J. A. Martín-González, E. Poves, F. J. López-Hernández
A novel method to be used in OCDMA systems is exhaustively described in this paper. It uses algorithmic optical codes (AOCs). They are based on the signature sequence idea. However patterns are constantly changing. A common seed for pseudo-random sequence is the signature element. In this paper a derivation of the probability of error due to the multiple-access interference is provided. An other contribution of this work is also the comparison between the AOCs and the orthogonal optical codes (OOCs) with (auto- and cross-) correlation equal to one. Attending to the cardinality limitation problem observed in OOCs, the comparison is focused on the number of users allowed by the two different systems aforementioned. As result we state that a system using AOCs allows more users than one using OOCs when the codes are long enough.
{"title":"Comparison between the Performance of Algorithmic Optical Codes and Orthogonal Optical Codes in OCDMA Systems","authors":"J. A. Martín-González, E. Poves, F. J. López-Hernández","doi":"10.1109/ISSSTA.2008.34","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.34","url":null,"abstract":"A novel method to be used in OCDMA systems is exhaustively described in this paper. It uses algorithmic optical codes (AOCs). They are based on the signature sequence idea. However patterns are constantly changing. A common seed for pseudo-random sequence is the signature element. In this paper a derivation of the probability of error due to the multiple-access interference is provided. An other contribution of this work is also the comparison between the AOCs and the orthogonal optical codes (OOCs) with (auto- and cross-) correlation equal to one. Attending to the cardinality limitation problem observed in OOCs, the comparison is focused on the number of users allowed by the two different systems aforementioned. As result we state that a system using AOCs allows more users than one using OOCs when the codes are long enough.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123312617","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 investigate the effect of imperfect channel estimation on the bit error rate (BER) performance of orthogonal space-time block codes (OSTBCs). The multiple-input multiple-output (MIMO) propagation channel is assumed to be affected by uncorrelated flat Rayleigh block fading. We consider a mismatched maximum-likelihood (ML) receiver, which estimates the channel matrix from known pilot symbols according to a minimum mean-square error (MMSE) criterion, and uses the channel estimate in the symbol-by-symbol detection algorithm as if it were the true channel matrix. For both PAM and QAM constellations and OSTBCs satisfying a proposed criterion, we present simple exact closed-form expressions for the BER of the mismatched receiver and the corresponding BER degradation as compared to a receiver that knows the true channel matrix. For OSTBCs that do not satisfy this criterion, a simple approximation of the BER and the associated BER degradation is derived, assuming PAM and QAM constellations. By means of computer simulations, this approximation is shown to be very accurate.
{"title":"Accurate BER Analysis of Orthogonal Space-Time Block Codes with MMSE Channel Estimation","authors":"L. Jacobs, M. Moeneclaey","doi":"10.1109/ISSSTA.2008.64","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.64","url":null,"abstract":"In this paper, we investigate the effect of imperfect channel estimation on the bit error rate (BER) performance of orthogonal space-time block codes (OSTBCs). The multiple-input multiple-output (MIMO) propagation channel is assumed to be affected by uncorrelated flat Rayleigh block fading. We consider a mismatched maximum-likelihood (ML) receiver, which estimates the channel matrix from known pilot symbols according to a minimum mean-square error (MMSE) criterion, and uses the channel estimate in the symbol-by-symbol detection algorithm as if it were the true channel matrix. For both PAM and QAM constellations and OSTBCs satisfying a proposed criterion, we present simple exact closed-form expressions for the BER of the mismatched receiver and the corresponding BER degradation as compared to a receiver that knows the true channel matrix. For OSTBCs that do not satisfy this criterion, a simple approximation of the BER and the associated BER degradation is derived, assuming PAM and QAM constellations. By means of computer simulations, this approximation is shown to be very accurate.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"86 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125884301","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 consider a wireless multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) uplink scenario, where the information sequences of all users are encoded by individual space-frequency block codes (SFBC). At the receiver, joint maximum likelihood detection is applied using the sphere decoding algorithm. Using a truncated union-bound approximation, we propose the design criteria of multiuser SFBCs for frequency selective fading MIMO multiple access channels (MAC). Next, we show how, by combining the structure of algebraic perfect space-time block codes, a family of multiuser SFBCs can be constructed to fulfill the design criteria. Finally, we show that the proposed SFBC outperforms previously known codes.
