MrFair: Misbehavior-resistant fair scheduling in wireless mesh networks

It is a critical issue to ensure that nodes and/or flows have fair access to the network bandwidth in wireless mesh networks (WMNs). However, current WMNs based on IEEE 802.11 exhibit severe unfairness. Several scheduling schemes have been proposed to ensure fairness in WMNs. Unfortunately, all of them implicitly trust nodes in the network, and thus are vulnerable to the misbehavior of nodes participating in scheduling. In this paper, we address the threats to fair scheduling in WMNs resulting from node misbehavior and present a generic verification framework to detect such misbehavior. Moreover, we develop two verification schemes based on this framework for distributed and centralized authentication environments, respectively. We validate our approach by extending an existing fair scheduling scheme and evaluating it through simulation. The results show that our approach improves misbehavior detection with light performance overhead.     

Distributed fair scheduling in a wireless LAN

Fairness is an important issue when accessing a shared wireless channel. With fair scheduling, it is possible to allocate bandwidth in proportion to weights of the packet flows sharing the channel. This paper presents a fully distributed algorithm for fair scheduling in a wireless LAN. The algorithm can be implemented without using a centralized coordinator to arbitrate medium access. The proposed protocol is derived from the Distributed Coordination Function in the IEEE 802.11 standard. Simulation results show that the proposed algorithm is able to schedule transmissions such that the bandwidth allocated to different flows is proportional to their weights. An attractive feature of the proposed approach is that it can be implemented with simple modifications to the IEEE 802.11 standard.     

On a joint temporal-spatial multi-channel assignment and routing scheme in resource-constrained wireless mesh networks

Use of multiple orthogonal channels can significantly improve network throughput of multi-hop wireless mesh networks (WMNs). In these WMNs where multiple channels are available, channel assignment is done either in a centralized manner, which unfortunately shows a poor scalability with respect to the increase of network size, or in a distributed manner, where at least one channel has to be dedicated for exchanging necessary control messages or time synchronization has to be utilized for managing the duration of data packet transmission, causing excessive system overhead and waste of bandwidth resource. In this paper, we first formulate multi-channel assignment as a NP-hard optimization problem. Then a distributed, heuristic temporal-spatial multi-channel assignment and routing scheme is proposed, assuming every wireless node in the network is equipped with a single-radio interface. Here the gateway node is set to use all the channels sequentially in a round-robin fashion. This temporal scheme ensures all the nodes that need to directly communicate with the gateway node shall have a fair access to it. For those non-gateway nodes, a spatial scheme where channels are assigned based on their neighbors’ channel usage is adopted to exploit parallel communications and avoid channel interference among nodes. Furthermore, since the routing factors, including channel usage of neighbor nodes, node hop count, node memory size, and node communication history, are all considered along with the channel assignment, network performance, measured by packet delivery latency, channel usage ratio, and memory usage ratio, tends to be considerably enhanced. The simulation results have confirmed that, compared with a couple of well-known multi-channel assignment schemes, such as LCM [21] and ROMA [15], the proposed scheme shows substantial improvement in network throughput with a very modest collision level. In addition, the proposed scheme is highly scalable as the algorithm complexity is only linearly dependent on the total number of channels that are available in the network and the number of neighbors that a network node directly connects to.     

Dynamic Bandwidth Management in Single-Hop Ad Hoc Wireless Networks

Distributed weighted fair scheduling schemes for Quality of Service (QoS) support in wireless local area networks have not yet become standard. Therefore, we propose an Admission Control and Dynamic Bandwidth Management scheme that provides fairness and a soft rate guarantee in the absence of distributed MAC-layer weighted fair scheduling. This scheme is especially suitable for smart-rooms where peer-to-peer multimedia transmissions need to adapt their transmission rates co-operatively. We present a mapping scheme to translate the bandwidth requirements of an application into its channel time requirements. The center piece of our scheme is a Bandwidth Manager, which allots each flow a share of the channel, depending on the flow's requirements relative to the requirements of other flows in the network. Admitted flows control their transmission rates so they only occupy the channel for the fraction of time allotted to them. Thus co-operation between flows is achieved and the channel time is fair shared. As the available channel capacity changes and the traffic characteristics of various flows change, the Bandwidth Manager dynamically re-allocates the channel access time to the individual flows. Our simulation experiments show that, at a very low cost and with high probability, every admitted flow in the network will receive at least its minimum requested share of the network bandwidth. We also present extensive testbed experiments with our scheme using a real-time audio streaming application running between Linux laptops equipped with standard IEEE 802.11 network cards.     

