L. Loyola - Academia.edu (original) (raw)
Papers by L. Loyola
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IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 2007
... MOBILE NETWORKS Eleni Kamateri and Lefteris Mamatas Demokritos University of Thrace Vas. ... ... more ... MOBILE NETWORKS Eleni Kamateri and Lefteris Mamatas Demokritos University of Thrace Vas. ... [4] J. Manner, G. Karagiannis, and A. McDonald. 'NSLP for Quality-of-Service signalling.' Internet Draft - Work in progress, Internet Engineering Task Force, January 2006. ...
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The proposed medium access protocol deals especially with the timely-transmission of real-time pa... more The proposed medium access protocol deals especially with the timely-transmission of real-time packets in wireless multimedia networks where users of various types of traffic are present. It works based on the time division multiple access (TDMA) with time division duplex (TDD) technique as well as fixed-length packet switching incorporating two policies, which work differently during non-congestion and congestion states. The simulation results show good performance of the proposed method, even under high-load conditions, and a good trade-off characteristic between real-time access delay and non-real time buffer occupancy, during periods of congestion
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2005 Asia-Pacific Conference on Communications
The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promis... more The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promising architecture for achieving a ubiquitous wireless Internet access in the future. However, the current IEEE 802.11 protocol is aimed at single access point (AP) environments and many problems related to the wireless meshed interconnection of APs and mobile terminals (MTs) remain to
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APCC/MDMC '04. The 2004 Joint Conference of the 10th Asia-Pacific Conference on Communications and the 5th International Symposium on Multi-Dimensional Mobile Communications Proceeding
We propose a new transmission and resource allocation technique based on multicarrier direct-sequ... more We propose a new transmission and resource allocation technique based on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers the scheme reduces the inter-carrier interference generated by high-speed users while keeping
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We propose a new transmission and resource allocation technique based on multicarrier direct-sequ... more We propose a new transmission and resource allocation technique based on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers, the scheme reduces the intercarrier interference generated by high-speed users while keeping the intersymbol interference at a low level due to multicarrier transmission. The analysis and results show that a substantial mitigation of both the intercarrier interference and bit error rate, without reducing the system bandwidth efficiency, can be achieved.
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Vehicular Technology Conference, 1988, IEEE 38th
We propose a new transmission and multiple access method for future broadband wireless networks. ... more We propose a new transmission and multiple access method for future broadband wireless networks. The scheme combines the advantages of orthogonal frequency division multiple access (OFDMA) and code division multiple access (CDMA) to cope simultaneously with both frequency spread produced by the Doppler effect, and time spread caused by the multipath channel. Through the code orthogonalization of neighboring (close) OFDM subcarriers, the method mitigates the intercarrier interference generated by high speed users while keeping the advantages offered by OFDMA to diminish the intersymbol interference produced by multipaths. In this way, the method optimizes the reliability of the communication channel provided to every user according to its speed, position and channel characteristics. The allocation of subcarriers and orthogonal codes to users is carried out dynamically with time by considering parameters such as required bitrate, speed, level of interference, multipath effects and phy...
