Patents by Inventor Raghuram Rangarajan
Raghuram Rangarajan has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).
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Publication number: 20150056936Abstract: A set of receiver path circuits is allocated for processing a radio-frequency (RF) signal provided by receive antennas coupled to the receiver path circuits. The RF signal may belong to a first signal class, such as Wi-Fi. A first gain control signal is applied to each of the allocated receiver path circuits to condition a signal level of the RF signal for the first signal class. A second gain control signal is applied to another set of receiver path circuits coupled to the receive antennas to condition the RF signal of a second signal class. First receive gain control signals are generated from the RF signals of the first signal class by the allocated set of the receiver path circuits. The first receive gain control signals are configured to optimize the signal level for processing the first signal class. A second receive gain control signal is generated to optimize the signal level of the RF signal for the second signal class.Type: ApplicationFiled: August 22, 2013Publication date: February 26, 2015Applicant: Cisco Technology, Inc.Inventors: Raghuram Rangarajan, David Kloper, Paul J. Stager
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Publication number: 20150009947Abstract: In an example embodiment, a channel that includes a plurality of sub-channels is sampled to detect pulses indicative of a presence of a radar signal. A frequency for the radar signal is determined. If the frequency of the radar signal maps to a selected subset of the plurality of sub-channels, the selected subset of the plurality of sub-channels are determined to be unavailable due to radar, while the remaining sub-channels remain available for use. The selected subset of the plurality of sub-channels determined to be unavailable due to radar may be selectively returned for use after the radar signal is no longer detected for a predetermined selected time period.Type: ApplicationFiled: July 2, 2013Publication date: January 8, 2015Inventors: Raghuram Rangarajan, Paul Stager, David S. Kloper
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Patent number: 8797881Abstract: In accordance with an example embodiment, there is disclosed herein a coexistence mechanism for multiple channels. A plurality of channels are monitored to determine which channels are available for communications. Upon receiving a request to establish communications on a channel set within the plurality of channels, a response is sent to the request on at least one in the channel set. The response comprises data representative of which channels from the channel set are available for communications. Optionally, the response may include data indicating how long the unavailable channels will be occupied.Type: GrantFiled: June 13, 2011Date of Patent: August 5, 2014Assignee: Cisco Technology, Inc.Inventors: Brian Donald Hart, Raghuram Rangarajan, Ahmadreza Hedayat
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Patent number: 8781040Abstract: A mid-packet detection technique is provided that detects a packet with periodic repetitions of a fixed duration at a point in time of the packet other than a start-of-packet pattern, e.g., a preamble, associated with the packet. The process performs packet detection without detecting a preamble and does not require carrier frequency recovery, timing recovery (synchronization) or channel estimation. In one embodiment, a doubly differential matched filter autocorrelation of the received signal is computed and used as a metric for packet detection when the preamble is not observed or to complement preamble detection. The metric is compared to a threshold to indicate detection of a packet.Type: GrantFiled: March 1, 2013Date of Patent: July 15, 2014Assignee: Cisco Technology, Inc.Inventors: Raghuram Rangarajan, Brian Donald Hart, Paul J. Stager
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Patent number: 8776221Abstract: Techniques are provided for receiving a transmitted first packet that was formatted using a known scrambling algorithm with an unknown scrambling seed. An encoded packet payload is extracted from the first packet header. The encoded packet payload header is decoded to obtain a first scrambled packet payload header. For each potential value of the unknown seed, the first scrambled packet payload header is descrambled to produce a first set of descrambled packet payload headers and for each potential value of initial register values associated with a cyclic redundancy check, the cyclic redundancy check is executed comprising polynomial division on each of the descrambled packet payload headers such that when the polynomial division results in a zero remainder, a potential unscrambled payload header for the first packet is obtained. Information about the first packet is obtained from the potential unscrambled payload header.Type: GrantFiled: January 3, 2012Date of Patent: July 8, 2014Assignee: Cisco Technology, Inc.Inventors: Raghuram Rangarajan, David Kloper, Yohannes Tesfai
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Publication number: 20140098681Abstract: In a wireless local are network, each of multiple access points, in a high density deployment, are configured to suppress co-channel interference. A first access point having a plurality of antennas beamforms a transmission to a wireless client device within a null-space or with the weakest singular eigenmodes of a wireless channel between the first access point and at least one co-channel second access point. Techniques are presented herein for situations in which any given access point has two or more co-channel access points. In addition, an access point may perform receive side suppression with respect to a transmission (made by a co-channel access point to one of its associated wireless client devices) that is received from that co-channel access point.Type: ApplicationFiled: October 5, 2012Publication date: April 10, 2014Applicant: CISCO TECHNOLOGY, INC.Inventors: Paul J. Stager, Matthew A. Silverman, Zhigang Gao, John Blosco, Raghuram Rangarajan
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Patent number: 8411807Abstract: A mid-packet detection technique is provided that detects a packet with periodic repetitions of a fixed duration at a point in time of the packet other than a start-of-packet pattern, e.g., a preamble, associated with the packet. The process performs packet detection without detecting a preamble and does not require carrier frequency recovery, timing recovery (synchronization) or channel estimation. In one embodiment, a doubly differential matched filter autocorrelation of the received signal is computed and used as a metric for packet detection when the preamble is not observed or to complement preamble detection. The metric is compared to a threshold to indicate detection of a packet.Type: GrantFiled: September 2, 2008Date of Patent: April 2, 2013Assignee: Cisco Technology, Inc.Inventors: Raghuram Rangarajan, Brian Donald Hart, Paul J. Stager
