Network-wide Throughput Research Articles

On the evaluation and selection of network-level traffic control policies: Perimeter control, TUC, and their combination

Perimeter control (PC) of urban traffic networks can be effective in increasing network-wide efficiency. PC operates on the border of a protected region of a traffic network. Most studies thus far considered fixed-time plans for the inner part of these regions. A few studies have shown that combining PC with locally actuated or decentralized traffic control systems may have positive effects on traffic performance, including better-defined Network Macroscopic Fundamental Diagrams (NMFDs), increased network throughput, and reduced delays. The Traffic-responsive Urban Control (TUC) is a real-time network-wide traffic control system with particular design characteristics, such as the balancing of link’s occupancies and an inherent gating feature. These characteristics suggest that TUC may enhance the traffic network performance when combined with PC whilst improving the resulting NMFDs and network throughput and delays. In this work, we investigate the effect of feedback perimeter control (FPC), TUC, and their combination on the NMFD and on the traffic conditions of general traffic and public transport in the microsimulation of a realistic model of the Christchurch Central Business District in New Zealand. We perform a thorough investigation of practical aspects of both control strategies and their combination, including parameter tuning and infrastructure requirements, and how they may affect the control system choice. Results show higher throughput and less hysteresis on the NMFDs, particularly when TUC is involved. PC provides benefits concentrated in the protected region which can greatly benefit public transportation if there is an overlap with the transit network. The combination of TUC and FPC boosts network-wide throughput.

Network-Wide Throughput Optimization for Highway Vehicle-To-Vehicle Communications

This letter analyzes the meta-distribution of the transmission success probability (TSP) for vehicular networks based on a one-dimensional Poisson point process (PPP). We also propose a method to maximize the throughput across the vehicular network. Compared to the conventional spatial average performance assessment, the meta-distribution reveals the fraction of vehicles that operate at a target success rate of transmission across the highway. To this end, we propose a per-vehicle rate selection scheme to keep a target quality of service (QoS) level for all vehicles. The results reveal that operating at the spatially-averaged maximum throughput may lead to excessive variation in the performance of individual vehicles. However, with the proposed meta-distribution-aware rate selection scheme, the throughput variation among the vehicles can be significantly reduced (e.g., up to a 60 % reduction).

Scalable Load Balancing and Flow Management in Dynamic Heterogeneous Wireless Networks

The number of connected devices has reached 18 billion in 2017 and this will nearly double by 2022, while also new wireless communication technologies become available. Since these modern devices support the use of multiple communication technologies, efforts have been made to enable simultaneous usage and handovers between the different technologies for these devices. However, existing solutions are missing the intelligence to decide on fine-grained (e.g. flow or packet level) optimizations that can drastically enhance the network’s performance (e.g., throughput) and user experience. To this extent, we present a multi-technology flow-management load balancing approach for heterogeneous wireless networks that dynamically re-routes traffic through heterogeneous networks, in order to maximize the global throughput. This dynamic approach can be deployed on top of existing solutions and takes into account the specific characteristics of the different technologies, as well as station mobility. We both present a mathematical problem formulation and a heuristic that ensures practical scalability. We demonstrate the heuristic’s ability to increase the network-wide throughput by more than 100% across a variety of scenarios and scalability up to 10,000 devices.

Efficient Traffic Load-Balancing via Incremental Expansion of Routing Choices

Routing policies play a major role in the performance of communication networks. Backpressure-based adaptive routing algorithms where traffic is load balanced along different routing paths on a per-packet basis have been studied extensively in the literature. Although backpressure-based algorithms have been shown to be networkwide throughput optimal, they typically have poor delay performance under light or moderate loads, because packets may be sent over unnecessarily long routes. Further, backpressure-based algorithms have required every node to compute differential backlogs for every per-destination queue with the corresponding per-destination queue at every adjacent node, which is expensive given the large number of possible pairwise differential backlogs between neighbor nodes. In this article, we propose new backpressure-based adaptive routing algorithms that only use shortest-path routes to destinations when they are sufficient to accommodate the given traffic load, but the proposed algorithms will incrementally expand routing choices as needed to accommodate increasing traffic loads. We show analytically by means of fluid analysis that the proposed algorithms retain networkwide throughput optimality, and we show empirically by means of simulations that our proposed algorithms provide substantial improvements in delay performance. Our evaluations further show that, in practice, our approach dramatically reduces the number of pairwise differential backlogs that have to be computed and the amount of corresponding backlog information that has to be exchanged, because routing choices are only incrementally expanded as needed.

