The WiMAX OFDMA environment is unique in that it requires a two-dimensional allocation i.e. simultaneously in time and frequency on the downlink. The downlink resource has to be broken into sub-rectangles, each of which is allocated to one or more flows. In this paper, we have proposed a fast allocation algorithm to allocate the downlink resource to multiple flows while honouring Quality of Service and concurrency requirements. We present simulation results to show the performance of the algorithm.
{"title":"A fast and efficient two-dimensional frame composer for OFDMA WiMAX base-stations using floorplan slicing","authors":"Abheek Saha","doi":"10.1109/EW.2008.4623858","DOIUrl":"https://doi.org/10.1109/EW.2008.4623858","url":null,"abstract":"The WiMAX OFDMA environment is unique in that it requires a two-dimensional allocation i.e. simultaneously in time and frequency on the downlink. The downlink resource has to be broken into sub-rectangles, each of which is allocated to one or more flows. In this paper, we have proposed a fast allocation algorithm to allocate the downlink resource to multiple flows while honouring Quality of Service and concurrency requirements. We present simulation results to show the performance of the algorithm.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123886072","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}
Phase noise, frequency dispersion and time shifts are main challenges that concern OFDM systems. However, perfect synchronization between a transmitter and a receiver cannot be accomplished. These difficulties are dilated in an OFDMA system and consequently the performance degradation due to synchronization errors is increased. The receiver has the task to choose optimal sampling instants and to align the subcarrier frequencies of an OFDM symbol that contains signals from multiple users. In this study the effects of time and frequency synchronization errors are examined. The presented results refer to adjacent subcarrier permutation OFDMA systems where users are separated in bands of adjacent subcarriers. First an uplink OFDMA system model is presented and analytical relations explaining how synchronization errors cause both intercarrier and intersymbol interference are extracted. Then simulation results that quantify the SNR degradation due to synchronization errors are presented. The system used as a reference in this current study is the mobile WiMax with subband OFDMA allocation strategy and 1024 subcarriers.
{"title":"SNR degradation due to timing and frequency synchronization errors for OFDMA systems with subband carrier allocation","authors":"K. Maliatsos, A. Adamis, P. Constantinou","doi":"10.1109/EW.2008.4623899","DOIUrl":"https://doi.org/10.1109/EW.2008.4623899","url":null,"abstract":"Phase noise, frequency dispersion and time shifts are main challenges that concern OFDM systems. However, perfect synchronization between a transmitter and a receiver cannot be accomplished. These difficulties are dilated in an OFDMA system and consequently the performance degradation due to synchronization errors is increased. The receiver has the task to choose optimal sampling instants and to align the subcarrier frequencies of an OFDM symbol that contains signals from multiple users. In this study the effects of time and frequency synchronization errors are examined. The presented results refer to adjacent subcarrier permutation OFDMA systems where users are separated in bands of adjacent subcarriers. First an uplink OFDMA system model is presented and analytical relations explaining how synchronization errors cause both intercarrier and intersymbol interference are extracted. Then simulation results that quantify the SNR degradation due to synchronization errors are presented. The system used as a reference in this current study is the mobile WiMax with subband OFDMA allocation strategy and 1024 subcarriers.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115947062","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}
Modulation with unequal power allocation (MUPA) is an unequal error protection technique (UEP) used when selective channel coding is barely suitable. This is the case of bandwidth constrained wireless communications where the overhead introduced by error control coding often turns out inefficient systems. On the other hand, MUPA protects data which exhibit different sensitivity to channel errors by distributing different transmission power to the modulation symbols according to the individual bit error sensitivities. MUPA has been studied in case of AWGN channel. In this work we propose an optimal power allocation scheme for the transmission of sensible data over fading channels. As to the optimization we rely on genetic algorithms (GA) which guarantee fast approximate solution with reduced complexity. Performance is evaluated on the Gilbert-Elliot (GE) model, extensively used in literature to reproduce the memory associated with radio channels.
