The IEEE 802.16 standard defines two main duplexing modes: Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). The FDD can be divided further into Full-FDD (F-FDD) and Half-FDD (H-FDD). F-FDD requires full duplexing support from subscriber stations and works with two frequency bands. TDD operates a single frequency band, but it does not need full-duplexing support. H-FDD is a combination of these: it works with two frequency bands and does not require full-duplexing support. The cost of this is a more complicated scheduling and added overhead. Still, H-FDD might be the only possible duplexing mode in some occasions. In this paper, these duplexing modes are compared and the H-FDD specific features, such as group balancing, are presented. The simulation results show that H-FDD does not quite match the performance of F-FDD or TDD. In the downlink direction, F-FDD and TDD have similar performance but in the uplink direction F-FDD can benefit from subchannelization gain with fewer bursts per frame.
{"title":"Analysis of duplexing modes in the IEEE 802.16 wireless system","authors":"H. Martikainen","doi":"10.1109/EW.2010.5483461","DOIUrl":"https://doi.org/10.1109/EW.2010.5483461","url":null,"abstract":"The IEEE 802.16 standard defines two main duplexing modes: Time Division Duplexing (TDD) and Frequency Division Duplexing (FDD). The FDD can be divided further into Full-FDD (F-FDD) and Half-FDD (H-FDD). F-FDD requires full duplexing support from subscriber stations and works with two frequency bands. TDD operates a single frequency band, but it does not need full-duplexing support. H-FDD is a combination of these: it works with two frequency bands and does not require full-duplexing support. The cost of this is a more complicated scheduling and added overhead. Still, H-FDD might be the only possible duplexing mode in some occasions. In this paper, these duplexing modes are compared and the H-FDD specific features, such as group balancing, are presented. The simulation results show that H-FDD does not quite match the performance of F-FDD or TDD. In the downlink direction, F-FDD and TDD have similar performance but in the uplink direction F-FDD can benefit from subchannelization gain with fewer bursts per frame.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129046530","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In a powerful secrecy attack, eavesdroppers can collude, i.e., they can share their observations. Securing information in such a scenario will be an even more challenging task compared to non-colluding case. We here analyze the effect of eavesdropper collusion on the achievable performance in both the path loss and ergodic multi-path fading models. We provide two results: 1) For the Poisson point process model in a random extended network, if the legitimate nodes have unit intensity (λ = 1) and the colluding eavesdroppers have an intensity of λe = O((log n)−(2+p)) for any p > 0, almost all of the nodes can achieve a secure rate of Ω(1/√n); I and 2) In the K-user Gaussian interference channel with E external colluding eavesdroppers, a secure degrees of freedom of η =[1/2−E/K]+ per frequency-time slot is achievable for each user in the ergodic setting (in the absence of the eavesdropper channel state information).
{"title":"On the effect of colluding eavesdroppers on secrecy capacity scaling","authors":"O. O. Koyluoglu, C. E. Koksal, H. E. Gamal","doi":"10.1109/EW.2010.5483463","DOIUrl":"https://doi.org/10.1109/EW.2010.5483463","url":null,"abstract":"In a powerful secrecy attack, eavesdroppers can collude, i.e., they can share their observations. Securing information in such a scenario will be an even more challenging task compared to non-colluding case. We here analyze the effect of eavesdropper collusion on the achievable performance in both the path loss and ergodic multi-path fading models. We provide two results: 1) For the Poisson point process model in a random extended network, if the legitimate nodes have unit intensity (λ = 1) and the colluding eavesdroppers have an intensity of λ<inf>e</inf> = O((log n)<sup>−(2+p)</sup>) for any p > 0, almost all of the nodes can achieve a secure rate of Ω(1/√n); I and 2) In the K-user Gaussian interference channel with E external colluding eavesdroppers, a secure degrees of freedom of η =[1/2−E/K]<sup>+</sup> per frequency-time slot is achievable for each user in the ergodic setting (in the absence of the eavesdropper channel state information).","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134533274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Offering throughput guarantees for wireless networks is of interest to both the network operators and the customers. In this paper, an optimization problem is formulated which aims at maximizing the throughput that can be guaranteed to the mobile users. Solution to this problem has already been found for users with different channel quality distributions. However, this solution is suboptimal for time-windows containing only a small amount of time-slots. Hassel et al. proposed an adaptive scheduling algorithm that showed good performance for short time-windows but that algorithm can only fulfill the throughput guarantees when the placement of the window is fixed and cannot promise the throughput guarantees within time-windows with a different duration or a different placement than that used by the algorithm. In this work, we propose a very simple adaptive scheduling algorithm that overcomes the problem of fixed window placement and provides similar throughput guarantees. Our simplified adaptive algorithm also performs significantly better than other well-known scheduling algorithms.
