Future Wireless Applications Research Articles

Analytic Framework for the Effective Rate of MISO Fading Channels

The delay constraints imposed by future wireless applications require a suitable metric for assessing their impact on the overall system performance. Since the classical Shannon's ergodic capacity fails to do so, the so-called effective rate was recently established as a rigorous alternative. While prior relevant works have improved our knowledge on the effective rate characterization of communication systems, an analytical framework encompassing several fading models of interest is not yet available. In this paper, we pursue a detailed effective rate analysis of Nakagami-m, Rician and generalized-K multiple-input single-output (MISO) fading channels by deriving new, analytical expressions for their exact effective rate. Moreover, we consider the asymptotically low and high signal-to-noise regimes, for which tractable, closed-form effective rate expressions are presented. These results enable us to draw useful conclusions about the impact of system parameters on the effective rate of different MISO fading channels. All the theoretical expressions are validated via Monte-Carlo simulations.

RF GaN HEMT Sensors for Detection of Caustic Chemicals

For future wireless sensor network applications, high-speed RF GaN HEMTs (high electron mobility transistor) are investigated for toxic industrial chemical detection, for the first time. RF GaN HEMTs with a Pt-based gate metal show reliable, repeatable, and distinctive responses toward Cl <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> gas and HCl vapor at room temperature.

Being mobile: future wireless technologies and applications

Do you need to get up to speed quickly on the technologies and services that could transform the wireless world over the coming decade? Whether you work directly with wireless or in a sector where wireless solutions could be beneficial (e.g. healthcare, transport, sensor networks, location and smart metering), this concise guide provides a critical insight into future developments. For the first time, you will have a clear view of all the key technologies, including mesh networks, white space/cognitive devices, 4G/LTE and femtocells, and all the sectors or applications in which they could be used, with a comparison of the positives and negatives of each technology and sector area. You'll also see where the technologies required overlap and so could bring benefits across multiple areas, as well as how the key drivers of change in the past may impact on the future.

A Comparison Between the Centralized and Distributed Approaches for Spectrum Management

There is a growing demand for spectrum to accommodate future wireless services and applications. Given the rigidity of current allocations, several spectrum occupancy studies have indicated a low utilization over both space and time. Hence, to satisfy the demands of applications it can be inferred that dynamic spectrum usage is a required necessity. Centralized Dynamic Spectrum Allocation (DSA) and Distributed Dynamic Spectrum Selection (DSS) are two paradigms that aim to address this problem, whereby we use DSS (distributed) as an umbrella term for a range of terminologies for decentralized access, such as Opportunistic Spectrum Access and Dynamic Spectrum Access. This paper presents a survey on these methods, whereby we introduce, discuss, and classify several proposed architectures, techniques and solutions. Corresponding challenges from a technical point of view are also investigated, as are some of the remaining open issues. The final and perhaps most significant contribution of this work is to provide a baseline for systematically comparing the two approaches, revealing the pros and cons of DSA (centralized) and DSS (distributed) as methods of realizing spectrum sharing.

A Unified Treatment of Superposition Coding Aided Communications: Theory and Practice

In this tutorial, a unified treatment of the topic of SuperPosition Coding (SPC) aided communications systems is offered, where we focus our attention not only on the theoretical background of SPC but also on its implementation techniques. The design methodology of SPC aided communications transceivers is described, including the Multiple Level Modulation (MLM) concept, the corresponding iterative Successive Interference Cancellation (SIC) aided receiver and the quasi-random coding principle. Building on these fundamental discussions, various future wireless applications of the SPC technique were provided, which encompass cooperative communications-assisted relay systems and cross-layer SPC aided multiplexed Hybrid Automatic Repeat reQuest (HARQ) techniques. Our discussions demonstrate that the SPC technique is a promising enabler for diverse future wireless communications scenarios, ranging from cellular networks to cooperative networks.

Experimental Investigation on Time Reversal Precoding for Space–Time Focusing in Wireless Communications

This paper presents the results of indoor wideband measurements investigating the space-time properties of wireless signal transmission with online time-reversal (TR) precoding. The measurements were conducted using a new TR wideband multiple-input-multiple-output (MIMO) channel sounder operating at 2.45 GHz with a bandwidth of 240 MHz. Both line-of-sight (LOS) and non-line-of-sight (NLOS) propagation conditions were investigated. Spatial focusing and temporal compression can clearly be seen with TR precoding, which may be useful for future wireless system applications. Channel hardening due to TR is also observed under both LOS and NLOS conditions.

