This paper presents a theoretical analysis of the performance of a filter bank-based multicarrier spread spectrum (FB-MC-SS) system. In FB-MC-SS, each data symbol is spread across multiple subcarriers, but - contrary to some other systems - there is no spreading in time. The results of this system are then compared with those of the well-known direct sequence spread spectrum (DS-SS) system with a rake receiver for its best performance. We compare the two systems when the channel noise is white. We prove that as the processing gains of the two systems tend to infinity both systems approach the same performance. However, numerical simulations show that in practice, where processing gain is limited, FB-MC-SS outperforms DS-SS.

Orthogonal frequency division multiplexing (OFDM), widely recommended for sharing the spectrum among different nodes in a dynamic spectrum access network, imposes tight timing and frequency synchronization requirements. We examine the use of filterbank multicarrier (FBMC), a somewhat lesser known and understood alternative, for dynamic spectrum access. FBMC promises very low out-of-band energy of each subcarrier signal when compared to OFDM. In order to fully understand and evaluate the promise of FBMC, we first examine the use of special pulse-shaping filters of the FBMC PHY layer in reliably transmitting data packets at a very high rate. Next, to understand the impact of FBMC beyond the PHY layer, we devise a distributed and adaptive medium access control (MAC) protocol that coordinates data packet traffic among the different nodes in the network in a best-effort manner. Using extensive simulations, we show that FBMC consistently achieves at least an order of magnitude performance improvement over OFDM in several aspects including packet transmission delays, channel access delays, and effective data transmission rate available to each node in static, indoor settings. Using measurements of power spectral density and high data rate transmissions from a transceiver that we build using our National Instruments hardware platform, we show that while FBMC can decode/distinguish all the received symbols without any errors, OFDM cannot. Finally, we also examine the use of FBMC in a vehicular network setup. We find that FBMC achieves an order of magnitude performance improvement over large distances in this setup as well. Furthermore, in the case of multihop vehicular networks, FBMC can achieve about 20 × smaller end-to-end data packet delivery delays and relatively low packet drop probabilities. In summary, FBMC offers a much higher performing alternative to OFDM for networks that dynamically share the spectrum among multiple nodes.

Implementation of any cognitive radio network requires an effective control channel that can operate under various modes of activity from the primary users. This paper reports the design and implementation of a filter bank multicarrier spread spectrum (FBMC-SS) system for use as the control channel in cognitive radio networks. The proposed design is based on a filtered multitone (FMT) implementation. Carrier and timing acquisition and tracking methods as well as a blind channel estimation method are developed for the proposed control channel. We also report an implementation of the proposed FBMC-SS system on a hardware platform; a FlexRIO FPGA module from National Instruments.