Ibrahim Korpeoglu

Bilkent University · Department of Computer Engineering

Data centers (DCs) became an important part of computing today. A lot of services in Internet are run on DCs. Meanwhile a lot of research is done to tackle the challenges of high-performance and energy-efficient data center networking (DCN). Hot node congestion, cabling complexity/cost, and cooling cost are some of the important issues about data c...

High data transfer rates achieved by 802.11ad at 60 GHz ISM band enables use of wireless communication in data centers. In this paper, we investigate the possibility of offloading traffic from wired to wireless network in hybrid data centers. By understanding the capabilities of the wireless network, we can design the hybrid data center network acc...

This paper introduces a distributed and energy-aware algorithm, called Minimum Drone Placement (MDP) algorithm, to determine the minimum number of base stations mounted on resource-rich Unmanned Aerial Vehicles (UAV-BS), commonly referred to as drone-BS, and their possible locations to provide fault tolerance with high network connectivity in heter...

Wireless sensor networks are application specific and necessitate the development of specific network and information processing architectures that can meet the requirements of the applications involved. A common type of application for wireless sensor networks is the event-driven reactive application, which requires reactive actions to be taken in...

With the popularization of mobile phone usage, telecommunication networks have turned into a socially binding medium. Considering the traces of human communication held inside these networks, telecommunication networks are now able to provide a proxy for human social networks. To study degree characteristics and structural properties in large-scale...

This paper introduces an adaptive, energy-aware and distributed fault-tolerant topology-control algorithm, namely the Adaptive Disjoint Path Vector (ADPV) algorithm, for heterogeneous wireless sensor networks. In this heterogeneous model, we have resource-rich supernodes as well as ordinary sensor nodes that are supposed to be connected to the supe...

Sink mobility is one of the most effective solutions for improving lifetime and has been widely investigated for the last decade. Algorithms for single-sink mobility are not directly applied to the multiple-sink case due to the latter’s specific challenges. Most of the approaches proposed in the literature use mathematical programming techniques to...

Although many applications use battery-powered sensor nodes, in some applications battery- and mains-powered nodes coexist. In this paper, we present a distributed algorithm that considers using mains-powered devices to increase the lifetime of wireless sensor networks for such heterogeneous deployment scenarios. In the proposed algorithm, a backbo...

The topic of network community identification at multiple resolutions is of great interest in practice to learn high cohesive subnetworks about different subjects in a network. For instance, one might examine the interconnections among web pages, blogs and social content to identify pockets of influencers on subjects like ‘Big Data’, ‘smart phone’...

Equipping mesh nodes with multiple radios that support multiple wireless channels is considered a promising solution to overcome the capacity limitation of single-radio wireless mesh networks. However, careful and intelligent radio resource management is needed to take full advantage of the extra radios on the mesh nodes. Flow-radio assignment and...

This paper introduces a distributed fault-tolerant topology control algorithm, called the Disjoint Path Vector (DPV), for heterogeneous wireless sensor networks composed of a large number of sensor nodes with limited energy and computing capability and several supernodes with unlimited energy resources. The DPV algorithm addresses the -degree Anyca...

Moving the sink node is an eective solution for improving the lifetime of wireless sensor networks (WSN). Dierent methods in the literature schedule sink movements and determine sink stay points. This paper provides another insight to the sink mobility problem in WSNs by incorporating node-load parameters into a matrix and using this matrix to dete...

In graph theory, $k$ -core is a key metric used to identify subgraphs of high cohesion, also known as the ‘dense’ regions of a graph. As the real world graphs such as social network graphs grow in size, the contents get richer and the topologies change dynamically, we are challenged not only to materialize $k$ -core subgraphs for one time but also...

A wireless sensor network (WSN) consists of hundreds or thousands of sensor nodes organized in an ad hoc manner to achieve a predefined goal. Although WSNs have limitations in terms of memory and processors, the main constraint that makes WSNs different from traditional networks is the battery problem which limits the lifetime of a network. Differe...

In this paper, we introduce BilMesh, an indoor 802.11 b/g mesh networking testbed we established, and we report about our performance experiments conducted on multi-hop topologies with single-radio and multi-radio relay nodes. We investigate and report the effects of using multi-radio, multi-channel relay nodes in the mesh networking infrastructure...

