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US 8,275,017 B2Granted
Method of packet transmission and reception of quadrature amplitude modulated signals in a frequency hopping radio system
AssigneeModesat Communications Ou
InventorsLeonid Letunov, Aleksandr Grigorjev
Life of this patent
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Abstract
The invention achieves carrier and clock frequency synchronization in QAD packet communications systems. The invention involves using frequency-hopping radio systems that use pseudo-noise data sequences to mark the beginning of data transmissions and carrier frequency switches. The invention involves transmitting in each of the quadrature channels at an initial carrier frequency a first signal over consecutive time intervals and after transmitting the first signal, transmitting in each of the quadrature channels at a second carrier frequency a second signal over consecutive time intervals.
Claims2
A method of transmitting frequency-hopping quadrature amplitude modulation data signals, comprising:
- transmitting in each of the quadrature channels at an initial carrier frequency f0 a first signal over consecutive time intervals T0S, TPN1, T01 and TPN2 comprising:
- transmitting during the time interval T0S only a first pilot tone signal
- A
- 0
- ·
- Sin
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- ,
- where fS is a symbol clock frequency and A0 is an amplitude, at a power equal to a total signal power during data transmission;
- transmitting during the time interval TPN1 a sum of a second pilot tone signal
- A
- 1
- ·
- Sin
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- ,
- where an amplitude A1 is between 0.05 A0 and 0.1 A0, and of a first pseudo noise sequence PN1 multiplied by a cosine signal
- Cos
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- ;
- transmitting during the time interval T01 a sum of the second pilot tone signal and of a first symbol data sequence multiplied by the cosine signal;
- transmitting during the time interval TPN2, a sum of the second pilot tone signal and of a second pseudo noise sequence PN2 multiplied by the cosine signal;
- after transmitting the first signal, transmitting in each of the quadrature channels at an second carrier frequency fi a second signal over consecutive time intervals TS, TPN1, T1 and TPN2 comprising:
- transmitting during the time interval TS only the first pilot tone signal at the power equal to the total signal power during data transmission;
- transmitting during the time interval TPN1 a sum of the second pilot tone signal, and of the first pseudo noise sequence PN1 multiplied by the cosine signal;
- transmitting during the time interval T1 a sum of the second pilot tone signal and of a second symbol data sequence multiplied by the cosine signal;
- and
- transmitting during the time interval TPN2, a sum of the second pilot tone signal and of the second pseudo noise sequence PN2 multiplied by the cosine signal;
- wherein TS is shorter than T0S and T1 is longer than T01;
- and
- wherein the second carrier frequency
- f
- i
- =
- f
- 0
- +
- c
- i
- m
- i
- ·
- f
- S
- 2
- ,
- where ci is a positive or negative integer and mi is a positive integer.
80 more elements
A method of receiving frequency-hopping quadrature amplitude modulation data signals, comprising:
- demodulating a received signal and forming two quadrature channels;
- receiving a pilot signal
- A
- 0
- ·
- Sin
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- ,
- where fS is a symbol clock frequency, during a time interval T0S, for synchronization of a carrier frequency and a clock frequency;
- in each of the quadrature channels, during a time interval TPN1, after the T0S, multiplying the received signal by a cosine signal
- Cos
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- and applying a filter corresponding to a first pseudo noise sequence PN1 to determine a starting time of a first transmitted data symbol sequence;
- in each of the quadrature channels, during a time interval T01, after the TPN1, multiplying the received signal by the cosine signal to recover the first transmitted data symbol sequence;
- in each of the quadrature channels, during a time interval TPN2, after the T01, multiplying the received signal by the cosine signal and applying a filter corresponding to a second pseudo noise sequence PN2 to determine a moment of a first carrier frequency switch;
- switching carrier frequency at the moment of the first carrier frequency switch;
- after the first carrier frequency switch, receiving the pilot signal, during a time interval TS, for synchronization of the carrier frequency and the clock frequency;
- in each of the quadrature channels, during a time interval TPN1, after the TS, multiplying the received signal by the cosine signal and applying the filter corresponding to the PN1 to determine a starting time of a second transmitted data symbol sequence;
- in each of the quadrature channels, during a time interval T1, after the TPN1, multiplying the received signal by the cosine signal to recover the second transmitted data symbol sequence;
- and
- in each of the quadrature channels, during a time interval TPN2, after the T1, multiplying the received signal by the cosine signal and applying the filter corresponding to the PN2 to determine a moment of a second carrier frequency switch;
- wherein during all the time intervals except T0S synchronizing the carrier frequency and a symbol frequency is using a pilot signal
- A
- 1
- ·
- Sin
-
- (
- 2
-
- π
-
-
- f
- S
- 2
-
- t
- )
- ;
- and
- wherein TS is shorter than T0S and T1 is longer than T01.
63 more elements
Dependencies are inferred from the claim text.