the management of interference from broadband over power ...€¦ · interference from broadband...

Australian Broadcasting Corporation Submission

The Management of Interference from Broadband over Power Line Applications

(Australian Communications Authority)

June 2005

Australian Broadcasting Corporation submission to the ACA Discussion paper on The management of Interference from Broadband over Power Line Applications The Australian Broadcasting Corporation (ABC) welcomes the opportunity to submit the following comments in response to the ACA’s discussion paper on “The Management of Interference from Broadband over Power Line Applications”. The ABC understands that there is interest in broadband over powerlines (BPL) as a potential means of delivering broadband services to regional Australia. However, the Corporation strongly believes that in considering proposals to allow PBL services, the principle of not interfering with existing radiocommunications services must be paramount. The evidence available to the ABC indicates that BPL is highly likely to interfere with existing broadcasting transmissions. The ABC notes that BPL is a fortuitous technology, in that existing power transmission is being adapted to carry information. However, a side effect of this capacity is the creation of unwanted emissions that have the strong capacity to interfere with planned and protected radiocommunications services, including broadcasting.

1. The ACA seeks comment on the potential for BPL operations to cause interference to radiocommunications services, telecommunication services and electrical or electronic equipment. The ABC has engaged an independent consultant, Keith Malcolm, a former Manager of the Federal Government’s Communications Laboratory, to research and verify the impact on radiocommunications services of BPL emissions, and to determine appropriate maximum emission levels for BPL systems in light of the need to prevent interference with broadcasting services. Mr Malcolm’s report is contained in Annex 1. The report concludes, on the basis of an analysis of trial reports, that permitted emission levels under all existing and proposed BPL standards would be of sufficient level to cause interference and loss of service to broadcasting signals in rural areas, and, under worst case conditions, in suburban areas. It notes that the BPL emission levels permitted under the proposed standards or regulations are comparable to the levels of the broadcast services with which they are likely to interfere and are thus highly likely to annihilate the broadcast services. The report also notes that interference with broadcasting services could potentially include disruption of emergency information broadcasts, and that the operation of current BPL systems in HF-band frequencies (3 to 30 MHz) have the potential to affect Digital Radio Mondiale (DRM) services, which are currently under consideration as a means of delivering digital radio to rural and regional Australia.

1

ABC Submission on The Management of Interference from BPL 2

The report makes three observations:

1. That existing and potential broadcasting services require, and should be provided with, protection from interference from BPL emissions.

2. That existing and proposed BPL emission limits fail to ensure protection for broadcasting services.

3. That the introduction of a BPL service using broadcasting frequencies should be prohibited unless an effective scheme for protection of rural area and weak signal reception of broadcasting services (such as dynamic allocation of BPL frequencies) is employed by the BPL system.

2. The ACA seeks comments on the adequacy and appropriateness of the interim guidelines. Stakeholders should be aware that these guidelines may be used as a model for future arrangements. The ABC has a number of concerns about the Access BPL Trial Guidelines. First, the Guidelines do not mention or incorporate as an operational assumption the fact that the HF spectrum is used for broadcasting and accordingly requires protection. Further, the guidelines do not emphasise the need for public awareness of the potential impact of BPL emissions on broadcasting services. In the ABC’s experience, this is a significant omission, as broadcasters invariably bear the brunt of public complaints about loss of signal quality caused by interference. Therefore, BPL providers should be obliged to inform the public of any potential impact of their services. It may be appropriate for this process to be conducted through indirect information channels, such as consumer electronics suppliers and retailers, repair centres and video hire stores. The Discussion Paper mentions that emission levels in recent BPL trials were in excess of US Federal Communications Commission (FCC) part 15 levels. As indicated in the attached consultant’s report, this is likely to have caused very significant interference to the broadcast services. The ABC notes that the Discussion Paper mentions the ARPANSA EMR standard in relation to BPL emissions. This standard is intended to ensure that humans are not adversely affected by radio waves and is not related the protection of radiocommunications services. The expected BPL emission levels would be extremely low when compared to those permitted by the ARPANSA EMR standard. While this is an excellent outcome in terms of public health and safety, it does nothing to prevent the interference problems associated with BPL emissions. 3. The ACA is unaware of any commercially available access BPL products capable of operating above the frequency of 42 MHz, but would be interested in information about products that operate above this frequency. BPL products operating above 42MHz would begin to potentially interfere with television broadcasting. The ABC considers that possibility deeply undesirable.


