Frequency Channel Assignment Research Articles

Design and Analysis of Energy-efficient Algorithm for Wireless Networks

The Industrial, Scientific, and Medical (ISM) frequency spectrum is used by the Wireless Local Area Network (WLAN) for its operation. Due to a limited number of available channels for WLAN operation, frequency channel assignment becomes very difficult. In WLAN, the access points (APs) are widely deployed, and because they share the same frequency, they start interfering with each other and causing more energy consumption. So WLAN frequency channels should be managed and assigned carefully to increase the energy efficiency of the wireless network. This paper proposes an energy-efficient channel assignment algorithm (EECAA) to improve the performance of the network. The suggested approach improves the network's energy efficiency in terms of global delay, packet data loss, and the count of data retransmissions. The extensive simulation study demonstrates that, when compared to the channel handoff scheme and D2MD channel allocation algorithm for various traffic and network conditions, the proposed EECAA method greatly increases network throughput.

A Survey on Scalable LoRaWAN for Massive IoT: Recent Advances, Potentials, and Challenges

Long-range (LoRa) technology is most widely used for enabling low-power wide area networks (WANs) on unlicensed frequency bands. Despite its modest data rates, it provides extensive coverage for low-power devices, making it an ideal communication system for many internet of things (IoT) applications. In general, LoRa is considered as the physical layer, whereas LoRaWAN is the medium access control (MAC) layer of the LoRa stack that adopts a star topology to enable communication between multiple end devices (EDs) and the network gateway. The chirp spread spectrum modulation deals with LoRa signal interference and ensures long-range communication. At the same time, the adaptive data rate mechanism allows EDs to dynamically alter some LoRa features, such as the spreading factor (SF), code rate, and carrier frequency to address the time variance of communication conditions in dense networks. Despite the high LoRa connectivity demand, LoRa signals interference and concurrent transmission collisions are major limitations. Therefore, to enhance LoRaWAN capacity, the LoRa Alliance released many LoRaWAN versions, and the research community has provided numerous solutions to develop scalable LoRaWAN technology. Hence, we thoroughly examine LoRaWAN scalability challenges and state-of-the-art solutions in both the physical and MAC layers. These solutions primarily rely on SF, logical, and frequency channel assignment, whereas others propose new network topologies or implement signal processing schemes to cancel the interference and allow LoRaWAN to connect more EDs efficiently. A summary of the existing solutions in the literature is provided at the end of the paper, describing the advantages and disadvantages of each solution and suggesting possible enhancements as future research directions.

Nonlinear Negotiation Approaches for Complex-Network Optimization: A Study Inspired by Wi-Fi Channel Assignment

At the present time, Wi-Fi networks are everywhere. They operate in unlicensed radio-frequency spectrum bands (divided in channels), which are highly congested. The purpose of this paper is to tackle the problem of channel assignment in Wi-Fi networks. To this end, we have modeled the networks as multilayer graphs, in a way that frequency channel assignment becomes a graph coloring problem. For a high number and variety of scenarios, we have solved the problem with two different automated negotiation techniques: a hill-climber and a simulated annealer. As an upper bound reference for the performance of these two techniques, we have also solved the problem using a particle swarm optimizer. Results show that the annealer negotiator behaves as the best choice because it is able to obtain even better results than the particle swarm optimizer in the most complex scenarios under study, with running times one order of magnitude below. Finally, we study how different properties of the network layout affect to the performance gain that the annealer is able to obtain with respect to the particle swarm optimizer.

Neural network-based path loss model for cellular mobile networks at 800 and 1800 MHz bands

Cellular radio communication systems have become essential for data/voice/video/multimedia applications. The performance of cellular communication radio systems is assessed by considering the design specifications of frequency planning, channel assignment and interference mitigation strategies among others. Frequency planning is the most important component to improve capacity or quality of cellular radio systems. Large-scale path loss values between the base station and mobile stations are the key regulating factors that limit the performance of cellular systems, especially in urban/vegetation region. There is a necessity to develop a suitable path loss prediction model for predicting path loss values based on received signal strength measurements. In this paper, an ANN-based path loss model was used for macro cell measurement data obtained in the Vijayawada urban region, India. The Multi-Layer Perceptron (MLP) neural network model was considered. The prediction results indicate that the ANN model outperformed the Auto Regressive Moving Average (ARMA) and COST-231-WImodels. The outcome of this research work will be immensely useful for improving coverage and ensuring better frequency planning of cellular radio systems.

