Sensys'12 (Day 1)

I am handle Sensys'12  at Toronto, which is a short distance from Buffalo. Sensys is a premiere conference for wireless sensor network and, to a greater extent than recently, smartphone sensing research. Here are my stone oil notes from the kickoff 24-hour interval of conference.

Energy-efficient GPS sensing alongside cloud offloading

This newspaper is actually good, it blew me away. Later at the conference banquet Wednesday night, the newspaper got selected equally the Best Paper. This piece of job aims to interruption upward the GPS equally a blackbox as well as run into how nosotros tin locomote into more energy-efficient. The newspaper goes into fairly technical especial nigh how GPS works, which I cannot replicate here. Some basics are: GPS uses CDMA to transmit 50bps information over a carrier indicate of 1.575Ghz. Seeing to a greater extent than satellites improves accuracy. GPS localization requires the next phases on the device: acquisition, tracking, decoding, code-phase, least-square calculation.

The insight of the newspaper is to offload some of these phases to the cloud, hence the device does less piece of job as well as spends less power. For example, the codephase involves getting the "ephemeris" from the indicate for learning the place of satellites, but this await upward tabular array is already made available past times NASA as well as alike inwards cloud. So that tin hold out easily offloaded to the cloud, as well as the device does non necessitate to do it. Another fob is coarse fourth dimension navigation. If a nearby landmark has same/close nms for the GPS signals (nms= position out of milliseconds for fourth dimension of flying of GPS signal), instead of calculating the location, run the landmark's location. If there is no such known location, hence leastsquare calculation may give several possible locations, but in that place is even hence hope. It is possible to run the elevation information (the superlative dimension oftentimes ignored inwards the lattitude-longitude pair) as a checksum as well as eliminate the spurious possibilities as well as to figure out the correct location. The elevation information as well as the computation ability to produce this is available at the cloud side.

Using similar tricks, they trim the duration of the acquisition stage at the device as well as the amount of information to hold out gathered past times the device from the satellites. They prepare hardware for this (they telephone shout out upward this Co-GPS design). The Cleon paradigm is comprised of max2769 gps receiver + msp430 equally the chip, and talks to the telephone or device (ipod?) using sound communication through the headphone jack. Cleon ends upward sampling GPS entirely for 2ms (16 mHz sampling, 2 bit/sample, 2ms) equally that is plenty for accurate localization (within 30meters) via offloading to the cloud-side. The awesome matter nigh Cleon is that it can run on 1.5 years on 2AA battery alongside continuous sampling. Wow! (This calculation does non accept into concern human relationship the communication toll to cloud equally this is done by the device Cleon connects to as well as tin hold out over wifi, bluetooth, etc.). A byproduct of Cleon is atomic fourth dimension stamping for outdoor sensors. They volition opensource the software as well as the hardware soon.

Indoor pseudo-ranging of mobile devices using ultasonic chirps

This piece of job presents an ultrasound-based smartphone ranging system. The transmitters for this organisation is regular speakers, which abound inwards halls, malls, classrooms, as well as offices. The sound used is slightly below "normal" human hearing range; they utilize a 4Khz band there. Localization is performed at the smartphone via calculating the time-difference of arrival of sound signals (sound is slow, hence this creates an payoff inwards achieving fine-grain localization) from the predetermined speakers. This is non a novel idea. MIT had the Cricket protocol that did this unopen to 2005 for the motes. This piece of job is a refined implementation of the same concepts. Instead of a mote as well as special receiver hardware, they were able to describe this off alongside regular smartphone (iphone) microphones. Other noteworthy special touches from the newspaper are as follows. They run chirp signals, because they constitute that chirps are error-prone and give amend accuracy. When using such chirps, human ear hears click sounds (demonstrated at the presentation). So they employ "psychoacoustic" (perception of sound) properties to solve this. The clicking sounds generated past times rapid frequency changes, hence they reshape them past times adding fading (fading inwards as well as fading out) betwixt the chirps, hence they acquire oblivious to your ears. They employ hamming codes inwards the chirp signals for mistake detection as well as correction. As a result, they acquire by to acquire localization accuracy alongside less than 10cm error. A disadvantage is that this method requires business of sight to the speakers, and also that speakers necessitate to hold out pre-localized as well as pre-arranged. Another nice touch, they tested this on their cat; the cat, although could listen the sound, didn't seem to hold out disturbed past times it. (They used nutrient association technique to show this.) Another interesting tidbit from the speak is that, 2 people out of the 200 people crowd said they were able to listen the ultrasound fifty-fifty alongside fading-in/out version. Some people guide maintain to a greater extent than sensitive ears it turns out.

