One of the challenges in design large-scale multiuser MIMO-OFDM systems is developing low-complexity detection algorithms. To achieve this goal, we leverage message passing algorithms over factor graph that represents and approximate original discrete messages with continuous Gaussian through use minimum Kullback-Leibler (KL) divergence criterion. Several signal processing techniques are then proposed to near-optimal performance at low complexity. First, principle expectation propagation...

Due to the non-uniform geographic distribution and time-varying characteristics of ground traffic request, how make full use limited beam resources serve users flexibly efficiently is a brand-new challenge for hopping satellite systems. The conventional greedy-based methods do not consider long-term reward, which difficult deal with demand. Meanwhile, heuristic algorithms such as genetic algorithm have slow convergence time, can achieve real-time scheduling. Furthermore, existing based on...

Due to the non-uniform distribution of ground traffic demand and high mobility non-geostationary orbit (NGSO) satellites, how make full use limited beam resources serve users flexibly efficiently is a brand-new challenge for NGSO communication systems. In order achieve efficient spectrum utilization, combination frequency multiplexing hopping major trend in future satellite However, conventional methods are mainly based on geostationary which do not take into account interference between...

Non-geostationary orbit (NGSO) constellations enabled by beam hopping (BH) technology are characterized wide coverage and high spectrum efficiency. However, how to efficiently schedule multi-satellite resources satisfy the heterogeneous uneven terrestrial traffic demands remains a huge challenge for satellite operators. This paper proposes satellite-terrestrial coordinated BH scheduling framework, where complex problem is formulated into long-term short-term subproblems. The subproblem...

In this paper, we address the design of message-passing receiver for massive multiple-input multiple-output orthogonal frequency division multiplex (MIMO-OFDM) systems. With aid central limit argument and Taylor-series approximation, a computationally efficient that performs joint channel estimation decoding is devised by framework expectation propagation. particular, local belief defined at transition function expanded up to second order with Wirtinger calculus, transform messages sent...

Satellite communications play an important role in future Internet of Things (IoT) networks, and megasatellite constellations can further provide global coverage high-quality services for IoT communications. In the megaconstellation, large-scale satellites are launched to enhance capacity. However, dense distribution brings intraconstellation interference, limiting performance. order evaluate restriction interference caused by system parameters, such as scale constellation or frequency reuse...

In this letter, we reveal that in the massive multiple-input multiple-output system with large bandwidth, sub-channels of orthogonal frequency division multiplexing share approximately sparse common support due to difference subcarriers. We use approximate message passing nearest neighbor sparsity pattern learning (AMP-NNSPL) algorithm adaptively learn underlying structure for improving accuracy channel estimation, where strategy is newly derived by solving an optimization problem. addition,...

Without control center assistance, it is difficult that users take traffic loads of whole Ad Hoc networks into account to utilize wireless resources collaboratively. Considering influence load differences between on resource allocation can be learned in advance, we construct a framework load-aware distributed for multiple frequencies time division access (MF-TDMA) based multi-agent deep reinforcement learning (DRL) with centralized training and execution. In this framework, each user...

Non-geostationary orbit (NGSO) satellite communication system plays an important role in achieving seamless global coverage and addressing the digital divide. The uneven distribution of terrestrial users high mobility NGSO satellites put forward higher requirements for resource management. In this letter, we propose a multi-satellite beam hopping scheme based on load balancing interference avoidance, where complicated joint problem is decomposed into two sub-problems, namely satellite-cell...

In this paper, we propose an expectation propagation based iterative multi-user detection algorithm for multiple input output interleave-division access (MIMO-IDMA) systems with high-order modulation. The proposed detector can be well integrated into the traditional structure of turbo receivers MIMO-IDMA systems. By formulating a scalar factor graph representation and choosing Gaussian distribution as projection set symbol belief, overall complexity reduced to scaling linearly number users,...

To address the challenging problem of downlink channel estimation with low pilot overhead in massive multiple-input multiple-output (MIMO) systems, an empirical Bayesian block expectation propagation (EP) algorithm is proposed. Specifically, a Bernoulli-Gaussian prior model proposed to fit underlying sparsity, and EP derived estimate channels more accurately by clustering all taps that pertain same delay, while parameters are learned minimizing Bethe free energy. Simulation results show...

We propose a message-passing algorithm of joint channel estimation and decoding for OFDM systems, where expectation propagation is exploited to deal with estimation. Specially, the message updating formulated into recursive form. As result, system K subcarriers L taps, only O(K + L) messages need be tracked, meanwhile they can efficiently calculated using FFT complexity O(K|A| log <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> K), |A|...

