Pub Date : 1998-09-02DOI: 10.1109/ISSSTA.1998.722523
S. Kim, Hokyu Choi
A nonorthogonal binary FSK (BFSK) is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmitted information bits per unit time, per unit bandwidth normalized throughput, is examined in Rayleigh channels. The tradeoff among tone spacing, code rate, and number of frequency slots in maximizing the normalized throughput is examined, keeping the total bandwidth fixed. The optimal tone spacing, code rate, and number of frequency slots in terms of the number of users and E~/sub b//N/sub 0/ is also discussed. The throughput gain attained by using the optimal tone spacing becomes more significant as the number of users is increased.
{"title":"Nonorthogonal BFSK/FHMA in Rayleigh fading channels","authors":"S. Kim, Hokyu Choi","doi":"10.1109/ISSSTA.1998.722523","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722523","url":null,"abstract":"A nonorthogonal binary FSK (BFSK) is considered in frequency-hopped multiple-access communication systems with Reed-Solomon coding. The effect of tone spacing on the average number of successfully transmitted information bits per unit time, per unit bandwidth normalized throughput, is examined in Rayleigh channels. The tradeoff among tone spacing, code rate, and number of frequency slots in maximizing the normalized throughput is examined, keeping the total bandwidth fixed. The optimal tone spacing, code rate, and number of frequency slots in terms of the number of users and E~/sub b//N/sub 0/ is also discussed. The throughput gain attained by using the optimal tone spacing becomes more significant as the number of users is increased.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"3 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":"128594525","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.1998.723868
M. Larva-aho
For pt.1 see ibid., p.652-7. The wideband code-division multiple access (CDMA) concept FMA2; developed in the European FRAMES project supports variable data rate transmission. The data rate can be altered by changing either the spreading factor or by using multiple spreading codes in parallel. In order to facilitate flexible changing of the data rate, variable length orthogonal Walsh codes are used for channel separation, followed by a scrambling code. Optional short scrambling codes can be used if interference suppression is used. In this paper the downlink performance of the FMA2 system using both the conventional RAKE and the LMMSE-RAKE receivers is studied. According to the results, the performance of the conventional RAKE receivers is insufficient at lowest spreading factors, whereas the LMMSE-RAKE receiver performs well regardless of the spreading factor.
{"title":"Modified LMMSE receiver for DS-CDMA-Part II. Performance in FMA2 downlink","authors":"M. Larva-aho","doi":"10.1109/ISSSTA.1998.723868","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.723868","url":null,"abstract":"For pt.1 see ibid., p.652-7. The wideband code-division multiple access (CDMA) concept FMA2; developed in the European FRAMES project supports variable data rate transmission. The data rate can be altered by changing either the spreading factor or by using multiple spreading codes in parallel. In order to facilitate flexible changing of the data rate, variable length orthogonal Walsh codes are used for channel separation, followed by a scrambling code. Optional short scrambling codes can be used if interference suppression is used. In this paper the downlink performance of the FMA2 system using both the conventional RAKE and the LMMSE-RAKE receivers is studied. According to the results, the performance of the conventional RAKE receivers is insufficient at lowest spreading factors, whereas the LMMSE-RAKE receiver performs well regardless of the spreading factor.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"39 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":"127283364","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.1998.723839
M. Hamalainen, J. Talvitie, V. Hovinen, P. Leppanen
The paper presents a propagation characterization based on wideband radio channel measurements made in a mine at a center frequency of 1 GHz. The main attention is focused on the path loss and the delay profile analysis. The path loss has been found to be 40 dB/dec in a straight cave and 80 dB/dec in a curved cave. the delay spread was less than 0.5 /spl mu/s. The radio channel in the mine proved to be non-reciprocal.
