This paper designs and characterizes an adaptive relaying protocol in a short-packet cooperative non-orthogonal multiple access (NOMA) network. Particularly, a base station broadcasts a superposed signal to a strong user and a weak user with the help of a dedicated relay. Compared with the conventional fixed decode-and-forward relaying protocol (DFRP) and amplified-and-forward relaying protocol (AFRP), we propose a novel adaptive hybrid relaying protocol (AHRP) for a short-packet cooperative NOMA network, in which the dedicated relay chooses the transmission modes adaptively to help the information transmission of the weak user according to the comparison between the achievable data rates and the target data rates. Moveover, the ergodic rates of the two users are approximated with closed-form expressions and an asymptotic performance comparison among the DFRP, AFRP, and AHRP is also provided. Simulation results indicate that the proposed AHRP outperforms the DFRP and AFRP in terms of users' ergodic rates. Furthermore, the AHRP can achieve higher user rate and robustness than the DFRP, AFRP, and cooperative orthogonal multiple access under various network settings.

In a cellular radio access network relying on control- and user-plane separation (RAN-CUPS), control base stations (CBSs) make up the control plane (CP) taking charge of coverage, and traffic base stations (TBSs) in the user plane (UP) are responsible for transmitting high-speed data under the umbrella of CP. In order to increase the coverage probability of CP, non-orthogonal multiple access (NOMA) is introduced into CP while UP adopts orthogonal frequency division multiple access (OFDMA). Then, we develop a tractable analytical model for NOMA-enabled RAN-CUPS based on stochastic geometry. Simulation results show that compared with OFDMA, NOMA could improve coverage probability, spectral efficiency, and energy efficiency of CP, which can further improve the spectral efficiency of UP.

This paper studies the performance of unmanned aerial vehicle (UAV)-enabled NOMA networks with selective incremental relaying and imperfect channel state information (CSI). In particular, an access point transmits a superposed signal based on NOMA principle to an UAV terminal (UT) which can act as a relay to assist the information transmission for a ground terminal (GT). Different from the conventional relaying protocol requiring UT to relay the message all the time no matter how the received signal quality of two terminals are, we propose a novel NOMA-based selective incremental relaying protocol that allows relay to forward messages on the condition of the received signal with satisfied quality at UT and the unsatisfied quality signal at GT. The closed-form solutions of outage probabilities for the two terminals are characterized with the elevation angle-based path loss exponent and small-scale fading. Moreover, the benchmark schemes are provided to exhibit the superiority of the proposed protocol. Finally, simulation and theoretical results validate the correctness of the outage analysis, demonstrate the advantage of the proposed relaying protocol over its counterparts, and show that the stronger impact of channel estimation error on GT than UT in terms of outage probability.

This paper studies the physical layer security for a cooperative non-orthogonal multiple access system with energy harvesting (EH) and full-duplex (FD) relaying. In particular, the base station transmits a superposed message to a dedicated EH-FD relay according to NOMA principle. Then, the relay forwards the decoded message to users. At the same time, the message transmitted by the relay can be wiretapped by an passive eavesdropper. The lower bound on the ergodic secrecy rates and the approximated secrecy outage probabilities of users are analyzed with closed-form solutions considering imperfect SIC. Finally, simulation results demonstrate the correctness of theoretical analysis, reflect the influence of the key parameters on the system performance and verify the better secrecy performance of the proposed scheme than its counterpart.

In this paper, an energy harvesting enabled cooperative non-orthogonal multiple access (NOMA) system for a multi-cell network is investigated. Particularly, during the direct transmission phase, base stations send their superposed messages to the near users and far users simultaneously according to a NOMA principle, while the near users act as energy harvesting enabled relays employing a power splitting protocol. During the cooperative phase, the near users transmit their decoded messages to the corresponding far users using harvested energy. Using tools from stochastic geometry, we firstly calculate the signal to interference ratios of the users in each NOMA group including one near user and one far user. Then, the closed-form expressions of the coverage probability, ergodic rate, and energy efficiency are derived respectively. Numerical results validate the derived expressions and show that the energy harvesting enabled cooperative NOMA system in a multi-cell network can improve the coverage probability, ergodic rate, and energy efficiency compared to its counterpart OMA system.

With the rapid growth of scientific literatures, it is very important to discover the implicit knowledge from the vast information accurately and efficiently. To achieve this goal, we propose a percolation approach to discovering emerging research topics by combining text mining and scientometrics methods based on Subject-Predication-Object (SPO) predications, which consist of a subject argument, an object argument, and the relation that binds them. Firstly, SPO predications are extracted and cleaned from content of literatures to construct SPO semantic networks. Then, community detection is conducted in the SPO semantic networks. Afterwards, two indicators of Research Topic Age (RTA) and Research Topic Authors Number (RTAN) combined by hypervolume-based selection algorithm (HBS) are chosen to identify potential emerging research topics from communities. Finally, scientific literatures of stem cells are selected as a case study, and the result indicates that the approach can effectively and accurately discover the emerging research topics.

