DMR LSNs For Tier-III Systems


Premium Subscriber
Feb 15, 2010
Fulton, NY
There seems to be an inconsistency between the way that DMR Tier III and DMR Cap/Con+ site frequencies are represented in the database.

For example, this Con+ system: Syracuse Site Details (SaiaNet) has a site frequency table with LCN, LSN, Frequency and Color Code.

But, this Tier-III system: Bill Williams Mt Site Details (Niles Radio) has a site frequency table with CH ID, Frequency and Color Code.

The Tier-III site frequency table CH ID value appears to be calculated the same as Logical Slot Numbers (LSN) in Con+ systems.

During decode for this particular Tier-III system, the neighbor report lists the control channel number for site 34828 (Niles Radio) as channel 916. In the radio reference site frequency table, this same channel is listed as CH ID 1833.

This follows the Logical Slot Number (LSN) formula for DMR systems:

LSN = (2 * LCN) + timeslot + 1
1833 = (2 * 916) + timeslot(0) + 1

However, the SiteFrequency record that is retrieved from the web service places this LSN value in the ChannelID field and instead of the actual LCN value (916 in this example), RR uses a 1-up sequence for LCN identifiers.

So in practice, for DMR Tier-III systems accessed via the RR web service, I have to check the site frequency record to see if there is a value in the string ChannelID field and use that for the LSN. Otherwise, I use the integer site frequency LCN value to calculate the LSN.

The Tier-III example in this case has this Site Frequency table:

But for consistency with other DMR systems, it would be:

1833 461.4375c (LCN 916 TS 0)
1834 461.4375 (LCN 916 TS 1)
2143 463.375 (LCN 1071 TS 0)
2144 463.375 (LCN 1071 TS 1)