{"title":"Wideband radio channel measurement in a mine","authors":"M. Hamalainen, J. Talvitie, V. Hovinen, P. Leppanen","doi":"10.1109/ISSSTA.1998.723839","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.723839","url":null,"abstract":"The paper presents a propagation characterization based on wideband radio channel measurements made in a mine at a center frequency of 1 GHz. The main attention is focused on the path loss and the delay profile analysis. The path loss has been found to be 40 dB/dec in a straight cave and 80 dB/dec in a curved cave. the delay spread was less than 0.5 /spl mu/s. The radio channel in the mine proved to be non-reciprocal.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"5 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":"129920914","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.1998.722484
Dong In Kim
A combined binary PPM/orthogonal modulation is used in cellular CDMA reverse links in which the multipath-diversity performance for Rayleigh-fading channels is evaluated and compared. As for diversity techniques, equal gain combining (EGC), selection combining (SC), and its generalization, second or third order SC (SC2, SC3), are considered for noncoherent reception. Theoretical analyses show that noncoherent combining loss (NCL) severely degrades the symbol error-rate (SER) performance of EGC when the modulation level M is small, but NCL can be greatly reduced by increasing M/spl ges/16. We also find that SC2 and SC3 significantly improve the SER compared to SC, especially outperforming EGC for small M.
{"title":"Multipath-diversity performance of direct-sequence CDMA using combined M-ary signalling","authors":"Dong In Kim","doi":"10.1109/ISSSTA.1998.722484","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722484","url":null,"abstract":"A combined binary PPM/orthogonal modulation is used in cellular CDMA reverse links in which the multipath-diversity performance for Rayleigh-fading channels is evaluated and compared. As for diversity techniques, equal gain combining (EGC), selection combining (SC), and its generalization, second or third order SC (SC2, SC3), are considered for noncoherent reception. Theoretical analyses show that noncoherent combining loss (NCL) severely degrades the symbol error-rate (SER) performance of EGC when the modulation level M is small, but NCL can be greatly reduced by increasing M/spl ges/16. We also find that SC2 and SC3 significantly improve the SER compared to SC, especially outperforming EGC for small M.","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":"130070001","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.1998.722519
J. Ramos, M. Zoltowski, M. Martínez‐Ramón
An algorithm that implements a 2D RAKE receiver for a cellular CDMA system that cancels strong multi-user access interference (MAI) and optimally combines multipath is presented in this paper. The algorithm asymptotically provides the optimum combination of space-time samples to maximize the SINR for the signal with the desired code (SDC) by optimally combining its multipath and canceling strong multi-user access interference (MUAI). This algorithm asymptotically provides the exact time of arrivals of the multipaths within a bit period, and subsequently the optimum space-time weights for combining the fingers across both space and time. The instrumental property exploited in this technique is the fact that although the respective spectra of the SDC and MUAI components at the output of the matched filter are statistically equal, the respective spectra of their squared values differ.
{"title":"Space-time optimal combination for DS-SS. The 2D RAKE receiver","authors":"J. Ramos, M. Zoltowski, M. Martínez‐Ramón","doi":"10.1109/ISSSTA.1998.722519","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722519","url":null,"abstract":"An algorithm that implements a 2D RAKE receiver for a cellular CDMA system that cancels strong multi-user access interference (MAI) and optimally combines multipath is presented in this paper. The algorithm asymptotically provides the optimum combination of space-time samples to maximize the SINR for the signal with the desired code (SDC) by optimally combining its multipath and canceling strong multi-user access interference (MUAI). This algorithm asymptotically provides the exact time of arrivals of the multipaths within a bit period, and subsequently the optimum space-time weights for combining the fingers across both space and time. The instrumental property exploited in this technique is the fact that although the respective spectra of the SDC and MUAI components at the output of the matched filter are statistically equal, the respective spectra of their squared values differ.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"3 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":"131086340","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.1998.722521
M. Lotter, P. van Rooyen
Space division multiple access (SDMA) will form an important part of the new wideband code division multiple access (W-CDMA) standard that will realise the Universal Mobile Telephone System (UMTS). This paper addresses a few issues of importance when SDMA techniques are used in a cellular CDMA system. Firstly a theoretical analysis of a SDMA/CDMA system is performed. The analysis is focused on a single cell, multipath Rayleigh fading scenario. As system performance measure, the bit error rate (BER) is used as the criterion to investigate the influence of user location and number of antennas. An important parameter in a SDMA system is the antenna array element spacing. In our analysis a uniform linear array (ULA) is considered and a measure is defined to determine the optimal antenna element spacing in a CDMA cellular environment. Normally the mobile users in a cell are assumed to be uniformly distributed in cellular performance calculations. To reflect a more realistic situation, we propose a novel probability density function for the nonuniform distribution of the mobile users in the cell. It is shown that multipath, even with antenna arrays, reduces the system performance substantially.