ORCHESTRA: Enabling Inter-Technology Network Management in Heterogeneous Wireless Networks

Modern connected devices are equipped with the ability to connect to the Internet using a variety of different wireless network technologies. Current network management solutions fail to provide a fine-grained, coordinated, and transparent answer to this heterogeneity, while the lower layers of the OSI stack simply ignore it by providing full separation of layers. To address this, we propose the ORCHESTRA framework to manage the different devices in heterogeneous wireless networks and introduce capabilities such as packet-level dynamic and intelligent handovers (both inter- and intra-technology), load balancing, replication, and scheduling. The framework is the first of its kind in providing a fine-grained packet-level control across different technologies by introducing a fully transparent virtual medium access control layer and an software-defined networking-like controller with global intelligence. Furthermore, we present a novel optimization problem formulation that can be solved to optimally configure the network. We provide a thorough evaluation through simulations and a prototype implementation. We show that our framework enables, in a real-life setting, transparent and real-time inter-technology handovers and that coordinated load balancing can double the network-wide throughput across different scenarios.

Full-Duplex MIMO Radios: A Greener Networking Solution

Relative to half-duplex (HD) radios, in-band full-duplex (FD) radios have the potential to double a link’s capacity . However, such gain may not necessarily extend to the network-wide throughput , which may actually degrade under FD radios due to excessive network interference. This paper identifies the unique advantages of FD radios and leverages multi-input multioutput (MIMO) communications to translate the FD spectral efficiency gain at the PHY level to the throughput and power efficiency gain at the network layer. We first derive sufficient conditions under which FD-MIMO radios can asymptotically double the throughput of the same network of HD-MIMO ones. Specifically, if a network of $2{N}$ HD radios ( ${N}$ links) can achieve a total throughput of dN bps (i.e., ${d}$ bps per link), then an FD-capable network with the same number of links and network/channel realization can achieve $2{N}$ ( $\textit{d}-1$ ) bps [i.e., ( ${d} -1$ ) bps per direction of a bidirectional link]. To leverage this theoretical gain, we exploit the “spatial signature” readily captured in the network interference to design an MAC protocol that allows multiple FD links to concurrently communicate while adapting their radiation patterns to minimize network interference. The protocol does not require any feedback nor coordination among nodes. Extensive simulations show that the proposed MAC design dramatically outperforms traditional CSMA-based and the non-orthogonal multiple access protocols with either HD or FD radios with respect to both throughput and energy efficiency. Note that in the literature, network interference is often treated as colored noise that then gets whiten during the signal detection process. However, through our MAC protocol, we emphasize that, unlike random noise, network interference has its own structure that can be “mined” for “intelligence” to better align the transceiver’s signal.

Post-CCA and Reinforcement Learning Based Bandwidth Adaptation in 802.11ac Networks

The new 802.11ac standard aims at achieving Gbps data throughput for individual users by exploiting enhanced physical-layer features, such as higher modulation levels, Multiple Input Multiple Output (MIMO), and wider bandwidths. However, the heterogeneity of bandwidth in a network can cause asymmetric interferences in which certain transmissions cannot be sensed by some other nodes. As a result, the conventional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) may not work well in 802.11ac networks. We call this the Hidden Channel (HC) problem, which is shown to be real via experiments with USRP and WARP boards. To solve this problem, we propose bandwidth adaptation based on post-CCA , which is a clear channel assessment (CCA) procedure performed after completing a transmission. Post-CCA in wireless networks helps mimic the CSMA with Collision Detection (CSMA/CD) mechanism in the wired Ethernet, thus enhancing channel assessment capability. Using post-CCA, we propose Post-CCA based Bandwidth Adaptation (PoBA) that alters bandwidth and channel configuration dynamically by applying a reinforcement learning mechanism. Post-CCA and PoBA do not require any hardware modification and are also compliant with the 802.11 standards. PoBA is shown via simulation to increase network-wide throughput, channel utilization and fairness, and also lower packet error probability.

