Homare Murakami

Energy Consumption Measurement of Wireless Interfaces in Multi-Service User Terminals for Heterogeneous Wireless Networks

For future generation mobile networks, we expect that the mobile devices like PDAs, note PCs or any VoIP-enabled communicators will have the feature of being always switched on, ready for service, constantly reachable by the wireless Internet. In addition to high access speed, attractive real-time contents or other expected spectacular features of the future wireless Internet environment, the mobile terminals has to be very much energy-aware to enable literal untethered movement of the user. Mechanisms for network activities like maintaining location information and wireless system discovery, which require regular network access, should be energy-efficient and resource-efficient in general. Cellular systems employ the notion of passive connectivity to reduce the power consumption of idle mobile hosts. In IP based Multi-service User Terminal (MUT) that may have multiple wireless interfaces for receiving various classes of services from the network, there should be an efficient addressing of the energy consumption issue. To devise an energy-efficient scheme for simultaneous or single operation of the wireless interfaces attached to such terminals we should have comprehensive understanding of the power consumption of the devices/modules in various operational states. This paper investigates the power consumption pattern or behavior of some selected wireless interfaces that are good candidates for being part of the future of the multi-service user terminals. We propose a simple model for predicting energy consumption in a terminal attributed to the wireless network interfaces. We measured the actual consumption pattern to estimate the parameters of the model.

A Software Defined Cognitive Radio System: Cognitive Wireless Cloud

This paper introduces the concept, features and architecture of a software defined cognitive radio system: Cognitive Wireless Clouds (CWC) that can realize user-centric and scalable network based on unique cognitive spectrum access, cross-network signaling, network optimization, and fast reconfiguration methods. Then, this paper shows results of feasibility studies on a software defined cognitive radio (SDCR) terminal that can access to the CWC. This includes the configuration of the SDCR terminal and a measurement data for spectrum sensing period and reconfiguration period by using software packages of W-CDMA and IEEE802.11a.

International standardization of cognitive radio systems

The current radio environment is characterized by its heterogeneity. Different aspects of this heterogeneity include multiple operators and services, various radio access technologies, different network topologies, a broad range of radio equipment, and multiple frequency bands. Such an environment has a lot of technical and business opportunities. Examples are joint management of several radio access networks within one operator to balance load of these networks, detecting and using unused spectrum in the allocated frequency bands without interrupting the operation of the primary users of such frequency bands, and spectrum trading between several operators. To exploit such opportunities, the concept of cognitive radio system has been developed. Many CRS usage scenarios and business cases are possible. This has triggered a lot of standardization activity at all levels, including in the International Telecommunication Union, IEEE, European Telecommunications Standards Institute, and European Association for Standardizing Information and Communication Systems; each of these organizations is considering multiple CRS deployment scenarios and business directions. This article describes the current concept of the CRS and shows the big picture of international standardization of the CRS. Understanding of these standardization activities is very important for both academia and industry in order to select important research topics and promising business directions.

Measurement and usage of power consumption parameters of wireless interfaces in energy-aware multi-service mobile terminals

For IP-based always-on type multi-service user terminals, which may have multiple wireless interfaces, energy-efficiency is a key requirement. It is crucial to take into account the power consumption behavior and delay patterns associated with each state and transitions of the wireless devices to formulate efficient operation of multi-module terminals, especially in services where media/session handover between wireless networks are targeted. This paper investigates the power consumption pattern or behavior of some selected wireless interfaces that are good candidates for being part of the future of the multi-service user terminals. We propose a simple model for predicting energy consumption in a terminal attributed to the wireless network interfaces. We measured the actual consumption pattern to estimate the parameters of the model.

Design and Implementation of Cognitive Wireless Network based on IEEE P1900.4

IEEE P1900.4 is an emerging standard for optimized radio resource utilization where cognitive radio technologies are used for efficient spectrum utilization. In this paper, we design and implement a cognitive wireless network system based on open documents of IEEE P1900.4, and evaluate its performance using UDP streaming and HTTP download. Our experiments show interesting results that total network throughput in the HDP streaming is improved by 30% although some of individual terminals can not necessarily obtain better throughput. Also, it is shown that performance in the HTTP download becomes worse by up to about 40% as the number of handover increases due to the TCP window control. Our analysis is expected to point out importance of higher layer coordination with lower layers for end-to-end performance improvements in cognitive wireless networks.

Research and development on heterogeneous type and spectrum sharing type cognitive radio systems

This paper introduces two cognitive radio (CR) systems: (a) heterogeneous type CR and (b) spectrum sharing type CR regarding its definition, usage model, fundamental system architecture, and developed prototype.

Dynamic Spectrum Assignment and Access Scenarios, System Architecture, Functional Architecture and Procedures for IEEE P1900.4 Management System

Implementing dynamic spectrum assignment and access technologies in heterogeneous wireless networks may lead to considerable improvement in spectrum usage. For this purpose, management system shall be added on top of existing heterogeneous wireless system. IEEE P1900.4 working group has been developing such management system. In this paper, we propose different scenarios for IEEE P1900.4 dynamic spectrum assignment and access use cases. We propose enhancements to IEEE P1900.4 system architecture. Also, we propose functional architecture for IEEE P1900.4 management system. Finally, we propose generic procedures to implement proposed scenarios using proposed system architecture.

The architecture and a business model for the open heterogeneous mobile network

The mobile communication market has grown rapidly over the past 10 years, but the market may reach saturation in the foreseeable future. More flexible mobile networks able to meet various user demands and create new market openings are needed for further growth. Heterogeneous networks are more suitable than homogeneous networks for meeting a wide variety of user demands. There are two types of heterogeneous network: a closed-type whose network resources are deployed and operated by communication carriers, and an open-type whose network resources would be deployed not only by existing operators but also by companies, universities and so on. It will be easy for newcomers to enter mobile businesses in an open heterogeneous mobile network, so many innovative services are likely to be provided through cooperation between various companies or organizations. This paper proposes revised architectures for TISPAN-NGN which corresponds to heterogeneous networks and open mobile markets, and presents new business models.

Context-Based Network and Application Management on Seamless Networking Platform

A context-based adaptive communication system is introduced for use in heterogeneous networks. Context includes the users presence, location, available network interfaces, network availability, network priority, communication status, terminal features, and installed applications. An experimental system was developed to clarify the feasibility of using context information to flexibly control networks and applications. The system operates on a seamless networking platform we developed for heterogeneous networks. By using contexts, the system can inform the caller and callee of applications they can access, which are available through the network before communication occurs. Changes in contexts can switch an on-going application to another during actual communication. These functions provide unprecedented styles of communication. A business scenario for a seamless networking provider is also presented.

Design and Implementation of A Distributed Radio Resource Usage Optimization Algorithm for Heterogeneous Wireless Networks

We have designed and implemented a radio access network selection algorithm for heterogeneous wireless network environment, in which mobile terminals can adaptively and seamlessly handover among different radio access technologies. We propose a radio resource usage optimization algorithm without centralized computation on the network side, which is based on the Hopfield neural network dynamics whose energy function autonomously minimizes by distributed update of each neuron. We have implemented the proposed algorithm on an experimental heterogeneous wireless network system, which includes functionalities defined in IEEE 1900.4. First, we show that the proposed algorithm can optimize fairness of the throughput by numerical simulation. Then, we show that our algorithm works correctly and optimizes radio resource usage also on the experimental wireless network by distributed handover decisions on the terminal side.