A critical performance issue in providing VoIP service over wireless LANs is the voice packet delay due to handoffs as the user roams across different radio coverage regions. Most the recent research has focused on proactive approaches where control messages are transmitted from the mobile to prepare the access point and the other network nodes before the actual handoff occurs. Consequently, there is an increase in handoff control message traffic which will reduce the wireless LAN capacity to provide VoIP service. In this paper, we present a model for analyzing the effect of handoff control messages on the network capacity. To model the special "ON-OFF" characteristic of the voice sources in the real world, the Markov Modulated Poisson Process Model (MMPP) is used in the analysis. We assume that the control messages have higher priority than voice packets so that the service for voice packets also has an "ON-OFF" characteristic. The MMPP/MMPP/1 model was analyzed for different traffic characteristics (arrival rate and message lengths) depending on the handoff scheme used by the mobile stations in the network. For example, we show that the VoIP system capacity is reduced by 23% when the utilization of the control traffic is 4%. This analysis can provide a useful framework for the future development of different handoff schemes, trading off the higher success rate of handoff and decrease in network capacity.
{"title":"Impact of handoff control messages on VoIP over wireless LAN system capacity","authors":"S. K. Chui, On-ching Yue, W. Lau","doi":"10.1109/EW.2008.4623920","DOIUrl":"https://doi.org/10.1109/EW.2008.4623920","url":null,"abstract":"A critical performance issue in providing VoIP service over wireless LANs is the voice packet delay due to handoffs as the user roams across different radio coverage regions. Most the recent research has focused on proactive approaches where control messages are transmitted from the mobile to prepare the access point and the other network nodes before the actual handoff occurs. Consequently, there is an increase in handoff control message traffic which will reduce the wireless LAN capacity to provide VoIP service. In this paper, we present a model for analyzing the effect of handoff control messages on the network capacity. To model the special \"ON-OFF\" characteristic of the voice sources in the real world, the Markov Modulated Poisson Process Model (MMPP) is used in the analysis. We assume that the control messages have higher priority than voice packets so that the service for voice packets also has an \"ON-OFF\" characteristic. The MMPP/MMPP/1 model was analyzed for different traffic characteristics (arrival rate and message lengths) depending on the handoff scheme used by the mobile stations in the network. For example, we show that the VoIP system capacity is reduced by 23% when the utilization of the control traffic is 4%. This analysis can provide a useful framework for the future development of different handoff schemes, trading off the higher success rate of handoff and decrease in network capacity.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"17 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":"124769062","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 paper addresses a method to mitigate the peak to mean power ratio (PMEPR) of orthogonal frequency division multiplexing (OFDM) signals. The idea is to use adjacent bands of the OFDM spectrum to allocate optimized subcarriers so as to decrease the signal PMEPR with the help of SOCP optimization process. This way of doing has only sense if additional subcarriers all fall under the standard spectrum mask. According to this, the proposed method does not degrade the bit error rate (BER), has no bandwidth loss, does not imply any modification of the receiver and is standard compliant.
{"title":"PMEPR mitigation using adjacent bands of standards under spectrum mask constraint","authors":"Y. Louët, J. Palicot, S. Zabre","doi":"10.1109/EW.2008.4623887","DOIUrl":"https://doi.org/10.1109/EW.2008.4623887","url":null,"abstract":"This paper addresses a method to mitigate the peak to mean power ratio (PMEPR) of orthogonal frequency division multiplexing (OFDM) signals. The idea is to use adjacent bands of the OFDM spectrum to allocate optimized subcarriers so as to decrease the signal PMEPR with the help of SOCP optimization process. This way of doing has only sense if additional subcarriers all fall under the standard spectrum mask. According to this, the proposed method does not degrade the bit error rate (BER), has no bandwidth loss, does not imply any modification of the receiver and is standard compliant.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"25 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":"124912498","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 present the evaluation of a receiver signal processing chain for a 3GPP long term evolution (LTE) terminal, including coarse synchronisation, channel estimation, fine syncronisation (tracking), MIMO equalization and detection. Algorithm blocks are first individually explained and simulatively evaluated with a realistic channel model. Adjustments of the blocks to each other for improved robustness are described, like interaction between time synchronization and channel estimation performance. After joint optimization, the performance of the complete chain is evaluated. Practical tradeoffs between complexity and performance are investigated and low-complexity algorithms are used. The presented receiver achieves an implementation loss of about 2 dB compared to perfect synchronization and channel estimation conditions.