{"title":"Performance analysis of modulation with unequal power allocations over fading channels: A genetic algorithm approach","authors":"M. Murroni","doi":"10.1109/EW.2008.4623838","DOIUrl":"https://doi.org/10.1109/EW.2008.4623838","url":null,"abstract":"Modulation with unequal power allocation (MUPA) is an unequal error protection technique (UEP) used when selective channel coding is barely suitable. This is the case of bandwidth constrained wireless communications where the overhead introduced by error control coding often turns out inefficient systems. On the other hand, MUPA protects data which exhibit different sensitivity to channel errors by distributing different transmission power to the modulation symbols according to the individual bit error sensitivities. MUPA has been studied in case of AWGN channel. In this work we propose an optimal power allocation scheme for the transmission of sensible data over fading channels. As to the optimization we rely on genetic algorithms (GA) which guarantee fast approximate solution with reduced complexity. Performance is evaluated on the Gilbert-Elliot (GE) model, extensively used in literature to reproduce the memory associated with radio channels.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116011791","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}
Relaying has been proposed to support users suffering from high shadowing or high interference and therefore being not able to receive high data rates. With adaptive relaying, a higher modulation and coding scheme (MCS) can be used which increases the feasible data rate. The investigation of relaying techniques widely concentrates on information theoretical methods. Instead, this paper focuses on system level simulations to exploit the achievable results within a realistic environment. The question which relaying methodology is the best choice if unicast and a multicast transmissions are possible is investigated. The results show that relaying techniques can improve the median cell throughput and decrease the outage probability in a mixed unicast and multicast environment. Cooperative relaying results in the lowest outage probability, whereas the introduced concept of dynamic resource relaying (DRR) offers a higher cell throughput. For the investigated LTE (3GPP long term evolution) system with a frequency re-use factor of one, the outage probability can be decreased by using relaying without further frequency planning.
{"title":"Performance evaluation of topologies for cooperative and Dynamic Resource Relaying","authors":"E. Reetz, R. Höckmann, R. Tönjes","doi":"10.1109/EW.2008.4623855","DOIUrl":"https://doi.org/10.1109/EW.2008.4623855","url":null,"abstract":"Relaying has been proposed to support users suffering from high shadowing or high interference and therefore being not able to receive high data rates. With adaptive relaying, a higher modulation and coding scheme (MCS) can be used which increases the feasible data rate. The investigation of relaying techniques widely concentrates on information theoretical methods. Instead, this paper focuses on system level simulations to exploit the achievable results within a realistic environment. The question which relaying methodology is the best choice if unicast and a multicast transmissions are possible is investigated. The results show that relaying techniques can improve the median cell throughput and decrease the outage probability in a mixed unicast and multicast environment. Cooperative relaying results in the lowest outage probability, whereas the introduced concept of dynamic resource relaying (DRR) offers a higher cell throughput. For the investigated LTE (3GPP long term evolution) system with a frequency re-use factor of one, the outage probability can be decreased by using relaying without further frequency planning.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"144 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116440570","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. Haustein, V. Venkatasubramanian, J. Eichinger, E. Schulz, T. Wirth, V. Jungnickel, A. Forck, S. Wahls, C. Juchems, F. Luhn, R. Zavrtak
In this paper we report the first real-time measurements of a 3GPP-LTE multiple antenna system in typical indoor and outdoor scenarios. In a single cell, single user scenario we demonstrate throughput exceeding 100 Mbit/s with a 2times2 MIMO configuration. This throughput gain is significant as compared to existing single antenna systems. We describe the basic LTE system design and prototype ingredients which were implemented to achieve these results. The highlight of our MIMO-OFDM system design is frequency dependent link adaptation. In principle, we show that this parallel link adaptation provides robust gains in a cellular broadband system. The robustness is seen in both our indoor and outdoor measurement results. The key feature of our work is implementation of multiple antenna concepts in such a broadband system.
