Chirp communications

1. A method of communicating a data chirp signal from a transmitter to a receiver, the data chirp signal comprising a sequence of symbols, each symbol encoding a first symbol value and a second symbol value such that the data chirp signal comprises a first symbol value sequence and a second symbol value sequence, the first and second symbol values being encoded via different properties of the symbol, the first symbol value sequence being selected from values in a primary predetermined sequence and a secondary predetermined sequence, the method comprising:

selecting consecutive values of the first symbol value sequence from values in consecutive sequence positions of the primary predetermined sequence and the secondary predetermined sequence;

encoding first data in the chirp signal via the selected first symbol value sequence;

encoding second data in the chirp signal via the second symbol value sequence; and

transmitting the data chirp signal to the receiver.

2. A method as claimed in claim 1 , wherein the first data encodes a link parameter renegotiation request.

3. A method as claimed in claim 2 , further comprising:

determining a drift between the transmitter and the receiver; and

determining that the drift is greater than a threshold value, wherein the first data encodes a request to increase the bandwidth of chirp communications between the transmitter and the receiver.

4. A method as claimed in claim 2 , each symbol comprising one or more identical chirps, further comprising:

determining a quality of the link between the transmitter and the receiver; and

determining that the link quality is below a threshold value, wherein the first data encodes a request to increase the length of each chirp in each symbol.

5. A method as claimed in claim 1 , the first symbol values being encoded via the gradients of the symbols.

6. A method as claimed in claim 1 , the first symbol values being encoded via the centre frequencies of the symbols.

7. A method as claimed in claim 1 , each symbol's first symbol value being encoded via the bandwidth of the symbol.

8. A method as claimed in claim 1 , each symbol comprising one or more identical chirps, each symbol's first symbol value being encoded via the length of each chirp in the symbol.

9. A method as claimed in claim 1 , further comprising each symbol encoding at least one further symbol value such that the data chirp signal comprises at least one further symbol value sequence, the at least one further symbol value being encoded via a different property of the symbol to the first and second symbol values, wherein encoding first data comprises encoding first data in the chirp signal via the selected first symbol value sequence and via the at least one further symbol value sequence.

10. A method as claimed in claim 9 , wherein the at least one further symbol value is encoded via one of: the gradient of the symbol, the centre frequency of the symbol, the length of each chirp in the symbol, and the bandwidth of each symbol.

11. A method as claimed in claim 1 , wherein the first symbol value sequence is selected from values in the primary predetermined sequence, the secondary predetermined sequence and at least one further predetermined sequence, the method comprising selecting consecutive values of the first symbol value sequence from values in consecutive sequence positions of the primary predetermined sequence, the secondary predetermined sequence and the at least one further predetermined sequence.

12. A transmitter for communicating a data chirp signal to a receiver, the data chirp signal comprising a sequence of symbols, each symbol encoding a first symbol value and a second symbol value such that the data chirp signal comprises a first symbol value sequence and a second symbol value sequence, the first and second symbol values being encoded via different properties of the symbol, the first symbol value sequence being selected from values in a primary predetermined sequence and a secondary predetermined sequence, the transmitter comprising:

a selector configured to select consecutive values of the first symbol value sequence from values in consecutive sequence positions of the primary predetermined sequence and the secondary predetermined sequence;

a first encoder configured to encode first data in the chirp signal via the selected first symbol value sequence;

a second encoder configured to encode second data in the chirp signal via the second symbol value sequence; and

a transmitter module configured to transmit the data chirp signal to the receiver.

13. A transmitter as claimed in claim 12 , further configured to:

determine a drift between the transmitter and the receiver; and

determine that the drift is greater than a threshold value, wherein the first data encodes a request to increase the bandwidth of chirp communications between the transmitter and the receiver.

14. A transmitter as claimed in claim 12 , each symbol comprising one or more identical chirps, the transmitter further configured to:

determine a quality of the link between the transmitter and the receiver; and

determine that the link quality is below a threshold value, wherein the first data encodes a request to increase the length of each chirp in each symbol.