{"title":"A simplified adaptive scheduling algorithm for increased throughput guarantees","authors":"Jawad Rasool, G. Øien","doi":"10.1109/EW.2010.5483411","DOIUrl":"https://doi.org/10.1109/EW.2010.5483411","url":null,"abstract":"Offering throughput guarantees for wireless networks is of interest to both the network operators and the customers. In this paper, an optimization problem is formulated which aims at maximizing the throughput that can be guaranteed to the mobile users. Solution to this problem has already been found for users with different channel quality distributions. However, this solution is suboptimal for time-windows containing only a small amount of time-slots. Hassel et al. proposed an adaptive scheduling algorithm that showed good performance for short time-windows but that algorithm can only fulfill the throughput guarantees when the placement of the window is fixed and cannot promise the throughput guarantees within time-windows with a different duration or a different placement than that used by the algorithm. In this work, we propose a very simple adaptive scheduling algorithm that overcomes the problem of fixed window placement and provides similar throughput guarantees. Our simplified adaptive algorithm also performs significantly better than other well-known scheduling algorithms.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129472763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
DS-CDMA is currently the most widely used multiple-access scheme in mobile communications. It uses spreading sequences to separate different links, e.g., the base-station to user links in the downlink or the user to base-station links in the uplink. These spreading codes are usually allocated when the link is set up and kept fixed for the duration of the transmission. Spreading sequences are designed to have good cross-correlation properties in order to avoid interference and to be easy to generate in order to reduce the implementation complexity. In addition, they are designed to have good autocorrelation properties or equivalently a flat spectrum since this guarantees the anti-fading capability of DS-CDMA links. This paper presents a new design paradigm where spreading codes are not kept fixed anymore but are adapted to channel variations. It will be shown that this scheme can significantly improve the DS-CDMA link performance. The resulting implementation problems and complexity will be discussed.
{"title":"Channel-dependent adaptation scheme for spreading codes in DS-CDMA","authors":"Abhijit K. Ambekar, H. Schotten","doi":"10.1109/EW.2010.5483489","DOIUrl":"https://doi.org/10.1109/EW.2010.5483489","url":null,"abstract":"DS-CDMA is currently the most widely used multiple-access scheme in mobile communications. It uses spreading sequences to separate different links, e.g., the base-station to user links in the downlink or the user to base-station links in the uplink. These spreading codes are usually allocated when the link is set up and kept fixed for the duration of the transmission. Spreading sequences are designed to have good cross-correlation properties in order to avoid interference and to be easy to generate in order to reduce the implementation complexity. In addition, they are designed to have good autocorrelation properties or equivalently a flat spectrum since this guarantees the anti-fading capability of DS-CDMA links. This paper presents a new design paradigm where spreading codes are not kept fixed anymore but are adapted to channel variations. It will be shown that this scheme can significantly improve the DS-CDMA link performance. The resulting implementation problems and complexity will be discussed.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133049907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Staub, M. Anwander, K. Baumann, T. Braun, M. Brogle, Kirsten Dolfus, Christian Félix, P. Goode
Wireless Mesh Networks (WMNs) operating in the 5 GHz band (IEEE 802.11 a/h) offer a great opportunity to function as wireless access networks. Remote sites that lack direct access to a wired/fibre network may benefit from this technology, as it can be used to bridge possibly large distances. The high gain of directional antennas improves the reception of signals in focused directions and reduces interference from unwanted sources. Therefore, they are the preferred choice for such bridging scenarios. In this paper, we present our experiences with setting up such a Wireless Access Network using directional antennas in the area of Neuchâtel, Switzerland. We describe the necessary equipment and planning steps, highlight common pitfalls and discuss gained insights as well as experimental results. Measured data supports the feasibility of our networking approach, yet reveals the high impact of general challenges that have to be overcome in real-world deployments.
