Easy Wireless: broadband ad-hoc networking for emergency services

Wireless ad-hoc networks will enable emergency services to continuously overview and act upon the actual status of the situation by retrieving and exchanging detailed up-to-date information between the rescue workers. Deployment of high-bandwidth, robust, self-organising ad-hoc networks will enable quicker response to typical what/where/when questions, than the more vulnerable low-bandwidth communication networks currently in use. This paper addresses a number of results of the Easy Wireless project that enable high bandwidth robust ad-hoc networking. Most of the concepts presented here have been experimentally verified and/or prototyped

Analysis of hybrid-ARQ based relaying protocols under modulation constraints

In a seminal paper published in 2001, Caire and Tuninetti derived an information theoretic bound on the throughput of hybrid-ARQ in the presence of block fading. However, the results placed no constraints on the modulation used, and therefore the input to the channel was Gaussian. The purpose of this thesis is to investigate the impact of modulation constraints on the throughput of hybrid-ARQ in a block fading environment. First, we consider the impact of modulation constraints on information outage probability for a block fading channel with a fixed length codeword. Then, we consider the effect of modulation constraints upon the throughput of hybrid-ARQ, where the rate of the codeword varies depending on the instantaneous channel conditions. These theoretical bounds are compared against the simulated performance of HSDPA, a newly standardized hybrid-ARQ protocol that uses QPSK and 16-QAM bit interleaved turbo-coded modulation. The results indicate how much of the difference between HSDPA and the previous unconstrained modulation bound is due to the use of the turbo-code and how much is due to the modulation constraints. (Abstract shortened by UMI.)

TD-SCDMA Relay Networks

PhDWhen this research was started, TD-SCDMA (Time Division Synchronous Code Division Multiple Access) was still in the research/ development phase, but now, at the time of writing this thesis, it is in commercial use in 10 large cities in China including Beijing and Shang Hai. In all of these cities HSDPA is enabled. The roll-out of the commercial deployment is progressing fast with installations in another 28 cities being underway now. However, during the pre-commercial TD-SCDM trail in China, which started from year 2006, some interference problems have been noticed especially in the network planning and initialization phases. Interference is always an issue in any network and the goal of the work reported in this thesis is to improve network coverage and capacity in the presence of interference. Based on an analysis of TD-SCDMA issues and how network interference arises, this thesis proposes two enhancements to the network in addition to the standard N-frequency technique. These are (i) the introduction of the concentric circle cell concept and (ii) the addition of a relay network that makes use of other users at the cell boundary. This overall approach not only optimizes the resilience to interference but increases the network coverage without adding more Node Bs. Based on the cell planning parameters from the research, TD-SCDMA HSDPA services in dense urban area and non-HSDPA services in rural areas were simulated to investigate the network performance impact after introducing the relay network into a TD-SCDMA network. The results for HSDPA applications show significant improvement in the TDSCDMA relay network both for network capacity and network interference aspects compared to standard TD-SCDMA networks. The results for non- HSDPA service show that although the network capacity has not changed after adding in the relay network (due to the code limitation in TD-SCDMA), the TD-SCDMA relay network has better interference performance and greater coverage

Resource Allocation in Ad Hoc Networks

Unlike the centralized network, the ad hoc network does not have any central administrations and energy is constrained, e.g. battery, so the resource allocation plays a very important role in efficiently managing the limited energy in ad hoc networks. This thesis focuses on the resource allocation in ad hoc networks and aims to develop novel techniques that will improve the network performance from different network layers, such as the physical layer, Medium Access Control (MAC) layer and network layer. This thesis examines the energy utilization in High Speed Downlink Packet Access (HSDPA) systems at the physical layer. Two resource allocation techniques, known as channel adaptive HSDPA and two-group HSDPA, are developed to improve the performance of an ad hoc radio system through reducing the residual energy, which in turn, should improve the data rate in HSDPA systems. The channel adaptive HSDPA removes the constraint on the number of channels used for transmissions. The two-group allocation minimizes the residual energy in HSDPA systems and therefore enhances the physical data rates in transmissions due to adaptive modulations. These proposed approaches provide better data rate than rates achieved with the current HSDPA type of algorithm. By considering both physical transmission power and data rates for defining the cost function of the routing scheme, an energy-aware routing scheme is proposed in order to find the routing path with the least energy consumption. By focusing on the routing paths with low energy consumption, computational complexity is significantly reduced. The data rate enhancement achieved by two-group resource allocation further reduces the required amount of energy per bit for each path. With a novel load balancing technique, the information bits can be allocated to each path in such that a way the overall amount of energy consumed is minimized. After loading bits to multiple routing paths, an end-to-end delay minimization solution along a routing path is developed through studying MAC distributed coordination function (DCF) service time. Furthermore, the overhead effect and the related throughput reduction are studied. In order to enhance the network throughput at the MAC layer, two MAC DCF-based adaptive payload allocation approaches are developed through introducing Lagrange optimization and studying equal data transmission period

Testing cooperative communication schemes in a virtual distributed testbed of wireless networks

It is expected that Next Generation Networks (NGNs) will offer seamless interoperability among heterogeneous access technologies in order to provide ubiquitous access. In such settings, short range technologies may be used in order to extend the coverage area of cellular systems while cooperative diversity can improve the efficiency of the wireless systems. An advanced, backward compatible, with the 802.11 standard, MAC protocol for cooperative ARQ scenarios in NGNs sets the research framework for this work. The functionalities of the RCSMA protocol 1 will be enhanced and the derived analytical models will be validated at the UNITE Virtual Distributed Testbed (VDT) (2).Peer ReviewedPostprint (published version

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

Application of MIH for the Lightweight Deployment of LTE-Advanced Systems through Mobile Relaying

[ES] Evaluación del uso de relays móviles Wifi en tecnología LTE-Advanced[EN] Evaluation of Wifi Mobile Relaying in LTE-Advanced SystemsGualda Romero, P. (2012). Application of MIH for the Lightweight Deployment of LTE-Advanced Systems through Mobile Relaying. http://hdl.handle.net/10251/27176.Archivo delegad