A method comprising: controlling, by an apparatus, at least one base station to establish an emulated long-term evolution, LTE, cell and an emulated non-LTE cell; controlling, by the apparatus, the at least one base station to receive a first mobility update request message from a subscriber entity through the emulated LTE cell, wherein the first mobility update request message is a part of an LTE mobility update procedure of the subscriber entity, and wherein the subscriber entity comprises a mobile device having an international mobile equipment identifier, IMEI, and a subscriber identity module, SIM, having an international mobile subscriber identifier, IMSI; controlling, by the apparatus, the base station to receive the IMSI from the subscriber entity as a part of identity verification comprised in the LTE mobility update procedure; storing, by the apparatus, the received IMSI in a database; controlling, by the apparatus, the at least one base station to receive a second mobility update request message from the subscriber entity through the emulated non-LTE cell, wherein the second mobility update request message is a part of a non-LTE mobility update procedure of the subscriber entity; controlling, by the apparatus, the at least one base station to receive the IMSI and the IMEI from the subscriber entity during identity verification comprised in the non-LTE mobility update procedure; providing the IMSI received through the emulated LTE cell with a time stamp indicating the reception timing of the IMSI received through the emulated LTE cell; upon receiving the IMSI and the IMEI through the emulated non-LTE cell, evaluating reliability of the IMEI on the basis of the time stamp and reception timing of the IMSI and the IMEI through the emulated non-LTE cell; wherein said evaluating the reliability of the IMEI comprises omitting storing, by the apparatus, on the basis of the IMSI received through the emulated LTE cell and the IMSI and IMEI received through the emulated non-LTE cell, a mapping between the IMSI and the IMEI in the database, if the time interval between the reception of the IMSI through the emulated LTE cell and the reception of the IMSI and IMEI through the emulated non-LTE cell is longer than a determined discarding threshold. controlling, by an apparatus, at least one base station to establish an emulated long-term evolution, LTE, cell and an emulated non-LTE cell; controlling, by the apparatus, the at least one base station to receive a first mobility update request message from a subscriber entity through the emulated LTE cell, wherein the first mobility update request message is a part of an LTE mobility update procedure of the subscriber entity, and wherein the subscriber entity comprises a mobile device having an international mobile equipment identifier, IMEI, and a subscriber identity module, SIM, having an international mobile subscriber identifier, IMSI; controlling, by the apparatus, the base station to receive the IMSI from the subscriber entity as a part of identity verification comprised in the LTE mobility update procedure; storing, by the apparatus, the received IMSI in a database; controlling, by the apparatus, the at least one base station to receive a second mobility update request message from the subscriber entity through the emulated non-LTE cell, wherein the second mobility update request message is a part of a non-LTE mobility update procedure of the subscriber entity; controlling, by the apparatus, the at least one base station to receive the IMSI and the IMEI from the subscriber entity during identity verification comprised in the non-LTE mobility update procedure; providing the IMSI received through the emulated LTE cell with a time stamp indicating the reception timing of the IMSI received through the emulated LTE cell; upon receiving the IMSI and the IMEI through the emulated non-LTE cell, evaluating reliability of the IMEI on the basis of the time stamp and reception timing of the IMSI and the IMEI through the emulated non-LTE cell; wherein said evaluating the reliability of the IMEI comprises omitting storing, by the apparatus, on the basis of the IMSI received through the emulated LTE cell and the IMSI and IMEI received through the emulated non-LTE cell, a mapping between the IMSI and the IMEI in the database, if the time interval between the reception of the IMSI through the emulated LTE cell and the reception of the IMSI and IMEI through the emulated non-LTE cell is longer than a determined discarding threshold.