4. The ACA seeks comments on whether there should be obligations placed on BPL operators to alert consumers to possible disturbance to consumer devices prior to deployment of BPL systems and what form these obligations might take. The ACA would also be interested in other devices not included above that operate in the BPL frequency range and any insights into their prevalence of use. Broadcasting is a protected service. The ABC is strongly of the view that obligations should be placed on BPL operators to alert the public when a BPL service is commencing and/or operational and that interference may occur. As indicated above (Q.2), broadcasters invariably bear the brunt of public complaints about loss of signal quality caused by interference. 5. The ACA would be interested in any information from prospective BPL providers about plans for BPL deployments. The ABC has no interest in providing BPL services. 6. Interested parties are invited to comment on the options discussed below, as well as other options they consider relevant. Regardless of the option chosen, the ABC is concerned that, according to the results of the trials observed by the ACA, the emissions produced would cause harmful interference to any co-frequency broadcast service. The Corporation is especially concerned that the usually non-technical audience for HF broadcasts will suffer signal quality loss as a result of BPL systems without understanding the cause; it is very likely interference from BPL systems will be attributed to other causes, such as propagation and not reported. 7. The ACA seeks comment on the importance of regulatory certainty to both BPL providers and stakeholders who could be subject to interference. The ABC’s research indicates that the only way to ensure no harmful interference into broadcast services is for the BPL system not to use frequencies used by broadcasters in each service area. The relevant frequencies can be easily specified for MF, FM and TV transmissions, but not for HF (shortwave) services whose frequencies change with time of day and solar activity. It should be noted that Digital Radio Mondiale (DRM) services, which are currently under consideration as a potential means of delivering digital radio in regional Australia, are HF services. A major concern for HF broadcasting is that BPL emissions are likely to propagate in the same way as HF transmissions. HF broadcasting uses “skywaves” (refraction from the ionosphere) to reach audiences. The skyward emissions from a BPL system will be refracted in a similar fashion and are thus have the potential to interfere with receivers thousands of kilometres from the transmitter, possibly in another administrative district. In such circumstances, it is likely to be difficult to identify the source of interference, let alone take action to have it suppressed.


The ABC believes it is necessary that maximum acceptable interference levels are agreed for the protection of potentially affected services, that the rationale be recorded and that a strict enforcement regime be instituted. 8. The ACA seeks views on the merits of allowing the BPL industry to develop its own arrangements. In addition, the ACA would like an indication of whether the BPL industry is interested in developing its own arrangements for managing interference issues. The ABC has reservations about the BPL industry developing its own arrangements in the total absence of input from other stakeholders. The BPL industry may be able to develop its arrangements for managing interference but the technical details (e.g. permissible emission level at a frequency into a particular service) need to be open to scrutiny and query by affected parties. 9. The ACA seeks comments on whether the adoption of a standard is considered appropriate and which international standard, or an Australian developed standard, is preferred. The ACA also seeks comments on whether a wholly standards based approach is sufficient to manage potential interference or whether an approach similar to the FCC’s might be more appropriate. The ABC would not agree with a standards-based approach using current or proposed standards mentioned in the Discussion Paper. All of the standards currently under consideration allow emission levels that would cause interference to existing services. 10. Stakeholder comment is sought on the appropriate body to develop a code or guideline under options 1, 2 or 3. The body could be a BPL industry body, a stakeholder body or the ACA in consultation with interested parties. In addition, comments are invited on the possible content of a code. Interested parties can use the interim access BPL trial guidelines as a reference point. The ABC’s primary concerns in the development of a BPL code or guideline are that interested parties are able to participate actively and that any finalised code or guideline reflect a consensus agreement. The Corporation believes that, in addition to administrative details, any code must specify the permissible levels of BPL emissions in the frequency bands occupied by services specified in the Australian Spectrum plan at any given location. 11. The ACA invites comment on licensing and imposing a fee on BPL providers for their spectrum use. Comments would also be welcomed on the possible licence conditions. The ABC believes that any BPL licence should incorporate clauses to cover the introduction of new and changes to radiocommunications services under broadcasting and other spectrum planning arrangements. The operating assumption of such clauses should be that, as BPL


