• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.395-402
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• 2003

The capacity of a CDMA cellular system is determined by the amount of interference, therefore the exact estimation of interference is important to evaluate the system performance. In this paper, we propose an approximated equation which calculates reverse link other cell interference in the CDMA cellular systems. The equation using Riemann-Zeta function has a property that it is useful in case of any radio propagation loss exponents. And we compare calculation results with simulation results in other to verify it's usefulness. The upper bound of system capacity calculated with the proposed approximated equation gives almost alike result with the simulation. The proposed interference bound is useful to calculate system capacity and to evaluate some algorithm in a hierarchical cellular system which must be considered various propagation exponents.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3B
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• pp.212-219
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• 2002

In this paper, how to perform beamforming and power control for the systems with smart antennas is introduced in consideration of macro-diversity, and cell capacity of the systems is analyzed. In the result, as the number of the base stations linked to mobiles increases, capacity increases in the reverse link. On the other hand, macro diversity causes capacity loss in forward link. It is expected that the result of this work may be used in designing the next generation mobile communication systems for high quality services such as multi media data and wireless internet etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.722-728
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• 2005

In this paper, the reverse-link performance of synchronous DS-CDMA cellular networks is investigated in Rician multipath fading environments. The system's performance is evaluated in terms of the achievable average bit error rate BER) and the user capacities of two different network layouts, namely those of a uniform grid of hexagonal multiple cells and a single isolated cell. In the multiple-cell scenario, the impact of the other cells' interference on the attainable capacity of the synchronous DS-CDMA uplink is investigated. Upon comparing both networks to a conventional asynchronous CDMA system, we demonstrate an achievable user capacity gain of $25\%$ to $56\%$ for synchronous uplink transmissions over that of the corresponding asynchronous transmission scenario at BER = $10^{-3}$.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.5
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• pp.1-9
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• 2000

In this paper, for the reverse link of a imperfect power controlled DS/CDMA cellular system when a mobile radio channel is a Rayleigh distributed multipath fading channel, A extended DS/CDMA blocking probability formula considering both shadowing and multipath fading is derived. Erlang capacity and equivalent channel number considering shadowing are analyzed and compared with those considering both shadowing and multipath fading, respectively. The DS/CDMA blocking probability is calculated based on the analysis method that obtains Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{0}$ corresponding to each reverse link user Assuming that the blocking probability set 2%, it is observed that the Erlang capacity is 19.97 Erlang at the data rate $R_{b}$=9.6 kbps and 11.67 Erlang at the data rate $R_{b}$=14.4 kbps and then is less 16% and 19% than the Erlang capacity considering shadowing only, respectively. It is also shown that the effect of multipath fading must not be ignored and then exact Erlang capacity and equivalent channel numbers that the DS/CDMA cellular system can support are provided.d.d.d.

• Journal of Communications and Networks
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• v.2 no.1
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• pp.5-17
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• 2000

cdma2000 offers several enhancement as compared to TIA/EIA-95, although it remains fully compatible with TIA/EIA-95 systems and allows for a smooth migration from one to the other-Major new capability include:1)connectivity to GSM-MAP in addition to IP and IS-41 networks; 2) new layering with new LAC and MAC architectures for improved service multiplexing and QoS management and efficient use of radio resource ;3) new bands and band widths of operation in support of various operator need and constraints, as well as desire for a smooth and progressive migration to cdma 2000; and 4) flexible channel structure in support of multiple services with various QoS and variable transmission rates at up to 1 Mbps per channel and 2 Mbps per user. Given the phenomenal success of wireless services and desire for higher rate wireless services. improved spectrum efficiency was a major design goal in the elaboration of cdma2000. Major capacity enhancing features include; 1) turbo coding for data transmission: 2)fast forward link power control :3) forward link transmit diversity; 4) support of directive antenna transmission techniques; 5) coherent reverse link structure; and 6) enhanced access channel operation. As users increasingly rely on their cell phone at work and at home for voice and data exchange, the stand-by time and operation-time are essential parameters that can influence customer's satisfaction and service utilization. Another major goal of cdma2000 was therefore to enable manufacturers to further optimize power utilization in the terminal. Major battery life enhancing features include; 1) improved reverse link performance (i.e., reduced transmit power per information bit; 2) new common channel structure and operation ;3) quick paging channel operation; 4) reverse link gated transmission ; and 5) new MAC stated for efficient and ubiquitous idle time idle time operation. this article provides additional details on those enhancements. The intent is not to duplicate the detailed cdma2000 radio access network specification, but rather to provide some background on the new features of cdma2000 and on the qualitative improvements as compared to the TIA/EIA-95 based systems. The article is focused on the physical layer structure and associated procedures. It therefore does not cover the MAC, LAC, radio resource management [1], or any other signaling protocols in any detail. We assume some familiarity with the basic CDMA concepts used in TIA/EIA-95.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1956-1959
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• 2002

