6LoWPAN vs Bluetooth LE

This is a complex debate and usually comes down to the exact requirements of you system which pick out a clear winner. There are a number of points to consider here:

1. The router/bridge/gateway HW (i.e. the thing that connects your device to the Internet router). For BLE this can be very simple and require no HW, it can be your smartphone as it has IP/WiFi connectivity and BLE. You need a dedicated box for 6LowPAN, of cause you can also use a dedicated box for BLE. So here is the first effort, you need to develop (or buy) a dedicated piece of HW for a 6LowPan "Boarder Router" to connect the 802.15.4 MAC/Phy to a WiFi or Enet MAC/Phy, for BLE this can be the SmartPhone that everyone already has in their pocket. For the 6LowPan boarder router there is open source HW and SW available.

2. The router/bridge/gw SW. For BLE (regardless if this is a smartphone App, or app on bridge HW) you need to develop some SW to transfer data from BLE to IP and to map BLE "addresses" to IP (if needed). For 6LowPan this becomes simpler, the devices already have their own IP address, so you just need to bridge the MAC/Phy. The other point here to consider is what you are connecting to in the internet. You may not need an IP address for each device (just an IP address for the bridge). Most of the time you just need a global unique ID (guid), which could be the MAC address.

3. Anther point is that BLE is single hop, so if your devices are out of radio range of the bridge there is nothing you can do. In 6lowPan you can add router and form a mesh network.

If you can live with the SmartPhone as the bridge and single hop then BLE is probably the way as there is a lot of effort in developing a GW. If not then effort in developing GW SW is probably simpler of for 6LowPan and there is an open source solution provided in Contiki (see processors.wiki.ti.com/.../Contiki-6LOWPAN), meaning there is little effort needed on the SW.

While you are considering this, ZigBee may be another option. This also requires a bridge, and the SW on that bridge is more complex than BLE or 6LowPan, but you benefit from off the shelf ZigBee devices, so all the effort is on the bridge. TI has a reference for such a bridge at www.ti.com/.../CC2531EM-IOT-HOME-GATEWAY-RD.

Regards, TC.

Thank you that is very useful information.

Furthermore, I have read that in a star topology, one BLE master can simultaneously communicate with 7 other BLE slaves. How many slaves can a single 6LoWPAN/ZigBee master simultaneously communicate with within a star topology?

For Zigbee, the default simultaneously communication is 20 in TI Z-Stack and it is configurable. I had configured it to 60.

You say you've configured the Z-Stack to 60 simultaneous communications. Is that the maximum limit? Can the BLE stack be configured to simultaneous communications to more than 7?

However, back to the IP debate. You mentioned that consideration should be made with what you are connecting to in the internet. So my question, in what situation will I need an IP address for each device and in what circumstance can I just use an IP address for the bridge that the wireless devices are connected to?

No, 60 is not the max limit. It can be even more. For BLE, it can't be more than 7 and it is majorly because of RAM and flash constrains. If you want to do P2P connection, a specific IP is better than no.

So, just to be clear. If I need one device from one network to communicate with another device from another network over the internet then 6LoWPAN is the best use case? However, if I know that the only time two devices will need to communicate with one another is when they are both under the same network then that means I would only need a single router for the entire network if I want internet access. In this case, BLE is best ?

For BLE, can virtually an unlimited amout of slaves stay connected to the master if I used the GTS protocol to transmit information from each slave within a predefined time slot?

I don't think this gonna work.

Why don't you think it will work? Is that not how TDMA works?

I don't think unlimited amout of slaves stay connected to the master is possible.

I mean theoretically connected or basically more than 7. Or does in order to use TDMA the BLE slaves already have to be connected and the master just collects data from them only at specific time intervals?

Andrew Butler said:

For BLE, can virtually an unlimited amout of slaves stay connected to the master if I used the GTS protocol to transmit information from each slave within a predefined time slot?

You should raise this BLE specific question in the BLE Forum: 

Regards, TC.