Multi-hop Scheduling Research Articles

A low-latency and reliable multihop D2D transmissions scheduling algorithm for guaranteed message dissemination

In critical alert services (e.g., a collision alert in a vehicular network) a message must reach all the recipients in a prespecified area within a maximum time, usually of few milliseconds, with guaranteed reliability. In this paper, we consider a Device-to-device (D2D)-enabled cellular network where User Equipments (UEs) use D2D transmissions to spread a message in their proximity, according to a centrally computed multihop schedule. Reception of D2D transmissions is probabilistic, with probabilities known a priori, e.g. based on the distance between two UEs. We want a given message to reach all the UEs in the network, within a maximum amount of time, with a pre-specified target probability. We show that the problem of computing: a) the minimal set of UEs that should initially possess the message to be disseminated, and b) the schedule that achieves the above objectives, is integer-non-convex, hence too complex to be solved optimally, and we propose a polynomial heuristic based on iterative decompositions, which always finds a feasible solution in negligible computation time. We analyze the performance of our scheme via simulation, showing that our centralized approach outperforms distributed ones relying on node cooperation, is considerably faster and requires far fewer transmissions.

Radio Resource Management for V2V Multihop Communication Considering Adjacent Channel Interference

This paper investigates schemes for multihop scheduling and power control for vehicle-to-vehicle (V2V) multicast communication, taking into account the effects of both co-channel interference and adjacent channel interference, such that requirements on latency or age of information (AoI) are satisfied. Optimal performance can be achieved by formulating and solving mixed Boolean linear programming (MBLP) optimization problems for various performance metrics, including network throughput and connectivity. Fairness among network nodes (vehicles) is addressed by considering formulations that maximizes the worst-case network node performance. Solving the optimization problem comes at the cost of significant computational complexity for large networks and requires that (slow) channel state information is gathered at a central point. To address these issues, a clustering method is proposed to partition the optimization problem into a set of smaller problems, which reduces the overall computational complexity, and a decentralized algorithm that does not need channel state information is provided.

<italic>DeAMON</italic>: A Decentralized Adaptive Multi-Hop Scheduling Protocol for 6TiSCH Wireless Networks

The IEEE 802.15.4-2015 standard provides a link-layer mechanism, based on time synchronized channel hopping (TSCH), to enable deterministic low-power wireless mesh networking. The emerging IPv6 over IEEE 802.15.4e TSCH (6TiSCH) working group aims at harmonizing an IP-enabled protocol stack with the IEEE 802.15.4e link layer. In 802.15.4-TSCH medium access control, nodes follow a communication schedule; however, the standard does not specify any scheduling policy. Therefore, a number of recent studies have investigated scheduling mechanisms for 6TiSCH wireless networks. This paper introduces DeAMON , which is decentralized adaptive multi-hop scheduling protocol for 6TiSCH wireless networks. The key features of DeAMON include traffic-awareness, sequential scheduling, parallel transmissions, robust over-provisioning, and adaptability to topology changes. Moreover, DeAMON incurs minimal signaling overhead. Performance evaluation demonstrates that DeAMON outperforms state-of-the-art distributed scheduling protocols in terms of reliability, latency, and resource utilization.

Boosting Spatial Reuse via Multiple-Path Multihop Scheduling for Directional mmWave WPANs

With huge unlicensed bandwidth available in most parts of the world, millimeter wave (mmWave) communications in the 60 GHz band has been considered as one of the most promising candidates to support multi-gigabit wireless services. Due to high propagation loss of mmWave channels, beamforming is likely to become adopted as an essential technique. Consequently, transmission in 60 GHz band is inherently directional. Directivity enables concurrent transmissions (spatial reuse), which can be fully exploited to improve network capacity. In this paper, we propose a multiple paths multi-hop scheduling scheme, termed MPMH, for mmWave wireless personal area networks, where the traffic across links of low channel quality is transmitted through multiple paths of multiple hops to unleash the potential of spatial reuse. We formulate the problem of multiple paths multi-hop scheduling as a mixed integer linear program (MILP), which is generally NP-hard. To enable the implementation of the multiple paths multi-hop transmission in practice, we propose a heuristic scheme including path selection, traffic distribution, and multiple paths multi-hop scheduling to efficiently solve the formulated problem. Finally, through extensive simulations, we demonstrate MPMH achieves near-optimal network performance in terms of transmission delay and throughput, and enhances the network performance significantly compared with existing protocols.

