Sequence constructions for delay-and-correlate transmitted reference signaling

• US 5,774,493 A
• Filed: 08/02/1996
• Issued: 06/30/1998
• Est. Priority Date: 08/02/1996
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Ross, John Anderson Fergus
• Primary Examiner(s): Tse, Young T.
• Application Number:
  US08/691,254
• Time in Patent Office: 697 Days
• Field of Search: 375/200, 375/202, 375/206-210, 375/343, 375/367, 370/342, 370/479, 370/515
• US Class Current: 375/142
• CPC Class Codes: H04B 1/70718 with asynchronous demodulation, i.e. not requiring code synchronisation
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/10 Code generation

Abstract

A direct conversion receiver for delay-and-correlate transmitted reference spread spectrum signaling apparatus improves the performance of a delay-and-correlate transmitted reference spread spectrum communication system with essentially no added complexity over prior designs. The message signal contains the information to be communicated, which has been spread through multiplication with a wide band spreading waveform. The reference signal consists of the spreading waveform itself which the receiver can use to despread the message signal and recover the information. Operation of the invention hinges on generation of a class of reference signals at the transmitter which produce more reliable data output signals at the receiver.

Claims

1. In a direct conversion delay-and-correlate transmitted reference spread spectrum signaling system, a transmitter comprising:

a sequence generator for generating a sequence signal characterized as x(1),x(2),x(3), . . . ,x(N), where x(j) are elements of the sequence, said sequence generator being adapted to modify the sequence signal to generate an enhanced sequence signal having improved autocorrelation properties;

a first multiplier for generating a first product signal by multiplying the sequence signal from the sequence generator and input data to be transmitted;

a first delay device for delaying the product signal from said multiplier by a delay d, where twice the delay, 2d, is an odd number of chip intervals;

a summer for generating a summed signal for summing the delayed product signal with the sequence signal from said sequence generator; and

first radio frequency means, including a mixer, for converting said summed signal to a signal for transmission.

2. The apparatus of claim 1 wherein said sequence generator is adapted to alter the sequence signal by replacing the term at 2d+j with x(j), j odd, over the length of the sequence, starting at 2d+1 to produce the sequence x(1),x(2),x(3), . . . x(2d),x(1), x(2d+2) ,x(3),x(2d+4),x(5), . . . that will provide a desirable autocorrelation peak at 2d.

3. The apparatus of claim 1 further comprising:

a receiver including

second radio frequency means, including a mixer, for converting a received signal to a baseband signal;

a second delay device coupled to the output of the second radio frequency means for delaying said baseband signal by a delay d;

a second multiplier for generating a second product signal by multiplying the baseband signal by the baseband signal delayed by delay d; and

a data detector responsive to said second product signal for detecting transmitted data.

4. The apparatus of claim 3 wherein the multiplication performed by said second multiplier is p(t)+m(t-d)p(t-d)!x p(t-d)+m(t-2d)p(t-2d)!=p(t)p(t-d)+p(t)p(t-2d)m(t-2d)+m(t-d)p(t-d)p(t-d)+m(t-d)p(t-d)p(t-2d)m(t-2d), where p(t) is a reference signal and m(t) is a message signal, and wherein the delay is such that the second term is small relative to a symbol interval producing a strong autocorrelation of p(t) at delay 2d.

5. A direct conversion delay-and-correlate transmitted reference spread spectrum signaling system comprising:

a transmitter including

a sequence generator for generating a sequence signal characterized as x(1),x(2),x(3), . . . ,x(N), where x(j) are elements of the sequence, said sequence generator being adapted to modify the sequence signal to generate an enhanced sequence signal having improved autocorrelation properties;

first multiplier for generating a first product signal by multiplying the sequence signal from the sequence generator and input data to be transmitted;

a first delay device for delaying the product signal from said multiplier by a delay d, where twice the delay, 2d, is an odd number of chip intervals;

a summer for generating a summed signal for summing the delayed product signal with the sequence signal from said sequence generator; and

first radio frequency means, including a mixer, for converting said summed signal to a signal for transmission;

said sequence generator being adapted to alter the sequence signal by replacing the term at 2d+j with x(j), j odd, over the length of the sequence, starting at 2d+1 to produce the sequence x(1),x(2),x(3), . . . x(2d),x(1), x(2d+2) ,(3),x(2d+4),x(5), . . . that will provide a desirable autocorrelation peak at 2d; and

a receiver including

second radio frequency means, including a mixer, for converting a received signal to a baseband signal;

a second delay device coupled to the output of the second radio frequency means for delaying said baseband signal by a delay d;

a second multiplier for generating a second product signal by multiplying the baseband signal by the baseband signal delayed by delay d, wherein the multiplication performed by said second multiplier is p(t)+m(t-d)p(t-d)!x p(t-d)+m(t-2d)p(t-2d)!=p(t)p(t-d)+p(t)p(t-2d)m(t-2d)+m(t-d)p(t-d)p(t-d)+m(t-d)p(t-d)p(t-2d)m(t-2d), where p(t) is a reference signal and m(t) is a message signal, and wherein the delay is such that the second term is small relative to a symbol interval producing a strong autocorrelation of p(t) at delay 2d; and

a data detector responsive to said second product signal for detecting transmitted data.