Capacity Analysis of Coordinated Multipoint Reception for mmWave Uplink With Blockages

Abstract

We consider an uplink coordinated multi-point (CoMP) transmission from a user served by multiple base stations (BSs) which are connected to each other via a central unit (CU). We model the millimeter-wave communication link with Nakahami-m fading and random blockage. In this paper, we investigate the impact of blockage on the system ergodic capacity and try to find analytical formulation which can be useful in future optimization problems such as power control and resource allocations. The system performance is analyzed by deriving the probability density function of the received signal and finding closed form solution of ergodic capacity. Finally, the analytical results are compared with simulations and the impact of blockage is studied numerically. Numerical results show the efficiency of using CoMP in capacity improvement and reducing the blockage effect, as well as necessity of considering the blockage effect in performance analysis. I. INTRODUCTIONMillimeter-wave (mmWave) communications is one of the main enabling technologies for 5G and Beyond mobile networks due to abundance of unused frequency bands in this spectrum. However, due to challenges such as high path loss and blockage, ultra-dense deployment of base stations (BSs) is required to improve the coverage. The further discussion of the above is given in [1], [2] and references therein. An efficient strategy to tackle adverse effects of mmWave communications is coordination among small cells by employing coordinated multi-point (CoMP) systems which is necessary to reduce handoff and inter-cell interference. The CoMP systems are employed in 4G LTE-A (see, e.g., [3]-[5]), especially for celledge users improvement. They will be also featured in 5G systems as a part of the cloud-radio access networks (C-RAN) architecture (see, e.g., [6], [7]). Despite the great potential of CoMP based mmWave cellular communications, there are many key technical challenges need to be addressed [5], [8], [9].The performance of CoMP system has been investigated in the literature. For instance, in [10], the outage probability of joint processing CoMP using maximum ratio transmission was presented. The capacity analysis for CoMP transmission over fading channels is also studied in a number of work such as [4] and [11], in which downlink and uplink scenarios were considered, respectively. Moreover, the devices in mmWave

A Stochastic Gradient Descent Approach for Hybrid mmWave Beamforming With Blockage and CSI-Error Robustness

“…Unlike preceding contributions, which employ either digital or fully connected hybrid beamforming architectures, the proposed scheme employs a virtually configured partially connected hybrid beamforming architecture, having therefore the advantage of being suitable for CoMP systems. This advantage is aligned with the existing theoretical findings [19], [20] that illustrate that the CoMP approach can achieve the full potential (i.e., capacity-approaching rates and low outages) of mmWave systems in the presence of path blockages.…”

“…It has been observed experimentally [7], [19] that mmWave channels are susceptible to path blockages of likelihood between 20% to 60%. Models for such path blockage processes have since been proposed [8], [10] and employed to demonstrate the severe impact of the phenomenon on system performance [20].…”

“…Consequently, the learning rates α v i to be employed at each iteration of equation (29a) in order to solve problem (20) and obtain the optimal digital baseband beamformer V according to equation (29b) are given by…”

“…An early proposal to combat such effects is the coordinated multipoint (CoMP) scheme described in [19], in which quality of service (QoS) was maintained despite path blockages by synchronizing transmissions from multiple base stations (BSs) and access points (APs). The CoMP approach is not only attractive in the context of mmWave systems owing to the reduced radio coverage, but it is also shown analytically to offer strong theoretical guarantees to achieve capacity in the presence of a path blockage [20], which, however, is unfortunately not accompanied by procedures for practical implementation.…”

“…Besides the coherent blockage assumption, the latter contribution did not consider the benefit of CoMP transmission, which was previously shown in [19], [20] to be crucial for high-performing mmWave systems. In turn, [27] considered a robust CoMP setup under the assumption that blockage affects line-of-sight (LoS) paths in an incoherent manner.…”