Árpád Huszák - Academia.edu (original) (raw)

Papers by Árpád Huszák

While IP is declared as the key technology of the future's wired and mobile communication, the cu... more While IP is declared as the key technology of the future's wired and mobile communication, the currently used version of IP, IPv4 itself is not suitable to be used in mobile scenarios. Next generation mobile users require special support to provide connectivity, although they change their place of attachment to the network frequently. The task of mobility management is to provide this support, and the management consists of two parts: location management and handover management [1]. The first one enables to originate and receive calls for the mobile terminals; the second is responsible for administering base station changes. In our work, we have created a network design algorithm and an agent (GMA/MAP) router selection algorithm in Regional Registration and Hierarchical Mobile IPv6 to optimise the handover management in IP based next generation mobile networks.

Multimedia applications are becoming increasingly popular in IP networks, while in mobile network... more Multimedia applications are becoming increasingly popular in IP networks, while in mobile networks the limited bandwidth and the higher error rate arise in spite of its popularity. These are restraining factors for mobile clients using multimedia applications such as voice over IP (VoIP) or video streaming. In some conditions the retransmission of lost and corrupted packets should increase the quality of the multimedia service, but these retransmissions should be enabled only if the network is not in congested state. Otherwise the retransmitted packet will intensify the congestion and it will have negative effect on the audio/video quality. Our proposed mechanism selectively retransmits the corrupted packets based on the TCP-Friendly Rate Control (TFRC) and the actual video bit rate.

Nowadays positioning based navigation is an integrated part of our everyday's routine. Hence,... more Nowadays positioning based navigation is an integrated part of our everyday's routine. Hence, it is hard to succeed without a GPS based navigation system in a bigger city today. However, indoor positioning and navigation are still in their infancy, although these services would be desirable in many areas. One obvious application domain is vehicle navigation in a parking garage. The use of an indoor vehicle navigation system is convenient for the drivers, decreases the unnecessary circling in the garage and reduces air pollution. In this paper, we introduce our iParking indoor positioning and navigation system which has been under development. Our system monitors the occupancy of the parking lots, and with the aid of a Wi-Fi based background wireless infrastructure tracks the position of the vehicle entering the parking garage and navigates the driver to an appropriate free parking lot. Lot selection is handled at the entry point of the garage based on simple preferences, eg., th...

Sensors can have big advantages in the process of mapping planets and inspecting the prevailing c... more Sensors can have big advantages in the process of mapping planets and inspecting the prevailing conditions on their surfaces. We can obtain broader and more thorough pictures about the solar system bodies around us. We can not only gain new information about them, but we can observe how fast and in what way the already known data changes, and how these planets forms. For this purpose, we examined a sensor network that can withstand the environment on a planet in our solar system. We analyzed the network’s performance as well as its cost-effectiveness. The network contains some higher performance sensors, whose dedicated purpose is to collect data from the other-, (smaller) sensors, and forward this information to the satellites, which can send it back to Earth. We created the sensor network’s structure in a specific way, which allows to pinpoint the location of these devices. Localization is an essential part of the mapping of any planet in the solar system.

As an integrated approach, we have proposed a monitoring network which is based on a satellite se... more As an integrated approach, we have proposed a monitoring network which is based on a satellite segment and a wireless sensor based ground network. The developed architecture can localize its elements with minimal required resources. For the position estimation process among the sensors, we used a recursive technique that extends the accessible coverage area deploying only three high performance devices with accurate positions that are used as initial references. We developed new algorithms to improve the precision of the recursive positioning scheme utilized in the proposed sensor network. In order to analyze the introduced sensor network architecture and evaluate its operation, a simulator tool was implemented. In the evaluation of the proposed model, we analyzed and compared the performances of different positioning algorithms in our simulator. Based on our results, an integrated service for satellite based remote sensing and positioning could be implemented for Earth environment and space exploration as well.

