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Wireless Telecommunications Symposium, 2004

Date 14-15 May 2004

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Displaying Results 1 - 25 of 51
  • Development and performance characterization of enhanced AODV routing for CBR and TCP traffic

    Page(s): 44 - 51
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (517 KB) |  | HTML iconHTML  

    We aim to modify an existing mobile ad-hoc network (MANET) reactive routing protocol (ad-hoc on-demand distance vector, AODV) into a hybrid protocol by introducing adaptive, proactive behavior to improve its performance. Under our proposed scheme, route maintenance decisions are based on predicted values of 'link-breakage times' (when the next-hop node will move out of transmission range) obtained from a series of position/speed estimates of the next-hop node. These estimates are based on the power level of the received MAC frames. If a link is about to break, proactive discovery of new routes to all destinations using the next-hop node depends on the history of traffic to that destination. We simulated (using the ns2 simulator) numerous test conditions using CBR and TCP traffic and compared performance metrics for the original and modified versions of the protocol. We have achieved (1) a significant reduction in mean packet latency for CBR traffic and (2) a reduction in control overhead in TCP traffic, while incurring other small penalties for both types of traffic. Also, a comparison of some performance metrics for TCP and CBR traffic leads us to conclude that slight modifications in TCP can lead to its improved performance over MANETs. View full abstract»

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  • Timer based dynamic location management

    Page(s): 55 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (406 KB) |  | HTML iconHTML  

    The mobility management schemes of current cellular systems (e.g., GSM) use spatially static location areas (LA). The mapping of cells to location areas is performed infrequently using heuristics and aggregate statistics and resulting location areas apply to all the mobile subscribers. As all the subscribers do not have the same mobility patterns, these static and globally applicable location areas are far from optimal. The paper introduces a timer based dynamic location management algorithm, which uses the mobility of an individual subscriber and a timer for the user's current cell to form individualized location areas dynamically. An activity based mobility model is used to evaluate the performance of the proposed algorithm and to compare it with dynamic location management with variable size location area (Ajit Pal and Digvijay Singh Khati, Int. Conf. on Computer Networks and Mobile Computing, 2001). According to simulation results, the proposed algorithm incurs significantly lower location management cost as compared to dynamic location management with variable size LA. View full abstract»

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  • Power-controlled wireless links for media streaming applications

    Page(s): 102 - 111
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (582 KB) |  | HTML iconHTML  

    We investigate a power-controlled transmission scheme for streaming media traffic over wireless links. The server (source) transmits encoded media packets to a client (user) over a fluctuating wireless channel. The client stores received packets into a fixed-size buffer and plays them out at a constant rate. Due to random channel interference, the source needs to adapt its transmission power and rate according to the channel conditions to guarantee a certain level of received media quality of service (QoS). The latter is primarily measured by the distortion due to packets missing their playtime deadlines at the receiver. The goal is to find an efficient power/rate control policy to minimize the average power (energy) consumption for a required quality level of media reception. We formulate a simple, yet powerful, model for media streaming over wireless links, allowing identification and characterization of optimal power/rate control policies, using dynamic programming methodologies. Furthermore, having observed the structural properties of optimal policies, we propose two practical heuristic algorithms for power and rate control. The proposed algorithms are extensively simulated and significant performance improvements are observed when compared to standard benchmarks. View full abstract»

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  • Impact of inactivity timer on energy consumption in WCDMA and cdma2000

    Page(s): 15 - 24
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (618 KB) |  | HTML iconHTML  

    The paper provides the comparison between WCDMA and cdma2000 of the impact of an inactivity timer on the energy consumption of a mobile station. Both simulation and analysis are utilized to investigate the impact of the inactivity timer and the performance comparison between WCDMA and cdma2000. The novel and practical models proposed analyze and quantify the energy consumption in the case of bursty and streaming traffic. The analytic models are verified extensively by simulation. View full abstract»

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  • Joint carrier frequency acquisition and channel estimation algorithms for OFDM systems

    Page(s): 161 - 165
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (369 KB) |  | HTML iconHTML  

    We present new carrier frequency acquisition and channel estimation algorithms for OFDM systems. Both new algorithms utilize only one training frame to carry out carrier frequency acquisition and channel estimation at the same time. The simulation results show that both algorithms are immune from timing error with a high precision and low computational complexity. View full abstract»

