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| 20090296096 | Interferometric Defect Detection - Methods and systems for using common-path interferometry are described. In some embodiments, a common-path interferometry system for the detection of defects in a sample is described. An illumination source generates and directs coherent light toward the sample. An optical imaging system collects light reflected from the sample including a scattered component of that is predominantly scattered by the sample, and a specular component that is predominantly undiffracted by the sample. A variable phase controlling system is used to adjust the relative phase of the scattered component and the specular component so as to improve the ability to detect defects in the sample. | 12-03-2009 |
| 20110075151 | INTERFEROMETRIC DEFECT DETECTION AND CLASSIFICATION - Systems and methods for using common-path interferometric imaging for defect detection and classification are described. An illumination source generates and directs coherent light toward the sample. An optical imaging system collects light reflected or transmitted from the sample including a scattered component and a specular component that is predominantly undiffracted by the sample. A variable phase controlling system is used to adjust the relative phase of the scattered component and the specular component so as to change the way they interfere at the image plane. The resultant signal is compared to a reference signal for the same location on the sample and a difference above threshold is considered to be a defect. The process is repeated multiple times each with a different relative phase shift and each defect location and the difference signals are stored in memory. This data is then used to calculate an amplitude and phase for each defect, which can be used for defect detection and classification. This method is expected to detect much smaller defects than current inspection systems and to find defects that are transparent to these systems. | 03-31-2011 |
| 20110075928 | High-resolution, common-path interferometric imaging systems and methods - High-resolution, common-path interferometric imaging systems and methods are described, wherein a light source generates and directs light toward a sample. An optical imaging system collects the resultant substantially scattered component and substantially unscattered component. A variable phase shifting system is used to adjust the relative phase of the scattered and unscattered light components. The interfered components are sensed by an image sensing system. The process is repeated multiple times with different phase shifts to form corresponding multiple electronic signals representative of raw sample images. The raw sample images are then processed by a signal processor to form a processed image, where each image pixel has an amplitude and a phase. This picture can be displayed directly using some combination of brightness and color to represent amplitude and phase. Multiple processed images, each corresponding to a different illumination azimuth angle, can be combined to substantially extend the resolution. The technique permits the optical aberrations in the imaging system to be measured and removed from each picture. The addition of phase and amplitude to microscopic images is expected to extend both the depth and breadth of the many applications of optical microscopy. | 03-31-2011 |
| 20110242528 | OPTICAL IMAGING SYSTEM WITH CATOPTRIC OBJECTIVE; BROADBAND OBJECTIVE WITH MIRROR; AND REFRACTIVE LENSES AND BROADBAND OPTICAL IMAGING SYSTEM HAVING TWO OR MORE IMAGING PATHS - An optical system may include an objective having at least four mirrors including an outermost mirror with aspect ratio <20:1 and focusing optics including a refractive optical element. The objective provides imaging at numerical aperture >0.7, central obscuration <35% in pupil. An objective may have two or more mirrors, one with a refractive module that seals off an outermost mirror's central opening. A broad band imaging system may include one objective and two or more imaging paths that provide imaging at numerical aperture >0.7 and field of view >0.8 mm. An optical imaging system may comprise an objective and two or more imaging paths. The imaging paths may provide two or more simultaneous broadband images of a sample in two or more modes. The modes may have different illumination and/or collection pupil apertures or different pixel sizes at the sample. | 10-06-2011 |
| 20110280038 | Systems for and methods of illumination at a high optical solid angle - Illumination systems and methods that utilize the higher or outer portions of the optical solid-angle space to increase the illumination intensity are disclosed. The illumination systems and methods include introducing illumination light through at least one side surface of a transparent slide that operably supports a sample on its top surface. The light fills at least a portion of the optical solid-angle space between 1 and n, and extends out to n. Light from the filled portion of the optical solid-angle space illuminates the sample through the top surface of the transparent slide. The disclosed illumination systems and methods are suitable for use in applications, such as dark-field imaging, fluorescence imaging, Raman spectroscopy, DNA analysis and like applications requiring high-intensity illumination. | 11-17-2011 |
