Power Line Communications: State of the Art and Future Trends

POWER LINE LOCALAREA NElWORKS - -a Power Line Communications: State of the Art and Future Trends

Niovi Pavlidou, Aristotle University of Thessaloniki A. 1. Han Vinck, University of Essen Javad Yazdani and Bahram Honaty, University of Lancaster

ABSTRACT mercial production of electromechanical meter rcpcatcrs took place. By late 1980, relatively This article constitutes an overview of the sophisticated error control coding techniques research, application, and regulatoly activities on within the hardware of PLC modems were pro- power line communications. Transmission issues posed. PLC standards have evolved constantly on the powcr line arc investigated and modeling over the years, especially the last 20, and result- approaches illustrated. Contemporary communi- ed after 1994 in the digital power line boost cation techniques and reliability issues are treat- promising new revenues for energy utilities and ed. A bricf description of regulatory activities cheap Internet access for consumers. worldwide is given. Finally, market perspectives Medium voltage lines used as hackhones for and promising applications are covered to assess telecom operators have become a mature tech- the viability of this communications environ- nology. Clearly the main focus is and will contin- ment. ue to he on the connection between house and transformer as a solution for the “last dirty mile” INTRODUCTION problem. Furthermore, new interest arises due to recent developments regarding in-house net- The usage of the power grid for control, mainte- working. However, to develop these applications nance, and charging purposes by the utility com- in a commercially attractive way seems to still he modities has a long history [l-31. The hard for various reasons. liberalization of telecomniunications and the Essentially, what is missing is a clear regula- dercgulation of electricity utilities have added tory framework. In Europe the CENELEC hand new dimensions to the potential application of (3-148.5 kHz) is currently allocated to classic the electricity infrastructu1:e for the most effi- narrowband applications, with a maximum signal cient use of the local loop. Furthermore, the power of 5 mW and rates up to 144 khls over birth and growth of the Internet accelerate the distances around 500 m. However, today these dcmand for digital telecommunications services applications seem very conservative, and to almost every premises. If such services can be research has focused on transmission Frequencies carried over electricity distribution networks, a via power lines above 1 MHz. Power line truly universal information superhighway might telecommunications (PLT) systems arc demand- be realized, with the cap;ibility of providing ed for data rates of sevcral megabits per second. interconnection to every hc)me, factory, office, These systems operate over low voltage electrici- and organization. ty distribution networks (LVEDNs) and are Electrical distribution circuits constitute a capable of providing commercially attractive universal wiring system, hut they were not built broadband digital access solutions. for communication purposos. Varying levels of The need to harmonize broadhand wireline impedance and attenuatiori due to switching of access technologies with existing radio services electrical equipment are frequent. Time-variant so that coexistence might be optimized will be a interference from various sources leads to a very key element in the rapid deployment of hroad- poor performance of the system. As a result the hand PLT systems. The subject of EMC and transmission capahility’is restricted resulting to broadhand power line communications (PLC) This study has been COT- severe bandwidth constraints, power limits, and applications, which propose to utilize sections of ried out in the context of high levels of noise. the high frequency bands, are now the focus of COSTAciion 262, COST In 1838 the first remote electricity supply much detailed research (www.plcforum.org) [l]. European Framework of metering and in 1897 [3] the first patent on The main issues encountered in such Coopemtion: power line signaling were proposed in the Unit- research are treated in brief in the following www.cordis.lulcostl~,~lti~t ed Kingdom. In 1905 applications wcre patented paragraphs. Academic and industrial activities home.him in the United States, and in 1913 the first com- are covered thoroughly, illustrating the open

34 0163-68041031$17.00 0 ZU03 IEEE IEEE Communications Magazine April 2003 topics for discussion and further interpretation. Then channel modeling and measurement tcch- niques are given, followed by communication Impulse noise Narrowband noise techniques. The hot topic of regulation is cov- Colored noise cred, and finally, market status and perspectives are investigated.

