Large-scale field trials of power-line communications technology (PLT) will begin this summer near the western Rhein/Ruhr region and in the southern part of Germany. Energie Baden-Wüerttemberg (EnBW) AG, a German municipal energy company, is launching a pilot service for about 7500 customers using devices developed by telecom company Ascom (Switzerland), according to the utility. RWE, another German utility, is launching services in the highly industrialized Ruhr region. The utility is targeting 100,000 users within two years. However, the technology, which has been promoted as a business breakthrough, has yet to overcome some critical technological and regulatory hurdles, and even has some companies opting out of the market.

Siemens AG, for example, dropped out of the power-line communications market because of the unstable legal and standardization issues. According to the financial news service AFX, Siemens did not believe that "the conditions, particularly the regulatory framework, were in place for such projects to be profitable." Nor.Web, a joint venture of a Canadian telecom company and a UK utility, also failed last year. The two companies cited limited market potential.

 

"Power lines have not been designed to handle deliberately injected digital signals." —Diethard Hansen

The idea behind power-line communications technology is that in-house electric-power lines can function as high-speed transmission lines for home networking. In March, the German Ministry of Economy passed three laws enabling the allocation of frequencies up to 30 MHz for the introduction of new technologies such as telecommunication via power lines. One new regulation, NB 30, became legally binding for frequencies below 30 MHz as of July 2001. PLT is designed to increase data rates to megabits per second, which would enable short-wave frequencies to be transmitted over the low-voltage distribution network in Germany. EnBW claims it will provide Internet speeds 20 times faster than integrated services digital network (ISDN).

Germany's economics minister, Werner Mueller, said the three laws would regulate an efficient and disturbance-free usage of frequencies. Although the ministry received 110 critical objections from spectrum users, including licensed radio amateurs, these objections were rejected in favor of arguments that passage of the legislation would provide jobs as well as make available speedy Internet access to schools via PLT.

However, although standards have been in place for years to control analog power interference over mains power lines, these power lines have not been designed to handle deliberately injected digital signals and the interference that could result from 230 V/50 Hz current, says Diethard Hansen, founder and president of Euro EMC Service (http://www.euro-emc-service.de) in Germany and Switzerland.

Hansen is also chairman of the Working Group for Technical Regulation in Telecommunications (Arbeitskreis für Technische Regulierung in der Telekommunikation; ATRT), a roundtable established by Germany's RegTP to address critical telecommunications electromagnetic compatibility issues. According to Hansen, power-line communication levels of –40 dBm/Hz could cause radiated emissions at 3-m distances with values 30–100 times above the new NB 30 limit for frequencies from 1 to 30 MHz. He points out that the problem is exacerbated by the required RFI bypass capacitors in the line filters of the associated equipment. Computers, stereos, and appliances all use RFI protection according to EMC requirements. He notes that these capacitors cause RF short circuits, a problem that needs to be addressed if the technology is to operate within homes.

The primary interference problems affect short-wave users because the noise leaks into this spectrum. Users of these frequencies include the International Red Cross, Germany's national defense system, embassy radio systems, and other security services. Because the interference perturbs the unshielded short-wave frequencies, such technology could pose serious problems for military users worldwide, for example. "Waves don't know international borders," says Hansen. "The Internet is not necessarily a suitable substitute for tactical applications."

In a newly deregulated market, PLT is seen as competition for power utilities against the advent of asymmetrical digital subscriber lines (ADSL), enabling utilities to provide services such as Internet access. According to PLCforum, a consortium of companies with interests in PLC technology, "PLC technology provides connection and data transfer over existing electricity networks and currently allows transmission speeds of 1 Mb/sec and beyond." ADSL streams at 700–800 Kb/sec. As a shared medium, however, Hansen says the quality is barely equal to that of an ISDN, and satellites are also now available for Internet access at several megabits per second.

To date, the European Commission has not controlled frequencies below 30 MHz in terms of magnetic fields, according to Hansen. Germany used to have such regulations (Vfg 1046) in place before the EMC Directive came into force. CENELEC TC 205A, which traditionally has addressed frequency issues up to about 150 kHz, has expanded its focus to frequencies up to 10 MHz in the outdoor access range to individual homes. With the introduction of power-line communications technology, the group has had to address frequencies up to 30 MHz to provide broadband Internet access inside individual homes. Unfortunately, tests have shown that cabling inside homes has resonated in that particular range, increasing electromagnetic interference levels.

ATRT will monitor the new German field trials, and measurements of the emissions levels will be taken through the end of the year, according to Hansen.

ESD Association Standards Update

Recent meetings of the ESD Association Standards Committee and working groups focused on reviewing existing documents and the continued development of technical reports. Three existing standards—STM 5.1, "Electrostatic Discharge Sensitivity Testing—Human Body Model;" STM 7.1, "Floor Materials—Resistive Characterization of Materials;" and STM 11.11, "Surface Resistance Measurement of Static Dissipative Planar Materials"—completed their five-year review process as required by ANSI and ESD Association procedures. No technical changes were made, and each document was reaffirmed as a standard test method.

