Link Scheduling In Wireless Networks Research Articles

Dynamic Link Scheduling in Wireless Networks Through Fuzzy-Enhanced Deep Learning

Dynamic Link Scheduling in Wireless Networks Through Fuzzy-Enhanced Deep Learning

Fast Link Scheduling in Wireless Networks Using Regularized Off-Policy Reinforcement Learning

The centralized-link-scheduling problem in a wireless network graph involves solving the maximum-weighted-independent-set (MWIS) problem on the conflict graph. In this paper, we propose a novel regularized off-policy reinforcement learning-based MWIS solver and use for the scheduling problem. The proposed MWIS algorithm achieves 17% improvement over state-of-the-art heuristic solver KaMIS, 60% over greedy solver, 16% and 17% over RL-based solvers LwD and S2V-DQN, respectively. We show that our scheduler achieves stable throughput values 14% and 22% higher than LwD and a distributed greedy scheduler, respectively. We demonstrate the flexibility of our RL algorithm by modifying it to create a time-since-last-service-aware scheduler.

Shortest link scheduling in wireless networks under the Rayleigh fading model

Many shortest link scheduling algorithms adopt non-fading SINR interference model, which assumes that the received signal power will always remain determinate as long as the transmission power of the corresponding sender is fixed. In fact, because environment always influences the propagation of radio signals, the received signal power is by no means a certain value. Rayleigh fading is a statistical model for radio signals propagation. It assumes that the strength of a signal on a receiver is a random variable, varying with the Rayleigh distribution. This paper proposes a shortest link scheduling algorithm under the Rayleigh fading model (SLSRF). The SLSRF partitions the wireless network area into hexagons and colors the hexagons with three different colors such that two neighboring hexagons have different colors. The senders of the links scheduled simultaneously are arranged in hexagons with the same color. The correctness of the SLSRF is proved through theoretical analysis, and the efficiency is illustrated by elaborate simulations. Our simulation results demonstrate that the schedule delay of SLSRF is less than that of some results under the non-fading SINR interference model. Furthermore, we extend the SLSRF to a distributed version, which is suitable for large wireless networks.

Shortest link scheduling in wireless networks with oblivious power control

Link scheduling has always been a fundamental problem in wireless networks for its direct impacts on the performance of wireless networks such as throughput capacity, transmission delay, lifetime, etc. Existing work is mainly established under graph-based models, which are not only impractical but also incorrect due to the essentially fading characteristics of signals. In this paper, we study the shortest link scheduling problem under two more realistic models, namely the signal to interference plus noise ratio (SINR) model and the Rayleigh fading model. We propose a centralized square-based scheduling algorithm (CSSA) with oblivious power control under the SINR model and prove its correctness under both the SINR model and the Rayleigh fading model. Furthermore, we extend CSSA and propose a distributed square-based scheduling algorithm (DSSA). Note that DSSA adopts CSMA/CA so that a wireless node can compete for the wireless channel before starting its communication. We also show theoretical analysis and conduct extensive simulations to exhibit the correctness and efficiency of our algorithms.

Distributed link scheduling in wireless networks

This work investigates distributed transmission scheduling in wireless networks. Due to interference constraints, “neighboring links” cannot be simultaneously activated, otherwise transmissions will fail. Here, we consider any binary model of interference. We use the model described by Bui et al. in [L. X. Bui, S. Sanghavi and R. Srikant, Distributed link scheduling with constant overhead, IEEE/ACM Trans. Netw. 17(5) (2009) 1467–1480; S. Sanghavi, L. Bui and R. Srikant, Distributed link scheduling with constant overhead, in Proc. ACM Sigmetrics (San Diego, CA, USA, 2007), pp. 313–324.]. We assume that time is slotted and during each slot there are two phases: one control phase in which a link scheduling algorithm determines a set of non-interfering links to be activated, and a data phase in which data is sent through these links. We assume random arrivals on each link during each slot, so that a queue is associated to each link. Since nodes do not have a global knowledge of the queues sizes, our aim (like in [L. X. Bui, S. Sanghavi and R. Srikant, Distributed link scheduling with constant overhead, IEEE/ACM Trans. Netw. 17(5) (2009) 1467–1480; S. Sanghavi, L. Bui and R. Srikant, Distributed link scheduling with constant overhead, in Proc. ACM Sigmetrics (San Diego, CA, USA, 2007), pp. 313–324.]) is to design a distributed link scheduling algorithm. To be efficient, the control phase should be as short as possible; this is done by exchanging control messages during a constant number of mini-slots (constant overhead). In this paper, we design the first fully distributed local algorithm with the following properties: it works for any arbitrary binary interference model; it has a constant overhead (independent of the size of the network and the values of the queues), and it does not require any knowledge of the queue-lengths. We prove that this algorithm gives a maximal set of active links, where for any non-active link there exists at least one active link in its interference set. We also establish sufficient conditions for stability under general Markovian assumptions. Finally, the performance of our algorithm (throughput, stability) is investigated and compared via simulations to that of previously proposed schemes.

