Aug 27, 2015

WiFi Three Ways from CEVA

posted by Bryon Moyer

WiFi, Bluetooth, and Zigbee are vying for primacy, and none of them is likely to disappear anytime soon (if ever). WiFi is the granddaddy, and arguably the most familiar. So, of course, WiFi is going onto all kinds of stuff. We see plenty of WiFi modules and chips, but CEVA suggests that you can save space if you integrate the WiFi directly into your SoC. (Assuming you’re doing an SoC…)

Sounds straightforward, but if you dig in just a little, an obvious question comes up: which WiFi? If you’re going the route of the PC, then you put on the most advanced version that has some level of support out there. Most likely, that’s still 802.11n, although (from a quick web scan) more expensive routers are now supporting 802.11ac.

But everything has a cost, and performance costs power, if nothing else. If you’re plugged into a wall, then wasted power is just wasted power. If you’re on a battery, on the other hand, then wasted power is a premature dead battery. So now there’s a choice to be made.

Another implication of the WiFi choice is the antenna arrangement. The newer versions support multiple-in/multiple-out (MIMO) configurations, which establish multiple “spatial channels.” You recognize these by the multiple antennas on a router (and the antenna configurations are typically indicated as AxB, where A is the number of antennas on the router and B is the number on the end station).

CEVA recently announced their RivieraWaves WiFi IP offering, and it’s divided three ways depending on how the WiFi will be used.

  • For power-sensitive applications that don’t need the speed – like Internet of Things (IoT) edge nodes filing their sensor data reports – they offer 802.11n in a 1x1 configuration, referring to it as their SENSE version.
  • For devices that need to shuttle more data around – surveillance, smartphones, wall-plugged smart-home IoT nodes – they bump up to 802.11ac in 1x1 or 2x2 configurations. They call this their SURF option.
  • For heavy data use – routers and infrastructure and such, scaling to hundreds of users – they have a third version that configures 802.11ac in a 4x4 arrangement, named the STREAM option.

 RivieraWaves-Target-markets-diagram---8-6-15.png

(Image courtesy CEVA)

The upper and lower MAC components are agnostic as to the processor or operating system is in charge. The modem functionality can be configured as optimized hardware or for software-defined radio for integration into a multi-protocol platform. And, of course, CEVA says that they’ve been designed to minimize power consumed – especially for the lower-end devices.

You can find more detail in their announcement.

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Aug 20, 2015

Why Nigerian Bank Scams Are So Obvious

posted by Jim Turley

The old "Nigerian bank scam" is so laughably obvious that nobody could possibly fall for it anymore, right? Not so, and some new research suggests that its cheesiness is actually deliberate.

The plaintive appeal to wire money to a certain displaced Nigerian prince is one of the oldest tricks in the book. It's so obviously bogus that it's become the archetype of low-end spam. Everybody's seen it a hundred times, and even the dumbest spam filter can spot it a mile off. The very presence of the word "Nigeria" sets off alarms. Can't the stupid spammers come up with even a little improvement on the old formula?

Nope, and for good reason. In a paper from Microsoft Research, Cormac Herley explains that the scam's obviousness is deliberate. It's carefully designed to appeal to only the most gullible segment of the population. Unlike most other types of spam or phishing scams, he explains, the Nigerian bank scam requires the scammer to put in some effort to reel in his victims. Thus, it's in his best interest to hook only the dumbest and most gullible targets and avoid the (relatively) smart ones. He doesn't want to waste time luring potential victims who might later see through his scheme and alert the authorities or waste his time. Only the dumbest need apply.

"Since gullibility is unobservable, the best strategy is to get those who possess this quality to self-identify... The goal of the email is not so much to attract viable users as to repel the non-viable ones, who greatly outnumber them. Failure to repel all but a tiny fraction of non-viable users will make the scheme unprofitable."

So count yourself lucky that you recognize the scam when you see it. And stand in wonder at those who don't.

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Aug 20, 2015

mCube’s New Low-Power Accel: What It Is and Isn’t

posted by Bryon Moyer

mCube made more noise recently with their announcement of a very small, low-power accelerometer. There were a number of aspects to the release; some intriguing, some… less so.

Let’s start with intrigue. The whole focus here is on a small device that can be used in space-constrained, power-stingy applications – like wearables. Obviously space is critical in any such device, but they point out that flexible circuit boards can enable more… well… flexible shape designs. And, while the accelerometer isn’t itself flexible, the closer you can come to an infinitesimal point on a flexible board, the more likely your connections are to remain intact. So, on flex boards, small=reliable.

They get the size by stacking a MEMS wafer with through-silicon vias (TSVs) over a CMOS wafer (all of which is then garnished with a cap wafer). This means that bond pads are needed only for actual connections to the outside world, not for intra-package die-to-die connections, which can take a lot of space.

mCube_figure.png 

Cost is also mitigated by using an old process with fully depreciated equipment. Right now, they’re at 180 nm; they could go to 150 without spiking the cost curve. In addition, all of the steps – from the different wafers to bonding them – are done in a single fab. This is as compared to other processes, where wafers have to be bundled up and sent to different fabs for different parts of the process.

They’ve also built in a couple key application-oriented features intended to go easy on battery life. First, you can tune the sample rate – fast for tablets and phones that need to be responsive enough for games (a couple thousand samples per second), slower (400 samp/s) for wearables. Second, they have power modes: a normal mode at 4.7 µA (50 Hz), a single-sample mode at 0.9 µA (25 Hz), and a “sniff mode” at 0.6 µA (6 Hz).

Sniff mode monitors for activity, sending an interrupt when detected. The threshold for what constitutes “active” can be tuned to suit the application.

So, functionally, this seems to compete pretty well. Which is really all that should matter. The less intriguing bits have to do with the marketing and what feels like playing a little loose with terminology. Any good marketer knows that it’s great if you can carve out for yourself a new market or “category” so that you have no competition. Problem is, too many folks have read that in their business books, and try it too often.

Here, mCube is trying to define the “IoMT” – Internet of Moving Things – as a separate thing. This suggests that, somehow, items with IMUs constitute this separate class of system. Sorry, but it just doesn’t work for me.

A little more worrisome is their use of the word “monolithic.” As in, they’re claiming a monolithic solution. First, “monolithic” literally means “from one stone.” This is not from one stone – it’s from three wafers. Monolithic would be if the MEMS and CMOS were fabricated out of the same wafer. (I won’t quibble about the cap wafer.)

They even use this to distinguish themselves from InvenSense, who uses what they call a “stacked” approach. They say that this distinction is significant enough to define the end of “Sensors 2.0” and the beginning of “Sensors 3.0.” Again, more new categories. Again, not working for me.

The only real difference here from InvenSense is that InvenSense inverts the MEMS wafer and bonds face-to-face (and does this in some other fab, by implication). mCube stacks bottom-to-top, connecting with TSVs. That has some benefits – don’t get me wrong – but it doesn’t feel to me like the revolutionary birth of a new category.

OK, kvetching over. You can find more information about the tiny new mCube accelerometer in their announcement.

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