Showing papers on "Wireless published in 2012"

Network Information Theory

Abstract: This comprehensive treatment of network information theory and its applications provides the first unified coverage of both classical and recent results. With an approach that balances the introduction of new models and new coding techniques, readers are guided through Shannon's point-to-point information theory, single-hop networks, multihop networks, and extensions to distributed computing, secrecy, wireless communication, and networking. Elementary mathematical tools and techniques are used throughout, requiring only basic knowledge of probability, whilst unified proofs of coding theorems are based on a few simple lemmas, making the text accessible to newcomers. Key topics covered include successive cancellation and superposition coding, MIMO wireless communication, network coding, and cooperative relaying. Also covered are feedback and interactive communication, capacity approximations and scaling laws, and asynchronous and random access channels. This book is ideal for use in the classroom, for self-study, and as a reference for researchers and engineers in industry and academia.

Wireless Communications: Principles and Practice (2nd Edition) by

Abstract: For cellular radio engineers and technicians. The leading book on wireless communications offers a wealth of practical information on the implementation realities of wireless communications. This book also contains up-to-date information on the major wireless communications standards from around the world. Covers every fundamental aspect of wireless communications, from cellular system design to networking, plus world-wide standards, including ETACS, GSM, and PDC. Theodore Rappaport is Series Editor for the Prentice Hall Communication, Engineering, and Emerging Technologies Series.

Spectrum Sensing for Cognitive Radio : State-of-the-Art and Recent Advances

Abstract: The ever-increasing demand for higher data rates in wireless communications in the face of limited or underutilized spectral resources has motivated the introduction of cognitive radio. Traditionally, licensed spectrum is allocated over relatively long time periods and is intended to be used only by licensees. Various measurements of spectrum utilization have shown substantial unused resources in frequency, time, and space [1], [2]. The concept behind cognitive radio is to exploit these underutilized spectral resources by reusing unused spectrum in an opportunistic manner [3], [4]. The phrase cognitive radio is usually attributed to Mitola [4], but the idea of using learning and sensing machines to probe the radio spectrum was envisioned several decades earlier (cf., [5]).

Operator controlled device-to-device communications in LTE-advanced networks

Abstract: This article studies direct communications between user equipments in the LTE-advanced cellular networks. Different from traditional device-to-device communication technologies such as Bluetooth and WiFi-direct, the operator controls the communication process to provide better user experience and make profit accordingly. The related usage cases and business models are analyzed. Some technical considerations are discussed, and a resource allocation and data transmission procedure is provided.

Wireless information and power transfer: Architecture design and rate-energy tradeoff

Abstract: Simultaneous information and power transfer over the wireless channels potentially offers great convenience to mobile users. Yet practical receiver designs impose technical constraints on its hardware realization, as practical circuits for harvesting energy from radio signals are not yet able to decode the carried information directly. To make theoretical progress, we propose a general receiver operation, namely, dynamic power splitting (DPS), which splits the received signal with adjustable power for energy harvesting and for information decoding. Moreover, we propose two types of practical receiver architectures, namely, separated versus integrated information and energy receivers. The integrated receiver integrates the front-end components of the separated receiver, thus achieving a smaller form factor. The rate-energy tradeoff for these two architectures are characterized by a so-called rate-energy (R-E) region. Numerical results show that the R-E region of the integrated receiver is superior to that of the separated receiver when more harvested power is desired.

1-Gb/s Transmission Over a Phosphorescent White LED by Using Rate-Adaptive Discrete Multitone Modulation

Abstract: Light-emitting diodes (LEDs), which will be increasingly used in lighting technology, will also allow for distribution of broadband optical wireless signals. Visible-light communication (VLC) using white LEDs offers several advantages over the RF-based wireless systems, i.e., license-free spectrum, low power consumption, and higher privacy. Mostly, optical wireless can provide much higher data rates. In this paper, we demonstrate a VLC system based on a white LED for indoor broadband wireless access. After investigating the nonlinear effects of the LED and the power amplifier, a data rate of 1 Gb/s has been achieved at the standard illuminance level, by using an optimized discrete multitone modulation technique and adaptive bit- and power-loading algorithms. The bit-error ratio of the received data was $1.5\cdot 10^{-3}$ , which is within the limit of common forward error correction (FEC) coding. These results twice the highest capacity that had been previously obtained.

