Communications systems and methods

1. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal;

a reference signal acquisition system coupled to said optical signal reception device and to said reference signal memory to determine said reference channel response signal from a received optical signal and to store said determined reference in said reference signal memory;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position; and

an output coupled to said correlator to provide pulse position data for said received optical pulse.

2. An optical data communications receiver as claimed in claim 1 wherein said reference signal acquisition system is configured to acquire a plurality of said reference channel response signals from a plurality of different optical transmitters and to store said plurality of reference channel response signals in said reference signal memory.

3. An optical data communications receiver as claimed in claim 1 comprising a plurality of said correlators coupled to said reference signal memory and to said signal reception device at successive respective relative delays between said stored reference channel response signal and said received optical pulse to determine said optical pulse position.

4. An optical data communications receiver as claimed in claim 1 wherein said optical pulse position is modulated by a pseudorandom sequence, the receiver further comprising a pseudorandom sequence generator for tracking said pseudorandom modulation.

5. An optical data communications receiver as claimed in claim 1 having a receiver front end including said optical signal reception device, and said front end further comprising an analogue-to-digital (A/D) converter coupled between an output of said optical signal reception device and said correlator.

6. An optical data communications receiver as claimed in claim 5 wherein said front end is configured to implement a peak detect Function for said optical signal reception device.

7. An optical data communications receiver as claimed in claim 6 wherein said A/D converter has a non-linear conversion Function to implement said peak detect Function.

8. An optical data communications receiver as claimed in claim 5 wherein said A/D converter has an offset to implement a peak detect Function.

9. An optical data communications receiver as claimed in claim 5 wherein said A/D converter comprises a one bit A/D converter.

10. An optical data communications receiver as claimed in claim 5 wherein said receiver front end further comprises a received signal level adjuster to adjust an input signal to said analogue-to-digital converter.

11. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal, wherein said reference channel response signal comprises a plurality of multipath components;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position; and

an output coupled to said correlator to provide pulse position data for said received optical pulse.

12. An optical data communications receiver as claimed in claim 11 wherein said reference signal memory has a data structure defining said channel response signal as at least two said multipath components separated by a delay.

13. An optical data communications receiver as claimed in claim 11 wherein said correlator includes partial correlation storage to accumulate a plurality of partial correlations for said multipath components to thereby correlate interleaved multipath components of successively transmitted optical pulses.

14. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position, wherein said correlator is configured to correlate, within a time window, a plurality of samples of said received optical pulse with a plurality of samples of stored reference channel response signal; and

an output coupled to said correlator to provide pulse position data for said received optical pulse.

15. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position, wherein said optical pulse position is modulated by a pseudorandom sequence;

a pseudorandom sequence generator for tracking said pseudorandom modulation, wherein said sequence generator is coupled to one or both of said reference signal memory and said correlator for correlating said received optical pulse with said stored reference channel response signal at positions in time determined by said pseudorandom sequence; and

an output coupled to said correlator to provide pulse position data for said received optical pulse.

16. An optical data communications receiver as claimed in claim 15 wherein said correlator is configured for correlating at least two said positions in time in parallel, each of said two positions corresponding to a possible value of an encoded bit of said data.

17. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position, wherein said optical pulse position is modulated by a pseudorandom sequence;

a pseudorandom sequence generator for tracking said pseudorandom modulation;

an output coupled to said correlator to provide pulse position data for said received optical pulse, wherein said data comprises packet data, a packet of said data including a header with data for identifying one or both of a pseudorandom sequence identifier and a pseudorandom sequence seed; and

a system coupled to said pseudorandom sequence generator for reading said packet header to determine data for initialising said pseudorandom sequence generator.

18. An optical data communications receiver for receiving data encoded using optical pulse position, the receiver comprising:

an optical signal reception device;

a reference signal memory for storing a reference channel response signal;

a correlator coupled to said reference signal memory and to said optical signal reception device for correlating a received optical pulse with said stored reference channel response signal to determine said optical pulse position; and

a receiver front end including:

said optical signal reception device;

an analogue-to-digital (A/D) converter coupled between an output of said optical signal reception device and said correlator; and

a received signal level adjuster to adjust an input signal to said analogue-to-digital converter, wherein said received signal level adjuster is responsive to said reference channel response signal; and

an output coupled to said correlator to provide pulse position data for said received optical pulse.