176 research outputs found
Outage Performance of Uplink Rate Splitting Multiple Access with Randomly Deployed Users
With the rapid proliferation of smart devices in wireless networks, more
powerful technologies are expected to fulfill the network requirements of high
throughput, massive connectivity, and diversify quality of service. To this
end, rate splitting multiple access (RSMA) is proposed as a promising solution
to improve spectral efficiency and provide better fairness for the
next-generation mobile networks. In this paper, the outage performance of
uplink RSMA transmission with randomly deployed users is investigated, taking
both user scheduling schemes and power allocation strategies into
consideration. Specifically, the greedy user scheduling (GUS) and cumulative
distribution function (CDF) based user scheduling (CUS) schemes are considered,
which could maximize the rate performance and guarantee scheduling fairness,
respectively. Meanwhile, we re-investigate cognitive power allocation (CPA)
strategy, and propose a new rate fairness-oriented power allocation (FPA)
strategy to enhance the scheduled users' rate fairness. By employing order
statistics and stochastic geometry, an analytical expression of the outage
probability for each scheduling scheme combining power allocation is derived to
characterize the performance. To get more insights, the achieved diversity
order of each scheme is also derived. Theoretical results demonstrate that both
GUS and CUS schemes applying CPA or FPA strategy can achieve full diversity
orders, and the application of CPA strategy in RSMA can effectively eliminate
the secondary user's diversity order constraint from the primary user.
Simulation results corroborate the accuracy of the analytical expressions, and
show that the proposed FPA strategy can achieve excellent rate fairness
performance in high signal-to-noise ratio region.Comment: 38 pages,8 figure
Transmission Scheme, Detection and Power Allocation for Uplink User Cooperation with NOMA and RSMA
In this paper, we propose two novel
cooperative-non-orthogonal-multiple-access (C-NOMA) and
cooperative-rate-splitting-multiple-access (C-RSMA) schemes for uplink user
cooperation. At the first mini-slot of these schemes, each user transmits its
signal and receives the transmitted signal of the other user in full-duplex
mode, and at the second mini-slot, each user relays the other user's message
with amplify-and-forward (AF) protocol. At both schemes, to achieve better
spectral efficiency, users transmit signals in the non-orthogonal mode in both
mini-slots. In C-RSMA, we also apply the rate-splitting method in which the
message of each user is divided into two streams. In the proposed detection
schemes for C-NOMA and C-RSMA, we apply a combination of
maximum-ratio-combining (MRC) and successive-interference-cancellation (SIC).
Then, we derive the achievable rates for C-NOMA and C-RSMA, and formulate two
optimization problems to maximize the minimum rate of two users by considering
the proportional fairness coefficient. We propose two power allocation
algorithms based on successive-convex-approximation (SCA) and
geometric-programming (GP) to solve these non-convex problems. Next, we derive
the asymptotic outage probability of the proposed C-NOMA and C-RSMA schemes,
and prove that they achieve diversity order of two. Finally, the
above-mentioned performance is confirmed by simulations.Comment: 32 pages, 13 figure
Low-complexity Resource Allocation for User Paired RSMA in Future 6G Wireless Networks
Rate-splitting multiple access (RSMA) uplink requires optimization of
decoding order and power allocation, while decoding order is a discrete
variable, and it is very complex to find the optimal decoding order if the
number of users is large enough. This letter proposes a low-complexity user
pairing-based resource allocation algorithm with the objective of minimizing
the maximum latency, which significantly reduces the computational complexity
and also achieves similar performance to unpaired uplink RSMA. A closed-form
expression for power and bandwidth allocation is first derived, and then a
bisection method is used to determine the optimal resource allocation. Finally,
the proposed algorithm is compared with unpaired RSMA, paired NOMA and unpaired
NOMA. The results demonstrate the effectiveness of the proposed algorithm
Multiple Access in Aerial Networks: From Orthogonal and Non-Orthogonal to Rate-Splitting
Recently, interest on the utilization of unmanned aerial vehicles (UAVs) has
aroused. Specifically, UAVs can be used in cellular networks as aerial users
for delivery, surveillance, rescue search, or as an aerial base station (aBS)
for communication with ground users in remote uncovered areas or in dense
environments requiring prompt high capacity. Aiming to satisfy the high
requirements of wireless aerial networks, several multiple access techniques
have been investigated. In particular, space-division multiple access(SDMA) and
power-domain non-orthogonal multiple access (NOMA) present promising
multiplexing gains for aerial downlink and uplink. Nevertheless, these gains
are limited as they depend on the conditions of the environment. Hence, a
generalized scheme has been recently proposed, called rate-splitting multiple
access (RSMA), which is capable of achieving better spectral efficiency gains
compared to SDMA and NOMA. In this paper, we present a comprehensive survey of
key multiple access technologies adopted for aerial networks, where aBSs are
deployed to serve ground users. Since there have been only sporadic results
reported on the use of RSMA in aerial systems, we aim to extend the discussion
on this topic by modelling and analyzing the weighted sum-rate performance of a
two-user downlink network served by an RSMA-based aBS. Finally, related open
issues and future research directions are exposed.Comment: 16 pages, 6 figures, submitted to IEEE Journa
Performance Enhancement Using NOMA-MIMO for 5G Networks