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  • Performance analysis of energy consumption in 3GPP networks

    Page(s): 67 - 72
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (427 KB) |  | HTML iconHTML  

    Energy conservation is critical for third generation (3G) cellular systems. In particular, future high-speed packet data services are expected to exhaust the energy of a mobile station rapidly. In 3GPP systems, the radio resource is mainly controlled by the radio resource control (RRC). This paper quantifies the energy consumption and the reconnection ratio for 3GPP systems based on the RRC state machine. Bursty and streaming packet data services are investigated. Through analytic models and comprehensive simulation with various traffic models, the impacts of diverse timer values on the RRC state machine are illustrated. In addition to quantifying energy consumption, appropriate timer values are suggested. View full abstract»

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  • Performance analysis of a cellular system supporting two types of services with different reuse factors using channel partitioning

    Page(s): 39 - 43
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (380 KB) |  | HTML iconHTML  

    The paper presents the performance analysis of a cellular system supporting two types of traffic with different reuse factors, using fixed channel allocation (FCA) and channel partitioning (CP), namely fixed channel partitioning (FCP). With CP, each cell is allocated two sets of channels and each set of channels supports different traffic, depending on the required reuse factor. The FCP system is modeled mathematically using queuing theory. A two-dimensional Markov chain model is developed to examine its performance. A scaling method is also proposed to deal with different call duration scenarios. As compared to the FCA system, we find that the FCP system can improve the system capacity depending on the traffic load fraction for each type of service. Analytical results are compared with the simulation results to verify our theoretical analysis. View full abstract»

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  • An efficient rate adaptation scheme in wireless mobile networks

    Page(s): 88 - 93
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    A new rate adaptation algorithm named the average degradation degree fair adaptation algorithm is defined and proposed for wireless networks with mobile hosts. It uses a novel quality of service index that expresses the degradation degree suffered by data packet flows in terms of bandwidth. The aim of the proposed algorithm is to distribute the effects of QoS degradation fairly among the cells visited by mobile hosts. The proposed algorithm has been compared with three schemes studied in the literature: fair adaptation; minimum adaptation; average fair adaptation. The performances are evaluated inside the single cell (intra-cell) and among the cells (inter-cell) in which the mobile host moves. Simulations results show that a reduction of the QoS degradation of flows and a preservation of inter- and intra-cell fairness properties are obtained, adding only a slight control overhead. View full abstract»

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  • Modeling and performance analysis of mobile communication systems using adaptive beamforming technique

    Page(s): 33 - 38
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (435 KB) |  | HTML iconHTML  

    We propose a novel mobile communication system which employs adaptive beamforming techniques. In the proposed system, the capacity is increased by reusing the same channel (frequency, time slot or code) in a cell. The QoS (quality of service) is improved by inherent properties of smart antennas, like reducing BER (bit error rate), multipath fading, etc. We provide an analytical model for the proposed system. The system is modeled and analyzed by a two-dimensional Markov chain. A new algorithm is derived to obtain the equilibrium state probabilities. We also investigate the QoS of the system in terms of the blocking probability of originating calls and the forced termination probability of handoff calls. As we expect, system capacity and performance are highly improved by employing smart antennas. We believe that the proposed system can be a candidate of future mobile communication systems to provide a service with high capacity and quality. View full abstract»

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  • A trivial denial of service attack on IEEE 802.11 direct sequence spread spectrum wireless LANs

    Page(s): 129 - 136
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (530 KB) |  | HTML iconHTML  

    The paper describes a trivial, but highly effective, denial of service attack based on commonly available IEEE 802.11 hardware and freely available software. The attack requires limited resources and is inexpensive to mount. The paper discusses the attack, its implementation, and provides an analysis of methods to achieve optimal denial of service results. While there is currently no defense against this type of attack, the paper also discusses possibilities for attack mitigation. View full abstract»

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  • Peak to average power ratio reduction in MC-CDMA using partial transmit sequences

