Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.723806
D.J. van Wykt, L. Linde
This paper presents the design of a turbo encoding scheme with embedded Walsh-Hadamard (WH) codewords, and a suitable decoder structure based on an iterative decoding technique, akin to the work on "superorthogonal" turbo codes presented by Pehkonen and Komulainen (see ISSSTA'96: International Symposium on Spread Spectrum Techniques & Applications, Mainz, Germany, p.580-4, 1995). The main contribution of this paper is a detailed design of the turbo decoder structure required to perform the required decoding steps, omitted by Pehkonen et al. The performance of the proposed iterative turbo coded DS/CDMA receiver is then studied in an mobile radio environment. Attention is focused on an 8-state rate 2/64 coded QPSK DS/CDMA system, in agreement with the rate offered by the IS-95 coding scheme. The bit error rate performance of the proposed coding scheme is evaluated by means of simulation and compared to that of a DS/CDMA system employing the IS-95 front-end coder for the reverse link channel.
{"title":"A turbo coded DS/CDMA system with embedded Walsh-Hadamard codewords: coder design and performance evaluation","authors":"D.J. van Wykt, L. Linde","doi":"10.1109/ISSSTA.1998.723806","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.723806","url":null,"abstract":"This paper presents the design of a turbo encoding scheme with embedded Walsh-Hadamard (WH) codewords, and a suitable decoder structure based on an iterative decoding technique, akin to the work on \"superorthogonal\" turbo codes presented by Pehkonen and Komulainen (see ISSSTA'96: International Symposium on Spread Spectrum Techniques & Applications, Mainz, Germany, p.580-4, 1995). The main contribution of this paper is a detailed design of the turbo decoder structure required to perform the required decoding steps, omitted by Pehkonen et al. The performance of the proposed iterative turbo coded DS/CDMA receiver is then studied in an mobile radio environment. Attention is focused on an 8-state rate 2/64 coded QPSK DS/CDMA system, in agreement with the rate offered by the IS-95 coding scheme. The bit error rate performance of the proposed coding scheme is evaluated by means of simulation and compared to that of a DS/CDMA system employing the IS-95 front-end coder for the reverse link channel.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"58 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114171211","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.722502
F. Ibikunle
This paper is motivated by the fact that, in a multi-user CDMA system, the conventional receiver suffers severe performance degradation as the relative powers of the interfering signals becomes large (i.e., "near-far problem"). Furthermore, in many cases the optimum multi-user receiver, which alleviates the near-far problem, is too complex to be of practical use. By viewing this optimum multi-user detector problem in a CDMA channel as an optimum nonlinear classification decision problem, we apply simple feedforward multilayered perceptrons referred to as the probabilistic neural network based maximum likelihood rule that has the abilities of arbitrary nonlinear transformations, adaptive learning and tracking to implement this classification decision optimally and adaptively. The performance of this proposed neural detector is evaluated via computer simulations in terms of the probability of detection and compared with other neural and conventional detector schemes in a multi-user environment.
{"title":"Optimum multi-user signal detector in SSMA communication systems based on neural networks","authors":"F. Ibikunle","doi":"10.1109/ISSSTA.1998.722502","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722502","url":null,"abstract":"This paper is motivated by the fact that, in a multi-user CDMA system, the conventional receiver suffers severe performance degradation as the relative powers of the interfering signals becomes large (i.e., \"near-far problem\"). Furthermore, in many cases the optimum multi-user receiver, which alleviates the near-far problem, is too complex to be of practical use. By viewing this optimum multi-user detector problem in a CDMA channel as an optimum nonlinear classification decision problem, we apply simple feedforward multilayered perceptrons referred to as the probabilistic neural network based maximum likelihood rule that has the abilities of arbitrary nonlinear transformations, adaptive learning and tracking to implement this classification decision optimally and adaptively. The performance of this proposed neural detector is evaluated via computer simulations in terms of the probability of detection and compared with other neural and conventional detector schemes in a multi-user environment.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116218968","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.722464
M. Jamil, L. Linde
This paper presents an overview and comparison of some of the known families of polyphase sequences for direct sequence spread spectrum multiple access (DS/SSMA) communication systems. A comparison between Zadoff and Chu (Frank and Zadoff 1962; Chu 1972) (ZC), Opperman and Vucetic (1997) (OV), and constant-envelope root-of-unity (CE-RU) filtered generalized chirp-like sequences is presented including the special class of analytical bandlimited complex (ABC) spreading sequences. The comparison is based on aperiodic correlation characteristics rather than traditionally discussed parameters like periodic, even, and odd correlations. The emphasis is based on practical considerations rather than rigorous mathematical derivation as found in literature. This paper is unique in the sense that it also presents the effects of filtering on polyphase sequences by using proper filtering methods.