emissions are an unplanned by-product of non-radiocommunications services, the needs of planned radiocommunications services should take precedence over BPL systems. 12. The ACA is interested in comments on these options, as well as any other options that are considered relevant. Are there any other issues relating to in-house BPL systems that the ACA should be aware of? The Discussion Paper considers amending CISPR22 for use with in-house BPL. The ABC is cautious about this approach, as previous experience indicates that compliance with CISPR 22 does not guarantee that interference will not occur to surrounding radiocommunications equipment. Of particular concern is interference with equipment in adjacent premises when the interferer is continuous. Further, it should be noted that systems and equipment which do not cause interference overseas can cause problems in Australia, which makes unique allocations for some services. Any problems of this kind will be more obvious where the radiocommunications or broadcast signal levels are low, as is the case towards the edge of their coverage. When subscription television was introduced into Australia, a number of viewers complained of interference (beats) into the Channel 2 (64.25MHz) picture, especially in Sydney, in areas which received a lower signal level but still had a very acceptable picture. The source of the interference was a pay TV set top box (STB), often in a neighbouring property. The particular model of STB had been tested to CISPR22 and had passed with emission levels well below those permitted. The STB manufacturer had supplied millions of these STBs to other markets with no complaints. Further investigation revealed that the interferer was the eighteenth harmonic (64.4MHz) of timing reference that was sourced from a NTSC colour burst crystal (3.58MHz). The vision carrier frequency of this channel in other countries is 62.25MHz, where the additional separation between the signals overcomes the visible picture interference. Similarly, there have been reports of switch-mode power supplies causing interference to UHF TV reception. Acknowledgements

The ABC has worked closely with FreeTV Australia in formulating the responses to this discussion paper and supports their research into describing what is occurring in the ITU and other forums.


ANNEX 1

COMPATIBILITY BETWEEN BROADCASTING SERVICES AND BROADBAND OVER

POWERLINE (BPL) SYSTEMS

A Report to the Australian Broadcasting Corporation Keith G Malcolm ARMIT, PEng June 2005


Introduction: This paper is intended to provide a technical basis for an ABC response to Issue 1 (The ACA seeks comment on the potential for BPL operations to cause interference to radiocommunications services, telecommunication services and electrical or electronic equipment.) in the ACA’s discussion paper “The Management of Interference from Broadband over Power Line Applications”. The paper reviews minimum signal levels used in the planning and protection of broadcasting services at MF, HF and low-VHF, together with background noise levels in the bands to derive requirements for protection of broadcasting services from BPL emissions. The paper reviews the results of recent BPL trials and notes that measurements made by the Australian Communications Authority at Queanbeyan and Moruya show that BPL emissions can be as large as the broadcasting signals to be protected. Background: Broadband over Power Lines systems (BPL or PLT) encompass techniques for using the electricity power distribution network to deliver broadband data signals to consumer premises. The electricity network has been used for many years to carry low frequency, narrow band data signals primarily for network control purposes. The opening of electricity supply and telecommunications utilities to competition has generated pressure for electricity supply entities to find additional ways of using their infrastructure. BPL is one such possible use that is intended to provide wide-band capacity to end users. BPL techniques use signals including spread-spectrum, frequency-hopping and COFDM and operate typically on frequencies between 3 and 30 MHz. These systems typically deliver a few Mbit/s data capacity. Newer systems claim data capacities of the order of 200 Mbit/s and occupy frequencies up to low VHF (approximately 80 MHz – TV Band 1 and Band 2). The electricity distribution network is designed to carry power at 50 Hz and not radio frequency signals which results in the electricity wiring being a lossy and radiating transmission line at BPL frequencies. Even worse, the characteristics of the network change with time as appliances are connected and disconnected. This means that the carriage of BPL signals has the potential to interfere with radio communications services that are operating on frequencies used by the BPL signal. This paper considers minimum protected broadcasting signal levels together with existing and proposed BPL emission standards and BPL trial results to evaluate the compatibility between broadcasting and BPL uses of the radio frequency spectrum.


