Showing papers by "Hiroshi Harada published in 2011"

Enabling coexistence of multiple cognitive networks in TV white space

Abstract: We address the problem of coexistence among wireless networks in TV white space. We present a standard independent framework to enable exchange of information relevant for coexistence based on two mechanisms: centralized and distributed. Both mechanisms introduce the use of multiradio cluster-head equipment (CHE) as a physical entity that acquires relevant information, identifies coexistence opportunities, and implements autonomous coexistence decisions. The major conceptual difference between them lies in the fact that the centralized mechanism utilizes coexistence database(s) as a repository for coexistence related information, where CHEs need to access before making coexistence decisions. On the other hand, the distributed mechanism utilizes a broadcast channel to distribute beacons and directly convey coexistence information between CHEs. Furthermore, we give a concise overview of the current activities in international standardization bodies toward the realization of communications in TVWS along with measures taken to provide coexistence between secondary cognitive networks.

IEEE 1900.6: spectrum sensing interfaces and data structures for dynamic spectrum access and other advanced radio communication systems standard: technical aspects and future outlook

Abstract: Currently, the IEEE Standards Association is very active in the framework of cognitive radio with an aim to provide a bridge between research results, implementation, and widespread deployment of this new communication paradigm. This article reports recent developments within the IEEE Dynamic Spectrum Access Network Standards Committee1 on dynamic spectrum access networks with particular consideration of IEEE 1900.6, "Spectrum Sensing Interfaces and Data Structures for Dynamic Spectrum Access and Other Advanced Radio Communication Systems." It outlines the current structure of the IEEE 1900.6 standard and its relationship with other related standardization activities. We provide application scenarios and topology briefly, and discuss open research issues that raise future challenges to the standardization community.

Coexistence of homogeneous and heterogeneous systems for IEEE 802.15.4g smart utility networks

Abstract: This paper presents the overview on coexistence of homogeneous and heterogeneous systems for the IEEE 802.15.4g Smart Utility Network (SUN), a low rate wireless personal area network (WPAN) standard for advanced utility service. The 802.15.4g specifies three alternative physical (PHY) layer designs, thus having multiple homogeneous systems within the SUN system. The three homogeneous systems are allocated across shared frequency bands dependent on different regulatory domains. Besides coexistence for homogeneous systems, the SUN system is also sharing several frequency bands with multiple heterogeneous systems across various other 802 standards. Understanding the details of these coexisting dissimilar systems is an essential step to creating a harmonious radio environment. Therefore, this paper provides the outline of the coexisting homogeneous and heterogeneous systems, as well as the corresponding frequency bands that are allocated in different regulatory domains. Secondly, the overview on the coexistence mechanisms applicable in the 802.15.4g system is presented. Thirdly, coexistence analysis is performed on two dissimilar systems, where the performance degradation of a victim system is evaluated in the presence of an interferer. As a collective result, it is shown that with victim-interferer separation of beyond approximately 30m, dissimilar systems are able to coexist even without higher layer coexistence mechanisms.

An investigation into the spectrum occupancy in Japan in the context of TV White Space systems

Abstract: This paper presents the results of spectrum occupancy measurements carried out in three locations of Kanto area in Japan. Moreover, the collected data corresponding to DTV broadcasting service is analyzed to evaluate the possibilities of secondary systems operating in TV White Spaces (TVWS) in the framework of FCC regulations and Japanese standards. Appropriate propagation models are considered for analyzing the conditions of operation for both, fixed and portable unlicensed devices.

Selection of modulation and coding schemes of single carrier PHY for 802.11ad multi-gigabit mmWave WLAN systems

Abstract: This paper presents the system design method to determine the modulation and coding schemes according to the given usage models of single carrier transmission in millimeter wave Wireless LAN systems. Various modulation and coding combinations are compared and analyzed based on the BER performance over both AWGN and fading channels. The effects of hardware impairments including power amplifier non-linear effects and phase noise, etc., are considered as well. The system design strategy provides a guideline for the selection of modulation and coding schemes in practical which can fulfill the realistic system requirements.

