"We cannot allow undue interference." —Patricia Hewitt

Broadband: UK Drafts New Laws to Address DSL Interference

Citing the Wireless Telegraphy Act of 1949, the United Kingdom is attempting to implement new regulations to prevent interference from digital subscriber lines, power line technology, and home local-area networks. The regulations will be based on a draft standard published by the Radiocommunications Agency (RA) in February 2001.

The European Commission, however, has questioned the legal basis of the UK's proposed regulations, according to an RA spokesperson. "The UK has received a detailed opinion from the European Commission about its notification of the MPT 1570 standard and its draft implementing regulations covering interference from DSL, PLT, and HomeLANS." The UK has until March 1 to respond to the commission's queries. If the commission has no further objections, the regulations will be sent to Parliament.

"I will be making regulations to implement this standard in due course. Safety-of-life radio services will be protected, as the Wireless Telegraphy Act of 1949 allows immediate close-down of interference sources where the regulations are breached," said Patricia Hewitt, former Minister for Small Business and E-Commerce at the Department of Trade and Industry.

One measure would adopt a standard to limit interference from DSL and similar broadband technologies that are based on the specification MPT 1570. MPT 1570 specifies radiation limits and measurements for electromagnetic radiation in the range of 9 kHz to 1.6 MHz from material substances that form part of a telecommunication system. Material substances are defined as metallic mediums, such as cables and wires, that do not form part of any equipment and are "conveyed by means of electromagnetic energy" in this frequency range. The standard specifies separate radiation limits for 9–150 kHz and for 150 kHz–1.6 MHz.

"[Assymetrical DSL technology] is an important technology in the development of the information society. However, because it operates at radio frequencies over cables that may become unbalanced and hence radiate, there is a risk of interference to medium-wave broadcasting and to some aeronautical and other services," says Hewitt. "There is a difficult balance to strike, as we want DSL and other similar broadband technologies to be deployable widely, but we cannot allow undue interference."

Along with any new laws, a procedure would be put in place to address complaints from consumers experiencing broadcast interference from DSL. According to Hewitt, the director general for telecommunications in the UK has proposed that DSL operators be required to take all reasonable steps to address any interference caused.

The regulations would affect not only actual undue interference, but also where undue interference is likely to affect a safety-of-life service, according to a notice published by the Radiocommunications Agency. The agency also notes that these regulations would not affect those devices covered by the EMC and R&TTE directives. Rather, these regulations would apply only to interference emanating from the cables or wires carrying the signals within relevant systems when they are in use, the notice says.

Hewitt believes such laws will provide a high level of protection to existing spectrum users while allowing deployment of new technology without undue constraint. "We will undertake a review in two years—less if necessary—to assess whether the level in the standard has been appropriately set and to decide the timing of any future reviews. We will make the standard tougher if necessary." The review will also cover unresolved complaints and new research on the cumulative effects of DSL.

Wireless Devices to Share the 2.4-GHz ISM Band in China

To correct problems related to using the 2400-MHz frequency range for short-range wireless devices, China has allocated the 2400–2483.5 MHz frequency range for micropower equipment. These short-range devices will share the spectrum with nonwireless communication equipment such as industrial, scientific, and medical devices.

Allocating this portion of the spectrum for wireless use enables China to adapt to the development of wireless communication techniques such as Bluetooth, indoor wireless local-area networks, digital wireless phones, and wireless automatic identification.

The new allocation satisfies the "demand of wireless communications services" in terms of both the Chinese government's use of its frequency resources and the international technical standard for wireless services, according to Notification IDW no. [2001] 653 from the Ministry of Information Industry (Beijing), which regulates telecom network and related services. To comply with the new requirements, short-range devices must have an effective isotropically radiated power (EIRP) of ≤10 mW. Transmission power requirements are ≤–36 dBm/100 kHz (30 MHz–1 GHz) and ≤–30 dBm/100 kHz (1–12.75 GHz), and the requirement for load frequency capacity is ±75 kHz.

