Method and apparatus for optimization of wireless communications

• US 5,822,373 A
• Filed: 08/17/1995
• Issued: 10/13/1998
• Est. Priority Date: 08/17/1995
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: Pittway Corporation (Honeywell International Inc.)
• Inventors: Addy, Kenneth Lyle
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): LUTHER, WILLIAM A
• Application Number:
  US08/516,162
• Time in Patent Office: 1,153 Days
• Field of Search: 375/259, 375/295, 375/309, 375/311, 375/344, 375/300, 332/149, 332/150, 455/78, 455/108, 455/150.1, 455/343, 455/161.1, 455/164.1, 455/192.2
• US Class Current: 375/259
• CPC Class Codes: H04L 1/0057 Block codes H04L1/0061, H04L1/0064 take precedence
• CPC Class Codes: H04L 1/24 Testing correct operation
• CPC Class Codes: H04L 27/066 Carrier recovery circuits H04L27/2271 takes precedence

Abstract

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.

Claims

1. A method of generating and receiving in a wireless transmission system, comprising the steps of:

a. generating a preamble, said preamble having a first bit rate;

b. generating a data portion, said data portion having a second, higher bit rate;

c. appending the data portion to the preamble to create a signal;

d. modulating a radio frequency with the signal; and

e. enabling a wireless receiver to select a wide bandwidth pre-detection filter and a narrow bandwidth post-detection filter during reception of the preamble and a narrow bandwidth pre-detection filter and a wide bandwidth post-detection filter during reception of the data portion.

2. The method of claim 1, wherein the data portion comprises digital data and further comprising before the step of modulating:

a. determining if the data portion contains more is than 0s; and

b. if the data portion is determined to have more is than 0s, inverting the data portion.

3. The method of claim 1, wherein the step of generating the preamble comprises the steps of:

a. generating a training sequence, said preamble comprising said training sequence; and

b. generating a starting sequence;

said preamble comprising said starting sequence.

4. The method of claim 1, wherein the step of generating the data portion comprises:

a. generating a data sequence, said data portion comprising said data sequence;

b. generating a cyclical redundancy check (CRC) sequence; and

c. appending the CRC sequence to the data sequence.

5. The method of claim 4, wherein the step of generating the data sequence comprises generating a nonreturn to zero signal.

6. The method of claim 4, wherein the step of generating the data sequence comprises generating a delay modulation signal.

7. The method of claim 1, wherein the step of generating the data portion comprises generating the data portion at a bit rate twice the preamble bit rate.

8. The method of claim 1, wherein the step of modulating comprises the step of on-off key amplitude modulating the signal.

9. A wireless transmission system, comprising:

a signal comprising

a. a preamble having a first data rate; and

b. a digital data portion appended to the preamble, said data portion having a second data rate, the second data rate being higher than the first data rate, the different data rates enabling a wireless receiver to select a wide bandwidth pre-detection filter and a narrow bandwidth post-detection filter during reception of the preamble and a narrow bandwidth pre-detection filter and a wide bandwidth post-detection filter during reception of the data portion, the digital data portion being configured to have no more 1s than 0s regardless of content of the digital data portions.

10. The wireless transmission system of claim 9, wherein the preamble comprises:

a. a training sequence having a first predetermined pattern of bits configured so a receiver will identify the preamble as an incoming signal, said preamble comprising said training sequence; and

b. a starting sequence having a second predetermined number of bits appended to the training sequence configured to indicate to the receiver that the data portion immediately follows, said preamble comprising said starting sequence.

11. The wireless transmission system of claim 10, wherein the training sequence comprises a repeating sequence of a 1 followed by a 0 at the first data rate.

12. The wireless transmission system of claim 9, wherein the second data rate is twice the first data rate.

13. The wireless transmission system of claim 12, wherein the training sequence is equal to a repeating sequence of two is followed by two 0s at the second data rate.

14. The wireless transmission system of claim 10, wherein the starting sequence comprises a single pattern of is and 0s.

15. The wireless transmission system of claim 10, wherein the starting sequence comprises at least one of a plurality of 0s and a plurality of 1s.

16. The wireless transmission system of claim 9, wherein the data portion comprises:

a. a data sequence, said data portion comprising said data sequence; and

b. a cyclical redundancy check sequence appended to the data sequence and being configured to check the integrity of the data sequence.

17. The wireless transmission system of claim 9, wherein the signal is modulated by on-off keyed amplitude modulation.

18. A wireless signal system, comprising:

a. a crystal oscillator

b. a frequency generator responsive to the crystal oscillator and configured to provide at least one radio frequency to a power amplifier;

c. the power amplifier configured to receive the at least one radio frequency from the frequency generator and being configured to receive a digital transmission signal, the amplifier transmitting the radio frequency at times when the digital transmission signal presents a 1 to the amplifier; and

d. a signal generation circuit, responsive to the crystal oscillator and configured to receive an input signal and to output the digital transmission signal, said signal generator configured to generate a preamble of the digital transmission signal at a first bit rate and a data portion of the digital transmission signal at a second bit rate, the different data rates enabling a wireless receiver to select a wide bandwidth pre-detection filter and a narrow bandwidth post-detection filter during reception of the preamble and a narrow bandwidth pre-detection filter and a wide bandwidth post-detection filter during reception of the data portion.

