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Vehicular Technology Conference Proceedings, 2000. VTC 2000-Spring Tokyo. 2000 IEEE 51st

Date 15-18 May 2000

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  • 2000 IEEE 51st vehicular technology conference proceedings [front matter]

    Publication Year: 2000 , Page(s): i - xlvi
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    Freely Available from IEEE
  • Author index

    Publication Year: 2000 , Page(s): xlvii - lvi
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  • PDF-transformation for the outdoor-indoor propagation model

    Publication Year: 2000 , Page(s): 1646 - 1650 vol.3
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB)  

    The main objective of this work is to provide the probability transformation for the parameters describing an impinging wave from the outdoor to the indoor environment. An approximated deterministic outdoor-indoor model already developed is utilised to extract the probability density function (PDF) transformation rule for the delay, azimuth and elevation spectra. Since the interface model is applicable for frequencies of 2.4 GHz, 5.2 GHz and 60 GHz, the transformation holds for these frequencies. View full abstract»

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  • Adaptive spatial-subcarrier trellis coded MQAM and power optimization for OFDM transmissions

    Publication Year: 2000 , Page(s): 2049 - 2053 vol.3
    Cited by:  Papers (5)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    Space-time coding or coded modulation has demonstrated that significant increases in system capacity and performance can be achieved by incorporating multiple antennas at the transmitter and (optional) multiple antennas at the receiver. In this paper, we propose an adaptive spatial-subcarrier trellis coded modulation using MQAM for orthogonal frequency division multiplexing (OFDM) transmission by using instantaneous channel state information and employing multiple antennas at both the transmitter and the receiver. In particular, our objective is to minimize the total transmit power required for each OFDM transmission, by optimizing the power allocation, code rate and modulation scheme in each spatial-subcarrier channel, while maintaining a given data rate and bit error probability. To illustrate the potential of our proposed system, Monte Carlo simulation results are provided View full abstract»

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  • Coherent multicarrier/DS-CDMA and MC-CDMA for broadband packet wireless access

    Publication Year: 2000 , Page(s): 1918 - 1922 vol.3
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    This paper compares the packet error rate (PER) performance levels of 3 access schemes, i.e., single-carrier (SC)/DS-CDMA, multi-carrier (MC)/DS-CDMA, and MC-CDMA assuming an over 100-MHz bandwidth for broadband packet wireless access. In a broadband propagation channel, severe multipath interference degrades the accuracy of path search and channel estimation for coherent detection. Computer simulation results show that, in the reverse link, SC/DS-CDMA achieves better performance than MC/DS-CDMA because the pilot signal power in one sub-carrier for path search and channel estimation decreases as the number of sub-carriers increases. The superiority of MC-CDMA to MC(SC)/DS-CDMA is demonstrated, and the results show that, in the forward link, frequency Rake diversity with MC-CDMA is more effective than time Rake diversity with DS-CDMA in a broadband multipath fading channel due to a large amount of multipath interference View full abstract»

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  • Performance of variable rate bit interleaved coding for high bandwidth efficiency

    Publication Year: 2000 , Page(s): 2054 - 2058 vol.3
    Cited by:  Papers (10)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    We propose a bandwidth efficient error correction scheme, namely the variable rate adaptive bit-interleaved coded modulation (ABICM), for wireless mobile channel. The code rate and modulation level are varied according to the current channel state to exploit the time-varying nature of the wireless channel. Design challenges to achieve symbol-by-symbol adaptation and component codes design are addressed. A multi-level puncturing scheme is proposed to solve the problem of symbol-by-symbol puncturing and interleaving. The optimal adaptation thresholds are derived. It is found that there are significant gains relative to the fixed rate coding in terms of SNR and throughput. It is also found that the ABICM scheme is essentially not degraded in small interleaving depths. This makes the ABICM very suitable for real time applications View full abstract»

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  • Adaptive channel estimation with velocity estimator for W-CDMA receiver

