Power LED's using RF transmitter and receiver with Arduino
you are comparing a single character, which may be 'S' which is the first character in teh string "Sensor 1", with, again, A string literal which you have declared as a character. 

In C programming a single quote '  mark means that its an ASCII character, like '&amp;' or 's'. If you want a string, you use doublequote, "Sensor" and even single character strings work "S". 

What you need to do is set up a char buffer as an empty "string" for the received data.

char rxbuffer[64]; //64 byte long char buffer!
memset (rxbuffer,0,64); //this clears the bytes to 0. otherwise could be garbage data


64 is arbitrary, but means it can hold 63 character long string, and a null terminator at the end. 

then you should use the arduino Serial.readBytesUntil()  function. http://arduino.cc/en/Serial/ReadBytesUntil

This would looke like:

//you need to include this at the top!! 
#include &lt;string.h&gt;

if(Serial.available()){
    Serial.readBytesUntil('\0', rxbuffer, 64);
    //use the C++ standard function call strstr to search buffer for matchin
    //input string

    //was it sensor 1 command?
    if( strstr(rxbuffer, "Sensor 1") ){
        digitalWrite(LED1, HIGH);
    }else{
        //maybe it was sensor 2?
        if( strstr(rxbuffer, "Sensor 2") ){
            digitalWrite(LED2, HIGH);
        }

    } //end if it wasnt first sensor message

}//end serial available, processing message after read


So there you go, that should work. change the LED pin numbers/names though