Friday, April 27, 2012

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.


Anonymous said...

Very interesting post... You prolly know T-Mobile already implements it via a sw client on android devices (with no vertical handover) and over UMA on older hw...

Keep up the good work


Santosh Kumar Dornal said...

Thanks Ric!

Ujjwal said...

Nice of you to address the hot topic today. WiFi is getting hot with operators now. It is a good way of offloading the resources and increasing coverage too. I have been reading about ePDG and recently SaMOG moving in LTE.
You can also see these solutions available in the market today.

Santosh Kumar Dornal said...

Hi Ujjwal

To my little knowledge, i haven't seen any deploy-able solutions yet. They all are under works or under lab trails. Let me know if there is something already in the market.

Thanks, Santosh

Johan Almbladh said...

Hi Santosh!

I work for Anyfi Networks. You should definitely check out our technology for Wi-Fi virtualization. It is a piece of software that goes into the Wi-Fi router itself and essentially solves all the issues on your list, and more.

The technology can be used to make every subscriber's home Wi-Fi available through every access point, or to distribute a SIM-authenticated 802.1X network terminated in the operators core or data center. It was covered in a GigaOM article today

We have quite extensive documentation on our website There you can also download evaluation firmware for some popular Wi-Fi routers and try it out.


Santosh Kumar Dornal said...

Very interesting Johan! Thanks for sharing and wish you luck with the venture.