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Topic: Space division multiple access

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Cellular network

	Space-division multiple access - Wikipedia, the free encyclopedia
		In traditional mobile cellular network systems the base station has no information on the position of the mobile units within the cell and radiates the signal in all directions within the cell in order to provide radio coverage.
		By using smart antenna technology and exploiting spatial information of the location of mobile units within the cell have led to the development of space-division multiple access (SDMA) techniques.
		The radiation pattern of the base station, both in transmission and reception is adapted to each user to obtain highest gain in the direction of the mobile user.
	en.wikipedia.org /wiki/SDMA (343 words)

	Smart Antenna Application for Sattelite Communication Systems with Space Division Multiple Access
		The significant factor in the performance of multiple access in a satellite communications system is interference.
		The work purpose is the description of the SDMA principles in satellite communication systems and development of effective adaptive algorithm with low cost implementation for digital processor.
		SDMA can be implemented with a broad range of array geometry and antenna types.
	jre.cplire.ru /jre/feb01/1/text.html (2629 words)

	Frequency-division multiple access - Wikipedia, the free encyclopedia
		FDMA is an access technology and stands for Frequency Division Multiple Access.
		The terminology “multiple access” implies the sharing of the resource amongst users and the “frequency division” describes how the sharing is done – by allocating users with different carrier frequencies of the radio spectrum.
		In contrast to this methodology with Time division multiple access (TDMA), where users are separated in time, Code Division Multiple Access CDMA where users are separated by codes and other multiple access schemes: SDMA – Space division multiple access, CSMA – Carrier sense multiple access, and MF-TDMA - Multi-Frequency TDMA
	en.wikipedia.org /wiki/Frequency-division_multiple_access (393 words)

	Wavion
		Conventional metro Wi-Fi access points use simple diversity antennas that suffer from short range and limited capacity and are adversely affected by multipath and omni-directional noise reception.
		SDMA augments beamforming by providing a higher level of processing enabling simultaneous downlink communications with multiple users over the same frequency channel.
		The improvement in capacity and range resulting from SDMA are presented in Figure 2, where Wavion's SDMA performance is compared to a conventional access point in typical non-line-of-sight propagation model.
	www.wavionnetworks.com /tech/index.html (892 words)

	Multiple access Information - ms access multiple query based on one parameter
		Multiple access Information - ms access multiple query based on one parameter
		The connection of a access labels multiple print user to two or more switching centers by separate microsoft access multiple entries access lines using a single message routing indicator code division multiple access or telephone number.
		The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
	www.inanot.com /Ina-Electronics_Topics_Me_-_N-/Multiple_access.html (188 words)

	Tekes teknologiapörssi - Hakutulokset
		The invention relates to an AWG-based (arrayed waveguide grating) multiple delay line with a configuration that is looped back by means of sections of a dispersive optical medium, in which the simultaneous use of multiple wavelengths (WDM) enables numerous delays to be obtained owing to the dispersion of the sections of the dispersive optical medium.
		This type of architecture can be applied nowadays to any field in which is necessary to obtain a plurality of different delays in a set of wavelengths, as happens in the optical set of beams for antenna arrays where the obtaining of the subsets of progressive delays is basic for its functioning.
		The principal advantages of this invention are the aptitude to generate multiple beams simultaneously (multibeam capability) and the low losses of insertion (there are no losses for division due to the use of several optical sources).
	www.tekes.fi /partner/fin/search/nayta_haku.asp?hakuid=24521 (942 words)

	3g-generation: Glossary
		Code Division Multiple Access (CDMA): A digital spread-spectrum wireless technology championned by Qualcomm and used in its digital phones, including the forthcoming pdQ smart phones.
		SDMA: Space division multiple access (SDMA): A variation of TDMA and CDMA that potentially will be used in high-bandwidth, third-generation wireless products.
		Wideband Code Division Multiple Access (WCDMA): A third-generation mobile communications protocol similar to GSM that is expected to provide enough bandwidth for wireless multimedia applications.
	www.3g-generation.com /glossary.htm (881 words)

