• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.9A
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• pp.1348-1358
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• 2000

The paper contributes to a traffic analysis for the CDMA cellular base station with repeater which are operated in a cell site. Usually the repeaters' traffic of the CDMA cellular system hardly could be separated from that of the base station because the links of the repeaters are divided from RF circuits of the base station. The paper introduces a traffic measuring method that separates the traffic of repeaters from that of the base station using time delay device. To get general results we use a single BTS(Base station Transceiver Subsystem) with three repeater as well as a single BTS with a single repeater. Then we proved that the traffic of the repeaters could separate from that of the base station clearly.

• 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 the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.59-67
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• 2008

Due to the fast increase in cellular phone users, public interest on health effect of electromagnetic fields(EMFs) by cellular phonos is gradually increasing. Some EHS(electromagnetic hypersensitivity) patients complain of psycho-neurophysiological symptoms such as headaches, insomnia, memory loss resulting from RF radiation by CDMA cellular phones. However, EHS is difficult to diagnose and depends on the individual's subjective judgement. And we don't know clearly if the cause of EHS is uneasiness or real exposure. There have been various EHS volunteer studies on heart rate, blood pressure and subjective symptoms using GSM phones. But there are few studies on experimental case-control study investigating physiological parameters, subjective symptoms, and perception of EMFs. In this study, two volunteer groups of 17 self-declared EHS and 19 controls were exposed to both sham and real RF exposure by CDMA cellular phones for half an hour each. We investigated not only the physiological parameters such as heart rates, respiration rates and HRVs(hear rate variability), but also the perception of EMFs and subjective symptoms. As the results, EMF exposure did not have any effects on the subjective symptoms or physiological parameters for both groups. For the EMF perception, there was no evidence that EHS group perceived the EMFs correctly than the control group.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.5 no.1
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• pp.22-30
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• 1994

The error probability of the DS-CDMA / DPSK cellular mobile communication system with CCI canceller and MRC diversity reception technique has been analyzed in the cellular radio channel which is characterized by AWGN, Multi-User Interference(MUI) and m-distribution fading. System capacity i. e., number of user per cell has been derived and the evaluated results are shown in figures as a function of PN code sequence length, fading index, BER, number of diversity branches and $E_b/N_o$, Here, the voice activity factor is assumed to be 3/8, the number of sectors in a cell 3 and Multi-User Iner- ference is modeled as Gaussian process.

• Journal of Communications and Networks
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• v.2 no.1
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• pp.76-84
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• 2000

Communication systems, including cell-based mobile communication systems, multiple satellite communication systems of multi-beam satellite systems, require reliable handoff methods between cell-to-cell, satellite-to-satellite of beam-to-team, respectively. Recent measurement of a CDMA cellular system indicates that the system is in handoff at about 35% to 70% of an average call period. Therefore, system reliability during handoff is one of the major system performance parameters and eventually becomes a factor in the overall system capacity. This paper presents novel and improved techniques for handoff in cellular communications, multi-beam and multi-satellite systems that require handoff during a session. this new handoff system combines the soft handoff mechanism currently implemented in the IS-95 CDMA with code and packet diversity combining techniques and an iterative decoding algorithm (Turbo Coding). the Turbo code introduced by Berrou et all. has been demonstrated its remarkable performance achieving the near Shannon channel capacity [1]. Recently. Turbo codes have been adapted as the coding scheme for the data transmission of the third generation international cellular communication standards : UTRA and CDMA 2000. Our proposed encoder and decoder schemes modified from the original Turbo code is suitable for the code and packet diversity combining techniques. this proposed system provides not only an unprecedented coding gain from the Turbo code and it iterative decoding, but also gain induced by the code and packet diversity combining technique which is similar to the hybrid Type II ARQ. We demonstrate performance improvements in AWGN channel and Rayleigh fading channel with perfect channel state information (CSI) through simulations for at low signal to noise ratio and analysis using exact upper bounding techniques for medium to high signal to noise ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.665-675
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• 2001

In this paper, the reverse link performance of a imperfect power controlled DS/CDMA cellular system that uses a base station array antenna which can effectively remove the multiple access interference is analyzed considering both beam forming algorithm and power control error in shadowing. The blocking probability of the DS/CDMA cellular system based on array parameters, $E_b/N_o$ and statistics of interference is derived, and then the system capacity corresponding to a certain blocking probability is calculated. On the assumption that the blocking probability is set 1%, the system capacity using MCGM algorithm with 12 antenna arrays is more increased maximum 32 times than that using a omni-directional antenna and about 2 times than that using MMSE algorithm, respectively.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.482-485
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• 2007

Recent generation of wireless computing has focus on the integrating of exisitng technologies to enhance the mobile capabilities and developing a new approaches to meet the needs of the growing pool of applications. This paper describes an integrated IEEE802.15.4 wireless CDMA based healthcare system that interacts and received the data wirelessly from wireless medical devices of patient and forward to medical center by using the cellular network. Mobile application had been developed not only as the middle ware to handle the receive and transmit of medical data between wireless sensor network and cellular network but also provides the interface for monitoring and analyzing the health condition of patients continuously at cellular phone regardless of its physical location. This system thus enables the remote healthcare monitoring and supports medical data seamlessly roams between IEEE802.15.4 wireless network and CDMA network beyond and outside the hospital environment.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.692-698
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• 1999

In this paper, we proposed the channel assignment scheme for the CDMA(Code Division Multiple Access) cellular system using power allocation concept. Also, the performance of the proposed scheme was analyzed and it was compared with the channel assignment scheme using the fixed power allocation method in the CDMA cellular system. The proposed scheme allocates the power adaptively in according to the traffic loads and the traffic distribution pattern of neighbor cells in the forward link. We found that total call blocking probability (Pr) is more dependent on blocking probability($P_B$) than outage probability (Po) under physical number of channels ($C_{th}$)=30. Pr(Call Blocking Probability) is dependent on $P_B$(Blocking Probability) and Po(Outage Probability) at the same ratio under $C_{th}$=32, in which case P$P_{TA}$(blocking probability for the adaptive power allocation) is greater than $P_{TF}$(blocking probability for the fixed power allocation) about 6%.

• The Transactions of the Korea Information Processing Society
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• v.7 no.5
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• pp.1500-1510
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• 2000

In this paper, a CDMA (Code Division Multiple Access) field engineering system is designed and implemented for managing cellular telecommunication base stations. For high quality of CDMA service, optimized cell planning is crucial. For such cell planning, base stations must be managed based on analysis of CDMA field dta. The proposed system consists of two modules: a measurement module and au analysis of CDMA field dta. eh proposed system consists of tow modules; a measurement module and an analysis module. The measurement module collects various CDMA field dta and displays them on a vector map in a real-time manner. The analysis module associates measured data with various related information, e.g. base station information, and process them statistically. The proposed system can drastically reduce base station management cost.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.3A
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• pp.334-341
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• 2000

This paper presents an analysis of the capacity, the interference of adjacent cells of a CDMA cellular system, depending on the soft handoff region and log-normal shadowing. The optimum soft handoff region is chosen by using Erlang capacity. It is shown that when the soft handoff region increases, the Erlang capacity increase due to a reduction of the interference power of adjacent cells. But if the region is increased above a certain value, there is no improvement in the system’s capacity. Furthermore as the standard deviation of the log-normal shadowing's normal distribution factor increases, the soft handoff region has to be increased linearly to achieve the same Erlang capacity.