Satellite networks have become central to the evolution of modern communications systems due to their potential for extensive global coverage. However, high latency in satellite systems poses critical challenges for delay-sensitive applications, underscoring the need for performance metrics that characterize ultra-reliable low-latency communications. To address these challenges, data-oriented approach, which is already widely studied in terrestrial networks, provides a fresh perspective by evaluating the transmission performance where it prioritizes both reliability and latency. This work introduces the data-oriented approach to uplink hybrid satellite-terrestrial networks (HSTNs), focusing on non-orthogonal multiple access (NOMA)-assisted semi-grant-free (SGF) transmission where terrestrial relays support the transmission between the satellite and users. Specifically, a novel grant-free user (GFU) admission protocol based on distributed contention control, the corresponding power allocation scheme for GFUs, and the relay selection procedure presented following the data-oriented approach. Then, the maximum number of GFUs that can be admitted under given data-oriented design requirements is determined. The analytical results are verified by extensive Monte-Carlo simulations, while a wide body of numerical results are also offered to understand and demonstrate the impacts of different system parameters. The proposed analytical framework offers useful insights toward the design of practical HSTNs, particularly in the context of delay-sensitive applications, by revealing the relationship between the amount of information data, the power consumption, and the satellite distance. The results demonstrate that the proposed scheme improves the DOR performance compared to conventional grant-free access and frequency division multiple access methods by dynamically selecting GFUs and allocating transmit power based on channel conditions. It is also shown that more GFUs can be admitted, especially with larger bandwidths and/or relaxed threshold settings.

Satellite networks have become central to advancing modern communication standards due to their potential for extensive global coverage. Despite this, high latency in satellite systems poses critical challenges for delay-sensitive applications, underscoring the need for reliable metrics that reflect ultra-reliable, low-latency communication. To address these challenges, data-oriented approaches, widely adopted in terrestrial networks, offer a fresh perspective by assessing transmission performance through delay outage rates. This work introduces the data-oriented approach to hybrid satellite-terrestrial networks (HSTNs), focusing on an uplink non-orthogonal multiple access (NOMA) scheme where grant-based and grant-free users coexist. The proposed analytical framework reveals the relationship between the amount of information data, power consumption, and the satellite distance, providing valuable pathway for optimizing the performance of HSTNs in the context of delay-sensitive applications.

In the next generation wireless communication paradigm, hybrid communication strategies and vertical network integration are critical to ensure high-capacity and resilient connectivity. In this manner, we consider a high-altitude platform station (HAPS)-assisted bidirectional relaying system operating with hybrid terahertz (THz)/free-space optical (FSO) links in a multi-satellite and multi-ground station communication scenario. Unlike conventional setups, both the satellite and ground station nodes are dynamically selected, and bidirectional relaying is employed to enhance spectral efficiency. Realistic physical impairments, such as beam divergence and misalignment are incorporated into the system model, and system outage probability expression is derived to evaluate the overall performance under various configurations. The results show that the hybrid THz/FSO approach not only enhances reliability against pointing errors but also benefits significantly from multi-node diversity, making it a strong candidate for future reliable and high-capacity integrated non-terrestrial network architectures.

As wireless systems move toward 6G, ensuring ultra-reliable low-latency communication (URLLC) securely is a key design challenge. Addressing the strict latency and reliability demands requires a shift in performance evaluation. The delay-outage rate (DOR) has recently emerged as a data-oriented metric that captures the probability of transmission time exceeding a threshold under ideal conditions. This work extends the data-oriented framework to include physical layer security, focusing on jamming and eavesdropping threats. We analyze how constant and random jamming affect DOR in the multi-antenna systems, highlighting the role of spatial and spectral resources in mitigation. Our analysis, supported by empirical simulations, offers new insights for designing secure, low-latency systems resilient to jamming—supporting robust ultra- or hyper-reliable low-latency communications in future 6G networks.

