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Topic: Adaptive modulation

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	Multiuser OFDM
		Using adaptive modulation the carrier modulation is matched to the SNR, maximising the overall spectral efficiency.
		Also as the mobility of the remote station is increased, the adaptive modulation process requires regular updates, further increasing the overhead.
		Adaptive frequency hopping reverts to normal random hopping when the velocity is too high for the hopping to keep up with the rate of change of the channel.
	www.skydsp.com /publications/MultiuserOFDM/index.htm (2686 words)

	Welcome to SkyDSP, OFDM systems, telemetry, software radio
		A new adaptive frequency hopping technique is proposed for multiuser OFDM such that blocks of carriers are hopped based on the current channel conditions.
		Adaptive frequency hopping achieves large performance gains by avoiding nulls in the channel frequency response caused by frequency selective fading.
		Adaptive frequency hopping for multiuser OFDM has been presented and shown to be a powerful technique for reducing the effects of frequency selective fading.
	www.skydsp.com /publications/AdaptMod/index.htm (3418 words)

	Welcome to EE359 Adaptive Modulation Home Page
		Adaptive MQAM (proposed in [1]) is a very powerful technique, it is 17 dB more power efficient than nonadaptive modulation in fading, assuming perfect channel estimates at the receiver with zero delay in the feedback path.
		Adaptive MQAM varies both the rate and the transmit power to maximize the throughput under the constraint of fixed average transmit power and the constraint of fixed instantaneous BER.
		The adaptive encoder is a turbo encoder E with b input bits, the turbo encoder is mad up of a set of two parallel concatenated convolutional encoders with an interleaver of size M preceding one of them.
	www.stanford.edu /~mmren (2211 words)

	Untitled Document (Site not responding. Last check: 2007-09-17)
		Adaptive Moduation(AM) is a technique where the modulation, coding rate, and other signal transmission parameters are dynamically adapted to the changing channel conditions.
		The goal of an Adaptive Modulation is to ensure that the most efficient mode is always used, over varying channel conditions, based on a mode selection criterion (maximum data rate, minimum transmit power, etc).
		The example in Fig 1 is ideal as it assumes that the modulation level is perfectaly adapted to the short term average SNR and the probability of error as a function of SNR is exactly known.
	www.cse.iitd.ernet.in /~csd02446/CS310 (551 words)

	Adaptive Coded Modulation for Fading Channels
		Adaptive modulation is a powerful technique to improve the energy efficiency and increase the data rate over a fading channel.
		Coset codes are a natural choice to use with adaptive modulation since the channel coding and modulation designs are separable.
		We first describe the methodology for combining coset codes with a general class of adaptive modulation techniques.
	www.comsoc.org /comm/private/1998/may/595_46comm05-goldsmith.html (546 words)

	Effect of Slow Fading and Adaptive Modulation on TCP/UDP Performance of High-Speed Packet Wireless Networks \| EECS at ...
		Adaptive modulation is used in the new generation of wireless systems to increase the system throughput and significantly improve spectral efficiency by matching parameters of the physical layer to the time-varying fading channels.
		The effect of adaptive modulation on TCP throughput is investigated.
		Based on the adaptive modulation information from the physical layer, the advertised receive window size of TCP ACK packets is dynamically changed to accommodate the rate changes resulting from adaptive modulation.
	www.eecs.berkeley.edu /Pubs/TechRpts/2006/EECS-2006-109.html (488 words)

	UCLA / ICSL DARPA Project: Detailed Discussion (Site not responding. Last check: 2007-09-17)
		Adaptive beamforming will be investigated for purposes of nulling out interferers, and increased gain in the direction of the desired signal.
		Adaptive channel allocation may be used to mitigate the interference conditions and more frequently allow high-rate transmission.
		Although the proposed adaptive modem represents a significant advance in the state of the art, several of the architectural ideas and circuit level building blocks have already been demonstrated at UCLA which should significantly minimize the risk of such an ambitious effort.
	www.janet.ucla.edu /wamis2/discussion.html (4540 words)

