Mobile Multimodality: A Theoretical Approach to Facilitate Virtual Device Environments

The classical strategy of multimodal interactions is to simultaneously utilise several modalities offered on a ‘single’ device. However, practical restrictions appear, especially in mobile communications, due to the limitations of device’s interfaces and the continuously changing communication conditions. Taking multimodality out of this single-device scenario, this paper introduces a theoretical framework for dynamic Multi User Interfaces-Device Binding (MID-B). MID-B facilitates dynamic adaptation and customisation of physically distributed devices (and their user interfaces) into one ‘virtual’ multimodal environment, thus introducing ambient awareness into user interfaces. In MID-B, one device assumes the role of a “controller” which detects and binds the interfaces and modalities available on devices in the vicinity. After discovery, it binds these modalities to deliver the actual mobile service.

Hardware Implementation of Skeletonization Algorithm for Parallel Asynchronous Image Processing

This paper presents an FPGA realisation of an application-specific cellular processor array designed for asynchronous skeletonization of binary images. The skeletonization algorithm is based on iterative thinning utilizing a ‘grassfire’ transformation approach. The purpose of this work was to test the performance of a fully parallel asynchronous processor array and to evaluate the inhomogeneity of wave propagation velocity. A proof-of-concept design has been implemented and evaluated, the results are presented and discussed.

Cognitive Radio Design on an MPSoC Reconfigurable Platform

Cognitive Radio has been proposed as a promising technology for solving today’s spectrum scarcity problem by means of dynamic spectrum access. The multiprocessor system-on-chip (MPSoC) reconfigurable platform is proposed as an enabling technology for cognitive radio. In this paper, we propose a design methodology based on task transaction level interface for the design of cognitive radio baseband on an MPSoC reconfigurable platform. The reconfiguration of a novel, low-complexity fast Fourier transform for orthogonal frequency-division multiplexing based Cognitive Radio is used as a design case to show the effectiveness of the methodology for modelling the dynamic behavior of Cognitive Radio and facilitating the platform implementation.

A Robust 130 nm-CMOS Built-In Current Sensor Dedicated to RF Applications

In this paper we present a design methodology that allows a dramatic reduction of the dependency on process variation, yielding to a new version of this BICS. Taking advantage of a 130 nm VLSI CMOS technology, the proposed BICS has a peak-to-peak dispersion lower than 10% of its output full-scale range. It makes it more suitable to implement the test functionality while maintaining the initial BICS intrinsic performances. The built-in self-test methodology is illustrated by monitoring the supply current of Low-Noise Amplifiers (LNAs). Measurements confirm the BICS’s transparency relative to the circuit-under-test (CUT) and its accuracy.

Terminal Management and Intelligent Access Selection in Heterogeneous Environments

This paper presents a mobile terminal architecture for devices operating in heterogeneous environments, which incorporates intelligence for supporting mobility and roaming across legacy access networks. It focuses on the structure and functionality of the proposed scheme that supports terminal-initiated and terminal-controlled access network selection in heterogeneous networks. It discusses the decomposition of the proposed Terminal Management System into separate modules, responsible for retrieving link-layer measurements from the attachment points in the terminal’s neighborhood, for handling the user’s profile and for performing intelligent access network selection. This latter function aims at independently determining the optimal local interface and attachment point through which applications can be obtained as efficiently as possible, by taking into account network status and resource availability, user preferences and service requirements.

Partial CRC Checksum of SCTP for Error Control over Wireless Networks

In the Stream Control Transmission Protocol (SCTP), when a portion of a packet is corrupted, the entire packet will be discarded at the receiver side. This may result in degradation of the throughput of SCTP over wireless networks with a high bit error rate. This paper proposes a new error control scheme of SCTP using a partial Cyclic Redundancy Check (CRC) checksum to enhance the throughput performance, in which a new ‘checksum chunk’ is introduced to effectively identify any corruptions of data chunks contained in the SCTP packet. In the proposed scheme, an SCTP data packet can carry one or more data chunks depending on the channel condition, and the newly defined ‘checksum’ chunk will contain the partial CRC checksums of the individual data chunks and/or the base header of the packet. By referring to these partial checksums, the receiver can discard only the corrupted data chunks, whereas the other available data chunks can be recovered. Simulation results show that the proposed scheme significantly provides better performance than the standard SCTP in the wireless networks.