Efficient Link Scheduling in Wireless Networks Under Rayleigh-Fading and Multiuser Interference

Link scheduling plays a key role in the network capacity and the transmission delay. In this paper, we study the problem of maximum link scheduling (MLS), aiming to characterize the maximum number of links that can be successfully scheduled simultaneously under Rayleigh-fading and multiuser interference. After analyzing the minimum distance between successful links in the existing GHW scheduling algorithm, we propose a DLS (Distance-based Link Scheduling) algorithm. Then, the global interference is characterized and bounded by introducing a separation distance between selected links, building on which we propose a distributed version of DLS (denoted by DDLS) that converges to a constant factor of the non-fading optimum within time complexity $O(n\ln n)$ , where $n$ is the number of links. Furthermore, we study the Shortest Link Scheduling (SLS) problem, which minimizes the number of time slots to successfully schedule each link for at least once. An algorithm for SLS with approximation factor of $O(\ln n)$ is obtained by executing DDLS. Extensive simulations show that DDLS greatly outperforms GHW and the other two popular algorithms.

Backbone colouring and algorithms for TDMA scheduling

We investigate graph colouring models for the purpose of optimizing TDMA link scheduling in Wireless Networks. Inspired by the BPRN-colouring model recently introduced by Rocha and Sasaki, we introduce a new colouring model, namely the BMRN-colouring model, which can be used to model link scheduling problems where particular types of collisions must be avoided during the node transmissions. In this paper, we initiate the study of the BMRN-colouring model by providing several bounds on the minimum number of colours needed to BMRN-colour digraphs, as well as several complexity results establishing the hardness of finding optimal colourings. We also give a special focus on these considerations for planar digraph topologies, for which we provide refined results.

Link Scheduling in Wireless Networks With RF Energy Harvesting Nodes

In a wireless network, a scheduler ensures links are given frequent transmission opportunities. A short schedule means links transmit frequently and thus the resulting network capacity is high. In this paper, we consider a novel aim: deriving a link schedule that supports both data and energy links; the latter type of links are used to fulfill the energy requirement of radio frequency energy harvesting (EH) devices. This aim is significant as we envisage future wireless routers to have dual roles: forwarding data and charging devices. To this end, we present a mixed integer linear program to derive the shortest link schedule for both types of links; each with a data rate or energy requirement. We consider transmission power control and the physical interference model. In addition, we present a heuristic algorithm called linear programming approximation algorithm (LPAA) to derive the schedule for large-scale topologies. Our results show that the schedule length is affected by the number of links, energy requirement and energy conversion rate of EH nodes, transmit power, and signal-to-interference-noise ratio threshold. Lastly, our experimental results indicate that LPAA is capable of producing schedules that are near optimal.

MDP based link scheduling in wireless networks to maximize the reliability

This paper considers wireless networks where communication links are unstable and link interference is a challenge to design high performance scheduling algorithms. Wireless links are time varying and are modeled by Markov stochastic processes. The problem of designing an optimal link scheduling algorithm to maximize the expected reliability of the network is formulated into a Markov Decision Process first. The optimal solution can be obtained by the finite backward induction algorithm. However, the time complexity is very high. Thus, we develop an approximate link scheduling algorithm with an approximate ratio of $$2(N - 1)(r_{M}\Delta - r_{m} \delta ),$$2(N-1)(rMΔ-rmź), where N is the number of decision epochs, rM is the maximum link reliability, rm is the minimum link reliability, Δ is the number of links in the largest maximal independent set and ź is the number of links in the smallest maximal independent set. Simulations are conducted in different scenarios under different network topologies.

An improved approximation algorithm for the shortest link scheduling in wireless networks under SINR and hypergraph models

Link scheduling is a fundamental problem in wireless ad hoc and sensor networks. In this paper, we focus on the shortest link scheduling (SLS) under Signal-to-Interference-plus-Noise-Ratio and hypergraph models, and propose an approximation algorithm $$SLS_{pc}$$SLSpc (A link scheduling algorithm with oblivious power assignment for the shortest link scheduling) with oblivious power assignment for better performance than GOW* proposed by Blough et al. [IEEE/ACM Trans Netw 18(6):1701---1712, 2010]. For the average scheduling length of $$SLS_{pc}$$SLSpc is 1 / m of GOW*, where $$m=\lfloor \varDelta _{max}\cdot p \rfloor $$m=źΔmax·pź is the expected number of the links in the set V returned by the algorithm HyperMaxLS (Maximal links schedule under hypergraph model) and $$0

