I had the opportunity, today, to be at the sigfox kickoff day, in Toulouse,  with the company I work for. This is an opportunity to post a summary of the technology as it is today.

Sigfox is a network operator for Internet Of Things running on free frequency band (868Mhz in France). Sigfox is deploying itself network in some countries like France. In some other they have partner to deploy it like arquiva in UK (on going actually 10 biggest cities); abertis in Spain, Aerea in Netherland. Actually some European cities are also deployed as pilot : Munich, Menlo, Milan, Warsaw, Dublin, Autria. San Fransisco & Silicon Valley will come soon this year. The target is to have 60 countries in the next 5 Years. Thanks to the long range radio characteristic of the network, Spain has been deployed in 7 months. As to now, the network does not includes roaming constraints & fee. A French licensed device works in any country where the network exists.

The network is high sensitivity with 2 way communication 140 *12 bytes messages a day uplink / 4 * 8 bytes messages downlink. Each of the messages are sent 3 times on different frequency to ensure it will be delivered. The devices are running ultra low energy with 10-25mW radio power. The technology is plug & play : you do not have any peering process to accomplish to make it works (but you have to activate the device in the backend at least…). Data are sent to a global backend whatever the network provider you are passing through and you have contract with. This backend will let you have access to your data in real time and will execute callback (data post) to you own specific backend to proceed your data.

Limits : due to low bandwidth / small messages architecture, the technology does not allow voice, video … transfer for sure. But it is really fitting security, smart cities (traffic, parking waste, street lights…) monitoring, automatic meter reading, leak detection, billing automation…, tracking & security, healthcare (fall detection, distress buttons…), Agriculture.

Ecosystem

Sigfox is not doing solution, devices, vertical platform neither address immediate business need. They are rooting to the right sigfox solution provider in the sigfox ecosystem.

SigFox Ready Programs : any manufacturer and device are certified SigFox Ready to ensure the quality of this ecosystem. The sigfox ready program have

• Technology enablers like TelecomDesign, Atmel, TI, SiliconLabs, Telitn Axsem, Atim ….
• Sigfox Network Operatord (SNO)
• Solution Enablers : Securitas, ClearChannels, SnootLab, Connit (sensors, supervision), snef, Traqueur, M2M (Container tracking), NigiLoc (stolen bike solution), sterela (parking management), world sensing(fastprk – parking), pioupiou (wind sensor), Salesforce (soft connector with sigfox backend) … who are a mix of end users and service providers

This includes about 54 companies in the eco-system.To be part of the eco-system, you have to follow. Each device type is validated through this process and allow to display the Sigfox the logo and use the network. The compatibility of the radio module and the performance of the radio system / antenna is certified. The module use is simplifying the design/time to market and certification vs volume price. This price for this registration is about 2.5K€ for end product already based on Sigfox ready transceiver/modules. Price decrease when you come from a second product or a new iteration of a certified product.

SigFox Partner Days : is a moment to meet the Sigfox ecosystem.

The network have different offers based on volume of device and number of messages transmitted per days:

• Platinum : 101 to 140 messages + 4 downlink
• Gold : 51 to 100 messages + 2 downlink
• Silver : 3 to 50 messages + 1 downlink
• One : 1 to 2 messages + no downlink

Some of customer applications

• General council of the Loiret (France) – Lysbox help to manage person coming to manage dependent persons. Deployed in 10K houses
• Securitas : Remote transmission of alarm – millions of device in deployment
• Smockeo : Fire detection
• Connit : Community of communes of Pays de Gex (France) – remote measure of consumed water meters for billing purpose.
  • Monitor trash level in compactors
  • Monitor water
  • Monitor light & temperature inside building
• Bayard : detection of Fire Hydrant leaks
• Ocea Soft : Cold Chain Management – track temperature, humididy, CO2 …

Hardware

Some of the existing chips running SigFox ; the list is growing, most soon !

• Texas Instrument : CC112x (transceiver)
• Silicon Labs : Si446X (transceiver)
• Axsem : AX 8052 (Soc – transceiver)
• Atmel : ATA8520 (Soc – transceiver)
• ATIM : ARM- NANO (module)
• Telecom Design : TD120x (module)
• Telit : LE51-868 S (module)
• StickNTrack : asset Tracking (bicycle, trucks, packages)
• Whislte : petTracking – fitbit for dogs

Telecom Design

Telecom Design modules are based on a EFM32 / Cortex M3 micro-controler with 128KB flash, 16KB RAM, ultra low power including a Silicon Labs transceiver.  (read mode in this blog ; other post)

Works as a standard modem based on AT commands.

Provides a SDK and development based on eclipse. About 150 customer are actually using this SDK for developing own firmware.

There are 3 different devices

• TD1208 – having a radio chip Si4461 allowing +14dB and multiple GPIOs
• TD1204 – having a radio chip Si4461 allowing +14dB and really limited GPIOs
• TD1205 – having a radio chip Si4463 allowing +20dB with no GPIOs

Check other post to get details on these chips.

Distributed by AvNet

Telit

Telit provides modules from market chipset ; LE51-868S is compatible with Sigfox network ; the family is covering different networks like ZigBeen M-Bus…  The module is based on TI and Atmel components. Standby consumption 1,5uA ; transmit consumption 55mA. Based on IAR development environment with 128Kb flash.

Coming soon, ME51-868 S, new component for supporting W-MBUS and integrated in a such environment.