1. Minimum Protected Signal Levels This part of the paper establishes the minimum signal levels that are used in broadcasting planning as a basis for determination of coverage and protection of the achieved coverage area. Identification of minimum useable signal levels is the basis for an assessment of the compatibility between broadcasting services and proposed BPL installations. The signal levels for MF-AM, VHF-FM and Band 1 TV services are drawn from the Australian Broadcasting Authority’s planning parameters document, while the HF values are obtained from ITU-R documents including the Radio Regulations and Recommendations. Since Australia is a signatory to the ITU it is assumed that protection would be afforded to these minimum useable signal levels. The protected field strength represents the minimum signal level that is required to delivered acceptable quality reception using a reasonable balance of receiver performance and cost. Planning of broadcasting services aims to protect these minimum signal levels from co-channel and adjacent-channel interference. The protection ratio is that value of signal to noise or signal to interference ratio that is needed to achieve the planned signal quality (audio or video signal to noise ratio) at the planned edge of coverage. These values are then used to derive the equivalent interference or noise level that would exist if the protected field strength just delivered the target signal quality. Table 1: Minimum Protected Signal Levels and Derived Equivalent Interference Levels

Service Zone Protected Field

Strength Protection Ratio Equivalent

Interference Level dBuV/m dB dBuV/m MF AM (1) Rural 54 30 24 Suburban 68 30 38 HF AM (2) 40 (3) (4) 34 (S/N) 6 FM (1) Rural 48 45 3 Suburban 60 45 15 Band 1 TV (1) Rural 50 52 -2 Suburban 65 52 13 Band 2 TV (1) Rural 50 52 -2 Suburban 65 52 13 (1) drawn from ABA Planning Parameters (2) ITU-R Res 543 (3) ITU-R App 11 (4) ITU-R Rec BS 703 The equivalent interference level is derived by subtracting the protection ratio required to achieve the planned signal quality from the minimum signal level that is protected during the planning process. In the absence of interfering signals, this gives an indication of the equivalent background noise level (whether man-made or naturally occurring). This derived background level then provides a “baseline” for the assessment of compatibility on the basis of the extent to which the introduction of the service seeking coordination raises the minimum useable signal level.


In spectrum sharing studies, it is common practice to accept an additional interfering source provided that the additional interference does not degrade existing system performance by more than 0.5 dB. If this limit is accepted then the acceptable level of BPL emissions is 9 dB below the “equivalent interference level” in the table above. This leads to the following requirements for protection of various broadcasting services against interference from BPL emissions:

Table 2: Derivation of Acceptable Interference Signal Level from the Equivalent Interference Level of Table 1


Strength Equivalent Interference

Level (from Table 1)

Acceptable BPL Emission Level (Derived from

planning parameters.)

dBuV/m dBuV/m dBuV/m MF AM Rural 54 24 15 Suburban 68 38 29 HF AM 40 6 -3 FM Rural 48 3 -6 Suburban 60 15 6 Band 1 TV Rural 50 -2 -11 Suburban 65 13 4 Band 2 TV Rural 50 -2 -11 Suburban 65 13 4 Since the BPL emission is in the form of a wide-band signal, it is necessary to measure the acceptable signal level across the whole of affected channel so the Band 1 and Band 2 TV protection case is the most stringent. 2. Validation of Minimum Useable Signal Levels: To validate these figures, it is necessary to compare them against the background noise levels expected at various locations. Information related to radio noise levels is given in ITU-R Recommendation P372 “Radio Noise”. Noise levels are both frequency and location dependent and time variable on a diurnal and seasonal basis. Analysis of Rec 372 shows that the minimum background noise levels for MF and HF bands are determined by man-made noise even in rural areas and that the minimum noise levels (and thus lowest useable signal levels) occur during local day-time. Using the Canberra region as an example and applying the ITU-R SG 3 software that is associated with Rec 372, we can derive the following Table. This computer program extracts naturally occurring and man-made noise data from Rec 372 to determine a value for “overall background noise” which sets the lower limit to the value of minimum useable signal.


