By using the gain expansive and compressive characteristics of two FET to compensate for the phase shift at large signal, one can greatly improve Adjacent Channel Power Ratio (ACPR) of the power amplifier. This 3 to 5 dB improvement result was verified experimentally by selecting the biasing point and the gain level of the first and second stage amplifiers. This MCM circuit-level technique is more attractive to achieve low cost and good ACPR design. As examples, some novel high efficiency power amplifiers with good ACPR for the handset applications are developed by this method. Those mass producible 0.12 cc volume (7.87.82.0 mm) multi-chip module power amplifiers (MCM PA) employ state-of-the-art enhancement GaAs HJFET devices that need only a single power supply.

In this paper, a multiuser receiver using a Hopfield network (Hopfield network receiver) for asynchronous codedivision multiple-access systems is proposed. We derive a novel likelihood function for the optimum demodulation of a data subsequence whose length is far shorter than that of the entire transmitted data sequence. It is shown that a novel Hopfield network receiver can be derived by exploiting the likelihood function, and the derived receiver leads to a low complexity receiver. The structure of the proposed receiver consists of a bank of correlators and a Hopfield network where the number of units is proportional to both the number of users and the length of a data sequence demodulated at a time. Computer simulation results are presented to compare the performance of the proposed receiver with those of the conventional multiuser detectors. It is shown that the proposed receiver significantly outperforms the correlation receiver, decorrelating detector and multistage detector, and provides suboptimum performnace.

This paper discusses encoding of vehicular position information using predictive algorithms in inter-vehicle communications (IVC) from the viewpoints of source coding and noisy channels. Two vehicular driving models are assumed; one is the 15-mode as a suburban rapid transit driving pattern, the other is called calming mode as a street-driving pattern. Three types of schemes are compared; a pulse code modulation (PCM) scheme, a predictive coding (PC) scheme, and the variable interval prediction (VIP) scheme that is proposed here. This paper assumes that precise position information is got from a positioning system, and that all the transmitters and receivers have common predictors. Performance comparisons of the three types of schemes are carried out both of noiseless and noisy channels. Results show that the VIP scheme is superior to any other scheme.

The recent progress in communication devices has reduced the cost of spread spectrum systems that have been mainly used in the military field, enabling the possibility of using spread spectrum systems for nonmilitary use. Nonmilitary communication networks are classified into two categories: public communication networks and consumer communication networks. At the present, the public communication network share is much larger than that of the consumer communication networks. Both of them will increase; however, the consumer communication network share will be comparable to the public one. The progress of consumer communications is due to inexpensiveness (without charge), user privacy, free design from regulations and advantages of local and small zone communications. To overcome fading, power restrictions, interference and interception is very important for its progress, One of the key technologies of consumer communications is the spread spectrum. Consumer communication networks are characterized by user possession of the network itself in addition to the possession of personal terminals. From the viewpoint of analogy between communication networks and transportation networks, "from public to individual" seems to be today's trend. Several spread spectrum applications for consumer communications in Japan have been introduced as follows: a home security system using power line communication as a wire spread spectrum communication system; a data carrier, a radio remote control, low-power radio systems and a clock rate modulation system as radio spread spectrum communication systems. In addition SAW device applications and digital signal processing applications are introduced.

In this paper, we propose a spread spectrum pulse position modulation (SS-PPM) system, and describe its basic performances. In direct sequence spread spectrum (DS/SS) systems, pseudo-noise (PN) matched filters are often used as information demodulation devices. In the PN matched filter demodulation systems, for simple structure and low cost of each receiver, it is desired that each demodulator uses only one PN matched filter, and that signals transmitted from each transmitter are binary. In such systems, on-off keying (SS-OOK), binary-phase-shift keying (SS-BPSK) and differential phase-shift keying (SS-DPSK) have been conventionally used. As one of such systems, we propose the SS-PPM system; the SS-PPM system is divided into the following two systems: 1) the SS-PPM system without sequence inversion keying (SIK) of the spreading code (Without SIK for short); 2) the SS-PPM system with SIK of the spreading code (With SIK for short). As a result, we show that under the same bandwidth and the same code length, the data transmission rate of the SS-PPM system is superior to that of the other conventional SS systems, and that under the same band-width, the same code length and the same data transmission rate, the SS-PPM system is superior to the other conventional SS systems on the following points: 1) Single channel bit error rate (BER) (BER characteristics of the SS-PPM system improve with increasing the number of chip slots of the SS-PPM system, and as the number of chip slots increases, it approaches Shannon's limit); 2) Asynchronous CDMA BER; 3) Frequency utilization efficiency. In addition, we also show that With SIK is superior to Without SIK on these points.

