Out-of-band power reduction by using computationally efficient cancellation pulses

Cancellation carrier technique is a well-known out-of-band (OOB) power suppressing method in orthogonal frequency-division multiplexing (OFDM) overlay systems. In this technique, OOB power emission reduction is achieved by employing additional carriers, known as cancellation carriers (CCs), and optimizing their amplitude and phase in order to satisfy the desired spectral mask. The more CCs we employ, the deeper spectrum mask we achieve; however, it is shown in this paper that the computational complexity of this optimization algorithm dramatically grows by increasing the number of total employed CCs. In order to reduce the complexity of this method, a class of unique offline-optimized cancellation pulses is introduced which can perform as well as conventional sinc-shaped CC, but with considerably less computational complexity. In fact for a particular set of reserved cancellation tones, we need fewer proposed cancellation pulses to suppress a certain amount of OOB radiations. Therefore, the number of parameters in the optimization algorithm is reduced and consequently the computational complexity is decreased. This complexity reduction has been achieved at no extra side cost in system performances. (C) 2014 Elsevier B.V. All rights reserved.