Sunday, November 6, 2005

Motorola: Three Lessons from Early HSDPA Trials

Motorola published a list of three key findings from its HSDPA (High Speed Downlink Packet Access) trials in Europe. The HSDPA trials focused on user experience and how service providers can ensure high customer satisfaction at the launch. Motorola's three key HSDPA findings include:

  • 1. Sufficient processing power needed to reduce latency

    HSDPA will provide high speed but can be prone to delays when using applications such as web browsing. These delays can be attributed to a mechanism known as "state switching". This effectively moves a user from a high to a low speed state based on user activity without the user being aware. When the user requests data, such as clicking a hyperlink for a web page, there can be delays of seconds as the radio network transitions back from a slow to a fast state. Users will not expect such delays for services marketed as "Mobile Broadband".

    There is a solution - avoid switching users down from a high to a low speed state regardless of user activity. As HSDPA enables radio resources to be dynamically shared between users (known as scheduling), the necessity to state switch should be reduced. However, scheduling requires intensive computer processing capabilities at the base station. Network operators should ensure that they have sufficient processing power at the base stations to schedule the highest possible number of calls at launch of the HSDPA service.

  • 2. Adopt key handset functionality for improved mobile performance

    The performance of HSDPA is heavily dependent on device or handset capability. A signal processing function known as an equaliser enhances performance when the user is moving. Initial trial results demonstrate an increase in data rates of as much as 40 percent for devices that support equalisation. Today only a few device manufacturers claim to have equaliser functionality.

  • 3. Video services need priority

    The trials have shown that video streaming performance degrades when a relatively modest number of users are active. As little as four active users are sufficient to cause video streaming to freeze if scheduling priorities are not set properly. To compensate for this, operators must actively prioritise video over other services or provide more capacity. Operators could defer video services on HSDPA to a later stage, but as video services consume a large amount of UMTS capacity they should be moved to HSDPA for improved efficiency. This will reduce the cost to deliver video services.

    To ensure a mobile broadband user experience Motorola recommends early introduction of Quality of Services features for video.

See also