4。2OPNET Simulation structure
Our ZigBee-RFID mixture model is based on the IEEE 802。15。4 Opnet model and RFID Opnet model。 Opnet model is the University of Porto, Portugal (University of Porto) R&D, RFID Opnet model is the University of Parma, Italy (University of Parma) research and development。 IEEE802。15。4 model is used to synchronize the introduction of networks nodes and save energy。 In addition, this model includes a battery model to evaluate equipment energy consumption。 On the other hand, Opnet-RFID model implementation of the ISO / IEC 18000-6 standard, taking into account the
wireless channel fading。 Because ZigBee and RFID model is not out of line, we have developed a hybrid model Opnet ZigBee and RFID, in which sub-components can communicate and co-operation。 Obviously, given the RFD can be transmitted in a frame, beacon mechanism needs to be modified。 Noted that, in our system is not used in BTP (embedded in the ISO / IEC 18000-6 standard), which is used only for switching the RFID tags (ZigBee) RFD, and do not need to be identified。 More specifically, RFID is in the ZigBee networks layer above the networks。 In our hybrid system, information is through the IEEE 802。15。4 (logic) networks transmission, and its networks in order to be RFID networks control。 Integration of AP, from the RFID reader, ZigBee coordinator and the combination of integrated node obtained。 The integrated node is combined with RFID tags and ZigBee RFD obtained。 We pointed out that the integrated node is battery-powered, however, AP connection power system integration, which the latter does not run out of battery problems, while the former will be。
4。3Algorithm for deep sleep
We now describe the ZigBee-RFID hybrid networks's basic functions。 When a RFD is sleeping, and was coordinator selected, the associated RFID tag reader of the signaling messages received (via RFID logical networks), and open their own RFD, began to enter the active communication (through the ZigBee logical networks 。) Similarly, when an RFD is active, and its residual energy below
the threshold, RFD to tell zigbee coordinator。 Coordinator to inform it of the appropriate RFID reader, the tag by sending an appropriate message, to force the selected RFD into sleep mode。 Because deep sleep is a ZigBee networks algorithm coordinator managed the activities of its remaining energy information RFD will be embedded in data packets, sent to the coordinator。 In this way, the coordinator kept informed of the activities of each of the remaining energy of RFD。 On the other hand, due to a sleep state of the RFD is not transmit any data packet, the coordinator can also use an algorithm to estimate the expected state of the RFD in a period of sleep, the energy consumption。
4。4virtual space grid algorithm for
deep sleep
When deep sleep algorithm considers the global space density of stations (taking into account the number of nodes covering the entire surface of all the networks), in several applications, it may be interesting to monitor the surface of the same networks, such as to ensure that local stations across the plane space density is almost constant。 To do this, we follow a networks-based virtual space using the grid method。
5Performance Analysis
Simulation concludes when the networks nodes N = 40 when, in all cases, RFD send packets directly to the integration of AP, for example, all networkss have a star-shaped structure。 Tint the packet arrival time of 0。25 seconds or a fixed Poisson distribution, with
an average of 0。25 seconds。 Consider the packet length L = 200bit/pck。 We assume that when all of the RFD energy level as the initial value of 80% of the networks does not work。 The results of each performance is the result, on average, including six networks topology to achieve (in accordance with 2D Poisson distribution)。 ZigBee-RFID混合网络的节电英文文献和中文翻译(4):http://www.youerw.com/fanyi/lunwen_101489.html