Roberto Hincapie

Fair Bandwidth Allocation in Wireless Mesh Networks With Cognitive Radios

Wireless mesh networks (WMNs) are considered to be an economical solution for last-mile broadband Internet access. In this paper, we study end-to-end bandwidth allocation in WMNs with cognitive radios, which involves routing, scheduling, and spectrum allocation. To achieve a good tradeoff between fairness and throughput, we define two fair bandwidth-allocation problems based on a simple max-min fairness model and the well-known lexicographical max-min (LMM) fairness model, respectively. We present linear programming (LP)-based optimal and heuristic algorithms to solve both problems. Extensive simulation results are presented to justify the effectiveness of the proposed algorithms.

QoS Routing in Wireless Mesh Networks with Cognitive Radios

In this paper, we study QoS routing in wireless mesh networks with cognitive radios, which involves route selection, channel allocation and scheduling. It turns out to be a hard problem because of the impact of interference and channel heterogeneity. We formally model it as an optimization problem and present an integer linear programming (ILP) formulation to provide optimal solutions. We then present a distributed routing protocol which can select a route and allocate resources for a connection request to satisfy its end-to-end bandwidth requirement. NS2 based simulation results show the performance given by our protocol is close to that of the optimal solution.

WiMAX channel: PHY model in network simulator 2

The IEEE 802.16 standard, also known as WiMAX is oriented to fixed broadband wireless metropolitan access. This work presents a novel proposal for the PHY layer and propagation model that allows a faster and more detailed the link level simulations execution. This paper describes the development process for the model and the implementation details in NS2 (Network Simulator NS2 v 2.8) for PMP (point multi point) topologies. We show the parameters used, the channel model, the PHY layer model and the SER (Symbol Error Rate) calculation method. We also present typical simulation scenarios and the results obtained.

Remote locations coverage analysis with wireless mesh networks based on IEEE 802.16 Standard

This article analyzes the wireless coverage problem of remote regions with low user density and propagation problems due to irregular terrain and high tree density. The use of a wireless mesh network is proposed as a solution where user data is transmitted directly to a base station when it is possible or relayed through other nodes in a multi-hop manner when there is not a direct link. The mesh topology uses short links with higher capacity instead of long links with low capacity. We analyze radio propagation and MAC protocols, including random sources, queues, and packet delays. The article is based on the coverage of a realistic rural region near Medellin, a mid size city in Colombia, and it shows that a wireless mesh network is an alternative to a typical cell based solution. It includes propagation analysis and MAC protocol behavior, so it is not limited to a radio coverage problem but also traffic, scheduling, and routing analysis

Wakeup Scheduling in Roadside Directional Sensor Networks

In this paper, we focus on a roadside directional sensor network where sensors with directional Field Of Views (FOVs) are placed along a roadway. We study the problem of wakeup scheduling, with the objective of maximizing network lifetime under the constraint that full coverage and network connectivity are maintained at all times. First, we present centralized polynomial time algorithms to optimally solve the problems of scheduling sensor nodes with fixed sensing orientations. Moreover, an effective heuristic algorithm is proposed to solve the problem of scheduling sensor nodes with variable sensing orientations. In addition, we also present distributed algorithms for both fixed and variable cases. Simulation results based on a roadway in the Yellowstone National Park have been presented to show the performance of the proposed algorithms.

Efficient Recovery Algorithms for Wireless Mesh Networks with Cognitive Radios

Cognitive radios allow unlicensed wireless users to access channels that are in the licensed spectrum bands. However, in a wireless network with cognitive radios, when a licensed user becomes active on a channel in a certain area, nodes and links that were using that channel must release it, which will cause traffic failures. Simple and effective recovery schemes are needed to re-allocate available resources for the failed traffic. In this paper, we study the failure recovery in wireless mesh networks with cognitive radios. We formally formulate the corresponding problems as integer linear programming problems. By solving them, we can obtain optimal solutions. Moreover, an efficient distributed heuristic algorithm is presented for fast recovery. Simulation results show that the performance given by our distributed algorithm is close to that of the optimal solutions.

