Idea Transcript
US005943606A
Ulllted States Patent [19]
[11] Patent Number:
Kremm et al.
[45]
[54] DETERMINATION OF FREQUENCY
Date of Patent:
[57]
5,943,606 Aug. 24, 1999
ABSTRACT
OFFSETS IN COMMUNICATION SYSTEMS
A method and apparatus for determining frequency offsets I75]
Inventorsi Steven A- Kremm, Boulder; Gordon 5-
caused by oscillator error or Doppler effects in a user
Skinner> deceased> late of Ly0n5> both
terminal (for example, a mobile Wireless telephone) in a
of CO1O'> by Margo Boodakiam legal
communication system. The system (100) includes at least
representanve
one user terminal (124, 126) and a base station (112), or
[73] Assigneez QUALCOMM Incorporated, San Diego, Calif
gateway (120, 122) for communicating With the user termi nal (124, 126) through a satellite (116, 118) With predeter
[21] APPL NO: 08/723,724
signal (130, 132, 146, 148) is precorrected for knoWn
mined knoWn orbital positions or patterns. Acommunication Doppler effects, such as betWeen a gateWay and a transfer
[22]
Filed:
Sep‘ 30’ 1996
[51] [52]
Int. Cl? ................................................... .. H04B 7/185 US. Cl. ........................ .. 455/121; 455/63; 455/671;
ring satellite (146, 148), When used, and transmitted to a user
[58]
Field of Search ......................... .. 455/10, 12.1, 13.2,
pler- The frequency difference is either transferred as data in
455/504, 63, 67.1, 67.3, 67.5, 69, 70, 71, 75, 517, 524, 427; 342/357, 358
reverse link transmissions (130, 132, 140, 142), or used as a pre-correction factor for such transmissions. The fre
455/71; 455/427; 342/358
_
[56]
terminal- The user termina1(124, 126) determines the signal frequency relative to a reference Oscillator (240)> and treats
any detected difference as resulting completely from Dop
quency of the reverse link user terminal signals is measured
References Clted
at the gateWay (120, 122), again compensating for knoWn
U_S_ PATENT DOCUMENTS
Doppler effects, to provide a nominal error measurement.
378647634
2/1975 Dragonem .
Measured frequency error or offsets ‘are then divided in half
5,095,538 5,613,193 5,742,908
3/1992 Durboraw, III ......................... .. 455/71 3/1997 Ishikawa et a1_ _ __ 455/121 4/1998 Dent ........................................ .. 455/63
to mm at a Doppler Shl? error’ or dlvlded 1“ half and Scaled to the appropriate frequency to arrive at a user terminal oscillator error. The detected error can be transmitted to the
user terminal (124, 126) for use in correcting the oscillator output frequency, or for adjusting the timing of, or time
FOREIGN PATENT DOCUMENTS 0337269
10/1989
9608882
3/1996
tracking for, the user terminal (124, 126). Alternatively, the
European Pat. Off. .
WIPO.
detected error can be included as data in subsequent signals
Primary Examiner—Doris H. To Attorney, Agent, or Firm—Russell B. Miller; Gregory D.
for use by gateWays (120, 122) or base stations (112).
Ogrod
32 Claims, 6 Drawing Sheets 500
GENERATE GW FORWARD LINK
528 ow TRACK/MEASURE / FREQUENCY
SIGNAL AT f]: PRE-CORRECT KNOWN SAT-GW DOPPLER
RETRIEVE OR COMPUTE DOPPLER
PRE-CORRECT KNOWN
I 512
530
MEASURE DIFFERENCE
BETWEEN fGrec AND
EXPECTED m
GW-SAT DOPPLER 514
TRANSMIT AND RECEIVE
532
DIVIDE BY 2 AND 516
FREQUENCY
TRACK/MEASU RE RECV'D SIGNAL FREQUENCY
T 518
MEAsuRE OFFSET FROM UT OSCILLATOR 0R
EXPECTED f]:
534
TRANSMIT OSCILLATOR ERROR
TO CORRESPONDING UT RECEIVE
GENERATE UT REV LINK SIGNAL
AND ADJUST
OSCILLATOR 538
k UT RECEIVE AND EMBED OFFSET
PRE-CORRECT BY OFFSET
FREQUENCY
FREQUENCY
524) \
426/
TRANSFER UT SIGNAL TO GW
STORE OSCILLATOR
ERROR 540
APPEND, IMBED, TRANSMIT OCSILLATOR ERROR
U.S. Patent
Aug. 24, 1999
Sheet 1 of6
5,943,606
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Li, mm?
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U.S. Patent
Aug. 24, 1999
Sheet 2 of6
K
5,943,606
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200
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