Joint Channel Assignment Research Articles

Joint link rate allocation, routing and channel assignment in multi-rate multi-channel wireless networks

In this paper we address the issue of joint routing, channel assignment, scheduling and link rate allocation in multi-rate multi-channel wireless networks with the goal of increasing network capacity. Many wireless standards support a variety of modulation and coding schemes, which allow devices to choose from several transmission rates. Typically, the highest possible rate is used for transmission, but the potential for increased spatial reuse and capacity exists when using lower rates due to higher interference tolerance. This problem of selecting link rates is further complicated in a multi-channel network. Channel assignment affects the sets of interfering links, and as such also influences the optimal choice of link rates. And there is also an interdependency between routing and both rate and channel assignment. In this work we analyze the joint problem and, due to its hardness, propose a fast heuristic algorithm (JMR) to solve it. We evaluate this algorithm through numerical experiments in a wide variety of configurations, showing that potential for improved capacity via link rate allocation depends on a variety of factors which relate to the capability and need of exploiting spatial reuse, and which include the transmission power, the number of channels and the network architecture and topology. In this work we also propose an architecture for wireless mesh networks with increased capacity and under which optimized rate allocation is shown to notably increase performance. Finally, we evaluate the solutions found by JMR under the ns-3 simulator using the 802.11a protocol stack, where it is shown that physical and MAC layer limitations reduce the performance gain of JMR.

Joint Channel Assignment and Routing Protocol for Cognitive Radio Ad Hoc Networks

Conventional single channel wireless ad hoc networks usually suffer from low network throughput owing to the higher number of packet transmissions required for multi-hop communication. Using multiple channels within a single network can improve the network throughput. In multi-channel communication networks, the channels must be assigned appropriately to maximise network performance. Existing channel assignment methods are usually based on the approach of interference reduction/minimisation, for example, by making a link to operate on only one channel and different links to operate on different channels. In this paper, we go in the opposite direction and propose to make links to operate on more channels. A new distributed joint channel assignment and routing protocol for cognitive radio ad hoc networks called cognitive radio-enhanced AOMDV is proposed. Simulation studies showed that our method outperforms other methods.

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.

Joint Mode Selection and Resource Allocation for Device-to-Device Communications

Device-to-device (D2D) communications have been recently proposed as an effective way to increase both spectrum and energy efficiency for future cellular systems. In this paper, joint mode selection, channel assignment, and power control in D2D communications are addressed. We aim at maximizing the overall system throughput while guaranteeing the signal-to-noise-and-interference ratio of both D2D and cellular links. Three communication modes are considered for D2D users: cellular mode, dedicated mode, and reuse mode. The optimization problem could be decomposed into two subproblems: power control and joint mode selection and channel assignment. The joint mode selection and channel assignment problem is NP-hard, whose optimal solution can be found by the branch-and-bound method, but is very complicated. Therefore, we develop low-complexity algorithms according to the network load. Through comparing different algorithms under different network loads, proximity gain, hop gain, and reuse gain could be demonstrated in D2D communications.

Multicast routing protocols in wireless mesh networks: a survey

Wireless mesh networks (WMNs) introduce a new type of network that has been applied over the last few years. One of the most important developing issues in WMNs is multicast routing, which is a key technology that provides dissemination of data to a group of members in an efficient way. In this article, after an introduction about the structure of a WMN, multicast routing algorithms and protocols in WMNs are surveyed in a detailed and efficient manner. Moreover, effort is made to scale the study into one of the important potential capabilities of multicast routing mechanisms in WMNs, which is taking advantage of using different channels and radios association. While nodes in a single-radio mesh network operating on single-channel have restrictions for capacity, equipping mesh routers with multiple radios using multiple channels can decrease the intention of capacity problem as well as increase the aggregate bandwidth available to the network and improving the throughput. Hence, the purpose of channel assignment is to decrease the interferences while increasing the network capacity and keeping the connectivity of the network. Therefore, this article investigates the multicast protocols considering a definition of three types of WMNs, based on channel-radio association including SRSC, SRMC and MRMC. In its follow, a classification for multicast routing algorithms regarding the achieved optimal solutions will be presented. Finally, a study of MRMC and its relevant problems will be offered, considering the joint channel assignment and the multicast tree construction problem.

