There is a growing demand that mobile networks should provide quality-of-service (QoS) to mobile users since portable devices become popular and more and more applications require real-time services. Providing QoS to mobile hosts is very difficult due to mobility of hosts. The resource ReSerVation Protocol (RSVP) establishes and maintains a reservation state to ensure a given QoS level between the sender and receiver. However, RSVP is designed for fixed networks and thus it is inadequate in wireless mobile networking environments. In this paper, we propose a resource reservation protocol for mobile hosts in mobile networks. The proposed protocol extends the RSVP by introducing RSVP agents in local networks to manage the reservations. The proposed protocol reduces packet delay, bandwidth overhead, and the number of RSVP messages to maintain reservation states. We examined the performance of the proposed protocol by simulation and we got an improved performance over the existing protocols.

Information services for drivers and passengers in land vehicles have been drastically increasing in recent years. Frequency spectra used in vehicle communications cover an extremely wide band ranging from the LF band to the millimeter-wave band. Today, a variety of properties are required of antennas depending on the types of radio systems; more than ten kinds of antennas are installed in land vehicles. Advances in such land vehicle antennas developed in Japan are reviewed in reference to antennas for broadcasting reception and mobile communication systems. Typical antennas are introduced for each system, and the technology and performance are described.

This paper reviews the historical development of adaptive antennas in Japan. First of all, we watch basic adaptive algorithms. In 1980s, particularly, the following issues were a matter of considerable concern to us; (a) behavior to the coherent interference like multipath waves or radar clutters, (b) signal degradation in case that the direction of arrival (DOA) of desired signal is different from the DOA specified beforehand in the adaptive antennas with the DOA of the desired signal as a prior knowledge, and (c) performance of adaptive antennas when the desired signal and interference are broadband. Although there are a lot of development and modification of adaptive algorithms in Japan, we refer in this paper only to the above-mentioned topics. Secondly, our attention is paid to implementation of adaptive antennas and advanced technologies. A large number of researches on the subjects have been carried out in Japan. Particularly, we focus on the initiative studies in Japan toward mobile communication application. They include researches of mobile radio propagation for adaptive antennas, calibration methods, and adaptive antenna for mobile terminals. As a matter of course, we also refer to adaptive antenna technologies for advanced communication schemes such as CDMA, SDMA, OFDM and so on. Finally, we take notice of some pilot products which were developed to verify the effect of the adaptive antenna in the practical environments. As the initiative ones, a couple of equipments are introduced in this paper.

In this paper, we investigate the performance of Mobile IP regional registration and compare it with that of Mobile IP. The performance measures used are registration delay and the CPU processing overheads loaded on the agents to handle mobility of mobile nodes. Through the investigation, the effectiveness of adopting Mobile IP regional registration in the wide-area wireless network in terms of reducing the CPU processing overheads on the home agent and lowering the signaling delay is observed. We also compare the scalability of Mobile IP regional registration schemes when two and three levels of foreign agent hierarchy are considered. Based on the comparison, we propose a network design strategy for achieving optimized performance and cost.

An adaptive congestion control scheme that can be applied to various random access protocols in mobile communication systems is proposed. Its main features are scalability for handling increasing numbers of mobile terminals and adaptability for coping with drastic changes in traffic load. These are achieved by controlling the traffic load adaptively to maintain maximum throughput even under overload conditions. Procedure for measuring and estimating offered traffic and a method of setting control thresholds that maximize the average throughput are analytically derived, and the algorithm for adaptively controlling the permission rate is described. This scheme was applied to both the slotted ALOHA and ICMA/CD protocols. For each protocol, three control parameters--the unsuccessful rate, optimal traffic, and control thresholds--were analytically derived. Then stationary throughput characteristics were numerically evaluated. We found that the scheme could achieve high throughput by regulating transmission adaptively depending on the offered traffic. The preferred range of the permission base rate that enables adaptive control and limits the amount of processing at terminals was also clarified. Since one of the main advantages of our scheme is its adaptability to drastic variations in traffic load, we simulated its transient characteristics with three types of time-variant input models. The results indicate that this control scheme achieved nearly theoretically optimal throughput even during an overload for each input model.