    Publication Year: 2000 , Page(s): 2024 - 2028 vol.3
    Cited by:  Papers (6)  |  Patents (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    Adaptive channel estimation with velocity estimator is proposed for the 3rd generation cellular system called IMT-2000. By using the proposed velocity estimator, we can select the best channel estimation mode depend based on the estimated vehicular speed. The comparison of several channel estimation schemes is studied analytically. Then each channel estimation's capability depend on vehicular speed is cleared. We studied the velocity estimator for channel estimation control. We evaluated the velocity estimator and adaptive channel estimation with velocity estimator under a multi-speed environment. The proposed adaptive channel estimator can accomplish conflicting features, a wide vehicular speed range, low speed to 300 km/h, good SNR performance, and low power consumption for the user equipment View full abstract»

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  • Performance evaluation of a JCDMA/NC-PRMA protocol with load balancing assignment scheme

    Publication Year: 2000 , Page(s): 2198 - 2202 vol.3
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    A joint code division multiple access and noncollision packet reservation multiple access (JCDMA/NC-PRMA) protocol is proposed and investigated as an uplink access scheme for the third-generation mobile systems. Being the underlying TDMA architecture of the CDMA transmissions, NC-PRMA enables the base station to have a centralized control over the slot allocation policy. In order to reduce the multiple access interference (MAI) variation in CDMA transmission, load balancing (LB) slot assignment policy is proposed and evaluated. Simulation results show that considerable improvement can be achieved over the joint code division multiple access and packet reservation multiple access (JCDMA/PRMA) protocol, in which the multiple access interference variation is reduced by way of a dynamic permission probability for contending terminals View full abstract»

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  • Turbo equalization for non-binary coded modulation schemes over frequency selective fading channels

    Publication Year: 2000 , Page(s): 2217 - 2221 vol.3
    Cited by:  Papers (6)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (348 KB)  

    This paper presents a new method of equalizing and decoding multilevel coded modulation signals over frequency selective Rayleigh fading channels. A combined receiver using iterative (turbo) concept is proposed. Reliability information coming out of the soft-input soft-output (SISO) equalizer is used to get soft values at the output of the channel decoder. Specific extrinsic values out of the decoder are then fed back to the equalizer to be used as the a priori inputs. Through simulation, after only a small number of iterations (2-3), error performance of the combined receiver can be improved with good coding gains to compare with the case of separate equalizer and decoder for TCM and TTCM schemes View full abstract»

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  • Combined coding and spreading in downlink CDMA systems

    Publication Year: 2000 , Page(s): 2403 - 2407 vol.3
    Cited by:  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB)  

    Changing from orthogonal spreading codes in a direct-sequence CDMA (DS-CDMA) system to more powerful forward error correcting convolutional codes is proven superior in an asynchronous uplink system. This approach is referred to as code-spread CDMA (CS-CDMA). In this paper these two systems are compared in a synchronous downlink scenario. Both systems are assumed to operate over channels with nonzero delay spread, making it difficult to maintain orthogonality between users at the receiver. Using synchronous transmission, the DS-CDMA system is found to outperform the CS-CDMA system at high loads on all simulated channels. However, it is found that if the CS-CDMA system is allowed to transmit different users asynchronously through independent fading channels, like in an uplink scenario, it outperforms the synchronous downlink DS-CDMA system already on channels with modest delay spread View full abstract»

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  • Novel adaptive transmitter power and rate control schemes for W-CDMA systems

