Jean-Francois Frigon

• Polytechnique Montréal

Dynamic spectrum access (DSA) for secondary networks has the potential to improve spectrum utilization and thus mitigate the problem of spectrum scarcity by finding spectrum opportunities and exploiting them efficiently. A key factor in DSA networks with multiple channels and multiple users is to establish efficient spectrum sensing and transmissio...

This paper explores the runtime behavior of a class of multiprocessor systems in specific contexts associated with cloud radio access network implementation. It specifically deals with task scheduling, run time behavior, and their characterization. It also relates to Network Functions Virtualization (NFVs) and especially with the constraints associ...

In this study, the authors analyse the impact of spatial correlation on the average bit error-rate (BER) performance of amplify-and-forward cooperative relay networks employing Alamouti orthogonal space-time block coding (OSTBC) over Rayleigh fading channels. Closed-form expressions are derived for the moment generating function of the total signal...

This study analyses the impact of antenna correlation on orthogonal space-time block coding in amplify-and-forward cooperative relay networks in conjunction with different adaptive transmission techniques over Rayleigh fading channels. Closed-form expressions are derived for the cumulative distribution function, and probability distribution functio...

Composite fading wireless channels possess both fast and slow fading dynamics. In such channels, the average bit error probability varies slowly over time, hence, it is feasible to harness a power control mechanism to effectively avoid the bit error outage (BEO). In this letter, we focus on a new adaptive power allocation scheme for M-ary phase shi...

This work explores different means to implement software defined cellular radio over the cloud, which sets stringent real-time requirements. DPDK and MKL are two technologies proposed by Intel that can be used for that purpose. In this paper, we explore those technologies and using operating system isolation to reduce the computation time variabili...

In this study, we propose a queueing model to analyse the performance of an opportunistic spectrum access (OSA) system with service interruptions operating over heterogeneous channels in which the service transmission rate and the service interruption rate after the transmission is resumed are generally different than their value prior to the inter...

Dynamic spectrum access (DSA) enables secondary networks to find and efficiently exploit spectrum opportunities. A key factor to design a DSA network is the spectrum sensing algorithms for multiple channels with multiple users. Multi-user cooperative channel sensing reduces the sensing time, and thus it increases transmission throughput. However, i...

In this paper, we present a new queueing model providing the accurate average system time for packets transmitted over a cognitive radio (CR) link for multiple traffic classes with the preemptive and non-preemptive priority service disciplines. The analysis considers general packet service time, general distributions for the channel availability pe...

We investigate in this paper the optimal power allocation in an OFDM-SDMA system when some users have minimum downlink transmission rate requirements. We first solve the unconstrained power allocation problem for which we propose a fast zero-finding technique that is guaranteed to find an optimal solution, and an approximate solution that has lower...

In this paper, we derive analytical expressions to compute the covariance matrix of the signals impinging on a reconfigurable antenna array. We consider a receiver equipped with a linear antenna array where each antenna element can be independently configured to create a directive radiation pattern toward a selected direction. In our derivation, we...

In this paper, we present an experimental study evaluating the performance of a reconfigurable antenna element for direction-of-arrival (DOA) estimation in wireless systems. We consider a reconfigurable antenna with directive radiation pattern and an electronic control mechanism to continuously scan its beam over the space. We implement a MUSIC-typ...

This paper addresses the problem of relay power adaption in time for half-duplex decode and forward cooperative system with channel side information knowledge at the relay. We derive the optimal power distribution as a solution of a convex optimization problem that maximizes the long-term average end-to-end spectral efficiency while respecting a ta...

Cognitive radio networks (CRNs) benefit from several features, such as decision-making, spectrum-awareness and reconfigurability over heterogeneous channels. After a link failure due to the appearance of primary users or if the channel quality becomes unacceptable, these features enable CRNs to perform a spectrum migration to a new channel to recov...

We provide in this paper a comprehensive delay and queueing analysis for two baseline medium access control (MAC) protocols for multi-user cognitive radio (CR) networks and investigate the impact of different network parameters, such as packet size, Aloha-type medium access probability and number of channels on the system performance. In addition t...