Existing research related to RSVP with mobility support has mainly focused on maintaining reservation state along the routing path, which changes continuously with the movements of mobile host (MH), without much overhead and delay. However, problems such as deepening RSVP's inherent scalability problem and requiring significant changes in the existing network infrastructure have not been adequately addressed. In this paper, we propose a new approach, known as Concatenation and Optimization for Reservation Path (CORP), which addresses these issues. In CORP, each BS pre-establishes pseudo reservations to its neighboring BSs in anticipation of the MH's movement. When the MH moves into another wireless cell, the associated pseudo reservation is activated and concatenated to the existing RSVP session to guarantee continuous QoS support. Because a pseudo reservation is recognized as a normal RSVP session by intermediate routers, little change is required in the current Internet environment to support both movements within a single routing domain and between two different routing domains. CORP also dynamically optimizes the extended reservation path to avoid the infinite path extension problem. Multicast addressing is used to further reduce resource consumption in the optimization process. The experimental results of the CORP implementation demonstrate that it significantly reduces the delay and overhead caused by handoffs compared to the case of establishing a new RSVP session. The improvement increases as the distance between the MH and its correspondent host (CH) grows.

In DS-CDMA mobile radio communications systems, transmit power control (TPC) is indispensable to regulate the variations in the received signal power produced by multipath fading. However, a practical TPC raises and lowers the mobile transmit power only at discrete time instants (the TPC rate is on the order of 1-2 kHz) and by a finite step size of the order of 1 dB. Therefore, TPC cannot completely compensate the received signal power variations and hence, the transmission performance degrades in a fast fading channel. The objective of this paper is to understand how TPC acts in a fast fading channel with antenna diversity reception and, based on this understanding, to model the TPC operation.

In wireless communications, a smart antenna system utilizes an antenna array to acquire the spatial signatures of transmitted signals. This system uses the difference in the spatial signatures or the direction of arrival (DOA) of signals to correctly obtain the desired signal. This can reduce co-channel interference, mitigate the fading phenomenon caused by multipath transmissions, improve the communication quality and increase the system capacity. The purpose of this paper is to evaluate the performance of smart antennas using four beamforming algorithms applied to a wideband code division multiple access (W-CDMA) system. The simulation results show that, based on the same power consumption at the transceiver and using a Rake receiver, a W-CDMA system with a smart antenna can operate at a lower bit error rate at the specific signal to noise ratio (SNR). Moreover, the smart antenna system accommodates more users at the specific signal to interference ratio (SIR), even though a certain angle difference exists between the actual DOAs and the estimated DOAs.

This paper proposes a new blind algorithm effective for multiuser detection with an adaptive array antenna. The conventional blind algorithm, known as the Constant Modulus Algorithm (CMA), has two major drawbacks: (i) the convergence speed is not sufficiently fast for usual applications in mobile communications, and (ii) the algorithm is very likely to lock on the path with the largest received power, which means the signal with the second largest power can hardly be extracted. This paper introduces the Recursive Least Squares algorithm for CMA (RLS-CMA) in order to speed the convergence up, and additionally introduces the concept of the orthogonal projection into CMA so as to extract signals with weak power. The proposed CMA with Orthogonal Projection (CMA-OP) sequentially calculates the weight vector of each user under a constraint that the weight vector should be orthogonal to the estimated array response vectors of previously extracted users. Computer simulations demonstrate that the proposed scheme can operate properly in the Rayleigh fading channels under the two-user condition.