{"title":"Algebraic Multiuser Space-Frequency Block Codes","authors":"Y. Hong, E. Viterbo","doi":"10.1109/ISSSTA.2008.66","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.66","url":null,"abstract":"In this paper, we consider a wireless multiuser multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) uplink scenario, where the information sequences of all users are encoded by individual space-frequency block codes (SFBC). At the receiver, joint maximum likelihood detection is applied using the sphere decoding algorithm. Using a truncated union-bound approximation, we propose the design criteria of multiuser SFBCs for frequency selective fading MIMO multiple access channels (MAC). Next, we show how, by combining the structure of algebraic perfect space-time block codes, a family of multiuser SFBCs can be constructed to fulfill the design criteria. Finally, we show that the proposed SFBC outperforms previously known codes.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130279031","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}
Won-Jae Shin, J. Kim, Kwang-Soo Jeong, J. Yi, Hyoung-Kyu Song, Y. You
In this paper, we present an improved scattered pilot synchronization (SPS) scheme in the digital video broadcasting-handheld (DVB-H) system, which detects the pilot pattern of currently received orthogonal frequency division multiplexing (OFDM) symbol. To reduce the SPS time and mitigate the influence of sampling frequency offset (SFO), the proposed SPS method is based on the conventional correlation-based SPS and adopts a partial correlation. By using computer simulation, the synchronization performance of the traditional SPS and the proposed SPS algorithms is evaluated in terms of probability of synchronization failure.
{"title":"An Improved Scattered Pilot Detection Scheme for OFDM-Based DVB-H","authors":"Won-Jae Shin, J. Kim, Kwang-Soo Jeong, J. Yi, Hyoung-Kyu Song, Y. You","doi":"10.1109/ISSSTA.2008.95","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.95","url":null,"abstract":"In this paper, we present an improved scattered pilot synchronization (SPS) scheme in the digital video broadcasting-handheld (DVB-H) system, which detects the pilot pattern of currently received orthogonal frequency division multiplexing (OFDM) symbol. To reduce the SPS time and mitigate the influence of sampling frequency offset (SFO), the proposed SPS method is based on the conventional correlation-based SPS and adopts a partial correlation. By using computer simulation, the synchronization performance of the traditional SPS and the proposed SPS algorithms is evaluated in terms of probability of synchronization failure.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126581005","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 introduce a general framework for characterizing the power spectrum of antipodal processes with finite memory m and exploit it to analyze the behavior of and LFSR in which the linear combination of the states is randomly flipped before being fed back into the register. The spectra reveal noteworthy regularities that can be explored by means of the proposed theory and give raise to some conjectures.
{"title":"Randomly-Flipped Linear Feedback Shift Registers: Spectral Analysis and Conjectures","authors":"G. Mazzini, R. Rovatti, G. Setti","doi":"10.1109/ISSSTA.2008.146","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.146","url":null,"abstract":"We introduce a general framework for characterizing the power spectrum of antipodal processes with finite memory m and exploit it to analyze the behavior of and LFSR in which the linear combination of the states is randomly flipped before being fed back into the register. The spectra reveal noteworthy regularities that can be explored by means of the proposed theory and give raise to some conjectures.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127095759","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 propose a novel list-based decoder for the layered groupwise space-time block code (GSTBC) in the case of single antenna at the receiver. The error floor problem associated with the single receive antenna is resolved and, as a result, a near maximum likelihood performance is obtained. To reduce complexity of the list-based decoder, we then apply a flexible list-length method to minimize the decoding efforts. Simulation results show that the list length is averagely reduced by half while obtaining the same performance as in the case of fixed list-length.
