Smart antennas increase capacity of wireless systems by allowing channel reuse by several users i... more Smart antennas increase capacity of wireless systems by allowing channel reuse by several users in the same cell through space division multiple access (SDMA). Orthogonal Frequency Division Multiplexing (OFDM) creates additional challenges in beam-forming when the beams that can be formed are limited due to transceiver unit limitations. We investigate the impact of smart antennas on channel allocation and propose meaningful heuristics to form beams and assign subcarriers and transceivers to users. Numerical ...
Proceedings of the 2nd International Conference on Energy-Efficient Computing and Networking - e-Energy '11, 2011
Abstract The smart power grid harnesses information and communication technologies to enhance rel... more Abstract The smart power grid harnesses information and communication technologies to enhance reliability and enforce sensible use of energy through effective management of demand load. We envision a scenario with real-time communication between the grid operator and the consumers. The operator controller receives consumer power demand requests with different power requirements, durations, and deadlines by which they are to be activated. The objective of the operator is to devise a power demand task scheduling ...
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
In the last decade testbeds have been set-up to evaluate network protocols and algorithms under r... more In the last decade testbeds have been set-up to evaluate network protocols and algorithms under realistic settings. In order to draw solid conclusions about the corresponding experimental results, it is important for the experimenter to have a detailed view of the existing channel conditions. Moreover, especially in the context of non-RF-isolated wireless testbeds, where external interference severely impacts the resulting performance, the requirement of experimenters for accurate channel monitoring becomes a prerequisite. ...
Proceedings of the 6th ACM international workshop on Wireless network testbeds, experimental evaluation and characterization - WiNTECH '11, 2011
Abstract In the last decade testbeds have been set-up to evaluate network protocols and algorithm... more Abstract In the last decade testbeds have been set-up to evaluate network protocols and algorithms under realistic settings. Moreover, wireless sensors have lately been integrated into testbeds in order to simulate application scenarios for lowpower sensor networks, such as environment monitoring. Due to the fact that such scenarios are usually designed to run for a relatively long duration, long-term experiments are rarely executed, in order to avoid blocking of testbed facilities. Toward, this direction, we propose the NITOS Sensors Toolkit ...
2011 International Symposium of Modeling and Optimization of Mobile, Ad Hoc, and Wireless Networks, 2011
Abstract Efficient association of a station with the appropriate access point has always been a c... more Abstract Efficient association of a station with the appropriate access point has always been a challenging problem. The standard approach of considering only the Received Signal Strength, has recently been substituted by more efficient schemes that consider channel conditions, cell population etc. However, in spite of the large variety of approaches, several factors that determine to a large extent user throughput after association with an access point have been overlooked. In this work, we propose innovative metrics on which ...
2003 IEEE Wireless Communications and Networking, 2003. WCNC 2003., 2003
Abstract The use of smart antennas in extending coverage range and capacity of wireless networks ... more Abstract The use of smart antennas in extending coverage range and capacity of wireless networks dictates the employment of novel media access control protocols, with which the base station (BS) or access point (AP) provides access to users by learning their locations. We consider the class of protocols that employ beam forming and use contention-based or contention-free polling methods to locate users residing in or out of coverage range of the AP. Such protocols allow rapid media access and can be embedded in existing MAC ...
ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240), 2001
Abstract Wireless broadband access is an appealing solution to the projected trend towards reliab... more Abstract Wireless broadband access is an appealing solution to the projected trend towards reliable and easily deployable high-speed connections. In order to enhance system capacity and tolerate volatility of the wireless medium, sophisticated adaptation techniques are required. In this paper, we consider the problem of efficient resource allocation with adaptive modulation techniques in a multi-carrier wireless cellular system. We identify the inherent complexity of the problem and propose a heuristic algorithm for carrier frequency ...
GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 2001
Abstract Wireless broadband access is becoming increasingly popular in the telecommunications mar... more Abstract Wireless broadband access is becoming increasingly popular in the telecommunications market due to the projected demand for high data-rate connections. Given the inherent volatility of the wireless channel, the accurate estimation of channel conditions and the adoption of sophisticated adaptation techniques is required, so that transmission parameters are selected based on link quality, and user throughput is maximized. We consider a simple wireless link monitoring method, which is based on ...
