Showing papers on "Communications system published in 2012"

Optimal Packet Scheduling in an Energy Harvesting Communication System

Abstract: We consider the optimal packet scheduling problem in a single-user energy harvesting wireless communication system. In this system, both the data packets and the harvested energy are modeled to arrive at the source node randomly. Our goal is to adaptively change the transmission rate according to the traffic load and available energy, such that the time by which all packets are delivered is minimized. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy amounts are known before the transmission starts. For the data traffic arrivals, we consider two different scenarios. In the first scenario, we assume that all bits have arrived and are ready at the transmitter before the transmission starts. In the second scenario, we consider the case where packets arrive during the transmissions, with known arrival times and sizes. We develop optimal off-line scheduling policies which minimize the time by which all packets are delivered to the destination, under causality constraints on both data and energy arrivals.

Intra-vehicle information conveyance system and method

Abstract: System and method for conveying data between vehicles includes a data generating system arranged on a first vehicle to obtain or generate information about the first vehicle or conditions around the first vehicle, a first communications system arranged on the first vehicle and coupled to the data generating system for communicating with a wireless Internet service provider (ISP) and a second communications system arranged on a second vehicle and communicating with an ISP. The first communications system enables the information obtained or generated by the data generating system to be transmitted via the Internet to the second communications system. The first and second communications systems can communicate with the same ISP or different ISPs linked to one another.

Cooperative communications for wireless networks: techniques and applications in LTE-advanced systems

Abstract: Cooperative communications enable efficient utilization of communication resources, by allowing nodes or terminals in a communication network to collaborate with each other in information transmission. It is a promising technique for future communication systems. In this article, we first survey cooperative communication schemes and discuss their advantages in improving system capacity and diversity. Following that, we examine the applications of cooperative relaying schemes in LTE-advanced systems. Specifically, we investigate two intra-cell coordinated multi-point schemes in LTE-advanced systems, and evaluate the performance of the schemes. It is shown that cooperative relaying leads to both network coverage extension and capacity expansion in LTE-advanced systems. Cooperative communications can significantly improve the system spectrum efficiency and performance.

A general framework for the optimization of energy harvesting communication systems with battery imperfections

Abstract: Energy harvesting has emerged as a powerful technology for complementing current battery-powered communication systems in order to extend their lifetime. In this paper a general framework is introduced for the optimization of communication systems in which the transmitter is able to harvest energy from its environment. Assuming that the energy arrival process is known non-causally at the transmitter, the structure of the optimal transmission scheme, which maximizes the amount of transmitted data by a given deadline, is identified. Our framework includes models with continuous energy arrival as well as battery constraints. A battery that suffers from energy leakage is studied further, and the optimal transmission scheme is characterized for a constant leakage rate.

Molecular Communication Using Brownian Motion With Drift

Abstract: Inspired by biological communication systems, molecular communication has been proposed as a viable scheme to communicate between nano-sized devices separated by a very short distance. Here, molecules are released by the transmitter into the medium, which are then sensed by the receiver. This paper develops a preliminary version of such a communication system focusing on the release of either one or two molecules into a fluid medium with drift. We analyze the mutual information between transmitter and the receiver when information is encoded in the time of release of the molecule. Simplifying assumptions are required in order to calculate the mutual information, and theoretical results are provided to show that these calculations are upper bounds on the true mutual information. Furthermore, optimized degree distributions are provided, which suggest transmission strategies for a variety of drift velocities.

A review of communication-oriented optical wireless systems

Abstract: This article presents an overview of optical wireless (OW) communication systems that operate both in the short- (personal and indoor systems) and the long-range (outdoor and hybrid) regimes. Each of these areas is discussed in terms of (a) key requirements, (b) their application framework, (c) major impairments and applicable mitigation techniques, and (d) current and/or future trends. Personal communication systems are discussed within the context of point-to-point ultra-high speed data transfer. The most relevant application framework and related standards are presented, including the next generation Giga-IR standard that extends personal communication speeds to over 1 Gb/s. As far as indoor systems are concerned, emphasis is given on modeling the dispersive nature of indoor OW channels, on the limitations that dispersion imposes on user mobility and dispersion mitigation techniques. Visible light communication systems, which provide both illumination and communication over visible or hybrid visible/infrared LEDs, are presented as the most important representative of future indoor OW systems. The discussion on outdoor systems focuses on the impact of atmospheric effects on the optical channel and associated mitigation techniques that extend the realizable link lengths and transfer rates. Currently, outdoor OW is commercially available at 10 Gb/s Ethernet speeds for Metro networks and Local-Area-Network interconnections and speeds are expected to increase as faster and more reliable optical components become available. This article concludes with hybrid optical wireless/radio-frequency (OW/RF) systems that employ an additional RF link to improve the overall system reliability. Emphasis is given on cooperation techniques between the reliable RF subsystem and the broadband OW system.