Cognitive radio-based Long Term Evolution (LTE) networks benefit from the powerful features of cognitive Radios (CR), such as learning and reconfigurability, enabling them to perform, if required, channel switching to a channel with higher quality. This process of searching and sensing other channels is a restoration (recovery) process where the ob...

We propose a space-frequency (SF) block coding scheme for a multiple-input multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) system using antennas with reconfigurable radiation patterns. In this system, each element of the antenna array at the transmitter side is assumed to be reconfigurable so that it can independently chang...

In this paper, we propose a multi-carrier transmission scheme to overcome the problem of intercar-rier interference (ICI) in orthogonal frequency division multiplexing (OFDM) systems. In the proposed scheme, called universal-filtered multi-carrier (UFMC), a filtering operation is applied to a group of consecutive subcar-riers (e.g. a given allocati...

In full duplex relaying, the direct link and the decode and forward processing delay are not always negligible. The signal transmitted by the source thus interferes, at the destination, with the delayed signal retransmitted by the relay. This paper presents a novel full duplex transmission scheme based on distributed Alamouti encoding (denoted by F...

Cognitive radio networks (CRNs) benefit from several features, such as decision-making, spectrum-awareness and reconfigurability, which enable them to perform spectrum migration in order to recover the link when the operating channel becomes occupied. The time spent for channel migration and recovery is a function of the order in which the channels...

4G wireless access systems require high spectral efficiency to support the ever increasing number of users and data rates for real time applications. Multi-antenna OFDM-SDMA systems can provide the required high spectral efficiency and dynamic usage of the channel, but the resource allocation process becomes extremely complex because of the augment...

The impact of outdated channel state information (CSI) on the performance of variable-rate adaptive M-ary quadrature amplitude modulation in amplify-and-forward (AF) opportunistic relaying systems over time-variant Rayleigh fading channels is analysed. Two rate-adaptive modulation techniques are considered. In the first scheme, the relay and the tr...

This paper presents an analysis of the performance of amplify-and-forward (AF) opportunistic relaying systems over independent and non-identically distributed (i.ni.d.) Rayleigh fading links with outdated channel state information (CSI). A closed-form expression is derived for the moment generating function (MGF) of the end-to-end SNR at the destin...

In this paper, we analyze the promising yet mostly unexplored ability of opportunistic spectrum access (OSA) based on cognitive radios (CR) to provide a robust infrastructure for wireless networks operating in challenging environments with frequent transmission link disruptions. We consider a general network model where the CR users can utilize spe...

Regarding the integration of services and applications, a requisite for the widely deployment of cognitive radio networks is the support of service differentiation to provide a higher reliable service for high priority traffic or nodes. In this paper, we propose a data structure called recovery table which is the set of the channel sensing orders o...

We consider multi-antenna base stations using orthogonal frequency division multiple access and space division multiple access techniques to serve single-antenna users. Some users, called real-time users, have minimum rate requirements and must be served in the current time slot while others, called non real-time users, do not have strict timing co...

In cooperative networks, mobile users do not only have the role of a data source or destination but also act as relays to help transmission from others. However, in a wireless network, there might be tens or even hundreds of mobile users that can play the role of relays for a given transmission. Relay selection strategies are, therefore, paramount...

In this study, the authors provide an analytical framework to assess network-level quality of service (QoS) measures for differentiated, non-saturated traffic in infrastructure-mode 802.11 wireless local area networks using the distributed coordination function access mechanism. The authors build on a general analytical framework that takes into ac...

In this paper, for the purpose of service differentiation in opportunistic spectrum access (OSA) enabled networks, we take different priority queueing disciplines into account as decision variables in a dynamic optimization model. The objective is to optimize, after the departure of each packet, a weighted utility function of the performance of dif...

This paper presents an evaluation of the impact of channel time variations on performance of multiuser selection diversity systems employing orthogonal space-time block coding (OSTBC) over MIMO Rayleigh fading channels. A rate-adaptive M-QAM modulation along with the maximum signal-to-noise ratio (SNR) based user selection diversity is considered....

In this paper, we study the performance of a reconfigurable multiple-input multiple-output (RE-MIMO) system in spatially correlated frequency- selective fading channels. In particular, we propose to use a RE-MIMO system to overcome the inter symbol interference (ISI) problem caused by multipath propagation. In the proposed system, we use a 3-dimens...

