RSSI and RSRP on THINGY.91

[Hoang]

Dear, 

Im trying to measure the RSSI with THINGY:91, I found on the document  nrf91_at_commands_v1.1.pdf about

1. AT+CSQ

      +CSQ: <rssi>,<ber>

Note: Not detectable, RAT not supported. Use +CESQ and %CESQ for E-UTRA signal quality.

2. AT + CESQ 

    +CESQ: <rxlev>,<ber>,<rscp>,<ecno>,<rsrq>,<rsrp>

<rsrp>
0 – RSRP < −140 dBm
1 – When −140 dBm ≤ RSRP < −139 dBm
2 – When −139 dBm ≤ RSRP < −138 dBm
...
95 – When −46 dBm ≤ RSRP < −45 dBm
96 – When −45 dBm ≤ RSRP < −44 dBm
97 – When −44 dBm ≤ RSRP
255 – Not known or not detectable

I am using AT+CESQ to find RSRP 

and, i found some document about RSRP range: 

https://wiki.teltonika.lt/view/RSRP_and_RSRQ

But, when I tested to measure it, i got: 

I set the devices (3) in my freezer, and got the RSRP < -100dBm, 

is it conflict here? On the document, they say: NO signal when RSRP < -100dBm, but, I measured -120dBm, and I still received the data from my THINGY:91 - it means : still signal 

I am using Telia NB-IOT( Unit1) Telia LTE-M(Unit2) and Telenor LTE-M(Unit3)

My question is: RSRP vs Signal strength range? RSRP for no signal?

Thanks 

BR, 

Hoang Nguyen

[Hakon]

Hello,

receiver sensitivity for Cat-M1 is -108 dBm and -107 dBm for low band and mid band respectively. For Cat-NB1/Cat-NB2 it's -114 and -113 dBm. It makes sense that you'll still receive something when the RSRP is close to -100 dBm.

[Hoang]

Dear Hakon

I am using THING:91 with NB-IoT of Telia (Norway)  to measure the temperature, .., RSRP, and send the data to my webserver.

It will send 1 package in each hour. and its staying underground, and I got the data from my thingy:91 (RSRP) 

My problem: when the signal is bad (RSRP < -130 dBM), it stopped working and couldnt reconnect at kl.19.24. 

At kl.13.20 , it did NOT send any package (because of bad signal), then, it sent again 14.23. 

My statemachine: 

 My main: 

void main(void)
{
      
     
      env_sensors_init();
      env_sensors_start_polling();
      battery_monitor_init();
      printk("modem_configure\n");
      modem_configure();
  
      while(1){
                                     
             
              
                printk("-----------------------\n\r");
                sensor_data_read();
                ENCR_HTTP_POST();
                k_sleep(DELAYPOST); 
            
               
        
       
      }

}

Connecting: modem_configure(); 

Read the temperature,battery,.., RSRP: sensor_data_read()

encrypted and send  (HTTP_POST): ENCR_HTTP_POST

sleep: 1hr

When the THINGY:91 stays underground, the signal is so bad ( RSRP = -130 dBm), and the worst case, NO signal, then, it couldnt POST (HTTP _POST), it will return ERROR, and I tried to reconnect:

void ENCR_HTTP_POST (void){
//FPOST: postData
int err = snprintk_post(FPost,HTTP_HOST,HTTP_PORT);
            
            if(!err){
                
                printk("done http post \n\r");
            }
            else {
                printk("httppost is error \n\r");
                 goto reconnect; 
            }
         return ; 
reconnect: 
      printk("reconnect network .......\n\r");
      reconnect_nw();
      //modem_configure(); 
     
}

my reconnect_nw() (similar to modem_configure()) 

void reconnect_nw(void){
                
                int err;
		printk("ReConnecting to LTE network. ");
		printk("This may take several minutes.\n");
		//ui_led_set_pattern(UI_LTE_CONNECTING);

		err = lte_lc_init_and_connect();
		if (err) {
			printk("LTE link could not be established.\n");
                        error_handler(ERROR_LTE_LC, err);
			