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| 20110149087 | Joint Bandwidth Detection Algorithm For Real-Time Communication - A video coding system and method for increasing a transmitted output bit rate of a video encoding system by altering the content of the bit stream. A video encoder may receive a coding mode signal from a computer application for coding source video data, the coding mode signal indicating a target bit rate having a risk factor related to transmission error associated to the target bit rate. The coded bitstream may be modified based on the risk factor indicated in the coding mode signal. A modified coded bitstream may be outputted at the target bit rate and at a reduced coding efficiency, and the channel may be tested for transmission errors. Based on the test results, a revised coding mode signal indicating the same target bit rate, but a revised risk factor may be provided. The coded bitstream may be revised by removing the modifications previously made to the coded bitstream and a revised coded bitstream having greater coding efficiency may be output at the target bit rate. | 06-23-2011 |
| 20110235709 | FRAME DROPPING ALGORITHM FOR FAST ADAPTATION OF BUFFERED COMPRESSED VIDEO TO NETWORK CONDITION CHANGES - A video coding and transmission system may employ techniques for adapting buffered video to network condition changes. Video data may be coded as reference data and non-reference data. According to the embodiments, non-reference frame may be detected in buffered video while awaiting transmission to a network. When network degradation is detected, one or more of the buffered non-reference frames may be dropped when network degradation is detected. Information about the dropped frames may be passed to an encoder for updating buffer parameters for future encoding. In this manner, a video coding system may provide faster responses to changing network conditions than systems without such buffer management techniques. | 09-29-2011 |
| 20110249074 | In Conference Display Adjustments - Some embodiments provide a method for modifying a composite display of a first mobile device that is engaged in a video conference with a second device. The method presents, on the first device, the composite display having a first video captured by the first device and a second video captured by the second device. The method receives, at the first device, an input for modifying the composite display during the video conference. The method modifies the composite display based on the received input. | 10-13-2011 |
| 20110249075 | Remote Control Operations in a Video Conference - Some embodiments provide a method for allowing a first device that is in a video conference with a second mobile device to remotely control the second mobile device. The method sends images captured by a camera of the first device to the second device. The method receives images captured by a camera of the second device. The method sends a command through a communication channel of a real-time communication session to the second device. The command is for instructing the second device to perform an operation that modifies the images captured by the camera of the second device. | 10-13-2011 |
| 20110249077 | Video Conference Network Management for a Mobile Device - Some embodiments provide a method for managing a video conference between a first device and a second device. The method identifies a first ceiling bit rate for transmitting video conference data to the second device through the communication channel. The method identifies a current bit rate that is less than the first ceiling bit rate. The method receives networking data regarding the communication channel from the second device. The method determines, from the received network data, that the communication channel will sustain an increase in the current bit rate. The method increments the current bit rate. The method iteratively performs the receiving, determining, and incrementing operations until a determination is made that the communication channel will not sustain the increase in the current bit rate. | 10-13-2011 |
| 20110249078 | Switching Cameras During a Video Conference of a Multi-Camera Mobile Device - Some embodiments provide a method for conducting a video conference between a first mobile device and a second device. The first mobile device includes first and second cameras. The method selects the first camera for capturing images. The method transmits images captured by the first camera to the second device. The method receives selections of the second camera for capturing images during the video conference. The method terminates the transmission of images captured by the first camera and transmits images captured by the second camera of the first mobile device to the second device during the video conference. | 10-13-2011 |
| 20110252090 | Dynamic Designation of a Central Distributor in a Multi-Participant Conference - Some embodiments dynamically designate one of several network nodes as a network hub of a star network, at the start of a network communication session among the several network nodes that is facilitated by a mesh network and the star network. Some embodiments dynamically designate a new network hub when the previously designated network hub leaves the communication session, which continues among the other network nodes. Different embodiments use different techniques to dynamically designate the network hub of the star network. For instance, some embodiments use communications transmitted along the mesh network to dynamically identify the network hub at the start of the network communication session or after the departure of a previously designated network hub. | 10-13-2011 |
