Modeling And Analysis Of Coexisting IEEE 802.15.4 Networks Based On Improved HCPP

Communication networks based on the IEEE 802.15.4 protocol have the advantages of low power consumption.However,precisely because of this,the wireless sensor networks are very vulnerable to interference from each other in the congested ISM(Industrial Scientific Medical)band,resulting in transmission interruptions or failure to access the channel.At present,there are the following inadequacies in the random access algorithm for a large number of coexisting IEEE802.15.4 networks: distributed access to the network results in long channel sensing period and high power consumption;at the same time,the networks in the sensing state cannot obtain channel selection information of others,resulting in overlapping of superframes and serious transmission collisions.Therefore,for a large number of coexisting IEEE 802.15.4 networks,it is of great significance to design a reasonable random access framework for improving the spectrum efficiency of the network.This paper proposes a renewal CSMA self-admission access algorithm to improve the spectral efficiency of a large number of coexisting IEEE 802.15.4networks.TS-HCPP(Time Space-Hard Core Point Process)is proposed to model the self-admission access process of a large number of coexisting IEEE 802.15.4networks,and the accuracy of the model is verified by simulation experiment.The network outage probability,transmission capacity,and optimal carrier sensing threshold are studied.The optimal access parameter combinations for heterogeneous services are explored to verify the spectral efficiency of the renewal CSMA(Carrier Sense Multiple Access)self-access access framework.Independent work and contributions are discussed below:One of the effective measures to improve the spectral efficiency of coexisting IEEE 802.15.4 networks is to make full use of the inactive time domain resources of superframes for data transmission.The traditional CSMA random access algorithm can not meet the requirement,and the binary exponent backoff algorithm has many variables,which are not conducive to parameter optimization.Therefore,based on the renewal access theory,the renewal CSMA self-admission access mechanism is proposed,which can fully utilize the time domain resources of the superframes of thesensor networks and improve the spectrum efficiency of networks.At the same time,in order to solve the underestimation problem of the density of retaining nodes when modeling the CSMA network by HCPP,this paper proposes TS-HCPP to model the self-admission access process of a large number of coexisting IEEE 802.15.4networks.Compared to HCPP,TS-HCPP fully considers the space time correlation of nodes,and determines whether there is strong interference according to the relationship between the physical distance of adjacent networks and the sensing radius,which avoids blindly selecting retaining nodes according to the number of channels in the sensing range of networks.That solves the problem of strong interference misjudgment in the same sensing range.In addition,it is one of the conditions of the retaining nodes that the transmission collisions don't occur in the random access process.The self-admission access process of the coexisting networks is accurately modeled,which lays a solid foundation for network performance analysis.Finally,the accuracy of TS-HCPP model is verified by simulation experiment.This paper analyzes the interference model of a large number of coexisting IEEE802.15.4 networks and deduces the outage probability.Combined with the results obtained by TS-HCPP,the transmission capacity is deduced.The reasonable range of the access parameters in the renewal CSMA self-admission algorithm is determined by the two goals of improving the channel utilization and the renewal access parameters without affecting the transmission capacity.Because various IEEE802.15.4 networks bear different traffics,the renewal CSMA self-admission algorithm gives different access parameters to each type of networks.This paper uses the enumeration method to obtain the optimal access parameter combination for heterogeneous traffics.And the spectrum efficiency of networks is increased under the combined influence of the access parameter combination.The effects of network density and carrier sensing threshold on the outage probability and transmission capacity are analyzed,and the spectrum efficiency of the renewal CSMA self-admission access algorithm is verified.The research provides the theoretical basis for the system design of a large number of coexisting IEEE 802.15.4 networks.