Talk:Digital mobile radio
|WikiProject Telecommunications||(Rated Start-class, Low-importance)|
So far only a few providers like Motorola and Hytera have launched DMR product range. Motorola dubbed its DMR portfolio as MOTOTRBO. — Preceding unsigned comment added by Wikitapas (talk • contribs) 14:06, 20 June 2010 (UTC)
The above statment is very out of date. The DMR Association at www.dmrassociation.org carries the list of the extenstive numbers of companies with DMR product. — Preceding unsigned comment added by TMMOS (talk • contribs) 12:59, 1 May 2012 (UTC)
Near/far interference, restrictions, and multipath
With regard to the constant changes to the DMR page on Near Far Interference and the Restrictions on DMR this is driven by the fact that the near far interference and restriction clauses are both very inaccurate and, it appears, deliberately negatively written statements.
- DMR and near far interference
- If you read the DMR standard clause quoted in this section properly (it is available by a link from the DMR Association web site at http://www.dmrassociation.org, or from the ETSI website) it is clear that the absolute limit in DMR before any near far interference occurs is 150 km less a distance that is calculated using a) duration of call b) distance of radio and c) the timing stability of the radio. An example is then given using a ridiculously long call time (225 seconds) and a radio with the worst possible timing stability which gives a range limit of 75 km. This is clearly not a real world example. Using typical call lengths and a radio with a typical time stability the range limitation is 150km less about 5 km. i.e. range before issues is over 140km. There is no distance limit if only one of the two time slots is being used. So the statement "DMR suffers from near far interference" quoting 75km is misleading to readers and not accurate. The relevant section of the standard will be amended by the ETSI committee responsible for DMR to stop this example being used out of context like this.
- The discussion on multipath fading is also misleading. Multipath fading causes coverage "holes" it does not impact range. All digital radio systems suffer from multipath to some extent. So again it appears that this is written in a non-objective way create a negative view of DMR rather than to inform.
- Restrictions on DMR
- Again the restrictions section is written in a very misleading way. It implies a general (worldwide) restriction. There is no such general restriction. There is currently an issue in the United States VHF band for public safety systems only, which runs to May 6 2012. The VHF band in the USA is characterized by having no systematic pairing between base station transmit and receive frequencies and therefore it is possible to have interference from one base station to another not possible where normal paired frequencies operate. The introduction of digital systems in this band has caused a very limited number of cases of interference which are being investigated. The way the piece is written does not therefore clearly explain what is going on and appears to be an attempt to deliberately write non-objectively about the subject.
Comment that MOTOTRBO products do not conform to DMR II standards
This comment was incorrect and has been edited out. MOTOTRBO products have passed all the interoperability tests (mandatory and optional) that are defined by the DMR Association for DMR II - the test results are available on the DMR Association web site. The DMR standard does allow manufacturers to implement proprietary additions to the functionality in the standard and many vendors have done this - driving innovation. All DMR II products, however, that have passed DMR Association IOP testing will inter-operate with each other for a range of functionality in the manner described in the test results. For DMR II the tests cover all the common voice call types + a range of status and control features. — Preceding unsigned comment added by 220.127.116.11 (talk) 09:30, 9 August 2013 (UTC)
No DMR Tier 1 products to date?
The statement that to date there have been no DMR Tier 1 products is incorrect. The cited website does not state this, it merely fails to list any; and since the statement was made, Hytera have launched tier 1 products - see http://www.dmrtier1.com/. Poglad (talk) 19:21, 20 January 2015 (UTC)
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