By Topic

Vehicular Technology Conference, 1999. VTC 1999 - Fall. IEEE VTS 50th

Date 19-22 Sept. 1999

Go

Filter Results

Displaying Results 1 - 25 of 119
  • IEEE VTS 50th Vehicular Technology Conference [front matter]

    Page(s): I - LXIX
    Save to Project icon | Request Permissions | PDF file iconPDF (3186 KB)  
    Freely Available from IEEE
  • PSAP (pre-selected artificial path) diversity system for indoor DS/CDMA

    Page(s): 2672 - 2676 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    In a typical indoor environment such as in a building, delay spread tends to be small, which causes frequency non-selective fading. Therefore the resolvable paths at the receiver matched filter can not be obtained, and the effective path diversity can not be achieved. This paper proposes a pre-selected artificial path diversity method with multiple sector antennas consisting of delayed PN codes, which is an effective power scheme in such an indoor environment. In the proposed system, only pre-selected sector antennas transmit the signal to reduce signal redundancy, therefore the transmission power is used efficiently at the base station. As a result, better BER performance and the reduction of interference signals between the different channels by means of sector selection can be achieved View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of an ISMA CDMA packet data network

    Page(s): 2865 - 2869 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB)  

    The efficiency of MAC protocols for a packet switching DS-CDMA network strongly depends on the offered traffic statistic. For bursty sources where transmission needs are restricted to short message lengths, a protocol such as S-ALOHA can be efficient. However, for longer messages, a reduction in the randomness is required in order to improve the system performance. This improvement can be provided by a protocol such as ISMA when combined with the DS-CDMA technique. In this paper an analytical approach to modeling the resulting ISMA CDMA scheme is presented, and some design issues regarding the number of codes to be used are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Satellite mobile multimedia services in the UMTS-the SUMO project

    Page(s): 2750 - 2754 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (376 KB)  

    The UMTS will become a global standard for third-generation mobile systems. Satellites will be an essential part of the UMTS without which global coverage will not be practicable. To provide mobile multimedia services seamlessly via satellites as well as radio-terrestrial networks, full interoperability needs to be ensured. Therefore a testbed representing a complete UMTS system is being developed in order to demonstrate mobile multimedia service provision from a multimode terminal. This terminal will allow a choice between different satellite access schemes, as well as constellations (LEO etc.), and radio-terrestrial access. A range of application services based on H.324M, MPEG-4 and others will be evaluated on the testbed. This paper describes the novel features of this testbed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dynamic bit rate assignment in wireless CDMA data transmissions

    Page(s): 2840 - 2844 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    This paper compares different schemes that can be used to improve the performance of CDMA in wireless data systems. In particular, we consider a closed-loop power control scheme and an adaptive coding scheme. The comparison between these different techniques is performed in terms of mean transmission time and energy efficiency. Our aim is to show that an adaptive coding scheme can allow good performance with respect to typical power control techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Virtual LAN supporting quality of service in wireless ATM networks

    Page(s): 2686 - 2690 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    This paper introduces virtual LAN (VLAN) services using ATM LAN emulation technology which operates on a client/server model. One of the attractive features of the VLAN is the capability to group users into a broadcast domain. The focus of this paper is the issue of supporting quality of service to mobiles in a wireless ATM network. An architecture based on emulated LAN is proposed which can efficiently provide the required bandwidth of mobiles as they migrate between cells View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Personalized high speed wireless LAN system-JPLAN

    Page(s): 2682 - 2685 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (264 KB)  

    To match the progress of computer networks, small high-throughput wireless LAN systems are required. To achieve this we have developed trial equipment for a personalized high-speed wireless LAN system called JPLAN. JPLAN has small units and transmission speeds as high as 10BASE-T. A new radio link control method is developed that observes the radio propagation conditions between base and terminal stations and gives communication start permission to terminal stations. JPLAN makes it easy to create data communication systems that offer high mobility and high bit-rate transmission capacity View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structure and performance of the HIPERLAN/2 physical layer

    Page(s): 2667 - 2671 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    At present, standards for broadband wireless multimedia communications in the 5 GHz band are being developed in Europe as well as in the USA and Japan. HIPERLAN/2 is an upcoming standard which is being specified by the ETSI Project BRAN and is intended to be finished in April 2000. The physical layers of the three systems will be well-harmonized whereas the upper layer protocols are different. In this paper, the concepts and parameters of the physical layer of HIPERLAN/2 are described. According to the harmonization with the American and the Japanese system similarities and differences are pointed out. Furthermore, exemplary performance results are included and discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Soft-decision redundant residue number system based error correction coding

    Page(s): 2546 - 2550 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    Soft-decision-based redundant residue number system (RRNS)-assisted error control coding is proposed and its performance is evaluated. An RRNS(n,k) code is a maximum-minimum distance block code, exhibiting identical distance properties to Reed-Solomon (RS) codes. Hence their error correction capability is given by t=(n-k)/2. Different bit mapping methods are proposed, which result in systematic and non-systematic RRNS encoders. We show that the classic Chase algorithm can be invoked, in order to contrive soft-decision detection for RRNS codes and to exploit the soft channel outputs, which provide the relative reliability of each of the received binary digits. We found that soft decision-based RRNS decoding is at least 1.5 dB better compared to hard decision-assisted RRNS decoding View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Link level performance results for a WCDMA random access scheme with preamble power ramping and fast acquisition indication