本文介绍了用于直接序列扩频多址(DS/SSMA)通信系统的几种已知多相序列的概况和比较。Zadoff和Chu的比较(Frank and Zadoff 1962;提出了Chu 1972) (ZC)、Opperman and Vucetic (1997) (OV)和恒包络单位根(CE-RU)滤波的广义类啁啾序列，其中包括一类特殊的解析限带复(ABC)扩展序列。这种比较是基于非周期相关特性，而不是传统上讨论的周期性、偶相关性和奇相关性等参数。重点是基于实际的考虑，而不是在文献中发现的严格的数学推导。本文的独特之处在于，它还通过使用适当的滤波方法来描述滤波对多相序列的影响。
{"title":"A comparison of unfiltered and filtered complex spreading sequences based on aperiodic correlation properties","authors":"M. Jamil, L. Linde","doi":"10.1109/ISSSTA.1998.722464","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722464","url":null,"abstract":"This paper presents an overview and comparison of some of the known families of polyphase sequences for direct sequence spread spectrum multiple access (DS/SSMA) communication systems. A comparison between Zadoff and Chu (Frank and Zadoff 1962; Chu 1972) (ZC), Opperman and Vucetic (1997) (OV), and constant-envelope root-of-unity (CE-RU) filtered generalized chirp-like sequences is presented including the special class of analytical bandlimited complex (ABC) spreading sequences. The comparison is based on aperiodic correlation characteristics rather than traditionally discussed parameters like periodic, even, and odd correlations. The emphasis is based on practical considerations rather than rigorous mathematical derivation as found in literature. This paper is unique in the sense that it also presents the effects of filtering on polyphase sequences by using proper filtering methods.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126227768","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.726222
J. Bakker, R. Prasad
This paper presents a method to implement a soft error decoder. The presented decoder is optimized for use in a high-bit rate data communications system using orthogonal frequency division modulation (OFDM) over an indoor fading channel. A short description of the target system is given, and boundary conditions for the propagation environment are derived. An estimator for the attenuation caused by frequency selective fading on each OFDM carrier is presented, together with a method to estimate the variance of the channel noise. An algorithm to determine a measure of per-bit correctness probability is developed, and a soft error decoder is presented using the per-bit correctness probability. Simulation results are presented for a simulated Rayleigh fading channel and for a measured indoor channel.
{"title":"An implementation of a soft error decoder in a multipath faded COFDM system","authors":"J. Bakker, R. Prasad","doi":"10.1109/ISSSTA.1998.726222","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726222","url":null,"abstract":"This paper presents a method to implement a soft error decoder. The presented decoder is optimized for use in a high-bit rate data communications system using orthogonal frequency division modulation (OFDM) over an indoor fading channel. A short description of the target system is given, and boundary conditions for the propagation environment are derived. An estimator for the attenuation caused by frequency selective fading on each OFDM carrier is presented, together with a method to estimate the variance of the channel noise. An algorithm to determine a measure of per-bit correctness probability is developed, and a soft error decoder is presented using the per-bit correctness probability. Simulation results are presented for a simulated Rayleigh fading channel and for a measured indoor channel.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"6 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126796697","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.726217
W. Haifeng, J. Lilleberg, K. Rikkinen
A joint multiuser detector with decoding and feedback for the convolutionally coded asynchronous code-division multiple-access (CDMA) system is proposed in this paper. This approach consists of generalized multistage processing and a decision feedback loop. The performance is verified by simulations in Rayleigh fading channels.