Scalable Distributed Communication Architectures to Support Advanced Metering Infrastructure in Smart Grid

Abstract: In this paper, we investigate the scalability of three communication architectures for advanced metering infrastructure (AMI) in smart grid. AMI in smart grid is a typical cyber-physical system (CPS) example, in which large amount of data from hundreds of thousands of smart meters are collected and processed through an AMI communication infrastructure. Scalability is one of the most important issues for the AMI deployment in smart grid. In this study, we introduce a new performance metric, accumulated bandwidthdistance product (ABDP), to represent the total communication resource usages. For each distributed communication architecture, we formulate an optimization problem and obtain the solutions for minimizing the total cost of the system that considers both the ABDP and the deployment cost of the meter data management system (MDMS). The simulation results indicate the significant benefits of the distributed communication architectures over the traditional centralized one. More importantly, we analyze the scalability of the total cost of the communication system (including MDMS) with regard to the traffic load on the smart meters for both the centralized and the distributed communication architectures. Through the closed form expressions obtained in our analysis, we demonstrate that the total cost for the centralized architecture scales linearly as O(λN), with N being the number of smart meters, and λ being the average traffic rate on a smart meter. In contrast, the total cost for the fully distributed communication architecture is O(λ2/3 N2/3), which is significantly lower.

How the Great Firewall of China is Blocking Tor

Abstract: Internet censorship in China is not just limited to the web: the Great Firewall of China prevents thousands of potential Tor users from accessing the network. In this paper, we investigate how the ...

Bandwidth and Latency Requirements for Smart Transmission Grid Applications

Abstract: The rapid increase of phasor measurements on the high voltage power system has opened opportunities for new applications to enhance the operation of the grid. To take advantage of the high sampling rates of these measurement data, these applications will require a high-bandwidth, networked communication system. The specifications for this next generation communication system that will overlay the continental power grids are under intense discussion at this time by organizations like the North-American Synchro-Phasor Initiative (NASPI). In this paper we present a method to simulate, design and test the adequacy of a communication system for a particular transmission grid. The main difference from typical communication system studies is that we formulate the communication requirements from the power grid application requirements, that is, the communication design, simulation and testing is from the viewpoint of the anticipated power applications. The method is demonstrated on a WECC 225 bus and a Polish 2383 bus transmission system models.

Method and system for long-range adaptive mobile beam-forming ad-hoc communication system with integrated positioning

Abstract: Method and system for provided a long range, high capacity ad-hoc mobile communication network where a narrow antenna beam formed by a plurality of antenna elements, radio transceivers and digital spatial signal processing is used to provide a high accuracy positioning system integrated into the communication system. The relative positions and directive orientation of all the units in the network is done by mutual exchange of positioning data as an element in the communication protocol in the network.

Magnetic Induction for Underwater Wireless Communication Networks

Abstract: Although acoustic waves are the most versatile and widely used physical layer technology for underwater wireless communication networks (UWCNs), they are adversely affected by ambient noise, multipath propagation, and fading. The large propagation delays, low bandwidth, and high bit error rates of the underwater acoustic channel hinder communication as well. These operational limits call for complementary technologies or communication alternatives when the acoustic channel is severely degraded. Magnetic induction (MI) is a promising technique for UWCNs that is not affected by large propagation delays, multipath propagation, and fading. In this paper, the MI communication channel has been modeled. Its propagation characteristics have been compared to the electromagnetic and acoustic communication systems through theoretical analysis and numerical evaluations. The results prove the feasibility of MI communication in underwater environments. The MI waveguide technique is developed to reduce path loss. The communication range between source and destination is considerably extended to hundreds of meters in fresh water due to its superior bit error rate performance.

