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Personal Mobile Communications Conference, 2003. 5th European (Conf. Publ. No. 492)

Date 22-25 April 2003

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Displaying Results 1 - 25 of 120
  • Mixing and combining with AOA and TOA for the enhanced accuracy of mobile location

    Page(s): 276 - 280
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (321 KB)  

    Position location has become a hot issue over the past few years in wireless communication. Providing the accurate location information of the mobile station (MS) is necessitated by the Emergent 911 call in United States. The angle of arrival (AOA), time of arrival (TOA), and time difference of arrival (TDOA) techniques have been proposed for providing location services in wireless networks. We present a method for the enhanced accuracy of mobile location. This method is mixing and combining with AOA and TOA in wireless networks and picks out mobile location with large deviation to enhance the accuracy of location estimation. Numerical results demonstrate that the proposed location scheme gives much higher location accuracy than the method that only used TOA and AOA location technique. View full abstract»

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  • A fast energy-efficient multicast tree recovery algorithm for ad hoc network

    Page(s): 281 - 285
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (467 KB)  

    Multicasting is an efficient communication tool for use in multi-point applications such as conferencing and information distribution. In ad hoc networks, node mobility causes frequent changes of network topology and may disrupt the structure of multicast trees; hence, reconstruction of the multicast tree in an efficient and effective manner becomes a critical issue. Most of the multicast tree construction protocols available presently require either a total re-build of the tree or the disconnected nodes to be reconnected to the multicast tree via the shortest path. This disrupts the optimising factors, such as energy consumption, which are used in the building of the original tree. We introduce an efficient recovery algorithm which also minimises the power consumption on the tree. View full abstract»

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  • A study of ambiguity in hyperbolic mobile position location

    Page(s): 157 - 161
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (398 KB)  

    The paper investigates the conditions in which the MS position estimation is subjected to ambiguous solutions when using the hyperbolic trilateration method in cellular systems. Given the BTSs positions, a mathematical framework based on the measurements of range differences is developed in order to map the ambiguity region. Evaluation of the size of this region with respect to the hearabilty area is performed, and under this viewpoint a comparison between different geometric arrangements of BTSs is made. View full abstract»

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  • Channel estimation of a space-time UMTS uplink system for future generation mobile radio communication systems

    Page(s): 71 - 75
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (454 KB)  

    A novel channel estimation method is proposed for the uplink of a combined space-time UMTS system. The method is based on the periodic transmission of very short sequences of pilot bits on the DPCCH channels of each transmitter element of the MIMO system. The key feature is that the pilot bit sequence used for each transmitter element is orthogonal to those used by the other transmitter elements in order to provide the necessary information about each path. In the receiver, a dedicated channel estimator is used to descramble and despread the signals from the DPCCH channel of each receiver element of the MIMO receiver to recover the pilot signals. This information is then used to estimate the channel matrix under Rayleigh flat fading conditions. The BER performance of the space-time/UMTS system with the new channel estimator is provided and compared with the performance of the system when perfect channel estimation is assumed. View full abstract»

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  • A simple space-frequency coding scheme with cyclic delay diversity for OFDM

    Page(s): 106 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    Cyclic delay diversity (CDD) is a simple approach to increase the frequency selectivity of the channel in an orthogonal frequency division multiplexing (OFDM) based transmission scheme. The reason for this is that CDD inserts virtual echoes. Due to these virtual multipath components carriers experience different channels if the antenna specific cyclic delays are chosen properly. Without any additional effort this increased frequency selectivity can be exploited by using a forward error correction (FEC) code, e.g., a convolutional code that benefits from an altered error distribution after demodulation. In this paper we investigate a simple multiple antenna transmission scheme that exploits the frequency selectivity of the channel even without FEC coding. On each antenna a shifted version of the signal is sent which enables the receiver to apply optimum demodulation. We analyze the choice of the cyclic delay and present a comparison with the well-known Alamouti scheme. View full abstract»

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  • Numerical analysis of detuning in printed inverted F antennas for Bluetooth applications

    Page(s): 96 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (378 KB)  

    In this paper the numerical modelling of an inverted-F antenna (IFA) integrated into a small PCB is described. The transmission line modelling method was used, and a good agreement was obtained between models and measurements. Computed far-field radiation patterns predict a gain of 2.7 dBi which is in line with previously published results. The validated antenna model was used to investigate the potential detuning effect caused by close proximity objects including a wooden desktop, a conducting bench and a plastic enclosure. Although acceptable performance was found in most cases tested, some conditions caused a significant degradation in performance which may affect the reliability of the communications link. This has important implications for a device designed to be held by a human, and highlights the advantage of modelling the mounted antenna with any conductors or dielectrics which might be placed in close proximity. View full abstract»

