Chapter 8 – Tree-based Anti-Collision Protocols for RFID tags

Figure 8.1 Illustration of (a) tag collision and (b) reader collision. Tag collision occurs at the reader RA. The reader collision occurs at tags τ2; τ3, but not at τ1; τ4. (Author saved all figures in pdf file, so I have to take screen shot for this chapter’s figures)

Figure 8.2 Time diagram that represents the channel over which the tag-reader arbitration and communication is done Probes are sent by the reader, while in the other slots the reader receives.

Figure 8.3 An instance of the binary tree algorithm for collision multiplicity of N = 8 Each vertex represents a slot that can be in one of the three states: Idle (I), Single (S) or Collision (C). For channel state “S”, τi denotes the resolved or singulated tag.

Figure 8.4 (a) The algorithm run at the reader

Figure 8.4 (b) The algorithm run at a tag

Figure 8.5 Timing diagram for part of the protocol execution described in Fig. 8.3 The notation (τi - τj) below a slot denotes the set of tags τi; τi+1; τi+2 : : : τj that transmits in that slot.

Figure 8.6 Binary tree from Fig. 8.3 Binary tree from Fig. 8.3 represented in the framework that uses tokens and sequence of enabled intervals. A rectangle denotes the interval enabled in a given slot. Shaded rectangle denotes collision; a rectangle labeled with τi denotes that only tag τi has its token that particular enabled interval.

Table 8.1 Time efficiency

Figure 8.7 General model that represents the errors at the reader

Figure 8.8 (a) RFID tags on a conveyor belt The reader covers length L on the belt

Figure 8.8 (b) RFID tags on a conveyor belt Equivalent representation in the two-dimensional arbitration space in one time snapshot. The abscissa represents the random token in [0; 1). The light shaded stripe is the coverage area of the reader in that snapshot, while the dark shaded stripe is the area enabled when the tree protocol enables the interval [0:25; 0:5).

Figure 8.9 Movement of the tags on a conveyor belt The shaded area represents the reader coverage.

Figure 8.10 Representation of the compound random process the tags are randomly distributed in a two-dimensional space and their tokens are randomly distributed in interval [0; 1). For a given tag, the random token represents its x coordinate and the random placement its y coordinate.

Figure 8.11 Different estimates of normalized by the total number of tags n

Figure 8.12 Possible spatial arbitration patterns for a system Possible spatial arbitration patterns for a system with a single reader and beamforming. The arbitration space is three-dimensional, one dimension being the random token and the other two dimensions are represented by the circle.