Cross-layer Flow Control for Dual-link Wireless Access of AGV in Factory

Wireless communication of Automated Guided Vehicle (AGV) is a key feature of modern factories that contribute to achievement of higher productivity. The quality of a wireless link between an AGV and an Access Point (AP) may change drastically during the movement of an AGV. Recently, it has become feasible to use two wireless interfaces devices that can link to different access points to increase robustness of wireless access. Therefore, methods are needed to efficiently coordinate the use of the two interfaces. In this paper, a method is proposed for cross-layer control which splits data flow over two-links based on lower layer information about the estimated flow rate of each link. The method is evaluated by simulation using a flow-level simulation model. Evaluation is done for a particular test scenario of an AGV trip in a factory requiring multiple handovers between APs while transmitting video camera data on an uplink using IEEE 802.11. Simulation results verify that the proposed method is effective in reducing latency of data transmissions to below 100ms and improving stability over the whole range of AGV movement. There results shows that proposed method is effective when the update interval of split ratio is short enough to match the changes of the AP link flow rates due to the movement of AGV.