Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2000-02-23
2001-11-27
Chin, Stephen (Department: 2734)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S367000
Reexamination Certificate
active
06324206
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to communication systems and, in particular, to a method and apparatus for spreading and despreading data in a spread-spectrum communication system.
BACKGROUND OF THE INVENTION
Next generation spread-spectrum communication systems incorporate both a direct-spread and a multi-carrier option for transmission. One such communication system currently being developed with direct-spread and multicarrier capabilities is the next generation Code-Division Multiple-Access (CDMA) cellular communication system, more commonly referred to as cdma2000, or IS95C.
During direct-spread transmission the communication systems transmit information over the bandwidth of interest by using a single short code. Unlike direct-spread transmission, multi-carrier transmission transmits information over the bandwidth of interest by using multiple short codes. For multi-carrier transmission, each portion of the user's data that is spread with a single short code is transmitted within its own frequency band. Such a multi-carrier transmitter and receiver is shown in FIG.
1
. As shown, data stream
101
enters demultiplexer
103
, where it is sent to three separate spreaders
105
. Each spreading circuitry
105
utilizes its own, unique Walsh code as well as a common pseudo-noise (PN) code When spreading data stream
101
. After low-pass filtering and digital-to-analog conversion, each data path is mixed to a separate frequency by mixers
107
. The output of mixers
107
is a portion of data stream
101
, mixed to a unique frequency. After bandpass filtering, the output from mixers
107
is summed by summer
109
and transmitted as signal
121
comprising three separate frequency bands, each frequency band utilizing a unique short code. During reception, the three separate frequency bands
121
are received by receiver
120
and downconverted to a single frequency by mixers
125
. After filtering and analog-to-digital conversion, the three signal paths are despread utilizing three separate despreaders (not shown), each using a similar PN code and a unique Walsh code.
The use of multiple spreaders
105
in multi-mode transmitters, makes multi-mode devices very expensive. Therefore a need exists for a method and apparatus for spreading and despreading data in a communication system utilizing both direct-spread and multi-carrier transmission, that is less costly than prior-art multi-mode transmitters and receivers.
REFERENCES:
patent: 5325394 (1994-06-01), Bruckert
patent: 5544156 (1996-08-01), Teder et al.
patent: 5748668 (1998-05-01), Tomita et al.
patent: 5870378 (1999-02-01), Huang et al.
patent: 6108369 (2000-08-01), Ovesjo et al.
Corke Robert John
Luz Yuda Yehuda
Rotstein Ron
Al-Beshrawi Tony
Chin Stephen
Haas Kenneth A.
Motorola Inc.
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