Mutual interference considered power allocation in OFDM-based cognitive networks: The single SU case

Efficient and conflict-free power allocation strategies in cognitive radio networks are being extensively studied in current research in order to meet the requirements of future wireless applications. In this paper, specifying the single secondary user (SU) with multiple primary user (PU) case, a novel power allocation scheme is developed for orthogonal frequency division multiplexing (OFDM) – based cognitive radio networks designed to maximize the capacity of the SU while limiting the interference to the PUs. First, the mutual interference between the SU and the PUs is comprehensively formulated as the restrictions on the SU’s transmission power. Secondly, the power allocation problem is analyzed and formulated as a constrained optimization problem which is concluded to a peak-power constrained water-filling formulation. Finally, a novel low-complexity water-filling algorithm is proposed to solve the optimization problem and the optimal power allocation result is achieved. In a simplified scenario, numerical results are exhibited to confirm the efficiency of the proposed water-filling algorithm, and the influence of the mutual interference on the power allocation and the system capacity is further illustrated.

Space shift keying modulation for MIMO channels

In this paper, we present space shift keying (SSK) as a new modulation scheme, which is based on spatial modulation (SM) concepts. Fading is exploited for multiple-input multiple-output(MIMO) channels to provide better performance over conventional amplitude/phase modulation (APM) techniques. In SSK, it is the antenna index used during transmission that relays information, rather than the transmitted symbols themselves. This absence of symbol information eliminates the transceiver elements necessary for APM transmission and detection (such as coherent detectors). As well, the simplicity involved in modulation reduces the detection complexity compared to that of SM, while achieving almost identical performance gains. Throughout the paper, we illustrate SSK's strength by studying its interaction with the fading channel. We obtain tight upper bounds on bit error probability, and discuss SSK's performance under some non-ideal channel conditions (estimation error and spatial correlation). Analytical and simulation results show performance gains over APM systems (3 dB at a bit error rate of 10-5), making SSK an interesting candidate for future wireless applications. We then extend SSK concepts to incorporate channel coding, where in particular, we consider a bit interleaved coded modulation (BICM) system using iterative decoding for both convolutional and turbo codes. Capacity results are derived, and improvements over APM are illustrated (up to 1 bits/s/Hz), with performance gains of up to 5 dB.

NUMERICAL STUDY OF A CIRCULATOR USING YIG THIN FILM WITH A COPLANAR STRUCTURE

This paper deals with the field of passive microwave components. Coming from the requirements of mobile communication devices, miniaturization of microwave components is needed. The DIOM laboratory is using the RF sputtering to realize magnetic thin films. The use of these magnetic thin films for a circulator design enables to develop a new manufacturing technique compatible with the miniaturization of these devices. These components are devoted to future wireless applications in the 8–12 GHz frequency range. The advantages of these components lie in using YIG thin film and in the fact that accesses to the device are coplanar waveguide (CPW). The CPW structure has a signal line and a ground in the same plane. Therefore, the circulator with a CPW structure will be easily fabricated using low cost lithography. Moreover, connections with other devices will be easier.

A Robust Error Detection Mechanism for H.264/AVC Coded Video Sequences Based on Support Vector Machines

Current trends in wireless communications provide fast and location-independent access to multimedia services. Due to its high compression efficiency, H.264/AVC is expected to become the dominant underlying technology in the delivery of future wireless video applications. The error resilient mechanisms adopted by this standard alleviate the problem of spatio-temporal propagation of visual artifacts caused by transmission errors by dropping and concealing all macroblocks (MBs) contained within corrupted segments, including uncorrupted MBs. Concealing these uncorrupted MBs generally causes a reduction in quality of the reconstructed video sequence.

Receiver Front-End Circuits for Future Generations of Wireless Communications

In this paper, new receiver concepts and CMOS circuits for future wireless communications applications are introduced. The concepts derived are applied to a few classes of wireless communications standards that are broad-band at radio frequencies and/or require a broad-band baseband circuitry. Multimode multiband operation and adaptivity as key requirements for future generation receivers are highlighted throughout the paper. The tradeoffs between power consumption, noise figure and linearity performance of low-noise amplifiers, mixers, and intermediate frequency filters are considered too.

