A survey of self organisation in future cellular networks

This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks

Device-to-Device Communication and Multihop Transmission for Future Cellular Networks

The next generation wireless networks i.e. 5G aim to provide multi-Gbps data traffic, in order to satisfy the increasing demand for high-definition video, among other high data rate services, as well as the exponential growth in mobile subscribers. To achieve this dramatic increase in data rates, current research is focused on improving the capacity of current 4G network standards, based on Long Term Evolution (LTE), before radical changes are exploited which could include acquiring additional/new spectrum. The LTE network has a reuse factor of one; hence neighbouring cells/sectors use the same spectrum, therefore making the cell edge users vulnerable to inter-cell interference. In addition, wireless transmission is commonly hindered by fading and pathloss. In this direction, this thesis focuses on improving the performance of cell edge users in LTE and LTE-Advanced (LTE-A) networks by initially implementing a new Coordinated Multi-Point (CoMP) algorithm to mitigate cell edge user interference. Subsequently Device-to-Device (D2D) communication is investigated as the enabling technology for maximising Resource Block (RB) utilisation in current 4G and emerging 5G networks. It is demonstrated that the application, as an extension to the above, of novel power control algorithms, to reduce the required D2D TX power, and multihop transmission for relaying D2D traffic, can further enhance network performance. To be able to develop the aforementioned technologies and evaluate the performance of new algorithms in emerging network scenarios, a beyond-the-state-of-the-art LTE system-level simulator (SLS) was implemented. The new simulator includes Multiple-Input Multiple-Output (MIMO) antenna functionalities, comprehensive channel models (such as Wireless World initiative New Radio II i.e. WINNER II) and adaptive modulation and coding schemes to accurately emulate the LTE and LTE-A network standards. Additionally, a novel interference modelling scheme using the ‘wrap around’ technique was proposed and implemented that maintained the topology of flat surfaced maps, allowing for use with cell planning tools while obtaining accurate and timely results in the SLS compared to the few existing platforms. For the proposed CoMP algorithm, the adaptive beamforming technique was employed to reduce interference on the cell edge UEs by applying Coordinated Scheduling (CoSH) between cooperating cells. Simulation results show up to 2-fold improvement in terms of throughput, and also shows SINR gain for the cell edge UEs in the cooperating cells. Furthermore, D2D communication underlaying the LTE network (and future generation of wireless networks) was investigated. The technology exploits the proximity of users in a network to achieve higher data rates with maximum RB utilisation (as the technology reuses the cellular RB simultaneously), while taking some load off the Evolved Node B (eNB) i.e. by direct communication between User Equipment (UE). Simulation results show that the proximity and transmission power of D2D transmission yields high performance gains for a D2D receiver, which was demonstrated to be better than that of cellular UEs with better channel conditions or in close proximity to the eNB in the network. The impact of interference from the simultaneous transmission however impedes the achievable data rates of cellular UEs in the network, especially at the cell edge. Thus, a power control algorithm was proposed to mitigate the impact of interference in the hybrid network (network consisting of both cellular and D2D UEs). It was implemented by setting a minimum SINR threshold so that the cellular UEs achieve a minimum performance, and equally a maximum SINR threshold to establish fairness for the D2D transmission as well. Simulation results show an increase in the cell edge throughput and notable improvement in the overall SINR distribution of UEs in the hybrid network. Additionally, multihop transmission for D2D UEs was investigated in the hybrid network: traditionally, the scheme is implemented to relay cellular traffic in a homogenous network. Contrary to most current studies where D2D UEs are employed to relay cellular traffic, the use of idle nodes to relay D2D traffic was implemented uniquely in this thesis. Simulation results show improvement in D2D receiver throughput with multihop transmission, which was significantly better than that of the same UEs performance with equivalent distance between the D2D pair when using single hop transmission

PACE: Simple Multi-hop Scheduling for Single-radio 802.11-based Stub Wireless Mesh Networks

