The Research And Implementation Of TDMA In OPNET

Wireless network is a very important part of the whole network system. In recent years, the development of wireless network has made a great progress. But the amount of wireless spectrums is limited. How to use the radio spectrums efficiently has become a hot topic. TDMA is such an access technology which utilizes spectrums efficiently. TDMA is a wireless multiple-access technology. In TDMA, time is divided into time frames which are periodic and the time frame is divided into some time slots. Each network device occupies a time slot for network communication. TDMA network has high transmission rate and strong adaptive equalization capability. TDMA access method can effectively avoid the conflict of network and improving the utilization rate of radio spectrums greatly.Network simulation technology is one of the primary means of network performance research. As the advantages of precise analog mode and intuitive results present, OPNET simulation platform becomes one of the most widely used simulation software. However, the MAC layer protocol of OPNET existence nodes is 802.11 and the access mode is Carrier Sense Multiple Access / Collision Avoidance(CSMA / CA) rather than TDMA access. In this paper, the method to implement TDMA access method in OPNET existence nodes is achieved. The feasibility and correctness of TDMA which is realized in OPNET is the main focus. The study of the effects and performance of TDMA in OPNET is also discussed.The TDMA algorithm which based on fixed time slot allocation is designed and implemented in OPNET by the study of the characteristics to some of the existence wireless nodes and the access mode of TDMA. The principle of frame division and time slot allocation is described firstly. The method to assign MAC address to each node in TDMA network automatically is discussed later. Then the packet format of TDMA is designed. After that the process of encapsulating and dis-encapsulating TDMA packet in MAC layer is designed and implemented. The discarding and forwarding packets in different case of OPNET MAC layer is described later. Finally, the simulation experiment is done in the case of MANET nodes. The experiment results show that each node can send and receive packets in its own time slots. The method to modify the access mode of OPNET existence nodes from CSMA/CA to TDMA is feasible and correct.