| 20110252144 | Apparatus and Method for Establishing and Utilizing Backup Communication Channels - An apparatus, method, and machine-readable medium are described for establishing, maintaining and utilizing backup channels in a peer-to-peer (“P2P”) network. For example, in one embodiment, each mobile device can establish a primary P2P communication channel with one or more other mobile devices. Once the primary channel is established, each mobile device can use the primary channel to exchange secondary channel connection data and can subsequently open one or more secondary P2P communication channels with the other mobile devices. Upon detecting that the primary P2P communication channel has failed or has degraded below a specified threshold (e.g., a bandwidth or bitrate threshold), one of the secondary P2P communication channels can be automatically promoted to a primary P2P communication channel. | 10-13-2011 |
| 20110252157 | AUDIO PROCESSING OPTIMIZATION IN A MULTI-PARTICIPANT CONFERENCE - A first computing device distributes audio streams to several computing devices of participants in a communication session. Some embodiments establishes a star network with the first computing device as a central network hub for receiving audio streams from other computing devices, compositing the audio streams and distributing the composited audio streams to the other computing devices. Through the star network, the first computing device receives audio streams from the other computing devices. The first computing device generates at least two different composite audio streams for at least two different computing devices by (i) identifying a set of silent participants in the communication session, and (ii) eliminating redundant audio processing operations that produce the same composite audio streams for different computing devices because of the identified set of silent participants. The first computing device sends each computing device the composited audio stream for the device. | 10-13-2011 |
| 20110252319 | MULTI-NETWORK ARCHITECTURE FOR MEDIA DATA EXCHANGE - Some embodiments use several different types of networks to relay several different types of media content among several different computing devices. The media content of some embodiments is data that a computing device can process in order to provide a presentation of the media content to a user of the device. Examples of types of such media content include audio data, video data, text data, picture data, game data, and/or other media data. In some embodiments, two different networks relay media content of two different types among multiple computing devices. Specifically, in some embodiments, a first network routes among the computing devices one type of media data content (e.g., game data), while a second network routes among the computing devices another type of media data content (e.g., audio and/or video data of game participants). The two networks differ in some embodiments based on their topology. | 10-13-2011 |
| 20110302473 | ERROR CORRECTION CODING - Coded video data may be transmitted between an encoder and a decoder using multiple FEC codes and/or packets for error detection and correction. Only a subset of the FEC packets need be transmitted between the encoder and decoder. The FEC packets of each FEC group may take, as inputs, data packets of a current FEC group and also an untransmitted FEC packet of a preceding FEC group. Due to relationships among the FEC packets, when transmission errors arise and data packets are lost, there remain opportunities for a decoder to recover lost data packets from earlier-received FEC groups when later-received FEC groups are decoded. This opportunity to recover data packets from earlier FEC groups may be useful in video coding and other systems, in which later-received data often cannot be decoded unless earlier-received data is decoded properly. | 12-08-2011 |
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| 20100080142 | Automatic Detection of Channel Bandwidth - A step-wise approach to automatically determining the bandwidth of a communication channel includes dividing the channel's potential bandwidth into a number of ranges. An initial range is then selected and a series of data packets specific to the selected range are transmitted from a first endpoint to a second endpoint, with the second endpoint determining one or more channel metrics based on the transmitted packets (e.g., measured transmission rates). If the metrics indicate the current range accurately reflects the channel's bandwidth, a measured transmission rate of the transmitted data packets is used as the channel's bandwidth. Otherwise, another range is selected and the process is repeated. The described approach rapidly determines channel bandwidth, even when the channel between the two endpoints is asymmetric. Techniques described herein are particularly beneficial when used in conjunction with multimedia conferencing applications. | 04-01-2010 |
