Publications
250 results found
Liu Z, Aditya S, Li H, et al., 2023, Joint transmit and receive beamforming design in full-duplex integrated sensing and communications, IEEE Journal on Selected Areas in Communications, Vol: 41, Pages: 2907-2919, ISSN: 0733-8716
Integrated sensing and communication (ISAC) has been envisioned as a solution to realize the sensing capability required for emerging applications in wireless networks. For a mono-static ISAC transceiver, as signal transmission durations are typically much longer than the radar echo round-trip times, the radar returns are drowned by the strong residual self interference (SI) from the transmitter, despite adopting sufficient SI cancellation techniques before digital domain - a phenomenon termed the echo-miss problem. A promising approach to tackle this problem involves the ISAC transceiver to be full-duplex (FD), and in this paper we jointly design the transmit and receive beamformers at the transceiver, transmit precoder at the uplink user, and receive combiner at the downlink user to simultaneously (a) maximize the uplink and downlink communication rate, (b) maximize the transmit and receive radar beampattern power at the target, and (c) suppress the residual SI. To solve this optimization problem, we proposed a penalty-based iterative algorithm. Numerical results illustrate that the proposed design can effectively achieve up to 60 dB digital-domain SI cancellation, a higher average sum-rate, and more accurate radar parameter estimation compared with previous ISAC FD studies.
Liu Z, Bhandari A, Clerckx B, 2023, λ–MIMO: massive MIMO via modulo sampling, IEEE Transactions on Communications, ISSN: 0090-6778
Massive multiple-input multiple-output (M-MIMO) architecture is the workhorse of modern communication systems. Currently, two fundamental bottlenecks, namely, power consumption and receiver saturation, limit the full potential achievement of this technology. These bottlenecks are intricately linked with the analog-to-digital converter (ADC) used in each radio frequency (RF) chain. The power consumption in M–MIMO systems grows exponentially with the ADC’s bit budget while ADC saturation causes permanent loss of information. This motivates the need for a solution that can simultaneously tackle the above-mentioned bottlenecks while offering advantages over existing alternatives such as low-resolution ADCs. Taking a radically different approach to this problem, we propose λ–MIMO architecture which uses modulo ADCs ( M λ –ADC) instead of a conventional ADC. Our work is inspired by the Unlimited Sampling Framework. M λ –ADC in the RF chain folds high dynamic range signals into low dynamic range modulo samples, thus alleviating the ADC saturation problem. At the same time, digitization of modulo signal results in high resolution quantization. In the novel λ–MIMO context, we discuss baseband signal reconstruction, detection and uplink achievable sum-rate performance. The key takeaways of our work include, (a) leveraging higher signal-to-quantization noise ratio (SQNR), (b) detection and average uplink sum-rate performances comparable to a conventional, infinite-resolution ADC when using a 1-2 bit M λ –ADC. This enables higher order modulation schemes e.g. 1024 QAM that seemed previously impossible, (c) superior trade-off between energy efficiency and bit budget, thus resulting in higher power efficiency. Numerical simulations and modulo ADC based hardware experiments corroborate our theory and reinforce the clear benefits of λ–MIMO approach.
Katwe M, Singh K, Clerckx B, et al., 2023, Improved Spectral Efficiency in STAR-RIS Aided Uplink Communication Using Rate Splitting Multiple Access, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 5365-5382, ISSN: 1536-1276
In this paper, a phase-shift coupled simultaneous transmitting/refracting and reflecting reconfigurable intelligent surface (STAR-RIS)-aided uplink (UL) rate-splitting multiple access (RSMA) system is investigated to achieve improved spectral efficiency. The considered UL RSMA system splits the rate for each user by dividing their message into multiple sub-messages and these sub-messages are transmitted to the base station (BS) via STAR-RIS as direct link between BS and user is absent. In particular, we formulate a resource allocation design problem which aim to maximize the overall rate-throughput of the considered system under the joint optimization of power allocation, decoding order, user-fairness and beamforming design at STAR-RIS for various operating modes of STAR-RIS modes, which is mixed- integer non-linear programming (MINLP). To solve the formulated non-convex complex problem, we first transform the original sum-rate maximization into its simplified form and then solved it using an alternating optimization algorithm where the sub-problems of power allocation and beamforming design under given decoding order are solved alternatively using general convex approximation and fractional programming approaches. Numerical simulation and computational complexity analysis validate that the proposed solution attains fast convergence. Moreover, the proposed RSMA scheme in STAR-RIS aided UL system outperforms the conventional nonorthogonal multiple access and orthogonal multiple access schemes in terms of overall rate-throughput and user-fairness.