A Joint Design for Distributed Stable Routing and Channel Assignment Over Multihop and Multiflow Mobile Ad Hoc Cognitive Networks

Data communication in mobile ad hoc cognitive networks (MACNets) significantly suffers from link instability and channel interference. The availability and stability of each link in MACNets highly depends on not only the relative movement of neighbor nodes but also the adjacent communication among primary nodes and among cognitive nodes. In multihop and multiflow MACNets, this problem becomes even worse because multiple links potentially interfere with each other. In this paper, we propose a cross-layer distributed approach, called mobility-prediction-based joint stable routing and channel assignment (MP-JSRCA), to maximize the network throughput by jointly selecting stable routes and assigning channels avoiding inter- and intra-flow interferences based on mobility prediction. To quantitatively measure the communication quality of links, we propose a new metric data transmission cost (DTC) that captures node mobility, impact to primary nodes, and channel conflict among cognitive nodes. In our MP-JSRCA, each relay node selects the best link with the smallest DTC as the next hop, within a specified sector region towards the destination. NS2-based simulation results demonstrate that our MP-JSRCA algorithm significantly improves network throughput, and the higher degree of interference MACNets experience, the more improvement can be achieved.

Joint Power Control and Channel Assignment for Congestion Avoidance in Cognitive Radio Mesh Network

Due to the limited radio spectrum resources and the differences of link loads,network congestion becomes one of the key issues in cognitive radio wireless mesh network.For this reason,by quantifying transmission power levels,the effect of network interference,link capacity and flow conservation are considered comprehensively.As a contribution,the congestion avoidance model joint with power control and channel assignment is presented.And then,a nested optimization technique is proposed to avoid the network congestion,which includes a genetic approach for joint power control and channel assignment,a genetic approach for route scheduling and an optimal routing algorithm.In order to guarantee the individual validity and fast convergence,the rules of combinatorial coding and sequence-based coding are designed respectively with appropriate constraint control mechanisms.Extensive simulation results show that the algorithm can effectively improve the network throughput,and meet the real-time data transfer requirements.

Spectrum Bonding and Aggregation with Guard-Band Awareness in Cognitive Radio Networks

Spectrum access/sharing algorithms for dynamic spectrum access (DSA) networks are often designed without accounting for adjacent-channel interference. In practice, guard bands are needed to prevent such interference. Introducing guard bands naturally constrains the effective use of the spectrum. In this work, we investigate the problem of assigning channels/powers to opportunistic transmissions, while accounting for such a constraint. Specifically, we propose a novel guard-band-aware channel assignment scheme for DSA systems. Our scheme reduces the number of required guard channels for a given transmission by exploiting the benefit of utilizing adjacent channels and considering already reserved guard channels. We analytically formulate the channel access problem as a joint power control and channel assignment optimization problem, with the objective of minimizing the required spectrum resource for a given CR transmission. We show that the optimization problem is a binary linear program (BLP), which is, in general, NP-hard. Accordingly, we present a near-optimal solution based on sequential fixing, where the binary variables are determined iteratively by solving a sequence of linear programs. Based on the proposed channel assignment algorithm, we develop an operational MAC protocol that enables DSA users to dynamically utilize the spectrum. The proposed protocol realizes our channel assignment algorithm in a distributed manner while relying only on information provided by the two communicating users. Simulation results are provided, which verify the effectiveness of our protocol and demonstrate the significant gain achieved through guard-band-aware channel assignment.

Joint channel assignment and routing in multiradio multichannel wireless mesh networks with directional antennas

SummaryThe aggregate capacity of a wireless mesh network (WMN) is severely affected by interflow interference. In this paper, we propose a network architecture that incorporates directional antennas with multiple orthogonal channels to effectively enhance the performance of WMNs. First, a sectored connectivity graph is introduced to model multiradio multichannel WMNs with directional antennas. Next we formulate the topology design, directional interface assignment, channel allocation, and routing mathematically as a mixed integer linear programming problem. This problem is solved using an iterated local search algorithm to obtain optimized network resource allocation. Simulation results indicate that the proposed architecture can achieve higher packet delivery ratio while providing better network fairness. Copyright © 2014 John Wiley & Sons, Ltd.

