• Proceedings of the IEEK Conference
• /
• 2002.06a
• /
• pp.77-80
• /
• 2002

In this paper, we analyze a physical layer of W-CDMA .system and design a transmitter and receiver by using ADS (Advanced Design System). Also, we simulated a link level performance with different channel estimation algorithm in Jakes fading channel environment. For the channel estimator, we used the WMSA(Weighted Multi-Slot Averaging) algorithm, EGE(Equal Gain Estimation) algorithm and SSE(Symbol-to-Symbol Estimation) algorithm. This study will be useful in the analysis and design of W-CDMA system.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9A
• /
• pp.722-728
• /
• 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 = $10^{-3}$.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.24 no.6A
• /
• pp.767-774
• /
• 1999

In this paper, we compare the performance of asynchronous W-CDMA system with different bandwidth. We take into consideration of wideband multipath channel environment which consists of discrete multipath components whose strength is Rayleigh distributed. Each CDMA system different bandwidth experience different effects of multipath because there are different number of multipath within one chip duration according to the spreading bandwidth. We derive the average error probability versus the capacity, and compare the capacity of W-CDMA systems using the RAKE receiver with EGC diversity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.9
• /
• pp.2035-2042
• /
• 1997

We consider the design of soft decision functions for each stage of multistage detection for coherent demodulation in an asynchronous code-division multiple-access(CDMA) system. In particular, the sigmoid function, which is shown to be optimal under the mean square error(MSE) criterion, andmultilevel quantizers that best approximate the sigmoid function are derived. At each stage of multistage detection, the parameters of these decision functions are adjusted depending on estimated input statistics. Computer simulation results demonstrate that multistage detectors employing these soft decision functions perform considerably better than those with hard decision.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.5B
• /
• pp.608-614
• /
• 2001

본 논문에서는 비동기 CDMA 시스템에서 다중 접속 간섭의 영향을 줄이기 위해 제안된 역상관기 중에서 반복연산을 사용하여 계산량을 개선한 반복적 역상관기의 수렴특성에 대하여 분석하였고 이를 모의 실험을 통하여 검증하였다. 반복적 역상관기에서 수렴특성을 결정하는 수렴 인자를 유도하였고, 가장 빠른 수렴 특성을 보장하는 최적의 수렴 상수를 상관행렬의 최대 및 최소 고유값으로 나타낼 수 있음을 증명하였다. 또한 반복 과정의 중간 결과에 대한 최대 오차 범위를 유도하였다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.3C
• /
• pp.228-236
• /
• 2006

A Multicarrier code division multiple access(MC-CDMA) is a scheme that combines multicarrier modulation with CDMA. It offers robustness to frequency selective fading effect and can support higher rate data transmission with higher spectral efficiency. The objective of this article is proposed and analyzed a new asynchronous MC-CDMA system with various kinds of data rates which employs a multiple access interference (MAI) canceller. The proposed multirate MC-CDMA system can be accomplished by changing the number of Parallel branch(P) according to their data rate and hybrid interference canceller(HIC) are used for MAI cancellation. We compare the performance of proposed system in terms of average bit error rate(BER) with that of a single rate MC-CDMA system. The results show the large improvement in performance that can be attained by the cancellation scheme under multipath environments.

• Journal of Korea Society of Industrial Information Systems
• /
• v.10 no.1
• /
• pp.1-8
• /
• 2005

Multicarrier code division multiple access(MC-CDMA) Is a scheme that combines multicarrier modulation with CDMA. It offers robustness to frequency selective fading and can support higher rate data transmission with higher spectral efficiency. The objective of this article to proposed a new asynchronous ME-CDMA system to implement multiple data rate communications. It can be accomplished by changing the number of parallel branch(.p). For the analysis of average BER performance, numerical method and computer simulation were used. After MAI power of received signal calculated, the average BER can be acriuired using Gaussian approximation to MAI. We also compare the system performance with that of a single rate MC-CDMA system.

• ETRI Journal
• /
• v.29 no.2
• /
• pp.143-152
• /
• 2007

In this paper, we propose a time-varying modified minimum mean-squared error (MMSE) detector for the detection of higher data rate signals in a multirate asynchronous code-division multiple-access (CDMA) system which is signaled in a fast Rayleigh fading channel. The interference viewed by a higher data rate symbol will be periodic due to the presence of a lower data rate symbol which spans multiple higher data rate symbols. The detection is carried out on the basis of a modified MMSE criterion which incorporates differential detection and the ratio of channel coefficients in two consecutive observation intervals inherently compensating the fast variation of the channel due to fading. The numerical results obtained by the MMSE detector with time-varying detection show around 3 dB (M=2) and 6 dB (M=4) performance improvement at a BER of $10^{-3}$ in the AWGN channel, while introducing more computational complexity than the MMSE detector without time-varying detection. At a higher $E_b/N_0$, the proposed scheme can achieve a BER of approximately $10^{-3}$ in the presence of fast channel variation which is an improvement over other schemes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.11C
• /
• pp.1059-1065
• /
• 2007

In this paper, we propose a class of polyphase signature sequences, whose general odd correlation properties are useful for M-ary phase signaling systems. The maximum magnitude of the general odd correlation functions of the proposed sequences are investigated and compared with those of FZC (Frank-Zadoff-Chu) sequences and those of EOE (equivalent odd and even correlation) sequences. The performance of the asynchronous M-ary phase signaling systems using the proposed sequences is simulated and compared with that using FZC sequences in direct sequence code division multiple access (DS/CDMA) systems. The performance of the system using the proposed sequence is shown to be better than that using FZC sequences when the multipath fading is in existence.

• Proceedings of the IEEK Conference
• /
• 2000.06a
• /
• pp.61-64
• /
• 2000

In this paper, we design up-down converter for asynchronous IMT-2000 base station using W-CDMA(Wideband Code Division Multiple Access) technology. This up-down converter(UDC) has AGC (Automatic Gain Control), TPTL(Transmitting Power Tracing Loop), RSSI(Received Signal Strength Indicator) function. And for the cell control of BS(Base Station), breathing, blossoming, wilting function also available. This UDC has diversity structure for better performance.