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Specification of the scope of work needed to determine the technical and operational impact of emissions from UTTNs interfering with aeronautical and navigational radio services in the UK

A report for the Radiocommunications Agency by York EMC Services Ltd, University of York

Authors: I D Flintoft, M H Capstick & A D Papatsoris


Objectives

A number of studies have suggested that using Unstructured Telecommunication Transmission Network (UTTNs) to delivered high data rate services may cause interference to radio services in the Medium Frequency (MF) and High Frequency (HF) bands. The aim of this study is to define the scope of work needed to reliably determine the interference potential of such UTTN systems to aeronautical and maritime radio services. The key objectives are to:

  1. Determine the victim aeronautical and maritime radio services that are at potential risk and state the required safeguarding criteria and technical parameters that must be considered;
  2. Provide an initial assessment of the probability of interference to each of the services due to the cumulative emissions from each UTTN technology;
  3. Determine the operation impact of interference to each of the radio services;
  4. Provide, in the form of a comprehensive terms of reference, a schedule of work to determine the potential for interference between UTTN technologies and all the aeronautical and maritime radio services identified.

The study encompasses the various types of Digital Subscriber Line (xDSL), Power Line Telecommunication/Communication (PLT/PLC) and Home Networking technologies operating in the 9 kHz to 30 MHz frequency range. The study has considered only the cumulative emissions from large-scale deployments of UTTN technologies and has not investigated the potential for near-field interference effects.

Radio Services and UTTN Technologies

A comprehensive review of all the aeronautical and maritime radio systems in the MF and HF bands that are used in the UK has been completed. The review summarises all of the characteristics of the radio systems that are pertinent to the assessment of the effects of interference from UTTNs, including receiver performance criteria, protection ratios and details of the deployment of the radio systems in the UK. The operational impact of interference to each of these radio services has been assessed based on information obtained from the CAA and MCA.

The properties of a wide range of UTTNs have been collocated, including what is known about their radiative characteristics and likely deployment. The power radiated by various UTTN elements is the source of greatest uncertainty in attempting to assess the probable levels of interference suffered by the various radio systems. Very little validated data exists in this area and the statistical variation of the radiated power with factors such as the quality of internal wiring in domestic dwellings is completely unknown.

Interference Analysis

A rigorous theoretical methodology for the estimation of the cumulative emissions from widespread deployments of UTTN technologies has been used to assess the level of interference at the locations of the various radio receivers identified. The methodology has been applied to provide an initial assessment of the probability of interference to aeronautical and maritime services operating in the MF and HF bands. The results are summarised in the table below. This assessment is critically dependent on the input parameters used in the analysis, in particular the effective radiated power of a UTTN element. This parameter is highly uncertain, a fact that must be borne in mind when considering these results. The ERA study on xDSL space wave emissions demonstrated the large variation in predicted interference levels that can be obtained by performing a sensitivity analysis to the input parameters.

Summary of probability of interference to UK aeronautical and maritime radio services from UTTNs.
ADSL
HDSL
SDSL
VDSL PLT access Home Networking
UTTN Mains Telephone
Radio System
Aeronautical systems
NDB/ADF High N/A N/A N/A N/A
HF broadcast N/A Low High+ High+ High+
HF comms N/A Medium High+ High+ High+
Maritime systems
DGPS Low N/A N/A N/A N/A
Loran-C Low N/A N/A N/A N/A
Navtex None N/A N/A N/A N/A
GMDSS N/A None High+ High+ High+
MSI N/A Low High+ High+ High+
SAR N/A * * * *

Grey boxes are not applicable since the technologies do not overlap in frequency.

* Insufficient data to complete.

+ In general the potential for interference is high, however, the specifications of these systems are ill-defined and subject to change and some systems with low power and/or which do not occupy the same spectrum as the radio services may be able to co-exist without adverse interference.

Conclusions

Currently the available knowledge about the radiation characteristics of UTTN systems is insufficient to provide a decisive assessment of the potential of interference to aeronautical and maritime radio services. Our analysis suggests that the window of opportunity for interference from xDSL systems encompasses both the "no interference likely" and the "significant risk of interference" cases. This large range of potential outcomes is almost entirely due to the lack of definite data on the effective power gain of the elements in the xDSL systems. The radio systems at most risk from xDSL have however been identified as aeronautical NBD/ADF and communication systems.

The situation with PLT Access and Home Networking Mains systems is somewhat different. A limited amount of measurement data is available to provide some evidence that the effective antenna gain of such systems is relatively high. A number of studies have concluded that emissions from PLT Access systems using input power spectral densities of about -40 dB/Hz in the HF band are likely to pose a major threat to "co-channel" radio systems. Which systems are affected will depend primarily on the frequency bands used. However, low power PLT systems, with power spectral densities of the order of -87 dBm/Hz, may be much less of a threat to radio services.

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Last Updated: 2006-Feb-01

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