<i>L</i>(<i>d</i>,1)-labellings of generalised Petersen graphs

An interesting graph distance constrained labelling problem can model the frequency channel assignment problem as well as code assignment in computer networks. The frequency assignment problem asks for assigning frequencies to transmitters in a broadcasting network with the aim of avoiding undesired interference. One of the graph theoretical models of The frequency assignment problem is the concept of distance constrained labelling of graphs. Let u and v be vertices of a graph G = (V (G),E(G)) and d(u, v) be the distance between u and v in G. For an integer d ≥ 0, an L(d, 1)-labelling of G is a function f : V (G) → {0, 1, · · · } such that for every u, v ϵ V (G), |f(u) – f(v)| ≥ d if d(u, v) = 1 and |f(u) – f(v)| ≥ 1 if d(u, v) = 2. The span of f is the difference between the largest and the smallest numbers in f(V (G)). The λd,1-number of G is the minimum span over all L(d, 1)-labellings of G. For natural numbers n and k, where n > 2k, a generalised Petersen graph P(n, k) is obtained by letting its vertex set be {u1, u2, · · · , un} υ {v1, v2, · · · , vn} and its edge set be the union of uiui+1, uivi, vivi+k over 1 ≤ i ≤ n, where subscripts are reduced modulo n. In this paper, we show the λd,1-numbers of the generalised Petersen graphs P(n, k) for n ≥ 5.

<i>L</i>(<i>d</i>,1)-labellings of generalised Petersen graphs

An interesting graph distance constrained labelling problem can model the frequency channel assignment problem as well as code assignment in computer networks. The frequency assignment problem asks for assigning frequencies to transmitters in a broadcasting network with the aim of avoiding undesired interference. One of the graph theoretical models of The frequency assignment problem is the concept of distance constrained labelling of graphs. Let u and v be vertices of a graph G = (V (G),E(G)) and d(u, v) be the distance between u and v in G. For an integer d ≥ 0, an L(d, 1)-labelling of G is a function f : V (G) → {0, 1, · · · } such that for every u, v ϵ V (G), |f(u) – f(v)| ≥ d if d(u, v) = 1 and |f(u) – f(v)| ≥ 1 if d(u, v) = 2. The span of f is the difference between the largest and the smallest numbers in f(V (G)). The λd,1-number of G is the minimum span over all L(d, 1)-labellings of G. For natural numbers n and k, where n > 2k, a generalised Petersen graph P(n, k) is obtained by letting its vertex set be {u1, u2, · · · , un} υ {v1, v2, · · · , vn} and its edge set be the union of uiui+1, uivi, vivi+k over 1 ≤ i ≤ n, where subscripts are reduced modulo n. In this paper, we show the λd,1-numbers of the generalised Petersen graphs P(n, k) for n ≥ 5.

Multichannel Assignment with Load Balance in Cognitive Radio Networks

Objectives: Based on a load balance perspective, a multichannel assignment model is raised for users whose applications require more than one channel, which achieves a more efficient use of spectral opportunities in cognitive radio networks. The proposed model makes a multiple frequency channel assignment to the secondary users who demand more than one frequency channel, under an equity environment. Methods: In order to achieve this, the model integrates the load balance in its assignment process taking into account historical data such as the equity level in the assignment and readjusting its assignment policies; likewise, it consists of a block which is in charge of setting an equity criterion for all users who want to transmit. The measurements made correspond to the average band width, the average delay and the fairness calculation when assigning various channels. Results: The obtained results were evaluated with spectral occupation data in the GSM frequency band. The developed model was compared to the MFACRN algorithm with no load balance and there´s an evidence of enhancement when assigning a higher average band width of transmission for each secondary user and thus, maintaining the equity criteria in channels assignment. Improvements: This work proposes a model of multichannel assignment that integrates a Fairness algorithm and load balance for cognitive radio networks with six evaluation metrics using experimental data of the GSM band.