NOMA in Downlink SDMA With Limited Feedback: Performance Analysis and Optimization

In this paper, the performance of non-orthogonal multiple access (NOMA) is investigated and optimized in a downlink space division multiple access network with a multi-antenna base station and randomly deployed users, under a general channel state information (CSI) limited feedback framework. We first propose a dynamic user scheduling and grouping strategy by leveraging limited feedback. Based on that, an analytical framework is proposed to obtain the outage probability of the network in closed form. The diversity order and the impacts of the number of feedback bits on the outage performance of NOMA are analyzed. Furthermore, the net throughput, which captures the network-wide throughput with the uplink feedback cost considered, is maximized by optimizing the number of feedback bits. Numerical results are demonstrated to verify our analytical findings and show that different from the perfect CSI case, there always exists a performance floor of outage probability in the considered network due to limited feedback. Moreover, the optimal number of feedback bits for net throughput maximization increases as the channel coherence time becomes longer.

Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks

In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relay’s operation setup to maximize the network-wide throughput while, simultaneously, we keep the relay’s queue stable and lower the relay’s receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relay’s receiver only.

Safeguarding Decentralized Wireless Networks Using Full-Duplex Jamming Receivers

In this paper, we study the benefits of full-duplex (FD) receiver jamming in enhancing the physical-layer security of a two-tier decentralized wireless network with each tier deployed with a large number of pairs of a single-antenna transmitter and a multi-antenna receiver. In the underlying tier, the transmitter sends unclassified information, and the receiver works in the halfduplex (HD) mode receiving the desired signal. In the overlaid tier, the transmitter deliveries confidential information in the presence of randomly located eavesdroppers, and the receiver works in the FD mode radiating jamming signals to confuse eavesdroppers and receiving the desired signal simultaneously. We provide a comprehensive performance analysis and network design under a stochastic geometry framework. Specifically, we consider the scenarios where each FD receiver uses single- and multi-antenna jamming, and analyze the connection probability and the secrecy outage probability of a typical FD receiver by providing accurate expressions and more tractable approximations for the two metrics. We further determine the optimal deployment of the FD-mode tier in order to maximize networkwide secrecy throughput subject to constraints including the given dual probabilities and the network-wide throughput of the HD-mode tier. Numerical results are demonstrated to verify our theoretical findings, and show that network-wide secrecy throughput is significantly improved by properly deploying the FD-mode tier.

WhiteFi Infostation: Engineering Vehicular Media Streaming With Geolocation Database

The TV white spaces (TVWS) enabled infostation has received significant attention due to its wide area coverage for cost-effective and media-rich content dissemination. In this paper, we engineer WhiteFi infostation, which is dedicated for Internet-based vehicular media streaming by leveraging geolocation database. After demonstrating the empirical observations of unique TVWS features and analyzing the real-world TVWS data collected from geolocation database, we first propose an optimal TVWS network planning to deploy WhiteFi infostation with the objective of maximizing network-wide throughput. The proposed TVWS network planning jointly considers the multi-radio configuration and the channel-power tradeoff, which can be realized by decentralized Markov approximation. Furthermore, we introduce a location-aware contention-free multi-polling access scheduling scheme for vehicular media streaming, which considered both the realistic vehicular applications and dynamics of wireless channel conditions. Through extensive simulations with real-world empirical TVWS data and urban vehicular traces, we demonstrate that our WhiteFi infostation solution can well support both the delay-sensitive and delay-tolerant vehicular media streaming services.

SDN-Based Virtual Machine Management for Cloud Data Centers

Software-defined networking (SDN) is an emerging paradigm to logically centralize the network control plane and automate the configuration of individual network elements. At the same time, in cloud data centers (DCs), although network and server resources are collocated and managed by a single administrative entity, disjoint control mechanisms are used for their respective management. In this paper, we propose a unified server-network resource management for such converged information and communication technology (ICT) environments. We present a SDN-based orchestration framework for live virtual machine (VM) management that exploits temporal network information to migrate VMs and minimize the network-wide communication cost of the resulting traffic dynamics. A prototype implementation is presented, and a cloud DC testbed is used to evaluate the impact of diverse orchestration algorithms. Our live VM management has been shown to reduce the network-wide communication cost, especially for the high-cost and congestion-prone core and aggregation layers of the DC. Our results show an increase in network-wide throughput by over six times, as well as over 70% communication cost reduction by migrating less than 50% of the VMs.

