ultra short range BLE

[Eric24]

We're working on an application that needs ultra-short range BLE, on the order of 50cm radius or less. I've found little discussion anywhere on that topic, likely because most applications are looking for the longest possible BLE range. The issue we have is that there will be dozens or possible a few hundred beacons in the same general area, with spacing as little as 1m between beacons, while my receiver (a typical smartphone) needs to pick up only on the beacon that the user is standing right next to. Using RSSI hasn't been good, due to the orientation of the user's body causing attenuation and making the nearest beacon appear to be the "next nearest", for example.

If anyone has any thoughts on this topic or links that you are aware of that explore this, possibly with custom directional antenna, etc., I'd be grateful.

[Mike S]

Hi, I found the Laird Tech module with integrated chip antenna has very low RF output power. This was not useful for me so I have switched to another module on Nordic's list. But, it might be useful for your application.

[chalecampb]

Try infocenter.nordicsemi.com/.../group___b_l_e___g_a_p___f_u_n_c_t_i_o_n_s.html

Have you tried setting the output power to the minimum? The default is 0, and ranges from -30 to 4.

If you select a module with a trace antenna, it will generally be lower than with a chip antenna.

It will still be difficult unless you are relaying known positions (eg, from an IMU located on the device).