Broadband Connectivity for Handheld Devices via LEO Satellites: Is Distributed Massive MIMO the Answer?

Abstract

Significant efforts are being made to integrate satellite and terrestrial networks into a unified wireless network. One major aspect of such an integration is the use of unified user terminals (UTs), which work for both networks and can switch seamlessly between them. However, supporting broadband connectivity for handheld UTs directly from low Earth orbit (LEO) satellite networks is very challenging due to link budget reasons. This paper proposes using distributed massive multiple-input multiple-output (DM-MIMO) techniques to improve the data rates of handheld devices with a view to supporting their broadband connectivity by exploiting the ultra-dense deployment of LEO satellites and high-speed inter-satellite links. In this regard, we discuss DM-MIMO-based satellite networks from different perspectives, including the channel model, network management, and architecture. In addition, we evaluate the performance of such networks theoretically by deriving closed-form expressions for spectral efficiency and using extensive simulations based on actual data from a Starlink constellation. The performance is compared with that of collocated massive MIMO connectivity (CMMC) and single-satellite connectivity (SSC) scenarios. The simulation results validate the analytical results and show the superior performance of DM-MIMO-based techniques compared to CMMC and SSC modes for improving the data rates of individual users.

Multi-Connectivity Between Terrestrial and Non-Terrestrial MIMO Systems

“…It has been shown that with adequately designed algorithms, MIMO is a promising approach to achieving significant performance gains. For distributed MIMO techniques in satellite networks, the authors of [34] and [35] explore the LEO satellite cooperation to support handheld devices using cross-layer design, artificial intelligence (AI)based implementation, and broadband connectivity, showing superior performance compared to CMM modes. While satellite networks have shown significance in the QoS for ground users, this complete dependence on satellite works neglects potential communication services brought by TN.…”

“…We consider using ZFBF strategy with equal power allocation across the satellite beams to null interference from/to intra-satellite users, while the MRTBF strategy is utilized at terrestrial BSs to enhance the desired signal strength of the associated user with a pointing beam 2 . Considering complicated communication environment and random distributions of users and BSs, we consider equal power allocation for LEO satellites and BSs and roundrobin scheduling for all users to obtain the basic outcomes as an average situation.…”

“…DS T k in (34) indicates the desired signal power at the user k from TN. I N k in (35) is the interference power at the user k generated from NTN. I T k in (36) denotes the interference power at the user k generated from TN.…”

“…Over the past years, the integration of terrestrial networks (TNs) and non-terrestrial networks (NTNs) has emerged as a promising avenue for advancing future communication systems. This development has sparked significant interest from standardization bodies, network operators, research institutes, and related industries [2]. Notably, the 3rd Generation Partnership Program (3GPP) [3] is spearheading the evolution of a fifth-generation (5G) radio access network (RAN) for high availability and high reliability, incorporating NTN for multi-connectivity and link aggregation, as demonstrated in Release 15 [4] and Release 16 [5].…”

“…It is worth noting that we assume the perfect CSI knowledge at satellites and BSs[52]-[55]. The derived coverage probability and data rate expressions give upper bound performance of the TN-NTN-combined multiconnectivity MIMO system 2. Note that for both TN and NTN, the beamforming strategies are flexible, which include but not limited to ZFBF and MRTBF.…”