    Publication Year: 2000 , Page(s): 2103 - 2107 vol.3
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    This paper proposes novel adaptive power control and rate change schemes and investigates the performance of a wideband code division multiple access (W-CDMA) system in conjunction with these adaptive techniques. In these schemes, the power and rate are adapted to the variations of the fading channel as forecasted by a novel long-range prediction algorithm. This algorithm characterizes the channel as an autoregressive model with lower channel sampling rate compared to the conventional data rate methods of fading estimations. The performance of this scheme is evaluated using a detailed block diagram simulation of a W-CDMA system. All major components of the system are modeled and simulated, including an accurate model for realistic mobile channels. The performance of these systems is compared to that of a system without adaptive power and rate control. The proposed novel scheme is superior to the traditional approach of transmitter power control and rate change based on the channel estimation and signal to interference calculation at the receiver View full abstract»

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  • Simple inter-cell coordination schemes for a high speed CDMA packet downlink

    Publication Year: 2000 , Page(s): 1845 - 1848 vol.3
    Cited by:  Papers (3)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB)  

    We consider a CDMA cellular downlink that uses variable spreading gain to achieve different data rates for users based on their received SINRs. Such schemes are highly efficient, but are not “fair” in that there is great inequality of the data rates achieved by various users. We investigate several forms of inter-cell coordination as a means to improve the fairness, while minimally reducing the overall system throughput. One type of coordination uses predetermined “off” periods with reduced other-cell interference, and another type uses scheduled soft handoff periods View full abstract»

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  • On uplink power control using two-level channel inversion: scheme, performance, and optimal design in a cellular CDMA system for data traffic

    Publication Year: 2000 , Page(s): 1678 - 1682 vol.3
    Cited by:  Papers (3)
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    We propose and analyze a simple adaptive uplink power control scheme, two-level channel inversion, for data traffic in a cellular CDMA system. The basic idea is to reduce out-cell interference by reducing the rate of, or even suspending, user transmission when the wireless channel is in a bad condition. We present a probabilistic analysis model and then evaluate the queueing delay and system throughput. Numerical results show that in comparison with the traditional channel inversion scheme, the two-level channel inversion scheme can substantially improve the system throughput at a moderate cost of extra queueing delay. Finally, we present a design algorithm to optimize the overall performance View full abstract»

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  • Combined effect of coherent adaptive antenna array diversity receiver and fast transmit power control in W-CDMA reverse link

    Publication Year: 2000 , Page(s): 2147 - 2151 vol.3
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    Wideband direct sequence code division multiple access (W-CDMA), employing an adaptive antenna array is a very promising technique to reduce severe multiple access interference (MAI) from high rate users. We previously proposed a pilot symbol-assisted coherent adaptive antenna array diversity (PSA-CAAAD) receiver comprising an adaptive antenna array based on a minimum mean square error (MMSE) criterion and a RAKE combiner. In this scheme, the adaptive antenna array forms an antenna beam that tracks only slow changes in the directions of arrival and average powers of the desired and interfering user signals, while the RAKE combiner maximize the instantaneous signal-to-interference plus background noise power ratio (SINR). Although the PSA-CAAAD receiver has a significant effect on interference suppression in low signal-to-interference power ratio (SIR) (interference is large) channels, it is inferior to space diversity (SD) with maximal ratio combining (MRC) in a noise limited channel (high SIR) since the fading correlation of PSA-CAAAD receiver is almost 1 due to the small antenna separation. Therefore, we apply SINR-based fast transmit power control (TPC) in order to overcome this degradation. This paper presents an evaluation of the combined effect of the PSA-CAAAD receiver and SINR-based fast TPC in the W-CDMA reverse link based on laboratory and field experiments. The experimental results show that the combination of PSA-CAAAD and fast TPC is a powerful means to reduce severe MAI from high rate users in a low-to-high SIR environment and is more effective than using a SD receiver with the same number of antennas, i.e., the measured average bit error rate (BER) is improved by approximately one order of magnitude in the field experiment, when the target SINR of the desired user is 8 dB with 2 antennas at the average received SIR=-12 dB View full abstract»

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  • Delay estimation of code-spread CDMA systems

