Introduction to DMR

Channel Operation and Configuration

Channel Configuration and Numbering

Channel Rotation

Channel rotation is used to avoid the situation when a channel may have problems, and the call won’t stay on that channel. The following details how channel rotation works.

One control channel at a site can handle multiple traffic channels. Any logical channel at a site apart from the control channel can become a logical payload channel or traffic channel. When channel rotation is enabled, each consecutive call is set up on the next highest traffic channel. This continues until the highest number traffic channel is involved in a call. The next channel used will be the lowest numbered channel.

The channel partitioning feature of channel rotation allows all of the channels at a site to be split in 20 different ways. This would allow a group of selected users to have dedicated channels for their own use. It could also be split on the call type. So, emergency calls could have their own dedicated channel group.

Channel Pooling

Channel pooling is a feature that allows the same frequencies to be used on multiple sites. Normally when common frequency is enabled, there will be interference. However, channel pooling switches the frequency so only one instance is used at a time. Channel pooling is mainly used where channel coverage overlaps. In other words, common frequencies will cause interference.

DMR networks typically use a selected portion of the RF spectrum. These are called trunked channel blocks. Each DMR system transmits in channel spaces of 12.5 kilohertz. So, it’s quite easy to calculate any given frequency and megahertz from a corresponding channel number. Over the year in a DMR network, the control channel transmits this actual calculated number along with the associated time slot.