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.
Highlights
One of the highest challenges for future wireless communication systems is to ensure the support for massive data traffic, while maintaining a low communication latency [1,2,3,4,5], support needed due to the continuous evolution of multimedia applications and a rapidly growing number of users that request simultaneously access to different network resources from everywhere and anytime while maintaining a good quality of service (QoS) as well as a high flexibility with respect to individual user requirements
First, we present the performance of an uplink massive MU-multiple input multiple output (MIMO) system when active users are separated by Walsh, pseudo-random noise (PN) spreading codes and by complex spreading codes
multiple-user shared-access (MUSA) (EMUSA) set of codes was created by extending the MUSA and MUSA0 from length 8 to length 32, obtaining extended MUSA (EMUSA) and EMUSA0 sets
Summary
One of the highest challenges for future wireless communication systems is to ensure the support for massive data traffic, while maintaining a low communication latency [1,2,3,4,5], support needed due to the continuous evolution of multimedia applications and a rapidly growing number of users that request simultaneously access to different network resources from everywhere and anytime while maintaining a good quality of service (QoS) as well as a high flexibility with respect to individual user requirements. Authors in [40] propose another high-overloaded autonomous grant-free MUSA transmission with 8 to 20 users, where the data is turbo-coded of rate 1⁄2 and BPSK-modulated and sent over a channel affected by flat fading. The authors present, in [44], a high-overloaded autonomous grant-free MUSA transmission with 8 to 20 users, where the data were LDPC-encoded and BPSK-modulated and sent over a channel affected by deep flat fading The performance of such a system was studied in the presence of real Fourier-related transform spreading OFDM (RFRT-s-OFDM). In [45], the authors compare the performance of three different NOMA schemes—MUSA, PDMA, and SCMA, a QPSK-modulated transmission over Rayleigh fading channels in underloaded, fully loaded, and overloaded scenarios, employing two different receivers that have perfect knowledge of the channels—ordered successive interference cancellation (OSIC)-based MUD and message-passing algorithm (MPA)-based MUD.
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