Uplink Non-Orthogonal Multiple Access with Finite-Alphabet Inputs

This paper focuses on the non-orthogonal multiple access (NOMA) design for a classical two-user multiple access channel (MAC) with finite-alphabet inputs. We consider practical quadrature amplitude modulation (QAM) constellations at both transmitters, the sizes of which are assumed to be not necessarily identical. We propose to maximize the minimum Euclidean distance of the received sum-constellation with a maximum likelihood (ML) detector by adjusting the scaling factors (i.e., instantaneous transmitted powers and phases) of both users. The formulated problem is a mixed continuous-discrete optimization problem, which is nontrivial to resolve in general. By carefully observing the structure of the objective function, we discover that Farey sequence can be applied to tackle the formulated problem. However, the existing Farey sequence is not applicable when the constellation sizes of the two users are not the same. Motivated by this, we define a new type of Farey sequence, termed punched Farey sequence. Based on this, we manage to achieve a closed-form optimal solution to the original problem by first dividing the entire feasible region into a finite number of Farey intervals and then taking the maximum over all the possible intervals. The resulting sum-constellation is proved to be a regular QAM constellation of a larger size. Moreover, the superiority of NOMA over time-division multiple access (TDMA) in terms of minimum Euclidean distance is rigorously proved. Furthermore, the optimal rate allocation among the two users is obtained in closed-form to further maximize the obtained minimum Euclidean distance of the received signal subject to a total rate constraint. Finally, simulation results are provided to verify our theoretical analysis and demonstrate the merits of the proposed NOMA over existing orthogonal and non-orthogonal designs.Comment: Submitted for possible journal publicatio

Performance Analysis of SSK-NOMA

In this paper, we consider the combination between two promising techniques: space-shift keying (SSK) and non-orthogonal multiple access (NOMA) for future radio access networks. We analyze the performance of SSK-NOMA networks and provide a comprehensive analytical framework of SSK-NOMA regarding bit error probability (BEP), ergodic capacity and outage probability. It is worth pointing out all analysis also stand for conventional SIMO-NOMA networks. We derive closed-form exact average BEP (ABEP) expressions when the number of users in a resource block is equal to i.e., $L=3$. Nevertheless, we analyze the ABEP of users when the number of users is more than i.e., $L\geq3$, and derive bit-error-rate (BER) union bound since the error propagation due to iterative successive interference canceler (SIC) makes the exact analysis intractable. Then, we analyze the achievable rate of users and derive exact ergodic capacity of the users so the ergodic sum rate of the system in closed-forms. Moreover, we provide the average outage probability of the users exactly in the closed-form. All derived expressions are validated via Monte Carlo simulations and it is proved that SSK-NOMA outperforms conventional NOMA networks in terms of all performance metrics (i.e., BER, sum rate, outage). Finally, the effect of the power allocation (PA) on the performance of SSK-NOMA networks is investigated and the optimum PA is discussed under BER and outage constraints

Investigation on Evolving Single-Carrier NOMA into Multi-Carrier NOMA in 5G

© 2013 IEEE. Non-orthogonal multiple access (NOMA) is one promising technology, which provides high system capacity, low latency, and massive connectivity, to address several challenges in the fifth-generation wireless systems. In this paper, we first reveal that the NOMA techniques have evolved from single-carrier NOMA (SC-NOMA) into multi-carrier NOMA (MC-NOMA). Then, we comprehensively investigated on the basic principles, enabling schemes and evaluations of the two most promising MC-NOMA techniques, namely sparse code multiple access (SCMA) and pattern division multiple access (PDMA). Meanwhile, we consider that the research challenges of SCMA and PDMA might be addressed with the stimulation of the advanced and matured progress in SC-NOMA. Finally, yet importantly, we investigate the emerging applications, and point out the future research trends of the MC-NOMA techniques, which could be straightforwardly inspired by the various deployments of SC-NOMA

QoE Driven Multimedia Service Schemes in Wireless Networks Resource Allocation: Evolution from Optimization, Game Theory, to Economics

