Analysis of Alternative Metrics for the PAPR Problem in OFDM Transmission

The effective PAPR of the transmit signal is the standard metric to capture the effect of nonlinear distortion in OFDM transmission. A common rule of thumb is the log$(N)$ barrier where $N$ is the number of subcarriers which has been theoretically analyzed by many authors. Recently, new alternative metrics have been proposed in practice leading potentially to different system design rules which are theoretically analyzed in this paper. One of the main findings is that, most surprisingly, the log$(N)$ barrier turns out to be much too conservative: e.g. for the so-called amplifier-oriented metric the scaling is rather $\log[ \log(N)]$. To prove this result, new upper bounds on the PAPR distribution for coded systems are presented as well as a theorem relating PAPR results to these alternative metrics.Comment: 5 pages, IEEE International Symposium on Information Theory (ISIT), 2011, accepted for publicatio

Universal-Filtered Multi-Carrier: A Waveform Candidate for 5G

The emerging Internet of Things will make the next generation 5G systems to support a broad range of diverse needs with greater efficiency requirements. The new class of services will need a higher data rates, to handle these demands, the lowest layer of the 5G systems must be flexible. Therefore, the waveform will have an important role in offering these new requirements. These waveforms should enable efficient multiple access to handle the requirements of the future wireless communication system. This means that the corresponding required waveforms should be able to handle as much different type of traffic as possible in the same band. In this paper we compare three candidate multicarrier waveforms for the air interface of 5G: the original cyclic prefix OFDM applied in the 4G systems today, the Filter Bank Multicarrier (FBMC) heavily discussed in previous papers, and Universal Filtered Multi-Carrier (UFMC) a new contender making its appearance recently. These new waveforms will be more robust against the time frequency synchronization problem, it has the potential for mixing different traffic specifications, and supports the scenarios of spectrum fragmentation, due to the improvement in the localization of spectrum. In the same time, they support all multiple input and multiple output (MIMO) scenarios and applications. The simulation results shown that there is a good difference in the time frequency efficiency for transmitting very small bursts where the response time is required (like car-to-car communications). Due to the cyclic prefix the FBMC and CP-OFDM suffer when transmitting short bursts, the UFMC outperforms CP-OFDM by 10% for any case and FBMC for the very short packets and it is similar to FBMC for long sequences. Other simulation results are shown, which demonstrate the potential of this waveform