Pub Date : 1998-09-07DOI: 10.1109/COMSIG.1998.736912
G. Madungwe, I. Takawira
The use of narrowband PMR channels for voice and data transmission is becoming attractive as spectral constraints and demand for mobile services continues to increase. The technology, in terms of channel utilisation, keeps on improving and efficient modulation techniques continually increase the data rates possible on such channels. Most mobile applications still employ speech transmission, hence it is necessary to encode speech in a way that uses as little spectrum as possible. Improved speech coding techniques are making toll quality voice transmission possible at 2.4 kbps.
{"title":"Integrated voice-data communications over narrowband PMR channels","authors":"G. Madungwe, I. Takawira","doi":"10.1109/COMSIG.1998.736912","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736912","url":null,"abstract":"The use of narrowband PMR channels for voice and data transmission is becoming attractive as spectral constraints and demand for mobile services continues to increase. The technology, in terms of channel utilisation, keeps on improving and efficient modulation techniques continually increase the data rates possible on such channels. Most mobile applications still employ speech transmission, hence it is necessary to encode speech in a way that uses as little spectrum as possible. Improved speech coding techniques are making toll quality voice transmission possible at 2.4 kbps.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127203536","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736941
M. Lotter, P. van Rooyen
This paper provides an overview of the basic principles of smart antenna techniques as applied to the introduction of space division multiple access (SDMA) techniques in current mobile radio networks, as well as in personal communication services (PCS), personal communications networks (PCN) and the universal mobile telecommunication system (UMTS). It is shown qualitatively how SDMA techniques can increase the capacity of cellular network. Furthermore, a new SDMA principle based on the nonhomogeneous quality of service requirements in mobile multimedia networks is introduced with application to systems proposed for UMTS.
{"title":"An overview of space division multiple access techniques in cellular systems","authors":"M. Lotter, P. van Rooyen","doi":"10.1109/COMSIG.1998.736941","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736941","url":null,"abstract":"This paper provides an overview of the basic principles of smart antenna techniques as applied to the introduction of space division multiple access (SDMA) techniques in current mobile radio networks, as well as in personal communication services (PCS), personal communications networks (PCN) and the universal mobile telecommunication system (UMTS). It is shown qualitatively how SDMA techniques can increase the capacity of cellular network. Furthermore, a new SDMA principle based on the nonhomogeneous quality of service requirements in mobile multimedia networks is introduced with application to systems proposed for UMTS.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115918638","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736950
J. Tapson
Recent studies have shown that stochastic resonance (SR) can occur in biological neurons (Douglas et al, 1993). This behaviour is characterised by possible enhancement of signal detection in the presence of increasing noise levels, and by phase locking between neuron activation and weak periodic input signals. It has been suggested that this behaviour may occur in the human nervous system, and may play an important part in sensory perception. In this paper we show that a single neuron in the presence of noise is capable of performing an autocorrelation an an incoming periodic stimulus, and thereby can even detect periodicities which have no spectral energy (so-called "missing fundamentals"). There is substantial evidence for this mechanism in the current data on acoustic perception (Horst et al, 1986, Wightman, 1973). Autocorrelation has been proposed in the past as a mechanism in sensory systems; these results suggest that it can take place at the simplest level in the human sensory system.
最近的研究表明，随机共振(SR)可以发生在生物神经元中(Douglas et al .， 1993)。这种行为的特点是在噪声水平增加的情况下可能增强信号检测，以及神经元激活和弱周期输入信号之间的相位锁定。有人认为，这种行为可能发生在人类的神经系统中，并可能在感觉知觉中起重要作用。在本文中，我们证明了存在噪声的单个神经元能够对传入的周期刺激进行自相关，从而甚至可以检测到没有光谱能量的周期性(所谓的“缺失基本原理”)。在当前的声学感知数据中，有大量证据表明这种机制(Horst et al .， 1986; Wightman, 1973)。自相关在过去被认为是感觉系统中的一种机制;这些结果表明，它可以发生在人类感觉系统中最简单的层面。
{"title":"Autocorrelation properties of single neurons","authors":"J. Tapson","doi":"10.1109/COMSIG.1998.736950","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736950","url":null,"abstract":"Recent studies have shown that stochastic resonance (SR) can occur in biological neurons (Douglas et al, 1993). This behaviour is characterised by possible enhancement of signal detection in the presence of increasing noise levels, and by phase locking between neuron activation and weak periodic input signals. It has been suggested that this behaviour may occur in the human nervous system, and may play an important part in sensory perception. In this paper we show that a single neuron in the presence of noise is capable of performing an autocorrelation an an incoming periodic stimulus, and thereby can even detect periodicities which have no spectral energy (so-called \"missing fundamentals\"). There is substantial evidence for this mechanism in the current data on acoustic perception (Horst et al, 1986, Wightman, 1973). Autocorrelation has been proposed in the past as a mechanism in sensory systems; these results suggest that it can take place at the simplest level in the human sensory system.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123556407","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736992
R. van Zyl, W. Perold, R. Botha
A short tutorial on the Gunn diode is presented. The principles underlying Gunn oscillations are discussed briefly and illustrated by relevant simulations. The simulation of a typical Gunn diode in a cavity is also presented. In conclusion, the fabrication process of low-power Gunn diodes is discussed.
