Multidimensional Index Modulation for 5G and Beyond Wireless Networks

This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of one-dimensional IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communication (URLLC). Additionally, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks.Comment: This work has been submitted to Proceedings of the IEEE for possible publicatio

Data confidentiality for IoT networks: cryptographic gaps and physical-layer opportunities

The conventional solution for providing data confidentiality is by means of encryption (a branch of cryptography). However, encryption schemes are generally designed to provide a certain level of security without necessarily taking resource consumption into account. This poses an issue for Internet of Things (IoT) devices which are limited in terms of storage capacity and computational capabilities. In this paper, we discuss the capabilities of cryptographic solutions for providing data confidentiality and we evaluate whether these solutions are appropriate for IoT networks in terms of resource consumption. Based on the identified drawbacks of cryptographic solutions, we discuss opportunities within the area of physical-layer security (PLS). Finally, we provide an overview of PLS schemes which aim to enhance data confidentiality in IoT networks

Multidimensional index modulation for 5G and beyond wireless networks

Index modulation (IM) provides a novel way for the transmission of additional data bits via the indices of the available transmit entities compared with classical communication schemes. This study examines the flexible utilization of existing IM techniques in a comprehensive manner to satisfy the challenging and diverse requirements of 5G and beyond services. After spatial modulation (SM), which transmits information bits through antenna indices, application of IM to orthogonal frequency-division multiplexing (OFDM) subcarriers has opened the door for the extension of IM into different dimensions, such as radio frequency (RF) mirrors, time slots, codes, and dispersion matrices. Recent studies have introduced the concept of multidimensional IM by various combinations of 1-D IM techniques to provide higher spectral efficiency (SE) and better bit error rate (BER) performance at the expense of higher transmitter (Tx) and receiver (Rx) complexity. Despite the ongoing research on the design of new IM techniques and their implementation challenges, proper use of the available IM techniques to address different requirements of 5G and beyond networks is an open research area in the literature. For this reason, we first provide the dimensional-based categorization of available IM domains and review the existing IM types regarding this categorization. Then, we develop a framework that investigates the efficient utilization of these techniques and establishes a link between the IM schemes and 5G services, namely, enhanced mobile broadband (eMBB), massive machine-type communications (mMTCs), and ultrareliable low-latency communication (URLLC). In addition, this work defines key performance indicators (KPIs) to quantify the advantages and disadvantages of IM techniques in time, frequency, space, and code dimensions. Finally, future recommendations are given regarding the design of flexible IM-based communication systems for 5G and beyond wireless networks

