Throughput maximization in multi-slice cooperative NOMA-based system with underlay D2D communications

Abstract-The paper studies a scheme that jointly considers beamforming based MU-MIMO and NOMA in a downlink cellular network with underlaid D2D users. Two different MU-MIMO beamforming schemes are developed. The first beamforming scheme aims to eliminate the interference caused by different beams while the second one aims to cancel out the interference from base stations to D2D users. An optimization problem is formulated to maximize the total system sum throughput of both cellular users and D2D users. Since the optimization problem is NP hard and difficult to solve, we develop a suboptimal sequential solution by determining the zero-forcing beamforming matrix for MU-MIMO first. Then a user grouping and optimal power allocation algorithm is proposed in order to maximize the capacity of cellular users in each beam. Simulation results show that MUMIMO beamforming, NOMA and D2D together will significantly improve the overall system throughput.

In this paper we investigate the effect of interference caused by in-band full-duplex radios in device-to-device communication (D2D). While using full-duplex radios in D2D, both users transmit, compared to half-duplex D2D in which one user transmits. This is going to cause more interference in underlay D2D communication since D2D link operates on the same radio resource blocks as cellular users. We consider uplink radio resource reuse of cellular users by D2D communication, and try to maximize the number of possible D2D links constrained to the interference on the cellular user. The number of D2D pairs that can be active in the full-duplex mode is smaller than in the half-duplex mode due to more interference from transmissions of both D2D nodes. We compare the total rate of half-duplex and full-duplex modes and evaluate the benefits of full-duplex radios.

Device-to-Device (D2D) underlaying communication system may be the solution to increase system data rate and reduce the workload of eNodeB. This communication system shares the same resources to two types of user, the cellular users and D2D pair. However, by using same resources, D2D underlaying communication system will increase the interference level among users. To overcome this problem, a good allocation algorithm is needed to allocate Resource Blocks (RB) which used by Cellular User Equipment (CUE) and D2D simultaneously. This work assumes all CUEs will use the RB first. The D2D pairs RB allocation take place after all CUEs get the resource. A modified Joint-Greedy algorithm is proposed to improve D2D pairs RB allocation process. The algorithm consist of two main phase. In the first phase, all D2D pairs will choose the best RB on the system, that being used by the CUE, and take that RB as a candidates. In the second phase, the eNodeB (eNB) will decides which of these candidates that will be allocated to D2D pair by searching the minimum impact of each CUE. From the simulation process, system with underlaying D2D communication can increase the system spectral efficiency system by 30%. Modified Joint-Greedy algorithm allocates can improve spectral efficiency of the system by 3.059% compared with mean-greedy allocation algorithm and 4.33% compared with a conventional greedy algorithm.

As an emerging paradigm, device-to-device (D2D) communication has the capability to complement and enhance the conventional cellular network by offering high spectral and energy efficiency. However, the problem of cochannel interference makes the resource allocation very complex and challenging in underlay D2D communication networks. This paper proposes a novel joint power control and resource scheduling scheme to enhance both the network throughput and the users’ fairness of the underlay D2D communication networks. Unlike other previous work in this area, our scheme aims at maximizing the sum of all users’ proportional fairness functions, while simultaneously taking into account factors such as fairness, signal-to-interference-plus-noise ratio requirements, and severe interference. The proposed scheme offers a practical solution because it works for lengthy time slots, a realistic scenario for the underlay D2D communication system. We also take into consideration the time-varying feature of user's channel condition in our proposed solution. Numerical results confirm that our proposed scheme not only dramatically improves the system throughput, but also boosts the system fairness while guaranteeing the Quality-of-Service levels of all D2D users and cellular users.

Non-orthogonal multiple access (NOMA) is the promising candidate to improve the spectral efficiency and system throughput in fifth-generation (5G) mobile communication networks. In this paper, we consider a co-operative non-orthogonal multiple access (CR-NOMA) system with dual users. The user closer to the base station (BS) acts as a full-duplex (FD) relay to assist the information transmission to the cell edge user. Instead of mitigating self-interference in FD systems, we propose to use the knowledge of Data information (DI) and the channel state information (CSI) at the BS to exploit the self-interference constructively rather than to suppress it. For Constructive interference based (CI) FD NOMA system, we derive an exact analytical expression for the outage probability of both users and system throughput. Numerical results are carried out to investigate the proposed CI FD-NOMA system and compared with the state of art HD and FD NOMA scenarios. It is observed that the proposed system performs better than the conventional HD/FD NOMA system.

