A new half-power beam width (HPBW) base station (BS) antenna is described for use in 26 GHz- and 38 GHz-band point-to-multipoint (P-MP) fixed wireless access (FWA) systems which is narrower than the conventional design, and which efficiently meets the prescribed carrier-to-thermal noise power ratio (C/N) quality requirements. This development results in a reduction in antenna volume and the installation costs of the system. The validity of the new design in terms of C/N, carrier-to-interference signal power ratio (C/I) performance and the visibility of the propagation path are estimated.

Research on the propagation characteristics in the microwave band aiming at broadband mobile services is attracting much attention. Typical examples are the Unlicensed-NII (U-NII) band in the U.S. and HIPER-LAN band in Europe, i.e. 5.2 GHz. An efficient approach to revealing the propagation characteristics in the 5-GHz band is to utilize the existing propagation data accumulated by many researchers on the 2-GHz band. This paper presents the differences in path loss between the 5.2-GHz and 2.2-GHz bands in a residential area by using a 5.2-GHz/2.2-GHz dual band antenna. This antenna enables a direct comparison of 5.2 GHz and 2.2 GHz in terms of the propagation characteristics. We found that the difference in path loss between the 2.2-GHz and 5.2-GHz bands depends on only the base/mobile station antenna height. Based on this, we formulate the relationship between the heights of the base/mobile station antennas and the difference in path loss between the 2.2-GHz and 5.2-GHz bands.

It is difficult for an adaptive array to reduce interference signals efficiently from received signals when the interference signals and desired signal are closely located. This is a problem for a spatial division multiple access (SDMA) system using the multibeam adaptive array as a multiuser detector. In this paper, we propose a space domain multistage interference canceller (SD-MIC) for the SDMA system. Its performance is evaluated by computer simulations, assuming Japanese personal handy phone system (PHS) uplink environments. The results show remarkable improvement in high spatial correlation situations.

This paper reports the field test performance of a base station (BS) equipped with a linear parallel multi-stage interference canceller for uplink of wideband CDMA in a suburban area. The field test was performed with one desired mobile station (MS) moving around the BS, and three fixed interfering MSs having a target SIR 11 dB higher than that of the desired MS. The field test clearly demonstrates that using interference cancellation with a proper suppression factor (or weighting factor), can reduce the transmission power of the desired MS by around 6 dB. This performance was also compared with calculated data and the interference canceller was verified to function as theoretically expected. The receive power capture ratio was estimated at around 96%. This paper therefore establishes that interference cancellation performance of CDMA systems in the field can be found by estimating the receive power capture ratio and the theoretical results of interference cancellation.

We propose a method to represent non-binary error patterns for Reed-Solomon codes using a trellis. All error patterns are sorted according to their Euclidean distances from the received vector. The decoder searches through the trellis until it finds a codeword. This results in a soft-decision maximum likelihood algorithm with lower complexity compared to other known MLD methods. The proposed MLD algorithm is subsequently modified to further simplify complexity, reflecting in a slight reduction in the error performance.

This paper presents a new and robust technique for a coarse frequency offset estimation in OFDM system. As an evaluation of the proposed algorithm, we apply it to Eureka 147 DAB system. The proposed coarse frequency offset estimation algorithm is based on the differential detection technique between adjacent subcarriers to eliminate the phase shift effects of symbol timing offset and fractional frequency offset. Coarse frequency offset is determined from the correlation outputs between a received intercarrier differential phase reference symbol and several locally generated but frequency shifted intercarrier differential phase reference symbols. The performance of our estimation algorithm is evaluated by means of computer simulation and compared with that of previous proposed algorithms for DAB transmission modes I, II, III and IV. Simulation results show that the proposed algorithm generates extremely accurate estimates with a low complexity irrespective of the symbol timing offset.

This paper compares the packet error rate (PER) performance of three access schemes, i.e., single-carrier (SC)/DS-CDMA, multi-carrier (MC)/DS-CDMA, and MC-CDMA assuming an 80-MHz bandwidth in order to achieve an optimum broadband packet wireless access scheme. In a broadband propagation channel, severe multipath interference degrades the accuracy of timing detection of multipath components (path search) and channel estimation required 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 required for path search and channel estimation decreases as the number of sub-carriers increases. The superiority of MC-CDMA to MC (SC)/DS-CDMA in the forward link is also demonstrated, because frequency diversity is effectively utilized in association with the mitigation of a much longer symbol duration than the delay spread in MC-CDMA, meanwhile a higher degree of multipath interference offsets the Rake time diversity in MC (SC)/DS-CDMA in a broadband multipath fading channel.

