Wireless Communication

With recent advances in micro-electromechanical systems technology, wireless communications, and digital electronics, the research on wireless sensor networks becomes a "hot" topic. Wireless sensor and actor network (WSAN) is referred to a group of sensors and actors linked by wireless medium to perform sensing and acting tasks. This paper is to present a comprehensive review of recent research achievements on WSANs, open research issues, and the simulation based actor-to-actor routing protocols performance analysis. The review is followed the layers of sensor networks: application, transport, network, link, transmission, and management (power, mobility, task). The performance analysis is considered for three popular ad-hoc networks routing protocols and investigated with respect to the routing packet delay and end-to-end throughput. As a result, the DSR protocol is proposed to handle actor-to-actor communications.

In this paper a new pedestrian mobility model for outdoor scenarios is presented. It captures realistic features like moving-in-groups, conscious traveling and smart traveling. The routing algorithm proposed within the model works under a step by step approach, leading users to their destination while, at the same time, using more attractable streets from a pedestrian point of view. The model concept is perfectly generic and applicable to any pedestrian outdoor scenario, provided that the street database and pedestrian traffic information is available. The mobility model was validated using Lisbon's downtown as a case study. The output shows a high correlation between simulated and real data, thus validating the approach.

In this paper is simulated the time-domain unit sample response of sine function and frequency-domain response of sine function. Digital filter plays an important role in today's world of communication and computation. Without digital filter we cannot think about proper communication because noise occurs in channel. For removing noise or cancellation of noise we use various type of digital filter. In signal processing, there are mainly two types of filters exist .they are the Finite Impulse Response (FIR) filter and Infinite Impulse Response (IIR) filter. Finite Impulse Response (FIR) filter can be designed form Infinite Impulse Response (IIR) filter by various techniques. The widely used technique is the window technique. This paper low-pass FIR filter is implemented using an efficient adjustable window function based on Hamming window and Blackman window function. The output of the FIR design by Blackman window and the Blackman window are shown in this paper by simulating the code in Matlab. The Matlab program returns with a satisfactory result with proper magnitude plotting.

Forward: The Public Safety Wireless Network (PSWN) Program is conducting an ongoing assessment of advancements in the wireless communications industry. The scope of this assessment is to identify emerging wireless services and technologies for potential public safety use in the near future and beyond. This particular document is the first of a series of emerging wireless technologies studies. This study will concentrate primarily on the fourth generation of mobile telecommunications and beyond.

Industrialised nations have dedicated significant investments toward the development of civil infrastructure. To preserve this investment, attention must be given to proper maintenance. Structural Health Monitoring (SHM) has emerged as a tool to support this task. Networks of smart sensors, built upon wireless communication, have the potential to significantly improve SHM. Numerous platforms for smart sensors have been developed, most of which utilise proprietary hardware/software. The Berkeley Mote, utilised in this study, was the first open hardware/software platform to be developed. However, the Berkeley Mote was designed for generic applications and therefore the available sensors are not optimised for use in civil infrastructure applications. Acceleration and strain are among the most important physical quantities to judge the health of a structure. Although commercially available sensor boards have accelerometers, their applicability towards civil infrastructure is limited. This paper presents the development of new acceleration and strain sensor boards based on the Berkely-Mote platform and provides experimental verification of their performance within civil infrastructure applications.

Routing systems for motorized vehicles in the internet are well known and widely used. But until recently, there had been no possibility to completely design and individually plan a tourist bicycle tour. This paper describes the conceptual design and implementation of such a bicycle routing system which has been operational since July 2001. Design and implementation of the routing system was done by the Research Center for Geoinformatics and Remote Sensing (FZG) at the University of Vechta in coorporation with the organization 'Verbund Oldenburger Münsterland e.V.'. To achieve the desired goals, a server/client architecture was used which was based on commercial GIS, database system, and internet components. It is planned that in the near future the bicycle routing system 'Fahrradies' will be extended with the data of neighboring tourist regions as well as with new functions. It will also prove necessary to adapt the system to the new developments of the underlying GIS software and emerging internet standards. Other options include the possibility to integrate the routing system with online navigation and positioning data in the field using wireless communication technology.