Interference-limited resource allocation for cognitive radio in orthogonal frequency-division multiplexing networks

Efficient and fair resource allocation strategies are being extensively studied in current research in order to address the requirements of future wireless applications. A novel resource allocation scheme is developed for orthogonal frequency-division multiplexing (OFDM) networks designed to maximise performance while limiting the received interference at each user. This received interference is in essence used as a fairness metric; moreover, by defining different interference tolerances for different sets of users, the proposed allocation scheme can be exploited in various cognitive radio scenarios. As applied to the scheme, the authors investigate a scenario where two cellular OFDM-based networks operate as primary and secondary systems in the same band, and the secondary system benefits by accessing the unused resources of the primary system if additional capacity is required. The primary system benefits either by charging the secondary system for the use of its resources or by some form of reciprocal arrangement allowing it to use the secondary system's licenced bands in a similar manner, when needed. Numerical results show our interference-limited scheduling approach to achieve excellent levels of efficiency and fairness by allocating resources more intelligently than proportional fair scheduling. A further important contribution is the application of sequential quadratic programming to solve the non-convex optimisation problems which arise in such scenarios.

A Cross Layer Scheduling Framework for Supporting Bursty Data Applications in WCDMA Networks

In future wireless networks multimedia applications are expected to finally dominate the overall traffic volume. Shared channels are more suitable for the transmission of this type of traffic, as they are able to periodically adjust their transmission rate. In this paper, we introduce a cross-layer framework for WCDMA based networks which aims to make the packet scheduling procedure more efficient. In addition to that, we further propose a traffic scheduling scheme which serves the connections not only according to their delay sensitivity, but also according to the predicted state of their wireless channel. The efficiency of the proposed scheme, in terms of average packet delay and channel utilization is verified via simulations.

COMPACT MONOPOLE EXCITED DRUM SHAPED ANTENNA FOR AWS/DCS/PCS/ DECT/3G/UMTS/BLUETOOTH APPLICATIONS

A compact monopole excited drum shaped antenna for broad band application is presented. The proposed antenna offers a 2:1 VSWR bandwidth greater than 50% (1690–2940 MHz). The wide bandwidth along with omni directional pattern and moderate gain makes it suitable for existing and future wireless applications. Details of the antenna design and a comparison of simulated and measured results are presented and discussed.

Reduced-Complexity Detection for DPC-OF/TDMA System Enhanced by Multi-Layer MIMO-OFDM in Wireless Multimedia Communications

During these years, we have been focusing on developing ultra high-data-rate wireless access systems for future wireless multimedia communications. One of such kind of systems is called DPC-OF/TDMA (dynamic parameter controlled orthogonal frequency and time division multiple access) which targets at beyond 100 Mbps data rate. In order to support higher data rates, e.g., several hundreds of Mbps or even Gbps for future wireless multimedia applications (e.g., streaming video and file transfer), it is necessary to enhance DPC-OF/TDMA system based on MIMO-OFDM (multiple-input multiple-output orthogonal frequency division multiplexing) platform. In this paper, we propose an enhanced DPC-OF/TDMA system based on Multi-Layer MIMO-OFDM scheme which combines both diversity and multiplexing in order to exploit potentials of both techniques. The performance investigation shows the proposed scheme has better performance than its counterpart based on full-multiplexing MIMO-OFDM scheme. In addition to the Exhaustive Detection (EXD) scheme which applies the same detection algorithm on each subcarrier independently, we propose the Reduced-Complexity Detection (RCD) scheme. The complexity reduction is achieved by exploiting the suboptimal Layer Detection Order and subcarrier correlation. The simulation results show that huge complexity can be reduced with very small performance loss, by using the proposed detection scheme. For example, 60.7% complexity can be cut off with only 1.1 dB performance loss for the 8 × 8 enhanced DPC-OF/TDMA system.

