The paper presents a study and a performance analysis of a modified version of the TCP (Transmission Control Protocol) over a GEO (geostationary orbit) satellite link. The round trip time (RTT) is above 500 ms. TCP has not been designed for these network characteristics: the high delay to receive acknowledgements decreases the performance and makes the quality perceived by the users really poor. The performance of TCP may be improved by properly tuning some parameters and modifying algorithms. The behaviour of the protocol with a modified slow start algorithm is investigated on the basis of previous work concerning variations of the buffer length and of the initial congestion window. Configurations that drastically improve the performance (measured by the throughput in bytes/s and by the overall transmission time) are proposed. A real test-bed, composed of two remote hosts connected through a satellite channel is adopted to obtain the results. The analysis has included both the single application case and the multiple application case, where several connections share the satellite link at the same time.
{"title":"Proposal of a modified version of the slow start algorithm to improve TCP performance over large delay satellite channels","authors":"M. Marchese","doi":"10.1109/ICC.2001.937252","DOIUrl":"https://doi.org/10.1109/ICC.2001.937252","url":null,"abstract":"The paper presents a study and a performance analysis of a modified version of the TCP (Transmission Control Protocol) over a GEO (geostationary orbit) satellite link. The round trip time (RTT) is above 500 ms. TCP has not been designed for these network characteristics: the high delay to receive acknowledgements decreases the performance and makes the quality perceived by the users really poor. The performance of TCP may be improved by properly tuning some parameters and modifying algorithms. The behaviour of the protocol with a modified slow start algorithm is investigated on the basis of previous work concerning variations of the buffer length and of the initial congestion window. Configurations that drastically improve the performance (measured by the throughput in bytes/s and by the overall transmission time) are proposed. A real test-bed, composed of two remote hosts connected through a satellite channel is adopted to obtain the results. The analysis has included both the single application case and the multiple application case, where several connections share the satellite link at the same time.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"436 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116013327","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 question of synchronization errors' polarity estimation is tackled directly in a systematic and mathematically effective manner. The proposed synthesis method contributes to the optimality of the symbol-rated polarity algorithms, since it proves that the ensuing error signal is based on optimally paired algebraic expressions constituting a minimum set of prime-implicants and therefore is characterized by maximum noise immunity. Statistical insight is obtained via S-curve analysis.
{"title":"Unified algebraic treatment of synchronization parameters estimation","authors":"Ilias Panayiotopoulos","doi":"10.1109/ICC.2001.936606","DOIUrl":"https://doi.org/10.1109/ICC.2001.936606","url":null,"abstract":"The question of synchronization errors' polarity estimation is tackled directly in a systematic and mathematically effective manner. The proposed synthesis method contributes to the optimality of the symbol-rated polarity algorithms, since it proves that the ensuing error signal is based on optimally paired algebraic expressions constituting a minimum set of prime-implicants and therefore is characterized by maximum noise immunity. Statistical insight is obtained via S-curve analysis.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122381360","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}
Co-channel interference (CCI) from other reuse cells restricts the channel capacity of cellular communication systems. In fixed wireless access systems, the deployment of directional antennas at the customer premises equipment (CPE) that point towards their base stations suggest a direct and easy method to combat CCI and enhance capacity in a line-of-sight (LOS) propagation scenario. However, in a non-line-of-sight (NLOS) scenario, the effect of using a directional antenna at the CPE depends on the multipath angle of arrival (AOA) distribution of the propagating channel. In this paper, we demonstrate and compare the downlink performance of the directional antenna at the CPE under different AOA conditions. Two multipath channel models are assumed: circular and elliptical scattering models. We also calculate the performance of the adaptive array antenna deployed at the CPE and calculate its beamwidth effect. The capacity performance of the adaptive array antenna is compared with that of the single directional antenna.
