Abstract: A security control method in a cable network dynamic multicast session, and more particularly, a method of controlling forward secrecy and backward secrecy in a Data Over Cable Service Interface Specifications (DOCSIS) 3.0 network dynamic multicast session is provided. A security control method in a cable network dynamic multicast session, includes: maintaining a multicast group that is allocated with a first Downstream Service Identifier (DSID) and a first Security Association Identifier (SAID) and that is joined by a first cable modem and a second cable modem; receiving a LeaveMulticastSession message from the second cable modem; exchanging, corresponding to the LeaveMulticastSession message, a Dynamic Bonding Change (DBC) message for changing a multicast parameter with the second cable modem; and updating a first Traffic Encryption Key (TEK) corresponding to the first DSID with a second TEK.

Abstract: Provided are a multi-channel tuning receiver, including: a broadband radio frequency (RF) tuner to receive a broadband signal, divide the broadband signal into a plurality of signals, tune the divided signals, combine the tuned signals into a single signal, and output the combined single signal; an analog-to-digital (A/D) converter to convert the combined single signal to digital signal; a channelizer to extract only a bonded channel from the digital signal; and a plurality of demodulators to demodulate the bonded channel, and a multi-channel tuning method thereof.

Abstract: Provided is a method for constructing a key graph for multi-group multi-casting service and managing a key. The method includes: searching for a user group set (common group set) having the same access right to each resource combination comprising multiple resource selected from resources for a service and non-overlapping with other resource combinations by using an access right relations between user groups and the resource; and constructing a key graph by interconnecting a user group key and a resource key using the access right relation, where user groups pertaining to the searched common group set are connected to corresponding resources via intermediate nodes.

Abstract: Provided is a channel bonding receiving apparatus and method for expanding a channel bonding receiving band in a cable modem. The channel bonding receiving apparatus includes a channel bonding dividing unit for dividing a channel bonding broadband signal into a plurality of band signals and extracting a corresponding channel bonding signal from each of the divided band signals; and a channel routing unit for routing each of the extracted channel bonding signals to a corresponding demodulator.

Abstract: Provided is an apparatus for estimating phase offsets of multiple survival paths and a satellite communication system using the same. The apparatus includes: upper/lower decoding units for obtaining a phase offset estimation value and estimating phase offsets of each survival path based on a stored parameter estimation value of a previous state inputted from an external device; an interleaving/de-interleaving unit for minimizing correlation between data used to estimate a parameter according to the estimated phase offset value from the upper/lower decoding means; and a phase offset outputting unit for outputting the phase offset value estimated through the upper decoding unit and the de-interleaving unit.

Abstract: Provided are an apparatus for estimating a phase error and a phase error correcting system using the phase error estimating apparatus. The apparatus includes: a probability value estimating unit for estimating a negative log probability value for each transmission symbol by transforming a soft output information transferred from the outside to a log A posterior probability ratio (LAPPR) value; an APP value calculating unit for calculating a posterior probability (APP) value by applying a negative exponential function to the transmission symbol; an average value deciding unit for deciding an average value for each transmission symbol using the probability information entirely, partially, or selectively according to a probability information type; and a symbol phase estimating unit for estimating a phase of a symbol based on the decided average value.

Abstract: Provided are a method of configuring a hierarchical network of user groups and resource groups, and a key distribution center. The method includes the steps of: analyzing hierarchical connection relationships between respective user groups and respective resource groups, comparing redundancy rates of the respective hierarchical connection relationships, and determining a connection mode having a larger redundancy rate; separating the respective user groups and resource groups and hierarchically connecting the user groups with the resource groups, according to the determined connection mode; comparing hierarchical connections between the respective separated user groups and resource groups, and removing an overlapping hierarchical connection; and recombining the separate hierarchical connections except for the overlapping hierarchical connection, and configuring an entire network.

