Ben WPAN

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Tuxbrain 6LoWPAN.jpg


Ben Nanonote + ATBEN
OpenWrt Router + ATUSB

Another, less in-depth, summary can be found here.

Ben WPAN is a project to create an innovative and unencumbered wireless personal area network (WPAN)[1] that is copyleft hardware. The primary protocols are IEEE 802.15.4 and 6LoWPAN[2], pronounced "SLoWPAN". The project lead is Werner Almesberger and it involves new hardware (for Ben Nanonote and for USB), along with new EDA tools, production process development, firmware, and contributions to Linux kernel support.

[edit] Goals

  • Ben Nanonote Connectivity
  • Internet Connectivity
  • Patent-Free Wireless Playground
  • Use in Sensor Networks
  • Use in Factory Automation

[edit] Reason

When you get wireless connectivity in a piece of copyleft hardware, we can expect it to:

  • be able to incrementally improve or modify many more things than you typically could without the need of a large investment or a large team.
  • be able to manufacture the same or an improved solution, because not only the result is published, but also the entire process. See for example the extensive test tools Werner created as part of the ben-wpan development, for antenna performance testing as an example.
  • be able to verify whether the communication protocols embody principles you find valuable, to avoid interested parties twisting the behavior of the network in their favor (net-neutrality, Quality of Service, lawful interception).

These are the core things that you will uniquely and typically find in copyleft hardware wireless solutions. On top of that of course we still have to implement useful applications. At the application layer, to the user it often does not matter whether they use a proprietary or a free network. The user rightfully only judges whether stuff works or not.

We are quite optimistic though that once we unleash the Ben WPAN, we will in fact see the most spectactular new wireless applications on copyleft hardware for the very reasons listed above.

ATBEN

[edit] FAQ and Innovation

[edit] What applications are possible from the creation of Ben WPAN? What does the future look like?

The 6LoWPAN protocol (IPv6 over Low power Wireless Personal Area Networks) used in Ben WPAN is designed for industrial control and monitoring applications where very low cost and power consumption are important. The future of computing is already towards lowering power consumption with an explosion of growth in mobile computing. The future is bright for Ben WPAN.

[edit] To call this Zigbee, do we have to pay a fee? Is the situation similar to the distinction between MESA and OpenGL?

If we called it ZigBee, maybe. But we shouldn't call it ZigBee, because it isn't ZigBee, not even ZigBee in disguise :-)

IEEE 802.15.4 is an open standard (specifications can be accessed without royalties, implementations are free from royalties (*)) for PHY and (bits of) MAC. Then you put the rest of your stack on top. This could be ZigBee, 6LoWPAN, or something else.

(*) Of course, with patents, there could always be issues. The standard explicitly warns that:

Attention is called to the possibility that implementation of this
standard may require use of subject matter covered by patent rights.
By publication of this standard, no position is taken with respect
to the existence or validity of any patent rights in connection
therewith. The IEEE shall not be responsible for identifying
patents or patent applications for which a license may be required
to implement an IEEE standard or for conducting inquiries into the
legal validity or scope of those patents that are brought to its
attention.

We don't know if contributors were asked to disclose any patent claims.

ZigBee is only royalty-free if not used for commercial purposes which makes it incompatible with the GPL and licenses with similar intent. The ZigBee Alliance explains the limits to free use of their specification here: [1]

The good news about ZigBee is, as various sources assure me, that it is gradually being replaced by 6LoWPAN. From the original ZigBee stack, only the top is preserved, and 6LoWPAN (and IEEE 802.15.4) is used underneath. This basically means that ZigBee is becoming or has already become irrelevant except for those who specifically seek ZigBee compatibility.

6LoWPAN is an open standard, specified in RFC4944 and other documents. Standardization work is still on-going (IETF's process regarding IPR claims is interesting[3]) IETF has many claims disclosed with regard to RFC4944 [4].

To the final question, no, Ben WPAN and Zigbee are not the same as the distinction between MESA and OpenGL.

