Vodafone takes Telecom to courts over interference of new network

Forums › Spark New Zealand (including Skinny and BigPipe) › Vodafone takes Telecom to courts over interference of new network

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#212791 6-May-2009 09:58

Sooo, 10am. Any idea how long these kind of things are likely to take? Half and hour? More than a day?

:grabs popcorn:

freitasm

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#212794 6-May-2009 10:14

Drinking more coffee to stay awake waiting for some results...

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#212796 6-May-2009 10:16

freitasm: Drinking more coffee to stay awake waiting for some results...

That's what happens when you get up at 4.45 am

pageweon

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#212801 6-May-2009 11:12

oh the tension!!.. i want to know what happened allready(this is better then a soap opera for me)

this is where a signature goes

Kickass

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#212806 6-May-2009 11:26

Stuff seems to be updating their page.

http://www.stuff.co.nz/business/industries/telecoms-it-media/2388714/Telecom-knew-of-XT-interference-Vodafone

JonC

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#212807 6-May-2009 11:27

I saw this intereresting piece on stuff:

Telecom released a Ministry of Economic Development review into the matter concluding Telecom was not violating the Radio Communications Act because it did not specifically require telcos to ensure all of their transmissions remained strictly within their allotted frequencies. However, it noted alternative interpretations of the act were possible.

No wonder VF went to court - the MED it seems can't intervene when transmissions don't remain strictly within the allotted frequencies. What is the point of the Radio Communications Act, if it doesn't require telcos to keep their transmissions within range?

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garvani

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#212808 6-May-2009 11:29

Im guessing no one is live blogging, thats disappointing! Guess ill have to wait for Mauricio to post something..

willnz

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#212809 6-May-2009 11:31

surely the initial hearing is over by now....

freitasm

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#212810 6-May-2009 11:32

garvani: Im guessing no one is live blogging, thats disappointing! Guess ill have to wait for Mauricio to post something..

I am actually out now for a lunch meeting so won't be posting much...

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#212823 6-May-2009 12:19

alexx:
grant_k: It's a very interesting read. From an RF Engineering point-of-view, the crux of this whole problem is the proximity of Vodafone's Rx band starting at 899.8MHz to the upper limit of Telecom's Tx band finishing at 885MHz.

They are only 1.7% apart in frequency terms meaning that a very complex high-order passive filter would be required on Telecom's transmitters in order to reduce the out-of-band emissions to acceptable levels.

Another alternative is a filter on Vodafone's receivers, but in this sort of situation, it is always preferable to remove the interference at its source i.e. the Tx output.

I'm not sure if a filter on Vodafone's receiver is an option... there are two main categories of interference we can be talking about, In-band interference and Out-of-Band Interference.

In-Band: This means that the interfering signal is being generated inside the Vodafone base station receive band - in Vodafone sites this means above 899.8MHz. In this case Vodafone would not be able to filter this out, as the interfering signal is already in the same band as the Vodafone customers mobiles.

Out of Band: This means that a strong signal outside the Vodafone base station receive band is causing some sort of overload - blocking or intermodulation - in the base station receiver. in this case it would mean that the filters are needed in the Vodafone base station - which I would think is something they should be reasonably familiar with, since those Out of Band frequencies are from the same band (below 880MHz) as previous generations of Telecom transmitters.

Great explanation Alexx, thanks for clearing that up.

So, in the case of Out-of-Band emissions from Telecom -- which is In-Band for Vodafone's receivers -- clearly the only option is to install filters on the outputs of Telecom's Txs. As pointed out earlier, these filters would need to be of a high order due to the very small frequency separation. Probably some sort of Elliptical Filter I am guessing.

Whereas, if the interference is due to Intermodulation or Blocking, the only solution is to install filters on the inputs to Vodafone's receivers i.e. before any active circuitry which will exhibit non-linearity in the presence of very strong signals. This would attenuate the Out-of-Band signals so far as Vodafone's Rxs are concerned (In-Band so far as Telecom's Txs are concerned), without significantly affecting the strength of the desired signals from Mobile Phones operated by Vodafone's customers. Again, an High Order filter will be needed, but it won't need to handle so much power as a Tx Output filter referred to in the previous paragraph.

Whether it ends up being a Tx Output filter that is needed, or an Rx Input filter, various documents from Vodafone and Telecom have referred to such filters as being "custom" i.e. not available off-the-shelf. This is where much of the delay will be incurred. A factory somewhere will have to produce a large number of such filters, and that will take time. Then they have to be installed, and finally, acceptance testing needs to take place before Telecom can launch their XT Mobile Network.

Now we will just have to wait with bated breath for somebody to post details of the court's decision...

SilentOne

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#212825 6-May-2009 12:22

Absolute gold!

"Vodafone was willing to carry customers already on Telecom's XT network for the duration of the injunction - a statement that drew chuckles from the public gallery."

-taken from this Stuff article

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exportgoldman

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#212827 6-May-2009 12:25

NZ Herald also has coverage here

http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=10570694

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#212829 6-May-2009 12:35

Telecom group general counsel Tristan Gilbertson claimed in an email to his Vodafone counterpart last Friday that engineers from both companies had agreed the issue could not be resolved until Vodafone rectified its own head amplifiers, which are attached to cellphone towers to pick up signals from phones.

If this turns out to be the reality, it equates to Out-of-Band interference (from Vodafone's point of view) which is equivalent to saying In-Band emissions from Telecom's point of view.

Therefore, it is Rx Input filters that would be needed on Vodafone's cellsites, at the front end, before the "Head Amplifiers" referred to above. Obviously, Vodafone's Head Amplifiers have less Dynamic Range than is desirable with spectrum allocations such as we have in NZ.

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#212832 6-May-2009 12:46

From what I have read up on this particular problem it would appear that Telecoms TX has some spurious emissions in vodafone's RX band. However, MED has said that those emissions are within accepted levels. It would seem that Voda's mast head amps are raising these emissions to a problematic level.
So, what to do?. If vodafone reduces the gain on the mast head amps it could solve the problem of interference but degrade the operation of their network. As the interference is on the 900mhz "rural" network any reduction of RX could knock out many outlying areas.
The problem was caused by Vodafone trying to drag as much performance from their network as they could and is now paying the price. Incumbency is no defence in this case.

limegreen

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#212833 6-May-2009 12:51

I was thinking yesterday that it would be good if this ends up in the hands of Justice Venning. He was formerly a Master of the High Court, specialising in business cases, and in my limited experience of watching his judgements, he seems to be very sensible.

UPDATE: Stuff seem to think it is before Justice Vernon. Heh

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