Adaptive Opportunistic Multicast Scheduling Over Next-Generation Wireless Networks

This paper considers the problem of opportunistic multicast scheduling in wireless time-division multiplexing systems with adaptive modulation and channel coding. The problem is first formulated and an effective scheduling scheme is proposed to maximize the multicast throughput while a desired packet error rate is guaranteed. The proposed scheme dynamically selects multicast rates by considering the configuration of the multicast group and instantaneous network states, and thus it can adapt well to network conditions. Extensive simulation results conclusively demonstrate that, compared to the worst-user multicast scheduling, the proposed approach can increase the wireless channel efficiency by large margins, especially when the channel is operating in a lower signal-to-noise ratio region and/or when the multicast group size increases. Besides, the simulations show that the proposed approach can work well in systems with imperfect channel estimation.     

Dynamic frame partitioning scheme for IEEE 802.16 mesh networks

The IEEE 802.16 mesh network is a promising next generation wireless backbone network. In the network, the allocation of minislots is handled by centralized scheduling and distributed scheduling, which are independently exercised. However, the standard does not specify how the frame can be partitioned among its centralized and distributed schedulers. Through efficient partitioning that dynamically adapts the partitioning based on demand, network can support more user applications. Although a dynamic frame partitioning scheme to use Markov model has been studied, the dynamic frame partitioning method has not been fully investigated. This paper proposes two novel and general dynamic frame partitioning scheme for IEEE 802.16 mesh networks so that the minislot allocation can be more flexible and the utilization is increased. The two schemes respectively use GM(1,1)‐Markov model and Grey–Verhulst–Markov model to predict efficient partitions for future frames according to the minislot utilization in current frames. Our study indicates that the two proposed schemes outperform the scheme of using Markov model. Copyright © 2012 John Wiley & Sons, Ltd.     

Proportional fair scheduling with reduced feedback

An opportunistic feedback technique is proposed for proportional fair (PF) scheduling in a downlink multi-user system. This technique requires each mobile station, the scheduling metric of which is higher than a threshold, to send one-bit feedback for PF scheduling. The scheduler determines the optimal modulation and coding scheme for a scheduled user based on channel quality indicator (CQI) update, which is sent on a longer period than the scheduling period. The simulation results indicate that PF scheduling with the proposed update scheme can achieve similar performance as PF scheduling with full CQI feedback. The feedback overhead can be reduced in comparison with typical PF scheduling provided that an optimal CQI update period is chosen.     

Distributed two‐hop proportional fair resource allocation in Long Term Evolution Advanced networks

In Long Term Evolution Advanced networks with Type I in‐band half‐duplex decode‐and‐forward relay nodes, proportional fair (PF) resource allocation is aiming at guaranteeing two‐hop match and optimising global proportional fairness. The two‐hop match is defined as equal data rates in the access links and the corresponding backhaul links. The global proportional fairness is between all the user equipments served by the evolved nodes B and the relay nodes. Existing centralised schemes achieve these targets at the cost of enormous channel state information (CSI) exchange. Existing distributed schemes focus on resource partitioning and employ a traditional single‐hop PF scheduling algorithm in access links, with less CSI exchange. The traditional PF scheduling algorithm maximises single‐hop proportional fairness between the data rates in the access links rather than two‐hop proportional fairness between the end‐to‐end data rates in the two hops. In order to reduce CSI exchange and at the same time to maximise the two‐hop proportional fairness, a distributed two‐hop PF resource allocation scheme is proposed. The proposed scheme includes two‐hop PF resource scheduling algorithms and adaptive resource partitioning algorithms, applied in different two‐hop transmission protocols. Simulation results demonstrate the proposed scheme is better than the existing distributed schemes in obtaining better proportional fairness and larger cell‐edge user equipment throughputs. Copyright © 2014 John Wiley & Sons, Ltd.     