{"title":"Connecting remote sites to the wired backbone by wireless mesh access networks","authors":"T. Staub, M. Anwander, K. Baumann, T. Braun, M. Brogle, Kirsten Dolfus, Christian Félix, P. Goode","doi":"10.1109/EW.2010.5483454","DOIUrl":"https://doi.org/10.1109/EW.2010.5483454","url":null,"abstract":"Wireless Mesh Networks (WMNs) operating in the 5 GHz band (IEEE 802.11 a/h) offer a great opportunity to function as wireless access networks. Remote sites that lack direct access to a wired/fibre network may benefit from this technology, as it can be used to bridge possibly large distances. The high gain of directional antennas improves the reception of signals in focused directions and reduces interference from unwanted sources. Therefore, they are the preferred choice for such bridging scenarios. In this paper, we present our experiences with setting up such a Wireless Access Network using directional antennas in the area of Neuchâtel, Switzerland. We describe the necessary equipment and planning steps, highlight common pitfalls and discuss gained insights as well as experimental results. Measured data supports the feasibility of our networking approach, yet reveals the high impact of general challenges that have to be overcome in real-world deployments.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133746909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Many location determination systems have been developed lately due to growing demands on location based applications and services, however, the performance of most systems is not well understood because a typical indoor system would depend on a lot of factors and the conditions under which reported tests were carried out could be very different. In this work, we analyze theoretical localization limits and propose a precision bound as a benchmark standard to evaluate the performance of indoor systems under different configuration settings and environmental dynamics. We examine a set of localization mechanisms using data sets measured from an underground floor plan. We compare the performance of these systems and analyze their unique responses to the change of system configurations (such as sniffer deployment methods and reference measurements) and localization processing techniques, we found that database-based indoor systems generally perform better than the distance-based systems. From the comparison study, we observed that while it appears difficult to interpret the relationship between the performance of a localization system and various environmental and system factors, the achievable precision of a location determination system deployed at a given building is bounded and this bound is predictable. Thus this research provides a valuable criterion for the evaluation of location determination systems.
{"title":"Ultimate precision bound and comparison study of dynamic indoor localization systems","authors":"Yiming Ji","doi":"10.1109/EW.2010.5483408","DOIUrl":"https://doi.org/10.1109/EW.2010.5483408","url":null,"abstract":"Many location determination systems have been developed lately due to growing demands on location based applications and services, however, the performance of most systems is not well understood because a typical indoor system would depend on a lot of factors and the conditions under which reported tests were carried out could be very different. In this work, we analyze theoretical localization limits and propose a precision bound as a benchmark standard to evaluate the performance of indoor systems under different configuration settings and environmental dynamics. We examine a set of localization mechanisms using data sets measured from an underground floor plan. We compare the performance of these systems and analyze their unique responses to the change of system configurations (such as sniffer deployment methods and reference measurements) and localization processing techniques, we found that database-based indoor systems generally perform better than the distance-based systems. From the comparison study, we observed that while it appears difficult to interpret the relationship between the performance of a localization system and various environmental and system factors, the achievable precision of a location determination system deployed at a given building is bounded and this bound is predictable. Thus this research provides a valuable criterion for the evaluation of location determination systems.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130170257","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper1 derives approximations allowing the estimation of outage probability for standard irregular LDPC codes and full-diversity Root-LDPC codes used over nonergodic block-fading channels. Two separate approaches are discussed: a numerical approximation, obtained by curve fitting, for both code ensembles, and an analytical approximation for Root-LDPC codes, obtained under the assumption that the slope of the iterative threshold curve of a given code ensemble matches the slope of the outage capacity curve in the high-SNR regime.
{"title":"Outage thresholds of LDPC codes over nonergodic block-fading channels","authors":"I. Andriyanova, E. Biglieri, J. Boutros","doi":"10.1109/EW.2010.5483531","DOIUrl":"https://doi.org/10.1109/EW.2010.5483531","url":null,"abstract":"This paper1 derives approximations allowing the estimation of outage probability for standard irregular LDPC codes and full-diversity Root-LDPC codes used over nonergodic block-fading channels. Two separate approaches are discussed: a numerical approximation, obtained by curve fitting, for both code ensembles, and an analytical approximation for Root-LDPC codes, obtained under the assumption that the slope of the iterative threshold curve of a given code ensemble matches the slope of the outage capacity curve in the high-SNR regime.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130214517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We analyze and compare the maximum-likelihood (ML) decoder and the maximum a-posteriori (MAP) decoder for coding over a decode-and-forward relay network with orthogonal channels. Using a specific model for the errors introduced by the relay, we derive an optimal MAP decoder that operates on a super-trellis and estimates jointly the transmitted codeword and the error pattern introduced by the relay. Furthermore we present analytical expressions for the error rates for both ML and MAP decoding.