Abstract: An apparatus and a method for controlling a gain of I-channel signal and compensating Q-channel signal in response to the gain imbalance based on the gain-controlled I-channel signal as a reference channel signal is disclosed. The apparatus includes: an auto gain controller for controlling a gain of a signal selected from the I-channel signal and the Q-channel signal to have a predetermined amplitude, thereby generating a gain-controlled signal; a detector for detecting a gain imbalance between the gain-controlled signal and the remaining channel signal; and a compensator for compensating the gain imbalance of the remaining channel signal based on the detected gain imbalance.

Abstract: The present invention provides an apparatus for compensating a phase difference of a receiver, the apparatus including: an accumulating unit for accumulating a radio frequency (RF) input signal and generating an accumulated RF signal in order to minimize an effect of a background noise of the RF input signal; a early-local oscillating unit for generating a phase-early local oscillated signal based on a local oscillated signal of the receiver; a late-local oscillating unit for generating a phase-late local oscillated signal based on a local oscillated signal of the receiver; a phase early-late compensating unit for compensating a phase early-late based on the accumulated RF input signal and the phase-early and phase-late local oscillated signals; a look-up table data mapping unit for controlling a phase of the local oscillated signal with respect to a phase difference; and a feedback transmitting unit for transmitting a phase compensating data to the local oscillator.

Abstract: An apparatus and method for compensating an imbalance of phase and gain between I-channel and Q-channel by using variable loop gains is disclosed. The apparatus includes: a phase error generator for generating a phase error signal by using the I-channel signal and the Q-channel signal; an average value calculator for calculating an average value of the phase error signal; a comparator for comparing the average value with a predetermined threshold; a selector for selecting a loop gain value among a set of loop gains based on the comparison result; a phase imbalance generator for generating a phase imbalance by using the selected loop gain value; and a compensator for compensating the Q-channel signal based on the phase imbalance.

Abstract: Provided is a method for estimating carrier wave or doppler frequency offset based on an approximated quadratic non-linear function in fine search, and a receiver employing the method. The method for estimating frequency offset includes the steps of: a) extracting more than three discrete samples in an order where the discrete samples are close to a maximum value of a power spectrum density function; b) inducing a quadratic non-linear function by using the extracted discrete samples; and c) estimating the frequency offset from a maximum point of the quadratic non-linear function. The technology of the present research makes it possible to exactly estimate frequency offset without increasing hardware complexity in estimation of carrier wave or doppler frequency offset.

Abstract: Disclosed is a quadrature demodulator for high-speed wireless communication, which comprises: an A/D converter for converting received signals into digital signals; a signal recovery unit for recovering carriers and symbol timing from the signals converted by the A/D converter; a decision unit for detecting recovered signals output by the signal recovery unit, and performing a decision process on them; an I/Q gain imbalance detector for detecting gain imbalances of the I and Q-phase components from the recovered signals, and outputting an I/Q gain compensation value for compensating for the gain imbalances; and an I/Q gain compensator, provided between the A/D converter and the signal recovery unit, for reflecting the I/Q gain compensation value output by the I/Q gain imbalance detector to the received signals.

Abstract: Provided are an apparatus for estimating frequency offset from received signal and method for the same. The apparatus and method estimates frequency offset precisely without increment of autocorrelator by performing moving average filtering on a noised signal to thereby alleviate jitter. The frequency offset estimating apparatus includes: moving average filter for alleviating jitter of received signal; multiplier for multiplying a filtered signal by conjugate complex operanded pilot signal; phase-rotation value calculator for calculating a phase-rotation value from multiplicand operanded signal by using of symbol delay and an autocorrelation function; frequency offset estimator for estimating frequency offset from the phase-rotation value based on a smoothing function multiplication.

Abstract: Disclosed is a method for detecting and correcting amplitude and phase imbalances between in-phase (I) and quadrature-phase (Q) components in a high-speed wireless communication quadrature demodulator, which comprises: a) comparing an input signal with a signal determined by a quadrant to which the input signal belongs, and detecting imbalances between I and Q components with respect to the input signal; and b) using the imbalances detected in a) to correct the input signal. The present invention prevents distorting of the demodulator's performance caused by the imbalances to between I and Q components and increases application to high-speed wireless communication.