Li H, Shen S, Clerckx B, 2023, Beyond Diagonal Reconfigurable Intelligent Surfaces: A Multi-Sector Mode Enabling Highly Directional Full-Space Wireless Coverage, IEEE Journal on Selected Areas in Communications, Vol: 41, Pages: 2446-2460, ISSN: 0733-8716
Reconfigurable intelligent surface (RIS) has gained much traction due to its potential to manipulate the propagation environment via nearly-passive reconfigurable elements. In our previous work, we have analyzed and proposed a beyond diagonal RIS (BD-RIS) model, which is not limited to traditional diagonal phase shift matrices, to unify different RIS modes/architectures. In this paper, we create a new branch of BD-RIS supporting a multi-sector mode. A multi-sector BD-RIS is modeled as multiple antennas connected to a multi-port group-connected reconfigurable impedance network. More specifically, antennas are divided into L ( L ≥ 2 ) sectors and arranged as a polygon prism with each sector covering 1/L space. Different from the recently introduced concept of intelligent omni-surface (or simultaneously transmitting and reflecting RIS), the multi-sector BD-RIS not only achieves a full-space coverage, but also has significant performance gains thanks to the highly directional beam of each sector. We derive the constraint of the multi-sector BD-RIS and the corresponding channel model taking into account the relationship between antenna beamwidth and gain. With the proposed model, we first derive the scaling law of the received signal power for a multi-sector BD-RIS -assisted single-user system. We then propose efficient beamforming design algorithms to maximize the sum-rate of the multi-sector BD-RIS -assisted multiuser system. Simulation results verify the effectiveness of the proposed design and demonstrate the performance enhancement of the proposed multi-sector BD-RIS.
Salem A, Masouros C, Clerckx B, 2023, Secure Rate Splitting Multiple Access: How Much of the Split Signal to Reveal?, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 4173-4187, ISSN: 1536-1276
Rate Splitting Multiple Access (RSMA) relies on multi-antenna rate splitting (RS) at the transmitter and successive interference cancellation (SIC) at the receiver. In RS the users' messages are split into a common message and private messages, where the common part is first decoded by the all users, while the private part is decoded only by the intended user using SIC technique. This split of the users ' signals into common and private parts raises some interesting tradeoffs between maximizing sum rate versus secrecy rate. In this work we consider the secrecy performance of RSMA in multi-user multiple-input single-output (MU-MISO) systems, where secrecy is defined by the ability of any user to decode the signal intended for user k in the system. To that end, new analytical expressions for the ergodic sum-rate and ergodic secrecy rate are derived for two closed-form precoding techniques of the private messages, namely, 1) zero-forcing (ZF) precoding approach, 2) minimum mean square error (MMSE) approach. Then, based on the analytical expressions of the ergodic rates, novel power allocation strategies that maximize the sum-rate subject to a target secrecy rate for the two precoding schemes are presented and investigated. Our Monte Carlo simulations show a close match with our theoretical derivations. They also reveal that, by tuning the split of the messages, our power allocation approaches provide a scalable tradeoff between rate benefits and secrecy.
