Design and capacity performance analysis of wireless mesh network

Proceedings of: 5th International Conference on Mobile Technology, Applications, and Systems (Mobility 2008), (September 10-12, 2008), Yilan (Taiwan)From the network operator’s point of view, the high CAPEX/OPEX cost resulting from fixed/wired backhaul links can be inhibitive to successful deployment of broadband wireless services. The emerging wireless mesh network (WMN) technology is seen as one of the potential solutions which may reduce wired backhaul dependency through multihop transmission. Despite the advantages, many remain sceptical on WMN’s network capacity and scalability performances particularly when the user density is high. This paper provides an insight on the best possible upper-bound capacity performance of WMN, taking into consideration three key design parameters namely 1) Percentage of wired backhaul points per network, 2) Mesh-to-Access Link-Rate Ratio (R) and 3) Number of radio interfaces per mesh node including hybrid radio options. These design options are compared and contrasted with different deployment densities. The results generally show that the higher the number of backhaul points, the higher the effective access capacity available to mesh node and hence user domain. Increasing the R and the number of radio per mesh node are two alternative means to push up the effective access capacity per mesh node without increasing the number of wired backhaul points. This is most significant in multi radio system where about 80% of the backhaul points can be eliminated with R= 3 in order to maintain effective access capacity close to full rate (Capacity, C=1) per mesh node. It is also found that 50% of the backhaul points can be eliminated with R=2 for all radio options (except for the pure single radio case).European Community's Seventh Framework ProgramThis work was partially funded by the European Commission within the 7th Framework Program in the context of the ICT project CARMEN (Grant Agreement No. 214994) http://www.ict-carmen.eu

Applications and case studies in oil refineries

The widespread adoption of wireless systems for industrial automation calls for the development of efficient tools for virtual planning of network deployments similarly as done for conventional Fieldbus and wired systems. In industrial sites the radio signal propagation is subject to blockage due to highly dense metallic structures. Network planning should therefore account for the number and the density of the 3D obstructions surrounding each link. In this paper we address the problem of wireless node deployment in wireless industrial networks, with special focus on WirelessHART IEC 62591 and ISA SP100 IEC 62734 standards. The goal is to optimize the network connectivity and develop an effective tool that can work in complex industrial sites characterized by severe obstructions. The proposed node deployment approach is validated through a case study in an oil refinery environment. It includes an ad-hoc simulation environment (RFSim tool) that implements the proposed network planning approach using 2D models of the plant, providing connectivity information based on user-defined deployment configurations. Simulation results obtained using the proposed simulation environment were validated by on-site measurements

In defense of wireless carrier sense

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references.Carrier sense, or clear channel assessment (CCA), is widely used in wireless medium access control (MAC) protocols as the means to arbitrate access and regulate concurrency, striking a balance between interference protection and spatial reuse. Criticized widely in the literature, carrier sense has been subject to many replacement attempts with sophisticated and complex alternatives, yet it remains extremely popular. Is the search for a superior alternative justified? In this thesis, we develop a physically motivated theoretical model for average case carrier sense behavior in the two-sender case, based upon radio propagation theory and Shannon capacity. We argue from our model that common notions about carrier sense, such as the hidden and exposed terminal phenomena, are inherently misleading in the context of adaptive bitrate, casting in black and white terms effects that often cause only mild reduction in throughput. The frequency of severe misbehavior is low. We also demonstrate that it is possible to choose a fixed sense threshold which performs well across a wide range of scenarios, in large part due to the role of the noise floor. The noise floor has a significant effect on fairness as well. Using our model, we show that, when implemented well, average-case carrier sense performance is surprisingly close to optimal. We conclude with experimental results from our indoor 802.11 testbed, which corroborate these claims.by Micah, Z. Brodsky.S.M

Bounding the Practical Error of Path Loss Models

We seek to provide practical lower bounds on the prediction accuracy of path loss models. We describe and implement 30 propagation models of varying popularity that have been proposed over the last 70 years. Our analysis is performed using a large corpus of measurements collected on production networks operating in the 2.4 GHz ISM, 5.8 GHz UNII, and 900 MHz ISM bands in a diverse set of rural and urban environments. We find that the landscape of path loss models is precarious: typical best-case performance accuracy of these models is on the order of 12–15 dB root mean square error (RMSE) and in practice it can be much worse. Models that can be tuned with measurements and explicit data fitting approaches enable a reduction in RMSE to 8-9 dB. These bounds on modeling error appear to be relatively constant, even in differing environments and at differing frequencies. Based on our findings, we recommend the use of a few well-accepted and well-performing standard models in scenarios where a priori predictions are needed and argue for the use of well-validated, measurement-driven methods whenever possible

