Four-Level FSK & Motorola RD-LAP Perhaps you have an interest in some of the following topics:
- Technical characteristics of Motorola's RD-LAP wireless data transmission protocol (same protocol as used on DataTAC networks).
- A real-world example of Trellis Coded Modulation (TCM). For a nice introduction to TCM please see tutorial 23b at complextoreal.
- Mobile Data Terminals (MDT) / Mobile Data Computers (MDC), especially as related to public safety and police use in the greater Huntsville, Alabama area.
- The FBI's NCIC database system
- Security aspects of such systems vis a vis the scanner radio enthusiast
- A delightfully stimulating application of the Ettus Research USRP and the GNU Radio based Software Defined Radio (SDR) systems
If so then the following PDF file may be of some interest: RD-LAPPROTOCOL.pdf
Summarized in one sentence: The Huntsville Alabama area public safety MDT system transmits all data unencrypted using the publicly documented RDLAP protocol in direct violation of FBI data security standards.
Examples: Four-level FSK modulation revisted - GNU Radio implementation details and sample source code has been put up on the four-level FSK page.
Aviation Transponders
A brief demonstration that the Ettus Research USRP and GNU Radio system is perfectly capable of handling 1090 MHz aircraft transponders can be found on the Aviation Transponders page.
Motorola IDEN + USRP
Some notes on receiving Motorola M16QAM iDEN data transmissions with the USRP have been put in the iDEN-USRP section.
Project currently stalled on higher level protocol issues.
Some Astro VSELP Notes
Some preliminary notes on the Motorola Astro VSELP digital voice transmission implementation as used with the APCO-25 Common Air Interface (CAI) have been put up. And yes, that would in the humorously titled Treading on VSELP Astro Turf section.
Project currently stalled on higher level protocol issues.
A quick look at OFDM issues encountered on the USRP using Qualcomm MediaFLO as an example.
Presidential or Vice-Presidential Visit to Your Neck of the Woods?
Ever wondered what your local law enforcement and emergency services are up during such an event? Here's an example.
Chipping Away at IS-95 A & B (cdmaOne), CDMA2000-1X and More
Fast Autocorrelations:
Some notes on GNU Radio, the USRP and Fast Autocorrelations. If you can run the GNU Radio FFT display code samples such as usrp_fft.py then you are really only a step away from displaying real time autocorrelations too. Take a look in the Fast Autocorrelations section.
Random Useful & Interesting Links:
The Federal Communications Commission (FCC) has various databases where one can search for every licensed non federal radio user by frequency, geographical location, name, et cetera. Search results can include antenna location, transmit power, number of users, coverage maps, and much more. Broadcast FM/AM/TV station licenses are located at the FCC's Audio Division. Pretty much everything else can be found via the Universal Licensing System (ULS). And one can do cross-linked searches (i.e. a broadcast station search result allows you to jump to the ULS system for related licenses such as studio to transmitter links). FCC databases are of course not 100% accurate. You will occasionally encounter improperly licensed transmitters. Example for Huntsville, Alabama: the Velocita Wireless Mobitex transmitter on 936.300 MHz is currently operating with no apparent license in FCC databases.
And Finally...
A special home for radio related tidbits concerning things that should not have happened, just plain make one scratch one's head, or otherwise seem particularly droll. You are invited to come see what has been dredged up and floated to the top at the Haul of Shame.
More delectable topics to come as time & motivation permit.
Dedication
To all those martyred by these paws
And now in paradise with a bunch of nuts