A Distributed Opportunistic Access Scheme and its Application to OFDMA Systems

Multiuser systems can provide multiuser diversity gains by assigning channels to users with higher channel gains. To avoid the extensive information exchange with the access point for the uplink access in centralized approaches, we propose in this paper a distributed opportunistic access scheme. Through a judicious design of a novel backoff mechanism to utilize the channel information and reduce collisions, significant multiuser diversity gains are achieved. To a user, the higher the channel gain is, the smaller the backoff time-slot and, hence, the higher the access priority of that user is. In addition, for heterogeneous systems, our proposed scheme can realize multiuser diversity gains and achieve fairness among the users at the same time. Finally, we design two distributed opportunistic access schemes for OFDMA systems. Users contend on all sub-channels in the first scheme and only on several strongest sub-channels in the second scheme. Compared with traditional centralized OFDMA systems and other distributed access schemes, our proposed schemes reduce overhead and achieve a higher throughput.     

Multi-sender diversity and its application in the uplink of ieee 802.11 WLANs

Multi-sender diversity is an opportunity to exploit channel fluctuation in the situation where multiple senders compete for the same wireless resources. To utilize this diversity in the uplink of WLANs, we propose a novel distributed opportunistic scheduling scheme. Under the constraint of access fairness, the proposed scheme maximizes the system throughput. Analysis and simulation results show that the throughput gain increases with the number of stations.     

Optimized in-band control channel with channel selection scheduling and network coding in distributed cognitive radio networks

This article proposes an optimized in-band control channel scheme with channel selection scheduling algorithm and network coding based transmission paradigm in the distributed cognitive radio network (...     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.     

Cooperative and opportunistic transmission for wireless ad hoc networks

Moving toward 4G, wireless ad hoc networks receive growing interest due to users' provisioning of mobility, usability of services, and seamless communications. In ad hoc networks fading environments provide the opportunity to exploit variations in channel conditions, and transmit to the user with the currently "best" channel. In this article two types of opportunistic transmission, which leverage time diversity and multi-user diversity, respectively, are studied. Considering the co-channel interference and lack of a central controller in ad hoc networks, the "cooperative and opportunistic transmission" concept is promoted. For opportunistic transmission that exploits time diversity, it is observed that the inequality in channel contention due to the hidden terminal phenomenon tends to result in energy inefficiency. Under this design philosophy, we propose a distributed cooperative rate adaptation (CRA) scheme to reduce overall system power consumption. Taking advantage of the time-varying channel among different users/receivers and being aware of the potential contention among neighboring transmissions, we propose a QoS-aware cooperative and opportunistic scheduling (COS) scheme to improve system performance while satisfying QoS requirements of individual flows. Simulation results show that by leveraging node cooperation, our proposed schemes, CRA and COS, achieve higher network throughput and provide better QoS support than existing work     

Three Scheduling Schemes for Amplify-and-Forward Relay Environments

This letter deals with the scheduling in basic amplify-and-forward relay environments, which are characterized by one source and two destinations. The scheduling strategy is required in order to decide which node will be used as a relay. The proposed schemes are the classical Round Robin, and a channel-based scheduling policy which requires a partial feedback from the channel. This scheme is implemented in a centralized and a distributed version. Simulations and analytical results show that the distributed algorithm outperforms the Round Robin and is 3 dB worse than the centralized algorithm, due to possible collisions or outage scheduling. This algorithm provides the best trade-off between performance and complexity and is attractive for practical implementations     

An Opportunistic Channel Quality Feedback Scheme for Proportional Fair Scheduling

In this paper, we propose a channel quality information (CQI) feedback load reduction scheme for proportional fair scheduling (PFS) in wireless systems. The proposed scheme induces select users to feed back CQI only when the probability of selection is high. It is shown that the proposed scheme achieves system throughput comparable to the conventional scheme, where each and every user feeds back its CQIs, with significant feedback load reduction for each of the users.     