ILP model for Greenfield WDM PON network design based on physical layer constraints

One of the main issues in the WDM PON networks design is the optimal dimensioning of the network. The network size usually depends on the traffic demand and the user density, taking in to account the active and passive equipment capacity and some physical layer constraints like the attenuation in the optical path. However, some physical layer limitations related with signal transmission in an optical fiber become more relevant in a WDM transmission and when operating at very high data rates, like 10 Gbps or beyond. In this paper we propose a novel physical layer restrictions based integer linear programming (ILP) model for greenfield next generation 10 Gbps WDM PON network design. The results of the model are validated by means of computational techniques. The proposed ILP model takes into account not only the attenuation of the signal in the optical path but also, through the use of the data obtained by simulation software. We take in to account the restrictions imposed by other phenomena like dispersion, cross talk and some non linear effects typically present in a dense WDM optical transmission.

Optimal dimensioning of FiWi networks over advanced metering infrastructure for the smart grid

In this paper, we propose a hybrid wireless mesh network infrastructure which connects the smart meters of each consumer with the data aggregation points (DAP). We suppose a set of smart meters that need to send information, and receive information from a central office on electrical enterprises, employing the meter data management system (MDMS), and so forming the advanced metering infrastructure (AMI) stage of smart grids. We consider a multi-hop system, where information is routed through several nodes which act as DAP. Wireless mesh networks are known to extend coverage and increase deployment efficiency, so they could be an alternative for the connection between Home Area Network (HAN) and the Neighborhood Area Network (NAN). However, the NAN data must be send through wider area cabled networks to Metropolitan Area Network (MAN), and based on the WDM-PON architecture. We consider a novel planning model which simultaneously solves both architectures and analyses the overall performance based on average packet delay.

FiWi Network Planning for Smart Metering Based on Multistage Stochastic Programming

This article presents a novel model of mixed integer linear programming (MILP) to conduct network planning (Fiber-Wireless-FiWi) that along a timeline space facilitates growth, expansion and scalability of resources involved in communications network, traditionally used in cellular telephony, and is possible that extends as a multiservice network to provide smart metering, as is the case in Advanced Metering Infrastructure (AMI) in Smart Grid, thus optimizing their infrastructure and minimizing investment costs. This paper proposes a hybrid architecture (fiber optic-wireless networks) with realistic approaches to planning and scalability considerations under scenarios that present uncertainty in the evolution of consumer demand, both for primary users of cell phone and smart metering as a secondary user. We propose a model for network planning based on Multistage Stochastic Programming (MSP) with a growth in demand for stochastic users and FiWi networks scalability through expected maximum benefit for their investment. The approach of this article shows that it is possible to design real FiWi large-scale networks under a cost-effective evolution considering a scheme appropriate growth in the timeline.

Optimization of multiple PON deployment costs and comparison between GPON, XGPON, NGPON2 and UDWDM PON

In this paper we propose an optimization framework for multiple deployment of PON in a wide region with very large number of users, with different bit rate demands, serviced by many central offices, as it may practically happen in a large city that plans a massive introduction of Fiber to the Home technologies using PON. We propose an algorithm called Optimal Topology Search (OTS), which is based on a set of heuristic approaches, capable of performing an optimal dimensioning of multiple PON deployments for a set of central offices (CO), including an optimal distribution of users among the CO. The set of heuristics integrated in OTS permit the efficient clustering of users for each CO, depending on their location and the bit rate demanded by them. It also permits the definition of optimal routes for optical cables and the allocation of branching devices. Taking into account hardware capacity restrictions and physical layer restrictions, we obtained solutions for different types of standardized PON technologies, like GPON, XGPON and NGPON2 as well as for future UDWDM-PON. We evaluate the optimal network deployment in a series of different minimum guaranteed bit rate demand scenarios, employing realistic maps of a large city in order to compare costs and portrait some reference points for deciding in which scenario a specific technology constitutes the best choice.