	EETimes.com - Broadband Access: Dynamic, flexible links key for user
		Adaptive MAC-layer parameters include adaptive frame size and adaptive automatic repeat request (ARQ), which is a retransmission protocol at the link layer of a wireless system that enables recovery from packet errors.
		Adaptive modulation is defined as the ability of a basestation to choose the right level of modulation for each transmission to or from a subscriber unit.
		Adaptive modulation can adapt in both directions, so if the co-channel interference goes down and the link quality improves, the modulation level should increase.
	www.eetimes.com /story/OEG20010606S0006 (1738 words)

	Adaptive modulation - Article from FactBug.org - the fast Wikipedia mirror site
		Adaptive modulation is a transmission scheme in digital communications where the transmitter adapts its transmission mode in accordance with the channel.
		This could be acquired in time division duplex systems where the channel from the transmitter to the receiver is approximately the same as the channel from the receiver to the transmitter.
		Adaptive modulation systems improve rate of transmission, and/or bit error rates by exploiting the channel information that is present at the transmitter.
	www.factbug.org /cgi-bin/a.cgi?a=1035659 (202 words)

	Anti-jam FM/CW radar - Patent 5892477
		In medium pulse radar, the transmit waveform modulation is a train of pulses, and the range to an object is determined by the delay between transmission and reception of the pulse.
		A radio frequency oscillator generates a carrier signal which is modulated by the modulation signal, and the modulated signal is transmitted by the radar system.
		The independent, adaptive local oscillators used in the present invention are sufficiently variable to enable varying the modulation and demodulation signals to while the range to the target and jammer are both changing.
	www.freepatentsonline.com /5892477.html (4471 words)

	Dept. of Electrical & Computer Engineering (Site not responding. Last check: 2007-09-17)
		The focus of this research is the analysis and design of both adaptive modulation and adaptive receivers for CDMA communication channels in the presence of uncertainty regarding relevant channel parameters, such as timing information, multipath structure, additive noise distribution, and the signal structure of interfering users.
		This study is focused on the analysis and design of adaptive procedures for estimation of multipath parameters on impulse radio channels.
		Barton and Jianjun Ni, “Joint Adaptive Modulation and Receiver Design for Rapidly Time-Varying CDMA Fading Channels,” Proceedings of the 2001 National Radio Science Meeting, Boulder, CO, January 8-11, 2001.
	www.egr.uh.edu /ece/faculty/barton (671 words)

	Technology Overview :: Motorola, formerly Orthogon Systems (Site not responding. Last check: 2007-09-17)
		Motorola employs Adaptive Modulation to optimize signals according to the conditions of the RF path, allowing transmissions to travel from one receiver to the next without signal loss.
		With Adaptive Modulation, the radio power output is dynamically modified according to the received signal level, upshifting or downshifting to overcome fading.
		Since the channel may vary in intensity on a sub-second basis, adapting the modulation dynamically allows the maximum amount of data possible to be sent across the path while keeping the link quality at the highest level.
	www.orthogonsystems.com /products/adaptive_modulation.html (126 words)

	On the Performance of Adaptive Modulation in Cellular Systems
		Adaptive modulation techniques have the potential to substantially increase the spectrum efficiency and to provide different levels of service to users, both of which are considered important for third-generation cellular systems.
		Specifically, we study the throughput performance gain that may be achieved by combining adaptive modulation and power control.
		Although presented in the context of adaptive modulation, the results also apply to other variable rate transmission techniques, e.g., rate adaptive coding schemes, coded modulation schemes, etc. This work provides valuable insight into the performance of variable rate transmission techniques in multi-user environments.
	www.comsoc.org /comm/private/1999/jun/884_47comm06-qiu.html (621 words)

	G.727 5, 4, 3 and 2- bits sample embedded adaptive differential pulse code modulation (ADPCM)
		In the Encoder, after the conversion of the A-law or mu-law PCM input signal to uniform PCM, a difference signal is obtained by subtracting an estimate of the input signal from the input signal itself.
		An adaptive 4-, 8-, 16- or 32-level quantizer is used to assign 2, 3, 4 or 5 binary digits to the value of the difference signal for transmission to the decoder.
		Both the reconstructed signal and the quantized difference signal are operated upon by an adaptive predictor which produces the estimate of the input signal, thereby completing the feedback loop.
	www.vocal.com /data_sheets/g727.html (922 words)

