Woon Hau Chin

Viavi Solutions | JDS · Wireless Engineering

The use of a large excess of service antennas brings a variety of performance benefits to distributed MIMO C-RAN, but the corresponding high fronthaul data loads can be problematic in practical systems with limited fronthaul capacity. In this work we propose the use of lossy dimension reduction, applied locally at each remote radio head (RRH), to r...

Security is one of the most important aspects of any network, but it is also one of the most overlooked aspects. In wireless networks, the main design focus is usually the data rate, with security being more of an afterthought than a design requirement. In an era when much of society spends a significant amount of time online, poor security can exp...

This paper proposes a dimension reduction-based signal compression scheme for uplink distributed MIMO cloud radio access networks (C-RAN) with an overall excess of receive antennas, in which users are jointly served by distributed multi-antenna receivers connected to a central processor via individual finite-capacity fronthaul links. We first show...

In this work we propose a fronthaul compression scheme for distributed MIMO systems with multi-antenna receivers, in which, prior to signal quantisation, dimension reduction is performed at each receiver by matched filtering the received signal with a subset of the local user channel vectors. By choosing these matched filter vectors based on global...

Ultra-dense networks (UDNs) are widely considered as an effective solution to greatly improve coverage by shortening the communication distance between user equipments (UEs) and base stations (BSs). The reality of UDN is that line-of-sight (LOS) communication becomes more likely to occur but this desirable result also complicates the performance an...

Cache-enabled small cells can be an effective solution to deliver contents to mobile users with much lower power and latency. While the trend for getting smaller and denser cells is clear, interference will soon become unmanageable and an obstacle when the number of content requests is massive. Moreover, content request is seldom a spatially homoge...

Soft random geometric graphs (SRGGs) have been widely applied to various models including those of wireless sensors, communication, and social and neural networks. SRGGs are constructed by randomly placing nodes in some space and making pairwise links probabilistically using a connection function that is system specific and usually decays with dist...

Soft Random Geometric Graphs (SRGGs) have been widely applied to various models including those of wireless sensor, communication, social and neural networks. SRGGs are constructed by randomly placing nodes in some space and making pairwise links probabilistically using a connection function that is system specific and usually decays with distance....

Electric vehicles (EVs) provide environmentally friendly transport and they are considered to be an important component of distributed and mobile electric energy storage and supply system. It is possible that EVs can be used to store and transport energy from one geographical area to another as a supportive energy supply. Electricity consumption ma...

This paper discusses malicious false data injection attacks on the wide area measurement and monitoring system in smart grids. First, methods of constructing sparse stealth attacks are developed for two typical scenarios: 1) random attacks in which arbitrary measurements can be compromised; and 2) targeted attacks in which specified state variables...

Phasor measurement units (PMUs) play a significant role in modern and future power grids. Since these advanced devices can provide accurate synchronous voltage phasor measurements, more robust power system state estimation (SE) can be achieved by using PMU measurements. The optimal PMU placement problem has been well investigated already in the lit...

Facilitated by advanced information and communication technologies (ICT) infrastructure and optimization techniques, smart grid has the potential to bring significant benefits to the energy consumption management. This paper presents a game theoretic consumption scheduling framework based on the use of mixed integer programming (MIP) to schedule co...

In this paper we introduce medium access control (MAC) protocol defined by ETSI TC (technical committee) SmartBAN (smart body area network). The key features of the protocol are a two-channel concept with different channels for data and control traffic, and a unique Multi-use Channel Access as one alternative channel access mode. The two-channel co...

This paper gives an overview of the European level standard proposal for smart wireless body area networks (WBAN). Under the mandate of European Telecommunication Standards Institute ETSI, a technical committee TC SmartBAN was formed in 2013. The goal of the TC SmartBAN is to define a standard for low power devices and networks to be used in short...

Electric vehicles (EVs) are considered to be an important component of distributed energy storage and supply devices in smart grids. EVs can serve as a distributed mobile energy resource in the electricity market. They can be used to store and transport energy from one geographical area to another as supportive energy supply. EVs should be included...

As the take-up of Long Term Evolution (LTE)/4G cellular accelerates, there is increasing interest in technologies that will define the next generation (5G) telecommunication standard. This paper identifies several emerging technologies which will change and define the future generations of telecommunication standards. Some of these technologies are...

Designing ultra low power MAC protocols for wireless body area sensor networks has been one of the interesting challenges due its unique channel characteristics and high reliability requirements. The recently published IEEE 802.15.6 standard offers a flexible superframe structure that can be adjusted by the hub to suit the communication requirement...

Antenna selection represents an attractive technique that allows to improve performance of wireless systems due to its simplicity and ease of implementation. Antenna selection is able to provide diversity through the use of multiple antennas while keeping low cost and energy consumption by selecting only a subset of the available elements at any gi...