IEEE 802.11-based Stub Wireless Mesh Networks (WMNs) are a cost-effective and flexible solution to extend wired network infrastructures. Yet, they suffer from two major problems: inefficiency and unfairness. A number of approaches have been proposed to tackle these problems, but they are too restrictive, highly complex, or require time synchronization and modifications to the IEEE 802.11 MAC. PACE is a simple multi-hop scheduling mechanism for Stub WMNs overlaid on the IEEE 802.11 MAC that jointly addresses the inefficiency and unfairness problems. It limits transmissions to a single mesh node at each time and ensures that each node has the opportunity to transmit a packet in each network-wide transmission round. Simulation results demonstrate that PACE can achieve optimal network capacity utilization and greatly outperforms state of the art CSMA/CA-based solutions as far as goodput, delay, and fairness are concerned

IST-2000-30148 I-METRA: D6.2 Implications in re-configurable systems beyond 3G (Part 2)

This activity evaluates the extension of the bandwidth of the UTRA MIMO HSDPA concept to 20 MHz, which is precisely the bandwidth of HIPERLAN/2. This would allow a fair comparison between the performance of UTRA MIMO HSDPA and the enhanced HIPERLAN/2. The bandwidth expansion would be the consequence of multiplying the chip rate of the W-CDMA spreading by four, i.e., 3.84 x 4 = 15.36 Mcps. A higher bandwidth MIMO channel model is necessary and this will be developed based on the channel model already developed in WP2. High data rates are required to satisfy the ever-increasing application requirements in future wireless communication systems. Recent investigations have indicated that a peak data rate of up to 20Mbps per user in the DL may be required for satisfactory reception of bursty traffic. As the transmission powers (of both mobile terminals and base stations) are limited, higher data rates lead to the reduction of the effective coverage area of a cell. That is, only users that are close to the base station will be able to communicate with high data rates, while users far away from the base station will only be able to use low data rates.Preprin

Routing Strategies for Capacity Enhancement in Multi-hop Wireless Ad Hoc Networks

This thesis examines a Distributed Interference Impact Probing (DIIP) strategy for Wireless Ad hoc Networks (WANETs), using a novel cross-layer Minimum Impact Routing (MIR) protocol. Perfonnance is judged in tenns of interference reduction ratio, efficiency, and system and user capacity, which are calculated based on the measurement of Disturbed Nodes (DN). A large number of routing algorithms have been proposed with distinctive features aimed to overcome WANET's fundamental challenges, such as routing over a dynamic topology, scheduling broadcast signals using dynamic Media Access Control (MAC), and constraints on network scalability. However, the scalability problem ofWANET cannot simply adapt the frequency reuse mechanism designed for traditional stationary cellular networks due to the relay burden, and there is no single comprehensive algorithm proposed for it. DIIP enhances system and user capacity using a cross layer routing algorithm, MIR, using feedback from DIIP to balance transmit power in order to control hop length, which consequently changes the number of relays along the path. This maximizes the number of simultaneous transmitting nodes, and minimizes the interference impact, i.e. measured in tenns of 'disturbed nodes'. The perfonnance of MIR is examined compared with simple shortest-path routing. A WANET simulation model is configured to simulate both routing algorithms under multiple scenarios. The analysis has shown that once the transmitting range of a node changes, the total number of disturbed nodes along a path changes accordingly, hence the system and user capacity varies with interference impact variation. By carefully selecting a suitable link length, the neighbouring node density can be adjusted to reduce the total number of DN, and thereby allowing a higher spatial reuse ratio. In this case the system capacity can increase significantly as the number of nodes increases. In contrast, if the link length is chosen regardless ofthe negative impact of interference, capacity decreases. In addition, MIR diverts traffic from congested areas, such as the central part of a network or bottleneck points

Multihop relay techniques for communication range extension in near-field magnetic induction communication systems

