Multi-channel Multi-hop Wireless Networks Research Articles

Capacity Performance for Full-Duplex Multihop Wireless Networks Using Channel Interference Balancing Allocation Scheme.

Full-duplex (FD) communication has been attractive as one of the research interests related to spectrum utilization for wireless networks from the previous evolution of communication systems. Previous studies discuss the realization of the FD system by focusing on self-interference cancellation and transmit power control in low-power wireless network scenarios. Today, capacity maximization is a key challenge in FD multihop wireless networks, in which the multi-channel allocation may lead to imbalance interference power due to the different number of simultaneous transmissions and its group selection that occurred on the same sub-channels. In this paper, we focus on the capacity maximization of the FD system by considering the influence of total interference power on each sub-channel and how to balance by selecting the different number of simultaneous transmissions to form a group that leads to a minimum difference in the total interference power on those sub-channels. Therefore, a channel interference balancing allocation (CIBA) scheme for balancing the total interference power in the multi-channel multihop wireless networks is proposed and further investigated by the idea of cooperative transmission. We also adopt the concept of interference distance to overcome the interference balancing problem of the proposed CIBA scheme. Performance evaluation results reveal that the proposed CIBA scheme achieves lesser total interference power and higher achievable capacity than other fixed channel allocation schemes.

Understanding Cooperative Data Exchange Problem in Multi-Hop Wireless Network

This letter theoretically formulates the coded cooperative data exchange (CCDE) problem in multi-channel multi-hop wireless networks, where a set of nodes initially hold a subset of packets and wish to retrieve all desired packets via multi-hop wireless communication. At first, we propose the model of tentative transmission, with which we can jointly consider resource allocation, transmission scheduling, and transmitted packet scheduling. Then, based on the time expanded graph, we convert the CCDE problem in multiple time slots into a single source and multiple sinks network (SSMN) within a time slot. Finally, the relationship between the required time slots and the number of channels is theoretically formulated based on the constructed SSMN. Experiments demonstrate that the gain due to the increasing number of channels flattens.

Coded Cooperative Data Exchange in Multichannel Multihop Wireless Networks

This article investigates the coded cooperative data exchange (CCDE) problem, where a set of nodes initially hold a subset of packets and wish to retrieve all desired packets via direct wireless communication with neighbors. The CCDE problem in multihop wired networks has seen significant research recently and is proved to be NP-hard. The CCDE problem in multihop wireless networks (MWNs) must additionally consider half-duplex constraint, interference constraint, and channel constraint. Channel assignment brings new challenges to the CCDE problem in MWN, since it is also a well-known NP-hard problem even with one channel. In this article, we study the CCDE problem in MWN with multiple channels. We first construct a path network to evaluate the priority for each possible transmission and then construct a conflict graph (CG). This graph depicts the half-duplex, interference, and channel constraints. After that, a greedy channel assignment algorithm is proposed to obtain the nonconflict transmissions based on the constructed CG and assign a channel for each selected transmission. Finally, based on the selected transmissions, we construct a single-source multicast network exploiting the time expanded network, with which the network encoding and decoding schemes can be computed within polynomial time. Extensive simulations are conducted to demonstrate the efficiency of the proposed algorithm.

Embedding and re-embedding of virtual links in software-defined multi-radio multi-channel multi-hop wireless networks

There is rising interest in applying Software Defined Networking (SDN) principles to wireless multi-hop networks, as this paves the way towards bringing the programmability and flexibility that is lacking in today’s distributed wireless networks (ad-hoc, mesh or sensor networks) with the promising perspectives of better mitigating issues such as scalability, mobility and interference management and supporting improved controlled QoS services.This paper investigates this latter aspect and proposes an Integer Linear Programming (ILP) based wireless resource allocation scheme for the provision of point-to-point and point-to-multipoint end-to-end virtual links with bandwidth requirements in software-defined multi-radio multi-channel wireless multi-hop networks. The proposed algorithm considers the peculiarities of wireless communications: the broadcast nature of wireless links which can be leveraged for point-to-multipoint links resource allocations, and, the interference between surrounding wireless links. It also considers switching resource consumption of wireless nodes since, for the time being, the size of SDN forwarding tables remains quite limited. We also consider the case where the requirements of already embedded virtual links evolve over time and propose a re-embedding strategy that meets the new requirements while minimizing service disruption. Genetic Algorithms derived from the ILP formulations are also proposed to address the case of large wireless networks. Our simulation results show that our proposed methods work effectively compared to shortest path based heuristics.

