We present an attractive approach for OFDM transmission using an adaptive pre-FFT equalizer, which can select ICI reduction mode according to channel condition, and a degenerated-inverse-matrix-based channel estimator (DIME), which uses a cyclic sinc-function matrix uniquely determined by transmitted subcarriers. In addition to simulation results, the proposed system with an adaptive pre-FFT equalizer and DIME has been laboratory tested by using a software defined radio (SDR)-based test bed. The simulation and experimental results demonstrated that the system at a rate of more than 100 Mbps can provide a bit error rate of less than 10-3 for a fast multi-path fading channel that has a moving velocity of more than 200 km/h with a delay spread of 1.9 µs (a maximum delay path of 7.3 µs) in the 5-GHz band.

A multiple-input multiple-output software defined radio (MIMO-SDR) platform was developed for implementation of MIMO transmission and propagation measurement systems. This platform consists of multiple functional boards for baseband (BB) digital signal processing and frequency conversion of 5 GHz-band radio frequency (RF) signals. The BB boards have capability of arbitrary system implementation by rewriting software on reconfigurable devices such as field programmable gate arrays (FPGAs) and digital signal processors (DSPs). The MIMO-SDR platform employs hybrid implementation architecture by taking advantages of FPGA, DSP, and CPU, where functional blocks with the needs for real-time processing are implemented on the FPGAs/DSPs, and other blocks are processed off-line on the CPU. In order to realize the hybrid implementation, driver software was developed as an application program interface (API) of the MIMO-SDR platform. In this paper, hardware architecture of the developed MIMO-SDR platform and its software implementation architecture are explained. As an application example, implementation of a real-time MIMO channel measurement system and initial measurement results are presented.

A new spectrum management architecture for a flexible software defined radio (SDR) is proposed. In this architecture, the SDR hardware and software are certified separately so as not to destroy the SDR flexibility, but to ensure that any combinations of hardware and software are compliant to the radio regulations even at the system (vertical) handover, global (horizontal) handover, and upgrade (forward) or downgrade (backward) handover. This architecture is based on automatic calibration & certification unit (ACU), built-in GPS receiver, and radio security module (RSM). The ACU is a hardware embedded RF manager that dynamically controls the output power spectrum to be compliant to the local radio regulation parameters. This local radio regulation parameters are securely downloaded to the hardware as an electronic label of the SDR software and stored in the RSM which is a security manager of the hardware. The GPS position check is used, especially during roaming, to keep the compliancy of the terminal to each local radio regulations managed by the geographical region. The principle parties involved in this architecture are telecommunication certification body (TCB), SDR hardware maker (HW maker), SDR software maker (SW maker), and SDR user. The roles and relationships of these four parties in the proposed architecture are clarified in this paper.

The software-defined radio technique translates the traditional hardware radio platform to a flexible software radio platform that can support multiple air interface standards. This work proposes an efficient IF processing architecture based on software-defined radio for 2G GSM/IS-95 and 3G W-CDMA systems. Hardware complexity is estimated by fixed-point simulation. IF processing architecture should be highly flexible and minimally complex. Firstly, a carrier channel is selected from a wide frequency band using a high-resolution numerically controlled oscillator (NCO). Wide-range interpolation/decimation is performed by the cascaded integrator comb (CIC) filter that involves no multiplier nor stores filter coefficients. Both the desired narrowband and the desired wideband signals can be extracted. The look-up table (LUT), based on the distributed arithmetic (DA) algorithm is used to implement the finite impulse response (FIR) filter. Therefore, a small area and high speed can be achieved. The errors caused by truncation, quantization, rounding-off and overflow are predicted using a fixed-point simulation. These predictions will help to evaluate the word-length for VLSI implementation. Finally, ALTERA APEX20KE is used as a target device. One hundred thousand gates are used for the implementation. Thus, the proposed architecture has high processing flexibility and small area.

In relation to the Software Defined Radio (SDR) concept, an experimental simulation system was developed. Likewise, verification tests were performed in order to validate the envisaged SDR certification processes including its development, certification, distribution, and software installation assuming the future possibility of exchanging the software in the field.

The Communications Research Laboratory (CRL) started a new project named the New Generation Mobile Network Project in April 2002. The target of this project is the development of new technologies to enable seamless and secure integration of various wireless access networks such as 3rd and 4th generation cellular, wireless LAN, high-speed mobile wireless, wired communications, and broadcasting networks. This paper presents an overview of CRL's new generation mobile communication system that is called The Multimedia Integrated Network by Radio Access Innovation Plus (MIRAI+), as well as details the role of Software Radio Technology (SDR) in MIRAI+.