The integration of MIMO and NOMA technologies addresses key challenges in 5G and beyond, such as connectivity, latency, and dependability. However, resolving these issues, especially in MIMO-enabled 5G networks, required additional research. This involved optimizing parameters like bit error rate, downlink spectrum efficiency, average capacity rate, and uplink transmission outage probability. The model employed Quadrature Phase Shift Keying modulation on selected frequency channels, accommodating diverse user characteristics. Evaluation showed that MIMO-NOMA significantly improved bit error rate and transmitting power for the best user in download transmission. For uplink transmission, there was an increase in the average capacity rate and a decrease in outage probability for the best user. Closed-form formulas for various parameters in both downlink and uplink NOMA, with and without MIMO, were derived. Overall, adopting MIMO-NOMA led to a remarkable performance improvement for all users, even in challenging conditions like interference or fading channels
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
Improving performance of far users in cognitive radio: Exploiting NOMA and wireless power transfer
In this paper, we examine non-orthogonal multiple access (NOMA) and relay selection strategy to benefit extra advantage from traditional cognitive radio (CR) relaying systems. The most important requirement to prolong lifetime of such network is employing energy harvesting in the relay to address network with limited power constraint. In particular, we study such energy harvesting CR-NOMA using amplify-and-forward (AF) scheme to improve performance far NOMA users. To further address such problem, two schemes are investigated in term of number of selected relays. To further examine system performance, the outage performance needs to be studied for such wireless powered CR-NOMA network over Rayleigh channels. The accurate expressions for the outage probability are derived to perform outage comparison of primary network and secondary network. The analytical results show clearly that position of these nodes, transmit signal to noise ratio (SNR) and power allocation coefficients result in varying outage performance. As main observation, performance gap between primary and secondary destination is decided by both power allocation factors and selection mode of single relay or multiple relays. Numerical studies were conducted to verify our derivations.Web of Science1211art. no. 220
Enabling non-linear energy harvesting in power domain based multiple access in relaying networks: Outage and ergodic capacity performance analysis
The Power Domain-based Multiple Access (PDMA) scheme is considered as one kind of Non-Orthogonal Multiple Access (NOMA) in green communications and can support energy-limited devices by employing wireless power transfer. Such a technique is known as a lifetime-expanding solution for operations in future access policy, especially in the deployment of power-constrained relays for a three-node dual-hop system. In particular, PDMA and energy harvesting are considered as two communication concepts, which are jointly investigated in this paper. However, the dual-hop relaying network system is a popular model assuming an ideal linear energy harvesting circuit, as in recent works, while the practical system situation motivates us to concentrate on another protocol, namely non-linear energy harvesting. As important results, a closed-form formula of outage probability and ergodic capacity is studied under a practical non-linear energy harvesting model. To explore the optimal system performance in terms of outage probability and ergodic capacity, several main parameters including the energy harvesting coefficients, position allocation of each node, power allocation factors, and transmit signal-to-noise ratio (SNR) are jointly considered. To provide insights into the performance, the approximate expressions for the ergodic capacity are given. By matching analytical and Monte Carlo simulations, the correctness of this framework can be examined. With the observation of the simulation results, the figures also show that the performance of energy harvesting-aware PDMA systems under the proposed model can satisfy the requirements in real PDMA applications.Web of Science87art. no. 81
Effective relaying mechanisms in future device to device communication : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Food and Advanced Technology at Massey University, Palmerston North, New Zealand
Listed in 2020 Dean's List of Exceptional ThesesFuture wireless networks embrace a large number of assorted network-enabled devices
such as mobile phones, sensor nodes, drones, smart gears, etc., with different applications
and purpose, but they all share one common characteristic which is the dependence
on strong network connectivity. Growing demand of internet-connected devices
and data applications is burdensome for the currently deployed cellular wireless networks.
For this reason, future networks are likely to embrace cutting-edge technological
advancements in network infrastructure such as, small cells, device-to-device communication,
non-orthogonal multiple access scheme (NOMA), multiple-input-multiple out,
etc., to increase spectral efficiency, improve network coverage, and reduce network latency.
Individual devices acquire network connectivity by accessing radio resources in
orthogonal manner which limits spectrum utilisation resulting in data congestion and
latency in dense cellular networks. NOMA is a prominent scheme in which multiple
users are paired together and access radio resources by slicing the power domain. While
several research works study power control mechanisms by base station to communicate
with NOMA users, it is equally important to maintain distinction between the
users in uplink communication. Furthermore, these users in a NOMA pair are able to
perform cooperative relaying where one device assists another device in a NOMA pair
to increase signal diversity. However, the benefits of using a NOMA pair in improving
network coverage is still overlooked. With a varierty of cellular connected devices, use
of NOMA is studied on devices with similar channel characteristics and the need of
adopting NOMA for aerial devices has not been investigated. Therefore, this research
establishes a novel mechanism to offer distinction in uplink communication for NOMA
pair, a relaying scheme to extend the coverage of a base station by utilising NOMA
pair and a ranking scheme for ground and aerial devices to access radio resources by
NOMA
- …