Difference between revisions of "RSS measurement"

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(Understanding the Code)
(Understanding the Code)
 
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== Introduction ==
 
== Introduction ==
  
This tutorial helps you to understand how to measure Radio Signal Strength (RSS) received by a Tmote Sky. In this tutorial we have one sender and one receiver. Receiver receives the packet and display the RSS value of the packet received.
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Radio Signal Strength (RSS) refers to the transmitter power output as received by a reference antenna (i.e. receiver) placed at a distance from the transmitting antenna.
  
You can find the step by step simulation in the next section "RSS Measurement Program on Cooja" and you can find the C code in the subsequent section.
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In this tutorial, we will learn how to measure the Radio Signal Strength received by a Tmote Sky module. The tutorial has two nodes, a transmitter and a receiver. The receiver node continuously receives packets from the transmitting node, measures its signal strength and displays the RSS value of the packet received.
  
 +
A step-by-step description of the simulation process and the C source code can be found in the subsequent sections.
  
== RSS Measurement Program on Cooja ==
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== RSS Measurement using Cooja Simulator ==
  
 
=== Step 1 ===
 
=== Step 1 ===
Create New Simulation on Cooja. Let's say we call our simulation as "RSS".
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Run 'ant' to start Cooja. Create New Simulation and let us say we name our simulation as "RSS".
  
  
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=== Step 2 ===
 
=== Step 2 ===
Create Motes.
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Add motes to the simulation. Go to Motes-> Add motes-> Create a new mote type-> and select Sky Mote to be added to the network.
  
  
 
[[File:RSS_2.png|center|800px]]
 
[[File:RSS_2.png|center|800px]]
  
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=== Step 3 ===
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Browse and select the firmware.
  
 
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'''Note''': You have to create a .c file for RSS measurement and the source code can be found in the next section.
=== Step 3 ===
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Browse the firmware.
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Note: You can find the code later in this tutorial.
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=== Step 4 ===
 
=== Step 4 ===
 
Compile the firmware.
 
Compile the firmware.
 
  
 
[[File:RSS_4.png|center|800px]]
 
[[File:RSS_4.png|center|800px]]
  
 +
=== Step 5 ===
 +
Select the number of motes required in the network. You may select any number of motes but for simplicity we are considering only 2 motes.
  
 
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'''Note''': We are uploading the same firmware on both the motes, one acting as Transmitter and the other as Receiver.
=== Step 5 ===
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Select number of new motes=2.
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Note: We are uploading same firmware on both the motes. One will act as Sender and another will act as Receiver.
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[[File:RSS_5.png|center|800px]]
 
[[File:RSS_5.png|center|800px]]
 
 
  
 
=== Step 6 ===
 
=== Step 6 ===
 
Start the simulation.
 
Start the simulation.
 
  
 
[[File:RSS_6.png|center|800px]]
 
[[File:RSS_6.png|center|800px]]
  
 +
=== Step 7 ===
 +
The 'Mote Output' window gives real time information of the events occurring in the simulation process.
  
 
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You can see the RSSI values for every packet received in the mote output window. These values are in '''dBm'''.
=== Step 7 ===
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You can see the RSSI value in the mote output window. These RSSI values are in '''dBm'''.
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[[File:RSS_7.png|center|800px]]
 
[[File:RSS_7.png|center|800px]]
  
== Code ==
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== Source Code ==
  
 
  <code><nowiki>
 
  <code><nowiki>
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== Understanding the Code ==
 
== Understanding the Code ==
  
::<code>1-static const struct collect_callbacks callbacks = { recv };</code>
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The functions of some code snippets are mentioned below,
 +
 
 +
* <code> static const struct collect_callbacks callbacks = { recv };</code>
 +
 
 
callbacks = { recv } calls the recv() function when a packet is received.
 
callbacks = { recv } calls the recv() function when a packet is received.
  
  
 +
* <code> collect_open(&tc, 130, COLLECT_ROUTER, &callbacks);</code>
  
::<code>2-collect_open(&tc, 130, COLLECT_ROUTER, &callbacks);</code>
 
 
Opens a connection.
 
Opens a connection.
  
  
 +
* <code> collect_set_sink(&tc, 1);</code>
  
::<code>3-collect_set_sink(&tc, 1);</code>
 
 
Sets the node as sink. Note that we are setting node 1.0 as the sink here.
 
Sets the node as sink. Note that we are setting node 1.0 as the sink here.
  
  
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* <code> collect_send(&tc, 15);</code>
  
::<code>4-collect_send(&tc, 15);</code>
 
 
Sends data through the link.
 
Sends data through the link.
  
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 +
* <code> etimer_set(&et, CLOCK_SECOND * 1);</code>
  
 
::<code>5-etimer_set(&et, CLOCK_SECOND * 1);</code>
 
 
This will set the timer to repeat the iterations every 1 seconds.
 
This will set the timer to repeat the iterations every 1 seconds.
  
  
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* <code>if(rimeaddr_node_addr.u8[0] != 1 )</code>
  
::<code>6-if(rimeaddr_node_addr.u8[0] != 1 )</code>
 
 
This if condition will work only for the source nodes i.e. node id != 1.
 
This if condition will work only for the source nodes i.e. node id != 1.
  