Table 3: Comparison of Rec 372 Overall Electrical Noise Level with the Derived Equivalent Interference Level (from Table 1)

Season Frequency Overall Electrical

Noise Level (En) min (1)(3)

Overall Electrical Noise Level

(En) max (1)(3)

Derived Equivalent Interference Level

(from Table 1) (2) MHz dBuV/m dBuV/m dBuV/m Winter 1 11 16 24 5 2 8 6 10 5 6 6 15 3.5 3.5 6 Summer 1 -1 23 24 5 2 13 6 10 4 9 6 15 2.5 7.5 6 All Year 57 6 -2 64 5 -2 98 4 3 Notes: 1. Derived from ITU-R Rec 372

2. Derived from ABA and ITU-R planning parameters 3. Equivalent single carrier signal level derived from noise power density

(dBm/Hz) data. This table indicates that the HF-AM and VHF-FM protected field strengths are sensibly related to background noise levels. The protected minimum MF-AM field strength is somewhat higher than that required to just overcome background noise levels. Section 4A.5 of the ABA Planning Parameters document indicates that the specified minimum useable signal level at MF is determined by the assumed receiver internal noise limited sensitivity. Comparison of these figures suggests that the “notional receiver” specification that is used to set the planning parameters may be a little pessimistic in terms of sensitivity. These factors are consistent with anecdotal evidence that day-time reception of MF-AM services is possible in rural areas at levels below those considered as indicating the limit of coverage. By way of comparison, the noise limited sensitivity for HF receivers was set at that level as determined by background electrical noise levels (from Rec 372) and experience shows that practical receivers easily achieve the assumed 40 dBuV/m sensitivity. The Band 2 and Band 3 TV minimum signal levels are similarly below the level indicated by background noise levels. This suggests that in rural areas at minimum signal levels the delivered signal at the limit of coverage will have reduced signal to noise ratio. Adjusting minimum wanted and acceptable interference levels to reflect background noise levels we can derive the following target values:


Table 4: Derived BPL Emission Levels to Protect Broadcasting Minimum Useable Signals


Strength Equivalent

Interference or Background Noise Level

(1)

Acceptable BPL Emission Level

(Based on background noise levels)

dBuV/m dBuV/m dBuV/m MF AM Rural 54 11 2 Suburban 68 38 29 HF AM 40 5 -4 FM Rural 48 4 -5 Suburban 60 15 6 Band 1 TV Rural 50 6 -3 Suburban 65 13 4 Band 2 TV Rural 50 4 -5 Suburban 65 13 4 Note: 1 Derived from minimum noise levels (Table 3) for rural areas and planning parameters

(Table 1) for suburban areas (suburban areas may be either noise or interference limited).

Preliminary noise level measurements in rural areas support these figures. 3. Existing & Proposed Standards and Trial Data Existing and Proposed Standards: The major existing emission standard relevant to BPL emissions is that of the USA FCC Rules Part 15. These rules permit the following emission levels:

1705 kHz to 30 MHz 30 uV/m (29.5 dBuV/m) @ 30 metres 30 MHz to 88 MHz 100 uV/m (40 dBuV/m) @ 3 metres 88 MHz to 216 MHz 150 uV/m (43.5 dBuV/m) @ 3 metres.

These emission levels are clearly well above (approximately 30 dB for MF and HF, and more than 40 dB for Band 1 TV and Band 2 FM services) the levels identified above (Section 2) as being required to protect existing broadcasting coverage. Indeed, continuous emissions at these levels (as are envisaged for access BPL systems) would have serious impact even on suburban area coverage of broadcasting services on frequencies used by BPL systems.


