Showing papers by "Ji-Yun Seol published in 2014"

Millimeter-wave beamforming as an enabling technology for 5G cellular communications: theoretical feasibility and prototype results

Abstract: The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

Apparatus and method for selecting transmit and receive beam in a wireless communication system

Abstract: A method for operating a receiving end in a wireless communication system includes receiving subset information on analog beams of a transmitting end, from a transmitting end, and determining a combination of transmit beams to be used for data signal transmission to the receiving end, on the basis of the subset information, wherein the subset information indicates at least one subset into which the analog beams are classified, and each analog beam of the at least one subset has a correlation equal to or less than a threshold, with one another. An apparatus for a receiving end includes a communication unit configured to receive subset information on analog beams of a transmitting end, from the transmitting end, and a controller configured to determine a combination of transmit beams to be used for data signal transmission to the receiving end, on the basis of the subset information.

QAM-FBMC: A New Multi-Carrier System for Post-OFDM Wireless Communications

Abstract: Recently, as asynchronous heterogeneous network scenario becoming one of the key features for next generation wireless communications, superior spectrum confinement as well as higher spectral efficiency compared to cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM) has been taken into consideration for future radio access technologies. In this paper, we propose a new quadrature amplitude modulation based filter-bank multi-carrier (QAM-FBMC) system that provides with an inherent spectral efficiency gain against CP-OFDM, which comes from reduction of the redundancies such as cyclic prefix (CP) and guard-band, while keeping the symbol rate same as in CP-less OFDM. We propose a new transceiver structure consisting of at least two different filter-bank bases at both transmitter and receiver sides. Practical algorithms including channel estimation and equalization to mitigate multi-path fading channel without CP are proposed. Various evaluation results show that the proposed system performs comparable to the CP-OFDM system even without CP and guard-band reduction is also available from the well-confined spectrum.

Apparatus and method for transmitting and receiving beam information in wireless communication system

Abstract: The present disclosure relates to transmitting and receiving beam information in a wireless communication system. An operation of a receiving end includes: generating a signal indicating two or more analogue transmission beams which are allocable to the receiving end; and transmitting the signal. In addition, the present disclosure includes other embodiments different from the embodiment described above.

Apparatus and method for transmission/reception in radio communication system

Abstract: A transmitter, a receiver, and a method for measuring a radio channel based on reference signals transmitted through a predetermined number of OFDM symbols by using multiple antennas in an ultra-high frequency band, and controlling a beam width of analog beams formed by transmission multiple antennas based on the measurement result. The transmitter uniquely distributes a predetermined number of analog beams among the analog beams formed by the array antenna in correspondence to each of the predetermined number of OFDM symbols, and repeatedly allocates the predetermined number of analog beams distributed for each of the predetermined number of OFDM symbols by targeting the subcarriers within the corresponding OFDM symbol. The receiver receives a channel measurement instruction message, measures a channel state based on reference signals transmitted through the analog beams allocated for respective subcarriers, and feeds the channel state measurement result back to the transmitter.

On the hybrid beamforming with shared array antenna for mmWave MIMO-OFDM systems

Abstract: Along with the attention drawn to the millimeter-wave frequency bands for the drastically increased data rate support for the next generation (5G) mobile communications, the hybrid beamforming architectures combining analog beamforming and digital precoding have been investigated as potential candidates to provide good compromise between the complexity and the performance. Among the different hybrid beamforming architectures, the architecture with so-called shared array antenna is analyzed with respect to the peak-to-mean envelope power ratio over antenna elements and the total average transmission power constraint upon multi-beam transmissions. It is shown that the non-trivial normalization coefficients should be applied to the hybrid beamforming architecture under consideration to achieve the average transmission power within the total power constraint. Taking into account the total power normalization for the hybrid beamforming architecture with shared array antenna, various simulation results are provided to show the performance of the multi-beam transmission diversity against the single-beam analog beamforming.