{"title":"Performance evaluation of a 3GPP LTE terminal receiver","authors":"K. Manolakis, A. Ibing, V. Jungnickel","doi":"10.1109/EW.2008.4623925","DOIUrl":"https://doi.org/10.1109/EW.2008.4623925","url":null,"abstract":"In this paper we present the evaluation of a receiver signal processing chain for a 3GPP long term evolution (LTE) terminal, including coarse synchronisation, channel estimation, fine syncronisation (tracking), MIMO equalization and detection. Algorithm blocks are first individually explained and simulatively evaluated with a realistic channel model. Adjustments of the blocks to each other for improved robustness are described, like interaction between time synchronization and channel estimation performance. After joint optimization, the performance of the complete chain is evaluated. Practical tradeoffs between complexity and performance are investigated and low-complexity algorithms are used. The presented receiver achieves an implementation loss of about 2 dB compared to perfect synchronization and channel estimation conditions.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"46 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":"128059172","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 two different approaches found in the literature for throughput maximization of an adaptive transmission system operating over a slowly-varying flat-fading wireless channel with limited channel state information at the transmitter. While both approaches employ a finite number of transmission power levels and capacity-achieving codes, they differ in the number of quantization levels for the channel state, and whether or not information outage is allowed. Focusing on reliable data communications, we extend earlier works in a cross-layered fashion by adding an ARQ protocol, such that data received during such an outage can be retransmitted. We accurately analyze and compare the performance of the two approaches in terms of average spectral efficiency, probability of outage, and average feedback load, here defined in terms of the entropy of the feedback source. Numerical results show that, in general, there is a trade-off between the two approaches in terms of spectral efficiency and feedback load. However, scenarios in which one of the schemes can achieve a higher throughput at a lower feedback load are also identified.
{"title":"Spectral efficiency vs. feedback load in discrete-rate link adaptation: Is a zero information outage constraint optimal or not?","authors":"A. Gjendemsjø, S. D. L. K. D. Ryhove, G. Øien","doi":"10.1109/EW.2008.4623874","DOIUrl":"https://doi.org/10.1109/EW.2008.4623874","url":null,"abstract":"We analyze two different approaches found in the literature for throughput maximization of an adaptive transmission system operating over a slowly-varying flat-fading wireless channel with limited channel state information at the transmitter. While both approaches employ a finite number of transmission power levels and capacity-achieving codes, they differ in the number of quantization levels for the channel state, and whether or not information outage is allowed. Focusing on reliable data communications, we extend earlier works in a cross-layered fashion by adding an ARQ protocol, such that data received during such an outage can be retransmitted. We accurately analyze and compare the performance of the two approaches in terms of average spectral efficiency, probability of outage, and average feedback load, here defined in terms of the entropy of the feedback source. Numerical results show that, in general, there is a trade-off between the two approaches in terms of spectral efficiency and feedback load. However, scenarios in which one of the schemes can achieve a higher throughput at a lower feedback load are also identified.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"4 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":"126748971","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}
There are two basic duplexing schemes for present and future mobile radio networks, frequency-division duplex (FDD) and time-division duplex (TDD). In general each of these methods has its benefits and drawbacks. However, both schemes have their scenarios where they perform best. In future mobile radio systems typical wireless data communication will not only occur in metropolitan area scenarios like hotspots in airports, city centres, exhibition halls, etc., but also in wide area environments, e.g. a moving car in a rural environment. In general TDD is more appropriate for dense metropolitan area scenarios whereas FDD has benefits in wide area environments. If an FDD terminal which transmitted and received simultaneously, it would need an expensive duplex-filter, in order to separate UL and DL channels. Half-duplex terminals do not need such a filter. Therefore, half-duplex FDD appears to be attractive in terms of cost. A Relay is a promising concept for next generation systems. It allows enlarging the cell coverage range and is increasing the total cell capacity. A relay is not connected by wire, but works in a decode-and-forward principle and consequently is a cost-efficient alternative to base stations. This paper introduces a protocol to support parallel operation of half- and full-duplex FDD terminals in a relay capable system.
