Using 51822 with BLE stack, I was faced with the problem of low transfer rates (5kb) on my android device (phone). It is very slow.
Can work 51822 with standart Bluetooth (not BLE)?
note also, to get those rates you will need to set the MIN_CONN_INTERVAL and MAX_CONN_INTERVAL to something smaller than the defaults they use in the sample apps. I've used SECOND_1_25_MS_UNITS / 20 for example, to get a nice steady stream of events from my device to my phone. The defaults are set to 1/2 a second which makes for a very low bandwidth indeed.
Yes, connection parameters will significantly affect the throughput. Take a a look at this question for details on what connection parameters are:
PS: In the latest SDKs, there is a nice macro you can use instead of the SECOND_1_25_MS_UNITS define, to set the intervals like this if you want 7.5 ms: