Chung Ang University Industry Academic Cooperation

Electronics and Telecommunications Research Institute

Samsung Electronics Co., Ltd.

Korea Electronics Technology Institute

Joong Ang University

Yong-Soo Cho

Sang-Boh Yun

Joo-Hyun Lee

Jae-Kwon Kim

Tae-Ho Im

Jae-Young Ahn

Kyung-Hi Chang

Kwang-Soon Kim

Kyung-Won Park

Jin-Woong Cho

Jong-Ho Paik

Jong-Ho Lee

Sung-Soo Hwang

Young-Hoon Kwon

Tae-Gon Kim

Yun-Hee Kim

Hyo-Jin Lee

Jin-Ghoo Choi

Soong-Yoon Choi

Hyun-Il Yoo

Suk-Seung Hwang

Yong-Bae Dhong

Hyung-gi Kim

Jung-Ryun Lee

Dong-Han Kim

Kyu-Jin Lee

Young-Hwan You

Hyun-Soo Ko

Kyung-Soo Woo

Kyu-In Lee

Suk-Won Ha

Yeong-Jun Kim

Yun-Jae Shin

Won-Young Yang

Hyoung-Kyu Song

Un-Ha Kim

A method and a system for synchronizing time information in an ad-hoc network are disclosed. According to the present invention, provided is a method for synchronizing time information in an ad-hoc network as a method by which a plurality of nodes included in an ad-hoc network synchronize a time, the method comprising the steps of: transmitting, by a first node, time information obtained by correcting an initial time using a first self-correcting value at an nth beacon interval, wherein the first self-correcting value is a self-correcting value or a local averaging value at an (n&#x2212;1)th beacon interval; and correcting, by a second node which has received the time information from the first node at the nth beacon interval, time information by calculating a second self-correcting value and a local average value, wherein the first self-correcting value is either the self-correcting value or the local averaging value calculated at the (n&#x2212;1)th beacon interval, and the local averaging value of the second node is an averaging value of time information of one or more neighboring nodes of the second node.

Method and system for synchronizing time information in ad hoc network

Disclosed are an apparatus and a method for detecting signals in a spatial multiplexing system. An embodiment of the invention provides a signal detection apparatus for a single receiver unit equipped with a plurality of antennas in a system having at least one transmitter unit configured to transmit data streams by spatial multiplexing, where the signal detection apparatus includes: a partial linear coefficient generator unit configured to generate a linear weighting matrix by using a preset algorithm on a channel matrix formed between the transmitter unit and the single receiver unit; a partial symbol remover unit configured to generate a first symbol vector by removing all transmittable symbols for each transmitting antenna from all received data streams; and a partial symbol detector unit configured to generate a transmission symbol candidate vector by using the linear weighting matrix and the first symbol vector.

Apparatus and method for detecting signal in spatial multiplexing system

Provided is a handover method of a wireless communication system using a hierarchical cellular scheme. In the method, signal quality of a serving node is measured, so that whether to start scanning for a handover is determined. When the scanning for the handover starts, signal qualities of a serving cell including the serving node and one or more neighbor cells are measured through a first preamble including a first identifier for distinguishing a cell. An intra-cell handover or an inter-cell handover is selected using the signal qualities of the serving cell and the neighbor cells. Therefore, a terminal can easily distinguish between the inter-cell handover and the intra-cell handover, and an overhead during a handover can be reduced because an intra-cell handover procedure is simplified.

Preamble design method for reducing overhead during handover in hierarchical cellular system

An apparatus and method for receiving signals in a multiple-input, multiple-output (MIMO) wireless communication system is provided. A receiving end using as many as N Receive (Rx) antennas includes a first detector, as many as (N&#x2212;2) ndetectors, and an Ndetector. A signal detection technique of the present invention has a low complexity and a throughput similar to that of a Maximum Likelihood (ML) scheme in a Multiple-Input Multiple-Output (MIMO) wireless communication system using a Spatial Multiplexing (SM) scheme.