{"title":"Parallel operation of half- and full-duplex FDD in future multi-hop mobile radio networks","authors":"A. Otyakmaz, R. Schoenen, S. Dreier, B. Walke","doi":"10.1109/EW.2008.4623892","DOIUrl":"https://doi.org/10.1109/EW.2008.4623892","url":null,"abstract":"There are two basic duplexing schemes for present and future mobile radio networks, frequency-division duplex (FDD) and time-division duplex (TDD). In general each of these methods has its benefits and drawbacks. However, both schemes have their scenarios where they perform best. In future mobile radio systems typical wireless data communication will not only occur in metropolitan area scenarios like hotspots in airports, city centres, exhibition halls, etc., but also in wide area environments, e.g. a moving car in a rural environment. In general TDD is more appropriate for dense metropolitan area scenarios whereas FDD has benefits in wide area environments. If an FDD terminal which transmitted and received simultaneously, it would need an expensive duplex-filter, in order to separate UL and DL channels. Half-duplex terminals do not need such a filter. Therefore, half-duplex FDD appears to be attractive in terms of cost. A Relay is a promising concept for next generation systems. It allows enlarging the cell coverage range and is increasing the total cell capacity. A relay is not connected by wire, but works in a decode-and-forward principle and consequently is a cost-efficient alternative to base stations. This paper introduces a protocol to support parallel operation of half- and full-duplex FDD terminals in a relay capable system.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"9 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":"126515594","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}
OFDM (orthogonal frequency division multiplex) achieves high spectral efficiency in broadband wireless communications but has poor amplification efficiency due to its large peak-to-average power ratio. This paper presents achievable average power efficiency for the OFDM signal when the Doherty and extended Doherty transmitters are employed. By modelling the envelope of OFDM signal as a Rayleigh-distributed signal, average power efficiency for the OFDM signal is calculated as a function of clipping probability. Numerical calculation results assuming an ideal class-B amplifier and predistortion linearizer show that average drain efficiency of the two amplifiers for a clipping probability of 0.1% are 50.5 and 55.6%, respectively. It is concluded that the extended Doherty amplifier can improve power efficiency by several percents by optimizing the main amplifier contribution ratio alpha.
{"title":"Power efficiency of OFDM signal amplification with Doherty and extended Doherty transmitters","authors":"Y. Yamao, Yoshikazu Toyama, Edwin M. Umali","doi":"10.1109/EW.2008.4623918","DOIUrl":"https://doi.org/10.1109/EW.2008.4623918","url":null,"abstract":"OFDM (orthogonal frequency division multiplex) achieves high spectral efficiency in broadband wireless communications but has poor amplification efficiency due to its large peak-to-average power ratio. This paper presents achievable average power efficiency for the OFDM signal when the Doherty and extended Doherty transmitters are employed. By modelling the envelope of OFDM signal as a Rayleigh-distributed signal, average power efficiency for the OFDM signal is calculated as a function of clipping probability. Numerical calculation results assuming an ideal class-B amplifier and predistortion linearizer show that average drain efficiency of the two amplifiers for a clipping probability of 0.1% are 50.5 and 55.6%, respectively. It is concluded that the extended Doherty amplifier can improve power efficiency by several percents by optimizing the main amplifier contribution ratio alpha.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"116 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":"127993845","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 optimization theoretic based rate allocation strategies have been developed for allocating some optimal rates to the competing users in wireless ad hoc networks. By considering different objective functions (such as congestion level, total packet loss and so on), the researchers propose some optimization framework by which the problem can be solved. Due to the rapid increase in the development of different video applications in such environments and the existence of difficulties in satisfying the prespecified QoS limits, increasing the received video quality can be considered as an important and challenging issue. The quality of the received video stream is inversely proportional to the amount of distortion which is being imposed on the video stream by the network packet loss and the video encoder. The main objective of the current paper is to introduce an optimization framework in which by optimal rate allocation to some competing video sources, the aggregate distortion of the all of the sources be minimized. The simulation results verify the claims.
{"title":"Minimum distortion video transmission over wireless ad hoc networks","authors":"P. Goudarzi","doi":"10.1109/EW.2008.4623863","DOIUrl":"https://doi.org/10.1109/EW.2008.4623863","url":null,"abstract":"Many optimization theoretic based rate allocation strategies have been developed for allocating some optimal rates to the competing users in wireless ad hoc networks. By considering different objective functions (such as congestion level, total packet loss and so on), the researchers propose some optimization framework by which the problem can be solved. Due to the rapid increase in the development of different video applications in such environments and the existence of difficulties in satisfying the prespecified QoS limits, increasing the received video quality can be considered as an important and challenging issue. The quality of the received video stream is inversely proportional to the amount of distortion which is being imposed on the video stream by the network packet loss and the video encoder. The main objective of the current paper is to introduce an optimization framework in which by optimal rate allocation to some competing video sources, the aggregate distortion of the all of the sources be minimized. The simulation results verify the claims.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"11 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":"132423571","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 wireless sensor networks (WSN) location awareness is required to use the communication advantages of adaptive antenna arrays (AAA) and use energy efficiency location based routing protocols. In this work, we introduce a simple and practical location estimation technique which uses AAAs at the central node in WSNs. This localization technique can be used at the setup phase in the location based routing protocol. This technique is based on scanning the desired region in azimuth and radial directions by changing parameters of downlink beam. This sweeping process can activate the nodes in the desired region which is specified by antenna beam width and beam direction of the localization beam and also by minimum and maximum thresholds (Rmin and Rmax) for the received signal strength indicator (RSSI). Active nodes in the desired region transmit their IDs and RSSI levels via multi hop communication to the central node. Unlike GPS-based or beacon based localization techniques, the proposed technique does not require any modification in the sensor nodes. We demonstrate different scenarios for performance analysis of this localization technique. The results show that by carefully adjusting these parameters, desired performance can be achieved. The accuracy of location estimation depends on beam direction, beam width and transmitting power for downlink beams.
