Mobile communications have been developing rapidly in recent years. In Japan, a new digital cellular system and digital trunked radio system were introduced. Soon a new personal communication system and road information system will be introduced. Other than those systems, many new mobile communication systems are being developed. These are new pager systems, future public land mobile communication systems, wireless card system and anti-collision radar system etc.

The advance of mobile network and radio techniques has been rapidly expanding the service area for mobile terminals. Thus, mobile communications have been devoted to the improvement of terminal mobility (TM). Recently, the personal mobility (PM) concept appeared which gives a freedom to use personal telecommunication numbers at any terminal. Therefore, mobile network must next enable a user to access telecommunication services with his/her personal telecommunication number from any terminal at any geographic location. In other words, the mobile network must implement universal mobility (UM) that integrates TM and PM. This paper first provides a definition of UM. Next, it describes the identity and number configurations for UM and then presents network techniques for UM, i.e., the network architecture and UM management procedures. It also presents the current status of standardization on UM in the Personal Digital Cellular system (PDC) and Future Public Land Mobile Telecommunication Systems (FPLMTS).

In this paper, we evaluate the performance of handoff schemes in microcellular personal communication systems (PCS) which cater to both pedestrian and vehicular users. Various performance parameters, including blocking of new calls,channel utilization, handoff blocking and call termination probabilities for each user type are evaluated. We study different queuing disciplines for handoff calls and their impact on system performance. We also study the tradeoff in handoff blocking and call termination probabilities between user types as the handoff traffic carried by the system from each user type is varied.

The performance of a cellular CDMA system operating over a flat-Rayleigh fading channel was previously considered, where it was assumed that the coherent bandwidth of a channel exceeded the spread bandwidth of a signal. This assumption may not be correct for a large degree of spreading. Therefore, the channel is modeled as exhibiting frequency-selectivity. In this paper, we consider a cellular radio DS/CDMA system operating over a frequency-selective fading channel. The base-to-mobile link is modeled as a Rician fading channel, with all signals transmitted from a given base station fading in unison. A similar model for the mobile-to-base link is used, except that the waveforms from all users are assumed to experience independent fading. The capacity of the cellular radio DS/CDMA system operating over a frequency-selective fading channel is evaluated and compared to that over a flat Rayleigh fading channel.

In this paper, the spread spectrum code hopping (CH) system, which has some analogy to frequency hopping systems, is described. The CH system has robustness to code interference that restriction of kinds of PN matched filters (MFs) will cause. The mean acquisition time is shown by theoretical analysis and computer simulation. The acquisition rate results under a single code interference, which seriously affects direct sequence systems, and an asynchronous two-user channels are obtained. Moreover, using theoretical analysis and computer simulation, the bit error rate (BER) performance under single code interference is evaluated. It is shown that CH systems perform better than conventional ones under single code interference.

We consider slotted ALOHA systems with a controlled output power level. The systems were proposed to improve the throughput performance by the capture effect. However widely used linear modulation systems have no capture effect, and a power level distribution dominates the performance in those systems. In this paper we consider linear modulation systems employing PSK. We introduce an average error probability of the highest power signal as a performance measure, and a uniform distribution is applied to the error probability analysis. Numerical results show the superiority of the systems with uniform distribution to a conventional slotted ALOHA in a heavy traffic condition. On the other hand, in a light traffic condition, the optimal power distribution which minimizes the error probability is obtained for 2-level ALOHA. We also propose the power level selection method to search the optimal power level. The validity of analytical results are confirmed by simulations.

We investigate the multipacket message transmissions and variable length message transmissions in slotted ALOHA systems with capture effect. First, we propose an approach that the transmission power level is controlled probabilistically depending on message length for multipacket messages. We consider the multipacket messages model with capture. We derive explicit equations of the effective channel utilization of the model. It is demonstrated that if we increase the numbar of power levels, we can get more effective channel utilization of the system. Secondly, we propose how to assign the slot size and show that the effective utilization of the channel is improved for variable length messages using the approach proposed for multipacket messages. Channel design issue about length of the slot depending on the number of power levels used for transmission is discussed. Thirdly, we propose the multiple messages per slot model with capture. The analytical results show that the multiple messages per slot model can achieve the highest channel utilization among the models discussed in this paper.

Packet Reservation Multiple Access (PRMA) is emerging as a possible multiple access scheme for the forth-coming Personal Communication systems, due to its inherent flexibility and to its capability to exploit silence periods to perform a statistical multiplexing of traffic sources, often characterised by a high burstiness. On the other hand, the current trend in reducing cell sizes and the more complex traffic scenarios pose major planning problems, which are best coped with by adaptive allocation schemes. The identification of adaptive schemes suitable to operate on a shorter time scale, which is typical of packetised information, disclose a number of problems which are addressed in this paper. A viable solution is provided by a well-known self-adaptive assignment method (Channel Segregation), originally developed for FDMA systems, provided it is conveniently adapted for PRMA operation. Simulations show good performance, provided that values of some system variables are correctly chosen. These results encourage further studies in order to refine adaptive methods suitable for cellular, packet switched personal communications systems.