Growing convergence among mobile computing devices and embedded technology sparks the development and deployment of "context-aware" applications, where location is the most essential context. In this paper we present LANDMARC, a location sensing prototype system that uses Radio Frequency Identification (RFID) technology for locating objects inside buildings. The major advantage of LANDMARC is that it improves the overall accuracy of locating objects by utilizing the concept of reference tags. Based on experimental analysis, we demonstrate that active RFID is a viable and cost-effective candidate for indoor location sensing. Although RFID is not designed for indoor location sensing, we point out three major features that should be added to make RFID technologies competitive in this new and growing market.

In recent years, many extensive studies have been performed that have attempted to improve the performance of TCP for wireless networks. The common assumptions made by TCP for wired networks definitely do not hold for wireless networks. TCP with its semantics such as end-to-end flow control, a congestion control mechanism and error recovery provide reliability in wired networks. Wireless communication has significantly different characteristics compared to wired networks such as higher bit error rates, higher latency, limited bandwidth, multi-path fading of the signals and handoff. In this paper, we propose an enhancement to TCP that will be referred to as E-TCP, which improves upon conventional TCP congestion and flow control in a wireless environment. Our simulation results show significant improvements to TCP performance can be achieved.

The proliferation of wireless broadband usage over the last decade has led to the development and deployment of multiple broadband wireless radio access technologies (RATs) such as EVDO, WiMAX, HSPA and LTE. To support the ever-increasing wireless traffic demand, researchers have worked on the concept of an integrated heterogeneous wireless environment that encompasses several of these RATs which makes the resource allocation process more efficient by assigning each user in the system to the best RAT/RATs. In this paper, for such an integrated heterogeneous wireless system, we show the possible gains in spectral efficiency at the cost of increased energy consumption for an unbalanced heterogeneous wireless network deployment scenario. In prior work, based on the assumption that all cellular operators under study were equally well-provisioned, we showed an increase in spectral efficiency of up to 75%. In the research presented in this paper, we assume the coverage of each operator might differ significantly in a given area. With this `unbalanced' scenario, we show that an ideal, centralized allocation strategy provides an almost linear tradeoff between gain in spectral efficiency (554%) and worst-case increase in energy consumption (615%) for users supporting elastic traffic.

It is important to characterise the indoor radio propagation channel to ensure satisfactory performance of a wireless communication system. Site measurements can be costly; propagation models have been developed as a suitable low-cost alternative. The existing models can be classified into two major classes: statistical models and site-specific propagation models. Statistical models rely on measurement data; site-specific propagation models are based on electromagnetic-wave propagation theory. The ray-tracing technique is very useful in site-specific propagation modelling. This paper gives an overview of indoor propagation modelling and concentrates on a discussion of the raytracing modelling technique because of its practical appeal and its applicability t o any environment.

With recent advances in micro-electromechanical systems technology, wireless communications, and digital electronics, the research on wireless sensor networks becomes a "hot" topic. Wireless sensor and actor network (WSAN) is referred to a group of sensors and actors linked by wireless medium to perform sensing and acting tasks. This paper is to present a comprehensive review of recent research achievements on WSANs, open research issues, and the simulation based actor-to-actor routing protocols performance analysis. The review is followed the layers of sensor networks: application, transport, network, link, transmission, and management (power, mobility, task). The performance analysis is considered for three popular ad-hoc networks routing protocols and investigated with respect to the routing packet delay and end-to-end throughput. As a result, the DSR protocol is proposed to handle actor-to-actor communications.

Wireless technology is already available and used in several industrial sectors. In the next few years it is envisaged that the technology will mature and converge with other technologies providing the ability to communicate and exchange data and information easily and effectively anytime, anywhere, and in any place. Alongside this, security technology will grow and mature providing a safe information technology (IT) networked environment. Where these two technologies combine, they will provide major benefits for the construction industry, particularly in the design, construction and operational stages of new build projects. This paper will explore the positive impacts that can be achieved from a secure and wireless IT infrastructure. This will be carried out through an in-depth analysis and investigation of current and future wireless and security technologies. The paper will also explore their impact on the construction industry through a series of scenarios with practicing professionals. This will provide the opportunity to demonstrate practical problems in day-to-day communications and how the technology can provide appropriate solutions. The foreseen industrial impact will be to promote wireless communications as a safe and secure medium for construction organisations. This will also provide the opportunity for enhanced collaborative working and information sharing throughout the supply chain and the various construction processes. Additionally, this will also help promote confidence in the use of the technology so that wireless communication systems become an integral part of work operations in the future.