    Page(s): 3 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    MC-CDMA is an attractive technique for achieving transmission in fading channels in high data rate mobile communications. However, it requires a high quality amplifier to cope with the large amplitude fluctuation at the transmitter side. The partial transmit sequences (PTS) scheme is one of the best methods to reduce peak to average power ratio (PAPR). A modified PTS scheme for uplink communications is proposed, in contrast to the original PTS, which is generally applied in the downlink in an OFDM system. While successfully reducing PAPR, PTS alters the code correlation property which affects bit error rate when applied to the MC-CDMA system uplink. Therefore, modified receivers to deal with this problem are also proposed. View full abstract»

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  • A dependence between average call duration and voice transmission quality: measurement and applications

    Page(s): 75 - 81
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (418 KB) |  | HTML iconHTML  

    The paper deals with the estimation of the relation between speech transmission quality and average call duration for a given network and portfolio of customers. It uses non-intrusive speech quality measurements on live speech calls. The basic idea behind this analysis is an expectation that the average call duration is higher for calls of a good quality since users are less disturbed during their conversation by transmission impairments. Both traditional and state of the art methods for non-intrusive speech transmission quality measurements and also for call duration monitoring are briefly described and two basic dependency analysis methods are shown. The relations for result uncertainty estimation are derived. A numerical example is given based on a limited training database that is constructed on the basis of real network data. Finally, potential applications are presented and discussed The first results indicate that, in the low to medium quality range (mean opinion scores between 1 and 3), the call duration increases with increasing speech quality. View full abstract»

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  • A model for evaluating multi-route routing in ad hoc networks

    Page(s): 149 - 153
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    An ad hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any centralized administration. In the absence of a centralized administration node, routing is a challenging issue. We focus on a particular source initiated on-demand protocol, called dynamic source routing (DSR), and show how use of multipath techniques can reduce the frequency of route discovery. The frequency of route discovery in DSR is one of the main performance metrics in mobile ad hoc networks. This performance metric was studied using an exponential model, which might be an appropriate model for voice traffic, but is not a suitable model for data traffic. Studies have shown that data traffic is more precisely characterized by heavy-tailed distributions. We present an approach to characterize data traffic through the compound log-normal distribution. Reliability archetypes of series and parallel connections have been used in developing these models. View full abstract»

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  • ML-based estimator for integer frequency offset estimation of OFDM systems

    Page(s): 27 - 30
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    A novel estimator for integer frequency offset estimation of OFDM systems is derived, which is based on the maximum likelihood (ML) technique and exploits the differential information between two consecutive blocks of OFDM data symbols in the frequency domain. The reason why the ML estimator has better performance than the conventional method is analyzed. How to select the differential sequence is also studied. By computer simulations, the performance of the ML estimator is compared with that of the conventional method for the additive white Gaussian noise (AWGN) channel and the multipath fading channel. The simulation results are in good agreement with the analytical study. View full abstract»

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  • Distributed rate and power control for CDMA uplink

    Page(s): 9 - 14
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (389 KB) |  | HTML iconHTML  

    We consider a distributed CDMA system in which mobiles are able to control their transmission rate and power based on their radio conditions. Each mobile is assumed to be myopic, that is, its solitary goal is to maximize the payoff, which is the difference between the effective throughput and the price that the system charges for the received power on behalf of the mobile. We prove that the distributed system converges to a Nash equilibrium such that users near the base station transmit in the full rate while farther users transmit at the full power. Our simulation results present a numerical view of this distributed scheme. View full abstract»

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  • Introducing feedback congestion control to a network with IEEE 802.11 wireless LAN

    Page(s): 61 - 66
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (494 KB) |  | HTML iconHTML  

    The interpretation by transmission control protocol (TCP) of loss of linkage as loss due to congestion causes significant inefficiency in a wireless network. Congestion that often occurs in a wireless LAN results in further reduced performance. The paper introduces a method of controlling congestion in a network via a feedback mechanism called fair intelligent congestion control (FICC) which is useful for improving TCP performance in such a network. FICC overcomes the inefficiency of TCP in misinterpreting the link loss as congestion loss. Simulation testing has demonstrated that, by eliminating buffer overflows caused by congestion, FICC provides desirable fairness, reduces delay variation and improves effective throughput. View full abstract»

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  • Impact of mobility on the performance of mobile ad hoc networks