In unplanned wireless deployments such as femto-cells, interference is a major barrier to achieving high data rate. While there exist numerous methods for dealing with planned deployments (macrocells), there are very few effective methods for managing interference in unplanned scenarios. Additionally, most techniques of dealing with interference in...

In outdoor to indoor relaying scenarios, the radio signals go through different propagation channels and the compounded channel may result in large delay spreads. In cases where spectral efficiency is important, shorter guard intervals would be favoured, but a combination of large delay spreads and shorter guard interval will result in drastic degr...

In bi-directional multi-antenna relaying with binary network coding, antenna selection can offer the benefits of full diversity at lower complexity. However, the rate at which the antennas are switched can also contribute to the complexity of the relaying scheme. In this paper, we explore a way of reducing this switching rate and study the implicat...

In this paper we study decode-and-forward multi-antenna relay systems that achieve bi-directional communication in two time slots. We investigate different downlink broadcast schemes which employ binary or analog network coding at the relay. We also analyze and compare their performances in terms of diversity order and symbol error probability. It...

Bi-directional relaying is an efficient way of exchanging messages between two devices through a relay. However, in multipath fading environments, using relays can increase the effective delay spread of the communication channel, causing inter-symbol interference in OFDM systems. In this paper, we look at the effect of using channel shorteners at r...

Co-channel interference is one of the major factors limiting the capacity in modern cellular networks. Interference rejection combining (IRC) is an effective technique to suppress co-channel interference, requiring receivers with multiple antennas. For terminals using IRC, the larger the number of available antennas, the more interfering signals th...

There are significant challenges as well as great opportunities for research at both policy and technology levels on the efficient use of energy. Most existing power generation and distribution systems are based on a century old mechanism where power grids are managed by vertically integrated utilities. Intelligent power grids known as smart grids...

In unplanned wireless deployments such as femtocells, interference is a major barrier to achieving high data rate. While there exist numerous methods for dealing with planned deployments (macrocells), there are very few effective methods for managing interference in unplanned scenarios. Additionally, most techniques of dealing with interference in...

Optimization of energy consumption in future in-telligent energy networks (or Smart Grids) will be based on grid-integrated near-real-time communications between various grid elements in generation, transmission, distribution and loads. This paper discusses some of the challenges and opportunities of communications research in the areas of smart gr...

We propose a consumption scheduling mechanism for home area load management in smart grid using integer linear programming (ILP) technique. The aim of the proposed scheduling is to minimise the peak hourly load in order to achieve an optimal (balanced) daily load schedule. The proposed mechanism is able to schedule both the optimal power and the op...

In this paper we present a case for Smart Metering to be a prime application of TV White Spaces (TVWS) and investigate network architecture to enable smart metering communication in TVWS that ensures access reliability, primary user protection (if one exists) and efficient use of spectrum. We consider the communication access network connecting the...

We propose a consumption scheduling mechanism for home and neighbourhood area load demand management in smart grid using integer linear programming (ILP) and game theory. The proposed mechanism is able to schedule both the optimal power and the optimal operation time for power-shiftable appliances and time-shiftable appliances respectively accordin...

Rising demands in energy due to increasing automation and expanding cities have put an enormous amount of stress on the power grid system over the past decades. There is growing awareness among governments that the current power grid will be insufficient to support our energy needs in the coming years. In the past decades, there have been several i...

The advent of femto-cellular base stations brings with it a promise for increased cellular coverage and capacity. However, several challenges need to be met in order to fulfil these promises. Femto-cells are likely to be deployed in an ad- hoc manner due to the infeasibility of carrying out comprehensive spectrum planning as in legacy cellular netw...

This paper presents experimental evaluation results from a practical LTE-FDD femtocell base-station employing uplink antenna switching. The effects of different antenna train- ing and channel variation rates are analysed under realistic propagation conditions. Significant performance gains in terms of average receiver SINR and error rates are obser...

Autonomic networking and cooperative communications paradigms have emerged as promising technologies that can pave the way for next generation networks. CONSERN project is focusing on cooperation and collaboration enablers, cooperative decision and control algorithms that will maximise the expected gains by utilising cooperative problem solving for...

Reduced-complexity receive antenna selection methods are proposed for interference rejection combining receiver of femtocell base stations. The methods are designed for cases with exact channel information and with channel covariance matrix of interference plus noise at the receiver. Simulation results show that the presented methods can almost ach...

In this paper, we study the performance of bi-directional (two-way) communication system using two different broadcast schemes with network coding. We propose the use of Max-Min criteria for antenna selection with binary network coding and transmit beamforming without binary network coding. We derive and show that unlike traditional antenna selecti...