Laptop + ATUSB

[edit] Is freedom really innovation? As in we have the freedom to make our own WPAN?

Freedom is an enabler for innovation. Remember the dark ages [5], when all the best universities involved in kernel-level research could do was to obtain a SunOS academic source license, and distribute their work in the form of precompiled object files?

[edit] Is Ben WPAN ONLY innovative in Free Software circles?

IEEE 802.15.4 and 6LoWPAN are also used outside Free Software circles.

There's the Contiki project (still under an Open license, i.e., 3-clause BSD) that can provide a code base for 6LoWPAN and maybe some bits of IEEE 802.15.4 too.

And then there are many vendor-specific stacks. You just don't hear so much about 6LoWPAN because it mainly targets industrial systems and integrated solutions and is not advertised as a standard for consumer products.

[edit] Is there an innovation in the software development connected to the linux kernel, mesh networking or some other non-process-based innovation?

At the moment, no. We don't even have proper support for the stack in Linux yet, let alone in mainline. So there's still a bit of work left to be done.

[edit] Or, are we caught just doing the same thing that is happening in industry, but without any money?

Before you can overtake the herd, you have to catch up with it.

Not having to start from zero should be a great benefit for any research/innovation project.

That is an unfortunate property of the current situation. Luckily, it's neither a prerequisite, nor has anyone here taken a vow of poverty. (Let's hope some sponsor reads this :-)

ATUSB

[edit] Is the Ben WPAN technology slow or slowfi?

ATBEN/ATUSB are not "slow." Slow is a cute term that makes better sense applied to radio technology such as HopeRF that works in lower frequency bands such as 800/900 MHz and indeed has low throughput, maybe 50-100 Kbps, while the basic radios Werner has made can deliver a megabit or better per second.

[edit] What would be the dream that can sell someone who is not a freedom advocate and is just interested in having connectivity? Is it simply so one can gain network connectivity to a hub, aka, get internet?

Connecting to the Internet is one application, although wifi to most people would make a LOT more sense. A more sensible use case is wireless connection between Ben (or any Linux computer) and one or many small. cheap sensor pods, such as Arduinos or similar cheap, low power intelligent units.

Ben has a display and keyboard, and Linux. It can operate as a "super node" talking to some number of dedicated sensor systems. The advantage of Ben is it requires very little power (easily fed by a small solar panel).

Connecting to the Internet is the primary use we have in mind. People who are building devices that need low-power and short-range communication may also find this technology interesting and may find a role for ATBEN/ATUSB.

Likewise, those who already have IEEE 802.15.4 devices may find a role for ATBEN/ATUSB.

We don't know enough about the industrial/sensor sector to venture a guess on whether ATBEN/ATUSB could be popular. There is a fair amount of activity in this area also in the Free Software community, e.g., with the Contiki OS[6]. They also have a list of hardware they support or are at least aware of[7].

[edit] What range can we expect?

The ATBEN/ATUSB prototypes produced good to acceptable BER for a distance between stations of 4-7 meters indoors in a residential area with relatively few interferences. First indoors tests of the production boards yielded an indoors range of 10 m and better.

WPAN is designed for a radius of about 10 m. Some manufacturers of similar chips boast outdoors distances of > 100 m.

Update: a pair of production devices (atben and atusb) could communicate over 10-12 m indoors at the standard rate of 250 kbps. At the non-standard rate of 2 Mbps, the indoors range was still about 5 m.

[edit] How many nanonotes could talk to each other at the same time?

This would mainly depend on the duty cycle of their application. If all they do is send a few bytes of sensor data every few hours, there could be tens of thousands nodes in a PAN. (PAN = Personal Area Network, the equivalent to a single LAN in WiFi terminology.)


[edit] How is this different from WiFi?

IEEE 802.15.4 (Low Rate WPAN) operates in the same frequency band as IEEE 802.11 WLAN/WiFi and IEEE 802.15.1 (Bluetooth) but cannot communicate directly with either.

