Kenneth P. Kearney

A resource block based filtered OFDM scheme and performance comparison

Dynamic spectrum sharing is a key technique to meet the high data rate demands of future wireless systems evolving towards heterogeneous networks. To make the best use of available frequency resources without creating interference to neighbor nodes, spectrally contained and scalable waveforms are needed. While OFDM has become the most popular multicarrier modulation (MCM) scheme, it suffers from high side lobes. Filtering is a popular technique used to reduce the out-of-band emission of OFDM. However, to utilize non-contiguous spectrum fragments, filters need to be dynamically designed for each fragment, making the use of filtered OFDM challenging. On the other hand, OFDM-OQAM, a filter bank based multicarrier (FBMC) modulation, has emerged as an alternative to OFDM to offer better spectral containment and more flexibility for dynamic spectrum allocations. In this paper, we first present a novel technique, called resource block (RB) filtered OFDM (RB-F-OFDM), which divides the available spectrum fragments into chunks of contiguous subcarriers, referred to RBs, and generates and filters the signal transmitted on each RB individually. This approach has the advantage of being modular and scalable since the same transmit and receive modules are used for all RBs. Then, we compare the performance of OFDM, filtered OFDM, RB F-OFDM, and OFDM-OQAM. The simulations are performed under various adjacent channel interference (ACI) conditions. Simulation results show that OFDM-OQAM offers the best performance under channels with moderate delay spread and ACI; however, it has the undesired high latency and its signal is not backwards compatible to legacy OFDM receivers. The performance of RB F-OFDM is similar to filtered OFDM while adding support for non-contiguous spectrum, making it a viable solution for dynamic spectrum sharing systems.