Joint Uplink/Downlink Coverage and Spectral Efficiency in Heterogeneous Cellular Network

In this paper, the joint uplink and downlink signal to interference plus noise ratio distribution have been analyzed in a two-tier heterogeneous cellular network. We assume that macro and pico base stations and user equipments are uniformly distributed in the network. User could be paired to its nearest base station or to the BS from which the average received power in the downlink is maximum. Uplink in both cases is coupled to downlink. For symmetric services both up and down links should be able to carry the information flow. Correlation between uplink and downlink coverage could be guessed even under independent Rayleigh fading. The symmetric spectral efficiency gathers both uplink and downlink capacities while forcing them to happen simultaneously. We used realistic spectral efficiencies as signaled by channel quality indicators in LTE. Fractional power control has also been included in the analysis. The results of coverage and spectral efficiency for marginal uplink, marginal downlink, and joint uplink/downlink has been obtained. The assumption of independence between both links is analyzed for the complex trade off of the parameters for network design to obtain the best symmetric efficiency.