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Dive into the research topics where Michael Fitch is active.

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Featured researches published by Michael Fitch.


IEEE Communications Magazine | 2011

Wireless service provision in TV white space with cognitive radio technology: A telecom operator's perspective and experience

Michael Fitch; Maziar Nekovee; Santosh Kawade; Keith Briggs; Richard MacKenzie

Currently there is a very fundamental change happening in spectrum regulation, possibly the most fundamental ever in its history. This is the enabling of spectrum sharing, where primary (licensed) users of the spectrum, are forced to allow sharing with secondary users, who use license-exempt equipment. Such sharing is free for the secondary users, subject to the condition that they do not cause harmful interference to the primary users. The first instance of such sharing is occurring with the UHF digital TV spectrum, in what is commonly called TV white space. Regulators such as the FCC in the United States and Ofcom in the United Kingdom have indicated that other spectrum will follow suit. Cognitive radio is an enabling technology that allows such sharing. Following recent rulings by FCC and Ofcom and the emergence of a series of related industry standards, CR operation in TVWS is moving from the research domain towards implementation and commercialization, with use-cases that are of interest to telecom operators. In this article we describe three such use cases: future home networks, coverage of the street from inside buildings, and broadband access to rural and underserved premises. We present results of modeling and trials of technical feasibility, undertaken by the Innovate and Design team at BT. Based on our experience we draw conclusions regarding the feasibility and commercial importance of these use cases, and identify some of the remaining technical and commercial challenges.


international conference on smart grid communications | 2011

UHF white space network for rural smart grid communications

Malcolm Ronald Brew; Faisal Darbari; Louise H. Crockett; Mark Waddell; Michael Fitch; Stephan Weiss; Robert W. Stewart

We present a white space communications test bed running in the Scottish Highlands and Islands, and discuss its feasibility for smart grid communications. The network aims to serve communities that have great potential for distributed generation of electricity, by means of wind, water, and tidal power. However, smart grid applications such as remote meter reading and load balancing are impaired by the scarcety or lack of communications infrastructure in remote rural areas such as the Scottish Highlands and Islands. We argue that the proposed system is based on a network of energy self-sufficient radio relay nodes that make it a robust and independent medium to support smart grid communications in rural settings.


personal, indoor and mobile radio communications | 2009

Impact of interference on throughput in dense WLANs with multiple APs

Micheal Drieberg; Fu-Chun Zheng; Rizwan Ahmad; Michael Fitch

The popularity of wireless local area networks (WLANs) has resulted in their dense deployments around the world. While this increases capacity and coverage, the problem of increased interference can severely degrade the performance of WLANs. However, the impact of interference on throughput in dense WLANs with multiple access points (APs) has had very limited prior research. This is believed to be due to 1) the inaccurate assumption that throughput is always a monotonically decreasing function of interference and 2) the prohibitively high complexity of an accurate analytical model. In this work, firstly we provide a useful classification of commonly found interference scenarios. Secondly, we investigate the impact of interference on throughput for each class based on an approach that determines the possibility of parallel transmissions. Extensive packet-level simulations using OPNET have been performed to support the observations made. Interestingly, results have shown that in some topologies, increased interference can lead to higher throughput and vice versa.


international symposium on wireless pervasive computing | 2009

Modelling Energy Consumption of Relay-Enabled MAC Protocols in Ad Hoc Networks

Rizwan Ahmad; Fu-Chun Zheng; Micheal Drieberg; Sverrir Olafsson; Michael Fitch

To enhance the throughput of ad hoc networks, dual-hop relay-enabled transmission schemes have recently been proposed. Since in ad hoc networks throughput is normally related to their energy consumption, it is important to examine the impact of using relay-enabled transmissions on energy consumption. In this paper, we present an analytical energy consumption model for dual-hop relay-enabled medium access control (MAC) protocols. Based on the recently reported Relay-enabled Distributed Coordination Function (rDCF), we have shown the efficacy of the proposed analytical model. This is a generalized model and can be used to predict energy consumption in saturated relay-enabled ad hoc networks via energy decomposition. This is helpful in designing MAC protocols for cooperative communications and it is shown that using a relay results not only in a better throughput but also better energy efficiency.


IEEE Communications Letters | 2015

Wireless Backhaul Networks With Precoding Complex Field Network Coding

Hoc Phan; Fu-Chun Zheng; Michael Fitch

In this paper, we propose a network coding scheme for up-link wireless backhaul networks to increase the throughput while guaranteeing full diversity order. The key advance proposed is the employment of precoding complex field matrices for two user and two base station backhaul networks to achieve throughput of 1 symbol/channel use while guaranteeing full diversity order for this one-way two-hop communications setting. In particular, the throughput of the considered wireless backhaul network using the proposed network coding scheme is 50% higher than that using conventional complex field network coding (CFNC) and 200% higher than that using conventional amplify-and-forward (AF) relay transmission. Importantly, the considered network obtains full diversity order, i.e., the diversity order is the same as that of the respective conventional CFNC and AF relay networks. Numerical results indicate that the simulation results of the pairwise error probability tightly converge to the asymptotic curves in the high signal-to-noise ratio.