Performance Analysis of Joint Base-Station Multiantenna Multibeam and Channel Assignment Scheme for Hierarchical Cellular System

Different from the traditional configuration of hierarchical cellular, we introduce the joint base-station multi-antenna multi-beam and channel assignment scheme for hierarchical cellular in this paper. The proposed scheme is based on multi-beam base-station antenna splitting in the elevation-radiating plane, and a dynamic channel allocation scheme by combining the adaptive antenna technologies. Simulation results show that the proposed configuration of the hierarchical cellular can enhance the spectral efficiency remarkably.

JORCA: joint opportunistic routing and channel assignment

Opportunistic routing (OR) can improve the throughput of wireless mesh networks (WMNs). Most existing studies on OR focus on single-radio WMNs, where the severe interference may largely decrease the performance. Only a few works have studied OR in multi-radio multi-channel WMNs, while they either select opportunistic route with given channel assignment, or assign channel based on selected opportunistic routing, which separate the interdependency of opportunistic routing and channel assignment, and can hardly achieve good performance. This paper formulates the joint problem of opportunistic routing and channel assignment as a mixed integer programming (MIP) problem and proves it to be NP-hard. To solve it, we propose a heuristic iterative algorithm named joint opportunistic routing and channel assignment (JORCA) which exploits multi-user diversity and channel resource. The simulation results demonstrate that, comparing with the two existing solutions, JORCA improves 44% and 15.5% in total throughput.

A Multi-Objective Optimization Approach for Joint Channel Assignment and Multicast Routing in Multi-Radio Multi-Channel Wireless Mesh Networks

Multicast routing is an effective mechanism for delivering data to a group of receivers. Due to intrinsic property of air medium in wireless mesh networks (WMN), interference is an important issue in determining the data rate for multicast services. Interference reduction is handled by assigning multiple orthogonal channels to multiple radios in multi-radio multi-channel WMNs. Channel assignment is known to be a NP-complete problem. Most prior methods have solved multicast routing and channel assignment problems sequentially and have not considered the interplay between these two problems. Focusing on this issue, we address joint channel assignment and routing problem for multicast applications. In this paper, a novel technique based on a multi-objective genetic algorithm is proposed to build a delay constrained minimum cost multicast tree with minimum interference. We have examined the proposed algorithm on different network configurations. Experimental results demonstrate that our method finds better trees in terms of cost, delay, and interference compared to prior methods.

Multicast With Intraflow Network Coding in Multirate Multichannel Wireless Mesh Networks

It has been shown that intraflow network coding (NC) can improve the multicast throughput in single-channel single-rate wireless mesh networks. Most existing studies focus on developing a practical intraflow NC multicast protocol. With the rise of wireless products supporting multirate multichannel communications nowadays, it has become increasingly important to improve the NC gain by utilizing multiple bit rates and nonoverlapping channels, but new challenges have also arisen due to various tradeoffs. In a multirate multichannel multihop network, overhearing opportunities and bandwidth utilization are highly correlated to the selection of the channel and rate, which in turn determines the achievable throughput of multicast with intraflow NC. Specifically, wireless nodes can transmit at higher bit rates over orthogonal channels to increase the forwarding throughput, but the strategy reduces overhearing opportunities and the coding gain in multicast with intraflow NC. To achieve the best tradeoff between the given two aspects, we formulate a new optimization model called multirate multichannel multicast with intraflow NC (RCMNC), which solves the joint channel assignment, rate selection, and flow allocation problems for multihop intraflow NC multicast. We then reformulate the primal problem as the Lagrangian dual problem and propose an algorithm to approximate the solution of the dual problem in polynomial time. Simulation results show that, by assigning a suitable rate and channel to each network interface, the multicast throughput with intraflow NC under RCMNC is up to 3.3 times higher than that achieved by the existing approach in a multirate multichannel wireless mesh network.

Downlink interference minimization in cooperative cognitive LTE-femtocell networks

