Register for free to
view the full innovation profile.
Orthogonal precoding is a promising, linear technique in which the null space of a precoding matrix with orthonormal columns is designed to suppress the sidelobes.
About
Sidelobe suppression has always been an important part of crafting communications signals to keep interference with users of adjacent spectrum to a minimum. Systems based on the discrete Fourier transform (DFT), such as OFDM and SC-FDMA are especially prone to out-of-band power leakage. Although many techniques have been proposed to suppress sidelobes in DFT-based systems, a satisfactory balance between computational complexity and the out-of-band power leakage has remained elusive. OFDM is part of communications standards for digital subscriber lines (DSL), cable broadband (DOCSIS), wireless local area networks (e.g. WiFi), digital video and audio broadcasting, fourth generation (4G) and fifth generation (5G) mobile communications and it has been proposed to remain in use for 6G protocols. Use of the DFT in OFDM improves spectral density, simplifies channel equalisation and minimises inter-symbol interference (ISI) in multi-path propagation. In an OFDM transmitter, portions of the transmitter’s bandwidth can be turned on and off flexibly and this underpins OFDM access. Orthogonal Precoding is a promising, linear technique in which the null space of a precoding matrix with orthonormal columns is designed to suppress the sidelobes. Orthogonal precoders have been proposed to yield excellent out-of-band suppression. However, they suffer from high arithmetic complexity- quadratic in the number of active subcarriers - which has limited their application. Former Associate Professor Vaughan Clarkson of The University of Queensland (UQ) School of Information Technology & Electrical Engineering (ITEE) has made the observation that the arithmetic complexity can be made linear instead of quadratic and dramatically reduce the computational cost. There is no penalty to be paid in the achieved bit-error rate. He shows by numerical simulation that the penalty in peak-to-average power ratio is also very small for OFDM. Analysis has shown that this orthogonal precoding technique can improve spectral efficiency by around 20 per cent.
Key Benefits
• Relevant to wide range of digital communications, including 5G and 6G • Potential 20 % spectral efficiency increase compared to industry-standard 5G approaches • Compatible with MIMO approaches
Applications
Digital communication including DSL, cable broadband, local wireless networks including emerging bands Whitespace, digital video and audio broadcasting, 4G/5G/6G/LTE mobile communications or other emerging technologies.