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Proceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems - MSWiM '08, 2008
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IEEE INFOCOM 2008 - The 27th Conference on Computer Communications, 2008
Abstract—Cooperative relaying has been shown to provide diversity gains which can significantly i... more Abstract—Cooperative relaying has been shown to provide diversity gains which can significantly improve the Packet Error Rate (PER) in wireless transmissions. In ad hoc wireless rout- ing where packets may travel over a number of hops before reaching the destination, hop-wise cooperative relaying may severely reduce network capacity. This approach was mainly addressed in literature so far. In this paper,
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GLOBECOM '05. IEEE Global Telecommunications Conference, 2005., 2005
The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promis... more The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promising architecture for achieving a ubiquitous wireless Internet access in the future. However, the current IEEE 802.11 protocol is aimed at single-AP (access point) environments and many problems related to the wireless meshed interconnection of APs and mobile terminals (MTs) remain to be solved. Some proposed solutions to build such mesh architectures are based on single-channel ad-hoc oriented schemes in which IEEE 802.11 protocol has been modified. The main problem with this type of schemes, however, lies in the very low performance of the single-channel architecture itself. The task group S of IEEE 802.11 is currently working out standards for IEEE 802.11-compliant mesh architectures in a number of usage scenarios including residential, office and campus/community/public access network but a lot of work remains to be done since the group was established just on last year. In this paper we propose a new multi-radio multi-channel mesh architecture for hot zones which works using a distributed coordination function (DCF)-based technique for interconnecting APs and a simple but effective radio routing mechanism. A major advantage of our proposed scheme is that, putting routing issues aside, it introduces no change into the MAC protocol of IEEE 802.11. Our simulations results obtained in OPNET show the great effectiveness of radio routing for balancing the traffic load within the network as well as interesting results related with the size of packets and the mesh architecture itself that could lead to further research in the future. Moreover, the results show the proposed architecture yields a very good performance in terms of total throughput and transmission delay
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14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003., 2003
In this paper, we propose a new transmission and resource allocation technique on multicarrier di... more In this paper, we propose a new transmission and resource allocation technique on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers the scheme reduces the inter-carrier interference generated by high-speed users
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Arquivos brasileiros de cardiologia, 1984
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Different cloud and data/video delivery applications require the use of high-speed links to fulfi... more Different cloud and data/video delivery applications require the use of high-speed links to fulfill a reasonable qu ality of experience. However, Internet connections in developing c ountries like Chile are -in many casesfar from being suitable for transferring large data files in a fast and efficient manner toend (non-business) users. These are usually non-dedicated lin ks, with no more than 10-20 Mbps at the user’s end, showing patterns of congestion (and high latency) when connecting to distant servers. In this context, it has been shown in controlled/l ab situationsthat certain UDP based protocols outperform TCP. In this work, we aim to empirically evaluate upper bounds of performance for a set of UDP-based protocols, comparing their efficiency with respect to TCP, in realistic settings. We performed a long-term measurement campaign, transmitting1 GB files from Santiago, Chile to Atlanta, US, allowing us to compute eventual efficiency gains of UDP, Tsunami and UDT over TCP. Our results show that UDT and UDP perform better than TCP and Tsunami when comparing their achievable rates, stability and completion time to download large files. In terms of their attainable throughput, UDP and UDT duplicate TCP (on average), where UDT has the added benefit of acknowledging receptions of data blocks, being then suitable for reliablehighspeed transmissions. Therefore, typical home-users with l imited download bandwidth would significantly improve their quali ty of experience if UDT is employed as an application-layer proto col for reliable transmissions, being not only transparent to them but also highly efficient.
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Bookmarks Related papers MentionsView impact
The 2010 14th International Conference on Computer Supported Cooperative Work in Design, 2010
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2007 16th IST Mobile and Wireless Communications Summit, 2007
The ambient networks project is developing advanced networking capabilities, such as dynamic mult... more The ambient networks project is developing advanced networking capabilities, such as dynamic multi-access, network mobility, together with availability of ensured service or network context. The Ambient framework offers a "plug-and-play" flexibility to accommodate different routing schemes for alternative scenarios, ranging from completely flat topologies hanging off a common core network to deeply nested topologies attached to a core. This paper
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VTC Spring 2008 - IEEE Vehicular Technology Conference, 2008
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2008 Fourth Workshop on Network Coding, Theory and Applications, 2008
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2010 10th International Symposium on Communications and Information Technologies, 2010
Video fingerprinting is one of the most promising technologies to uniquely identify video content... more Video fingerprinting is one of the most promising technologies to uniquely identify video content in the Internet in a totally format-independent way. The logic behind the creation of the video fingerprints or perceptual hashes is a key factor for the performance of the system, especially in terms of storage and search efficiency. Although several video fingerprinting methods have been proposed,
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 2007
... MOBILE NETWORKS Eleni Kamateri and Lefteris Mamatas Demokritos University of Thrace Vas. ... ... more ... MOBILE NETWORKS Eleni Kamateri and Lefteris Mamatas Demokritos University of Thrace Vas. ... [4] J. Manner, G. Karagiannis, and A. McDonald. 'NSLP for Quality-of-Service signalling.' Internet Draft - Work in progress, Internet Engineering Task Force, January 2006. ...
