Irregular repetition slotted ALOHA (IRSA) has received growing attention to alleviate random access collisions in next-generation (5G) networks. The performance of irregular repetition slotted ALOHA (IRSA) in single-cell scenarios has been analyzed extensively. However, the performance of IRSA in multi-cell scenarios remains unexplored due to stochastic base station and user distributions, irregular repetition rates and complex inter-cell interference. Motivated by this, we propose an analytical framework of the performance of IRSA in large cellular networks which takes into account user location distributions, uplink power control, fading, and inter-cell interference. Moreover, an optimization problem aimed at finding the optimal repetition degree profile to support the highest system load is proposed. We show that the optimal average repetition rate in multi-cell scenarios differs from that in single-cell scenarios.

This paper introduces a novel satellite handover scheme considering the link outage probability (SHLOP). It aims to improve the resource utilization of satellite handover processes in satellite- UAV integrated networks and address the limitations that the state-of-the-art failed to consider the impact of intermittent satellite-ground and inter-satellite links in UAV collaborative penetration scenarios. SHLOP dynamically adjusts the ratio of allocated channel resources for handover according to the link outage probability and the number of UAVs, which helps to reach a compromise between handover success probability and resource efficiency excluding wasted resources. Besides, a performance evaluation model is developed to analyze the relationship between resource utilization, the ratio of reserved resources, the number of users, and the link outage probability. The formulated model identifies a closed-form solution for the optimal reserved resource ratio, which optimizes the SHLOP performance. Numerical evaluation results show that SHLOP outperforms the PDRA and DCR-DQN by at least 11% in terms of resource utilization with intermittent links.

Target the increasing access demand in the upcoming sixth-generation (6G) wireless networks, this paper firstly introduces an efficient non-orthogonal neighbor election random access scheme with immediate neighborhood information maintenance, successive interference cancellation (SIC) and iterative decoding. We firstly derive the distribution of the number of transmitting neighbors and reveal that there are up to two neighboring transmitters in over 98% of cases, which is naturally suitable for SIC procedures. Accordingly, an approximated analytical model of NO-NERA performance is established. Numerical results verify the validity of the approximations and show that NO-NERA can improve both the area spectrum efficiency and mean delay of the existing distributed neighbor election scheme in both unicast and broadcast traffic scenarios.

This paper develops an analytical framework for multi-cell uplink NOMA systems based on stochastic geometry. We propose two scenarios for the clustering of NOMA UEs and derive the Laplace transform of the inter-cell interference taking into account uplink power control. We utilize two different ordering techniques, namely mean signal power- (MSP-) and instantaneous signal-to-intercell-interference-and-noise-ratio- (ISĨNR-) based, for the successive interference cancellation process at the BSs. For each technique, we present a signal-to-interference-and-noise-ratio (SINR) analysis and derive the transmission success probabilities for the NOMA UEs. We show that uplink power control, which generally reduces the signal power disparity between UEs, does not necessarily degrade the NOMA performance. We discuss how UE clustering and the power control exponent impact this finding. ISĨNR-based ordering, which jointly considers path loss, fading, inter-cell interference, and noise, is generally superior to MSP-based ordering. Moreover, we show that the advantage of NOMA vanishes when the target SINR exceeds a certain threshold. A comparison of the two UE clustering scenarios indicates that excluding the UEs which are relatively far from the serving BS may improve the NOMA performance.

Providing reliable and efficient multicast services is one of the most important issues of the emerging 5G network. As the number of users grows rapidly, non-feedback multicast schemes are more suitable for bandwidth efficiency. However, conventional non-feedback multicast solutions, like the well-known Random Linear Network Coding (RLNC) and Systematic Network Coding (SNC), are suffering from complicated packet decoding and redundant packet reception at the unsaturated users. In this paper, we propose a reliable Hybrid Systematic Network Coding (HSNC) scheme to fully solve these problems. HSNC utilizes both deterministic and randomly generated coding vectors over the same finite field. By subtracting coding vectors with zero elements from a Reed- Solomon coding matrix, the goal to maximize the number of linear independent rows of a coding matrix can be easily realized. Close-form expressions of bit overhead ratio, decoding probability and computational cost are derived out. Numerical results show that HSNC, with or without a sliding window, outperforms RLNC and SNC in terms of the decoding probability. Moreover, HSNC has lower bit overhead and computational cost.

