A method of determining a location of a mobile device using 3GPP LTE Positioning Protocol, LPP, comprising: defining a type of location related data for transferring between a location server and the mobile device using a first transaction, wherein the first transaction includes an LPP request message and at least one response message carrying: a first transaction identifier (T1), and a session identifier (S), which is different from any other LPP session ID currently in use between the location server and the mobile device, and wherein the last message of the first transaction carries an end transaction indicator; transferring location related data of the defined type between the location server and the mobile device using a second transaction, wherein the second transaction includes: a second transaction identifier (T2), and the same session identifier (S) as the first transaction; in which the first and second transactions are transactions defined for LPP; and modifying at least one of the type of location related data, periodicity for transferring data, triggering criteria, or termination condition as defined by the first transaction using a third transaction, while the transferring is still in progress; wherein the third transaction includes an LPP request message and at least one response message carrying a third transaction identifier (T3) which is different from the second transaction identifier (T2), and the same session identifier (S) as the first and second transaction in which the third transaction is a transaction defined for LPP. defining a type of location related data for transferring between a location server and the mobile device using a first transaction, wherein the first transaction includes an LPP request message and at least one response message carrying: a first transaction identifier (T1), and a session identifier (S), which is different from any other LPP session ID currently in use between the location server and the mobile device, and a first transaction identifier (T1), and a session identifier (S), which is different from any other LPP session ID currently in use between the location server and the mobile device, and wherein the last message of the first transaction carries an end transaction indicator; transferring location related data of the defined type between the location server and the mobile device using a second transaction, wherein the second transaction includes: a second transaction identifier (T2), and the same session identifier (S) as the first transaction; a second transaction identifier (T2), and the same session identifier (S) as the first transaction; in which the first and second transactions are transactions defined for LPP; and modifying at least one of the type of location related data, periodicity for transferring data, triggering criteria, or termination condition as defined by the first transaction using a third transaction, while the transferring is still in progress; wherein the third transaction includes an LPP request message and at least one response message carrying a third transaction identifier (T3) which is different from the second transaction identifier (T2), and the same session identifier (S) as the first and second transaction in which the third transaction is a transaction defined for LPP. <EOS>