In this paper, we introduce a queueing approach with server interruptions to analyze the performance of a cognitive radio (CR) link subject to recurrent failures and interruptions. This general model can be used to analyze the traffic metrics as a function of different recovery schemes, channel bandwidth variations and service differentiation. As a...

In this paper, we study the performance of the MUltiple SIgnal Classification (MUSIC) direction-of-arrival (DoA) estimation algorithm in a clustered channel model. We examine the effect of angular spread on the estimation accuracy of the MUSIC algorithm. Simulation result shows that the performance of the MUSIC algorithm degrades as the angular spr...

This paper discusses radiation pattern selection in multiple-input multiple-output (MIMO) wireless systems. Each receive antenna can be reconfigured to P distinct radiation patterns. We select radiation patterns in order to maximize instantaneous channel capacity. And we prove that for arbitrary correlation the maximum achievable diversity order of...

This letter analyzes the impact of feedback delay on the performance of multiuser selection diversity systems employing orthogonal space-time block coding (OSTBC) and rate adaptive modulation over time-varying MIMO Rayleigh fading channels. Rate-adaptive $M$ -QAM modulation along with a user selection diversity is considered in this letter. Analyti...

The popularity of opportunistic spectrum access (OSA), implemented by cognitive radios (CRs), necessitates that these networks should be able to provide service differentiation for different classes of traffic. One of the classic schemes for such a goal is through priority queueing. As link interruptions in OSA networks are frequent, we discuss in...

Variations of the Channel State Information (CSI) between 2 CSI samples is a major source of performance degradation for Adaptive Modulation and Coding (AMC) schemes on fast fading channel. In this paper, we present a novel AMC design that highly improves the channel availability in those conditions. Based on a low complexity design which uses only...

To ensure widespread deployment and popularity, next generation wireless services will require a Quality of Service (QoS), and particularly a reliability, that is independent of the radio transmission medium. However, because of the failure-prone nature of wireless networks, providing a reliable communication link and guaranteeing a consistent QoS...

In this paper, we derive probability density function (PDF) and cumulative distribution function (CDF) expressions for the end-to-end signal-to-noise ratio (SNR) of an opportunistic relaying amplify-and-forward (AF) cooperative diversity system over independent and non-identically distributed (i.ni.d.) Rayleigh fading links where outdated channel s...

We consider multi-antenna base stations using orthogonal frequency-division multiple access (OFDMA) and space division multiple access (SDMA) techniques to serve single antenna users, where some of those users have minimum rate requirements and must be served in the current time slot (real time users), while others do not have strict timing constra...

In this paper, we present the PolyMAX module which enhances network simulator 2 (ns-2), the most popular network simulator used in academia, to provide one of the most complete simulation tools to evaluate the performance of Mobile WiMAX networks. PolyMAX is based on the National Institute of Standards and Technology (NIST) module and our specific...

The impact of outdated channel state information (CSI) on the performance of variable-rate adaptive M-ary quadrature amplitude modulation (M-QAM) in an amplify-and-forward (AF) opportunistic relaying system over Rayleigh fading channels is analyzed. Closed-form expressions are derived for the average spectral efficiency, outage probability and the...

Cognitive radios (CR) are an efficient approach to deploy a secondary network in the vacant portions of the spectrum licensed to primary networks. However, when primary users return to a channel used by a CR, the later should vacate the channel and start a restoration process by searching and sensing other channels. The restoration process objectiv...

In this paper we consider an Interference Alignment (IA) approach for intercell interference coordination for the downlink of a MIMO multi-user cellular network. We determine the maximum degrees of freedom (DoF) of the network and give the feasibility proof of perfect IA. Furthermore, we consider the problem of approximate IA and the Mean-Squared E...

This paper investigates the average bit error rate (BER) performance of reconfigurable single-input single-output (RE-SISO) antenna systems in the clustered channel model. The main focus of the paper is to evaluate the impacts of angle of arrival (AoA) estimation errors, angular spread and antenna beamwidth on the performance of a reconfigurable sy...

Cognitive radios (CR) are an efficient approach to deploy a secondary network in the vacant portions of the spectrum licensed to primary networks. However, when the quality of the channel being used by a CR user is degraded due to environmental impacts or the return of primary users, the CR should vacate the channel and start a restoration process...

