EE Seminar: Multicarrier Communication in the Presence of Clipping
Speaker: Igal Kotzer
Ph.D. student under the supervision of Prof. Simon Litsyn
Sunday, February 9th, 2020 at 15:00
Room 011, Electrical Eng. Bldg., Faculty of Engineering
Multicarrier Communication in the Presence of Clipping
Abstract
Clipping of an analog signal at the transmitter is a significant impediment in practical multicarrier systems. As clipping is an irreversible operation, it inherently introduces distortion to the signal. Much of the ongoing research in the area of clipping and multicarrier signals focuses on methods that reduce the Peak to Average Power Ratio (PAPR) of the signal with the aim of reducing the probability of clipping. However, reducing the PAPR to a level at which the probability of clipping is negligible to the extent that it does not significantly impact the communication fidelity is still an ongoing quest.
The evaluation of the PAPR statistics and overall system effect of clipping in any given system is done by simulations as no good computational methods exist. This evaluation requires running a lengthy simulation with all relevant parts of the signal path well modeled. Any change made to the system design requires running the simulations all over again to evaluate the effect of clipping on the overall system performance.
This work focuses on analytical tools to quantify the impairment inflicted on the multicarrier signal in the presence of clipping, so that a decision on whether further PAPR reduction needs to be pursued for the desired overall system performance can be made. The analytical tools make the lengthy simulation process unnecessary for estimating the PAPR statistics, as the required statistics can be obtained computationally.
We first present a novel model for constant-energy constellation (the data is drawn from equi-energy symbols) discrete-time multicarrier signals. We next present an analytical approach to the calculation of the Error Vector Magnitude (EVM) in clipped multicarrier signals. This work is then extended to more practical cases of a multicarrier signal that involve carriers modulated by different constellations and with different power levels. We finally compute the information theoretic achievable rates of a clipped multicarrier signal by way of mutual information based on the Gaussian approximation for a family of clipping functions.
