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Fixed wireless access has been spreading recently as a complement to wired or fiber solutions, and its implementation on millimeter waves has attracted attention for its potentially high data rates, achievable also in densely populated areas. New hardware and software solutions are needed to overcome various technical issues at those frequencies. We propose a novel modular hybrid beamforming (MHB) architecture, whereby, in receive mode, each module comprises a set of antennas connected to fixed analog beamformers, in turn connected by configurable switches to a smaller set of radio frequency chains. The outputs of all modules are then jointly processed by a digital beamformer. In particular, an MHB performing discrete Fourier transform beamforming for uniform linear arrays is studied. We address the problems of a) switch configuration, b) power allocation and digital beamformer design, and c) channel estimation. For both a) and b) we target the maximization of the total weighted spectral efficiency (WSE) under power and per-user average spectral efficiency (SE) constraints, and we propose greedy efficient solutions. For c) we propose a multistage scheme. We assess the MHB performance in terms of WSE, estimation accuracy, estimation overhead, and computational complexity, and compare them with existing solutions in literature. [ABSTRACT FROM AUTHOR]

Interference control is crucial to reach the expected spectral efficiencies in femtocell systems. Centralized and joint baseband (BB) processing of all femtocell signals can reduce inter-cell/intra-cell interference at the expense of fast signaling and strict synchronization to coordinate the multiple femtocell links. In this article, we revisit the conventional femtocell architecture by proposing the multi-cell baseband processing for interference mitigation based on a distributed antennas system. The proposed configuration resorts to the wireless over cable (WoC) paradigm and is based on the concept of replacing the in-house base station (Femtocell Access Point) with a home-device that simply transfers the analog radio frequency (RF) signals from the air-link to the existing cable connections. These home-devices act as bidirectional amplify-and-forward (AF) relays of air signals toward cable (and vice-versa) by operating a frequency conversion of the wireless spectrum to accommodate the cable specifications and coexistence with other services. Splitting RF processing (at home) from baseband processing (centralized at the nearest street cabinet or central office collecting multiple cables) guarantees that multi-cell processing exploits the same advantages as MIMO systems. The analysis of WoC for twisted pair telephone lines shows the advantages of the FemtoWoC architecture despite the coexistence with other interfering xDSL services over the cable, or the propagation over the widely deployed copper wirelines. [ABSTRACT FROM PUBLISHER]

Fifth generation (5G) and beyond communication systems open the door to millimeter wave (mmWave) frequency bands to leverage the extremely large operating bandwidths and deliver unprecedented network capacity. These frequency bands are affected by high propagation losses that severely limit the achievable coverage. The simplest way to address this problem would be to increase the number of installed mmWave base stations (BSs), at the same time augmenting the overall network cost, power consumption, and electromagnetic field (EMF) levels. As alternative direction, here we propose to complement the macro-layer of mmWave BSs with a heterogeneous deployment of smart electromagnetic (Smart EM) entities—namely IAB nodes, smart repeaters, reconfigurable intelligent surfaces (RISs) and passive surfaces—that is judiciously planned to minimize the total installation costs while at the same time optimizing the network spectral efficiency. Initial network planning results underline the effectiveness of the proposed approach. The available technologies and the key research directions for achieving this view are thoroughly discussed by accounting for issues ranging from system-level design to the development of new materials. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a wireless communication scenario, where polarization multiplexing is exploited to increase the spectral efficiency. Independent modems over each polarization are considered, with communication links affected by phase noise and cross-polarization interference (XPI). We devise a novel per-polarization soft decision-directed iterative receiver with separate a posteriori probability-based synchronization and decoding. The synchronization algorithm relies on a minimum mean square error-based master–slave phase estimation followed by the cancellation of the XPI on the polarization of interest and requires no statistical knowledge of the phase noise process. The performance of the proposed iterative receiver is investigated for a pilot symbol-assisted low-density parity-check-coded quadrature amplitude modulation scheme. [ABSTRACT FROM AUTHOR]