Intellectual Property

OFDM Transmission and elimination of channel estimation using PPC

OFDM Transmission and elimination of channel estimation using PPC

A novel scheme for fast, efficient, resilient wideband OFDM


OFDM Transmission and Elimination of Channel Estimation using Passive Phase Conjugation: Researchers at ECIT have developed a novel technology that enables OFDM data to be recovered after traversing a noisy multipath channel without the need for a channel equalizer, which is normally a pre-requisite for OFDM signal recovery.

The uniqueness of this solution is that a channel equalizer is not required, therefore the system is capable of operating in propagating environments whose characteristics are either unknown or are subject to change during operation (for example air or water).

The key innovation is the use of Passive Phase Conjugation (PCC) in an OFDM scheme. A conventional OFDM receiver is modified, replacing the standard equaliser with a PCC block. The approach requires only minor modification to existing OFDM demodulation and as the transmit section remains the same, there is compatibility with legacy as well as new systems.

Competitive advantage

  • Speed of establishing transmission – existing OFDM using a channel equalizer will require time to probe the channel and carry out compute intense mathematical process to choose the coefficients and therefore set-up appropriate transmission.
  • Lower power – No need for the computational intense channel equalizer.
  • Resilience to changing environment - when using OFDM, if the medium of transmission changes a new coefficient would need to be selected. In shallow water, or noisy air communications the transmission medium changes constantly.
  • Providing wideband digital communications in harsh environments – The scheme can provide up to 100Mbps (HD Video etc) in environments where wideband comms would normally be difficult to achieve (underwater or in noisy environments ie war-zone).
Market potential
  • Mainstream Communications Market - The invention would have numerous communications related applications, including radio, optical and acoustic. Many companies in the radio field are looking at OFDM for high data rate transmission, as new commercial opportunities arise especially as carrier frequency increases and channel models are not available / applicable then the approach we propose here would be extremely attractive.
  • Military - In the battlefield there is often deliberate clutter in the transmission environment that make communications difficult. This use of PCC in an OFDM scheme would actually benefit from the clutter, thus allowing robust wideband communication links ‘In-theatre’. Also, the ability to establish comms quicker more robustly and with wider bandwidth would allow driverless vehicles in convoy, controlled via video link remotely or via UAV.
  • First Responder Application – This technology would be well suited to first responder requirements. Where arriving at a disaster zone, an ad-hoc wireless network could be established instantly without the need to train signals and establish correct coefficients.


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