This paper investigates an integrated wireless communication system including non-orthogonal multiple access, full-duplex relaying, and energy harvesting techniques (named as EH-FD-NOMA). In this scheme, an energy-limited full-duplex relay harvests energy from a source at the first stage. Then, the relay detects the superimposed signal from the source and transmits the decoded signal to destination. Closed-form outage probabilities and ergodic rates at the relay and destination are derived. Numerical results verify the analytical results and show the superior performance of the EH-FD-NOMA if compared to its counterparts.

Successive interference cancellation (SIC) has been regarded as the de facto decoding method in the non-orthogonal multiple access (NOMA) system. However, SIC often requires the paired users to have significantly different received power levels for the uplink scenario. This is problematic in terms of fairness and outage probabilities when the paired users are close to each other. To address this challenge, we propose a new decoding method for uplink NOMA based on compute-and-forward. In particular, we show that our method achieves better fairness and smaller average outage probabilities while enjoying essentially the same complexity as SIC decoding.

Coordinated multipoint (CoMP) has been applied as a key technology to enhance the coverage of cell and mitigate the intercell interference (ICI) in LTE-A. Traditional fundamental research of cell clustering for CoMP concentrates on both static and dynamic clustering. However, in the high data demands and heavy ICI scenario, both the static and dynamic clustering cannot ensure good Quality of Service (QoS) for User Equipments (UEs). Hence, in this paper, we formulate the problem to maximize cell-edge throughput and analysis the system complexity, and the time detection based hybrid clustering strategy for JP (Joint Processing)-CoMP is proposed to solve this problem. Based on LTE system level platform, simulation results show that the proposed scheme has better performance than static clustering even gets close to dynamic clustering with less complexity.

Dealers in securities markets are standing ready immediately to trade certain amounts of securities at stated bid and ask prices. This paper assumes that the amount of transactions follows an uncertain mean-reverting process associated with the bid and ask prices. In order to maximize the dealer’s total wealth, an optimal dealer pricing model under transaction uncertainty is established. And the optimal bid price and ask price over time are derived. Finally, the variations of the optimal bid and ask prices with different parameters are presented.

In order to achieve array gain and spatial diversity or multiplexing gain simultaneously, a novel joint beamforming based on MIMO and array antenna techniques, referred to as J-BF, is proposed for the LTE and Wifi downlink. Array gain is achieved from array antenna based beamforming, referred to as AA-BF. Spatial diversity and multiplexing gains are achieved from MIMO based beamforming, referred to as MIMO-BF. To implement J-BF, i.e., joint AA-BF and MIMO-BF, an access point (AP) is equipped with separate array antennas. Before sending any data-frame in the J-BF mode, firstly, based on the estimated omni-directional CSI, the directional beam can be formed by the array antenna, and the array gain is achieved. Secondly, based on the estimated directional CSI, MIMO-BF is implemented to achieve the spatial diversity or multiplexing gain. More importantly, the J-BF algorithm maintains compatibility with 802.11n and there is not any change in terminals. Simulation results show that the proposed scheme can support the joint AA-BF and MIMO-BF effectively and provide much higher array gain or spatial gains than the traditional MIMO or array antenna respectively.

To support space division multiple access (SDMA) in the IEEE 802.11n downlink, a joint beamforming based MAC protocol, J-MAC is presented in this paper. An access point (AP) follows J-MAC, which employs multiple array antennas, and user equipments (UEs) follow the IEEE 802.11x standard which employ omni-directional MIMO antennas. J-MAC maintains full compatibility with 802.11x, and UEs do not change any more. In J-MAC, firstly, the AP achieves the weight vector for the array antenna-based beamforming, and updates it periodically. Secondly, before transmitting any data-frame, the AP achieves the weight vector for the MIMO-based beamforming, which should be updated in each transmission. Finally, after getting the joint beamforming, the AP transmits its data-frames to multiple UEs simultaneously. Simulation results show that J-MAC can support the joint beamforming effectively and provide much higher network throughput, lower delay, jitter and packet-loss-rate than DCF does.

Recently, Green Radio, which aims to reduce energy consumption of information and communication technologies (ICTs), has been concerned by telecommunication operators and researchers and can be applied to emergency scenarios. However, the communication system in emergency situation is pursuing not only energy reduction, but the large number of serviced users. In this paper, in order to provide telecommunication services for a great number of clients with low energy consumption in emergency scenarios, a capacity-and-energy efficient radio resource allocation mechanism is proposed, which is modeled as a Sigmoid-based optimization problem. Our simulation results demonstrate that compared with the conventional resource allocation algorithms, the proposed one achieves the largest capacity-and-energy efficiency, i.e., the largest number of serviced users per power unit.