PMSE in Aircraft Frequencies?

Introduction

In the Radio Band 960 to 1215 MHz (sometimes named as Aircraft Frequencies or DME Band) is mainly operated the Distance Measuring Equipment (DME), a transponder-based radio navigation technology.
This Radio Band is currently in discussion, if Audio PMSE can be operated there. Therefore, in the text below we present some details and like to invite our homepage reader for discussion and/or to present further information.

Systems operated in 960 to 1215 MHz

(Section updated in December 2016)

Among others the following services are currently operating in this band:
* Airborne collision Avoidance System (ACAS)
* Distance Measuring Equipment (DME)
* Secondary Surveillance Radars (SSR)
* TACtical Air Navigation (TACAN) System
* Global Navigation Satellite System (GNSS)
* Joint Tactical Information Distribution System (JTIDS)
* Multifunctional Information Distribution System (MIDS)
* Multilateration (MLAT)
* Identification Friend or Foe, Mode 1 to 5 (IFF)
* Reverse-Identification Friend-Foe (Reverse IFF)
* Radiotechniczny system bliskiej nawigacji (RSBN)
* Wide Aera Multilateration (WAM)

Further systems will be operated in this band. For example, still in research might be L-DACS.
Update: already end of 2014 ICAO was noting the Status of LDACS Development.

In addition, WRC-15 agreed the implementation of a new Flight Tracking System.
This might be operated in the lower band segment, e.g. GFT in 1087.7-1092.3 MHz.

Picture 1

Various frequency allocations in the 960-1215 MHz, Source: Navigation System Panel at WRC-07

Question before PMSE starts in 960 to 1215 MHz

(Section updated in October 6, 2016)

With regards to current discussion in UK, we summarize:

1) Legal Aspects with reference to Aviation Safety


In the case of an air traffic accident, caused by interference to systems and equipment belonging to the safety of life service Aeronautical Radio Navigation System (ARNS) in the band 960 -1215 MHz, what is the liability of PMSE operators when PMSE signals are identified to be at least in part the cause for the accident?

Will operation of PMSE equipment operating on frequencies and within the parameter assigned by OFCOM relieve PMSE operator of any responsibility at a later date, when research concludes that that signals originating from PMSE equipment alone or in combination with other signals from non ARNS systems in the band, like JTIDS/MIDS, are responsible?

Evaluation: This position is legally controversial. A dispute before the court takes a long time and is expensive.

2) Aircraft World might change

Will PMSE operators receive financial reimbursement and new frequency band compensating for their investment into PMSE equipment operating in the band 960 to 1215 MHz, if more stringent protection is found to be necessary for existing ARNS systems. In addition, if new aeronautical systems and equipment are standardized and put into operation, such as Modes S phase overlay or L-Band Digital Communication System (LDACS) where does that leave the PMSE user?
Note: see below the section "Expected Effect of new LDACS1 System"

3) PMSE Quality Assurance

Aviation Products are subject to strict quality control. If PMSE share Air bands, there is the question whether PMSE must meet similar requirements in the future. Who will take responsibility for problems?

4) Who will pay finally?

Will PMSE operator be reimbursed for payment withheld or refused if the program making product delivered is found substandard due to interference by signals generated in the band 960 - 1215 MHz?

Expected Effect of new LDACS1 System

In current discussions it is suggested that PMSE is to be operated in the gaps between DME channels. But these frequencies have been discussed for a number of years with regards to the implementation of a new L-DACS 1 system. This might have a significant impact on the remaining empty DME gaps that can be used for PMSE.

Get further information in this presentation: LDACS1 - Overview and Current Status [803 KB]

Mobile Spectrum Recording in UK

(Section added in August 2016)

In late 2015 Ofcom UK consulted on the possible future use of two new frequency bands for audio PMSE. They were; 960-1164 MHz and 1525-1559 MHz. In the end, Ofcom UK decided, that of the two bands, 960-1164 MHz (the air band) was the most suitable. Therefore, the APWPT made a scanning roundtrip over about 1500 km across the United Kingdom. For the first time, a spectrum recording of the band 960 to 1170 MHz was carried out, seen through the eyes of the current PMSE technology (e.g. in the antenna size and the audio PMSE receiver class B/C).

APWPTs Report: Spectrum Recording in UK [5.439 KB]

Spectrum Scans

Spectrum scans can show the distribution and density of operated wireless devices. The pictures below show a typical indoor scenario.

Picture 2

In a time frame of about 8 hours were aggregated the scans of a professional Spectrum Analyser. One can see, the DME band is completely in use, Source: APWPT

Picture 3

Timing of narrowband signals close or above a threshold of -85 dBm, Source: APWPT

What's the problem in this spectrum recording?
* For several hours the lower spectrum is completely empty
* But later we see an intensive spectrum use in the lower band

How to set-up your Spectrum Analyser?

If you are interested in further spectrum scans, how to set-up your Spectrum Analyser?

The typical default configuration of your Spectrum Analyser will show incorrectly the signals in band 960 to 1215 MHz. Therefore, it is suggested to set-up your scanner to this parameter:
- Detector; set to (Positive) Peak
- Resolution bandwidth; set to..
..1) 100 kHz (for scans using PMSE bandwidth) and/or
..2) 1 or 3 MHz (for scans using DME bandwidth)
- Sweep Counter; set to 1
- Sweep Time; set 5 times higher that default Sweep Time value
- Trace Mode; set to Max Hold

Please note:
Below 960 MHz are operated a number of high-power application. This might provide interference to your scans. Therefore it is suggested to add a High-Pass Filter, i.e. NHP-1000+, close to input of Spectrum Analyser.

Feel free for any comments to office@apwpt.org

How to Summarize RF Scans that can be Compared?

Above, the Picture 2 and 3 were made by a special scanning software, “PMSE Occupation Recorder”. This a tool of the PMSE working group in German DIN/VDE.
If you are interested on further information send a mail to matthias.fehr@apwpt.org.

How to get Information on PMSE Interference?

So far we know, there is now PMSE on market that can be operated in 960 to 1215 MHz.
If the DME band signal will be mixed down to an existing PMSE tuning range, the effect of interference can be studied.

Picture 4

Test Set-Up, Source: APWPT

Links to Data Sheets of used RF Component

Combiner ZAPD-2-252-N+ or ZAPD-2-252-S+: ZAPD-2-252.pdf

RF Amplifier ZX60-33LN-S+: ZX60-33LN+.pdf

RF Mixer ZEM-4300MH: ZEM-4300MH.pdf

RF Filter VBFZ-1065: VBFZ-1065+.pdf

PMSE Operation between two DME Signals

DME is operated in a 1 MHz channel grid. There is the question if PMSE can be operated in between.
The DME signal behaviour was examined by scientific facilities. Find below a typical picture:

Picture 5

L-DACS 1 and DME signals with frequency offsets -500 kHz and +500 kHz, Source: {hirschbeck,huber}@LNT.de at SCC 2015

There is the question how the PMSE operation is affected in those scenarios?

Please listen a few typical Sound Files

Find below two indoor-recorded Sound Files. Please note:
The Sound will change if different PMSE are operated or the sound test will take part on a different Location.

Indoor DME Sound in an adjacent Channel Scenario

Indoor DME Sound in a Co-Channel Scenario

We like to invite you

Do you have any question or can you provide further information? Please contact info@apwpt.org