Pub Date : 2000-12-17DOI: 10.1109/ICPWC.2000.905860
A. Eckford, S. Pasupathy
In this paper, we give a graphical interpretation of the multiuser detection problem for interference limited channels, using generalized inference techniques on graphs. One impediment to the implementation of multiuser detection techniques in practical systems (such as in DS-CDMA) has been the difficulty of dealing with the large number of random variables present in such systems. Graphical techniques, which have been previously applied to inference problems in many random variables, can give new insight into the handling of this problem. The main focus of our work is on asynchronous channels, which may be effectively modeled with a Markov chain model. A new implementation of the EM (expectation maximization) algorithm over factor graphs is introduced. Modifications to the EM algorithm to implement approximate inference with reduced complexity are discussed.
{"title":"Iterative multiuser detection with graphical modeling","authors":"A. Eckford, S. Pasupathy","doi":"10.1109/ICPWC.2000.905860","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905860","url":null,"abstract":"In this paper, we give a graphical interpretation of the multiuser detection problem for interference limited channels, using generalized inference techniques on graphs. One impediment to the implementation of multiuser detection techniques in practical systems (such as in DS-CDMA) has been the difficulty of dealing with the large number of random variables present in such systems. Graphical techniques, which have been previously applied to inference problems in many random variables, can give new insight into the handling of this problem. The main focus of our work is on asynchronous channels, which may be effectively modeled with a Markov chain model. A new implementation of the EM (expectation maximization) algorithm over factor graphs is introduced. Modifications to the EM algorithm to implement approximate inference with reduced complexity are discussed.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116274589","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905918
L. C. Ramac, P. Varshney
A wavelet domain diversity combining method to combat errors during wireless image transmission has been presented recently. For images represented in the wavelet domain, diversity is used to obtain multiple data streams corresponding to the transmitted image at the receiver. These individual image data streams are combined to form a composite image with higher perceptual quality. The SPIHT (set partitioning in hierarchical trees) algorithm is used for image compression, and diversity combining methods for the compressed images exploit the characteristics of the wavelet transform. For these images, unequal error protection is employed in conjunction with diversity combining. Performance of this scheme over Rayleigh fading channels is evaluated in this paper. Simulation results demonstrate that the quality of the received image can be significantly improved.
{"title":"Performance of the wavelet domain diversity method for image transmission over Rayleigh fading channels","authors":"L. C. Ramac, P. Varshney","doi":"10.1109/ICPWC.2000.905918","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905918","url":null,"abstract":"A wavelet domain diversity combining method to combat errors during wireless image transmission has been presented recently. For images represented in the wavelet domain, diversity is used to obtain multiple data streams corresponding to the transmitted image at the receiver. These individual image data streams are combined to form a composite image with higher perceptual quality. The SPIHT (set partitioning in hierarchical trees) algorithm is used for image compression, and diversity combining methods for the compressed images exploit the characteristics of the wavelet transform. For these images, unequal error protection is employed in conjunction with diversity combining. Performance of this scheme over Rayleigh fading channels is evaluated in this paper. Simulation results demonstrate that the quality of the received image can be significantly improved.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"131 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116547134","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905824
K. Rambabu, R. Rajagopal
This paper presents a novel hybrid beam steering scheme for mobile cellular applications. In this scheme, a linear equispaced sensor array of N antenna elements at the base station is used to form a fixed beam pattern in a fixed number of directions covering the cell area. In addition an adaptive pilot beam also is formed by using the same set of antenna elements whose direction can be made to be variable depending upon the traffic requirements. The advantages of the proposed scheme are illustrated by computer simulation results.