19. The wireless signal system of claim 18, wherein the signal generation circuit comprises:

a. a preamble register responsive to the crystal oscillator and configured to generate said preamble of the digital transmission signal;

b. a data register connected to the preamble register responsive to the crystal oscillator and to the input signal, and configured to generate said data portion of the digital transmission signal;

c. a cyclical redundancy check (CRC) register connected to the data register, responsive to the crystal oscillator, and configured to generate a CRC portion of the digital transmission signal;

d. a counter connected to the CRC register to determine whether the number of is exceeds the number of 0s in the data and CRC portions;

e. a data inverter connected to the counter, responsive to the crystal oscillator, and configured to invert the data and CRC portions of the digital transmission signal if the number of is exceeds the number of 0s in the data and CRC portion; and

a message generator configured to output the digital transmission signal.

20. The wireless signal system of claim 18, wherein the frequency generator is a variable frequency generator configured to output a plurality of radio frequencies.

21. The wireless signal system of claim 18, wherein the frequency generator includes a dual modulus divider responsive to the signal generation circuit, and configured to vary the radio frequency.

22. A wireless signal receiver, comprising:

a. an automatic frequency control (AFC) circuit responsive to a processing circuit and configured to generate an AFC signal;

b. a bandwidth adjustable pre-detection processor responsive to the AFC signal and configured to receive a wireless signal and configured to have a first bandwidth at times when the receiver is scanning for a signal and to have a second, narrower bandwidth at times when a signal is received and having an output;

c. the processing circuit connected to receive the bandwidth adjustable pre-detection processor output;

d. a bandwidth adjustable post-detection filter connected to the processing circuit and configured to have a third, narrow bandwidth at times when a preamble of the signal is received and to have a fourth bandwidth wider than the third bandwidth when a data portion of the signal is received; and

e. a control device for decoding the signal.

23. The wireless signal receiver of claim 22, wherein the AFC circuit further comprises:

a. frequency detector circuit responsive to the processing circuit and configured to generate an error voltage; and

b. a local oscillator responsive to the error voltage and configured to generate the AFC signal.

24. The wireless signal receiver of claim 23, wherein the frequency detector circuit comprises:

a. a discriminator connected to the processing circuit and configured to generate an output voltage; and

b. a differential amplifier configured to receive the discriminator output voltage and a reference voltage, and configured to generate the error voltage.

25. The wireless signal receiver of claim 23, wherein the local oscillator further comprises a dual modulus divider responsive to the control device, the dual modulus divider being configured to alter a frequency of the local oscillator.

26. The wireless signal receiver of claim 22, wherein the bandwidth adjustable pre-detection processor comprises:

a. a mixer responsive to the AFC signal and configured to receive the wireless signal and to mix the received wireless signal to an intermediate frequency; and

b. an adjustable pre-detection filter responsive to the control device to switch between the first and second bandwidths.

27. The wireless signal receiver of claim 22, wherein the post-detection filter is configured to be responsive to the control device to switch between the third and fourth bandwidths.

28. A method of wireless communication, comprising the steps of:

a. transmitting a wireless signal having a preamble portion comprising a training sequence and a start sequence, the preamble portion having a first data rate, and a data portion having a second data rate, the second data rate being higher than the first data rate;

b. receiving the wireless signal, wherein;

(i) during reception of the training sequence;

(1) receiving the preamble at a receiver;

(2) mixing the received preamble to an intermediate frequency;

(3) selecting a pre-detection filter, which receives the intermediate frequency, to have a wide bandwidth; and

(4) selecting a post-detection filter, which receives the filtered intermediate frequency, to have a narrow bandwidth;

(ii) during reception of the starting sequence;

(1) selecting the pre-detection filter to have a narrow bandwidth; and

(2) selecting the post-detection filter to have a wide bandwidth; and

(iii) during reception of the data portion of the signal;

(1) receiving the data portion at the receiver; and

(2) mixing the received data portion to the intermediate frequency; and

(3) decoding the data portion at the control device.

29. The method of claim 28, wherein the step of transmitting comprises transmitting the signal at a plurality of transmission frequencies.

30. The method of claim 29, wherein the step of mixing further comprises adjusting a mixing frequency at predetermined time intervals to mix each of the plurality of transmission frequencies to the intermediate frequency.

31. The method of claim 28, further comprising the steps of:

a. during reception of the training sequence;

(i) converting the intermediate frequency into a voltage;

(ii) comparing the voltage to a reference voltage; and

(iii) generating an error voltage based on the comparison;

b. during reception of the start sequence;

(i) adjusting a mixing frequency according to the error voltage; and

(ii) mixing the received signal to the intermediate frequency using the adjusted mixing frequency.

32. The method of claim 28, further including before the step of transmitting the preamble and the data portions, on-off key amplitude modulating the signal.