		}

		printk("Connected to LTE network\n");
}

and, my snprintk_post(): ( I m using http post from : https://github.com/Rallare/fw-nrfconnect-nrf/blob/nrf9160_samples/samples/nrf9160/https_simple/src/main.c is it your? )

int snprintk_post (char *PostString, char *HTTP_HOST, int HTTP_PORT)
{
     
   int poststat = '0';
   struct sockaddr_in local_addr;
   struct addrinfo *res;
   printk("Webserver: http://%s:%d \n\r",HTTP_HOST,HTTP_PORT); 

   local_addr.sin_family = AF_INET;
   local_addr.sin_port = htons(0);
   local_addr.sin_addr.s_addr = 0;
 
    int err = getaddrinfo(HTTP_HOST, NULL, NULL, &res);
    printk("get addrinfo\n\r");
    printk("getaddrinfo err: %d\n\r", err);
    
    if(!err) {
       printk("network is OK: \n\r");
    }

    else {
         printk("network is error: \n\r");
         return CONFIG_LTE_ERR ; 
    }
    
    ((struct sockaddr_in *)res->ai_addr)->sin_port = htons(HTTP_PORT);
    
   
    char send_buf[MAXLINE + 1];
    int send_data_len_post  = snprintk(send_buf,
				         500, 
				         POST_TEMPLATE, HTTP_PATH,
				         HTTP_HOST, strlen(PostString),
				         PostString);

     printf("send_buf is: %s \n",send_buf);
     printk("send_data_len_post: %d\n\r", send_data_len_post);
     
     int client_fd = socket(AF_INET, SOCK_STREAM, 0);

     printk("client_fd: %d\n\r", client_fd);
     err = bind(client_fd, (struct sockaddr *)&local_addr, sizeof(local_addr));
     printk("bind err: %d\n\r", err);
     if(!err )
        {
          printk("bindnetwork is OK: \n\r");
          
         }
     else
        {
          printk("network is error: \n\r");
          return CONFIG_LTE_ERR ; 
         }
    

    
     //err = blocking_connect(client_fd, (struct sockaddr *)res->ai_addr,sizeof(struct sockaddr_in));

      err = connect(client_fd, (struct sockaddr *)res->ai_addr, sizeof(struct sockaddr_in));
	if (err > 0) {
		printk("connect err: %d\n", errno);
		goto clean_up;
	}
     //err = blocking_connect(client_fd, (struct sockaddr *)res->ai_addr,sizeof(struct sockaddr_in));
     printk("connect err: %d\n\r", err);
     
     int num_bytes = send(client_fd, send_buf, send_data_len_post, 0);
    
     printk("send err: %d\n\r", num_bytes);
     
     
     printk("Close socket \n\r");
     err = close(client_fd);
     
     freeaddrinfo(res);
     printk("============================== DONE SENDING =============================================== \n\r");
    
     return 0; 
     
clean_up:
	freeaddrinfo(res);
	err = close(client_fd);
        
}

Could you plz help me. I dont know why, it stopped working. 

 I tested it many times before I put it underground ( try to put it in the freezer, ..., somewhere with bad signal), and it worked

Thanks so much 

MVH, 

Hoang Nguyen 

[Hoang]

Thanks for suggestion, i will try it later

[Hoang]

Dear Hakon, 

Hakon said:

NVIC_SystemReset

I tried NVIC_SystemReset(), after modem_configure(), 1time, then, my THINGY:91 has a problem: 

Connecting to LTE network. This may take several minutes.
[00:00:28.564,514] [1B][0m<dbg> lte_lc.at_handler: recv: +CEREG: 2,"9D6D","0125DF64",9
[1B][0m
[00:00:32.653,900] [1B][0m<dbg> lte_lc.at_handler: recv: +CEREG: 4,"9D6D","0125DF64",9
[1B][0m
[00:01:31.799,346] [1B][0m<dbg> lte_lc.at_handler: recv: +CEREG: 4,"FFFE","FFFFFFFF",9
[1B][0m
[00:01:58.508,422] [1B][0m<dbg> lte_lc.at_handler: recv: +CEREG: 2,"0C98","01FEC912",9
[1B][0m
[00:02:25.204,986] [1B][0m<dbg> lte_lc.at_handler: recv: +CEREG: 2,"FFFE","FFFFFFFF",9
[1B][0m

It couldnt do anything else now, just stuck here. Could you plz tell me why?

I want to reset my THINGY:91. 

Mvh

Hoang 

[Hakon]

Ok, try setting CONFIG_REBOOT=y in .conf and try again.

[Hoang]

I had this setting when I ran it

[Hakon]

Try sys_reboot(SYS_REBOOT_COLD) instead then. See if that works.