Scenario Analysis for Co-existence/Joint Use Between Analogue and DMR Systems
19 Sep. 2016 Information
Digital DMR to Analogue
This is where a user belonging to a DMR user group wishes to transmit on a shared channel when the channel is already in use by analogue users; the analogue/digital users can be from either the same or different licensees.
The DMR terminals currently available on the market can comply with current regulations applicable in various jurisdictions by correctly configuring internal software parameters inside the terminals.
These parameters being those discussed in section 4 above i.e. :
• "Listen Before Transmit" mode which can be set on the
DMR radios to:
• Impolite
• Polite to all
• Polite to own colour code: before enabling transmission, the radio checks that the specified colour code is not currently in use.
• "Time Out Timer" i.e. maximum transmission length
• "Time Out Timer Reactivation Delay" i.e. enforced delay before re-transmission
So in this case an analogue user sharing a channel with a DMR user will have the same experience as if sharing with other analogue users. The only difference will be in the operationally unusual case where an analogue user has configured their radio to un-mute on the receipt of any traffic, irrespective of whether it is targeted at them. In this case the analogue user will hear the digital modulation of DMR which will sound different to analogue traffic on the channel, but functionally there is no difference – a busy channel is a busy channel.
Analogue to Digital DMR
This is where a user belonging to an analogue user group wishes to transmit on a shared channel when the channel is occupied by users with DMR radios; the analogue/DMR users can be from either the same or different licensees.
The analogue terminals currently available on the market can comply with current regulations by correctly configuring some internal software parameters inside the terminals themselves; the most common parameters are the following:
• "Listen Before Transmit" for sharing the channel which can be set on the analogue radios to:
• Impolite
• Polite to all
• "Time Out Timer"
• "Time Out Timer Reactivation Delay"
So in this case a DMR user sharing with an analogue user will have an experience of channel sharing that is just like analogue users sharing. In practice today all DMR products on the market have both an analogue and digital mode with automatic switching between modes when analogue or digital traffic is detected. As a result interfering analogue traffic will be heard by the DMR radios in analogue mode in the event that user’s radios are configured to un-mute speakers for all traffic. For digital only radios in future the interfering analogue signal will be heard as noise if the DMR radios are configured to un-mute to all detected signals.
Digital DMR to Digital DMR
This concerns the situation where a user belonging to a DMR user group wishes to use a shared channel, which is occupied by another group of DMR users; the two groups can belong to either the same or different licensees.
The terminals currently available on the market comply with current regulations by configuring the internal software parameters inside the terminals themselves. These parameters being those discussed in section 4 above i.e.:
• "Listen Before Transmit" mode which can be set on the DMR radios to:
• Impolite
• Polite to all
• Polite to own colour code: before enabling transmission, the radio checks that the specified colour code is not currently in use.
• "Time Out Timer" i.e. maximum transmission length
• "Time Out Timer Reactivation Delay" i.e. enforced delay before re-transmission
So in this case a DMR user sharing with another DMR user will have an experience of channel sharing that is just like analogue users sharing except that existing traffic on the channel will sound digital if a radio un-mutes to it.
The short discussion above demonstrates that both from the perspective of the user and from that of a regulator the DMR standard was designed to facilitate easy co-existence of analogue and digital radios in shared and adjacent channels. This easy co-existence enables the migration from analogue to digital in a seamless manner. Both users and regulators will have their different requirements met without disrupting legacy channel plans or services, or requiring changes in regulations or user behaviour. All the extensive benefits of digital DMR (6.25 kHz spectrum efficiency, efficient use of infrastructure, power saving, easier use of data, novel voice features) can easily be realised.
(Resource: Abstracted from
DMR RADIO PERFORMANCE CHARACTERISTICS AND CHANNEL SHARING WITH OTHER RADIO TYPES- DMR Association White Paper)