Working group activities included the following:

WG-3, Ionization, reviewed its draft technical report covering alternate test methods to the charged-plate monitor for determining discharge time and offset voltage in ionizers. The group discussed test results using smaller-sized plates, determined that stray capacitance was an important issue, and developed a list of improvements to the test fixture to address the issue. Future work will include an investigation of plate-perimeter versus plate-area effects on discharge time testing.

WG-4, Worksurfaces, reviewed comments on its draft technical report, "A Survey of Static Control Worksurfaces and Grounding Mechanisms." A revised draft of the document is targeted for completion by early September this year.

WG-5.2, Machine-Model Device Testing, continued its review of a proposed technical report discussing the reasons for not reducing the number of pulses per stress level from three to one and reducing the time between pulses from 1 second to 0.5 second. The group is also planning an industry survey on machine-model ESD.

WG-5.3.1, Charged-Device-Model (CDM) Device Testing, is coordinating inputs and issues to define direction and action items for future work.

WG-5.3.2, Socket-Discharge-Model (SDM) Device Testing, completed work on an article, "The SDM Test Method: Past, Present, and Future" for publication in this issue of Compliance Engineering. The group has also developed a survey of CDM test equipment. Work is continuing on a draft standard practice document based on the 1994 draft document and the technical report prepared in 1999. A draft document for comment and review is expected in September 2001.

WG-5.4, Transient Latch-Up Device Testing, completed writing and technical review of an initial draft standard practice covering transient latch-up and submitted it to the Technical and Administrative Support Committee for further review and comment.

WG-5.5, Transmission-Line Pulsing, held its first formal meeting for developing a standard practice for TLP testing. Planning and work on an initial draft is under way.

WG-9, Footwear, is working on editorial revisions to an initial draft standard for measuring the electrical resistance of foot grounders.

WG-10, Handlers, reviewed comments on its draft technical report on automated handlers. The group is clarifying references to CDM and human-body models, as well as issues concerning soft grounds versus hard grounds. The group anticipates a revised draft also by September 2001.

WG-11, Packaging, expects to finalize a draft revision EIA-541 in early September. Initial work with a proposed probe by WG-11.13, Two-Point Resistance (Packaging), has shown good repeatability in initial testing, and the proposed procedure is ready for round-robin testing.

WG-14, Simulators, is looking at the effects of radiated fields on equipment and measurement procedures. The group will be polling industry for input and interest.

WG-15, Gloves, is evaluating fixtures for measuring resistance of gloves. Variables affecting the measurements are being identified. Possible measurement methods under discussion include measuring between the thumb and forefinger, between a gloved finger and an ungloved finger, and between a gloved finger and the body.

WG-53, Workstations, is continuing a five-year review of the existing advisory and is working on a section on troubleshooting guidance to assist users in meeting the compliance verification requirements of ANSI/ESD S20.20. The existing advisory is being updated with the goal of converting it to a standard practice or standard test method.

WG-55, Cleanrooms, has nearly completed its technical report, which should be ready for publication in spring 2002. The group is also working on future additions covering garments and packaging.

Information provided courtesy of the ESD Association. For more about the ESD Association and its activities, visit http://www.esda.org.

Big Steps for DSR Services

The 3rd Generation Partnership Project (3GPP) Services and System Aspects Technical Specification Group has agreed to the inclusion of distributed speech recognition (DSR) services, resulting in the creation of a new work item. Being a new work item in 3GPP is the first step toward enabling speech-driven services for mobile devices.

Medium- and large-vocabulary speech recognition systems are beyond the memory and computational capacity of mobile devices used to access data. DSR eliminates the speech channel and instead uses an error-protected data channel to send a parameterized representation of speech. The front-end recognizer terminal extracts the feature parameters. The feature parameters are then transmitted over a data channel to a remote back-end recognizer. The speech processing is distributed between the terminal and the network.

Because it uses the data channel instead of the voice channel, DSR allows for new applications combining voice and data. Applications include form filling, dictation, voice-activated wireless-application protocol pages, voice browsing, and large directory assistance.

The European Telecommunications Standards Institute Aurora Group has begun work on standardizing an extended front end for tonal language recognition and speech reconstruction for DSR systems.

Currently, the Mel-Cepstrum front end and the new noise-robust front end define the extraction of spectral features on the mobile terminal. The front-end standardization process includes recognition tests performed in several European languages and in American English.

However, because recognition of some Asian languages such as Cantonese, Mandarin, and Thai can be improved by the addition of tonal information, standards will be needed for extracting and compressing tonal information for DSR systems. The standardization of extended tonal capabilities for front-end recognizers will promote DSR standards in Asia.

For further details on standards for DSRs with Mel-Cepstrum front ends, visit http://pda.etsi.org/pda/home.asp?wki_id=9948, and for DSRs with the new noise-robust front end, visit http://webapp.etsi.org/WorkProgram/Report_WorkItem.asp?WKI_ID=6402.

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