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Publication number: 20120314583Abstract: In accordance with an example embodiment, there is disclosed herein a coexistence mechanism for multiple channels. A plurality of channels are monitored to determine which channels are available for communications. Upon receiving a request to establish communications on a channel set within the plurality of channels, a response is sent to the request on at least one in the channel set. The response comprises data representative of which channels from the channel set are available for communications. Optionally, the response may include data indicating how long the unavailable channels will be occupied.Type: ApplicationFiled: June 13, 2011Publication date: December 13, 2012Inventors: Brian Donald HART, Raghuram Rangarajan, Ahmadreza Hedayat
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Publication number: 20120291127Abstract: Techniques are provided for receiving a transmitted first packet that was formatted using a known scrambling algorithm with an unknown scrambling seed. An encoded packet payload is extracted from the first packet header. The encoded packet payload header is decoded to obtain a first scrambled packet payload header. For each potential value of the unknown seed, the first scrambled packet payload header is descrambled to produce a first set of descrambled packet payload headers and for each potential value of initial register values associated with a cyclic redundancy check, the cyclic redundancy check is executed comprising polynomial division on each of the descrambled packet payload headers such that when the polynomial division results in a zero remainder, a potential unscrambled payload header for the first packet is obtained. Information about the first packet is obtained from the potential unscrambled payload header.Type: ApplicationFiled: January 3, 2012Publication date: November 15, 2012Applicant: Cisco Technology, Inc.Inventors: Raghuram Rangarajan, David Kloper, Yohannes Tesfai
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Publication number: 20120275423Abstract: Disclosed, in example embodiment herein, is an apparatus comprising an interface and channel selection logic coupled to the interface. The channel selection logic is operable to receive data representative of neighboring wireless devices to a wireless device occupying a channel for a plurality of channels via the interface. The channel selection logic is responsive to receiving the data representative of neighboring wireless devices occupying the plurality of channels to generate a graph for each of the plurality of channels, wherein vertices of the graph represent the wireless device and neighboring wireless devices occupying the channel and edges of the graph represent wireless devices with overlapping coverage areas. The channel selection logic selects the channel for the wireless device whose graph has the smallest radius.Type: ApplicationFiled: July 12, 2012Publication date: November 1, 2012Inventors: Brian HART, Raghuram RANGARAJAN
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Patent number: 8243671Abstract: Disclosed, in example embodiment herein, is an apparatus comprising an interface and channel selection logic coupled to the interface. The channel selection logic is operable to receive data representative of neighboring wireless devices to a wireless device occupying a channel for a plurality of channels via the interface. The channel selection logic is responsive to receiving the data representative of neighboring wireless devices occupying the plurality of channels to generate a graph for each of the plurality of channels, wherein vertices of the graph represent the wireless device and neighboring wireless devices occupying the channel and edges of the graph represent wireless devices with overlapping coverage areas. The channel selection logic selects the channel for the wireless device whose graph has the smallest radius.Type: GrantFiled: September 10, 2009Date of Patent: August 14, 2012Assignee: Cisco Technology, Inc.Inventors: Brian Hart, Raghuram Rangarajan
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Publication number: 20110058524Abstract: Disclosed, in example embodiment herein, is an apparatus comprising an interface and channel selection logic coupled to the interface. The channel selection logic is operable to receive data representative of neighboring wireless devices to a wireless device occupying a channel for a plurality of channels via the interface. The channel selection logic is responsive to receiving the data representative of neighboring wireless devices occupying the plurality of channels to generate a graph for each of the plurality of channels, wherein vertices of the graph represent the wireless device and neighboring wireless devices occupying the channel and edges of the graph represent wireless devices with overlapping coverage areas.Type: ApplicationFiled: September 10, 2009Publication date: March 10, 2011Inventors: Brian Hart, Raghuram Rangarajan
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Patent number: 7764218Abstract: Described in an example embodiment herein is a procedure that comprises sampling one or more channels that are not in use for a short time at certain intervals. In particular embodiments, the interval duration is irregular so as to prevent “out of step” lock with a radar's pulses. During the sampling period, detection events are stored in terms of start time and duration. If potential radar events are detected, the channels are sampled for a longer, second interval to determine whether the detection events are indicative of radar. The length of the sampling period determines the number of samples needed to get an acceptable detection probability.Type: GrantFiled: July 23, 2008Date of Patent: July 27, 2010Assignee: Cisco Technology, Inc.Inventors: Johannes Kruys, Hari Narayanan Rangarajan, Raghuram Rangarajan, Christopher Meil
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Publication number: 20100019947Abstract: Described in an example embodiment herein is a procedure that comprises sampling one or more channels that are not in use for a short time at certain intervals. In particular embodiments, the interval duration is irregular so as to prevent “out of step” lock with a radar's pulses. During the sampling period, detection events are stored in terms of start time and duration. If potential radar events are detected, the channels are sampled for a longer, second interval to determine whether the detection events are indicative of radar. The length of the sampling period determines the number of samples needed to get an acceptable detection probability.Type: ApplicationFiled: July 23, 2008Publication date: January 28, 2010Inventors: Johannes Kruys, Hari Narayanan Rangarajan, Raghuram Rangarajan, Christopher Meil