We analyze the performance of the amplify-and-forward (AF) opportunistic relaying technique in cooperative systems with adaptive transmission over Rayleigh fading channels. We first consider four adaptive transmission techniques: optimal power and rate adaptation, constant power with optimal rate adaptation, truncated channel inversion with fixed r...

Although the main objectives of dynamic spectrum access and cognitive radios are to solve the problem of spectrum scarcity and usage inefficiency, we show in this paper that such capabilities can also be used to improve other performance metrics in wireless networks. We compare the performance of a Cognitive Radio (CR) network using nodes that are...

This paper investigates the downlink capacity of wideband high speed MIMO cellular networks for urban spatially correlated channels. Simulation results are presented illustrating the impact on the capacity of different channel models, including the 3GPP SCM model, the number of transmit/receive antennas and their spacing, and the available channel...

MISO-OFDM systems enable the allocation of resources in the frequency and spatial domain to increase the data throughput of wireless systems. In this paper, we initially present a near-optimal solution to the MISO-OFDM Resource Allocation (RA) problem. This solution performs an exhaustive search over all possible user sets and then uses a dual-base...

In this paper, we analyze a multiple-input multiple-output (MIMO) wireless system with dynamic radiation pattern diversity provided by composite right/left-handed (CRLH) leaky-wave antennas (LWA's). The CRLH-LWA is electronically reconfigurable with real time continuously direction-steerable radiation pattern and adjustable beamwidth. Analysis show...

User cooperation enables single antenna terminals to benefit from spatial diversity by partnering with other users to create a virtual transmit antenna array. A promising form of cooperation is called coded cooperation which integrates cooperation with channel coding, showing great performance gains. However, the optimal degree of cooperation betwe...

In this paper, we evaluate the impact of the wireless channel and physical layer parameters on the performance of VoIP traffic in IEEE 802.11g networks. The wireless channel is modeled using a finite state Markov chain based on an adaptive modulation and coding scheme. The transition probabilities encompass the effects of the time-varying wireless...

User cooperation enables single antenna terminals to benefit from spatial diversity by partnering with other users to create a virtual transmit antenna array. A promising form of cooperation is called coded cooperation which integrates cooperation with channel coding, showing great performance gains. However, the optimal degree of cooperation betwe...

The convergence of different classes of traffic with different priorities over the wireless network has become a reality. To insure that the users of key applications such as VoIP are satisfied with the service they receive, one must insure that the QoS criteria for these applications, such as delay, jitter or packet loss, are met This in turn mean...

In this paper, we analyze transmission techniques for multiple-input-multiple-output (MIMO) systems from a link-layer perspective using frame error rate (FER), frame loss rate, and link throughput metrics. We introduce two new layered space-time coding variants adapted for transmission at the frame level in MIMO systems with no channel state inform...

In this paper we consider a two-hop MIMO parallel relay channel where a source-destination pair both equipped with M antennas, communicate via K N-antenna half-duplex amplify-and-forward relays (K,N ges M). Multi-user beamforming techniques are jointly applied at the source and destination to respectively multiplex and recover the data streams. In...

Some of the laboratory results obtained with new radios using linear interferometers to modulate and demodulate ultra-wide-band (UWB) signals are discussed. Six-port interferometers (SPI) radio design concepts is going to include QAM?MPSK data transmissions in addition to QPSK/BPSK transmissions. SPI radios use PSMS modulation whereas other UWB rad...

This paper presents a dynamic radiation pattern diversity (DRPD) MIMO wireless system where the antennas radiation patterns are electronically controlled in real-time. The adopted antenna elements are composite right/left-handed (CRLH) microstrip leaky-wave (LW) antennas for which the beam direction can be electronically scanned in a continuous man...

In this paper, we consider a class of wireless ad hoc networks, namely two-hop MIMO interference relay network, where L M-antenna source-destination pairs communicate via K relay nodes each equipped with N antennas. Based on recent advances on characterizing the limits of MIMO X channel and the concept of interference alignment, we treat this netwo...