Traffic Light Based Intelligent Routing Strategy for Satellite Network

This scheme investigates a traffic-light-based intelligent routing strategy for the satellite network, which can adjust the pre-calculated route according to the real-time congestion status of the satellite constellation. In a satellite, a traffic light is deployed at each direction to indicate the congestion situation, and is set to a relevant color, by considering both the queue occupancy rate at a direction and the total queue occupancy rate of the next hop. The existing scheme uses TLR based routing mechanism based on two concepts are DVTR Dynamic Virtual Topology Routing (DVTR) and Virtual Node (VN). In DVTR, the system period is divided into a series of time intervals. On-off operations of ISLs are supposed to be performed only at the beginning of each interval and the whole topology keeps unchanged during each interval. But it has delay due to waiting stage at buffer. So, this method introduces an effective multi-hop scheduling routing scheme that considers the mobility of nodes which are clustered in one group is confined within a specified area, and multiple groups move uniformly across the network.

Aggregation for adaptive and energy-efficient MAC in wireless sensor networks

Time Division Multiple Access (TDMA) protocols are considered an energy-efficient solution to prolong wireless sensor network lifetime. However, their drawbacks such as the complexity of slot assignment and schedule maintenance, clock synchronization and low channel utilization during low traffic conditions are to be overcome in a good and efficient way. In this paper we present On-demand Convergecast Sensor MACS (OCSMACS), a centralized and adaptive multihop scheduling-based TDMA protocol for Wireless Sensor Networks. OCSMACS achieves high energy efficiency by adopting a novel requests aggregation mechanism for adaptive slot assignments such that all requests generated by active nodes are aggregated in a very few small size packets. In addition, knowledge of data correlation is integrated in the design of underlying multihop scheduling schemes to improve energy efficiency and extend network lifetime. Furthermore, OCSMACS adopts an energy-efficient protocol called PROGRESSIVE for the topology discovery and setup phases. The performance of OCSMACS is compared against existing protocols based on simulations using ns-2 and the results show that OCSMACS outperforms these protocols in terms of energy efficiency and network lifetime. Also, the integration of correlation knowledge in the scheduling process improves performance and extends network lifetime.

A High Throughput MAC Protocol for Wireless Sensor Networks in Surveillance Applications

Monitoring a given environment is a kind of major applications in wireless sensor networks. These WSNs should often meet special requirements, such as high throughput support, service differentiation support and energy efficiency. However, related works always emphasis on one or two of them, and hardly consider comprehensively. In this paper, we propose a new-style MAC protocol, which based on the above-mentioned factors. Cluster-based multi-hop scheduling and priority-aware schedule switching are crucial technologies in the MAC protocol. Moreover, idle listening energy consumption is reduced by using a synchronized duty cycle. Experiments show that the proposed strategy achieves our goals. The energy consumption of the radio module is reduced while high throughput is provided.

MAC Protocol for Energy Efficiency and Service Differentiation with High Goodput in Wireless Sensor Networks

SUMMARY In the sensor networks for surveillance, the requirements of providing energy efficiency and service differentiation, which is to deliver high-priority packets preferentially, while maintaining high goodput, which is to deliver many packets within their deadline are increasing. However, previous works have difficulties in satisfying the requirements simultaneously. Thus, we propose GES-MAC, which satisfies the requirements simultaneously. GES-MAC reduces idle listening energy consumption by using a duty cycle, periodic listen (i.e., turn on radio module) and sleep (i.e. turn off radio module) of sensor nodes. Cluster-based multi-hop scheduling provides high goodput in a duty-cycled environment by scheduling clusters of nodes in the listen period and opportunistically forwarding data packets in the sleep period. Priority-aware schedule switching makes more highpriority packets reach the sink node by letting high-priority packets preempt the schedules of low-priority packets. In experiments with MICA2 based sensor nodes and in simulations, the energy consumption of the radio module is reduced by 70% compared to the approaches without a duty cycle, while providing 80% ∼ 100% goodput of the approaches that provide high goodput. Service differentiation is also supported with little overhead.

Approximation Algorithms for a Link Scheduling Problem in Wireless Relay Networks with QoS Guarantee

The emerging wireless relay networks (WRNs) are expected to provide significant improvement on throughput and extension of coverage area for next-generation wireless systems. We study an optimization problem for multihop link scheduling with bandwidth and delay guarantees over WRNs. Our optimization problem is investigated under a more general interference model with a generic objective. The objective can be based on various kinds of performance indexes (e.g., throughput, fairness, and capacity), which can be determined by service providers. Through our theoretical analysis, the intractability and inapproximability of the optimization problem are shown. Due to the intractable computational complexity, we present efficient algorithms to provide a reasonable small approximation factor against any optimal solution even for a worst-case input. Furthermore, some experimental results indicate that our algorithms yield near-optimal performance in the average case.