Fast heuristics for the frequency channel assignment problem in multi-hop wireless networks

Communication links connect pairs of wireless nodes in a wireless network. Links can interfere with each other due to their proximity and transmission power if they use the same frequency channel. Given that a frequency channel is the most important and scarce resource in a wireless network, we wish to minimize the total number of different frequency channels used. We can assign the same channel to multiple different links if the assignment is done in a way that avoids co-channel interference. Given a conflict graph which shows conflicts between pairs of links if they are assigned the same frequency channel, assigning channels to links can be cast as a minimum coloring problem. However the coloring problem is complicated by the fact that acceptably small levels of interference between pairs of links using the same channel can accumulate to cause an unacceptable level of total interference at a given link. In this paper we develop fast and effective methods for frequency channel assignment in multi-hop wireless networks via new heuristics for solving this extended coloring problem. The heuristics are orders of magnitude faster than an exact solution method while consistently returning near-optimum results.

The research of (2,1)-total labelling of trees basen on Frequency Channel Assignment problem

Let T be a tree, Let DΔ (T) denote the set of integers k for which there exist two distinct vertices of maximum degree of distance at k in T. The (2,1)-total labelling number of a graph G is the width of the smallest range of integers that suffices to label the vertices and the edges of G such that no two adjacent vertices have the same label, no two adjacent edges have the same label and the difference between the labels of a vertex and its incident edges is at least 2. In this paper, we prove that if T is a tree with Δ≥5 and 34 ( ) DT , then T is Type 1.

Novel Channel and Polarization Assignment Schemes for 2–11 GHz Fixed–Broadband Wireless Access Networks

The scarcity of available spectrum in the 2---11 GHz frequency range and the continuously increasing number of users that require broadband communication services suggest that emerging fixed-broadband wireless access (F-BWA) networks will be deployed with aggressive frequency re-use to cope with capacity demands. In this context, co-channel interference may arise in high levels compromising the system's capacity and robust operation. Interference is further increased when limited directionality terminal antennas are employed to support non line-of-sight operation and in the case where an adaptive-time division duplex is selected for efficient radio resource management in asymmetric and time-varying traffic conditions. In this paper frequency channel assignment (CA) and antenna polarization assignment (PA) are considered as a means of mitigating interference. Two novel CA schemes that consider the distinct characteristics of F-BWA are proposed; the rotated-interleaved channel assignment and the non-uniform channel assignment. According to statistical interference simulation analysis the proposed schemes are more efficient in suppressing interference, achieving higher capacity compared to existing schemes while incurring no further complexity. In addition, instead of exploiting the performance of CA and PA schemes independently a framework for a joint CA-PA consideration is presented, where for a particular CA scheme an optimized PA pattern is developed. Results show that this approach improves the CA-PA interoperability increasing the overall performance. The efficiency of the proposed schemes is investigated for both FDD and adaptive-TDD schemes and is verified for various sectorization, frequency re-use and terminal antenna directivity configurations to ensure compatibility with different deployment scenarios.

Base station location and channel allocation in a cellular network with emergency coverage requirements

The location of base stations (BS) and the allocation of channels are of paramount importance for the performance of cellular radio networks. Also cellular service providers are now being driven by the goal to enhance performance, particularly as it relates to the receipt and transmission of emergency crash notification messages generated by automobile telematics systems. In this paper, a Mixed Integer Programming (MIP) problem is proposed, which integrates into the same model the base station location problem, the frequency channel assignment problem and the emergency notification problem. The purpose of unifying these three problems in the same model is to treat the tradeoffs among them, providing a higher quality solution to the cellular system design. Some properties of the formulation are proposed that give us more insight into the problem structure. An instance generator is developed that randomly creates test problems. A few greedy heuristics are proposed to obtain quick solutions that turn out to be very good in some cases. To further improve the optimality gap, we develop a Lagrangean heuristic technique that builds on the solution obtained by the greedy heuristics. Finally, the performance of these methods is analyzed by extensive numerical tests and a sample case study is presented.