Hardware impairments, such as phase noise, quantization errors, non-linearities, and noise amplification, have baneful effects on wireless communications. In this paper, we investigate the effect of hardware impairments on multipair massive multiple-input multiple-output (MIMO) two-way full-duplex relay systems with amplify-and-forward scheme. More specifically, novel closed-form approximate expressions for the spectral efficiency are derived to obtain some important insights into the practical design of the considered system. When the number of relay antennas N increases without bound, we propose a hardware scaling law, which reveals that the level of hardware impairments that can be tolerated is roughly proportional to √N. This new result inspires us to design low-cost and practical multipair massive MIMO two-way full-duplex relay systems. Moreover, the optimal number of relay antennas is derived to maximize the energy efficiency. Finally, Motor-Carlo simulation results are provided to validate our analytical results.

In this paper, we pursue a detailed outage probability analysis of multihop relaying systems taking into account the practical constraint of cochannel interferences (CCIs). Different from previous works, both relaying transmission and CCIs are performed over generalized -μ fading channels. For both independent identically and non-identically distributed -μ faded CCIs, the exact end-to-end signal-to-interference ratio expressions of the multihop relaying system are obtained. Moreover, we derive new, analytical outage probability expressions of multihop relaying systems in the presence of CCIs. In the high-power regime, simplified expressions are provided, revealing the implications of the channel parameters on the outage performance. These tractable results enable us to draw useful engineering insights about the impact of system and channel parameters on the outage probability of multihop relaying systems. Finally, simulation results are provided to validate our derived expressions.

The massive amounts of machine-type user equipments (UEs) will be supported in the future fifth generation (5G) networks. However, the potential large random access (RA) delay calls for a new RA scheme. Motivated by the key idea of non-orthogonal multiple access, the non-orthogonal random access (NORA) scheme is proposed in this paper to alleviate the access congestion problem. Specifically, NORA utilizes the difference of time of arrival to identify multiple UEs with the identical preamble, and enables power domain multiplexing of collided UEs in the following access process, while the base station performs successive interference cancellation (SIC) based on the channel conditions obtained through preamble detection. Our analysis shows that the performance of NORA is superior to the conventional orthogonal random access (ORA) scheme in terms of collision probability and throughput. Simulation results verify our analysis and further show that our NORA scheme can improve the number of the supported UEs by more than 30%. Moreover, the access delay for successfully accessed UEs are also reduced significantly by using the proposed random access scheme.

The satellite relaying system is a promising network architecture in next generation wireless communication systems, due to its large coverage and stability. In this paper, the performance of a dual-hop decode-and-forward based satellite relaying system over κ-μ shadowed fading channels is investigated, where a source earth station transmits information to a destination earth station via a satellite relay. We first obtain the exact closedform expressions of the outage probability of such a system in terms of bivariate confluent hypergeometric functions. By using a novel gamma approximation to the κ-μ shadowed distribution, the simple outage expression is derived. Moreover, the accurate expression of the average bit error rate (ABER) and the ergodic capacity are obtained in terms of Appell hypergeometric functions and hypergeometric functions, respectively. Again, with the help of the gamma approximation, we derive the approximate ABER and capacity expressions. In the high signal-to-noise ratio regime, the asymptotic ABER expression is obtained in terms of elementary functions. Finally, numerical and Monte-Carlo simulation results are provided to demonstrate the validity of the proposed unified expressions.

The practical deployment of massive multiple-input multiple-output (MIMO) in the future fifth generation (5G) wireless communication systems is challenging due to its high-hardware cost and power consumption. One promising solution to address this challenge is to adopt the low-resolution analog-to-digital converter (ADC) architecture. However, the practical implementation of such architecture is challenging due to the required complex signal processing to compensate the coarse quantization caused by low-resolution ADCs. Therefore, few high-resolution ADCs are reserved in the recently proposed mixed-ADC architecture to enable low-complexity transceiver algorithms. In contrast to previous works over Rayleigh fading channels, we investigate the performance of mixed-ADC massive MIMO systems over the Rician fading channel, which is more general for the 5G scenarios like Internet of Things. Specially, novel closed-form approximate expressions for the uplink achievable rate are derived for both cases of perfect and imperfect channel state information (CSI). With the increasing Rician K-factor, the derived results show that the achievable rate will converge to a fixed value. We also obtain the power-scaling law that the transmit power of each user can be scaled down proportionally to the inverse of the number of base station (BS) antennas for both perfect and imperfect CSI. Moreover, we reveal the tradeoff between the achievable rate and the energy efficiency with respect to key system parameters, including the quantization bits, number of BS antennas, Rician K-factor, user transmit power, and CSI quality. Finally, numerical results are provided to show that the mixed-ADC architecture can achieve a better energy-rate tradeoff compared with the ideal infinite-resolution and low-resolution ADC architectures.