Mishra A, Mao Y, Thomas CK, et al., 2023, Mitigating Intra-Cell Pilot Contamination in Massive MIMO: A Rate Splitting Approach, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 3472-3487, ISSN: 1536-1276
Massive multiple-input multiple-output (MaMIMO) has become an integral part of the fifth-generation (5G) standard, and is envisioned to be further developed in beyond 5G (B5G) networks. With a massive number of antennas at the base station (BS), MaMIMO is best equipped to cater prominent use cases of B5G networks such as enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC) and massive machine-type communications (mMTC) or combinations thereof. However, one of the critical challenges to this pursuit is the sporadic access behaviour of a massive number of devices in practical networks that inevitably leads to the conspicuous pilot contamination problem. Conventional linearly precoded physical layer strategies employed for downlink transmission in time division duplex (TDD) MaMIMO would incur a noticeable spectral efficiency (SE) loss in the presence of this pilot contamination. In this paper, we aim to integrate a robust multiple access and interference management strategy named rate-splitting multiple access (RSMA) with TDD MaMIMO for downlink transmission and investigate its SE performance. We propose a novel downlink transmission framework of RSMA in TDD MaMIMO, devise a precoder design strategy and power allocation schemes to maximize different network utility functions. Numerical results reveal that RSMA is significantly more robust to pilot contamination and always achieves a SE performance that is equal to or better than the conventional linearly precoded MaMIMO transmission strategy.
Cui H, Zhu L, Xiao Z, et al., 2023, Energy-Efficient RSMA for Multigroup Multicast and Multibeam Satellite Communications, IEEE Wireless Communications Letters, Vol: 12, Pages: 838-842, ISSN: 2162-2337
This letter studies energy-efficient rate-splitting multiple access (RSMA) for multigroup multicast and multibeam satellite communication systems. Specifically, we minimize the unmet system capacity, which means the rate difference between the requested user rate and the effective achieved rate, and communication energy consumption by optimizing the power allocation and rate allocation under the per-feed power and sum radiated power constraints. To solve the non-convex optimization problem, auxiliary variables and epigraph method are introduced to transform the original problem into a difference of convex functions programming. Then, the successive convex approximation (SCA) technique is used to obtain a suboptimal solution. Numerical results verify the superiority of our proposed solution compared to the benchmark methods.
Nerini M, Rizzello V, Joham M, et al., 2023, Machine Learning-Based CSI Feedback With Variable Length in FDD Massive MIMO, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 2886-2900, ISSN: 1536-1276
To fully unlock the benefits of multiple-input multiple-output (MIMO) networks, downlink channel state information (CSI) is required at the base station (BS). In frequency division duplex (FDD) systems, the CSI is acquired through a feedback signal from the user equipment (UE). However, this may lead to an important overhead in FDD massive MIMO systems. Focusing on these systems, in this study, we propose a novel strategy to design the CSI feedback. Our strategy allows to optimally design variable length feedback, that is promising compared to fixed feedback since users experience channel matrices differently sparse. Specifically, principal component analysis (PCA) is used to compress the channel into a latent space with adaptive dimensionality. To quantize this compressed channel, the feedback bits are smartly allocated to the latent space dimensions by minimizing the normalized mean squared error (NMSE) distortion. Finally, the quantization codebook is determined with k -means clustering. Numerical simulations show that our strategy improves the zero-forcing beamforming sum rate by 17%, compared to CsiNetPro. The number of model parameters is reduced by 23.4 times, thus causing a significantly smaller offloading overhead. At the same time, PCA is characterized by a lightweight unsupervised training, requiring eight times fewer training samples than CsiNetPro.
