1. Need to have a good understanding Bluetooth Basics

• Bluetooth HCI commands, events
• Simple secured pairing 
• GAP command formats for discoverable mode, end discoverable mode, establish link
• Power saving modes

2. Bluetooth low energy specs 4.0

• BLE roles (peripheral, broadcaster, Central and about possible combinations of these roles)
• Good understanding on connection interval, supervision timeout, slave latency etc (Connection parameters)
• Gatt profile , How to simulate classic profile using the existing profiles
• GATT profile apis like Gatt_notification, Gatt_indications, gatt_addservice, GATT_Displayservices

3. Bluetooth tools.

• Sniffers like frontline analyzer (any one sniffer tool ), Ellisys Bluetooth Analyzer.
• RF studio (Very much needed)
• HCI Tool

4. Communication protocols like SPI, USART, USB

5. Should be able to quickly understand FW requirements like transmission/reception of continuous signal modulated/unmodulated, channel selection, packet transmission/reception.  (EMC tests for HW team), production test modes.

6. BT Tool, bluetooth lowenergy PC applications