On the duality of multi-carrier spread spectrum and single-carrier transmission
Multi-carrier spread-spectrum
BER minimized OFDM systems with channel independent precoders
IEEE Transactions on Signal Processing
An underwater acoustic implementation of DFT-spread OFDM
EURASIP Journal on Advances in Signal Processing - Special issue on advances in signal processing for maritime applications
OFDMA-based MAC protocol for adhoc and multihop networks
Proceedings of the 6th International Conference on Ubiquitous Information Management and Communication
Cross-layered OFDMA-based MAC and routing protocol for multihop adhoc networks
ICCSA'13 Proceedings of the 13th international conference on Computational Science and Its Applications - Volume 1
| Hi-index | 0.00 |
The Orthogonal Frequency Division Multiplexing (OFDM) transmission technique can efficiently deal with multi-path propagation effects especially in broadband radio channels. It also has a high degree of system flexibility in multiple access schemes by combining the conventional TDMA, FDMA and CDMA approaches with the OFDM modulation procedure which is particularly important in the uplink of a multi-user system. In OFDM-FDMA schemes carrier synchronization and the resulting subcarrier orthogonality plays an important role to avoid any multiple access interferences (MAI) in the base station receiver. An additional technical challenge in system design is the required amplifier linearity to avoid any non-linear effects caused by a large peak-to-average ratio (PAR) of an OFDM transmission signal. A specific OFDM-FDMA uplink procedure is proposed and will be designed in this paper which can be seen as a combination of a specific subcarrier spreading scheme and subcarrier selection process. The resulting transmit signal consists of a periodic extension and multiple repetition of all modulation symbols and leads therefore to an extremely low computation complexity in the transmitter. Furthermore, the transmit signal shows simultaneously a constant envelope to avoid any non-linear effects in the amplification process. This uplink scheme can be considered as a trade off between low computation complexity and system performance.