e. Enhanced Messaging Service (EMS) EMS includes SMS and adds simple graphics and sound. It is based on the SMS standard SO no new functions are needed in the operators' networks. It was generally introduced during 2001 and it goes under the same subscription as SMS. New, slightly modified mobile phones are required. Services Multimedia Messaging Services (MMS) MMS makes it possible to send text, music, photos and moving pictures between mobile phones. The size of the memory in the receiver's phone sets the limit of the message size. MMS cannot be used in circuit-switched 2G networks such as GSM or CDMA but was introduced in 2.5G, i.e. GPRS. MMS can be fully utilized in 3G networks as W-CDMA within UMTS. In 3G networks the quality of the services will improve and video streaming will be added. MMS requires new functions in the operators' networks and new mobile phones. Use of SMS The magazine Mobile Choice carried out a poll during August and September 2001 of the preferences of 1100 British mobile phone users. The survey results illustrate to some extent the relationship between telecommunication and the previously described human needs, and make the use of SMS clearer: To start a relationship - 17 % To break a relationship - % While driving a car - 21 % During work hours - 86 % While having sex - 14 % The conclusion was drawn that mobile phones and text messaging are the ubiquitous communication phenomena of our time. 5.4 SERVICE SEGMENTATION FOR PLANNING Service segmentation is based on a pragmatic selection. Since QoS and security are success factors used in this book, the majority of classes come from these two areas. In UMTS four traffic classes have been identified, which can be used as a definition of service requirements: conversational streaming interactive background The services are characterized by the QoS parameter, which is related to different radio access bearer attributes. The main QoS attributes used to define a service are bit rate, transfer delay, transfer delay variations/jitter and bit erro