Mike Puchol

Sagem’s SIMFi – not so fast

There have been a ton of posts around Sagem Orga’s SIMFi, presented at the Mobile World Congress. In essence it claims to add WiFi circuitry and intelligence to a standard SIM card. Supposedly, it then creates a WiFi mini-hotspot that can be used by nearby devices to share the 3G connection on the phone bearing the SIMFi. By now you’re thinking “why is this guy so skeptical?”. Let me explain.

The need for speed

The SIM card that your mobile phone is wearing is defined by a set of standards, mostly by GSM 11.11 [PDF] and ETSI TS 102 221 [PDF]. The ISO/IEC 7816-3 standard also defines some of the commands and procedures used by SIM cards.

In essence, a slow-speed startup sequence is performed after the initial card reset, at a preset speed of 9600bps. Yes, bits per second – you may start to infer where I’m getting at. After this sequence, the host is free to clock the SIM card up to 10MHz, which at the defined baud rate of c3/327, C3 being the clock frequency, means it can achieve a top speed of 30581bps. Or 30kbps.

Now correct me if I’m wrong, but bog-standard 3G being offered at 3.6Mbps. Sagem claims they can deliver this to a WiFi chipset on the SIM card…over a 30kbps bus. Somehow, I don’t buy it – and maybe that’s why they wouldn’t show any actual SIMFi cards, and only performed demos on closed terminals. And I bet they used a Sagem phone, and not a Nokia 6110.

InterChip USB to the rescue

IC-USB is an addendum to USB forum’s USB 2.0 specification, which enables USB communication between embedded chipsets at high(ish) speeds, using low power, short distance links. Wikipedia cites the maximum link length at 10cm. Gemalto provides a presentation [PDF] that has some plain-language information on the new card format, and what it can do. Finally, this GSMA document [PDF] provides some background information on the implementation of advanced functionality into new-generation SIM cards. It talks about minimum bus speeds of 200kbps. For the purpose of IC-USB, high speed means 12Mbps, which is respectable for what SIMFi tries to achieve.

Contacts? We don’t need no stinkin’ contacts!

This is what a normal SIM card reader looks like (there are many variations), as found on all phones in the market today:

Note that it has six contacts. The new IC-USB and UICC-ME protocols call for eight contacts on the SIM card, in order to fully accommodate the bus requirements. To put it bluntly, this means that the SIMFi will NOT be compatible with any existing mobile phone, and will only be compatible with phones sporting the new card reader and IC-USB protocol. I imagine Sagem made a phone specifically to work with the SIMFi for demos, but the claims that “In practical terms, this means that you’re able to turn virtually any phone (or “classic handsets,” as the company calls them) into a WiFi hotspot” (Engadget) are wildly over-stated.