27 research outputs found
Hybrid generalized non-orthogonal multiple access for the 5G wireless networks.
Master of Science in Computer Engineering. University of KwaZulu-Natal. Durban, 2018.The deployment of 5G networks will lead to an increase in capacity, spectral efficiency, low latency
and massive connectivity for wireless networks. They will still face the challenges of resource and
power optimization, increasing spectrum efficiency and energy optimization, among others.
Furthermore, the standardized technologies to mitigate against the challenges need to be developed
and are a challenge themselves. In the current predecessor LTE-A networks, orthogonal frequency
multiple access (OFDMA) scheme is used as the baseline multiple access scheme. It allows users to
be served orthogonally in either time or frequency to alleviate narrowband interference and impulse
noise. Further spectrum limitations of orthogonal multiple access (OMA) schemes have resulted in
the development of non-orthogonal multiple access (NOMA) schemes to enable 5G networks to
achieve high spectral efficiency and high data rates. NOMA schemes unorthogonally co-multiplex
different users on the same resource elements (RE) (i.e. time-frequency domain, OFDMA subcarrier,
or spreading code) via power domain (PD) or code domain (CD) at the transmitter and successfully
separating them at the receiver by applying multi-user detection (MUD) algorithms. The current
developed NOMA schemes, refered to as generalized-NOMA (G-NOMA) technologies includes;
Interleaver Division Multiple Access (IDMA, Sparse code multiple access (SCMA), Low-density
spreading multiple access (LDSMA), Multi-user shared access (MUSA) scheme and the Pattern
Division Multiple Access (PDMA). These protocols are currently still under refinement, their
performance and applicability has not been thoroughly investigated. The first part of this work
undertakes a thorough investigation and analysis of the performance of the existing G-NOMA
schemes and their applicability.
Generally, G-NOMA schemes perceives overloading by non-orthogonal spectrum resource
allocation, which enables massive connectivity of users and devices, and offers improved system
spectral efficiency. Like any other technologies, the G-NOMA schemes need to be improved to
further harvest their benefits on 5G networks leading to the requirement of Hybrid G-NOMA
(G-NOMA) schemes. The second part of this work develops a HG-NOMA scheme to alleviate the
5G challenges of resource allocation, inter and cross-tier interference management and energy
efficiency. This work develops and investigates the performance of an Energy Efficient HG-NOMA
resource allocation scheme for a two-tier heterogeneous network that alleviates the cross-tier
interference and improves the system throughput via spectrum resource optimization. By considering
the combinatorial problem of resource pattern assignment and power allocation, the HG-NOMA
scheme will enable a new transmission policy that allows more than two macro-user equipment’s
(MUEs) and femto-user equipment’s (FUEs) to be co-multiplexed on the same time-frequency RE
increasing the spectral efficiency. The performance of the developed model is shown to be superior to
the PD-NOMA and OFDMA schemes
Low complexity physical layer security approach for 5G internet of things
Fifth-generation (5G) massive machine-type communication (mMTC) is expected to support the cellular adaptation of internet of things (IoT) applications for massive connectivity. Due to the massive access nature, IoT is prone to high interception probability and the use of conventional cryptographic techniques in these scenarios is not practical considering the limited computational capabilities of the IoT devices and their power budget. This calls for a lightweight physical layer security scheme which will provide security without much computational overhead and/or strengthen the existing security measures. Here a shift based physical layer security approach is proposed which will provide a low complexity security without much changes in baseline orthogonal frequency division multiple access (OFDMA) architecture as per the low power requirements of IoT by systematically rearranging the subcarriers. While the scheme is compatible with most fast Fourier transform (FFT) based waveform contenders which are being proposed in 5G especially in mMTC and ultra-reliable low latency communication (URLLC), it can also add an additional layer of security at physical layer to enhanced mobile broadband (eMBB)
Capacity-Achieving MIMO-NOMA: Iterative LMMSE Detection
This paper considers a low-complexity iterative Linear Minimum Mean Square
Error (LMMSE) multi-user detector for the Multiple-Input and Multiple-Output
system with Non-Orthogonal Multiple Access (MIMO-NOMA), where multiple
single-antenna users simultaneously communicate with a multiple-antenna base
station (BS). While LMMSE being a linear detector has a low complexity, it has
suboptimal performance in multi-user detection scenario due to the mismatch
between LMMSE detection and multi-user decoding. Therefore, in this paper, we
provide the matching conditions between the detector and decoders for
MIMO-NOMA, which are then used to derive the achievable rate of the iterative
detection. We prove that a matched iterative LMMSE detector can achieve (i) the
optimal capacity of symmetric MIMO-NOMA with any number of users, (ii) the
optimal sum capacity of asymmetric MIMO-NOMA with any number of users, (iii)
all the maximal extreme points in the capacity region of asymmetric MIMO-NOMA
with any number of users, (iv) all points in the capacity region of two-user
and three-user asymmetric MIMO-NOMA systems. In addition, a kind of practical
low-complexity error-correcting multiuser code, called irregular
repeat-accumulate code, is designed to match the LMMSE detector. Numerical
results shows that the bit error rate performance of the proposed iterative
LMMSE detection outperforms the state-of-art methods and is within 0.8dB from
the associated capacity limit.Comment: Accepted by IEEE TSP, 16 pages, 9 figures. This is the first work
that proves the low-complexity iterative receiver (Parallel Interference
Cancellation) can achieve the capacity of multi-user MIMO systems. arXiv
admin note: text overlap with arXiv:1604.0831
Performance analysis of biological resource allocation algorithms for next generation networks.