    Page(s): 154 - 160
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (450 KB) |  | HTML iconHTML  

    In ad hoc networks, the mobility of nodes affects the system performance. Considerable attention has been paid to mobility models. However, most work is confined to simulation. A novel method is proposed to analyze the performance of mobile ad hoc networks (MANETs) considering the node's mobility. In the proposed method, of each communicating pair, one is considered to be stationary while the second is moving with a velocity relative to the first one. Using this method, system performance parameters, such as the average radio range dwell time of mobile nodes, link holding time, link breaking probability, and throughput of CSMA/CA protocols, are obtained by a theoretical framework. The results obtained from the proposed analytical model are observed to match well with simulation results. View full abstract»

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  • Decentralized access point selection architecture for wireless LANs

    Page(s): 137 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (626 KB) |  | HTML iconHTML  

    Wireless LANs have been widely deployed, and multiple access points (APs) are likely to become much more available for wireless stations (STAs) which can roam from one AP to another by some rule. We focus on an efficient and fair way to use the wireless access resources provided by multiple APs. In particular, our major concern is to develop a decentralized way to enable each STA to select an appropriate available AP independently. A straightforward way is to select the AP with the strongest signal; however, this is shown to need further improvement. Hence, we propose decentralized AP selection strategies to achieve an efficient and fair share of wireless access resources, and evaluate them by simulations. The results show that the proposed strategies can attain an excellent throughput performance by use of the number of active STAs sharing each AP, even if STAs employ the strategies only when entering the wireless LAN. In addition, if STAs roam from one AP to another, the total throughput and fairness can be further improved very much. View full abstract»

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  • QoS management in service specific label switched wireless networks

    Page(s): 82 - 87
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (657 KB) |  | HTML iconHTML  

    We consider a campus environment connected using multiple WLANs and WLAN routers providing interconnection between the WLAN networks. The servers part of WLANs in a campus network provide various services to users across the network. We have extended our earlier work related to service- and session-specific labeling, path, and switching. The extension is to support service-specific QoS and this is achieved by identifying an SSP (service-specific path) tree (a collection of SSPs) rooted at the WLAN router connected to the server hosting the service. Further, the service QoS parameters are distributed across the SSP tree for network resource reservation purposes. This reserved SSP tree is used to set up bidirectional QoS supported session-specific paths. View full abstract»

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  • Middleware for multimedia mobile collaborative system

    Page(s): 112 - 119
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (561 KB) |  | HTML iconHTML  

    Although various collaborative systems have successfully improved enterprise work efficiency, mobile collaborative systems, which allow collaboration via wireless networks and mobile devices, still lack robust functionality and content representation support. The paper proposes a novel mobile collaboration framework for multimedia content generation, representation and delivery. A unified file format and a message queue management middleware, designed for, and employed in, a heterogeneous computing environment, are also discussed. View full abstract»

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  • A handoff scheme with probability-based channel borrowing in integrated wireless mobile networks

    Page(s): 97 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (405 KB) |  | HTML iconHTML  

    We propose and analyze a handoff scheme with channel borrowing in integrated wireless mobile networks. Channels in each cell are divided into two parts and pre-allocated to real-time and non-real-time services. Each type of service is allowed to borrow channels from the other under certain conditions. A non-real-time service call can borrow an unused channel assigned to real-time service but it can be preempted by a real-time service call. A real-time service call borrows a channel from non-real-time service with a certain probability which depends on the number of available idle non-real-time service channels. We model the system by a six-dimensional Markov chain and compute the system performance in terms of blocking probability of originating calls, forced termination probability of real-time service calls, and average transmission delay of non-real-time service calls. The proposed scheme maximizes the resource utilization and keeps a certain quality of service (QoS) for each service at the time of congestion. View full abstract»

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  • 2004 Wireless Telecommunications Symposium (IEEE Cat. No.04EX784)

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    Freely Available from IEEE
  • Copyright

    Page(s): 0_2 - ii
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  • 2004 Wireless Telecommunications Symposium - WTS 2004 - Title

    Page(s): i
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    Freely Available from IEEE
  • WTS 2004 - Table of contents

    Page(s): iii - v
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    Freely Available from IEEE