New non-orthogonal transmission schemes for achieving highly efficient, reliable, and secure multi-user communications

Next-generation wireless communication paradigms demand poperties such as high reliability, low power consumption, and enhanced security. Also, the ever-increasing demand for better wireless services has led to the continuous improvement and emergence of various wireless networks such as 5G and beyond networks. Beyond 5G communication systems (i.e., 6G) are envisioned to utilize technologies such as artificial intelligence, ultra-dense small cells, reconfigurable antennas, distributed networks, multi-band and full-duplex communications, as well as novel non-orthogonal multiple access methods. In this work, we first revisit and review the various current non-orthogonal multiple access (NOMA) techniques available in the literature and proposed by both academia and industry. Then, we discuss their strengths and weaknesses in different application areas. To address the limitations of the existing NOMA schemes, we develop and propose novel NOMA communication paradigms designed for achieving highly efficient, reliable, and secure multi-user communications using superimposed auxiliary signals and pre-coded matrices methods. The new proposed NOMA systems are motivated by the many limitations faced by current NOMA-based systems. For instance, power-domain NOMA is not included in release 17 of 3GPP as a work item. This is due to its performance degradation, resulting from successive interference cancellation (SIC) and channel estimation errors. The efficiency and novelty of the proposed models are presented via mathematical analysis and validated by Monte Carlo simulations.This work was supported in part by the Scientific and Technological Research Council of Turkey (TUBITAK), under project grant No. 119E392

Orthogonal frequency division multiplexing with subcarrier power modulation for doubling the spectral efficiency of 6G and beyond networks

With the emergence of new applications (eg, extended reality [XR] and haptics), which require to be simultaneously served not just with low latency and sufficient reliability, but also with high spectral efficiency, future networks (ie, 6G and beyond) should be capable of meeting this demand by introducing new effective transmission designs. Motivated by this, a novel modulation technique termed as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM) is proposed for providing highly spectral-efficient data transmission with low-latency and less-complexity for future 6G wireless communication systems. OFDM-SPM utilizes the power of subcarriers in OFDM blocks as a third dimension to convey extra information bits while reducing both complexity and latency compared to conventional schemes. In this article, the concept of OFDM-SPM is introduced and its validity as a future adopted modulation technique is investigated over a wireless multipath Rayleigh fading channel. The proposed system structure is explained, an analytical expression of the bit error rate (BER) is derived, and numerical simulations of BER and throughput performances of OFDM-SPM are carried out. OFDM-SPM is found to greatly enhance the spectral efficiency where it is capable of doubling it. In addition, OFDM-SPM introduces negligible complexity to the system, does not exhibit error propagation, reduces the transmission delay, and decreases the transmission power by half.Türkiye Bilimsel ve Teknolojik Araştirma Kurumu, 119E40

Gelecekteki kablosuz sistemler için yeni dalga şekli tasarımları: eşevreli olmayan OFDM ile alt taşıyıcı güç modülasyonu (NC-OFDM-SPM) & çok kullanıcı yardımcı sinyal süperpozisyon iletimi (MU-ASST)