Antenna grouping based feedback reduction for FDD-based massive MIMO systems

Abstract: Recent works on massive multiple-input multiple-output (MIMO) have shown that a potential breakthrough in capacity gains can be achieved by deploying a very large number of antennas at the basestation. Although transmit-side channel state information (CSI) can be obtained by employing channel reciprocity in time division duplexing (TDD) systems, explicit feedback of CSI from the user to the basestation is required for frequency division duplexing (FDD) systems. In this paper, we propose an antenna grouping based feedback reduction technique for FDD-based massive MIMO systems. The proposed algorithm, dubbed antenna group beamforming (AGB), groups antenna elements using pre-designed patterns. The proposed method introduces the concept of using a header of overall feedback resources to select a suitable group pattern and the payload to quantize the effective channel vector. Simulation results show that the proposed method achieves significant feedback overhead reduction over conventional approach.

Apparatus and method for transmitting and receiving feedback information in beamforming communication system

Abstract: A method for operating a mobile station in a mobile communication system. The method includes: receiving a plurality of transmit (Tx) beam signals from a base station; generating indication information for indicating a difference in arrival time between effective Tx beam signals selected from the received Tx beam signals; and transmitting feedback information including the indication information to the base station.

Method and apparatus for allocating wireless resources

Abstract: Provided are a method and apparatus for radio resource allocation. The radio resource allocation method for a base station may include: obtaining at least one of beamforming structure information and frame structure information; generating resource allocation information for a CSI-RS (channel state information reference signal) on the basis of at least one of the beamforming structure information and the frame structure information; and transmitting the resource allocation information. As a result, it is possible to efficiently perform resource allocation.

Method and apparatus for measuring and feeding back channel information in communication system using beam forming

Abstract: A method of feeding back channel information by a receiver in a communication system beam forming is provided. The method includes determining an optimum reception beam using intensities of reference signals received through transmission beams of a base station for a first period through a first path for mapping analog beams of an input signal, and determining an optimum transmission beam of the transmission beams using intensities of reference signals received through the optimum reception beam for a second period through a second path for mapping analog beams of the input signal, and transmitting channel information measured by using a reference signal received through the optimum transmission beam and the optical reception beam to a transmitter.

Apparatus and method for transmitting/receiving reference signal in wireless communication system supporting beam forming scheme

Abstract: A method for transmitting by a reference signal transmitting apparatus a reference signal in a wireless communication system supporting a beam forming scheme is provided. The method includes transmitting beam pattern measurement window indication information including information related to at least two beam pattern measurement windows which each of reference signal receiving apparatuses will use to the reference signal receiving apparatuses; and transmitting reference signals based on beam patterns which the reference signal transmitting apparatus supports during a preset number of time units.

Precoder selection method and apparatus for performing hybrid beamforming in wireless communication system

Abstract: One or more embodiments provides a precoder selection method for performing hybrid beamforming in a wireless communication system. The method includes selecting a predetermined number of candidate transmit beams using a signal strength received through each of first combinations with receive beams that can be mapped to each transmit beam of each of transmit antennas mounted on a transmitter. The method also includes selecting a precoder using signal strength received through each of second combinations with receive beams that can be mapped to each of the candidate transmit beams.

Apparatus and method for adaptive transmission power normalization in wireless communication system

Abstract: A transmission normalization in a wireless communication system adopting hybrid beamforming is provided. An operating method of a transmitter includes transmitting control information on transmission power normalization, receiving information indicating a precoding matrix and an analog beam selected based on the control information, and transmitting a signal normalized using a normalization coefficient corresponding a combination of the precoding matrix and the analog beam.

Method and apparatus for fast beam-link construction in mobile communication system

Abstract: A method of forming a beam-link by a Base Station (BS) in a wireless communication system using a beamforming scheme includes determining at least one downlink beams to be used for downlink transmission and/or reception, transmitting a reference signal to a Mobile Station via the at least one downlink beam, receiving the reference signal via an uplink beam from the Mobile station, and updating the at least one downlink beam to increase a Signal-to-Noise Ratio (SNR). Accordingly, a beam-link using an initial beam-link between the BS and the MS and adaptive beamforming can be rapidly constructed in a high frequency band BDMA cellular system.