This paper experimentally evaluates the bit error rate (BER) performance of single-carrier broadband DS-CDMA (B-CDMA) scheme using a 100-MHz bandwidth (chip rate of 81.92 Mcps) in frequency-selective multipath fading channels. The achievable information bit rate is 20.36 (2.5) Mbps when the spreading factor (SF) is SF = 4 (32). In order to achieve a high data-rate transmission with high quality (i.e., average BER is below 10^-6), we apply pilot symbol-assisted coherent Rake receiving with a large number of Rake fingers (maximum number of Rake fingers is SF2), 2-branch antenna diversity reception, convolutional coding, and signal-to-interference power ratio (SIR) measurement-based fast closed-loop transmit power control (TPC). Experimental results show that the average BER of 10^-6 for the 20.36 (2.5)-Mbps transmission is achieved at the required average transmit E_b/N₀ of approximately 6.7 (5.0) dB when the number of multipaths is L = 2 and the maximum fading Doppler frequency is f_D = 20 Hz. We also show that Rake time diversity and fast TPC are effective in a broadband propagation channel where many resolvable paths (such as 12 paths) are observed.

This paper evaluates through laboratory and field experiments the combined effect of the coherent adaptive antenna array diversity (CAAAD) receiver and signal-to-interference plus background noise ratio (SINR)-based fast transmit power control (TPC) in order to improve performance beyond that of space diversity (SD) with maximal ratio combining (MRC) in all low-to-high signal-to-interference power ratio (SIR) channels in the W-CDMA reverse link. Although the previously proposed CAAAD receiver comprising an adaptive antenna array based on the minimum mean square error (MMSE) criterion and a coherent Rake combiner was very effective in suppressing interference in low SIR (interference is severe) channels, SD employing MRC in noise limited channels (high SIR) outperformed the CAAAD because of its uncorrelated reception of fading variation due to its large antenna separation. The laboratory experimental results showed that the required average transmit signal energy per bit-to-background noise spectrum density (E_b/N₀) with the CAAAD receiver using fast TPC is lower than that with an SD receiver over a wide range of maximum Doppler frequency values from f_D = 5 Hz to 500 Hz in a low-to-high SIR channel. The results of the field experiments also showed that combining CAAAD and fast TPC is a powerful means to reduce severe multiple access interference (MAI) from high rate users in a low-to-high SIR environment and is more effective than using the SD receiver with the same number of antennas, i.e., the measured BER was improved by approximately one order of magnitude, when the relative transmit power of the desired user was 8 dB with two antennas at the average received SIR at the antenna input of -12 dB.

This paper proposes an inter-cell site diversity scheme based on 2-step selection combining (SC) and investigates through experimentation the effect of inter-cell site diversity in the transmit power-controlled wideband direct sequence code division multiple access (W-CDMA) reverse link. In the proposed algorithm, the decoded data sequence after soft-decision Viterbi decoding at each base station (BS) is transferred via the backhaul (wired line between BS and radio network controller (RNC) simulator) to the RNC simulator accompanied by reliability information of cyclic redundancy check (CRC) results per frame and the average signal-to-interference power ratio (SIR) calculated over the interleaving interval. The 2-step SC for each frame is performed at the RNC simulator using these two types of reliability information. We conclude from the laboratory experiments that the transmit power of a mobile station (MS) can be decreased since the selection period, T_SEL, is shorter irrespective of the interleaving length, T_ILV, and that the required transmit power of a MS satisfying the average BER of 10^-3 in inter-cell site diversity among 2 and 3 cell sites can be decreased by approximately 1.0 (0.5) dB and 1.3 (0.7) dB for fading maximum Doppler frequency f_D = 5 (80) Hz, respectively, compared to a one-site connection (T_ILV = 80 msec, T_SEL = 10 msec, path loss difference between 2 BSs and MS is 0 dB). We also confirmed by field experiments that the required transmit power of a MS in inter-cell site diversity between 2 cell sites can be decreased by approximately 2.0 dB compared to that of a one-site connection.