To facilitate coexistence, China is encouraging "technical innovation and independent intellectual property rights of every system." China will diligently enforce antiinterference in the shared environment and will enforce reliability and usability of the spectrum.

To prevent interference to short-range wireless equipment in highly populated areas, China has prohibited spread-spectrum wireless communication base stations that do not meet the technical requirements. Base stations that have been previously approved for use in these areas have until Dec. 31, 2004, to cease operation. In wide-open, less-populated areas, short-range wireless devices must meet the technical requirements. Set-up or use of base stations in these areas must follow procedures set forth in Notification SWOF [1997] 11, which regulates technical indices relevant to expanded frequency communication.

China is also restricting the use of point-to-multipoint structures or netlike structures in these base stations. Adding power magnifiers at the outlets of transmitters is prohibited when building or using such stations, and the EIRP is limited to ≤500 mW.

FCC Adopts New SDR Rules

FCC has adopted rules that allow software modifications in a software-defined radio (SDR) to be made through a permissive change, streamlining the filing process. Originally developed for unified communications among U.S. military allies, SDRs will now enable wireless operators to update their networks or phones to accommodate new standards.

In SDR devices, functions formerly carried out by hardware, including the generation of transmitted radio signal and the tuning of the received signal, are performed by software, allowing the device to transmit and receive over a wide range of frequencies and to emulate virtually any desired transmission format. SDR provides improved service coverage and fewer dropped calls because it can jump among different frequencies and different formats, finding the clearest one that is the most open.

SDR technology provides a mechanism for integrating a variety of mobile applications over multiple wireless interfaces. SDR unifies the alphabet soup of disparate radio technologies, such as global system for mobile telecommunications (GSM), code-division multiple access (CDMA), time-division multiple access, and general packet radio service, that cellular phones and other wireless devices employ.

When a user moves among cells, an SDR device can download the protocol used by the current cell, allowing for seamless switching between networks and radio standards as the user roams. This technology can effectively bridge the gap between Europe's GSM and North America's CDMA.

An SDR base station can communicate with any kind of terminal, such as cellular or wireless local-area network, by changing its software. SDR base stations allow operators to retain their current network hardware while supporting multiple standards and protocols. This is particularly applicable during the switch from second- to third-generation service.

As a result of SDR technology, one phone can be designed for the world market. Depending on location, the user could select which standard to follow. A phone can be instantly upgraded to support services such as stock quotes.

The adaptability of SDRs could facilitate a more-efficient use of the available spectrum. By jumping from one frequency to another, SDRs can allow operators to share unused bandwidth, accommodating areas that experience usage spikes without having to increase their spectrum allocation. However, FCC is investigating whether the ability to jump from frequency to frequency could interfere with other wireless communications.

With the new rules, other parties—apart from the original grantee of equipment authorization—could be granted equipment approval and assume responsibility for the SDR. To allow for changes to equipment by parties such as software developers, an optional electronic label for SDRs would display the FCC identification number on a liquid-crystal display or similar screen, forestalling the dilemma of endlessly relabeling equipment already in use.

FCC's first report and order can be downloaded from http://www.fcc.gov/Bureaus/Engineering_Technology/Orders/2001/fcc01264.pdf.

FYI An article in the November/December 2001 issue of CE titled "Shielding: Fabric-Over-Foam EMI Gaskets" contains transposition errors in the legends of Figures 10 and 11. Both figures appeared on page 42. Figure 10 shows the different compression-set performance between FR urethane foams both with and without the particulate additives. The corrected figure demonstrates the negative effect that additives have on the long-term performance of the foam. Figure 11 shows a plot of two gasket samples, one with a urethane core, and the other with a neoprene core. As the foam begins to take a set, electrical contact between the gasket and the mating surface is reduced. It can be seen in the corrected figure that the neoprene core led to an increase in resistance over time, whereas the urethane core allowed the gasket to maintain steady contact.

Figure 10. Modified ASTM D3574 average compression set versus time by urethane foam type. Figure 11. The 500-hour z-axis resistivity test (50% compression at 65°C on 0.2 x 0.5 in. rectangular gaskets).