Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
2000-11-10
2002-07-23
Vu, Huy D. (Department: 2663)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S364000, C370S337000
Reexamination Certificate
active
06424673
ABSTRACT:
FIELD OF THE INVENTION
This invention relates in general to wireless communication systems, and more specifically to a method and apparatus in a wireless communication system for facilitating detection of, and synchronization with, a predetermined synchronization signal selected from a plurality of different synchronization signals.
BACKGROUND OF THE INVENTION
Prior art digital wireless communication systems have utilized fixed synchronization codes for synchronizing receiver timing with that of a received signal. Such synchronization codes have been transmitted either at predetermined intervals or following a preamble. Because a fixed synchronization code does not change from transmission to transmission, the transmitted energy of the synchronization code does not change. Thus, the synchronization code can be detected by simply locating a cross-correlation peak between the fixed synchronization code and the received signal.
Some recently proposed systems, such as Bluetooth, utilize non-fixed synchronization codes. The non-fixed synchronization codes, also referred to as access codes, combine addressing and synchronization in a single, longer code. An access code is assigned on a temporary basis to a receiver. These codes vary significantly in energy from one synchronization code to another, thus making it difficult to reliably detect a wanted synchronization signal while avoiding a false detection on an unwanted synchronization code, or a false detection on pure noise.
Thus, what is needed is a method and apparatus in a wireless communication system for facilitating detection of, and synchronization with, a predetermined synchronization signal selected from a plurality of different synchronization signals. Preferably, the method and apparatus will operate reliably with synchronization signals having a wide range of energy levels and will not false on noise or on unwanted synchronization codes.
REFERENCES:
patent: 5177740 (1993-01-01), Toy et al.
patent: 5590160 (1996-12-01), Ostman
patent: 5982763 (1999-11-01), Sato
patent: 6226336 (2001-05-01), Atarius et al.
Chen Weizhong
Dehner Leo
Breeden R. Louis
Motorola Inc.
Nguyen Phuongchau Ba
Vu Huy D.
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