Software radio has emerged as a focus of both academic research and commercial development for future wireless systems. This paper briefly reviews the foundation concepts of the software radio. It then characterizes the tradeoffs among core software-radio technologies. Object-oriented analysis leads to the definition of the radio reference platform and the related layered object-oriented architecture supporting simultaneous hardware and software evolution. Research issues include layering, tunneling, virtual machines and intelligent agents.

The potential of Software Radio (SR) has been slow to materialize. Born out of the spoils of the Cold War, the SR concept has remained prisoner of its origin, mainly focused on the terminal, and still under considerable military influence. Such narrow perspective does not fit with our long held conviction that SR has far-reaching potential, and much broader application. While some saw it as "simply" freeing us from standards, by allowing the definition of the radio terminal in software (hence Software Defined Radio, SDR), we see it as changing not only the way we think radio systems and networks, but also the way we define and provide the services and adapt the applications that ran on top of them. We discuss here this much broader, all encompassing approach. While the "canonical" SDR approach concentrates on the terminal side, ours covers the whole system, extending through the network into service creation and application development. Instead of settling for defining the radio in software, we envision Re-configuring on demand not only the terminal but also the serving network(s) and the services they provide (hence Re-configurable Radio Systems and Networks). To illustrate aspects of this novel approach, we discuss past and ongoing research in Europe on Re-configurable Radio Systems and Networks, and identify areas requiring further attention.

This paper reports the prehistory of software defined radio (SDR) studies in Japan. In 1999, a boom in the field of SDR started in Japan, and this year an ARIB study group completed its final report on SDR. SDR is a recently proposed technology concept and has attracted the attention of many communication engineering researchers. SDR will become one of the most important technologies in advanced communication, broadcasting and intelligent transportation systems on the 21st century. Although SDR has several attractive features, there are also many design issues to be solved. In this work we have examined these issues and discussed a new design methodology for wireless receivers in the SDR era.

Software radio or software defined radio (SDR) is a quite attractive field of research in terms of theoretical cross-over research themes between radio engineering and computer science in academia as well as new multi-standard or all-purpose radio system products in industry. In order to promote research and development in a field of SDR this paper briefly introduces some prospective aspect and research themes on SDR. There are many approaches to research SDR such as architectures, devises, algorithms, description languages and API (application program interface) for achieving reconfigurability and downloadability in an SDR system. One of the approaches is to focus on an antenna for SDR. Although a baseband circuit is generally programable and reconfigurable, an antenna and a RF circuit are used to be less flexible and hardware-dependent and then result in a bottleneck for implementing an SDR system. However, an adaptive array antenna or a smart antenna named a software antenna is adaptively controllable and reconfigurable because it can be programable to form a desired beam pattern if an appropriate set of antenna weights is provided with software. It must be a vital tool for carrying out an SDR system. A software antenna can be considered as an adaptive filter in space and time domains for radio communications, so that the communication theory can be generalized from a conventional time domain into both space and time domains. This paper also introduces structures and theories of a software antenna which I have been studying before this millennium.

It is expected that software receivers will be widely available for radio communication, broadcasting and radio monitoring applications because they are able to be equipped with multimode, multirate and multiband functions in a single hardware platform. This paper describes the basic techniques required for software receivers for both hardware and software. The evaluation items and methods were studied and some evaluations done with an experimental software receiver model fabricated for radio monitoring applications. Future concepts in radio communication, broadcasting and radio monitoring applications where software receivers are thought to be suitable, were studied, and problems for realization identified.

In recent years, the concept of the software radio has been put forward by the international communication society. It is well known that software radio will play an important role in third generation wireless communication systems. But until now there is not an acceptable concept of software radio. How to make software radio be applicable authentically, and how to develop its ascendancy? This paper introduces some new ideas about the key issues of software radio, including software radio architecture and its hardware platform, and it focuses on the design considerations of the hardware platform. Conventional software radio systems use pipeline architecture, which is not scalable and cannot fulfill the inherent requirements of software radios. In this paper a new layer structure of the hardware platform is proposed. It is an open architecture with flexibility and scalability. Then three schemes for hardware platform realization are introduced: bus architecture, switched network architecture, and fat tree architecture. An extensive analysis on advantages and disadvantages of each architecture is given. Then an application example is proposed. The switched network architecture is applied in the cellular wireless communication systems. The basestation is divided into four components according to their functions: antenna, IF, baseband, and control, which are connected by the ATM network. We call this virtualization of wireless communication systems. This will bring great benefits such as fast handoff, easily realization of different macrodiversity algorithm.

