CC2650EM-5XD-RD: End device behavior?

1. When ZED loses connection with its parent and cannot find a new parent node to rejoin, it will turn into orphan state.
2. ZED shouldn't send leave automatically.

When ZED loses connection with its parent?

Yes. ZED should do polling to its parent and if there is no ack of polling, it will turn to orphan state.

so ZED send mac data request to keep the connection alive and polls for mac ack from parent.
1) for how much it waits for mac ack ?
2) how many times ZED retries sending mac frames?
3) how to change these parameters in z-stack??

1. If I remember correctly ZED would open RX several mili-seconds for MAC ack.
2&3 It's defined by MAX_POLL_FAILURE_RETRIES in f8wconfig.cfg.

ZED would open RX several mili-seconds for MAC ack.>

/* The number of milliseconds to wait between data request polls to the coordinator. */
-DPOLL_RATE=1000

is this the correct parameter w.r.t your above statement.

POLL_RATE is nothing to do with the RX open duration after ZED sends data request.

which variable is used to defined RX open duration and where it is defined?

It is controlled by Z-Stack library and you cannot change it. Why do you have to do so?

ZED are entering into ORPHAN state and then rejoining frequently ....so i want to prevent the ZED to enter into ORPHAN state

you are suggesting to do per test or any other method is there to check RF performance

PER test is usually the latest steps we use to check RF performance. In general, we would use spectrum analyzer to check TX power and RX sensitivity first.