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Wireless and Mobile Communications (ICWMC), 2010 6th International Conference on

Date 20-25 Sept. 2010

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Displaying Results 1 - 25 of 107
  • [Front cover]

    Page(s): C1
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  • [Title page i]

    Page(s): i
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  • [Title page iii]

    Page(s): iii
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  • [Copyright notice]

    Page(s): iv
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  • Table of contents

    Page(s): v - xiii
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  • Preface

    Page(s): xiv
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  • Committee

    Page(s): xv - xviii
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  • list-reviewer

    Page(s): xix - xxi
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  • A Time-Domain Precoder to Improve the Bandwidth Efficiency of TD-LTE Systems

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (367 KB) |  | HTML iconHTML  

    This paper designs a new precoding for an OFDM system without cyclic prefix (CP), to achieve the same function with CP used in CP-OFDM system. After the analysis of CP-OFDM system, this paper constructs a modulation matrix; on this basis, introduces memory characteristics, as well as symbols feedback, and designs a time domain precoding (TDP) module. By adding the TDP module into TD-LTE link, its bit error ratio (BER) performance decreases slightly, compared to the CP system; however, due to the new system, it does not need to send CP signals; therefore, it eliminates redundancy, so the bandwidth efficiency increases. View full abstract»

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  • Realization of a CDMA-based RFID System Using a Semi-active UHF Transponder

    Page(s): 5 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (809 KB) |  | HTML iconHTML  

    RFID systems may increase the efficiency of logistic systems, e.g., inventory of stocks. Unfortunately, present existing systems come fast to their limits if a great amount of RFID transponder must be inventoried in very short time, as the channel access method of current RFID systems is Time Division Multiple Access. To shorten the inventory process, this work shows a first realization of an RFID-based semi-active UHF transponder using a Code Division Multiple Access method. The work concentrates on the uplink channel (tag to reader) that covers the transponder's backscattered signals. This channel access method enables simultaneous transfer of data, meaning that all transponder in the field may respond at the same time within the same frequency band. The data transfer realized for the uplink channel, uses a certain set of orthogonal spreading sequences (modified Gold codes) being different for every transponder. The RFID reader used in this work despreads the backscattered signals and decodes the data of the different transponder. Briefly, this work shows, in principle, the opportunity for a simultaneous data transfer on the uplink channel in RFID systems, which in turn may shorten very much the time for a complete inventory round. View full abstract»

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  • A Novel Structured Markovian Model for Burst-Error Channels

    Page(s): 11 - 15
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (324 KB) |  | HTML iconHTML  

    A new Markovian model for burst-error processes is herein presented. Our basic idea consists of imposing a convenient structure on this model, with the double purpose of reproducing the generation of some typical patterns of burst error sequences and facilitating the maximum-likelihood estimation of the model's parameters. A simple procedure for calculating the maximum-likelihood metric of those parameters is derived and numerically maximized to fit the model to data. Some numerical results are presented that illustrate the effectiveness of this approach in reproducing very well important statistics of burst-errors processes. View full abstract»

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  • Subspace Channel Estimation Assisted by Block Matrix Scheme for ZP-OFDM Systems

    Page(s): 16 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (401 KB) |  | HTML iconHTML  

    Novel subspace-based channel estimation is proposed for single-input multiple-output (SIMO) zero-padded orthogonal frequency-division multiplexing (ZP-OFDM) systems. By stacking all the received OFDM symbols, the stacked channel matrix is of block Toeplitz. The block matrix scheme is then presented such that a group of subvectors are formed from the stacked OFDM signal and the number of equivalent samples is increased. With the extra samples, the perturbations of sample correlation matrix and the noise subspace are reduced, which lowers the channel estimation error. The novel channel estimator can also work very well even with only a few OFDM symbols. Computer simulations demonstrate that the proposed channel estimation is effective and robust compared with existed methods. View full abstract»

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  • Novel Antenna Configurations for Wireless Broadband Vehicular Communications

    Page(s): 21 - 26
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (569 KB) |  | HTML iconHTML  

    In this paper, mobile WiMAX trials are analysed to investigate the vehicular down-link performance for a number of on-car antenna configurations. The directionality and optimum polarization of the vehicular antennas are shown to improve both the range and throughput of the system. These improvements are attributed to the additional directive gain, and the reduced multi-input multi-output spatial correlation that results from orthogonal polarization. The mobile-WiMAX trials cover an urban vehicular scenario using a 2x2 MIMO system configuration. Results show that the throughput can be doubled for a wide range of received SNR levels (via STBC or SM) when a pair of directional dual polarized antennas are used at the vehicle (compared to omni-directional devices). View full abstract»

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  • Compensation for Nonlinear Distortion in OFDM Systems Using a Digital Predistorter Based on the SCPWL Model

    Page(s): 27 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (491 KB) |  | HTML iconHTML  