Apparatus and method for receiving signals in multiple-input multiple-output wireless communication system

A method for selecting beams, a switched beam operation method during an initial synchronization process, and an initial synchronization method using it are provided for selecting beams to minimize the probability of occurrence of interferences between cells by considering a distance between beams within neighboring sectors during an initial synchronization process using switched beams, in an orthogonal frequency division multiplexing (OFDM) cellular system employing a smart antenna. The inventive method comprises the steps of dividing each cell into sectors, and counting the number of fixed beams per cell, and selecting a switched beam for minimizing probability of interference, from fixed beams presenting in a corresponding sector, based on distances between a selected beam and beams of all of adjacent cells and the number of cases to be selected in a subsequent time slot, according to the counted number of the fixed beams existing in each sector.

Method for selecting beams during initial synchronization process using switched beam, switched beam operation method and initial synchronization using the same

A method and an apparatus for detecting a signal in a multi-antenna system using a spatial multiplexing are provided. The apparatus includes at least one antenna for receiving a signal, a channel estimator for estimating a channel using the received signal, a detector for calculating multiplication values commonly used to determine a Euclidean distance using the receive signal and channel information and for detecting a transmitted signal by calculating Euclidean distances of one or more candidate symbols using the receive signal and the determined multiplication values and a decoder for demodulating and decoding the detected signal. Hence, the computational complexity of the signal detection can be mitigated.

Apparatus and method for detecting signal in multi-antenna system

The present invention relates to an apparatus and method for estimating a channel in a wireless communication system. The apparatus according to the present invention includes an estimator for initially estimating a channel response value by using a predetermined signal among reception signals, a detector for detecting transmission signals by using the channel response value and an operator for updating the channel response value by using detected transmission signals, a detection accuracy and reception signals.

Apparatus and method for estimating channel in multi antenna wireless communication system

Receiving apparatus and method in a Multiple-Input Multiple-Output (MIMO) wireless communication system are provided. The receiver having N-ary receive antennas includes a decomposer for decomposing a channel matrix to a matrix Q and a matrix R through a QR decomposition; a detector for determining a candidate group of an n-th phase by estimating a plurality of transmit signal vectors by substituting a plurality of transmittable symbols into symbol combinations of a candidate group of a (n&#x2212;1)-th phase as an n-th symbol and detecting (n+1)-th through N-th symbols using characteristics of the matrix R; a calculator for calculating square Euclidean distance values between the transmit signal vectors and a receive signal vector; and a determiner for determining the candidate group of the n-th phase by selecting transmit signal vectors having the smallest square Euclidean distance value among the transmit signal vectors.

Apparatus and method for detecting signal in multiple-input multiple-output (MIMO) wireless communication system

Provided are a virtual multi-antenna method for an orthogonal frequency division multiplexing (OFDM) system and an OFDM-based cellular system. The virtual multi-antenna method includes grouping sub-carriers in a frequency domain of an OFDM symbol and generating at least one group including G sub-carriers; and regarding the G sub-carriers included in the at least one group as multiple channels used in a multi-antenna technique and virtually applying the multi-antenna technique to the transmission and reception of the OFDM symbol. The virtual multi-antenna method can effectively reduce an interference signal and obtain the effects of a spatial division multiple access (SDMA) technique without physically using multiple antennas.

Virtual multi-antenna method for OFDM system and OFDM-based cellular system

An apparatus for estimating an antenna weight vector in an Orthogonal Frequency Division Multiple Access System (OFDMA) having a smart antenna. The apparatus includes receiving and storing training symbols in the time domain transmitted to estimate an antenna weight vector during a training symbol transmission interval; estimating carrier frequency offsets using training symbols in the frequency domain that are obtained by performing a Fast Fourier Transformation (FFT) algorithm with respect to the training symbols received during the training symbol transmission interval; compensating the stored training symbols in the time domain based on the estimated carrier frequency offsets; and estimating an antenna weight vector using training symbols in the frequency domain that are obtained by applying an FFT algorithm with respect to the training symbols in the time domain derived by compensating the carrier frequency offsets during the training symbol transmission interval.