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
A fundamental unresolved problem in wireless networks is that of distinguishing packet errors tha... more A fundamental unresolved problem in wireless networks is that of distinguishing packet errors that are caused by deteriorated link conditions and noise, from errors that occur due to packet collisions. In this paper, we develop advanced algorithms based on Cyclic Redundancy Check (CRC)[10] that solve this problem. Specifically, our innovation is that we form multiple CRCs, each of which is responsible for a different segment in a packet. The CRCs are appended after each segment. In this way, we can essentially visualize the ...
2013 IEEE International Conference on Communications (ICC), 2013
ABSTRACT This paper explores the problem of virtual machine (VM) allocation in a network of cloud... more ABSTRACT This paper explores the problem of virtual machine (VM) allocation in a network of cloud server facilities which are deployed in different geographical areas. Each cloud server facility is connected to the conventional power grid network and in addition it is supported by an attached renewable energy source (RES). We address the problem of energy-efficient task allocation in the system in the presence of a time-varying grid energy price and the unpredictability and time variation of provisioned power by the RES. The objective is to reduce the total cost of power consumption for the operator. The key idea is to match the VM load with the RES provisioned power. Each request for a task to be executed in the cloud is associated with a VM request with certain resource requirements and a deadline by which it needs to be completed. The cloud provider has to create a VM with the resource requirements of the request and to execute the VM before the deadline. We propose an online algorithm with given look-ahead horizon, in which the grid power prices and patterns of output power of the RESs are known a priori and we compare it with a greedy online algorithm. Numerical results on real traces of cloud traffic and renewable source generation patterns are encouraging in terms of the performance of our techniques and motivate further research on the topic.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
The gradually growing demand for experimentation of protocols designed for wireless networks in r... more The gradually growing demand for experimentation of protocols designed for wireless networks in real environments has resulted in the development of experimental network facilities (testbeds). Most currently deployed testbeds have been designed so as to offer services to experimenters that lie within the testbed's premises, thus limiting the accessibility to external users. The requirement for multi-user access of network resources has led several large-scale testbeds to provide remote access services to certified experimenters. ...
Smart antennas increase capacity of wireless systems by allowing channel reuse by several users i... more Smart antennas increase capacity of wireless systems by allowing channel reuse by several users in the same cell through space division multiple access (SDMA). Orthogonal Frequency Division Multiplexing (OFDM) creates additional challenges in beam-forming when the beams that can be formed are limited due to transceiver unit limitations. We investigate the impact of smart antennas on channel allocation and propose meaningful heuristics to form beams and assign subcarriers and transceivers to users. Numerical ...
Proceedings of the 2nd International Conference on Energy-Efficient Computing and Networking - e-Energy '11, 2011
Abstract The smart power grid harnesses information and communication technologies to enhance rel... more Abstract The smart power grid harnesses information and communication technologies to enhance reliability and enforce sensible use of energy through effective management of demand load. We envision a scenario with real-time communication between the grid operator and the consumers. The operator controller receives consumer power demand requests with different power requirements, durations, and deadlines by which they are to be activated. The objective of the operator is to devise a power demand task scheduling ...
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
In the last decade testbeds have been set-up to evaluate network protocols and algorithms under r... more In the last decade testbeds have been set-up to evaluate network protocols and algorithms under realistic settings. In order to draw solid conclusions about the corresponding experimental results, it is important for the experimenter to have a detailed view of the existing channel conditions. Moreover, especially in the context of non-RF-isolated wireless testbeds, where external interference severely impacts the resulting performance, the requirement of experimenters for accurate channel monitoring becomes a prerequisite. ...
Proceedings of the 6th ACM international workshop on Wireless network testbeds, experimental evaluation and characterization - WiNTECH '11, 2011
Abstract In the last decade testbeds have been set-up to evaluate network protocols and algorithm... more Abstract In the last decade testbeds have been set-up to evaluate network protocols and algorithms under realistic settings. Moreover, wireless sensors have lately been integrated into testbeds in order to simulate application scenarios for lowpower sensor networks, such as environment monitoring. Due to the fact that such scenarios are usually designed to run for a relatively long duration, long-term experiments are rarely executed, in order to avoid blocking of testbed facilities. Toward, this direction, we propose the NITOS Sensors Toolkit ...
