Mid Sweden University

A multi-hop ad hoc network requires no infrastructure, like base stations or routers to function. This means that it can quickly be deployed and in movement, making it ideal for scenarios like natural disasters or battlefield communication. A single-frequency network (SFN) is the idea that transmitters can cooperate to send the same signals simultaneously over the same frequency channel, such that the signals are amplified. It was previously proposed that SFNs could be created in multi-hop ad hoc networks. According to simulations, this could improve the energy consumption, signal reachability, and data transfer rate. As this has only been simulated, the purpose of this project is to experimentally verify that SFN is attainable in a multi-hop ad hoc network, and to assess what the difficulties are of an actual implementation. The method involved synchronizing the transmission of two devices operating under the 802.11a standard. A multi-hop ad hoc network was created by changing the settings of the network interface cards. The devices used were mainly laptops and transmissions were monitored in Wireshark. The laptops were forced to send on one frequency channel to make interference possible, and identical packets were sent. Experiments were made to assess whether SFN was attained. The packet loss rate and distance were used to evaluate the results. The results suggest that a synchronized transmission off by less than 2 μs was attained. However, the error of these measurements were neither known nor approximable. This meant it was hard to know when a SFN was formed. The results indicate that SFN was attained, as the packet loss rate decreased significantly when employed. The effectiveness of SFN was hard to assess because the results were not comparable with the simulation values. The difficulty of an actual implementation is deemed to be the synchronization of transmissions.