I'm brand new to this world of trunked mobile so please bear with me. I've been trying to read all I can on Smartnet and trunked radio in general. Smartnet is particularly frustrating as it seems to be reverse engineered but I can't find a single good reference on some of the design, it's scattered in bits and pieces all over.
A little background. I'm an electrical engineer and I work primarily in the DSP field. I just got a USRP and I want to play with detecting and understanding various trunked systems that are out there. Which leads me to my questions:
1. Is there some sort of frequency allocation plan for Smartnet? I know there are the FCC approved bands in the US, but is there an equation or standard for what might be mandatory base frequencies? In looking through the database they seem to at least be multiples of 6.25 kHz. Is that always the case? Is there any equation governing them that incorporates offsets? I can tell it's not difficult once you have the base frequency to get to the channels, it's just a matter of knowing which channels can be used and what the range is. Seems similar to MPT1327 without the documentation.
2. For the lower frequencies is there a standard duplex spacing (I know 45 MHz is standard >=800 MHz)? It's nice in some other technologies because the duplex separation means you know if a given band it is either uplink or downlink. Is it that way for Smartnet or can they be randomly interspersed? For instance, in iDEN it looks like this, so if I detect something on a frequency I know if it's uplink or downlink
806-821 - Uplink
851-866 - Downlink
821-825 - Uplink
866-870 - Downlink
etc.
3. Is there a better sub-forum to be asking these questions?
4. I know iDEN is proprietary but I found a good "Technical Overview" document. Does something like that exist for Motorola Trunking systems (most interested in Type II - Smartnet)?
A little background. I'm an electrical engineer and I work primarily in the DSP field. I just got a USRP and I want to play with detecting and understanding various trunked systems that are out there. Which leads me to my questions:
1. Is there some sort of frequency allocation plan for Smartnet? I know there are the FCC approved bands in the US, but is there an equation or standard for what might be mandatory base frequencies? In looking through the database they seem to at least be multiples of 6.25 kHz. Is that always the case? Is there any equation governing them that incorporates offsets? I can tell it's not difficult once you have the base frequency to get to the channels, it's just a matter of knowing which channels can be used and what the range is. Seems similar to MPT1327 without the documentation.
2. For the lower frequencies is there a standard duplex spacing (I know 45 MHz is standard >=800 MHz)? It's nice in some other technologies because the duplex separation means you know if a given band it is either uplink or downlink. Is it that way for Smartnet or can they be randomly interspersed? For instance, in iDEN it looks like this, so if I detect something on a frequency I know if it's uplink or downlink
806-821 - Uplink
851-866 - Downlink
821-825 - Uplink
866-870 - Downlink
etc.
3. Is there a better sub-forum to be asking these questions?
4. I know iDEN is proprietary but I found a good "Technical Overview" document. Does something like that exist for Motorola Trunking systems (most interested in Type II - Smartnet)?