{"title":"Effect of customer premises directional antennas on fixed wireless access systems in the downlink multipath channel","authors":"H. Seki, O. Ata, A. Paulraj","doi":"10.1109/ICC.2001.937068","DOIUrl":"https://doi.org/10.1109/ICC.2001.937068","url":null,"abstract":"Co-channel interference (CCI) from other reuse cells restricts the channel capacity of cellular communication systems. In fixed wireless access systems, the deployment of directional antennas at the customer premises equipment (CPE) that point towards their base stations suggest a direct and easy method to combat CCI and enhance capacity in a line-of-sight (LOS) propagation scenario. However, in a non-line-of-sight (NLOS) scenario, the effect of using a directional antenna at the CPE depends on the multipath angle of arrival (AOA) distribution of the propagating channel. In this paper, we demonstrate and compare the downlink performance of the directional antenna at the CPE under different AOA conditions. Two multipath channel models are assumed: circular and elliptical scattering models. We also calculate the performance of the adaptive array antenna deployed at the CPE and calculate its beamwidth effect. The capacity performance of the adaptive array antenna is compared with that of the single directional antenna.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122387220","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}
A multiple-antenna receiver is proposed for achieving a diversity effect that partly overcomes the severity of continuous-time frequency-flat Rayleigh fading channels, and fast fading channels in particular. The error performance is also improved by bit interleaving and channel coding, where the encoders/channel is viewed as a serially concatenated system: a convolutional code constitutes the outer code, whereas a differential encoder and the fading channel (having truncated memory) form a joint inner code. In order to obtain a feasible detector structure it is desirable to perform iterative decoding by applying some a posteriori probability (APP) algorithms. For this purpose, we derive a novel generalization of the well known BCJR (due to Bahl, Cocke, Jelinek, and Raviv 1974) algorithm that calculates the APPs for fading channels-or for channels having memory. Numerical results indicate that iterative decoding becomes more powerful when the exploited channel memory depth is extended, but the chief performance gain is achieved by introducing multiple antennas.
{"title":"Iterative array detection of CPM over continuous-time Rayleigh fading channels","authors":"A. Hansson, T. Aulin","doi":"10.1109/ICC.2001.937050","DOIUrl":"https://doi.org/10.1109/ICC.2001.937050","url":null,"abstract":"A multiple-antenna receiver is proposed for achieving a diversity effect that partly overcomes the severity of continuous-time frequency-flat Rayleigh fading channels, and fast fading channels in particular. The error performance is also improved by bit interleaving and channel coding, where the encoders/channel is viewed as a serially concatenated system: a convolutional code constitutes the outer code, whereas a differential encoder and the fading channel (having truncated memory) form a joint inner code. In order to obtain a feasible detector structure it is desirable to perform iterative decoding by applying some a posteriori probability (APP) algorithms. For this purpose, we derive a novel generalization of the well known BCJR (due to Bahl, Cocke, Jelinek, and Raviv 1974) algorithm that calculates the APPs for fading channels-or for channels having memory. Numerical results indicate that iterative decoding becomes more powerful when the exploited channel memory depth is extended, but the chief performance gain is achieved by introducing multiple antennas.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"68 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122817004","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 investigates the problem of blindly acquiring the channel gains for a synchronized multiuser system using the expectation maximization (EM) algorithm. The EM algorithm takes advantage of the finite alphabet property of the transmitted signal. It also provides MMSE estimates of the transmitted data that can be used by the receiver for decoding purposes. The algorithm has been applied to a multicarrier system and results show that the application of EM in the high SNR case provides significant improvement over traditional channel estimation techniques.
{"title":"Channel tracking for multiple input, single output systems using EM algorithm","authors":"C. Aldana, J. Cioffi","doi":"10.1109/ICC.2001.937007","DOIUrl":"https://doi.org/10.1109/ICC.2001.937007","url":null,"abstract":"This paper investigates the problem of blindly acquiring the channel gains for a synchronized multiuser system using the expectation maximization (EM) algorithm. The EM algorithm takes advantage of the finite alphabet property of the transmitted signal. It also provides MMSE estimates of the transmitted data that can be used by the receiver for decoding purposes. The algorithm has been applied to a multicarrier system and results show that the application of EM in the high SNR case provides significant improvement over traditional channel estimation techniques.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"265 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122907732","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 studies the TCP performance over a DMT based ADSL network. The impact of DMT subchannel bit loading on the TCP throughput performance is studied. The simulation results show that there is a threshold for the signal-to-noise ratio (SNR) gap or bit error rate (BER) above which TCP throughput drops quickly. This threshold takes its value in a wide range depending on the TCP round-trip time as well as channel noise. This suggests that it would be insufficient to set a fixed target BER at, e.g., 10/sup -7/, when calculating the number of bits to be loaded in each subchannel. Instead, the bit loading should take TCP performance into account. Finally a dynamic bit loading scheme is proposed, which jointly optimizes the channel bit rate and TCP throughput performance.
{"title":"TCP performance analysis and optimization over DMT based ADSL systems","authors":"Xiaoning He, Hao Che","doi":"10.1109/ICC.2001.936676","DOIUrl":"https://doi.org/10.1109/ICC.2001.936676","url":null,"abstract":"This paper studies the TCP performance over a DMT based ADSL network. The impact of DMT subchannel bit loading on the TCP throughput performance is studied. The simulation results show that there is a threshold for the signal-to-noise ratio (SNR) gap or bit error rate (BER) above which TCP throughput drops quickly. This threshold takes its value in a wide range depending on the TCP round-trip time as well as channel noise. This suggests that it would be insufficient to set a fixed target BER at, e.g., 10/sup -7/, when calculating the number of bits to be loaded in each subchannel. Instead, the bit loading should take TCP performance into account. Finally a dynamic bit loading scheme is proposed, which jointly optimizes the channel bit rate and TCP throughput performance.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121991404","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 partial response systems with maximum likelihood sequence estimation a short list of error events dominate. In this paper we introduce a graph-based construction of high rate codes capable of correcting errors from a given list. We define a directed graph describing a universe of error-event-detecting codes, and construct a code by tracing a path through the graph that gives the best probability of error. We demonstrate a substantial SNR gain when these codes are used in a scheme which combines the error event detection and the list soft decoding.