In order to increase the link capacity in the wideband direct sequence code division multiple access (W-CDMA) reverse link, employing a parallel-type coherent multi-stage interference canceller (COMSIC) is more practical than employing a serial (successive)-type due to its inherent advantage of a short processing delay, although its interference suppression effect is inferior to that of the serial-type. Therefore, this paper proposes a parallel-type COMSIC with iterative channel estimation (ICE) using both pilot and decision-feedback data symbols at each canceling stage in order to improve the interference suppression effect of the parallel-type COMSIC. Computer simulation results demonstrate that by applying the parallel-type COMSIC with ICE after FEC decoding, the capacity in an isolated cell can be increased by approximately 1.6 (2.5) times that of the conventional parallel-type COMSIC with channel estimation using only pilot symbols (the MF-based Rake receiver) at the required average transmit E_b/N₀ of 15 dB, i.e. in the interference-limited channel. The results also show that, although the capacity in the isolated cell with the parallel-type COMSIC with ICE after FEC decoding is degraded by approximately 6% compared to that with the serial-type COMSIC with ICE after FEC decoding, the processing delay can be significantly decreased owing to the simultaneous parallel operation especially when the number of active users is large.

In this paper, CAC (Call Admission Control) algorithms where decisions are based on total received power for the reverse link in CDMA systems with multiple types of services are proposed. The proposed CAC schemes have advantages in that they have control over the cell load dynamically and guarantee the required SIR, that is, QoS (quality of service). The optimal ratio of required transmission power that achieves the maximum capacity is derived for evaluating the cell load and SIR (signal to interference ratio) reflected in total received power at base stations. Allocation of different thresholds can be made for different services which can be regarded as priority based schemes. Two types of services, voice and data, are considered and the maximum throughput is obtained when threshold values are the same. In addition, the transmitter removal scheme is adopted that eliminates calls when the system does not meet the required SIR. Simulation results are provided to evaluate the performance.

As mobile communication systems have been widespread and the needs for new service grows, IMT-2000 systems have largely been researched and developed for standardization. Among them, Wideband CDMA (WCDMA) solution is standardized in the 3rd Generation Partnership Project. In WCDMA system, voice and high data rate services are supported through dedicated traffic channels, however other packet based services with short duration are provided by using common channels. Data users are allowed to transmit a short message based on a contention manner via the reverse common channels. The basic Common Packet Channel (CPCH) mechanism has been proposed and adopted for accessing common channels. It consists of three phases: Random Access Phase, Collision Resolution Phase, and Data Transmission Phase. To enhance the resource usage efficiency, the CPCH mechanisms with channel assignment or status monitoring have been proposed. They can improve the performance, however increase the system complexity. Up to now, performances of the CPCH mechanisms have been discussed and studied based on computer simulations. Numerical results have been obtained by using S-G analysis, but they are different from simulation results. In this paper, we analyze the CPCH mechanisms by using the Equilibrium Point Analysis (EPA). And we compare computer simulation results with analytical results.

Automatic repeat request (ARQ) for wireless ATM (WATM) operating at 20 Mbit/s or higher is required to achieve high throughput performance as well as high transmission quality, i.e., low CLR (cell loss ratio). Selective Repeat (SR) and Go-Back-N (GBN) are typical ARQ schemes. Though SR-ARQ is superior to GBN-ARQ in throughput performance, the implementation complexity of SR-ARQ's control procedures is disadvantageous to its application to high-speed wireless systems. In addition, when PDU (protocol data unit) length on wireless link is short, the capacity for ARQ control messages can be significantly large. GBN-ARQ, on the other hand, cannot avoid serious throughput degradation due to fairly high BER caused by multipath fading and shadowing, though its implementation is simple. To solve the above-mentioned problems, this paper proposes a novel ARQ scheme named PRIME-ARQ (Partial selective Repeat superIMposEd on gbn ARQ). PRIME-ARQ achieves high throughput performance, almost equal to selective repeat ARQ, with a simple algorithm resulting in reduced implementation complexity for high speed operation. This paper describes the design, implementation, and performance of the proposed PRIME-ARQ. In addition, it shows the experimental results using an experimental PRIME-ARQ hardware processor and proto-type AWA equipment.

