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  Reply # 212288 4-May-2009 22:37
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w2krules: The obvious question of course is why are Vodafone having interference issues when Telecom are not?

It's very simple:

-  Telecom's Receive band is 835 to 845.8MHz

-  Vodafone's Transmit band is 944.8MHz to 960MHz

The nearest frequencies between those two bands are 845.8MHz and 944.8MHz which are 11.7% apart.

Compare this with the 1.7% separation in the reverse situation (as explained in my post above), and you can see why the problem is so much more severe from the perspective of Vodafone's receivers, compared to Telecom's receivers.

I don't know what the MED's rationale was for allocating two frequency pairs to competing networks which so obviously have the potential to cause interference in one direction i.e. from Telecom to Vodafone.  From an RF Engineering perspective, it seems like asking for trouble.  No doubt there are good reasons why this was done, but as can be seen from the separation percentages above, there are equally good technical reasons why it is going to be quite a challenge to nail this issue.

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  Reply # 212295 4-May-2009 22:49
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grant_k:
w2krules: The obvious question of course is why are Vodafone having interference issues when Telecom are not?

It's very simple:

-  Telecom's Receive band is 835 to 845.8MHz

-  Vodafone's Transmit band is 944.8MHz to 960MHz

The nearest frequencies between those two bands are 845.8MHz and 944.8MHz which are 11.7% apart.

Compare this with the 1.7% separation in the reverse situation (as explained in my post above), and you can see why the problem is so much more severe from the perspective of Vodafone's receivers, compared to Telecom's receivers.

I don't know what the MED's rationale was for allocating two frequency pairs to competing networks which so obviously have the potential to cause interference in one direction i.e. from Telecom to Vodafone.  From an RF Engineering perspective, it seems like asking for trouble.  No doubt there are good reasons why this was done, but as can be seen from the separation percentages above, there are equally good technical reasons why it is going to be quite a challenge to nail this issue.


Thanks for the actual RF point of view! Looking at what you have said and based on Telecom building there network to spec & with in guidelines (if that is the case), would it not be the MED's fault for the poor allocation, not Telecoms?

Obviously filters would be required to fix this from either side but Telecom are quite possibly operating in accordance to their license but the allocations between carriers are way to close for comfort?  Simple view there!

 
 
 
 


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  Reply # 212297 4-May-2009 22:49
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What kind of effects on coverage would be the result of switching the TX and RX bands?





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  Reply # 212298 4-May-2009 22:51
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The bands are set in the standards for UMTS and GSM - you cant swap them since the radios in phones are made to work with them that way around.




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  Reply # 212299 4-May-2009 22:53
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There must be some flexibility in actually freq?

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  Reply # 212300 4-May-2009 22:53
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Fascinating stuff. That statement makes no mention of any attempts at mitigating the issue which Telecom insist they have been doing.

nitrotech: As mentioned the statement of claim is void of any technical information in relation to the interference eg. field strength of the spurious signals and are they within permissible limits as specified in their license conditions?

Interesting that Voda claims telecom should know Voda have a 900MHz network and design their network around it, however I would expect that under law the only thing Telecom have to prove is that they built their network around the conditions of their license (which will be designed to minimise interference).

It's RSM's job to ensure good spectrum design.

Telecom can equally argue most of the points that Voda have in their statement also apply to them.


I think this case will come down to that - the next statement referring to Telecom causing out-of-band interference in Vodafone's RX band sounds a little suspect - there is no attempt at quantifying the levels or spectrum of the interference.

Sounds to me like Vodafone are claiming the 'we were here first' defence - Telecom have previously made reference to their poor network design causing the issue.

The rest of the claims about customer loss etc are a bit dodgy - no reference is made to whether these percentages are due to the interference issue or other reasons - eg Vodafone's terrible fringe reception which is becoming more obvious as more people move to 3G and find out just how badly 2100mhz propagates...

In reference to the q's about how this works elsewhere - doesn't Aussie have 850mhz (Telstra WCMDA) and 900mhz (3 WCDMA & VF GSM) networks operating side-by-side?

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  Reply # 212301 4-May-2009 22:53
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There must be some flexibility in actual freq?

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  Reply # 212302 4-May-2009 22:54
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How do all these problems relate to Vodafone's 3G issues?



I've experienced months of ongoing call/txt/data issues with Vodafone, but my understanding was their network in main centres was 2100mhz...

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  Reply # 212305 4-May-2009 22:57
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Regs: since when does "vodafones right to the use and enjoyment of land"(*) have anything to do with interference on licenced spectrum?

