1,258 research outputs found
A Survey on Delay-Aware Resource Control for Wireless Systems --- Large Deviation Theory, Stochastic Lyapunov Drift and Distributed Stochastic Learning
In this tutorial paper, a comprehensive survey is given on several major
systematic approaches in dealing with delay-aware control problems, namely the
equivalent rate constraint approach, the Lyapunov stability drift approach and
the approximate Markov Decision Process (MDP) approach using stochastic
learning. These approaches essentially embrace most of the existing literature
regarding delay-aware resource control in wireless systems. They have their
relative pros and cons in terms of performance, complexity and implementation
issues. For each of the approaches, the problem setup, the general solution and
the design methodology are discussed. Applications of these approaches to
delay-aware resource allocation are illustrated with examples in single-hop
wireless networks. Furthermore, recent results regarding delay-aware multi-hop
routing designs in general multi-hop networks are elaborated. Finally, the
delay performance of the various approaches are compared through simulations
using an example of the uplink OFDMA systems.Comment: 58 pages, 8 figures; IEEE Transactions on Information Theory, 201
Coexistence of OFDM and FBMC for Underlay D2D Communication in 5G Networks
Device-to-device (D2D) communication is being heralded as an important part
of the solution to the capacity problem in future networks, and is expected to
be natively supported in 5G. Given the high network complexity and required
signalling overhead associated with achieving synchronization in D2D networks,
it is necessary to study asynchronous D2D communications. In this paper, we
consider a scenario whereby asynchronous D2D communication underlays an OFDMA
macro-cell in the uplink. Motivated by the superior performance of new
waveforms with increased spectral localization in the presence of frequency and
time misalignments, we compare the system-level performance of a set-up for
when D2D pairs use either OFDM or FBMC/OQAM. We first demonstrate that
inter-D2D interference, resulting from misaligned communications, plays a
significant role in clustered D2D topologies. We then demonstrate that the
resource allocation procedure can be simplified when D2D pairs use FBMC/OQAM,
since the high spectral localization of FBMC/OQAM results in negligible
inter-D2D interference. Specifically, we identify that FBMC/OQAM is best suited
to scenarios consisting of small, densely populated D2D clusters located near
the encompassing cell's edge.Comment: 7 pages, 9 figures, Accepted at IEEE Globecom 2016 Workshop
Analysis Framework for Opportunistic Spectrum OFDMA and its Application to the IEEE 802.22 Standard
We present an analytical model that enables throughput evaluation of
Opportunistic Spectrum Orthogonal Frequency Division Multiple Access (OS-OFDMA)
networks. The core feature of the model, based on a discrete time Markov chain,
is the consideration of different channel and subchannel allocation strategies
under different Primary and Secondary user types, traffic and priority levels.
The analytical model also assesses the impact of different spectrum sensing
strategies on the throughput of OS-OFDMA network. The analysis applies to the
IEEE 802.22 standard, to evaluate the impact of two-stage spectrum sensing
strategy and varying temporal activity of wireless microphones on the IEEE
802.22 throughput. Our study suggests that OS-OFDMA with subchannel notching
and channel bonding could provide almost ten times higher throughput compared
with the design without those options, when the activity and density of
wireless microphones is very high. Furthermore, we confirm that OS-OFDMA
implementation without subchannel notching, used in the IEEE 802.22, is able to
support real-time and non-real-time quality of service classes, provided that
wireless microphones temporal activity is moderate (with approximately one
wireless microphone per 3,000 inhabitants with light urban population density
and short duty cycles). Finally, two-stage spectrum sensing option improves
OS-OFDMA throughput, provided that the length of spectrum sensing at every
stage is optimized using our model
Electromagnetic emission-aware schedulers for the uplink of OFDM wireless communication systems