In this article, we shall propose an efficient anonymous channel protocol for wireless communications. The most important feature of our proposed protocol has the property of untraceability. In our scheme, the mobile stations (MSs) and the home network (HN) must authenticate each other. Moreover, the HN is untraceable in such a way that supports location anonymity and MSs identity anonymity for MSs roaming, dynamic channel assignment and broadcasting. Compare our protocol with Juang et al.'s protocol, our mobile agent communication cost is 3m which is more efficient than the Juang et al.'s protocol 5m. At the same time, our mobile agent computation cost is 2T_h which is also more efficient than the Juang et al.'s protocol 1T_public+1T_h. We can avoid employing public key cryptography in the anonymous channel ticket authentication phase since to keep the computation cost down.

FDMA/TDMA non-geostationary earth orbit satellite systems (Non-GEOS) generally require a pre-planned pool of radio resource, i.e., frequency and time slot plan (FTSP), for each gateway earth station (GES) prior to the real-time channel assignment by the multiple GES's sharing the resources harmoniously. The time-variant nature of those systems implies that a dynamic FTSP planning method is crucial to the operation to cope with the time-variant traffic demand and the inter-beam interference condition. This paper proposes and compares three algorithms (Serial-numbering, DP-based, and Greedy algorithms) mixed with two strategies (concentrated- and spread-types) for the resource allocation. The numerical evaluation demonstrates that Greedy algorithm with the spread-type strategy is very effective and promising with feasible calculation time for the FTSP generation.

In software-based wireless multimedia communications systems, each mobile terminal will be able to select its best-suited transmission format according to its quality of service (QoS) and channel condition. In this paper, we focus attention on "access scheme selectability" in such a software-based system, and discuss the traffic performance improvement due to adaptive access scheme selection. Assuming a software-based TDMA/CDMA system where time division multiple access (TDMA) and direct sequence code division multiple access (DS-CDMA) schemes are flexibly selectable, we evaluate the traffic performance in terms of average delay with a typical multimedia service model to be supported in future wireless communications systems. In the TDMA/CDMA system, how to determine an appropriate access scheme for a user is a key issue. Therefore, we discuss the selection algorithm for efficiently supporting heterogeneous multimedia services. Our computer simulation results show that the software-based system with a simple access scheme selection algorithm can significantly improve the traffic performance as compared with conventional hardware-based systems.

A modified version of the SAGE algorithm is presented for joint delay-azimuth-attenuation parameters' estimation in a multiuser DS-CDMA system. The introduced modification consists of using different time interval lengths when calculating the time correlations for optimizing the different channel parameters. This modification was proposed for the purpose of a further reduction in the algorithm's computational weight in case of receiving sufficiently resolvable waves. Specifically, we found that short interval windows are sufficient for estimating delays and azimuth angles, which is quite effective in reducing the computational burden in their optimization processes. As for the estimation of the attenuation parameters, a longer time window, equal to the preamble length, is considered for more accurate estimation. Also two other estimators are proposed. The first one combining the modified SAGE with a sequential estimation of the attenuation parameters, suitable for slowly varying channels. Another one, similar to the first, and primarily designed to alleviate the influence of present strong interferers. Through a numerical example, the performances of the three presented estimation schemes, in terms of their near-far resistance, are compared. And it is shown that the proposed second combined estimator outperforms the modified SAGE in environments with high MAI levels.

In CDMA mobile cellular systems, wireless quality is improved by soft handoff techniques. However, it requires to hold multiple channels of cells, which is likely to increase call blocking at wired channels. It is therefore necessary to consider the entire system including the wired and wireless portions of systems for investigating an effectiveness of the soft handoff. In this paper, we also clarify the effect of interference power from mobile stations that are not in the soft handoff because of lack of wired channels. In the analysis, we model three-way soft handoff which has not been considered in past researches. We also show the effect of a call admission control to wireless quality.

In this paper, we propose an analytical procedure for the Erlang capacity in the reverse link of the DS-CDMA systems supporting voice and data services with the limited number of channel elements. Especially, we focus on IS-95B type systems with sectorized directional antenna that support the medium data rates for data traffic by aggregating multiple codes in both directions, to and from the mobile device. For the performance analysis, a 6-dimensional Markov chain model is developed, and the Erlang capacity is depicted as a function of the offered traffic loads of voice and data. The call blocking is caused not only by the scarcity of channel elements that perform the baseband spread spectrum signal processing for the given channel in the base station, but also by insufficient available channels per sector. The effect of the different Grade of Service (GoS) requirements on the Erlang capacity is observed, and the optimum values of the system parameters such as channel elements are selected with respect to the Erlang capacity. Furthermore, we expand our approach to the multi-FA systems that support multiple CDMA carriers more than one. It is observed that Erlang capacity for a high FA can be well estimated through the linear regression with the Erlang capacity results of low FAs.

