Channel Assignment Scheme Research Articles

Clustering algorithm of hierarchical structures in large-scale wireless sensor and actuator networks

In this study, we propose a clustering algorithm to enhance the performance of wireless sensor and actuator networks (WSANs). In each cluster, a multi-level hierarchical structure can be applied to reduce energy consumption. In addition to the cluster head, some nodes can be selected as intermediate nodes (INs). Each IN manages a subcluster that includes its neighbors. INs aggregate data from members in its subcluster, then send them to the cluster head. The selection of intermediate nodes aiming to optimize energy consumption can be considered high computational complexity mixed-integer linear programming. Therefore, a heuristic lowest energy path searching algorithm is proposed to reduce computational time. Moreover, a channel assignment scheme for sub-clusters is proposed to minimize interference between neighboring subclusters, thereby increasing aggregated throughput. Simulation results confirm that the proposed scheme can prolong network lifetime in WSANs.

Stochastic Guard-Band-Aware Channel Assignment With Bonding and Aggregation for DSA Networks

Fading and shadowing along with the primary user dynamics make channel quality in dynamic spectrum access networks uncertain. Furthermore, the imperfect design of filters and amplifiers in wireless devices motivates the need for guard-bands (GBs) to prevent adjacent-channel interference. In this paper, we develop novel stochastic GB-aware sequential and batch channel assignment schemes that aim at maximizing the spectrum efficiency. In line with recent IEEE 802.11 and LTE standards, our schemes support bonding and aggregation. We propose two assignment models for each of the sequential and batch schemes: a static single-stage and an adaptive two-stage . In the static model, channel assignment is performed once such that the rate demands are probabilistically met. The adaptive model is a two-stage model, where the initial assignment may be corrected once uncertainties are partially revealed. We refer to our formulations of the sequential and batch static assignments as c hance-constrained stochastic s ubset- s um p roblem (CSSP) and c hance-constrained stochastic m ultiple s ubset- s um p roblem (CMSSP) , respectively. Moreover, we develop stochastic formulations for the sequential and batch adaptive assignments, which we refer to as two-stage CSSP with r ecourse (CSSPR) and two-stage CMSSP with r ecourse (CMSSPR) , respectively. Finally, we present computationally efficient simplified versions of CSSP and CSSPR with near-optimal performance.

Combined channel assignment and network coded opportunistic routing in cognitive radio networks

In this paper, we investigate the joint opportunistic routing and channel assignment problem in multi-channel multi-radio (MCMR) cognitive radio networks (CRNs) for improving the aggregate throughput of the secondary users. We first present the nonlinear programming optimization model for this joint problem, taking into account the feature of CRNs-channel uncertainty. In order to reduce the computational complexity of the problem, we present a heuristic algorithm to select forwarding candidates and assign channels in CRNs, including candidate selection algorithm considering the queue state of a node and expected transmission count (ETX), and channel assignment algorithm taking into account the transmission time and the available time of a given channel. Our simulation results show that the proposed scheme Channel Assignment and Network Coded Opportunistic Routing, (CANCOR) performs better than the traditional routing and classical opportunistic routing in which channel assignment strategy is employed.

Interference mitigation in wireless mesh networks through radio co-location aware conflict graphs

Wireless Mesh Networks (WMNs) have evolved into a wireless communication technology of immense interest. But technological advancements in WMNs have inadvertently spawned a plethora of network performance bottlenecks, caused primarily by the rise in prevalent interference. Conflict Graphs are indispensable tools used to theoretically represent and estimate the interference in wireless networks. We propose a generic algorithm to generate conflict graphs which is independent of the underlying interference model. Further, we propose the notion of radio co-location interference, which is caused and experienced by spatially co-located radios in multi-radio multi-channel WMNs. We experimentally validate the concept, and propose a new all-encompassing algorithm to create a radio co-location aware conflict graph. Our novel conflict graph generation algorithm is demonstrated to be significantly superior and more efficient than the conventional approach, through theoretical interference estimates and comprehensive experiments. The results of an extensive set of ns-3 simulations run on the IEEE 802.11g platform strongly indicate that the radio co-location aware conflict graphs are a marked improvement over their conventional counterparts. We also question the use of total interference degree as a reliable metric to predict the performance of a Channel Assignment scheme in a given WMN deployment.