	Fictionwise eBooks: Space Division Multiple Access for Wireless Local Area Networks by P. Vandenameele
		Two major challenges in developing such high data-rate wireless networks are the channel distortion caused by multipath propagation and the limitations on bandwidth usage.
		By exploiting the parallelism in the data-model and the frequency-selectivity of the propagation channel, high-performance non-linear detection algorithms with modest complexity requirements are obtained.
		Space Division Multiple Access for Wireless Local Area Networks is appropriate for practitioners and researchers in the mobile communications and wireless fields.
	www.fictionwise.com /ebooks/eBook10852.htm (275 words)

	Research - Electrical, Electronic and Computer Engineering - University of Newcastle
		Linear and nonlinear adaptive algorithms are investigated for Space Division Multiple Access (SDMA).
		SDMA is one of the emerging techniques for multiple access of users in mobile radio, which used spatial distribution of users for their differentiation.
		The performance of SDMA-RNN is also compared with that of Code Division Multiple Access (CDMA) systems, showing that it could be used as a viable alternative scheme for multiple access of users.
	www.ncl.ac.uk /eece/research/publication/33054 (216 words)

	Markov Models for Limited Feedback MIMO Systems (Site not responding. Last check: 2007-10-25)
		During a training phase, the base station modulates a training sequence on multiple sets of randomly generated orthogonal beamforming vectors.
		The main advantage of the proposed system is that it provides throughput gains for the MIMO broadcast channel with a small feedback overhead, and provides these gains even with a small number of active users.
		Numerical simulations show that a 20% gain in sum capacity is achieved (for a small number of users) over conventional opportunistic space division multiple access, and a 100% gain (for a large number of users) over conventional opportunistic beamforming.
	www.ece.utexas.edu /~rheath/papers/2006/globecom (166 words)

	Research Project Code Division Multiple Access at the Department of Telecommunications at the University of ...
		CDMA is the third multiple access technique among the two more classical schemes FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access).
		Besides of the multiple access schemes explained above there is also SDMA (Space Division Multiple Access), which uses the spatial dimension.
		This multiplication with a sequence of higher frequency also yields a resulting signal of higher rate, therefore the spectrum of the original signal is spread by the factor SF.
	www.ant.uni-bremen.de /research/cdma (1783 words)

	Welcome to multiple antennas
		Multiple antenna transmission allows significantly boosting the capacities of future WLANs without needing to increase bandwidth or transmit power.
		Multiple antenna systems are the key to the high-capacity wireless universe.
		This includes future scenarios where both ‘current single-antenna’ terminals could benefit from a multiple-antenna enhanced Access Point, and scenarios where ‘multiple antenna –enhanced’ terminals feature better performance even when communicating with less advanced, single antenna access points or terminals.
	www.imec.be /wireless/mimo (467 words)

	New Page 0
		Abstract: Space division multiple access (SDMA) has attracted considerable attention as a means for increasing the capacity in cellular communications.
		In this paper, we develop a tool for evaluating the use of SDMA in time division multiple access (TDMA) systems.
		The approach is based on evaluating the outage probability due to cochannel interference in fading at the basestation of a TDMA system assuming an ideal beamformer model.
	www.coe.uncc.edu /~ilhowitt/Publications/abstract/evaluation.htm (219 words)

	Performance of Space-Division Multiple-Access (SDMA) With Scheduling
		The improved protocol performs scheduling based on users' spatial characteristics and quality-of-service parameters to achieve throughput multiplication and packet delay reduction.
		Performance of SDMA with scheduling is evaluated under mixed audio and data traffic patterns and results show that significant improvement in network performance can be achieved under the new protocol.
		S. Kumar and D. Vaman, "An access protocol for supporting multiple classes of service in a local wireless environment", IEEE Trans.
	www.comsoc.org /twc/public/2002/oct/611_01twc04-yin.html (514 words)

