A low loss magnetic plate positioned near an antenna is proposed to increase radiation efficiency of cellular phones. This magnetic plate is used to control the nearby magnetic field around the cellular phone's antenna, and this field controlling is shown to be effective for the improvement of radiation efficiency and far-field pattern. As for the material design of the plate, a magnetic plate having high µr and low µr" (complex relative permeability: µr = µr - j µr") is found to be effective for achieving high performance. In our sample fabrication, a low loss magnetic sample with µr = 5.7 - j 0.7 at 900 MHz is realized. It is demonstrated that this low loss sample contributes to increased efficiency and improved far-field characteristics.

Mobile IP can provide macro mobility for a mobile node (MN) instead of the original IP communication. Since the orignal Mobile IP does not consider micro mobility, it can not avoid handoff latency. The latency causes packets loss or large variations of the delivery times. To prevent it, several methods are proposed to improve the orignal Mobile IP handoff method. In our previous work, we proposed the fast registration method which enabled an MN to have two communication routes from the home agent (HA), and realized lower latency in the handoff procedures by the doublecasting on the two communication routes. But, the simulation results also show that the proposed method still has large overhead. This paper presents a seamless handoff method, which improves the fast registration method. In the method, the MN can know the first and second suitable base stations for the communications through information from the MAC media. The control helps for seamless handoff in case that the MN must frequently change its current base station (BS). The computer simulations for Constant Bit Rate (CBR) over real-time transport protocol (RTP) flow shows that the proposed method provides no handoff latency with low overhead even if the MN must occur frequent handoffs in a second.

Understanding traffic characteristics in mobile communications is invaluable for planning, designing, and operating cellular networks, and various mobility models have therefore come to be developed to predict traffic characteristics. In this paper, cell-dwell-time distribution and transition probability in a virtual cellular system are first estimated from the results of measuring taxi motion using the Global Positioning System (GPS) for large-city and small-city ranges of motion. Then, on the basis of simulations using these estimations, traffic characteristics like handoff rate and channel blocking probability in a cellular system are evaluated. It was found that a difference between large and small cities could be observed in speed distribution and direction-of-travel probability, but only a slight difference in cell-dwell-time distribution.

The third generation cellular system will provide high bandwidth data service and multimedia applications are proposed on the high-speed data link. On the other hand, cellular handsets are getting equipped with a short-range radio communication device that is mainly targeted to connect cellular handsets to computers. In this paper, we propose a percolating data delivery mechanism for a cellular-ad hoc integrated network utilizing multicast/broadcast communication, which is endorsed by data synchronization, and single-hop ad hoc networks for information shower/exchange services. The mechanism lessens data traffic in both the cellular and the ad hoc network for data delivery and tolerates unexpected disconnection in the ad hoc network. The mechanism also compensates data delivery in areas out of the cellular service. Our implementation of the data delivery mechanism utilizes Bluetooth for an ad hoc network configuration, and delivers data in the cellular network to the Bluetooth ad hoc network via the data synchronization mechanism. We evaluate communication traffic and delivery time on the prototype system and discuss about the efficiency of the mechanism.

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.

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.

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.

In this paper, we present an alternative design, RBMoM (Range-Based Mobile Multicast), for efficiently supporting multicast for mobile hosts on the Internet. The current version of Mobile IP proposes two approaches to support mobile multicast, which are remote subscription and bi-directional tunneling. The former provides the shortest routes for delivery of multicast datagrams to mobile hosts; the latter hides host mobility from all other members of the group (therefore, no any overhead in the multicast tree maintenance). RBMoM intends to trade off between the shortest delivery path and the frequency of the multicast tree reconfiguration by controlling the service range of the multicast home agent (MHA). Actually, we will find that remote subscription and bi-directional tunneling are the extremes of RBMoM. From the point of view of the MHA and the service range concepts, RBMoM is a generalization of both approaches and a unifying mobile multicast approach. The simulation results show that RBMoM can adapt to the fluctuation of both host movement and the number of mobile group members, and has much better performance than the current two IP mobile multicast solutions.

This paper describes the results of a series of laboratory experiments for performance evaluations of our proposed Maximum Likelihood Sequence Estimation (MLSE) based interference canceller, the Interference Canceling Equalizer (ICE), which can cancel both co-channel interference (CCI) and inter-symbol interference (ISI). To verify the feasibility of ICE for the Japanese cellular communications system, a standard of which has been released under the name of Personal Digital Cellular (PDC) system, a prototype system was constructed using 27 TI TMS320C40 Digital Signal Processor (DSP) chips. The ICE prototype works in real-time on the PDC air interface, major specifications of which are π/4 QDPSK 21 k symbols/s 3-channel time-division multiple-access (TDMA). Two-branch diversity reception is used to enhance the signal detection performance of ICE. In the experiments, BER performances were evaluated using the prototype system. Under a single-path Rayleigh fading and a single CCI condition, the ICE receiver attains the BER of less than 310-2 with the negative values of the average CIR: for fD = 5 Hz and 40 Hz, the average CIR more than -20 dB and -10 dB, respectively. Under a double-path Rayleigh fading and a single CCI condition, the ICE receiver attains the BER of less than 1.510-2 with the negative values of the average CIR: for fD = 5 Hz and 40 Hz, the average CIR more than -20 dB and -10 dB, respectively. The laboratory test results suggest that the ICE receiver has potential for system capacity enhancement.

