from the cap idp location information e g cell global identifier cgi providing the reported location of the calling mobile station charging information the new sip invite sent by the mgc shall include in p charging vector pcv additional charging information the charging information e g call reference number crn msc address is received by the mae in the cap idp this will allow billing and accounting systems to correlate gsm based call data records cdrs for a specific call with charging records generated by the ims for the same call although the above described information looks straight forward and some element might look retrievable from the isup iam received by the mgc some other information is not retrievable from the isup iam for that very purpose the sip invite generated by mgc has to traverse the mae server so the mae server can ensure that the required information is added to the sip invite as described in the present disclosure this is achieved by mae server through an enhanced redirect response message the information as described above is contained in header uri parameters of the contact header see ietf rfc 3261 section 8 1 3 4 an example of such a contact header enhanced in accordance with the present disclosure is the following the values stated in the example are for illustrative purposes only actual values and layout is operator and call dependent a first implementation is shown in fig2 and 3 by means of a modified mae.