A Survey on MAC Strategies for Cognitive Radio Networks

Abstract: Dynamic spectrum policies combined with software defined radio are powerful means to improve the overall spectral efficiency allowing the development of new wireless services and technologies. Medium Access Control (MAC) protocols exploit sensing stimuli to build up a spectrum opportunity map (cognitive sensing). Available resources are scheduled (dynamic spectrum allocation), improving coexistence between users that belong to heterogeneous systems (dynamic spectrum sharing). Furthermore, MAC protocols may allow cognitive users to vacate selected channels when their quality becomes unacceptable (dynamic spectrum mobility). The contribution of this survey is threefold. First, we show the fundamental role of the MAC layer and identify its functionalities in a cognitive radio (CR) network. Second, a classification of cognitive MAC protocols is proposed. Third, advantages, drawbacks, and further design challenges of cognitive MAC protocols are discussed.

Systems and methods for providing positioning freedom, and support of different voltages, protocols, and power levels in a wireless power system

Abstract: Systems and methods for modifying the magnitude and/or phase of an electromagnetic field in one or multiple dimensions. Applications for use in charging or powering multiple devices with a wireless power charger system are also described. Applications include beam shaping, beam forming, phase array radar, beam steering, etc. and inductive charging and power, and particularly usage in mobile, electronic, electric, lighting, or other devices, batteries, power tools, kitchen, industrial applications, vehicles, and other usages. Embodiments of the invention can also be applied generally to power supplies and other power sources and chargers, including systems and methods for improved ease of use and compatibility and transfer of wireless power to mobile, electronic, electric, lighting, or other devices, batteries, power tools, kitchen, military, industrial applications and/or vehicles.

Wireless Myths, Realities, and Futures: From 3G/4G to Optical and Quantum Wireless

Abstract: 1) The Myth: Sixty years of research following Shannon's pioneering paper has led to telecommunications solutions operating arbitrarily close to the channel capacity-“flawless telepresence” with zero error is available to anyone, anywhere, anytime across the globe. 2)The Reality: Once we leave home or the office, even top of the range iPhones and tablet computers fail to maintain "flawless telepresence" quality. They also fail to approach the theoretical performance predictions. The 1000-fold throughput increase of the best third- generation (3G) phones over second-generation (2G) GSM phones and the 1000-fold increased teletraffic predictions of the next decade require substantial further bandwidth expansion toward ever increasing carrier frequencies, expanding beyond the radiofrequency (RF) band to optical frequencies, where substantial bandwidths are available. 3) The Future: However, optical and quantum-domain wireless communications is less developed than RF wireless. It is also widely recognized that the pathloss of RF wireless systems monotonically increases with the carrier frequency and this additional challenge has to be tackled by appropriate countermeasures in future research. Hence, we set out to seek promising techniques of tackling the aforementioned challenges and for resolving the conflicting design constraints imposed on the flawless telepresence systems of the future. To disspell the myth, we evaluate both the operational 3G as well as the emerging fourth-generation (4G) wireless systems and demonstrate that there is a substantial difference between their theoretical and their practically attainable performance. The reality is that the teletraffic predictions indicate further thirst for bandwidth, which cannot be readily satisfied within the most popular 1-2-GHz carrier-frequency range, where the best propagation conditions prevail. We briefly consider the 10-300-GHz unlicensed band as a potential source of further spectrum, followed by a review of advances way beyond the upper edge of the RF range at 300 GHz, namely to the realms of optical wireless (OW) communications. As the carrier frequency is increased, the pathloss is also increased, which results in ever smaller cells. Furthermore, the high-frequency RF waves predominantly obey line-of-sight (LOS) propagation-like visible light. The future requires advances in both infrared and visible-light communications for circumventing the LOS nature of light. We hypothesize that light-emitting diode (LED) arrays acting as "massive" multiple-input-multiple-output (MIMO) components as well as transmitter/receiver cooperation might be conceived. The heterogeneous networks of the near future will rely on seamless, near-instantaneous handovers among OW hotspots, RF hotspots, and oversailing larger cells. These "massive" MIMOs might impose a high complexity, hence their reduced-complexity noncoherently detected counterparts might be favored. Finally, we conclude by touching upon the promising research area of quantum-domain communications, which might be expected to circumvent the aforementioned complexity problem of massive MIMOs with the aid of efficient quantum-domain search techniques-a truly exciting research era