Development of a TV white space cognitive radio prototype and its spectrum sensing performance

Abstract: In this paper, we describe a recently developed television white space (TVWS) hardware prototype. The prototype includes the following components: a cognitive management entity (CME), a sensing module, a geolocation device, a TV band database, a transmitter and a receiver. The prototype is developed in compliance with recent Singapore TVWS test trial regulations. The prototype operates within 630 MHz to 742 MHz bands, within Singapore TV channels 41 to 54, except channels 50 and 52. The prototype is able to search for existing TV signals in the aforementioned channels by looking at a TV band database, as well as, a by performing sensing. Once the TV channel(s) is/are found vacant, the prototype can intelligently decide to use a single or 2/4/8 continuous TV channels of 8 MHz each. It has the capability to transmit BPSK and OFDM signals and decode the transmitted signals in the receiver. While in operation, if TV signal appears in a single or multiple channel(s), the prototype can switch to vacant channel(s), if available. Otherwise, it ceases operation. The sensing module has capability to sense analog (PAL) and digital (DVB-T) TV signals. Some sensing performance of analog TV signal detection is also presented.

Performance Evaluation of IEEE 802.19.1 Coexistence System

Abstract: In this paper we analyze mechanisms of coexistence between different cognitive radio systems operating as secondary users in white space frequency bands. In particular, our focus is coexistence mechanisms that can be provided by IEEE 802.19.1 coexistence system. IEEE 802.19.1 standard is at the early stage of its development. At this stage it is very important to consider different design directions and focus areas. This paper presents results of performance evaluation of the IEEE 802.19.1 coexistence system based on simulation. We believe that simulation results shown in this paper and analysis of these results are very important for the future of both IEEE 802.19.1 standard and products based on this standard.

Spectrum sensing for cognitive radio systems: technical aspects and standardization activities of the IEEE P1900.6 working group

Abstract: The evolution of future wireless communication systems imposes a strong requirement on the efficiency of spectrum usage, which is expected to be leveraged by interacting and cooperating cognitive radios forming wider cognitive radio systems. Dynamic spectrum access is a potential means to improve spectrum usage. A key step in realizing DSA is to obtain spectral occupancy information provided by spectrum sensors. Subsequently, nodes in a CRS analyze spectrum usage to find unused spectrum (often referred to as white spaces). Then the system makes a decision on the best opportunities considering regulatory policy, transceiver capacity, and so on. In such an operation, sensing information exchange plays a fundamental and key role in enabling efficient DSA. This article presents the technical issues and IEEE standardization activities related to sensing information exchange. In particular, the IEEE P1900.6 working group activities aimed at standardizing logical interfaces and data structures required for exchange of sensing related information between sensors and their clients are discussed. By explaining the objective, use cases, reference model, data structure, data representation, and generic procedures developed so far, the article presents the main technical aspects of the IEEE P1900.6 sensing interface and its usefulness in CRSs.

Wireless communication system, coexistence manager installed in said system, and method for wireless communication

Abstract: Disclosed is a wireless communication system capable of avoiding interference even when a network including a secondary user coexists. The wireless communication system includes a primary user belonging to a first network, a first secondary user belonging to a second network, and a coexistence manager (CM). The coexistence manager (CM) acquires information relating to spectrum holes that are, at least temporarily, not in use by the primary user. In addition, the coexistence manager (CM) determines whether or not usage of the spectrum holes by the first secondary user causes interference. If the determination result is that interference is caused, coexistence manager (CM) notifies to this effect a second secondary user belonging to a third network, which differs from the second network.

