BLE long range (coded phy) is same than 1MBit

[RichardHdrd]

Dear Community,

I implemented the beacon-example with S112 and 1MBit mode and with S140 and coded-phy 125k sending one beacon per second continuously at +0dBm (sd_ble_gap_tx_power_set).

I implemented a BLE scanner with S140 and choice of 1MBit and coded-phy 125k mode reception, the latter using the cfg:

static ble_gap_scan_params_t const m_scan_param_coded_phy =
{
    .extended       = 1,
    .active        = 0x00,
    .interval      = NRF_BLE_SCAN_SCAN_INTERVAL,
    .window        = NRF_BLE_SCAN_SCAN_WINDOW,
    .timeout       = NRF_BLE_SCAN_SCAN_DURATION, // No timeout.
    .scan_phys     = BLE_GAP_PHY_CODED,
    .filter_policy = BLE_GAP_SCAN_FP_ACCEPT_ALL,
};

Now performing tests, I get similar results for both, 1MBit and coded-phy 125k mode.

As I can well understand, that the RSSI values don't differ as there is no difference in expected transmission/reception signal strength, I do not understand, why devices in both modes stop detecting beacons at an RSSI value of about -92dBm.

The vendor (FANSTEL) states for the BM833(A) module which uses a nordic 52811 chip:

BLE Sensitivity is increased to -97 dBm at 1Mbps and -104 dBm at 125 kbps with CODED PHY.

So is there any reason, why reception stops at RSSI -92dBm, especially for coded-phy mode?

Best regards,

Richard

[RichardHdrd]

Hi,

So, when my RSSI measures are OK, I still wonder, why I get only about 30m range (40m when measuring outside) for BLE coded-phy. Is there any visible reason for that behaviour; how important is a clear line of sight when dealing with bluetooth?

Best regards,

Richard

[Sigurd]

RichardHdrd said:

how important is a clear line of sight when dealing with bluetooth?

 It depends on the environment, but if you are trying to get 100 meters+ with range, then line of sight is pretty important.

From this page, "Path loss, or path attenuation, occurs naturally over distance and is impacted by the environment in which the signal is being transmitted. Obstacles between the transmitter and the receiver can deteriorate the signal. Attenuators can be anything from humidity and precipitation, to walls, windows, and other obstacles made of glass, wood, metal, or concrete, including metal towers or panels that reflect and scatter radio waves. While radio waves can pass through objects, the amount of attenuation and effective path loss varies with the type and density of the obstruction."