Low-latency and highly reliable communication on wireless LAN (WLAN) is difficult due to interference from the surroundings. To overcome this problem, we have developed a scheme called Clear to Send-to-Station (CTS-STA) frame transmission control that enables stable latency communication in environments with strong interference from surrounding WLAN systems. This scheme uses the basic functions of WLAN standards and is effective for both the latest and legacy standard devices. It operates when latency-strict transmission is required for an STA and there is interference from surrounding WLAN devices while minimizing the control signal overhead. Experimental evaluations with prototype systems demonstrate the effectiveness of the proposed scheme.

To sustain and expand the agricultural economy even as its workforce shrinks, the efficiency of farm operations must be improved. One key to efficiency improvement is completely unmanned driving of farm machines, which requires stable monitoring and control of machines from remote sites, a safety system to ensure safe autonomous driving even without manual operations, and precise positioning in not only small farm fields but also wider areas. As possible solutions for those issues, we have developed technologies of wireless network quality prediction, an end-to-end overlay network, machine vision for safety and positioning, network cooperated vehicle control and autonomous tractor control and conducted experiments in actual field environments. Experimental results show that: 1) remote monitoring and control can be seamlessly continued even when connection between the tractor and the remote site needs to be switched across different wireless networks during autonomous driving; 2) the safety of the autonomous driving can automatically be ensured by detecting both the existence of people in front of the unmanned tractor and disturbance of network quality affecting remote monitoring operation; and 3) the unmanned tractor can continue precise autonomous driving even when precise positioning by satellite systems cannot be performed.

A method is presented for increasing wireless LAN (WLAN) capacity in high-density environments with IEEE 802.11ax systems. We propose using coordinated scheduling of trigger frames based on our mobile cooperative control concept. High-density WLAN systems are managed by a management server, which gathers wireless environmental information from user equipment through cellular access. Hierarchical clustering of basic service sets is used to form synchronized clusters to reduce interference and increase throughput of high-density WLAN systems based on mobile cooperative control. This method increases uplink capacity by up to 19.4% and by up to 11.3% in total when WLAN access points are deployed close together. This control method is potentially effective for IEEE 802.11ax WLAN systems utilized as 5G mobile network components.