2011 International Symposium of Modeling and Optimization of Mobile, Ad Hoc, and Wireless Networks, 2011
Abstract Efficient association of a station with the appropriate access point has always been a c... more Abstract Efficient association of a station with the appropriate access point has always been a challenging problem. The standard approach of considering only the Received Signal Strength, has recently been substituted by more efficient schemes that consider channel conditions, cell population etc. However, in spite of the large variety of approaches, several factors that determine to a large extent user throughput after association with an access point have been overlooked. In this work, we propose innovative metrics on which ...
2003 IEEE Wireless Communications and Networking, 2003. WCNC 2003., 2003
Abstract The use of smart antennas in extending coverage range and capacity of wireless networks ... more Abstract The use of smart antennas in extending coverage range and capacity of wireless networks dictates the employment of novel media access control protocols, with which the base station (BS) or access point (AP) provides access to users by learning their locations. We consider the class of protocols that employ beam forming and use contention-based or contention-free polling methods to locate users residing in or out of coverage range of the AP. Such protocols allow rapid media access and can be embedded in existing MAC ...
ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240), 2001
Abstract Wireless broadband access is an appealing solution to the projected trend towards reliab... more Abstract Wireless broadband access is an appealing solution to the projected trend towards reliable and easily deployable high-speed connections. In order to enhance system capacity and tolerate volatility of the wireless medium, sophisticated adaptation techniques are required. In this paper, we consider the problem of efficient resource allocation with adaptive modulation techniques in a multi-carrier wireless cellular system. We identify the inherent complexity of the problem and propose a heuristic algorithm for carrier frequency ...
GLOBECOM'01. IEEE Global Telecommunications Conference (Cat. No.01CH37270), 2001
Abstract Wireless broadband access is becoming increasingly popular in the telecommunications mar... more Abstract Wireless broadband access is becoming increasingly popular in the telecommunications market due to the projected demand for high data-rate connections. Given the inherent volatility of the wireless channel, the accurate estimation of channel conditions and the adoption of sophisticated adaptation techniques is required, so that transmission parameters are selected based on link quality, and user throughput is maximized. We consider a simple wireless link monitoring method, which is based on ...
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
A fundamental unresolved problem in wireless networks is that of distinguishing packet errors tha... more A fundamental unresolved problem in wireless networks is that of distinguishing packet errors that are caused by deteriorated link conditions and noise, from errors that occur due to packet collisions. In this paper, we develop advanced algorithms based on Cyclic Redundancy Check (CRC)[10] that solve this problem. Specifically, our innovation is that we form multiple CRCs, each of which is responsible for a different segment in a packet. The CRCs are appended after each segment. In this way, we can essentially visualize the ...
2013 IEEE International Conference on Communications (ICC), 2013
ABSTRACT This paper explores the problem of virtual machine (VM) allocation in a network of cloud... more ABSTRACT This paper explores the problem of virtual machine (VM) allocation in a network of cloud server facilities which are deployed in different geographical areas. Each cloud server facility is connected to the conventional power grid network and in addition it is supported by an attached renewable energy source (RES). We address the problem of energy-efficient task allocation in the system in the presence of a time-varying grid energy price and the unpredictability and time variation of provisioned power by the RES. The objective is to reduce the total cost of power consumption for the operator. The key idea is to match the VM load with the RES provisioned power. Each request for a task to be executed in the cloud is associated with a VM request with certain resource requirements and a deadline by which it needs to be completed. The cloud provider has to create a VM with the resource requirements of the request and to execute the VM before the deadline. We propose an online algorithm with given look-ahead horizon, in which the grid power prices and patterns of output power of the RESs are known a priori and we compare it with a greedy online algorithm. Numerical results on real traces of cloud traffic and renewable source generation patterns are encouraging in terms of the performance of our techniques and motivate further research on the topic.
Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 2012
The gradually growing demand for experimentation of protocols designed for wireless networks in r... more The gradually growing demand for experimentation of protocols designed for wireless networks in real environments has resulted in the development of experimental network facilities (testbeds). Most currently deployed testbeds have been designed so as to offer services to experimenters that lie within the testbed's premises, thus limiting the accessibility to external users. The requirement for multi-user access of network resources has led several large-scale testbeds to provide remote access services to certified experimenters. ...
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