Institution
Qualcomm
Company•Farnborough, United Kingdom•
About: Qualcomm is a company organization based out in Farnborough, United Kingdom. It is known for research contribution in the topics: Wireless & Signal. The organization has 19408 authors who have published 38405 publications receiving 804693 citations. The organization is also known as: Qualcomm Incorporated & Qualcomm, Inc..
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21 Dec 1988TL;DR: In this article, the authors present a message communication system employing one or more centralized communication stations transferring messages through Earth orbit repeater satellites to or from mobile terminals with at least one central communication station having a first transceiver for transmitting a first communication signal to mobile terminals, and at least another mobile terminal having a second transceiver having a predetermined duty cycle of the second transceivers, a second communication signal is transmitted to at most one of the central communication stations.
Abstract: A message communication system employing one or more centralized communication stations transferring messages through Earth orbit repeater satellites to or from mobile terminals with at least one central communication station having a first transceiver for transmitting a first communication signal to one or more mobile terminals and at least one mobile terminal having a second transceiver for receiving the first communication signal and demodulating it, and for transmitting at a predetermined duty cycle of the second transceiver, a second communication signal to at least one of the central communication stations. The preferred duty cycle over which the second communication signal is transmitted is about fifty percent of the second transceiver duty cycle. The communication system uses Time Division Multiplexed (TDM) communication signals using a number of channels as designated address channels with the remainder being used for data transfer. Information transmitted on the address channels is used by terminals to determine both the presence of a message and its corresponding data transmission or reception channel. In addition the terminals use the reception of the first communication signal to adjust return link transmission frequency to compensate for transmission path errors. The alternating duty cycle allows mobile terminals to use a single set of local oscillators for both transmission and reception modes of operation. To decrease interference with other systems the present system employs a power dispersal modulation function to achieve the footprint of a video signal for high transfer rate digital communication signals.
178 citations
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TL;DR: The results demonstrate that for block fading channels, sending a periodic preamble and causally receiving channel state information via a feedback channel can lead to substantial gains in the outage performance over any nonfeedback scheme, and can be translated into improvements in frame error rate performance of systems using space-time codes.
Abstract: Multiple antenna transmission and reception have been shown to significantly increase the achievable data rates of wireless systems. However, most of the existing analysis assumes perfect or no channel information at the receiver and transmitter. The performance gap between these extreme channel assumptions is large and most practical systems lie in between. Therefore, it is important to analyze multiple antenna systems in the presence of partial channel information. We upper bound the outage probability performance of multiple antenna systems with preamble-based channel estimation and quantized feedback. We design causal feedback and power control schemes to minimize this upper bound on outage probability. We consider the following practical issues in our analysis and design: (1) the channel information is imperfect both at the receiver and at the transmitter and (2) part of the total available resources for the system need to be used for estimation and feedback. Our results demonstrate that for block fading channels, sending a periodic preamble and causally receiving channel state information via a feedback channel can lead to substantial gains in the outage performance over any nonfeedback scheme. Most of the gains achieved by perfect feedback can be achieved by very few bits of feedback. Furthermore, it is demonstrated that these outage probability gains can be translated into improvements in frame error rate performance of systems using space-time codes. Thus, implementing a power control, even at the cost of reduced spectral resources for the forward channel is beneficial for block fading channels.
177 citations
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13 Aug 2001TL;DR: The wireless subscriber device that is operable in a communique system for cellular communication networks operates with existing cellular communication network to provide communique communication services to subscribers as discussed by the authors, and is typically full function communication devices that include: WAP enabled cellular telephones, personal digital assistants, Palm Pilots, personal computers, and the like or special communications devices that are specific to communique reception; or MP3 audio players (essentially a radio receiver or communique radio); or an MPEG4 video receiver (communique TV); or other such specialized communication device.
Abstract: The wireless subscriber device that is operable in a communique system for cellular communication networks operates with existing cellular communication networks to provide communique communication services to subscribers. The wireless subscriber devices used to communicate with the communique system for cellular communication networks are typically full function communication devices that include: WAP enabled cellular telephones, personal digital assistants, Palm Pilots, personal computers, and the like or special communique only communication devices that are specific to communique reception; or MP3 audio players (essentially a radio receiver or communique radio); or an MPEG4 video receiver (communique TV); or other such specialized communication device.
177 citations
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01 Mar 2002
TL;DR: In this paper, a system for automatically reconfiguring a mobile telephone based on geographic location is presented, which includes a storing unit (40) and an execution unit (70), which allows the user to save a particular location and the desired configurations corresponding to that location.
Abstract: A system for automatically reconfiguring a mobile telephone based on geographic location. In the illustrative embodiment, the invention includes a storing unit (40) and an execution unit (70). The storing unit (40) allows the user to save a particular location and the desired configurations corresponding to that location. The execution unit (70) monitors the position of the telephone and, upon entering a saved location, executes the configurations corresponding to that location. The execution unit (70) also returns the configurations to their previous settings after the telephone has exited from the saved location.
177 citations
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TL;DR: In this paper, the authors explore design aspects of adaptive modulation based on orthogonal frequency division multiplexing (OFDM) for underwater acoustic (UWA) communications, and study its performance using real-time at-sea experiments.
Abstract: In this paper, we explore design aspects of adaptive modulation based on orthogonal frequency-division multiplexing (OFDM) for underwater acoustic (UWA) communications, and study its performance using real-time at-sea experiments. Our design criterion is to maximize the system throughput under a target average bit error rate (BER). We consider two different schemes based on the level of adaptivity: in the first scheme, only the modulation levels are adjusted while the power is allocated uniformly across the subcarriers, whereas in the second scheme, both the modulation levels and the power are adjusted adaptively. For both schemes we linearly predict the channel one travel time ahead so as to improve the performance in the presence of a long propagation delay. The system design assumes a feedback link from the receiver that is exploited in two forms: one that conveys the modulation alphabet and quantized power levels to be used for each subcarrier, and the other that conveys a quantized estimate of the sparse channel impulse response. The second approach is shown to be advantageous, as it requires significantly fewer feedback bits for the same system throughput. The effectiveness of the proposed adaptive schemes is demonstrated using computer simulations, real channel measurements recorded in shallow water off the western coast of Kauai, HI, USA, in June 2008, and real-time at-sea experiments conducted at the same location in July 2011. We note that this is the first paper that presents adaptive modulation results for UWA links with real-time at-sea experiments.
176 citations
Authors
Showing all 19413 results
Name | H-index | Papers | Citations |
---|---|---|---|
Jian Yang | 142 | 1818 | 111166 |
Xiaodong Wang | 135 | 1573 | 117552 |
Jeffrey G. Andrews | 110 | 562 | 63334 |
Martin Vetterli | 105 | 761 | 57825 |
Vinod Menon | 101 | 269 | 60241 |
Michael I. Miller | 92 | 599 | 34915 |
David Tse | 92 | 438 | 67248 |
Kannan Ramchandran | 91 | 592 | 34845 |
Michael Luby | 89 | 282 | 34894 |
Max Welling | 89 | 441 | 64602 |
R. Srikant | 84 | 432 | 26439 |
Jiaya Jia | 80 | 294 | 33545 |
Hai Li | 79 | 570 | 33848 |
Simon Haykin | 77 | 454 | 62085 |
Christopher W. Bielawski | 76 | 334 | 32512 |