Bookmarks Related papers MentionsView impact
The proposed medium access protocol deals especially with the timely-transmission of real-time pa... more The proposed medium access protocol deals especially with the timely-transmission of real-time packets in wireless multimedia networks where users of various types of traffic are present. It works based on the time division multiple access (TDMA) with time division duplex (TDD) technique as well as fixed-length packet switching incorporating two policies, which work differently during non-congestion and congestion states. The simulation results show good performance of the proposed method, even under high-load conditions, and a good trade-off characteristic between real-time access delay and non-real time buffer occupancy, during periods of congestion
Bookmarks Related papers MentionsView impact
2005 Asia-Pacific Conference on Communications
The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promis... more The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promising architecture for achieving a ubiquitous wireless Internet access in the future. However, the current IEEE 802.11 protocol is aimed at single access point (AP) environments and many problems related to the wireless meshed interconnection of APs and mobile terminals (MTs) remain to
Bookmarks Related papers MentionsView impact
APCC/MDMC '04. The 2004 Joint Conference of the 10th Asia-Pacific Conference on Communications and the 5th International Symposium on Multi-Dimensional Mobile Communications Proceeding
We propose a new transmission and resource allocation technique based on multicarrier direct-sequ... more We propose a new transmission and resource allocation technique based on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers the scheme reduces the inter-carrier interference generated by high-speed users while keeping
Bookmarks Related papers MentionsView impact
We propose a new transmission and resource allocation technique based on multicarrier direct-sequ... more We propose a new transmission and resource allocation technique based on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers, the scheme reduces the intercarrier interference generated by high-speed users while keeping the intersymbol interference at a low level due to multicarrier transmission. The analysis and results show that a substantial mitigation of both the intercarrier interference and bit error rate, without reducing the system bandwidth efficiency, can be achieved.
Bookmarks Related papers MentionsView impact
Vehicular Technology Conference, 1988, IEEE 38th
We propose a new transmission and multiple access method for future broadband wireless networks. ... more We propose a new transmission and multiple access method for future broadband wireless networks. The scheme combines the advantages of orthogonal frequency division multiple access (OFDMA) and code division multiple access (CDMA) to cope simultaneously with both frequency spread produced by the Doppler effect, and time spread caused by the multipath channel. Through the code orthogonalization of neighboring (close) OFDM subcarriers, the method mitigates the intercarrier interference generated by high speed users while keeping the advantages offered by OFDMA to diminish the intersymbol interference produced by multipaths. In this way, the method optimizes the reliability of the communication channel provided to every user according to its speed, position and channel characteristics. The allocation of subcarriers and orthogonal codes to users is carried out dynamically with time by considering parameters such as required bitrate, speed, level of interference, multipath effects and phy...
Bookmarks Related papers MentionsView impact
Proceedings of the 11th international symposium on Modeling, analysis and simulation of wireless and mobile systems - MSWiM '08, 2008
Bookmarks Related papers MentionsView impact
IEEE INFOCOM 2008 - The 27th Conference on Computer Communications, 2008
Abstract—Cooperative relaying has been shown to provide diversity gains which can significantly i... more Abstract—Cooperative relaying has been shown to provide diversity gains which can significantly improve the Packet Error Rate (PER) in wireless transmissions. In ad hoc wireless rout- ing where packets may travel over a number of hops before reaching the destination, hop-wise cooperative relaying may severely reduce network capacity. This approach was mainly addressed in literature so far. In this paper,
Bookmarks Related papers MentionsView impact
GLOBECOM '05. IEEE Global Telecommunications Conference, 2005., 2005