Understanding the Scheduling Performance in Wireless Networks with Successive Interference Cancellation

Successive interference cancellation (SIC) is an effective way of multipacket reception to combat interference in wireless networks. We focus on link scheduling in wireless networks with SIC, and propose a layered protocol model and a layered physical model to characterize the impact of SIC. In both the interference models, we show that several existing scheduling schemes achieve the same order of approximation ratios, independent of whether or not SIC is available. Moreover, the capacity order in a network with SIC is the same as that without SIC. We then examine the impact of SIC from first principles. In both chain and cell topologies, SIC does improve the throughput with a gain between 20 and 100 percent. However, unless SIC is properly characterized, any scheduling scheme cannot effectively utilize the new transmission opportunities. The results indicate the challenge of designing an SIC-aware scheduling scheme, and suggest that the approximation ratio is insufficient to measure the scheduling performance when SIC is available.

Throughput Optimizing Localized Link Scheduling for Multihop Wireless Networks under Physical Interference Model

We study throughput-optimum localized link scheduling in wireless networks. The majority of results on link scheduling assume binary interference models that simplify interference constraints in actual wireless communication. While the physical interference model reflects the physical reality more precisely, the problem becomes notoriously harder under the physical interference model. There have been just a few existing results on link scheduling under the physical interference model, and even fewer on more practical distributed or localized scheduling. In this paper, we tackle the challenges of localized link scheduling posed by the complex physical interference constraints. By cooperating the partition and shifting strategies into the pick-and-compare scheme, we present a class of localized scheduling algorithms with provable throughput guarantee subject to physical interference constraints. The algorithm in the linear power setting is the first localized algorithm that achieves at least a constant fraction of the optimal capacity region subject to physical interference constraints. The algorithm in the uniform power setting is the first localized algorithm with a logarithmic approximation ratio to the optimal solution. Our extensive simulation results demonstrate correctness and performance efficiency of our algorithms.

Delay analysis of randomised algorithms for link scheduling in wireless networks

To design a link scheduling algorithm that can maximise the throughput region yet meet the average delay constraint is a challenging issue in wireless networks. In this paper we aim to analyse and improve the delay performance of the well–studied randomised link scheduling algorithms. To this end, we first introduce a novel concept, the average hitting time, and analyse its impact on the upper bound of the average delay. We analytically show that for two given randomised algorithms achieving the same throughput region, the one with a smaller average hitting time has less average delay bound. We also show that by assigning traffic priorities in some specific applications, the achievable throughput region delivered by the randomised algorithm remains intact. This result is much valuable in the design of algorithms for some real–time applications by prioritising the traffic to reduce the average delay of those applications. The simulation results are consistent with our theoretical analysis.

Link scheduling in wireless networks with successive interference cancellation

Successive interference cancellation (SIC) is an effective way of multipacket reception (MPR) to combat interference at the physical layer. To understand the potential MPR advantages, we study link scheduling in an ad hoc network with SIC at the physical layer. The fact that the links detected sequentially by SIC are correlated at the receiver poses key technical challenges. A link can be interfered indirectly when the detecting and removing of the correlated signals fail. We characterize the link dependence and propose a simultaneity graph (SG) to capture the effect of SIC. Then interference number is defined to measure the interference of a link. We show that scheduling over SG is NP-hard and the maximum interference number bounds the performance of a maximal greedy scheme. An independent set based greedy scheme is explored to efficiently construct a maximal feasible schedule. Moreover, with careful selection of link ordering, we present a scheduling scheme that improves the bound. The performance is evaluated by both simulations and measurements in a testbed. The throughput gain is on average 40% and up to 120% over IEEE 802.11. The complexity of SG is comparable with that of conflict graph, especially when the network size is not large.

Approximation Algorithms for Wireless Link Scheduling With SINR-Based Interference

In this paper, we consider the classical problem of link scheduling in wireless networks under an accurate interference model, in which correct packet reception at a receiver node depends on the signa-to-interference-plus-noise ratio (SINR). While most previous work on wireless networks has addressed the scheduling problem using simplistic graph-based or distance-based interference models, a few recent papers have investigated scheduling with SINR-based interference models. However, these papers have either used approximations to the SINR model or have ignored important aspects of the problem. We study the problem of wireless link scheduling under the exact SINR model and present the first known true approximation algorithms for transmission scheduling under the exact model. We also introduce an algorithm with a proven approximation bound with respect to the length of the optimal schedule under primary interference. As an aside, our study identifies a class of “difficult to schedule” links, which hinder the derivation of tighter approximation bounds. Furthermore, we characterize conditions under which scheduling under SINR-based interference is within a constant factor from optimal under primary interference, which implies that secondary interference only degrades performance by a constant factor in these situations.