A simplified analysis is presented for the reverse link maximum capacity trade-offs between each layer, spectrum efficiency and its multi-rate features of TDMA/W-CDMA and N-CDMA/W-CDMA overlaid systems with the perfect power control based on the measurement of signal-to-interference ratio (CIR). In order to suppress the multi-cross interference, the other important techniques used in the analysis are the ideal notch filtering and the signal level clipper for W-CDMA system transmitters and receivers. We firstly propose the concepts of the notch filtering depth and signal level clipping depth in the paper. The numerical results can be adopted as a guideline in designing the overlaid systems in the various cases as well as a means to investigate the flexibility of sharing of the spread spectrum and their feasibility in the future mobile communication system.

In cellular networks, the system performance can be degraded because of the inefficient use of channels with the two types of traffic, that is, the new call traffic and handover call traffic. This problem can be alleviated if the channels are used efficiently for new call traffic and handover call traffic. In this paper, we consider the proper ratio of the number of channels for new calls to the number of total channels denoted as α. We introduce the new call channel limiting technique incorporating velocity of mobile user. We model one-dimensional cellular networks and evaluate the performance in terms of the blocking probabilities, the probability of call dropping and the probability of incomplete call. We show with numerical examples that the system performance can be improved by selecting the appropriate α for various velocities of mobile users.

The cellular-communication systems of the future will be required to provide multimedia services to users moving about in a variety of ways (on foot, in automobiles etc.). Different forms of motion have different characteristics. The characterization of the different forms of motion and their effects on telecommunications traffic is important in the planning, design and operation of mobile communication networks. The characterization of the motion of various platform types (inter-city buses, recreational vehicles, freight trucks, and taxis) based on measurements using Global Positioning System is presented in this paper. The measured characteristics of motion are then used to evaluate teletraffic statistics such as cell cross-over rate and cell dwell time by overlaying hypothetical cell systems on the measured loci of vehicles. Self-similarity was discovered in the cell dwell time characteristic of the taxis.

This paper proposes an autonomous relay access algorithm that provides an intelligent wireless network structure for inter-vehicle communication systems. The proposed algorithm introduces a special classification among mobile terminals and assigns terminals to one of several terminal groups, which are adaptively and autonomously constructed according to traffic conditions. The proposed algorithm uses the terminal groups to conduct relay access transmission among terminals, and achieves a high rate of successful inter-terminal transmission. Computer simulation confirms that the proposed algorithm can achieve a lower blocking probability than that without a relay access scheme.

In this letter, we present a method to generate sets of sequences suitable for multicode transmission in quasi-synchronous (QS) CDMA systems. We focus on Gold code but extension to orthogonal Gold code is straightforward. We show that by appropriate classification of sequences, it is possible to have sets whose cross correlation is small in QS situations.

This paper discusses a communication system with a multiple-access channel where two users simultaneously send complex-valued signals in the same frequency-band. In this channel, ambiguity in decoding occurs when receiver trying to estimate each users' signal. In order to solve the ambiguity problem, a family of uniquely decodable code is derived in this paper. The uniquely decodable code is designed by using trellis-coded modulation (TCM) pair where the trellis structure of one TCM is a transformation of the other in the pair. It is theoretically proved that, with the proposed coding scheme, the composite received signal can be uniquely decomposed into the two constituent signals for any power ratio and any phase difference between the received two users' signals. Improvement of BER performance over non-uniquely decodable code is illustrated by computer simulation.

In this paper, a novel adaptive beamforming scheme is described. This scheme basically employs the GSC algorithm which is one of the famous adaptive interference suppression schemes. The implementation of the GSC algorithm requires complex computations due to the adaptive filtering. Therefore, we propose an efficient GSC algorithm based on the split RLS algorithm. In order to reduce the estimation error caused by the correlation between the splitted blocks, the modified GSC is employed with Walsh blocking matrix instead of Bi-diagonal one. In conclusion, the SINR of the proposed method is very close to the SINR obtained by the full tap solution, e.g. when the system complexity decreases nearly half, the SINR of the proposed method becomes 1 dB worse than that of full tap solution.

