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CMOS based decision directed costas carrier recovery loop (DDC-CRL) for a DSSS communication system 基于CMOS的DSSS通信系统决策定向costas载波恢复环路(DDC-CRL)
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401590
N. Naudé, L. Linde, S. Sinha
{"title":"CMOS based decision directed costas carrier recovery loop (DDC-CRL) for a DSSS communication system","authors":"N. Naudé, L. Linde, S. Sinha","doi":"10.1109/AFRCON.2007.4401590","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401590","url":null,"abstract":"For the discussed DSSS (direct sequence spread spectrum) communication system to be successful, accurate carrier recovery and phase estimation are required in the receiver. This paper presents an analogue DDC-CRL which performs both of these functions as well as the despreading, demodulation and bit detection operations performed by an ideal DSSS receiver. The DDC-CRL presented in this paper operates at bit rates up to 1.53 Mbps and accommodates arbitrary sequence length. The loop operates anywhere over a 20 MHz bandwidth within the 2.4 GHz to 2.4835 GHz ISM (industrial, scientific and medical) band. The DDC-CRL is designed for the 0.35 mum CMOS process from Austria Microsystems (AMS).","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"143 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128120980","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}
引用次数: 0
Bit error probability performance of MIMO-OFDM in multi-tone interference MIMO-OFDM在多音干扰下的误码概率性能
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401607
C. Esli, H. Deliç, M. Koca
{"title":"Bit error probability performance of MIMO-OFDM in multi-tone interference","authors":"C. Esli, H. Deliç, M. Koca","doi":"10.1109/AFRCON.2007.4401607","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401607","url":null,"abstract":"We consider an orthogonal space-frequency block coded (OSFBC) orthogonal frequency-division multiplexing (OFDM) system under multi-tone interference and multi-path fading environment. An approximate analytic expression for the bit error probability of OSFBC-OFDM system with a block code matrix for four transmit antennas is derived and the derivation methodology for other code matrices is summarized. The bit error rate simulations are performed for QPSK signals and compared with the theoretical results. The influences of the total energy of multi-tone interference and the fraction of interfered bandwidth are investigated.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"214 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133874840","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}
引用次数: 0
A bitemporal multilevel secure database system 双时态多级安全数据库系统
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401491
W. Meanrach, S. Chittayasothorn
{"title":"A bitemporal multilevel secure database system","authors":"W. Meanrach, S. Chittayasothorn","doi":"10.1109/AFRCON.2007.4401491","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401491","url":null,"abstract":"Multilevel database security is a security management which provides clearance levels for users. It also provides classification labels for the data. Most multilevel secure database systems employ the mandatory access control as proposed by Bell and La Padula. Most research works apply the multilevel secure technique to conventional relational databases. This research project proposes an extension to the mandatory access control so that it suits our application requirements. Moreover, the support of bitemporal database features is also included. Both valid time and transaction time are added to the already complex multilevel secure relational database. Integrity rules for this new model are introduced and finally, an extension to the SQL language is proposed to be used on the data model.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"92 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122445496","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}
引用次数: 2
Experience in using MALTLAB Power System Toolbox (PST) for transient stability study of an AC/DC interconnected power system 有使用MALTLAB电力系统工具箱(PST)进行交/直流互联电力系统暂态稳定性研究的经验
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401463
K. Folly, B.S. Limbo
{"title":"Experience in using MALTLAB Power System Toolbox (PST) for transient stability study of an AC/DC interconnected power system","authors":"K. Folly, B.S. Limbo","doi":"10.1109/AFRCON.2007.4401463","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401463","url":null,"abstract":"This paper discusses the experience of the authors in using Matlab power system toolbox for the transient stability studies of an AC/DC interconnection power system. The modified two-area power system model with HVDC Link is used in the investigation. It is shown that as the AC line became weaker (as compared to the DC line), the transient stability of the interconnected AC/DC system is negatively affected. The use of power system stabilizer (PSS) was critical in maintaining the stability of the system.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121206305","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}
引用次数: 3
Enhancing telecommunications business operations and service level agreements by incorporating operational risk management 透过纳入营运风险管理，加强电讯业务运作及服务水平协议
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401613
M. dos Santos, W. A. Clarke, A. Nel
{"title":"Enhancing telecommunications business operations and service level agreements by incorporating operational risk management","authors":"M. dos Santos, W. A. Clarke, A. Nel","doi":"10.1109/AFRCON.2007.4401613","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401613","url":null,"abstract":"In this paper, the need for integrating operational risk management into service level management for telecommunication service providers is discussed, where business operations are predominantly governed by a service level agreement. Operational risks that do or could effect the organization and its ability to comply with service level agreement requirements can then be determined and appropriately managed. Further, service level agreement management and compliance in terms of customer quality of service definitions and metrics can be better defined and monitored, and business operations more effectively aligned to the delivery of customer required services. These needs and benefits also tie in with the fact that enterprise risk management has become mandatory since the introduction of regulatory requirements such as the Sarbanes-Oxley act and Basel II.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129166480","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}
引用次数: 6
A cost-sensitive approach to laboratory work for a fourth-semester course in digital modulation 数字调制第四学期课程的成本敏感实验方法
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401561