	Aperto - PacketWave Family
		The Aperto system has the ability to dynamically adapt modulation and coding levels as a function of the link between the base station and each subscriber unit.
		Dynamic modulation extends the radius of coverage of the cell, so that subscribers that are closer to the base station receive 16QAM reception, while those further away receive QPSK
		Adaptive coding and modulation helps to capture the best of both worlds, since the system is able to supply Level 1 to all subscriber units that have a good link to the base station, and Levels 2 and higher to subscriber units whose link is not as good.
	www.apertonet.com /products/adaptivecodingandmodulation_ptop.html (508 words)

	Adaptive Equalization (Site not responding. Last check: 2007-09-17)
		In conjunction with Wideband Modulation, Adaptive's products use an Adaptive Equalizer in which each node on the network is an independent transceiver able to adaptively equalize to powerline distortion at different locations and different times.
		The equalizer boosts the signal at different frequencies to account for differences in attenuation caused by the powerline, allowing the receiver to "hear" the powerline signal as it was intended.
		Combined with maximum probability of reception enabled by fast synchronization and short frames, adaptive equalization serves as the foundation for very low latency isochronous communications.
	www.adaptivenetworks.com /AdaptiveEqualization.htm (220 words)

	An Adaptive Modulation Scheme for Simultaneous Voice and Data Transmission over Fading Channels
		We propose a new adaptive modulation technique for simultaneous voice and data transmission over fading channels and study its performance.
		It uses fixed-rate binary phase shift keying (BPSK) modulation on the Q channel for voice, and variable-rate M -ary amplitude modulation (M -AM) on the I channel for data.
		As the channel degrades, the modulation gradually reduces its data throughput and reallocates most of its available power to ensure a continuous and satisfactory voice transmission.
	www.comsoc.org /sac/private/1999/may/837_17sac05-alouini.html (963 words)

	search Abstract
		For such channels, we propose novel adaptive power control and bit loading algorithms to maximize the spectral efficiency of the OFDM system while minimizing the required transmit power at some specified BER level.
		Unlike its existing counterparts, our adaptive modulation algorithm adapts the subcarrier transmission parameters based on the subcarrier fading statistics rather than the instantaneous channel conditions.
		A new closed-form expression with good inversion property for QAM BER in Rician fading channel is also developed to facilitate the computation of the optimum adaptive modulation settings.
	www.ntu.edu.sg /centre/pwtc/Download/eylguan_19.htm (142 words)

	Research (Site not responding. Last check: 2007-09-17)
		Optimal and practical adaptive modulation techniques are well established for single input single output (SISO) systems in many publications.
		Adaptive modulation techniques for multiple antenna systems are current issues in recent wireless data transmission.
		My attention in research is to design a novel system with an adaptive modulation and coding technique coupled with space-time processing for MIMO systems.
	www.public.asu.edu /~yko01/research.html (194 words)

	PRMA-assisted Adaptive Modulation
		Since the required SNR difference amongst the various modulation schemes used is compensated by the internal sub-division of the cell, in all areas of the cell a similar speech quality can be maintained.
		However, in the proposed PRMA-assisted adaptive modulation scheme mobile stations (MS) can reserve more than one slot in order to deliver up to four bursts per speech frame, when DPSK is invoked towards the cell edges.
		The BER curves for these modulation schemes in narrow-band Rayleigh channels with second order diversity, a propagation frequency of 2 GHz and a vehicular speed of 15 m/s are shown in Figures 1 and 2 in case of the GSM- and DECT-type systems, respectively.
	www-mobile.ecs.soton.ac.uk /hanzo/papers/bath31/node2.html (933 words)

	index
		Developed cross-layer designs of adaptive modulation and coding at PHY with (hybrid) ARQ protocols at MAC, which enhance the systems' spectral efficiency and enable the robustness to estimation errors of channel quality induced by channel variation and feedback latency.
		Developed cross-layer designs of scheduling at MAC using adaptive modulation and coding at PHY to guarantee prescribed QoS for heterogeneous service requirements.
		Analyzed the impact of adaptive modulation and coding at PHY and queuing at MAC on the TCP throughput at transport layer and proposed an optimal wireless link design to maximize the TCP throughput in wired-cum-wireless networks.
	www.ece.umn.edu /users/qliu/research.htm (263 words)