{"title":"Layered Groupwise STBC: List-Based Decoding Using Flexible Length","authors":"X. Nguyen, Jinho Choi","doi":"10.1109/ISSSTA.2008.137","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.137","url":null,"abstract":"In this paper, we propose a novel list-based decoder for the layered groupwise space-time block code (GSTBC) in the case of single antenna at the receiver. The error floor problem associated with the single receive antenna is resolved and, as a result, a near maximum likelihood performance is obtained. To reduce complexity of the list-based decoder, we then apply a flexible list-length method to minimize the decoding efforts. Simulation results show that the list length is averagely reduced by half while obtaining the same performance as in the case of fixed list-length.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"59 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127576701","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}
For fast-fading time-varying channels, channel variations over an OFDM symbol destroy the orthogonality among subcarriers. The resulting intercarrier interference (ICI) degrades the system performance. The degradation becomes severer as mobile speed, carrier frequency, or symbol duration increase. In this work, based on the existing data detection methods, several modifications are proposed to improve the system performances and to reduce the computational complexity. The proposed methods effectively use frequency diversity provided by time-varying channels. As a result, the proposed techniques noticeably outperform the conventional methods, including the ICI cancellation method and zero-forcing (ZF) detection. For implementation, the proposed methods are modified to have acceptable complexity.
{"title":"Effective Data Detection Algorithms for OFDM Systems over Time-Varying Multipath Fading Channels","authors":"C. Tsai, Sau-Gee Chen, Hsiao-Lan Chiang","doi":"10.1109/ISSSTA.2008.94","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.94","url":null,"abstract":"For fast-fading time-varying channels, channel variations over an OFDM symbol destroy the orthogonality among subcarriers. The resulting intercarrier interference (ICI) degrades the system performance. The degradation becomes severer as mobile speed, carrier frequency, or symbol duration increase. In this work, based on the existing data detection methods, several modifications are proposed to improve the system performances and to reduce the computational complexity. The proposed methods effectively use frequency diversity provided by time-varying channels. As a result, the proposed techniques noticeably outperform the conventional methods, including the ICI cancellation method and zero-forcing (ZF) detection. For implementation, the proposed methods are modified to have acceptable complexity.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116640495","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}
Network MIMO uses the coherent coordination of the transmitted signals from a cluster of bases to greatly reduce other-cell interference and improve spectral efficiency. Zero-forcing transmission is a simple and readily implemented form of Network MIMO that can give good performance gains over conventional systems. In this paper, we consider regularized ZF as a simple modification and explore the potential benefits for an indoor wireless system comprising 8 access points. The ZF solution is scaled to obey either sum-power or per-antenna power constraints. In the context of this simplified evaluation we find that regularization gives no gain in indoor systems, but the results hint that gain may be achieved in outdoor systems.
{"title":"Indoor Network MIMO Performance with Regularized Zero-Forcing Transmission","authors":"L. Mailaender","doi":"10.1109/ISSSTA.2008.30","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.30","url":null,"abstract":"Network MIMO uses the coherent coordination of the transmitted signals from a cluster of bases to greatly reduce other-cell interference and improve spectral efficiency. Zero-forcing transmission is a simple and readily implemented form of Network MIMO that can give good performance gains over conventional systems. In this paper, we consider regularized ZF as a simple modification and explore the potential benefits for an indoor wireless system comprising 8 access points. The ZF solution is scaled to obey either sum-power or per-antenna power constraints. In the context of this simplified evaluation we find that regularization gives no gain in indoor systems, but the results hint that gain may be achieved in outdoor systems.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"142 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124574922","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 closed-loop future time division duplex (TDD) wireless systems, where channel reciprocity is maintained, uplink (UL) channel sounding method is considered as one of the most promising feedback methods due to its bandwidth and delay efficiency. However, in TDD interference-limited systems, conventional channel sounding pilots only provide instantaneous channel state information at the transmitter (CSIT), but knowledge about the level of the interference at the receiver cannot be obtained. Therefore, a scheduler cannot optimally exploit the available degree of freedom (DoF) in order to maximize the system capacity (e.g. the downlink (DL) sum capacity). In this paper, a novel interference feedback scheme is proposed to provide the base station (BS) with implicit knowledge about the interference level received by each mobile station (MS). It is proposed to weight the uplink channel sounding pilots by the level of the received interference at each MS. The weighted uplink channel sounding pilots act as a bandwidth-efficient and delay-efficient means for providing the BS with both, CSIT and the level of interference received by each active user. The performance of a system using weighted sounding pilots is compared against a system using non- weighted sounding pilots for both greedy (maximum capacity) as well as fair scheduling criteria such as proportional fair and score based scheduling policies. It is shown that the throughput is increased while fairness is not compromised.