Improved algorithms for latency minimization in wireless networks

In the interference scheduling problem, one is given a set of n communication requests described by source–destination pairs of nodes from a metric space. The nodes correspond to devices in a wireless network. Each pair must be assigned a power level and a color such that the pairs in each color class can communicate simultaneously at the specified power levels. The feasibility of simultaneous communication within a color class is defined in terms of the Signal to Interference plus Noise Ratio (SINR) that compares the strength of a signal at a receiver to the sum of the strengths of other signals. The objective is to minimize the number of colors as this corresponds to the time needed to schedule all requests. We introduce an instance-based measure of interference, denoted by I , that enables us to improve on previous results for the interference scheduling problem. We prove the upper and lower bounds in terms of I on the number of steps needed for scheduling a set of requests. For general power assignments, we prove a lower bound of Ω ( I / ( log Δ log n ) ) steps, where Δ denotes the aspect ratio of the metric. When restricting to the two-dimensional Euclidean space (as in the previous work) the bound improves to Ω ( I / log Δ ) . Alternatively, when restricting to linear power assignments, the lower bound improves even to Ω ( I ) . The lower bounds are complemented by an efficient algorithm computing a schedule for linear power assignments using only O ( I log n ) steps. A more sophisticated algorithm computes a schedule using even only O ( I + log 2 n ) steps. For dense instances in the two-dimensional Euclidean space, this gives a constant factor approximation for scheduling under linear power assignments, which shows that the price for using linear (and, hence, energy-efficient) power assignments is bounded by a factor of O ( log Δ ) . In addition, we extend these results for single-hop scheduling to multi-hop scheduling and combined scheduling and routing problems, where our analysis generalizes the previous results towards general metrics and improves on the previous approximation factors.

Efficient multi-hop scheduling algorithms for packet transmissions in WDM optical star networks

This paper proposes multi-hop scheduling algorithms for the All-to-All Broadcast (AAB) problem in Wavelength Division Multiplexed (WDM) optical star networks. The multi-hop AAB problem can be split into two subproblems: Logical Topologies Construction (LTC) problem, and Transmission Scheduling (TS) problem. For improving the efficiency of multi-hop scheduling, we focus on a new multi-hop transmission model and transfer the LTC problem to a special case of the Round Robin Tournament (RRT) problem. In the proposed logical topologies, our multi-hop scheduling algorithms can easily overlap the tuning latency and reduce the number of tuning operations on each node. We compare our results with previous research in terms of schedule length. Overall results indicate that our multi-hop scheduling algorithms have better performance than previous algorithms.

Improvement of multi-hop packet transmission scheduling in WDM optical star networks

This paper addresses the design of multi-hop packet transmissions for the all-to-all broadcast ( AAB) problem in a wavelength division multiplexing (WDM) optical star network with N nodes. We assume that each node is equipped with a tunable transmitter and a fixed-tuned receiver (TT-FR), and each tunable transmitter needs a non-negligible tuning latency δ to switch between wavelengths. To reduce the number of O/E/O conversions in the multi-hop scheduling, the maximum hop distance of packet transmissions is limited to ρ . We propose an improved multi-hop scheduling algorithm to shorten the duration of scheduling periods. As ρ is odd, the number of tuning operations on each node is at most ⌈ 2 N / ( ρ + 1 ) ⌉ - 1 and the schedule length of our multi-hop scheduling is at most ( ⌈ 2 N ρ + 1 ⌉ - 1 ) ρ ( ρ + 1 ) 2 + δ . As ρ is even, the tuning time on each node is at most ⌈ 2 N / ρ ⌉ - 1 and the schedule length is at most ( ⌈ 2 N / ρ ⌉ - 1 ) ρ ( ρ - 1 ) 2 + δ . For general case, when ρ < 1 + δ + δ 2 - 6 δ + 5 2 , the schedule length of our multi-hop scheduling algorithm will be less than that of the optimal single-hop scheduling algorithm. This also improves the previous result on the multi-hop schedule length of the AAB problem.