A Channel Allocation Algorithm for Reducing the Channel Sensing/Reserving Asymmetry in 802.11ac Networks

The major goal of IEEE 802.11ac is to provide very high throughput (VHT) performance while at the same time guaranteeing backward compatibility. To achieve this goal, 802.11ac adopts the channel bonding technique that makes use of multiple 20 MHz channels in 5 GHz band. Due to the heterogeneity of bandwidth that each device exploits, and the fixed total transmission power in the standards, a problem called `Hidden Channel' arises. In this paper, we first analyze the problem and show how the contention parameters and transmission time affect collision probability and fairness in some deployment scenarios. Then, we propose a heuristic channel allocation algorithm that aims to avoid such problematic situations effectively. Through simulations, we demonstrate that our proposed channel allocation algorithm lowers the packet error rate (PER) compared to uncoordinated and received signal strength indicator(RSSI) based allocation schemes and increases the network-wide throughput as well as the throughput of a station that experiences poor performance. This implies improved fairness performance among transmission pairs with various channel bandwidths.

On relay selection and power allocation in cooperative free-space optical networks

Drawing increasing attention, free-space optics (FSO) is a cost-effective technology to support data intensive communications. Cooperative diversity is considered to be an effective means for combating weather turbulence in FSO networks. In this paper, we consider the challenging problem of joint relay selection and power allocation in FSO networks. The objective was to maximize the FSO network-wide throughput under constraints of a given power budget and a limited number of FSO transceivers. The problem is formulated as a mixed integer nonlinear programming (MINLP) problem, which is NP-hard. We first adopt the reformulation-linearization technique (RLT) to derive an upper bound for the original MINLP problem. Due to the relaxation, the solutions obtained from RLT are infeasible. We then propose both centralized and distributed algorithms using bipartite matching and convex optimization to obtain highly competitive solutions. The proposed algorithms are shown to outperform the noncooperative scheme and an existing relay selection protocol with considerable gains through simulations.

Network Coding Based Link Scheduling for QoS Provisioning in Multi-radio and Multi-channel Wireless Mesh Networks

This paper addresses Quality-of-Service (QoS) improvement in wireless mesh networks (WMNs) with multi-radio multi-channel by applying a novel network coding technique. It is known that network coding over wired networks enables connections at rates that cannot be achieved by traditional routings. However, the properties of wireless networks (e.g., omnidirectional transmissions, destructive interference, single transceiver per node, finite energy) modify the formulation of network coding and deviate from the classical network coding approach used in wired networks. In this paper, we investigate the problem of network-wide data transmission under the consideration of QoS requirements (namely packet delivery ratio, packet delay) over multi-radio and multi-channel WMNs. To solve this problem, we first introduce a network coding method, namely COPE, which is used to increase network-wide throughput for unicast wireless networks, and then present an Integer Linear Programming formulation of a given multi-radio and multi-channel WMN for addressing network coding traffic, routing, QoS requirements and scheduling optimizations. The proposed analytical formulation increases the network-wide throughput while satisfying the generalized QoS requirements by combining network coding strategy and interference free schedules. Our evaluations both in 16-node graph topology and 32-node random topology network show that a route selection strategy that is aware of network coding leads to higher in end-to-end throughput when compared to coding-oblivious routing strategies.

When Channel Bonding is Beneficial for Opportunistic Spectrum Access Networks

Transmission over multiple frequency bands combined into one logical channel speeds up data transfer for wireless networks. On the other hand, the allocation of multiple channels to a single user decreases the probability of finding a free logical channel for new connections, which may result in a network-wide throughput loss. While this relationship has been studied experimentally, especially in the WLAN configuration, little is known on how to analytically model such phenomena. With the advent of Opportunistic Spectrum Access (OSA) networks, it is even more important to understand the circumstances in which it is beneficial to bond channels occupied by primary users with dynamic duty cycle patterns. In this paper we propose an analytical framework which allows the investigation of the average channel throughput at the medium access control layer for OSA networks with channel bonding enabled. We show that channel bonding is generally beneficial, though the extent of the benefits depend on the features of the OSA network, including OSA network size and the total number of channels available for bonding. In addition, we show that performance benefits can be realized by adaptively changing the number of bonded channels depending on network conditions. Finally, we evaluate channel bonding considering physical layer constraints, i.e. throughput reduction compared to the theoretical throughput of a single virtual channel due to a transmission power limit for any bonding size.