It differs from WiFi in data rate (lower), typical range (shorter), power consumption (lower), spectral efficiency (better), and transceiver complexity (much simpler). Similarly, data rate and modulation are different from Bluetooth.

The standard data rate of IEEE 802.15.4 is 250 kbps (although non-standard extensions for higher data rates exist), it uses 16 non-overlapping channels in the 2.4 GHz band, and - like the rest of the WPAN technologies - it is designed for a typical range of 10 m using low power, although transceivers with higher power output and thus a longer range are possible.

Protocols layered on top of IEEE 802.15.4, a child of the 3rd millennium, focus on IPv6 instead of IPv4 or the emulation of legacy link layers.

[edit] Why not just make a WiFi Project (since that is what people are using now)?

The trouble with WiFi is that all the "interesting" chips are considered too valuable to give into the hands of the unwashed masses without due precautions. Such precautions include niceties like handing out hardware design documentation only under NDA, keeping register-level interface descriptions under NDA, requiring closed sources firmware, only selling large minimum orders through official channels, and so on.

All this means that such technology is currently incompatible with the goals of copyleft hardware, and would also be expensive to implement or, in the case of using modules instead of chips, severely limit our design choices.

Things will probably improve in the future (e.g., some chips intended for much larger devices than the Ben are already reasonably open), at which time it may be relatively painless to add WiFi compatibility.

IEEE 802.15.4 also has several technical benefits over WiFi, including much lower power requirements and better spectral efficiency. Furthermore, with IEEE 802.15.4 being considerably less complex than WiFi, the possibility to migrate from chips with fixed functionality to an SDR solution is more likely.

IEEE 802.15.4 is used extensively for sensor networks and similar applications, opening the potential of further uses beyond the beaten path. (E.g., applications in Domotics.)

[edit] How is this patent free wireless?

There are probably countless patents surrounding this technology a court would accept as the basis for a lawsuit. Whether these patents are actually valid and apply to the respective use would then either be determined in due time by the legal system, at great cost to both sides, or the defendant yields to the extortion and accepts the terms of the plaintiff, reinforcing the business model of the latter.

While it is thus presently impossible to defend ourselves against patent attacks in general, this risk can be greatly reduced in several ways. Among the technical choices that affect such risks is the use of open standards that are not a current hotbed of patent litigation. An "open standard" means in this context that the specification is publicly accessible without royalties and confidentiality constraints, that it can be implemented without (known) licensing requirements or similar restrictions, and also that suitable hardware (chips, in this case) can be obtained without undue difficulties.

We consider IEEE 802.15.4 to be currently one of the safest wireless technologies in this regard.

[edit] Progress

Wpan-ipv4.ogg
Ben and Ben talking. [3:30 min, 14.9 MB]
(background info: the video was cut using the command-line melt utility from the MTL framework, sound track P97 made with Korg Kaossilator, scripts)

As of mid-April 2011, the hardware design is complete, and several hand-made prototypes of the two boards exist and have been shipped to people who may be willing to test the design. The two board are:

~~ ATBen: plugs into Ben's 8:10 port

~~ ATUsb plugs into a USB port on a Linux computer

Testing by the designer (Werner Almesberger, wpwrak on IRC) has succeeded.

http://Tuxbrain.net in Spain now has the devices available for purchase.

Also, a lot of software work still needs to be done. The driver level code for 802.15.4 has been demo'd. A production test program is working which verifies that a board is not severly compromised.

There are a small number of programs to send and receive data. However, there's still a lot to do in order to have a useable 6LoWpan stack.

[edit] Production Notes

[edit] PCB

As mentioned above, Tuxbrain is leading the production of the first batch assessed by the project leader Werner. PCBs are already done and sent to SMT vendor to perform the integration of components; here are some pics of the PCBs.