{"title":"The Gunn-diode: fundamentals and fabrication","authors":"R. van Zyl, W. Perold, R. Botha","doi":"10.1109/COMSIG.1998.736992","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736992","url":null,"abstract":"A short tutorial on the Gunn diode is presented. The principles underlying Gunn oscillations are discussed briefly and illustrated by relevant simulations. The simulation of a typical Gunn diode in a cavity is also presented. In conclusion, the fabrication process of low-power Gunn diodes is discussed.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"346 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123561621","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736969
K. Palmer
This paper presents an overview of antenna engineering education in Germany, along with a summary of the activities of the major academic and industrial players.
本文概述了德国天线工程教育的概况，并总结了主要学术和工业参与者的活动。
{"title":"An overview of antenna engineering in Germany","authors":"K. Palmer","doi":"10.1109/COMSIG.1998.736969","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736969","url":null,"abstract":"This paper presents an overview of antenna engineering education in Germany, along with a summary of the activities of the major academic and industrial players.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"107 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123230291","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736961
A. Hnatiw, D. W. Boertjes, R. DeCorby, J. McMullin, R. MacDonald, D. Corazza, E. Johnson
This paper describes the architecture, performance and applications of a 7 GHz bandwidth 4/spl times/4 optoelectronic switch. The switch is constructed using hybrid integration techniques and may be configured as electrical-in/electrical-out or optical-in/optical-out.
{"title":"4/spl times/4 broadband optoelectronic switch for telecommunications and signal processing","authors":"A. Hnatiw, D. W. Boertjes, R. DeCorby, J. McMullin, R. MacDonald, D. Corazza, E. Johnson","doi":"10.1109/COMSIG.1998.736961","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736961","url":null,"abstract":"This paper describes the architecture, performance and applications of a 7 GHz bandwidth 4/spl times/4 optoelectronic switch. The switch is constructed using hybrid integration techniques and may be configured as electrical-in/electrical-out or optical-in/optical-out.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122743518","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.737008
L. de Vries-Venter, D. C. Baker
The paper looks at the reverberation chamber as an alternative test method for radiated immunity testing of electrical devices. An overview is presented of its operation, some of the mathematics involved and the considerations that have to be given to its design. Some information about repeatability and the uncertainties encountered are also given.
{"title":"EMC: radiated immunity testing an overview of the reverberation chamber","authors":"L. de Vries-Venter, D. C. Baker","doi":"10.1109/COMSIG.1998.737008","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.737008","url":null,"abstract":"The paper looks at the reverberation chamber as an alternative test method for radiated immunity testing of electrical devices. An overview is presented of its operation, some of the mathematics involved and the considerations that have to be given to its design. Some information about repeatability and the uncertainties encountered are also given.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125027968","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736917
D. Saban, R. Braun
A multicarrier direct sequence code division multiple access (MC-DS-CDMA) technique is proposed for point-to-multipoint communication systems. Time delays and related interference phenomenon are discussed and multicarrier techniques for mitigating multipath effects are highlighted. An independent two-ray multipath model is used for determining the major channel effects that influence multicarrier DS-CDMA. In particular, time dispersion and frequency distortion are examined in terms of their effect on multicarrier modulation schemes. Empirical simulated analysis is presented for additive white Gaussian and multipath channels in order to highlight the bandwidth efficiency, interference generation and the bit error rate (BER) of multicarrier DS-CDMA under selected multipath configurations. Coding strategies are discussed for mitigating multipath induced error and their expense on the bandwidth efficiency is emphasized.
