Abstract: Provided is a hybrid beaconing method in which a centralized beaconing scheme and a distributed beaconing scheme are combined.

Abstract: A data transmitter and receiver for improving a data rate, and more particularly, to an apparatus and method of transmitting and receiving an orthogonal frequency division multiplexing (OFDM) symbol in which a pilot signal is added to a data signal is provided.

Abstract: Provided is a large range management device (LRMD) of managing a communication between a plurality of small range devices (SRDs) and a plurality of large range devices (LRDs), the SRDs and the LRDs being located in a single cell and having different transmission coverage, the LRMD including an access slot allocation unit to allocate an SRD access slot to a radio resource for a downlink, to enable a first SRD to request an association from a network, a selection unit to select a communication relay device for relaying relay data of the first SRD, a relay slot allocation unit to allocate at least one SRD relay slot to a radio resource for an uplink, to enable the communication relay device to relay the relay data to a second SRD or another LRD, and a receiving unit to receive the relay data based on the at least one SRD relay slot

Abstract: Provided are a transmitter and a receiver. The transmitter combines N data signals received from an encoded bit stream to generate N symbols; maps the N symbols to subcarriers that are spaced more than a coherent bandwidth apart; and receives and moves the N symbols, which are mapped to the subcarriers that are spaced more than a coherent bandwidth apart, to their own positions. The receiver demodulates N pieces of data using the N symbols received from the transmitter in a manner similar to that used by the transmitter.

Abstract: Provided is a method of generating a pilot pattern capable of perform adaptive channel estimation, and a method and apparatus of a base station and a method and apparatus of a terminal using the pilot pattern. The pilot pattern selects pilot symbol positions based on distances from pilots of previous orthogonal frequency division multiple access (OFDMA) symbols to a subcarrier position of a current OFDMA symbol in the frequency domain and the time domain, so that a low pilot density is maintained so as to effectively transmit data, and stable channel estimation performance can be obtained even in a bad channel environment. In addition, the minimum burst allocation size is determined according to the channel environment between the base station and the terminal, guaranteeing channel estimation performance suitable for the channel environment, and improving granularity, channel estimation latency, and channel estimation memory size.

Abstract: Provided is a method of generating a pilot pattern capable of perform adaptive channel estimation, and a method and apparatus of a base station and a method and apparatus of a terminal using the pilot pattern. The pilot pattern selects pilot symbol positions based on distances from pilots of previous orthogonal frequency division multiple access (OFDMA) symbols to a subcarrier position of a current OFDMA symbol in the frequency domain and the time domain, so that a low pilot density is maintained so as to effectively transmit data, and stable channel estimation performance can be obtained even in a bad channel environment. In addition, the minimum burst allocation size is determined according to the channel environment between the base station and the terminal, guaranteeing channel estimation performance suitable for the channel environment, and improving granularity, channel estimation latency, and channel estimation memory size.

Abstract: Provided is a contention-based data communication apparatus and method that may notify that a radio resource is to be used using a search signal prior to transmitting a communication frame, and may transmit data based on a priority when a search signal received from another communication apparatus is detected.

Abstract: Provided is a method of generating a pilot pattern capable of perform adaptive channel estimation, and a method and apparatus of a base station and a method and apparatus of a terminal using the pilot pattern. The pilot pattern selects pilot symbol positions based on distances from pilots of previous orthogonal frequency division multiple access (OFDMA) symbols to a subcarrier position of a current OFDMA symbol in the frequency domain and the time domain, so that a low pilot density is maintained so as to effectively transmit data, and stable channel estimation performance can be obtained even in a bad channel environment. In addition, the minimum burst allocation size is determined according to the channel environment between the base station and the terminal, guaranteeing channel estimation performance suitable for the channel environment, and improving granularity, channel estimation latency, and channel estimation memory size.

Abstract: A CR apparatus for performing communication in a CR network includes: a communication unit configured to measure a channel estimation signal, transmit measured channel state information to a master device, and, when a QP of a reference channel arrives, make a communication channel transition to a candidate channel and perform communication; and a channel information management unit configured to receive and manage the channel state information measured by the communication unit and channel information comprising a candidate channel, into which a channel transition is to be made during a QP of the reference channel, received from the master device and control channel transition of the communication unit based on the channel information.

Abstract: In a cognitive radio system, when communication in an operational channel is determined to be discontinued due to that an incumbent user (IU) entering the operational channel that is currently being used or due to that an excessive interference occurring in the operational channel, the operational channel is switched to a pre-arranged channel. However, since some parameters are different between the operational channel and the pre-arranged channel, an initialization procedure has to be performed to allow the cognitive radio system to be adapted to those some parameters. Since an initialization technique aiming for this situation is not developed yet, a conventional cognitive radio system uses a general initialization technique used to initially operate a system. However, the general initialization technique has to allow the system to be adapted to many parameters so that it takes a relatively long initialization time.