{"title":"Implicit Pilot-Borne Interference Feedback for Multiuser MIMO TDD Systems","authors":"Rami Abu-Alhiga, Harald Haas","doi":"10.1109/ISSSTA.2008.67","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.67","url":null,"abstract":"In closed-loop future time division duplex (TDD) wireless systems, where channel reciprocity is maintained, uplink (UL) channel sounding method is considered as one of the most promising feedback methods due to its bandwidth and delay efficiency. However, in TDD interference-limited systems, conventional channel sounding pilots only provide instantaneous channel state information at the transmitter (CSIT), but knowledge about the level of the interference at the receiver cannot be obtained. Therefore, a scheduler cannot optimally exploit the available degree of freedom (DoF) in order to maximize the system capacity (e.g. the downlink (DL) sum capacity). In this paper, a novel interference feedback scheme is proposed to provide the base station (BS) with implicit knowledge about the interference level received by each mobile station (MS). It is proposed to weight the uplink channel sounding pilots by the level of the received interference at each MS. The weighted uplink channel sounding pilots act as a bandwidth-efficient and delay-efficient means for providing the BS with both, CSIT and the level of interference received by each active user. The performance of a system using weighted sounding pilots is compared against a system using non- weighted sounding pilots for both greedy (maximum capacity) as well as fair scheduling criteria such as proportional fair and score based scheduling policies. It is shown that the throughput is increased while fairness is not compromised.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128629387","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}
For MIMO data detection methods, sphere decoding (SD) algorithms have been shown to achieve similar performance to the maximum-likelihood detection (MLD) algorithm with acceptable computational complexity. Based on different search strategies, SD can be divided into two parts: depth-first search SD and breadth-first search SD. In this work, by combining the advantages of these two search schemes, we propose a novel hybrid sphere decoding to effectively reduce the complexity. Besides, a layer reordered method is adopted to improve the performance. Compared with other SD algorithms, the proposed one has not only good performance but also lower complexity.
{"title":"An Efficient Hybrid Sphere Decoding Algorithm for MIMO Systems","authors":"Hsiao-Lan Chiang, Sau-Gee Chen","doi":"10.1109/ISSSTA.2008.68","DOIUrl":"https://doi.org/10.1109/ISSSTA.2008.68","url":null,"abstract":"For MIMO data detection methods, sphere decoding (SD) algorithms have been shown to achieve similar performance to the maximum-likelihood detection (MLD) algorithm with acceptable computational complexity. Based on different search strategies, SD can be divided into two parts: depth-first search SD and breadth-first search SD. In this work, by combining the advantages of these two search schemes, we propose a novel hybrid sphere decoding to effectively reduce the complexity. Besides, a layer reordered method is adopted to improve the performance. Compared with other SD algorithms, the proposed one has not only good performance but also lower complexity.","PeriodicalId":334589,"journal":{"name":"2008 IEEE 10th International Symposium on Spread Spectrum Techniques and Applications","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128463656","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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