In this article, we study the timely notion of short-packet communications, with specific focus onuplink rate-splitting multiple access (RSMA) systems under the finite blocklength regime. Specifically, we consider rate-adaptive and power-adaptive uplink RSMA mechanisms, incorporating multiple user groups, and derive analytical expressions for the fundamentaldelay-outage rate (DOR)metric. The analytical derivations are validated through the corresponding Monte Carlo numerical simulations, reflecting high accuracy. Then, the derived DOR expressions are exploited for providing optimal DOR performance under diverse individual transmission parameters, such as different information delivery time thresholds, varying blocklengths and channel bandwidths, while also considering the non-orthogonal multiple access (NOMA) as a particular special case. Importantly, DOR optimization in terms of the message splitting ratio is also pursued, and a feasible optimization algorithm is proposed. A vast collection of numerical results is then provided, comparing between the rate-adaptive and the power-adaptive schemes, assessing the impact of message splitting ratio optimization while also comparing between RSMA and NOMA. Additionally, the overall power efficiency and impacts of imperfect channel state information (CSI) are assessed and shown. Overall, the offered analysis methods and numerical results provide valuable tools and insight for deploying, designing and optimizing data-oriented uplink RSMA mechanisms in future wireless systems such as the emerging 6G networks.

The so-called data-oriented approach has gathered significant attention in the context of short-packet communications in fifth-generation (5G) and beyond networks. Specifically, it introduces a transient performance metric for small data transmissions, where the amount of data and available bandwidth play crucial roles. Such data-oriented approach has recently been introduced in downlink rate-splitting multiple access (RSMA) system context, which represents a flexible and promising non-orthogonal multiple access paradigm. Building upon such prior-art, this paper introduces the data-oriented approach to uplink RSMA systems under the finite blocklength regime. Specifically, we consider rate-adaptive and power-adaptive uplink RSMA mechanisms, under the data-oriented approach, and derive analytical expressions for the delay-outage ratio (DOR) metric. The analytical derivations are validated through corresponding Monte Carlo numerical simulations. The numerical results show that the DOR performance is directly linked with the transmit antenna diversity, while being also dependent on the accuracy of the channel state information as well as on the power budget of the uplink users. The obtained results highlight the importance of the new data-oriented DOR metric for efficient design of the uplink RSMA mechanism in future networks.

Reconfigurable intelligent surface (RIS)-empowered communication has emerged as a novel concept for customizing future wireless environments in a cost- and energy-efficient way. However, due to double path loss, existing fully passive RIS systems that purely reflect the incident signals into preferred directions attain an unsatisfactory performance improvement over the traditional wireless networks in certain conditions. To overcome this bottleneck, we propose a novel transmission scheme, named hybrid reflection modulation (HRM), exploiting both active and passive reflecting elements at the RIS and their combinations, which enables to convey information without using any radio frequency (RF) chains. In the HRM scheme, the active reflecting elements using additional power amplifiers are able to amplify and reflect the incoming signal, while the remaining passive elements can simply reflect the signals with appropriate phase shifts. Based on this novel transmission model, we obtain an upper bound for the average bit error probability (ABEP), and derive achievable rate of the system using an information theoretic approach. Moreover, comprehensive computer simulations are performed to prove the superiority of the proposed HRM scheme over existing fully passive, fully active and reflection modulation (RM) systems.

Media-based modulation (MBM), exploiting rich scattering properties of transmission environments via different radiation patterns of a single reconfigurable antenna (RA), has brought new insights into future communication systems. In this study, considering this innovative transmission principle, we introduce the realistic, two-dimensional (2D), and open-source SimMBM channel simulator to support various applications of MBM systems at sub-6 GHz frequency band in different environments.

In this paper, a novel circular space-time block coding (CSTBC)-based index modulation (IM) technique, which achieves various orders of transmit diversity gains, is introduced. In the proposed system, a promising IM concept, media-based modulation (MBM), which carries additional information bits through the available radio frequency (RF) mirrors of transmit antennas, is considered. Unlike traditional STBC-based IM concepts, the proposed technique provides various orders of transmit diversity gains and attains higher spectral efficiency values with a single RF chain. The bit error rate (BER) performance of the proposed system is theoretically analyzed and an upper bound expression for the average bit error probability (ABEP) is derived. Moreover, via comprehensive computer simulations, the improved BER performance of the proposed CSTBC-IM is demonstrated over the-stateof-the-art IM schemes.