{"title":"Measurements of multi-antenna gains using a 3GPP-LTE air interface in typical indoor and outdoor scenarios","authors":"T. Haustein, V. Venkatasubramanian, J. Eichinger, E. Schulz, T. Wirth, V. Jungnickel, A. Forck, S. Wahls, C. Juchems, F. Luhn, R. Zavrtak","doi":"10.1109/EW.2008.4623926","DOIUrl":"https://doi.org/10.1109/EW.2008.4623926","url":null,"abstract":"In this paper we report the first real-time measurements of a 3GPP-LTE multiple antenna system in typical indoor and outdoor scenarios. In a single cell, single user scenario we demonstrate throughput exceeding 100 Mbit/s with a 2times2 MIMO configuration. This throughput gain is significant as compared to existing single antenna systems. We describe the basic LTE system design and prototype ingredients which were implemented to achieve these results. The highlight of our MIMO-OFDM system design is frequency dependent link adaptation. In principle, we show that this parallel link adaptation provides robust gains in a cellular broadband system. The robustness is seen in both our indoor and outdoor measurement results. The key feature of our work is implementation of multiple antenna concepts in such a broadband system.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"57 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131657001","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 this paper we evaluate the performance of our earlier proposed enhanced relay-enabled distributed coordination function (ErDCF) for wireless ad hoc networks. The idea of ErDCF is to use high data rate nodes to work as relays for the low data rate nodes. ErDCF achieves higher throughput and reduced energy consumption compared to IEEE 802.11 distributed coordination function (DCF). This is a result of. 1) using relay which helps to increase the throughput and lower overall blocking time of nodes due to faster dual-hop transmission, 2) using dynamic preamble (i.e. using short preamble for the relay transmission) which further increases the throughput and lower overall blocking time and also by 3) reducing unnecessary overhearing (by other nodes not involved in transmission). We evaluate the throughput and energy performance of the ErDCF with different rate combinations. ErDCF (11,11) (ie. R1=R2=11 Mbps) yields a throughput improvement of 92.9% (at the packet length of 1000 bytes) and an energy saving of 72.2% at 50 nodes.
{"title":"Performance evaluation of Enhanced relay-enabled Distributed Coordination Function","authors":"R. Ahmad, F. Zheng, M. Drieberg, S. Ólafsson","doi":"10.1109/EW.2008.4623903","DOIUrl":"https://doi.org/10.1109/EW.2008.4623903","url":null,"abstract":"In this paper we evaluate the performance of our earlier proposed enhanced relay-enabled distributed coordination function (ErDCF) for wireless ad hoc networks. The idea of ErDCF is to use high data rate nodes to work as relays for the low data rate nodes. ErDCF achieves higher throughput and reduced energy consumption compared to IEEE 802.11 distributed coordination function (DCF). This is a result of. 1) using relay which helps to increase the throughput and lower overall blocking time of nodes due to faster dual-hop transmission, 2) using dynamic preamble (i.e. using short preamble for the relay transmission) which further increases the throughput and lower overall blocking time and also by 3) reducing unnecessary overhearing (by other nodes not involved in transmission). We evaluate the throughput and energy performance of the ErDCF with different rate combinations. ErDCF (11,11) (ie. R1=R2=11 Mbps) yields a throughput improvement of 92.9% (at the packet length of 1000 bytes) and an energy saving of 72.2% at 50 nodes.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132045702","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}
Multihop techniques are known as a practical solution for covering huge radio cell areas when there are only very few base stations (BS). This is the case when fiber access is limited and BS CAPEX and OPEX are very expensive. For WiMAX and 3GPP-LTE it is possible to operate relay stations which are only fed over the air link. While having some inherent overhead due to increased radio resource usage, there are nevertheless impressive gains in the coverage compared to a BS alone and also in the capacity of the whole radio cell. Near relay nodes (RN) there is not only better SINR to the user, which is obvious, but it is often more efficient to associate to a RN instead of the BS, taking into account all resources used for the first and second hop. Therefore this is a low cost measure to increase the system efficiency. This has been shown in the literature for artificial scenarios so far. In this paper we study a realistic scenario using data from topology information and raytracing. The city of Jersey was taken as example. The data is analyzed numerically, with all layer-1 and layer-2 performance models specified analytically. We study the case of one base station only, one BS with four RNs, and the latter plus another ring of nine RNs. The BS has fiber access, while the first hop of relays (H1) is fed over the air from BS and the second hop H2 is fed by the RNs of group H1. We present results for the gains in coverage and capacity that are obtained by these multihop techniques.
