Patent ID: 6731669
Filing Date: 2004-05-04
Classification: H04B

Abstract:
A method of establishing in a station synchronous communication with an access point selected among a plurality of access points in a frequency-hopped radio LAN system, each of the access points being assigned a hopping pattern of hopping frequencies and a dwell time determined for the hopping pattern, the access points transmitting frames which include control frames, said method comprising:selecting a communication frequency of the station among the hopping frequencies; receiving, as reception frames, the frames which are transmitted from the access points through the selected communication frequency; extracting control frames from the reception frames; monitoring the extracted control frames during a monitoring time interval which is predetermined in consideration of the dwell times assigned for the access points; determining the selected access point and the hopping pattern assigned for the selected access point, on the basis of the results of the monitoring; and synchronizing the station with the selected access point on the basis of information included in the extracted control frames, together with the dwell time assigned for the selected access point, wherein: each of the hopping patterns corresponds to one of the access points and has the hopping frequencies which are hopped at every dwell time, the hopping frequencies being distinguished form each other by hopped frequency indexes; and the synchronizing comprises: deciding a time instant at which the station will be synchronized with the selected access point, in consideration of ability of the station; calculating the hopped frequency index corresponding to the decided time instant; predicting, as a predicted frequency, a usable one of the hopping frequencies that will be used for the selected access point at the decided time instant, by using the calculated hopped frequency index and the hopping pattern of the selected access point; obtaining a remnant time from the decided time instant to an end time instant at which the dwell time of the predicted frequency will be finished; and adjusting a communication frequency of the station to the predicted frequency at the decided time instant, so as to communicate with the selected access point on the predicted frequency during remnant time.