Angular Spread Quantification of Multi-Antenna Vehicular Radio Communication Channels

The deployment of multi-antenna systems with software defined reconfigurable beam patterns can potentially benefit vehicle-to-vehicle (V2V) communications by increasing the channel coherence time. This in turn necessitates an accurate characterization and modeling of the angular statistics of vehicular radio propagation environments. This work proposes an improved three-dimensional (3-D) spatial description of vehicular propagation environments and derives the closed-form analytical expressions for the joint and marginal statistics of the 3-D angle-of-arrival (AoA) and angle-of-departure (AoD). Then, based on the proposed geometric channel model, the AoA and AoD angular spreads are quantified in terms of the joint angular spread, elevational constriction, and the azimuthal constriction. These considered quantifiers are shown to be of high significance in quantification of angular spread in V2V radio propagation environments. The impact of various physical parameters on the angular spread is also investigated. These parameters include the link-distance, scattering volume, and the number of scatterers along the azimuth and elevation axes. The derived analytical expressions are also validated by simulations

Location-aware and Superimposed-Pilot based Channel Estimation of Sparse HAP Radio Communication Channels

A superimposed (arithmetically added) Pilot (SiP) sequence based channel estimation method for beamforming assisted multi-antenna High Altitude Platform (HAP) land mobile radio communication systems is proposed, which exploits the prior available information of users’ spatial location, density of users, and beam-width of HAP directional antenna. A thorough characterization of HAP sparse multipath radio propagation channels’ is presented in first part of the paper, where mathematical relationship of HAP antenna beam-width with channel’s delay span and optimal length of SiP base sequence are presented. Further, a location information aided and lowpower SiP sequence based Stage-wise Orthogonal Match Pursuit (StOMP) algorithm is proposed for estimation of channels from single-antenna user terminals to beamforming assisted large scale multiple-antenna HAP. A thorough analysis on the basis of Normalized Channel Mean Square Error (NCMSE) and Bit Error Rate (BER) performance of proposed method is presented; where the effect of channels’ sparsity level, Pilot-to-Information power Ratio (PIR), beam-width of HAP’s directional antenna, amount of HAP antenna elements, density of interfering users, and spatial location of active user terminal are thoroughly studied. A comparison of the proposed method with a notable reference technique available in the literature is also presented