2010 4th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010

Video streaming applications are commonly used in both wired and wireless environment; however, w... more Video streaming applications are commonly used in both wired and wireless environment; however, wireless links are burden by higher packet loss ratio and delay variation. In order to make video transmission possible in wireless networks MPEG video coding is usually used to reach the bandwidth constrains of the links. The video quality and compression ratio depends on Group of Pictures

2010 IEEE International Conference on Communications, 2010

In order to fulfill the users' requirements, today's mobile devices are equipped with multiple in... more In order to fulfill the users' requirements, today's mobile devices are equipped with multiple interfaces to make the connection possible to different type of networks. To select dynamically the best interface according to different network attributes, such as delay, bandwidth, cost, etc. must be taken into account. Grey Relational Analysis (GRA) is a promising algorithmic approach that can realize dynamic interface selection with multiple alternatives (interfaces) and attributes; however, similarly to some other decision methods, GRA also suffers from rank reversal phenomenon. In this paper alternative solutions are introduced to reduce and eliminate the probability of rank inconsistency, caused by the addition or deletion of an interface. The proposed methods are analyzed analytically and by simulations. Our results confirm that the proposed normalization methods significantly reduce, while one of it eliminates the rank reversal phenomenon.

Proceedings of the 6th International Conference on Advances in Mobile Computing and Multimedia - MoMM '08, 2008

Retransmission-based error recovery is the simplest technique to minimize the overall packet loss... more Retransmission-based error recovery is the simplest technique to minimize the overall packet loss ratio in order to increase the quality of the applications. Multimedia applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. Retransmission can be also used for loss recovery in media applications, but the number of retransmissions is limited by the playout buffer and the recent network delay.

2009 IEEE Symposium on Computers and Communications, 2009

Retransmission based error recovery is not always applicable for multimedia applications; however... more Retransmission based error recovery is not always applicable for multimedia applications; however it can be used if the transmission characteristics and network conditions are examined before. Retransmissions can be carried out only if there is no congestion in the network and the network delay is low enough to receive the retransmitted packet before the playout. These two attributes are depending and one can be estimated from the other. In this paper we introduce a TFRC and RTT threshold interdependence model to determinate network delay thresholds for the retransmission decision algorithm. Using the calculated sending rate of the TFRC (TCP Friendly Rate Control) to estimate the congestion level in the network, we can set up a threshold of disabling/enabling the retransmissions. Our goal was to determinate a matching RTT threshold to gain similar retransmission behavior as using the sending rate threshold. We found that using our threshold estimating model, the number of retransmitted packets was similar, using the TFRC-based sending rate threshold and the RTT retransmission threshold.

Lecture Notes in Computer Science, 2012

Wireless indoor positioning has been a popular research topic for years because it provides the b... more Wireless indoor positioning has been a popular research topic for years because it provides the basis for a broad domain of location-based applications. Especially the usage of WLAN (Wireless Local Area Network) technology is widespread to build an indoor positioning system due to the reuse of existing and almost ubiquitous WLAN infrastructure worldwide lowering the costs. However, these WLAN systems were not originally designed for positioning services, thus the provided accuracy might be low. The accuracy can be increased by the careful placement of WLAN access points to cover the given area appropriately. In this paper, we propose a method based on simulated annealing to find the optimal number and placement of WLAN access points for indoor positioning and show its investigation using simulations.

IFIP International Federation for Information Processing, 2008

Streaming media is becoming increasingly prominent on the Internet, although multimedia applicati... more Streaming media is becoming increasingly prominent on the Internet, although multimedia applications have very stringent bandwidth, delay and loss requirements. In mobile environment the limited bandwidth and the higher error rate arise as an obstacle of its popularity. In many cases retransmission-based error recovery can be an attractive solution to improve the quality of the video stream, because it requires minimal network bandwidth and processing cost. In this paper we propose a content-aware selective retransmission scheme which allows the retransmission of all packets when the risk of congestion is low, but as it rises the retransmission is disabled step-by-step, but not all at once, in order of packet importance. In this work the heterogenity of H.264 streams were utilized for the determination of packet importance. The advantage of this transmitter controlled procedure is that all the needed information is available at the source due to DCCP transport protocol and its congestion control algorithm. The effectiveness of the proposed method was examined in Ns2 network simulator.

