Mesh range, power and mode

[Damien Berger]

Hi, 

In this topic, i was asking about how to increase range in mesh networks. I did some outdoors tests (clear field), changing power (-40, +4, +8 dBm) and mode (1MB and Long Range). Here are my results using light switch example:

nRF52832 / 1MB / +4dBm : ~420 m

nRF52840 / 1MB / +8dBm : ~420 m                                       nRF52840 / 1MB / -40dBm : ~1.3 m

nRF52840 / LR / +8dBm    : ~422 m                                       nRF52840 / LR / -40dBm    : ~1.5 m

It seems that my implementation of the "+8dBm" (which is not defined in Nordic mesh examples) is not correct since i got the same range. I just added a line in the typedef enum "radio_tx_power_t" in radio_config.h. Do i have to do something more to make it work ? What did i miss ? 

/**
 * @brief The tx power configuration values.
 *
 * @note NRF52 does not have -30DBm setting, instead it can be configured to -40DBm,
 * the value of -40DBm and -30DBm are kept the same for code compatibility.
 */
typedef enum
{
    RADIO_POWER_NRF_POS8DBM  = 0x08,
    RADIO_POWER_NRF_POS4DBM  = 0x04,
#ifdef NRF52_SERIES
    RADIO_POWER_NRF_POS3DBM  = 0x03,
#endif
    RADIO_POWER_NRF_0DBM     = 0x00,
    RADIO_POWER_NRF_NEG4DBM  = 0xFC,
    RADIO_POWER_NRF_NEG8DBM  = 0xF8,
    RADIO_POWER_NRF_NEG12DBM = 0xF4,
    RADIO_POWER_NRF_NEG16DBM = 0xF0,
    RADIO_POWER_NRF_NEG20DBM = 0xEC,
    RADIO_POWER_NRF_NEG30DBM = 0xD8,
#ifdef NRF52_SERIES
    RADIO_POWER_NRF_NEG40DBM = 0xD8
#endif
} radio_tx_power_t;

Then, about Long Range, i followed all the steps defined in this thread and the increase in range is really small (about 2 meters out of 420m in +8dBm and 0,20m at -40dBm). 
Could we not expect better results with long range ? Would the difference be greater in indoors environment (I will test this soon, but I think I am missing something when I see my results...).

[Susheel Nuguru]

Hi Damien,

Do you know that LR is not part of the Mesh spec and if you use this feature in your product, you will not be able to qualify it ?

The thread where Hung Bui gave a solution is very experimental and is not intended to be used in final products.

There are many other conventions that the Mesh stack assumes and I am not sure if every aspect of long range is taken into account here. 

Since using LR with Mesh is out of our offering for now, I would not be able to spend time to assist in that. But, i would like to know why changing TX power from 4dBm to 8dBm had no effect. 

Can you attach part of your code where you are changing the tx power

[Damien Berger]

Thank you i did not realize that it was not part of the mesh spec.
I completely understand if you can't assist us on this point.

Regarding the +8dBm, i added the line "  RADIO_POWER_NRF_POS8DBM = 0x08," in the typedef definition as i showed before. Then i changed the tx_power in this function in advertiser.c:

static inline void set_default_broadcast_configuration(broadcast_t * p_broadcast)
{
    p_broadcast->params.access_address = BEARER_ACCESS_ADDR_DEFAULT;
    p_broadcast->params.radio_config.payload_maxlen = RADIO_CONFIG_ADV_MAX_PAYLOAD_SIZE;
    p_broadcast->params.radio_config.radio_mode = RADIO_MODE_BLE_1MBIT;
    p_broadcast->params.radio_config.tx_power = RADIO_POWER_NRF_POS8DBM;
}

and in this funcion in scanner.c:

void scanner_init(bearer_event_flag_callback_t packet_process_cb)
{
    memset(&m_scanner, 0, sizeof(m_scanner));

    packet_buffer_init(&m_scanner.packet_buffer, m_scanner.packet_buffer_data, SCANNER_BUFFER_SIZE);
    scanner_config_reset();
    m_scanner.config.radio_config.tx_power = RADIO_POWER_NRF_POS8DBM;
    m_scanner.config.radio_config.payload_maxlen = RADIO_CONFIG_ADV_MAX_PAYLOAD_SIZE;
    m_scanner.timer_window_end.cb = scan_window_end;
    m_scanner.timer_window_start.cb = scan_window_start;
    m_scanner.state = SCANNER_STATE_IDLE;
    m_scanner.window_state = SCAN_WINDOW_STATE_ON;
    m_scanner.nrf_mesh_process_flag = bearer_event_flag_add(packet_process_cb);
}

That's all, and when i change this two lines with "RADIO_POWER_NRF_NEG40DBM" it clearly works since the range is reduced to something like 1 meter.

[Susheel Nuguru]

There seems to be a lot of places where i see RADIO_POWER_NRF_0DBM is hardcoded into the tx_power setting.Just to make sure can you set the tx power in radio_config.c file radio_config_config() function and set directly NRF_RADIO->TXPOWER =  RADIO_POWER_NRF_POS8DBM 

I am still wondering which version of the chip you are using for nRF52840

 

[Damien Berger]

I am using nRF52840 Rev1 sorry.
Yes i can try with this setting if you think it would work but i would be strange since it works with -40dBm, isn't it ?

[Susheel Nuguru]

it would mean that there is a bug in mesh code somewhere if my proposed patch works.