THE CHANNEL s(t) r(t) CHANNELCHARACTERISTICS Power lines constitute a rathcr hostile medium E4 Figure 1, Conzmunicution model of a puwerline chunnel. for data transmission. Varying impedance, con- siderahle noise, and high attenuation are the main issucs. The channel mixes the nasty behav- 5-30 MHz’in both European appliances as well ior of a power line with that of a communica- as in the U.S. infrastructure resulted in some tion channel. Thc transmission environment for general and common conclusions for the abso- PLC seems much worse than that for mobilc lute value Id of thc impedance: communicalions, so we need to not only utilize - The magnitude I ZI increases with frequency cxisting advanced technologies, but also create in the range of 5-20 MHz. novel ones. * It shows strong fluctuation between-a maxi- Channel characteriStics can be both time- and mum and a minimum value. frequency-dependent, and also dependent on the - Its mean value increases from -5 R at 20 location of transmitter and receiver in the specif- kHz to -120 Rat 30 MHr ic power line infrastructure. Hencc, the channel * Thcre are nu big differences between the can in general bc described’as random time mean values of impedance presented varying with a frequency-dependent signal-to- throughout the 30 kHz-1 MHz spectrum noise ratio (SNR) Over the communication band- range; whereas throughout 1-30 MHz they width. Gellerdlly, a measured in-house (10 m) are almost uniform. transfer function shows some deep narrowband * The European impedance values do not notches spread over the whole frequency range. vary significantly from country to country. Phase angles decrease with frequency, and at Resonanccs can occur in residential net- amplitude notches we note phase nonlinearitics works, usually above 40 kHz. They makc (Fig. I). the impedance at higher frequencies more Quite a fcw measurements in the frequency unpredictable than that at the frequency and time domains for high-hit-rate transmission range of 5-20 kHz. have been reported, converging essentially to - Of various loads, resistive heating loads some gcneral conclusions (Fig. 2). cause the grcatest rcsidential impcdance Impedance is highly varying with frequency changes for lower frequencies. and ranges hetwccn a fcw ohms and a few kilo- Carrying out impedance measurements ont- ohms with pcaks at some frequencies where the side buildings from 9 to 95 kHz, we find that the network behaves like a parallel resonant circuit. residential power circuit has extremely low In most frequency rdngcs the impcdance shows impedancc in most cases. The impedance varies inductivc or capacitive behavior around 90 R tu with time and location. A maximum value that 100 Cl. The net impedance is strongly influenccd was measured was 4 R at 9 kHz at the rural by the network topology and connected loads, so location, and a minimum valuc was 0.4 R at 40 we can say that the low voltagc mains do not kHz,at the suburban location. These low values have essentially characteristic impedancc since arc attributed to “the large capacitor that is used loads hcing switched vn and oIf randomly intro- for powcr factor corrcction at 50 Hz that rcpre- duce a change in impcdance [l]. scnts a’short circuit in 9-95 kHz range reducing Measurcments in houses for frequencies of cvcn lower overall impedance values” [4]. Mea- -

0 5 10 15 20 25 30 0 5 10 15 20 25 30 Frequency (MHr) Frequency (MHz)

W Figure 2. Trunsferfiinction and phase characteristics of meusurement.?und echo model by Holger Pliilipps [I/.

IEEE Communicalions Magazine April 203 35 stations, the horizontal retrace frequency for television, etc.). .Asynchronous impulsive UOiSC (noise bursts of switching operations). 111, attenuation as wcll as impulse and background noise mcasuremcnts are reported. The noise power level ranges according to the distance between the noise source and receiver, and in most cases was found to be below 40dB . (WlkHz). Significant noise sources are universal motors to frequencies up to 50 kHz. It is worth ...... ,...... mentioning that, sincc noise as well as wanted signals are subject to attenuation, noise sources close to the.receiver will have the greatest effect on the received noise structure, particularly when the network attenuation is large.

