Interference mitigation method for single or MIMO receiver devices
View Patent ↗A cognitive radio signal processing method suitable for single receiver devices where interference is mitigated using projection of received multi-dimensional signal space to maximize SNR by orthogonalizing interference is described. The method is based on a well-known LMS solution that is computed from received multi antenna and multicarrier signals in a novel way. This method solves the requirement of multiple RF chains in low cost handsets by introducing a protocol synchronous antenna switcher that allows, for example, a LTE handset with a single antenna to benefit from algorithms that typically require multiple receivers for the same frequency, i.e. MIMO.
1. A system for interference mitigation caused by undesired signals received by a receiver device using LTE protocol comprising:
said receiver device having an antenna switch that is synchronized to a frame timing of a Hybrid Automatic Repeat ReQuest process in an LTE compatible mobile device or base station;
wherein said antenna switch switches between N antennas allowing the receiver to synchronously rotate between said N antennas in accordance with said frame timing;
said receiver then creating a matrix of channel sounding or reference symbols and then said receiver using said matrix to mitigate interference from undesired signals by said receiver orthogonalizing said undesired signals to a desired signal being received by using subspace projection in frequency domain to orthogonalize interference from undesired signals to the desired signal wherein the undesired signals are transformed into frequency domain using Fourier or Fast Fourier Transform and some or all of the complex outputs from the transform are subcarriers; and,
wherein when processing the undesired signals a signal matrix A is created by concatenating k adjacent subcarriers data from channel sounding or reference symbols into a matrix creating an M*(N*k) matrix where k is an integer representing the number of consecutive training symbols used and then transposing said matrix M*(N*k) and then a vector W of M complex coefficients is computed using the formula W=(A T A) −1 *A T *d and then the vector d is concatenated from k symbols.
2. The system of claim 1 wherein N is 2 to 4.
3. The system of claim 1 having a MIMO receiver comprising multiple sets of antennas that are switched in parallel.
4. The system of claim 1 that uses polarized antennas where different polarizations are used successively by said antenna switch.