Future wireless systems are expected to serve very challenging requirements such as enhancing the spectral efficiency and transmission reliability, securing the transmission and guaranteeing low-complexity and low latency communications. In this scope, we investigate and propose in this work some promising research directions for ensuring an effective design for future wireless systems: 1) we study the combination of multi-dimensional OFDM modulations and non-coherent detection for enhancing the spectral efficiency and reducing the complexity in the design of future wireless systems. Particularly, in this regard, we propose and study a new technique termed as ’Non-Coherent Orthogonal Frequency Division Multiplexing with Subcar rier Power Modulation (NC-OFDM-SPM)’ for doubling the spectral efficiency per receiving user/device through the exploration of the power of the subcarriers inside an OFDM block as an additional dimension for conveying extra information. The use of non-coherent detection en sures low-design complexity in this idea. 2) We propose a novel physical layer security design for effective and secure future multiple access communications. The proposed design is called ’Multi-User Auxiliary Signal Superposition Transmission (MU-AS-ST)’ which is presented as an alternative design for the current conventional Power Domain NOMA which was studied by the 3GGP (3rd Generation Partnership Project) from release 13 till 16 under the name ’Multi User Superposition Transmission (MUST)’ before being eliminated from the study items in release 17. The proposed design superimposes auxiliary signals with the users data for can celling the inter-user interference fully while achieving perfect secrecy against both internal (presence of an untrusted legitimate user) and external eavesdroppers. MU-AS-ST achieves better reliability than conventional NOMA and does not use Successive Interference Cancel lation. Moreover, this design works for the combination of any two users regardless of their distance from the base station unlike conventional NOMA which works only for the cases where there exists a significant path-loss channel difference between paired (or super-imposed) users. Furthermore, carrying all the processing at the base station makes this design an appeal ing choice for processing-restricted communication devices such as IoT devices. 3) We study the integration of multi-dimensional OFDM modulation formats in multiple access setups for enhancing the spectral efficiency per area and per device for a more optimal usage of the spec trum allocated for wireless communications. As an example of this integration, we study the combination of OFDM-SPM with MU-AS-ST where we show that this leads to doubling the spectral efficiency per area and per device. The proposed designs were studied thoroughly and their performance was evaluated in terms of different performance metrics such as bit error rate, spectral efficiency, design complexity and peak to average power ratio (PAPR).Gelecekteki kablosuz sistemlerin, spektral verimliliği ve iletim güvenilirliğini artırmak, iletimi güvence altına almak ve düşük karmaşıklık ve düşük gecikmeli iletişimleri garanti etmek gibi çok zorlu gereksinimleri karşılaması beklenmektedir. Bu kapsamda, bu çalışma içerisinde gelecekteki kablosuz sistemler için etkili bir tasarım sağlamak için bazı umut verici araştırma yönlerini araştırıyor ve öneriyoruz: 1) spektral verimliliği artırmak ve gelecekteki kablosuz sistemlerin tasarımındaki karmaşıklığı azaltmak için çok boyutlu OFDM modülasyonları ve eşevreli olmayan (non-coherent) modülasyon tabanlı tekniklerin kombinasyonunu inceliyoruz. Özellikle,bu bağlamda, alıcı kullanıcı / cihaz başına spektral verimliliği iki katına çıkarmak için Non-Coherent Orthogonal Frequency Division Multiplexing with Subcarrier Power Modulation(NC-OFDM-SPM) olarak adlandırılan yeni bir teknik öneriyor ve üzerinde çalışıyoruz. Ek bitler, bir OFDM bloğu içindeki alt taşıyıcıların gücünün ek bilgi iletimi için ek bir boyut olarak manipülasyonu yoluyla gönderilir. Ayrıca eşevreli olmayan (non-coherent) modülasyonun kullanılması, bu teknikte düşük tasarım karmaşıklığı sağlamaktadır. 2) Gelecekteki etkili ve güvenli çoklu erişim iletişimleri için yeni bir fiziksel katman güvenliği tasarımı öneriyoruz. Önerilen tasarım, Multi-User Auxiliary Signal Superposition Transmission (MU-ASST) olarak adlandırılır ve mevcut geleneksel Power Domain NOMA için alternatif bir tasarım olarak sunulur. Power Domain NOMA, sürüm 17’deki çalışma öğelerinden çıkarılmadan önce, sürüm 13’ten 16’ya kadar 3GGP (3. Nesil Ortaklık Projesi/ 3rd Generation Partnership Project) tarafından Multi-User Superposition Transmission (MUST) adı altında incelenmiştir. Önerilen tasarım, kullanıcı verilerinin üzerine bindirilmiş yardımcı sinyalleri kullanarak hem dahili (güvenilmeyen meşru kullanıcı) hem de harici dinleyicilere karşı mükemmel gizlilik sağlarken, kullanıcılar arası müdahaleyi (inter-user interference) tamamen iptal etmektedir. MU-AS-ST, geleneksel NOMA’dan daha iyi güvenilirlik sağlar ve Successive Interference Cancellation (SIC) kullanmamaktadır. Dahası, bu tasarım, yalnızca eşleştirilmiş (veya süper empoze edilmiş) kullanıcılar arasında önemli bir kanal farkının olduğu durumlarda çalışan geleneksel NOMA’nın aksine, baz istasyonuna olan uzaklıklarından bağımsız olarak herhangi iki kullanıcının kombinasyonu için çalışır. Ayrıca, tüm işlemlerin baz istasyonuna taşınması, bu tasarımı IoT cihazları gibi işlemle sınırlı iletişim cihazları için cazip bir seçim haline gelir. 3) Kablosuz iletişim için ayrılan spektrumun daha optimum kullanımı için alan ve cihaz başına spektral verimliliği artırmak için çoklu erişim kurulumlarında çok boyutlu OFDM modülasyon formatlarının entegrasyonunu inceliyoruz. Bu çalışmada, OFDM-SPM’nin MUAS-ST ile kombinasyonunu inceliyoruz, burada bu kombinasyonun alan ve cihaz başına spektral verimliliği iki katına çıkardığını gösteriyoruz. Önerilen tasarımlar, spektral verimlilik, iletim güvenilirliği, tasarım karmaşıklığı ve tepe / ortalama güç oranı (PAPR) gibi farklı performans ölçütleri açısından kapsamlı bir şekilde incelenmiştir.No sponso