{"title":"Joint multiuser detector with decoding and feedback in asynchronous CDMA systems","authors":"W. Haifeng, J. Lilleberg, K. Rikkinen","doi":"10.1109/ISSSTA.1998.726217","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726217","url":null,"abstract":"A joint multiuser detector with decoding and feedback for the convolutionally coded asynchronous code-division multiple-access (CDMA) system is proposed in this paper. This approach consists of generalized multistage processing and a decision feedback loop. The performance is verified by simulations in Rayleigh fading channels.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127288514","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.723847
H. Olson, D. Kerek, H. Tenhunen
RAKE combining at high symbol rates f/sub sym/ is addressed. A scheme designed for such implicitly low normalized Doppler (f/sub dn/=f/sub d//f/sub sym/) multipath channels and for reception with a carrier frequency offset /spl delta//spl middot/f/sub sym/ is presented. The phases of the different paths are estimated using what we refer to as Kalman phase tracking (KPT). This closed loop estimator employs decision feedback to remove the data dependency in the received signal and a multi I/O Kalman filter to track the phases, In addition, the KPT performs carrier frequency estimation and compensation. The results from simulations of two different 3-branch, time-invariant AWGN channels and three values of /spl delta/ show that near-optimal bit error rates can be achieved but that the receiver in its present form requires a post-detection differential decoder in order to become completely reliable.
{"title":"Low-complexity coherent RAKE combining with a Kalman phase tracker","authors":"H. Olson, D. Kerek, H. Tenhunen","doi":"10.1109/ISSSTA.1998.723847","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.723847","url":null,"abstract":"RAKE combining at high symbol rates f/sub sym/ is addressed. A scheme designed for such implicitly low normalized Doppler (f/sub dn/=f/sub d//f/sub sym/) multipath channels and for reception with a carrier frequency offset /spl delta//spl middot/f/sub sym/ is presented. The phases of the different paths are estimated using what we refer to as Kalman phase tracking (KPT). This closed loop estimator employs decision feedback to remove the data dependency in the received signal and a multi I/O Kalman filter to track the phases, In addition, the KPT performs carrier frequency estimation and compensation. The results from simulations of two different 3-branch, time-invariant AWGN channels and three values of /spl delta/ show that near-optimal bit error rates can be achieved but that the receiver in its present form requires a post-detection differential decoder in order to become completely reliable.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"140 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121778294","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.726249
Walter Kellermann, W. Granzow
This paper examines a class of PSK-based, linear modulation schemes for application in direct-sequence CDMA systems with respect to the variation of the (complex) baseband signal envelope. A minimum peak-to-average ratio (PAR) of the envelope reduces the linearity requirements of the power amplifier and increases the power amplifier efficiency, which is of great importance especially for mobile terminals. A generalization of the PAR-efficient /spl pi//4-QPSK, denoted as /spl phi/-QPSK, was proposed for a wideband-CDMA concept for UMTS/IMT-2000 and is investigated here: fundamental mechanisms determining PAR are identified for both real and complex chip sequences. Theoretical PAR values are derived and lead the way to the design of new concepts for PAR-optimal spread spectrum modulation.
