Constrained pre-equalization accounting for multi-path fading emulated using large RC networks: applications to wireless and photonics communications

Multi-path propagation is modelled assuming a multi-layer RC network with randomly allocated resistors and capacitors to represent the transmission medium. Due to frequency-selective attenuation, the waveforms associated with each propagation path incur path-dependent distortion. A pre-equalization procedure that takes into account the capabilities of the transmission source as well as the transmission properties of the medium is developed. The problem is cast within a Mixed Integer Linear Programming optimization framework that uses the developed nominal RC network model, with the excitation waveform customized to optimize signal fidelity from the transmitter to the receiver. The objective is to match a Gaussian pulse input accounting for frequency regions where there would be pronounced fading. Simulations are carried out with different network realizations in order to evaluate the sensitivity of the solution with respect to changes in the transmission medium mimicking the multi-path propagation. The proposed approach is of relevance where equalization techniques are difficult to implement. Applications are discussed within the context of emergent communication modalities across the EM spectrum such as light percolation as well as emergent indoor communications assuming various modulation protocols or UWB schemes as well as within the context of space division multiplexing

An experimental diffuse optical wireless link employing DPIM

The paper presents the design for an experimental indoor optical wireless (OW) diffuse link using the digital pulse interval modulation (DPIM) scheme. Complete system implementation and procedure for carrying out the measurement are given. The system performance in the presence of artificial ambient light (AAL) sources is given. A high pass filter (HPF) with a cut-on frequency of 50 kHz is found to be sufficient to reject the interference signal from all AAL sources with the exception of the high-frequency (HF) fluorescent lamp (FL). Optical filtering reduces the average optical power penalty by 1 dB and 0.2 dB for the low-frequency (LF) FL, and the daylight. For the lowest error rate, the optimum HPF cut-on frequency in the presence of the HF-FL is found to be 884 kHz. The incandescent bulb introduces the largest average optical power penalty of 2.3 dB