2007 IEEE Symposium on Computers and Communications, 2007

Multimedia applications are becoming increasingly popular in IP networks, while in mobile environ... more Multimedia applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. The wireless network characteristics make the deployment of these applications more challenging.

2009 International Conference on Telecommunications, 2009

Today's mobile devices are equipped with multiple interfaces to make the connection possible to d... more Today's mobile devices are equipped with multiple interfaces to make the connection possible to different type of networks. In order to efficiently utilize the interface capabilities, multi-path streaming can be used. Resource intensive applications can deliver high bitrate streams over multiple paths by cumulating the available bandwidth of the different subpaths. In this paper we propose a multi-path streaming method that chooses a set of paths maximizing the overall quality at the client. While the available paths have different bandwidth, delay and loss probability constrains, the packet distributor must take the video packet importance and the dependencies between packets into account. Transmitting the reference video frames on the most reliable links will decrease the loss probability of important data packets and increase the measured video quality. Both analytical and simulation analysis were performed to examine the behavior of the presented content-aware interface selection model. The results show that the proposed solution provides higher video quality than common scheduling algorithms.

Lecture Notes in Computer Science, 2003

While IP is declared as the key technology of the future's wired and mobile communication, the cu... more While IP is declared as the key technology of the future's wired and mobile communication, the currently used version of IP, IPv4 itself is not suitable to be used in mobile scenarios. Next generation mobile users require special support to provide connectivity, although they change their place of attachment to the network frequently [1]. In our work, we have created a network design algorithm and an agent (GMA/MAP) router select ion algorithm in Regional Registration and Hierarchical Mobile IPv6 to optimise the handover management in IP based next generation mobile networks.

A mobil távközlési piac nagy mértékû fellendülése túlnyomórészt a mobil beszédszolgáltatás növekv... more A mobil távközlési piac nagy mértékû fellendülése túlnyomórészt a mobil beszédszolgáltatás növekvô népszerûségének volt köszönhetô az elmúlt évtizedben. Elérve a lehetséges mobil felhasználók számának felsô korlátját, már nem várhatjuk a há- lózati forgalom további növekedését csupán a beszéd alapú szolgáltatástól, így a jövôben egyre inkább a multimédia továb- bítása fogja adni a hálózati terhelés nagy részét. A multimédia ilyen arányú

International Journal of Communication Networks and Distributed Systems, 2010

Multihoming is one of the most attractive features of SCTP (Stream Control Transmission Protocol)... more Multihoming is one of the most attractive features of SCTP (Stream Control Transmission Protocol) aiming to make this prosperous transport scheme competitive in mobile environments when the mobile hosts are equipped with multiple interfaces. The complementary characteristic of the 3G UMTS (Universal Mobile Telecommunications System) and WLAN (Wireless Local Area Network) architectures motivates operators to integrate these two successful technologies. Recently spreading wireless devices are increasingly provided with multiple networking interfaces such enabling end-users to access Internet services using e.g. the WLAN's higher bandwidth wherever available, and connecting to the UMTS network in other cases. This paper investigates the performance of multihomed SCTP hosts through extensive experimental studies in such an integrated heterogeneous environment. In order to do this we designed and implemented a real native IPv6 UMTS-WLAN testbed equipped with novel IPv6-based mobile technologies, such providing ideal conditions for SCTP multihoming performance analysis. In this testbed architecture we analyzed numerous settings to measure the handover behavior of the protocol in terms of handover effectiveness, link changeover characteristics, throughput and transmission delay. As our results show, accurate SCTP parameter setup can significantly decrease the handover delay and eliminate the data transmission interrupts.

