**5. Conclusions**

14 Radio Frequency Identification

**Figure 10.** Throughput (*T*) vs. reader and tag transmissions probabilities (*pr* and *pt*) of a symmetrical NDMA MPR protocol for

**Figure 11.** Throughput (*T*) vs. reader and tag transmissions probabilities (*pr* and *pt*) of an asymmetrical ALOHA protocol for

all readers transmit with the same parameter *pr*. A tag activation probability of *q* = 0.7 and a tag detection probability at the reader side of *Q* = 0.95 have been used in the theoretical calculations. A probability of false alarm for the NDMA protocol has been set to *PF* = 0.01. The results of Fig. 11 and Fig. 12 have been obtained using three groups of tags with *<sup>J</sup>*<sup>1</sup> = 3,*J*<sup>2</sup> = 5 and *<sup>J</sup>*<sup>3</sup> = 7 tags, and two groups of readers with *<sup>K</sup>*<sup>1</sup> = 5 and *<sup>K</sup>*<sup>2</sup> = 10 readers. While Fig. 11 shows the results of an ALOHA protocol without MPR capabilities (*M* = 1), Fig. 12 shows the results of the proposed NDMA protocol with *M* = 1. In both cases, the readers and tags are assumed to transmit in different channels, thereby avoiding interference between their transmissions. It can be observed the significant gain provided by the NDMA

reader and tag anti-collision assuming no interference between readers and tags.

reader and tag anti-collision without interference between readers and tags.

protocol for all values of *pt* and *pr*.

This chapter presented a novel algorithm for passive RFID anti-collision based on the concepts of multi-packet reception and retransmission diversity. In addition, the design of the algorithm has been based on a new design paradigm called cross-layer design, where physical and medium access control layers are jointly designed, and where reader and tag anti-collision components are also jointly considered. The proposed Markov model is a new approach for the modeling of RFID networks, as it captures both the activation process given by the operation of readers sending requests to tags, and the tag detection process that results from tags randomly transmitting their information back to the readers that previously activated them. The results for tag throughput showed considerable improvement over conventional ALOHA solutions that have been implemented in current deployments and commercial platforms for RFID. This opens an interesting area for the design of advanced random access protocols for future RFID systems and for the internet of things.

### **Author details**

Ramiro Sámano-Robles1, Neeli Prasad2 and Atílio Gameiro1

1 Instituto de Telecomunicações, Campus Universitário, Aveiro, Portugal

2 Center for TeleInfrastruktur, Department of Electronic Systems, Aalborg University, Aalborg, Denmark