{"title":"Smart base station antenna","authors":"K. Rambabu, R. Rajagopal","doi":"10.1109/ICPWC.2000.905824","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905824","url":null,"abstract":"This paper presents a novel hybrid beam steering scheme for mobile cellular applications. In this scheme, a linear equispaced sensor array of N antenna elements at the base station is used to form a fixed beam pattern in a fixed number of directions covering the cell area. In addition an adaptive pilot beam also is formed by using the same set of antenna elements whose direction can be made to be variable depending upon the traffic requirements. The advantages of the proposed scheme are illustrated by computer simulation results.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123492751","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905803
D. Baum, D. Gore, R. Nabar, S. Panchanathan, K. Hari, V. Erceg, A. Paulraj
We study the channel typical for cellular broadband fixed wireless applications. A measurement system for a two-element-transmit by two-element-receive antenna configuration was built, Measurements were conducted in a suburban environment with dual antenna polarization and transmit separation. We present results on K-factor, cross-polarization discrimination (XPD) and Doppler spectrum. Our results address the influence of distance and antenna height for K-factor and XPD. We also comment on the properties of a fixed wireless channel and describe its Doppler spectrum.
{"title":"Measurement and characterization of broadband MIMO fixed wireless channels at 2.5 GHz","authors":"D. Baum, D. Gore, R. Nabar, S. Panchanathan, K. Hari, V. Erceg, A. Paulraj","doi":"10.1109/ICPWC.2000.905803","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905803","url":null,"abstract":"We study the channel typical for cellular broadband fixed wireless applications. A measurement system for a two-element-transmit by two-element-receive antenna configuration was built, Measurements were conducted in a suburban environment with dual antenna polarization and transmit separation. We present results on K-factor, cross-polarization discrimination (XPD) and Doppler spectrum. Our results address the influence of distance and antenna height for K-factor and XPD. We also comment on the properties of a fixed wireless channel and describe its Doppler spectrum.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123550297","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905765
V. Sahula, C. Ravikumar
In this paper, we present a design planning paradigm for the design of a wireless mobile transceiver. We consider the digital part in a single chip implementation of a transceiver based on the CDMA spread spectrum technique. The complexity of such a chip implementation makes the design process complex and very expensive. The desired characteristics of a mobile transceiver are low cost, small size, and low power. Design cost forms a major portion of total system cost. In order to reduce design cost, design completion time should be reduced. We assume hardware-software design flow for design of the transceiver. We analyze the design flow using the hierarchical concurrent flow graph (HCFG) approach. We illustrate, using AND and OR concurrent constructs of the HCFG approach, how the design process completion time can be reduced by employing concurrent design efforts. We also present an approach for completion time improvement which considers the sensitivity of completion time with respect to task completion time and probabilities. HCFG analysis facilitates a pre-execution "what-if" analysis to determine the suitable design flow which provides lowest process completion time.
{"title":"Design planning for single chip implementation of digital wireless mobile transceiver","authors":"V. Sahula, C. Ravikumar","doi":"10.1109/ICPWC.2000.905765","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905765","url":null,"abstract":"In this paper, we present a design planning paradigm for the design of a wireless mobile transceiver. We consider the digital part in a single chip implementation of a transceiver based on the CDMA spread spectrum technique. The complexity of such a chip implementation makes the design process complex and very expensive. The desired characteristics of a mobile transceiver are low cost, small size, and low power. Design cost forms a major portion of total system cost. In order to reduce design cost, design completion time should be reduced. We assume hardware-software design flow for design of the transceiver. We analyze the design flow using the hierarchical concurrent flow graph (HCFG) approach. We illustrate, using AND and OR concurrent constructs of the HCFG approach, how the design process completion time can be reduced by employing concurrent design efforts. We also present an approach for completion time improvement which considers the sensitivity of completion time with respect to task completion time and probabilities. HCFG analysis facilitates a pre-execution \"what-if\" analysis to determine the suitable design flow which provides lowest process completion time.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125420042","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905919
Adrish Banerjee, D. Costello, T. Fuja
In this paper, two classes of retransmission strategies in time-varying mobile radio channels are studied for bandwidth efficient hybrid-ARQ (HARQ) schemes using turbo coded modulation. These schemes combine the power efficiency of turbo codes with the bandwidth efficiency of trellis-coded modulation (TCM) to create an effective hybrid FEC/ARQ system. Different retransmission schemes provide a trade-off in terms of throughput, delay, implementation complexity, and error performance.
