Shih-Fu Chang - New York NY Justin Che-I Chuang - Holmdel NJ Gustavo De Los Reyes - Fair Haven NJ Amy Ruth Reibman - Matawan NJ
Assignee:
ATT Corp - New York NY Columbia University - New York NY
International Classification:
H04N 704
US Classification:
348470, 348192, 348466
Abstract:
A method and system for maintaining the quality of video transported over wireless channels uses a transcoder to modify and maintain the optical resilience of an encoded bitstream. The transcoder increases the spatial resilience by reducing the number of blocks per slice, and increases the temporal resilience by increasing the proportion of I-blocks that are transmitted in each frame. Also, the transcoder maintains the same input bit rate by dropping less significant coefficients as it increases resilience. The transcoder of the present invention maintains the resilience at an optimal level to accommodate the prevailing channel conditions as measured by the BER of the wireless channel. Rate distortion theory is applied to determine the optimal allocation of bit rate among spatial resilience, temporal resilience and source rate, where it is has been found that the optimal allocation of the present invention (which occurs in near-real time) provides nearly the same result as doing an exhaustive search.
Kapil K. Chawla - Scotch Plains NJ Justin Che-I Chuang - Holmdel NJ Xiaoxin Qiu - Bridgewater NJ Nelson Ray Sollenberger - Farmingdale NJ
Assignee:
ATT Corp. - New York NY
International Classification:
H04Q 720
US Classification:
455450, 455 671, 455451, 455452, 370341
Abstract:
This invention provides wireless resource allocation techniques where the wireless network resource allocation is based on maximum system gain. System gain may be the difference between a maximum performance (e. g. , throughput rate) for a requested link and a performance loss of all currently active links affected by the requested link. A currently active link is affected if the requested link is within its link neighborhood. Wireless network resources are allocated to optimize system performance. Inter-base communication may be used to facilitate information exchange among base stations to optimize system performance. The performance loss experienced by any currently active link is called damage to that link. Damage may be determined in a pair-wise fashion based on a nominal performance which may be defined as the performance of a link if interference is experienced only from links which are outside the link neighborhood of the link or as a system parameter. The damage is the difference between the nominal performance and the performance for the link if experiencing interference only from the requested link.
System For Near Optimal Joint Channel Estimation And Data Detection For Cofdm Systems
Justin C. Chuang - Holmdel NJ Ye Li - Marietta GA Lang Lin - Piscataway NJ
Assignee:
ATT Corp. - New York NY
International Classification:
H03D 100
US Classification:
375340, 370210
Abstract:
Joint channel estimation and maximum likelihood decoding method for Coded Orthogonal Frequency Division Multiplexing (COFDM) systems are presented. Using this method in conjunction with convolutional coding, robust and nearly optimal coherent detection can be achieved in rapid dispersive fading channels. Significant performance gain in packet data throughput is realized in a system with aggressive frequency reuse. A system for estimating channel characteristics in a multicarrier transmission system comprising means for receiving a multicarrier signal, means for applying Fast Fourier transformations to the multicarrier signal, means for estimating channel characteristics of a multicarrier channel over which the multicarrier signal was transmitted using iterative processing and means for decoding the transformed multicarrier signal is presented.
Li Fung Chang - Holmdel NJ Kapil K. Chawla - Middletown NJ Justin C. Chuang - Holmdel NJ Zoran Kostic - Holmdel NJ Nelson Sollenberger - Tinton Falls NJ Xiaoxin Qiu - Bridgewater NJ
Assignee:
ATT Corp. - New York NY
International Classification:
H04J 1306
US Classification:
375133, 455452
Abstract:
This invention provides a dynamic frequency hopping system that utilizes information from multiple base stations. The system assigns frequency hopping patterns based on current interference and traffic environments to avoid interference thus gaining the benefits of interference averaging and interference avoidance. The system imposes less stringent measurement requirements on terminals (wireless mobile devices) because many measurement requirements are replaced by generating estimates based on measurement data received from other base stations within a base station neighborhood. The system may continuously verify that the frequency hopping patterns assigned to the links of the system optimizes system performance. The system compares system performance of possible frequency hopping patterns against currently assigned frequency hopping pattern to optimize system performance. When a request for a link is received, a similar process as above is performed where the request is granted/denied/delayed based on system optimization requirements.
Medium Access Control Layer For Packetized Wireless Systems
Li Fung Chang - Holmdel NJ Kapil K. Chawla - Middletown NJ Justin C. Chuang - Holmdel NJ Xiaoxin Qiu - Bridgewater NJ Nelson R. Sollenberger - Tinton Falls NJ
Assignee:
ATT Corp - New York NY
International Classification:
H04Q 728
US Classification:
370341
Abstract:
An arrangement where, in addition to the control channels that are used to set up sessions, there is a logically and physically separate and independent set of control channels that can be used as session control channels. Illustratively, the physical GSM frame arrangement that employs 8 logical slots is used, with one slot both in the uplink and downlink dedicated to these separate control channels. In the downlink, such a control channel provides channel grant information, requests to make and transmit power measurements, poll mobile units, etc. In the uplink, such a control channel can be used to request access to a traffic channel, to report on power measurements, to request special hand-off handling, to respond to polling, etc. Because the uplink session control channel does not need to carry a significant amount of information, the GSM slot can be divided into minislots, with each minislot constituting a session control channel for a group of mobile units.
Tdma Communication System Having Enhanced Power Control
Li Fung Chang - Holmdel NJ Kapil K. Chawla - Scotch Plains NJ Justin Chi-I Chuang - Holmdel NJ Zoran Kostic - Holmdel NJ Xiaoxin Qiu - Bridgewater NJ Nelson Ray Sollenberger - Farmingdale NJ Shailender B. Timiri - Bellevue WA
Assignee:
ATT Wireless Services, Inc. - Redmond WA
International Classification:
H04Q 720
US Classification:
455522, 455 69, 4552451
Abstract:
A TDMA wireless communication system adjusts the power control target and transmission power based upon link quality to enhance voice capacity. The power can be adjusted in response to the average SNIR and number of decoding errors in a link quality reporting period. The power control target can be increased and decreased in discrete intervals after evaluating the number of decoding errors in the reporting period. The transmission power can be adjusted towards the new power control target based upon the average SNIR.
Link Adaptation In Wireless Networks For Throughput Maximization Under Retransmissions
The present invention implements a method and system for dynamically adapting the modulation and coding scheme for radio links in a wireless communications network based on a retransmission environment model in order to maximize throughput and most efficiently allocate bandwidth resources. The present invention encompasses a refined calculus and methodology for deriving the link adaptation thresholds in a retransmission environment using a complex model and analysis of the retransmission environment. The present invention holds particular application for wireless data communications as opposed to real time data services because it is based on a retransmission model applicable primarily for data services. A critical component of this new link adaptation system is a âno transmissionâ cutoff mode that is selected for SIR below a base threshold value. This new mode prevents system instability and misallocation of bandwidth in a wireless communication system.
Wireless Network Having Joint Power And Data Rate Adaptation