Multi-sector multi-range control for self-organizing wireless networks

In this paper, we propose a distributed multi-sector multi-range (MSMR) control algorithm for supporting self-organizing wireless networks. The algorithm enables us to reduce the unnecessary coverage with fine-tuned range control and also to increase the network-wide capacity with enhanced spatial reusability. The proposed algorithm discovers neighboring nodes within the maximum transmission range at every node, divides its transmission area into multiple non-overlapping angular sectors of a given degree, chooses the home sector for each neighboring node according to its relative position, and constructs a spanning subgraph per sector by determining appropriate transmission range to maintain connectivity. Since the range control influences on network connectivity directly, we prove in the first place that the proposed algorithm preserves both network-wide and local connectivity as far as both connectivity exist in the network that uses the maximum transmission range. In order to investigate the performance of the proposed algorithm, we implemented it in the ns-2 simulator, and performed an extensive set of simulation study in comparison with other transmission range control schemes. The simulation results indicate that the proposed scheme is superior to other schemes with respect to the network-wide throughput and its normalized value per energy in various simulation configurations. In specific, the algorithm achieves minimally one order and maximally two orders of magnitude improvement in those performance evaluations. The improvement becomes more salient as the number of nodes increases and is immune to traffic type, network size, node distribution, or node density.

Fast performance assessment of IEEE 802.11-based wireless networks

In this paper, we introduce a brand new analytical perspective for analyzing and evaluating the IEEE 802.11-based networks. We identify a tightly-coupled relationship between the number of contending nodes and their contention window sizes in the networks. Based on the relationship, we propose a downsizing model for reducing the computational complexity and for improving the simulation performance in the evaluation of the IEEE 802.11-based networks. We first formally prove that the proposed model preserves the operational characteristics of the original networks in their downsized networks through well-known analytical frameworks, such as the models proposed by Bianchi (2000) [7], Calí et al. (2000) [2], and Hu et al. (2006) [8]. We then demonstrate that the proposed model speeds up the simulation by maximally two orders of magnitude. Even though the simulation shows some difference between the results from an original network and those in its corresponding downsized networks in a wide range of network sizes and traffic patterns, the difference is acceptable since it has minimal values of 1% in most cases and maximum values of 10% in a very few cases. We also present the effectiveness of both the downsizing model and the downsizing-model-based simulation in comparison with other performance models and simulation techniques. As the size and complexity of wireless networks are increasing nowadays, we vision that the new proposed model will be of great advantage in conducting fast and accurate packet-level wireless simulations, as well as being a helpful tool for performing the numerically tractable theoretical studies for extensive performance evaluations, such as determining the network-wide throughput or end-to-end delays.

System Design and Throughput Analysis for Multihop Relaying in Cellular Systems

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Wireless multihop relaying can provide a great improvement in systemwide throughput and coverage in a cellular system. However, since additional resources (time or frequency slots) and overhead are required to perform relaying, the addition of relays into a cellular system must be carefully designed for the system's specific geometry, topology, and propagation environment. Maximizing the benefit of multihop relaying requires that the medium access control (MAC) layer scheduler be aware of physical (PHY) layer conditions. Multihop relaying increases networkwide throughput by enabling spatial reuse within a cell and by significantly reducing the path loss on each hop. The most significant gain results from adding enough relays to create line-of-sight (LOS) paths on all relay hops. To assist with system design, we present a methodology of analyzing network throughput and area-averaged spectral efficiency for multihop relay-enhanced cellular systems, including cross-layer considerations. In addition, we describe a technique that may be used to determine spatial reuse schedules. In this paper, we use a realistic model and typical cellular scenarios to show how relaying can be used to improve coverage and throughput in a real-world system. </para>