(*) see VodafoneStatementOfClaim.pdf linked a few posts back


It's more of a legal term, as by NZ law radio spectrum is defined as a land right. A little weird I know, but lawyers are funny creatures.

See here for more http://www.answers.com/topic/frequency-allocation

Here's a snippit

The radio frequency (RF) electromagnetic spectrum is an aspect of the physical world which, like land, water, and air, is subject to usage limitations. Use of radio frequency bands of the electromagnetic spectrum is regulated by governments in most countries, in a Spectrum management process known as frequency allocation or spectrum allocation. Like weather and pollution, radio propagation does not stop at national boundaries. Giving technical and economic reasons, governments have sought to harmonise the allocation of RF bands and their standardisation.




Tyler - Parnell Geek - iPhone 3G - Lenovo X301 - Kaseya - Great Western Steak House, these are some of my favourite things.

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  Reply # 212306 4-May-2009 22:57
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but wouldn't one think that vodafone should have complained to the med/rsm and to Telecom directly.

What seems to be really missing from the claim is
- details from the med or some other independant body doing the tx/rx bleed analysis
- a long list of emails between voda and tnz rf engineers where they are trying to sort it out.

Come on the network has been transmitting for some months now so you would think it would be in everyones interest to raise this a little sooner than a few weeks before launch.

As long as the med can prove that tnz are compliant with their license then there isn't much voda can do I think.

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  Reply # 212307 4-May-2009 22:58
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hmmm thats a really good point, if the issues are with GSM & not 3G where a lot of the problems seem to be (2100mhz) they cannot justify there customer issues claim, good point caldazar!

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  Reply # 212308 4-May-2009 22:59
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manhinli: 32 b)

No technically and economically justifiable measures are available to reduce the susceptibility of Vodafone's receiving equipment on Vodafone's 900 RX band to interference from Telecom's W-CDMA transmissions on Telecom's 850 TX band.


Vodafone can't do anything?


They key word is 'justifiable' - you can always do something.

This has been put together pretty quickly (give a lawyer time and he will produce more pages) so I would suggest VF has not been sitting on this for a while.

If it is true then the problem only gets worse once traffic goes on the XT network.  The court will only hear whether this is injunctable (not the technical evidence). My guess is they will get told to sort it out between them

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  Reply # 212310 4-May-2009 23:05
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One thing I noticed on the TVNZ news, is that Vodafone are claiming that these problems could cause 111 calls not to get through, yet they have known of these problems since last year, which is over 6 months ago. Why haven't they disclosed this problem before, to warn their customers that there are problems? People’s lives have potentially been put at risk, because of VF not disclosing these problems earlier. I thought Vodafone had a duty of care to inform there customers if there are known problems that could have life threatening consequences, which they should have done over 6 months ago. I wonder how many people have tried to phone 111, and not been connected?

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  Reply # 212312 4-May-2009 23:11
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mattwnz: One thing I noticed on the TVNZ news, is that Vodafone are claiming that these problems could cause 111 calls not to get through, yet they have known of these problems since last year, which is over 6 months ago. Why haven't they disclosed this problem before, to warn their customers that there are problems? People’s lives have potentially been put at risk, because of VF not disclosing these problems earlier. I thought Vodafone had a duty of care to inform there customers if there are known problems that could have life threatening consequences, which they should have done over 6 months ago. I wonder how many people have tried to phone 111, and not been connected?


Now thats crap service, no 111 call guarantee... realistically when has any network guaranteed call connectivity all the time! But Vodafone should have done something sooner if this was an issue. it just suits them now to make Telecom look bad & them to look like the inocent party.

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  Reply # 212313 4-May-2009 23:13
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BarTender: but wouldn't one think that vodafone should have complained to the med/rsm and to Telecom directly.



What seems to be really missing from the claim is

- details from the med or some other independant body doing the tx/rx bleed analysis

- a long list of emails between voda and tnz rf engineers where they are trying to sort it out.



Come on the network has been transmitting for some months now so you would think it would be in everyones interest to raise this a little sooner than a few weeks before launch.



As long as the med can prove that tnz are compliant with their license then there isn't much voda can do I think.


That exactly what I think. Essentially going to court, means that they are going over the head of the MED, and saying that we don't trust you to sort this out. They won't win friends with the MED for doing that. There is no contract between telecom and vodafone anyway, it is basically goodwill and goodfaith. The policing of these frequencies is not done by the court, so I hope the court tells them that this is not the right forum for this problem, and to go back to the MED to sort it out. I can understand vodafone may have problems, but to blame these directly on telecom, who appear to have followed the correct proceedures set down for them by the MED,  is not on.

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