Topology and interference analysis in macrocellular environment

In the present day, mobile based data services have become increasingly popular among end users and businesses and thus considered as one of the important issues in the telecommunication network, because of its high demand. The telecommunication industry is continuously striving to fulfil this demand in a cost-efficient manner. Fundamentally, the performance of a mobile communication network is constrained by the propagation environment and technical capabilities of the network equipment. The target of radio network engineers is to design and deploy a mobile network that provides effective coverage and capacity solution with a profitable implementation cost. In order to reach this target, careful examination of radio network planning and choosing the right tools are the key methods. Network densification is considered as a feasible evolutionary pathway to fulfil the exponentially increasing data capacity demand in mobile networks. The objective of this thesis work is to study and analyse the densification of classical macrocellular network, which is still the dominant form of deployment worldwide. The analysis is based on deep ray-tracing based propagation simulations in the outdoor and indoor environment, and considers two key performance metrics; cell spectral efficiency and area spectral efficiency. For analysing the impact of network densification, different cell densities, obtained from varying the inter-site distances are considered. Furthermore, the network is assumed to be operating in a full load condition; an extreme condition in which the base stations are transmitting at full power. From the simulations, it has been illustrated that as a result of densifying the network, the inter-cell interference increases, which reduce the achievable cell spectral efficiency. The system capacity, on the other hand, is shown to improve due to the increase in the area spectral efficiency, as a result of high-frequency re-use, in the outdoor settings. Nevertheless, it is observed that the densification of macrocellular network experience inefficiency in the indoor environment; mainly arising from coverage limitation due to extreme antenna tilt angles. This calls for sophisticated methods such as base station coordination or inter-cell interference cancellation technique to be employed for future cellular network. For fulfilling the indoor capacity demand in a cost-efficient manner, the operators will be required to deploy dedicated indoor small cells based solutions

Development and evaluation of advanced traveler information system (ATIS) using vehicle-to-vehicle (V2V) communication system

This research develops and evaluates an Advanced Traveler Information System (ATIS) model using a Vehicle-to-Vehicle (V2V) communication system (referred to as the GATIS-V2V model) with the off-the-shelf microscopic simulation model, VISSIM. The GATIS-V2V model is tested on notional small traffic networks (non-signalized and signalized) and a 6X6 typical urban grid network (signalized traffic network). The GATIS-V2V model consists of three key modules: vehicle communication, on-board travel time database management, and a Dynamic Route Guidance System (DRGS). In addition, the system performance has been enhanced by applying three complementary functions: Autonomous Automatic Incident Detection (AAID), a minimum sample size algorithm, and a simple driver behavior model. To select appropriate parameter ranges for the complementary functions a sensitivity analysis has been conducted. The GATIS-V2V performance has been investigated relative to three underlying system parameters: traffic flow, communication radio range, and penetration ratio of participating vehicles. Lastly, the enhanced GATIS-V2V model is compared with the centralized traffic information system. This research found that the enhanced GATIS-V2V model outperforms the basic model in terms of travel time savings and produces more consistent and robust system output under non-recurrent traffic states (i.e., traffic incident) in the simple traffic network. This research also identified that the traffic incident detection time and driver's route choice rule are the most crucial factors influencing the system performance. As expected, as traffic flow and penetration ratio increase, the system becomes more efficient, with non-participating vehicles also benefiting from the re-routing of participating vehicles. The communication radio ranges considered were found not to significantly influence system operations in the studied traffic network. Finally, it is found that the decentralized GATIS-V2V model has similar performance to the centralized model even under low flow, short radio range, and low penetration ratio cases. This implies that a dynamic infrastructure-based traffic information system could replace a fixed infrastructure-based traffic information system, allowing for considerable savings in fixed costs and ready expansion of the system off of the main network corridors.Ph.D.Committee Chair: Hunter, Michael; Committee Member: Fujimoto, Richard; Committee Member: Guensler, Randall; Committee Member: Leonard, John; Committee Member: Meyer, Michae

Geostatistical Techniques for Practical Wireless Network Coverage Mapping

The problem of mapping the extent of “usable” coverage of an existing wireless network is important in a large number of applications, including communicating the abilities of the network to users, identifying coverage gaps and planning expansion, discovering opportunities for spectrum reuse, and determining possible sources of interference with other networks. This thesis addresses fundamental but unsolved problems of measurement-based wireless coverage mapping: where should measurements be made, how many are necessary, and what can be said about the coverage at points that have not been measured. To address these problems, this thesis advocates a geostatistical approach using optimized spatial sampling and ordinary Kriging. A complete system for coverage mapping is developed that systematically addresses measurement, sampling, spatial modeling, interpolation, and visualization. This geostatistical method is able to produce more accurate and robust coverage maps than the current state of the art methods, and is able to discover coverage holes as effectively as dedicated heuristic methods using a small number of measurements. Several important practical extensions are investigated: applying these methods to drive-test measurements which have been resampled to alleviate effects from sampling bias, and crowd-sourced coverage mapping applications where volunteer-collected measurements may be sparse or infrequent. The resulting maps can then be refined iteratively, and updated systematically over time using an optimized iterative sampling scheme. An extensive validation is performed using measurements of production WiFi, WiMax, GSM, and LTE networks in representative urban and suburban outdoor environments