Wi-Fi Offload

Small cells are good way to increase coverage of mobile network and serve densely populated areas like malls, concert halls etc. A Femto cell is one solution while other seems to be Wi-Fi. Wi-Fi Offload is becoming a lucrative option to offload mobile data for service providers, as Wi-Fi is cheap; Wi-Fi is everywhere and is integrated into the most of hand held devices. But there are quite a few hurdles to pass through before offloading the data over a Wi-Fi. There is quite a lot of work going on in 3GPP standards to smoothly integrate the Wi-Fi network into 3GPP network.

 

You can download it from flickr.

I saw that ATT gives away connectivity to their Wi-Fi hotspots free as part of mobile data subscription. To understand Wi-Fi offload better, I picked an ATT IPhone and drove to nearest Starbucks with a Laptop running Ubuntu and tcpdump, in an attempt to capture the traces and understand protocols. To my surprise I observed that Wi-Fi network was free to everybody, with some terms and conditions to accept, and not to just ATT subscribers. Also the whole Wi-Fi network was un-encrypted. 1 minute capture lead to 8 mega bytes of data from all the users.  I got back and did a Google search. It seems that ATT hotspot at Starbucks is free for everybody and is un-encrypted. Some more research showed that all premium subscriptions for Wi-Fi needed users to login into an http portal for authentication. Even the premium subscription doesn’t get you encryption over Wi-Fi RAN. ATT on their website recommends connecting to VPN when connected to publicly available Wi-Fi.  With these challenges, I personally wouldn’t want to connect any publicly available Wi-Fi.

What will make a Wi-Fi offload truly a small cell solution and attract many more subscribers?

• -          Wi-Fi network connection should be seamless with minimum user interaction

• -          No web portal authentication. If I am subscribed to a premium service, let the network figure it out and award me services without my interaction.

• -         Encrypted Wi-Fi RAN.

• -          IP address preservation upon moving to a mobile network.

Requirements for one may be different from other and depends on the business model.  I believe we should be able to at-least achieve these requirements to call offload a “true” offload. The technology exists and inter-connections should be laid out.

EAP-SIM exists for seamless authentication and Wi-Fi RAN encryption. Stick up a gateway in between Wi-Fi RAN and mobile network to maintain the same IP address across the networks and enforce the mobile network policy. Connect AAA/HLR to the Wi-Fi gateway for authentication/accounting. This is an immature description, will post more call-flows and adjust the network diagram soon.