In this paper, we propose and evaluate the performance of new link layer frame transmission techniques for MIMO (multiple input multiple output) wireless systems from a link layer perspective using frame error rate (FER), frame loss rate (FLR) and link layer throughput metrics. We first introduce a novel link layer transmission scheme for wireless...

A significant amount of work has been carried out on the application of six-port receivers for single carrier communications and for the impulse ultra-wideband radio, however a small interest has been shown on the research of its use for orthogonal frequency division multiplexing (OFDM) communication systems. OFDM and its derived forms are now esse...

The design and implementation of a baseband wide-band code-division multiple access (WCDMA) dual-antenna mobile terminal system-on-a-chip (SoC) is presented in this paper. Spatial diversity processing mitigates wireless channel impairments and is a key enabling technology for WCDMA to support high quality of service at high data rates and capacity....

In this paper, we present and analyze a novel link layer transmission strategy for wireless networks using multiple input multiple output (MIMO) technology at the physical layer. When the channel state information (CSI) is available at the transmitter (CSIT), we present an adaptation algorithm that selects the proper orthogonal sub-channels of the...

Smart antenna array technology has been shown to greatly improve the performance of wireless communication systems. In this article, we describe the impact of smart antenna array processing at the mobile terminal for Wideband Code Division Multiple Access (WCDMA) cellular networks. Using system simulations we demonstrate the quality of service, net...

In this paper, we propose a multi(six)-port radio frequency (RF) front-end including both modulator and demodulator for impulse ultra-wideband (UWB) communication systems. This RF front-end validates full channel (3GHz-4GHz) uniform phase spectrum modulation scheme by using a six-port phase modulator and demodulator. Both the modulator and demodula...

This paper presents a short-range positioning system based on six-port technology and the corresponding signal processing algorithms. Accurate positioning with high resolution of detected targets is achieved by utilizing both the impulse signal and the wideband phase discrimination characteristic of a six-port circuit operating in ultra-wideband (U...

A software defined radio (SDR) receiver architecture is proposed in this paper for ultra-wideband (UWB) applications. Both UWB data communication and positioning functions are implemented in a single hardware platform and using suitable demodulation and positioning algorithms respectively. This architecture adopts a direct conversion radio frequenc...

A direct quadrature phase shift keying modulator based on six-port technology is presented. The modulator comprises a six-port circuit, a switch matrix and open and short terminations. Using this modulator, direct phase shift keying modulation was achieved. Six-port technology has the advantage of signal integrity, low power consumption and physica...

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In this paper a novel timing tracking circuit for CDMA applications is presented. The circuit utilizes a linear interpolator and a Schmitt quantizer to achieve the optimal tradeoff between design complexity and robustness. System simulations, experimental measurements, gate counts and power consumption issues are presented and analyzed.

An ASIC implementation of a WCDMA mobile terminal with 2-dimensional adaptive antenna-rake combining is presented in this paper. System analysis shows that adaptive antenna-rake combining techniques can significantly enhance the performance and capacity of cellular systems compared to conventional CDMA systems. A hardware efficient receiver archite...

A MIMO OFDM receiver with interference cancellation requires a channel estimation and matrix inversion on a sub-carrier basis. This is computationally intensive and can prevent a practical implementation. In this paper, we propose new interpolation algorithms for this type of receiver. To eliminate the need for a matrix inversion for each OFDM sub-...

This paper investigates link layer data units (frames) transmission strategies for MIMO wireless systems using spatial multiplexing. A new effective transmission strategy is proposed in this paper in order to decrease the frame error rate by making use of the multi-channel transmission characteristics provided in MIMO systems. The main idea is to s...

The third generation (3G) of cellular communications standards is based on wideband CDMA. The wideband signal experiences frequency selective fading due to multipath propagation. To mitigate this effect, a RAKE receiver is typically used to coherently combine the signal energy received on different multipaths. An effective multipath searcher is, th...

This paper investigates the adaptation of data link error control protocols to be more efficient over MIMO wireless links. Data link mechanisms control, among other things, the transmission errors at the link layer, whereas MIMO is a physical layer technology that handles the wireless link with a notably high efficiency and flexibility. A new cross...

Wireless communication systems present unique challenges and trade-offs at various levels of the system design process. Since a variety of performance measures are important in wireless communications, a family of testbeds becomes essential to validate the gains reported by the theory. Wireless testbeds also play a very important role in academia f...