Iet Communications | 2013

Physical layer network coding with channel and delay estimation

Yixin Li; Fu-Chun Zheng; Michael Fitch

Decode-and-forward physical layer network coding (PLNC) is one of the promising high-performance techniques for wireless relay networks, but little has been reported on the case of asynchronous senarios. This paper presents a channel and delay estimation algorithm along with a detection scheme for Two-Way-Relay-Network (TWRN) in Rayleigh block- flat-fading channels. Prefix and suffix training sequences are added for frame-based synchronization and channel estimation. The Cramer-Rao Bound (CRB) is given, and simulations show that the mean square error(MSE) of channel estimation of the proposed scheme could reach the CRB. The end-to-end BER performance is also shown in simulation.


vehicular technology conference | 2016

A Context-Aware User-Driven Framework for Network Selection in 5G Multi-RAT Environments

Faouzi Bouali; Klaus Moessner; Michael Fitch

To improve the inter-working of future 5G systems with existing technologies, this paper proposes a novel context-aware user-driven framework for network selection in multi-RAT environments. It relies on fuzzy logic to cope with the lack of information usually associated with the terminal side and the intrinsic randomness of the radio environment. In particular, a fuzzy logic controller first estimates the out-of-context suitability of each RAT to support the QoS requirements of a set of heterogeneous applications. Then, a fuzzy multiple attribute decision making (MADM) methodology is developed to combine these estimates with the various components of the context (e.g., terminal capabilities, user preferences and operator policies) to derive the in-context suitability level of each RAT. Based on this novel metric, two spectrum selection (SS) and spectrum mobility (SM) functionalities are developed to select the best RAT in a given context. The proposed fuzzy MADM approach is validated in a dense small-cell environment to perform a context-aware offloading for a mixture of delay-sensitive and best-effort applications. The results reveal that the fuzzy logic component is able to efficiently track changes in the operating conditions of the different RATs, while the MADM component enables to implement an adjustable context-aware strategy. The proposed fuzzy MADM approach results in a significant improvement in achieving the target strategy, while maintaining an acceptable QoS level compared to a traditional offloading based on signal strength.


vehicular technology conference | 2009

Analysis of Enhanced Relay-Enabled Distributed Coordination Function under Transmission Errors

Rizwan Ahmad; Fu-Chun Zheng; Micheal Drieberg; Michael Fitch

This paper analyzes the performance of enhanced relay-enabled distributed coordination function (ErDCF) for wireless ad hoc networks under transmission errors. The idea of ErDCF is to use high data rate nodes to work as relays for the low data rate nodes. ErDCF achieves higher throughput and reduces energy consumption compared to IEEE 802.11 distributed coordination function (DCF) in an ideal channel environment. However, there is a possibility that this expected gain may decrease in the presence of transmission errors. In this work, we modify the saturation throughput model of ErDCF to accurately reflect the impact of transmission errors under different rate combinations. It turns out that the throughput gain of ErDCF can still be maintained under reasonable link quality and distance.


IEEE Wireless Communications | 2017

Multi-RAT Dynamic Spectrum Access for 5G Heterogeneous Networks: The SPEED-5G Approach

Ioannis-Prodromos Belikaidis; Andreas Georgakopoulos; Panagiotis Demestichas; Benoit Miscopein; Marcin Filo; Seiamak Vahid; Bismark Okyere; Michael Fitch

Research and development of technologies that address the challenges of predicted growth in mobile connections and traffic volume is well known. A major challenge is the cost of meeting the objective, in terms of both infrastructure and deployment. Today, lack of dynamic control across wireless network resources is leading to unbalanced spectrum loads and a perceived capacity bottleneck. The solutions proposed by SPEED-5G through extended dynamic spectrum access (eDSA) address traffic allocation over heterogeneous wireless technologies, better load balancing across available spectrum bands, and capacity boosting through aggregation of available resources while ensuring fair coexistence. The objective of this article is to present a new framework for MAC and RRM layers for supporting eDSA and requirements of the next-generation networks.


vehicular technology conference | 2009

Metrics to Decide the Feedback Interval in Closed-Loop MIMO-OFDM Systems

Michael Fitch; Hui Xiao; Alister G. Burr

In a closed-loop multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) system, the receiver estimates the channel and sends updates on the channel state back to the transmitter. The issue of deciding when to send updates is addressed in this paper and two metrics for making this decision are compared. One is obtained from the correlation matrix distance (CMD) which measures how far the MIMO channel has moved over a time interval, the other is a novel approach using mutual information (MI), whereby two calculations of MI are made, the first assuming that water-filling is employed at the transmitter and the second assuming that it is not. Using CMD, updates are sent when the correlation distance becomes greater than a given threshold. Using MI, updates are sent when the channel changes to the extent that the capacity with water-filling becomes less than that without. Matlab simulation results for a 2 * 2 MIMO system show that the two metrics result in a similar overhead, both being more efficient than constant interval. Extension to larger antenna arrays should be straightforward. MI, although computationally more intensive, can extend easily to decide when to switch between spatial multiplexing (SM) and diversity modes using space-time block coding (STBC) if the channel rank collapses.

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Micheal Drieberg

Universiti Teknologi Petronas

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Rizwan Ahmad

National University of Sciences and Technology

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Faouzi Bouali

Polytechnic University of Catalonia

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