65 research outputs found
Distributed MIMO for 6G sub-Networks in the Unlicensed Spectrum
In this paper, we consider the sixth generation (6G) sub-networks, where
hyper reliable low latency communications (HRLLC) requirements are expected to
be met. We focus on a scenario where multiple sub-networks are active in the
service area and assess the feasibility of using the 6 GHz unlicensed spectrum
to operate such deployment, evaluating the impact of listen before talk (LBT).
Then, we explore the benefits of using distributed multiple input multiple
output (MIMO), where the available antennas in every sub-network are
distributed over a number of access points (APs). Specifically, we compare
different configurations of distributed MIMO with respect to centralized MIMO,
where a single AP with all antennas is located at the center of every
sub-network.Comment: This paper is accepted for publication in 2023 IEEE Conference on
Standards for Communications and Networking (CSCN
Enhancing Coexistence in the Unlicensed Band with Massive MIMO
We consider cellular base stations (BSs) equipped with a large number of
antennas and operating in the unlicensed band. We denote such system as massive
MIMO unlicensed (mMIMO-U). We design the key procedures required to guarantee
coexistence between a cellular BS and nearby Wi-Fi devices. These include:
neighboring Wi-Fi channel covariance estimation, allocation of spatial degrees
of freedom for interference suppression, and enhanced channel sensing and data
transmission phases. We evaluate the performance of the so-designed mMIMO-U,
showing that it allows simultaneous cellular and Wi-Fi transmissions by keeping
their mutual interference below the regulatory threshold. The same is not true
for conventional listen-before-talk (LBT) operations. As a result, mMIMO-U
boosts the aggregate cellular-plus-Wi-Fi data rate in the unlicensed band with
respect to conventional LBT, exhibiting increasing gains as the number of BS
antennas grows.Comment: To appear in Proc. IEEE ICC 201
Indoor Massive MIMO Deployments for Uniformly High Wireless Capacity
Providing consistently high wireless capacity is becoming increasingly
important to support the applications required by future digital enterprises.
In this paper, we propose Eigen-direction-aware ZF (EDA-ZF) with partial
coordination among base stations (BSs) and distributed interference suppression
as a practical approach to achieve this objective. We compare our solution with
Zero Forcing (ZF), entailing neither BS coordination or inter-cell interference
mitigation, and Network MIMO (NeMIMO), where full BS coordination enables
centralized inter-cell interference management. We also evaluate the
performance of said schemes for three sub-6 GHz deployments with varying BS
densities -- sparse, intermediate, and dense -- all with fixed total number of
antennas and radiated power. Extensive simulations show that: (i) indoor
massive MIMO implementing the proposed EDA-ZF provides uniformly good rates for
all users; (ii) indoor network densification is detrimental unless full
coordination is implemented; (iii) deploying NeMIMO pays off under strong
outdoor interference, especially for cell-edge users
Uplink Sounding Reference Signal Coordination to Combat Pilot Contamination in 5G Massive MIMO
To guarantee the success of massive multiple-input multiple-output (MIMO),
one of the main challenges to solve is the efficient management of pilot
contamination. Allocation of fully orthogonal pilot sequences across the
network would provide a solution to the problem, but the associated overhead
would make this approach infeasible in practical systems. Ongoing
fifth-generation (5G) standardisation activities are debating the amount of
resources to be dedicated to the transmission of pilot sequences, focussing on
uplink sounding reference signals (UL SRSs) design. In this paper, we
extensively evaluate the performance of various UL SRS allocation strategies in
practical deployments, shedding light on their strengths and weaknesses.
Furthermore, we introduce a novel UL SRS fractional reuse (FR) scheme, denoted
neighbour-aware FR (FR-NA). The proposed FR-NA generalizes the fixed reuse
paradigm, and entails a tradeoff between i) aggressively sharing some UL SRS
resources, and ii) protecting other UL SRS resources with the aim of relieving
neighbouring BSs from pilot contamination. Said features result in a cell
throughput improvement over both fixed reuse and state-of-the-art FR based on a
cell-centric perspective
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