Beyond fifth-generation (5G) heterogeneous networks (HetNets) are facing the challenge of accommodating enormous mobile users and data traffic with scarce spectrum resources in the microWave (µWave) band. In this work, we consider both challenges in HetNets comprising large size, high power base station (LHB) and relay operating in µWave band and small size, low power base station (SLB) and device-to-device (D2D) operating in millimeter wave (mmWave) band. We formulate user association optimization problems to pitch user association schemes based on downlink uplink decoupled (DU-DPL) access against traditional downlink uplink coupled (DU-CPL) access in HetNets to gauge the performance of these access schemes in terms of accommodating users and spectrum efficiency in µWave and mmWave bands. Formulated problems are non-deterministic polynomial-time hard (NP-hard) and solved using ϵoptimal algorithm. Simulation results show the edge of DU-DPL access over DU-CPL access in terms of users association and spectrum efficiency.

No abstract

Best Complex Antipodal Spherical Codes (BCASC) and Coherence Based Grassmannian Codebooks (CBGC) are state of the art algorithms to produce minimal coherence codebooks, however have high running time (relatively more in BCASC search than CBGC algorithm) which restricts their wider application. BCASC and CBGC algorithms are modified in a novel way by incorporating additional parameters adapted to three categories of codebook overcompleteness to check stagnance of optimization and divergent behaviour to achieve faster convergence. The proposed algorithms are compared with BCASC and CBGC algorithms to achieve similar coherence results in much less time.

Mm-wave MIMO communication makes a hybrid combination of analog RF and digital baseband processing more attractive, where digital baseband precoders/combiners able to adapt to the pre-defined analog (switch based) RF processors. Non-uniform two-dimensional quantized azimuth and elevation angle grid antenna array responses are suggested for uniform planar array (UPA) and are proven orthogonal. Training vectors (or sensing matrix) are designed for suggested antenna array response with unitary RF processing for UPA in mm-wave hybrid MIMO system. Proposed training vectors achieve minimized total coherence of the equivalent sensing matrix for hybrid MIMO system. Open-loop channel estimation of the mm-wave channel is done by using iterative re-weight based super resolution algorithm to exploit its sparse nature. Extensive simulations reveal the benefit of coherence optimization where normalized mean squared error is reduced and spectral efficiency is improved in comparison to existing methods.

No abstract