Kısa menzil, çoklu kullanıcılı, sualtı akustik iletişimi için ofdm kullanımı analizi

Acoustic waves are being used in several underwater applications, suchas SONARs, underwater communication systems. Most of already developedand deployed underwater communication systems use narrow bandcommunication and lacks layered communication approach. In this thesis, wepropose a spread spectrum, layered architecture for underwater communicationsystem, such as for SCUBA divers. The communication device shall bedesigned such that divers can communicate with each other in shallow water,short range in a multi-user fashion and provide not only voice communicationbut also data transmission as well. The device shall use Orthogonal FrequencyDivision Multiplexing (OFDM) as a spread spectrum technique. The OFDMtechnique is selected from other spread spectrum techniques due to it?s inherentability to combat the channel impairments and flexibility of implementing thecommunication system using software defined radio (SDR). The spreadspectrum system shall operate in 100 kHz to 300 kHz frequency band usingwideband acoustic transducers. In this work, we studied a layered architecturefor the communication device. We mainly studied the application layer, dataiiilink layer and physical layer in order to analyze the achievable data rate andperformance. In this work, we tried to find the optimal communicationparameters to achieve guaranteed communication performance for possiblescenarios. The communication parameters are set in order to achieve bestperformance for the worst condition. Using the optimal parameters, the systemshall occupy 5 users voice and data communication at the same time using theentire frequency band at the same time, however with certain Grade of Service(GOS) the capacity shall be increased. The capacity of the system shall furtherbe increased if the system uses adaptive communication parameters that areadapted to changing channel and user conditions. The system using adaptivecommunication parameters shall provide at most 16 users? voice and datacommunication using the entire frequency band at the same time.Keywords: Underwater Acoustic Communications, Spread SpectrumCommunications, Orthogonal Frequency Division Multiplexing (OFDM),Coded OFDM (COFDM), Layered Communication Architectureiv