  
 +
To understand the calculations performed in '''recv()''' function, see page 49 at http://web.stanford.edu/class/cs244e/papers/cc2420.pdf
  
To understand the calculations performed in recv() function, see page 49 on this link http://web.stanford.edu/class/cs244e/papers/cc2420.pdf
 
  
 
[[Contiki_tutorials | Back to Contiki Tutorials]]
 
[[Contiki_tutorials | Back to Contiki Tutorials]]
  
 
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Edited by : Nitin, Samarth Pai
Edited by : Nitin
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http://web.stanford.edu/class/cs244e/papers/cc2420.pdf
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Latest revision as of 12:04, 7 October 2016

Back to Contiki Tutorials

Introduction

Radio Signal Strength (RSS) refers to the transmitter power output as received by a reference antenna (i.e. receiver) placed at a distance from the transmitting antenna.

In this tutorial, we will learn how to measure the Radio Signal Strength received by a Tmote Sky module. The tutorial has two nodes, a transmitter and a receiver. The receiver node continuously receives packets from the transmitting node, measures its signal strength and displays the RSS value of the packet received.

A step-by-step description of the simulation process and the C source code can be found in the subsequent sections.

RSS Measurement using Cooja Simulator

Step 1

Run 'ant' to start Cooja. Create New Simulation and let us say we name our simulation as "RSS".


RSS 1.png


Step 2

Add motes to the simulation. Go to Motes-> Add motes-> Create a new mote type-> and select Sky Mote to be added to the network.


RSS 2.png

Step 3

Browse and select the firmware.

Note: You have to create a .c file for RSS measurement and the source code can be found in the next section.


RSS 3.png

Step 4

Compile the firmware.

RSS 4.png

Step 5

Select the number of motes required in the network. You may select any number of motes but for simplicity we are considering only 2 motes.

Note: We are uploading the same firmware on both the motes, one acting as Transmitter and the other as Receiver.


RSS 5.png

Step 6

Start the simulation.

RSS 6.png

Step 7

The 'Mote Output' window gives real time information of the events occurring in the simulation process.

You can see the RSSI values for every packet received in the mote output window. These values are in dBm.


RSS 7.png

Source Code


<HEADER FILES>

static struct collect_conn tc;

PROCESS(example_collect_process, "RSS Measurement");
AUTOSTART_PROCESSES(&example_collect_process);

static void recv(const rimeaddr_t *originator, uint8_t seqno, uint8_t hops)
{
  static signed char rss;
  static signed char rss_val;
  static signed char rss_offset;
  printf("Sink got message from %d.%d, seqno %d, hops %d: len %d '%s'\n",originator->u8[0], originator->u8[1],seqno, hops,packetbuf_datalen(),
         (char *)packetbuf_dataptr());
  rss_val = cc2420_last_rssi;
  rss_offset=-45;
  rss=rss_val + rss_offset;
  printf("RSSI of Last Packet Received is %d\n",rss);
}

static const struct collect_callbacks callbacks = { recv };

PROCESS_THREAD(example_collect_process, ev, data)
{
  static struct etimer periodic;
  static struct etimer et;
  
  PROCESS_BEGIN();

  collect_open(&tc, 130, COLLECT_ROUTER, &callbacks);

  if(rimeaddr_node_addr.u8[0] == 1 && rimeaddr_node_addr.u8[1] == 0) 
  {
    printf("I am sink\n");
    collect_set_sink(&tc, 1);
  }

  /* Allow some time for the network to settle. */
  etimer_set(&et, 120 * CLOCK_SECOND);
  PROCESS_WAIT_UNTIL(etimer_expired(&et));

  while(1) 
  {

    /* Send a packet every 1 seconds. */
    if(etimer_expired(&periodic)) 
    {
      etimer_set(&periodic, CLOCK_SECOND * 1 );
      etimer_set(&et, random_rand() % (CLOCK_SECOND * 1));
    }

    PROCESS_WAIT_EVENT();


    if(etimer_expired(&et)) 
    {
      static rimeaddr_t oldparent;
      const rimeaddr_t *parent;
      if(rimeaddr_node_addr.u8[0] != 1 )
      {
        printf("Sending\n");
        packetbuf_clear();
        packetbuf_set_datalen(sprintf(packetbuf_dataptr(),"%s", "Fight On") + 1);
        collect_send(&tc, 15);

        parent = collect_parent(&tc);
        if(!rimeaddr_cmp(parent, &oldparent)) 
        {
           if(!rimeaddr_cmp(&oldparent, &rimeaddr_null))
           {
              printf("#L %d 0\n", oldparent.u8[0]);
           }
           if(!rimeaddr_cmp(parent, &rimeaddr_null)) 
           {
              printf("#L %d 1\n", parent->u8[0]);
           }
           
           rimeaddr_copy(&oldparent, parent);
        }
      }
    }

  } //end of while

  PROCESS_END();
} //end of process thread
 

Understanding the Code

The functions of some code snippets are mentioned below,

  • static const struct collect_callbacks callbacks = { recv };

callbacks = { recv } calls the recv() function when a packet is received.


  • collect_open(&tc, 130, COLLECT_ROUTER, &callbacks);

Opens a connection.


  • collect_set_sink(&tc, 1);

Sets the node as sink. Note that we are setting node 1.0 as the sink here.


  • collect_send(&tc, 15);

Sends data through the link.


  • etimer_set(&et, CLOCK_SECOND * 1);

This will set the timer to repeat the iterations every 1 seconds.


  • if(rimeaddr_node_addr.u8[0] != 1 )

This if condition will work only for the source nodes i.e. node id != 1.


To understand the calculations performed in recv() function, see page 49 at http://web.stanford.edu/class/cs244e/papers/cc2420.pdf


Back to Contiki Tutorials

Edited by : Nitin, Samarth Pai