	Bookpool: Third-Generation Systems & Intelligent Wireless Networking
		The employment of adaptive antennas has numerous benefits and advantages.
		These include reducing the co-channel interference imposed on other system users, increasing the user capacity and the area spectral efficiency, improving the power efficiency, and reducing the number of handovers as well as transmission errors.
		By providing an all-encompassing self-contained treatment of adaptive modulation, adaptive antennas and adaptive networking, this volume will inspire researchers, practising engineers and advanced students in the areas of wireless communications and networking.
	www.bookpool.com /sm/0470845198 (274 words)

	Improving amplifier's efficiency using a linearizer in conjunction with adaptive bias modulation - improving amplifier ...
		By employing a hybrid combination of adaptive bias and linearization, it is possible to improve amplifier efficiencies over a range of RF powers for a varied type of modulation scheme.
		In the case of a Class AB amplifier, the efficiency with adaptive bias does decrease with falling drive as Class AB transistor are sensitive to external biasing arrangements and efficiencies fall away more rapidly than theory would suggest.
		It is possible to use dynamic modulation of the power supply to track the signal but this generates distortion products with the systems that are problematic (alteration of the bias and power supply results in unwanted modulation of the RF signal).
	www.rfdesign.com /vlf_to_uhf/rf_circuits/radio_improving_amplifiers_efficiency (2236 words)

	Channel-adaptive Modulation (Site not responding. Last check: 2007-09-17)
		Packet Reservation Multiple Access (PRMA) assisted adaptive modulation using 1, 2 and 4 bit/symbol transmissions is proposed as an alternative to Dynamic Channel Allocation (DCA) in order to maximise the number of users supported in a traffic cell.
		The cell is divided in three concentric rings and in the central high Signal-to-noise ratio (SNR) region 16-level Star Quadrature Amplitude Modulation (16-StQAM) is used, in the first ring Differential Quaternary Phase Shift Keying (DQPSK) is invoked, while in the outer ring Differential Phase Shift Keying (DPSK) is utilised.
		A 4.7 kbps Algebraic Code Excited Linear Predictive (ACELP) speech codec is favoured, which is protected by a quad-class source-sensitivity matched BCH coding scheme, yielding a total bit rate of 8.4 kbps.
	www-mobile.ecs.soton.ac.uk /hanzo/papers/bath31/bath31.html (194 words)

	Dr. Dobb's \| Algorithm Alley \| July 22, 2001
		Delta modulation is a data-encoding technique that's particularly useful for transmitting fewer bits and archival storage.
		One common method of data compression is delta modulation, a technique that's typically used for sound and/or video digital radio transmissions and recordings as well as other types of signals.
		Delta modulation is a data-encoding technique that also compresses the sequence of sampled function values being encoded.
	www.ddj.com /184410540 (2083 words)

	Rf transceiver having adaptive modulation patent invention
		A modulation control module for use in an RF transceiver, the modulation control module includes a processing module and memory.
		The data modulation stage converts raw data into baseband signals in accordance with a particular wireless communication standard.
		Each of the receiver paths processes the received RF signals to produce digital signals, which are combined and then processed to recapture the transmitted data.
	www.freshpatents.com /Rf-transceiver-having-adaptive-modulation-dt20061026ptan20060239366.php (1994 words)

	Press Releases (2000 - 2005)
		This standard provides definition, methods of measurements and performance standards for radio equipment used in the private (dispatch) land mobile services that employ scalable adaptive modulation, for transmission and receptions of data using digital techniques, with or without encryption, with a frequency of 1 GHz or less.
		The definition and description of the system in which this equipment operates is given in the document TIA/EIA-902.A. The TIA Wide Air Interface Standard (TIA-902.CAAB) defines the requirements of both the physical layer and data link layer in the OSI reference model for the radio interface in which this equipment operates.
		However, this standard is not intended to cover transceiver equipment employing any or all modulation types or access methods.
	www.tiaonline.org /business/media/press_releases/legacy.cfm?parelease=03-88 (339 words)

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