Performance Analysis Of Indoor Wireless OCDMA System

As an innovation technology, optical wireless communication (OWC) has plenty of advantages over radio frequency wireless technology. For example, OWC requires no frequency license and can provide higher data rate and wider bandwidth theoretically. In the present, OWC attracts a growing number of research efforts. Indoor wireless optical communication takes advantage of the short-distance features of OWC to achieve the high bandwidth and data rate requirements. However, the indoor wireless optical communication is easily affected by strong ambient light noise, multipath dispersive and distance effect. Studies focused on how to overcome these shortcomings.In this thesis, the indoor wireless optical communication system was modelled by code division multiple access technique which is of high security, flexible accessing and so on. Optical orthogonal code (OOC) acts as the address code of optical code division multiple access (OCDMA) technology, which is widely used in this field. At the same time, the thesis introduced the classification of the OWC link channel models. The classification is according to the degree of directionality and the existence of line of sight (LOS) path between the transmitter and receiver. The spatial power distribution diagrams allow us to have a better understanding of the channel models. In this thesis, we study the non-LOS non-directed channel model which has no alignment requirements and better robustness. It’s also called the diffuse channel model.The research results are as follows:(1) We proposed optimal parameter selection of OOC. We derived the BER of the indoor wireless OCDMA system model within the eye-safe power range using BPPM modulation and considering the impact of multipath interference. Through calculating the BER of the system model, we studied how the parameters of OOC affects the performance of the indoor wireless OCDMA system, including the length, the weight and the cross correlation of OOC. Also we studied the impact of number of cellular users and the peak transmission power on the system performance. At last, we obtained the best performance of OOC within the given scope of the code length between 100 and 260. In conclusion, optimal parameter selection can improve system performance greatly.(2) We introduced the power control mechanism into the indoor wireless OCDMA communication system model. The function of the power control mechanism is to equalize the power of light signals emitted by all the transmitters. We analyzed and calculated the BERs of power controlled system. When compared with the normal system, we found that the power controlled system has better system performance with lower power consumption. In conclusion, the power control mechanism can reduce the impact of distance effect on system performance.(3) We proposed the dynamic resource manage algorithm (DRMA) to optimize the power controlled indoor wireless OCDMA system. The principle of the algorithm is to establish priority classification in the system, different priorities guarantee different communication performance. In this thesis, we simulate and calculate how the system redistribute power, when the target users change the priority. The algorithm enables the power resources to be more effectively utilized.