Handover decisions for multi-radio devices

Gave a guest lecture at U of Delaware the other day on the DNA of Mobile Data – Devices, Networks & Applications.  Focused on the explosion of mobile data and the impact this is having and will have on carrier economics going forward.  The graph illustrates the problem.  At the margin, more and more bytes are being sent for fewer and fewer cents.

Two forces are coming together to offer some relief in this area. First, devices are emerging with multiple radios – Wi-Fi, 3G, WiMAX, etc.  In fact, this is becoming the standard for smartphones.  Second, carriers are warming up to Wi-Fi and are starting to bring more access types into their portfolio – Sprint & Clearwire for example; ATT acquiring Wayport; VZW partnering with Boingo.

Carriers, motivated by the decoupling of mobile traffic and mobile revenues, seem to be finally waking up to the opportunities of offloading data onto more economical access networks.

Plenty of protocols exist to handover sessions across access networks – MIP and its many variants like CMIP and PMIP as well as application-layer approaches using SIP. Once initiated, these protocols will execute the switch.  I call this the “how” of handover.

The trick is knowing the “when” and “where” of handover.  This is the handover decision process and it should be separated from the handover execution process.  Handover decisions must be driven by information, much of which is not locally available or could be beneficially augmented with global information available from the network.

The decision making process includes network discovery, evaluation and selection.  Typically this is done through static preference lists using local info only but this isn’t very rich or dynamic and can lead to suboptimal decisions both for the end-user and for the carrier.  The IEEE 802.21 Information Service was designed to support better handover decisions by spreading information to the parties that need it when they need it, but it has not achieved much traction with carriers to date, recent FMCA trials notwithstanding.

There are still many issues before data offloading becomes and effective solution, including tons of UX questions.  But my hope is to see more focus on information, rules, policies and frameworks for better handover decisions.


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