Vision based tracking of a mobile device is used to remotely control a robot. The light emitting portion, the intermediate portion, and the supporting portion connected to the connecting portions may rotate with respect to each other based on the connecting portions to form a three-dimensional shape, and may be arranged in a single plane when the light emitting portion, the intermediate portion, and the supporting portion are unfolded based on the connecting portions. A coarse parameter estimation is performed to obtain a coarse estimate of the symbol rate and the center frequency of the channel. An application running on an initiator or target can in certain instantiations register a region of memory, which is made available to its peer for access directly without substantial host intervention through RDMA data transfer. A pressurized container of hydrated super absorbent polymer is coupled to the ladder.