0 5 10 15 20 25 30 MODELINGAND SIMULATION TOOLS Frequency (MHz) For efficient communications a thorough under- I standing of the power line channel described W Figure 3. Noise distribution meauremenr and modelin): by Holger Phtlipps with as few parameters as possible is required. The modeling approach is generally based on 111. the transfer function and additive noise studies. The received signal is often modeled as the sum of a filtered version of the transmitted and inter- surements and models for the frequency range fering signals. These characteristics are depen- of 500 kHz-20 MHz can be f'ound.in [I, 51. dent on frequency, time, and location of the Characteristic indoor and outdoor records of transmitter and receiver in a spccific powcr line attenuation have been reporled in the literature. infrastructure. Measurements show that channel Measurements have been made at a voltage of characteristics do not change very quickly, and 0.35 V rms on in-house line;, resulting in about coherence time is large compared to typical sym- 15 dB attenuation, and on a 1 km cable feeding bol duration; hence, the channel model is quasi- a cluster of houses, resulting in 50 dB attenua- stationary. tion. In the range of frequency of 9-95 kHz the There are sevcral approaches to modeling the line losses ranged between 40-100 dB/km transfer characteristics of power lines that we depending on the location where the attenuation can classify in two categories: . was measured [4]. *The hardware approach, based on So far research has focused on LVEDNs, but impedance of the cables and network topol- some studies on mediu,m voltage cables (10-30 oa. kV) were reported in [I]. A large variety of - The communication approach, where the cables exist differing in general structure, num- channel is modeled by its attenuation, phase ber of cores, conductor material, and insulation shift or noise sources, insertion losses, and used. so on. This model permits us to use classical communi- NOISE cation methodologies and tools to estimate Communication signals at low frequency are expected performance [I, 51. propagated along the low voltage power line Some modeling tools have been developed through conducted emission with very little ener- based on transmission line theory using a mathe- gy radiated from the line causing interfcrence to matical approach, while others are based on other communication services. Different noise physical measurements of the nodes. Figure 4 sources, motors, radio signals, and power sup- shows a single loads magnitude frequency and plies result in a noise CUIVI: very much depen- phase response using PLAT, Power Line AnalJIz- dent on location and time. Generally, channel ing Tool [SI, which is one such mathematical noise varies strongly with frequency, load, time approach used to measure the characteristic of day, and geographical location. Figure 3 impedance of the power line channel in a multi- depicts typical noise distribui.ion and modeling. nodal situation. The noise spectrum in the frequency range up to 145 kHz consists of four types of noise [4, COMMUNICATIONSTECHNIQUES 6, 71: Colored background noise, which is the MODULATIONTECHNIQUES summation of low power-sources like uni- Generally, different modulation schemes such as versal motors. Its power spectral density is frequency shift keyi.ng (FSK), code-division mul- frequency-dependent and decreases for tiple access (CDMA), and orthogonal frequency- increasing frequencies. division multiplexing (OFDM) are discussed as - Periodic impulse noise (synchronous and appropriate choices for PLC [9]. Depending on asynchronous to the powe:r frequency) stem- the target application, each modulation tech- ming from appliances that produce har- nique has certain advantages. For a lowest-cost monics of 50 or 100 Hz. and low-data-ratc power line systcm FSK seems - Narrowband noise consisting of sinusoidal to be a good solution. For higher data rates up signals with modulated amplitudes (radio to 1Mb/s CDMA offers the advantage of using