In this paper algorithmic and implementation innovations for a novel diversity processing based WCDMA synchronization system are presented. The system employs a dual antenna front end system and a three stage pipelined synchronization technique to achieve slot, frame and code synchronization. The slot boundary section employs a hybrid matched filte...

A wideband signal experiences frequency selective fading due to multipath propagation. The multipath searcher must identify the delayed versions of the transmitted signal with low probability of false alarm and misdetection. This paper presents an efficient and novel multipath searcher algorithm and a VLSI architecture that provides a good compromi...

A silicon implementation of a dual antenna mobile station modem for 3G WCDMA is presented. Diversity processing is used to support data rates up to 2 Mb/s while reducing power consumption. An average SNR improvement of 7 dB has been observed yielding up to a 4x increase in capacity with no change to the exisiting network infrastructure.

This paper reports on field measurements of point-to-point indoor high-speed (10 Mbit/s to 30 Mbit/s at 5 Mbaud) wireless communications realized using a flexible multilevel quadrature amplitude modulation (M-QAM) testbed that features real-time equalization and smart antenna-array technology. The results from an extensive set of measurements, 5926...

A new receiver structure able to deliver high data rates in a multiple input-multiple output (MIMO) frequency selective wireless environment is proposed and investigated in this paper. The optimal solution for the finite-length MIMO decision feedback equalizer (DFE) with cancellation is derived and used to illustrate the potential of this architect...

A new receiver structure able to deliver high data rates in a multiple-input multiple-output (MIMO) frequency selective wireless environment is proposed and investigated. The optimal solution for the finite length MIMO decision feedback equalizer (DFE) with cancellation is derived and used to illustrate the potential of this architecture for space-...

A dynamic reservation time division multiple access (DR-TDMA) control protocol that extends the capabilities of asynchronous transfer mode (ATM) networks over the wireless channel is proposed in this paper. DR-TDMA combines the advantages of distributed access and centralized control for transporting constant bit rate (CBR), variable bit rate (VBR)...

In reservation-based multiple access protocols, before obtaining a contention-free access to the channel, a mobile terminal must wait for its request packet to be successfully sent to the base station. A pseudo-Bayesian ALOHA algorithm with multiple priorities is proposed in this paper to reduce the waiting time of delay sensitive request packets i...

A resource allocation algorithm for variable bit rate (VBR) sources using the Dynamic Reservation TDMA (DRTDMA) medium access control protocol is proposed in this paper. DR-TDMA combines the advantages of distributed access and centralized scheduling to multiplex VBR traffic efficiently over a wireless ATM channel, and can be easily extended to int...

This paper reports on the development of a flexible 5-MBd equalized M-QAM testbed for high-speed wireless data communications. The unit operates in real time and was field tested in typical indoor environments. A total of 3600 independent experiments were conducted using the testbed where one of 4-, 16-, 64-QAM constellations were transmitted, and...

This paper proposes data and voice scheduling algorithms for the dynamic reservation time division multiple access (DR-TDMA) MAC protocol for wireless ATM networks. Featuring a novel framed pseudo-Bayesian priority ALOHA algorithm that provides access priority to voice control packets, DR-TDMA improves the quality-of-service offered to voice connec...

A resource allocation algorithm for variable bit rate (VBR) sources using the dynamic reservation TDMA (DR-TDMA) medium access control protocol is proposed in this paper, DR-TDMA combines the advantages of distributed access and centralized scheduling to multiplex VBR traffic efficiently over a wireless ATM channel, and can be easily extended to in...

This paper reports on field measurements of indoor high speed (10 Mbps to 30 Mbps) wireless data communications realized with a flexible M-QAM prototype featuring a real-time adaptive equalizer and a high speed real-time adaptive beamformer (smart antenna array). The wireless testbed operates at a carrier frequency of 2.44 GHz, transmits 1 or 10 mW...

In reservation MAC protocols, before obtaining a contention free access to the channel, a mobile must wait for its request packet to be successfully sent to the base station. A pseudo-Bayesian Aloha algorithm with multiple priorities is proposed in this paper to reduce the waiting time of delay sensitive request packets in a multimedia environment....