Distributed by Arrow

Atim

Atim have two modules based on a ARM core and a RF part. The first module have a 25mv module when the second one integrate an amplifier to provide 500mW RF module. These modules includes a modem firmware. ATIM module are pin compatible with other module they are providing like the one for LoRa. By-The-way, I assume the reality is that if you change the network you also have to rewrite many things, so it is mainly a commercial argument. Atim module are basically expensive (my opinion)

Radio

The radio is basically based on low power emission system allow to emit 14dBm in Europe corresponding to 25mW and an ultra-sensitive basestation on reception. This one is able to receive at -142dBm. The link budget is so about 160dBm allowing long distance transmission (up to the horizon).

There is no synchronization between device and network avoiding extra energy consumption for synchronization. The communication is based on ultra narrow band (100Hz) , small messages and 100bps to work well.

France is covered with (near) 1000 antennas vs 15.000 for standard GSM solution

The network have to support a large density of connected object. The main matter is to avoid collision. The information is broadcasted and every base-station on the perimeter are listening (object is not attached to a base-station); Having multiple base-station reduce the risk of collision (collisioned message can be received on a base-station when two others are receiving correctly each one). On top of that, each message is transmitted on 3 different radio frequency this is also reducing the statistic of collision. The channel hop is semi-random. The base-station is listening a 200KHz spectrum and will get the message on these frequency. This gives a high protection to sigfox against other communications running in parallel on the same frequency/modulation.

The radio container for the payload is 0, 4, 8, 12 byte. A sigfox message is 2s transmission on each of the frequency. The total transmission time is as a consequence 6s long. Time depends on size of the message :

• 1 bit : 3 x 1.12s
• 1 byte : 3 x 1.2s
• 2-4 bytes : 3 x 1.44s
• 5-8 bytes : 3 x 1.76s
• 9-12 bytes : 3 x 2.08s

The protocol overhead contains : Unique device ID (32b) and a Hash for authentication of the sigfox message. The total size is 26 bytes. The other bytes are used for security and to certify the content of the message (crc and stuff like this).

The downlink mode only works as an acknowledgement of the network to a sent message. Basically, the device is transmitting the message on the 3 frequencies. After the emission on the first frequency the device have a 20s time of sleep to let time to backed to transfer the data and get the ack. Then the device can go on reception and will get the message from the base station in a maximum of 25 seconds. We must not send a new message in the next 6s after the reception.  The payload of the downlink is 8 bytes.

In term of capacity, one Sigfox base-station can receive million per day and transmit 100k messages per day.

As the number of device is millions and the life cycle is decade, all the evolutions of the protocol have to be backward compatible.

In Europe the access to the 863-870MHz is subject to ETS 300-220 regulation. The rules are 25mW max and duty cycle is 1% meaning we have a maximum of 140 messages / day.

In Americas the access to the 902-928MHz band, the FCC part 15-247 requires a maximum radiated power of 150mW (up to 4W possible but not use by Sigfox) and allow 15% of bandwidth usage;  This can allow up to 450 msg / hour. By-the-way sigfox is offering the same think in every country based on Europe rules as minimal. The transmission is 600bps in USA and transmission is really shorted that way. As a consequence, actually the device working in Europe are not able to run with the USA base-station. It is part of the roadmap to make the device/base-station supporting this.

The base-station are listening 200KHz and receive, in parallel any messages transmitting in this area. This is mostly software based radio. The base-station is connected to satellite, adsl, Ethernet Ip network… to the backend. A 3G connection is also used as backup. By-the-way, messages are secured as the base-station is able to store messages until network is back.

The modulation for up-link is BPSK at 100bps on 100Hz “channels” ; here is the main complexity : being able on the reception side to monitor a large frequency bandwidth to track the signal even if it have a frequency variation during the emission. The technology behind is mainly Software Defined Radio able to scan all the frequency at once and proceed signal to track it. The base-station is listening the whole bandwidth (no channel consideration) so any frequency variation on the emitter is not a problem if stable during message transmission. The base-station respond for down-link on the same frequency.

The modulation for down-link is GFSK at 500bps on a 600Hz band

Radio Qualification

Device are qualified in the qualification process, explained before, in different categories:

• 0u – 14dB +/- 2dB
• 1u – between 12dBm and 7dBm
• 2u – between 7dBm and 0dBm
• 3u – below 0dBm

This is mostly depending on antenna and package quality when based on standard module.

Regarding this qualification, Sigfox is able to predict a service level. The coverage is accessible in the back-end regarding the device class, the localization (indoor / outdoor / underground) and the location in France.

Backend

Backed allow Operation support and Business support. It allow to manage users, data collection, billing…

Consumer can access the device different ways :

• Sigfox back-end – Web portal : good for debugging / prototyping
• API : it is basically a pull mechanism ; same function as web portal can be achieve by scripting. It is not recommended to use this to receive message as most of the time back-end will be pulled for nothing. By the way, it is the right way to manage devices (register & so on)
• Callbacks : Each time a device transmit, the back-end is triggering the customer back-end. Http(s) is use to push the data. The message can also be transferred to an email address ; the content is written by user and completed with the expected fields by the system.

Time between activation request and activation of a device sounds to be 1 hour actually.

In the message view, the redundancy is indicating the number of base-station that have received the message. It is possible to receive one callback per base-station per message ; (this will give you the information of the of RSSI per base station) by selecting “duplicate” option.

(About usage, take a look here, here …)