| 20100174765 | PERFORMING VARIABLE AND/OR BITWISE SHIFT OPERATION FOR A SHIFT INSTRUCTION THAT DOES NOT PROVIDE A VARIABLE OR BITWISE SHIFT OPTION - Some embodiments present a method of performing a variable shift operation. This method can be used by a microprocessor that does not allow variable shift operation for certain operand sizes. The method simulates a shift instruction that shifts an operand by a shift count. The method identifies a first shift command and a second shift command. The method computes a mask value. The mask value depends on whether the shift count is less than half of the operand size or greater than or equal to half of the operand size. The method uses the mask value to cause one of the first shift command and the second shift command to produce no shift. In some embodiments, the method allows for the shift count to be specified in bytes or in bits. | 07-08-2010 |
| 20100189178 | VIDEO ENCODING IN A VIDEO CONFERENCE - Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved. | 07-29-2010 |
| 20100321469 | Video Processing in a Multi-Participant Video Conference - Some embodiments provide an architecture for establishing multi-participant video conferences. This architecture has a central distributor that receives video images from two or more participants. From the received images, the central distributor generates composite images that the central distributor transmits back to the participants. Each composite image includes a set of sub images, where each sub image belongs to one participant. In some embodiments, the central distributor saves network bandwidth by removing each particular participant's image from the composite image that the central distributor sends to the particular participant. In some embodiments, images received from each participant are arranged in the composite in a non-interleaved manner. For instance, in some embodiments, the composite image includes at most one sub-image for each participant, and no two sub-images are interleaved. | 12-23-2010 |
| 20110074914 | AUDIO PROCESSING IN A MULTI-PARTICIPANT CONFERENCE - Some embodiments provide an architecture for establishing multi-participant audio conferences over a computer network. This architecture has a central distributor that receives audio signals from one or more participants. The central distributor mixes the received signals and transmits them back to participants. In some embodiments, the central distributor eliminates echo by removing each participant's audio signal from the mixed signal that the central distributor sends to the particular participant. | 03-31-2011 |
| 20110116409 | MULTI-PARTICIPANT CONFERENCE SETUP - Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants. | 05-19-2011 |
| 20110181686 | FLOW CONTROL - A method, apparatus, system, and signal-bearing medium that in an embodiment determine at least one capability of a transfer of data, set at least one parameter that affects performance of the transfer to an initial state based on the capability, detect performance of the transfer, and modify the parameter based on the performance. In this way, the data transfer can adapt to changing capabilities of the network and the devices that send and receive the data. | 07-28-2011 |
| 20110205332 | HETEROGENEOUS VIDEO CONFERENCING - Some embodiments provide an architecture for establishing a multi-participant conference. This architecture has one participant's computer in the conference act as a central content distributor for the conference. The central distributor receives data (e.g., video and/or audio streams) from the computer of each other participant, and distributes the received data to the computers of all participants. In some embodiments, the central distributor receives A/V data from the computers of the other participants. From such received data, the central distributor of some embodiments generates composite data (e.g., composite image data and/or composite audio data) that the central distributor distributes back to the participants. The central distributor in some embodiments can implement a heterogeneous audio/video conference. In such a conference, different participants can participate in the conference differently. For instance, different participants might use different audio or video codecs. Moreover, in some embodiments, one participant might participate in only the audio aspect of the conference, while another participant might participate in both audio and video aspects of the conference. | 08-25-2011 |
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| 20090061739 | POLISHING APPARATUS AND METHOD FOR POLISHING SEMICONDUCTOR WAFERS USING LOAD-UNLOAD STATIONS - A polishing apparatus and method for polishing semiconductor wafers uses multiple load-unload stations and at least one turn-over robotic wafer handing device to process the wafers so that the wafer can be polished at multiple polishing tables. The turn-over robotic wafer handing device operates to turn over the wafers so that one side of the wafers can be polished at a first polishing table and the other side of the wafers can then be polished at a second polishing table. | 03-05-2009 |
| 20090278161 | Method of fabricating vertical structure LEDs - A method of fabricating semiconductor devices, such as GaN LEDs, on insulating substrates, such as sapphire. Semiconductor layers are produced on the insulating substrate using normal semiconductor processing techniques. Trenches that define the boundaries of the individual devices are then formed through the semiconductor layers and into the insulating substrate, beneficially by using inductive coupled plasma reactive ion etching. The trenches are then filled with an easily removed layer. A metal support structure is then formed on the semiconductor layers (such as by plating or by deposition) and the insulating substrate is removed. Electrical contacts, a passivation layer, and metallic pads are then added to the individual devices, and the individual devices are then diced out. | 11-12-2009 |