36 IEEE Communrcations Magazine April 2003 ---.---.-A L B Figure 4. Single loadfiequency and amplitude response (71. the system’s inherent processing gain to meet multipath propagation in wireless broadband radiation allowance limits. For FSK a significant transmission systems as well as with radio inter- part of the spectrum is attenuated more than 40 ference in asymmetrical digital suhscribcr line. dB (3-6 MHz range):There are also parts that Due to the very low transmit power permitted are not flat for FSK transmission. Transmission and the high attenuation expected, only a very rates up to 10 Mhis can he achieved with more low SNR is present at the receiver input. Hence, band-efficient modulation techniques such as channel coding is unavoidable. OFDM. The exploitation of elcctric power distrihu- CODING tion networks appears under completely new In the low frequency range helow 150 kHz. a aspects whcn spread specrrum (SS) techniques combination of M-ary FSK modulation and cod- are involved. Spread spectrum, due to its robust- ing can provide a constant envelope modulation ness against interference and its ability for multi- signal, frequency spreading to avoid bad parts of ple access operation, has been considered as a the frequency spectrum, and time spreading to solution for PIX. Around 1985 several Japanese facilitate correction of frequency disturbances manufacturing companies as well as the Japanese and impulse noise simultaneously. A transmis- Post Office Ministry worked enthusiastically sion scheme (in agreement with the existing toward planning a power line home bus system. CENELEC.norms) combining M-ary FSK modu- The first proposal using SS was put forward by lation with diversity and coding can make trans- NEC in 1983. NEC Home Electronics Co., Ltd. mission over power lines robust against developed a SS power line home communication permanent.frequency disturbances and impulse system at a 10-450 kHz frequency band and a hit noise. It can he considered a form of coded fre- rate of 9.6 khis, with a processing gain of 31. auencv hovoine and is easy extendable to any 1 , .. L Some work on phase hopping has also been frequency range. reported, hut an essential drawback is that the Coded OFDM schemes with combined adap- resulting spectrum is continuous [IO]. tive modulation have been proposed recentiy. In SS systems a cost-effective solution of the Furthermore, space time coding is a new cod- synchronization prohlem is of decisive impor- ingimodulation technique for multiple-antenna tance. The power line network provides a volt- wireless systems. Simulation results demonstrate age with relativcly high stability of frequency and that significant gains are achieved over the use moderate corruption by interference. The zero of single-input single-output (SISO) systems crossings of the voltage represent basic synchro- VI. nization reference instants 191. Some basic attempts at synchronization error analysis in MEDIUMACCESS CONTROL ISSUES mains-borne systems have hecn made. Adaptive Generally, most medium access control (MAC) cross-correlation cancellers have been proposed techniques are candidates for this communica- to suppress co-channel interference [IO]. tions environment: fixed access, dynamic proto- Recently OFDM and discrete multitone cols with contention, arbitration protocols (DMT) have been proposed as very good candi- (token, polling), and reservation protocols. dates for transmission due to their merits in sim- Power grid networks usually form a bus or tree plifying channel estimation, and high bandwidth topology (Fig. S), where in the latter case the efficiency and flexibility in high bit rates. The mediumilow voltage (MVILV) transformer is total bandwidth is divided into N parallel sub- located at the root of the tree. Communication channels, and bits are assigned to subchannels in between any pair of terminals is possible; howev- direct proportion to the suhchannel SNRs. The er, most traffic is expected to be from and to a scheme that assigns the energy and hits to the terminal serving as the network gateway and is different subchannels is called a loading algo- usually placed on the MVLV transformer. rirhm. OFDM has proven its ability to deal with Polling and Aloha are two of the most stud-