{"title":"Comparison of different retransmission strategies for bandwidth efficient hybrid ARQ schemes using turbo codes","authors":"Adrish Banerjee, D. Costello, T. Fuja","doi":"10.1109/ICPWC.2000.905919","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905919","url":null,"abstract":"In this paper, two classes of retransmission strategies in time-varying mobile radio channels are studied for bandwidth efficient hybrid-ARQ (HARQ) schemes using turbo coded modulation. These schemes combine the power efficiency of turbo codes with the bandwidth efficiency of trellis-coded modulation (TCM) to create an effective hybrid FEC/ARQ system. Different retransmission schemes provide a trade-off in terms of throughput, delay, implementation complexity, and error performance.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"80 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115367529","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905836
C. Elliott, B. Heile
Self-organizing, self-healing networks, also called "ad hoc" networks, are perhaps the most exciting new trend in networking research and development. Every node in such a network has sufficient intelligence to continuously sense and discover other nearby nodes, dynamically determine the optimal path for forwarding data packets from itself hop by hop through the network to any other node in the network, and automatically heal any ruptures in the network fabric that are caused by ongoing movement of the nodes themselves, changes in RF propagation, destruction of nodes, etc. In essence; one need merely launch such radio nodes into some space and they will not only organize themselves into a network but also adapt continuously to changes in the network's connectivity. The field is currently evolving at "Internet speed" - the first large-scale systems are now being fielded into the USA military and yet many of the field's research fundamentals are at present only very poorly understood. This paper begins with an example that introduces some of the fundamental issues for ad hoc networks (hidden terminals, channel access, mobility, scalability, and power constraints). It then discusses the two dominant approaches in current ad hoc networking technologies, "proactive" and "on-demand" path discovery, and compares the strengths and weaknesses of each approach. The paper then presents two brief case studies with which the authors were intimately involved - of a 400-node, terrestrial, vehicle-based system and of a high-capacity voice and data network deployed among drone aircraft - and concludes with highlights of the current research topics in the field.
{"title":"Self-organizing, self-healing wireless networks","authors":"C. Elliott, B. Heile","doi":"10.1109/ICPWC.2000.905836","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905836","url":null,"abstract":"Self-organizing, self-healing networks, also called \"ad hoc\" networks, are perhaps the most exciting new trend in networking research and development. Every node in such a network has sufficient intelligence to continuously sense and discover other nearby nodes, dynamically determine the optimal path for forwarding data packets from itself hop by hop through the network to any other node in the network, and automatically heal any ruptures in the network fabric that are caused by ongoing movement of the nodes themselves, changes in RF propagation, destruction of nodes, etc. In essence; one need merely launch such radio nodes into some space and they will not only organize themselves into a network but also adapt continuously to changes in the network's connectivity. The field is currently evolving at \"Internet speed\" - the first large-scale systems are now being fielded into the USA military and yet many of the field's research fundamentals are at present only very poorly understood. This paper begins with an example that introduces some of the fundamental issues for ad hoc networks (hidden terminals, channel access, mobility, scalability, and power constraints). It then discusses the two dominant approaches in current ad hoc networking technologies, \"proactive\" and \"on-demand\" path discovery, and compares the strengths and weaknesses of each approach. The paper then presents two brief case studies with which the authors were intimately involved - of a 400-node, terrestrial, vehicle-based system and of a high-capacity voice and data network deployed among drone aircraft - and concludes with highlights of the current research topics in the field.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115482956","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905766
C. Giardina, A. Rudrapatna
Systems of quasi-Walsh functions are developed which simultaneously enable multiple access as well as secure communication and jamming resistance. In this system, a pseudo random sequence of diagonal isometries post multiplies a Hadamard matrix, thereby generating the orthogonal direct spreading sequences. Minimal mutual interference is a consequence of the resulting orthogonal spreading. Utilizing bit-by-bit distinct orthogonal codes gives the added benefit of high signal hiding capability and jamming resistance. An encoding scheme is presented which uniquely determines the actual quasi-Walsh system in use.