Ultra-wideband (UWB) has been proposed for physical layer standard for high speed wireless personal area networks (WPAN). It has emerged as cost effective and reliable alternative to traditional wireless technologies in WPANs. This paper describes low complexity high data rate Ultrawideband system based on Wimedia communication protocol. It intends to evaluate the performance of Wimedia-UWB wireless networks communication for spatial and aeronautic systems. The paper suggests a simulation model using NS-2 simulator to assess the feasibility of such networks and analyses it performance by providing high data-rate wireless communication.

To improve interference robustness of wireless communication, spread spectrum techniques are often used. We use the chirp spreading technique along with FSK and PSK binary modulation schemes to obtain interference robust radio communication. The performance of chirped-FSK and chirped-PSK modulation through a white gaussian noise channel is simulated assuming a synchronized clock between transmitter and the receiver. We analyzed and simulated the error probability (BER) of the overall system in the presence of partial band of interference in the channel. The simulated BER is close to the estimated BER and they prove the superior performance of chirp-based modulation in the presence of interference.

Modern wireless communication demands reliable data communication at high throughput in severe channel conditions like narrowband interference, frequency selective fading due to multipath and attenuation of high frequencies. Traditional single carrier systems address this set of problems by the use of complex, computationally intensive equalization filters. The Orthogonal Frequency Division Multiplexing (OFDM) based system, as opposed to single-carrier systems, is considered to be the future of the wireless communication and is being used to achieve high data rate by overcoming severe channel conditions without the use of these complex filters. This paper discusses the problem of Adaptive Modulation scheme selection through an OFDM based system over parallel frequency selective fading channels. An adaptive coding scheme is proposed by using Generalized Concatenated Codes (GCC), which have simple structure and are designed in such a way that they are best suited for fading channels. GCC are based on binary cyclic codes. The criterion of the proposed research is to optimize the throughput of a wireless system. Depending on the quality of sub-channels an adaptive modulation selection scheme and code assigning method is proposed. The proposed research combats against channel impairments better than those used in conventional systems by exploiting individual sub-channel condition. Results show better performance in terms of higher throughput by minimizing the bit error rate.

We investigate microdiversity-augmented macrodiversity techniques in wireless communication networks. The setup consists of K widely separated access ports each carrying N antennas. The conventional selection macrodiversity (Scheme I) and two proposed methods (Scheme II and Scheme III) for port selection are investigated and their performance are compared. Scheme II utilizes the advancement in distributed antennas and radio-on-fiber technologies whereas Scheme III utilizes these technologies in a way similar to the soft handover of CDMA systems. After the port selection, the microdiversity uses n strongest signals (n les N) of the selected port for diversity combining if practical constraints preclude the use of all N signals. Analytical performance expressions for the probability of error and outage probability for Scheme I are developed. Simulations are used to investigate Scheme II and Scheme III and it is observed that these latter schemes exhibit performance superiority over the conventional macrodiversity selection method. The power savings obtained using the proposed architecture and new selection schemes could be used either for coverage extension or to increase capacity in wireless networks

Minimizing blind zones and providing stable wireless communications are serious concerns in setting up wireless LAN access systems along meandering passages in buildings and underground facilities. To solve the problem, we have developed a dual band long leaky coaxial cable for the 2.4 and 5 GHz bands. Experiments conducted with meandering cable configuration show that communications over distances of more than 100 m at maximum transmission rates of more than 10 Mbps for IEEE802.11a and IEEE802.11g are available. We confirmed that this leaky coaxial cable is beneficial for dual-band operation with faster and wider communication for indoor use.