Method and apparatus for transmitting/receiving signal in wireless communication system

Abstract: One or more embodiments provides method for transmitting a signal by a transmitting apparatus in wireless a communication system supporting a modulation scheme based on a quadrature amplitude modulation (QAM) scheme and a frequency shift keying (FSK) scheme. The method includes determining at least one first bit which will be mapped to at least one QAM symbol and at least one second bit which will be mapped to at least one FSK symbol among bits included in an encoded input bit stream; and generating a modulation symbol by mapping the at least one first bit to the at least one QAM symbol and mapping the at least one second bit to the at least one FSK symbol based on a Hamming distance of the at least one second bit.

Hybrid beamforming-based open-loop mimo transmission method and apparatus therefor

Abstract: A method for a transmitter of a mobile communication system transmitting and receiving signals according to an embodiment of the present specification comprises the steps of: transmitting to a receiver system information for transmitting a signal to the receiver including a connection between a wireless resource and a transmitting antenna; transmitting a reference signal to the receiver based on the system information; and receiving from the receiver feedback information generated based on the reference signal. According to an embodiment of the present specification, in a beamforming transmission method of a mobile communication system, a transmitter can determine whether to perform digital pre-coding without advance information from a receiver and can consequently perform a transmission, and can thereby perform lower-overhead and efficient signal transmission/reception.

Method and apparatus for grouping antennas in multiple-input multiple-output antenna system

Abstract: Disclosed are a method and an apparatus for grouping antennas in a multiple-input multiple-output antenna system. The method of the present invention comprises the steps of: measuring a channel vector for a plurality of antennas of a base station; grouping channel coefficients of the channel vector in accordance with a plurality of antenna grouping patterns and determining grouped codebook vectors corresponding to the grouped channel coefficients; selecting one of the antenna grouping patterns using the grouped codebook vectors for the antenna grouping patterns; and feeding back, to the base station, a pattern index indicating the selected antenna grouping pattern and a codebook index indicating the grouped codebook vector corresponding to the selected antenna grouping pattern.

Codebook for multiple-input multiple-output system and communication method and device using same

Abstract: Embodiments of the present invention provide a scheme for reducing feedback overhead when quantizing and feeding back channel state information in a multiple-input multiple-output (MIMO) system. A method for operating a receiver in a MIMO system, according to one embodiment of the present invention, comprises the steps of: performing Trellis coded quantization for received channel information by using a codebook selected from a plurality of codebooks; and transmitting, to a transmitter, feedback information including the quantization result. The step of performing Trellis coded quantization for the received channel information comprises a step of truncating the received channel information and codewords included in the selected codebook into multiple groups of channel vectors and multiple groups of codewords, respectively, and performing Trellis coded quantization for each of the groups of channel vectors by using each of the groups of codewords.

Performance comparison between single- and multiple-arrays for 3D-beamsteering multi-user detection

Abstract: Single-array and multiple-array structures were applied to a large-scale planar array for use in uplink space-division multiple access, and their simulated data throughputs were compared. In both structures, a subarray-processing iterative soft-input-soft-output multi-user detector efficiently recovers multi-user signals from multiple RF chains. The phased-array directivity is controlled on the basis of inter-subarray phase shift minimization. The multiple-array structure performed better due to larger space diversity provided by uncorrelated fading between the arrays in non line-of-sight environments. Moreover, uncorrelated noise was generated in the subarray output signals, resulting in better user separation.

Antenna Grouping based Feedback Reduction for FDD-based Massive MIMO Systems

Abstract: Recent works on massive multiple-input multiple-output (MIMO) have shown that a potential breakthrough in capacity gains can be achieved by deploying a very large number of antennas at the basestation. In order to achieve the performance that massive MIMO systems promise, accurate transmit-side channel state information (CSI) should be available at the basestation. While transmit-side CSI can be obtained by employing channel reciprocity in time division duplexing (TDD) systems, explicit feedback of CSI from the user terminal to the basestation is needed for frequency division duplexing (FDD) systems. In this paper, we propose an antenna grouping based feedback reduction technique for FDD-based massive MIMO systems. The proposed algorithm, dubbed antenna group beamforming (AGB), maps multiple correlated antenna elements to a single representative value using pre-designed patterns. The proposed method modifies the feedback packet by introducing the concept of a header to select a suitable group pattern and a payload to quantize the reduced dimension channel vector. Simulation results show that the proposed method achieves significant feedback overhead reduction over conventional approach performing the vector quantization of whole channel vector under the same target sum rate requirement.