    Page(s): 2581 - 2585 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    Advanced packet-access based services play a key role in third-generation mobile communication systems. Thus, flexible and power-efficient random and packet access schemes with low access delay are identified as an important feature. This paper describes the random access proposal adopted for WCDMA, the third-generation system jointly specified by several standardization bodies within the 3rd-Generation Partnership Project (3GPP). Link level performance results for this method with preamble power ramping and fast acquisition indication are presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Space-time block codes over frequency selective Rayleigh fading channels

    Page(s): 2541 - 2545 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (308 KB)  

    This paper proposes the combination of space-time block codes (ST-BC) with multiple input multiple output equalizer (MIMO-EQ) for achieving transmit diversity in a frequency-selective Rayleigh fading channel. In the proposed system, MIMO-EQ equalizes the channel into a temporal intersymbol interference (ISI)-free channel, and then a simple linear processing is used to perform the maximum likelihood (ML) decoding for ST-BC. Also the impacts of antenna correlations on the performance of ST-BC are investigated. Our simulation results show that the proposed system can achieve the full spatial diversity gain, and the SNR loss due to the antenna correlations is within 0.5 dB at 1% of block error rate if the correlation coefficient is less than 0.5 View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Radio resource sharing and capacity of some multiple access methods in hierarchical cell structures

    Page(s): 2825 - 2829 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    To decrease total system cost and improve efficiency, in future mobile communication systems, we can implement a structure of multiple cells covering an area. This is often referred to as a hierarchical cell structure, HCS. We compare five methods of sharing the scarce radio resources in a two-layer HCS: (i) DS-CDMA in macrocells and TDMA in microcells; (ii) TDMA in macrocells and DS-CDMA in microcells; (iii) DS-CDMA in both macrocells and microcells on the same frequency band; (iv) TDMA in both layers with frequency splitting; and (v) TDMA in both layers with reuse of macro frequencies in microcells. Through simulation we study the system capacities, i.e., the number of users supported per cell. Highest capacities are achieved by method (iv) and (v). Method (v) could also be used in a CDMA type of system if it is possible to have more than one carrier View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mobile host protocols for the Internet

    Page(s): 2790 - 2794 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    This paper describes a new Mobile IP protocol supporting wide area networks. The Scalable Mobile IP (SMIP) allows any mobile host to move inside a large-scale area while being transparently connected to the Internet by using its permanent IP address. This protocol does not need to change other applications used to communicate with mobile hosts (MH), and has some new features over other mobile host IP, for instance, it is more scalable, faster, and more secure View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Partial correlations and cyclic prefixes in direct sequence spread spectrum

    Page(s): 2696 - 2700 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The RAKE receiver for direct sequence (DS) spread spectrum can separate energy received over multiple propagation paths with different time delays. Each finger in the RAKE sees signals with a specific time delay, but it also sees some unwanted residual crosstalk from signals over differently delayed paths. If bit transitions occur in delayed reflection, the crosstalk between two fingers in the RAKE detector is determined by two partial correlation functions, which exhibit substantially inferior properties than can be achieved for the full (or periodic) autocorrelation function. The aim of this paper is twofold: (1) to propose a new model to estimate the variance of partial correlations; (2) to show that cyclic prefixes improve the BER experienced when DS is transmitted over a dispersive multipath channel View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of MAC protocol for packet data service in CDMA based mobile communication systems

    Page(s): 2860 - 2864 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    We propose a MAC protocol that consists of a channel access mechanism and transmission mechanism to support effective wireless packet data service. In the channel access mechanism, a broadcast channel announces the status information of the random access channel, and the mobile station tries random access based on status information. Also, the mobile station has access probability to prevent collision increase due to the transmission of short messages. For effective transmission, the mobile station changes the transmission rate based on the transmission queue status to adapt the burst traffic characteristics. In restricted environments of transmission code and bandwidth, the proposed protocol shows better performance than the cdma2000 system View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A coding and retransmission protocol for mobile radio data transmission

    Page(s): 2505 - 2509 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    Mobile radio systems suffer from severe channel impairments. As services are moving toward a full extension of those available over fixed networks, new coding strategies are being developed to support data traffic beside the more usual voice communication. This paper presents a modified type II hybrid FEC/ARQ protocol in which each packet to be transmitted is decomposed into sub-packets each of which can be independently tested for correctness and retransmitted if necessary. The complete coding and transmission scheme is designed to be compatible with the frame format used in GSM networks. The performances of the proposed algorithm are evaluated by computer simulation using the system specifications contained in the ETSI-GSM recommendations. Throughput comparison with a traditional selective repeat (SR) protocol is presented to support the robustness and effectiveness of the presented scheme View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Coded modulation using differential encoding over Rayleigh fading channels