Abstract Femtocell is considered to be one of the most promising solutions for future indoor wireless communication. Due to the scarcity of spectrum resources, femtocells need to share the spectrum with other networks, which will inevitably bring in severe interference. Therefore, minimizing the cross-tier and co-tier interference while maintaining high system throughput or spectrum efficiency is one of main challenges before largely deploying femtocell networks. In order to effectively mitigate the interference, cognitive radio-enabled techniques can play a key role by providing more secondary spectrum access opportunities, especially in dense femtocells deployment scenarios. Supported by cognitive radio functionality, femtocell users can access and share these licensed spectra including the frequency bands of both macrocells and other licensed systems (e.g., TV white spaces) as long as not causing harmful interference to the coexisting licensed systems. In this paper, based on cognitive sensing, we propose a joint channel assignment and power allocation scheme, aiming to minimize the aggregate interference from multiple femtocells to the licensed users while satisfying the constraints of each femtocell’s capacity and power budget. It is believed that the cooperation among multiple femtocells is quite helpful in mitigating the interference considering the mobility of the licensed users. Specifically, Hungarian algorithm is involved in our scheme to address the co-tier femtocell interference issue. In order to illustrate our scheme more explicitly, we come up with the concepts of Physical Cluster and Virtual Cluster and synthetically apply the related algorithms to reduce the interference step by step. Finally, the performances of employed algorithms are evaluated and analyzed. Numerical results have validated that the proposed scheme is viable and effective in managing the femtocell interference.

On the optimal, fair and channel-aware cognitive radio network reconfiguration

In this work, we focus on the Joint Channel Assignment and Routing (JCAR) problem in Cognitive Radio Networks (CRNs) and especially on the optimal reconfiguration of secondary networks under the presence of primary users. Secondary CRN users need to adapt their transmission channels promptly, while effectively limit additional or escalating system modifications triggered by the intertweaved primary user activity. Our approach takes into consideration the underlying spectrum switching dynamics and concurrently aims at a fair resource allocation among the active network flows. We take an optimization perspective and formulate the JCAR and network reconfiguration problems as mixed integer linear programs, addressing fairness concerns as well. We propose a heuristic approach which is based on a sequential reduced search space methodology, in order to obtain efficiently solutions of otherwise tough and demanding reconfiguration problems. The operation, effectiveness and performance of the proposed mechanisms are evaluated through analysis and simulations under various working conditions. The obtained numerical results indicate the benefits of the proposed schemes in terms of overhead performance and their scaling properties with respect to more realistic and thus demanding topologies.

On channel assignment and multicast routing in multi-channel multi-radio wireless mesh networks

Multicast is a key networking service, enabling one-shot delivery of information from a source to multiple destinations and is considered underlying for collaborating multimedia applications such as video conferencing, distance learning and other forms of content distributing over Multi-Channel Multi-Radio Wireless Mesh Networks MCMR WMNs. Multicast protocol as designed in these networks, however, is tightly coupled with the specifics of the nodes' channel-radio associations to realise minimum interference communication. The mainstream of research in WMN multicasting is oriented towards heuristic or meta-heuristic strategies which basically take on a sequential approach to solve the channel assignment and the multicast routing as two disjoint sub-problems. The resulting network configurations would be sub-optimal in this case. It is given that the cross-interaction between the two sub-problems is an effect of the problem's specifications. In this paper, first, we propose a cross-layer mathematical formulation of joint channel assignment and multicast tree construction in MCMR WMNs, which, opposed to the existing schemes guarantees optimal solution. The simulation results demonstrate that our cross-layer design outperforms the Level Channel Assignment LCA, Multi-Channel Multicast MCM, the Genetic Algorithm GA, Simulated Annealing SA and the Tabu Search TS-based methods proposed by Zeng et al. 2010 and Cheng et al. 2011 respectively, in terms of inter-channel interference. Second, since joint optimisation modelling has been relatively demanding in terms of complexity, we relax the optimality requirement and alternatively explore the option of a layered formulation in which to ensure an optimal solution for each sub-problem. Our alternative design is proved superior to the prior art in terms of interference minimisation too. We conduct an extensive series of simulations to analyse the optimality and complexity of our two design strategies. The overall result of the interference, is our optimality measurement. Also, complexity is evaluated in terms of the memory consumption as well as the required time to solve the multicast problem.

An efficient joint channel assignment and QoS routing protocol for IEEE 802.11 multi-radio multi-channel wireless mesh networks