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  • Thin vibrators with arbitrary surface impedance as a handset antennas

    Page(s): 16 - 20
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    The asymptotic expression for current in the thin vibrator with an arbitrary surface impedance was obtained. Expressions of vibrator radiation fields corrected at the any distance from the vibrator axis was founded. Calculations were carried out and theirs results are represented as graphs of the dependence of input characteristics and near and far fields distribution on the surface impedance of the vibrator. View full abstract»

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  • Coherence bandwidth characterisation for 4th generation WLANs

    Page(s): 176 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (485 KB)  

    Wideband propagation measurements undertaken in two different worst case broadband WLANs indoor radio channels to measure spaced-frequency correlation functions are presented. The 90th percentile values of the coherence bandwidth at correlation level of 0.9 for all locations stay below 72 MHz. Minimum and maximum B0.9 coherence bandwidths obtained in a long narrow corridor with a directional horn transmit and an omnidirectional receive antenna are 1.10 MHz. and 105.33 MHz respectively. It has been observed that the coherence bandwidth is highly variable with the location of the receiver with respect to the base station. View full abstract»

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  • The effect of antenna parameters on the performance analysis of different antenna array architectures

    Page(s): 5 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    An extensive investigation involving many different antenna parameters on handset antenna arrays is described. The antenna parameters under study include types of antenna arrays, type of antenna elements, mutual coupling, antenna spacing and number of receive antennas. These investigations provide invaluable insight into the feasibility of introducing compact antenna arrays on the mobile terminal. Results show that the application of compact antenna arrays is practical in both indoor and outdoor environments except in the strong street canyon effect scenario. View full abstract»

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  • Channel estimation error and fading correlation effect on the performance of G2 STB and MRRC systems

    Page(s): 328 - 331
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (294 KB)  

    This paper shows analytically and through bit error rate (BER) simulations that both the G2 space-time block (STB) and the maximal ratio receive combining (MRRC) systems suffer a BER performance degradation as a consequence of channel estimation errors, suffering the G2 STB system the greatest degradation. Also, it is shown that both systems suffer equal performance degradation due to fading correlation. View full abstract»

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  • Multi-user detection in OFDM systems using CDMA and multiple antennas

    Page(s): 116 - 120
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (417 KB)  

    In this paper multiuser detection in OFDM systems is examined. The separation of concurrently transmitted signals is based on space division and code division multiple access (SD/CDMA). The achievable bit error ratio and the peak to average power ratio (PAPR) are evaluated for different spreading strategies. A novel time domain spreading technique for OFDM systems is proposed for which the PAPR is independent of the processing gain. The examined OFDM techniques are compared with single-carrier transmission using equalization in the frequency domain (SC/FDE), which shows strong similarities to OFDM systems. View full abstract»

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  • Downlink slot allocation strategies for a wireless IP network

    Page(s): 199 - 203
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (442 KB)  

    The paper introduces an advanced slot allocation strategy for the downlink of a packet based mobile communications system. We show that careful consideration of a number of aspects unique to the system downlink greatly improves the multiplexing and resource allocation performance of the communications system, especially when compared to previous multiple access and resource allocation techniques that tend to ignore the downlink aspect of the system. An OPNET simulation model is used to analyse the performance of the proposed algorithms. View full abstract»

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  • A tuneable electrically-small antenna operating in the 'DC' mode

    Page(s): 524 - 528
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    The introduction of a shorting pin to the centre of an annular slot results in an additional, 'DC', mode being excited. Operation in this mode results in an electrically small structure, which is inherently narrow-band. Through the addition of a simple varactor diode we show that this narrow-band 'DC' mode may essentially be made wide-band through frequency tuning. The results presented in this paper consider the input response, 3-D radiation pattern, gain, directivity and efficiency. View full abstract»

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  • Indoor channel measurements for a body-worn 5.2 GHz receiver

    Page(s): 191 - 194
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (365 KB)  

    An important aspect of emerging wireless networking standards for indoor environments is the use of body-worn or handportable terminals. The proximity to the user's body has a direct impact on the nature of the propagation channel. The paper reports narrowband propagation measurements for a 5.2 GHz receiver worn by a male volunteer walking indoors at 0.5 m/s. Two indoor environments were considered: an 18 m long corridor and a 42 m2 office. The results show that local mean values were dependent on whether or not the users body obstructed the direct ray from the transmitter. For the corridor, the average non-line-of-sight (NLOS) path loss was 5.4 dB greater than with line-of-sight (LOS). However, the power decay index (n) was 1.2 in both cases. In the small office, the difference between LOS and NLOS conditions was strongly dependent on the location within the room. All of the measured results were evaluated in terms of their impact on wireless systems. Without multipath effects, the two measured environments could comfortably support an IEEE 802.11a full-rate system. However, it was shown that this rate could not be guaranteed under low-mobility conditions, particularly in the small office. View full abstract»