Masters Degree. University of KwaZulu-Natal, Durban.Abstract available in PDF.Publications listed on page iii
A survey of 5G technologies: regulatory, standardization and industrial perspectives
In recent years, there have been significant developments in the research on 5th Generation (5G) networks. Several enabling technologies are being explored for the 5G mobile system era. The aim is to evolve a cellular network that is intrinsically flexible and remarkably pushes forward the limits of legacy mobile systems across all dimensions of performance metrics. All the stakeholders, such as regulatory bodies, standardization authorities, industrial fora, mobile operators and vendors, must work in unison to bring 5G to fruition. In this paper, we aggregate the 5G-related information coming from the various stakeholders, in order to i) have a comprehensive overview of 5G and ii) to provide a survey of the envisioned 5G technologies; their development thus far from the perspective of those stakeholders will open up new frontiers of services and applications for next-generation wireless networks. Keywords: 5G, ITU, Next-generation wireless network
Resource allocation in non-orthogonal multiple access technologies for 5G networks and beyond.
Doctoral Degree. University of KwaZulu-Natal, Durban.The increasing demand of mobile and device connectivity poses challenging requirements for 5G wireless communications, such as high energy- and spectral-efficiency and low latency. This necessitates a shift from orthogonal multiple access (OMA) to Non-Orthogonal Multiple Access
(NOMA) techniques, namely, power-domain NOMA (PD-NOMA) and code-domain NOMA (CD-NOMA). The basic idea behind NOMA schemes is to co-multiplex different users on the same resource elements (time slot, OFDMA sub-carrier, or spreading code) via power domain (PD) or code domain (CD) at the transmitter while permitting controllable interference, and their successful multi-user detection (MUD) at the receiver albeit, increased computational complexity. In this work, an analysis on the performance of the existing NOMA schemes is carried out.
Furthermore, we investigate the feasibility of a proposed uplink hybrid-NOMA scheme namely power domain sparse code multiple access (PD-SCMA) that integrates PD-NOMA and CD-NOMA based sparse code multiple access (SCMA) on heterogeneous networks (HetNets). Such hybrid schemes come with resource allocation (RA) challenges namely; codebook allocation, user pairing and power allocation. Therefore, hybrid RA schemes namely: Successive Codebook Ordering Assignment (SCOA) for codebook assignment (CA), opportunistic macro cell user equipment (MUE)- small cell user equipment (SUE) pairing (OMSP) for user pairing (UP), and a QoS-aware power allocation (QAPA) for power allocation (PA) are developed for an energy efficient (EE) system. The performance of the RA schemes is analyzed alongside an analytical RA optimization algorithm. Through numerical results, the proposed schemes show significant improvements in the EE of the small cells in comparison with the prevalent schemes. Additionally, there is significant sum
rate performance improvement over the conventional SCMA and PD-NOMA.
Secondly, we investigate the multiplexing capacity of the hybrid PD-SCMA scheme in HetNets.
Particularly, we investigate and derive closed-form solutions for codebook capacity, MUE multiplexing and power capacity bounds. The system’s performance results into low outage when the system’s point of operation is within the multiplexing bounds. To alleviate the RA challenges of such a system at the transmitter, dual parameter ranking (DPR) and alternate search method (ASM) based RA schemes are proposed. The results show significant capacity gain with DPR-RA in comparison with conventional RA schemes.
Lastly, we investigate the feasibility of integrating the hybrid PD-SCMA with multiple-input multipleoutput (MIMO) technique namely, M-PD-SCMA. The attention to M-PD-SCMA resides in the need of lower number of antennas while preserving the system capacity thanks to the overload in PDSCMA. To enhance spectral efficiency and error performance we propose spatial multiplexing at the transmitter and a low complex joint MUD scheme based on successive interference cancellation (SIC) and expectation propagation algorithm (EPA) at the receiver are proposed. Numerical results exhibit performance benchmark with PD-SCMA schemes and the proposed receiver achieves guaranteed bit error rate (BER) performance with a bounded increase in the number of transmit and receive antennas. Thus, the feasibility of an M-PD-SCMA system is validated
Cellular, Wide-Area, and Non-Terrestrial IoT: A Survey on 5G Advances and the Road Towards 6G
The next wave of wireless technologies is proliferating in connecting things
among themselves as well as to humans. In the era of the Internet of things
(IoT), billions of sensors, machines, vehicles, drones, and robots will be
connected, making the world around us smarter. The IoT will encompass devices
that must wirelessly communicate a diverse set of data gathered from the
environment for myriad new applications. The ultimate goal is to extract
insights from this data and develop solutions that improve quality of life and
generate new revenue. Providing large-scale, long-lasting, reliable, and near
real-time connectivity is the major challenge in enabling a smart connected
world. This paper provides a comprehensive survey on existing and emerging
communication solutions for serving IoT applications in the context of
cellular, wide-area, as well as non-terrestrial networks. Specifically,
wireless technology enhancements for providing IoT access in fifth-generation
(5G) and beyond cellular networks, and communication networks over the
unlicensed spectrum are presented. Aligned with the main key performance
indicators of 5G and beyond 5G networks, we investigate solutions and standards
that enable energy efficiency, reliability, low latency, and scalability
(connection density) of current and future IoT networks. The solutions include
grant-free access and channel coding for short-packet communications,
non-orthogonal multiple access, and on-device intelligence. Further, a vision
of new paradigm shifts in communication networks in the 2030s is provided, and
the integration of the associated new technologies like artificial
intelligence, non-terrestrial networks, and new spectra is elaborated. Finally,
future research directions toward beyond 5G IoT networks are pointed out.Comment: Submitted for review to IEEE CS&