The frequency scarcity imposed by fast growing demand for mobile data service requires promising spectrum aggregation systems. The so-called higher order statistics (HOS) of the channel capacity is a suitable metric on the system performance. While prior relevant works have improved our knowledge on the HOS characterization of spectrum aggregation systems, an analytical framework encompassing generalized fading models of interest is not yet available. In this paper, we pursue a detailed HOS analysis of κ-μ and κ-μ shadowed fading channels by deriving novel and exact expressions. Furthermore, the simplified HOS expressions for the asymptotically low and high signal-tonoise regimes are derived. Several important statistical measures, such as amount of fading, amount of dispersion, reliability, skewness, and kurtosis, are obtained by using the HOS results. More importantly, the useful implications of system and fading parameters on spectrum aggregation systems are investigated for channel selection. Finally, all derived expressions are validated via Monte Carlo simulations.

The massive amounts of machine-type user equipments (UEs) will be supported in the future fifth generation (5G) networks. However, the potential large random access (RA) delay calls for a new RA scheme and for a detailed assessment of its performance. Motivated by the key idea of non-orthogonal multiple access, the non-orthogonal RA (NORA) scheme based on successive interference cancellation (SIC) is proposed in this paper to alleviate the access congestion problem. Specifically, NORA utilizes the difference of time of arrival to identify multiple UEs with the identical preamble, and enables power domain multiplexing of collided UEs in the following access process, while the base station performs SIC based on the channel conditions obtained through preamble detection. Our analysis shows that the performance of the NORA is superior to the conventional orthogonal RA (ORA) scheme in terms of the preamble collision probability, access success probability, and the throughput of RA. Simulation results verify our analysis and further show that our NORA scheme can improve the number of the supported UEs by more than 30%. Moreover, the number of preamble transmissions and the access delay for successfully accessed UEs are also reduced significantly by using the proposed RA scheme.

This paper presents an analytical model for analyzing the performance of the TDMA-based distributed reservation protocol for wireless multi-hop ad hoc networks. A novel three-way handshake process is presented which considers the hold-off and competition process before the transmission of scheduling messages. An explicit expression of expectation of the average delay of the three-way handshake process is further derived. Regarding throughput, the concepts of forwarding traffic and pseudo-collision traffic are brought up to evaluate the MAC layer effective throughput. The forwarding characteristic of multi-hop ad hoc networks is studied to calculate the forwarding traffic while the pseudo-collision traffic is derived based on the premise that the nodes are not allowed to transmit while their one-hop neighbors receive. An analytical model which jointly considers the impacts of network parameters, scheduling parameters and frame structure design is constructed. The optimal number of control slots that maximizes the effective throughput is further obtained under certain traffic volume, node density and hold-off exponent. Simulation results show the effectiveness of the theoretical model. The upper bound of MAC layer effective throughput under different network settings is presented.

Group team communication serving for collaboration-work of special members, is an important application of MANET. In which, multicast protocol is a key technique to the group team application, which must guarantee the performance requirements: adaptable to the dynamic change of network topology, timeliness, minimizing routing overhead etc. This paper focuses on the improvement of MAODV applied to group team communication. Considering the existence of special nodes and determining the optimal repair node, GT-MAODV is proposed. After discussing the problems of link repair process of MAODV, a link repair mechanism--GTR-MAODV which improves the successful repair rate effectively through distinguishing different multicast tree branches is proposed on the basis of GT-MAODV. Through analysis and simulation, it is showed that the GTR-MAODV provides better performance than MAODV and GT-MAODV on successful repair rate, packet delivery rate and end to end delay.