236 research outputs found
Cooperative Multi-Bitrate Video Caching and Transcoding in Multicarrier NOMA-Assisted Heterogeneous Virtualized MEC Networks
Cooperative video caching and transcoding in mobile edge computing (MEC)
networks is a new paradigm for future wireless networks, e.g., 5G and 5G
beyond, to reduce scarce and expensive backhaul resource usage by prefetching
video files within radio access networks (RANs). Integration of this technique
with other advent technologies, such as wireless network virtualization and
multicarrier non-orthogonal multiple access (MC-NOMA), provides more flexible
video delivery opportunities, which leads to enhancements both for the
network's revenue and for the end-users' service experience. In this regard, we
propose a two-phase RAF for a parallel cooperative joint multi-bitrate video
caching and transcoding in heterogeneous virtualized MEC networks. In the cache
placement phase, we propose novel proactive delivery-aware cache placement
strategies (DACPSs) by jointly allocating physical and radio resources based on
network stochastic information to exploit flexible delivery opportunities.
Then, for the delivery phase, we propose a delivery policy based on the user
requests and network channel conditions. The optimization problems
corresponding to both phases aim to maximize the total revenue of network
slices, i.e., virtual networks. Both problems are non-convex and suffer from
high-computational complexities. For each phase, we show how the problem can be
solved efficiently. We also propose a low-complexity RAF in which the
complexity of the delivery algorithm is significantly reduced. A Delivery-aware
cache refreshment strategy (DACRS) in the delivery phase is also proposed to
tackle the dynamically changes of network stochastic information. Extensive
numerical assessments demonstrate a performance improvement of up to 30% for
our proposed DACPSs and DACRS over traditional approaches.Comment: 53 pages, 24 figure
Cache-Aided Non-Orthogonal Multiple Access
In this paper, we propose a novel joint caching and non-orthogonal multiple
access (NOMA) scheme to facilitate advanced downlink transmission for next
generation cellular networks. In addition to reaping the conventional
advantages of caching and NOMA transmission, the proposed cache-aided NOMA
scheme also exploits cached data for interference cancellation which is not
possible with separate caching and NOMA transmission designs. Furthermore, as
caching can help to reduce the residual interference power, several decoding
orders are feasible at the receivers, and these decoding orders can be flexibly
selected for performance optimization. We characterize the achievable rate
region of cache-aided NOMA and investigate its benefits for minimizing the time
required to complete video file delivery. Our simulation results reveal that,
compared to several baseline schemes, the proposed cache-aided NOMA scheme
significantly expands the achievable rate region for downlink transmission,
which translates into substantially reduced file delivery times.Comment: Accepted for presentation at IEEE ICC 201
A Review of Power Domain Non-Orthogonal Multiple Access in 5G Networks
This paper highlights the fundamentals of the strong candidate Power Domain Non-Orthogonal Multiple Access (PD-NOMA) technique, and how it can best fit the requirements of fifth Generation (5G) in practical applications. PD-NOMA ensures flexibility in radio resource to improve user’s access performance. Multiple users share the same radio resources in PD-NOMA, and therefore better spectrum efficiency can be achieved. The practical system design aspects of PD-NOMA are considered in this paper by exploring different network scenarios. Optimal performances of PD-NOMA system can be obtained by suitable power allocation schemes, with reduce the computational complexity, and advanced user pairing strategy. Theoretical formulation and solutions are also explained prior to the concept of downlink PD-NOMA. Challenges and future research windows are discussed before conclusion of this paper
General Framework and Novel Transceiver Architecture based on Hybrid Beamforming for NOMA in Massive MIMO Channels
Massive MIMO and non-orthogonal multiple access (NOMA) are crucial methods
for future wireless systems as they provide many advantages over conventional
systems. Power domain NOMA methods are investigated in massive MIMO systems,
whereas there is little work on integration of code domain NOMA and massive
MIMO which is the subject of this study. We propose a general framework
employing user-grouping based hybrid beamforming architecture for mm-wave
massive MIMO systems where NOMA is considered as an intra-group process. It is
shown that classical receivers of sparse code multiple access (SCMA) and
multi-user shared access (MUSA) can be directly adapted. Additionally, a novel
receiver architecture which is an improvement over classical one is proposed
for uplink MUSA. This receiver makes MUSA preferable over SCMA for uplink
transmission with lower complexity. We provide a lower bound on achievable
information rate (AIR) as a performance measure. We show that code domain NOMA
schemes outperform conventional methods with very limited number of radio
frequency (RF) chains where users are spatially close to each other.
Furthermore, we provide an analysis in terms of bit-error rate and AIR under
different code length and overloading scenarios for uplink transmission where
flexible structure of MUSA is exploited.Comment: Partially presented at IEEE ICC 2020 Workshop on NOMA for 5G and
Beyond and to be submitted to IEEE Transactions on Communication
Low-complexity dynamic resource scheduling for downlink MC-NOMA over fading channels
In this paper, we investigate dynamic resource scheduling (i.e., joint user,
subchannel, and power scheduling) for downlink multi-channel non-orthogonal
multiple access (MC-NOMA) systems over time-varying fading channels.
Specifically, we address the weighted average sum rate maximization problem
with quality-of-service (QoS) constraints. In particular, to facilitate fast
resource scheduling, we focus on developing a very low-complexity algorithm. To
this end, by leveraging Lagrangian duality and the stochastic optimization
theory, we first develop an opportunistic MC-NOMA scheduling algorithm whereby
the original problem is decomposed into a series of subproblems, one for each
time slot. Accordingly, resource scheduling works in an online manner by
solving one subproblem per time slot, making it more applicable to practical
systems. Then, we further develop a heuristic joint subchannel assignment and
power allocation (Joint-SAPA) algorithm with very low computational complexity,
called Joint-SAPA-LCC, that solves each subproblem. Finally, through
simulation, we show that our Joint-SAPA-LCC algorithm provides good performance
comparable to the existing Joint-SAPA algorithms despite requiring much lower
computational complexity. We also demonstrate that our opportunistic MC-NOMA
scheduling algorithm in which the Joint-SAPA-LCC algorithm is embedded works
well while satisfying given QoS requirements.Comment: 39 pages, 11 figure
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