In designing WLAN MAC protocols, several issues must be considered. Among them, the hidden-terminal and exposed-terminal problems are two of the most important issues. The hidden-terminal problem has been analyzed by many researchers and significant improvements have been made. The exposed-terminal problem, however, has not been fully considered in the design of WLAN MAC protocols. In this paper, we propose two protocols. In the first one, referred to as channel splitting protocol, the channel is split into two subchannels--the control channel and the data channel--to solve several problems inherent in existing protocols, including hidden terminal and exposed terminal problems. With channel splitting, a control frame is transmitted through the control channel alternatively of a data frame which is transmitted through the data channel. In the second protocol, referred to as RTR/ATR reservation protocol, hosts that want to transmit data reserve several slotted data channels in advance to increase performance, while the first protocol reserves only one transmission. In the second protocol, control frames are transmitted through the control channel independently of data frames. The performance of the proposed protocols is evaluated by simulation and compared with existing protocols.

The CDMA system can provide more capacity than other systems and the hierarchical layer of cells is required for system design to provide a balance between maximizing the number of users perfrequency band and minimizing the network control associated with handoff. However, the co-channel interference from microcell to macrocell and vice versa in such a two-tier structure is different from that in a homogeneous structure. In order to avoid the serious interference, different RF channels should be used in microcell and macrocell in hierarchical structure. The efficient usage of multi-channels for macrocell and microcell is of primary concern herein. In this study, we investigate the channel segregation in a two-tier cellular system. Moreover, we intentionally arrange the procedures for the MS in macrocell and microcell to choose the channel. The macrocell's (resp., microcell's ) channels to be accessed are sorted into three priority groups. In order to justify the merits of the proposed channel segregation method, we define the following three performance measures including capacity gain, response to the variation of traffic loading and system stability. Under the condition of steady-state traffic load, capacity gain is 10% on the average. If the traffic load vary, the system can respond quickly and retrieve the borrowed channels with 2tp time interval as long as appropriate system parameters are chosen.

In this paper, we propose a generalized frequency assignment algorithm to minimize the intermodulation products caused by nonlinear amplification in satellite transponder. We also analyze the performance of proposed algorithms in terms of C/IM and execution time. Most of the published algorithms are too restrictive to be applied to the frequency planning of many realistic systems that are usually characterized by multi-level and/or multi-bandwidth. In developing the proposed "TDTI algorithm," we utilized and modified basic concepts of Okinaka's DELINS-INSDEL algorithm to extend its applicability from one-level systems to more general systems. We also propose a modified version of TDTI algorithm called "WTDI-SDELINS" to circumvent the problem of relatively long execution time.

As noncoherent direct sequence code-division multiple-access (DS-CDMA) mobile satellite communications, two typical transmission schemes are compared; one is a quasi-synchronous differential BPSK (QS-DBPSK) where orthogonal signals are used for reducing the multiple access interference and the other is M-ary orthogonal signaling (MOS) scheme where orthogonal signals are used for exploiting more efficient modulation. The performances are evaluated in additive white Gaussian noise (AWGN) and shadowed Rician fading (SRF) channels and the effects of timing misalignments in the QS-DBPSK system and the amount of Doppler shifts of a SRF channel are investigated. The results show that MOS much outperforms QS-DBPSK in the region of low system loading up to about 50% and a precise chip synchronization is required for QS-DBPSK. In a SRF channel, it is also shown that QS-DBPSK much outperforms MOS in a slow fading channel but MOS has a performance gain against the large Doppler shift.

We have developed a new traffic measuring tool and applied it to the real-time simulation of a network. It monitors IP traffic on an ATM link and continuously transfers the length and timestamp of each IP packet to a post-processing system. The post-processing system receives the data, estimates the cell's arrival epoch at the transmission queue of the ATM link, and simulates the queueing behavior on-line if conditions differ from those of the actual system. The measuring tool and real-time simulation represent a new approach to traffic engineering. A new estimation problem, the arrival sequence estimation, is shown and some algorithms are proposed and evaluated. Also, a new dimensioning algorithm called the queue decay parameter method, which is expected to be robust and applicable to real-time control, is proposed and evaluated.

