Kazunori Akabane

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.

Ubiquitous Networks with Radio Space Extension over Broadband Networks

Many devices are expected to be networked with wireless appliances such as radio frequency identification (RFID) tags and wireless sensors, and the number of such appliances will greatly exceed the number of PCs and mobile telephones. This may lead to an essential change in the network architecture. This paper proposes a new network architecture called the appliance defined ubiquitous network (ADUN), in which wireless appliances will be networked without network protocol standards. Radio space information rather than individual appliance signals is carried over the ADUN in the form of a stream with strong privacy/security control. It should be noted that this is different from the architectural principles of the Internet. We discuss a network-appliance interface that is sustainable over a long period, and show that the ADUN overhead will be within the scope of the broadband network in the near future.

Error control scheme for TCP packet radio systems

To meet a demand of convenient mobile computing, we studied an error control scheme mounted on a conventional radio packet system. Two error control schemes for the transmission control protocol (TCP) connection on a wireless network are proposed that can minimize the degradation in the radio link throughput due to the TCP retransmission. One scheme is based on the discard of the TCP retransmission packets, and the other is based on the suppression of transmission delay fluctuation on the radio link. These schemes can be mounted without changing the existing TCP scheme. Simulation results show that the degradation in throughput is reduced by 11% by using either scheme when the frame error rate is 10/sup -2/ under the indoor-B condition and pedestrian condition that are defined as the standard simulation condition for IMT-2000.

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

Spectrum Sensing for Networked System Using 1-Bit Compressed Sensing with Partial Random Circulant Measurement Matrices

Recently developed compressed sensing theory enables signal acquisition and reconstruction from incomplete information with high probability provided that the signal is sparsely represented in some basis. This paper applies compressed sensing for spectrum sensing in a networked system. To tackle the calculation and communication cost problems, this paper also applies structured compressed sensing and 1-bit compressed sensing. Measurement using the partial random circulant matrices can reduce the calculation cost at the sacrifice of a slightly increased number of measurements by utilizing the fact that a circulant matrix is decomposed by multiplications of structured matrices. This paper investigates the tradeoff between calculation cost and compression performance. 1-bit compressed sensing extracts only sign data (1-bit quantization) from measured data, and reconstructs the original signal from the extracted sign data. Therefore, 1-bit compressed sensing can save communication costs associated with spectrum sensing in a networked system. This paper evaluates the efficiency of 1-bit compressed sensing. In addition, this paper also proposes a block reconstruction algorithm for 1-bit compressed sensing that uses the block sparsity of the signals. Empirical study shows that partial random circulant matrices work as efficient as completely random measurement matrices for spectrum sensing and that 1-bit compressed sensing can be used for spectrum sensing with greatly reduced communication costs.

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.

1-bit compressed sensing with edge detection for compressed radio wave data transfer

The “Flexible Wireless System (FWS)” has been proposed as a networked system for the “User-Centric Wireless Network (UCWN)”. The UCWN will allow users to make network connections easily at all times without being conscious of any upgrades or differences in wireless systems. The FWS is a unified wireless platform that simultaneously deals with various types of wireless signals. It consists of flexible access points and a wireless signal processing platform. Various types of wireless signals are received at a distributed flexible access point and transferred to a server in the wireless signal processing platform through the wired access line. Transferred signals are separated and demodulated at the server. To achieve highly flexible and efficient radio wave data transfer between the access point and the FWS server, we consider compression of transfer data. In this paper, we propose 1-bit compressed sensing with smoothed edge detection, which enhances compression and reconstruction performance. This paper shows the performance of the proposed method by using computer simulations to explore the methods validity for transferring compressed radio wave data.

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.

Prototype of a Cognitive Radio System with Cooperative Sensing and Interference Alerting

Cognitive radio systems provide dynamic spectrum access, which is expected to improve frequency use efficiency. These systems need a sensing function to avoid interference from other radio stations. However, it is impossible to completely avoid interference because no perfect sensing function has been developed. To solve this problem, we propose using a new cognitive radio system with three main functions: cooperative sensing, interference alerting, and frequency management. We developed and evaluated a prototype of the system and found that the system is effective.

Invited Talk: Appliance Defined Ubiquitous Network

Many devices are expected to be networked with wireless appliances such as radio frequency identification (RFID) tags and wireless sensors, and the number of networked wireless appliances will greatly exceed the number of PCs and mobile telephones . This may lead to an essential change in the network architecture. This paper proposes a new network architecture called the appliance defined ubiquitous network (ADUN), in which wireless appliances will be networked without network protocol standards. Wireless space information rather than an individual appliance signal is carried over the ADUN in the form of a stream with strong privacy/security control. It should be noted that this is different from the architectural principles of the Internet. We discuss a network-appliance interface that is sustainable over a long term, and show that the overhead of the ADUN will be within the scope of the broadband network in the near future