Design Of Indoor Optical Communication System Mac Layer Protocol

With the development and mature of LED technology, indoor white LED visible light communication technology attracts more and more attention of research organizations from different nations. Compared to the restrictions of conventional radio frequency wireless communication technology such as scarcity of spec-trum resources and harmful radiation to human bodies, indoor visible light communication technology, with advantages like rich spectrum resources, environmental protection, safety to human bodies and high security, is regarded as one of highly competitive short distance wireless communication technology. Currently, the research on indoor visible light communication technology focuses on how to achieve a higher rate of point to point data transmission, while research on MAC layer protocol of indoor optical communication system is less. This dissertation focuses on the research on design and implementation of the MAC layer protocol of indoor optical communication system.Firstly, This thesis studies the IEEE 802.15.7 standard and 1CT-213311 OMEGA standards for the design methods of visible light communication MAC layer protocol, and analyzes and compares the differences between the MAC layer protocols of two standards. Then the thesis proposes a kind of indoor visible light communication MAC layer protocol according to the characteristics of the indoor visible light communication scenarios and the system requirements of MAC layer protocol design. The new protocol is based on IEEE 802.15.7 standard and makes the following improvements:the new protocol allows each LED clusters to create independent VPAN, to increase the total capacity of the system; the new protocol makes optimization for indoor optical communication system does not support CSMA/CA channel access algorithm to reduce the probability of message collision; the adjacent LED clusters will collaborate while allocating GTS to guarantee the communication quality of devices in overlapping coverage areas of adjacent VPAN; device can switch quickly between VPAN to maintain the continuity of communications while the device move freely in room.Secondly, this thesis introduces the implementation method of indoor visible light communication MAC layer protocol. In the third chapter, the MAC layer is divided into multiple such modules that each module has single function and relatively simple logic because the MAC layer involves multiple functions and has complex control flow logic. As the coordinator side and device side MAC layer has different functions, the modules divided is also different. All the MAC layer modules are divided into three categories, namely the scheduling module, the function implementation module and the infrastructural support module. The third chapter firstly describes the overall structures of coordinator side and device side MAC layer, then introduces the function and implementation method of each module. For some modules with complex logic, the flow chart is given.Finally, we use the C language to implement most of the indoor visible light communication MAC layer modules described in the third chapter. While programming we take full advantage of multitasking capabilities and inter-process communication mechanism of the operating system so as to ensure collaboration between modules to provide a complete MAC layer service. In order to verify the correctness of the MAC layer protocol design, we run the coordinator side program in PC and run the device side program on the Raspberry Pi. Both the PC and the Raspberry Pi run the Linux operating system and the transmission of frames is simulated through network port. We do module testing and system testing and the test results are consistent with the expected results.