Computer Communications, 2008

In the past few years we have witnessed an explosive growth in the usage of media streaming appli... more In the past few years we have witnessed an explosive growth in the usage of media streaming applications. The newly appeared audio/video applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. Retransmission-based error recovery is considered inappropriate for multimedia applications, because of its latency. However, this solution can be attractive because it requires minimal network bandwidth, processing cost and efficiently improves the quality. Despite its latency, retransmission can be used successfully in many cases, especially if playout buffering is employed. Only the successfully retransmitted packets will improve the quality parameters of the multimedia stream, therefore it is worth to examine which packets should be retransmitted. In this paper a source controlled selective retransmission algorithm is presented with a decision algorithm based on the actual RTT and sending rate determined by the TFRC. In our scheme the transmitter determines the playout delay caused by the playout buffer using the proposed Flood method. The needed information about the network congestion state and the network delay are provided by the TFRC (TCP Friendly Rate Control) algorithm. Our proposal does not need additional administration messages because the decision procedure and its inputs are at the transmitter. The obtained results show that significant quality improvement can be achieved with the proposed selective retransmission scheme.

Internet multimedia streaming is becoming increasingly popular to access multimedia information. ... more Internet multimedia streaming is becoming increasingly popular to access multimedia information. Two major issues arise in spite of its popularity. First, limited bandwidth restricts high bit rate video transmission. Second, wireless transmission by its nature may introduce higher rate of errors during transmission. The frequent errors should cause deterioration of the quality of multimedia streams. In this paper we present

2008 The Second International Conference on Next Generation Mobile Applications, Services, and Technologies, 2008

In wireless networks, congestion control, alone, may not be enough to ensure good quality of mult... more In wireless networks, congestion control, alone, may not be enough to ensure good quality of multimedia streaming and efficient utilization of the network. Packet losses due to the high bit error rate not only degrade the multimedia quality, but render the current congestion control algorithms as inefficient: these algorithms back-off on every packet loss even when there is no congestion.

While IP is declared as the key technology of the future's wired and mobile communication, the cu... more While IP is declared as the key technology of the future's wired and mobile communication, the currently used version of IP, IPv4 itself is not suitable to be used in mobile scenarios. Next generation mobile users require special support to provide connectivity, although they change their place of attachment to the network frequently. The task of mobility management is to provide this support, and the management consists of two parts: location management and handover management [1]. The first one enables to originate and receive calls for the mobile terminals; the second is responsible for administering base station changes. In our work, we have created a network design algorithm and an agent (GMA/MAP) router selection algorithm in Regional Registration and Hierarchical Mobile IPv6 to optimise the handover management in IP based next generation mobile networks.

Multimedia applications are becoming increasingly popular in IP networks, while in mobile network... more Multimedia applications are becoming increasingly popular in IP networks, while in mobile networks the limited bandwidth and the higher error rate arise in spite of its popularity. These are restraining factors for mobile clients using multimedia applications such as voice over IP (VoIP) or video streaming. In some conditions the retransmission of lost and corrupted packets should increase the quality of the multimedia service, but these retransmissions should be enabled only if the network is not in congested state. Otherwise the retransmitted packet will intensify the congestion and it will have negative effect on the audio/video quality. Our proposed mechanism selectively retransmits the corrupted packets based on the TCP-Friendly Rate Control (TFRC) and the actual video bit rate.

Nowadays positioning based navigation is an integrated part of our everyday's routine. Hence,... more Nowadays positioning based navigation is an integrated part of our everyday's routine. Hence, it is hard to succeed without a GPS based navigation system in a bigger city today. However, indoor positioning and navigation are still in their infancy, although these services would be desirable in many areas. One obvious application domain is vehicle navigation in a parking garage. The use of an indoor vehicle navigation system is convenient for the drivers, decreases the unnecessary circling in the garage and reduces air pollution. In this paper, we introduce our iParking indoor positioning and navigation system which has been under development. Our system monitors the occupancy of the parking lots, and with the aid of a Wi-Fi based background wireless infrastructure tracks the position of the vehicle entering the parking garage and navigates the driver to an appropriate free parking lot. Lot selection is handled at the entry point of the garage based on simple preferences, eg., th...