Comments and Further Results on ‘Performance Evaluation of a New BPSK-OFDM Timing Estimation Algorithm’

This comment first points out some inaccurate formulae and irrelevant comparisons between Wen’s algorithm and Beek’s one. Then, the correct formulae are provided, the limitations of these two estimators are discussed and some investigations on the local maximum in timing estimation are also presented. Both the simulation and the analysis demonstrate that the timing precision of Wen’s algorithm highly depends on the length of cyclic prefix (CP) and the channel fading rate. On the other hand, Beek’s algorithm will work better under a large CP length and in fast fading channels.

Dynamic Channel Selection for Cognitive Radios with Heterogenous Primary Bands

Technological advances coupled with regulatory initiative for more efficient utilization of radio spectrum resulted in the introduction of dynamic spectrum access enabled radio called Cognitive Radio (CR). A CR network is allowed to access a frequency band owned by primary user, which can provide higher throughput and better serviceability in wireless networks. The availability of multiple primary bands requires a CR network to select the best operating band which can maximize the total system performance. The selection should be made according to heterogenous properties of primary bands which offer different maximum data rate for secondary use and generate diverse traffic pattern. In this paper, assuming such heterogenous primary bands for secondary use, simple and distributed dynamic channel selection strategies are proposed and evaluated. In addition, we introduce a measurement metric for interference experienced by primary users due to secondary network’s access in primary band. We investigate the impact of different channel selection strategies and parameters on the primary and secondary performance.

Range-Based Sleep Scheduling (RBSS) for Wireless Sensor Networks

Sleep scheduling in a wireless sensor network is the process of deciding which nodes are eligible to sleep (enter power-saving mode) after random deployment to conserve energy while retaining network coverage. Most existing approaches toward this problem require sensor’s location information, which may be impractical considering costly locating overheads. This paper proposes range-based sleep scheduling (RBSS) protocol which needs sensor-to-sensor distance but no location information. RBSS attempts to approach an optimal sensor selection pattern that demands the fewest working (awake) sensors. Simulation results indicate that RBSS is comparable to its location-based counterpart in terms of coverage quality and the reduction of working sensors.

Cognitive Radio with Single Carrier TDCS and Multicarrier OFDM Approach with V-BLAST Receiver in Rayleigh Fading Channel

This article presents the performance comparison of TDCS and OFDM based cognitive radio for MIMO system using VBLAST receiver architecture to reconstruct the transmitted data. The interference avoidance performance in terms of BER and bitrate are improved by adding multiple antennas to the system and the use of V-BLAST technique at the receiver. The results show the most promising interference avoidance technique combined with MIMO V-BLAST architecture to be applied in the CR system.

Looking for New DNA: The World Around IMT-advanced

Technology, such as IMT-2000 and IMT-A, plays an important role in our society. A number of prominent authors and thinkers have judged the impact of technology as being increasingly radical. This paper connects different visions on technology, thereby bringing different perspectives on innovation into line. An important motivation for this paper has been the predominantly instrumental vision on technology that is present at most European governments. The paper shows that this is an imbalanced vision that neglects the renewing and radical power of technology. On the other hand, the paper focuses on the required skills (‘DNA’) that are needed to help companies bridge the gap from radical innovation to user centred innovation. The paper concludes with an example from personal network technology, illustrating the main concepts and claims.

Multi-Agent Radio Resource Allocation

This paper presents a spatially distributed and dynamic billing, pricing and allocation mechanism for which a user terminal requires Cognitive Radio abilities. That is, the Cognitive Radio abilities will be applied to the economical environment. The radio resource goods are allocated to the users by a multi-unit sealed-bid auction. Intelligent entities like the bidding strategy have to represent operator’s and users’ behavior and to make decisions for them in order to fulfill the preferences and QoS. The main functionalities, used to execute the dynamic auction sequence and located in the MAC are described, assuming the entities possess Cognitive Radio abilities.