This paper proposes a three-step cell search algorithm that utilizes only the common pilot channel (CPICH) in the forward link and employs spreading by a combination of a cell-specific scrambling code (CSSC) and an orthogonal short code for Orthogonal Frequency and Code Division Multiplexing (OFCDM) broadband packet wireless access. In the proposed cell search algorithm, the OFCDM symbol timing, i.e., Fast Fourier Transform (FFT) window timing, is estimated by detecting the guard interval timing in the first step. Then, in the second step, the frame timing and CSSC group are simultaneously detected by taking the correlation of the CPICH based on the property yielded by shifting the CSSC phase in the frequency domain. Finally, the CSSC within the group is identified in the third step. The most prominent feature of the proposed cell search algorithm is that it does not employ the conventional synchronization channel (SCH), which is exclusively used for the cell search. Computer simulation results elucidate that when the transmission power ratio of the CPICH to one code channel of the traffic channel (TCH) is 12 dB, the proposed cell search method achieves faster cell search time performance compared to the conventional method using the SCH with the transmission power ratio of the SCH to one code channel of the TCH of 6 dB. Furthermore, the results show that it can accomplish the cell search within 1.7 msec at 95% of the locations in a 12-path Rayleigh fading channel with the maximum Doppler frequency of 80 Hz and the r.m.s. delay spread of 0.32 µs.

Randomly addressed polling was proposed as a multiple access control protocol for wireless local area networks (LANs). However, the protocol has difficulties in supporting real-time services such as voice transmission. We propose a reservation scheme and make it possible to support real-time services. The scheme is described in detail. Efficiency and average access delay are analyzed.

This paper presents the results of field experiments on the pilot symbol assisted (PSA) coherent multistage interference canceller (COMSIC) receiver in the direct sequence code division multiple access (DS-CDMA) reverse link. The implemented COMSIC receiver comprising three cancellation stages employs PSA channel estimation and replica generation of multiple access interference (MAI) of other users. The experimental results demonstrate that the COMSIC receiver associated with antenna diversity reception and fast transmission power control (TPC) exhibits effectiveness in suppressing severe MAI in actual multipath fading channels. The transmission power of a mobile station (MS) when the COMSIC receiver is employed at a base station (BS) is reduced by approximately 2.0 and 4.0 dB compared to that with the matched filter (MF)-based Rake receiver when the ratios of the target signal energy per bit-to-interference power spectrum density ratio (Eb/I0) of the desired user to the target user are Δtarget= -6 and -9 dB, respectively. Furthermore, for the COMSIC receiver, the transmission power of a MS at the average bit error rate (BER) of 10-3 with antenna diversity is decreased by approximately 7.5 and 11 dB compared to that without antenna diversity when the Δtarget values are -6 and -9 dB, respectively.

This paper proposes a new method to estimate the channel impulse response for Orthogonal Frequency Division Multiplexing (OFDM) mobile radio transmission. The method employs the Recursive Least Squares (RLS) algorithm so as to exploit the correlations in frequency and time domains, and can improve the estimation accuracy. It is also applicable to both the regular and scattered pilot schemes. Computer simulations demonstrate effectiveness of the method applied to the scattered pilot scheme.

This paper presents the theoretical analysis of subband adaptive array combining cyclic prefix transmission scheme (SBAA-CP) in multipath fading environment. The exact expressions for optimal weights, array outputs and the output signal to interference plus noise ratio (SINR) are derived. The analysis shows that use of the cyclic prefix data transmission scheme can significantly improve the performance of subband adaptive array (SBAA). An example of implementing SBAA-CP as a software antenna is also presented.