    Orthogonal frequency division multiplexing (OFDM) is an attractive technique for achieving high-bit-rate wireless data transmission. However, multicarrier systems such as OFDM show great sensitivity to nonlinear distortion. In this paper, we propose a simplicial canonical piecewise-linear (SCPWL) model based digital predistorter to compensate for nonlinear distortion introduced by a high power amplifier (HPA) in OFDM systems. The performance of the new predistortion scheme for OFDM systems is evaluated in terms of bit error rate (BER) and total degradation (TD). The simulation results demonstrated that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinear distortion introduced by the HPA. View full abstract»

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  • On-the-Fly Syndrome Check for LDPC Decoders

    Page(s): 33 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (446 KB) |  | HTML iconHTML  

    Modern VLSI decoders for low-density parity-check (LDPC) codes require high throughput performance while achieving high energy efficiency on the smallest possible footprint. In this paper we present a valuable optimization to the processing step known as syndrome check. After each decoding iteration the updated posterior values are used to verify the validity of the codeblock and halt the decoding task. We partition this task and perform it on-the-fly in order to speed up the total task latency and eliminate hardware components. We present results for applying this technique to an LDPC decoder for the IEEE 802.11n standard. View full abstract»

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  • Channel Estimation Technique by Hidden Signal: Application in the SC-FDMA Context

    Page(s): 38 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB) |  | HTML iconHTML  

    This paper deals with a new channel estimation technique for Single Carrier FDMA (SC-FDMA) currently adopted for mobile radio uplink communications in 3GPP LTE standard. The principle is to exploit the statistical advantages of a specific signal added in the transmitter to estimate the channel coefficients. In contrast to a pilots signal, the added signal covers the entire useful signal band during all of the communication delay. The advantage of this proposal is to estimate the channel by kipping the same spectral efficiency. This proposal is compared to Zero-Forcing estimator with LS equalizer and MMSE equalizer. The results are very convincing in term of symbol error rate; the gain is up to 2.5 dB. View full abstract»

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  • Electromagnetic Exposure and Quality of Service in the Downlink of Wireless Cellular Networks

    Page(s): 42 - 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (335 KB) |  | HTML iconHTML  

    We study in this paper both the electromagnetic exposure and the quality of service perceived by the users in the downlink of wireless cellular networks. We calculate the cumulative electromagnetic radiation received at each location from the interfering base stations in a large (eventually infinite) hexagonal cellular network. We establish a lower bound of the cell radius above which the safety zone has not to be increased due to this cumulative effect compared to the situation when one accounts only for the power received from the serving base station. On the other hand, fixing some quality of service target, we calculate the minimal emitted power required to serve a given traffic demand density with cells of a given radius. This permits to see whether the operator may reduce the power emitted currently in some parts of his network without degrading the quality of service. This is particularly interesting in the perspective of a potential reduction of the regulatory exposure threshold. Thus the present study shows when and of how much can be reduced the exposure of the people without sacrificing the users quality of the service. View full abstract»

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  • Using Pseudonoise Sequence Subcarrier Shuffling for Peak-to-Average Power Ratio Reduction in OFDM Systems

    Page(s): 49 - 55
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (430 KB) |  | HTML iconHTML  

    In this paper, we propose a new subcarrier assignment technique that is capable of substantially reducing the peak-to-average power ratio in orthogonal frequency division multiplexing wireless communication systems. The new technique is based on using pseudonoise sequence shuffling of the subcarrier assignments to data symbols within an orthogonal frequency division multiplexing block. Simulation results confirm the success of the proposed techniques in reducing the peak-to-average power ratio. View full abstract»

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  • Performance Model for Orthogonal Sub Channel in Noise-Limited Environment

    Page(s): 56 - 61
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (454 KB) |  | HTML iconHTML  

    Orthogonal Sub Channel (OSC) is a voice enhancement for the GSM evolution. It allows in principle a double capacity with the same hardware compared to the previous GSM Half Rate (HR) mode. This paper investigates the effects of OSC on the radio performance as function of the OSC capable handset penetration compared to the GSM HR mode. A set of test cases was carried out in GSM network in order to evaluate the radio performance of OSC in terms of the carrier per noise level. The tests were performed in noise-limited indoor environment, and the quality and received power level distributions were analyzed. As a main achievement, a generic model for estimating the effect of OSC on the GSM radio performance was developed. The model is based on the network statistics and performance indicators of GSM. View full abstract»

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  • Capacity Gain Estimation for Orthogonal Sub Channel

    Page(s): 62 - 67
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB) |  | HTML iconHTML  

    OSC (Orthogonal Sub Channel) is an enhancement for the GSM voice traffic. It provides up to double capacity in the GSM radio interface with the same hardware compared to the previous GSM Half Rate (HR) mode. This paper investigates the effects of the OSC on the capacity utilization compared to the GSM HR as function of the OSC capable handset penetration. The variation of the radio network capacity is studied by taking into account the division of the time slot usage between HR and OSC capable terminals. The results show the achievable capacity gains in terms of reduced time slots and transceiver units with given blocking rate. View full abstract»

