摘要:
An up-link channel assignment scheme for cellular mobile communications systems employing multibeam antennas with beam selection, in which a channel that is selected from among all variable channels in the same frequency band may be assigned to each of the antenna beams in a base station for communications. Channel selection for a base station takes place independently of that for other cells, such that the process is autonomous. Channel selection is based upon an estimate of the signal-to-interference power ration ("SIR") in which a channel having the smallest SIR estimate that is larger than or equal to a given threshold value is chosen. Alternatively, a channel having the largest SIR estimate is selected.
摘要:
The present invention provides acetic anhydride, a method of purifying crude acetic anhydride, and a method of producing polyoxytetramethylene glycol using acetic anhydride.A method of producing polyoxytetramethylene glycol by ring-opening-polymerizing tetrahydrofuran in the presence of acetic anhydride and an acid catalyst, wherein said ring-opening polymerization is conducted using acetic anhydride having a diketene concentration of 10 ppm or less to produce polyoxytetramethylene glycol.