This paper analyzes the efficacy of decoupled wireless access in a two-tier heterogeneous network. The decoupled wireless access and its performance benefits have been studied in different scenarios recently. In this paper, an in-depth analysis on its efficacy from spectral efficiency perspective is provided. To achieve this task, (i) new closed form expressions for probability of association of user equipment with different tiers employing different frequency bands (i.e., microwave and millimeter wave) with different pathloss exponents are derived using univariate Fox's H-functions; (ii) Distributions of the distance to the serving base stations are also derived; (iii) Exact expressions of spectral efficiency for different association cases are further obtained using bivariate Fox's H-functions. Furthermore, rigorous simulation results are provided which validate the aforementioned analytical results. In addition to that, a detailed discussion on the decoupling gain of decoupled wireless access and its efficacy is also provided. Lastly, despite the improvement provided by the decoupled wireless access, which is evident from the results presented in this paper, few questions are raised on its pragmatic value.
In dense and heterogeneous cellular networks (HetNets), significant imbalance between uplink (UL) and downlink (DL) transmissions may happen in regard to signal-to-interference-and-noise ratio and traffic load. Under this circumstance, decoupled UL DL access (DUDA) is proposed for HetNets for improving system performance. In this paper, we theoretically investigate UL performance improvement brought by a DUDA mode over a conventional coupled UL DL access (CUDA) mode based on stochastic geometry theory. We employ fractional power control to determine location-dependent user transmit power. We consider two kinds of user equipment distributions, namely uniform and clustered distributions, which are modeled as Poisson point and Neyman–Scott cluster processes, respectively. Numerical results reveal that system performance in terms of spectral efficiency and energy efficiency of the DUDA mode is better than or equal to that of the CUDA mode in HetNets. We identify the conditions under which the DUDA mode performs significantly better than the CUDA mode. Numerical results also show that the DUDA mode can improve load balance and fairness. In addition, we find that the DUDA mode is more beneficial for ultradense networks. Simulation results further validate the effectiveness and accuracy of our analytical model. In this paper we develop a tractable framework for SINR analysis in downlink heterogeneous cellular networks (HCNs) with flexible cell association policies. The HCN is modeled as a multi-tier cellular network where each tier's base stations (BSs) are randomly located and have a particular transmit power, path loss exponent, spatial density, and bias towards admitting mobile users. For example, as compared to macrocells, picocells would usually have lower transmit power, higher path loss exponent (lower antennas), higher spatial density (many picocells per macrocell), and a positive bias so that macrocell users are actively encouraged to use the more lightly loaded picocells. In the present paper we implicitly assume all base stations have full queues; future work should relax this. For this model, we derive the outage probability of a typical user in the whole network or a certain tier, which is equivalently the downlink SINR cumulative distribution function. The results are accurate for all SINRs, and their expressions admit quite simple closed-forms in some plausible special cases. We also derive the average ergodic rate of the typical user, and the minimum average user throughput - the smallest value among the average user throughputs supported by one cell in each tier. We observe that neither the number of BSs or tiers changes the outage probability or average ergodic rate in an interference-limited full-loaded HCN with unbiased cell association (no biasing), and observe how biasing alters the various metrics.