{"title":"Error bounds for decode-and-forward relaying","authors":"Alexandre Graell i Amat, I. Land, L. Rasmussen","doi":"10.1109/EW.2010.5483536","DOIUrl":"https://doi.org/10.1109/EW.2010.5483536","url":null,"abstract":"We analyze and compare the maximum-likelihood (ML) decoder and the maximum a-posteriori (MAP) decoder for coding over a decode-and-forward relay network with orthogonal channels. Using a specific model for the errors introduced by the relay, we derive an optimal MAP decoder that operates on a super-trellis and estimates jointly the transmitted codeword and the error pattern introduced by the relay. Furthermore we present analytical expressions for the error rates for both ML and MAP decoding.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131610053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rate-Compatible/Quasi-Cyclic LDPC codes are gaining importance because of their tradeoff between performance and simplicity. For these reasons, RC/QC LDPC codes have been included in several recent standards such as 802.20 and 3GPP2. General proposals for hardware encoding of this kind of LDPC codes either consume a lot of area to increase the throughput or are slow-encoding schemes to reduce the area consumption. Some others have to pre-compute a non-sparse generator matrix and store it in memory in order to encode. In contrast, by exploiting the number of null matrices in the mother parity check matrix defined in these standards, this proposal defines a low-cost encoder with high input packet throughput (little time between input frames). Moreover, as the encoding is performed using the original parity check matrix, there is no need to pre-compute or store the dense generation matrix in memory.
{"title":"3GPP2/802.20 RC/QC-LDPC encoding","authors":"Jesús M. Pérez, V. Fernández","doi":"10.1109/EW.2010.5483407","DOIUrl":"https://doi.org/10.1109/EW.2010.5483407","url":null,"abstract":"Rate-Compatible/Quasi-Cyclic LDPC codes are gaining importance because of their tradeoff between performance and simplicity. For these reasons, RC/QC LDPC codes have been included in several recent standards such as 802.20 and 3GPP2. General proposals for hardware encoding of this kind of LDPC codes either consume a lot of area to increase the throughput or are slow-encoding schemes to reduce the area consumption. Some others have to pre-compute a non-sparse generator matrix and store it in memory in order to encode. In contrast, by exploiting the number of null matrices in the mother parity check matrix defined in these standards, this proposal defines a low-cost encoder with high input packet throughput (little time between input frames). Moreover, as the encoding is performed using the original parity check matrix, there is no need to pre-compute or store the dense generation matrix in memory.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131660236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Serrano, Andres Garcia-Saavedra, M. Hollick, A. Banchs
Understanding the energy consumption of wireless interfaces is critical to provide guidelines for the design and implementation of new protocols or interfaces. In this work we analyze the energy performance of an IEEE 802.11 WLAN. Our contributions are as follows: i) we present an accurate analytical model that is able to predict the energy consumption, ii) we present an approximate model that sacrifices accuracy for the sake of analytical tractability, iii) based on this simplified analysis, we derive the optimal configuration to maximize energy efficiency of a WLAN, and iv) finally, we also analyze the tradeoff between throughput and energy efficiency that IEEE 802.11 imposes. While most of these results consider a homogeneous WLAN scenario where all stations share the same energy features, we also discuss the case of heterogeneous environments, where different devices show different power consumption characteristics.
{"title":"On the energy efficiency of IEEE 802.11 WLANs","authors":"P. Serrano, Andres Garcia-Saavedra, M. Hollick, A. Banchs","doi":"10.1109/EW.2010.5483505","DOIUrl":"https://doi.org/10.1109/EW.2010.5483505","url":null,"abstract":"Understanding the energy consumption of wireless interfaces is critical to provide guidelines for the design and implementation of new protocols or interfaces. In this work we analyze the energy performance of an IEEE 802.11 WLAN. Our contributions are as follows: i) we present an accurate analytical model that is able to predict the energy consumption, ii) we present an approximate model that sacrifices accuracy for the sake of analytical tractability, iii) based on this simplified analysis, we derive the optimal configuration to maximize energy efficiency of a WLAN, and iv) finally, we also analyze the tradeoff between throughput and energy efficiency that IEEE 802.11 imposes. While most of these results consider a homogeneous WLAN scenario where all stations share the same energy features, we also discuss the case of heterogeneous environments, where different devices show different power consumption characteristics.","PeriodicalId":232165,"journal":{"name":"2010 European Wireless Conference (EW)","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2010-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131785103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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