DYNAMIC OPTIMISATION OF BLOCK TRANSMISSIONS FOR INTERFERENCE AVOIDANCE

Abstract

Spectral shaping for narrowband interference avoidance is an important part in cognitive radio, and is essential in ultra wideband (UWB) communication systems. Typically, interference occurs when a broadband user's signal collides with a narrowband user's signal, thus resulting in degradation in performance for the two communication links. It has been proposed that, in some applications, the broadband user should modify his signal such that little or no energy is transmitted on the frequencies on which the narrowband user's signal resides. This ‘interference avoidance’ (IA) technique provides some separation of users' signals such that, with the possible aid of signal processing, both communication links do not significantly suffer from multi-user interference.

Description

These and other aspects of the invention will now be further described, by way of example only, with reference to the accompanying figures in which:

FIG. 1 illustrates an example of a narrowband and a broadband signal occupying overlapping bandwidth in the frequency domain.

FIG. 2 illustrates an example of narrowband interference avoidance in the frequency domain.

FIG. 3 illustrates the distribution of AIC subcarriers and OFDM symbol structure in the frequency domain.

FIG. 4 shows the performance of a cyclic-prefixed single-carrier system using AIC.

FIG. 5 shows a block diagram of a baseband transmitter structure according to the invention.

FIG. 6 illustrates the envelope function processing.

FIG. 7 illustrates an example of the fractional tones in dynamically optimised interference avoidance.

FIG. 8 illustrates an example of envelope scaling for a constant modulus constellation (QPSK).

FIG. 9 shows the packet error rate vs. SNR for three single-carrier block transmission systems: a reference system; one employing AIC; and one employing the proposed dynamically optimised interference avoidance invention.

Claims

1. A method of shaping the spectrum of a signal in a block transmission system by applying a time-domain envelope function comprising: optimising the time-domain envelope function under one or more constraints selected from a set of predetermined constraints;applying the optimised time-domain envelope function to the signal.

2. The method of claim 1 in which the optimised time-domain envelope function is applied in a dynamic manner.

3. The method of claim 1 in which the time-domain envelope function is optimised in a dynamic manner.

4. The method of claim 3 in which the dynamic optimisation is applied to each symbol transmission.

5. The method of claim 1 in which the set of constraints is chosen in order to establish interference avoidance, a cost function, or a utility function.

6. The method of claim 1 in which the signal transmission system is a single-carrier, a multi-carrier, or an OFDM block transmission system.

7. The method of claim 1 in which the envelope function is applied to all time-domain samples in a data block.

8. The method of claim 1 in which the envelope function is applied to all time-domain samples in a subset of a data block.

9. The method of claim 1 in which the criterion selected is interference avoidance.

10. The method of claim 1 in which the predetermined constraints comprise signal transmission characteristics, selected from among the group comprising PAPR, total power, and dynamic range.

11. The method of claim 1 in which the dynamic optimisation of the envelope function is performed numerically in an iterative manner.

12. The method of claim 11 wherein the numerical optimisation technique is selected from the group comprising a gradient method, a steepest descent method, Newton's method, the barrier method, or the primal-dual method.

13. The method of claim 11 wherein the envelope function is constrained to be real-valued and positive so as to facilitate blind detection at the receiver.

14. The method of claim 11 wherein the constellation of the data signal is constrained to be constant modulus so as to facilitate blind detection at the receiver.

15. The method of claim 11 wherein the parameters of the numerical optimisation technique, such as the stopping criteria, can be tuned.

16. A computer program comprising data processing device program code means adapted to perform the method of any of claims 1 to 15 when said program is run on a data processing device.

17. A computer-readable medium comprising computer-executable instructions to configure a signal transmission system to operate in accordance with any one of claim 1 to 15.

18. A spectrum-shaped signal generated by the method according to any one of claim 1 to 15.

19. A signal transmission system comprising means for operating in accordance with any one of claims 1 to 15.

20. A receiver comprising means for receiving a spectrum-shaped signal in accordance with any of claims 1 to 15.