2,020 research outputs found
On the Spectral and Energy Efficiencies of Full-Duplex Cell-Free Massive MIMO
In-band full-duplex (FD) operation is practically more suited for short-range communications such as WiFi and small-cell networks, due to its current practical limitations on the self-interference cancellation. In addition, cell-free massivemultiple-input multiple-output (CF-mMIMO) is a new and scalable version of MIMO networks, which is designed to bring service antennas closer to end user equipments (UEs). To achieve higher spectral and energy efficiencies (SE-EE) of a wireless network, it is of practical interest to incorporate FD capability into CF-mMIMO systems to utilize their combined benefits. We formulate a novel and comprehensive optimization problem
for the maximization of SE and EE in which power control, access point-UE (AP-UE) association and AP selection are jointly optimized under a realistic power consumption model, resulting in a difficult class of mixed-integer nonconvex programming. To tackle the binary nature of the formulated problem, we propose an efficient approach by exploiting a strong coupling between binary and continuous variables, leading to a more tractable problem. In this regard, two low-complexity transmission designs based on zero-forcing (ZF) are proposed. Combining tools from inner approximation framework and Dinkelbach method, we develop simple iterative algorithms with polynomial computational complexity in each iteration and strong theoretical performance guaranteed. Furthermore, towards a robust design for FD CFmMIMO, a novel heap-based pilot assignment algorithm is proposed to mitigate effects of pilot contamination. Numerical results show that our proposed designs with realistic parameters significantly outperform the well-known approaches (i.e., smallcell and collocated mMIMO) in terms of the SE and EE. Notably, the proposed ZF designs require much less execution time than the simple maximum ratio transmission/combining
Integrated Sensing and Communication for Network-Assisted Full-Duplex Cell-Free Distributed Massive MIMO Systems
In this paper, we combine the network-assisted full-duplex (NAFD) technology
and distributed radar sensing to implement integrated sensing and communication
(ISAC). The ISAC system features both uplink and downlink remote radio units
(RRUs) equipped with communication and sensing capabilities. We evaluate the
communication and sensing performance of the system using the sum communication
rates and the Cramer-Rao lower bound (CRLB), respectively. We compare the
performance of the proposed scheme with other ISAC schemes, the result shows
that the proposed scheme can provide more stable sensing and better
communication performance. Furthermore, we propose two power allocation
algorithms to optimize the communication and sensing performance jointly. One
algorithm is based on the deep Q-network (DQN) and the other one is based on
the non-dominated sorting genetic algorithm II (NSGA-II). The proposed
algorithms provide more feasible solutions and achieve better system
performance than the equal power allocation algorithm.Comment: 14 pages, 7 figures,submit to China Communication February 28, 2023,
date of major revision July 09, 202
Ubiquitous Cell-Free Massive MIMO Communications
Since the first cellular networks were trialled in the 1970s, we have
witnessed an incredible wireless revolution. From 1G to 4G, the massive traffic
growth has been managed by a combination of wider bandwidths, refined radio
interfaces, and network densification, namely increasing the number of antennas
per site. Due its cost-efficiency, the latter has contributed the most. Massive
MIMO (multiple-input multiple-output) is a key 5G technology that uses massive
antenna arrays to provide a very high beamforming gain and spatially
multiplexing of users, and hence, increases the spectral and energy efficiency.
It constitutes a centralized solution to densify a network, and its performance
is limited by the inter-cell interference inherent in its cell-centric design.
Conversely, ubiquitous cell-free Massive MIMO refers to a distributed Massive
MIMO system implementing coherent user-centric transmission to overcome the
inter-cell interference limitation in cellular networks and provide additional
macro-diversity. These features, combined with the system scalability inherent
in the Massive MIMO design, distinguishes ubiquitous cell-free Massive MIMO
from prior coordinated distributed wireless systems. In this article, we
investigate the enormous potential of this promising technology while
addressing practical deployment issues to deal with the increased
back/front-hauling overhead deriving from the signal co-processing.Comment: Published in EURASIP Journal on Wireless Communications and
Networking on August 5, 201
A Novel Heap-based Pilot Assignment for Full Duplex Cell-Free Massive MIMO with Zero-Forcing
This paper investigates the combined benefits of
full-duplex (FD) and cell-free massive multiple-input multipleoutput
(CF-mMIMO), where a large number of distributed
access points (APs) having FD capability simultaneously serve
numerous uplink and downlink user equipments (UEs) on the
same time-frequency resources. To enable the incorporation of
FD technology in CF-mMIMO systems, we propose a novel heapbased
pilot assignment algorithm, which not only can mitigate
the effects of pilot contamination but also reduce the involved
computational complexity. Then, we formulate a robust design
problem for spectral efficiency (SE) maximization in which the
power control and AP-UE association are jointly optimized,
resulting in a difficult mixed-integer nonconvex programming.
To solve this problem, we derive a more tractable problem
before developing a very simple iterative algorithm based on
inner approximation method with polynomial computational
complexity. Numerical results show that our proposed methods
with realistic parameters significantly outperform the existing
approaches in terms of the quality of channel estimate and SE
- …