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  • The path toward the 4G network and services: the WINE GLASS vision

    Page(s): 169 - 175
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (617 KB)  

    The paper presents and explains the architecture and the solutions adapted for supporting enhanced services in the integrated UMTS-WLAN environment of the WINE GLASS (wireless IP network as generic platform for location aware service support) project, included in the IST (Information Society Technologies) research program of the European Community. With the innovative solutions proposed not only for the architecture but also for network services like authentication, authorization, accounting (AAA), QoS mobility management issues and the location and service platform, this study aims to contribute to the technical innovation of 3G systems by exploiting the potential of IP-based wireless mobile multimedia networking in the evolution towards 4G systems. The main WINE GLASS objective is in fact to exploit and enhance new IP-based techniques to support terminal mobility and soft-guaranteed QoS in a wireless Internet architecture. The proposed framework incorporates both UMTS and WLAN access technologies, enhancing the UMTS backbone in order to support fully an all-IP solution. View full abstract»

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  • Overview and implementation of scheduling algorithms for wireless environments

    Page(s): 441 - 446
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (425 KB)  

    Bandwidth in wireless systems is a scarce resource which has to be controlled intelligently to provide the required quality of service (QoS) for each distinct mobile user. Based on wireline approaches, we present and discuss some of the main scheduling schemes proposed for wireless data transmission. A new supporting scheme called "wireless weighted fair queueing" (W2FQ) allows one to implement schemes based on the weighted fair queueing approach in distributed wireless environments. View full abstract»

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  • Miniature dielectrically loaded GPS antennas for robust US E-911 position location

    Page(s): 21 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    Hard lessons have been learned about the performance that is required from the antenna as GPS positioning systems come into use in wireless communication products. As handsets reach more compact size there has as a result been a reduction in volume available to house antennas. Whilst size/performance tradeoffs in the terrestrial system have accommodated the consequent reductions in radiation efficiency, there is no available way to mitigate this loss for the GPS system as it uses signals that are transmitted from satellites. This reduction in radiation efficiency may not be so critical in some applications, but when applied to finding ones location in emergency circumstances, the loss in the GPS antennas performance should not be taken frivolously. What is required is antenna technology, which maintains a high enough performance despite occupying a small volume, being in close proximity to energy absorbing human tissues of the user and in the presence of noise and distortion from the radios that share the handset platform. View full abstract»

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  • Low complexity algorithm for optimal hard decoding of convolutional codes

    Page(s): 332 - 336
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    It is well known that convolutional codes can be optimally decoded by the Viterbi algorithm (VA). We propose an optimal hard decoding technique where the VA is applied to identify the error vector rather than the information message. We show that, with this type of decoding, the exhaustive computation of a vast majority of state to state iterations is unnecessary. Hence, under certain channel conditions, optimum performance is achievable with an order of magnitude reduction in complexity. Besides, additional complexity reduction can be achieved by detecting the frames which have a low probability of being successfully decoded. View full abstract»

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  • Load shared integrated networks

    Page(s): 225 - 229
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (453 KB)  

    Fourth generation networks lead to multiple distributed wireless networks, including cellular networks of different generations, frequencies and cell sizes; wireless LAN and PAN networks, and potentially satellite and other networks. Existing studies on hierarchical networks, integrated networks, and dual mode studies show how higher efficiency can be achieved in a distributed cellular super-network. Load sharing, in distributed operating systems, strives to assist overloaded resources by overflowing tasks between systems. We consider how 3G/4G wireless networks can load share traffic using vertical handovers. This study integrates and builds upon simulation studies of hierarchical and integrated networks, and in addition, considers the impact of overflowing sessions to potentially multiple components. View full abstract»

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  • Secure access to corporate resources in a multi-access perspective: needs, problems, and solutions

    Page(s): 482 - 489
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    The modern businessman needs to access corporate resources constantly, regardless of the access location, thus improving effectiveness. In order to accomplish this, a number of access technologies allow mobile users to be connected to some kind of network almost in every situation. The enterprise resources, however, must be protected from unauthorized accesses, disclosures, and modification of data there stored. An employee accessing the enterprise network remotely might represent a serious vulnerability by exposing the network to several threats. This paper analyzes the needs, the problems, and some of the related issues of secure remote corporate access, i.e. allowing employees to access the intranet even when not connected directly to the corporate network without compromising the security of the data. Furthermore, it outlines a possible solution to solve some of the problems illustrated throughout the discussion. View full abstract»