    Publication Year: 2000 , Page(s): 2029 - 2033 vol.3
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    Delay estimation of a code-spread code division multiple access (CS-CDMA) system using low-rate maximum free distance (MFD) convolutional codes for bandwidth expansion is studied. Using the repetitive structure of the low-rate MFD codes, the codewords are first permuted using a criterion based on the Cramer-Rao bound that results in good delay estimation properties. Thereafter, an approximate maximum-likelihood estimator that jointly estimate the channel gain, the codewords and the delay is used. Using the derived algorithm we show that it is in fact possible to estimate the delay in a code-spread system View full abstract»

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  • OVSF code channel assignment for IMT-2000

    Publication Year: 2000 , Page(s): 2188 - 2192 vol.3
    Cited by:  Papers (34)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    Code channel assignment deals with the problem that how different codes are allocated to different connections. In the 3GPP technical specifications, the channelization codes used for spreading are orthogonal variable spreading factor (OVSF) codes. It can preserve the orthogonality between user's physical channels. OVSF codes are valuable resources in CDMA systems and should be properly managed. The objective of this paper is to find a code channel assignment method to support as many users as possible with less complexity. We proposed a code channel assignment method for user equipment (UE) that has the capability to support multi-rate services using multi-code transmission. A single table is used to allocate codes to a UE according to its requested data rate. Therefore, the allocation and releasing procedures, which can be accomplished in a very short period of time, are efficient View full abstract»

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  • Capacity enhancement with adaptive arrays in a CDMA-based LEO satellite system

    Publication Year: 2000 , Page(s): 1979 - 1982 vol.3
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    The capacity enhancement achieved by adaptive antenna arrays at the base station in a CDMA-based multi-beam LEO system is investigated. The system outage probability is evaluated based on a comprehensive analysis of multiple access interference which includes the effects of power control algorithm, the channel fading and shadowing, and the antenna characteristics. Because the statistically optimal beams can be formed by adaptive arrays, the severe multiple access interference in satellite CDMA can be significantly suppressed. The numerical results demonstrate that there is a substantial increase in the uplink capacity by employing adaptive arrays at the base station View full abstract»

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  • Performance impact of limited downlink dynamic range of power control on 3G WCDMA

    Publication Year: 2000 , Page(s): 2413 - 2417 vol.3
    Cited by:  Papers (1)
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    This paper investigates the behavior of the signal-to-interference-plus-noise requirement as a function of the average transmitted power for the downlink of a WCDMA voice or 384 kbps data bearer in a pedestrian environment. It is shown that variations of the requirement as a function of the link loss are significant and should be accounted for in assessing the downlink capacity or service footprint View full abstract»

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  • Performance of list Viterbi equalizers with metric-criteria combining

    Publication Year: 2000 , Page(s): 1869 - 1873 vol.3
    Cited by:  Patents (1)
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    This paper discusses performance of a list Viterbi equalizer (LVE) employing a metric-criteria combining (MCC) scheme, which weighted-combines the squared Euclidean metric and the modified metric proposed by Ungerboeck (1974). First, it evaluates hardware implementation aspects of LVEs. Next, it discusses performance aspects of the metric criteria. Finally, it is confirmed by computer simulation that MCC-LVEs can cope with the path diversity gain at relatively small hardware complexity in the presence of wide spread ISI and MCC-LVEs with diversity reception improve the packet error rate (PER) performance even if there exist large number of effective fading paths View full abstract»

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  • Temporal variations characterization for fixed wireless at 29.5 GHz

    Publication Year: 2000 , Page(s): 2178 - 2182 vol.3
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (420 KB)  

    The reliability of the communication channel is one of the most important issues for successful deployment of LMCS/LMDS systems. This paper focuses on the temporal variations of the signal because of passing vehicles and foliage movement imparted from wind. CW measurements at 29.5 GHz with the transmitter and receiver at fixed locations were carried out for a maximum distance of 1.5 km between transmitting and receiving antennas. The presented results include power profile at various locations, cumulative distribution function of received signal strength, autocorrelation function, power spectral density, level crossing rates, duration of fades and interfade statistics. The Kolmogrov Smirnov test is also performed to find the closeness of the acquired data with standard fading channel models View full abstract»