Wireless Sensor Network Applications: A Study in Environment Monitoring System

Abstract: Development in the technology of sensor such as Micro Electro Mechanical Systems (MEMS), wireless communications, embedded systems, distributed processing and wireless sensor applications have contributed a large transformation in Wireless Sensor Network (WSN) recently. It assists and improves work performance both in the field of industry and our daily life. Wireless Sensor Network has been widely used in many areas especially for surveillance and monitoring in agriculture and habitat monitoring. Environment monitoring has become an important field of control and protection, providing real-time system and control communication with the physical world. An intelligent and smart Wireless Sensor Network system can gather and process a large amount of data from the beginning of the monitoring and manage air quality, the conditions of traffic, to weather situations. In this paper, we discuss and review wireless sensor network applications for environmental monitoring. In order to implement a good monitoring system, there are several requirements to be followed. From the studies, it has been proved to be an alternative way to replace the conventional method that uses men force to monitor the environment. It is also proven that these approaches can improve the system performance, provide a convenient and efficient method and can also fulfill functional requirements.

Making sensor networks immortal: an energy-renewal approach with wireless power transfer

Abstract: Wireless sensor networks are constrained by limited battery energy. Thus, finite network lifetime is widely regarded as a fundamental performance bottleneck. Recent breakthrough in the area of wireless power transfer offers the potential of removing this performance bottleneck, i.e., allowing a sensor network to remain operational forever. In this paper, we investigate the operation of a sensor network under this new enabling energy transfer technology. We consider the scenario of a mobile charging vehicle periodically traveling inside the sensor network and charging each sensor node's battery wirelessly. We introduce the concept of renewable energy cycle and offer both necessary and sufficient conditions. We study an optimization problem, with the objective of maximizing the ratio of the wireless charging vehicle (WCV)'s vacation time over the cycle time. For this problem, we prove that the optimal traveling path for the WCV is the shortest Hamiltonian cycle and provide a number of important properties. Subsequently, we develop a near-optimal solution by a piecewise linear approximation technique and prove its performance guarantee.

Design and Analysis of a Hardware-Efficient Compressed Sensing Architecture for Data Compression in Wireless Sensors

Abstract: This work introduces the use of compressed sensing (CS) algorithms for data compression in wireless sensors to address the energy and telemetry bandwidth constraints common to wireless sensor nodes. Circuit models of both analog and digital implementations of the CS system are presented that enable analysis of the power/performance costs associated with the design space for any potential CS application, including analog-to-information converters (AIC). Results of the analysis show that a digital implementation is significantly more energy-efficient for the wireless sensor space where signals require high gain and medium to high resolutions. The resulting circuit architecture is implemented in a 90 nm CMOS process. Measured power results correlate well with the circuit models, and the test system demonstrates continuous, on-the-fly data processing, resulting in more than an order of magnitude compression for electroencephalography (EEG) signals while consuming only 1.9 μW at 0.6 V for sub-20 kS/s sampling rates. The design and measurement of the proposed architecture is presented in the context of medical sensors, however the tools and insights are generally applicable to any sparse data acquisition.

Robust Beamforming for Wireless Information and Power Transmission

Abstract: In this letter, we study the robust beamforming problem for the multi-antenna wireless broadcasting system with simultaneous information and power transmission, under the assumption of imperfect channel state information (CSI) at the transmitter. Following the worst-case deterministic model, our objective is to maximize the worst-case harvested energy for the energy receiver while guaranteeing that the rate for the information receiver is above a threshold for all possible channel realizations. Such problem is nonconvex with infinite number of constraints. Using certain transformation techniques, we convert this problem into a relaxed semidefinite programming problem (SDP) which can be solved efficiently. We further show that the solution of the relaxed SDP problem is always rank-one. This indicates that the relaxation is tight and we can get the optimal solution for the original problem. Simulation results are presented to validate the effectiveness of the proposed algorithm.

Wireless Information Transfer with Opportunistic Energy Harvesting

Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the narrowband flat-fading channel subject to time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy opportunistically via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any time due to the practical circuit limitation. Therefore, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference condition. In this paper, we derive the optimal mode switching rule at the receiver to achieve various trade-offs between wireless information transfer and energy harvesting. Specifically, we determine the minimum transmission outage probability for delay-limited information transfer and the maximum ergodic capacity for no-delay-limited information transfer versus the maximum average energy harvested at the receiver, which are characterized by the boundary of so-called "outage-energy" region and "rate-energy" region, respectively. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control, information and energy transfer scheduling, and the receiver's mode switching. Our results provide useful guidelines for the efficient design of emerging wireless communication systems powered by opportunistic WEH.