Lagrangean based methods for solving large-scale cellular network design problems

The cellular network design (CND) problem is formulated as a comprehensive linear mixed integer programming model integrating the base station location (BSL) problem, the frequency channel assignment (FCA) problem and the topological network design (TND) problem. A solution algorithm based on Lagrangean relaxation is proposed for solving this complex cellular network design problem. Pursuing the optimum solution through exact algorithms to this problem appears to be unrealistic considering the large scale nature and NP-hardness of the problem. Therefore, the solution algorithm strategy consists in computing effective lower and upper bounds for the problem. Lower bounds are evaluated through a Lagrangean relaxation technique and subgradient method. A Lagrangean heuristic is developed to compute upper bounds based on the Lagrangean solution. The bounds are improved through a customized branch and bound algorithm which takes in account specific knowledge of the problem to improve its efficiency. Thirty two random test instances are solved using the proposed algorithm and the CPLEX optimization package. The results show that the duality gap is excessive, so it cannot guarantee the quality of the solution. However, the proposed algorithm provides optimal or near optimal solutions for the problem instances for which CPLEX also provides the optimal solution. It further suggests that the proposed algorithm provides optimal or near optimal solutions for the other instances too. Finally, the results demonstrate that the proposed algorithm is superior to CPLEX as a solution approach for the CND problem.

Further Results on T-Coloring and Frequency Assignment Problems

A graph coloring problem (called T-coloring) is investigated in which integers are assigned to the vertices of a graph G, under the constraint that the absolute value of the difference between integers assigned to adjacent vertices does not belong to a forbidden set (called the T-set). The T-coloring problem has applications in the radio frequency channel assignment problem. T-sets of the form $\{0,s,23,\ldots,ks\}\cup S$, where $s,k\geq 1$ and $S\supseteq\{s+1,s+2,\ldots,ks-1\}$, are considered. This set has been named the k-multiple of s set. Values of interest are the minimum cardinality, $\chi_T(G)$, and the minimum span ${\rm sp}_T(G)$, of the set of assigned integers, over all possible T-colorings of G. A greedy algorithm, which T-colors perfectly orderable graphs in $\chi_T(G)$ colors with span ${\rm sp}_T(G)$ (for a k-multiple of s set), is given.

An assessment of alternative wireless access technologies for PCS applications

The results of studies on three important wireless access technology issues in the personal communications services (PCS) arena are described. They are signal duplexing, multiplexing on the downlink, and channel frequency assignment. Each of these issues was addressed through the comparison of two competing technologies. In the area of duplexing, frequency division duplexing (FDD) was compared to time division duplexing (TDD) with the result that FDD is preferred if appropriate spectrum is available. Multiplexing on the downlink examined time division multiplexing (TDM) versus a burst downlink (TDMA). TDM is preferred for the wide-area local-exchange environment, but in certain indoor, office applications, TDMA may prove advantageous. The two methods of frequency channel assignment investigated are quasi-state autonomous frequency assignment (QSAFA) and dynamic channel assignment (DCA). QSFA is generally preferred, although indoor, multitenent environments with low port loading may benefit from the use of DCA. These analyses assume that the system uses time-division multiple access (TDMA).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A new frequency channel assignment algorithm in high capacity mobile communication systems

A new algorithm for frequency channel assignment in mobile radio communication is proposed. The algorithm uses flexible fixed channel assignment which enables the calls having all their nominal channels busy to borrow channels from the neighboring cells provided that co-channel interference will not result. The borrowed channel cannot be used in three interfering cells; therefore reassignment strategy is used when a call is terminated on a nominal channel to switch a call in progress in a borrowed channel to that nominal one and set free the borrowed channel in the three interfering cells. Thus the traffic carried on borrowed channels is minimized. Also different call switching strategies are proposed to give priority to some channels to be used by the nominal cells and other channels to be borrowed by neighboring cells. These strategies considerably reduce the blocking probability. A simulation study of the algorithm was carried out on 49 hexagonal zones having uniform traffic density. Also a combined telephone and dispatch traffic was included in the simulation study. The results showed that the new algorithm is better than the other channel assignment schemes. This can be applied in high capacity mobile communications systems to utilize the spectrum efficiently.