How to achieve 2Mbps data rate?

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Int the website:

link text

FEATURES show the nordice nRF51822 has 3 data rates (2Mbps/1Mbps/250kbps).

But , I set

number of packets transmitted per connection event 20

Connection interval 7.5

I can't achieve 2Mbps throughput ?

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How can I obtain/get the BLE with “proprietary protocol” ?

Does the BLE with 1Mbps/0.25Mbps data rates also need to use “proprietary protocol” ?