Method and apparatus for uplink carrier frequency synchronization and antenna weight vector estimation in OFDMA system having smart antenna

Method for providing frequency-hopping OFDMA using symbols of comb patter, the method including the steps of: a) assigning frequency domain signal X(k) of comb pattern (comb symbol, k is frequency index) to modulated data sequence, the comb symbol comprising predetermined number of sub carriers (sub carrier group) which are placed with predetermined interval in the whole available frequency band; b) getting the comb symbol hopped for the comb symbol to have independent frequency offset; and c) inverse fast fourier transforming the comb symbol to time domain signal x(n) (n is time index) and transmitting the signal.

Frequency hopping ofdma method using symbols of comb pattern

In an OFDMA-based cellular system, a frame of a downlink signal includes a common slot and traffic slots. The common slot includes a synchronization preamble and a cell search preamble. The synchronization preamble has a structure for synchronizing time and frequency, and the cell search preamble has a cell search structure. The traffic slot includes pilot symbols provided on the time and frequency axes. A cyclic prefix is used to estimate initial symbol synchronization, and the initial symbol synchronization and the synchronization preamble are used to synchronize the frame. The synchronization frame and the cell search preamble are used to estimate time and frequency synchronization. The cell search preamble is used to search cells. When the initial synchronization is performed, the cyclic prefix is used to track the frequency, the synchronization preamble is used to track symbol synchronization, and the cell search preamble is used to track fine frequency synchronization.

Method and apparatus for embodying and synchronizing downlink signal in mobile communication system and method for searching cell using the same

Disclosed is a transmitting and receiving method for reducing a time-varying channel distortion in an orthogonal frequency division multiplex (OFDM) system. In the present invention, the transmitter defines M sub-channels in one data group, mathematically analyzes a change of channel for each path causing a time-varying channel distortion in a high-speed mobile environment by approximation, calculates a weight value based on the mathematical analysis and assigns the calculated weight value to transmit data of each sub-channel. Subsequently, the receiver combines the signals of these M sub-channels and demodulates the combined signals. Accordingly, the present invention greatly reduces a distortion caused by the time-varying channel to improve a bit error rate and a channel estimation performance.

Transmitting and receiving method for reducing distortion caused by a time-varying channel in an orthogonal frequency division multiplex system

Disclosed is a zipper type Very high bit-rate Digital Subscriber Line (VDSL) system which comprises a transmitter including an inverse fast Fourier transformer for performing an inverse fast Fourier transform on input data, and a cyclic extension adder for adding a cyclic extension for each symbol to the data output from the inverse fast Fourier transformer and outputting the data to a transmission channel; and a receiver including a cyclic extension remover for removing the cyclic extension from the data received through the transmission channel, and a fast Fourier transformer for performing a fast Fourier transform on the data output from the cyclic extension remover. The cyclic extension adder copies a first predetermined number of data starting from the leading part of the input symbol data received from the inverse fast Fourier transformer into a first cyclic suffix for removing interference between symbols and maintaining orthogonality between sub-carriers; adds the first cyclic suffix to the end of the symbol data; copies a second predetermined number of data subsequent to the first predetermined number of data into a second cyclic suffix for maintaining orthogonality between upstream and downstream; and adds the second cyclic suffix to the end of the first cyclic suffix.

Zipper type VDSL system

Disclosed is a method of estimating carrier frequency offset in an OFDM system. The method includes the steps of forming one OFDM symbol which has M repeated identical signal block, being a base sub-block; forming a 2 number of identical ith sub-blocks using an M/2 number of the M number of base sub-blocks as a unit; and estimating an ith carrier frequency offset &egr; using a correlation between two adjacent ith sub-blocks in the 8 number of the ith sub-blocks.

Growing community of inventors

Seoul, South Korea

Yong-Soo Cho