Cognitive wireless network infrastructure and restoration activities for the earthquake disaster

Abstract: Cognitive radio is a key technology for optimized and efficient radio resource utilization. However, cognitive radio systems achieve most performance not as individual radio devices, but as a wireless network infrastructure comprising a number of radio devices deployed over geographically wide area. This paper describes a world first trial of cognitive wireless network infrastructure with about 500 cognitive wireless routers, which have been originally developed by the authors, throughout a city cooperatively managed from an operation center. Part of the design has been contributed and adopted by IEEE 1900.4. The test-bed was partly reinstalled in North-east area of Japan for the restoration of the Internet access after the earthquake disaster occurred in March 11, 2011, where stability and applicability of the system is verified by analysis of obtained measurements. Tendency of internet access in terms of traffic amount and user connections is also analyzed as well as raising requirements for wireless network infrastructure in disaster cases.

Traffic allocation control using support vector machine in heterogeneous wireless link aggregation

Abstract: In heterogeneous wireless network environment, various radio access networks (RANs) are available for mobile terminals which have multiple wireless network interfaces to connect to each different RAN. However, it is very difficult to improve the throughput by aggregating different RANs, which have different quality of service (QoS) in the throughput, the delay, the packet loss, and so on. In this paper, we propose a traffic allocation control scheme using a machine learning algorithm to improve the link aggregation throughput in such heterogeneous wireless networks. We introduce the support vector machine, which has an advantage on generalization to have good performance for unknown input patterns. By our experiments using a cognitive wireless network system, called Cognitive Wireless Clouds, it is clarified that our proposed scheme improves the throughput higher than the conventional methods based on the throughput of each RAN.

Performance analysis of low duty FSK system for Smart Utility Network

Abstract: This paper presents the performance analysis of a realistic Smart Utility Network (SUN) system with low duty signaling design. The main focus of this paper is to evaluate the performance of the SUN system based on the specifications in an on-going industrial standardization activity, the IEEE 802.15.4g. For this purpose, a theoretical framework is constructed to model the transceiver with low duty signals over a realistic SUN channel based on actual measurements. The theoretical framework provides the models of multiple access interference (MAI) and inter-symbol interference (ISI). To align the analysis with actual industrial requirements, the developed framework is substituted with parameters from the IEEE 802.15.4g specifications. As a result, it is found that the low duty system (i.e. 0.1%) is capable of supporting up to 100 users in a single network. Additionally, by reducing the duty factor (e.g. from 1% to 0.1%), a 2-digit performance improvement (e.g. bit error rate (BER)=10–5 to BER=10–7) can be achieved as compared to the requirement of IEEE 802.15.4g specifications (i.e. BER ≈ 10–5).

New robust sensing methods for DVB-T signals

Abstract: The regulations for operation in the TV white space (TVWS) have been developed and released in USA and UK It is believed that the ongoing TVWS related standardization projects, such as IEEE P802.19.1, IEEE P802.11af and IEEE P802.22, will encourage the regulation development in more countries and regions. Current regulations commonly require the TV band device (TVBD) or the sensing only TVBD to be capable of detecting incumbent TV signals of very low power level within a short time. To fulfill the strict requirements on both of sensitivity and sensing time while keeping the hardware implementation cost below a desired level, we propose two new sensing methods for DTV signals of DVB-T standard: the optimal one requires time synchronization and is therefore called The Proposed_Syn while the sub-optimal one requires no time synchronization and is called The Proposed_Asyn. Both computer simulation results and hardware testing results are shown in this paper. Simulation results show that for achieving a goal of high detection probability (≥90%) and low false alarm probability (≤1%) at a very low SNR (=−20dB) in AWGN channel, in comparison with conventional sensing methods, The Proposed_Syn reduces sensing time by 50% and both proposed methods can significantly reduce hardware implementation cost by potentially reducing multiplexer number more than 99%. Hardware sensing prototype testing results have further verified the improved performance by using the proposed sensing methods.

