectral efficiency in multi-tier heterogeneous networks:performance and tradeoffs

The exponential growth in the number of cellular users along with their increasing demand of higher transmission rate and lower power consumption is a dilemma for the design of future generation networks. The spectral efficiency (SE) can be improved by better utilisation of the network resources at the cost of reduction in the energy efficiency (EE) due to the enormous increase in the network power expenditure arising from the densification of the network. One of the possible solutions is to deploy Heterogeneous Networks (HetNets) consisting of several tiers of small cell BSs overlaid within the coverage area of the macrocells. The HetNets can provide better coverage and data rate to the cell edge users in comparison to the macrocells only deployment. One of the key requirements for the next generation networks is to maintain acceptable levels of both EE and SE. In order to tackle these challenges, this thesis focuses on the analysis of the EE, SE and their tradeoff for different scenarios of HetNets. First, a joint network and user adaptive selection mechanism in two-tier HetNets is proposed to improve the SE using game theory to dynamically re-configure the network while satisfying the user's quality-of-service (QoS) requirements. In this work, the proposed scheme tries to offload the traffic from the heavily loaded small cells to the macrocell. The user can only be admitted to a network which satisfies the call admission control procedures for both the uplink and downlink transmission scheme. Second, an energy efficient resource allocation scheme is designed for a two-tier HetNets. The proposed scheme uses a low-complexity user association and power allocation algorithm to improve the uplink system EE performance in comparison to the traditional cellular systems. In addition, an opportunistic joint user association and power allocation algorithm is proposed in an uplink transmission scheme of device to device (D2D) enabled HetNets. In this scheme, each user tries to maximise its own Area Spectral Efficiency (ASE) subject to the required Area Energy Efficiency (AEE) requirements. Further, a near-optimal joint user association and power allocation approach is proposed to investigate the tradeoff between the two conflicting objectives such as achievable throughput and minimising the power consumption in two-tier HetNets for the downlink transmission scheme. Finally, a multi-objective optimization problem is formulated that jointly maximizes the EE and SE in two-tier HetNets. In this context, a joint user association and power allocation algorithm is proposed to analyse the tradeoff between the achievable EE and SE in two-tier HetNets. The formulated problem is solved using convex optimisation methods to obtain the Pareto-optimal solution for the various network parameters

Energy-efficient location estimation using variable range beacons in wireless sensor networks

In a randomly deployed wireless sensor network, sensor nodes must determine their own geographic position coordinates so that the collected data can be ascribed to the location from where it was gathered. We propose a localization algorithm which uses variable range beacon signals generated by varying the transmission power of beacon nodes. The algorithm does not use any additional hardware resources for ranging and estimates position using only radio connectivity by passively listening to the beacon signals. The algorithm is distributed, so each sensor node determines its own position and communication overhead is avoided. As the beacon nodes do not always transmit at maximum power and no transmission power is used by unknown sensor nodes for localization, the algorithm is also energy efficient. It also provides control over localization granularity. Simulation results show that the algorithm provides good accuracy under varying radio conditions

Performance analysis of hybrid 5G cellular networks exploiting mmWave capabilities in suburban areas

Millimeter wave (mmWave) technology is considered as a key enabler for fifth generation (5G) networks to achieve higher data rates with low transmission power by offloading the users with low signal-to-noise-ratios. Millimeter wave networks operating at E and W frequency bands have available bandwidth of 1 GHz or more to provide higher data rates whereas their propagation characteristics differ greatly from the conventional Ultra High Frequency (UHF) networks operating at sub 6 GHz frequency band. The purpose of this paper is to investigate the performance in terms of coverage and rate, of hybrid cellular networks where base stations (BSs) operating at mmWave and sub 6 GHz bands coexist in suburban environment such as a university campus. The actual building locations within a suburban university campus are modeled as blockages and the analysis is carried out for different densities of UHF and mmWave BSs for different densities of outdoor users. Our analysis also highlight the fact that mmWave cellular networks are predominantly noise-limited due to larger available bandwidth in comparison to the interference limited conventional UHF networks. Extensive simulation results demonstrate the effectiveness of dense deployment of mmWave BSs to achieve better coverage and rate probabilities in comparison to the stand alone UHF network

A game theoretical network-assisted user-centric design for resource allocation in 5G heterogeneous networks

For the past few years, 5G heterogeneous networks (HetNets) have gain phenomenal attention in the wireless industry. In this paper, we propose a hierarchical game theoretical framework for the optimal resource allocation on the uplink of a heterogeneous network with femtocells overlaid on the edge of a macrocell. In the first game, the femtocell access points (FAPs) play a non- cooperative game to choose their access policy between open and closed in order to maximize the rate of their home subscribers. The second game of the algorithm allows macrocell user equipments (MUEs) to decide their connectivity between the FAPs and the macrocell base station (MBS) with the goal of maximizing their rates and the overall network performance; thereby, distributing intelligence and control to the users. The FAPs and the MUEs are the players of two different games that strategically decide their policies in an ordered fashion. Simulation results show that this hierarchical game approach with network- assisted user-centric design offers a significant improvement in terms of the performance of HetNets relative to an closed and only network-centric access policy schemes

