Abstract: Proposed are a multi-access method and apparatus for a LoRa tag using backscatter communication. The multi-access apparatus for a LoRa tag using backscatter communication may include a contention slot unit configured to receive a signal for a contention participation request from a base station and participate in a contention according to a distributed queuing (DQ) protocol using a backscatter signal if data to be transmitted is present, an FBP unit configured to receive a result of the contention from the base station and check whether the result of the contention is a success, and a data slot unit configured to transmit sensed data to the base station using the backscatter signal if the result of the contention is a success.

Abstract: Proposed are a multi-access method and apparatus for a LoRa tag using backscatter communication. The multi-access apparatus for a LoRa tag using backscatter communication may include a contention slot unit configured to receive a signal for a contention participation request from a base station and participate in a contention according to a distributed queuing (DQ) protocol using a backscatter signal if data to be transmitted is present, an FBP unit configured to receive a result of the contention from the base station and check whether the result of the contention is a success, and a data slot unit configured to transmit sensed data to the base station using the backscatter signal if the result of the contention is a success.

Abstract: Disclosed are a network coding method and apparatus for reliable communication in a LoRa communication system. The network coding apparatus may include a network server connected to an end node over a network to receive a packet transmitted by the end node in a LoRa communication system, a stationary gateway positioned between the network server and the end node to deliver the packet, transmitted by the end node, to the network server, and a temporary gateway positioned between the stationary gateway and the end node to deliver the packet, transmitted by the end node, to the stationary gateway.

Abstract: In an autofocus method, an electron beam is scanned onto a subject through a condensing member. A setting condition of the condensing member is changed within a first range. An image evaluation value is measured using a secondary electron current from the subject according to the setting condition within the first range. A second range adjacent to the first range and including the setting condition corresponding to the first maximum is set when a first maximum of the image evaluation value is not a peak value. The setting condition is changed within the second range. An image evaluation value is measured using a secondary electron current according to the setting condition within the second range. The condensing member is set with the setting condition corresponding to a second maximum of the image evaluation value when the second maximum value is the peak value.