Xu Y, Mao Y, Dizdar O, et al., 2023, Max-Min Fairness of Rate-Splitting Multiple Access With Finite Blocklength Communications, IEEE Transactions on Vehicular Technology, Vol: 72, Pages: 6816-6821, ISSN: 0018-9545
Rate-Splitting Multiple Access (RSMA) has emerged as a flexible and powerful framework for wireless networks. In this paper, we investigate the user fairness of downlink multi-antenna RSMA in short-packet communications with/without cooperative (user-relaying) transmission. We design optimal time allocation and linear precoders that maximize the Max-Min Fairness (MMF) rate with Finite Blocklength (FBL) constraints. The relation between the MMF rate and blocklength, as well as the impact of cooperative transmission are investigated. Numerical results demonstrate that RSMA can achieve the same MMF rate as Non-Orthogonal Multiple Access (NOMA) and Space Division Multiple Access (SDMA) with smaller blocklengths (and therefore lower latency), especially in cooperative transmission deployment. Hence, we conclude that RSMA is a promising multiple access for guaranteeing user fairness in low-latency communications.
Clerckx B, Mao Y, Jorswieck EA, et al., 2023, Guest Editorial Rate Splitting for Future Wireless Networks, IEEE Journal on Selected Areas in Communications, Vol: 41, Pages: 1259-1264, ISSN: 0733-8716
Rate splitting (RS) and rate splitting multiple access (RSMA) have emerged as a promising and powerful multiple access, interference management, and multi-user strategy for next-generation wireless systems and networks. This Special Issue is entirely dedicated to the theory, design, optimization, and applications of RS and RSMA in various network configurations. It starts with a guest editor-authored tutorial paper [A1] that delineates the basic principles and applications of RS and RSMA. The tutorial paper is then followed by 17 technical papers.
Clerckx B, Mao Y, Jorswieck EA, et al., 2023, A Primer on Rate-Splitting Multiple Access: Tutorial, Myths, and Frequently Asked Questions, IEEE Journal on Selected Areas in Communications, Vol: 41, Pages: 1265-1308, ISSN: 0733-8716
Rate-Splitting Multiple Access (RSMA) has emerged as a powerful multiple access, interference management, and multi-user strategy for next generation communication systems. In this tutorial, we depart from the orthogonal multiple access (OMA) versus non-orthogonal multiple access (NOMA) discussion held in 5G, and the conventional multi-user linear precoding approach used in space-division multiple access (SDMA), multi-user and massive MIMO in 4G and 5G, and show how multi-user communications and multiple access design for 6G and beyond should be intimately related to the fundamental problem of interference management. We start from foundational principles of interference management and rate-splitting, and progressively delineate RSMA frameworks for downlink, uplink, and multi-cell networks. We show that, in contrast to past generations of multiple access techniques (OMA, NOMA, SDMA), RSMA offers numerous benefits: 1) enhanced spectral, energy and computation efficiency; 2) universality by unifying and generalizing OMA, SDMA, NOMA, physical-layer multicasting, multi-user MIMO under a single framework that holds for any number of antennas at each node (SISO, SIMO, MISO, and MIMO settings); 3) flexibility by coping with any interference levels (from very weak to very strong), network loads (underloaded, overloaded), services (unicast, multicast), traffic, user deployments (channel directions and strengths); 4) robustness to inaccurate channel state information (CSI) and resilience to mixed-critical quality of service; 5) reliability under short channel codes and low latency. We then discuss how those benefits translate into numerous opportunities for RSMA in over forty different applications and scenarios of 6G, e.g., multi-user MIMO with statistical/quantized CSI, FDD/TDD/cell-free massive MIMO, millimeter wave and terahertz, cooperative relaying, physical layer security, reconfigurable intelligent surfaces, cloud-radio access network, internet-of-things, massive acce
Katwe M, Singh K, Clerckx B, et al., 2023, Rate Splitting Multiple Access for Sum-Rate Maximization in IRS Aided Uplink Communications, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 2246-2261, ISSN: 1536-1276
In this paper, an intelligent reflecting surface (IRS) aided uplink (UL) rate-splitting multiple access (RSMA) system is investigated for dead-zone users where the direct link between the users and the base station (BS) is unavailable and the UL transmission is carried out only through IRS. In the considered RSMA system, a message of each user is split into several sub-messages and each part contributes to the rate of that user and depending upon split proportions BS decodes them using appropriate decoding order. The problem of sum-rate maximization is formulated to jointly design the optimal power allocation at each UL user, passive beamforming at the IRS under optimal decoding order of sub-messages. Due to non-convexity and discrete non-linear programming of the formulated problem, the original problem is intractable and hence, we decouple the problem into different sub-problems in which the problems of power allocation and passive beamforming are alternatively solved under using successive convex approximation and Riemaniann conjugate gradient algorithms, respectively. Moreover, the decoding order strategy is analytically derived which confirm that the optimal decoding order strategy depend upon decreasing order of channel gain of users and increasing order of split proportions of sub-messages. Later, the unified solution based on block-coordinate descent (BCD) algorithm is proposed. Simulation results validate that the proposed decoding order scheme attains performance closer to the optimal solution with low computational complexity. Moreover, the proposed IRS aided RMSA system outperforms the system with non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) schemes in terms of achievable sum-rate throughput.
