Chipless radio frequency identification (RFID) tags are dummy, memoryless, with limited number of bits, very low backscattered power, and short reading range. Therefore, the existing RFID standards and protocols designed for the chipped RFID systems are not applicable for the chipless systems. Main objective of this contribution is to introduce a novel real-world testbed for multi-tag ultra-wideband (UWB) chipless RFID system. In this testbed, a new Notch Position Modulation scheme is implemented as the first medium access control algorithm for handling the multi-tag identification scenario of the frequency signature based chipless RFID tags. This intelligent Notch Position Modulation algorithm reduces the sensing and identification time and accordingly the overall system latency. The proposed protocol enables fetching the frequency signatures of the chipless RFID tags through the whole UWB range effectively. Moreover, an advanced signaling scheme is designed for the RFID reader in order to make the best use of the Federal Communications Commission UWB regulations for increasing the maximum transmitted power and the corresponding reading range. The signaling scheme, real-time channel estimation, and clutter removal technique are implemented on the software defined radio platform in a heavily dense multipath indoor environment. Based on the medium access control protocol, the mitigation of the undesired environmental reflections as well as the interference between the chipless RFID tags is well demonstrated in the developed testbed. |