In this paper we consider multiuser detection using a neural network in a synchronous code-division multiple-access channel. In a code-division multiple-access channel, a matched filter is widely used as a receiver. However, when the relative powers of the interfering signals are large, i.e. the near-far problem, the performances of the matched filter receiver degrade. Although the optimum receiver for multiuser detection is superior to the matched filter receiver in such situations, the optimum receiver is too complex to be implemented. A simple technique to implement the optimum multiuser detection is required. Recurrent neural networks which consist of a number of simple processing units can rapidly provide a collectively-computed solution. Moreover, the network can seek out a minimum in the energy function. On the other hand, the optimum multiuser detection in a synchronous channel is carried out by the maximization of a likelihood function. In this paper, it is shown that the energy function of the neural network is identical to the likelihood function of the optimum multiuser detection and the neural network can be used to implement the optimum multiuser detection. Performance comparisons among the optimum receiver, the matched filter one and the neural network one are carried out by computer simulations. It is shown that the neural network receiver has a capability to achieve near-optimum performance in several situations and local minimum problems are few serious.

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.

In this paper, we build a microscopic simulator of traffic flow in a three-modal transport society for pedestrians/slow vehicles/vehicles (P/SV/V) to evaluate a post P/V society. The simulator assumes that the SV includes bicycles and micro electric vehicles, whose speed is strictly and mechanically limited up to 30 km/h. In addition, this simulator adopts an SV overtaking model. Modal shifts caused by modal diversity requires new valuation indexes. The simulator has a significant feature of a traveler-based traffic demand simulation not a vehicle-based traffic demand simulation as well as new evaluation indexes. New assessment taking this situation into account is conducted and the results explain new aspects of traffic flow in a three-mode transport society.

This paper describes a new individual identification system employing a novel application of the PC/SS scheme. Since the proposed system requires no magnetic information, it is robust to various changes in environment. Moreover, it is applicable to contemporary identification systems as an officer identifies one's face with the card's portrait at immigration. In addition, cooperation with existing identification systems using magnetic information and this proposed system provides more secure identification. The proposed system embeds a cardholder-related information that forms a watermark generated by the modulating manner of the PC/SS scheme into cardholder's portrait printed on the card using a simple watermarking scheme also proposed in this paper. Experimental results show that the proposed system extracts embedded information correctly as its fundamental ability. Furthermore, various properties of this system have been investigated, and it has been found that the spatial resolution of scanners is the most dominant to the performance of the proposed system.

This paper describes diffusion of electric vehicles and novel social infrastructure from the viewpoint of systems innovation theory considering both human society aspects and elemental technological aspects. Firstly, fundamentals of the systems innovation theory and the platform theory are mentioned. Secondly, discussion on mobility from the viewpoint of the human-society layer and discussion of electrical vehicles from the viewpoint of the elemental techniques are carried out. Thirdly, based on those, R & D, measures are argued such as establishment of the ubiquitous noncontact feeding and authentication payment system is important. Finally, it is also insisted that after the establishment of this system the super smart grid with temporal and spatial control including demand itself with the low social cost will be expected.

Synchronization has been one of the problems in M–ary spread spectrum communication systems. In this letter, we propose the frame synchronization method using the Hadamard matrix and a frame synchronization method of PCM communication systems. Moreover, we analyze the probabilities of keeping synchronous state and frame renewal rates, and we evaluate the relationship between these probabilities and the number of stages of counters.

