Currently in GSM, there are two facsimile services specified: teleservice TS61 "Alternate speech/facsimile G3" and TS62 "Automatic facsimile G3". These two services utilise the T.30 [2] protocol between the mobile station and the facsimile machine at the other end. . Both services exist in two modes, transparent (acc. GSM TS 03.45) and non-transparent (acc. GSM TS 03.46). Although the transparent modeis designed to be transparent to the network, intervention of the IWF is needed whenever this service is used. The reasons for this are explained in GSM TS 03.45 [6] and are briefly summarised below:

• The GSM speech bearers are not adequate for transporting the modulated information transmitted between the fax machines. A data bearer must be set up between the IWF and the MS and the IWF must convert the modem signals to digital form as for all modem services.
• Not all messages defined in the T.30 protocol are applicable in the mobile case. The IWF must filter the messages sent from the facsimile machine in the fixed network.
• Fall back messages require that a different rate adaptation is applied on the mobile leg or that a different channel is used

High failure rates depending on the equipment used are often experienced. This is mainly due to the high error rates on the radio interface and to long transmission delays. Different manufacturers have implemented various procedures to handle these problems, but due to the large variety of facsimile machines used in the fixed network and their various implementations of the T.30 protocol, it is not possible to guarantee acceptable performance. The cost experienced by manufacturers for development, trouble shooting and maintenance related to the facsimile services is high. Alternative ways of transmitting facsimile messages to and from mobile users need to be investigated. In contrast to the quality provided by the transparent mode, the quality provided by non-transparent mode is much better provided that the bit error rate is low. However, for bit error rates exceeding a certain threshold it is not possible at all to transmit a facsimile document and the transmission results in the following behaviour. The sending Fax equipment expects the acknowledgement on the partial page within a certain time frame. The RLP entity of the receiver delivers the first part of a T.30 partial page without any error to the receiving Fax equipment. Due to the RLP retransmissions the receiving Fax equipment is not able to send the acknowledgement in time. Therefore the sending Fax equipment aborts the transmission of the document. The aim of this report is to show that alternative solutions exist. Given that most of the problems experienced today can be traced to the termination of the T.30 in the mobile station, the alternative solutions described in this report, which have initially been developed for usage in the Internet, will all be based on terminating the T.30 protocol in the network and using some alternative transmission method to and from the mobile user. In addition to the development problems listed above, one may argue that the GSM facsimile services TS61 and TS62 are not appropriate. Mobile terminated facsimile calls are rare, because the mobile user equipment is seldom ready to accept such calls. Also, most user equipment do not allow the user to switch between speech and facsimile mode, which implies that the alternate facsimile/speech service is almost not used. This argument applies to both modes of transmission, transparent and non-transparent. This report studies the applicability of two particular protocols: T.37 [3] and T.38 [4] which in turn are based on many IETF RFCs. It does not intend to express any preference for one or the other as both can be applied. They may be integrated either together or separetely with already established GSM/Internet specific services. Although this report is the result of a UMTS work item, it is intended to be applied to GSM as well, thereby increasing the interoperability between UMTS and GSM networks.

This document gives guidance on how facsimile services can be provided in a GSM or UMTS network. It studies how facsimile messages can be exchanged between mobile equipment and a PSTN facsimile machine. Although the approaches described herein can be applied to cases where none of the end points are connected to a PSTN, the study of such cases are out of the scope of this document. The Scope shall not contain requirements.