different-type network connection for dynamic … journal of advanced technology, vol. 1, no. 1...

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NEC Journal of Advanced Technology, Vol. 1, No. 1 43

Advanced Technologies Driving “Dynamic Collaboration” — Featuring System Technologies

Different-Type Network Connection forDynamic CollaborationBy Akira KATO,* Masanobu ARAI* and Ryuhei FUJIWARA†

*System Platforms Research Laboratories†Ubiquitous Platform Development Division

This paper discusses two research and development items that present good examples of how newforms of convenience can be created when different types of networks interwork while taking

advantage of one another’s strong points. One is the prototype of a mobile phone equipped with a terrestrialdigital TV receiver, which can serve as an interactive portable TV terminal targeted at individualusers. Sharing resources with the existing third-generation cellular telephony service, the prototype is almostthe same in size as the mobile phones currently on the market and is suitable for practical use. The other is anad-hoc system aimed at collecting sensor data. We have developed a wireless sensor terminal that can operateon a tiny solar cell the size of a business card, as well as an ad-hoc multi-hop sensor network system wherebysensor terminals are located in a mesh topology, with each several hundred meters apart, thus autonomouslyestablishing a network of multi-hop transmission routes. We believe that having these networks of differenttypes interwork closely with the Internet will create new business in the coming years.

KEYWORDS Terrestrial digital TV, ISDB-T, OFDM, Third-generation cellular phone, Wireless sensor terminal,Solar cell, Ad-hoc multi-hop radio sensor network

1. INTRODUCTION

As the use of portable terminals, such as notebookPCs, PDAs, and mobile phones, has grown, techno-logical advances in these devices have improved theirdata processing capability. Also, in addition to wiredconnector-based connection to fixed Ethernet net-works, many other different forms of communicationsinfrastructures have been put into practical use. Ex-amples include wireless connection approaches whereusers gain LAN access using wireless LAN links orconnect to the Internet via cellular radio systems.Under these circumstances, terminals and accessnodes that are capable of switching access networksor simultaneously accessing different networks havepotential for new markets.

Described below is the status of the work that theNetwork Development Laboratories is conducting todevelop technologies for connection between networksof different types. The topics discussed are a mobilephone terminal equipped with terrestrial digital TVcapability integrating broadcasting and communica-tion, and an ad-hoc system that uses remote termi-nals as relay stations to collect sensor data. Neithersystem is technologically innovative. However, theypresent good examples of how new forms of conve-

nience can be created when different types of net-works interwork while taking advantage of oneanother’s strong points, as compared to when thosenetworks operate independently.

· Development of an integrated communication/broadcasting terminal (3G cellular phone terminalwith terrestrial digital TV capability)In Japan, full-fledged terrestrial digital TV broad-

casting started in December 2003. The signaling sys-tem of this broadcasting service has a broadcastingslot intended for mobile terminals. In addition to thehigh definition television broadcasting service forresidential TV receivers (fixed reception service), an-other service aimed at mobile receivers such as cellphones (mobile reception service) is slated to belaunched in 2005. Integrating a broadcasting receiverwith a mobile phone allows individual users to par-ticipate in broadcast programs in real time and toenjoy on-demand services. Furthermore, users will beviewing programs at different times for differentlengths of time at different locations from when theywatch TV in their homes. These and other changeshave potential for overturning the conventional TVbusiness model whose primary revenue source is ad-vertisement fees. Also, it will become possible forusers to view the content, received with their homeTV sets or PCs, on their mobile terminals by usingsome sort of memory device as a carrying medium.Also likely is the deployment of DRM (Digital RightsManagement) technology that links the usage of

ABSTRACT

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NEC J. of Adv. Tech., Winter 200444

content to charging activity via communication. Ourprototype of the mobile terminal is described in detailbelow.

Figure 1 illustrates the characteristics of Japan’sterrestrial digital TV broadcasting system (ISDB-T).ISDB-T employs OFDM as the digital modulationtechnique, making the system robust againstmultipath fading and Doppler shift. Also, the systemdeploys several measures aimed at mobile reception,such as making it possible to select the parameters ofcarrier modulation technique and error correctiongeared to program reception by mobile terminals.Furthermore, ISDB-T adopts a method whereby asingle channel is divided into 13 frequency blocks(segments) and these segments are grouped into up tothree hierarchical layers, permitting different broad-casting parameters to be set for each layer indepen-dently (hierarchical transmission method). Thismechanism allows a dedicated frequency block withina single channel to be secured for broadcasting tomobile terminals (one segment of layer A in Fig. 1).

Photo 1 shows the appearance of the prototypethat we developed in cooperation with the MobileTerminals Division and released in September 2003.Figure 2 gives the function block diagram of thisprototype. The upper part of the terminal that folds in

Fig. 1 Outline of Japan’s terrestrial digital TV broadcasting system.

Photo 1 Appearance of the prototype.

two contains a TV receiver, and the lower part isequipped with a 3G cellular radio set.