With the emerging of video, voice over IP (VoIP) and other real-time multimedia services, more and more people pay attention to quality of service (QoS) issues in terms of the bandwidth, delay and jitter, etc. As one effective way of broadband wireless access, it has become imperative for wireless mesh networks (WMNs) to provide QoS guarantee. Existing works mostly modify QoS architecture dedicated for ad hoc or sensor networks, and focus on single radio and single channel case. Meanwhile, they study the QoS routing or MAC protocol from view of isolated layer. In this paper, we propose a novel cross-layer QoS-aware routing protocol on OLSR (CLQ-OLSR) to support real-time multimedia communication by efficiently exploiting multi-radio and multi-channel method. By constructing multi-layer virtual logical mapping over physical topology, we implement two sets of routing mechanisms, physical modified OLSR protocol (M-OLSR) and logical routing, to accommodate network traffic. The proposed CLQ-OLSR is based on a distributed bandwidth estimation scheme, implemented at each node for estimating the available bandwidth on each associated channel. By piggybacking the bandwidth information in HELLO and topology control (TC) messages, each node disseminates information of topology and available bandwidth to other nodes in the whole network in an efficient way. From topology and bandwidth information, the optimized path can be identified. Finally, we conduct extensive simulation to verify the performance of CLQ-OLSR in different scenarios on QualNet platform. The results demonstrate that our proposed CLQ-OLSR outperforms single radio OLSR, multi-radio OLSR and OLSR with differentiated services (DiffServ) in terms of network aggregate throughput, end-to-end packet delivery ratio, delay and delay jitter with reasonable message overheads and hardware costs. In particular, the network aggregate throughput for CLQ-OLSR can almost be improved by 300% compared with the single radio case.

Leveraging Cooperative, Channel and Multiuser Diversities for Efficient Resource Allocation in Wireless Relay Networks

Relay stations can be deployed between mobile stations and base stations in a single-hop wireless network to extend its coverage and improve its capacity. In this paper, we exploit cooperative diversity, channel diversity and multiuser diversity gains in an OFDMA-based wireless relay network. We study a joint channel and relay assignment problem with the objective of maximizing a well-adopted utility function that can lead to a stable system. This problem turns out to be NP-hard. First, a mixed integer linear programming formulation is presented to provide optimal solutions. We then present three simple greedy algorithms to solve the problem in polynomial time, namely, Greedy-ChannelFirst, Greedy-RelayFirst and Greedy-Joint. We also perform a comprehensive theoretical analysis for the performance of the proposed algorithms. Our analytical results show the Greedy-ChannelFirst algorithm is a constant factor approximation algorithm which always provides a solution whose objective value is guaranteed to be no smaller than the optimal value multiplied by a constant less than 1; however, the other two algorithms do not provide a similar performance guarantee. Extensive simulation results have been presented to show that all three proposed algorithms perform very well on average cases.

Joint routing and channel assignment algorithms in cognitive wireless mesh networks

ABSTRACTMultiple channels can increase network capacity by transmitting traffic on different channels in an interference area. To resolve the channel interference problem in cognitive wireless mesh networks, first, a new channel assignment algorithm based on hierarchy interference model for the cognitive wireless mesh networks is proposed in this paper. Second, a distributed capacity and interference based channel assignment and routing algorithm is proposed. Third, an efficient channel diversity based channel allocation algorithm is proposed. The main purpose of this channel allocation algorithm is to maintain the channel diversity in the neighborhood channels. Fourth, a novel joint multi‐path routing and channel assignment algorithm based on path crossing is proposed. On the basis of simulations, results show that compared with the link‐based channel allocation algorithm in wireless multi‐channel networks, the new four algorithms have an obvious advantage in the performance of delay and throughput, and the performance of the joint multi‐path routing and channel assignment algorithm is the best. Lastly, a channel merging algorithm is also proposed in the channel constrained situation. Simulation results also show that, after the implementation of the channel merging algorithm, the network average throughput and delay performance have been further improved significantly. Copyright © 2012 John Wiley & Sons, Ltd.

Probabilistic quality-aware routing in cognitive radio networks under dynamically varying spectrum opportunities

In this paper, we introduce a probabilistic routing metric that considers the peculiar characteristics of the operating environment of cognitive radio networks (CRNs). This metric captures the dynamic changes in channel availabilities due to the randomness of primary user’s activity and the rich channel diversity due to the fact that a CRN is expected to operate over highly separated frequency channels with different propagation characteristics. Our metric, Probability of Success (PoS), statistically quantifies the chances of a successful cognitive radio (CR) packet transmission over a given channel. Based on the PoS metric, we propose a joint probabilistic routing and channel assignment protocol for multi-hop CRNs that attempts at selecting the path with the maximum probability of success among all possible paths for a given CR source-destination pair. Selecting such a path results in minimizing the number of disruptions to CR packet transmissions, which consequently improves network throughput. Simulation results verify the significant throughput improvement achieved by our protocol compared to reference CRN routing protocols.