Optimal Spectrum Management Research Articles

A hybrid meta-heuristic approach for optimization of routing and spectrum assignment in Elastic Optical Network (EON)

ABSTRACT In next-generation high-speed networks, Elastic Optical Networks (EONs) play a promising role due to its more flexibility and optimal spectrum management. Some of the key facts of EON that have to be addressed are Routing and Spectrum allocation. In this paper, an efficient routing algorithm is proposed along with optimization of spectrum allocation for EON. Improved Bellman Floyd Warshall (IBFW) shortest path routing and Enhanced Shuffled Frog Leaping Algorithm (ESFLA) are used in our proposed work. Simulation results are compared with recent RSA algorithms with appropriate metrics where it achieves better spectrum utilisation and reduced number of blocking.

An Improved Iterative Water Filling Algorithm in Multiuser DSL Environment

In digital subscriber line system, crosstalk is created among a bundle of twisted copper pairs due to the effect of an electromagnetic coupling. In very high bit rate digital subscriber line system, higher frequencies are used for data transmission. At these higher frequencies crosstalk seriously affects the system performance. The crosstalk from the near end users in upstream data transmission at higher frequency band significantly declines the bit rate of far end users. In order to resolve this `Near-Far' problem the effective spectrum management techniques are used. Iterative water-filling (IWF) is one of the spectrum management techniques in which power from all subcarriers of near end user are reduced in order to remove crosstalk at far end user. IWF algorithm has low complexity but due to inefficient use of bandwidth it does not give optimal result. In this paper a modified IWF algorithm is proposed in which power from only those subcarriers of near end user are reduced which has a worst effect on bit rates of far end users. The power back off from these subcarriers is done by reducing power spectral masks at these subcarriers. The simulation results of the proposed algorithm give significant performance advantage in terms of data rate over the traditional IWF algorithm. These results approach near to the performance of highly complex optimal spectrum management algorithms while maintaining the complexity as that of traditional IWF algorithm.

A dynamic spectrum management algorithm in VDSL systems

A modified iterative water-filling algorithm is proposed in which power from only those subcarriers of the near end user are reduced, which has the worst effect on bit rates of far end users. The power back off from these subcarriers is done by reducing power spectral masks at respective subcarriers. The results after simulating the proposed algorithm give significant performance advantages in terms of data rate over the traditional iterative water-filling algorithm. These results approach the performance of highly complex optimal spectrum management algorithms while maintaining the complexity of the traditional iterative water-filling algorithm.

Optimal Spectrum Management in Multiuser Interference Channels

In this paper, we study the problem of continuous frequency optimal spectrum management in multiuser frequency selective interference channels. We assume that interference is treated as noise by the decoders, and separate encoding is applied. First, a simple pair-wise channel condition for frequency division multiple access schemes to achieve all Pareto optimal points of the rate region is derived. It enables fully distributed global optimal decision making on whether any two users should use orthogonal channels. Next, we present an analytical solution to finding the maximum sum-rate in two-user symmetric frequency flat channels. Generalizing this solution to frequency selective channels, a convex optimization is established that yields the global optimum. Finally, we show that our method generalizes to <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$K$</tex></formula> -user <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(K \geq 2)$</tex></formula> weighted sum-rate maximization in asymmetric frequency selective channels, and we transform this classic nonconvex optimization to an equivalent convex optimization in the primal domain.

Optimal Spectrum Management of DSL With Nonstrictly Convex Rate Region

Recently, the problem of optimal spectral balancing (OSB) for digital subscriber lines (DSL) with constrained transmit power has been solved using Lagrange's dual optimization technique and a weighted sum rate maximization (WSRM) approach. In many cases, the total power constraint is not binding. Although, this means a huge computational complexity reduction, the algorithm fails to reach certain points on the rate region (RR). In this paper, an in-depth analytical view of the WSRM approach is provided, and it is shown that when the RR is not strictly convex, the WSRM approach fails to reach certain points on the RR. Moreover, using N-dimensional geometry, a novel iterative facet dividing algorithm (IFDA) capable of reaching any point on the RR is proposed. Analytical and simulation results show that our technique is much more reliable and considerably faster than current algorithms. Moreover, it can be used for a wide range of problems which use WSRM approach, including OSB in the general case.