A proper design and analysis of future wideband wireless communication systems require an accurate radio channel model. This model is claimed to characterize both the spatial and temporal channel characteristics. This paper investigates the spatio-temporal channel modeling based on a ray-tracing approach. The temporal channels are characterized by a delay profile. The statistical median and fading-fluctuation range of delay profiles are predicted from ray tracing by incorporating the random phase approach. A high level of agreement between predicted results and measured ones is observed in the verification. The spatio-temporal channel impulse response (CIR) predicted from ray tracing is also transformed to have limited band-width and limited beam-width characteristics. The applicability of this transformation is also verified by the comparison with measurement. These verifications prepare the ground for the use of ray-tracing approaches to evaluate system performance in real environments.

A feasibility study has been made of the detection possibility of radio wave noises, i.e., Martian atmospherics, emitted from discharges in the Martian atmosphere during large dust storms. The spacecraft NOZOMI, which was launched in 1998, is to be placed on an elliptic orbit around Mars with perigee of 150-200 km. An onboard-equipment LFA (Low Frequency Plasma wave Analyzer) has capability to measure the low frequency plasma waves in the frequency range from 10 Hz to 32 kHz. In order to know if the LFA can detect the atmospheric radio noises, the propagation characteristics of electromagnetic waves through the Martian ionosphere are studied theoretically by using a full-wave method. The ionosphere is modeled as a magneto-ionic medium based on the recent observations of magnetic anomaly by Mars Global Surveyor spacecraft, and the atmospheric constituent and electron density by Viking observations. Our calculation shows that the waves at frequencies less than a hundred hertz can propagate with low attenuation and reach to altitudes above 200 km in the whistler-mode in the regions of magnetic anomalies in the dayside ionosphere. It is shown that the radio noises emitted from electric discharge in an intense dust storm, with the intensity over -30 dBV/m/Hz at the ionospheric entry point, can be sensed by the LFA. The observational identification of Martian atmospherics will contribute to the physical study of charge/discharge process in the Martian atmosphere.

Many experimentally and theoretically based models have been proposed to predict, quantitatively evaluate, and combat the fading phenomenon in mobile communication systems. However, to the best of the authors' knowledge, up to now there is no objective method to determine which is the most suitable distribution to model the fading phenomenon based on experimental data. In this work, the Minimum Description Length (MDL) criterion for model selection is proposed for that purpose. Furthermore, the MDL analysis is performed for some of the most widely used fading models based on measurements taken in a sub-urban environment.

This paper proposes a media synchronization scheme with causality control for distributed multimedia applications in which the temporal and causal relationships exist among media streams such as computer data, voice, and video. In the scheme, the Δ-causality control is performed for causality, and the Virtual-Time Rendering (VTR) algorithm, which the authors previously proposed, is used for media synchronization. The paper deals with a networked shooting game as an example of such applications and demonstrates the effectiveness of the scheme by experiment.

In this paper, the performance of OFDM-CDMA system in mobile communication channels with different detection algorithms is evaluated in terms of the probability of bit error as a function of processing gain. Both the frequency diversity and multi-user interference (MUI) are taken into account. The simulation results show that MUI is the dominant factor that affects system performance, and MMSE outperforms the other algorithms. Based on the simulation results, a modified system scheme is proposed which performs better than the conventional method.

This letter presents a channel estimation and a DC-offset estimation technique in a short-ranged Bluetooth system. Each of the Bluetooth devices in the connection state knows the access codes used in the ad-hoc networks, which is utilized as a reference signal for the parameter estimation. The proposed estimators can be implemented without degradation of frame and spectral efficiency thanks to using the access code specified for the Bluetooth system.

In this paper, outage performance of a turbo-coded CDMA system is analyzed and simulated in a multiple-beam satellite channel. From the simulation results, it is confirmed that turbo coding provides considerable coding gain over an uncoded system. And, it is demonstrated that Max-Log-MAP decoding algorithm is most promising in terms of performance and complexity.

This letter presents a new transformation technique of series solution to asymptotic solution for a perfectly conducting wedge illuminated by E-polarized plane wave. This transformation gives an analytic manipulation example of the Weber-Schafheitlin integral for diffraction problem.

To reduce an amount of computation of full search algorithm for fast motion estimation, we propose a new and fast matching algorithm without any degradation of predicted images. The computational reduction without any degradation comes from adaptive matching scan algorithm according to the image complexity of the reference block in current frame. Experimentally, we significantly reduce the computational load compared with conventional full search algorithm.