Performance Comparison of Massive MIMO System with Orthogonal and Nonorthogonal Multiple Access for Uplink in 5G Systems

Abstract

In the attempt to respond to market demands, new techniques for wireless communication systems have been proposed to ensure, to all active users that are sharing the same network cell, an increased quality of service, regardless of any environmental factors, such as their position within the cell, time, space, climate, and noise. One example is the nonorthogonal multiple access (NOMA) technique, proposed within the 5G standard, known for supporting a massive connectivity and a more efficient use of radio resources. This paper presents two new sets of complex codes— multiple-user shared-access (MUSA) and extended MUSA (EMUSA), and an algorithm of allocation such that the intercorrelation should be as reduced as possible that can be used in MUSA for 5G NOMA-based technique scheme. Also, it analyzes the possibility of creating complex codes starting from PN (cPN), which is a novel idea proposed in this paper, whose results are promising with respect to the overall system performances. First, a description of the basic principles of MUSA are presented; next, the description of the proposed system will be provided, whose performance will be tested using Monte Carlo MATLAB simulations based on bit error rate (BER) versus signal-to-noise ratio (SNR). The system performances are evaluated in different scenarios and compared with classical code division multiple access (CDMA) having the following system parameters in sight: the number of antennas at the receiver side and the number of active users.

The performance of complex spreading codes within a Massive MIMO OFDM-based system with relays

“…2 represents the first two scenarios in which the performance of our proposed system is being evaluated. Walsh-Hadamard complex spreading codes of length 32 were used obtained following the steps in the algorithm presented in article [2]. Increasing the number of antennas at the relay and at the receiver, the results are better due to the gain obtained from spatial diversity offered by MIMO technique, while the number of active users remains the same.…”

“…In this section, it is described the proposed system model used for the simulation partan uplink wireless communication single-cell system using a multiple access technique with complex spreading codes obtained from orthogonal Walsh-Hadamard spreading codes. These codes are obtained following the algorithm presented in [2], codes that are of length 16 or 32 and have zero correlation. In the following it is presented the matrix of these codes of length 32, but being able to ensure good QoS for many users, we chose to present, in the equation below, the codes used only for 9 users…”

“…They are characterized using multiple access techniques, which for 5G standard are identified with NOMA [1]. There are different types of NOMA schemes, but the main point of interest of this paper are the code domain NOMA schemes that perform user multiplexing in code domain using unique spreading sequences for each user with low inter-correlation properties [2]. Following these premises, an algorithm to obtain complex spreading codes from orthogonal Walsh-Hadamard spreading codes is proposed.…”

“…Following these premises, an algorithm to obtain complex spreading codes from orthogonal Walsh-Hadamard spreading codes is proposed. The idea started from the article [2] where an algorithm for obtaining complex pseudorandom (PN) spreading codes was proposed obtaining encouraging results and by following it will lead to generating complex Walsh-Hadamard spreading codes.…”

User Clustering and Power Allocation for Energy Efficiency Maximization in Downlink Non-Orthogonal Multiple Access Systems

“…To satisfy the multiplied demands in system capacity and throughput performance, non-orthogonal multiple access (NOMA) has been widely considered a novel and promising candidate cellular multiple access scheme for the fifth generation (5G) mobile communication systems [1][2][3][4][5][6]. Many theoretical analyses and experimentation have proved that NOMA can achieve a higher sum rate than orthogonal multiple access (OMA) adopted in the fourth generation (4G) wireless networks [7][8][9][10][11][12]. In NOMA, multiple users with different channel gains can be multiplexed together in the same subchannel and decoded at the receivers through successive interference cancellation (SIC) techniques [13][14][15][16][17][18].…”