Wireless communication system, cluster head equipment (che) installed in wireless communication system, and wireless communication method

Abstract: Disclosed is a wireless communication system and the like that can avoid interference even if a plurality of networks coexist. The wireless communication system includes a primary user, cluster head equipment, and a secondary user. The cluster head equipment is for providing a local area network to a cluster region containing the abovementioned primary user. Also, the cluster head equipment contains: an acquisition means that acquires one or both—of information regarding the primary user and information regarding a primary signal—and the like; and a transmission means that transmits information to the secondary user. Then, using this wireless communication system, the secondary user performs cognitive wireless communication or the like on the basis of the information received from the transmission means of the cluster head equipment.

Autonomous Dynamic Frequency Selection for WLANs Operating in the TV White Space

Abstract: This paper describes the challenges of frequency channel selection for WLANs operating in the TV White Space (TVWS) and proposes a dynamic frequency selection (DFS) technique as a solution. Based on the statistics gained from past usage experience of channels, of the TVWS channels' vacancies and channel occupation by the adjacent WLANs, each WLAN evaluates and prioritize the channels independently using a priority function. Then by selecting the channel of the highest priority among vacant channels, each WLAN can quickly find a channel in the low interference regime and whose vacancy is adaptive to its traffic load distribution as well. Performance of the proposed DFS is evaluated through simulation using QualNet, based on TVWS channels with realistic feature and by setting the weight factors of different metrics in the priority function to different values. The evaluation results show that compared to conventional DFS, the proposed DFS avoids adjacent APs selecting the same channel and reduces channel switch rate, and is more adaptive to diverse environments. As a consequence, it maximally reduces total time consumption of channel switch by 40% than random selection.

Radio communication system, coexistence manager installed in the system, and radio communication method

Abstract: PROBLEM TO BE SOLVED: To provide a radio communication system capable of preventing interference even when a network including a secondary user coexists, and the like. SOLUTION: The radio communication system includes a primary user belonging to a first network, a first secondary user belonging to a second network, and a coexistence manager (CM). The coexistence manager (CM) acquires information related to a spectrum hole without being at least temporarily used by the primary user. The coexistence manager (CM) determines whether interference occurs in the first network by usage of the spectrum hole by the first secondary user. When interference occurs as a result of the determination, the occurrence of the interference is reported to a second secondary user belonging to a third network different from the second network. COPYRIGHT: (C)2011,JPO&INPIT

Proposal and hardware implementation of smart threshold setting methods for spectrum sensing

Abstract: For spectrum sensing in very low SNR regime, noise uncertainty (Nu), either arises from change of environment or hardware noise of a sensing device, could make proper setting of threshold difficult and therefore, is recognized as a challenge for achieving robust sensing. This paper proposes two smart threshold setting methods, called dynamic threshold selection (DTS) and realtime threshold setting (RTTS), respectively, to overcome the NU produced by hardware system noise in spectrum sensing. In DTS based sensing, a threshold table, which shows corresponding thresholds for non-overlapping noise variance ranges, is produced by the sensing device in advance through a study process; during sensing, the sensing device estimates the instantaneous noise variance and by mapping which to the threshold table it finds the proper threshold. In RTTS based sensing, the sensing device isolates itself from receiving any signals, computes threshold statistics immediately prior to sensing and accordingly decides the proper threshold for subsequent sensing. Computer simulation results show that by adopting the proposed methods, degradation of sensing performance caused by Nu can be largely compensated. The hardware implementation of DTS into a sensing prototype with complete hardware and software design is also shown, and the hardware test results further verify the novelty of proposed methods.