Abstract: The present invention provides an apparatus for compensating a phase difference of a receiver, the apparatus including: an accumulating unit for accumulating a radio frequency (RF) input signal and generating an accumulated RF signal in order to minimize an effect of a background noise of the RF input signal; a early-local oscillating unit for generating a phase-early local oscillated signal based on a local oscillated signal of the receiver; a late-local oscillating unit for generating a phase-late local oscillated signal based on a local oscillated signal of the receiver; a phase early-late compensating unit for compensating a phase early-late based on the accumulated RF input signal and the phase-early and phase-late local oscillated signals; a look-up table data mapping unit for controlling a phase of the local oscillated signal with respect to a phase difference; and a feedback transmitting unit for transmitting a phase compensating data to the local oscillator.

Abstract: An apparatus and a method for controlling a gain of I-channel signal and compensating Q-channel signal in response to the gain imbalance based on the gain-controlled I-channel signal as a reference channel signal is disclosed. The apparatus includes: an auto gain controller for controlling a gain of a signal selected from the I-channel signal and the Q-channel signal to have a predetermined amplitude, thereby generating a gain-controlled signal; a detector for detecting a gain imbalance between the gain-controlled signal and the remaining channel signal; and a compensator for compensating the gain imbalance of the remaining channel signal based on the detected gain imbalance.

Abstract: An apparatus and method for compensating an imbalance of phase and gain between I-channel and Q-channel by using variable loop gains is disclosed. The apparatus includes: a phase error generator for generating a phase error signal by using the I-channel signal and the Q-channel signal; an average value calculator for calculating an average value of the phase error signal; a comparator for comparing the average value with a predetermined threshold; a selector for selecting a loop gain value among a set of loop gains based on the comparison result; a phase imbalance generator for generating a phase imbalance by using the selected loop gain value; and a compensator for compensating the Q-channel signal based on the phase imbalance.

Abstract: Disclosed is a quadrature demodulator for high-speed wireless communication, which comprises: an A/D converter for converting received signals into digital signals; a signal recovery unit for recovering carriers and symbol timing from the signals converted by the A/D converter; a decision unit for detecting recovered signals output by the signal recovery unit, and performing a decision process on them; an I/Q gain imbalance detector for detecting gain imbalances of the I and Q-phase components from the recovered signals, and outputting an I/Q gain compensation value for compensating for the gain imbalances; and an I/Q gain compensator, provided between the A/D converter and the signal recovery unit, for reflecting the I/Q gain compensation value output by the I/Q gain imbalance detector to the received signals.

Abstract: An apparatus for recovering a decision-directed carrier according the present invention comprises a) a first conjugate complex sample generating part for generating a first conjugate complex sample in accordance with an received complex sample; b) a frequency recovering part for receiving the first conjugate complex sample and for recovering a carrier frequency of the first conjugate complex sample by compensating a carrier frequency offset of the input signal; c) a phase recovering part for receiving the first conjugate complex sample and for recovering a carrier phase of the input signal by compensating a carrier phase offset of the input signal; and d) a symbol decison part for selecting a symbol in accordance with the output value from said means c) and for outputting the selected symbol to said means a).

Abstract: Disclosed is a method for detecting and correcting amplitude and phase imbalances between in-phase (I) and quadrature-phase (Q) components in a high-speed wireless communication quadrature demodulator, which comprises: s a) comparing an input signal with a signal determined by a quadrant to which the input signal belongs, and detecting imbalances between I and Q components with respect to the input signal; and b) using the imbalances detected in a) to correct the input signal. The present invention prevents distorting of the demodulator's performance caused by the imbalances to between I and Q components and increases application to high-speed wireless communication.