Strange RSSI beviour

Gabriel_1231 · February 26, 2020, 10:26pm

Hello

I have noticed a strange RSSI behaviour during a range test. I was usuing the pingpong example from https://github.com/HelTecAutomation/ASR650x-Arduino/blob/master/libraries/LoRa/examples/LoRaBasic/pingpong/pingpong.ino

With +22dbm setup, SF12 and standard antenna I was able to get over 1.5km line of sight with a RSSI of -89 to -92.

I went 50m more away and suddendly it was not possible to get a signal anymore. Is there a possibility to improve the sensitivity of the CubeCell board?

According to the Semtech SX1262 datasheet the sensitivity does down to -148 dBm.

Best regards

Gabriel_1231 · February 27, 2020, 7:35pm

Do you have any ideas?

Aaron · February 28, 2020, 10:19am

Indeed I still don’t fully understand the mechanism of RSSI calculation… please refer to this code from the original Semtech LoRaMac-Node code:

github.com

Lora-net/LoRaMac-node/blob/develop/src/radio/sx1276/sx1276.c

/*!
 * \file      sx1276.c
 *
 * \brief     SX1276 driver implementation
 *
 * \copyright Revised BSD License, see section \ref LICENSE.
 *
 * \code
 *                ______                              _
 *               / _____)             _              | |
 *              ( (____  _____ ____ _| |_ _____  ____| |__
 *               \____ \| ___ |    (_   _) ___ |/ ___)  _ \
 *               _____) ) ____| | | || |_| ____( (___| | | |
 *              (______/|_____)_|_|_| \__)_____)\____)_| |_|
 *              (C)2013-2017 Semtech
 *
 * \endcode
 *
 * \author    Miguel Luis ( Semtech )
 *

This file has been truncated. show original

Here, it’s fixed by software… I don’t know how and why, so I just refer it.

I believe is a software problem, the communication distance is correct. you need place one node on a higher place.

As we tested with gateway (470~510MHz CubeCell and HT-M02 gateway), in CN470-510 band, the node’s maximum output power should lower than 17dB, in this situation, maximum distance is 4.5Km.

Gabriel_1231 · February 29, 2020, 11:33pm

Hello Aaron

I don’t use a gateway, I just operate with two CubeCell boards. Are the 4.5km in LOS conditions or through buildings?

Best regards

Aaron · March 6, 2020, 10:45am

Hi, sorry for my poor English, is the LOS conditions means open area?

Yes, we tested in open area. If without a high gain PA/FEM, I think no normal LoRa node device can reach 4.5Km through many buildings.

johnarnoldbrown · March 6, 2020, 11:54am

Line Of Sight…