New wireless communications, user mobility and the growing need of taking into account the characteristics of the context make feasible the development of advanced frameworks to support context-aware knowledge systems. In this paper we present the design of the contextual information for an airport domain using a platform that exploits the modular and distributed architecture to develop context-aware applications.

In this research work, a survey on Wireless Sensor Networks (WSN) and their technologies, standards and applications was carried out. Wireless sensor networks consist of small nodes with sensing, computation, and wireless communications capabilities. Many routing, power management, and data dissemination protocols have been specifically designed for WSNs where energy awareness is an essential design issue. Routing protocols in WSNs might differ depending on the application and network architecture. A multidisciplinary research area such as wireless sensor networks, where close collaboration between users, application domain experts, hardware designers, and software developers is needed to implement efficient systems. The flexibility, fault tolerance, high sensing fidelity, low cost, and rapid deployment characteristics of sensor networks create many new and exciting application areas for remote sensing. In the future, this wide range of application areas will make sensor networks an integral part of our lives. However, realization of sensor networks needs to satisfy the constraints introduced by factors such as fault tolerance, scalability, cost, hardware, topology change, environment, and power consumption.

In wireless environment, the channels are really affected by a number of factors such as: fading, interference, noise. In most of wireless communications, we have applied the training sequences as known signal at the receiver for estimating the channel as well as the transmitted signal. Nowadays, many paid services in the entertainment industry have required the high security for their data and this issue is challenge which needs to be solved. Recently, the semi-blind channel estimations have contributed in term of remarkable enhancement in the total bandwidth efficiency of multipleinput multiple-output (MIMO) systems. To obtain the high data rate demands, there is a fewer training symbols using in these semi-blind algorithms. However, each system model must be satisfied the safe data for both the suppliers and the customers. Based on the information theory, we propose the new transmit structure with the training data embedding secure symbols for distinguishing authorized users and the eavesdroppers. This solution is so-called security on the physical level which is considered as the robust solution for processing by the traditional software. In this investigation, we also focus on normalized mean square error (NMSE) analysis for different performance of two types of users mentioned. Simulation results confirm our modified scheme and illustrate that the semi-blind channel estimation with embedded secure data is capable of improving the security of the overall system.

Ahsrrcict-Th is paper proposes I IP(I ntel I igent Internet Protocol) which effectively addresses the issues involved in wireless communication at Network Layer such a s support for mobility, frequent loss of connection due to fading, handoffs and security. We have chosen to use Intelligent Agent technology for our architecture of 1IP because it provides desirable properties such as Speed-up and Efficiency, Robustness and Reliability, Scalability and Flexibility, Development and Re-usability. We make use of .four Intelligent Agents namely Principal Agent(PA), Agent for Address Resolution and Mobility Support(AARMS), Agent for Error Handling and Recovcry(AEHR), Agent for Network Security(ANS) and design each Agent bused on BDI(Belief-Desire-Intention) Architecture. A variant of Blackboard architecture is used for inter-agent communication. Special carc has been taken to make proposed IP compatible with existing Networks. The proposed work has been simulated and verified for its operational effectiveness.

In this paper, we present channel estimation methods for space-time block coding (STBC) transmissions using constant modulus algorithm (CMA). The channel estimates are directly calculated from the convergence value of the CMA. Two algorithms using the channel-vector-based and channel-gain-based constant modulus (CM) criteria are proposed. An approximation of the CM cost function is introduced to allow the use of the recursive least-square (RLS) technique in designing fast RLS-CMA's. Performance of the proposed schemes is evaluated and compared with others using simulation. Illustrative results show that the proposed scheme outperforms the cross-correlated method and can approach the performance of the training-based method.

Considering the dynamic nature of portable computing devices with wireless communication capability, an extended model is introduced for worm spreading in the wireless ad hoc network, with a population of mobile agents in a planar distribution, starting from an initial infected seed. The effect of agents' mobility on worm spreading is investigated via extensive Monte Carlo simulations. The threshold behavior and the dynamics of worm epidemics in the wireless networks are greatly affected by both agents' mobility and spatial and temporal correlations. The medium access control mechanism for the wireless communication promotes the sensitivity of the spreading dynamics to agents' mobility.

