• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.9
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• pp.861-869
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• 2014

This paper shows the research of a platform architecture relates to the LTE-based macro basestation; the proposed platform architecture is designed with the interface between the baseband signal and IF (Intermediate Frequency) per codeword. Using this method, we can smoothly transmit/receive a large amounts of data regardless of the number of antenna in a macro base station which is used technology such as massive MIMO. In this paper, We analyzed the evolution of LTE technology and the trend in the development of the LTE-based system. For validation of the proposed architecture, we compare the general architecture of a conventional with the proposed architecture. From the calculation results of transmission quantity data, we see that the proposed architecture can give better performance than the existing architecture. By presenting this architecture, we hope to provide a new foundation for Design and Implementation of a LTE base station platform which is used technology such as massive MIMO, carrier aggregation (CA), coordinated multi point (CoMP).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.4
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• pp.371-377
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• 2013

Fishing boats more than 5 tons is obliged to VHF DSC by Fishing Vessels Act and Vessel Safety Act. The owner of the fishing vessel is equipped to the automatic position reporting device in accordance with the Notice of the Minister of Land, Transport and Maritime Affairs to regulations, shall be ensure to navigations safety and in order to respond quickly in the event of maritime accidents on fishing vessels. East sea set up to start in 2012, which is now underway the annual install plain to the yellow sea and the south sea for VHF coast stations. It is web-based remote operation of DSC on the remote control and monitoring in Fishery Information Communication Station for the coastal VMS construction project. All fishing vessels is VHF DSC in conjunction with the GPS that location information transmitted to the coast station. automatically by the DSC call. This paper has been studied on the communications coverage set up and traffic operation for realization a roaming service by navigation route tracking and RSSI techniques in parallel algorithm refer to VHF DSC coast stations in east sea.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1131-1137
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• 2009

In this paper, a resource management technique for digital duplexing (DD) systems using orthogonal frequency division multiple access (OFDMA) is proposed. The proposed technique can reduce the dynamic range of the signal received at the subscriber station (SS) and minimize the effects of inter-symbol interference (ISI) and inter-carrier interference (ICI) due to the time difference of arrival (TDoA) without using a cyclic suffix. It is shown by computer simulation that the proposed technique can reduce the number of bits for an analog-to-digital converter (ADC) and increase the signal-to-interference and noise ratio (SINR) significantly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.166-173
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• 2004

Satellite communication system uses a high non-linear HPA(high power amplifiers) in the earth station and satellite transponder. Therefore, it is important to consider the nonlinear effect of HPA on the communication system. In this paper, we find the variation of power spectrum density by nonlinearity HPA and the change of harmonic component according to IBO (input back-off). When the BPSK is used for satellite communication system, we analyze BER performance including the external co-channel interference (CCI) and the adjacent channel interference (ACI) resulting from the HPA nonlinearity. BER degrades as ACI magnitude grows up when the uplink SNR, uplink SIR (signal to co-channel interference power ratio) and downlink SIR are constant at some level. In case there is only non-linear HPA in the satellite, it is shown that BER considerably depends on the ACI magnitude ACI. When there are two non-linear HPAs in the both earth station and satellite, much BER degradation results from the CCI and ACI.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.10A
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• pp.796-806
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• 2009

This paper presents the method of emergency warning system operation based on T-DMB and the design of T-DMB AEAS receiver model. The proposed receiver model compares the geographical location of emergency with the location of DMB transmitting station from T-DMB broadcasting signal and classifies the receiver location into alert region, neighboring region and non-alert region and transmits the emergency alert message according to each region. The geographical location of emergency can be obtained from FIG 5/2 EWS data field for AEAS message and the location of DMB transmitting station can be estimated from either the latitude and the longitude in main identifier and sub identifier in FIG 0/22 data filed for TII(Transmitter Identification Information) or TII distribution database. In our experiment, we implemented the proposed receiver model with display section, storage section, DMB module for receiving broadcasting signal and control section and performed test emergency alert broadcasting using T-DMB signal generator.

• Journal of Communications and Networks
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• v.15 no.4
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• pp.352-361
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• 2013

Combining multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) with a massive number of transmit antennas (massive MIMO-OFDM) is an attractive way of increasing the spectrum efficiency or reducing the transmission energy per bit. The effectiveness of Massive MIMO-OFDM is strongly affected by the channel state information (CSI) estimation method used. The overheads of training frame transmission and CSI feedback decrease multiple access channel (MAC) efficiency and increase the CSI estimation cost at a user station (STA). This paper proposes a CSI estimation scheme that reduces the training frame length by using a novel pilot design and a novel unitary matrix feedback method. The proposed pilot design and unitary matrix feedback enable the access point (AP) to estimate the CSI of the signal space of all transmit antennas using a small number of training frames. Simulations in an IEEE 802.11n channel verify the attractive transmission performance of the proposed methods.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.9-18
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• 2004

Self-encoded multiple access (SEMA) is a unique realization of random spread spectrum. As the term implies, the spreading code is obtained from the random digital information source instead of the traditional pseudo noise (PN) code generators. The time-varying random codes can provide additional security in wireless communications. Multi-rate transmissions or multi-level grade of services are also easily implementable in SEMA. In this paper, we analyze the performance of SEMA in additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. Differential encoding eliminates the BER effect of error propagations due to receiver detection errors. The performance of SEMA approaches the random spread spectrum discussed in literature at high signal to noise ratios. For performance improvement, we employ multiuser detection and Turbo coding. We consider a downlink synchronous system such as base station to mobile communication though the analysis can be extended to uplink communications.

• Journal of Communications and Networks
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• v.18 no.3
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• pp.429-438
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• 2016

In this paper, we investigate an interference mitigation scheme by antenna selection in device-to-device (D2D) communication underlaying downlink cellular networks. We first present the closed-form expression of the system achievable rate and its asymptotic behaviors at high signal-to-noise ratio (SNR) and the large antenna number scenarios. It is shown that the high SNR approximation increases with more antennas and higher ratio between the transmit SNR at the base station (BS) and the D2D transmitter. In addition, a tight approximation is derived for the rate and we reveal two thresholds for both the distance of the D2D link and the transmit SNR at the BS above which the underlaid D2D communication will degrade the system rate. We then particularize on the small cell setting where all users are closely located. In the small cell scenario, we show that the relationship between the distance of the D2D transmitting link and that of the D2D interfering link to the cellular user determines whether the D2D communication can enhance the system achievable rate. Numerical results are provided to verify these results.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.520-530
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• 2016

Since FDD massive MIMO (multiple-input multiple-output) system deploys hundreds of transmit antennas at base station (BS) compared to conventional MIMO system, the overhead of transmitting channel state information reference signal (CSI-RS) increases proportionally to the number of transmit-antennas. To overcome these disadvantages, we proposed beamforming based CSI-RS transmission technique for FDD massive MIMO system which transmit CSI-RS by limited amount of downlink resources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.601-609
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• 2002

In multi-path wireless channels with time-variant delay profile, a mobile station measures the received signal strength and report it to network which performs network control function such as handover. In order to improve the maximum ratio combining (MRC) gain, it also should search the strongest signal paths and measure their time offsets fast and exactly. This paper proposes some methods of fast and exactly measuring the multi-path signal strength and time offset. Since the W-CDMA system adopts antenna diversity technique for the next generation high speed packet access (HSDPA) service, we derive the optimum design parameter values for the proposed methods through computer simulations under the HSDPA conditions o( low speed of mobile, of no power control, and of multi-path wireless environment with transmit and receive antenna diversity. Finally, we prove the validity of the proposed methods by showing the improvement of the bit error rate (BER) performance.