Role of Convergence in GIMCV Development: A Vision

Path to Global Information Multimedia Communication Village (GIMCV) can be seen as a convergence process among telephony, data exchange and television. Convergence refers not only to various services provided by the same operator but also by the same device, the same access network, the same transport network, etc. This paper present authors’ vision on how convergence will lead the GIMCV development.

Cross-layer Routing Design in Cognitive Radio Networks by Colored Multigraph Model

In this paper, the cross-layer design routing in cognitive radio(CR) networks is studied. We propose a colored multigraph based model for the temporarily available spectrum bands, called spectrum holes in this paper. Based on this colored multigraph model, a polynomial time algorithm with complexity O(n ²) is also proposed to develop a routing and interface assignment, where n is the number of nodes in a CR network. Our algorithm optimizes the hop number of routing, meanwhile, the adjacent hop interference (AHI) is also optimized locally.

Cognitive Radio Dynamic Access Techniques

The ever growing demand for wireless services has placed enormous burden on valuable resources such as spectral bandwidth. This has resulted in a major rethinking in resource allocation policies culminating in an explosion of research activity in the field of Cognitive Radio (CR) towards optimum resource usage. In this tutorial paper the physical layer design and transmission techniques for CR in the context of efficient spectrum utilization are discussed. Spectrum sensing as the key element of CR awareness is described. Orthogonal frequency division multiplexing (OFDM) as a spectrally efficient modulation scheme is discussed and the rationale for its use in the CR system is explained. Spectrum pooling for efficient use of spectrum is studied and the role of adaptive OFDM techniques in this method is highlighted. Wavelet basis function as a replacement of Fourier transform in OFDM is evaluated. MIMO system as an added value to the CR performance is described. Adaptive Waveform and beamforming as alternative techniques in CR are reviewed.

Improving Spectral Capacity and Wireless Network Coverage by Cognitive Radio Technology and Relay Nodes in Cellular Systems

Methods to enhance the use of the frequency spectrum by automatical spectrum sensing plus spectrum sharing in a cognitive radio technology context have been presented and discussed in this paper. Ideas to improve the wireless transmission by orthogonal OFDM-based communication and to increase the coverage of cellular systems by future wireless networks, relay channels, relay stations and collaborate radio have been presented as well. A revised hierarchical deployment of the future wireless and wired networks are shortly discussed.

Uplink Channel Estimation for Multi-user OFDM-based Systems

In this paper we propose a simple, yet flexible and efficient, channel estimator for the uplink in broadband orthogonal frequency division multiplexing (OFDM) systems. The processing is performed in the time-domain, by extracting the Channel’s Impulse Response (CIR) for each user from a joint training signal. In this OFDM system, the pilot sequence we advocate, where all users share the same pilot sub-carriers, consists of one OFDM-symbol endowed with time-shifted properties per user, which isolates each user’s CIR and is robust against multi-user interference. The feasibility of our approach is substantiated by system simulation results obtained using BRAN-A broadband mobile wireless channel model.

A Novel Carrier Frequency Offset Estimation for OFDM Systems Over Time-Varying Multipath Channels

This paper introduces a novel method to estimate fractional carrier frequency offset (CFO) under time-varying multipath channels in OFDM systems based on the approximation of Basis Expansion Model (BEM). Due to the symmetrical character of the BEM basis, we propose a new design of training sequence with trailing zeros. This training sequence can be used at the receiver to estimate the frequency offset without channel estimation only in one OFDM symbol. We also compare our method with Beek’s ML estimator and Lv’s fine synchronization estimator. The numerical results demonstrate that the proposed method provides an improved performance when the training sequence has a short length.

The Negative Two’s Complement Number System

The two’s complement fractional fixed-point number system is widely used to implement digital signal processing on VLSI chips. It has a range of values from −1 to one least significant bit below +1. Either the multiplication of −1 • −1 or taking the absolute value of −1 produces a result (+1) that cannot be represented. A new system, the negative two’s complement number system, is described here that has a range of one least significant bit above −1 to +1 which eliminates the problem. This paper presents the new number system and describes algorithms for the basic arithmetic operations.