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

[ovrebekk]

In the proprietary mode there are very few limitations. You can do any type of network topology, and in theory you can support as many nodes as the 40-bit address allows (within reason of course, the available bandwidth and number of channels limit how many nodes can communicate simultaneously).

It is true that a single radio can only transmit or receive on one frequency at the time. The beacon device will typically have to dedicate timeslots to the different channels. For instance you can send a beacon on channel 1, switch to receive and receive packets from all the nodes on channel 1. Then you switch to channel 2, send a beacon, receive packets, switch to channel 3 and so forth... As long as the interval between each beacon remains fixed the sensor nodes will know that if they miss the beacon on one channel they can switch to the next channel in the list and try to get that beacon.