A Space-Time Scheduling Assisted Cooperative Relay for mmWave WLAN/WPAN Systems with Directional Antenna

Abstract: This paper proposes a space-time scheduling algorithm that improves the throughput performance of millimeter-wave wireless personal/local area network(mmWave WPAN/WLAN) systems. The upcoming mmWave WPAN/WLAN systems are designed to support high definition TV (HDTV) transmission, high speed wireless docking and gaming, etc. These data-rate-greedy applications require Gbits/s or even multi-Gbits/s transmission capacity which can be provided by the mmWave bands. Directional antenna are preferred in these bands to compensate high path loss. However the narrowed transmission angle of directional antenna makes the system susceptible to blockage of human body or furniture. Consequently, the throughput performance is compromised and may not meet the requirement of the targeting applications. Cooperative relay with time slot sharing is a solution to guarantee throughput under such situation. Compared with lower frequency bands, it is easier in mmWave bands to share time slot between the direct path and relay path, due to less co-channel interference constrained by path loss. In this paper, we propose a space-time scheduling algorithm to assist cooperative relay. The algorithm is based on graph theory and designed to find optimized relay station and time slot to maximize the system throughput. Computer simulations demonstrate over 25 percent throughput improvement is achieved under conference room None-line-of-sight (NLOS) environment with human blockage. The achieved performance meets the requirement of uncompressed HDTV transmission.

Wireless communication system applied to aviation industry and airband interference detection method

Abstract: Provided is a wireless communication system capable of increasing safety in the aviation industry, and applicable to the aviation industry. The wireless communication system comprises a control device and a spectrum sensor. The spectrum sensor performs spectrum sensing using a measurement SAP, receives a signal from a wireless communication device, and transmits information relating to the received signal as sensing information through a communication SAP. On the other hand, the control device receives the sensing information from the spectrum sensor through the communication SAP. Subsequently, the sensing information is analyzed using an application SAP. Thereby, whether or not the signal from the wireless communication device interferes with the radio waves of the airband used in the aviation industry is specified.

Performance of Common Signaling Mode for Multi-PHY Management in Smart Utility Networks

Abstract: This paper presents the performance evaluation of a common signal employed to enable coexistence between heterogeneous physical (PHY) layer designs in the Smart Utility Networks (SUNs). The coexistence mechanism, known as Multi-PHY Management (MPM) uses a common PHY signaling specification known as the Common Signaling Mode (CSM) to facilitate interference avoidance/mitigation among the three specified alternative PHYs in the on-going industrial standardization for SUN, namely the IEEE 802.15.4g. The CSM is a signaling design commonly supported by all three PHYs in the 802.15.4g. In this paper, we have analyzed the performance of the CSM from the perspectives of receiver type, likelihood of detection and achievable range. The effectiveness of CSM is an essential factor for the performance of MPM. It is found that by using a correlator receiver, the likelihood of detecting the CSM is typically 20-25dB better than an energy detection receiver. The achievable transmission range of the CSM is 90m with a correlator receiver and is decreased to 30m with an energy detector.

60 GHz wideband antena with air filled stacked patch structure

Abstract: A wideband antenna is designed and implemented by using air filled stacked structure on thin PTFE substrate for millimeter wave personal network area (WPNA) application. The optimized antenna achieves more than 22% impedance bandwidth and more than 9 dBi gain over the frequency band 57 – 66 GHz.

Periodically Loaded Straight Wires for Radio Wave Transmission Control

Abstract: Calculating current distributions along conducting straight wires reveals that the electric influence of the wires is more effectively reduced by loading reactances than it is by disconnecting the loading ports. With the electric influence almost eliminated, a sheet consisting of reactively loaded straight wires can almost perfectly transmit a radio wave of a frequency determined by the interval between the loading ports and the reactance value. The frequency responses of radio wave transmissions for a normal incident plane wave are numerically calculated, and it is shown that by controlling the reactance value, the transmission can be changed more than 30 dB. Thus, a sheet by which radio wave transmission can be electronically controlled is proposed, and its operation is experimentally examined.

Efficiency of short-distance wireless transmission considering radiation loss

Abstract: To evaluate radiation loss and conductor loss which are the cause of deterioration in the wireless electric power transmission, a calculation method of a transmission electric power, a radiated power, and a conductor loss as a ratio to the input electric power is proposed. The dependency of these ratios on the resistance and the reactance of the receiving circuit are clarified for the short distance wireless electric power transmission between small dipoles, and the method to improve the transmitting efficiency is investigated.