In this study, the authors combine physical layer network coding (PLNC) and space‐time trellis coding (STTC) techniques to improve the error performance of vehicle‐to‐vehicle (V2V) communication systems where all fading channels are assumed to undergo double Rayleigh fading (DRF) which is worse than Rayleigh fading used in cellular communications. In the authors' analysis, they show that the DRF channels can be modelled by using the mixture gamma distribution. After that, pairwise error probability (PEP) analysis is performed for a fixed‐gain amplify‐and‐forward PLNC V2V system employing STTC over the DRF channels, and an upper bound for the PEP is obtained. By examining the behaviour of the upper bound expression in the high SNR region, they derive a new design criterion for STTCs. Finally, using this criterion they propose novel STTCs with 4 and 8 states for V2V systems employing PLNC over the DRF channels.

In this paper, performance of two-way full-duplex cooperative systems under residual loop- interference (LI) is analyzed in terms of outage probability over Nakagami-$m$ fading channels. At the relay node of the proposed system, physical- layer-network-coding technique and variable-gain full-duplex amplify-and-forward relaying method are combined for two-way transmission. End-to-end signal-to-interference-plus-noise-ratio (SINR) expression is derived for different power transmissions at the source and relay nodes. New exact outage probability expression is obtained in a single-integral form by using cumulative distribution function of the end-to-end SINR. The analytical results are verified by Monte-Carlo simulations. We also provide lower-bound and asymptotic expressions in closed-form for the outage performance. It is shown that the outage performance of the system is enhanced as long as either the transmit power or the efficiency of LI cancellation process increases. We also observe that the outage probability converges to an error floor due to the residual LI component at the source and relay nodes.

This work focuses on the relay antenna selection problem in a Vehicle-to-Vehicle (V2V) communication system employing physical layer network coding (PLNC) with amplify-and-forward (AF) scheme on a multi-antenna relay under double-Nakagami-m fading channel conditions. We obtain lower and upper bounds of end-to-end signal-to-noise ratio (E2E-SNR) and their cumulative density functions (CDF). Employing the CDFs, performance of the system is evaluated in terms of outage probabilities. We analyze asymptotic diversity order of the system and express it as a function of number of relay antennas and channels' parameters. Finally the analytical results are verified by the simulations.

Continuous phase modulation (CPM) is a non‐linear power/bandwidth efficient modulation method. Linear modulation methods such as phase shift keying or quadrature amplitude modulation produce large power drain at the power amplifier of the transmitter. Therefore CPM may be an alternative to these modulations in relay/cooperative systems because of its constant envelope property, which enables us to use inexpensive and energy‐efficient non‐linear power amplifiers. In this study, the authors investigate optimum distributed space‐time CPM trellis codes for amplify and forward relaying systems with one to four relays and specifically consider minimum shift keying and quaternary continuous phase frequency shift keying with modulation indices of 1/2 and 1/4. Novel distributed space‐time CPM trellis codes are obtained. Error performances of the novel codes and their classical counterparts are compared over frequency non‐selective quasi‐static Rayleigh‐fading channels using the Viterbi algorithm at the destination terminal and superiority of the novel codes are presented.

ABSTRACT In this paper, error performances of multiple‐input multiple‐output systems that employ Alamouti‐coded transmission with transmit antenna selection are examined for binary phase‐shift keying, binary frequency‐shift keying, M‐ary phase‐shift keying, and M‐ary quadrature amplitude‐modulation signals in independent but non‐identically distributed flat Nakagami‐m fading channels. Exact symbol error rate expressions are derived by using the moment‐generating function‐based analysis method. Upper bound expressions have been obtained in order to examine the asymptotic diversity order of transmit antenna selection/Alamouti scheme. Also, outage probability analysis of investigated systems has been given in order to examine the system capacity. Monte Carlo simulations have validated the analytical symbol error rate performance results. Copyright © 2011 John Wiley & Sons, Ltd.

