• ETRI Journal
• /
• v.20 no.1
• /
• pp.16-27
• /
• 1998

In this paper, we consider the acquisition performance of an IS-95 reverse link access channel slot as a function of system design parameters such as postdetection integration length and the number of access channel message block repetitons. The uncertainty region of the reverse link spreading codes compared to that of forward link is very small, since the uncertainty region of the reverse link is determined by a cell radius. Thus, the parallel acquisiton technique in the reverse link is more efficient than a serial acquisition technique in terms of implementation and of acquisition time. The parallel acquisition is achieved by a bank of N parallel I/Q noncoherent correlator are analyzed for band-limited noise and the Rayleigh fast fading channel. The detection probability is derived for multiple correct code-phase offsets and multipath fading. The probability of no message error is derived when rake combining, access channel message block combining, and Viterbi decoding are applied. Numerical results provide the acquisition performance for system design parameters such as postdetection integration length and number of access channel message block repetitions in case of a random access on a mobile station.

• Journal of the Korean Society of Visualization
• /
• v.5 no.1
• /
• pp.37-42
• /
• 2007

Reverse flow occurs in a channel when there is an obstruction at the entry. However it has been shown recently that reverse flow can be realized without an obstruction, by staggering the sides of the channel and placing it at an angle of attack to the oncoming flow. In this study the latter flow is computationally investigated. Studies have been carried out for different widths (gap between the two walls forming the channel), and at an angle of attack of 30. The results have captured all the essential features of this complex phenomenon and show the time dependent pumping mechanism which leads to the occurrence of reverse flow.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.22 no.3
• /
• pp.562-570
• /
• 1997

In Direct Sequence Code Division Multiple Access(DS/CDMA) communication systems, it is important to contraol the power of reverse link channel evenly for overall channel capacity. To control the reverse link powers efficiently, it is necessary to estimate signal quality of each reverse link channel. In this paper, we discuss a method to estimate the signal-to-noise ratio(SNR) for each channel by measuring the powers of pilot and noises. Computer simulations are done to show the effectiveness of the scheme.

• 한국가시화정보학회:학술대회논문집
• /
• 2006.12a
• /
• pp.11-16
• /
• 2006

Reverse flow occurs in a channel when there is an obstruction at the entry, However it has been shown recently that reverse flow can be realized without an obstruction, by staggering the sides of the channel and placing it at an angle of attack to the oncoming flow. In this study the latter flow is computationally investigated. And the mechanism is investigated using PIV (Particle Image Velocimetry) method. The results have captured all the essential features of this complex phenomenon and show the time dependent pumping mechanism which leads to the occurrence of reverse flow.

• 한국가시화정보학회:학술대회논문집
• /
• 2006.12a
• /
• pp.36-41
• /
• 2006

Reverse flow (i.e. flow in the direction opposite to the free stream) inside a channel occurs when an obstruction is placed at certain positions near the near to the channel, placed in another wider channel. In this paper the reverse flow in a duct (diameter D) with an obstruction at the front (which is a disc), is investigated using PIV. The gap g between the obstruction and the entry to the duct is systematically varied and it is found that maximum reverse flow occurs at a g/D value of 0.5. The flow is stagnant around g/D of 1.25 and forward flow occurs for g/D values of 1.5 and above.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.51 no.3
• /
• pp.99-104
• /
• 2002

lateral insulated gate bipolar transistors(LIGBTs) are extensively used in high voltage power IC application due to their low forward voltage drops. One of the main disadvantages of the LIGBT is its scow switching speed when compared to the LDMOSFET. And the LIGBT with reverse channel structure is lower current capability than the conventional LIGBT at the forward conduction mode. In this paper, the LIGBT which included p+ ring and p-channel gate is presented at the reverie channel structure. The presented LIGBT structure is proposed to suppress the latch up, efficiently and to improve the turn off time. It is shown to improve the current capability too. It is verified 2-D simulator, MEDICI. It is shown that the latch up current of new LIGBT is 10 times than that of the conventional LIGBT Additionally, it is shown that the turn off characteristics of the proposed LIGBT is i times than that of the conventional LIGBT. It is net presented the tail current of turn off characteristics at the proposed structure. And the presented LIGBT is not n+ buffer layer because it includes p channel gate and p+ ring.

• Journal of the Institute of Convergence Signal Processing
• /
• v.2 no.2
• /
• pp.55-61
• /
• 2001

In this paper, a synchronous reverse link DS-CDMA system with cdma2000 standard is simulated to analyze performance of system and to find the optimum power ratio between pilot channel and traffic channel. In the cdma2000 the pilot channel is used to estimate fading channel, in contract to IS-95 and it compensates phase variation of received signal due to channel environment. When the length of channel estimation is 31pcg symbols, we can find the optimum power ratio of pilot channel to traffic channel. And also we find Eb/No satisfying target FER when the power control is applied and analyze performance of system with multiuser transmission.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2000.05a
• /
• pp.222-225
• /
• 2000

In this paper, a synchronous CDMA system accepted for the cdma2000 standard is simulated to propose optimized reverse link power ratio and channel estimation lengths. Differently from IS-95, the pilot channel is used in the proposed system to estimate fading channel, so optimized estimation lengths are needed. Therefore, in this paper we analyze optimized estimation lengths which is needed to decide the power ratio of pilot channel and fundamental channel. From fixed estimation lengths, we calculate FER with various power ratio values.

• Proceedings of the IEEK Conference
• /
• 2000.07b
• /
• pp.982-985
• /
• 2000

This paper presents channel estimation of an asynchronous W-CDMA reverse link using the interpolation and moving average algorithm in frequency-selective Rayleigh fading channel. The proposed algorithm is an interpolated decision-directed (IDD) block-wise moving average (BWMA) algorithm. The IDD-BWMA algorithm performs two- stage processes. The first stage performs data decision to make a virtual pilot channel by using linear interpolation channel estimation scheme. Then, the second stage performs the channel estimation of the “block-wise moving average” type by using a virtual pilot channel obtained in the first stage. By using Monte-Carlo computer simulations, we show that the proposed channel estimator is superior to other estimation schemes such as the WMSA(K=1) and DD-RAKE at higher Doppler frequencies, especially.

• Journal of Mechanical Science and Technology
• /
• v.17 no.6
• /
• pp.879-887
• /
• 2003

The flow in a parallel walled test channel, when obstructed with a geometry at the entrance, can be forward, reverse and stagnant depending on the position of the obstruction. This interesting flow phenomenon has potential benefit in the control of energy and various flows in the process industry In this experiment, the flat plate obstruction geometry was used as an obstruction at the entry of the test channel. The parameters that influence the flow inside and around the test channel were the gap (g) between the test channel and the obstruction geometry, the length (L) of the test channel and the Reynolds number (Re). The effect of the gap to channel width ratio (g/w) on the magnitude of the velocity ratio (V$\_$i/ / V$\_$o/ : velocity inside/ velocity outside the test channel) was investigated for a range of Reynolds numbers. The maximum reverse flow observed was nearly 20% to 60% of the outside velocity for Reynolds number ranging from 1000 to 9000 at g/w ratio of 1.5. The maximum forward velocity inside the test channel was found 80% of the outside velocity at higher g/w ratio of 8. The effect of the test channel length on the velocity ratio was investigated for different g/w ratios and a fixed Reynolds number of 4000. The influence of the Reynolds number on the velocity ratio is also discussed and presented for different gap to width ratio (g/w). The flow visualisation photographs showing fluid motion inside and around the test channel are also presented and discussed.