Enabling technologies for a practical wireless communication system operating in TV white space

Abstract: This paper proposes the design of enabling technologies for practical wireless communication systems operating in the TV white space (TVWS). The main objective of this paper is to cover a macro perspective on the system design blocks including: (a) targeted use case applications and governing regulations, (b) channelization, physical (PHY) layer and medium access control (MAC) layer designs, and (c) achievable throughput and range. It is the intention of this paper to serve as a general guideline for designing wireless communication systems operating in TVWS. The core system design addresses both PHY and MAC layer issues with realistic system considerations. In the PHY layer, a channelization design that fits into the area-specific TV channels and a transceiver that enables data exchange in the TV bands are designed. In the MAC layer, a cognitive engine that manages access to vacant TV channels and MAC functionalities that facilitate effective medium access are also proposed. As a result, the system is capable of supporting up to a typical throughput of 80Mbps, and a maximum number of 40 users, assuming all users performing the most bandwidth-hungry application in the use case scenario. The corresponding operating range is found reach up to 400 m.

Feasibility study on spectrum sharing type cognitive radio system with outband pilot channel

Abstract: This paper proposes a spectrum sharing type cognitive radio system integrated with a dedicated radio system called out-of-band pilot channel (OPC). The OPC notifies the radio configuration information of cognitive base station (CBS), such as operational frequency and PHY/MAC parameters, to cognitive terminal (CT) so that the CT does not need to sense throughout a large range of potential frequency bands and immediately configure itself to connect to the CBS. Experimental evaluation shows that the proposed system takes 2.80 seconds to obtain the information on accessible CBS, whereas the conventional system without the OPC takes 8.09 seconds for sensing just 4 frequency channels. It is confirmed that the proposed system achieves a drastic time reduction to obtain the CBS radio configuration information.

Method of sharing information in cognitive radio communication, cognitive radio communication device, and cognitive radio communication system

Abstract: PROBLEM TO BE SOLVED: To provide a method of sharing information in cognitive radio communication for efficiently and effectively exchanging sensing information and sensing control information among a plurality of cognitive radio communication devices SOLUTION: In the method of sharing information in cognitive radio communication, first a common channel usable among a plurality of radio communication devices is detected Then, the detected common channel is utilized to share the sensing information and the sensing control information among the plurality of radio communication devices COPYRIGHT: (C)2011,JPO&INPIT

Interference Mitigation Capability of a Low Duty DS-Multiband-UWB System in Realistic Environment

Abstract: In this paper, the performance of a low duty factor (DF) hybrid direct sequence (DS) multiband (MB)-pulsed ultra wideband (UWB) system is evaluated over realistic propagation channels to highlight its capability of interference mitigation. The interference mitigation techniques incorporated in the DS-MB-UWB system is a novel design that includes the utilization of the frequency-agile multiple sub-band configuration and the coexistence-friendly low DF signaling. The system design consists of a Rake type receiver over multipath and multi-user channel in the presence of a coexisting narrowband interferer. The propagation channels are modeled based on actual measurement data. Firstly, by suppressing the power in the particular sub-band coexisting with the narrowband signal, performance degradation due to narrowband interference can be improved. It is observed that by fully suppressing the sub-band affected by the narrowband signal, a typical 1-digit performance improvement (e.g. BER improves from 10-3 to 10-4) can be achieved. Secondly, by employing lower DF signaling, self interference (SI) and multi-user interference (MUI) can be mitigated. It is found that a typical 3dB improvement is achieved by reducing the DF from 0.5 to 0.04. Together, the sub-band power suppression and low DF signaling are shown to be effective mitigation techniques against environment with the presence of SI, MUI and narrowband interference.