Sun May 19, 2019 12:02 am #1694540
Straight Level wrote:gaznav wrote:The problem for 1090 is the overuse of 1030 interrogations by TCAS and SSR and the continued use of Mode 3/A - they are the 1090 big spectrum killers. As the US decided they would continue with Mode 3/A (they even continue to sell brand new ones) they had to go with the 978 fix. Europe is different and Mode S is far more efficient with 1090 - the word ‘Select’ is the clue.
Somewhat of a subjective term
Have you reference to a 'independent scientific study' to quantify that Gaz?
Lots of research papers on the internet. Here is just one: https://www.researchgate.net/publicatio ... ion_detail
Most studies cite the reduction measures for 1090MHz congestion to include one or all of the following:
1. Use of ACAS X/Hybrid Surveillance (EASA’s SESAR quoted that as much as a 50% reduction).
2. Use of WAM/MLAT in passive mode.
3. Reducing the use of Mode 3/A.
This is what Eurocontrol had to say:
126.96.36.199 1030/1090 MHz Frequency Band
The high number of SSR Mode A/C radars configured with relatively high interrogation rates and interrogator power has, over recent years, lead to congested usage of the 1030/1090 MHz frequency band.
As ACAS and all the cooperative surveillance techniques are dependent upon this frequency band its use is considered to be fundamental to the future of surveillance. Deploying an alternative band would be expensive, time consuming and would introduce technical difficulties. It is preferable to manage, monitor and protect the current frequency assignments in recognition that the 1030/1090MHz as a valuable asset that is to be used with care. The protection of the 1030/1090 MHz frequencies is a key objective of this surveillance roadmap.
Various measures ranging from the removal of spectrally inefficient Mode A/C SSRs (such as promoted through the Implementing Regulation No 1206/2011 Ref Doc 6) through to improvements in ACAS technologies (hybrid surveillance) or the clustering of SSR Mode S ground-stations will lead to improvements in this band and obviate the need for deployment of an alternative frequency band. The deployment of WAM techniques has the potential to reduce excessive transmissions in the 1030/1090 MHz band when compared with conventional SSR systems. However it should be noted that Active Wide Area Multilateration systems configured with broad-beam or omni-directional transmit stations can also place a significant impact upon this frequency band and the surveillance sensors that depend upon it.
Here is another Eurocontrol snippet:
Deployment of ACAS Hybrid Surveillance supports continuing improvements to 1030/1090 occupancy and contributes to a reduction in the need for a second/alternative data link for ADS-B.
https://www.eurocontrol.int/sites/defau ... -2v1.1.pdf
Hence, I’m kind of getting tired with the congestion argument and ADS-B. It’s not ADS-B that causes the 1090 congestion problem (in fact it should help!), it is people using inefficient Mode 3/A transponders, inefficient pre-TCAS 7.1 with Hybrid Surveillance and old bandwidth-hogging Mode 3/A/C Secondary Surveillance RADARs (SSR).