In small cell networks, high mobility of users results in frequent handoffand thus severely restricts the data rate for mobile users. To alleviate thisproblem, we propose to use heterogeneous, two-tier network structure wherestatic users are served by both macro and micro base stations, whereas themobile (i.e., moving) users are served only by macro base stations havinglarger cells; the idea is to prevent frequent data outage for mobile users dueto handoff. We use the classical two-tier Poisson network model with differenttransmit powers (cf [1]), assume independent Poisson process of static usersand doubly stochastic Poisson process of mobile users moving at a constantspeed along infinite straight lines generated by a Poisson line process. Usingstochastic geometry, we calculate the average downlink data rate of the typicalstatic and mobile (i.e., moving) users, the latter accounted for handoff outageperiods. We consider also the average throughput of these two types of usersdefined as their average data rates divided by the mean total number of usersco-served by the same base station. We find that if the density of ahomogeneous network and/or the speed of mobile users is high, it isadvantageous to let the mobile users connect only to some optimal fraction ofBSs to reduce the frequency of handoffs during which the connection is notassured. If a heterogeneous structure of the network is allowed, one canfurther jointly optimize the mean throughput of mobile and static users byappropriately tuning the powers of micro and macro base stations subject tosome aggregate power constraint ensuring unchanged mean data rates of staticusers via the network equivalence property (see [2]).
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