This paper studies the relay preceding design for a MIMO relay network, where the relay only possesses imperfect channel state information (CSI). We consider a downlink nonregenerative MIMO relay network comprised of a base station (BS, or the source S), a fixed relay (the relay R) and a mobile station (MS, or the destination D). We model the discr...

Femtocell access points (FAPs), also popularly known as Home Base Stations, are small base stations for use within indoor environments to improve coverage and capacity. FAPs have a limited range (e.g. limited to a home or office area) but offer immense capacity improvements for the network due to the ability to reuse a frequency more often as a res...

In this paper, we look into the channel allocation problem for a non-cooperative cognitive vehicular ad-hoc communication network with multiple communicating pairs distributed spatially apart. An algorithm which can search for all pure Nash Equilibrium (NE) solutions is presented. We study how the number of pure NEs grows when either the size of th...

Conclusion drawn from field measurement is that the allocation of radio spectrum to operators in a static manner does not make efficient use of the scarce spectrum resources. Dynamically allocating radio spectrum based on the demands using auction is one possible approach to improve spectrum utilization efficiency. In this paper, we consider a spec...

In this paper, we consider a network consisting of one source, one destination and two relays, under a half duplex constraint. We analyze an amplify-and-forward (AF) two-path relaying scheme where one of the relays additionally performs inter-relay interference cancellation. With this inter-relay self interference cancellation, we show that degrada...

Two-way relaying is a way of improving the band- width efficiency of a half-duplex relay system. In such scenarios, network coding can also be applied to improve the system if there exist sufficient degrees of freedom to decode the received messages at the relay node. In this paper, we look at two specific transmission schemes employed at the multi...

Time domain equalization (TEQ) methods based on the maximum shortening signal-to-noise ratio (MSSNR) criterion is one of the most commonly used criterion for shortening impulse responses as it is computationally efficient and simple. However, the MSSNR method tends to design a TEQ with a bandpass-like frequency response, resulting in a spectrally u...

Using relays to extend the coverage of base-stations in cellular systems has been of interest in recent years as it can reduce the cost of installing more base-stations and yet cater to mobile terminals within a wider coverage area. There have been recent advances where two or more half duplex relay stations are used to recover the loss of bandwidt...

The six articles in this feature topic cover various aspects of cooperative and relay communications involving physical later (PHY), MAC, network layer, and cross-layer modeling and design.

In this paper, the average sum rate of two-way amplify-and-forward (AF) half-duplex relaying system is analyzed. To this end, we first derive the harmonic mean of two independent gamma distributed random variables which have the same shape parameter but different scale parameters. By deriving tight upper and lower bounds for the average sum rate of...

Space-time block coding is a way of introducing multiplexing and diversity gain in wireless systems equipped with multiple antennas. There are several classes of codes tailored for different channel conditions. However, in almost all the cases, maximum likelihood detection is required to fully realize the diversity introduced. In this chapter, we p...

Game theory is a useful tool that can be used to study the distributed resource allocation problem, since each node in the network tries to maximize his own payoff and hence a need to resolve their conflicting interests. In this paper, we introduce utility functions so that the strategy set of each node allows no transmission. We incorporate the ef...

Network coding has the potential to improve the overall throughput of a network by combining different streams of data and forwarding them. In wireless networks, the wireless channel provide an excellent medium for physical layer network coding as signals from different transmitters are combined automatically by the wireless channel. In such scenar...

In this paper, we derive tight upper and lower bounds for the average sum rate of two-way amplify-and-forward (AF) half-duplex relaying, which show that two-way AF half-duplex relaying can significantly mitigate the spectral efficiency loss of conventional one-way AF half-duplex relaying. We then extend the AF half-duplex two-way relaying to the ca...

In this paper, we analyze a full rate cooperative communication system using amplify-and-forward (AF) two-path relaying scheme with inter-relay interference cancellation at the relay. By treating AF two-path relaying as an equivalent MIMO system, we derive the pairwise error probability (PEP) of this system. Given one source node, two half duplex r...

In situations where the channels are fast changing, systems that require channel state information at the transmitter would need frequent feedback from the receiver. Low rate feedback will be required in these cases, and there have been many proposals on how to compress channel state information to enable a fast feedback to the transmitter. Of thes...

Cooperative diversity systems rely on using relay nodes to relay copies of transmitted information to the destination such that each copy experiences different channel fading, hence increasing the diversity of the system. However, without proper processing of the message at the relays, the performance of the cooperative system may not necessarily p...

The feedback of channel state information have always posed a problem for the design of a communications system where the information is required at the transmitter. In most cases, changing the quantization levels or size of the codebook is used to control the amount of feedback bits. However, the number of quantization levels must be maintained at...

