228 research outputs found
Nearly Optimal Resource Allocation for Downlink OFDMA in 2-D Cellular Networks
In this paper, we propose a resource allocation algorithm for the downlink of
sectorized two-dimensional (2-D) OFDMA cellular networks assuming statistical
Channel State Information (CSI) and fractional frequency reuse. The proposed
algorithm can be implemented in a distributed fashion without the need to any
central controlling units. Its performance is analyzed assuming fast fading
Rayleigh channels and Gaussian distributed multicell interference. We show that
the transmit power of this simple algorithm tends, as the number of users grows
to infinity, to the same limit as the minimal power required to satisfy all
users' rate requirements i.e., the proposed resource allocation algorithm is
asymptotically optimal. As a byproduct of this asymptotic analysis, we
characterize a relevant value of the reuse factor that only depends on an
average state of the network.Comment: submitted to IEEE Transactions on Wireless Communication
Energy minimization based Resource Scheduling for Strict Delay Constrained Wireless Communications
This paper investigates the energy consumption minimization
for resource scheduling in a wireless communication.
We propose to take into account a strict delay constraint for each
queued packet rather than an average delay constraint, in addition
to a buffer overflow constraint. The associated optimization
problem can be modeled as Constraint Markov Decision Problem
where the actions are the number of packets sent on the known
channel at each slot. The optimal random policy is exhibited
through the resolution of standard linear programming. We show
the gain in energy is substantial compared to naive policy
A survey on fiber nonlinearity compensation for 400 Gbps and beyond optical communication systems
Optical communication systems represent the backbone of modern communication
networks. Since their deployment, different fiber technologies have been used
to deal with optical fiber impairments such as dispersion-shifted fibers and
dispersion-compensation fibers. In recent years, thanks to the introduction of
coherent detection based systems, fiber impairments can be mitigated using
digital signal processing (DSP) algorithms. Coherent systems are used in the
current 100 Gbps wavelength-division multiplexing (WDM) standard technology.
They allow the increase of spectral efficiency by using multi-level modulation
formats, and are combined with DSP techniques to combat the linear fiber
distortions. In addition to linear impairments, the next generation 400 Gbps/1
Tbps WDM systems are also more affected by the fiber nonlinearity due to the
Kerr effect. At high input power, the fiber nonlinear effects become more
important and their compensation is required to improve the transmission
performance. Several approaches have been proposed to deal with the fiber
nonlinearity. In this paper, after a brief description of the Kerr-induced
nonlinear effects, a survey on the fiber nonlinearity compensation (NLC)
techniques is provided. We focus on the well-known NLC techniques and discuss
their performance, as well as their implementation and complexity. An extension
of the inter-subcarrier nonlinear interference canceler approach is also
proposed. A performance evaluation of the well-known NLC techniques and the
proposed approach is provided in the context of Nyquist and super-Nyquist
superchannel systems.Comment: Accepted in the IEEE Communications Surveys and Tutorial
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