There are a number of existing or proposed standards that have been developed in response to the BPL issue. These include the German NB30 standard and ETSI TR102324 and Cenelec prTS50437 proposed standards. TR102324 and prTS50437 are very similar and specify emission levels in magnetic field terms (dbuA/m). For HF frequencies the proposed limit is 4 dBuA/m at 3 metres which equates to 55.5 dBuV/m at 3 metres while for VHF frequencies the proposed limit is 40 dBuA/m at 3 metres which equates to 91.5 dBuV/m at 3 metres. The NB30 limit varies from 40 dBuV/m (at 3 metres) for 1 MHz falling to 10 dBuV/m for 30 MHz. Once again, these permitted emission levels are all well above existing background noise levels and provide no protection to broadcasting services. The ACA discussion paper makes reference to Australian Standard AS/NZS2344:1997 which is a generic standard dealing with electromagnetic disturbances (emissions) from overhead powerlines. While this standard is not aimed specifically at BPL systems, it would provide a little more protection than the above referenced standards. Permitted emission limits (for temperate zones) range from 36 dBuV/m at MF down to 23 dBuV/m at 30 MHz. Limits for frequencies above 30 MHz are “under consideration”. These limits alone are not sufficient to provide protection for HF broadcasting services. However, for the low/medium voltage distribution lines typical of residential locations, the compliance measurement distance is 0 metres (that is, directly below the line) which provides some possibility that distance separation between the BPL activated line and the receiving antenna would deliver additional protection. A cogent summary of the issues and activities recently undertaken is available at http://www.elmac.co.uk under the title “Why broadband PLT is bad for EMC”. This paper notes that a number of BPL trials have been conducted in Europe – with consistent outcomes, that BPL emissions are high enough to interfere with radiocommunications services. The following part of the paper makes use of the published results from observations of three BPL trials: Queanbeyan NSW, Moruya NSW and Crieff Scotland. Reports on the Queanbeyan and Moruya trials have been published by the ACA while a report on the trials in Crieff has been published by the UK OFCOM.


Queanbeyan Trial: The ACA report indicates the following results were obtained during the Queanbeyan trial:

Table 5: Extract from ACA Queanbeyan Report Note: although not mentioned explicitly, the reported results appear to be equivalent

single carrier signal levels- the BPL system operates with multiple narrow band carriers. The results report the maximum signal levels observed at each test site, not necessarily at the same frequency.

As noted in the ACA report, the magnetic field measurements can be converted to equivalent electric field values as follows:

Table 6: Derivation of E-Field Values from ACA Queanbeyan Report

Queanbeyan Site No Measured H Field (dBuA/m)

Equivalent E Field (dBuV/m)

1 18 69.5 2 8 59.5 3 10 61.5 4 5 56.5 5 16 67.5 6 18 69.5 7 5 56.5 8 12 63.5 9 20 71.5


Moruya Trial: Similarly, the ACA report for the Moruya trial provides the following results:

Table 7: Extract from ACA Moruya Report Note: although not mentioned explicitly, the reported results appear to be equivalent

single carrier signal levels – the BPL system operates with multiple narrow band carriers. The results report the maximum signal levels observed at each test site, not necessarily at the same frequency.

from which we can derive the following:

Table 8: Derivation of E-Field Values from ACA Moruya Report

Moruya Site No Measured Magnetic Field (dBuA/m)

Equivalent Electric Field (dBuV/m)

1 29 80.5 2 28 79.5 3 23 74.5 4 12 63.5 5 8 59.5 6 29 80.5 7 15 66.5 8 11 62.5 9 11 62.5 10 20 71.5

In both cases, regardless of differences in measurement distances, the BPL emission levels are not only so high as to interfere with any affected broadcasting signals, but are equal to or greater than the expected wanted signal levels in the areas.