S. MacPherson, M. McLeod, S. Shi
{"title":"A cost-sensitive approach to laboratory work for a fourth-semester course in digital modulation","authors":"S. MacPherson, M. McLeod, S. Shi","doi":"10.1109/AFRCON.2007.4401561","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401561","url":null,"abstract":"A set of proposed practical laboratory tasks for the final semester technician-level subject Radio Engineering 3 at the Durban University of Technology (DUT) is presented and justified. The tasks involve work with physical instruments as well as design and simulation software. A minimal instrument inventory is proposed and low-cost software options are explored. The use of student projects as a source of functional laboratory modules is described. The potential for using FPGA technology in this area is outlined.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128595902","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}
引用次数: 1
Temperature management strategies for a 9kw hybrid FIR-convective fruit dryer 9kw混合冷杉-对流水果干燥机的温度管理策略
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401622
M. Adonis, M. Kahn
{"title":"Temperature management strategies for a 9kw hybrid FIR-convective fruit dryer","authors":"M. Adonis, M. Kahn","doi":"10.1109/AFRCON.2007.4401622","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401622","url":null,"abstract":"A range of infrared heater temperature management mechanisms for a hybrid FIR-convective fruit dryer were designed and tested. The dryer was implemented in order to produce commercial grade apple chips. The infrared heater was subjected to a step-down power converter under current-mode and voltage-mode control. A buck converter was designed and tested to gauge its effectiveness. Simulations were performed on the various system configurations incorporating the buck converter in order to observe their responses to disturbances. In addition these systems were placed under classical control methods and a basic synergetic control scheme.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"205 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128611493","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}
引用次数: 0
Performance of sparse graph codes on a four-dimensional CDMA system in AWGN and multipath fading 基于AWGN和多径衰落的四维CDMA系统稀疏图码性能研究
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401523
A. Merensky, J. V. Wyk, L. Linde
{"title":"Performance of sparse graph codes on a four-dimensional CDMA system in AWGN and multipath fading","authors":"A. Merensky, J. V. Wyk, L. Linde","doi":"10.1109/AFRCON.2007.4401523","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401523","url":null,"abstract":"This paper presents the uncoded and coded multiuser error performance results of a novel super-orthogonal (SO) 4D CDMA communication platform under AWGN and multi- path fading channel conditions. The communication platform employs a special class of root-of-unity filtered (RUF) constant- envelope (CE) complex spreading sequences (CSS) with zero cross-correlation (ZCC) properties. The uncoded communication platform employs multi-layered-modulation (MLM) to improve spectral efficiency compared with existing multi-level modulation techniques, and the coded system uses the multiple dimensions to transmit redundancy to improve error performance. Three classes of sparse graph coding schemes are evaluated and compared on the multi-dimensional (MD) communication platform. The channel codes include a 3D block-turbo-code (BTC) with extended Reed-Muller (RM) constituent codes, low- density parity-check (LDPC) codes and repeat-accumulate (RA) codes. It is shown that the three channel codes have comparable error performance results and approximately 6 dB performance improvement over BPSK is achieved at Pc(bit) = 1 x 10 -5.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117065262","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}
引用次数: 2
Recovery of small bursts of voice packets using RS erasure code with low decoding delay 恢复语音数据包的小爆发使用RS擦除码与低解码延迟
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401448
S. Jharee, K. Soyjaudah
{"title":"Recovery of small bursts of voice packets using RS erasure code with low decoding delay","authors":"S. Jharee, K. Soyjaudah","doi":"10.1109/AFRCON.2007.4401448","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401448","url":null,"abstract":"It is well known that packet losses in the networks are mainly due to congestion because of the finite buffer capacity of queues in routers. Forward error correction (FEC) can recover from losses without retransmissions of lost packets. However, FEC faces with two main drawbacks: firstly, the redundancy generated by the sender increases the overall load of the network resulting in an increase of loss rate and secondly, waiting for redundant information to be able to recover lost packets results in additional delay. In this paper we employ the Reed Solomon erasure (RSE (7, 4)) code to recover lost packets. We apply the adaptive differential pulse code modulation (ADPCM) compression technique to make room for the redundant packets and thus reduce the additional load due to redundancy. We further modify the recovery scheme to bring down the decoding delay from a maximum of 6 packets to a maximum of 3 packets. Results of informal mean opinion score (MOS) listening test show that the modified RSE code is capable of correcting any burst of two packets and provides a tradeoff between quality, network load and decoding delay.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126081342","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}
引用次数: 2
Sensorless predictive control of three-phase parallel active filter 三相并联有源滤波器的无传感器预测控制
AFRICON 2007 Pub Date : 2007-12-12 DOI: 10.1109/AFRCON.2007.4401599
D. Wojciechowski
{"title":"Sensorless predictive control of three-phase parallel active filter","authors":"D. Wojciechowski","doi":"10.1109/AFRCON.2007.4401599","DOIUrl":"https://doi.org/10.1109/AFRCON.2007.4401599","url":null,"abstract":"The paper presents the control system of parallel active power filter (APF) with predictive reference current calculation and model based predictive current control. The novel estimator and predictor of grid emf is proposed for AC voltage sensorless operation of APF, regardless of distortion of this voltage. Proposed control system provides control of APF current with high precision and dynamics limited only by filter circuit parameters. There are presented simulation and experimental results achieved for 50 kVA APF, including a comparison of filtering properties with and without reference current prediction.","PeriodicalId":112129,"journal":{"name":"AFRICON 2007","volume":"42 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128126398","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}
引用次数: 29
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