Sensors can have big advantages in the process of mapping planets and inspecting the prevailing c... more Sensors can have big advantages in the process of mapping planets and inspecting the prevailing conditions on their surfaces. We can obtain broader and more thorough pictures about the solar system bodies around us. We can not only gain new information about them, but we can observe how fast and in what way the already known data changes, and how these planets forms. For this purpose, we examined a sensor network that can withstand the environment on a planet in our solar system. We analyzed the network’s performance as well as its cost-effectiveness. The network contains some higher performance sensors, whose dedicated purpose is to collect data from the other-, (smaller) sensors, and forward this information to the satellites, which can send it back to Earth. We created the sensor network’s structure in a specific way, which allows to pinpoint the location of these devices. Localization is an essential part of the mapping of any planet in the solar system.

As an integrated approach, we have proposed a monitoring network which is based on a satellite se... more As an integrated approach, we have proposed a monitoring network which is based on a satellite segment and a wireless sensor based ground network. The developed architecture can localize its elements with minimal required resources. For the position estimation process among the sensors, we used a recursive technique that extends the accessible coverage area deploying only three high performance devices with accurate positions that are used as initial references. We developed new algorithms to improve the precision of the recursive positioning scheme utilized in the proposed sensor network. In order to analyze the introduced sensor network architecture and evaluate its operation, a simulator tool was implemented. In the evaluation of the proposed model, we analyzed and compared the performances of different positioning algorithms in our simulator. Based on our results, an integrated service for satellite based remote sensing and positioning could be implemented for Earth environment and space exploration as well.

2010 4th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2010

Video streaming applications are commonly used in both wired and wireless environment; however, w... more Video streaming applications are commonly used in both wired and wireless environment; however, wireless links are burden by higher packet loss ratio and delay variation. In order to make video transmission possible in wireless networks MPEG video coding is usually used to reach the bandwidth constrains of the links. The video quality and compression ratio depends on Group of Pictures

2010 IEEE International Conference on Communications, 2010

In order to fulfill the users' requirements, today's mobile devices are equipped with multiple in... more In order to fulfill the users' requirements, today's mobile devices are equipped with multiple interfaces to make the connection possible to different type of networks. To select dynamically the best interface according to different network attributes, such as delay, bandwidth, cost, etc. must be taken into account. Grey Relational Analysis (GRA) is a promising algorithmic approach that can realize dynamic interface selection with multiple alternatives (interfaces) and attributes; however, similarly to some other decision methods, GRA also suffers from rank reversal phenomenon. In this paper alternative solutions are introduced to reduce and eliminate the probability of rank inconsistency, caused by the addition or deletion of an interface. The proposed methods are analyzed analytically and by simulations. Our results confirm that the proposed normalization methods significantly reduce, while one of it eliminates the rank reversal phenomenon.

Proceedings of the 6th International Conference on Advances in Mobile Computing and Multimedia - MoMM '08, 2008

Retransmission-based error recovery is the simplest technique to minimize the overall packet loss... more Retransmission-based error recovery is the simplest technique to minimize the overall packet loss ratio in order to increase the quality of the applications. Multimedia applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. Retransmission can be also used for loss recovery in media applications, but the number of retransmissions is limited by the playout buffer and the recent network delay.