IEEE Communications Magazine April 2003 37 STANDARDS AND REGULATORY ISSUES

onc of the major issues currently under debate is the radiation emission of power lines. Sources “f emission from powcrlines networks can he the upstrcam signals at customer premises, the upstream signals at adjacent customer prcmises, and downstream signals at the substation. For mains-bornc communications, there is a European standard, ENS0065-1:1991 [16]. This standard actually regularizes PLC but only in a small frequency band (see introduction). Outside International Telecommunication Union (ITU) Figure 5.A PLCdistribution network. Rcgion 1 (Europe) there is IEC61000-3-8 for up to 525 kHz. Also, concrete detector structures are considered for the analysis. ied protocols for medium a,xess. The main dis- Above 150 kHz, EN50065-1 specifies much advantage of Aloha is the low throughput as lower limits that are the same as the Class B lim- the offered load increases, as well as its lack of its in the ENS5022 standard for ITE and the support for quality of service. On the contrary, generic emission standard ENS0081-1. Similarly, polling can handle heavy traffic and inherently above 525 kHz in ITU Regions 2 and 3, the rele- provides quality of service guarantees. Howev- vant electromagnetic compatibility (EMC) stan- er, polling can be inefficient under light or dards for mains communications systems specify highly asymmetric traffic patterns or when conducted emission limits that arc the same as polling lists must he update:d frequently as net- for equipment such as ITE. In both cases, the work terminals are added cir removed. Similar- limits are small compared to the levels of signal ly, token passing schemes (token ring, token injection, which would normally be required for bus) are efficient under heavy symmetric loads, a practical mains-borne communication system, but can be expensive to implement and serious particularly if communication is required outside problems could arise with lost tokens on noisy the confines of a single building. unreliable media such as the power grid used Efforts are going on in the United States in PLC. through the Electronics Industry Association Carrier sense multiple ai:cess (CSMA) is also (EIA), IEEE, and Automatic Meter Reading proposed with overload detection. CSMA is effi- Association (AMRA) Committee SCC31, and in cient under light to medium traffic loads and for Europe via CENELEC, to develop new EMC many low-dutycycle bursty terminals (i.e., Inter- standards for PLC systems from 2 MHz up to 30 net browsing). The primary advantage of CSMA MHz. It is doubtful whether practical PLC sys- is its low implementation cost, since it is the tems can operate under the EN55022 regime dominant technique in today’s wired data net- because of the trade-off between interference works. Collision detection (CSMAICD) could and perform”. enhance the performanci: of CSMA, but on A CENELECEuropean Telecommunications power line networks the wide variation of the Standards Institute (ETSI) joint working group received signal and noise kvels makes collision has been set up to develop EMC requirements detection difficult and unreliable. An alternative for transmission networks (power line, coaxial, to collision detection that can he easily employed telephone). This group is dealing with the in cases of PLC is collision avoidance intended single general EMC emission standard. (CSMAICA), a technique that uses random This standard covers emission limits and mea- backoffs to further reduce the collision probabil- surement methods for all types of telecommuni- ity. The Bluetooth protocol is another choice, cation networks to ensure that the various and of course proposals on time-division multi- technologies are treated cqually. ple acccss (TDMA) are found in the literature. Generally a detailed treatment of the protocol stack is still needed [12-14]. MARKET In parallel, well-known emor handling mecha- PERSPECTIVES~APPLICATIONS nisms can be applied to solve the problem of errors, but the use of there mechanisms con- The PLC market is expanding dynamically sumes part of the transmission capacity and (www.plcforum.org). Some applications arc decreases the already limited data rate of PLC reported in the ISPLC conferences [I]. systems. Application of autcimatic repeat request Advanced energy services include applications (ARQ) and hybrid schcmei can avoid the influ- such as automatic mcter reading, programmable ence of short-term disturba.nces, while dynamic controllers, and demandisupply management. strategies for capacity allociition can successfully Traditionally, this application area has been confront long-term disturbances [IS] (Fig. 6). pushed by energy companies and related manu- Furthermore, power line networks present a facturers. Permanent cnnncction via PLC offers number of security challenges duc to their open utility companies a possibility to get real-time insecure bus structure. Two services that are information that may he of stratcgic relevance, necessary for those networks arc confidentiality especially by creating differentiation concepts in and identity authcnticativn. the liberalized energy markets. Numerous prod-