{"title":"A new wireless sensor networks localization scheme with antenna arrays","authors":"K. Küçük, A. Kavak, H. Yiğit, C. Özdemir","doi":"10.1109/EW.2008.4623908","DOIUrl":"https://doi.org/10.1109/EW.2008.4623908","url":null,"abstract":"In wireless sensor networks (WSN) location awareness is required to use the communication advantages of adaptive antenna arrays (AAA) and use energy efficiency location based routing protocols. In this work, we introduce a simple and practical location estimation technique which uses AAAs at the central node in WSNs. This localization technique can be used at the setup phase in the location based routing protocol. This technique is based on scanning the desired region in azimuth and radial directions by changing parameters of downlink beam. This sweeping process can activate the nodes in the desired region which is specified by antenna beam width and beam direction of the localization beam and also by minimum and maximum thresholds (Rmin and Rmax) for the received signal strength indicator (RSSI). Active nodes in the desired region transmit their IDs and RSSI levels via multi hop communication to the central node. Unlike GPS-based or beacon based localization techniques, the proposed technique does not require any modification in the sensor nodes. We demonstrate different scenarios for performance analysis of this localization technique. The results show that by carefully adjusting these parameters, desired performance can be achieved. The accuracy of location estimation depends on beam direction, beam width and transmitting power for downlink beams.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"87 3-4 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":"116562906","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}
Cluster-based architectures are one of the most practical solutions in order to cope with the requirements of large-scale WSNs. In this work a new cluster-based architecture for sparse WSNs is introduced, the key issue of the solution presented is the multihop approach that is followed both in the communication from sensors to cluster-heads and from cluster-heads to the sink. Intercluster multihop communication allows the deployment of sparse WSNs in which cluster-heads can not communicate directly to the sink or to other cluster-heads. Results show that the total information forwarded decreases if compared to a flat topology allowing to increase either the size of the network or the battery duration.
{"title":"Multihop cluster-based architecture for sparse wireless sensor networks","authors":"C. Cano, B. Bellalta, P. Villalonga, J. Perelló","doi":"10.1109/EW.2008.4623891","DOIUrl":"https://doi.org/10.1109/EW.2008.4623891","url":null,"abstract":"Cluster-based architectures are one of the most practical solutions in order to cope with the requirements of large-scale WSNs. In this work a new cluster-based architecture for sparse WSNs is introduced, the key issue of the solution presented is the multihop approach that is followed both in the communication from sensors to cluster-heads and from cluster-heads to the sink. Intercluster multihop communication allows the deployment of sparse WSNs in which cluster-heads can not communicate directly to the sink or to other cluster-heads. Results show that the total information forwarded decreases if compared to a flat topology allowing to increase either the size of the network or the battery duration.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"19 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":"132533370","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 present a realtime implementation of the time-critical core functions for 12 times 12 MIMO-OFDM (12 data streams) with LTE parameters on a cell broadband engine processor. An MMSE equalizer matrix update interval of 1 ms (high mobility) is achieved with less than 50% CPU utilization. Concurrent bidirectional processing (precoding and postprocessing) is shown to be feasible with this update rate.
{"title":"12x12 MIMO-OFDM realtime implementation for 3GPP LTE+ on a Cell Processor","authors":"David Kühling, A. Ibing, V. Jungnickel","doi":"10.1109/EW.2008.4623917","DOIUrl":"https://doi.org/10.1109/EW.2008.4623917","url":null,"abstract":"We present a realtime implementation of the time-critical core functions for 12 times 12 MIMO-OFDM (12 data streams) with LTE parameters on a cell broadband engine processor. An MMSE equalizer matrix update interval of 1 ms (high mobility) is achieved with less than 50% CPU utilization. Concurrent bidirectional processing (precoding and postprocessing) is shown to be feasible with this update rate.","PeriodicalId":237850,"journal":{"name":"2008 14th European Wireless Conference","volume":"297 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":"132234881","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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