In this paper, a new configuration method of multimode software radio system by parameter controlled and telecommunication component block embedded digital signal processing hardware (DSPH) is proposed for the future flexible multimedia communications. In this method, in advance, basic telecommunication component blocks are implemented in the DSPH like DSP and FPGA. And, external parameters, which are simple but important information, change the specification of each block. This proposed method has the following features: i) People need to have only one mobile handset and select communication services as they like. ii) The volume of download software is reduced drastically in comparison with conventional full-download-type software radio system. iii) Since important component blocks have already been implemented into the DSPH except for some external parameters in advance, the know-how related to the implementation of DSPH never leak out. In this paper, we evaluate the effectiveness of the proposed configuration method by using computer simulation and developed experimental prototype and comparing with full-download-type software radio system from the viewpoint of the volume of download software. Finally, we introduce several new software radio systems by using the proposed configuration method.

A software antenna, which will be a key device realizing flexible and highly reliable wireless communications systems, is inherently matched with software defined radios (SDR). In this paper, first, key technologies on the software antenna are introduced. The technologies contain i) how to recognize the radio environment, ii) how to determine the optimum adaptive signal processing algorithm, and iii) how to reconfigure the digital beamforming circuit. Then, an image of a software antenna with reconfigurable eigenvector-beamspace configuration is presented. Finally, by assuming various propagation conditions, performance of the software antenna in terms of algorithm diversity is demonstrated.

Interference suppression is one of the important functions for mobile communications and software radio. First, this paper shows a new type of interference suppression method by P-RCE (Probability-Restricted Coulomb Energy) which is applicable to mobile communications and software radio. P-RCE is one of the neural networks and mainly used in the field of pattern classification. Secondly, this paper presents several characteristics of this method. For example, it is found from our studies that good suppression effects can be performed even when the interference signals exist closely adjacent to the desired signal and/or total number of signals is more than that of the antenna elements. Next, this paper discusses two types of improvement of processing speed for new suppression method. One is the setting up the learning and non-learning intervals, and the other is the restriction of the number of prototype cells. According to the results, fairly good improvement is realized.

A broadband and flexible receiver architecture is investigated for the handheld software defined radio (SDR). The proposed SDR architecture is based on the direct conversion and low intermediate frequency (low-IF) principle with digital channel filtering, which provides the receiver with flexibility for the multi-standard application. This architecture also enables analog-to-digital converter activating essentially in baseband or low frequency so that the clock jitter, which serves as an important subject in the well-known IF sampling method, can be reduced. Basic performance of the proposed architecture has been confirmed by the experimental model.

An architecture for a digital-to-RF converter for a software defined radio (SDR) transmitter is proposed. The ideal hardware architecture for an SDR is a digital-signal to RF-signal direct conversion transmitter. However no conventional digital-to-analog converter (DAC) has converted over 1-GHz RF signal with enough resolution, in the present condition. In this paper, a digital-to-RF direct converter architecture using a ΔΣ modulation technique is proposed for the amplitude-phase modulated signal. The experimental results show that the proposed direct converter outputs a sufficiently accurate signal.

Software radio base and personal station prototypes are proposed and implemented. The prototypes are composed of RF/IF, A/D and D/A, pre- and post-processors, CPU, and DSP parts. System software is partitioned into CPU program and DSP program to use processor resources effectively. They support various air interfaces, some of which are equivalent to the 384 kbit/s transmission rate PHS (personal handy phone system) and a 96 kbit/s transmission rate system. The base station can also be used as a communication bridge between two systems. In order to ease IF filter requirements, the zero-stuff method is employed. Basic transmission and receiving performances are evaluated in an experiment and their results agree well with those expected.

A new type of Meteor Burst Communication (MBC) network is developed. Each unit of the network is based on a DSP board running a modem software. All the fundamental blocks and functions of a modem are implemented in software. Unlike hardware modems, this software modem has flexibility of system configuration and operation. The system implements adaptability in terms of modulation type (number of phases in MPSK) using a unique dynamic channel estimation scheme appropriate for MBC channel. An MBC network protocol is implemented within the modem software. Some preliminary experiments were carried out for differential BPSK and differential QPSK modulations over a practical meteor burst link, and the results are presented.