In this paper, multihop relaying in RF-based com munications and near field magnetic induction communication (NFMIC) is discussed. Three multihop relay strategies for NFMIC are proposed: Non Line of Sight Magnetic Induction Relay (NLoS-MI Relay), Non Line of Sight Master/Assistant Magnetic Induction Relay1 (NLoS-MAMI Relay1) and Non Line of Sight Master/Assistant Magnetic Induction Relay2 (NLoSMAMI Relay2). In the first approach only one node contributes to the communication, while in the other two techniques (which are based on a master-assistant strategy), two relaying nodes are employed. This paper shows that these three techniques can be used to overcome the problem of dead spots within a body area network and extend the communication range without increasing the transmission power and the antenna size or decreasing receiver sensitivity. The impact of the separation distance between the nodes on the achievable RSS and channel data rate is evaluated for the three techniques. It is demonstrated that the technique which is most effective depends on the specific network topology. Optimum selection of nodes as relay master and assistant based on the location of the nodes is discussed. The paper also studies the impact of the quality factor on achievable data rate. It is shown that to obtain the highest data rate, the optimum quality factor needs to be determined for each proposed cooperative communication method. © 2013 ACADEMY PUBLISHER

Medium Access Control and Routing Protocols Design for 5G

In future wireless systems, such as 5G and beyond, the current dominating human-centric communication systems will be complemented by a tremendous increase in the number of smart devices, equipped with radio devices, possibly sensors, and uniquely addressable. This will result in explosion of wireless traffic volume, and consequently exponential growth in demand of radio spectrum. There are different engineering techniques for resolving the cost and scarcity of radio spectrum such as coexistence of diverse devices on the same pool of radio resources, spectrum aggregations, adoption of mmWave bands with huge spectrum, etc. The aim of this thesis is to investigate Medium Access Control (MAC) and routing protocols for 5G and beyond radio networks. Two scenarios are addressed: heterogeneous scenario where scheduled and uncoordinated users coexist, and a scenario where drones are used for monitoring a given area. In the heterogeneous scenario scheduled users are synchronised with the Base Station (BS) and rely on centralised resource scheduler for assignment of time slots, while the uncoordinated users are asynchronous with each other and the BS and rely unslotted Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) for channel access. First, we address a single-hop network with advanced scheduling algorithm design and packet length adaptation schemes design. Second, we address a multi-hop network with novel routing protocol for enhancing performance of the scheduled users in terms of throughput, and coexistence of all network users. In the drone-based scenario, new routing protocols are designed to address the problems of Wireless Mesh Networks with monitoring drones. In particular, a novel optimised Hybrid Wireless Mesh Protocol (O-HWMP) for a quick and efficient discovery of paths is designed, and a capacity achieving routing and scheduling algorithm, called backpressure, investigated. To improve on the long-end-to-end delays of classical backpressure, a modified backpressure algorithm is proposed and evaluated

Self organization of tilts in relay enhanced networks: a distributed solution

Despite years of physical-layer research, the capacity enhancement potential of relays is limited by the additional spectrum required for Base Station (BS)-Relay Station (RS) links. This paper presents a novel distributed solution by exploiting a system level perspective instead. Building on a realistic system model with impromptu RS deployments, we develop an analytical framework for tilt optimization that can dynamically maximize spectral efficiency of both the BS-RS and BS-user links in an online manner. To obtain a distributed self-organizing solution, the large scale system-wide optimization problem is decomposed into local small scale subproblems by applying the design principles of self-organization in biological systems. The local subproblems are non-convex, but having a very small scale, can be solved via standard nonlinear optimization techniques such as sequential quadratic programming. The performance of the developed solution is evaluated through extensive simulations for an LTE-A type system and compared against a number of benchmarks including a centralized solution obtained via brute force, that also gives an upper bound to assess the optimality gap. Results show that the proposed solution can enhance average spectral efficiency by up to 50% compared to fixed tilting, with negligible signaling overheads. The key advantage of the proposed solution is its potential for autonomous and distributed implementation