NC-OFDM-SPM: a two-dimensional non-coherent modulation scheme for achieving the coherent performance of OFDM along with sending an additional data-stream

A promising candidate solution for reducing complexity in future wireless systems is the use of non-coherent designs; however, it is very well known in the literature that non-coherent schemes perform worse than their coherent counterparts. To address this longstanding challenging trade-off, we demonstrate and prove in this work the ability of the proposed two-dimensional modulation scheme termed as non-coherent orthogonal frequency division multiplexing with subcarrier power modulation and differential phase shift keying in achieving the performance of a coherent design, while reducing complexity. Although the proposed design is non-coherent (i.e., it uses differential phase shift keying and power difference to convey information), it achieves the same bit error rate (BER) performance as conventional OFDM with coherent BPSK. Furthermore, since the proposed scheme employs two-dimensional modulations simultaneously (i.e., DPSK and subcarrier power levels), an additional data stream can be transmitted through the power subcarriers’ levels. Thus, the proposed design not only solves the trade-off between coherent and non-coherent modulations in terms of reliability by achieving the same BER, but also provides higher data rates by exploring the power domain as an additional dimension for conveying extra data bits, while maintaining low complexity transceiver design, thus making it very appealing for IoT applications.No sponso

Non-coherent OFDM-subcarrier power modulation for low complexity and high throughput Iot applications

Aiming to reduce the transceiver complexity and power consumption of communication systems dedicated to serving future Internet of Things (IoT) applications, researchers have taken many approaches with varying degrees of success. A promising candidate solution that can reduce complexity significantly and thus also enhance power-saving is the use of non-coherent modulation-based schemes. Utilizing a non-coherent structure rids the system of any dependency on the knowledge of the phase of the transmitted signal during demodulation. However, although most of the available non-coherent techniques in the literature reduce the complexity of the system, they, unfortunately, suffer from a drawback of some sort, especially in reducing the overall spectral efficiency of the system. To address this problem, we propose a new non-coherent modulation scheme called orthogonal frequency division multiplexing with subcarrier power modulation and differential phase-shift keying (OFDM-SPM-DPSK), as an effective modulation technique for future 6G and beyond systems. The proposed technique has the potential to reduce complexity, enhance power-saving while improving spectral efficiency significantly, resulting in a spectral efficiency performance twice that of a conventional non-coherent OFDM system. Furthermore, receive diversity is implemented through maximal ratio combining to overcome the bit error degradation brought by the adoption of a non-coherent structure. Additionally, the computational complexity is discussed and shown to be as efficient as OFDM, where the proposed scheme does not add further complexity over conventional OFDM.This work was supported in part by the Scientific and Technological Research Council of Turkey (TUBITAK), under project grant No. 119E408