Power control (PC) on the reverse link of CDMA cellular system is important to increase system capacity. PC eliminates fluctuations in the received signal level and hence reduces the required signal-to-interference ratio. However, both perfect PC and imperfect PC depend on number of interferences as number of users, which by using smart antenna system can decrease number of interferences in any directions except interferences from the main beam direction. In this paper , number of elements in smart antenna system, which directly relates to the main beam pattern, is studied to find the effects on the outage probability , bit energy-to-interference density ratio (Eb/Io) and the capacities of both perfect and imperfect PC.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.54-67
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• 2000

It is known that the performance of a DS-CDMA system mainly depends on Multiple Access Interference(MAI). The effect of MAI in a reverse link is larger than that of a forward link because of the absence of orthogonality among mobile stations. In this paper we investigate the effect of synchronous transmission in the reverse link, which is compared to the performance of asynchronous transmission in the reverse link. In addition, we consider the effect of interference from Mobile Stations(MSs) in a hand-over region. That is, if we assume that a MS is moving from a serving base station(sowing BS) to a target base station(target BS), the signal of the MS is not orthogonal with the signals of all other MSs within the target BS because the MS is only synchronized with the serving BS. Finally we suggest an interference cancellation scheme to reduce the interference from MSs in the region of hand-over, which can be one of solutions for the capacity degradation due to interference from the MSs in the hand-over region in reverse link synchronous transmission.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.804-811
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• 1997

In the CDMA mobile communication system, reverse power control can be used to minimize the interference level for a good quality of the voice channel, and used to maxmize the system capacity. In this paper, we have analyed the environment of the K-parameter and the access procedure for the mobile station, and proposed a new algorithm for the access probe procedure of the station. K-parameter is determined according to the environment of the base station and access probe can adaptively control the power according to the position changes of the mobile station or the rapid and various state changes of the channel. Simulation results in the limited test environment show that it can increase the system capacity and decrease the power comsumption of the mobile station while maintaining the good and stable quality of the voice channel.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.5
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• pp.376-379
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• 2021

The design and performance of a SiC-MOSFET-based 11-kW bi-directional on-board charger (OBC) for electric vehicles is presented. The OBC consists of a three-phase two-level AC/DC converter and a CLLLC resonant converter. All the power devices are implemented with SiC-MOSFETs to reduce the conduction losses generated in the OBC, and the DC-link voltage is designed to track the level of battery voltage in the forward and reverse powering modes. As a result, the CLLLC resonant converter always runs at the switching frequency near the resonant frequency, resulting in high-efficiency operation at the maximum powering modes. As the DC-link voltage varies according to the battery voltage, the AC/DC converter in the proposed OBC adopts an adaptive DC-link voltage controller. The performance of the proposed 11-kW OBC is verified by a prototype converter with the following specifications: three-phase 60-Hz 380-V input, 11-kW capacity, and battery voltage range of 214-413-V, resulting in the conversion efficiency of over 95.0-% in the forward and reverse powering modes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.421-428
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• 2009

Inter-cell coordination has been an emerging issue for mitigating inter-cell interference in broadband wireless access networks such as IEEE802.16 and 3GPP LTE (Long Term Evolution). This paper proposes uplink/downlink hybrid inter-cell coordination patterns for a TDD (Time Division Duplex)/MC-CDMA (Multi-Carrier Code Division Multiple Access) system. For the performance analysis, closed forms of inter-cell interferences are derived when uplink and downlink transmissions coexist over a multi-cell environment. In the analysis, we find an optimal ratio of downlink transmit powers of BSs (Base Stations) based on the target outage probability and the performance according to ratios of uplink/downlink transmit powers of MSs (Mobile Stations)/BSs is explored. Our numerical results show that interference mitigation utilizing the characteristics of the uplink and downlink power ratio is very effective in improving system performance in terms of QoS.