{"title":"Space division multiple access for cellular CDMA","authors":"M. Lotter, P. van Rooyen","doi":"10.1109/ISSSTA.1998.722521","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.722521","url":null,"abstract":"Space division multiple access (SDMA) will form an important part of the new wideband code division multiple access (W-CDMA) standard that will realise the Universal Mobile Telephone System (UMTS). This paper addresses a few issues of importance when SDMA techniques are used in a cellular CDMA system. Firstly a theoretical analysis of a SDMA/CDMA system is performed. The analysis is focused on a single cell, multipath Rayleigh fading scenario. As system performance measure, the bit error rate (BER) is used as the criterion to investigate the influence of user location and number of antennas. An important parameter in a SDMA system is the antenna array element spacing. In our analysis a uniform linear array (ULA) is considered and a measure is defined to determine the optimal antenna element spacing in a CDMA cellular environment. Normally the mobile users in a cell are assumed to be uniformly distributed in cellular performance calculations. To reflect a more realistic situation, we propose a novel probability density function for the nonuniform distribution of the mobile users in the cell. It is shown that multipath, even with antenna arrays, reduces the system performance substantially.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"EM-11 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":"132865391","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.1998.726231
Jung-Shyr Wu, Jen-Kung Chung, Kung-Hwa Lee
The CDMA system promisingly provides more capacity than AMPS. However, providing multi-channels for a CDMA system is a requisite to satisfy the demand of capacity. Two schemes of multi-channel assignment are proposed. Based on the formulation of intra-cell interference and inter-cell interference, the capacity can be determined. The Markov chain approach is adopted to model the intra-cell-interference and inter-cell interference for the proposed channel assignment schemes. By solving the state probabilities, performance measures, e.g. blocking probabilities, the overall capacity and the capacity of each channel are obtained. Analytical results indicate that SIR-based selection scheme is preferable to the other.
{"title":"Performance analysis for multi-channel assignment schemes in CDMA cellular systems","authors":"Jung-Shyr Wu, Jen-Kung Chung, Kung-Hwa Lee","doi":"10.1109/ISSSTA.1998.726231","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726231","url":null,"abstract":"The CDMA system promisingly provides more capacity than AMPS. However, providing multi-channels for a CDMA system is a requisite to satisfy the demand of capacity. Two schemes of multi-channel assignment are proposed. Based on the formulation of intra-cell interference and inter-cell interference, the capacity can be determined. The Markov chain approach is adopted to model the intra-cell-interference and inter-cell interference for the proposed channel assignment schemes. By solving the state probabilities, performance measures, e.g. blocking probabilities, the overall capacity and the capacity of each channel are obtained. Analytical results indicate that SIR-based selection scheme is preferable to the other.","PeriodicalId":116377,"journal":{"name":"1988 IEEE 5th International Symposium on Spread Spectrum Techniques and Applications - Proceedings. Spread Technology to Africa (Cat. No.98TH8333)","volume":"49 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":"130464983","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.1998.726243
G. Judge, F. Takawira
An analytical and simulation performance evaluation is presented for a proposed multi-access protocol for data traffic in a packet radio network. The network employs direct-sequence code division multiple access (DS-CDMA) in a centralised channel load-sensing scheme with channel overload (collision) detection and blocking. A finite population, packetisation of variable length messages and partial message retransmission scheme are considered in the protocol. For a given maximum bit error rate due to mutual multi-access interference (MAI), an upper threshold (/spl beta/) for the number of users allowed in the channel can be determined. This paper proposes a second lower threshold, /spl alpha/, to improve the system performance by adding an access control mechanism. The results show that an improved throughput/delay performance can be obtained by implementing a centralised load sensing scheme and dynamic channel control mechanism.