The applicability of Dynamic Channel Assignment methods to a Reuse Partitioning system in cellular radio systems is investigated in this paper. The investigations indicate that such a system has a tendency to increase the difference between blocking probability for the partitioning two coverage areas in comparison with the conventional Reuse Partitioning system employing Fixed Channel Assignment method. Two schemes using new Channel Rearrangement algorithms are also proposed in order to alleviate the difference as a disadvantage which gives unequal service to the system. The simulation results show that the proposed schemes are able to reduce the difference significantly while increasing the carried traffic by 10% as compared with the conventional system.

We compared--for the same propagation conditions and parameters--the performances of distributed dynamic channel assignment (DDCA) strategies and the performance of fixed channel assignment (FCA). This comparison quantitatively showed the effects of DDCA strategies in increasing spectrum efficiency. It also showed that using DDCA with transmitter power control (TPC) increases the system capacity to 3 4 times what it is with FCA and to 1.4 1.8 times what it is when using DDCA without TPC. We also evaluated the blocking rate and the interference probability for the inside of a cell and found that these are generally much higher close to the cell border than they are near the base station.

This paper presents a new structure for noise and echo cancelers based on a combined fast abaptive algorithm. The main purpose of the new structure is to detect both the double-talk and the unknown path change. This goal is accomplished by using two adaptive filters. A main adaptive filter F_n, adjusted only in the non-double-talk period by the normalized LMS algorithm, is used for providing the canceler output. An auxiliary adaptive filter F_f, adjusted by the fast RLS algorithm, is used for detecting the double-talk and obtaining a near optimum tap-weight vector for F_n in the initialization period and whenever the unknown path has a sudden or fast change. The proposed structure is examined through computer simulation on a noise cancellation problem. Good cancellation performance and stable operation are obtained when signal is a speech corrupted by a white noise, a colored noise and another speech signal. Simulation results also show that the proposed structure is capable of distinguishing the near-end signal from the noise path change and quickly tracking this change.

In the correspondence discrete Wigner higher order spectra (WHOS) of harmonizable random signals are addressed and their relations with polyspectra (HOS) are illustrated. It is shown, that discrete WHOS of a random stationary signal do not reduce to the aliased polyspectra in a similar way as Wigner distribution (WD) reduces to the power spectrum of a random signal. Wigner 2nd-order time-frequency distribution of deterministic signals and the 3rd-order spectrum of stationary signals are presented in their modified forms to be used to estimate time-varying third-order spectrum of discrete nonstationary random harmonizable processes.

A P-Fuzzy Switching Function is a meaningful class of fuzzy switching functions that is representable by a logic formula consisting of prime implicants. This paper aima at extracting knowledge represented as prime implicants from a given learning data. The main results are the necessary and sufficient conditions for the learning data to be representable with P-fuzzy switching functions, and to be determined by unique logic formula.

The dynamics of an artificial neural network derived from a biological system, and its two applications to engineering problems are examined. The model has a multi-layer structure simulating the primary and secondary components in the olfactory system. The basic element in each layer is an oscillator which simulates the interactions between excitatory and inhibitory local neuron populations. Chaotic dynamics emerges from interactions within and between the layers, which are connected to each other by feedforward and feedback lines with distributed delays. A set of electroencephalogram (EEG) obtained from mammalian olfactory system yields aperiodic oscillation with 1/f characteristics in its FFT power spectrum. The EEG also reveals abrupt state transitions between a basal and an activated state. The activated state with each inhalation consists of a burst of oscillation at a common time-varying instantaneous frequency that is spatially amplitude-modulated (AM). The spatial pattern of the activated state seems to represent the class of the input ot the system, which simulates the input from sensory receptors. The KIII model of the olfactory system yields sustained aperiodic oscillation with "1/f" spectrum by adjustment of its parameters. Input in the form of a spatially distributed step funciton induces a state transition to an activated state. This property gives the model its utility in pattern classification. Four different methods (SD, RMS, PCA and FFT) were applied to extract AM patterns of the common output wave forms of the model. The pattern classification capability of the model was evaluated, and synchronization of the output wave form was shown to be crucial in PCA and FFT methods. This synchronization has also been suggested to have an important role in biological systems related to the information extraction by spatiotemporal integration of the output of a transmitting area of cortex by a receiving area.

In this paper we present a design method for all-pass networks with consideration of the stability. It is based on the eigen filter method and Remez exchange algorithm is used to obtain the equiripple phase error solution. In the iteration of the proposed algorithm, the eigen values besides maximum eigen value are used in order to obtain a stable all-pass networks.

An adaptive joint-process IIR filter with generalized lattice structure is constructed. This filter can borrow both FIR and IIR features and simultaneously holds the well-known merits of lattice structure.