Abstract: Provided are a method of managing multiple channels in a single network, and a network management device, also referred to as a network management system. According to the method and the network management device, all devices in one network that operate by using multiple channels share core information, and are effectively controlled.

Abstract: Provided are a beacon re-broadcasting apparatus, a beacon re-broadcasting method, and an initial access request method in a wireless network. In the re-broadcasting apparatus and method, a beacon frame including beacon information for communications in the wireless network and information on an echo beacon slot allocated for beacon re-broadcasting among time slots of a superframe is received from a management device for managing the wireless network in which a plurality of terminals communicated with each other through the superframe including time-divided time slots, and the beacon information is re-broadcasted during the echo beacon slot. Accordingly, the beacon information can be received in various environments, and the beacon information can be received to an adjacent network in addition to the corresponding network. Therefore, frequency resources can be shared and effectively used between networks, and convenience and efficiency in network operation can be maximized.

Abstract: Provided are a network communication method and a network device using a preamble. According to the network communication method and the network device, network coexistence is easily achieved by using network identification transmitted in the preamble, and an unknown terminal, which has a low reception signal to noise ratio (SNR) and has not yet been connected to an existing network, is easily connected to the existing network.

Abstract: Provided are a method of adaptively allocating appropriate hybrid bursts according to terminal attributes including terminal position, channel state, and service type in an orthogonal frequency-division multi-access (OFDMA) system, and an upstream-MAP information element (US-MAP IE) structure supporting the method. The method includes dividing an upstream subframe into a plurality of zones depending on the number of OFDMA symbols and allocating bursts of a zone to a terminal according to the terminal attributes. Bursts are formed by allocating slots along a time axis in the upstream subframe, and are formed by allocating slots along a frequency axis in a downstream subframe.

Abstract: Provided is a method and apparatus of generating signals for initial ranging in an Orthogonal Frequency Division Multiple Access (OFDMA) system. The method, includes: generating a plurality of ranging symbols by cyclic-shifting sample data of a ranging symbol in one OFDMA symbol period as much as a value obtained by multiplying a cyclic prefix size by a symbol index; generating a ranging signal by copying a rear part corresponding to the cyclic prefix size in the sample data with respect to each of the ranging symbols and inserting the copied rear part in front of the sample data as a cyclic prefix.

Abstract: The present invention relates to relay customer premises equipment (RCPE) for exchanging operational information and coexistence information of each cell between adjacent cells in a cellular system. The present invention enables effective control between multiple cells by directly transmitting operational information and coexistence information between cells over air links.

Abstract: A method and apparatus for allocating subchannels in an orthogonal frequency division multiple access (OFDMA) system is provided. In the method and apparatus, mixed bands in each of which adjacent subcarriers and distributed subcarriers are mixed are used to form a band of a basic physical resource. Accordingly, diversity subchannels each comprised of distributed subcarriers distributed over the whole band and band subchannels each comprised of adjacent subcarriers adjacent to parts of the band are formed in a single OFDMA symbol, thereby simultaneously and flexibly allocating subchannels to users.

Abstract: Provided is a method of generating a pilot pattern capable of perform adaptive channel estimation, and a method and apparatus of a base station and a method and apparatus of a terminal using the pilot pattern. The pilot pattern selects pilot symbol positions based on distances from pilots of previous orthogonal frequency division multiple access (OFDMA) symbols to a subcarrier position of a current OFDMA symbol in the frequency domain and the time domain, so that a low pilot density is maintained so as to effectively transmit data, and stable channel estimation performance can be obtained even in a bad channel environment. In addition, the minimum burst allocation size is determined according to the channel environment between the base station and the terminal, guaranteeing channel estimation performance suitable for the channel environment, and improving granularity, channel estimation latency, and channel estimation memory size.

Abstract: Provided are a method for using a flexible bandwidth in an orthogonal frequency division multiple access (OFDMA)-based cognitive radio system, and a base station (BS) and a subscriber station using the method. The method includes: allocating a channel band from among unused channel bands having a bandwidth that is a natural number times a bandwidth resolution to customer premises equipment (CPE), wherein the bandwidth resolution is a predetermined bandwidth smaller than a bandwidth of a broadcast channel band, and transmitting an OFDMA-based signal comprising band allocation information indicating information regarding the allocated channel band.