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A MAC Protocol for Wireless Sensor Networks with Multiple Selectable, Fixed-Orientation Antennas

One of the open issues in sensor network research is the efficient operation while having energy constraint sensor nodes and dense networks. One potential approach to improve the energy usage is the application of directed data transmission / reception in order to improve the energy usage and decreases the probability of transmission conflicts. To do so, appropriate medium access control protocols are required that decide which antennas to use for sending and receiving, in a distributed fashion. We extend existing protocols for selectable antennas and study their performance. As a main result of this performance evaluation, we derive recommendations on how many antennas per node should be used and how high the performance benefits for an increasing number of antennas is. We show considerable improvements in number of retries (up to 87 %) and per-hop delay (up to 24 %), depending on load characteristics and network density.