Method for improving the reliability of a handover and call establishment, and a cellular radio system

A method for improving the reliability of call establishment in a cellular radio system which comprises at least one base station in each cell, and a group of subscriber terminal equipments which communicate with one or more base stations, comprising steps of:

• measuring at a base station a total interference level of signals received from the terminal equipments, and
• transmitting a pilot signal with a known transmit power,
• measuring, at a subscriber terminal equipment, in order to determine the need for a handover, the power levels of pilot signals received from those base stations which are on the terminal equipment maintained list of near-by base stations, and in which
• a path loss between the terminal equipment and the base stations is estimated by means of the received pilot signals,
• wherein the signal to noise ratio between the terminal equipment and the base station in the transmission direction from the terminal equipment to the base station is estimated on the basis of the total interference measured at the base station, the path loss, and the terminal equipment transmit power, and wherein
• said estimate is utilized in selecting the base station to which the terminal equipment seeks to establish a connection when it requires a traffic channel.

A cellular radio system which comprises at least one base station in each cell, and a group of subscriber terminal equipments which communicate with one or more base stations, which base stations comprise

• a means for measuring total interference level of signals they have received from the terminal equipments, and
• a means for transmitting a pilot signal with a known transmit power, and which terminal equipments comprise
• a means for measuring power levels of pilot signals they have received from different base stations, and in which in the cellular radio system at least some transceivers comprise
• a means for estimating, by means of the pilot signals, the path loss between the terminal equipment and the base stations,
• wherein at least some transceivers in the cellular radio system comprise means for estimating the signal to noise ratio between the terminal equipment and the base station in the transmission direction from the terminal equipment to the base station on the basis of the total interference measured at the base station, the path loss, and the terminal equipment transmit power.