1. Test purpose
The packet error ratio (PER) is the number of incorrectly received data packets divided by the total number of received packets. A packet is declared incorrect if at least one bit is erroneous.
A PER of 0% indicates that all packed transmitted are received, while a PER of 100% indicates that all packed transmitted are lost.
In this flow, a transmitter and a receiver are used. AT commands are sent to transmitter and receiver, then ratio of correct packet received vs packet transmitted is used for PER calculation. In the same time RSSI (Received Signal Strength Indication) and SNR (Signal Noise Ratio) are calculated.
2. Explaining the dashboard
The PER dashboard is divided in four groups: The group Lora PER test Parameters, where all parameters regarding configuration are located. The group Lora PER test Results where results, RSSI, SNR, PER and a table are showed. The group Lora PER Multiple frequencies where user can set the range and step of frequencies on which PER is calculated. The group Lora PER Single frequency where user can set the frequency on which PER is calculated in number of repetition of this test.
Groups “Lora PER Multiple frequencies” and “Lora PER Single frequency” are displayed according to the state of the switch named “Multiple Frequencies” (in group Parameters).
With Group Lora PER test Parameters user is able to :
- set the RF Frequency
- set the bandwidth (7.8125, 15.625, 31.25, 62.5, 125, 250 or 500 kHz)
- set the spreading factor (from 5 to 12)
- set the coding rate (4/5, 4/6, 4/7 or 4/8)
- set the TX power (from -9 to 22)
- set the number of frame sent (from 1 to 10)
- choose “multiple” or “single” frequency test
- see the connected status (red or green); Green status indicates that emitter and receiver boards are connected. Red status indicates that at least one one board is not connected.
- launch the test (if connected status is green).
With Group FSK PER test Parameters user is able to :
- set the RF Frequency
- set the bandwidth (from 4800 to 467000 Hz)
- set the spreading factor (from 600 to 300000 bits/s))
- set the TX power (from -9 to 22)
- set the number of frame sent (from 1 to 10)
- choose “multiple” or “single” frequency test
- see the connected status (red or green); Green status indicates that emitter and receiver boards are connected. Red status indicates that at least one one board is not connected.
- launch the test (if connected status is green).
With group Lora PER Multiple frequencies user is able to :
- set the “start PER frequency”
- set the “max PER frequency”
- set the “step frequency”
3. Explaining the flow
The emitter must be connected to Serial Port A. The receiver must be connected to Serial Port B.
The flow is divided in four majors parts.
The part “Initialization parameters” provides a default configuration to the user. This part allows to display dynamically groups “multiple frequencies” or “Single frequency” according to the state of switch “Multiple Frequencies”.
The part “Board Connection management” ensures that emitter and receiver board are connected to the PC. If yes, then user is able to launch the test. If not, the “LED” stays red, indicating that emitter, receiver or both are not connected to the PC. A simple FSM (Finite State Machine) node is used to that purpose.
The part “Frequency management” is used to handle the two modes of testing : Multiple frequencies or Single frequency. The FSM node manage the launch of basic PER test with the right frequency. The main function “RunNoRun” allow to continue or stop the test sequence, according to the test mode.
The part “PER Test Management” handles the launch of a basic PER test by launching a sequence of AT command to emitter and receiver boards. This group allow to collect and displays results in the dashboard.
4. AT commands for PER estimation
AT commands listed below are sent to emitter and receiver
4.1. Emitter :
ATZ Reset
AT+TCONF=freq:pow:bw:sf:cr:lna:pa:modulation:payloadLen:fskDeviation:lowDrOpt:BTproduct. Sets the configuration for RF test. For example : AT+TCONF=868000000:14:4:12:4/5:0:0:1:16:25000:2:3
AT+TTX[=nb_packets_sent] Sets the number of packets to be sent for PER Tx LoRa test.
4.2. Receiver:
AT+Z Reset
AT+TCONF=freq:pow:bw:sf:cr:lna:pa:modulation:payloadLen:fskDeviation:lowDrOpt:BTproduct. Sets the configuration for RF test. For example : AT+TCONF=868000000:14:4:12:4/5:0:0:1:16:25000:2:3
AT+TRX [=nb_packets_received] Sets the number of packets to be received for PER Tx LoRa test.