Performance Analysis of THz Enabled HetNets in Diverse Building Densities

Beyond 5G networks require low latency, high throughput and high data rates while maintaining appreciable coverage. To achieve this, a wider bandwidth is required. Terahertz (THz) band can provide such large bandwidth, however, it is not as reliable as the sub 6 GHz band due to absorption effects. Hence, we need infrastructure level approaches such as heterogeneous networks (HetNet) that provide backwards compatibility to increase coverage and reliability. In this paper, we consider a HetNet comprised of small base stations at THz and mmWave frequencies, and macro base station at sub-6 GHz frequency at different building densities based on multiple cities around the world. For quality of service (QoS) performance metrics, we take data rate coverage and power efficiency. Different system parameters are varied for six different locations to analyze the effectiveness of the proposed HetNet. Our results show that B5G networks are considerably more effective in environments with low building densities

Beyond the Horizon, Backhaul Connectivity for Offshore IoT Devices

The prevalent use of the Internet of Things (IoT) devices over the Sea, such as, on oil and gas platforms, cargo, and cruise ships, requires high-speed connectivity of these devices. Although satellite based backhaul links provide vast coverage, but they are inherently constrained by low data rates and expensive bandwidth. If a signal propagated over the sea is trapped between the sea surface and the Evaporation Duct (ED) layer, it can propagate beyond the horizon, achieving long-range backhaul connectivity with minimal attenuation. This paper presents experimental measurements and simulations conducted in the Industrial, Scientific, and Medical (ISM) Band Wi-Fi frequencies, such as 5.8 GHz to provide hassle-free offshore wireless backhaul connectivity for IoT devices over the South China Sea in the Malaysian region. Real-time experimental measurements are recorded for 10 km to 80 km path lengths to determine average path loss values. The fade margin calculation for ED must accommodate additional slow fading on top of average path loss with respect to time and climate-induced ED height variations to ensure reliable communication links for IoT devices. Experimental results confirm that 99% link availability of is achievable with minimum 50 Mbps data rate and up to 60 km distance over the Sea to connect offshore IoT devices

A Multi-Criteria Decision Making (MCDM) network selection model providing enhanced QoS differentiation to customers

This paper proposes a radio resource management framework for integrated network selection mechanism control in multi- network environment as an interaction between the service providers and users in competitive manner to admit high priority users or the services that maximize their rewards. The proposed scheme comprises of three steps namely as user profile, service profile and access network selection. The priorities are assigned to the users depending on their grade and category. The users belonging to same categories have same preferences for the decision factors (or QoS parameters). Different policies are defined according to the network load to prioritize high priority users as compared to the type of service requested. The access network selection mechanism calculates the payoffs based on their relative weights calculated using AHP and a utility function evaluation by each wireless network for each user. The proposed model is preliminary and its contribution is to create an admission policy that can adapt to different coverage areas of a wireless network and depends on the priority of users and their requirements

Enhanced cooperation in heterogeneous wireless networks using coverage adjustment

This paper illustrates an approach to improving the user perceived QoS in heterogeneous networks through the use of a two layered optimization. The top layer views the problem of prediction of the network that would be chosen by a user where the criteria are offered bit rate, price, mobility support and reputation. At the second level, conditional on the strategies chosen by the users, the network operator hypothetically, reconfigures the network, subject to the network constraints of bandwidth and acceptable SNR and optimizes the network coverage to support users who would otherwise not be serviced adequately. This forms an iterative cycle until a solution that optimizes the user satisfaction subject to the adjustments that the network operator can make to mitigate the binding constraints, is found. The process is illustrated through a simple example using a Wi-Fi and a WiMAX network

A game theoretic based Call Admission Control scheme for competing WiMAX networks

Call Admission Control (CAC) is one of the most important parts in radio resource management of the wireless networks and it has a huge impact on the quality of service (QoS).Traditional CAC strategies focus on increasing the radio resource utility by decreasing the service blocking probabilities. In this paper, a new CAC scheme based on game theory is introduced to analyze the conflicts and rewards for different network operators. The game theoretic based CAC scheme contains two parts, utility function computation and a non-cooperative game between two networks to maximize their rewards. The proposed framework is preliminary and its objective is investigate the possibility that networks should be able to autonomously define policies for different parts of a coverage area depending on the priority of users and their requirements. In this approach, the two simulated WiMAX networks compete with each other for traffic units in overlapping coverage area and maximize their rewards. The proposed scheme is illustrated with the help of an example in which most of the traffic units lie close to one network as compared to the other network. Future work will present results of simulation studies for more detailed experiments

Game theoretical formulation of network selection in competing wireless networks:an analytic hierarchy process model

Network Selection mechanisms play an important role in ensuring quality of service for users in a multi-network environment. These mechanisms handle the selection of an optimal wireless network to satisfy a user request. This paper proposes a radio resource management framework for integrated network selection mechanism control in multi- network environment as an interaction game between the service providers and customers in non-cooperative manner to maximize their rewards. The proposed scheme comprises two steps. The first applies the analytic hierarchy process (AHP) to determine the relative weights of the evaluative criteria according to customer preferences and network condition. The second calculates the payoffs based on the relative weights calculated in the previous step and a utility function evaluation by each wireless network of each customer. Analytical and simulation results demonstrate the effectiveness of proposed model to achieve optimum network utility for the wireless networks along with optimizing the customer's satisfaction. The proposed model is preliminary and its contribution is to create an admission policy that can adapt to different coverage areas of a wireless network and depends on the priority of customers and their requirements