Crieff Report: The OFCOM Crieff study was undertaken during a trial of BPL undertaken by Scottish and South-Eastern Electricity using Amperion equipment. The study includes a comprehensive collection of data gathered at a range of distances along the powerline from the BPL injection point and at a range of distances from the powerline. Objectives of the study included both observation of emitted signal levels and the rate of attenuation of signal level with distance from the powerline. The report indicates that maximum emitted signal levels at 10 metres from the powerline were 60 dBuV/m below 30 MHz and 59 dBuV/m above 30 MHz. Although Amperion has subsequently submitted information to the FCC that questions some of the parameter values used during the OFCOM study, the observed signal levels are so far above both background noise levels and minimum protected broadcast signal levels as to represent a real potential hazard to reception of broadcasting services in rural and suburban environments. NTIA Phase 1 Report: This report covers a comprehensive series of measurements at a number of locations looking at signal levels at various distances along the line from the BPL equipment and distances from the powerline. In all cases the measurements are at distances equal to or greater than the FCC Part 15 measurement distance. The reported signal levels vary widely including from system noise level to substantially above system noise level. The report notes that separation distances of 100’s of metres between the BPL activated powerline and receiving antenna was needed to ensure that emission levels had fallen to background levels. The report data indicates that there is a substantial potential for BPL systems complying with Part 15 requirements to cause interference to radiocommunications services. 4. Discussion and Analysis: It is clear from analysis of trial reports that BPL systems result in significant levels of emissions from the energised powerlines. Indeed, it appears that the operating parameters for existing systems are intended to be adjusted, on a case-by-case basis so as to just achieve Part 15 compliance. Examination of the protected minimum signal levels for broadcasting services indicates that the observed and permitted emission levels (under all existing and proposed standards) would be of sufficient level to cause interference and loss of service to broadcasting signals in rural areas. Loss of service means loss of reception – that is, an inability to receive broadcast signals. Broadcasting services provide an essential part of emergency related communications services including pre-emergency warning and post-disaster information dissemination especially in regional and rural areas. Because disasters such as cyclones can cause loss of local services, it is essential to community safety that weak signal reception of broadcasting services should be protected. Under worst case conditions, reception even in suburban areas would be impaired by BPL emissions falling on frequencies occupied by broadcasting services.


Current BPL systems operate on frequencies in the HF bands (3 to 30 MHz) with emerging systems expected to also operate on frequencies up to about 80 MHz. The HF bands are used for both domestic and international sound broadcasting services in Australia including services received from overseas by Australian residents. These services are planned in accordance with the provisions of the ITU-R Radio Regulations and are entitled to protection from interference. HF services provide a capability to deliver emergency communications both from within and outside a disaster zone but only if weak signal reception is protected from interference. In particular, HF services using near-vertical-incidence technique are provided in the Northern Territory. These services not only provide coverage for their immediate target areas, but also provide a back-up to local MF-AM and VHF-FM services in the northern coastal zones that may, for example, be susceptible to damage or service interruption by cyclones. Similarly, the Radio Australia services to the South West Pacific and Islands will provide a back-up for coastal domestic services in the northern zones. The emergence of the Digital Radio Mondiale (DRM) technique for digital sound broadcasting provides additional opportunities to improve and expand sound broadcasting services to regional, rural and remote parts of Australia. Digital HF broadcasting provides a real prospect to deliver a greater number of sound broadcasting services to portable and mobile receivers in regional, rural and remote areas of Australia to supplement those available to fixed receivers via satellite broadcasting services. It is considered important that this potential wider application for domestic HF broadcasting services should not be precluded by the introduction of BPL systems. Observation (i). That existing and potential broadcasting services require, and

should be provided with, protection from interference from BPL emissions.