I-QCA: An intelligent framework for quality of service multicast routing in multichannel multiradio wireless mesh networks

Multicast routing has brought a revolution by enabling the delivery of the same content to a group of receivers simultaneously. However, multicast routing in multichannel multiradio wireless mesh networks has been proved to be an NP-hard problem. To achieve optimal performance in multichannel multiradio wireless mesh networks the channel assignment strategy plays an important role. In this paper, we present an intelligent Quality of service multicast routing and Channel Assignment (i-QCA) algorithm which solves the multicast tree construction and channel assignment problem conjointly by intelligent computational methods. The multicast tree construction algorithm is based on the differential evolution approach. The channel assignments in prior works are mostly oriented toward heuristic or meta heuristic approaches and hence produce suboptimal results. The proposed algorithm consists of a genetic algorithm based channel assignment strategy and determines a delay, jitter bounded minimal interference lowcost multicast tree. Our experimental results clearly show that the proposed algorithm achieves much better performance as compared to Multi Channel Multicast (MCM) and QoS Multicast Routing and Channel Assignment (QoS-MRCA) algorithm in multichannel multiradio wireless mesh network environments.

Distributed joint flow-radio and channel assignment using partially overlapping channels in multi-radio wireless mesh networks

Equipping mesh nodes with multiple radios that support multiple wireless channels is considered a promising solution to overcome the capacity limitation of single-radio wireless mesh networks. However, careful and intelligent radio resource management is needed to take full advantage of the extra radios on the mesh nodes. Flow-radio assignment and channel assignment procedures should obey the physical constraints imposed by the radios as well as the topological constraints imposed by routing. Varying numbers of wireless channels are available for the channel assignment procedure for different wireless communication standards. To further complicate the problem, the wireless communication standard implemented by the radios of the wireless mesh network may define overlapping as well as orthogonal channels, as in the case of the IEEE 802.11b/g family of standards. This paper presents Distributed Flow-Radio Channel Assignment, a distributed joint flow-radio and channel assignment scheme and the accompanying distributed protocol in the context of multi-channel multi-radio wireless mesh networks. The scheme’s performance is evaluated on small networks for which the optimal flow-radio and channel configuration can be computed, as well as on large random topologies.

Aeronautical Central Cognitive Broadband Air-to-Ground Communications

Due to the typical features of Air-to-Ground (A/G) communications, such as the dominant requirement for safety, as well as the high-speed mobile and three-dimensional macrocells, etc., traditional terrestrial cognitive radio communication schemes cannot be directly transplanted. In particular, the scheme of spectrum decisions only depending on spectrum sensing in the mobile terminals, i.e., the aircrafts in A/G communications, should be abandoned because of safety requirements. A novel central cognitive structure for broadband A/G communications is established in this paper. Meanwhile, Interference Cognition Table (ICT) is maintained in the database of the Central Management Station (CMS) with electromagnetic computation and modified strong tracking Kalman filtering of the spectrum sensing result. With the prior computation based on ICT, the potential harmful interference to the primary user is avoided, and the safety is guaranteed. In addition, a fast channel assignment scheme with low complexity and the corresponding Non-Continuous Interferometry Orthogonal Frequency Division Multiplex (NCI-OFDM) transmission are highlighted for improving the system capacity and transmission efficiency.

Capacity‐Based Channel Assignment Scheme in Multi‐radio Multi‐channel Wireless Mesh Networks

The capacity of wireless mesh networks can be greatly enhanced by equipping each mesh router with multiple radios and by exploiting multiple channels to reduce network interference. It has been proved that an efficient channel assignment scheme is critical to achieve the optimal network throughput. This paper presents a centralized channel assignment scheme for multi-radio multichannel wireless mesh networks. The scheme includes a spanner-based topology control operation and a linkranking channel assignment algorithm. In the topology control procedure, several links that cause intense interference are removed from the network without damage to the basic network connectivity. The channel assignment procedure improves the network throughput via ranking links based on the principle of load balance. The simulation results demonstrate that the proposed scheme outperforms the compared centralized channel assignment approach in terms of network throughput. The experimental results also indicate that the effectiveness of the proposed scheme is even evident in the case of heavy input traffic load where the potential interference in the network is severe.