{"title":"A graph based construction of high-rate soft decodable codes for partial response channels","authors":"B. Vasic","doi":"10.1109/ICC.2001.936644","DOIUrl":"https://doi.org/10.1109/ICC.2001.936644","url":null,"abstract":"In partial response systems with maximum likelihood sequence estimation a short list of error events dominate. In this paper we introduce a graph-based construction of high rate codes capable of correcting errors from a given list. We define a directed graph describing a universe of error-event-detecting codes, and construct a code by tracing a path through the graph that gives the best probability of error. We demonstrate a substantial SNR gain when these codes are used in a scheme which combines the error event detection and the list soft decoding.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129023458","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 study the delay characteristics of voice packets that share a transmission medium with bursty data traffic. In order to model the data traffic accurately, we used real data traffic traces upon which we superimposed simulated voice sources generating real time traffic at a constant rate. Our simulation environment allows us to easily develop and compare different adaptive algorithms for the play-out delay of voice streams. We motivate and compare the performance of three algorithms based on exponential smoothing techniques. We test the algorithms in the context of a shared 10 Mbps Ethernet LAN, using the CSMA/CD protocol.
{"title":"Adaptive play-out algorithms for voice packets","authors":"D. Jeske, W. Matragi, B. Samadi","doi":"10.1109/ICC.2001.937344","DOIUrl":"https://doi.org/10.1109/ICC.2001.937344","url":null,"abstract":"We study the delay characteristics of voice packets that share a transmission medium with bursty data traffic. In order to model the data traffic accurately, we used real data traffic traces upon which we superimposed simulated voice sources generating real time traffic at a constant rate. Our simulation environment allows us to easily develop and compare different adaptive algorithms for the play-out delay of voice streams. We motivate and compare the performance of three algorithms based on exponential smoothing techniques. We test the algorithms in the context of a shared 10 Mbps Ethernet LAN, using the CSMA/CD protocol.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123854074","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 examines the potential merits of pre-distortion equalization as a novel measure to mitigate the distortion imposed by multipath dispersion in optical wireless communication links. It is demonstrated that the technique is able to reduce the required transmission power though, owing to a necessary signal content in the emitted zero-slot, this reduction is only possible when multipath dispersion has a significant influence. To attain the required transmission power, the authors propose a method that is based on a sensitivity assessment of the signal reception. Analytical details of this approach are provided demonstrating its ability to account for the received pulse shape which, in an optical wireless environment, is often irregular.
{"title":"On the use of pre-distortion equalization in infrared wireless communication links","authors":"K. Sterckx, J. Elmirghani","doi":"10.1109/ICC.2001.937040","DOIUrl":"https://doi.org/10.1109/ICC.2001.937040","url":null,"abstract":"This paper examines the potential merits of pre-distortion equalization as a novel measure to mitigate the distortion imposed by multipath dispersion in optical wireless communication links. It is demonstrated that the technique is able to reduce the required transmission power though, owing to a necessary signal content in the emitted zero-slot, this reduction is only possible when multipath dispersion has a significant influence. To attain the required transmission power, the authors propose a method that is based on a sensitivity assessment of the signal reception. Analytical details of this approach are provided demonstrating its ability to account for the received pulse shape which, in an optical wireless environment, is often irregular.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123888697","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 presents a worst-case pairwise codeword error probability analysis, under arbitrary block fading, for wireless communication systems with multiple transmit and receive antennas. Our results generalize the Rayleigh-fading space-time code design criteria (full rank and maximum determinant) to arbitrary fading.
{"title":"Code design metrics for space-time systems under arbitrary fading","authors":"Cenk Köse, R. Wesel","doi":"10.1109/ICC.2001.936824","DOIUrl":"https://doi.org/10.1109/ICC.2001.936824","url":null,"abstract":"This paper presents a worst-case pairwise codeword error probability analysis, under arbitrary block fading, for wireless communication systems with multiple transmit and receive antennas. Our results generalize the Rayleigh-fading space-time code design criteria (full rank and maximum determinant) to arbitrary fading.","PeriodicalId":203874,"journal":{"name":"ICC 2001. IEEE International Conference on Communications. Conference Record (Cat. No.01CH37240)","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124037529","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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