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  • An Alternative QoS Architecture for Integrating WLAN/3G Networks

    Page(s): 68 - 77
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (721 KB) |  | HTML iconHTML  

    The integration of heterogeneous wireless networks has been studied for some time. Wireless networks can be complementary by providing additional resources to one another if properly integrated. For example, 3G networks offer increased coverage, but they have a low capacity for data transmission. In contrast, WLANs (Wireless Local Networks) offer a limited coverage range while allowing high rates of data transmission. Some aspects of integration and interoperation between these network technologies have been analysed in articles, books and tutorials. However, video delivery services involving these networks still deserve further attention, especially scenarios in which the two technologies are properly integrated. In this paper, we introduce a novel QoS Architecture composed of a provider-independent CAC (PI-CAC) for mobile network selection, a session proxy (SP) for video session management during handovers, and a specialized MIP implementation (S-MIP) to reduce native MIP latency into a scenario in which Wireless Local Network (WLAN) and 3G cellular networks are integrated using peer-to-peer architecture. This solution attempts to preserve the quality of the streaming video during each handover and recover the user video session damaged by high delays caused by MIP. The performance of our solution was evaluated using a testbed implementation into a real scenario and the results were better when compared with solutions based on traditional approaches. View full abstract»

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  • On IMS-based Fast Session Handover Based on Available Network Resources of Access Networks

    Page(s): 78 - 85
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2417 KB) |  | HTML iconHTML  

    Mobile users' demand for using the best available network connection encourages mobile network operators (MNOs) to construct multi-access networks managed by all-IP based mobile networks. For such an MNO, the IP Multimedia Subsystem (IMS) is a promising service control infrastructure to provide IP-based multimedia services with QoS guarantee in the multi-access network. The service centralization and continuity application server (SCC AS), which is a dedicated application server cooperating with the IMS, enables user equipments (UEs) to continuously use IMS-based services (e.g., VoIP) even when the UEs make handovers between different access networks. In the case where the UE cannot simultaneously use multiple wireless devices, there is the possibility of occurring a long media disruption time during handovers. This is caused by several consecutive handovers as a result of attempting to ensure the QoS-guaranteed communications. In this paper, we propose a method for reducing the media disruption time when the UE makes handovers between different access networks. In the proposal, the UE proactively performs the service continuity procedure, and selects the access network that can provide the required network resources to the UE. We implement and evaluate the proposed method, and show how the media disruption time can be reduced. View full abstract»

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  • Design and Implementation of a RESTful IMS API

    Page(s): 86 - 91
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (381 KB) |  | HTML iconHTML  

    Web 2.0 has been happening on the fixed Internet side for several years already. This phenomenon has forced traditional Telco operators to consider new business models. One of the possible models is to utilize the IP Multimedia Subsystem (IMS) network architecture. Using the IMS, Telco operators have more control over the data instead of becoming just bit pipes. In addition, operators interest in providing open Application Programming Interfaces (APIs) exposing IMS and network assets has grown. In this paper, a RESTful IMS API implementation, is represented. The design and implementation of the API exposing IMS functionality is shown. In addition, the implementation of a REST application using the API is described. View full abstract»

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  • SIP Back to Back User Benchmarking

    Page(s): 92 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (857 KB) |  | HTML iconHTML  

    In the branch of performance testing of SIP based infrastructure no standardized methodology has been adopted yet. This is why we decided to develop a methodology suitable for testing and evaluating SIP server's performance. This paper should open a discussion about defining the parameters and methodology for benchmarking SIP based infrastructure, because it is the keystone in modern NGN voice communications. The methodology presented in this paper focuses on one particular variant of the SIP server - the Back to Back User Agent (B2BUA), as it is one of the most commonly used solution in the VoIP. The method is enhanced by the definition of the performance rating factor, which allows for comparing the performance of the different B2BUAs platform independently. This factor utilizes one of the features of the B2BUA - the fact that media during the call are passing through the SIP server. The whole method is described in this paper and confirmed experimentally as well. View full abstract»

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  • Design, Investigation and Optimization of a Compact UWB Antenna

    Page(s): 97 - 101
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (589 KB) |  | HTML iconHTML  

    In this paper, a simple, low-profile, and wideband planar antenna with a pure rectangular radiator fed by a simple 50Ω microstrip line for multiple applications is designed. By investigating the feeding position and ground plane size, the antenna is properly designed to have a very wide bandwidth covering the whole FCC allocated ultra-wideband. Due to the additional patch underneath the radiator at a proper position, the bandwidth can be further increased towards the lower side of the frequency spectrum. This antenna is finally modified to have a bandwidth ranging from 2GHz-11.3GHz, which satisfies the system requirements for SDMB, WiBro, WLAN, CMMB and the entire UWB with S1,1 <; -10dB. View full abstract»

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