MLMAC-UL and ECTS-MAC - Two MAC Protocols for Wireless Sensor Networks with Unidirectional Links

Unidirectional links are a common property of all wireless networks. In many cases, the range of these links exceeds that of bidirectional links by far. Still, most protocols ignore their existence or simply discard them. In this paper we introduce two new medium access control (MAC) protocols called MLMAC-UL and ECTS-MAC that are able to transmit data over unidirectional links and receive acknowledgment messages for them using a neighborhood discovery protocol. Both protocols, as well as two reference protocols, were evaluated in simulations and using a real sensor network consisting of TMote Sky sensor nodes.