基于OMNET平台实现ALOHA协议

Aloha ===== This model makes it possible to measure the efficiency of the Aloha and slotted Aloha protocols. The model is similar to the original University of Hawaii radio network: "hosts" talk to a central "server" via a shared radio channel. In this model we're only interested in the achievable channel utilization, so we ignore the "downstream" link (TDM broadcast from the server) and retransmissions. Hosts transmit according to Poisson process. The protocol choice (slotted or "pure" Aloha) is encode in the slotTime parameter of the host model -- if a nonzero slotTime is given, transmissions are aligned to the next slot boundary. The model of the central server checks for collisions and computes statistics. The internal state of the server and all statistics are visible in the GUI The most important statistics is channel utilization. It is also recorded in omnetpp.vec, and can be plotted using the Analysis Tool in the IDE. The supplied omnetpp.ini file contains six predefined 6 predefined configurations: - pure Aloha at high load - pure Aloha at moderate load (utilization =~ max) - pure Aloha at low load - slotted Aloha at high load - slotted Aloha at moderate load (utilization =~ max) - slotted Aloha at low load - In addition it contains a predefined experiment scenario called PureAlohaExperiment where it explores the channel utilization in the function of number of hosts and packet generation frequency. According to some descriptions of the Aloha protocol, hosts have to listen on the channel before they start to transmit anything. This "listen before talk" behavior is not part of the current model. (One reason is that with the radio nodes scattered around, the propagation delays of radio signals are different for every host pair, and it becomes very complex to accurately model whether any host can hear any transmission at any given moment.)