This paper presents two new types of markers of M-CubITS (M-sequence Multimodal Markers for ITS; M-Cubed for ITS) that is a ground-based positioning system, in order to advance the WYSIWYAS (What You See Is What You Are Suggested) navigation environments providing intuitive guidance. One of the new markers uses warning blocks of textured paving blocks that are often at important points as for pedestrian navigation, for example, the top and bottom of stairs, branch points, and so on. The other uses interlocking blocks that are often at wide spaces, e.g., pavements of plazas, parks, sidewalks and so on. Furthermore, we construct the integrated pedestrian navigation system equipped with the automatic marker-type identification function of the three types of markers (the warning blocks, the interlocking blocks, and the conventional marker using guidance blocks of textured paving blocks) in order to enhance the spatial availability of the whole M-CubITS and the navigation system. Consequently, we show the possibility to advance the WYSIWYAS navigation environments through the performance evaluation and the operation confirmation of the integrated system.

The maximum amounts of embedded information that is important in practical system design of two watermarking methods based on the parallel combinatorial spread spectrum (PC/SS) scheme are discussed in this paper. One is a private watermarking method proposed in this paper and has a practical strong point to make the quality of the watermarked image to be constant in any images. The other is a public watermarking method that was previously proposed by the authors. Through this study, the minimum number of orthogonal sequences for embedding the required amount of information under the condition that quantization noise is only assumed is found in each watermarking method.

This paper describes code assignment and the multicode sense scheme for an inter-vehicle CDMA communication network. When considering an inter-vehicle broadcasting CDMA communication network, spreading code assignment and notification problems arise. In such a CDMA network, the use of common codes is a solution. Then an objective function of common code assignment in an IVCN is formulated as a combinatorial optimization problem. In addition, a multicode sense (MCS)/CDMA system is proposed as a simple code assignment scheme. Computer simulations show that the MCS/CDMA system can autonomously perform spatial rearrangement of the common codes using only local information that each vehicle can obtain by sensing the code channels.

In the ITS (Intelligent Transport Systems), it is an essential condition (mixed environment) that vehicles that have communication equipment and vehicles that do not have it simultaneously run in the same road. In this paper, a vehicular driving assistant system that is applicable to the mixed environment is proposed. The proposed system uses spread spectrum techniques and consists of several new systems such as a PN code assignment system, new vehicle position systems, and a vehicle map update system. In the proposed system, the wireless broadcast CDMA is used for inter-vehicle communications. This paper also shows preexaminations of the proposed system by using an autonomous traffic flow simulator including inter-vehicle communications. It is shown that the traffic safety can be improved by using inter-vehicle communications.

In this paper, a simple frame synchronization method for the SS-CSC syytem is proposed, and the synchronization performance is analyzed. There have been growing interests in the M-ary/SS communication system and the bi-orthogonal modulation system because these systems can achieve the high frequency utilization efficiency. However, the frame synchronization is difficult. We proposed the SS-CSC system, and evaluated the bit error rate (BER) performance of the SS-CSC system under the completed synchronization. The BER performance of the SS-CSC system is much the same as that of the bi-orthogonal modulation system. In this paper, a frame synchronization method using the differential detector and racing counters is proposed. In particular, the lose lock time, the recovery time and the BER performance considering the synchronizing performance are analyzed. In consequence, the BER performance considering the synchronization performance can approach the lower bound of the SS-CSC system by tuning the number of the stages in racing counters.

Recently, there has been increasing interest in Code Division Multiplex (CDM) systems. We reported the CDM system using the -chip shift multiplex operation. So far the performance of this system evaluated under the optimum . In this letter, we evaluate an influence of the phase difference between the groups on BER performance in 2M-plex system.

This paper presents a design methodology for positioning sub-platform from the viewpoint of positioning for smartphone-based location-based services (LBS). To achieve this, we analyze a mechanism of positioning error generation including principles of positioning sub-systems and structure of smartphones. Specifically, we carry out the experiments of smartphone positioning performance evaluation by the smartphone basic API (Application Programming Interface) and by the wireless LAN in various environments. Then, we describe the importance of considering three layers as follows: 1) the lower layer that caused by positioning sub-systems, e.g., GPS, wireless LAN, mobile base stations, and so on; 2) the middle layer that caused by functions provided from the platform such as Android and iOS; 3) the upper layer that caused by operation algorithm of applications on the platform.