| 20100009599 | APPARATUS AND METHOD FOR POLISHING SEMICONDUCTOR WAFERS USING ONE OR MORE POLISHING SURFACES - An apparatus and method for polishing objects, such as semiconductor wafers, utilizes one or more polishing surfaces, multiple wafer carriers and at least one load-and-unload cup. The load-and-unload cup may be configured to move to and from the wafer carriers in a pivoting manner. The load-and-unload cup may be configured to move to and from the wafer carriers in a linear reciprocating manner. The wafer carriers may be configured to move to and from the load-and-unload cup in a pivoting manner. The wafer carriers may be configured to move to and from the load-and-unload cup in a linear reciprocating manner. | 01-14-2010 |
| 20100308368 | METHOD OF FABRICATING VERTICAL STRUCTURE LEDS - A method of fabricating semiconductor devices, such as GaN LEDs, on insulating substrates, such as sapphire. Semiconductor layers are produced on the insulating substrate using normal semiconductor processing techniques. Trenches that define the boundaries of the individual devices are then formed through the semiconductor layers and into the insulating substrate, beneficially by using inductive coupled plasma reactive ion etching. The trenches are then filled with an easily removed layer. A metal support structure is then formed on the semiconductor layers (such as by plating or by deposition) and the insulating substrate is removed. Electrical contacts, a passivation layer, and metallic pads are then added to the individual devices, and the individual devices are then diced out. | 12-09-2010 |
| 20110104997 | APPARATUSES AND METHODS FOR POLISHING AND CLEANING SEMICONDUCTOR WAFERS - Wafer processing apparatuses and methods for polishing and cleaning semiconductor wafers with high productivity, small footprint, easy maintenance and low defectivity are provided. The apparatuses comprise a polishing apparatus and a cleaning apparatus. The polishing apparatus comprises at least one polishing module. Each module comprises at least one polishing surface, at least one polishing head, at least one wafer transfer station and a transport mechanism to transfer the at least one polishing head between the at least one polishing surface and the at least one wafer transfer station. The polishing module may comprise a shield member and fluid injection devices to protect the at least one polishing surface from foreign particles. The cleaning apparatus can comprise two or more dry chambers for high productivity. The wafer processing apparatuses can comprise two cleaning apparatuses for high productivity. | 05-05-2011 |
| 20110193128 | METHOD OF FABRICATING VERTICAL STRUCTURE LEDS - A method of fabricating semiconductor devices, such as GaN LEDs, on insulating substrates, such as sapphire. Semiconductor layers are produced on the insulating substrate using normal semiconductor processing techniques. Trenches that define the boundaries of the individual devices are then formed through the semiconductor layers and into the insulating substrate, beneficially by using inductive coupled plasma reactive ion etching. The trenches are then filled with an easily removed layer. A metal support structure is then formed on the semiconductor layers (such as by plating or by deposition) and the insulating substrate is removed. Electrical contacts, a passivation layer, and metallic pads are then added to the individual devices, and the individual devices are then diced out. | 08-11-2011 |
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| 20090086666 | METHOD FOR ARQ-ENABLED PRE-TRANSMISSIONS IN MULTICAST AND BROADCAST SERVICES OF RELAY NETWORKS UTILIZING THE IDLE PERIODS - A method and apparatus is disclosed herein for transmitting data in a network (e.g., a relay network). In one embodiment, the method comprises performing pre-transmission of a packet to hops to enable the base station and the plurality of hops to transmit the packet synchronously to one or more mobile stations in the wireless communication system; and performing one or more re-transmissions of the packet at a first set of one or more hops in the system during a delay due to pre-transmissions at a second set of one or more hops in the system. | 04-02-2009 |
| 20090116420 | SYNCHRONIZED MULTI-LINK TRANSMISSION IN AN ARQ-ENABLED MULTI-HOP WIRELESS NETWORK - A method and apparatus is disclosed herein for synchronized multi-link transmission in an ARQ-enabled multi-hop wireless network. In one embodiment, the method comprises performing pre-transmission of a packet to hops to enable a base station and the plurality of hops in the network to transmit the packet synchronously to one or more mobile stations in the wireless communication system; and performing one or more re-transmissions of the packet at a set of one or more hops forming a path in the network if time remaining before a synchronized transmission time for the path as a whole is greater than a threshold. | 05-07-2009 |