A very compact 62‐GHz transmitter LTCC SiP module for wireless terminals applications

AbstractA 10 × 21 × 1 mm3, very compact low temperature cofired ceramic (LTCC) system‐in‐package (SiP) transmitter module is presented for future wireless terminal applications. Five GaAs monolithic microwave integrated circuits (MMIC) chipsets including a power amplifier, driver amplifier, mixer, and two frequency multipliers are integrated into a LTCC multilayer circuit for the heterodyne transmitter. The fabricated transmitter module achieves an output of 13 dBm at a RF frequency of 62 GHz, an IF frequency of 2.4 GHz, and an local oscillator frequency of 59.6 GHz. The up‐conversion gain is 11 dB; while the local oscillator signal is suppressed below −20.6 dBc with the image rejection mixer, and the image and spurious signals are also suppressed below −29.6 dBc. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 575–578, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22211

Wireless Telecommunications Issues: Cell Phone TV, Wireless Networks in Disaster Management, Ubiquitous Computing, and Adoption of Future Wireless Applications

This paper is a summary of a 2007 Association for Information Systems Americas Conference on Information Systems (AMCIS) panel discussion regarding current mobile wireless issues and technologies. The invited panelists are four faculty members specializing in information systems from the United States. The covered topics included cell phone TV and misconceptions surrounding it, wireless networks in disaster management, ubiquitous computing including “anatomy of a mote” and sensors, and the adoption of future wireless applications. First, we present wireless cell phone TV as a functioning multipurpose computer, or a “Swiss army knife,” of media devices. The misconceptions are stated, influenced by preconceived notions by the media critics as well as users. Next we discuss a range of wireless technologies including wearable computing, ad hoc and mesh wireless networks as a means of providing communications for first respondents during a natural or man-made disaster. Then we examine the anatomy of motes and RFIDs, including sensors, in an era of ubiquitous computing and a world of (inter-)connected objects. Finally, we discuss the socio-cultural constructs impacting users’ intentions to adopt future wireless applications.

On the Variable Capacity Property of CC/DS-CDMA Systems

A complete complementary code based direct sequence code division multiple access (CC/DS-CDMA) system has been proposed recently as a potential candidate for beyond third generation (B3G) wireless communications. This paper addresses the issues that design of efficient code assignment schemes should be based on a flexible physical layer support, which is extremely important for emerging cross-layer designs in future wireless applications. The study in this paper considers a CC/DS-CDMA system with multiple time slots, three traffic classes and two dynamic code-flock assignment schemes, namely random assignment (RA) and compact assignment (CA). Simulation results show that the CC/DS-CDMA system has variable capacity property (VCP), which is sensitively affected by different code-flock assignment schemes. In general, CA can offer lower blocking probability, whereas RA can offer a larger mean system capacity and higher throughput when offered traffic is heavy

Optically Based Direct Sequence Binary Phase Shift Keying Modulation Scheme for Indoor Ultrawide-Band Wireless Systems

In this study, we focus on the design of an optical-based ultrawide-band (UWB) transmission system with a direct sequence-binary phase shift keying (DS-BPSK) modulation scheme for indoor wireless communication environments. The distinct pseudorandom noise (PN) code sequences are assigned to users that share a channel in the UWB multiple-access system. Filtered second-order Gaussian monocycle pulses can provide large bandwidths for very high-speed communications. Moreover, fiber dispersion and intersymbol interference (ISI) problems can be avoided by properly adjusting pulse width. The simulation and analytical results demonstrate that the presented scheme indeed provides several GHz bandwidths for future indoor UWB wireless applications.

Eighteen-pole superconducting CQ filter for future wireless applications

A recent development of an eighteen-pole high-temperature-superconducting (HTS) bandpass filter with group delay self-equalisation for future wireless applications is reported. The filter is designed to have a 15 MHz pass-band at a centre frequency of 1967.5 MHz. The filter exhibits a quasi-elliptic function response implemented with a cascaded quadruplet (CQ) coupling structure. Two particular cross-coupled quadruplet realisations have been developed to implement either attenuation poles at finite frequencies or linear phase for group delay self-equalisation. The Monte-Carlo sensitivity analysis was performed and the results were used as guidelines for tuning the filter. The filter was fabricated on a 0.43 mm-thick sapphire wafer with double-sided YBCO films. Measured responses are presented to demonstrate the validity of the design as well as the potential of the filter.