D-SEAD: a novel multi-access multi-dimensional transmission technique for doubling the spectral efficiency per area and per device

The world of today is characterized by a very huge inter-connectivity of data-hungry devices. This imposes on wireless system designers not only developing techniques that are spectrally efficient at the area level where many users are served with the same resources simultaneously but also developing techniques that are spectrally efficient at the device level as well. For addressing this problem, we propose in this paper a technique that is capable of doubling the spectral efficiency per area and per device by modulating a recently developed multiple access design called multi-user auxiliary signal superposition transmission (MU-AS-ST) through a multi-dimensional OFDM technique termed OFDM with subcarrier power modulation (OFDM-SPM). This integration results in the technique proposed in this paper and yields, with doubling the spectral efficiency, merits such as robust security, low complexity, and enhanced transmission reliability.No sponso

A spectrally efficient OFDM-based modulation scheme for future wireless systems

A novel modulation technique termed as orthogonal frequency division multiplexing with subcarrier power modulation (OFDM-SPM) for efficient data transmission in wireless communication systems is proposed. OFDM-SPM uses the power of each subcarrier in an OFDM block as a third dimension to carry data, where different power levels correspond to different bits. In this paper, the concept of OFDM-SPM is applied to conventional OFDM using binary phase shift keying (BPSK) symbol modulation over an additive white Gaussian noise channel (AWGN). The system and its validity as a future adopted modulation technique is investigated, where a general overview of the system is given. Simulation results regarding the bit error rate (BER) and the throughput of the system are displayed, and the merits of this scheme are discussed. Results show that compared to other proposed modulation techniques which add a third dimension to carry data, OFDM-SPM vastly improves spectral efficiency, where it is capable of doubling the spectral efficiency in addition to reducing the transmission power of the system by half. Although this results in a degradation in the system bit error rate performance, the scheme suggests that this can be overcome by reallocating the saved power to the transmitted OFDM subcarriers.No sponso

Mathematical model of the ventricular action potential and effects of isoproterenol-induced cardiac hypertrophy in rats

Mathematical action potential (AP) modeling is a well-established but still-developing area of research to better understand physiological and pathological processes. In particular, changes in AP mechanisms in the isoproterenol (ISO) -induced hypertrophic heart model are incompletely understood. Here we present a mathematical model of the rat AP based on recordings from rat ventricular myocytes. In our model, for the first time, all channel kinetics are defined with a single type of function that is simple and easy to apply. The model AP and channels dynamics are consistent with the APs recorded from rats for both Control (absence of ISO) and ISO-treated cases. Our mathematical model helps us to understand the reason for the prolongation in AP duration after ISO application while ISO treatment helps us to validate our mathematical model. We reveal that the smaller density and the slower gating kinetics of the transient K+ current help explain the prolonged AP duration after ISO treatment and the increasing amplitude of the rapid and the slow inward rectifier currents also contribute to this prolongation alongside the flux in Ca2+ currents. ISO induced an increase in the density of the Na+ current that can explain the faster upstroke. We believe that AP dynamics from rat ventricular myocytes can be reproduced very well with this mathematical model and that it provides a powerful tool for improved insights into the underlying dynamics of clinically important AP properties such as ISO application.This study was supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Project No: 117F020). These funding sources had no involvement in study design, writing of the report, decision to publish, or the collection, analysis, and interpretation of data