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Method and apparatus for optimization of wireless communications
| Details |
Inventors: Addy, Kenneth Lyle;
Assignee: Pittway Corporation (Chicago, IL)
Primary Examiner: Pham; Chi H.
Assistant Examiner: Luther; William
Attorney, Agent or Firm: Barkume, P.C.; Anthony R.
A unique wireless transmission signal structure has a preamble at a first data rate and a data portion including the base band signal at a second, higher data rate. The signal is generated in a manner which ensures that the transmitted signal is "on" no more than one half the entire transmission time. A unique wireless transmitter generates the inventive transmission signal. A crystal oscillator drives both a signal generation circuit and a frequency generator. This provides accurate timing and allows the transmission signal to be not self-clocked. A unique wireless transmission receiver has adjustable pre-detection and post-detection filters. When the receiver is scanning for an incoming transmission signal, the pre-detection filter has a wide bandwidth to receive incoming transmission signals within a predictable range of variations due to inaccuracies in the transmitter and receiver. At this time, the post-detection filter has a narrow bandwidth to pass the low bit rate preamble data and reject noise. When a preamble has been detected, the incoming signal is "locked onto" and the pre-detection filter is adjusted to a narrow bandwidth which reject signals other than the incoming signal. The post-detection filter is switched to a wide bandwidth to accept the higher data rate data/CRC portion of the signal. This arrangement allows the transmitter to be relatively inexpensive and to transmit efficiently maintaining short on air time yet the receiver may be selected and sensitive. |
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DETAILED DESCRIPTION These and other objects of the present invention are achieved by the method and apparatus according to the present invention.
The present invention comprises a unique wireless transmission structure, a unique wireless transmitter, and a unique wireless transmission receiver.
The inventive signal structure comprises a signal having a preamble at a first data rate and a data portion including a base band signal at a second, higher data rate.
The signal is generated in a manner which ensures that the transmitted signal is "on" no more than one half the entire signal transmission time.
In a preferred embodiment, the signal is an OOK-AM modulated signal.
The preamble preferably allows the receiver to "lock onto" the transmission frequency and to determine the signal strength of the incoming transmission.
In a preferred embodiment, the preamble portion of the signal comprises a training sequence and a starting sequence.
The training sequence is a sequence a receiver will detect as an incoming signal.
The starting sequence indicates to the receiver that data follows.
In a preferred embodiment, the data portion includes a data sequence, which may be a baseband NRZ signal, and a cyclical redundancy check (CRC) sequence, which the receiver uses to check the integrity of the data sequence.
The data portion is generated so that the transmission "on" time does not exceed half of the total transmission time.
The inventive transmitter generates the inventive transmission signal.
A crystal oscillator drives both a signal generation circuit and a frequency generator.
This provides accurate timing and allows the transmission signal to be not self-clocked.
Preferably, the frequency generator is a variable frequency generator which provides a plurality of transmission frequencies.
This allows the transmitter to transmit the signal at a plurality of frequencies, thus overcoming multipath fading and transmission "clash" problems.
The inventive receiver has adjustable pre-detection and post-detection filters
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Communications 
