Pulse or digital communications – Receivers – Interference or noise reduction
Reexamination Certificate
1998-03-06
2001-01-23
Chin, Stephen (Department: 2734)
Pulse or digital communications
Receivers
Interference or noise reduction
C375S293000, C455S503000, C455S303000
Reexamination Certificate
active
06178210
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a communication device, such as a selective call receiver, and more particularly to a communication device and method capable of detecting simulcast conditions and limiting distortion caused by Simulcast Delay Spread distortion.
BACKGROUND OF THE INVENTION
When designing a communications system, it is often desired to cover an area larger than can be economically covered by a single transmitter site. In such cases, multiple transmitter sites are employed, each transmitting substantially the same data on substantially the same channel, in a process known as simulcasting. Due to differences in propagation delays and other factors, a receiver in the coverage area may receive signals from two or more transmitters at slightly different times, leading to a form of distortion known as Simulcast Delay Spread (SDS) distortion. Under certain conditions this distortion may become severe and corrupt the received data to an unacceptable degree.
Receiver modifications to reduce the effects of SDS distortion are known in the art; however, these modifications tend to degrade static (i.e., non-simulcast) sensitivity, adjacent channel selectivity (or rejection), or other desirable receiver performance parameters. Conversely, methods of optimizing the receiver to achieve maximum static sensitivity tend to degrade the receiver's performance in the presence of SDS distortion.
Since it is difficult to simultaneously optimize a receiver for best SDS distortion and static sensitivity performance, a need exists not only for a method at a receiver which can reliably discern between a signal subject to SDS and a signal that is not, but for a method or an apparatus that simply reduces the effects of SDS distortion once a simulcast signal is known to exist. If this were available, an adaptable receiver optimized for static sensitivity could be used that employed SDS distortion mitigation methods only when in a simulcast environment, and therefore achieve optimum performance in both static and simulcast environments.
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Virginia Tech Symposium 1991, vol. 16, entitled “Transmitter Timing Optimization in Digital Simulcast Networks” by Rade Petrovic, Center for Wireless Communications, Univeristy of Mississippi, pp. 167-176.
Carsello Stephen R.
Craig Ronald A.
Powell, II Clinton C.
Ramirez Dalier J.
Chin Stephen
Meles Pablo
Motorola
Rupert Paul N.
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