{"title":"Analysis of low-PAR modulation schemes for wideband-CDMA","authors":"Walter Kellermann, W. Granzow","doi":"10.1109/ISSSTA.1998.726249","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726249","url":null,"abstract":"This paper examines a class of PSK-based, linear modulation schemes for application in direct-sequence CDMA systems with respect to the variation of the (complex) baseband signal envelope. A minimum peak-to-average ratio (PAR) of the envelope reduces the linearity requirements of the power amplifier and increases the power amplifier efficiency, which is of great importance especially for mobile terminals. A generalization of the PAR-efficient /spl pi//4-QPSK, denoted as /spl phi/-QPSK, was proposed for a wideband-CDMA concept for UMTS/IMT-2000 and is investigated here: fundamental mechanisms determining PAR are identified for both real and complex chip sequences. Theoretical PAR values are derived and lead the way to the design of new concepts for PAR-optimal spread spectrum modulation.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126451742","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.723844
B. Kraemer
Software radios are an attractive alternative to conventional designs. However, they place rather extreme demands upon the analog to digital and digital to analog converters in the signal processing chain. This paper explores the detailed requirements of data converters in software radios.
{"title":"Data conversion considerations for software radios","authors":"B. Kraemer","doi":"10.1109/ISSSTA.1998.723844","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.723844","url":null,"abstract":"Software radios are an attractive alternative to conventional designs. However, they place rather extreme demands upon the analog to digital and digital to analog converters in the signal processing chain. This paper explores the detailed requirements of data converters in software radios.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131800168","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.722481
A. Hottinen, R. Wichman
We study transmit diversity concepts in DS/CDMA wireless networks with multiple transmit antennas. The previously proposed diversity techniques are reviewed and their performance is compared to a selective transmit diversity (STD) concept, proposed here for CDMA systems. In all the competing concepts the encoded bits are distributed to all transmit antennas, whereas in the proposed concept bit are transmitted only from the best antenna as indicated by a closed loop antenna selection (CL-AS) subchannel from the terminal to the base. We quantify the achievable gains for these transmit diversity concepts with Monte-Carlo simulations.
{"title":"Transmit diversity by antenna selection in CDMA downlink","authors":"A. Hottinen, R. Wichman","doi":"10.1109/ISSSTA.1998.722481","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722481","url":null,"abstract":"We study transmit diversity concepts in DS/CDMA wireless networks with multiple transmit antennas. The previously proposed diversity techniques are reviewed and their performance is compared to a selective transmit diversity (STD) concept, proposed here for CDMA systems. In all the competing concepts the encoded bits are distributed to all transmit antennas, whereas in the proposed concept bit are transmitted only from the best antenna as indicated by a closed loop antenna selection (CL-AS) subchannel from the terminal to the base. We quantify the achievable gains for these transmit diversity concepts with Monte-Carlo simulations.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124697924","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}
Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.726220
A. Nahler, J. Kuhne, G. Fettweis
In this paper, a multi-carrier spread-spectrum (MC-SS) code division multiple access (CDMA) system with RAKE receiver is investigated in a multi-user environment. The impact of the non-ideal MC-SS code signal auto- and cross-correlation properties on the system performance is examined. Terms for the probability of bit errors are derived considering these correlation behaviors. Furthermore, the performance of a MC-SS CDMA system is compared with a direct-sequence spread-spectrum (DS-SS) system based on Gold sequences.
{"title":"Investigations of bit error floors for multi-carrier spread-spectrum CDMA systems with RAKE receiver in frequency-selective channels","authors":"A. Nahler, J. Kuhne, G. Fettweis","doi":"10.1109/ISSSTA.1998.726220","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726220","url":null,"abstract":"In this paper, a multi-carrier spread-spectrum (MC-SS) code division multiple access (CDMA) system with RAKE receiver is investigated in a multi-user environment. The impact of the non-ideal MC-SS code signal auto- and cross-correlation properties on the system performance is examined. Terms for the probability of bit errors are derived considering these correlation behaviors. Furthermore, the performance of a MC-SS CDMA system is compared with a direct-sequence spread-spectrum (DS-SS) system based on Gold sequences.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132439413","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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