Flip-OFDM for Unipolar Communication Systems

Abstract: Unipolar communications systems can transmit information using only real and positive signals. This includes a variety of physical channels ranging from optical (fiber or free-space), to RF wireless using amplitude modulation with non-coherent reception, to baseband single wire communications. Unipolar OFDM techniques can efficiently compensate frequency selective channel distortion in unipolar communication systems. One of the leading example of unipolar OFDM is asymmetric clipped optical OFDM (ACO-OFDM) originally proposed for optical communications. Flip-OFDM is an alternative approach that was proposed in a patent, but its performance and full potentials have never been investigated in the literature. In this paper, we first compare Flip-OFDM and ACO-OFDM, and show that both techniques have the same performance but different complexities. In particular, Flip-OFDM offers 50% saving in hardware complexity at the receiver over ACO-OFDM. We then propose a new detection scheme, which enables to reduce the noise at the Flip-OFDM receiver by almost 3dB. The analytical performance of the noise filtering schemes is supported by the simulation results.

Joint Mode Selection and Power Allocation Scheme for Power-Efficient Device-to-Device (D2D) Communication

Abstract: This paper proposes a power-efficient mode selection and power allocation scheme in device-to-device (D2D) communication system as an underlay coexistence with cellular networks. The proposed scheme is performed based on the exhaustive search of all possible mode combinations of the devices which consist of the mode indices for all devices in the system. Specifically, the proposed scheme consists of two steps. First, we calculate the optimal power with respect to the maximum power-efficiency for all possible modes of each device. Since the power-efficiency is not a concave function for the transmission power, we obtain the suboptimal solution by using the concavity of the lower and upper bound for the power-efficiency. The powerefficiencies for all possible modes of each device are obtained by the suboptimal power allocation in the first step. In the second step, we select a mode sequence which has the maximal power-efficiency among all possible mode combinations of the devices based on the obtained power-efficiencies in the first step. Then we can jointly obtain the suboptimal transmission power and the mode maximizing the power-efficiency. The proposed suboptimal scheme for the power allocation and mode selection performs close to the upper bound with respect to the power-efficiency. The simulation results also show that the proposed scheme outperforms the conventional schemes with respect to the power-efficiency and system capacity.

Secure Communication in Stochastic Wireless Networks—Part I: Connectivity

Abstract: The ability to exchange secret information is critical to many commercial, governmental, and military networks. Information-theoretic security-widely accepted as the strictest notion of security-relies on channel coding techniques that exploit the inherent randomness of the propagation channels to strengthen the security of digital communications systems. Motivated by recent developments in the field, we aim to characterize the fundamental secrecy limits of wireless networks. The paper is comprised of two separate parts. In Part I, we define the intrinsically secure communications graph (iS-graph), a random graph which describes the connections that can be securely established over a large-scale network. We provide conclusive results for the local connectivity of the Poisson iS-graph, in terms of node degrees and isolation probabilities. We show how the secure connectivity of the network varies with the wireless propagation effects, the secrecy rate threshold of each link, and the noise powers of legitimate nodes and eavesdroppers. We then propose sectorized transmission and eavesdropper neutralization as viable strategies for improving the secure connectivity. Our results help clarify how the spatial density of eavesdroppers can compromise the intrinsic security of wireless networks. In Part II of the paper, we study the achievable secrecy rates and the effect of eavesdropper collusion.

System and method for peer-to-peer communication in cellular systems

Abstract: Systems and methods are provided for delivering both PMP communications, for example standard cellular communications via a base station, and also delivering P2P communications, for example, communications between two mobile stations, using the same spectral resources for both types of communication.

On the Application of Cooperative Transmission to Secrecy Communications

Abstract: Information theoretic security has recently emerged as an effective physical layer approach to provide secure communications. The outage performance of such a secrecy communication system is considered in this paper, since it is an important criterion to measure whether users' predefined quality of service can be met. Provided that the legitimate receiver and eavesdropper have the same noise power, many existing secure schemes cannot achieve outage probability approaching zero, regardless of how large the transmission power is. By introducing cooperative transmission into secrecy communication systems, it will be shown here that outage probability approaching zero can be achieved. In particular, scenarios with single-antenna nodes and multiple-antenna nodes will both be addressed, and the optimal design of beamforming/precoding will be investigated. Explicit expressions of the achievable outage probability and diversity-multiplexing tradeoff will be developed to demonstrate the performance of the proposed cooperative secure transmission schemes, and numerical results are presented.