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  • Achievable bit rates of DMT and FMT systems in the presence of phase noise and multipath

    Publication Year: 2000 , Page(s): 2108 - 2112 vol.3
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    We examine a modulation technique related to orthogonal frequency division multiplexing (OFDM), called filtered multitone (FMT) modulation, which exhibits significantly lower spectral overlapping between adjacent subchannels than other OFDM schemes like discrete multitone (DMT). In particular, we compare FMT and DMT systems in the presence of phase noise due to the frequency down-conversion circuit, as well as multipath fading of the radio channel. As a measure of system performance we consider the achievable bit rate, which is given by the sum of the bit rates each subchannel is eligible to deliver with a certain bit error probability View full abstract»

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  • Cellular network capacity planning using the combination algorithm for total optimisation

    Publication Year: 2000 , Page(s): 2512 - 2516 vol.3
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB)  

    The combination algorithm for total optimisation (CAT) is proposed to support smooth upgrading of third generation systems and to fulfil the requirements of current cellular networks. The CAT algorithm solves the problem of base-station location in different environments. Until now experiments were based on simple statistical propagation models such as Okumura-Hata. In this paper new results based on the use of a more complex ray-tracing approach combined with inhomogeneous capacity requirements are presented and discussed. Example results are given for various capacity and coverage targets View full abstract»

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  • Performance analysis of a CDMA network with mixed traffic using unequal power control

    Publication Year: 2000 , Page(s): 1683 - 1687 vol.3
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    This paper considers the effect of unequal power control in direct sequence CDMA cellular networks in the reverse direction to achieve differentiated quality of service. In particular, power control can be used to maintain the required Eb/I0 for a given type of traffic to meet the desired service quality. Here, an analytical approach is used to determine the probability of outage when two types of traffic with different quality of service requirements coexist. Results are presented for systems with equal and unequal power control View full abstract»

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  • A new MSE approach for combined linear-Viterbi equalizers

    Publication Year: 2000 , Page(s): 1707 - 1711 vol.3
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Combined linear-Viterbi equalization (CLVE) is a technique that employs a linear pre-filter in conjunction with the Viterbi algorithm (VA) to mitigate the effects of intersymbol interference. The aim of the linear pre-filter is to shape the original channel impulse response to some shorter desired impulse response (DIR) in order to reduce the complexity of the VA. In this paper, we present a new MSE based approach for optimizing CLVEs. This approach takes advantage of the modifications to the VA which are suitable for channels having coarsely located coefficients. Specifically, the new approach has the flexibility in choosing the positions and optimizing the values of nonzero coefficients of DIR. As a result, it includes the conventional MSE-based approaches as a special case. Simulation results have been presented to illustrate the performance of proposed method View full abstract»

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  • Sectoring of a locally centralized communication system in an indoor environment

    Publication Year: 2000 , Page(s): 2384 - 2388 vol.3
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    Future indoor communication systems will support different services with varying quality demands. Centralized radio resource management (RRM) is suitable for these types of systems. With central control the existing users can be protected and given priority over new allocations. The drawback is generally considered to be increased complexity. By dividing the coverage area into smaller segments using multiple controllers, the computational complexity can be reduced. The price for reduced complexity is lost capacity compared with a single controller system. We introduce sector antennas in a locally centralized radio communication system covering one building floor and investigate their ability to increase the capacity with maintained low complexity. The results show that the capacity can be almost as high for a sectorized system with two central units as for a system using one central unit covering the floor with omnidirectional antennas. The results also indicate how well the studied wireless system can coexist with similar systems located in the vicinity. Sectoring reduces the transmitter powers and therefore improves the performance of closely located wireless networks View full abstract»

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