	SPACE.com -- Slippery Surface of Europa Slides, Migrates around Moon
		The effect is somewhat like squeezing a stress ball in multiple ways, and resulting friction heats Europa from within.
		The University of Arizona's Greg Hoppa, Randy Tufts, and Paul Geissler also worked on the study, which was detailed Thursday at a meeting of the American Astronomical Society's Division for Planetary Sciences in New Orleans.
		Get space news, mission coverage, and much more directly on your mobile.
	www.space.com /scienceastronomy/solarsystem/europa_icecrust_011130.html (641 words)

	Antenna-Sector Time-Division Multiple Access for Broadband Indoor Wireless Systems
		However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.
		It is shown that portables which are located in different sectors of an indoor microcell may be able to reuse the same frequency and the same time slot.
		Mahmoud, D. Falconer, and S. Mahmoud, "A multiple access scheme for wireless access to a broadband ATM LAN based on polling and sectored antennas," in PIMRC'95, vol.
	www.comsoc.org /sac/private/1998/aug/937_16sac06-macedo.html (644 words)

	SPACE.com -- Scientists Seek Scent of Life in Methane at Mars
		Mumma reported last year at the American Astronomical Society’s Division for Planetary Sciences that methane had been detected using super-sensitive infrared spectrometers mounted to the Gemini South telescope on Cerro Pachón in Chile and at the W.M. Keck Observatory on Mauna Kea, Hawaii.
		His advice, as a NASA scientist steeped in ever-growing volumes of new Mars data: proceed with caution, examine multiple lines of detection and then the basic chemistry of the processes - before leaping to conclusions.
		Garvin noted that the PFS on Mars Express is an outstanding Fourier spectrometer which could, under appropriate circumstances, detect methane at 10's of parts per billion levels - but across a large control volume of the martian atmosphere which is relatively well mixed.
	www.space.com /scienceastronomy/mars_methane_040824.html (1310 words)

	Antennas
		The advantage of the methods are their eficiency and high resolution in space domain.
		To achieve the required position detection accu- racy in SDMA systems the parameter estimations of the transmitters are performed either by parametrical or non-parametrical high resolution methods like ESPRIT, Prony or Pencil-of- function.
		Special methods of noise parameter averaging in the multi-channel correlation matrix are explained in this paper to reduce the signal-to-noise-ratio.
	www.hft.ei.tum.de /en/hft_lit-node2.html (122 words)

	A Novel MAC Layer Protocol for Space Division Multiple Access in Wireless Ad - Lal, Toshniwal, Radhakrishnan, Agrawal, ...
		These protocols, however, are unable to attain substantial performance improvements because they do not enable the nodes to perform multiple simultaneous...
		Summarizing, the use of multiple antennas at both the BTS and CPE can improve cellular capacity and link reliability.
		Lal, R. Toshniwal, R. Radhakrishnan, D. Agrawal, and J. Caffery, "A Novel MAC Layer Protocol for Space Division Multiple Access in Wireless Ad Hoc Networks," in Proceedings oflC3N, Miami, Florida, 2002.
	citeseer.ist.psu.edu /552046.html (537 words)

	Wavion to launch MIMO-ready outdoor APs \| InfoWorld \| News \| 2006-05-25 \| By Ephraim Schwartz
		The products will be one of the first to incorporate MIMO (Multimedia Input Multimedia Output), SDMA (Space Division Multiple Access) and beam-forming technology in a metropolitan scale outdoor access point, according to Alan Menezes, vice president of business development at Wavion.
		MIMO technology, which will be incorporated in the upcoming IEEE 802.11n specification, creates a standard for using multiple radios and antennas in an access point.
		The beam-forming technology will increase the range of a conventional access point from 600 feet to 1,500 feet by focusing the energy transmitted from six radios and six antennas.
	www.infoworld.com /article/06/05/25/78688_HNwavion_1.html (1042 words)