It is clear that existing and proposed BPL emission standards fail to ensure protection of broadcasting services on two counts. First, the permitted emission levels are too high – even the lowest permitted limits are sufficient to degrade existing reception and the higher limits are equal to, or greater than, minimum planned signal levels. Secondly, the compliance distances (that is the distance from the emission source at which emissions are to be measured) are too large to be meaningful. It is important to remember that sound broadcasting reception typically operates using built-in or indoor antennas that will be in proximity to house wiring connected to the BPL energised lines. The FCC Part 15 limits for frequencies up to 30 MHz are particularly unhelpful as the compliance distance is 30 metres. There is no realistic situation in which a sound broadcasting receiving antenna could be located more than 30metres from a BPL activated powerline intended to provide BPL service in the vicinity of the receiver. Observation (ii). That existing and proposed BPL emission limits fail to ensure

protection for broadcasting services. 5. Protection of Broadcasting Services: The simplest approach to protection of broadcasting services from BPL emissions would be to simply establish permitted emission limits at a level below that of the background noise at each frequency.


The observations of emissions from existing trial installations suggest that control of emission levels sufficient to protect broadcasting services would result effectively in prohibition of BPL services using broadcasting spectrum. Since other radiocommunications services also occupy the MF, HF and VHF bands, this approach would preclude any BPL emissions on any occupied frequencies. Because of the level of emissions expected from BPL systems, if it is necessary to permit BPL operations then the emissions from BPL systems need to be managed as any other source of interference to radiocommunications services. This means that it is necessary to consider the various options available to coordinate BPL use with existing radiocommunications usage. These options include:

location sharing time sharing frequency sharing.

Broadcasting services are ubiquitous and reception is expected to be possible anywhere and everywhere that people are located included fixed, mobile and portable locations. This aspect precludes location sharing as there is no point to providing BPL services if there are no users. In this context, it is to be recognised that listeners expect to be able to receive broadcast services even in such locations as moving vehicles (including while travelling through industrial zones) or uninhabited areas such as beaches and parks. The planning of broadcasting services in Australia is undertaken on the basis of being able to deliver services 24 hours per day. In general, broadcasting services operate 24 hours per day and listeners expect to be able to obtain reception 24 hours per day so simple time sharing is not possible. The above notes show that frequency sharing is similarly impractical. Noting that not all available frequencies are simultaneously in use at all locations and times, it is possible to contemplate a coordination method based on dynamic allocation of frequencies to the BPL system. One way of implementing such a system would require that the BPL system continuously monitors all of its possible transmission channels so as to avoid transmitting on frequencies that are in use by other services (that is, the frequency is occupied or signals are detectable) in the vicinity of the BPL system. Such a scheme would need to meet a specified minimum sensitivity performance level so as to not miss weak signals. Further discussion of this possible approach to BPL coordination and introduction is available in the White Paper published by the BBC Research Department and available at http://www.bbc.co.uk/rd/pubs/whp/whp099.shtml . Observation (iii). That BPL service introduction using broadcasting frequencies

should be prohibited unless an effective scheme for protection of rural area and weak signal reception of broadcasting services (such as dynamic allocation of BPL frequencies) is employed by the BPL system.


Acknowledgements: Valuable review, comment and discussion of the draft by Colin Elston, ABC, and Roger Bunch, FreeTV Australia, is appreciated. References: 1. Australian Broadcasting Authority, “Technical Planning Parameters and Methods for

Terrestrial Broadcasting” April 2004 2. International Telecommunications Union Radiocommunications Sector (ITU-R)

Recommendation P372-8 “Radio Noise” (2003) Resolution 543 Radio Regulations Appendix 11 Recommendation BS703 “Characteristics of AM Sound Broadcasting Reference Receivers for Planning Purposes”

3. Australian Communications Authority ACA Field Report Country Energy BPL Trial Queanbeyan NSW – Feb 2005 ACA Field Report Woomera On-Line BPL Trial Moruya NSW – Oct and Dec 2004

4. OFCOM (UK) “Amperion PLT Measurements in Crieff” 11 May 2005 5. NTIA (USA) Report 04-413 “Potential Interference From Broadband Over Power

Line (BPL) Systems To Federal Government Radiocommunications at 1.7 - 80 MHz” 6. BBC (UK) R&D White Paper WHP099 “PLT and Broadcasting – Can They Co-

Exist” November 2004 7. ELMAC Services “Why broadband PLT is bad for EMC” 20 April 2005.

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