Analysis and Solutions to 3G Gateway Issues in Agriculture WSNs

Wireless sensor networks (WSN) are used extensively in various important areas of agriculture. Many of the associated activities involve the transmission of data or control commands through gateways that connect the servers to 3G networks. In this paper, we investigate the issues caused by Radio Resource Control (RRC) state transitions, which introduce high sudden delays in TCP packets. The packets that are subjected to these delays are then usually retransmitted because of timeouts. Further, the recently recommended TCP retransmission timer settings (RFC6298) reduce the initial retransmission timeout (RTO) from the previous three seconds to one second, further exacerbating the phenomenon of SYN packet retransmission, because a SYN packet is always the first packet to trigger the RRC state to change. We conduct a number of tests to examine the phenomenon and analyze the effect of this spurious retransmission timeout. Consequently, we propose recommendations for improvement.