Overview of 3GPP LTE-advanced carrier aggregation for 4G wireless communications

Abstract: To satisfy the ever increasing demand for higher throughput and data rates, wireless communication systems need to operate in wider bandwidths 3GPP LTE-Advanced with carrier aggregation enables operators to maximally and optimally utilize their available spectrum resources for increased data rates and user experience while reducing their incurred OPEX and CAPEX This article provides a tutorial overview of 3GPP LTE-Advanced with carrier aggregation as specified in Rel-10 including deployment scenarios of interest, main design features, PHY/MAC procedures, and potential enhancements for future standard releases

Wireless information transfer with opportunistic energy harvesting

Abstract: Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the flat-fading channel subject to the time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any given time due to the practical circuit limitation. As a result, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference conditions. In this paper, we derive the optimal mode switching rule at the receiver to achieve various tradeoffs between the minimum transmission outage probability for ID and the maximum average harvested energy for EH, which are characterized by the boundary of a so-called “outage-energy” region. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control and scheduling for information and energy transfer with the receiver's mode switching. Our results provide useful insights to the optimal design of emerging wireless communication systems powered by opportunistic WEH.

Robust Beamforming for Wireless Information and Power Transmission

Abstract: In this letter, we study the robust beamforming problem for the multi-antenna wireless broadcasting system with simultaneous information and power transmission, under the assumption of imperfect channel state information (CSI) at the transmitter. Following the worst-case deterministic model, our objective is to maximize the worst-case harvested energy for the energy receiver while guaranteeing that the rate for the information receiver is above a threshold for all possible channel realizations. Such problem is nonconvex with infinite number of constraints. Using certain transformation techniques, we convert this problem into a relaxed semidefinite programming problem (SDP) which can be solved efficiently. We further show that the solution of the relaxed SDP problem is always rank-one. This indicates that the relaxation is tight and we can get the optimal solution for the original problem. Simulation results are presented to validate the effectiveness of the proposed algorithm.

Mirror mirror on the ceiling: flexible wireless links for data centers

Abstract: Modern data centers are massive, and support a range of distributed applications across potentially hundreds of server racks. As their utilization and bandwidth needs continue to grow, traditional methods of augmenting bandwidth have proven complex and costly in time and resources. Recent measurements show that data center traffic is often limited by congestion loss caused by short traffic bursts. Thus an attractive alternative to adding physical bandwidth is to augment wired links with wireless links in the 60 GHz band.We address two limitations with current 60 GHz wireless proposals. First, 60 GHz wireless links are limited by line-of-sight, and can be blocked by even small obstacles. Second, even beamforming links leak power, and potential interference will severely limit concurrent transmissions in dense data centers. We propose and evaluate a new wireless primitive for data centers, 3D beamforming, where 60 GHz signals bounce off data center ceilings, thus establishing indirect line-of-sight between any two racks in a data center. We build a small 3D beamforming testbed to demonstrate its ability to address both link blockage and link interference, thus improving link range and number of concurrent transmissions in the data center. In addition, we propose a simple link scheduler and use traffic simulations to show that these 3D links significantly expand wireless capacity compared to their 2D counterparts.

Multi-RAT carrier aggregation for integrated WWAN-WLAN operation

Abstract: Systems and methods for Multi-Radio Access Technology (RAT) Carrier Aggregation (MRCA) wireless wide area network (WWAN) assisted wireless local area network (WLAN) flow mapping and flow routing are disclosed. One system comprises a dynamic flow mapping module that is configured to form a flow-mapping table to dynamically map service flows between the WWAN radio and the WLAN radio in the wireless device. A flow routing module is configured to route data packets to one of the WWAN radio and the WLAN radio in the wireless device based on the flow-mapping table to transmit and receive the data packets via the wireless device.

Wireless power component selection

Abstract: Described herein are improved configurations for a wireless power transfer. The parameters of components of resonators in a system are calculated and adjusted. Some adjustments are performed using a temporary matching resistor chosen to simulate the loading of at least one additional resonator.