This paper presents the results on IF/baseband up/down direct digital conversion and multiple channel analysis/synthesis software defined radio modules which are implemented using high speed ADC, DAC and FPGA, for IS-95 code division multiple access (CDMA) systems. The implemented system can directly down-convert multiple channel IS-95 CDMA IF signals to the baseband, and selectively analyze specific channel signals based on polyphase analysis filter bank techniques. Moreover, the analyzed baseband signals of multiple channels can be directly up-converted and synthesized in the same system. We have deployed the implemented system in IS-95 CDMA optical digital repeaters for PCS applications.

The transmission performance of WDM transmission systems is influenced by many effects according to the type of optical fiber employed in the system. Japanese high-speed transmission systems use dispersion-shifted fiber (DSF). It is well known that the transmission distance of WDM systems employing DSF is restricted by fiber four-wave mixing (FWM). Unequally spaced channel allocation (USCA) was proposed to mitigate the FWM effect. However, if no FWM light is allowed to fall on any optical channel, the number of channels is limited. This paper proposes a new method to extend the number of USCA channels to more than 16 under the optical bandwidth limitation. This method determines channel allocation by considering the distribution of the zero-dispersion wavelength of the optical fiber. The transmission performance of a WDM transmission system employing the proposed USCA methodology is clarified by numerical simulation to confirm that the optical bandwidth requirements can be reduced without degrading transmission performance. As a result, for 16 2.5 Gbit/s, if the fiber input power ranges from -3 dBm/ch to 3 dBm/ch, the achievable transmission distance is 700 km; the fluctuation in zero-dispersion wavelength is assumed to have the standard deviation of 5 nm. For 16 10 Gbit/s, if the fiber input power ranges from 0 dBm/ch to 3 dBm/ch, the achievable transmission distance is 400 km.

This paper introduces the construction of a family of complex-valued scaling functions and wavelets with symmetry/antisymmetry, compact support and orthogonality from the Daubechies polynomial, and applies them to solve electromagnetic scattering problems. For simplicity, only two extreme cases in the family, maximum-localized complex-valued wavelets and minimum-localized complex-valued wavelets are investigated. Regularity of root location of the Daubechies polynomial in spectral factorization are also presented to construct these two extreme genus of complex-valued wavelets. When wavelets are used as basis functions to solve electromagnetic scattering problems by the method of moment (MoM), they often lead to sparse matrix equations. We will compare the sparsity of MoM matrices by the real-valued Daubechies wavelets, minimum-localized complex-valued Daubechies and maximum-localized complex-valued Daubechies wavelets. Our research summarized in this paper shows that the wavelets with smaller signal width will result in a more sparse MoM matrix, especially when the scatterer is with many corners.

The essence of this work is to introduce an interaction between the physical layer and higher network layers, thus enabling a more practical utilization of multiuser detection and supporting services with different QoS parameters. In this paper, a new hybrid TDMA/ Multicode (MC)-CDMA medium access control utilizing multiuser detection is proposed and analyzed. Further, two traffic flow control approaches accompanied the TDMA/MC-CDMA system are proposed. One approach deterministically controls the flow of traffic into the TDMA slots, while the other statistically controls the flow of traffic depending on the instantaneous changes in the traffic load. The two approaches have been examined under a wide range of traffic characteristics where AWGN is only considered besides the mutual interferers from other intracell users. Both approaches show superiority as well as less sensitivity in terms of BER to the traffic changes compared with the conventional system.

This paper proposes a survivor-correction Viterbi algorithm (SCVA) and presents its application to an iterative sequence estimation in order to improve bit error rate performance of decision-feedback sequence estimation (DFSE) in the presence of intersymbol interference. The SCVA can mitigate erroneous survivor selections due to DFSE, because it modifies the add-compare-select operation to an add-correct-compare-select operation. Finally, it is confirmed by computer simulation that complexity of the proposed scheme is independent of delay of the main delayed ray and its performance is superior to that of DFSE at the same number of states.