Conflict-free many-to-one data aggregation in multi-channel multi-hop wireless networks

In this paper, we study the minimum latency conflict-free many-to-one data aggregation scheduling problem in multi-channel multi-hop wireless sensor networks: given a set of sensor nodes along with a base station, and a subset of this set as the source nodes, find a schedule with the minimal latency, in which the data from all source nodes can be transmitted to the base station and no conflict happens. We assign each sensor three parameters: the transmission range r, the interference range αr and the carrier sensing range βr, where α, and β are constants. λ ≥ 1 channels are available for communication. We design a centralised algorithm with latency bound as (⌈a/λ⌉ + 11⌈b/λ⌉)R + (Δ − 23)⌈b/λ⌉ − ⌈a/λ⌉ + 12, where a and b are two integer constants derived from α and β, Δ is the maximum degree of the network, and R is the latency's trivial lower bound. Our algorithm has an approximation ratio (⌈a/λ⌉ + 11⌈b/λ⌉). When λ=1, the performance ratio is a + 11b, which improves the result in Zhu et al. (2009). We evaluate our algorithm's performance through extensive simulations.

Performance Comparison for Routing Protocols in Multi-Radio Multi-Channel Multi-Hop Wireless Networks

In this paper, we consider a TDMA-based wireless network and address two major issues, fading and interference, existing in wireless networks since fading will lead to low quality links and interference may lead to unfair channel allocation. Because channel allocation selects the proper channel for each logical link and routing determines through which logical links the packets should be forwarded, there is strong interaction between MAC layer and network layer. In this paper, we seek for the performance trend with more channels allocated and further compare the performances of Bellman-Ford and AODV routing protocols based on the Packet Deliver Rate (PDR) to MAC layer in multi-radio multi-channel multi-hop wireless networks. Numerical results are given and discussions as well as insights into performance aspects for multi-radio multi-channel deployment are provided.

An efficient approximation for minimum energy broadcast in multi-channel multi-hop wireless network with directional antennas

In this paper, We discuss the minimum energy broadcast problem (MEB) in multi-channel multi-hop wireless networks with directional antennas (MEB-MB). This problem is NP-hard since its special version, MEB in single-channel network with directional antennas (MEB-SB) is proved to be NP-hard. We design an efficient approximation for MEB-MB problem, analyze its approximation ratio, and evaluate its performance via numerical experiments.

Opportunistic Routing in Multi-Radio Multi-Channel Multi-Hop Wireless Networks

Two major factors that limit the throughput in multi-hop wireless networks are the co-channel interference and unreliability of wireless transmissions. Multi-radio multi-channel technology and opportunistic routing (OR) have shown their promise to significantly improve the network capacity by combating these two limits. It raises an interesting problem on the tradeoff between multiplexing and spatial diversity when integrating these two techniques for throughput optimization. It is unknown what the capacity of the network could be when nodes have multiple radios and OR capability. In this paper, we present our study on optimizing an end-to-end throughput of the multi-radio multi-channel network when OR is available. First, we formulate the end-to-end throughput bound as a linear programming (LP) problem which jointly solves the radio-channel assignment, transmission scheduling, and forwarding candidate selection. Second, we propose an LP approach and a heuristic algorithm to find a feasible scheduling of opportunistic forwarding priorities to achieve the capacity. Simulations show that the heuristic algorithm achieves desirable performance under various number of forwarding candidates. Leveraging our analytical model, we find that 1) OR can achieve better performance than traditional routing (TR) under different radio/channel configurations, however, in particular scenario (e.g. bottleneck links exist between the sender and relays), TR is preferable; 2) OR can achieve comparable or better performance than TR by using less radio resource.

An efficient approximation for minimum latency broadcast in multi-channel multi-hop wireless networks

In this paper, we discuss the minimum latency broadcast problem (MLB) in multi-channel multi-hop wireless networks (MLB-MC). This problem is NP-hard since its special version, MLB in single-channel network (MLB-SC) is proved to be NP-hard . We design an efficient approximation for MLB-MC, analyze its approximation ratio, and evaluate its performance via numerical experiments. Furthermore, we give a general theorem as an upper bound to compare the performance between approximations for MLB-MC and MLB-SC.

