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In indoor positioning,the main advantage of pedestrian dead reckoning(PDR)is that the user only needs to have a smart phone to realize positioning,without relying on the external environment.However,there is a large cumulative error.Ge-nerally,it is necessary to combine Bluetooth,WiFi,geomagnetic or other technologies to improve the positioning accuracy.How-ever, this method requires some hardware nodes and a fingerprint database to be built for this purpose.To solve this problem,an indoor positioning method based on correcting PDR in machine to machine(M2M)area is proposed.Firstly,a distance measurement area is set up during pedestrian travel.Secondly,the distance between pedestrian mobile phones and other mobile phones is measured in this region.Finally,the positioning error and accuracy of PDR are corrected by trilateral positioning method.The method has the advantages that no additional hardware facilities are required.Experimental results show that,compared with the traditional PDR positioning,this method is suitable for long-time positioning,and the average positioning error is reduced to 0.36 m,with high positioning accuracy.

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A flow control random access protocol for event-driven machine-to-machine traffics in LTE network is pro-posed.The beta distribution is adopted to model the event-driven M2M traffics.This protocol uses the random access preamble free ratio in a fixed number of slots to estimate the channel load and calculate the flow control factor to control the flow.The throughput performance of the proposed protocol is modeled and analyzed,and compared with the random access protocol in LTE system.It is shown that the proposed protocol performs much better because it can estimate the system load accurately in most situations and reduce collision by flow control factor.

M2M is one key technology for smart city. Both communication characteristics and business characteristics of M2M have raised new requirements for mobile networks. For communication characteristics, the network improvement work by 3GPP and 3GPP2, two different network adaptation ways, and three phases of network evolution for M2M were discussed. For business characteristics, SCS from 3GPP, manageable M2M communication pipe, and GSMA eSIM were described.