This paper proposes a three-step cell search algorithm utilizing a synchronization channel (SCH) and common pilot channel (CPICH) in the forward link for OFCDM (Orthogonal Frequency and Code Division Multiplexing) broadband packet wireless access, and evaluates the cell search time performance by computer simulation. In the proposed three-step cell search algorithm, the OFCDM symbol timing, i.e., Fast Fourier Transform (FFT) window timing is estimated employing SCH or guard interval (GI) correlation in the first step. Then, the frame timing is detected by employing the SCH and the cell-specific scrambling code (CSSC) is identified by the CPICH in the second and third steps, respectively. Computer simulation results elucidate that the proposed three-step cell search algorithm achieves fast cell search time performance, i.e., cell detection probability of 90% within approximately 50 msec, assuming the number of CSSCs of 512 in a 19 hexagonal-cell model. We also clarify that there is no prominent difference in cell search time performance between the two employed SCH structures, time-multiplexed and frequency-multiplexed, assuming that the total transmit power of the SCH is the same. Based on the comparison of four substantial cell search algorithms, the GI-plus-SCH correlation method, in which FFT windowing timing detection, frame timing detection, and CSSC identification are performed by GI correlation, frequency-multiplexed SCH, and CPICH, respectively, exhibits the cell search time of approximately 44 msec at the detection probability of 90% with an optimized averaging parameter in each step.

This paper evaluates the bit error rate (BER) performance of high rate data transmission such as at 64 and 384 kbits/s (kbps) with high quality (average BER is below 10-6) using turbo/convolutional coding associated with Rake time diversity, antenna diversity, and fast transmission power control (TPC) in multipath fading channels for W-CDMA mobile communications. Laboratory experiments using multipath fading simulators elucidate the superiority of turbo coding over convolutional coding when the channel interleaving length is 40 msec. The required average transmission power for the average BER of 10-6 using turbo coding is decreased by approximately 1.1-1.5 dB and 1.5-1.6 dB for 64 and 384 kbps data transmissions, respectively, compared to that using convolutional coding for a two-path Rayleigh fading channel with the fading maximum Doppler frequency of fD = 5-200 Hz. Furthermore, field experimental results elucidate that the required transmission power for the average BER of 10-6 employing turbo coding is decreased by approximately 0.6 dB and 2.0 dB compared to convolutional coding for 64 and 384 kbps data transmissions, respectively, without antenna diversity reception, while that with antenna diversity reception exhibits only an approximate 0.3-0.5 dB decrease. This decrease in improvement with antenna diversity reception indicates that in an actual fading channel in the field experiments, the impact of the error in path search for Rake combining and SIR measurement for fast TPC diminishes the performance improvement of the turbo coding due to a very low received signal power.

A hybrid location system for a mobile station consists of a wireless-assisted GPS and a kind of cellular signals. This letter presents a location estimator improving the performance of the hybrid mobile station location for all terrain environments including inside or between buildings. An estimation structure eliminating non-line-of-sight propagation-delay error effectively improves location accuracy of the hybrid location system.

Recent cellular systems have excellent performances, such as high quality, compactness, low power consumption and low cost, owing not only to digital technologies but also to various RF device technologies, especially amplifier technologies. This paper describes base station RF technologies that contributed for the improvement of base station equipment. Future mobile system will provide much higher bitrate services in the higher frequency band. Requirements and new technologies that are expected for RF equipment of the future base stations are also discussed.

DS-CDMA provides a flexible support for the low-to-high bit rate of multimedia services upon a specific user's request. A simple capacity expression is derived for a power-controlled reverse link of orthogonal multi-code DS-CDMA with multiple connections. It is found that an orthogonal multi-code user having multiple connections is equivalent to a single connection user, but with a spreading factor reduced by a factor of the total number of parallel codes and a required signal energy per symbol-to-interference plus noise power spectrum density ratio which is the average taken over multiple connections. Furthermore, the use of antenna diversity is found equivalent to the use of higher spreading factor increased by a factor of the number of antennas.

Interoperability between different systems is becoming a more important issue for open distributed systems. In this paper, we investigate what kind of framework we need for constructing open distributed systems. Firstly, we enumerate the features and functions which the framework should have. We then evaluate a proposed multi-agent framework, Bee-gent, by using a typical example of open distributed systems. Lastly, we show clearly what is required for such a framework.