In order to deal with the Quality of Experience (QoE) improvement issue in the wireless networks services. In this dissertation we first investigated the Device to Device (D2D) relaying approach in the conventional Base Station (BS) to User Equipment (UE) two entities multimedia service system. In this part, the Multiple Input Multiple Output (MIMO) technology will be implemented in the D2D communication. Furthermore, factors such as the multimedia content distribution (i.e., Quad-tree fractal image compression method), the power allocation strategy, and modulation size are jointly considered to improve the QoE performance and energy efficiency. In addition, the emerging Non-Orthogonal Multiple Access (NOMA) transmission method is becoming very popular and being considered as one of the most potential technologies for the next generation of wireless networks. For the purpose of improving the QoE of UE in the wireless multimedia service, the power allocation method and the corresponding limitations are studied in detail in the wireless system where the traditional Orthogonal Multiple Access (OMA) technology and the promising NOMA technology are compared. At last, facing the real business model in the wireless network services, where the Content Provider (CP), Wireless Carrier (WC), and UE are included, we extend on work from the conventional BS-UE two entities research model to the CP-WC-UE three entities model. More specifically, a generalized best response Smart Media Pricing (SMP) method is studied in this dissertation. In our work, the CP and WC are treated as the service provider alliance. The SMP approach and the game theory are utilized to determine the data length of UE and the data price rate determined by the CP-WC union. It is worth pointing out that the concavity of utility function is no longer necessary for seeking the game equilibrium under the proposed best response game solution. Numerical simulation results also validate the system performance improvement of our proposed transmission schemes

A Systematic Review of NOMA Variants for 5G and Beyond

With the fast expansion of the Internet of Things (IoT), there is an exponential need for mobile intelligent terminals .However, the connectivity of large-scale intelligent terminals is constrained by increasingly restricted spectrum resources. To address this issue, non-orthogonal multiple access (NOMA) technology, which can handle more users with less resources, is predicted to enable future wireless networks beyond 5G,., 6G, to give huge terminal access. The fundamental idea behind NOMA is to superimpose signals from numerous users on the same time-frequency resource prior to transmission. At the receiver, serial interference cancellation (SIC) technology is used to reduce interference among users. In this  review paper  we discusses the principles of the strong candidate Non-Orthogonal Multiple Access (NOMA) approach, as well as how it can best match the requirements of the Fifth Generation (5G) requirements in practical applications.  

On the Fundamentals of Power Allocation Strategies for Non-Orthogonal Multiple Access Downlink Systems

The fundamentals of non-orthogonal multiple access (NOMA) power allocation strategies for downlink wireless transmissions are investigated, based on improving the performance over downlink transmissions using orthogonal multiple access (OMA). First, the scenario where the base-station possesses the perfect channel state information (CSI) is considered. For this scenario, the power allocation region is defined for a two-user downlink NOMA system. The expressions for the ergodic capacities and outage probabilities are derived for the case when the two users are pair randomly, each user with independently identically distributed (i.i.d.) fading channel gains. These results are then extended to the case where a cell-center user and cell-edge user are paired together, and a closed-form expression for the gap in ergodic capacity between NOMA and OMA is derived when SNR is large. This scenario is then extended to the general multi-user case, and it is proved that there always exists a power allocation strategy which allows all users to achieve a higher capacity when compared to OMA. In the second scenario, the effects of users with cached files on power allocation are investigated. When a user with weak channel condition has cached a file which a user with strong channel condition is requesting, these two users downlink transmissions are paired. An approximation of the optimum power allocation is derived, and the union-outage probability of this system is shown to improve over conventional NOMA and OMA. In the final scenario, the complete description of power allocation strategies is derived for more realistic wireless systems, where it is not assumed that the base-station possesses perfect CSI. Based on the target rates of each user, the fundamental properties of the power allocation strategy are derived, and the approach for selecting a strategy which improves the outage probability of each user is outlined. The existence of the power allocation strategies and their optimal energy efficiency is proved to be functions of the target rates and the OMA system parameters which they are compared to