130 research outputs found
Revolutionizing Future Connectivity: A Contemporary Survey on AI-empowered Satellite-based Non-Terrestrial Networks in 6G
Non-Terrestrial Networks (NTN) are expected to be a critical component of 6th
Generation (6G) networks, providing ubiquitous, continuous, and scalable
services. Satellites emerge as the primary enabler for NTN, leveraging their
extensive coverage, stable orbits, scalability, and adherence to international
regulations. However, satellite-based NTN presents unique challenges, including
long propagation delay, high Doppler shift, frequent handovers, spectrum
sharing complexities, and intricate beam and resource allocation, among others.
The integration of NTNs into existing terrestrial networks in 6G introduces a
range of novel challenges, including task offloading, network routing, network
slicing, and many more. To tackle all these obstacles, this paper proposes
Artificial Intelligence (AI) as a promising solution, harnessing its ability to
capture intricate correlations among diverse network parameters. We begin by
providing a comprehensive background on NTN and AI, highlighting the potential
of AI techniques in addressing various NTN challenges. Next, we present an
overview of existing works, emphasizing AI as an enabling tool for
satellite-based NTN, and explore potential research directions. Furthermore, we
discuss ongoing research efforts that aim to enable AI in satellite-based NTN
through software-defined implementations, while also discussing the associated
challenges. Finally, we conclude by providing insights and recommendations for
enabling AI-driven satellite-based NTN in future 6G networks.Comment: 40 pages, 19 Figure, 10 Tables, Surve
On delay-sensitive communication over wireless systems
This dissertation addresses some of the most important issues in delay-sensitive
communication over wireless systems and networks. Traditionally, the design of communication
networks adopts a layered framework where each layer serves as a “black
box” abstraction for higher layers. However, in the context of wireless networks with
delay-sensitive applications such as Voice over Internet Protocol (VoIP), on-line gaming,
and video conferencing, this layered architecture does not offer a complete picture.
For example, an information theoretic perspective on the physical layer typically ignores
the bursty nature of practical sources and often overlooks the role of delay in
service quality. The purpose of this dissertation is to take on a cross-disciplinary
approach to derive new fundamental limits on the performance, in terms of capacity
and delay, of wireless systems and to apply these limits to the design of practical
wireless systems that support delay-sensitive applications. To realize this goal, we
consider a number of objectives.
1. Develop an integrated methodology for the analysis of wireless systems that
support delay-sensitive applications based, in part, on large deviation theory.
2. Use this methodology to identify fundamental performance limits and to design
systems which allocate resources efficiently under stringent service requirements.
3. Analyze the performance of wireless communication networks that takes advantage of novel paradigms such as user cooperation, and multi-antenna systems.
Based on the proposed framework, we find that delay constraints significantly
influence how system resources should be allocated. Channel correlation has a major
impact on the performance of wireless communication systems. Sophisticated power
control based on the joint space of channel and buffer states are essential for delaysensitive
communications
Phase-Shift Cyclic-Delay Diversity for MIMO OFDM Systems
Phase-shift cyclic-delay diversity (PS CDD) scheme and space-frequency-block-code (SFBC) PS CDD are developed for multiple-input-multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. The proposed PS CDD scheme preserves the diversity advantage of traditional CDD in uncorrelated multiantenna channels, and furthermore removes frequency-selective nulling problem of the traditional CDD in correlated multiantenna channels
Detect to Learn: Structure Learning with Attention and Decision Feedback for MIMO-OFDM Receive Processing
The limited over-the-air (OTA) pilot symbols in
multiple-input-multiple-output orthogonal-frequency-division-multiplexing
(MIMO-OFDM) systems presents a major challenge for detecting transmitted data
symbols at the receiver, especially for machine learning-based approaches.
While it is crucial to explore effective ways to exploit pilots, one can also
take advantage of the data symbols to improve detection performance. Thus, this
paper introduces an online attention-based approach, namely RC-AttStructNet-DF,
that can efficiently utilize pilot symbols and be dynamically updated with the
detected payload data using the decision feedback (DF) mechanism. Reservoir
computing (RC) is employed in the time domain network to facilitate efficient
online training. The frequency domain network adopts the novel 2D multi-head
attention (MHA) module to capture the time and frequency correlations, and the
structural-based StructNet to facilitate the DF mechanism. The attention loss
is designed to learn the frequency domain network. The DF mechanism further
enhances detection performance by dynamically tracking the channel changes
through detected data symbols. The effectiveness of the RC-AttStructNet-DF
approach is demonstrated through extensive experiments in MIMO-OFDM and massive
MIMO-OFDM systems with different modulation orders and under various scenarios.Comment: Accepted to IEEE Transactions on Communication
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