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Any single type of existing wireless and mobile network cannot provide all types of services, e.g., wide coverage and high bandwidth. An integrated wireless and mobile network is introduced by combining different types of networks to provide more comprehensive services. Although an integrated wireless and mobile network provides more connection options for mobile users than a single wireless and mobile...
Summary form only given. Indoor tracking and localization is a crucial ingredient in many ubiquitous computing applications and robotics. In many applications there is the need to know the location of the objects. While in the near future everything will be tagged with radio frequency identification (RFID) tags, the localization of these tags in their environment is becoming an important feature for...
Summary form only given. With the current prevalence of content-oriented communication services, the service environment for end-users to learn and to configure one's device has become more complicated and demanding. In particular, the device should be dynamically configured in accordance with the service subscription profile of the user and requires the timely changes in application modification...
Facing increasing levels of competition and regulation in their maturing domestic markets some prominent telecommunications service providers (TSPs) have begun to expand their wireless operations internationally. This paper investigates the geographic expansion strategies of five major TSPs: Telefonica, Deutsche Telekom, Singapore Telecommunications, Vodafone, and America Movil. All of these companies...
In this paper, we propose an optimized OFDM iterative ARQ receiver, suitable for application in rapidly varying multipath channels. The receiver is an optimized MAP Turbo processor that exploits log likelihood ratio (LLR) information from previously failed transmissions. We show that this configuration achieves very high gains compared to a standard ARQ system by virtue of two co-operative mechanisms:...
Summary form only given. In this paper, we focus on trust establishment in mobile wireless networks and introduce the idea of TrustRings. The concept of TrustRings facilitates the calculation of trust-values for nodes in mobiity networks based on an egocentric network model. Each node concentrates autonomously on the establishment of its own TrustRings by placing itself as the centric node in the...
In this paper the competitive Hopfield neural network method for finding a broadcasting schedule in the satellite system will be described. The satellite broadcast scheduling (SBS) problem is known as an NP-complete problem. Communication links between satellites and ground terminals are provided in a repetition of time slots. The goal of the proposed algorithm is to find the broadcasting schedule...
Wireless sensor network (WSN) consists of a group of sensors or nodes, linked by a wireless medium (infrared or radio frequency) to perform distributed sensing tasks. The dynamic and lossy nature of wireless communication poses major challenges for highly dense WSN. In our previous work, we proposed a new networking topology, the Cayley pseudo-random protocol (Arden, 1991) (Noel, 2006) for large wireless...
Summary form only given. Anonymity is the state of not being identifiable within a set of subjects. Different strategies exist for assuring anonymity in computer networks, such as the dining cryptographers network and mix networks. But these strategies were designed for wired networks requiring direct communication links or fixed infrastructure. Therefore they are not applicable to multi hop wireless...
Orthogonal frequency division multiplexing (OFDM) has been proposed for use in ultra-wideband (UWB) communication systems. In a UWB-OFDM transceiver, resource efficient FFT/IFFT hardware is a necessity due to minimal silicon area and low power requirements. Resource requirements can be reduced by using finite precision arithmetic in the FFT/IFFT algorithms. However, this introduces round-off and overflow...
In most contemporary phase lock loops (PLLs) used in high-datarate wireless receivers, some or all of the PLL 's components are implemented digitally, in particular the PLL's loop filter. In this paper we develop the theory behind new efficient structures for the implementation of loop filters within FPGAs (field programmable gate arrays) using fixed-point arithmetic. The theory is then investigated...
In this paper, a power-loading technique is presented for OFDM systems, which is a modified version of an existing power-loading algorithm that exhibits enhanced performance when compared to the latter under certain conditions. The impact of power loading on the coded OFDM system that uses convolutional codes is also studied. A comparative study is done to show the differences in performance of the...
In this paper, we propose a new scheme for maximum-likelihood (ML) estimation of both carrier- frequency offset (CFO) and channel coefficients in multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. To reduce the prohibitive complexity of ML estimate, the expectation-maximization (EM) algorithm is employed. From Simulations, it is shown that the accuracy...
Ad hoc and sensor networks is a new area of research which is rapidly growing due to the development of new technologies in inexpensive sensors. These electronic devices have increased capabilities in processing speed, memory, communication and networking [21][22]. Such sensor networks have a vast amount of applications including environmental monitoring, military, ecology, agriculture, inventory...
The ns-2 network simulator is one of the most widely used packet network simulators. In version 2.1b9 its old random number generator was replaced by an implementation of MRG32k3a to fix sensitivity to seeds. Due to bad documentation and re-use of old scripts many people still use the old API functions to explicitly set seeds. Unfortunately, this corrupts the correct function of the new generator...
Network convergence across different access technologies holds a promise of enabling ubiquitous service availability but faces several technical challenges. With anticipated proliferation of multimode IP devices, the optimal selection of a service delivery network among multiple IP based wireless access alternatives is one of the important issues that is actively studied and discussed in several standardization...
Saving energy is an important issue in IEEE 802.16e Broadband Wireless Access (BWA) networks. Sleep-mode operation in the IEEE 802.16e effectively saves energy consumption in order to extend life time of a Mobile Subscribe Station (MSS). However, frame response delay is another important performance metric. The constraint is that the sleep- mode operation can reduce consumed energy, but it must guarantee...
Explicit Congestion Notifications are used to notify TCP when imminent congestion is about to happen. In this work we use this feature to design an error discriminator that can be added to a TCP sender to differentiate between congestion drops and drops because of wireless link failure. By distinguishing between error types, TCP can avoid unnecessary cuts of congestion window when non congestion error...
In this paper, we propose to add a new queue in IEEE 802.11 MAC protocol for real-time multimedia traffic in wireless LAN. The queue contributes to improving multimedia service quality by reducing end to end delay, a QoS parameter. To control two queues, we use a scheduler based on the PAD algorithm which selects a packet from one of two queues appropriately for forwarding. Moreover, we adapt the...
Recent studies report that in wireless networks, schedulers exploiting multiuser diversity can substantially enhance the maximum throughput of the overall system. In this paper, we focus on a scheduler which maximizes the throughput of the overall system by exploiting multiuser diversity and is combined with adaptive modulation and coding. We numerically study the statistical time-access fairness...
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