How can I build Wireless sensor network using nRF51422

[Alok]

I have about 200-300 sensors, each requiring to send data at around 0.5-1Kbps to a central node (coordinator/master node), what will be the network configuration/topology using nRF51422 (or any other better suited Nordic IC) to send the data of all the sensors to the central node?

[ovrebekk]

Hi

If you want to support this many sensors sending that much data you need to implement some kind of timeslot mechanism, where each sensor gets a unique time in which to send data to the central node.

One way to do this is to have the central node send a beacon packet to all the sensors at a regular interval. Each sensor will have to be configured with a unique ID, and based on this ID each sensor can calculate a unique timeslot some time after the beacon packet was received. The central node will then switch to receive mode to pick up all the packets from the various sensors.

The beacon packet from the central node will have to be broadcast to all the sensors (ACK's disabled), while the packets sent from the sensors to the central could have ACK's enabled.

You probably want to use the micro ESB library as a basis, since it introduces less overhead than the standard ESB library available in the SDK:
https://github.com/NordicSemiconductor/nrf51-micro-esb

Bets regards
Torbjørn

[Alok]

Thanks for your reply, it makes sense however the clocks of all the nodes are not synchronized in such case each node will transmit in their time slot but it will calculate its time slot based on the local clock, will this not cause problem in synchronization? Secondly which radio (BLE or ANT) should the sensor node use for transmission so that all 300 nodes (@ ~0.5-1kbps rate) can successfully able to send their respective data to the central node. What I know is that BLE supports star topology with 1 Master and 7 slaves only (network size limited) and ANT has max. of 20Kbps in burst mode (throughput limited). Thanks.