Automatic Modulation Recognition of Communication Signals.

Abstract: The project is aimed at designing an intelligent communication system where the receiver is able to detect the modulation scheme of the signal it receives using Automatic Modulation Recognition (AMR) algorithms, without having minimum or no prior knowledge of the transmitted signal. Six digital modulation schemes namely QPSK, BPSK, 2ASK, 4ASK, 2FSK, 4FSK and 16QAM were used. Algorithms based on deriving key statistical features from the communication signal, were formed. Features were also extracted using Azzouz and Nandi‟s techniques. Neural Networks were applied to the extracted features to distinguish between signals having different modulation schemes. The simulations were performed for different SNR values as well as different number of neurons in a one and two hidden layers.

On the Energy Efficiency-Spectral Efficiency Trade-off over the MIMO Rayleigh Fading Channel

Abstract: Along with spectral efficiency (SE), energy efficiency (EE) is becoming one of the key performance evaluation criteria for communication system. These two criteria, which are conflicting, can be linked through their trade-off. The EE-SE trade-off for the multi-input multi-output (MIMO) Rayleigh fading channel has been accurately approximated in the past but only in the low-SE regime. In this paper, we propose a novel and more generic closed-form approximation of this trade-off which exhibits a greater accuracy for a wider range of SE values and antenna configurations. Our expression has been here utilized for assessing analytically the EE gain of MIMO over single-input single-output (SISO) system for two different types of power consumption models (PCMs): the theoretical PCM, where only the transmit power is considered as consumed power; and a more realistic PCM accounting for the fixed consumed power and amplifier inefficiency. Our analysis unfolds the large mismatch between theoretical and practical MIMO vs. SISO EE gains; the EE gain increases both with the SE and the number of antennas in theory, which indicates that MIMO is a promising EE enabler; whereas it remains small and decreases with the number of transmit antennas when a realistic PCM is considered.

Underwater wireless sensor communications in the 2.4 GHz ISM frequency band.

Abstract: One of the main problems in underwater communications is the low data rate available due to the use of low frequencies. Moreover, there are many problems inherent to the medium such as reflections, refraction, energy dispersion, etc., that greatly degrade communication between devices. In some cases, wireless sensors must be placed quite close to each other in order to take more accurate measurements from the water while having high communication bandwidth. In these cases, while most researchers focus their efforts on increasing the data rate for low frequencies, we propose the use of the 2.4 GHz ISM frequency band in these special cases. In this paper, we show our wireless sensor node deployment and its performance obtained from a real scenario and measures taken for different frequencies, modulations and data transfer rates. The performed tests show the maximum distance between sensors, the number of lost packets and the average round trip time. Based on our measurements, we provide some experimental models of underwater communication in fresh water using EM waves in the 2.4 GHz ISM frequency band. Finally, we compare our communication system proposal with the existing systems. Although our proposal provides short communication distances, it provides high data transfer rates. It can be used for precision monitoring in applications such as contaminated ecosystems or for device communicate at high depth.

Network entity, communication device, mobile communication device and method thereof

Abstract: A communication system is described in which a mobile communication device receives MDT configuration requests from a base station or radio network controller to initiate an MDT measurement session for obtaining measurement data and location related data for identifying a location to which said measurement data relates. The mobile communication device checks a user consent indicator in memory and only provides the location related data if the user consent indicator indicates that a user of the mobile communication device consents to the provision the location related data.

Reference signal transmission and reception method and equipment

Abstract: A communications system and a method for performing communications are provided. User Equipments (UEs) are provided with UE-specific configuration information, such as CSI-RS (Channel Status Indication-Reference Signal) patterns, antenna port groupings, reference signal configurations, subframe configurations, and/or scrambling codes. The UEs process the received reference signals in accordance with the received configuration information and feedback measurement information for, e.g., PMI/CQI/RI (Precoding Matrix Indicator/Channel Quality Indicator/Rank Indicator of the precoding matrix) and/or the RLM/RRM (Radio Link Monitor/Radio Resource Management).

