Yong Seouk Choi

A new CDMA-based bandwidth request method for IEEE 802.16 OFDMA/TDD systems

This paper proposes an efficient bandwidth request method for a non-real-time polling service and best effort service in the IEEE 802.16 system. The proposed method produces a bandwidth request code to indicate the channel quality and the necessary number of slots. The base station allocates uplink bandwidth depending on the bandwidth request code. Thus, the proposed method can omit the transmission procedure of the bandwidth request message. The performance analysis results show that the proposed method can reduce the delay for the uplink data transmission.

The displacement of base station in mobile communication with genetic approach

This paper addresses the displacement of a base station with optimization approach. A genetic algorithm is used as optimization approach. A new representation that describes base station placement, transmitted power with real numbers, and new genetic operators is proposed and introduced. In addition, this new representation can describe the number of base stations. For the positioning of the base station, both coverage and economy efficiency factors were considered. Using the weighted objective function, it is possible to specify the location of the base station, the cell coverage, and its economy efficiency. The economy efficiency indicates a reduction in the number of base stations for cost effectiveness. To test the proposed algorithm, the proposed algorithm was applied to homogeneous traffic environment. Following this, the proposed algorithm was applied to an inhomogeneous traffic density environment in order to test it in actual conditions. The simulation results show that the algorithm enables the finding of a near optimal solution of base station placement, and it determines the efficient number of base stations. Moreover, it can offer a proper solution by adjusting the weighted objective function.

The Positioning of Base Station in Wireless Communication with Genetic Approach

This paper addresses the displacement of a base station with optimization approach. A genetic algorithm is used as optimization approach. A new representation that describes base station placement, transmitted power with real numbers and new genetic operators is proposed and introduced. In addition, this new representation can describe the number of base stations. For the positioning of the base station, both coverage and economy efficiency factors were considered. Using the weighted objective function, it is possible to specify the location of the base station, the cell coverage and its economy efficiency. The economy efficiency indicates a reduction if the number of base stations for cost effectiveness. To test the proposed algorithm, the proposed algorithm was applied to homogeneous traffic environment. Following this, the proposed algorithm was applied to an inhomogeneous traffic density environment in order to test it in actual conditions. The simulation results show that the algorithm enables the finding of a near optimal solution of base station placement and it determines the efficient number of base stations. Moreover, it can offer a proper solution by adjusting the weighted objective function.

System capacity enhancement of MmWave based 5G mobile communication system

The millimeter wave (mmWave) frequency band is being considered as a candidate for new radio bands that lead to capacity enhancement for emerging 5G mobile communication systems. But, in order to overcome propagation limitations of mmWave band, beamforming technology can be a solution and multi-beam based communication system using fixed beamforming is considered as a communication system structure for 5G mobile. In this paper, we propose inter-beam interference mitigation method for the multi-beam based 5G communication system using fixed beamforming. The proposed method mutes beams that have an effect on inter-beam interference based on proportional fair metric by beam, and improves signal to interference plus noise ratio (SINR) and system capacity.

Performance of MIMO-OFDM System with Adaptive Beamforming Algorithm

In this paper, the new technique combining space- time decoder with beamforming is proposed for an orthogonal frequency division multiplexing (OFDM) system with multi- input multi-output (MIMO). Through the proposed technique for MIMO-OFDM, the multibeams are formed toward each multi-transmitter antenna of the desired user. Therefore, the performance of MIMO-OFDM system is very improved by the proposed techniques that can reduce cochannel interference(CCI) and obtain diversity gain. BER performance improvement of the proposed approach is investigated through computer simulation in the multi-users environment.

GMPS(Group based multi-level packet scheduling) method in multi-beam based mobile communication system

The exponential increase of global mobile data traffic requires future 5G system. Millimeter Waveform (mmWave) band is being considered as a candidate for new radio bands for 5G systems. In this paper, we present beam-forming technology on patch antenna array to cope path loss of mmWave band. In order to reduce the interference between beams and to compensate for this problems of limitation of user number, we proposed beam group method and GMPS(Group based MultiLevel Packet Scheduling) in 5G system based multi-beam. This paper evaluates performance of the GMPS in beam-forming system through the system level simulation.

A contention based uplink scheduling request method in LTE-A

In this paper, a contention based uplink scheduling request method is proposed to enable low transmission latency in LTE-A systems. The proposed method transmits a BSR message over PUCCH which includes uplink resource information required by the UE. On the other hand, in LTE-A systems, a positive signal for scheduling request is transmitted over PUCCH. Performance analysis results show that the proposed method can significantly reduce the delay for uplink data transmission compared to that of the uplink SR method in LTE-A systems.

System coverage of Mm wave based 5G mobile communication system

To meet avalanche of traffic volume, the mmWave band in the 30-300GHz range is being considered as a candidate for new radio bands for 5G mobile communication systems. ETRI is developing mmWave based 5G mobile communication system in the Giga KOREA 5G (GK-5G) project. This paper introduces overview and features of the GK-5G mobile communication system and evaluates system coverage of the GK-5G mobile communication system through the system level simulation considering real geospatial information.

An efficient negative acknowledgment method for CDMA-based ranging in IEEE 802.16 OFDMA systems

Ranging in IEEE 802.16 systems is used to synchronize an uplink or to request an uplink bandwidth. The base station sends a ranging response message as a positive acknowledgment of a successfully received code. However, the base station does not provide a negative acknowledgment; hence, a mobile station is unable to determine if its ranging code is unsuccessfully transmitted. This paper proposes a negative acknowledgment method based on a ranging slot indicator and the frame number of a ranging response message. The results of the performance analysis show that the proposed method can reduce the delay of a code retransmission.