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Tham khảo tài liệu 'wireless sensor networks application centric design 2011 part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Urban Microclimate and Traffic Monitoring with Mobile Wireless Sensor Networks 79 simulation run ends when the decoding is finished and all the original data packets are retrieved. All the presented results are obtained by performing 1000 simulation runs for each set of parameters. System Parameter Value AP transmission range 400 m Nap no. of APs in the system 40 Ns no. of sensor nodes per AP 50 k no. of data packets 2000 L data packet length 250 byte k L total amount of original data 4 Mbit ÍV 0.48 Mbyte c Ỗ rateless code parameters 0.03 0.5 kAP no. of encoded packets per AP 3600 R bit-rate 6 11 12 24 Mbit s Tsp superframe duration 100 ms tHO handover time 0.5 s Ppl packet-loss probability 0.3 road-segment length 150 m velocity 4-17 m s acceleration 0.6 m s2 mobility model time-slot duration 2s Table 1. Simulation Parameters Table 1 summarizes the values for the communication and mobility model parameters used in simulations. The number of APs is chosen such that it provides a coverage area which is approximately equal to a medium-sized city area. The data packet length is estimated in such way that is sufficient to accommodate single sensor readings and additional headers i.e. IEEE 802.11 MAC and LLC network and transport layer . The values for bit-rate and superframe duration are selected as suggested in Bohm Jonsson 2008 and Eriksson et al. 2008 pessimistic assumption on packet-loss rate and estimate of the mean MC handover time were taken from Bychkovsky et al. 2006 the average road segment length i.e. average distance between two intersections from Peponis et al. 2007 . The number of encoded packets per AP k-Ap is chosen such that a MC could decode all original data with probability of 0.99 when downloading from a single AP and considering employed rateless code properties and assumed link-layer packet-loss rate. In other words kAP 1 e ma k L 1 - PPL . Fig. 3 presents the probability Psd that the MC successfully decodes the sensor data as a BC function of .
