AUTOMATIC ISW DECODE WINDOW ALIGNMENT
Original Publication Date: 1994-Feb-01
Included in the Prior Art Database: 2002-Feb-22
This paper describes a method for automatically setting the Inbound Signaling Word (ISW) decode window opening time in an Intellirepeater. The ISW decode window is the window in time during which an ISW must arrive in the station for proper decoding. Time is measured with respect to Word Frame Inter- rupt (WFI), the timing signal to which all control channel signaling is synchronized in Motorola trunking systems. The ISW decode window is sup- posed to occur 13.66 ms after WFI, but because of variations in signal time delay in the base station transmitters and receivers for different bands, the actual time at which this window is opened needs to be adjusted for each band. Currently, delay meas- urements must be made for each band. These meas- urements are converted into constants which are then hard coded into the DSP sohware of the Station Con- trol Board. Ifat any time a receiver or transmitter is redesigned, then these measurements need to be repeated, and the DSP code modified.