David C Chadwick

US Patent:

54426464, Aug 15, 1995

Filed:

Feb 1, 1994

Appl. No.:

8/189715

Inventors:

David J. Chadwick - Great Falls VA
Howard H. Ma - Lexington MA
Frank J. Mammano - Forestville MD
James W. Marshall - Sterling VA
Vijaykumar M. Patel - Fairfax VA
Lyle G. Saxton - Broad Run VA

Assignee:

The Mitre Corporation - Bedford MA

International Classification:

H04B 110
H04B 1500
H04L 120
H04L 100

US Classification:

371 43

Abstract:

A communication system (100) is provided for transmitting data to mobile receivers utilizing a subcarrier within a commercial FM channel of a radio station (55). The data transmitted is first encoded in encoder (112), utilizing a forward error correction code. The sequence of the encoded data is altered in interleaver (116), subdivided into a plurality of subframes, in framing and synchronization circuit (120), which also adds channel state bits to each subframe. The framed data is modulated onto the subcarrier in the differential quadrature phased shift keying modulator (130), the output of which is coupled to the FM modulator (52) of radio station transmitter (50). The transmitted radio frequency signals may be received by a vehicle antenna (12) for coupling to the vehicle's FM receiver (80). The modulated subcarrier is recovered from the FM demodulator (84) of the receiver (80), the modulated subcarrier being demodulated to recover the encoded digital data therefrom. The channel state bits included with the data are extracted from the digital data and utilized to form a data reliability factor for each bit of the encoded data.