{"title":"Performance analysis of a channel load sensing protocol for CDMA packet radio networks with finite populations and variable length messages","authors":"G. Judge, F. Takawira","doi":"10.1109/ISSSTA.1998.726243","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726243","url":null,"abstract":"An analytical and simulation performance evaluation is presented for a proposed multi-access protocol for data traffic in a packet radio network. The network employs direct-sequence code division multiple access (DS-CDMA) in a centralised channel load-sensing scheme with channel overload (collision) detection and blocking. A finite population, packetisation of variable length messages and partial message retransmission scheme are considered in the protocol. For a given maximum bit error rate due to mutual multi-access interference (MAI), an upper threshold (/spl beta/) for the number of users allowed in the channel can be determined. This paper proposes a second lower threshold, /spl alpha/, to improve the system performance by adding an access control mechanism. The results show that an improved throughput/delay performance can be obtained by implementing a centralised load sensing scheme and dynamic channel control mechanism.","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":"129000819","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.1998.726229
E. Kudoh, S. Ogose
It is necessary to establish high data rate transmission to support multimedia services. This requires a determination of access scheme's performance and a clarification of the selection criteria. We present the transmission performance of a CDMA system with a RAKE receiver. The relationship between the root mean square delay spread normalized by the chip period at a minimum BER and the number of RAKE fingers is evaluated. The BER performance of CDMA multi-code transmission is also evaluated. It is found that single code transmission has a better performance than multi-code transmission. The BER performance of a TDMA system with an equalizer is also presented. It is found that as the number of combined symbols becomes larger the root mean square delay spread normalized by the symbol period at the minimum BER increases. The TDMA system BER performance is compared with the CDMA system performance. For example, when the processing gain is 16, the number of RAKE fingers is 4, and the number of combined delayed symbols in the equalizer is 4, if the root mean square delay spread normalized by the information symbol period is larger than 0.27, TDMA offers a better BER performance.
{"title":"Performance comparison on wireless access scheme for high data rate transmission in mobile radio","authors":"E. Kudoh, S. Ogose","doi":"10.1109/ISSSTA.1998.726229","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726229","url":null,"abstract":"It is necessary to establish high data rate transmission to support multimedia services. This requires a determination of access scheme's performance and a clarification of the selection criteria. We present the transmission performance of a CDMA system with a RAKE receiver. The relationship between the root mean square delay spread normalized by the chip period at a minimum BER and the number of RAKE fingers is evaluated. The BER performance of CDMA multi-code transmission is also evaluated. It is found that single code transmission has a better performance than multi-code transmission. The BER performance of a TDMA system with an equalizer is also presented. It is found that as the number of combined symbols becomes larger the root mean square delay spread normalized by the symbol period at the minimum BER increases. The TDMA system BER performance is compared with the CDMA system performance. For example, when the processing gain is 16, the number of RAKE fingers is 4, and the number of combined delayed symbols in the equalizer is 4, if the root mean square delay spread normalized by the information symbol period is larger than 0.27, TDMA offers a better BER performance.","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":"129079515","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.1998.726198
V.S. Nikolajevic, M. Dukic, A. Marinčić
In this paper the fiber optical local area networks (FO-LANs) performance analysis, using modified prime sequence codes (MPSC) is presented. A particular attention is devoted to the influence of multiuser interference effects to the system capacity. The analytical expression for bit error probability (BER) is derived, and two modifications of the receiver are introduced. The adaptive decision threshold receiver has better performance and greater complexity comparing to the hard-limiter receiver.
{"title":"Performance comparison of different receivers of synchronous CDMA techniques for fiber optic LANs","authors":"V.S. Nikolajevic, M. Dukic, A. Marinčić","doi":"10.1109/ISSSTA.1998.726198","DOIUrl":"https://doi.org/10.1109/ISSSTA.1998.726198","url":null,"abstract":"In this paper the fiber optical local area networks (FO-LANs) performance analysis, using modified prime sequence codes (MPSC) is presented. A particular attention is devoted to the influence of multiuser interference effects to the system capacity. The analytical expression for bit error probability (BER) is derived, and two modifications of the receiver are introduced. The adaptive decision threshold receiver has better performance and greater complexity comparing to the hard-limiter receiver.","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":"128785718","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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