38 IEEE Communications Magazine - April 2003 ucts enabling advanccd energy services are already commercially available, especially due to the fact that the required data rates can he realized within the cuirent frequency allocation E3Application (CENELEC band). EIectricitC de'France (EDF) has used PLC for a long time for managemcnt and their own transmission network, in energy control, street lighting, and remote service ( a large project with 3600 terminals). Around 1998 the Tokyo Electronic Power Company (TEPCO) was involved in several projects linking consumers and utilities for meter reading and lowering.peak loads. PLC networking in the home is another application area serving two goals: providing a local home network with the advantages of the power Lmechanismn line, and combining access and in-home network capabilities for service and system integration. There are several applications for a PLC net- Figure 6. The data link layer of the OS1 model used forpower line protocol. work in the home: shared Internet, printers; files, homc control, games, distributed video, remote monitoringisecurity. The key asset is ':no Even if the technology works for some time, new wires." Available products are in net-con- the biggest question remains unanswered: can nected security, safety, and convenience service services built on this technology,compete in systems using narrowband communications. price (and quality) with services already offered In the United States, home networking is by digital subscriber line or cable? The technolo- becoming a mass market (10 percent over PLC). gy probably has a future in,remote areas served In the beginning of 2000 the HomePlug Power- by power cablcs that cable and telecom opera- line Alliance, Cogency, Conexant, Enikia, Intel- tors find too expensive to conncct to their hroad- Ion, Netgear, RadioShack Co., Sharp, and Texas band services [17]. Instruments, together with several other major companies as participants and adopters (http://homeplug.com), began work toward a CONCLUSIONS common standard in the United States. The The power line communication field still consti- HomcPlug Powerline Alliance is a non-profit tutes an open and attractive research area. Many corporation formed to provide a forum for the studies are still nccessary to better understand creation.of open specifications for high-speed and improve the performancc of power lines for home power line networking products and ser- high-bit-rate transmission. So far measurements, vices. Adopters of the HomePlug 1.0 standard modeling, and transmission techniques have have developed products for in-home network- been the first priority in the activities of the ing reaching 14 Mhis. invcstigators in thc area, but now a stimulus in The European Home Systcm (EHS) consor- enhanced performance, coding, and MAC proto- tium [www.ehsa.com] defines a bus and commu- cols and applications is noticed. nication protocol for communications between Finally, the most crucial issues remain the appliances and a central processing unit in the treatment of emissions of high-frequency signals home. The EHS specification, EHS 1.3, covers through the line and the standardization proce- several medium types to transport control data, dures. power,and information, all sharing the logical link control (LLC) sublayer. At the moment, the REFERENCES best supported medium types are power line car- I11 Proc. ISPLC. http:llnewton.ee.auth.g~~~p1~2002 rier (230 Vac + data, 2.4 khk, CSMNack, topol- 121 A. 1. Han Vinck and G. Lindell. "Summary of Contribu- ogy-free) and low-speed twisted pair (15 Vdc, 48 tions at the International Symposium on Power Line kbis, CSMNCG topology-frec). Communications and Its Applications.'' ISPLC 2001: . In parallel, some EU projects have covered Mar. 2001. Malm6 Sweden. pp. 383413. 131 1. Tengdin. "Distribution Line Carrier Communications the topic, such as INSONET (http://www.cordis. an Historical Perspective," IEEE Trans. Power Delivery. lu/ist/projects/99-l0358.htm), Palas (http://palas. 1998, pp. 321-26. regiocom.net), and 6POWER (http://www. I41 0. Haoijen. "Channel Model far the Residential Power 6power.net); they are proof of the existing interest in this field. .. Design of Systems on Silicon (DSZ) is the far the Powerline Channel." IEEETrans. Cob".. vol. lead partner in the European Commission sup- 50, Apr. 200, pp. 553-59. ported R&D project Mixed Analog Digital I61 R. Vines et al.. "Noise on Residential Power Distribution Broadband Integrated Circuits (MADBRIC). Ciruiti," IEEE Trans. Electromagnetic Compatibility. vol. EMC-26. Nov. 1998..,. DO. 161-68. The consortium includes Cisco, Electricit6 de I71 M. Tanaka. "High frequency Noire Power Spectrum. France, and the Switzerland Institute of Tech- Impedance and Tranrmission LOIS of Powerline in Japan nology, Zurich (ETH-2). Their products can an lntrabuilding Powerline Communications," IEEE achieve speeds up to 45 Mbls. They have recent- Trans. Consumer Electro. 34. 198. pp. 321-26. I81 1. Yazdani. M. Naderi. and B. Hanary, "Power Liner ly announced a next generation of 200 Mb/s PLC Analysing Tool (PLAT) for Channel Mqdelling." 5th lnt'l. technology products. Symp. PLC. Malma, Sweden. npr. 46. 2001. pp. 21-28.