{"title":"Multi-carrier direct sequence CDMA in fading situations","authors":"D. Saban, R. Braun","doi":"10.1109/COMSIG.1998.736917","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736917","url":null,"abstract":"A multicarrier direct sequence code division multiple access (MC-DS-CDMA) technique is proposed for point-to-multipoint communication systems. Time delays and related interference phenomenon are discussed and multicarrier techniques for mitigating multipath effects are highlighted. An independent two-ray multipath model is used for determining the major channel effects that influence multicarrier DS-CDMA. In particular, time dispersion and frequency distortion are examined in terms of their effect on multicarrier modulation schemes. Empirical simulated analysis is presented for additive white Gaussian and multipath channels in order to highlight the bandwidth efficiency, interference generation and the bit error rate (BER) of multicarrier DS-CDMA under selected multipath configurations. Coding strategies are discussed for mitigating multipath induced error and their expense on the bandwidth efficiency is emphasized.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"100 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127175888","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.737000
M. Bingle, J. Cloete, D. Davidson
A theoretical and experimental study is conducted to investigate the role of chirality in synthetic microwave absorbers. Three closely related anisotropic unit cells of thin wire objects, one chiral, one racemic and one non-chiral, are studied around resonance in a rectangular waveguide. Conducting thin wire chiral and non-chiral objects, embedded in an absorbing dielectric host and positioned in a rectangular waveguide, are numerically analysed with the finite difference time domain method. Measured and predicted results for the scattering parameters are presented.
{"title":"Microwave absorption by chiral, racemic and non-chiral unit cells: the role of chirality in absorbing materials","authors":"M. Bingle, J. Cloete, D. Davidson","doi":"10.1109/COMSIG.1998.737000","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.737000","url":null,"abstract":"A theoretical and experimental study is conducted to investigate the role of chirality in synthetic microwave absorbers. Three closely related anisotropic unit cells of thin wire objects, one chiral, one racemic and one non-chiral, are studied around resonance in a rectangular waveguide. Conducting thin wire chiral and non-chiral objects, embedded in an absorbing dielectric host and positioned in a rectangular waveguide, are numerically analysed with the finite difference time domain method. Measured and predicted results for the scattering parameters are presented.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126883245","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 : 1998-09-07DOI: 10.1109/COMSIG.1998.736940
R. Majoor, F. Takawira
Several MAC protocols for wireless ATM have been described in the literature; TDMA and FDMA combinations making up the bulk of these. Very little has appeared on MAC protocols for ATM over CDMA channels. This paper introduces a protocol for carrying ATM cells over a wireless CDMA channel between a mobile and a base station. The paper considers CBR, VBR and ABR traffic. QoS is guaranteed in the CAC scheme, and implemented using a power control mechanism. The protocol makes use of a movable boundary mechanism to partition the bandwidth in proportion to traffic demand. The soft capacity nature of CDMA is exploited by allowing CBR and VBR traffic to 'steal' bandwidth from ABR traffic. Simulation results show that this leads to a greater throughput than would be achieved without this mechanism.
{"title":"A MAC protocol for wireless ATM over CDMA","authors":"R. Majoor, F. Takawira","doi":"10.1109/COMSIG.1998.736940","DOIUrl":"https://doi.org/10.1109/COMSIG.1998.736940","url":null,"abstract":"Several MAC protocols for wireless ATM have been described in the literature; TDMA and FDMA combinations making up the bulk of these. Very little has appeared on MAC protocols for ATM over CDMA channels. This paper introduces a protocol for carrying ATM cells over a wireless CDMA channel between a mobile and a base station. The paper considers CBR, VBR and ABR traffic. QoS is guaranteed in the CAC scheme, and implemented using a power control mechanism. The protocol makes use of a movable boundary mechanism to partition the bandwidth in proportion to traffic demand. The soft capacity nature of CDMA is exploited by allowing CBR and VBR traffic to 'steal' bandwidth from ABR traffic. Simulation results show that this leads to a greater throughput than would be achieved without this mechanism.","PeriodicalId":294473,"journal":{"name":"Proceedings of the 1998 South African Symposium on Communications and Signal Processing-COMSIG '98 (Cat. No. 98EX214)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129065645","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：