A Metric for DISH Networks: Analysis, Implications, and Applications

In wireless networks, node cooperation has been exploited as a data relaying mechanism for decades. However, the wireless channel allows for much richer interaction among nodes. In particular, Distributed Information SHaring (DISH) represents a new improvement to multi-channel MAC protocol design by using a cooperative element at the control plane. In this approach, nodes exchange control information to make up for other nodes' insufficient knowledge about the environment, and thereby aid in their decision making. To date, what is lacking is a theoretical understanding of DISH. In this paper, we view cooperation as a network resource and evaluate the availability of cooperation, $p_{co}$. We first analyze $p_{co}$ in the context of a multi-channel multi-hop wireless network, and then perform simulations which show that the analysis accurately characterizes $p_{co}$ as a function of underlying network parameters. Next, we investigate the correlation between $p_{co}$ and network metrics such as collision rate, packet delay, and throughput. We find a near-linear relationship between $p_{co}$ and the metrics, which suggests that $p_{co}$ can be used as an appropriate performance indicator itself. Finally, we apply our analysis to solving a channel bandwidth allocation problem, where we derive optimal schemes and provide general guidelines on bandwidth allocation for DISH networks.

Intersection-Aware Channel Assignment and Routing in Multi-Channel Multi-Hop Wireless Networks with a Single Transceiver

This article proposes an intersection-aware channel assignment and routing protocol for wireless ad hoc networks with a single transceiver. This protocol increases the network capacity of an IEEE 802.11 network by exploiting frequency diversity. Using the proposed protocol, multiple communications can simultaneously take place in a region without interfering with each other. However, it must avoid a multi-channel hidden terminal problem for designing channel assignment and routing protocol. This paper considers issues regarding multiple channels at the network layer, assuming a single channel MAC protocol such as IEEE 802.11 DCF. Also, the proposed protocol assumes that each node in the network is equipped with a single transceiver. This set of assumptions is very practical, because most devices have a single wireless card implementing the IEEE 802.11 DCF protocol. Each node uses modular exponentiation congruence to represent the channel schedule, which assures that each pair of nodes has common channels for communication in every cycle. Each node switches across channels in such a manner that each pair of nodes works on the same channel when they desire to communicate; otherwise they work on a different channel, and hence do not interfere with each other. However, for the intersecting node, there is no benefit in using single radio multiple channels since the capacity around the intersection node can at most be O (W), W is the link capacity, regardless of the number of channels. The protocol lets the intersecting node always work on the same channel whereas the nonintersecting node can work on different channels. The two states for every node in the network are the state of an intersecting node and the state of non-intersecting node. Using the proposed protocol, nodes discover multiple routes to the destination node; the node selects the path with most intersecting nodes to avoid more nodes become intersecting nodes when the number of flows increases greatly. Once a node becomes an intersecting node, it will work on the same channel in a cycle. Simulation results show that the proposed protocol significantly increases the aggregate end-to-end throughput and network capacity greatly over a single-channel protocol and some other channel assignment and routing protocols in several wireless networking scenarios.

Dynamic Channel Selection with Snooping for Multi-Channel Multi-Hop Wireless Networks

The dynamic channel selection mechanism used in existing multi-channel MAC protocols selects an idle data channel based on channel usage information from one-hop neighbor nodes. However, this method can cause multi-channel hidden node problem in multi-hop wireless networks. This letter proposes a new approach to channel selection. Nodes snoop data channels during idle times and then select an idle data channel within the carrier sensing range using both the snooping results and the channel usage information. Our simulation results verify that the proposed channel selection approach can effectively avoid the multi-channel hidden node problem and improve the networkwide performance.

Distributed Channel Assignment and Routing in Multiradio Multichannel Multihop Wireless Networks

In this paper, we first identify several challenges in designing a joint channel assignment and routing (JCAR) protocol in heterogeneous multiradio multichannel multihop wireless networks (M3WNs) using commercial hardware [e.g., IEEE 802.11 Network Interface Card (NIC)]. We then propose a novel software solution, called Layer 2.5 JCAR, which resides between the MAC layer and routing layer. JCAR jointly coordinates the channel selection on each wireless interface and the route selection among interfaces based on the traffic information measured and exchanged among the two-hop neighbors. Since interference is one of the major factors that constrain the performance in a M3 WN, in this paper, we introduce an important channel cost metric (CCM) which actually reflects the interference cost and is defined as the sum of expected transmission time weighted by the channel utilization over all interfering channels (for each node). In CCM, both the interference and the diverse channel characteristics are taken into account. An expression for CCM is derived in terms of equivalent fraction of air time by explicitly taking the radio heterogeneity into consideration. Using CCM as one of the key performance measures, we propose a distributed algorithm (heuristic) that produces near-optimal JCAR solution. To evaluate the efficacy of our heuristics, we conduct extensive simulations using the network simulator NS2. To demonstrate implementation feasibility, we conducted various experiments for the proposed distributed JCAR algorithm on a multihop wireless network testbed with nine wireless nodes, each is equipped with single/multiple 802.11a/g cards. Both experimental and simulation results demonstrate the effectiveness and implementation easiness of our proposed software solution