IEEE Communications Magazine * April 2003 39 I91 P. K. Van der Gracht and R. W. Donaldron. 'Tommunib the Universityof Eindhoven. The Netherlands. where he cations Using Pseudonoire Modulation On Electric obtained his Ph.D. in 1980. His interest is in inf0m"iOn -The powerline and theory. and coding and network Power Distribution cirCUitS,"lEil Trans. Commun., vol. COM-33, Sept. 1985. pp. 964-74. in digital communications. From 1991 to 1993 and ' communication I101 R. Kahno et al.. "An Adaptive Canceller of Cochannel 1998 to 2000 he was the director of the Institute for Interference for Spread SpeCtrm Multiple A~erCom- Experimental Mathematics in Essen. He war the director field still munication Networks in a PowG?~.Line.'' IEEE JSAC. May (1997-1999) of the Port-Graduate School On Networking. constitutes an 1999. pp. 691-99. CINEMA. In 2000 he became the chairman of the commu- 11 I1 B. Hanary. J. Yazdani. and P. Brown. "Application of nication division of the Institute for Critical lnfrartructurer Space Time DiverrityICoding to Power tine communica- (CRIS). He serves on the Board of Governors of the IEEE open and tion Systems." Int'l. patent. 0130043.3, ~ec.2001. Information Theory Society since 1997 (until 2006). In attractive research I121 1. 0. Onunga and R. W. Donaldson, "personal Com- 2003 he war elected president of the IEEE Information the^ puter Communications on lntrabuilding powerline LAN3 ory Society. In 1999 he was the Program Chairman far the using CSMA with Priority Acknowledgmentr." IEEE IEEE IT Workshop in Kruger Park. South Africa. In 1997 he area. Many studies JSAC, vol. 7,1989, pp. 180-91. acted as Co-chair of the 1997 IEEE Information Theory are still necessary [I31 S. Vuong and A. Ma. "A Iow-cOIt and Portable Local Area Symposium in Ulm. Germany (704 participants). He was Network for Interconnecting PC's using Electric Power founding Chairman (1995-1998) of the IEEE German lnfor~ for better Liner."IEEElSAC,vol. 7, no. 2. Feb. 1989. pp.~192-201. mation Theory chapter. In 1990 he organized the IEEE I141 R. Gershon. D. ~ropp,and M. I'ropp. "A Token ~as~ing Information Theory Workshop in Veldhoven, the Nether- understanding Network for Powerlines Communications:' ran^. con. lands. He is the initiator of the Japan-Benel"~workshops sumer Eleb. May 199. pp. 129--34. on information theory ( now ~~ia-~urope)and the Interna- and to improve 1151 M. Chan, D. Friedman, and .3. Donaldron, "Perfor. tional Winter Meeting on Coding. Cryptography and Infor- mance Enhancement using Forward Error Correction on mation Theory He started (Essen, 19 97) and Still supports Powerline Communication Channels," IEEE Trans. Power the organization of the series of conferences on Power Line the performance Delivery. vol. 9. no. 2. Apr. 199.1. pp. 645-53. Communications and Its Applications. He is co-founder and of powerlines for I161 CENELEC, "Part 1: General Rt,quirementr. Frequency president of the Shannon and GauR Foundations. There Bands and Electromagnetic Disturbances in Signaling foundations stimulate research and help young scientists in an Low-voltage Electrical Installations in the frequency the fields of information theory and digital communica- high bit rate Range 3 kHz to 148.5 kHz." 19!31 tions. From 1999 to2000 he war chairman of the Benelux I171 1. Newbury and W. Miller, "Potential communication Information and Communication Theory Society. transmission. Services Using Powerline Carrit!rr and Broadband Inte- grated Services Digital Netwclrk." IEEE Trans. Power JAVA0 YAIDANI (j.yardaniQlancr.ac.uk) graduated with his Delivery,uol. 14. no. 4. 