In this paper, we study efficient scheduling algorithms that are suitable for ATM networks. In ATM networks, all packets have a fixed small length of 53 bytes and they are transmitted at very high rate. Thus time complexity of a scheduling algorithm is quite important. Most scheduling algorithms proposed so far have a complexity of O(log N) per packet, where N denotes the number of connections sharing the link. In contrast, weighted round robin (WRR) has the advantage of having O(1) complexity; however, it is known that its delay property gets worse as N increases. To solve this problem, in this paper we propose two new variants of WRR, uniform round robin (URR) and idling uniform round robin (I-URR). Both disciplines provide end-to-end delay and fairness bounds which are independent of N. Complexity of URR, however, slightly increases as N increases, while I-URR has complexity of O(1) per packet. I-URR also works as a traffic shaper, so that it can significantly alleviate congestion on the network. We also introduce a hierarchical WRR discipline (H-WRR) which consists of different WRR servers using I-URR as the root server. H-WRR efficiently accommodates both guaranteed and best-effort connections, while maintaining O(1) complexity per packet. If several connections are reserving the same bandwidth, H-WRR provides them with delay bounds that are close to those of weighted fair queueing.

Today's market share of Intelligent Network (IN) service is growing rapidly in wireless networks due to the rapid advances in wireless telecommunication and IN technology. To guarantee network independent IN services, mobility of IN service subscribers has to be taken into account. This paper proposes new designs of Global Service Logic for the IN service enhancement, which increase call completion rates in wired and wireless intelligent networks. In order to apply this logic to wireless service subscribers as well as wired service subscribers, we implement a Queue Manager applied to the call queuing service feature in the Service Control Point (SCP). In the case of wireless service subscribers, the Home Location Register (HLR) handles the service registration flags to notify the Queue Manager of the corresponding service subscribers' mobility. In addition, we present a dynamic queue management mechanism, which dynamically manages the queue size based on the parallel server queuing model as the wireless subscribers roam the service groups due to their mobility characteristics. In order to determine the queue size allocated by the dynamic queue manager, we simulate the relationship between the number of the subscriber's terminals and the drop rate by considering the service increment rate. Moreover, the appropriate waiting time in the queue as required is simulated according to the above relationship. We evaluate call completion rates of the proposed mechanism in the paper by comparing to that of the existing mechanism.

This paper discusses and clarifies effectiveness of data-driven implementation of protocol handling system to access TINA (Telecommunications Information Networking Architecture) network and internet. TINA is a networking architecture that achieves networking services and management ubiquitously for users and networks. Many TINA related ACTS (Advanced Communication Technologies and Services) projects have been organized in Europe. In Japan, The TINA Trial (TTT) to achieve ATM network management and services based on TINA architectures was done by NTT and several manufactures from April 1997 to April 1999. In these studies and trials, much effort is devoted to development of software based on service architecture and network architecture being standardized in TINA-C (TINA Consortium). In order to achieve TINA environment universally in customers and network sides, we have to consider how to deploy TINA environment onto user side and how to use access transmission capacity as efficiently as possible. Recent technology can easily achieve application and environment downloading from the network side to user side by use of e. g. , JAVA. In accessing the network, there are several possible bottlenecks in information exchange in customer side such as PC processing capability, access protocol handling capability, intra-house wiring bandwidth. Authors, in parallel with TINA software architecture study, have been studying versatile requirements for hardware platform of TINA network. In those studies, we have clarified that the stream-oriented data-driven processor authors have been studying and developing have high reliability, high multiprocessing and multimedia information processing capability. Based on these studies, this paper first shows Von Neumann-based protocol handler is ineffective in case of multiprocessing through mathematical and emulation studies. Then, we show our data-driven protocol handling can effectively realize access protocol handling by emulation study. Then, we describe a result of first step of implementation of data-driven TCP/IP protocol handling. This result proves our TCP/IP hub based on data-driven processor is applicable not only for TINA/CORBA network but normal internet access. Finally, we show a possible customer premises network configuration which resolves bottleneck to access TINA network through ATM access.

In the Internet and Mobile communication environment, authentication of the users is very important. Although at present password is extensively used for authentication, bare password transmission suffers from some inherent shortcomings. Several password-based authentication methods have been proposed to eliminate such shortcomings. Those proposed methods have relative demerits as well as merits. In this letter we propose a method where those demerits are eliminated. The prominent feature is security improvement apart from low processing, storage and transmission overheads compared to previous methods. This method can be used in several applications like remote login, encrypted and authenticated communication and electronic payment etc.

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.

An analytical error characteristics of GPS compass which determines heading and elevation of the vehicle using carrier phase measurements from 2 antennae is given. It is also shown that to obtain more precise heading, longer baseline along the vehicle is preferred and the accuracy of heading is always better than that of elevation since the vertical measurement uncertainty caused by geometry of satellites affects only on that of elevation. These results can be applied as basic directions for attitude determination: to what direction should the baseline be located to minimize the error, which satellites should be selected to minimize the error.