This prototype, which is built on the basis of a 3Gmobile phone model, features an additional functionto receive on a dedicated frequency for mobile receiv-ers of terrestrial digital broadcasting. As hardware

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Different-Type Network Connection for Dynamic Collaboration

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components to be added to the prototype, we devel-oped a small-size TV antenna, a UHF tuner, and asystem LSI chip for OFDM demodulation. Also, asbuilt-in software for the mobile phone, we created TVreception control software that exerts control overthese hardware components so as to enable the selec-tion of the desired TV channel, and software thatprocesses received broadcast streams (MPEG2 trans-port streams) to reproduce images and sound. Of par-ticular note is that the digital stream decoding capa-bility necessary for image and sound reproductionwas realized in the form of firmware on the DSP builtin the mobile phone, keeping the amount of addition-ally required resources to a minimum. This has en-abled us to complete the prototype, which is virtuallythe same size as mobile phones currently on the mar-ket, ahead of competitors around the world. In fiscal2004, we will need to add functionality for data broad-casting reception that has yet to be standardized,while no substantial change is likely to be necessary.The development of this terminal has made it pos-sible for individuals to use video, audio, and databroadcasting services offered by the terrestrial digital

Fig. 2 Function block diagram of the prototype.

TV broadcasting system anywhere anytime, while atthe same time enjoying the interactive Internet com-munication capability of the 3G mobile phone in realtime.

2. DEVELOPMENT OF AN AD-HOC MULTI-HOP SENSOR NETWORK SYSTEM

Today, the Internet is spreading to every corner ofthe globe. However, there are instances where returnon investment in installing wired Internet infrastruc-ture over a wide area cannot be expected due to aninsufficient amount of information or where physicallimitations make such Internet infrastructure diffi-cult to implement. We have devised two innovationsto counter these situations. One is a “power-savingwireless sensor terminal (hereinafter referred to as asensor terminal).” A group of sensor terminals, eachequipped with a standalone power source that re-quires no external power supply or maintenance byhuman personnel, autonomously form a network andrelay environmental data, collected by their sensors,from one terminal to another to a remote location.

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The other is an “ad-hoc multi-hop sensor networksystem,” which allows elaborate wide-area environ-mental monitoring by having sensor terminals lo-cated several hundred meters apart in a mesh topol-ogy. With this system, sensor terminals can beinstalled in various locations such as forests, rivers,and mountains, where it has previously been difficultto install such devices. The characteristics of the sys-tem are described below.

1) Ad-hoc multi-hop communicationA group of newly developed sensor terminals ar-

ranged in a mesh topology communicate with adja-cent terminals via radio links, thus implementing apower-saving network. The ad-hoc multi-hop commu-nication technology enables the autonomous setup ofmulti-hop transmission routes and maintenance andmanagement of the network. Use of this technologyallows sensor terminals, located several hundredmeters apart in a mesh topology, to form a networkautonomously and to relay collected environmentaldata from one terminal to another to the monitoringcenter at a remote location over radio (the specifiedlow-power radio frequency of 429MHz is used). Also,as shown in the configuration diagram of Fig. 3, if asensor terminal fails, an alternative route is auto-matically found, enabling the reconfiguration of thenetwork to ensure an optimum networking environ-ment. Thanks to this feature, a highly reliable wide-area monitoring system can be established.

2) Development of a “power-saving wireless sensorterminal” equipped with ultra-low power con-sumption technologyBy exploiting a unique intermittent reception tech-

Photo 2 Tiny solar cell’s size of a businesscard.

nique and circuit technology that reduce power con-sumption substantially while the terminal is not en-gaged in communication, the sensor terminal oper-ates on a very small amount of power, about 3mW aday on average (assuming that there are 30 nodes andthat 30 measurements are made every day), as illus-trated in Fig. 4. This permits the sensor terminal tooperate solely on a tiny solar cell the size of a businesscard, like the one shown in Photo 2, while making itpossible to use the sensor terminal even in a sunlessplace or during the nighttime and rainy season.Table I shows the specifications of this newlydeveloped terminal. We intend to make the terminalmore compact and to reduce power consumption fur-ther.

3) Elaborate wide-area environmental monitoring ca-tering to diverse needsSeveral different types of sensors can be mounted

Fig. 3 Configuration diagram of ad-hoc multi-hop communication.



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on a sensor terminal as appropriate for the intendedpurposes such as measurements of temperature, hu-midity, and sunlight. Terminals can communicatewith one another over distances of up to 1km or so.Installing sensor terminals several hundred metersapart in a mesh topology realizes elaborate wide-areaenvironmental monitoring.

The “sensor terminal” can easily be installed by alayman without expertise in networking technology.By taking advantage of this feature of the sensor

terminal, we intend to develop solutions that allowpeople to obtain a more detailed and scientific under-standing of natural or urban environments withwhich they are familiar. In this way, we shall en-deavor to create new areas of business while alwaystaking into consideration symbiosis with nature andpreservation of the environment.