Proportional Fair Scheduling with Capacity Estimation for Wireless Multihop Networks

In this paper, we investigate the scheduling problem to achieve the proportional fairness among the flows in wireless multihop networks with time-varying channel capacity. Using the signal to interference noise ratio and the outage probability, we present an estimate of time-varying capacity. Then, we achieve the proportional fairness in terms of maximizing the network utility function with consideration of fast fading without measurement of channel state information. Finally, we show that the proposed scheme results in better performance compared to the existing schemes through the simulation results.     

Evaluation of channel dependent bandwidth allocation in wireless access networks: centralized and distributed approach

The problem of bandwidth allocation in wireless access networks is studied in this paper, investigating the performance of two approaches. Firstly, we use centralized algorithms, such as bankruptcy division rules and Nash bargaining. Secondly, a distributed algorithm is proposed in order to find the optimal solution of the bandwidth allocation problem. In both approaches, the allocation rules are properly modified to incorporate the influence of the channel state resulting in a more efficient and fair bandwidth allocation. The channel dependent centralized and distributed schemes are compared in terms of efficiency and fairness with a view to highlighting the advantages and disadvantages of every approach.     

Design and performance analysis on adaptive reservation-assisted collision resolution protocol for WLANs

In conventional IEEE 802.11 medium access control protocol, the distributed coordination function is designed for the wireless stations (WSs) to perform channel contention within the wireless local area networks (WLANs). Packet collision is considered one of the major issues within this type of contention-based scheme, which can severely degrade network performance for the WLANs. Research work has been conducted to modify the random backoff mechanism in order to alleviate the packet collision problem while the WSs are contending for channel access. However, most of the existing work can only provide limited throughput enhancement under specific number of WSs within the network. In this paper, an adaptive reservation-assisted collision resolution (ARCR) protocol is proposed to improve packet collision resulting from the random access schemes. With its adaptable reservation period, the contention-based channel access can be adaptively transformed into a reservation-based system if there are pending packets required to be transmitted between the WSs and the access point. Analytical model is derived for the proposed ARCR scheme in order to evaluate and validate its throughput performance. It can be observed from both analytical and simulation results that the proposed protocol outperforms existing schemes with enhanced channel utilization and network throughput.     

Asynchronous Congestion Control in Multi-Hop Wireless Networks With Maximal Matching-Based Scheduling

We consider a multi-hop wireless network shared by many users. For an interference model that constrains a node to either transmit to or receive from only one other node at a time, and not to do both, we propose an architecture for fair resource allocation that consists of a distributed scheduling algorithm operating in conjunction with an asynchronous congestion control algorithm. We show that the proposed joint congestion control and scheduling algorithm supports at least one-third of the throughput supportable by any other algorithm, including centralized algorithms.      

Self-coordinating localized fair queueing in wireless ad hoc networks

Distributed fair queueing in a multihop, wireless ad hoc network is challenging for several reasons. First, the wireless channel is shared among multiple contending nodes in a spatial locality. Location-dependent channel contention complicates the fairness notion. Second, the sender of a flow does not have explicit information regarding the contending flows originated from other nodes. Fair queueing over ad hoc networks is a distributed scheduling problem by nature. Finally, the wireless channel capacity is a scarce resource. Spatial channel reuse, i.e., simultaneous transmissions of flows that do not interfere with each other, should be encouraged whenever possible. In this paper, we reexamine the fairness notion in an ad hoc network using a graph-theoretic formulation and extract the fairness requirements that an ad hoc fair queueing algorithm should possess. To meet these requirements, we propose maximize-local-minimum fair queueing (MLM-FQ), a novel distributed packet scheduling algorithm where local schedulers self-coordinate their scheduling decisions and collectively achieve fair bandwidth sharing. We then propose enhanced MLM-FQ (EMLM-FQ) to further improve the spatial channel reuse and limit the impact of inaccurate scheduling information resulted from collisions. EMLM-FQ achieves statistical short-term throughput and delay bounds over the shared wireless channel. Analysis and extensive simulations confirm the effectiveness and efficiency of our self-coordinating localized design in providing global fair channel access in wireless ad hoc networks.