Kablosuz haberleşmenin geleceği için girişim ve kanal kontrol teknikleri

Interference and random behavior of the propagation environment are the main impediments to serve a broad range of applications and use-cases in modern communication systems. Although conventional orthogonal multiple accessing (OMA) schemes are prominent for achieving high reliability, they are far from reaching the goals of 5G and beyond networks in terms of system capacity, massive connectivity, and latency. On the other hand, interest in high-frequency bands is growing due to the enormous amount of spare spectrum that has the potential to realize the aspirations of future communication systems. In addition to these considerations, next-generation communication systems require a flexible and scalable design to meet user equipment (UE) demands. For these reasons, this thesis study focuses on three pivotal research directions that control of interference in communication systems, control of channel randomness in millimeter wave (mmWave) bands, and the richness and flexibility of multidimensional signal transmission. In particular, non-orthogonal multiple accessing (NOMA) caused by partial and fully overlapping of the existing UEs, adaptive directional communication against low penetration capabilities in mmWave frequency band, and index modulation (IM)-aided multidimensional transmission for achieving flexibility are studied in the scope of this thesis. Despite all the efforts, having effective multiple access under non-orthogonal conditions is still a conundrum in the literature. As a promising approach, waveform domain NOMA concept is introduced for serving multiple users with different requirements. The goal of waveform domain NOMA is to control interference by means of unique waveform features and consequently ensuring the separability of the overlapped UEs at the receiver. Specifically, the control of interference distribution is provided via the coexistence of appropriate waveforms while the average power of the interference remains the same. Moreover, diversity gain is achieved through interference hopping during repetitions. Moreover, intercarrier-interference (ICI) control for asynchronous networks and inter-numerology interference (INI) control for OFDM systems with multi-numerologies are studied via the exploitation of frequency domain IM, i.e., OFDM-IM, with the design of novel subcarrier mapping schemes. Directional communication in mmWave bands provides opportunities to combat high-level propagation loss. However, initiating communication over a certain direction makes the link vulnerable against low penetration capabilities, i.e., blockage impact. Beamwidth optimization in mmWave frequency bands is proposed in order to combat high path loss and blockage impact. Lastly, IM-aided multidimensional communication opportunities are surveyed in a comprehensive manner. Specifically, a framework is developed for the purpose of efficient utilization of signal dimensions in order to address diverse requirements of 5G and beyond systems.Girişim ve yayılma ortamının rastgele davranışı, modern iletişim sistemlerinin hedeflerine ulaşmak için temel engellerdir. Öte yandan, geniş uygulama yelpazisini bünyesinde barındırmak için yeni nesil haberleşme sistemlerinin esnek bir yapıya sahip olması gerekmektedir. Bu yüzden, mevcut kullanıcı ekipmanlarının (UE) kısmi ve tamamen çakışması kaynaklı dikey olmayan çoklu erişim (NOMA), mmWave frekans bandında düşük penetrasyon özelliklerine karşı adaptif yönlü iletişim, ve esneklik açısından çok boyutlu haberleşme imkanları bu tez kapsamında çalışılmıştır. Gelecek vaat eden bir yaklaşım olarak, farklı gereksinimleri olan birden fazla kullanıcıya hizmet vermek için dalga formu tabanlı NOMA konsepti tanıtılmıştır. Dalga formu tabanlı NOMA'nın amacı, benzersiz dalga formu özellikleri aracılığıyla paraziti kontrol etmek ve sonuç olarak alıcıda üst üste binen UE'lerin ayrılabilirliğini sağlamaktır. Özellikle, uygun dalga formlarının bir arada bulunmasıyla parazitin ortalama gücü aynı kalırken parazit dağılımının kontrolü sağlanmıştır. Milimetre (mmWave) dalga bantlarında yönlü iletişim, yüksek seviyeli yayılım kaybıyla mücadele etme fırsatları sunar. Ancak, belirli bir yönde iletişim, bağlantıyı düşük penetrasyon özelliklerine, yani tıkanma etkisine karşı savunmasız hale getirir. Yüksek yol kaybı ve tıkanma etkisi ile mücadele etmek için mmWave bantları için hüzme genişliği optimizasyonu önerilmiştir. Son olarak, indis modulasyonu (IM) tabanlı çok boyutlu iletişim fırsatları kapsamlı bir şekilde incelenmektedir. Özellikle, 5G ve ötesindeki sistemlerin farklı gereksinimlerini karşılamak için sinyal boyutlarının verimli bir şekilde kullanılması amacıyla bir çerçeve geliştirilmiştir

Non-orthogonal radio access technologies

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Inter-numerology interference in OFDM-IM systems

In 5G and beyond communication systems, distinct numerologies can coexist to serve diverse requirements for users and applications. However, the inter-numerology interference (INI) is a main challenge that significantly impacts the system performance. Therefore, the performance under INI has become an essential evaluation metric for the suitability of the different transmission schemes in the future communication systems. This paper analyzes the impact of INI on the performance of orthogonal frequency division multiplexing with index modulation (OFDM-IM) systems. Specifically, an analytical expression of the INI level in OFDM-IM systems is presented as a function of the subcarrier activation ratio (SAR) and subcarrier activation probability (SAP). Furthermore, aiming at reducing the INI level, an adaptive subcarrier mapping scheme (SMS) is proposed based on the conventional combinatorial mapping scheme. Moreover, analysis and evaluation of SAR and SAP are performed regarding the requirements of 5G and beyond services. It is proved that the INI level in OFDM-IM systems is highly dependent not only on the number of active subcarriers but also on their position in an OFDM block.Qatar National Research Fun

Index modulation-based flexible waveform design

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NOMA with Index modulation for uplink URLLC through grant-free access

This paper proposes non-orthogonal sharing of available resources between latency-critical and latency-tolerant communication for fulfilling tight requirements of ultra-reliable low-latency communication (URLLC) as well as avoiding inefficient spectrum utilization of grant-based (GB) access for sporadic URLLC traffic. In the proposed system, grant-free (GF) access is adopted for URLLC to reduce transmission latency, while GB access is used for latency-tolerant communication. Due to GF access, collision emerges between the communications, and use of OFDM technology for both communications leads to wideband interference (WB-I) on URLLC. Therefore, a novel non-orthogonal multiple accessing (NOMA) scheme based on orthogonal frequency division multiplexing (OFDM) and OFDM with index modulation (OFDM-IM) is proposed in order to reduce the impact of the collision on URLLC, that requires 99.999% success probability within 1ms. OFDM-IM technology is used for latency-tolerant communication since WB-I is converted to either narrowband dominant interference (NB-DI) or narrowband interference (NB-I) by fractional subcarrier activation in OFDM-IM. In this way, URLLC is partially affected by latency-tolerant communication. It is shown that the proposed NOMA scheme significantly reduces the latency in comparison to classical NOMA scheme based on pure OFDM while guaranteeing $10^{-5}$ reliability for URLLC, via both computer-based simulations and theoretical analysis