    Page(s): 2525 - 2529 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    Multilevel coding and bit-interleaved coded modulation using differential encoding and non-coherent reception over flat fading channels are assessed. In order to achieve high bandwidth efficiencies differential encoding is done with respect to phase, as well as with respect to amplitude of APSK constellations. Assuming the channel to be slowly time-varying, encoding and detection are based on blocks of N consecutive symbols (multiple symbol detection). In this paper, we provide the code design and present simulation results. It is shown that only for multilevel coding multiple symbol detection provides significant gains View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • On the Doppler probability density function within a low Earth orbit satellite spot beam and its application to the code acquisition procedure

    Page(s): 2711 - 2715 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    The probability density function of the Doppler shift in a LEO satellite spot beam has been found for both a circular and elliptical shaped spot beam. The Doppler PDF was used as a priori information in order to achieve better mean acquisition time which is critical in any LEO satellite communication system. It is shown that the Doppler PDF can be very well approximated by a parabola-shaped function. The direct approach is used for the calculation of the mean acquisition time while various searching strategies of the Doppler ambiguity area are analysed and simulated using the parabolic Doppler PDF. The overall analysis shows that the use of the Doppler PDF combined with an appropriate search strategy can reduce the mean acquisition time significantly View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of a two layer hierarchical cellular system with variable mobility users using multiple class applications

    Page(s): 2835 - 2839 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    This work deals with the performance evaluation of a two-layer hierarchical cellular network. Lower coverage is achieved by microcells that accommodate both new and handover requests, and can handle all types of multimedia traffic (voice, video, data). Macrocells, which are overlaid over the microcells, can also accommodate both new and handover requests but have limited application-handling capabilities (reduced quality video). A number of layer assignment techniques are compared, for the four mobility classes considered View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Space-time codes for fading channels

    Page(s): 2495 - 2499 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    Space-time codes are designed for efficient transmission using multiple transmit antennas. In this paper, we propose space-time codes which combine the Ungerboeck one-size larger constellation principle with the simple transmit diversity technique of Alamouti (1998). The proposed codes provide several dB additional coding gain over the well-known space-time codes while keeping the complexity almost the same View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Adaptive multishot canceler for the wideband CDMA systems

    Page(s): 2785 - 2789 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    With the demand for high-capacity (multimedia) services, wideband CDMA (WCDMA) has become an attractive multiple access scheme for third-generation wireless systems. Coming with higher data rate, the application of WCDMA brings with it new challenges in terms of multiple access interference (MAI) and intersymbol interference (ISI) suppression due to the fact that compared to the `regular' CDMA, the delay spread is no longer only a few chips. Most of the literature on multiuser detection so far has focused on algorithms which, due to high computational/hardware complexity, are unsuitable for large delay spread channels. In this paper, we present an adaptive symbol-based signal separator based on multishot matched filtering which is suitable for the asynchronous large delay spread fading channel characteristics View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance analysis of trellis coded M-PSK systems over Rician fading channels with phase jitter

    Page(s): 2561 - 2565 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB)  

    In this paper, the performance of trellis coded M-PSK systems in the fading environment is investigated. The combined effects of the fading and the non-ideal coherent receiver on the phase of the received signal are taken into account. Thus, performance analysis results will reflect the degradations both due to the effects of the fading on the amplitude of the received signal and of a noisy carrier reference, each modeled by the Rician and Tikhonov distributions, respectively View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of burst noise channel and hidden terminals over the IEEE 802.11 wireless LANs

    Page(s): 2641 - 2645 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    The overall performance of IEEE 802.11 wireless LAN is examined with respect to the “hidden terminal” problem under burst-error channel conditions. Only the ad-hoc portion of the wireless network architecture, with stations generating time-insensitive asynchronous data traffic, is considered. The simulation clearly shows that both the burst-error medium and the hidden terminals have negative impact on the maximum achievable throughput and the delay. However, the channel fading tends to dominate the performance over the influence of hidden terminals, as BER increases View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Evaluation of interference between uplink and downlink in UTRA/TDD

    Page(s): 2616 - 2620 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (384 KB)  

    An ideal TDD system offers high capacity, dynamic asymmetry between uplink and downlink and no coordination requirements between operators and base stations. This paper studies the performance of UTRA/TDD and how close to the ideal TDD system UTRA/TDD could be. Since both uplink and downlink share the same frequency in TDD, those two transmission directions can interfere with each other. This interference can occur between two mobile stations or between two base stations within one carrier or between two operators. This interference scenario is evaluated here. The results show that for UTRA/TDD operation dynamic channel allocation, synchronization of base stations and cooperation between the operators is preferred to obtain the maximum performance. The most difficult interference situations occur between base stations within one operator's band and between two operators if they are not synchronized View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance of ARQ and NAK-based ARQ on a correlated fading channel

    Page(s): 2706 - 2710 vol.5
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB)  

    Acknowledgment messages in conventional ARQ operations include both ACK and NAK (ACK/NAK-based ARQ). In NAK-based ARQ, there is no ACK message. This paper examines the difference between the two ARQ approaches, presenting performance comparisons in terms of throughput and delay. Both random error channel and correlated fading channel are considered. The impact of a noisy feedback channel is also investigated View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.