• ETRI Journal
• /
• v.30 no.4
• /
• pp.495-505
• /
• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39C no.9
• /
• pp.870-879
• /
• 2014

In this paper, we propose an initial timing acquisition algorithm for terrestrial cloud transmission (CTxn) systems. By combining auto-correlations of several repetition patterns within preamble symbols, the proposed scheme can improve the reliability of the timing metric for CTxn system with co-channel interferences. Simulation results show that the proposed scheme improves the reliability of the timing metric for terrestrial CTxn systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.5
• /
• pp.493-502
• /
• 2009

In this paper, we compare the performance of initial timing acquisition in direct sequence ultra-wideband(DS-UWB) systems with different transmit pulse shaping filters through extensive computer simulations. Simulation results show that the timing acquisition performance of the DS-UWB system, whose chip rate is 1.32 Gchip/s, employing a rectangular transmit filter is similar to that employing a square root raised cosine(SRRC) filter with an interpolation factor of 4 in the realistic UWB channels(CM1 and CM3) as well as the additive white Gaussian noise(AWGN) channel. Additionally, we present both a 24-parallel digital correlator structure and a 24-parallel processing searcher operating at a 55 MHz system clock, and then briefly discuss the initial timing acquisition procedure. Because we can adopt an 1.32 Gsample/s digital-to-analog(D/A) converter and an 1.32 Gsample/s analog-to-digital(AID) converter in the DS-UWB system by employing the rectangular transmit filter, we have a realistic solution for the DS-UWB chipset development.

• ETRI Journal
• /
• v.29 no.5
• /
• pp.596-606
• /
• 2007

It is well known that an OFDM receiver is vulnerable to synchronization errors. Despite fine estimations used in the initial acquisition, there are still residual synchronization errors. Though these errors are very small, they severely degrade the bit error rate (BER) performance. In this paper, we propose a residual error elimination scheme for the digital OFDM baseband receiver aiming to improve the overall BER performance. Three improvements on existing schemes are made: a pilot-aided recursive algorithm for joint estimation of the residual carrier frequency and sampling time offsets; a delay-based timing error correction technique, which smoothly adjusts the incoming data stream without resampling disturbance; and a decision-directed channel gain update algorithm based on recursive least-squares criterion, which offers faster convergence and smaller error than the least-mean-squares algorithms. Simulation results show that the proposed scheme works well in the multipath channel, and its performance is close to that of an OFDM system with perfect synchronization parameters.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.7A
• /
• pp.733-742
• /
• 2008

In 3GPP LTE downlink system, initial cell search is essential for mobile station to connect to base station. In order to obtain information of the base station, the mobile station detects frame timing, frequency offset, and cell identification using primary synchronization channel(PSC) and secondary synchronization channel(SSC), which are defined in downlink OFDMA specification. In this paper, we analyze various detection algorithms in practical environment of inter-cell-interference, frequency offset, and multi-path fading channel and propose the optimal algorithm. Simulation results show that partial correlation method (for PSC acquisition) and interference cancellation method (for SSC detection) are the most superior algorithms among the applicable algorithms. Employ these two algorithms for receiver design, initial cell search is performed with 99% probability within 70ms in the channel environment considered.

• Journal of The Korean Society of Emergency Medicine
• /
• v.29 no.6
• /
• pp.624-635
• /
• 2018

Objective: This study examined whether emergency department (ED) crowding influences the timing of the initial assessment and treatment in severe trauma patients, as well as their mortality rates. Methods: This retrospective, observational study was conducted between January 2015 and October 2016, and included adult severe trauma patients who presented to the ED. The emergency department occupancy rate (EDOR) was used to measure ED crowding. The patients were divided into four groups using the EDOR quartile. The timeliness of the initial assessment and treatment in the four groups as well as the mortality rates were compared. Results: This study investigated 307 patients. The timing of the first computed tomography (CT) and laboratory test order, CT and laboratory test result acquisition, first transfusion, and patient transfer from the ED to the operating room were similar in the four groups. Multivariable logistic regression analysis did not show a significant difference in mortality between the groups. Conclusion: ED crowding was not associated with delays in the initial assessment and treatment of severe trauma patients, or in their mortality rates.