Real-time information exchange on traffic and channel selection results among users in dynamic spectrum access (DSA) system consumes scarce resources. However, it is difficult to avoid collision improve system-wide global utility simultaneously without assistance of these a distributed way. To solve this problem, we propose multi-agent deep reinforcement learning (RL) based priority-aware multi-user DSA scheme for multiple orthogonal channels scenario. Different from the conventional...

Acquisition and tracking are two crucial stages necessary to the carrier frequency synchronization in orthogonal division multiplexing (OFDM) systems. In this letter, by employing rotation property of OFDM data subcarriers, a simple time-frequency decision-feedback loop without use pilot subcarriers is proposed for fine offset (CFO) tracking. Specifically, with proper parameters, residual CFO less than 10% subcarrier spacing may be well tracked quarternary phase-shift keying (QPSK)...

A carrier frequency offset (CFO) tracking scheme without the use of any pilot subcarriers for uplink orthogonal division multiple access (OFDMA) system is proposed in this paper. We first analyze interference due to CFO OFDMA systems, then, an presented. The employs time-frequency decision-feedback recovery loops individual users restore original symbols. Moreover, a modularized and flexible structure design achieved low-complexity implementation loop. Simulation results show that resistant...

For the spatially correlated multiuser MIMO-OFDM channels, conventional iterative MMSE-SIC detection suffers from a considerable performance loss. In this paper, we use factor graph framework to design robust algorithms by clustering group of symbols combat spatial correlation and using principle expectation propagation improve message passing. Furthermore, as complexity becomes one issues in large-scale systems, propose low-complexity approximate message-passing algorithm opening channel...

Unmanned Aerial Vehicle (UAV) technology has been widely applied in both military and civilian applications. With the increasing complexity of application scenarios, coordination multiple UAVs become a hot topic. However, limited capability make it hard to achieve stable reliable control. Considering this practical problem, we propose cloud-based UAV system. It extricates computing data storage from utilizes cloud process sensor maintain operation multi-UAV systems. Firstly, analyze system's...

In helicopter satellite communication systems, the received signal is blocked by rotor blades during propagation, incurring unstableness of traditional methods channel estimation due to unknown state. To this end, a joint occlusion detection and phase algorithm proposed factor graph in paper. For acquire state, model established relying on Markov chain with priori blocking ratio, which probability distribution state calculated message-passing algorithm. obtain position update...

Due to limited volume, weight and power consumption, micro-satellite has reduce data transmission storage capacity by image compression when performs earth observation missions. However, the quality of images may be unsatisfied. This paper considers problem recovering sparse signals exploiting their unknown sparsity pattern. To model structured sparsity, prior correlation support is encoded imposing a transformed Gaussian process on spike slab probabilities. Then, an efficient approximate...

A novel low-complexity multiuser detection scheme is proposed for the asynchronous non-orthogonal multiple access (NOMA). Directly applying conventional symbol-synchronous techniques NOMA would result in high complexity. For low-complexity, we divide one frame with a large number of symbols into several small blocks. Furthermore, real-time and low-delay processing under scenario users, each block independently processed parallel way by an approximate message passing-based algorithm. jointly...

Because of the high system capacity and excellent capability against narrowband interference (NBI), Direct Sequence-Code Division Multiple Access (DS-CDMA) is widely used in Geosynchronous Earth Orbit satellite systems. However, due to existence uncertain non-cooperative external interference, traditional colored noise suppression methods cannot achieve performance DS-CDMA In this paper, based on spectrum shaping, combining with feature analysis an eigen-based spreading sequences design...

Grant-free non-orthogonal multiple access (NOMA) is highly expected to support massive connectivity and reduce the transmission latency for future wireless communications. In this paper, we present a joint active user data detection with no priori knowledge of users relying on expectation propagation (EP) Gaussian approximation (GA) algorithm. To detect activity, structured spike slab prior introduced sparsity signal. Further, parameters unknown are learned via maximization (EM), which...

In the multi-antenna satellite communication system, beamforming and artificial noise are usually adopted to enhance physical layer security. However, due long distance between terrestrial terminal, coverage of main lobe in downlink is so large that eavesdropper can get into easily despite using spot beams. When close legitimate user, difference channel wiretap small, which makes secrecy capacity decrease rapidly. This paper proposes a novel scheme solve this problem by two different beams...