In this paper, we consider a single-cell system where the same radio resources are simultaneously used by a cellular user and a pair of device-to-device (D2D) terminals. The optimization objective is to minimize the sum transmission power of the system while satisfying the user specific minimum rate constraints. We propose joint power control and beamforming algorithms to solve the power minimization problem optimally both in uplink and downlink. In the uplink, the optimal transmit powers for the cellular and D2D users are obtained via fixed-point iterations, whereas the linear minimum mean squared error receiver is used for optimal reception at the base station (BS). In the downlink, the problem is equivalently reformulated as a second-order cone program (SOCP). As a result, the optimal transmit beamformer for the cellular user and the optimal transmit power for the D2D user can be efficiently computed via standard SOCP solvers. Simulation results demonstrate that the sum power performance can be significantly improved as compared with the conventional cellular system. Results also illustrate that the power consumption of the network is highly affected by the locations of the cellular and D2D users, and whether the resources are shared in the uplink or downlink.

Physical layer network coding (PNC) is a promising technique used to enhance the throughput in relay based communication systems. Meanwhile, non-orthogonal multiple access (NOMA) is a technique which enhances the throughput in communication systems by communicating multiple parallel data streams within the same frequency band, using power domain multiplexing. In this paper, joint NOMAPNC in a set of parallel relay channels is investigated. Due to parallel communications, there are additional interferences present which could hinder the performance of the system. Nevertheless, through a theoretical performance evaluation, we demonstrate that a considerable throughput enhancement is achieved by the proposed scheme in comparison with NOMAcooperative communication and PNC-parallel relay communication. Furthermore, simulation results generated confirm the superior throughput of the proposed communication over the NOMA-cooperative communication and PNC-parallel relay communication.

In this paper, we investigate resource allocation in a downlink cooperative communication system. In the scenario where cellular users (CUs) and the base station (BS) cannot communicate directly, D2D user pairs participate in the cooperative communication to complete forwarding information required by CU and themselves through non-orthogonal multiple access (NOMA). The application of simultaneous wireless information and power transfer (SWIPT) ensures that D2D users save their own energy during the forwarding process. The ultimate optimization goal is to maximize the achievable rate of D2D user pairs under the condition of guaranteeing CU's quality of service (QoS). A stepwise iterative algorithm is proposed to obtain the suboptimal solution to the problem. By comparing with the ergodic optimal solution, numerical simulations show that the proposed algorithm can approximate the optimal solution with low computational cost in a certain error range.

Device-to-Device (D2D) communication has been proved to be a promising technique to efficiently utilize the radio spectrum thereby enhancing the capacity and meeting the huge data rate requirements of the future wireless networks. However, in underlay D2D communications, channel allocation (CA) is a challenging problem so as to limit the cross-tier interferences below a certain threshold. Most of the existing works on CA are based on maintaining minimum quality-of-service (QoS) requirements only for cellular users (CUs), or the D2DQoS constraints in a non-fading scenario. Moreover, most of them assume that the central controlling entity has all the prior information about the incoming D2D users, which appears unfeasible. In this work, we consider a more realistic underlay D2D communication scenario, and introduce an outage probability-based QoS constraint on the D2D links for enhanced reliability; in the presence of the combined effect of path-loss and fading. The channels are allocated online by maximizing the sum-outage-capacity of the full-duplex D2D network. The efficacy of the CA algorithm has been evaluated through rigorous simulations and the results have been numerically analyzed.

Performance of a nonlinear energy harvesting CR-enabled D2D network with censoring and NOMA

In this paper, we present the joint optimization of sum rate and fairness for contention based uplink multiple access with non-orthogonal multiple access (NOMA) communication system by resource allocation and user grouping. In particular, we study the cases of many users sharing the same resources that address application of the the internet of things (IoT). The key feature of contention based multiple access is to serve multiple users at the same time and frequency. With different power levels and user grouping, it can achieve better spectral efficiency over conventional orthogonal multiple access (OMA). However, unlike the OMA system, NOMA results in additional inter-user interference (IUI). It has also been shown that, without proper resource allocation for users in the uplink NOMA, the weak users can always be in outage. In this work, we have developed algorithms on subbands assignment, user grouping, and power allocation for joint optimization of sum rate and fairness. The algorithm allocates resources iteratively to handle the IUI in each iteration. Given a number of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> subbands allocation to each user, we could prevent starvation of poor users, e.g. cell edge users. We have also compare and analyze the sum rate and fairness performance with different combination of L and N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</sub> . We also find that, by properly limiting the maximum number of subbands each user can use, the system could better exploit multi-user diversity to improve the sum rate and hence the energy efficiency. The numerical simulations are also conducted to verify the results.

