Polarization Based Interference Mitigation for OFDM Signals

Technology #4087

Background: Orthogonal Frequency Divisional Multiplexing (OFDM) is a communication protocol that is commonplace in the wireless communication space. It enables enhanced data transmission and reception from different types of wireless devices and systems (e.g. smart phones, base-stations, WiFi routers). OFDM provides the advantage of interleaving multiple dimensions such as time, frequency and power to achieve much higher efficiency and lower signal-to-noise (SNR) characteristics. It achieves some of these characteristics by polarization (i.e. orienting the direction of travel) of the signal to be transmitted.

Technology: The invention focuses on the use of polarization-based architectures to mitigate interference in wirelessly transmitted and received signals. It enables using polarization-frequency (PF) processing with OFDM protocol to increase interference suppression of signals. This is especially applicable when a dual-polarized antenna is used in channels that exhibit polarization mode dispersion for investigation and suppression of polarization based interference. In this technique, a set of filter weights are computed and applied to assist in interference mitigation.

These filter weights help to suppress and mitigate co-channel interference in the frequency domain. Clean soft decisions are enabled by applying the set of polarization filter weights for each OFDM subcarrier. Using such a set of minimum mean square error (MMSE) filter weights also allows for the application of the right polarization to the signal so as to offset small and large interference effects. The maximum signal-to-interference-to-noise ratio (SINR) that should be mitigated for the problem of co-channel interference using polarization processing is proven especially for the case of frequency-domain interference cancellation when using OFDM techniques.

Potential Commercial Applications: This invention would have direct application in OFDM-based wireless communication protocols and techniques. It can further enhance data fidelity and enable lower power data communications which would be very valuable for devices such smart phones, laptops, tablets and other devices which operate in a constantly connected state and where reduced power consumption is a critical consideration.

Benefits / Advantages:

  • Demonstrates that polarization-based processing techniques can effectively mitigate co-channel interference in the frequency domain where OFDM protocols are used
  • Computes a set of MMSE filter weights that can be applied to different signals based on whether the interference is large or small
  • For large interference, filter weights that are closer to the polarization orthogonal of the interference are used
  • Small interference results in the use of weights that correspond to the polarization of the desired signal