Community identification in social networks is of great interest and with dynamic changes to its graph representation and content, the incremental maintenance of community poses significant challenges in computation. Moreover, the intensity of community engagement can be distinguished at multiple levels, resulting in a multi-resolution community re...

In wireless sensor network applications where data gathered by different sensor nodes is correlated, not all sensor nodes need to be active for the wireless sensor network to be functional. Given that the sensor nodes that are selected as active form a connected wireless network, the inactive sensor nodes can be turned off. Allowing some sensor nod...

Wireless communication technologies divide their available spectrum into pre-defined channels. Some wireless technologies, such as the IEEE 802.11b/g, define their channels in such a way that adjacent channels share the spectrum. When two distinct channels share some part of their spectrum, simultaneous transmissions on these channels cause what is...

Forest fires are one of the main causes of environmental degradation nowadays. Current surveillance systems for forest fires lack in supporting real-time monitoring of every point of a region at all times and early detection of fire threats. Solutions using wireless sensor networks, on the other hand, can gather sensory data values, such as tempera...

ZigBee is a recent wireless networking technology built on IEEE 802.15.4 standard and designed especially for low-data rate and low-duty cycle applications such as home and building automation and sensor networks. One of the primary goals of ZigBee is low power consumption and therefore long-living networks. Despite this goal, current network forma...

For wireless sensor network applications that require location information for sensor nodes, locations of nodes can be estimated by a number of localization algorithms, which inevitably may introduce various types of errors in their estimations. How an application is affected from errors and a location error metric’s response to errors may depend o...

Wireless mesh networks (WMNs) have emerged as a key technology having various advantages, especially in providing cost-effective coverage and connectivity solutions in both rural and urban areas. WMNs are typically deployed as backbone networks, usually employing spatial TDMA (STDMA)-based access schemes which are suitable for the high traffic dema...

Sleep scheduling, which is putting some sensor nodes into sleep mode without harming network functionality, is a common method to reduce energy consumption in dense wireless sensor networks. This paper proposes a distributed and energy efficient sleep scheduling and routing scheme that can be used to extend the lifetime of a sensor network while ma...

Supporting real-time and quality-of-service (QoS) traffic in multi-hop wireless mobile networks is challenging due to the high level of dynamism involved. In this paper, we propose a network layer solution in the form of a hybrid routing protocol to enable QoS traffic support in this class of networks. Our proposed protocol combines link state topo...

We propose localized, self organizing, robust, and energy-efficient data aggregation tree approaches for sensor networks, which we call Localized Power-Efficient Data Aggregation Protocols (L-PEDAPs). They are based on topologies, such as LMST and RNG, that can approximate minimum spanning tree and can be efficiently computed using only position or...

Sink mobility is an effective solution in the literature for wireless sensor network lifetime improvement. In this paper, we propose a set of algorithms for sink site determination (SSD) and movement strategy problems of sink mobility. We also present experiment results that compare the performance of our algorithms with other approaches in the lit...

Due to the limited energy-source and mostly unattended nature of the wireless sensor networks, efficient use of energy has a critical importance on the lifetime of the applications accomplished by such networks. Although in most of the cases sensor nodes are battery-powered, there are application scenarios in which battery- and mains-powered nodes...

IEEE 802.16 standard (also known as WiMAX) defines the wireless broadband network technology which aims to solve the so called last mile problem via providing high bandwidth Internet even to the rural areas for which the cable deployment is very costly. The standard mainly focuses on the MAC and PHY layer issues, supporting two transmission modes:...

Wireless multi-hop networks such as mobile ad-hoc (MANET) or wireless mesh networks (WMN) have attracted big research efforts during the last years as they have huge potential in several areas such as military communications, fast infrastructure replacement during emergency operations, extension of hotspots or as an alternative communication system...

Channel access scheduling is one of the key components in the design of multihop wireless mesh networks (WMNs). This paper addresses the allocation/demand mismatch problem observed in oblivious WMN channel access scheduling schemes and proposes Utilization-Based Scheduling (UBS). UBS is a Spatial-TDMA- (STDMA-) based dynamic channel access scheduli...

Peer-to-peer networks are rather well-studied and currently there are numerous systems based on peer-to-peer principles running on the Internet. On the other hand peer-to-peer networks for mobile ad-hoc networks have attracted attention only in the recent years. In this paper, we propose a novel peer-to-peer file sharing system particularly designe...