The popularity and convergence of wireless communications have resulted in continuous network upgrades in order to support the increasing demand for bandwidth. However, given that wireless communication systems operate on radiofrequency waves, the health effects of electromagnetic emission from these systems are increasingly becoming a concern due to the ubiquity of mobile communication devices. In order to address these concerns, we propose two schemes (offline and online) for minimizing the EM emission of users in the uplink of OFDM systems, while maintaining an acceptable quality of service. We formulate our offline EM reduction scheme as a convex optimization problem and solve it through water-filling. This is based on the assumption that the long-term channel state information of all the users is known. Given that, in practice, long-term channel state information of all the users cannot always be available, we propose our online EM emission reduction scheme, which is based on minimizing the instantaneous transmit energy per bit of each user. Simulation results show that both our proposed schemes significantly minimize the EM emission when compared to the benchmark classic greedy spectral efficiency based scheme and an energy efficiency based scheme. Furthermore, our offline scheme proves to be very robust against channel prediction errors
A Framework for Uplink Intercell Interference Modeling with Channel-Based Scheduling
This paper presents a novel framework for modeling the uplink intercell
interference (ICI) in a multiuser cellular network. The proposed framework
assists in quantifying the impact of various fading channel models and
state-of-the-art scheduling schemes on the uplink ICI. Firstly, we derive a
semianalytical expression for the distribution of the location of the scheduled
user in a given cell considering a wide range of scheduling schemes. Based on
this, we derive the distribution and moment generating function (MGF) of the
uplink ICI considering a single interfering cell. Consequently, we determine
the MGF of the cumulative ICI observed from all interfering cells and derive
explicit MGF expressions for three typical fading models. Finally, we utilize
the obtained expressions to evaluate important network performance metrics such
as the outage probability, ergodic capacity, and average fairness numerically.
Monte-Carlo simulation results are provided to demonstrate the efficacy of the
derived analytical expressions.Comment: IEEE Transactions on Wireless Communications, 2013. arXiv admin note:
substantial text overlap with arXiv:1206.229
Performance of an Uplink OFDMA System Using Subcarrier Allocation
OFDMA (Orthogonal Frequency Division Multiple Access) suffers from destruction of orthogonility if a channel betweenthe mobile user and a base station is rapidly time varying. This channel between the mobile user and a base station is called an Uplink-OFDMA.
The OFDMA uplink resource allocation undergoes from Inter carrier interference (ICI), multiuser interference (MUI) if a nearby subcarrier is assigned to different user, high peak to average power ratio (PAPR) and high bit error rate (BER).This results in performance degradation. In
order to provide a significant improvement in performance, a practical OFDMA system detection is required. The proposed system consists of a new sub-carrier allocation method using a successive interfer
ence cancelation (SIC) detector at the receiver side. The proposed system is designed and simulated using MATLAB tool.
Simulation results show that the proposed subcarrier allocation and ―Interleaved Aǁ allocation method has an average Bit errorprobability of 10 -0.5 and 10-0.2 respectively. Thus Average Bit error probability of around 32% is reduced compared to the ―Interleaved Aǁallocation method. Further, simulations also demonstrate a gradual decrease in MUI power from -15db to -20db for interleaved al
location and subcarrier allocation method respectively
OFDMA/SC-FDMA aided space-time shift keying for dispersive multi-user scenarios
Motivated by the recent concept of Space-Time Shift Keying (STSK) developed for achieving a flexible diversity versus multiplexing gain trade-off, we propose a novel Orthogonal Frequency Division Multiple Access (OFDMA)/Single Carrier Frequency Division Multiple Access (SC-FDMA) aided multi-user STSK scheme for frequency-selective channels. The proposed OFDMA/SC-FDMA STSK scheme is capable of providing an improved performance in dispersive channels, while supporting multiple users in a multiple antenna aided wireless system. Furthermore, the scheme has the inherent potential of benefitting from the low-complexity single-stream Maximum-likelihood (ML) detector. Both an uncoded and a sophisticated near-capacity coded OFDMA/SC-FDMA STSK scheme were studied and their performances were compared in multiuser wideband Multiple-Input Multiple-Output (MIMO) scenarios. Explicitly, OFDMA/SC-FDMA aided STSK exhibits an excellent performance even in the presence of channel impairments due to the frequency-selectivity of wideband channels and proves to be a beneficial choice for high capacity multi-user MIMO systems
- …