ABSTRACT Error performance of a cooperative system can be enhanced by using transmit and receive diversity techniques at transmission links. The number of transmit/receive RF chain pairs required to achieve full diversity can be decreased to one for each link by using transmit antenna selection (TAS) method at the transmitter and selection combining (SC) method at the receiver. Thus, hardware complexity of a multiple input multiple output (MIMO) cooperative scheme can be significantly reduced when compared to systems that use TAS and maximum ratio combining (MRC). In this paper, we investigate the performance of an amplify‐and‐forward cooperative system where TAS/SC is utilized. We derive the probability density function (pdf) of end‐to‐end SNR of the system for Rayleigh fading channels. By using this pdf, we obtain the exact symbol error rate expressions for M‐PSK and M‐QAM modulations and the exact outage probability expression. We also obtain the asymptotical diversity order using upper and lower bounds of the outage probability expression and show that our system provides the same diversity order as the cooperative system where TAS/MRC is utilized. We verify our results via computer simulations. Copyright © 2010 John Wiley & Sons, Ltd.

In this study, the authors investigate the error rate performance of amplify-and-forward relaying over N*Nakagami fading channels. This is a recently introduced channel model that involves the product of N Nakagami-m-distributed random variables. Employing the moment generating function approach, the authors derive symbol error rate expressions for a single-relay system under instantaneous power scaling (IPS) and average power scaling (APS) factors at the relay node, that is, variable and fixed gains. The results achieved by the authors demonstrate that the achievable diversity order is a function of Nakagami fading parameter (m) and degree of cascading (N). An identical diversity order is obtained under both scaling factors when the relay is close to the destination. When the relay is close to the source, IPS becomes advantageous over APS. Monte–Carlo simulations are further provided to confirm the analytical results.

Performance of cooperative communication systems can be improved effectively by using multiple input multiple output (MIMO) techniques at transmission links. We make use of amplify and forward cooperative relaying techniques with transmit antenna selection (TAS) and selection combining (SC) methods to present an effective transmission scheme. Applying TAS method at the transmitter and SC method at the receiver reduces hardware complexity at both sides as the required number of radio frequency chains is decreased. We assume that Rayleigh fading takes place at all links. We derive the probability density function of end-to-end SNR. Using this, we obtain the exact symbol error rate expression analytically for M-PSK modulation and verify our results via computer simulations for BPSK. We also derive a bound for error probability, assuming the link between relay and destination has sufficiently larger SNR than the other links. Using this bound, we analyze asymptotic diversity orders for several system configurations.

Super-orthogonal space–time trellis (SOSTT) codes provide a significant coding gain with respect to the conventional space–time trellis (STT) codes without increasing the decoding complexity at the receiver. Transmit antenna selection (TAS) is an important technique to solve the implementation complexity problems of multiple-antenna systems that arise from employing a separate RF chain for each antenna. This study treats a scheme combining SOSTT coding with TAS in order to exploit performance improvements provided by SOSTT codes while realising the promises made by the TAS technique. In the proposed scheme, transmit antennas that maximise the signal-to-noise ratio at the receiver are chosen and activated out of all available transmit antennas for transmission of the baseline SOSTT code, whereas all other transmit antennas are silent. The error performance of the proposed structure is investigated by deriving moment generating function (MGF)-based upper bound expressions on the pairwise error probability in quasi-static flat Rayleigh fading channels for both perfect and imperfect antenna subset selection. The performance analysis demonstrates that the proposed scheme provides full diversity order as if all transmit antennas were used when antennas are perfectly selected. Moreover, it is shown that this structure provides better error performance almost at the same decoding complexity compared to the previous STT coding structures with TAS in the literature.

Cooperative communication techniques promise the advantages of MIMO (multi-input multi-output) communications for wireless scenarios with single-antenna terminals. In this paper, we investigate the performance of a vehicle-to-vehicle cooperative scheme where another vehicle in the vicinity of the source vehicle acts as a relay. The underlying source-to-relay, relay-to-destination, and source-to-destination links are modeled as cascaded (double) Rayleigh fading. This statistical model provides a realistic description of inter-vehicular channel where two or more independent Rayleigh fading processes are assumed to be generated by independent groups of scatterers around the two mobile terminals. We derive a pairwise error probability (PEP) expression for the inter-vehicular cooperative scheme under consideration and show that the full distributed spatial diversity is extracted. Based on the derived PEP expressions, we obtain union bounds on the bit error rate performance which are then minimized to optimally allocate power between broadcasting and relaying phases. Optimum power allocation brings performance gains up to 3dB depending on the relay location and deployed modulation scheme.