Communication apparatus and method

Abstract: A detection system for use with a communications system and an associated communication systems, methods, portable electronics devices and geolocation and/or reporting devices, the detection system comprising at least one radiation detector for receiving a radiation signal, wherein the at least one radiation detector comprises a plurality of sensing elements, and wherein the detection system is configured to detect the radiation signal using differing subsets of sensing elements at differing times and determine data encoded in the radiation signal based on the radiation detected by the different subsets of sensing elements. A transmission system and an associated receiver, communications system and methods, the transmission system comprising at least one transmitter element, the transmission system being configured to encode at least one data symbol or element by providing one or more signals on or in selected transmission carriers or channels, the selection of transmission carriers or channels being representative of the at least one data symbol or element, the transmission system being configured to vary the output power of the transmission system by varying the number of carriers or channels used to encode each data symbol or element. A transmission system for transmitting data as part of a communications system and an associated receiver, communications system and methods, the data comprising a plurality of data symbols or elements, the transmission system being configured to divide the data into at least a first data portion and a second data portion, wherein the first data portion is communicated by transmitting signals in selected carrier channels, wherein the transmission system is configured to encode at least one data symbol or element by selecting a relative order of at least one first carrier channel having a first operational state and at least one second carrier channel having a second operational state.

Security system for handheld wireless devices using time-variable encryption keys

Abstract: In one embodiment, the invention provides a portable wireless personal communication system for cooperating with a remote certification authority to employ time variable secure key information pursuant to a predetermined encryption algorithm to facilitate convenient, secure encrypted communication. The disclosed system includes a wireless handset, such as PDA, smartphone, cellular telephone or the like, characterized by a relatively robust data processing capability and a body mounted key generating component which is adapted to be mounted on an individual's body, in a permanent or semi-permanent manner, for wirelessly broadcasting, within the immediate proximity of the individual, a secret or private key identifying signal corresponding to a time variable secure key information under the control of the certification authority. The key identifying signal is generated in a format that facilitates secure wireless communication with the individual in accordance with a predetermined encryption algorithm including a PKI encryption algorithm. The disclosed system may be used with a console for coordinating access to a variety of different communication system and networks.

Smart Transmitters and Receivers for Underwater Free-Space Optical Communication

Abstract: The number of unmanned vehicles and devices deployed underwater is increasing. New communication systems and networking protocols are required to handle this growth. Underwater free-space optical communication is poised to augment acoustic communication underwater, especially for short-range, mobile, multi-user environments in future underwater systems. Existing systems are typically point-to-point links with strict pointing and tracking requirements. In this paper we demonstrate compact smart transmitters and receivers for underwater free-space optical communications. The receivers have segmented wide field of view and are capable of estimating angle of arrival of signals. The transmitters are highly directional with individually addressable LEDs for electronic switched beamsteering, and are capable of estimating water quality from its backscattered light collected by its co-located receiver. Together they form enabling technologies for non-traditional networking schemes in swarms of unmanned vehicles underwater.

Dead zone for wireless communication device

Abstract: I have invented a communication system illustratively comprising: a wireless communication device; a network for controlling wireless communication over said network, said network tracking a location of said wireless communication device based on location data pertaining to said wireless communication device, said network comprising a no communication zone register including a database of predetermined zones in which predetermined communication by, to, or by and to said wireless communication device is to be disabled; wherein when said wireless communication device is in one of said predetermined zones in which communication by, to, or by and to wireless communication device is not permitted, said network disables said predetermined communication by, to, or by and to said wireless communication device. The “dead zones” where the wireless device may be disabled illustratively may include a speeding zone, a hospital zone, a movie theater zone, a church zone, and a performing arts theater zone or be based upon the law of a state on the use of said wireless communication device in a moving vehicle. The device may include GPS acquisition circuitry and the system may use assisted GPS for use in calculating the location of the wireless communication device. On disablement a message may display on the wireless communication device that the wireless communication device is in a “dead zone”. While in the “dead zone”, my invention allows for disablement of voice communication, text messages, emails, and/or data communication. Disablement may occur by service disablement or disablement of the password or keyboard entry feature of the wireless device. “Dead zones” may be determined by default or subscription. My inventive device and method for dead zoning a wireless communication device are also disclosed.