| 20090207758 | Fast Active Scanning Wireless Network Apparatus and Method - In a fast active scanning wireless network apparatus and method for quick determination of available access points, information about a candidate set of available access points is obtained, and a candidate access point is identified from the candidate set. A mobile station then queries the candidate access point with a probe request that designates the candidate access point as a sole responder. The probe request prevents other access points from contending for the medium of communication between the mobile station and the designated sole responder access point by excluding the attempt by other access points to transmit probe responses. The apparatus and method thus increases the probability of a fast and successful probe request from the mobile station and subsequent response from the designated access point. The designated access point may also respond with a probe response of high priority, preventing intervention of communication. | 08-20-2009 |
| 20110237243 | SYSTEM AND METHOD FOR INTER-CELL INTERFERENCE AVOIDANCE IN CO-CHANNEL NETWORKS - Systems and methods are provided for a distributed inter-cell interference avoidance (ICIA) technique for avoiding co-channel interference between femtocell networks and macrocell networks. At the macrocell, user equipments sense the downlink (DL) spectrum and detects whether there are any nearby interfering femtocells. If there is any interference, a macrocell base station appropriately re-schedules the DL resources and also uses a mapping function to re-schedule uplink (UL) resources based on the re-scheduled DL resources. At the femtocell, a femtocell base station senses the UL spectrum to detect for interference from nearby macrocell users. If there is interference, femtocell gives priority for use of the resources to the macrocell by releasing UL resources. Femtocell may also use the same mapping function to obtain the DL resources used by the macrocell and to re-schedule DL and UL resources of the femtocell to avoid using the DL and UL resources of the macrocell. | 09-29-2011 |
| 20120003985 | CO-CHANNEL INTERFERENCE REDUCTION IN FEMTOCELL NETWORKS - Co-channel macrocell users will inherently produce co-channel interference at a nearby femtocell base station. To reduce the peak co-channel interference power, the femtocell users adjust their symbol timing with regard to the macrocell users so as to maximize a spreading of the co-channel interference spectrum. In this fashion, the peak co-channel interference power is reduced, thereby leading to improved bit error rates for the femtocell users. | 01-05-2012 |
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| 20080247488 | UPLINK MULTIPLE-INPUT-MULTIPLE-OUTPUT (MIMO) AND COOPERATIVE MIMO TRANSMISSIONS - A method is provided for MIMO uplink communications between a base station and a wireless station with more than two antennae. The method includes: (a) negotiating between the base station and the wireless station uplink MIMO/cooperative MIMO capabilities, using a message exchange protocol in which a message exchanged comprises a field for specifying uplink MIMO/cooperative MIMO capabilities; (b) the base station receiving a request from the wireless station for data transmission; (c) the base station sending the wireless station an allocated resource and an uplink MIMO/cooperative MIMO method for uplink transmission; (e) the wireless station mapping data symbols to the allocated resource with proper pilot pattern; and (f) the base station detecting the data symbols from the channel. | 10-09-2008 |
| 20090221295 | OFDMA-based co-channel femtocell - A femtocell increases efficiency and coverage of a macrocellular network operating in a co-channel manner within the macrocell spectrum by selecting subcarriers for its mobile station using both the subcarrier allocation map received from the macrocell and a spectrum sensing operation. Interference is avoided by selecting only subcarriers not allocated by the macrocell and subcarriers allocated to users not nearby to the femtocell. Interference is eliminated from the received signals using co-channel interference avoidance techniques. Selection of subcarriers for femtocell use may take into consideration inter-carrier interference detected. | 09-03-2009 |
| 20090291690 | Femtocell Channel Assignment and Power Control for Improved Femtocell Coverage and Efficient Cell Search - A method and a communication system including femtocells within a macrocell efficiently manage interference between the different femtocells, and between each femtocell and a macrocell. An efficient frequency assignment scheme for the femtocells minimizes interference between a femtocell and a macrocell and among different femtocells using a spectrum-sensing technique carried out by the femtocells. The frequency assignment scheme selects a suitable channel from a set of candidate channels and ensures that the femtocell has an acceptable coverage area even when it is close to the macrocell base station (BS). The frequency assignment scheme favors a co-channel implementation to take advantage of the hand-off and cell search characteristics of the co-channel implementation. In one embodiment, a joint power control and frequency band assignment technique is used, which partitions the coverage area of the macrocell into an inner region, a power control region, and an outer region. Depending on a femtocell's location, it is assigned a certain power level and a frequency band. Power control may be used within the power-control region while, in the other regions, a fixed transmission power may be used. | 11-26-2009 |