The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promis... more The mesh topology based on the standard IEEE 802.11 for wireless LANs appears to be a very promising architecture for achieving a ubiquitous wireless Internet access in the future. However, the current IEEE 802.11 protocol is aimed at single-AP (access point) environments and many problems related to the wireless meshed interconnection of APs and mobile terminals (MTs) remain to be solved. Some proposed solutions to build such mesh architectures are based on single-channel ad-hoc oriented schemes in which IEEE 802.11 protocol has been modified. The main problem with this type of schemes, however, lies in the very low performance of the single-channel architecture itself. The task group S of IEEE 802.11 is currently working out standards for IEEE 802.11-compliant mesh architectures in a number of usage scenarios including residential, office and campus/community/public access network but a lot of work remains to be done since the group was established just on last year. In this paper we propose a new multi-radio multi-channel mesh architecture for hot zones which works using a distributed coordination function (DCF)-based technique for interconnecting APs and a simple but effective radio routing mechanism. A major advantage of our proposed scheme is that, putting routing issues aside, it introduces no change into the MAC protocol of IEEE 802.11. Our simulations results obtained in OPNET show the great effectiveness of radio routing for balancing the traffic load within the network as well as interesting results related with the size of packets and the mesh architecture itself that could lead to further research in the future. Moreover, the results show the proposed architecture yields a very good performance in terms of total throughput and transmission delay
Bookmarks Related papers MentionsView impact
14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003., 2003
In this paper, we propose a new transmission and resource allocation technique on multicarrier di... more In this paper, we propose a new transmission and resource allocation technique on multicarrier direct-sequence CDMA (MC-DS-CDMA). The proposed system allocates subcarriers and spreading codes to users by considering their current bandwidth requirements and frequency shifts caused by their movement. Through the use of low-correlation spreading codes in close subcarriers the scheme reduces the inter-carrier interference generated by high-speed users
Bookmarks Related papers MentionsView impact
Arquivos brasileiros de cardiologia, 1984
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Different cloud and data/video delivery applications require the use of high-speed links to fulfi... more Different cloud and data/video delivery applications require the use of high-speed links to fulfill a reasonable qu ality of experience. However, Internet connections in developing c ountries like Chile are -in many casesfar from being suitable for transferring large data files in a fast and efficient manner toend (non-business) users. These are usually non-dedicated lin ks, with no more than 10-20 Mbps at the user’s end, showing patterns of congestion (and high latency) when connecting to distant servers. In this context, it has been shown in controlled/l ab situationsthat certain UDP based protocols outperform TCP. In this work, we aim to empirically evaluate upper bounds of performance for a set of UDP-based protocols, comparing their efficiency with respect to TCP, in realistic settings. We performed a long-term measurement campaign, transmitting1 GB files from Santiago, Chile to Atlanta, US, allowing us to compute eventual efficiency gains of UDP, Tsunami and UDT over TCP. Our results show that UDT and UDP perform better than TCP and Tsunami when comparing their achievable rates, stability and completion time to download large files. In terms of their attainable throughput, UDP and UDT duplicate TCP (on average), where UDT has the added benefit of acknowledging receptions of data blocks, being then suitable for reliablehighspeed transmissions. Therefore, typical home-users with l imited download bandwidth would significantly improve their quali ty of experience if UDT is employed as an application-layer proto col for reliable transmissions, being not only transparent to them but also highly efficient.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
The 2010 14th International Conference on Computer Supported Cooperative Work in Design, 2010
Bookmarks Related papers MentionsView impact
2007 16th IST Mobile and Wireless Communications Summit, 2007
The ambient networks project is developing advanced networking capabilities, such as dynamic mult... more The ambient networks project is developing advanced networking capabilities, such as dynamic multi-access, network mobility, together with availability of ensured service or network context. The Ambient framework offers a "plug-and-play" flexibility to accommodate different routing schemes for alternative scenarios, ranging from completely flat topologies hanging off a common core network to deeply nested topologies attached to a core. This paper
Bookmarks Related papers MentionsView impact
VTC Spring 2008 - IEEE Vehicular Technology Conference, 2008
Bookmarks Related papers MentionsView impact
2008 Fourth Workshop on Network Coding, Theory and Applications, 2008
Bookmarks Related papers MentionsView impact
2010 10th International Symposium on Communications and Information Technologies, 2010
Video fingerprinting is one of the most promising technologies to uniquely identify video content... more Video fingerprinting is one of the most promising technologies to uniquely identify video content in the Internet in a totally format-independent way. The logic behind the creation of the video fingerprints or perceptual hashes is a key factor for the performance of the system, especially in terms of storage and search efficiency. Although several video fingerprinting methods have been proposed,
Bookmarks Related papers MentionsView impact