Wireless sensor networks are application-specific networks, and usually a new network design is required for a new application. In event-driven wireless sensor network applications, the sink node of the network is generally concerned with the higher level information describing the events happening in the network, not the raw sensor data of individ...

In this paper, we present OA-TDMA (OLSR-Aware TDMA), a TDMA based cross-layer channel access scheduling scheme which uses the information collected by the OLSR routing protocol. In OA-TDMA, each node makes decisions in a distributed manner with no central control, using the local information disseminated by the OLSR protocol. The distinctive featur...

Free riding in peer-to-peer (P2P) networks poses a serious threat to their proper operation. Here, the authors present a variety of approaches developed to overcome this problem. They introduce several unique aspects of P2P networks and discuss free riding's effects on P2P services. They categorize proposed solutions and describe each category's im...

Deployment of traditional peer-to-peer file sharing systems on a wireless ad-hoc network introduces several challenges. Information and workload distribution as well as routing are major problems for members of a wireless ad-hoc network, which are only aware of their immediate neighborhood. In this paper, we propose a file sharing system that is ab...

Multicast routing protocols in wireless sensor networks are required for sending the same message to multiple different destinations. In this paper, we propose two different distributed algorithms formulticast routing in wireless sensor networks which make use of location information of sensor nodes. Our first algorithm groups the destination nodes...

This paper aims at comparing through simulations the network lifetime of a wireless sensor network using Bluetooth-enabled or IEEE 802.15.4 compliant devices. The evaluation is performed under a common reference framework, namely the EMORANS scenario for wireless sensor networks. Since the two enabling technologies rely on different MAC paradigms,...

The existence of a high degree of free riding in Peer-to-Peer (P2P) networks is an important threat that should be addressed while designing P2P protocols. In this paper we propose a connection-based solution that will help to reduce the free riding effects on a P2P network and discourage free riding. Our solution includes a novel P2P connection ty...

The existence of a high degree of free riding is a serious threat to Peer-to-Peer (P2P) networks. In this paper, we propose a distributed framework to reduce the adverse effects of free riding on P2P networks. Our solution primarily focuses on locating free riders and taking actions against them. We propose a framework in which each peer monitors i...

Today, consumer electronic devices and PCs are inevitable parts of our daily life. Controlling those devices remotely is an important aspect of the technology. We have already universal remote control devices for controlling consumer electronic devices. Similarly, we may control our desktop and laptop PCs and their applications remotely via portabl...

In this paper we propose a distributed, self organizing, robust and energy efficient data gathering algorithm for sensor networks operating in environments where all the sensor nodes are not in direct communication range of each other and data aggregation is used while routing. Proposed algorithm is based on local minimum spanning tree (LMST) struc...

This paper presents DSSP (dynamic sleep scheduling protocol), a centralized scheme for extending the lifetime of densely deployed wireless sensor networks by keeping only a necessary set of sensor nodes active. We present an algorithm for finding out which nodes should be put into sleep mode, and the algorithm preserves coverage and connectivity wh...

Bluetooth networks can be constructed as piconets or scatternets depending on the number of nodes in the network. Although piconet construction is a well-defined process specified in Bluetooth standards, scatternet formation policies and algorithms are not well specified. Among many solution proposals for this problem, only a few of them focus on e...

We consider the problem of reliable data dissemination in the context of wireless sensor networks. For some application scenarios, reliable data dissemination to all nodes is necessary for propagating code updates, queries, and other sensitive information in wireless sensor networks. Epidemic algorithms are a natural approach for reliable distribut...

This paper studies the performance of Bluetooth broadcasting scheme. The transmission of a Bluetooth broadcast packet is repeated several times to increase the reliability of broadcast. We have analyzed the effects of baseband ACL packet type preference, on the broadcast performance in terms of reliability and effective throughput, over different c...

Recent technological advances enable realization of wireless sensor networks suitable for many applications including environmental monitoring, biological and chemical contamination detection, earthquake management. Depending on the application, the properties of sensor network databases include a distributed environment, approximate and long-runni...

A P2P network that is overlayed over Internet can consist of thousands, or even millions of nodes. To analyze the performance of a P2P network, or an algorithm or protocol designed for a P2P network, simulation studies have to be performed quite often, and simulation stud- ies require the use of appropriate models for various components and paramet...

