Effect of High Pass Filtering and Matched Filtering on Baseline Wander

Optical Wireless Communication (OWC) channel can be the best suitable substitute of Radio Frequency (RF) channel. The high data rate transmission capability and reliable connectivity makes it eligible to support the IoT requirements. There are some unavoidable drawbacks associated with OWC channel in different environments. In this paper a drawback of indoor OWC channel has been discussed which is known as fluorescent light interference (FLI). While using the OWC transmission in indoor environment in form of LiFi, the background light coming from the other radiation sources present inside makes undesirable interference with the signal. The effect of this interference can be mitigated by applying various techniques. One of the techniques is the use of High Pass filter. As the FLI affects the low frequency components, the application of HPF with a suitable cut off frequency can be seemed to reduce the effect of FLI. But this HPF technique produces a form of Inter symbol interference (ISI) which is also known as Baseline Wandering (BW) that has a negative influence on the performance of the base band modulation technique. An alternative way to detect the signal can be the use of Matched Filter (MF) which always tries to match the signal with the original shape. In this paper the performance of a simple BPSK based system under FLI has been analyzed where the signal has been detected by using two different methods, that is by using HPF and by using HPF followed by MF. In both the cases the variation that causes baseline wandering has been found. The comparative studies of both the cases show that the system employing MF exhibits better performance as compared to the system with HPF. Also to verify the effect of this baseline wander on the system performance, the BER of both systems has been compared. By comparing the BER for the system with HPF and MF with the theoretical value of BER, it has been observed that the BER curve of the system with MF is closer to the theoretical BER curve. For the given scenario the minimum achievable BER for the MF based system comes down to a value about the order of 10-
³
at an SNR of 8dB whereas for HPF based system it comes down to an order of 10
^-1
even at an SNR of 12dB, which proves that the MF based optical receiver performs better as compared to HPF based optical receiver.