TDMA scheduling algorithms for wireless sensor networks

Algorithms for scheduling TDMA transmissions in multi-hop networks usually determine the smallest length conflict-free assignment of slots in which each link or node is activated at least once. This is based on the assumption that there are many independent point-to-point flows in the network. In sensor networks however often data are transferred from the sensor nodes to a few central data collectors. The scheduling problem is therefore to determine the smallest length conflict-free assignment of slots during which the packets generated at each node reach their destination. The conflicting node transmissions are determined based on an interference graph, which may be different from connectivity graph due to the broadcast nature of wireless transmissions. We show that this problem is NP-complete. We first propose two centralized heuristic algorithms: one based on direct scheduling of the nodes or node-based scheduling, which is adapted from classical multi-hop scheduling algorithms for general ad hoc networks, and the other based on scheduling the levels in the routing tree before scheduling the nodes or level-based scheduling, which is a novel scheduling algorithm for many-to-one communication in sensor networks. The performance of these algorithms depends on the distribution of the nodes across the levels. We then propose a distributed algorithm based on the distributed coloring of the nodes, that increases the delay by a factor of 10–70 over centralized algorithms for 1000 nodes. We also obtain upper bound for these schedules as a function of the total number of packets generated in the network.

Optimization of logical rings for multi-hop transmissions in WDM optical star networks

In this paper, we present a multi-hop scheduling algorithm for the All-to-All Broadcast ( AAB) problem in Wavelength Division Multiplexed (WDM) optical star networks with N nodes. To decrease the packet delay in packet transmissions, our scheduling algorithm will limit the hop distance to a constant ρ. We transfer the ρ-hop AAB problem to the Hamiltonian cycles problem and then generate the logical rings for physical packet transmissions. In order to minimize the scheduling length, the problem of selection of logical rings is to minimize the number of tuning operations to reduce the influence of tuning latency δ for the AAB problem. We propose a 2-approximation algorithm that needs only 2⌈( N − 1)/ ρ⌉ tuning operations in an AAB scheduling. When ρ < δ + δ 2 - 8 δ 2 , the schedule length of our algorithm will be shorter than that of the optimal single-hop scheduling algorithm.

Cross-layer adaptive control for wireless mesh networks

This paper investigates optimal routing and adaptive scheduling in a wireless mesh network composed of mesh clients and mesh routers. The mesh clients are power constrained mobile nodes with relatively little knowledge of the overall network topology. The mesh routers are stationary wireless nodes with higher transmission rates and more capabilities. We develop a notion of instantaneous capacity regions, and construct algorithms for multi-hop routing and transmission scheduling that achieve network stability and fairness with respect to these regions. The algorithms are shown to operate under arbitrary client mobility models (including non-ergodic models with non-repeatable events), and provide analytical delay guarantees that are independent of the timescales of the mobility process. Our control strategies apply techniques of backpressure, shortest path routing, and Lyapunov optimization.

A survey of quality of service in IEEE 802.11 networks

Developed as a simple and cost-effective wireless technology for best effort services, IEEE 802.11 has gained popularity at an unprecedented rate. However, due to the lack of built-in quality of service support, IEEE 802.11 experiences serious challenges in meeting the demands of multimedia services and applications. This article surveys 802.11 QoS schemes, including service differentiation in the MAC layer, admission control and bandwidth reservation in MAC and higher layers, and link adaptation in the physical layer, designed to meet these challenges by providing the necessary enhancements for the required QoS. Furthermore, the article addresses issues that arise when end-to-end QoS has to be guaranteed in today's pervasive heterogeneous wired-cum-wireless networks. Among these challenges, protocol interoperability, multihop scheduling, full mobility support, and seamless vertical handoff among multiple mobile/wireless interfaces are specifically addressed.

Coordinated multihop scheduling: a framework for end-to-end services

In multihop networks, packet schedulers at downstream nodes have an opportunity to make up for excessive latencies due to congestion at upstream nodes. Similarly, when packets incur low delays at upstream nodes, downstream nodes can reduce priority and schedule other packets first. The goal of this paper is to define a framework for design and analysis of coordinated multihop scheduling (CMS) which exploits such internode coordination. We first provide a general CMS definition which enables us to classify a number of schedulers from the literature, including G-EDF, FIFO+, CEDF, and work-conserving CJVC as examples of CMS schedulers. We then develop a distributed theory of traffic envelopes which enables us to derive end-to-end statistical admission control conditions for CMS schedulers. We show that CMS schedulers are able to limit traffic distortion to within a narrow range resulting in improved end-to-end performance and more efficient resource utilization. Consequently, our technique exploits statistical resource sharing among flows, classes, and nodes, and our results provide the first statistical multinode multiclass admission control algorithm for networks of work conserving servers.