Bluetooth networks can be constructed as piconets or scatternets depending on the number of nodes in the network. Although piconet construction is a well-defined process specified in Bluetooth standards, scatternet construction policies and algorithms are not well specified. Among many solution proposals for this problem, only a few of them focus o...

This paper introduces a new data transport architecture and protocol for storage that is implemented on wireless devices and that can be accessed through a short-range wireless access technology such as Bluetooth or 802.11. We call the protocol WATA (Wireless ATA), as its architecture is similar to current ATA and ATA-based technologies. In this pa...

In this paper, we propose an energy-efficient scatternet formation algorithm for Bluetooth based sensor networks. The algorithm is based on first computing a shortest path tree from the base station to all sensor nodes and then solving the degree constraint problem so that the degree of each node in the network is not greater than seven, which is a...

We propose a distributed and measurement-based method to reduce the degree of free riding in P2P networks. We primarily focus on developing schemes to locate free riders and on determining policies that can be used to take actions against them. Our proposed schemes require each peer to monitor its neighboring peers, make decisions if they exhibit a...

Peer-to-peer networks have attracted a significant amount of interest as a popular and successful alternative to traditional client-server networks for resource sharing and content distribution. However, the existence of high degrees of free riding may be an important threat against P2P networks. In this paper , we propose a distributed and measure...

This paper 1 studies the performance of current Blue-tooth broadcasting scheme. Current Bluetooth broadcast-ing scheme may repeat transmitting (broadcasting) the same broadcasted baseband ACL packet several times to in-crease the reliability of broadcast over an unreliable Blue-tooth radio channel. We have analyzed the effects of differ-ent Bluetoo...

Recent developments in processor, memory and radio technology have enabled wireless sensor networks which are deployed to collect useful information from an area of interest. The sensed data must be gathered and transmitted to a base station where it is further processed for end-user queries. Since the network consists of low-cost nodes with limite...

Cell delay variation (CDV) is one of the quality of service parameters that can be negotiated between applications and an ATM network. The network should check during connection setup, as part of call admission control, whether it can satisfy the requested CDV of an application. For this comparison, the network should estimate the end-to-end CDV th...

Palmtop computers are rapidly becoming the popular platform of choice for running personal productivity applications, but their networking capabilities axe still lagging behind user expectations. Due to memory size, cost, and power considerations most palmtop computers support only limited form of point-to-point communication, namely, connection vi...

Palmtop computers which consume very little power, have very small size, and are much cheaper compared to their laptop counterparts are proliferating in the market. However, there exist no satisfactory wireless connectivity solution in terms of cost and power consumption to connect these devices to the network. This paper describes a cost-effective...

The emergence of battery powered handheld devices as popular computing devices is presenting new challenges. Among the most important challenges is the need to provide a low cost, low power, indoor wireless networking access to handheld devices. The constraints posed by battery power and cost require a careful re-evaluation of system design issues...

Paltmtop computers are rapidly becoming the popular platform of choice for running personal productivity applications, but their networking capabilities are still lagging behind user expectations. Due to memory size, cost, and power considerations most palmtop computers support only limited form of point-to-point communication, namely, connection v...

The emergence of battery powered handheld devices as popular computing devices is presenting new challenges. Among the most important challenges is the need to provide a low cost, low power, indoor wireless networking access to handheld devices. The constraints posed by battery power and cost require a careful re-evaluation of system design issues...

New short-range wireless communication technologies would enable environment-aware, mobile, personal area networks. These new technologies will serve as enablers for ubiquitous, low-cost, low-complexity, small-sized information appliances. These appliances will serve as interaction tools between humans and computer-driven services and applications...

The cell delay variation (CDV) is one of the quality of service parameters that can be negotiated between applications and an ATM network. The network should check during connection setup, as part of call admission control, whether it can satisfy the requested CDV of an application. For this comparison, the network should estimate the end-to-end CD...

Current general purpose mobility solutions likeMobile-IP involve multiple router-crossings even whenthe mobile host moves within an intranet from one subnetof a router to another. An environment consisting of a large number of mobile hosts would congestthe router causing hosts to experience high latency andjitter. This paper presents a mechanism to...

The interactive video (IV) market has been expected to capture a significant share of the huge potential revenues to be generated by the business and residential markets. The level of revenues generated depends on the completion rate of calls the service provider can support, no matter what the IV system or network condition. Thus, a cost-effective...