Fuzzy call admission control combined with distributed dynamic channel assignment and reassignment for cellular mobile systems

In a cellular mobile system (CMS), the service area is divided into cells, each of which has numerous channels, which are shared by two types of call - new calls and handoff calls. Giving a higher priority to handoff calls than new calls is common practice. However, giving too much priority to handoff calls will result to excessive blocking of new calls. This work firstly proposes a distributed dynamic channel assignment and reassignment (DDCAR) scheme to satisfy three types of constraint - co-channel constraint (CCC), adjacent channel constraint (ACC), and co-site constraint (CSC), simultaneously. The purpose is to minimize the number of available channels that become unavailable for the assignment to new calls and to maximize the number of unavailable channels that become available for release when calls complete. To provide a higher priority to handoff calls, a fuzzy call admission control (FCAC) scheme, combined with the DDCAR, is proposed herein for implementation at the base station. A 7 × 7 CMS with two traffic patterns is employed as the test example. The test results reveal that the FCAC scheme significantly reduces the dropping probability of handoff calls at the cost of increasing the blocking probability of new calls to an acceptable level.

Modeling and Performance Analysis of an Improved Data Channel Assignment (DCA) Scheme for 3G/WLAN Mixed Cells

In this paper, we present an efficient data channel assignment (DCA) scheme for a mixed cell (i.e., a 3G cell with embedded WLANs). Our effort is essential to increase the data request (i.e., a call) handling capacity in 3G systems, with a ‘low request dropping probability’. In UMTS-first DCA scheme prefers 3G channel in dual coverage and reduces vertical handoffs from 3G to WLAN. But it deprives some users of high speed service of WLAN even when WLAN facility is available. On the contrary, a WLAN-first DCA scheme overcomes this problem by preferring WLAN system. But the overall call request dropping probability increases with increasing WLAN traffic and at some point, the benefit of WLAN cannot be achieved in a mixed cell. Further, most of the existing models do not consider the reality of non-identical WLAN-hotspots and bidirectional vertical handoffs, restricting the free mobility of the users across 3G and WLAN systems. We propose an improved DCA scheme based on WLAN-first access technique to maximize the usage of WLAN. The proposed model considers the reality of non-identical WLAN-hotspots and allows free mobility between 3G and WLAN. A proposed DCA scheme improves the dropping probability as blocked call request of WLAN are transferred to 3G. Our DCA scheme drops a request only when all the channels of both 3G and WLAN systems are busy. We derive an analytical model for proposed scheme and validate the same with a set of simulation results. We provide an extensive number of numerical results to show that our scheme performs far better than the existing models. The DCA modeling approach can be quite conveniently used for better planning of WLAN hotspots in the mixed cell.

English

Wireless local area network (WLAN’s) using single channel have limited bandwidth. Channel interference between Access Points (APs) of WLAN also decreases the network throughput. The solution of this problem is to transmit data simultaneously on multiple channels is considered as an alternative. In this paper, we propose a channel assignment algorithm for wireless local area network (WLAN) to analyse and enhance the network performance. The proposed algorithm finds the best suitable channel assignment option in order to attain desired performance. We use the RIVERBED MODELER simulator to simulate the WLAN environment with different channel assignment schemes. Simulation results with fixed and mobile (STA) stations demonstrate that our proposed channel assignment algorithm improve the network throughput 2 times higher as compare to other channel assignment schemes.