[edit] SMT

[edit] Depanelization and Grinding

  1. Numbered list item

[edit] atusb Flashing

Bus 002 Device 055: ID 20b7:1540 Qi Hardware ben-wpan, AT86RF230-based 
Device Descriptor:
 bLength                18
 bDescriptorType         1
 bcdUSB               2.00
 bDeviceClass          255 Vendor Specific Class
 bDeviceSubClass         0 
 bDeviceProtocol         0 
 bMaxPacketSize0        64
 idVendor           0x20b7 Qi Hardware
 idProduct          0x1540 ben-wpan, AT86RF230-based
 bcdDevice            0.01
 iManufacturer           0 
 iProduct                0 
 iSerial                 1 4630333438371501040e
 bNumConfigurations      1
 Configuration Descriptor:
   bLength                 9
   bDescriptorType         2
   wTotalLength           34
   bNumInterfaces          2
   bConfigurationValue     1
   iConfiguration          0 
   bmAttributes         0x80
     (Bus Powered)
   MaxPower               40mA
   Interface Descriptor:
     bLength                 9
     bDescriptorType         4
     bInterfaceNumber        0
     bAlternateSetting       0
     bNumEndpoints           1
     bInterfaceClass       255 Vendor Specific Class
     bInterfaceSubClass      0 
     bInterfaceProtocol      0 
     iInterface              0 
     Endpoint Descriptor:
       bLength                 7
       bDescriptorType         5
       bEndpointAddress     0x81  EP 1 IN
       bmAttributes            2
         Transfer Type            Bulk
         Synch Type               None
         Usage Type               Data
       wMaxPacketSize     0x0040  1x 64 bytes
       bInterval               0
   Interface Descriptor:
     bLength                 9
     bDescriptorType         4
     bInterfaceNumber        1
     bAlternateSetting       0
     bNumEndpoints           0
     bInterfaceClass       254 Application Specific Interface
     bInterfaceSubClass      1 Device Firmware Update
     bInterfaceProtocol      1 
     iInterface              0 
Device Status:     0x0000
 (Bus Powered)

[edit] Production Test

The full production test process is described here: http://downloads.qi-hardware.com/people/werner/wpan/prod/

[edit] First Batch

[edit] Better Picture Galleries

[edit] Outcomes

  • The first batch of Ben WPAN ATBEN and ATUSB devices are available for purchase from certain resellers. See the Shipping Notes page for details.
  • The first batch consists of 120 atusb and 135 atben.

[edit] Future

[edit] Hardware

  • Currently, the units don't have a case. Tuxbrain put sugru on an atusb but it dampened the signal considerably. Then someone got his gadgets for a photo session and we have to wait for them to return before we can see if curing improved the sugru's RF transparency. This needs to be completed for the next batch.
  • The boards are a little tweakable:
    • you can make a one-way modification to add an U.FL connector (not for the faint of heart, but doable)
    • there is an unpopulated capacitor and a 0R resistor that can be used/changed for RF tuning.
  • One could think of adding an RF amplifier, to extend the range (significant new work at ~2 more chips, and so on)
  • Also, the transceiver supports antenna diversity, which could be interesting for utilizing.
  • There's also one competing chip that could be interesting to try in a future batch. That one has an internal balun, reducing the component count. But of course, totally incompatible in terms of layout and low-level driver, so would require significant work.

[edit] Software

[edit] Beyond Ben WPAN First Batch

  • Until we have a case defined, the software is fully plug-and-play and atusb is supported on kernel main line, the market for the Ben WPAN units is hackers and Nanonote owners.
  • Seek sponsors and improve the units
  • Increase users of the device
  • Get feedback and plans for second batch
  • Investigate if the devices need certification

[edit] HOWTO Get Involved

[edit] See Werner's Development page

[edit] Qi Hardware Community


  1. http://en.wikipedia.org/wiki/Wireless_personal_area_network
  2. http://en.wikipedia.org/wiki/6loWPAN
  3. http://tools.ietf.org/html/bcp79
  4. https://datatracker.ietf.org/ipr/search/?option=rfc_search&rfc_search=4944
  5. http://en.wikipedia.org/wiki/History_of_Free_Software
  6. http://www.sics.se/contiki/
  7. http://www.sics.se/contiki/wiki/index.php/Hardware_Specific_Guides
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