In wireless sensor networks, sensor data messages are required to be transmitted along a wireless multihop transmission route with shorter delay. For avoidance of corruption of sensor data messages, the RTS/CTS control is introduced in wireless LAN protocols which solves the hidden terminal problem among 2-hop neighbor wireless nodes. However, it causes additional transmission delay and various methods have been proposed to apply the RTS/CTS control conditionally. This paper proposes introduction of directional intermediate sensor nodes distributed sparsely in the sensor networks. Directional sensor nodes with directional antennas for space-division multiplexing reduces interferences among sensor nodes. It results in conditional omissions of the RTS/CTS control without collisions of data message transmissions among 1- and 2-hop neighbor nodes. Thus, it is expected for sensor data message transmissions to reduce transmission delay without additional losses of them.
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