In this paper, as an important technology for the software-defined radio, a novel scheme of adaptive array antenna utilizing bandpass sampling technique is proposed. For adaptive signal processing, it is necessary to convert the radio frequency signal received by the antenna that is given by real number into baseband region, i.e., complex number region. Then, the method for dividing the bandpass sampled signal to in-phase and quadrature components is analyzed. The sampling scheme is called the IQ-division bandpass sampling. An adaptive array antenna based on the IQ-division bandpass sampling is characterized by the signal processing at the bandpass sampled signal stage, namely, intermediate frequency stage, not baseband. Finally, we will confirm the validity of the proposed scheme through an experiment in a radio anechoic chamber.

This paper presents the summarized achievements of "Study Group on Software Technology for Radio Equipment" held at TELEC from April 2000 to March 2003. The Study Group specified the essential issues on Software Defined Radio (SDR), and discussed desirable methods to evaluate conformity to technical regulations in radios that can change RF characteristics only by changing software. The biggest objective in SDR is to build the architecture to allow users to install software exclusively in the combination of hardware and software that have passed the certification test. The Study Group has reached a solution by introducing the idea of "tally." This paper explains the concept of tally, and proposes two types of systems to use tallies in checking adaptability in combinations of hardware and software.

Interest in the regulatory issues for Software Defined Radio (SDR) is spreading worldwide since the Federal Communications Commission (FCC) recently recognized SDR and created a new category for SDR authorization. SDR technology will bring enormous benefits to the field of wireless services. However, in order to ensure such benefits, revisions of the radio law and/or related ordinances are required regardless of standardization of the software downloading and other implementation details. In order to define the issues peculiar to SDR and to investigate how conformity evaluation should be conducted for radio equipments whose RF characteristics can be altered by software changes in the field, "Study Group on Software Technology for Radio Equipment" was organized by the Telecom Engineering Center (TELEC) in 2000. This paper summarizes a report of the Study Group that was published in March 2003 including the proposal for "Technical regulation conformity evaluation system," the principal output of the study, which proposes how to prevent unauthorized changes to radio equipment in the field.

Many carriers are introducing multi-media services to satisfy customer demands for these services. In order to provide such services, carrier must increase their system capacity. It is well known that space division multiple access (SDMA) improves system capacity and is compatible with existing access systems. In order to evaluate the performance of SDMA, we developed an SDMA test bed. The test bed maintains the personal handy phone systems (PHS). The PHS adopts time division multiple access (TDMA). Aiming to compare the performance of SDMA and TDMA using the same analog hardware, the SDMA test bed employs a software-defined radio (SDR) technique. This paper shows the outline and performance of the test bed. The results of laboratory tests indicate that the bit error rate (BER) of the test bed operated in the SDMA mode at under 10-3 when the carrier-tointerference ratio (CIR) was larger than approximately -22 dB. Antenna patterns measured in an anechoic chamber show that the SDMA test bed produces correct antenna patterns when there are three desired signals and one interference signal. The results of the four field tests confirm that the test bed operated while two-multiplex SDMA mode doubled of the traffic and decreased the interference level as compared with the TDMA mode. Furthermore, the test bed operated while threemultiplex SDMA mode improves the traffic about 2.4 to 2.7 times. The SDMA test bed decreased the impact of the adjusted TDMA base station (BS). Therefore, we confirmed that the SDMA improves system capacity without any degradation.

This paper outlines the perspectives on Software Defined Radio (SDR) technology in viewpoint of the standardization of the future mobile communication systems. The activities of ITU-R SG8 Working Party 8F (WP8F) and mITF (mobile IT Forum) of Japan for systems beyond IMT-2000 (B3G) or 4-th generation mobile systems are firstly summarized. The latest discussions relating to SDR technology in the both parties are reported. It is followed by consideration on both expectations and technical issues on SDR in order to realize the technology in the future mobile communication systems. They are clarified in the viewpoint of standardization activity on B3G. Also some regulation issues are lastly summarized.

Adaptive arrays have been recognized as an attractive mean for overcoming multipath fading and interference rejection in the field of mobile communications. In, an adaptive array applicable to single-user spread spectrum (SS) systems has been proposed. In this system, any a priori information concerning incoming signal, even the spreading code and synchronization, is not necessary while it achieves equalizing, beamforming and despreading of a received signal, simultaneously. In this paper, we propose a multistage blind adaptive array antenna based on the above-mentioned adaptive algorithm in order to realize blind signal processing that is applicable to multi-user SS systems. Behavior and performance of the proposed multistage system are examined through computer simulations.