2009 IEEE Symposium on Computers and Communications, 2009

Retransmission based error recovery is not always applicable for multimedia applications; however... more Retransmission based error recovery is not always applicable for multimedia applications; however it can be used if the transmission characteristics and network conditions are examined before. Retransmissions can be carried out only if there is no congestion in the network and the network delay is low enough to receive the retransmitted packet before the playout. These two attributes are depending and one can be estimated from the other. In this paper we introduce a TFRC and RTT threshold interdependence model to determinate network delay thresholds for the retransmission decision algorithm. Using the calculated sending rate of the TFRC (TCP Friendly Rate Control) to estimate the congestion level in the network, we can set up a threshold of disabling/enabling the retransmissions. Our goal was to determinate a matching RTT threshold to gain similar retransmission behavior as using the sending rate threshold. We found that using our threshold estimating model, the number of retransmitted packets was similar, using the TFRC-based sending rate threshold and the RTT retransmission threshold.

Lecture Notes in Computer Science, 2012

Wireless indoor positioning has been a popular research topic for years because it provides the b... more Wireless indoor positioning has been a popular research topic for years because it provides the basis for a broad domain of location-based applications. Especially the usage of WLAN (Wireless Local Area Network) technology is widespread to build an indoor positioning system due to the reuse of existing and almost ubiquitous WLAN infrastructure worldwide lowering the costs. However, these WLAN systems were not originally designed for positioning services, thus the provided accuracy might be low. The accuracy can be increased by the careful placement of WLAN access points to cover the given area appropriately. In this paper, we propose a method based on simulated annealing to find the optimal number and placement of WLAN access points for indoor positioning and show its investigation using simulations.

IFIP International Federation for Information Processing, 2008

Streaming media is becoming increasingly prominent on the Internet, although multimedia applicati... more Streaming media is becoming increasingly prominent on the Internet, although multimedia applications have very stringent bandwidth, delay and loss requirements. In mobile environment the limited bandwidth and the higher error rate arise as an obstacle of its popularity. In many cases retransmission-based error recovery can be an attractive solution to improve the quality of the video stream, because it requires minimal network bandwidth and processing cost. In this paper we propose a content-aware selective retransmission scheme which allows the retransmission of all packets when the risk of congestion is low, but as it rises the retransmission is disabled step-by-step, but not all at once, in order of packet importance. In this work the heterogenity of H.264 streams were utilized for the determination of packet importance. The advantage of this transmitter controlled procedure is that all the needed information is available at the source due to DCCP transport protocol and its congestion control algorithm. The effectiveness of the proposed method was examined in Ns2 network simulator.

2007 IEEE Symposium on Computers and Communications, 2007

Multimedia applications are becoming increasingly popular in IP networks, while in mobile environ... more Multimedia applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. The wireless network characteristics make the deployment of these applications more challenging.

2009 International Conference on Telecommunications, 2009

Today's mobile devices are equipped with multiple interfaces to make the connection possible to d... more Today's mobile devices are equipped with multiple interfaces to make the connection possible to different type of networks. In order to efficiently utilize the interface capabilities, multi-path streaming can be used. Resource intensive applications can deliver high bitrate streams over multiple paths by cumulating the available bandwidth of the different subpaths. In this paper we propose a multi-path streaming method that chooses a set of paths maximizing the overall quality at the client. While the available paths have different bandwidth, delay and loss probability constrains, the packet distributor must take the video packet importance and the dependencies between packets into account. Transmitting the reference video frames on the most reliable links will decrease the loss probability of important data packets and increase the measured video quality. Both analytical and simulation analysis were performed to examine the behavior of the presented content-aware interface selection model. The results show that the proposed solution provides higher video quality than common scheduling algorithms.

Lecture Notes in Computer Science, 2003

While IP is declared as the key technology of the future's wired and mobile communication, the cu... more While IP is declared as the key technology of the future's wired and mobile communication, the currently used version of IP, IPv4 itself is not suitable to be used in mobile scenarios. Next generation mobile users require special support to provide connectivity, although they change their place of attachment to the network frequently [1]. In our work, we have created a network design algorithm and an agent (GMA/MAP) router select ion algorithm in Regional Registration and Hierarchical Mobile IPv6 to optimise the handover management in IP based next generation mobile networks.