Reputation-based crowdsourced Wi-Fi topology discovery

The ubiquity of Wi-Fi networks, coupled with their anarchic deployment, gives rise to the problem of accurately determining their topology in order to employ it for tuning and optimization. Knowledge of the Wi-Fi topology is particularly important for reconfiguration mechanisms, such as channel assignment and power control schemes, which depend on it to operate. Furthermore, with the advent of WLAN-based positioning schemes, the robustness of the spatial databases where wireless topology is encoded becomes crucial for the accuracy of the respective localization algorithms. In this work, we propose a scheme where monitoring the topology of Wi-Fi deployments is crowdsourced to mobile users, who submit reports about Wi-Fi coverage in their vicinity. However, users cannot be assumed trustworthy. They can engage in fraudulent reporting, which, unless specific countermeasures are in place, can severely impact one’s view of the network topology. To this end, we have designed and implemented an architecture for accurate Wi-Fi topology discovery, devising a reputation-based mechanism to tackle realistic and simple to implement (and therefore potentially widespread) attacks. We show analytically and via simulation that, even in the presence of large numbers of attackers, our user-centric scheme significantly outperforms pure infrastructure-based approaches, where monitoring is carried out only by trusted Access Points.

Interference-Aware Channel Segregation Based Dynamic Channel Assignment for Wireless Networks

SUMMARY Recently, we proposed an interference-aware channel segregation based dynamic channel assignment (IACS-DCA). In IACS-DCA, each base station (BS) measures the instantaneous co-channel interference (CCI) power on each available channel, computes the moving average CCI power using past CCI measurement results, and selects the channel having the lowest moving average CCI power. In this way, the CCI-minimized channel reuse pattern can be formed. In this paper, we introduce the autocorrelation function of channel reuse pattern, the fairness of channel reuse, and the minimum co-channel BS distance to quantitatively examine the channel reuse pattern formed by the IACS-DCA. It is shown that the IACSDCA can form a CCI-minimized channel reuse pattern in a distributed manner and that it improves the signal-to-interference ratio (SIR) compared to the other channel assignment schemes.

On channel assignment for multicast in multi-radio multi-channel wireless mesh networks: A survey

The major challenge faced by wireless mesh networks is the capacity reduction caused by interference, and interference can be reduced or even eliminated through appropriate channel assignment. This article presents a comprehensive survey of channel assignment schemes for multicast in multi-radio multi-channel wireless mesh networks. We analyze the state-of-the-art channel assignment schemes for multicast and provide comprehensive taxonomy of the latest work. In general, we classify the channel assignment schemes for multicast into two types, that is, sequential multicast routing and channel assignment (SMRCA) and joint multicast routing and channel assignment (JMRCA). Detailed review of channel assignment schemes in each category is provided. Possible future research directions and corresponding solutions are also explored to motivate research interests in the field of channel assignment for multicast in wireless mesh networks.

Opportunistic Spectrum Access with Two Channel Sensing in Cognitive Radio Networks

Efficient discovery and effective sharing of spectrum opportunities are the most challenging issues in a multi-channel cognitive radio network (CRN) with multiple secondary users (SUs). In this paper, we propose a novel spectrum sensing and access protocol in CRNs where SUs are allowed to sequentially sense two channels in a single time slot and are coordinated to access the potentially unused channels. The proposed protocol is formulated as a channel selection problem coupled with a channel assignment problem. We subsequently investigate the myopic sensing policy and propose a Markov chain-based greedy channel assignment scheme (MCGA) to maximize the expected total SU throughput. Moreover, we extend our proposal to the scenario with imperfect spectrum sensing and obtain the optimal sensing time to enhance the performance improvement by considering spectrum sensing and spectrum access in a joint manner. Finally, we evaluate the performance of our proposal in a saturated network. Numerical and simulation results demonstrate that compared to the existing work, our approach can achieve significant performance improvements in SU throughput.

Understanding channel selection dynamics in dense Wi-Fi networks

This paper aims to explain and analyze a growing problem in dense-urban wireless networks, that of co-existence between low-cost residential access points (APs) and activelymanaged service provider APs in overlapping spatial, frequency, and time domains. Through detailed simulations and testbed experiments, the impact of increasing density of highly-adaptive service provider APs on the performance of typical residential APs is measured in terms of their respective channel assignment schemes. Simulation results with dense deployment of up to 500 APs/sq.km. show the benefits of centralized channel assignments, even in the presence of independent APs. In addition, it is shown that for a fixed AP density, an increase in the percentage of AP under the centralized scheme results in an increase in the throughput of surrounding independent APs. The broader implications of the simulation findings are discussed in order to develop a better macro-level understanding of dense Wi-Fi networks.