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  • Reduced complexity channel parameters estimation with multi-dimensional Unitary-SAGE algorithm

    Page(s): 54 - 59
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (482 KB)  

    Estimating channel parameters from measured data using maximum-likelihood methods can be very time-consuming due to the iterative nature of these algorithms. Although the SAGE algorithm has a faster convergence speed compared to the classical EM algorithm, it could still be computational-intensive. Since most of the computations of the SAGE algorithm are concentrated in the M-step, we propose a new implementation of the algorithm, namely the Unitary-SAGE algorithm, that is able to implement the entire M-step throughout the iterations in the real-valued domain. This helps to reduce the processing time and memory consumption of the original SAGE algorithm since all computations in the M-step are performed in the real-valued domain with efficient matrix manipulation. We present the general implementation of the Unitary-SAGE algorithm in the frequency domain when applied in both the element-space and the newly developed beamspace domains. View full abstract»

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  • The analytic hierarchy process applied to best effort QoS routing with multiple metrics: a comparative evaluation

    Page(s): 539 - 544
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (445 KB)  

    We propose a new algorithm called enhanced best effort quality of service routing with multiple metrics (EBQRMM). It is proposed for connection oriented point-to-point communications. It applies the concept of the analytic hierarchy process (AHP) which is a well-known model in the area of decision making with multiple objectives. Four metrics have been considered: delay, bandwidth, security and loss probability. Its performance is compared to the single compounded metric, SCM, algorithm. It is found that EBQRMM outperforms SCM over the utilisation range (0-90)% by an average of 10.6% with 1.2% standard deviation. The main novelty of this paper is the application of the AHP approach which provides an opportunity to consider multiple metrics and path selection in the proposed algorithm. View full abstract»

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  • Path expiration times in mobile ad hoc networks

    Page(s): 27 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (454 KB)  

    Mobile ad hoc networks are infrastructure free, dynamic and wireless networks. Nodes within a network are able to create connections over several intermediate relays to distant nodes. Nodes establish connections by setting up determined paths through the network. The path expiration time (PET) is the path lifetime and unpredictable node movements limit it. Whenever adjacent nodes, used as connection relays, leave each others radio range they cause a failure within the path. The source must then reestablish the connection using another path, which avoids the broken link. We describe a statistical method to forecast PETs over an arbitrary number of hops, independent from radio transmission ranges, maximum node velocities and external sensor data. This probability distributions can be exploited for dimensioning ad hoc networks, therewith they comply certain requirements of path stability, e.g. by limiting the maximum number of hops over which a path can be set up. View full abstract»

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  • Code acquisition in narrow-band interference using MUSIC with differential correlations

    Page(s): 251 - 255
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    In this paper we consider code timing acquisition in the direct-sequence code-division multiple access (DS-CDMA) communication system. Recently, traditional MUSIC utilizing differential correlations, DC-MUSIC, was proposed. Here DC-MUSIC is applied in narrowband interference and simulation results are presented. They indicate a clear improvement in acquisition performance compared to traditional MUSIC, conventional and differentially coherent acquisition schemes. In addition, DC-MUSIC is found to be a robust scheme due to the possibility of coherent integration also in the case of interference. View full abstract»

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  • New Bluetooth inter-piconet schedule with a slave to slave piconet formation

    Page(s): 81 - 85
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (478 KB)  

    The growing use of information intensive consumer devices such as cell phones, personal digital assistants (PDAs), and laptop computers have called for a new networking paradigm for their interconnection. Up to 8 Bluetooth devices can form a centralized network, called a piconet, controlled by a master node, which allocates transmission slots to all other nodes (slaves) in the piconet. Bluetooth achieves robustness against interference from nearby devices by employing a frequency hopping code division multiple access (FH-CDMA) technique. This facilitates a high density of communicating devices, making it possible for dozens of piconets to co-exist and independently communicate in close proximity without significant performance degradation. In this paper we investigate two important performance measures: the amount of time to form a scatternet to minimize the delay experienced by the user; and the number of messages sent between the devices. By reducing the number of messages sent, power consumption is conserved. We propose new policies where the slave could enter in contact with other slaves without passing through the master. This is an alternative approach to inter-piconet schedules: the SSPF (slave to slave piconet formation). These policies can have a significant impact on the packets delays, throughput and power management. View full abstract»

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