US : A new report from The UMTS Forum into the potential impact of real-world mobile multimedia applications on use of 3G mobile radio spectrum has concluded that at least twice as much data traffic will flow to customers on radio downlinks as will be carried "upstream" from users' mobile devices to 3G networks.

Available free to UMTS Forum web site visitors, Report #33 - titled "3G Offered Traffic Characteristics" - examines the nature of traffic driven by internet, content and other services that is likely to flow across UMTS networks.

Traditionally, traffic studies for the purpose of spectrum requirement calculations have only considered the technical characteristics of a mobile service or application rather than any likely asymmetry in the traffic characteristics. Mobile multimedia services, therefore, introduce new challenges driven by the wide variety of multimedia-based activities available to the user.

Unlike two-way voice communications that are essentially "symmetric" in their use of radio up- and downlinks, many 3G mobile service categories - such as web browsing or streaming live video - place greater demands on the radio downlink than the uplink, with more traffic coming to the user (downlink) than from the user (uplink). Parameters assessed in the report that will have an impact on overall traffic flows include: file sizes for non-real time sessions; expected data rates over up- and down-links of the air interface; session frequency and duration; "busy hour" traffic characteristics; and mobile subscribers' adoption of individual 3G services.

Concluding that data traffic on downlinks will exceed uplink traffic by a factor of 2.3, the report also observes that the possibility exists for mobile operators to control this asymmetry through their choice of pricing plans, traffic shaping and service definition.

"There is little historical experience of the varied multimedia, content, messaging and internet/intranet services that will be supported by UMTS", comments UMTS Forum Spectrum Aspects Group Chair Anne-Tuulia Leino. "This is the first cross-industry study that has examined the real-world factors shaping customers' demand for 3G services and the impact that this is likely to have on operators' technical, operational and marketing plans."