Li H, Shen S, Clerckx B, 2023, Beyond Diagonal Reconfigurable Intelligent Surfaces: From Transmitting and Reflecting Modes to Single-, Group-, and Fully-Connected Architectures, IEEE Transactions on Wireless Communications, Vol: 22, Pages: 2311-2324, ISSN: 1536-1276
Reconfigurable intelligent surfaces (RISs) are envisioned as a promising technology for future wireless communications. With various hardware realizations, RISs can work under different modes (reflective/transmissive/hybrid) or have different architectures (single/group/fully-connected). However, most existing research focused on single-connected reflective RISs, mathematically characterized by diagonal phase shift matrices, while there is a lack of a comprehensive study for RISs unifying different modes/architectures. In this paper, we solve this issue by analyzing and proposing a general RIS-aided communication model. Specifically, we establish an RIS model not limited to diagonal phase shift matrices, a novel branch referred to as beyond diagonal RIS (BD-RIS), unifying modes and architectures. With the proposed model, we develop efficient algorithms to jointly design transmit precoder and BD-RIS matrix to maximize the sum-rate for RIS-aided systems. We also provide simulation results to compare the performance of BD-RISs with different modes/architectures. Simulation results show that under the same mode, fully- and group-connected RIS can effectively increase the sum-rate performance compared with single-connected RIS, and that hybrid RIS outperforms reflective/transmissive RIS with the same architecture.
Nerini M, Clerckx B, 2023, Overhead-Free Blockage Detection and Precoding Through Physics-Based Graph Neural Networks: LIDAR Data Meets Ray Tracing, IEEE Wireless Communications Letters, Vol: 12, Pages: 565-569, ISSN: 2162-2337
In this letter, we address blockage detection and precoder design for multiple-input multiple-output (MIMO) links, without communication overhead required. Blockage detection is achieved by classifying light detection and ranging (LIDAR) data through a physics-based graph neural network (GNN). For precoder design, a preliminary channel estimate is obtained by running ray tracing on a 3D surface obtained from LIDAR data. This estimate is successively refined and the precoder is designed accordingly. Numerical simulations show that blockage detection is successful with 95% accuracy. Our digital precoding achieves 90% of the capacity and analog precoding outperforms previous works exploiting LIDAR for precoder design.
Xu J, Dizdar O, Clerckx B, 2023, Rate-Splitting Multiple Access for Short-Packet Uplink Communications: A Finite Blocklength Analysis, IEEE Communications Letters, Vol: 27, Pages: 517-521, ISSN: 1089-7798
In this letter, we investigate the performance of Rate-Splitting Multiple Access (RSMA) for an uplink communication system with finite blocklegnth (FBL). Considering a two-user Single-Input Single-Output (SISO) Multiple Access Channel (MAC), we study the impact of blocklength and target rate on the throughput and error probability performance of RSMA where one user message is split. We demonstrate that RSMA can outperform Non-Orthogonal Multiple Access (NOMA) in terms of throughput and error probability performance.
