Graph coloring to maximize the number of communicating mobiles in wireless networks (original) (raw)

DISTRIBUTED DYNAMIC FREQUENCY ALLOCATION IN WIRELESS CELLULAR NETWORKS USING GRAPH MULTICOLORING

Frequency Allocation Problem in wireless cellular networks is a major area of research in telecommunication industries. Since users of mobile phones are increasing exponentially, the existing limited frequency spectrum is unable to provide services efficiently. To enhance the performance of the networks, some measures must be taken to reduce drop call probabilities due to non availability of free frequency. The existing frequency allocation scheme call " hybrid with borrow " drops the calls regularly if frequencies are not free in a given cell. In this paper, we have developed a new scheme called " HYBORROW " , which elegantly increases the utilization of new drop call probability by 20% over an existing scheme by borrowing the frequencies from neighbor cells.

Distributed graph coloring for self-organization in LTE networks

2010

Primary Component Carrier Selection and Physical Cell ID Assignment are two important self-configuration problems pertinent to LTE-Advanced. In this work, we investigate the possibility to solve these problems in a distributive manner using a graph coloring approach. Algorithms based on real-valued interference pricing of conflicts converge rapidly to a local optimum, whereas algorithms with binary interference pricing have a chance to find a global optimum. We apply both local search algorithms and complete algorithms such as Asynchronous Weak-Commitment Search. For system level performance evaluation, a picocellular scenario is considered, with indoor base stations in office houses placed in a Manhattan grid. We investigate a growing network, where neighbor cell lists are generated using practical measurement and reporting models. Distributed selection of conflict-free primary component carriers is shown to converge with 5 or more component carriers, while distributed assignment of confusionfree physical cell IDs is shown to converge with less than 15 IDs. The results reveal that the use of binary pricing of interference with an attempt to find a global optimum outperforms real-valued pricing.

Directed weighted improper coloring for cellular channel allocation

Discrete Applied Mathematics, 2015

Given a directed graph with weights on the vertices and on the arcs, a θ-improper k-coloring is an assignment of at most k different colors to the vertices of G such that the weight of every vertex v is greater, by a factor 1 θ , than the sum of the weights on the arcs (u, v) entering v with the head u of the same color as v. For a given real number θ, we consider the problem of determining the minimum integer k such that G has a θ-improper k-coloring. Also, for a given integer k, we consider the problem of determining the minimum real number θ such that G has a θ-improper k-coloring. We show that these two problems can be used to model channel allocation problems in wireless communication networks, when it is required that the power of the signal reveived at a base station is greater, by a given factor, than the sum of interfering powers received from mobiles which are assigned the same channel. We propose set partitioning fromulations for both problems and describe branch-and-price algorithms to solve them. Computational experiments are reported for instances having a similar structure as real channel allocation problems.

A randomized saturation degree heuristic for channel assignment in cellular radio networks

IEEE Transactions on Vehicular Technology, 2001

In this paper, we investigate the channel assignment problem, that is, the problem of assigning channels (codes) to the cells of a cellular radio network so as to avoid interference and minimize the number of channels used. The problem is formulated as a generalization of the graph coloring problem. We consider the saturation degree heuristic, first proposed as a technique for solving the graph coloring problem, which was already successfully used for code assignment in packet radio networks. We give a new version of this heuristic technique for cellular radio networks, called randomized saturation degree (RSD), based on node ordering and randomization. Furthermore, we improve the solution given by RSD by means of a local search technique. Experimental results show the effectiveness of the heuristic both in terms of solution quality and computing times.

A Graph Theoretic Approach for Channel Assignment in Cellular Networks

2001

We define a cellular assignment graph to model the channel assignment problem in a cellular network where overlapping cell segments are included in the model. Our main result is the Capacity-Demand Theorem which shows a channel assignment function is always possible unless there is a connected subregion of cells and overlap segments containing more channel requests then the total capacity of all transceivers within or on the boundary of the subregion and covering any part of the subregion with an overlapping segment. We further describe the simplicity and regularity of our proposed cellular assignment graphs and their accessibility for simulation and theoretical investigation without artifacts from the overall geographical region boundaries.

Graph coloring based physical-cell-ID assignment for LTE networks

Proceedings of the 2009 International Conference on Wireless Communications and Mobile Computing Connecting the World Wirelessly - IWCMC '09, 2009

Autoconfiguration of the radio parameters is a key feature for next generation mobile networks. Especially for LTE the NGMN Forum has brought it up as a major requirement. It is indispensable that algorithms used for autoconfiguration terminate quickly and do not cause infinite iterative reconfigurations within the network.

Algorithms for Dynamic Channel Allocation In Cellular Networks

1999

In our project we discuss the problem of channel allocation in cellular networks and analyze different channel allocation algorithms. Each cell can use any channel, subject to the interference constraints. The main criterion is to provide maximum number of network users with service capabilities in networks with limited transmission resources. Channel allocation algorithms are executed by network switch in a centralized way. We analyze three specific channel allocation policies, based on three different objective functions.

An efficient algorithm for channel assignment in cellular mobile networks

2010

This paper deals with the channel assignment problem in a hexagonal cellular network, having non-homogeneous demands in a 2-band buffering system. We first partition the given problem into smaller subproblems each of which is constituted by a homogeneous demand vector on a simple subgraph of the original network graph. The subgraphs and the demands on each node of these subgraphs are chosen in such a way that all the required channels can be assigned to these nodes with the minimum bandwidth by repeating an appropriate sequence of channels in a regular and systematic manner, without causing any interference. Based on this idea, we next present an algorithm for solving the channel assignment problem with non-homogeneous demands. When tested on the Philadelphia benchmark problems, the proposed algorithm assigns the channels with a bandwidth always within 5% more than the optimal bandwidth, requiring a very small execution time (less than 50 mSec on a HPxw8400 workstation). In contrast to this, the best known algorithm generates optimal assignments with about 10-20 seconds on a comparable workstation. This makes our proposed algorithm attractive for very fast assignments of channels in real-life situations, with a marginally small deviation from the optimal bandwidth.

Online frequency allocation in cellular networks

Proceedings of the nineteenth annual ACM symposium on Parallel algorithms and architectures - SPAA '07, 2007

Given a mobile telephone network, whose geographical coverage area is divided into cells, phone calls are serviced by assigning frequencies to them, so that no two calls emanating from the same or neighboring cells are assigned the same frequency. Assuming an online arrival of calls and the calls will not terminate, the problem is to minimize the span of frequencies used. By first considering χ-colorable networks, which is a generalization of (the 3-colorable) cellular networks, we present a (χ + 1)/2-competitive online algorithm. This algorithm, when applied to cellular networks, is effectively a positive solution to the open problem posed in [8]: Does a 2-competitive online algorithm exist for frequency allocation in cellular networks? We further prove a lower bound which shows that our 2-competitive algorithm is optimal. We discover that an interesting phenomenon occurs for the online frequency allocation problem when the number of calls considered becomes large: previously-derived optimal (lower and upper) bounds on competitive ratios no longer hold true. For cellular networks, we show new asymptotic lower and upper bounds of 1.5 and 1.9126, respectively, which breaks through the optimal bound of 2 shown previously.