UWB Antennas for Communication Systems

Abstract: Since the U.S. Federal Communications Commission (FCC) opened the spectrum from 3.1 to 10.6 GHz for unlicensed radio applications with an EIRP of up to 41.3 dBm/MHz, numerous papers have been published on ultrawideband (UWB) antennas. Often the goal in these publications is to present an antenna, which has a satisfactory input reflection coefficient and a reasonable, constant radiation diagram versus frequency. However, in the case of UWB, there are numerous additional critical characteristics, which must be considered in the proper wireless system design. The publications, which treat this topic with sufficient proficiency, use such quantities as transient gain, group delay, ringing, dispersion, signal fidelity, polarization, efficiency, and the peak value of the transient response. For practical applications based on signals with an UWB instantaneous bandwidth occupation, all criteria are of vital importance, because they determine the sensor resolution, accuracy, or increase the bit error rate in communications systems. This paper gives an overview of UWB antenna designs together with their suitability for different applications with respect to the aforementioned critical characteristics. Additionally, UWB antenna array design, polarization diversity, and application in body area network (BAN) will be discussed. In nearly all cases the time-domain characteristics are taken into account, as they are more intuitive to interpret and very convenient for time-domain UWB system design.

Method for device-to-device communication based on cellular telecommunication system

Abstract: Disclosed is device-to-device communication based on a cellular communication network. A method of operating a terminal capable of supporting D2D (device to device) communication based on a cellular communication network may include: determining whether to perform central control D2D communication or distributed control D2D communication; and performing the distributed control D2D communication, or requesting a setting for the central control D2D communication to a base station on the basis of the determination. With the D2D communication based on the cellular communication network, the cellular communication, the central control D2D communication, or the distributed control D2D communication may flexibly and selectively operate in the cellular network.

Channel Estimation of Dual-Hop MIMO Relay System via Parallel Factor Analysis

Abstract: The optimal source precoding matrix and relay amplifying matrix have been developed in recent works on multiple-input multiple-output (MIMO) relay communication systems assuming that the instantaneous channel state information (CSI) is available. However, in practical relay communication systems, the instantaneous CSI is unknown, and therefore, has to be estimated at the destination node. In this paper, we develop a novel channel estimation algorithm for two-hop MIMO relay systems using the parallel factor (PARAFAC) analysis. The proposed algorithm provides the destination node with full knowledge of all channel matrices involved in the communication. Compared with existing approaches, the proposed algorithm requires less number of training data blocks, yields smaller channel estimation error, and is applicable for both one-way and two-way MIMO relay systems with single or multiple relay nodes. Numerical examples demonstrate the effectiveness of the PARAFAC-based channel estimation algorithm.

Throughput maximization for an energy harvesting communication system with processing cost

Abstract: In wireless networks, energy consumed for communication includes both the transmission and the processing energy. In this paper, point-to-point communication over a fading channel with an energy harvesting transmitter is studied considering jointly the energy costs of transmission and processing. Under the assumption of known energy arrival and fading profiles, optimal transmission policy for throughput maximization is investigated. Assuming that the transmitter has sufficient amount of data in its buffer at the beginning of the transmission period, the average throughput by a given deadline is maximized. Furthermore, a “directional glue pouring algorithm” that computes the optimal transmission policy is described.

A distributed relay selection method for relay assisted Device-to-Device communication system

Abstract: Relay assisted transmission could efficiently enhance the performance of Device-to-Device (D2D) communication when D2D user equipments (UEs) are too far away from each other or the quality of D2D channel is not good enough for direct communication. The relay selection problem for D2D communication underlaying cellular network is studied in this paper. We proposed a distributed relay selection method for relay assisted D2D communication system. The method firstly coordinates the interference caused by the coexistence of D2D system and cellular network and eliminates improper relays correspondingly. Next, the best relay is chosen among the optional relays using a simple distributed method. Numerical results show that performance of the proposed method is close to the optimal (centralized) method.