Simulating Heterogeneous and Larger-Scale Wireless Sensor Networks with TOSSIM TinyOS Emulator

TOSSIM is a wireless sensor network (WSN) emulator which is useful for assessing and evaluating application code in TinyOS operating system and Mica mote based environments. Although TOSSIM provides a high-fidelity and very accurate emulation environment for WSN applications, there are some significant drawbacks that might hinder simulation of larger scale WSNs. TOSSIM can simulate WSNs with up to 1,000 motes under certain conditions. Another fundamental shortcoming of TOSSIM is that it does not support heterogeneous networks, although this issue originates as a result of a limitation imposed by TinyOS, where every mote must run the same code. In furtherance, the TOSSIM memory space allocation for the application program running on motes appears to be fixed regardless of the number of motes in the WSN. This leads to having to write smaller application for a mote as the mote count increases. Finally, because of its bit-level granularity, TOSSIM simulation time increases quickly to several weeks for larger-scale sensor networks with around 1000 motes. We propose a number of suggestions and workarounds to facilitate larger-scale WSNs to be simulated with reasonably-functional application code and within quicker simulation time periods in the TOSSIM environment. In order to simulate heterogeneous networks, a simple If- Then control structure is proposed for the application code. Packet-TOSSIM is an option to reduce the simulation time if bit- level granularity is not required. The nesC application code must be compact and optimized for size for larger mote counts so that the entire simulation can fit into the TOSSIM process memory space.