Wireless sensor networks (WSNs) consist of miniature devices with sensing, computation and wireless communication capabilities. They are typically designed for hostile environments, where recharging a node is impractical. Thus, energy efficiency is vital. For substantial energy savings, cross-layer information sharing and in-network processing among sensors have emerged as promising solutions. In this paper, we propose an energy-aware cross-layer data-gathering protocol for WSNs, termed RMC. By integrating the routing, MAC and clustering protocols, RMC is a scalable collision-free protocol. RMC is designed to address the overhead caused by managing the transmissions schedule. To this end, RMC works by defining a dependence relation between a node's transmission schedule and its location. Therefore, each node can determine its schedule and forwarding path entirely locally. Its performance is extensively evaluated through simulations and is shown to have significant improvement over well-known comparable crosslayer scheme.

This paper evaluates the possibility of using a general purpose superscalar architecture as the main computational engine for high performance DSP algorithms. Real-time sample rate conversion (SRC) in a software defined radio (SDR) has been taken as an example representing a class of computationally demanding DSP tasks. This scenario corresponds to digital filters operating at a high sampling rate in intermediate frequency (IF) stage of a multi-standard wireless transceiver. However, instead of a dedicated signal processing engine, a superscalar processor is designed for SRC implementation. An iterative, SimpleScalar based architectural modeling tool has been developed to analyze various parameters of superscalar processors. Both power and performance metrics have been taken under consideration to come up with an efficient design. It has been shown that the resulting superscalar architecture can provide a fully programmable solution capable of supporting future wireless communication standards in real-time. The design methodology explored in this work can be extended to obtain efficient processor architectures for a range of other applications.

A rush forward of research activities in wireless communication has been seen in last decade. There are new points of view on how to communicate effectively over wireless channels from this research drive. The purpose or aim of this paper is to study the basics as well as new research developments. We studied four types of wireless communication technology that are Bluetooth, Cellular, Wi-Fi and WiMAX in this paper. we have described architecture and working of these technologies to understand them easily. we have concluded which one is the best through comparative study and analysis.

Broadband wireless communications services provided from a High Altitude Long Operation (HALOTM) aircraft are now feasible. The authors emphasize the conceptual design of a “bandwidth-on-demand” wireless network whose data rates to and from the user is in the multi-megabit per second range. The network uses the millimeter wave range of the spectrum (>20 GHz). The HALO TM aircraft is specially designed for stratospheric operation (>50,000 feet). The HALOTM aircraft fuselage houses packet switching circuitry and fast digital network functions. The communications antenna and related components are located in a pod suspended below the aircraft fuselage. To offer “ubiquitous” service throughout a large region, the HALOTM antenna utilizes multiple spot beams arranged in a typical cellular pattern. Broadband channels to users in adjacent cells are separated in frequency. As the beams traverse over a user location, the virtual path through the packet switch is changed to perform a bea...

Presently, mobile handheld device has successfully replaced traditional telephone to become the most popular wireless communication tools. Mobile Short Message Service (SMS) and Multimedia Message Service (MMS) fulfill almost all the user requirements as an effective communication and information delivering service. Since SMS/MMS become so popular on daily communication, there is a demand to communicate or exchange confidential information in a secure environment. Public Key Infrastructure (PKI) is a proven solution, which using pairing of key, for secure communication encryption. In this paper, M-PKI is introduced to provide PKI encryption to the mobile SMS and MMS.

Abstract: The size, complexity and performances of modern wireless communication circuits are getting more and more challenging whereas marketing time and cost must be reduced as much as possible. In order to fill the current lack in CAD tools, this work is dedicated to the mixed simulation of complete communication systems driven by digital and digitally modulated RF signals. This paper describes a methodology for top-down design, modeling, and simulation of complete RF system using hardware description language VHDL-AMS (Very high speed integrated circuit Hardware Description Langage – Analog Mixed Signal). As application, we consider a complex M-QAM system (transmitter, channel, and receiver) and we show some details of