In this paper, we consider a two-way or bidirectional communications system with a relay equipped with multiple antennas. We show that when the downlink channel state information is not known at the relay, the benefit of having additional antennas at the relay can only be obtained by using decode and forward (DF) but not amplify and forward (AF). T...

Cooperative diversity is a method to enhance throughput in a wireless network by cooperating with neighboring terminals to transmit signals. In the circumstance where multiple terminals cooperate, the throughput can be further improved if the relaying terminals weigh their transmit signals. In this paper, we study such a cooperative system and its...

In this paper, we analyze a full rate cooperative communication system using amplify-and-forward (AF) two-path relaying scheme with inter-relay interference cancellation at the relay. By treating AF two-path relaying as an equivalent MIMO system, we derive the pairwise error probability (PEP) of this system. Given one source node, two half duplex r...

The problem of channel estimation and symbol detection in fast fading channels using multiple antennas is dealt with. This is one of the many challenges faced by extending spatial multiplexing to mobile terminals. A commonly used method of resolving this problem is pilot-aided channel interpolation. An iterative algorithm that substantially improve...

In this paper, we present a detailed study of the performance of hybrid STBC wireless LAN systems. In particular, we look at the performances of hybrid STBC systems with two different antenna configurations. We analyze the performance and advantages of using hybrid STBC over spatial multiplexing and of using "even" and "uneven" modulation and codin...

This paper is concerned with the problem of channel estimation and symbol detection in fast fading channels, which is one of the challenges faced by extending spatial multiplexing to mobile terminals. A method of resolving this problem is the use of pilot aided channel interpolation techniques which are common in single channel systems. We propose...

In fast time varying systems, the problem of acquiring the channel coefficients required for symbol decoding commonly arises. A method of resolving this problem is the use of pilot aided channel interpolation techniques which are common in single channel systems. This paper is concerned with the problem of symbol decoding in fast fading space time...

In this paper we study a hybrid space time block coded system with four transmit antennas. The system consists of one Alamouti space time block coded stream, and two spatial multiplexing streams which are transmitted using two antennas each. The paper also describes and analyze the merits and performance of several detection schemes for a hybrid sp...

The interest in near-ML detection algorithms for multiple-input/multiple-output (MIMO) systems have always been high due to their drastic performance gain over suboptimal algorithms. Algorithms such as the M algorithm and the stack algorithm yields near-ML performance while only requiring a fraction of the computational complexity of an ML receiver...

Due to the capacity achievable, multiple-input/multiple-output (MIMO) systems has gained popularity in recent years. While several data detection algorithms are available for MIMO systems, simple algorithms usually perform unsatisfactorily, while more complex ones are infeasible for hardware implementation. In this paper, we compare two QRD based t...

Space time block coding (STBC) is often used as it is able to exploit the spatial diversity of multiple antenna systems to improve the performance of such systems. While the main advantage of using STBC lies in the simplicity of the decoder, the special structure of STBCs can also be exploited for other purposes such as channel equalization. In thi...

In a wireless cellular phone system, the channel impulse responses between the mobile terminal and the base station are time varying due to the movement of the mobile terminal or changes in the environment. These channels are frequently tracked using adaptive algorithms to assist in the decoding of the transmitted symbols.

In multiple antenna communications, the impulse responses of the channels are frequently assumed to be fixed. However, if multiple antennas are used in mobile terminals, this assumption is weakened. In this paper, we propose using a sequential Monte Carlo method, which is robust even in non-Gaussian environments, in conjunction with current detecti...

A parallel detection method is proposed for use in the context of uncoded multiple antenna communication. The method does not require power reordering and helps reduce the system delay at the cost of higher computational complexity. The scheme also shows marked improvement in performance over the classical scheme

In a wireless cellular phone system, the channel impulse responses be- tween the mobile terminal and the base station are time varying due to the movement of the mobile terminal or changes in the environment. These channels are frequently tracked using adaptive algorithms to assist in the decoding of the transmitted sym- bols. However, the tracked...

In space-time block coded systems, the channel responses are assumed to be quasi-stationary. However, in many situations, this may not be the case and yields unsatisfactory performance. Therefore, there is a need to address the problem by tracking the channel responses in some way. We propose the use of particle filters for tracking the channel res...

Adaptive filtering in subbands was originally proposed to overcome the limitations of conventional least-mean-square (LMS) algorithms. In general, subband adaptive filters offer computational savings, as well as faster convergence over the conventional LMS algorithm. However, improvements to current subband adaptive filters could be further enhance...

A novel time domain equaliser (TEQ) design is proposed for discrete wavelet multitone (DWMT) systems. The proposed scheme is tested on a number of carrier-serving-area (CSA) loops. The results show the DWMT systems using the proposed TEQ outperform their discrete multitone (DMT) counterparts by 5 to 10 dB