This paper proposes and investigates a coding and decoding scheme to achieve adaptive channel coding using a Finite State Machine (FSM) for Software Defined Radio (SDR). Adaptive channel coding and decoding systems that can switch between different coding rates and error correcting capabilities in order to adapt to changing applications and environments, are effective for SDR. However, in these systems, a receiver cannot always select the correct decoder which causes decoding errors, usually referred to as Decoder-Selection-Errors (DSE). We propose a trellis encoder estimation scheme that compensates for this problem. This scheme uses the circuit of FSM to limit the encoder transition and the Viterbi algorithm for maximum likelihood trellis encoder estimation. Computer simulations are applied for evaluating the DSE rate, the Bit Error Rate (BER) and Throughput of the proposed scheme in comparison with a conventional scheme.

In this paper, we focus attention on the development of security techniques using software defined radio (SDR) technologies. We propose a new secure download system which uses the characteristics of the field programmable gate arrays (FPGAs) composing the SDR. The proposed system has the novelty that realization of high security encipherment is possible. This is achieved using the characteristic of FPGAs which allows systems to be arranged in a variety of different layouts, as well as by using the configuration information as the key. This unifies the renewal of the key and the encipherment. In addition the proposed system has the merit that it has high security against illegal acquisition such as a wiretapping, and can also be used in conjunction with any other current cipher algorithm. As an evaluation of the security, we show that the proposed system has high immunity to illegal acquisition of software using replay attack, by verification of the protocol as well as by numerical computation. The proposed system can therefore realize high security software downloads based on SDR.

This paper presents an adaptive burst-mode M-QAM modem architecture suitable for variable rate broadband wireless packet data networks. The core signal processing functions for the modem are common to all constellations resulting in an efficient hardware architecture for field programmable gate array (FPGA) implementation.

Software Defined Radio is beyond the education and initiation phase. The industry is addressing the needs of reconfigurable radio technology development, implementation, and application in a variety of marketplaces. Regulatory decisions are being formulated to facilitate SDR adoption and deployment. Continued dialog and cooperation among the industry organizations is an important factor in the rate of progress.

To promote the commercial implementation of software download for software defined radio (SDR) terminals, a secure method of download is vital. This paper examines the needs of software download for SDR, and proposes a comprehensive system framework within which secure download can be carried out. The features of the proposed system include unique individual encryption to each terminal and secure exchangeability of any cryptographic components. The main goals of the security system are the following: (i) verification of the identity of the source of the software; (ii) control and verification of the integrity of the downloaded data; (iii) disabling of the ability to run unauthorized software on the software defined terminal; (iv) secrecy of the transmitted data. The proposed system is flexible and in harmony with current requirements regarding the SDR security issues.

A software defined radio (SDR) prototype based on a multiprocessor architecture (MPA) is developed. Software for Japanese personal handy phone system (PHS) of a 2G mobile system, and IEEE 802.11 wireless LAN, which has much wider bandwidth than the 2G systems, is successfully implemented. Newly developed flexible-rate pre-/ post-processor (FR-PPP) achieves the flexibility and wideband performance that the platform needs. This paper shows the design of the SDR prototype and evaluates its performance by experiments that include PHS processor load and wireless LAN throughput characteristics and processor load.

This paper discusses a design methodology suitable for the development of software defined radio platforms. A flexible digital receiver was designed and implemented using a multi-port direct converter and an FPGA-based platform. The design starts with a hardware-oriented top-level system model. The model is built based on basic signal processing blocks connected together in a graphical tool. Carrier symbol timing recovery is implemented in the discrete-time (digital) domain with an interpolator-based synchronizer. Carrier phase and frequency are recovered using a feedback synchronization algorithm (a second-order type-II digital PLL). Experimental results of the platform and its simulation results demonstrate the effectiveness of the proposed design methodology.

As a center of mobile multimedia of the 21st century, it is very much looking forward to explosion of R&D and business of the next generation of mobile communication systems and the ITS (Intelligent Transport Systems) because ITS will enable information-oriented in the field of the road, traffic and vehicles, by using the most advanced technologies of mobile communications and devices, for the various purposes such as decrease of the traffic accident, the reduction of traffic jam, the increase in efficiency of the logistics and the harmony with the earth environment. This invited paper will first briefly introduce evolution of mobile communications and ITS in ministries, industries and academia in Japan. Then core communication technologies for ITS will be overviewed such as spread spectrum CDMA, adaptive antenna array, and software radio or software defined radio. Demands of SoC (System on a Chip) to carry out the core technologies will be addressed.