With the integration of heterogeneous network protocols, roaming among different networks becomes feasible. The subjects with most attention are the guaranteed quality of services (QoS) and the handoffs without disconnections. This paper proposes a roaming node encoding algorithm in wireless communications, in order to define nested network nodes, without duplicate encodings, and to rapidly confirm the existence of the surrounding base stations and the amount of their resources. It also proposes four resource reservation methods --Random Destined, Direction Destined, Walking Path Destined, and Historical Path Destined --to predict the walking path and provide resource reservation services. To solve the problems of resource waste and low utilization due to resource reservation at mobile nodes, we give each direction a competition weight based on its fan-shaped walking patterns, and through this weight a resource reservation competition is performed. In this way, resource utilization is increased and the goal of QoS-guaranteed roaming provided with path prediction and resource reservation is achieved. The paper also verifies the performance of the proposed methods by means of constructing a simulated environment of Taiwan's national highways and county highways.

Coexistence issues between IEEE 802.11b wireless communication networks and IEEE 802.15.4 wireless sensor networks, operating over the 2.4-GHz industrial, scientific, and medical band, are assessed. In particular, meaningful experiments that are performed through a suitable testbed are presented. Such experiments involve both the physical layer, through measurements of channel power and the SIR, and the network/transport layer, by means of packet loss ratio estimations. Different configurations of the testbed are considered; major characteristics, such as the packet rate, the packet size, the SIR, and the network topology, are varied. The purpose of this paper is to gain helpful information and hints to efficiently face coexistence problems between such networks and optimize their setup in some real-life conditions. Details concerning the testbed, the measurement procedure, and the performed experiments are provided.

Mobile ad hoc networks are a new wireless networking paradigm for mobile hosts. Unlike traditional mobile wireless networks, ad hoc networks do not rely on any fixed infrastructure. Instead, hosts rely on each other to keep the network connected. The military tactical and other securitysensitive operations are still the main applications of ad hoc networks. One main challenge in design of these networks is their vulnerability to Denial-of-Service (DoS) attacks. In this paper, we consider a particular class of DoS attacks called Jamming. The objective of a jammer is to interfere with legitimate wireless communications. A jammer can achieve this goal by either preventing a real traffic source from sending out a packet, or by preventing the reception of legitimate packets. We propose in this study a new method of detection of such attack by the measurement of error distribution.

This paper investigates implementation and design issues for a heterogeneous network for structural monitoring. The proposed application uses wireless sensors and the controller area network (CAN) to provide energy efficient monitoring. The contributions include: implementation of the PIC18f4680 platform in TinyOS, creating a message protocol over CAN, and developing a sensor board.

Discontinuous transmission based on speech/pause detection represents a valid solution to improve the spectral efficiency of new-generation wireless communication systems. In this context, robust voice activity detection (VAD) algorithms are required, as traditional solutions present a high misclassification rate in the presence of the background noise typical of mobile environments. This paper presents a voice detection algorithm which is robust to noisy environments, thanks to a new methodology adopted for the matching process. More specifically, the VAD proposed is based on a pattern recognition approach in which the matching phase is performed by a set of six fuzzy rules, trained by means of a new hybrid learning tool. A series of objective tests performed on a large speech database, varying the signal-to-noise ratio (SNR), the types of background noise, and the input signal level, showed that, as compared with the VAD recently standardized by ITU-T in Recommendation G.729 annex B, the fuzzy VAD, on average, achieves an improvement in reduction both of the activity factor of about 25% and of the clipping introduced of about 43%. Informal listening tests also confirm an improvement in the perceived speech quality.

... and small scale fading in indoor wireless communication channels. Reinaldo A. Valenzuela, Dmitry Chizhik and Jonathan Ling ... References [I] R. A. Valenzuela, 0. Landron, DL Jacobs, "Estimating Local Mean Signal Strength of Indoor Multipath Propagation", IEEE Trans. ...

This paper presents a DSP/FPGA hardware/software partitioning methodology for signal processing workloads. The example workload is the channel equalization and user-detection in HSDPA wireless standard for 3.5G mobile handsets. Channel equalization and user-detection is a major component of receiver baseband processing and requires strict adherence to real time deadlines. By intelligently exploring the embedded design space, this paper presents a hardware/software system-on-chip partitionings that utilizes both DSP and FPGA based coprocessors to meet and exceed the real time data rates determined by the HSDPA standard. Hardware and software partitioning strategies are discussed with respect to real time processing deadlines, while an SOC simulation toolset is presented as vehicle for prototyping embedded architectures.