1999. pp. 1197-1201 B.Eng. and M.Eng. Hons degrees in mechatronics engineering in 1991. He war also awarded an M.Sc. in digital signal procerring and a PR.D. in high-frequency digital power line BIOGRAPHIES tranimirsion for terrestrial and marine networks from Lan- caster University in 1996 and 2002, respectively. His major Fo~i~i-NioviPAVLIDOU ISM1 (nioui,Overgina.eng.auth.gr) area of research is focused on the transmission of multime- received a Ph.D. degree in electrical engineering from the dia information reliably atrorr the power line infrastructure Arixtotle University of Therraloniki. Greece, in 1988 and a of marine vessels. This also includes the derign and devel- Diploma in mechanical-electrical engineering in 1979 from opment of protocols specific to point-to-multipoint PLT the same institution. She is currently with the Department networking. His Current research activities include the of Electrical and Computer Engineering of the above insti- application of space-time diversity and coding to power tution engaged in teaching and rerearch on mobile com- line communication channels to optimize channel through^ munications and telecommunications networks. Her put. This focuser on the investigation of multiple conduc- rerearch interests include traffic analysis and design of net^ tors and implementation of smart modem technology works, performance evaluation and QoS studies of mobile bared on PLT multiconductor techniques with FPGA tech- communications multimedia applications over the Internet. nOloQv. He is now a Dostdoctoral rerearch fellow in the and multicarrier communicaticni techniques. She is Depaxment of Commhnication Systems at Lancaster. involved in European projects (Telematics, COST Actions. Tempus, Isn ar well as national pn>jectr in the referred ~ci- BAHRAM HONMY received his MSc. in digital cammunica- entific areas. She has served on the Program Committees tionr and his Ph.D. in error orotecfion techniauer for (as a member or charperson) of many conferences and bursty channels from the Univirsrty of Kent at C.&terbury workshops supported by IEEUIEE including the 6th Interna- in 1976 and 1982. respectively. He war also a lecturer at tional Symposium on Power Line Communications and Itr the University of Science and Technology. Tehran between Applications in 2002. She war the chairperson of the COST 1976 and 1979. In 1984. after one year of postdoctoral 262 Action an Spread Spectrum fl,pplicationr far Wireless studies at the University of York. he war appointed to a and Wired Communications and iicurrently the delegate senior lectureship at Coventry University. In 1988 he joined of Greece in the COST program. She has published about the Department of Engineering, University of Warwick. In 80 technical papers in jaurnalr or conferences. She was the 1992 he took up a Chair in Communication$ Engineering guest editor of a Special lrrue on Ad HOCNetworks far the at Lancaster University. Current research interests include InternationalJournal for Wireless Information Networks. channel coding and its application to radio communication She is Chairperson of the Joint 'VT and AES Chapter in channels. secure communication applications. modem Greece, and a member of the Techilical Chamber of Greece. design. and synchronization with over 300 publications attributed.Hir most recent book is Trellis Decoding for A. J. HANVINCI (vinck~exp-math.uni-ersende)is a full pro- Block Codes (Kluwer. 1997). He is Chairman of the IEEE fessor in digital communications al: the University of Essen. Chapter of Information Theory for the United Kingdom and Germany. since 1990. He studied electrical engineering at the Republic of Ireland.

40 IEEE Communications Magazine * April 2003