A mobil távközlési piac nagy mértékû fellendülése túlnyomórészt a mobil beszédszolgáltatás növekv... more A mobil távközlési piac nagy mértékû fellendülése túlnyomórészt a mobil beszédszolgáltatás növekvô népszerûségének volt köszönhetô az elmúlt évtizedben. Elérve a lehetséges mobil felhasználók számának felsô korlátját, már nem várhatjuk a há- lózati forgalom további növekedését csupán a beszéd alapú szolgáltatástól, így a jövôben egyre inkább a multimédia továb- bítása fogja adni a hálózati terhelés nagy részét. A multimédia ilyen arányú

International Journal of Communication Networks and Distributed Systems, 2010

Multihoming is one of the most attractive features of SCTP (Stream Control Transmission Protocol)... more Multihoming is one of the most attractive features of SCTP (Stream Control Transmission Protocol) aiming to make this prosperous transport scheme competitive in mobile environments when the mobile hosts are equipped with multiple interfaces. The complementary characteristic of the 3G UMTS (Universal Mobile Telecommunications System) and WLAN (Wireless Local Area Network) architectures motivates operators to integrate these two successful technologies. Recently spreading wireless devices are increasingly provided with multiple networking interfaces such enabling end-users to access Internet services using e.g. the WLAN's higher bandwidth wherever available, and connecting to the UMTS network in other cases. This paper investigates the performance of multihomed SCTP hosts through extensive experimental studies in such an integrated heterogeneous environment. In order to do this we designed and implemented a real native IPv6 UMTS-WLAN testbed equipped with novel IPv6-based mobile technologies, such providing ideal conditions for SCTP multihoming performance analysis. In this testbed architecture we analyzed numerous settings to measure the handover behavior of the protocol in terms of handover effectiveness, link changeover characteristics, throughput and transmission delay. As our results show, accurate SCTP parameter setup can significantly decrease the handover delay and eliminate the data transmission interrupts.

Computer Communications, 2008

In the past few years we have witnessed an explosive growth in the usage of media streaming appli... more In the past few years we have witnessed an explosive growth in the usage of media streaming applications. The newly appeared audio/video applications are becoming increasingly popular in IP networks, while in mobile environment the limited bandwidth and the higher error rate arise in spite of its popularity. Retransmission-based error recovery is considered inappropriate for multimedia applications, because of its latency. However, this solution can be attractive because it requires minimal network bandwidth, processing cost and efficiently improves the quality. Despite its latency, retransmission can be used successfully in many cases, especially if playout buffering is employed. Only the successfully retransmitted packets will improve the quality parameters of the multimedia stream, therefore it is worth to examine which packets should be retransmitted. In this paper a source controlled selective retransmission algorithm is presented with a decision algorithm based on the actual RTT and sending rate determined by the TFRC. In our scheme the transmitter determines the playout delay caused by the playout buffer using the proposed Flood method. The needed information about the network congestion state and the network delay are provided by the TFRC (TCP Friendly Rate Control) algorithm. Our proposal does not need additional administration messages because the decision procedure and its inputs are at the transmitter. The obtained results show that significant quality improvement can be achieved with the proposed selective retransmission scheme.

Internet multimedia streaming is becoming increasingly popular to access multimedia information. ... more Internet multimedia streaming is becoming increasingly popular to access multimedia information. Two major issues arise in spite of its popularity. First, limited bandwidth restricts high bit rate video transmission. Second, wireless transmission by its nature may introduce higher rate of errors during transmission. The frequent errors should cause deterioration of the quality of multimedia streams. In this paper we present

2008 The Second International Conference on Next Generation Mobile Applications, Services, and Technologies, 2008

In wireless networks, congestion control, alone, may not be enough to ensure good quality of mult... more In wireless networks, congestion control, alone, may not be enough to ensure good quality of multimedia streaming and efficient utilization of the network. Packet losses due to the high bit error rate not only degrade the multimedia quality, but render the current congestion control algorithms as inefficient: these algorithms back-off on every packet loss even when there is no congestion.