Using Grid Storage, users can remotely store their data and enjoy the on-demand high quality applications and services from a shared networks of configurable computing resources, without the burden of local data storage and maintenance. In this project based on the dynamic secrets proposed design an encryption scheme for SG wireless communication, named as dynamic secret-based encryption (DSE). Dynamic encryption key (DEK) is updated by XOR the previous DEK with current DS. In this project based on the dynamic secrets proposed design an encryption scheme for SG wireless communication, named as dynamic secret-based encryption (DSE). The basic idea of dynamic secrets is to generate a series of secrets from unavoidable transmission errors and other random factors in wireless communications In DSE, the previous packets are coded as binary values 0 and 1 according to whether they are retransmitted due to channel error. This 0/1 sequence is called as retransmission sequence (RS) which is applied to generate dynamic secret (DS). Dynamic encryption key (DEK) is updated by XOR the previous DEK with current DS.

Design of a compact dual frequency microstrip antenna is presented. The structure consists of a slotted circular patch with a dielectric superstrate. The superstrate, not only acts as a radome, but improves the bandwidth and lowers the resonant frequency also. The proposed design provides an overall size reduction of about 60% compared to an unslotted patch along with good efficiency, gain and bandwidth. The polarization planes at the two resonances are orthogonal and can be simultaneously excited using a coaxial feed. Parametric study of this configuration showed that the frequency ratio of the two resonances can be varied from 1.17 to 1.7 enabling its applications in the major wireless communication bands like AWS, DECT, PHS, Wi.Bro, ISM, and DMB. Design equations are also deduced for the proposed antenna and validated.

he continuing evolution of mobile communications has spawned several radio technologies (e.g., orthogonal frequency-division multiplexing [OFDM], code-division multiple access [CDMA]) and mobile network architectures (e.g., Third Generation Partnership Project [3GPP], 3GPP2) over the last few years. This technological proliferation has, in turn, brought on an unprecedented increase in the number of wireless access standards and their associated protocol stacks. The need for ever faster standardization cycles and the urgent demand to support access to the Internet by these mobile network architectures called for a "mix-and-match" approach to the definition of the associated protocol stacks. As individual protocols are typically specified with different assumptions in mind, the end-to-end performance of these protocol stacks in deployed mobile networks has not always been satisfactory.

We demonstrate a 60 GHz broadband picocellular Radio-over-Fiber network architecture that enables seamless connectivity for highly mobile end-users. Its seamless communication capabilities arise by the supported handover scheme that relies on a novel Moving Extended Cell (MEC) concept. MEC exploits user-centric virtual groups of adjacent cells that transmit the same data content to the user and utilizes a switch mechanism for restructuring the virtual multi-cell area according to the user's mobility pattern, so that a virtual antenna group moves together with the mobile user. We present the theoretical formulation for MEC and show that it can provide zero packet loss and call dropping probability values in high-rate wireless services for a broad range of mobile speeds up to 40 m/sec, independently of the fiber link distances. We also demonstrate the physical layer network architecture and switch mechanism both for a RoF network with a single 60 GHz radio frequency (RF) over each wavelength, as well as for a RoF configuration supporting simultaneous multi-RF channel transmission over each optical wavelength. The performance of the multi-RF-over-network implementation is evaluated via simulations showing successful 100 Mb/s radio signal transmission over fiber links longer than 30 km. To this end, MEC can enable seamless connectivity and bandwidth guarantees in 60 GHz picocellular RoF networks being also capable of serving multiple users over the same wavelength in a RF frequency-division-multiplexed (FDM) approach.

In the battlefield of the future, more and more information will be available for making decisions on a tactical level, provided that this information can be dispersed rapidly and accurately. As a consequence, advanced tactical decision support that now is limited to advanced platforms (e.g. combat aircrafts) will become available at a much lower level, ranging from different kind of