Modified water-filling algorithm for deliberately clipped OFDM signals

The most well-known drawback of multi-carrier (MC) communication systems such as orthogonal frequency division multiplexing is the high dynamic range of its transmitted signal. However, it still has many advantages. One important advantage is the high spectral efficiency in a frequency selective channel environment. This spectral efficiency entitled MC system as 'capacity achieving' and indeed, nowadays, MC systems are able to get very close to the Shannon capacity bound. A very important element of the 'capacity achieving' is the water-filling (WF) power-loading method. This paper presents an innovative concept of combining the WF method with the 'clipping and filtering' peak to average power ratio reduction technique into a unified approach. The proposed system optimizes the channel capacity by controlling both the clipping amount together with the sub-carrier power-loading coefficients. This method will be shown to give greater performance than the traditional WF that does not use the clipping model. In addition, a computationally efficient algorithm that is suitable for real-time implementation is proposed here.