Figure 5 illustrates an example of the applicationof this concept. In this example, a network comprisingelementary schools in the basin of a lake is

Table I Specifications of the newly developed terminal.

Specifications

10(W) × 6.5(D) × 2(H) cm (main unit) 10(W) × 6.5(D) × 2(H) cm (battery)

−10°C − 60°C

ARIB STD-T67 specified low-power radio - 429MHz

The base station issues two types of command to drive the terminal.(A) Ad-hoc multi-hop route setup, (B) Specified node measurement + data collection

ID node specification by intermittent reception; andIntermittent activation by a built-in clock (time-specified)

Serial interface, or interrupt + RS-232C data

Retransmission in the event of a timeout or bit errorAd-hoc reconfiguration triggered by data acquisition failure

To be supported.

JIS IP64

Item

Size

Operating temperature

Radio system

Driving systemCommand

Activation method

Sensor interface

Reliability enhancementmeasures

Data encryption

Waterproof standard

Fig. 4 Average power consumption with respect tomeasurement frequency (assuming 30 nodes).

Continuous activation

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established for wide-area monitoring with the aim ofrestoring the natural environment of the lake. Theproject is slated to start in November 2003, withsensor terminals installed around biotopes of threeelementary schools near the Kasumigaura Lake inIbaraki Prefecture, Japan. Students of these elemen-tary schools will collect data about the environmentin and around their schools and keep records on ob-servations of the wildlife in their respective areas,such as water plants, frogs and dragonflies. The el-ementary schools will share collected data with oneanother and use it for their environment educationprograms. We plan to promote the introduction of thissystem to all other schools in the Kasumigaura re-gion, and to schools across the country, as part ofenvironment preservation efforts and environmenteducation activities. By encouraging the building ofcommunities aimed at realizing an eco-friendly soci-ety not only in this and other regions of the countrybut also in other nations, we aim to achieve the resto-ration of the environment.

By working together with companies in variousfields of business as well as with NPOs, NEC willmake aggressive efforts to develop wide-area environ-mental monitoring solutions that are best suited tothe specific needs of individual customers, includingthe following:

① Environmental monitoring for ecosystem manage-ment

② Environmental monitoring for city planning③ Environmental monitoring for disaster prevention④ Environmental monitoring for educational pur-

poses⑤ Environmental monitoring for building construc-

tion⑥ Environmental monitoring for agriculture

3. CONCLUSION

In this paper, we have discussed two research anddevelopment items, which present good examples ofhow new forms of convenience can be created whendifferent types of networks interwork while takingadvantage of one another’s strong points. When thepurpose of a terminal is to implement multiple meansof communication, it is important that the terminalshould not only support physical implementations ofthose means but also feature middleware that guar-antees service continuity and integrity without usersbeing aware of differences in the means of communi-cation. Such middleware establishes a communica-tion path best suited to the service being requested,according to the security policy of the network towhich the terminal has moved, while using theterminal-stored data about the individual in a securemanner. Although details are omitted here due tolimitations of space, we have continuously been ex-tending and improving this type of middleware as ourcore technology. It is featured in both of the systems

Fig. 5 Example of the application.



49

Received January 27, 2004

described in this paper.In addition to the two items discussed herein, the

Network Development Laboratories is conductingR&D work on different-type network connection withrespect to such items as interworking between wire-less LAN and cellular wireless system and inter-working between non-contact IC card and cellularwireless system. We are considering presenting theresults of these R&D efforts on future occasions. Ourunderstanding is that the full-fledged embodiment

and commercialization of the “new forms of conve-nience” stemming from these inter-network connec-tion technologies should be promoted as we developmore ways to use them based on feedback from themarket. We will appreciate requests and advice fromany division concerned.

* * * * * * * * * * * * * * *

* * * * * * * * * * * * * * *

Akira KATO received his B.S. degree fromSaitama University in 1975. He joined NECCorporation in 1975. He is engaged in the de-velopment of application platform for mobileterminal. He is now Senior Manager of SystemPlatforms Research Laboratories.

Masanobu ARAI received his B.S. degree fromTokyo University in 1979, and his M.S. degreein 1981. He joined NEC Corporation in 1981.He was engaged in the development of digitalswitching systems and their interface key de-vices such as BORSCHT and ISDN, and is

recently engaged in optical switching and ubiquitous sensornetwork system. He is now an Executive Manager at NECSystem Platforms Research Laboratories.

Mr. Arai is a member of the Institute of Electronics, Infor-mation and Communication Engineers of Japan.

Ryuhei FUJIWARA received his B.S. degreefrom Tokyo Denki University in 1975. Hejoined NEC Corporation in 1975. He is en-gaged in the development of ubiquitous net-work services platform. He is now a ChiefManager at NEC Ubiquitous Platform Devel-opment Division.

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