The reverse-link of the DS-CDMA cellular system requires transmit power control (TPC) and diversity reception. This paper develops the expression of the received signal-to-interference ratio (SIR), and evaluates the outage probability using the Monte Carlo simulation to obtain the link capacity. The link capacities with received signal strength (SS)-based TPC and SIR-based TPC are compared. This paper investigates the required maximum and minimum transmit powers and the capacity gain of the SIR-based TPC over SS-based TPC as well as the effect of the diversity reception on the link capacity and transmit power. The reverse-link capacity is compared with the forward-link capacity to check the balance of capacities between both links.

In this paper, we propose a mathematical model for one-dimensional finite linear cellular automata and show connections between our model and the classical one. We then demonstrate, through some examples, that our model is a useful tool for analyzing one-dimensional finite linear cellular automata. We also extend this model to the D-dimensional case and give an algebraic characterization for it.

This study presents two new bit-parallel cellular multipliers based on an irreducible all one polynomial (AOP) over the finite field GF(2m). Using the property of the AOP, this work also presents an efficient algorithm of inner-product multiplication for computing AB2 multiplications is proposed, with a structure that can simplify the time and space complexity for hardware implementations. The first structure employs the new inner-product multiplication algorithm to construct the bit-parallel cellular architecture. The designed multiplier only requires the computational delays of (m+1)(TAND+TXOR). The second proposed structure is a modification of the first structure, and it requires (m+2) TXOR delays. Moreover, the proposed multipliers can perform A2iB2j computations by shuffling the coefficients to make i and j integers. For the computing multiplication in GF(2m), the novel multipliers turn out to be efficient as they simplify architecture and accelerate computation. The two novel architectures are highly regular, simpler, and have shorter computation delays than the conventional cellular multipliers.

To provide cellular data services with differentiated QoS, a shared resource scheme, based on the optimization theory and LaGrange λ-calculus was developed. This scheme can generate a fair schedule for a diverse mix of traffic with diverse QoS requirements in a limited radio spectrum. We define the acceptance indication, AI, as the QoS measurement for the shared resource scheme. The experimental results show that this approach outperforms other existing schemes.

A hybrid system in which mobile terminals (MTs) themselves select whether to communicate directly or via base stations (BSs) from communication conditions, "cellularad-hoc united communication system," has been proposed by the authors. It has been confirmed to have effective channel usage and battery consumption, especially for MTs which tend to communicate with partners which are close together, such as operational mobile robots. In this paper, the hybrid system is examined with respect to handoff rate. This hybrid system uses two modes, a cellular mode and an ad-hoc mode. The former mode is for communication using BSs and the latter is for direct communication. Thus, there will be two kinds of handoffs. One is the ordinary one between BSs and the other is between the two modes. Such a system may suffer from frequent handoffs. Thus the handoff rate of the system was examined. However, by the addition of a simple hysteresis characteristic, the handoff rate was held down closer to that of a pure cellular system in a multipath environment.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

Cellular Digital Packet Data (CDPD) provides wireless data communication services to mobile users by sharing unused RF channels with AMPS on a non-interfering basis. To prevent interference on the voice activities, CDPD makes forced hop to a channel stream when a voice request is about to use the RF channel occupied by the channel stream. The number of forced hops is affected by the voice channel selection policy. We propose analytic models to investigate the CDPD channel holding time for the the least-idle and random voice channel selection policies. Under various system parameters and voice channel selection policies, we provide guidelines to reduce the number of forced hops.

We investigate traffic performance of CBWL schemes with multimedia services on non-homogeneous cellular network in which cut-off priority is given to handoff calls. Two generic routing schemes are analyzed: one is the randomized routing and the other is the least loaded routing. The performance measures that we focus on are the new call blocking probabilities and the handoff failure probabilities. To evaluate blocking probabilities of interest, we construct a generalized access network whose blocking probabilities are same as ones for CBWL systems. For analysis of generalized access network, we apply the reduced load approximation. The computational complexity and memory requirements of proposed algorithm are linear so that we can use this algorithm to approximate blocking probabilities of CBWL systems of large size. The proposed approximations are tested on a number of simple examples. Numerical results for 12 cells and 36 cells networks are given. The comparison between approximation and simulation results shows that the proposed approximation method is quite accurate.

We analyze the performance of soft handoff used as intergroup handoff in the fiber-optic cellular system. Performance is evaluated in view of blocking and handoff refused probability. The numerical results show that the smaller the handoff region or the more the channel, the larger the system capacity.

In this work, distributed dynamic channel assignment strategies with violation to the reuse pattern using vehicular mobility information for highway microcellular environments are proposed. It is shown that, when vehicular mobility information is included in the acquisition channel policy, the outage probability degradation because of the use of channels with one violation to the reuse pattern is negligible. Also, it is shown that, using different moving direction strategies it is possible to control the tradeoff between capacity and quality of service. The local packing algorithm (LP), was modified to allow the use of two different moving direction strategies with violation to the reuse pattern, resulting the VDLP1 and VDLP2 algorithms. The characteristics of user mobility are considered and a free-flowing vehicular traffic is assumed. Simulation results show that the use of vehicular mobility information in the distributed dynamic channel algorithms with violation to the reuse pattern, produce a considerable increase in the system capacity at the expense of an insignificant degradation of the quality of service. For a grade of service (GOS) of 0.1, the VDLP1 and VDLP2 carry 4% and 1.5% more traffic than the maximum packing algorithm, respectively. For the same GOS, the VDLP1 and VDLP2 carry 68% and 64% more traffic than the fixed channel assignment algorithm, respectively.

A new computational method for evaluating the reverse-link interference distribution in a cellular CDMA system is proposed. In particular, a positive feedback effect of the reverse-link closed-loop power control has been taken into account to precisely capture a realistic effect of unequal cell loading on system capacity. It subsequently facilitates computing the frequency reuse efficiency of the cellular CDMA system under unequal cell loading.