OpenRadio: a programmable wireless dataplane

Abstract: We present OpenRadio, a novel design for a programmable wireless dataplane that provides modular and declarative programming interfaces across the entire wireless stack. Our key conceptual contribution is a principled refactoring of wireless protocols into processing and decision planes. The processing plane includes directed graphs of algorithmic actions (eg. 54Mbps OFDM WiFi or special encoding for video). The decision plane contains the logic which dictates which directed graph is used for a particular packet (eg. picking between data and video graphs). The decoupling provides a declarative interface to program the platform while hiding all underlying complexity of execution. An operator only expresses decision plane rules and corresponding processing plane action graphs to assemble a protocol. The scoped interface allows us to build a dataplane that arguably provides the right tradeoff between performance and flexibility. Our current system is capable of realizing modern wireless protocols (WiFi, LTE) on off-the-shelf DSP chips while providing flexibility to modify the PHY and MAC layers to implement protocol optimizations.

Wireless power receiver and control method thereof

Abstract: Methods and apparatus are provided for controlling a wireless power receiver for wirelessly receiving power. A drive power for driving the wireless power receiver is received from a wireless power transmitter. A communication network is established with the wireless power transmitter. A wireless power network that is controlled by the wireless power transmitter is joined. A charge power is received from the wireless power transmitter.

Position-Based Modeling for Wireless Channel on High-Speed Railway under a Viaduct at 2.35 GHz

Abstract: This paper presents a novel and practical study on the position-based radio propagation channel for High-Speed Railway by performing extensive measurements at 2.35 GHz in China. The specification on the path loss model is developed. In particular, small scale fading properties such as K-factor, Doppler frequency feature and time delay spread are parameterized, which show dynamic variances depending on the train location and the transceiver separation. Finally, the statistical position-based channel models are firstly established to characterize the High-Speed Railway channel, which significantly promotes the evaluation and verification of wireless communications in relative scenarios.

On physical-layer identification of wireless devices

Abstract: Physical-layer device identification aims at identifying wireless devices during radio communication by exploiting unique characteristics of their analog (radio) circuitry. This work systematizes the existing knowledge on this topic in order to enable a better understanding of device identification, its implications on the analysis and design of security solutions in wireless networks and possible applications. We therefore present a systematic review of physical-layer identification systems and provide a summary of current state-of-the-art techniques. We further present a classification of attacks and discuss the feasibility, limitations, and implications in selected applications. We also highlight issues that are still open and need to be addressed in future work.

Method for performing device-to-device communication in wireless access system and apparatus therefor

Abstract: The present invention provides a method for performing device-to-device communication in a wireless access system that supports the device-to-device communication and an apparatus therefor. Specifically, the invention comprises the steps of: receiving, from a base station, device-to-device communication parameters for broadcasted device-to-device communication; transmitting a detection signal to one or more devices using the received device-to-device communication parameters; receiving, from the one or more devices, link measurement information for measuring a link between a first device and the one or more devices using the detection signal; selecting a second device for performing the device-to-device communication from the one or more devices using the link measurement information; and performing the device-to-device communication with the selected second device.

When the Smart Grid Meets Energy-Efficient Communications: Green Wireless Cellular Networks Powered by the Smart Grid

Abstract: Recently, there is great interest in considering the energy efficiency aspect of cellular networks. On the other hand, the power grid infrastructure, which provides electricity to cellular networks, is experiencing a significant shift from the traditional electricity grid to the smart grid. When a cellular network is powered by the smart grid, only considering energy efficiency in the cellular network may not be enough. In this paper, we consider not only energy-efficient communications but also the dynamics of the smart grid in designing green wireless cellular networks. Specifically, the dynamic operation of cellular base stations depends on the traffic, real-time electricity price, and the pollutant level associated with electricity generation. Coordinated multipoint (CoMP) is used to ensure acceptable service quality in the cells whose base stations have been shut down. The active base stations decide on which retailers to procure electricity from and how much electricity to procure. We formulate the system as a Stackelberg game, which has two levels: a cellular network level and a smart grid level. Simulation results show that the smart grid has significant impacts on green wireless cellular networks, and our proposed scheme can significantly reduce operational expenditure and CO_2 emissions in green wireless cellular networks.

Flexible power modeling of LTE base stations

Abstract: With the explosion of wireless communications in number of users and data rates, the reduction of network power consumption becomes more and more critical. This is especially true for base stations which represent a dominant share of the total power in cellular networks. In order to study power reduction techniques, a convenient power model is required, providing estimates of the power consumption in different scenarios. This paper proposes such a model, accurate but simple to use. It evaluates the base station power consumption for different types of cells supporting the 3GPP LTE standard. It is flexible enough to enable comparisons between state-of-the-art and advanced configurations, and an easy adaptation to various scenarios. The model is based on a combination of base station components and sub-components as well as power scaling rules as functions of the main system parameters.