IOdetector: a generic service for indoor outdoor detection

This newspaper aims to supply a service for the smartphone to uncovering whether it is currently outdoor, semi-outdoor, indoor. The application of this service is to automatically as well as inwards "an energy-efficient manner" uncovering when the telephone should not fifty-fifty bother activating the GPS for an app because the telephone is indoor or semi-outdoor as well as the GPS mistake volition hold out big, as well as it would non justify the energy wasted past times the GPS. The service uses 3 modalities: lite signal, cellular signal, magnetic plain signal. Also secondarily, acceleration as well as proximity & time (to sanitize lite readings) are employed. These are all real depression energy sensors. The lite detector accounts for 24-hour interval or night, as well as tin uncovering indoor fluorescent lighting. The cellular indicate detector uses indicate from multiple celltowers to avoid the corner-turning effect. However, each subdetector cannot completely assort the 3 types (indoor, outdoor, semi), hence they fuse these subdetectors employing the confidence results provided past times them.

Musical Heart : A hearty way to heed to music

It is a proven fact that music has profound final result on human optic rates. Some music calms, some music gets you lot worked up. This piece of job presents a biofeedback-based context-aware music recommendation app for smartphones, MusicalHeart. This app requires its ain special sensor equipped earphones to achieve the biofeedback part. More specifically, in that place is an IMU (inertial measurement unit) as well as a microphone embedded inwards the headphone. The microphone is used for heart-rate detection (requires some filtering), as well as the IMU for activity detection (employs k-means clustering). These sensors communicates to the smartphone app via the sound jack, as well as they are powered past times a thin cinema battery. In add-on to the sensors inwards the headphone MusicalHeart app also uses telephone GPS as well as WAP information for context detection.

MusicalHeart detects what type of activeness you lot are doing (light L1, medium L2, high-level L3) as well as plays you lot the "appropriate" music to endeavour to acquire your heart-rate into the suggested/desired heartbeats per second. The speaker claimed that in that place is a desired/suggested heartbeat for activeness levels, as well as this is documented inwards the medical literature. (I am hearing nigh this the kickoff time.) So, MusicalHeart "custom"-selects a vocal to fill upward inwards the gap betwixt the desired heartrate for your activeness as well as your electrical flow detected optic rate. It may run a fast vocal to increment your heartrate or a irksome vocal to irksome your optic rate. Of course things are non that simple. Actually 3 dissimilar features are considered for each song; tempo, pitch, energy. Increase inwards release energy increases your heart-rate to a greater extent than effectively for L1 activities, as well as increment inwards tempo increases your heart-rate to a greater extent than effectively for L3 activities. The "custom" part of MusicalHeart is because the app learns over fourth dimension what sort of music work better on you lot for the desired effects. The piece of job was evaluated alongside an empirical written report over 37 volunteers. I am still skeptical nigh if whatsoever vocal tin irksome my optic charge per unit of measurement at L3. I volition endeavour this at the demo Th (today). Yes, several of the papers below also look inwards the demo session so the audience tin endeavour if they piece of job equally advertised.

The Banquet

The conference banquet was held at the the Mobicom'11 banquet. The CN tower was a very interesting as well as exciting venue to guide maintain the banquet. Especially alongside the drinking glass floor!

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