	A. Lee Swindlehurst (Site not responding. Last check: 2007-10-25)
		A current area of emphasis is the exploitation of both temporal and spatial information in extracting signals that overlap in both time and frequency.
		A typical application would be the characterization of the communication channel between the user of mobile cellular radio and the cell base station.
		Swindlehurst's research has focused on the use of multiple antennas at the base station to achieve so-called spatial-division (as opposed to time- and frequency-division) multiple access.
	www.ee.byu.edu /grad1/users/swindle/www_docs (372 words)

	natasha's research (Site not responding. Last check: 2007-10-25)
		This relates to work on wireless channels with side information at the encoder, cooperation between senders, as well as the interference, mutliple access, and broadcast channels.
		I'm also interested in the scheduling of variable-length packets for a Space Division Multiple Access system, or base station.
		Raymond Yim and myself have also written a paper on a generalization of generalized processor sharing for network switches.
	www.people.fas.harvard.edu /~ndevroye/research.html (476 words)

	Find in a Library: Space division multiple access for wireless local area networks
		Find in a Library: Space division multiple access for wireless local area networks
		Space division multiple access for wireless local area networks
		WorldCat is provided by OCLC Online Computer Library Center, Inc. on behalf of its member libraries.
	worldcatlibraries.org /wcpa/ow/0b520cc6859aed2aa19afeb4da09e526.html (75 words)

	Space-Time Division Multiple Access (STDMA)* and Coordinated, Power-Aware MACA for Mobile Ad-Hoc Networks ...
		If your firewall is blocking outgoing connections to port 3125, you can use these links to download local copies.
		Abstract: Space-Time Division Multiple Access (patent pending) is the first position-based TDMA scheduling protocol for mobile ad-hoc networks, and is the generalization of the cellular TDMA with spatial re-use bandwidth allocation paradigm that is encountered in cellular TDMA networks.
		In STDMA, space is divided into virtual geographic cells (space slots) that are grouped into periodically repeating virtual frames (space frames) in order to facilitate spatial re-use, and time slots are assigned to space...
	citeseer.ist.psu.edu /501485.html (296 words)

	:: OZ Communications :: mobilizing IM and Email messaging :: (Site not responding. Last check: 2007-10-25)
		A digital cellular phone that has text messaging, web access and other data services along with voice.
		SS7 is a separate signaling network that is used in Class 4 and Class 5 voice switches.
		Shared Wireless Access Protocol, the protocol used in HomeRF
	www.oz.com /glossary_s.html (229 words)

	A Survey on Recent Approaches to Using Directional Antennas in Mobile Ad Hoc Networks (Site not responding. Last check: 2007-10-25)
		There are multiple channels used with a single frequency for each, one for control, one for Busy Tone Transmit (BTT), one for Busy Tone Receive (BTR), and spread spectrum for data.
		It was also found that the probability of collision decreased dramatically as the number of contention slots per phase increased, and the number of antenna sectors per node had virtually no effect on the probability of collision.
		In [6], the authors used directional antennas proposed a MAC layer protocol that uses Space Division Multiple Access, directional reception to receive more than one packet from transmitters in different sectors.
	www-unix.oit.umass.edu /~vnambood/papers/survey.htm (3637 words)

	Data Communications EEE846 - Electrical, Electronic and Computer Engineering - University of Newcastle (Site not responding. Last check: 2007-10-25)
		Advancing the general knowledge of current data communication technology with emphasis on cellular systems and multiple access methods.
		Goals and worldwide standards, access to trunking systems, duplex schemes, physical layer.
		To provide students with an understanding of recent developments in cellular mobile systems and access technology by considering the main interernational standards and multiple access systems currently in service world-wide.
	www.ncl.ac.uk /eece/Modules/module/eee846 (230 words)

	Multiple Antenna Signal Processing in High Altitude Platforms
		High Altitude Platforms (HAPs) are a promising new technology to meet the needs of ever increasing demands for high capacity wireless services.
		Alternative adaptive array algorithms will be compared, focusing on their performance such as convergence speed, mis-adjustment, weight fluctuation and so on.
		In this project we will also consider and select the optimum multiple access technology, such as Space Division Multiple Access (SDMA), Time Division Mutiple Access (TDMA), and Code Division Multiple Access (CDMA).
	www.elec.york.ac.uk /comms/projects/zhengyixu.html (140 words)

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