{"title":"Quasi-Walsh PN sequences and their applications in robust CDMA communication systems","authors":"C. Giardina, A. Rudrapatna","doi":"10.1109/ICPWC.2000.905766","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905766","url":null,"abstract":"Systems of quasi-Walsh functions are developed which simultaneously enable multiple access as well as secure communication and jamming resistance. In this system, a pseudo random sequence of diagonal isometries post multiplies a Hadamard matrix, thereby generating the orthogonal direct spreading sequences. Minimal mutual interference is a consequence of the resulting orthogonal spreading. Utilizing bit-by-bit distinct orthogonal codes gives the added benefit of high signal hiding capability and jamming resistance. An encoding scheme is presented which uniquely determines the actual quasi-Walsh system in use.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127173447","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905762
M. Hefnawi, G. Delisle
Adaptive antenna array systems have been shown to play a central role in removing narrowband multiple-access interference (MAI) in wireless communications. However, due to the actual need for increasing channel capacity, the required bandwidth is becoming wider and can bring significant deterioration to narrowband adaptive systems. These performance degradations are mainly caused by the fact that the inter-element phase shift becomes a function of the frequency while the adaptation weights are kept independent of frequency. This paper specifically deals with the effects of wideband CDMA signals on the narrowband adaptive system. The performance evaluation for different chip rates is carried out in terms of the adaptive array pattern. The basic adaptive algorithm used is the CMA (constant modulus algorithm), which has the major advantage of not requiring an estimate of the desired signal for its implementation.
{"title":"Impact of wideband CDMA signals on smart antenna systems","authors":"M. Hefnawi, G. Delisle","doi":"10.1109/ICPWC.2000.905762","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905762","url":null,"abstract":"Adaptive antenna array systems have been shown to play a central role in removing narrowband multiple-access interference (MAI) in wireless communications. However, due to the actual need for increasing channel capacity, the required bandwidth is becoming wider and can bring significant deterioration to narrowband adaptive systems. These performance degradations are mainly caused by the fact that the inter-element phase shift becomes a function of the frequency while the adaptation weights are kept independent of frequency. This paper specifically deals with the effects of wideband CDMA signals on the narrowband adaptive system. The performance evaluation for different chip rates is carried out in terms of the adaptive array pattern. The basic adaptive algorithm used is the CMA (constant modulus algorithm), which has the major advantage of not requiring an estimate of the desired signal for its implementation.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114628708","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 : 2000-12-17DOI: 10.1109/ICPWC.2000.905923
L. Schiff
The IMT-2000 process of the ITU is intended to provide standardized ways of providing high data rate and multimedia services to the wireless user. The cdma2000 proposal for a 3rd generation terrestrial standard is a way of providing these services in a backwardly compatible and evolutionary way for the IS-95 user. The Globalstar LEOS MSS system uses waveforms and procedures derived from IS-95. Our purpose in this paper is to show that many of the features of cdma2000 can be appliqued onto the Globalstar system in an evolutionary way that achieves backward compatibility.
{"title":"Appliqueing IMT-2000 features onto Globalstar","authors":"L. Schiff","doi":"10.1109/ICPWC.2000.905923","DOIUrl":"https://doi.org/10.1109/ICPWC.2000.905923","url":null,"abstract":"The IMT-2000 process of the ITU is intended to provide standardized ways of providing high data rate and multimedia services to the wireless user. The cdma2000 proposal for a 3rd generation terrestrial standard is a way of providing these services in a backwardly compatible and evolutionary way for the IS-95 user. The Globalstar LEOS MSS system uses waveforms and procedures derived from IS-95. Our purpose in this paper is to show that many of the features of cdma2000 can be appliqued onto the Globalstar system in an evolutionary way that achieves backward compatibility.","PeriodicalId":260472,"journal":{"name":"2000 IEEE International Conference on Personal Wireless Communications. Conference Proceedings (Cat. No.00TH8488)","volume":" 16","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132124012","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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