![]() ![]() Meanwhile, the delay increases by almost 69 ms when the propagation speed decreases from 1500 to 1450 m/s at a distance of 3 kilometers. A small move of 100 m will cause a variation of 2 × 67 milliseconds.The multiplier 2 means both the sender and the receiver may move in the opposite direction from each other. The small moves of transceivers, the drift with the wave, the variation of the propagation speed, and multipath propagation can cause a small variation of propagation delay, which is however not negligible. For example, the delay varies from 1 second to 2 seconds for the propagation distances from 1.5 kilometers to 3 kilometers at the propagation speed of 1500 m/s. The large-scale delay variation is generated by the different geographic distributions of nodes. There exist large-scale and small-scale delay variations in the underwater environment. We note that the long propagation delay also varies within a wide range due to the low acoustic propagation speed and the dynamic ocean environment. Particularly, the Slotted-FAMA with an adaptive slot length achieves more than double the throughput than the Slotted-FAMA with a fixed slot length in a network with six nodes. Both the analytical and simulation results show that our proposed slot length adaptation improves significantly the throughput of MAC in underwater acoustic networks. We further model an absorbing Markov chain to derive the closed-form equation for the throughput of MAC with adaptive slot length. We carry out simulations to study the impact of delay variations on MAC, and the results suggest a slot length adaptation scheme for the handshake and slotting based MAC. This paper identifies an important characteristic of two-scale delay variations by field test results. The low acoustic propagation speed and wide area of the acoustic communication range led to a wide range of variations in the propagation delay. It’s been well overdue for a full overhaul for years, but as it stands, there are legacy bugs that keep popping back up.The long propagation delay in underwater acoustic channels has attracted tremendous attentions in designing Medium Access Control (MAC). ![]() Those six steps listed above make Android File Transfer sound nice and easy to use, but anyone who has attempted this ostensibly simple process will know that it usually takes several attempts and many error messages to get the app to recognize your phone.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |