Abstract: A reference is made to ATM cells by dividing the cells into groups (31, 32, 33, 34) which are identified on the basis of a group-oriented serial number and/or on the basis of the combination of identifiers included in the cells of the group. In the latter case, the combination of the identifiers is compared with a given predefined aperiodic character string. A given cell within the group is identified on the basis of which cell it is counting from the beginning and/or from the end of the group, or on the basis of the identifier included in the cell.

Abstract: In a radio data transmission system which transmits data in cell form, the risk of cell loss or the risk of out-of-ordering during handover can be diminished by synchronizing the cell transmission between the new (50) and the old (40) base stations. The old base station (40) delivers to the new base station (50) and/or the switch (51), information on the last cell that was transmitted successfully and in the right order through the old base station, whereby the new base station continues the transmission by starting from the first failed cell. Cells need not be identified one by one if group numbering is applied in which the first or the last cell of a given group (31, 32, 33, 34) or a given counter cell is numbered, and the rest can be indicated, where necessary, by counting the distance from the numbered cell.

Abstract: In a radio extension of an ATM network, prior to establishing a given connection the switch of a fixed network enquires access points as to what is the resource situation in said access points. After receiving responses the switch decides to which access point the connection is allocated. During handover, the resource enquiry is accomplished as a response to the handover request sent by the mobile terminal, which request is transmitted either when the connection to the old access point still operates or after the connection is closed; in the latter case, the request is retransmitted through the new access point.

Abstract: In the handover of a radio extension of an ATM network there are used markers that are located at fixed locations in the ATM cell stream in order to indicate the ending of an uplink and downlink cell stream, so that the switching of cell streams can be carried out in a synchronised fashion, and cells are not lost and their relative order does not change. If a downlink data transmission via the old access point succeeds, the old access point attaches to the last forwarded information field a notice of closing the traffic, in which case the mobile terminal transfers the information of successful transmission to the new access point. In another case, the old access point sends the unforwarded cells to the new access point and terminates the transaction with the same marker that generally indicates the end of a downlink cell stream.