Optimized Group Channel Assignment Using Computational Geometry over Wireless Mesh Networks

Wireless Mesh Networks (WMNs) are an evolving division in the field of wireless networks due to their ease of deployment and assured last mile connectivity. It sets out a favorable situation to guarantee the Internet connectivity to all the mobile and static nodes. A wireless environment is dynamic, heterogeneous, and unpredictable as the nodes communicate through the unguided links called channels. The number of nonoverlapping channels available is less than the number of mesh nodes; hence, the same channel will be shared among many nodes. This scarcity of the channels causes interference and degrades the performance of the network. In this paper, we have presented a group based channel assignment method to minimize the interference. We have formulated a mathematical model using Nonlinear Programming (NLP). The objective function defines the channel assignment strategy which eventually reduces the interference. We have adapted the cognitive model of Discrete Particle Swarm Optimization (DPSO), for solving the optimization function. The channel assignment problem is an NP hard problem; hence, we have taken the benefits of a stochastic approach to find a solution that is optimal or near optimal. Finally, we have performed simulations to investigate the efficiency of our proposed work.

Joint anti-attack scheme for channel assignment in multi-radio multi-channel wireless mesh networks

Nowadays, multi-radio multi-channel wireless mesh networks have been widely exploited to provide high-speed Internet access. By assigning different channels, the interference between wireless mesh network nodes can be greatly reduced, leading to a better network performance. However, the channel assignment attacks have imposed a serious security problem, where the diverse messages, that is, Channel Usage Message CUM, Channel Change Message CCM, Channel Switch Operation CSO and Security Alarm Message SAM, are often used to launch attacks by the malicious nodes in order to disturb the normal channel assignment and thus the overall network performance. In this paper, we propose a joint anti-attack scheme JAS against the channel assignment attacks. Our JAS is composed of four key components: CUM, CCM, CSO and SAM defense schemes to protect the channel assignment. The CUM defense scheme verifies the CUM messages and their sender. The CCM defense scheme employs three rounds of CCM verifications. Furthermore, three control messages are exploited by the CSO defense scheme. The SAM defense scheme offers two rounds of verification for the alarm messages. Moreover, we apply our JAS to a popular distributed channel assignment algorithm, that is, Hyacinth. Through extensive simulation, the performance of the proposed scheme is evaluated by comparing with SeCA and SmartC in terms of Goodput and additional overhead. Observed from the simulation results, our scheme is demonstrated to outperform the best-known secure channel assignment algorithms. Copyright © 2014 John Wiley & Sons, Ltd.

Reducing Call Blocks in Cellular Network with Non-Uniform Traffic Conditions

Abstract In cellular networks, while the motivation behind all basic channel assignment strategies is the better utilization of the available frequency spectrum with the consequent reduction of the call blocking probability in each cell, very few of them deal with the problem of non-uniform traffic demand in different cells which may lead to a gross imbalance in the system performance. Mobile users in hot cells (the cells with heavy traffic loads) may suffer from low throughput due to the load imbalance problem. In this paper, we propose a cost effective and simple load balancing scheme that can effectively reduce the overall call blocking. A common set of channels are determined dynamically which can be used simultaneously in all the cells. Cell tiers with different radii are used to cope with the interference introduced by using same set of channels simultaneously in all cells. The performance of the proposed scheme is presented in terms of call blocking probability and channel utilization. Simulation results show that the proposed scheme can reduce the call blocking significantly in highly congested cell.

Modeling Handover in Satellite Communications

The Handover is one of the key subjects in maintaining the quality of service offered by non-geostationary constellation systems. As the satellite coverage moves according to the satellite motion, the continuity of a call must be maintained from one satellite to another. In case of the Handover fails, the call is dropped, resulting in a quality degradation of service. In this paper, the performance of several channel assignment strategies for a LEO satellite constellation is evaluated. The FCA and DCA methods are considered where its advantages and disadvantages are highlighted. Moreover, the Handover process implication in the call blocking probability is assessed via simulation. Strategies able to cope with the high number of Handovers, due to the high speed of the satellites, without affecting strongly the capacity of the system are investigated. Simulation models have been developed to implement all the features evaluated in this paper including the mobility model. An analytical description and interpretation of results are also presented.