{"title":"Raising coverage and capacity using fixed relays in a realistic scenario","authors":"R. Schoenen, W. Zirwas, B. Walke","doi":"10.1109/EW.2008.4623913","DOIUrl":"https://doi.org/10.1109/EW.2008.4623913","url":null,"abstract":"Multihop techniques are known as a practical solution for covering huge radio cell areas when there are only very few base stations (BS). This is the case when fiber access is limited and BS CAPEX and OPEX are very expensive. For WiMAX and 3GPP-LTE it is possible to operate relay stations which are only fed over the air link. While having some inherent overhead due to increased radio resource usage, there are nevertheless impressive gains in the coverage compared to a BS alone and also in the capacity of the whole radio cell. Near relay nodes (RN) there is not only better SINR to the user, which is obvious, but it is often more efficient to associate to a RN instead of the BS, taking into account all resources used for the first and second hop. Therefore this is a low cost measure to increase the system efficiency. This has been shown in the literature for artificial scenarios so far. In this paper we study a realistic scenario using data from topology information and raytracing. The city of Jersey was taken as example. The data is analyzed numerically, with all layer-1 and layer-2 performance models specified analytically. We study the case of one base station only, one BS with four RNs, and the latter plus another ring of nine RNs. The BS has fiber access, while the first hop of relays (H1) is fed over the air from BS and the second hop H2 is fed by the RNs of group H1. We present results for the gains in coverage and capacity that are obtained by these multihop techniques.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132353489","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}
The goal of this work is to analyse how UMTS behaves when HSDPA is implemented. A theoretical model was developed, calculating network capacity, for a sector of a cell, focusing on the analysis of parameters, such as the number of served users, throughput, and cell radius. Two scenarios were assessed with different userspsila distribution. Two analyses are done: one until the network saturates, and another for a percentage of rejected users of 5 %. For the latter, one verifies that the limitative factor is the spreading factor, obtaining a maximum number of simultaneous users of approximately 33 for a service distribution profile based on voice, and 24 for one based on data services. An analysis of the global traffic processed by the Node B is also done, obtaining 350 MB/h as a maximum for a heavy data profile, and 140 MB/h for a service profile based on voice.
{"title":"Impact of HSDPA implementation on UMTS capacity and cell coverage","authors":"Monica Antunes, L. Correia, C. Caseiro","doi":"10.1109/EW.2008.4623912","DOIUrl":"https://doi.org/10.1109/EW.2008.4623912","url":null,"abstract":"The goal of this work is to analyse how UMTS behaves when HSDPA is implemented. A theoretical model was developed, calculating network capacity, for a sector of a cell, focusing on the analysis of parameters, such as the number of served users, throughput, and cell radius. Two scenarios were assessed with different userspsila distribution. Two analyses are done: one until the network saturates, and another for a percentage of rejected users of 5 %. For the latter, one verifies that the limitative factor is the spreading factor, obtaining a maximum number of simultaneous users of approximately 33 for a service distribution profile based on voice, and 24 for one based on data services. An analysis of the global traffic processed by the Node B is also done, obtaining 350 MB/h as a maximum for a heavy data profile, and 140 MB/h for a service profile based on voice.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124528658","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}
F. Bernardo, N. Vucevic, A. Umbert, M. López-Benítez
Next generation wireless networks will encompass a wide range of heterogeneous technologies in the radio access part. In such networks, the all-IP paradigm has been identified as a promising solution that will contribute benefits by providing IP-based transport through the radio and core network parts. However, this concept requires a precise management of the userpsilas mobility, especially in order to preserve userpsilas quality of service (QoS) throughout the sessionpsilas lifetime. The aim of this paper is to evaluate the quality of experience (QoE) that users perceive when the different QoS-aware mobility management strategies adopted in the AROMA project are applied. A real-time testbed that provides end-to-edge QoS in all-IP heterogeneous wireless access networks has been employed to obtain QoE results that hardly could be obtained by means of simulations.
{"title":"Quality of experience evaluation under QoS-aware mobility mechanisms","authors":"F. Bernardo, N. Vucevic, A. Umbert, M. López-Benítez","doi":"10.1109/EW.2008.4623860","DOIUrl":"https://doi.org/10.1109/EW.2008.4623860","url":null,"abstract":"Next generation wireless networks will encompass a wide range of heterogeneous technologies in the radio access part. In such networks, the all-IP paradigm has been identified as a promising solution that will contribute benefits by providing IP-based transport through the radio and core network parts. However, this concept requires a precise management of the userpsilas mobility, especially in order to preserve userpsilas quality of service (QoS) throughout the sessionpsilas lifetime. The aim of this paper is to evaluate the quality of experience (QoE) that users perceive when the different QoS-aware mobility management strategies adopted in the AROMA project are applied. A real-time testbed that provides end-to-edge QoS in all-IP heterogeneous wireless access networks has been employed to obtain QoE results that hardly could be obtained by means of simulations.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114931192","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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