Zhao Y, Wu Y, Hu J, et al., 2023, Energy Harvesting Modulation for Integrated Control State and Energy Transfer in Industrial IoT, IEEE Wireless Communications Letters, Vol: 12, Pages: 292-296, ISSN: 2162-2337
With the development of wireless communications, the technology of industrial Internet of Things (IIoT) has been considered as a candidate for the next generation of mobile communications, which could provide automatic services for the smart factory. Massive low-power devices are swarming into the scenario for providing network intelligence. These energy-thirsty devices all require efficient control state delivery. In this letter, an energy harvesting modulation (EHM) scheme is proposed for integrated control state and energy transfer (ICSET) towards these low-power devices. The performance of wireless energy transfer (WET) and wireless control state transfer (WCST) are also analysed theoretically. The ICSET performance is optimized by ensuring the control reliability. Simulation results validate the theoretical analysis. They also demonstrate that an appropriate time slot number within a period should be selected to increase the effective control rate, while ensuring the energy harvesting performance and the control reliability of IIoT.
Yin L, Clerckx B, 2023, Rate-Splitting Multiple Access for Satellite-Terrestrial Integrated Networks: Benefits of Coordination and Cooperation, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, Vol: 22, Pages: 317-332, ISSN: 1536-1276
Shen S, Kim J, Clerckx B, 2023, Closed-loop wireless power transfer with adaptive waveform and beamforming: design, prototype, and experiment, IEEE Journal of Microwaves, Vol: 3, Pages: 29-42, ISSN: 2692-8388
A closed-loop far-field wireless power transfer (WPT) system with adaptive waveform and beamforming using limited feedback is designed, prototyped, and experimented. Spatial domain and frequency domain are jointly exploited by utilizing waveform and beamforming at the transmitter in WPT system to adapt to the multipath fading channel and boost the output dc power. A closed-loop architecture based on a codebook design and an over-the-air limited feedback with low complexity is proposed. The codebook consists of multiple codewords where each codeword represents particular waveform and beamforming. The transmitter sweeps through the codebook and the receiver then feeds the optimal codeword index back to the transmitter, so that the waveform and beamforming can be adaptive for maximizing the output dc power without requiring explicit channel estimation and the knowledge of accurate Channel State Information. The proposed closed-loop WPT with adaptive waveform and beamforming using limited feedback is prototyped using a Software Defined Radio equipment and measured in two real indoor environments. It is experimentally shown that the proposed closed-loop WPT with adaptive waveform and beamforming is able to enhance the output dc power by up to 14.7 dB in comparison with conventional 1-tone 1-antenna WPT system.
Zhang Y, Clerckx B, 2023, Waveform Design for Wireless Power Transfer With Power Amplifier and Energy Harvester Non-Linearities, IEEE Transactions on Signal Processing, Vol: 71, Pages: 2638-2653, ISSN: 1053-587X
Waveform optimization has shown its great potential to boost the performance of far-field wireless power transfer (WPT). Current research has optimized transmit waveform, adaptive to channel state information, to maximize the harvested power in WPT while accounting for the energy harvester (EH)'s non-linearity. However, the existing transmit waveform design disregards the non-linear high power amplifiers (HPA) at the transmitter. Driven by this, this article optimizes a multi-carrier waveform at the input of HPA to maximize the harvested DC power considering both HPA's and EH's non-linearities. Two optimization models are formulated based on whether the frequencies of the input waveform are concentrated within the transmit pass band or not. Analysis and simulations show that, while EH's non-linearity boosts the power harvesting performance, HPA's non-linearity degrades the harvested power. Hence, the optimal waveform shifts from multi-carrier that exploits EH's non-linearity to single-carrier that reduces HPA's detrimental non-linear distortion as the operational regime of WPT becomes more sensitive to HPA's non-linearity and less sensitive to EH's non-linearity (and inversely). Simultaneously, operating towards HPA's non-linear regime by increasing the input signal power benefits the harvested power since HPA's DC power supply is better exploited, whereas the end-to-end power transfer efficiency might decrease because of HPA's increasing non-linear degradation. Throughout the simulations, the proposed waveforms show significant gain over those not accounting for HPA's non-linearity, especially in frequency-flat channels. We also compare the two proposed waveforms and show that the severity of HPA's non-linearity dictates which of the two proposed waveforms is more beneficial.