Although there has been a growing literature on cooperative diversity, the current literature is mainly limited to Rayleigh fading channel model which typically assumes a wireless communication scenario with a stationary base station antenna above roof-top level and a mobile station at street level. In this paper, we investigate cooperative diversity for inter-vehicular communication based on cascaded Rayleigh fading. This channel model provides a realistic description of inter-vehicular channel where two or more independent Rayleigh fading processes are assumed to be generated by independent groups of scatterers around the two mobile terminals. We investigate the performance of amplify-and-forward relaying for an inter-vehicular cooperative scheme assisted by a road-side access point which acts as a relay. Our diversity analysis reveals that the cooperative scheme is able to extract the full distributed spatial diversity. We further formulate a power allocation problem for the considered scheme to optimize the power allocated to broadcasting and relaying phases. Performance gains up to 2.8 dB are observed through optimum power allocation depending on the relay location.

In this paper, error performance of a serially concatenated QPSK space-time system is investigated on quasi-static, block and rapid fading channels. We consider outer nonrecursive convolutional and inner recursive space-time trellis code case and iterative decoding based on the maximum a posteriori (MAP) algorithm. The performance is evaluated by means of computer simulations and it is observed that when the recursive versions of some of the previously known space-time trellis codes are used as the inner codes, the Euclidean distance criterion based spaced-time codes lead to better error performance for both quasi-static and rapid fading channels. We also investigate the effects of various system parameters on the performance. We obtain the error performance for the large number of transmit and/or receive antennas increases the error performance improves.

We consider the design of convolutional codes and low density parity check (LDPC) codes with minimum-shift keying (MSK) when the receiver employs iterative decoding and demodulation. The main idea proposed is the design of coded schemes that are well matched to the iterative decoding algorithm being used rather than to hypothetical maximum-likelihood decoding. We first show that the design is crucially dependent on whether the continuous phase encoder (CPE) is realized in recursive form or in nonrecursive form. We then consider the design of convolutionally coded systems and low density parity check codes with MSK to obtain near-capacity performance. With convolutional codes, we show that it is possible to improve the performance significantly by using a mixture of recursive and nonrecursive realizations for the CPE. For low density parity check codes, we show that codes designed for binary phase shift keying are optimal for MSK only if the nonrecursive realization is used; for the recursive realization, we design new LDPC codes based on the concept of density evolution. We show that these codes outperform the best known codes for MSK and have lower decoding complexity.

We investigate serial concatenation of low-density parity check (LDPC) codes and minimum shift keying (MSK) with iterative decoding. We show that the design of LDPC codes is crucially dependent on the realization of the MSK modulator. For MSK modulators with nonrecursive continuous phase encoders (CPEs), optimal codes for BPSK are optimal, whereas for MSK modulators with recursive CPEs, the BPSK codes are not optimal. We show that for nonrecursive CPEs, iterative demodulation and decoding is not required even though the CPE has memory. However, iterative demodulation is essential for recursive CPEs. For recursive CPEs, we design LDPC codes using density evolution and differential evolution considering iterative demodulation and decoding. The resulting codes provide significantly improved performance over the existing codes.

In this paper, we introduce multilevel coded continuous-phase frequency-shift keying (CPFSK) systems for both additive white Gaussian noise and fading channels based on multilevel coding and multistage decoding techniques. These schemes are designed under the constraint M/spl ges/2P for M-ary CPFSK with modulation index J/P. In order to maintain the phase continuity property after multilevel coding, we use some specific set partitioning rules. We construct examples to show that the proposed systems outperform the corresponding conventional one-level schemes. For the fading case, we consider an ideal fading channel where adjacent fading symbols are assumed to be independent and a correlated fading channel where bit interleavers are needed at each coding level. The computer simulation results show that the proposed systems have bit-error performance and decoder complexity advantages over the corresponding reference codes taken from the literature. It is also shown that there is only a slight degradation on the bit-error performance for correlated fading, compared to the ideal fading case.