• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제31권10A호
• /
• pp.982-987
• /
• 2006

In this paper, ranging code collision probability and ranging period which are two important performance measures for code division multiple access (CDMA)-type ranging in wireless broadband (WiBro) system are mathematically derived. Based on the analysis, the appropriate ranging management solution for maintaining the ranging collision probability below a certain threshold level and correctly recognizing the transmitted ranging code against propagation delay is obtained in terms of the number of ranging codes, the number of ranging regions, and ranging period. In this analysis, user mobility features such as speed and moving direction are also considered.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• 제37권1호
• /
• pp.32-43
• /
• 2000

In this paper, we investigate the existing medium access control (MAC) protocols to integrate the voice and data services in packet-based CDMA networks and furthermore, propose a new approach to circumvent the operational limits inherent in them. We propose the $P^2R$-CDMA (Prioritized Packet Reservation Code Division Multiple Access) protocol for the uplink in the synchronous multi-code CDMA system, which employs the centralized frame-based slot reservation along with the dynamic slot assignment in the base station using the QoS-oriented dynamic priority of individual terminal. The simulation results show that, as compared with the existing scheme based on the adaptive permission probability control (APC), the proposed approach can significantly improve the system capacity while guaranteeing the real-time requirement of voice service.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• 제27권3B호
• /
• pp.251-258
• /
• 2002

In this paper, an adaptive convolutional coding method in multicarrier direct sequence code division multiple access (DS/CDMA) systems is considered. In order to accommodate a number of coding rates easily and make the encoder and decoder structure simple, we use the rate compatible punctured convolutional (RCPC) code. To achieve maximum data throughput, an adaptive rate system based on the channel state information (the SINR estimate) is proposed. We show that the proposed adaptive rate convolution coded multicarrier DS/CDMA systems can enhance spectral efficiency and provide frequency diversity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• 제17권3호
• /
• pp.272-279
• /
• 2006

In this paper, we evaluate the performance of frame synchronization words of pilot bit patterns which are used for the channel estimation and frame synchronization confirmation in W-CDMA(Wide band Code Division Multiple Access) system. W-CDMA system also uses compressed mode to make measurements from another frequency without a full dual receiver terminal. It is confirmed by using computer simulation that the proposed frame synchronization words also maintain the frame synchronization property in the compressed mode by using the complementary mapping relationship of preferred pair ROC(Receiver Operating Characteristic) curves with probability of detection and false alarm are used to analized the performance of the proposed frame synchronization words by using the various detection metrics such as LLRT(Log Likelyhood Ratio Test), GLRT(Generalied Likelyhood Ratio Test), soft and hard correlation tests in AWGN and Rayleigh fading channels. It is expected that the research results fer the performance of pilot bit patterns of this paper can be useful reference for the design and implementation of frame synchronization in 3rd generation W-CDMA system.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• 제16권4호
• /
• pp.730-736
• /
• 2012

PN(Pseudo Noise) sequences play an important role in wireless communications, such as in a CDMA(code division multiple access) communication system. If there is a crash when multiple users simultaneously connected to a system, then PN sequences with low correlation help to minimize multiple access interference in such communication system. In this paper we propose a family of non-linear extended binary sequences with low cross-correlations and the family include $m$-sequence, GMW sequence, Kasami sequence and No sequence with optimal cross-correlation in terms of Welch bound. And we analyze cross-correlation of these sequences.

• ETRI Journal
• /
• 제19권1호
• /
• pp.1-12
• /
• 1997

In this paper, we present an improved multicarrier direct sequence (DS) code division multiple access (CDMA) scheme by modifying the system originally proposed by Kondo and Milstein [13]. In this modified system, different spreading sequences multiplied by a data sequence modulate different carriers. This is to prevent the multiple access capability from reducing when the fading characteristics of different carrier frequencies are highly correlated. We have derived a formula which determines the mean values of the relative received signal strength in a single carrier DS CDMA rake system and in a multicarrier DS-CDMA system. We present results on the comparison of the bit error rate (BER) performance of the two systems including the effect of correlation between fading characteristics of different frequencies under various multipath fading conditions. The results indicate that with 50 users the modified multicarrier DS CDMA system can achieve an uncoded irreducible BER of $1.7{\times}10^{-3}$ with an average received signal-to-noise ratio per bit of 10dB, which is better that $3.0{\times}10^{-3}$ achieved by the single carrier DS CDMA rake system, and also show that if multicarrier CDMA system is used with respect to single carrier CDMA system, the SNR gain is up to 4.5 dB for the uncode BER of $10^{-3}$ being achieved.

• ETRI Journal
• /
• 제27권3호
• /
• pp.273-279
• /
• 2005

Toward code division multiple access (CDMA) communications and data protection, we propose and analyze pseudorandom noise (PN) sequences generated from a 2-dimensional array structure of shift-registers. For any positive integers m and n, we construct PN sequences of period $2^{mm}-1$ using an $m{\times}n$ array of registers and show that we can generate all shifted PN sequences as required by IS-95x with the proper linear combination of available sequences.

• Proceedings of the IEEK Conference
• /
• 대한전자공학회 1998년도 추계종합학술대회 논문집
• /
• pp.63-66
• /
• 1998

MC-CDMA(Multi-Carrier Code Division Multiple Access) 시스템에서 전송 신호의 피크 전력 대 평균 전력(Peak-to-Average Power: PAP)율을 낮추는 방안을 제시한다. 확산 코드에 의해 결정된 각 부 캐리어의 위상 오프셋은 전송 신호의 복소 포락선 형성에 영향을 주게 되어 전송 신호의 PAP 율을 결정하게 된다. 따라서 각 부 캐리어의 위상 오프셋을 적절히 조정함으로써 PAP율을 낮출수 있다. 본 논문에서는 PAP 율을 감소시키는 부 캐리어 위상 오프셋 코드의 한 예를 제시하며, 모의 실험을 통하여 전송신호의 크기 분포 특성과 PAP 율의 감소를 확인한다.

• IE interfaces
• /
• 제17권4호
• /
• pp.466-471
• /
• 2004

In this paper, I develop a simple dynamic resource allocation algorithm that reduces the call blocking rate by improving the resource utilization of the WCDMA (Wideband Code Division Multiple Access) systems under multimedia service environment. Simulation results show that the proposed algorithm significantly reduces the blocking rate of high speed multimedia calls. The algorithm developed in this paper is currently working in the commercial WCDMA IMT-2000 system.

• Proceedings of the IEEK Conference
• /
• 대한전자공학회 1999년도 추계종합학술대회 논문집
• /
• pp.763-766
• /
• 1999

Direct-Sequence code-division multiple access(DS/CDMA) is considered by many to be a promising technology for future wireless communication networks. In this paper, we report new analysis for probability of BPSK CDMA hypothesis test in jointly distributed AWGN Rayleigh-fading received signal. In previous method, analysis is performed on AWGN or Rayleigh-faded signal in separately. In this paper, we propose model for hypothesis test system of the AWGN Rayleigh-faded received signal.