Chapter 7 – Aloha-Based Protocol

Table 7.1 RFID standards and products

Figure 7.1 Reader and tags interactions

Figure 7.2 Pure Aloha with muting

Figure 7.3 Pure Aloha with slow down

Figure 7.4 Pure Aloha with fast mode

Figure 7.5 Slotted Aloha with early end

Figure 7.6 λ = 20, K = 5 λ is the offered load and K is the maximum retransmission delay Klair et al. 2009

Figure 7.7 Number of collision to read n tags

Figure 7.8 Number of idle slots encountered when reading n tags

Table 7.2 Optimal frame sizes for a given tag range

Figure 7.9 (a) A CD frame precedes each jump frame. The number of slots in each jump frame corresponds to the number of successful transmissions in the CD frame; in this example, only two tags successfully transmitted their ID. Tags that transmitted successfully in the CD frame then send their full ID in the jump frame.

Figure 7.9 (b) Collision detection using Manchester encoding no transition in the middle of a bit indicates a collision

Table 7.3 EDFSA frame sizes n denotes the number of tags, N is the frame size, and M is the number of tag groups.

Figure 7.10 ResMon Frames

Figure 7.11 An example showing QT being used to identify the following tags: A (0111), B (0000), C (0101) and D (0001). In scenario (ii), only tags A and B contend with each other. Tag C and D will contend at a different time.

Figure 7.12 Reading delay of BFSA, DFSA, and EDFSA variants

Figure 7.13 Average number of collisions encountered when reading n tags

Figure 7.14 Average number of idle slots encountered when reading n tags