Hiroyuki Shiba

A Novel Cooperative Sensing Technique for Cognitive Radio

Cognitive radio, which utilizes frequency effectively, needs a highly reliable sensing technique. Cooperative sensing techniques have been studied to meet this need. However, conventional techniques have a high false alarm rates. To solve this problem, we propose an innovative cooperative sensing technique in which the power levels at several radio stations are multiplied by different weights and added. Whether or not radio waves are present is determined based on this added power level. We used computer simulations to evaluate the proposed technique and demonstrated that it can perform at the required misdetection rate but has a lower false alarm rate than conventional techniques. We also propose an improved technique that takes account of correlated shadowing and is more effective in correlated shadowing environments.

Performance of IEEE 802.11 wireless LAN implemented on software defined radio with hybrid programmable architecture

This paper describes a prototype software defined radio (SDR) transceiver on a distributed and heterogeneous hybrid programmable architecture; it consists of a central processing unit (CPU), digital signal processors (DSPs), and pre/postprocessors (PPPs), and supports both Personal Handy Phone System (PHS), and IEEE 802.11 wireless local area network (WLAN). It also supports system switching between PHS and WLAN and over-the-air (OTA) software downloading. In this paper, we design an IEEE 802.11 WLAN around the SDR; we show the software architecture of the SDR prototype and describe how it handles the IEEE 802.11 WLAN protocol. The medium access control (MAC) sublayer functions are executed on the CPU, while the physical layer (PHY) functions such as modulation/demodulation are processed by the DSPs; higher speed digital signal processes are run on the PPP implemented on a field-programmable gate array (FPGA). The most difficult problem in implementing the WLAN in this way is meeting the short interframe space (SIFS) requirement of the IEEE 802.11 standard; we elucidate the potential weakness of the current configuration and specify a way of implementing the IEEE 802.11 protocol that avoids this problem. This paper also describes an experimental evaluation of the prototype for WLAN use, the results of which agree well with computer-simulation results.

A broadband low-noise wide dynamic range SiGe front-end receiver IC for multi-band access points

A broadband, low-noise, wide dynamic range front-end receiver IC is reported. It uses 0.25 μm SiGe BiCMOS process technology and consists of broadband variable gain low noise amplifiers (VGLNAs), down-conversion mixers, step attenuators, and buffer amplifiers. It can receive triple-band signals concurrently, and the chip size is only 3mm × 3mm. Its measured noise figure was under 3.2 dB and the measured conversion gain was around 30 dB in the broad frequency range from 300 MHz to 3 GHz. It has a wide gain control range of around 100 dB; 50 dB is controlled by the VGLNA and the step attenuator, and 50 dB by the mixer with novel relative power control method using dual LO signal. The gain control enhances the input 1dB compression point from -40 dBm to -21 dBm.

Performance Evaluation of Reconfigurable Processor for SDR Mobile Terminals and SDR Base Station using Autonomous Adaptive Control Technology

It is expected that software defined radio (SDR) technology that can access multiple wireless communication systems will be applied to mobile terminals and base stations as a beyond 3G wireless system. An SDR wideband mobile terminal must be capable of high-speed data processing and low power consumption. To evaluate the performance of reconfigurable processors for SDR wideband mobile terminals, we developed software that runs on a reconfigurable processor for the IEEE 802.11a wireless LAN baseband part, and evaluated the performance of the reconfigurable processor. Moreover, we describe the system design of the new SDR base station, which uses autonomous adaptive control technology. We evaluated the characteristic performance through computer simulations, and confirmed its efficiency

Design and Performance Evaluation of IEEE 802.11a SDR Software Implemented on a Reconfigurable Processor

Software defined radio (SDR) mobile terminals that can access multiple wireless communication systems are the trend of the future. An SDR wideband mobile terminal must be capable of high-speed data processing and low power consumption. We focused on reconfigurable processors with these features. To evaluate the performance of reconfigurable processors for SDR wideband mobile terminals, we developed and evaluated software that runs on a reconfigurable processor for the IEEE 802.1 la wireless local area network (LAN) baseband part, which requires high-speed data processing. This paper describes the configuration of the SDR IEEE 802.11a software for the reconfigurable processor and its performance evaluation results. Moreover, we showed the requirements for applying the reconfigurable processor to SDR wideband mobile terminals, and confirmed that the reconfigurable processor could be applied to SDR mobile terminals by slight oroeresses.

Proposal and evaluation of security schemes for software-defined radio

The functions of software-defined radio (SDR) can be changed by changing its software. Therefore, many security problems that have never been seen in the conventional fixed wireless terminals have arisen. We assess the security issues of the SDR system by taking the distribution model of SDR terminal software into account. A universal security architecture for the SDR systems is proposed. In the security architecture, security layer 1, involved with radio regulations, is mandatory regardless of the use. In order to keep security, we propose security schemes that use digital signatures in the distribution chain. Three concrete methods are quantitatively compared and discussed. The proposed method can certify the legitimacy of SDR terminals by detecting tampered software and preventing it from being installed on the hardware.

System re-configuration and over-the-air download functions of the software radio prototype supporting PHS and wireless LAN

Software radio, whose functions can be changed simply by replacing only software, is the key to next generation wireless communication systems. We have constructed a software radio prototype based on a multiprocessor architecture. This prototype supports the Japanese personal handy-phone system (PHS) and IEEE 802.11 wireless LAN systems. The paper reports the performance of the prototype. The system re-configuration function and the over-the-air (OTA) download protocol of the prototype are described in detail. The system re-configuration function changes the wireless communication mode of the software radio by replacing the software. To enter the PHS mode takes about ten seconds. The proposed general-purpose OTA download protocol works over TCP/IP. It is very secure because it uses secure socket layer (SSL). It is confirmed that the software can be downloaded from the download server normally.

Design and evaluation of software radio prototype with over-the-air download function

Over-the-air (OTA) download technology will play an important role in realizing software radio. We have already constructed software radio prototypes based on multiprocessor architecture. This paper reports on the implementation of the OTA download function in the software radio prototypes. OTA download time and reconfiguration time were evaluated and analyzed. The results show that PHS mode software could be downloaded within two minutes while prototype reconfiguration took about ten seconds. The current version of this OTA download function suits services that do not have severe time limits, such as updating programs held in memory.

Design of software radio for cellular communication systems and wireless LANs

Software radio base and personal station prototypes for cellular communication systems are designed and implemented. The prototypes are composed of commercial multipurpose DSPs and CPU, pre- and post-processors, A/D/A converters, and RF/IF units. In order to use processor resources effectively, the DSP program handles signal processing in physical and data-link protocol-layers, while the CPU program takes charge of high protocol-layers including call control and system control. The prototypes 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 FDMA/TDD system. Excellent transmitting and receiving performance, compared to conventional hardware radios, is achieved. In addition, expanding the prototypes to support IEEE 802.11 wireless LANs is examined. This paper describes the design and evaluation of the prototypes for cellular systems, and discusses issues and strategies for supporting IEEE 802.11 wireless LANs.

A dual-band simultaneous receiving mixer with independent and linear gain control

A dual-band mixer that can receive multiple band signals simultaneously is reported. Using dual local oscillator (LO) signals simultaneously, the mixer achieves independent gain control through relative power control of the signals. Linear conversion gain control is also achieved through dual LO signal input with total LO power control. The new topology using two MOSFETs is adopted without the need for an additional LO power combiner. Test measurement results confirm that the mixer achieves independent and linear conversion gain control in dual-band simultaneous receiving. The new mixer has higher conversion gain than that of the previously reported single MOSFET mixer in the dual-band receiving.