SummaryIn this paper, we propose an energy‐efficient power control and harvesting time scheduling scheme for resource allocation of the subchannels in a nonorthogonal multiple access (NOMA)–based device‐to‐device (D2D) communications in cellular networks. In these networks, D2D users can communicate by sharing the radio resources assigned to cellular users (CUs). Device‐to‐device users harvest energy from the base station (BS) in the downlink and transmit information to their receivers. Using NOMA, more than one user can access the same frequency‐time resource simultaneously, and the signals of the multiusers can be separated successfully using successive interference cancellation (SIC). In fact, NOMA, unlike orthogonal multiple access (OMA) methods, allows sharing the same frequency resources at the same time by implementing adaptive power allocation. Our aim is to maximize the energy efficiency of the D2D pairs, which is the ratio of the achievable throughput of the D2D pairs to their energy consumption by allocating the proper subchannel of each cell to each device user equipment (DUE), managing their transmission power, and setting the harvesting and transmission time. The constraints of the problem are the quality of service of the CUs, minimum required throughput of the subchannels, and energy harvesting of DUEs. We formulate the problem and propose a low‐complexity iterative algorithm on the basis of the convex optimization method and Karush‐Kuhn‐Tucker conditions to obtain the optimal solution of the problem. Simulation results validate the performance of our proposed algorithm for different values of the system parameters.

The upcoming mega low-earth orbit (LEO) high-throughput satellite constellation is regarded as an emerging paradigm shift in the fifth-generation-advance (5GA) networks. In this article, we propose a multitype services coexistence handover (MSCH) nonorthogonal multiple access (NOMA) scheme for a dual-layer mega LEO satellite constellation, which can simultaneously and efficiently provide uplink NOMA for three types of fifth-generation user equipments (UEs): 1) mission-critical communications (MCCs) UEs (CUs); 2) massive machine-type communications (mMTCs) UEs (MUs); and 3) enhanced mobile broadband (eMBB) UEs (EUs). The EUs are mainly served in the higher layer satellites for longer service duration and may handover to the lower layer satellites to coexist with CUs or MUs. Moreover, the CUs and MUs perform grant-based (GB) and grant-free (GF) NOMA on resource blocks (RBs) in the lower layer satellites, respectively. Then, we derive the closed-form expressions of three specific key performance indicators (KPIs), i.e., outage probability (OP), system throughput (ST), and ergodic capacity (EC) in the MSCH NOMA scheme, and design five corresponding NOMA algorithms. Simulation results verify the accuracy of our theoretical derivations and show that the proposed NOMA schemes can achieve a better KPI performance than the state-of-the-art ones.

The combination of non-orthogonal multiple access (NOMA) and transmit antenna selection (TAS) techniques has recently attracted significant attention due to the low cost, low complexity, and high diversity gains. Meanwhile, random linear coding (RLC) is considered to be a promising technique for achieving high reliability and low latency in multicast communications. In this paper, we consider a downlink system with a multi-antenna base station and two multicast groups of single-antenna users, where one group can afford to be served opportunistically, while the other group consists of comparatively low-power devices with limited processing capabilities that have strict quality of service (QoS) requirements. In order to boost reliability and satisfy the QoS requirements of the multicast groups, we propose a cross-layer framework, including NOMA-based TAS at the physical layer and RLC at the application layer. In particular, two low-complexity TAS protocols for NOMA are studied in order to exploit the diversity gain and meet the QoS requirements. In addition, RLC analysis aims to facilitate heterogeneous users, such that sliding window-based sparse RLC is employed for computational restricted users, and conventional RLC is considered for others. Theoretical expressions that characterize the performance of the proposed framework are derived and verified through simulation results.

In the fifth generation (5G) wireless communication network, to better offer service for different vertical industry applications, network slicing is needed to meet the differential requirements. In this paper, we study the joint problem of radio resource allocation and power resource allocation in the radio access network (RAN) to improve the radio resource utilization with multi-user demands in smart grid scenario. Different with conventional single-agent algorithm, we propose a non-orthogonal multiple access (NOMA) based multi-agent deep deterministic policy gradient (MADDPG) algorithm to solve this dynamic optimization problem. The scheme determines the remote radio unit (RRU) and physical resource block (PRB) allocation for each user, and updates the neural network to dynamically adjust the resource allocation strategy to maximize the long-term rate of network slices. The reliability and latency requirements of network slicing are guaranteed as well. Simulation results show the convergence and efficiency of the proposed algorithm.