Singh SK, Agrawal K, Singh K, et al., 2023, RSMA for Hybrid RIS-UAV-aided Full-Duplex Communications with Finite Blocklength Codes under Imperfect SIC, IEEE Transactions on Wireless Communications, ISSN: 1536-1276
In this work, we consider a hybrid aerial full-duplex (FD) relaying consisting of a reconfigurable intelligent surface (RIS) mounted over an FD unmanned aerial vehicle (UAV) relay operating in decode and forward mode to assist the information transfer between the base station and multiple users. For better spectral efficiency, we investigate the use of rate splitting multiple access (RSMA) in such networks and focus on joint optimization of RSMA parameters, 3D-coordinates of the UAV/RIS, and phase shift matrix at the RIS along with analyzing the outage probability, block error rate (BLER) and achievable weighted sum rate for finite blocklength (FBL) and infinite blocklength (IBL) codes under imperfect successive interference cancellation (SIC) at each user and residual-self interference (RSI) at the UAV. We first formulate the weighted sum rate maximization problem and adopt the block coordinate descent (BCD) method to deal with the non-convex nature of the problem. Thereafter, we propose a BCD-based algorithm that jointly optimizes these parameters using a heuristic approach for optimum power allocation, a Riemannian conjugate gradient-based algorithm to get the optimal phase shift at the RIS, and an iterative algorithm to obtain the optimal UAV/RIS position. It also distributes the common rate among the users optimally. Next, with obtained optimal parameters, we further analyze the performance of the network and derive the closed-form expressions of BLER, outage probability, and average weighted sum rate. We present Monte Carlo simulation-based results to validate the accuracy of the proposed algorithms and derived expressions, and demonstrate the superiority of RSMA over non-orthogonal multiple access (NOMA) and conventional orthogonal multiple access (OMA) schemes.
Aditya S, Dizdar O, Clerckx B, et al., 2022, Sensing using Coded Communications Signals, IEEE Open Journal of the Communications Society, Vol: 4, Pages: 134-152, ISSN: 2644-125X
A key challenge for common waveforms for Integrated Sensing and Communications – widely regarded as a resource-efficient way to achieve high performance for both functionalities – lies in leveraging information-bearing channel-coded communications signal(s) (c.c.s) for sensing. In this paper, we investigate the range-Doppler sensing performance of c.c.s in multi-user interference-limited scenarios, and show that it is affected by sidelobes whose form depends on whether the c.c.s modulates a single-carrier or OFDM waveform. While uncoded signals give rise to asymptotically zero sidelobes due to the law of large numbers, it is not obvious that the same holds for c.c.s, as structured codes (e.g., linear block codes) induce dependence across codeword symbols. In this paper, we show that c.c.s also give rise to asymptotically zero sidelobes – for both single-carrier and OFDM waveforms – by deriving upper bounds for the tail probabilities of the sidelobe magnitudes that decay as exp(−O(code rate×block length)) . Consequently, for any code rate, c.c.s are effective sensing signals that are robust to multi-user interference at sufficiently large block lengths, with negligible difference in performance based on whether they modulate a single-carrier or OFDM waveform. We verify the latter implication through simulations, where we observe the sensing performance (i.e., the detection and false-alarm probabilities) of a QPSK-modulated c.c.s (code rate = 120/1024, block length = 1024 symbols) to match that of a comparable interference-free FMCW waveform even at high interference levels (SIR of −11dB), for both single-carrier and OFDM waveforms.
Katwe M, Singh K, Clerckx B, et al., 2022, Rate-Splitting Multiple Access and Dynamic User Clustering for Sum-Rate Maximization in Multiple RISs-Aided Uplink mmWave System, IEEE TRANSACTIONS ON COMMUNICATIONS, Vol: 70, Pages: 7365-7383, ISSN: 0090-6778
Xu Y, Mao Y, Dizdar O, et al., 2022, Rate-Splitting Multiple Access With Finite Blocklength for Short-Packet and Low-Latency Downlink Communications, IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, Vol: 71, Pages: 12333-12337, ISSN: 0018-9545
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Bastami H, Moradikia M, Abdelhadi A, et al., 2022, Maximizing the Secrecy Energy Efficiency of the Cooperative Rate-Splitting Aided Downlink in Multi-Carrier UAV Networks, IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, Vol: 71, Pages: 11803-11819, ISSN: 0018-9545
Yin L, Mao Y, Dizdar O, et al., 2022, Rate-Splitting Multiple Access for 6G-Part II: Interplay With Integrated Sensing and Communications, IEEE COMMUNICATIONS LETTERS, Vol: 26, Pages: 2237-2241, ISSN: 1089-7798
Mishra A, Mao Y, Dizdar O, et al., 2022, Rate-Splitting Multiple Access for 6G-Part I: Principles, Applications and Future Works, IEEE COMMUNICATIONS LETTERS, Vol: 26, Pages: 2232-2236, ISSN: 1089-7798
Li H, Mao Y, Dizdar O, et al., 2022, Rate-Splitting Multiple Access for 6G-Part III: Interplay With Reconfigurable Intelligent Surfaces, IEEE COMMUNICATIONS LETTERS, Vol: 26, Pages: 2242-2246, ISSN: 1089-7798
Xiao Z, Han Z, Nallanathan A, et al., 2022, Antenna Array Enabled Space/Air/Ground Communications and Networking for 6G, IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, Vol: 40, Pages: 2773-2804, ISSN: 0733-8716
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Feng Z, Clerckx B, Zhao Y, 2022, Waveform and beamforming design for intelligent reflecting surface aided wireless power transfer: single-user and multi-user solutions, IEEE Transactions on Wireless Communications, Vol: 21, Pages: 5346-5361, ISSN: 1536-1276
In this paper, we study the waveform and passive beamforming design for intelligent reflecting surface (IRS)-aided wireless power transfer (WPT). Generalized multi-user and low complexity single-user algorithms are demonstrated based on alternating optimization (AO) framework to maximize the weighted sum output direct current (DC), subject to the transmit power constraints and passive beamforming modulus constraints. The input signal waveform and IRS passive beamforming phase shifts are jointly designed as a function of users’ individual frequency-selective channel state information (CSI). The energy harvester nonlinearity is explored and two IRS deployment schemes, namely frequency selective IRS (FS-IRS) and frequency flat IRS (FF-IRS), are modeled and analyzed. This paper highlights the fact that IRS can provide an extra passive beamforming gain on output DC power over conventional WPT designs and significantly influence the waveform design by leveraging the benefit of passive beamforming, frequency diversity and energy harvester nonlinearity. Even though FF-IRS exhibits lower output DC than the ideal FS-IRS, it still achieves substantially increased DC power over conventional WPT designs. Performance evaluations confirm the significant benefits of a joint waveform and passive beamforming design accounting for the energy harvester nonlinearity to boost the performance of single-user and multi-user WPT systems.
Zhou G, Mao Y, Clerckx B, 2022, Rate-Splitting Multiple Access for Multi-Antenna Downlink Communication Systems: Spectral and Energy Efficiency Tradeoff, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, Vol: 21, Pages: 4816-4828, ISSN: 1536-1276
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- Citations: 8
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