• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.5
• /
• pp.831-835
• /
• 2016

In this paper, a dual-channel feed-forward transimpedance(TIA) array is realized in a standard $0.18-{\mu}m$ CMOS technology which exploits automatic gain control function to provide 40-dB input dynamic range for either detecting targets nearby or sensing imminent danger situations. Compared to the previously reported conventional feed-forward TIA, the proposed automatic-gain-control feed-forward TIA(AFF-TIA) extends the input dynamic range 25 dB wider by employing a 4-level automatic gain control circuit. Measured results demonstrate the linearly varying transimpedance gain of 47 to $72dB{\Omega}$, input dynamic range of 1:100, the bandwidth of $${\geq_-}670MHz$$, the equivalent input referred noise current spectral density of 6.9 pA/${\surd}$HZ, the maximum sensitivity of -26.8 dBm for $10^{-12}BER$, and the power consumption of 27.6 mW from a single 1.8-V supply. The dual-channel chip occupies the area of $1.0{\times}0.73mm^2$ including I/O pads.

• International Journal of Contents
• /
• v.1 no.2
• /
• pp.31-34
• /
• 2005

The new realtime applications like multimedia and realtime services in a wireless network will be dramatically increased. However, many realtime services of mobile hosts in a cell cannot be continued because of insufficiency of useful channels. Conventional channel assignment approaches didn't properly consider the problem to serve realtime applications in a cell. This paper proposes a new realtime channel assignment algorithm based on time constraint analysis of channel requests. The proposed algorithm dynamically borrows available channels from neighboring cells. It also supports a smooth handoff which continuously serves realtime applications of the mobile hosts.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.43 no.5 s.347
• /
• pp.104-112
• /
• 2006

In this thesis, we analyze performance related to reduction scheme of intercell interference causing serious problems in wiBro system. Frequency reusing factor(FUF) is 1 in WiBro system, and it means that a adjacent cell uses same frequency band. This channel environment raises intercell interference problem, which provokes serious problems related to system performance and channel capacity. Consequently, it affects deterioration in system performance as a whole. We analyze intercell interference when appling a various schemes such as (DCA)Dynamic Channel Allocation, CS(Channel Segregation), IMUFR(Interference Mitigation Using Frequency Reuse), IDMA(Interleave Division Multiple Access), IDMA(Interleave Division Multiple Access), FH-OFDM, CRSA(Conceptual Random Subcarrier Allocation), and HDD

• Korean Journal of Materials Research
• /
• v.18 no.9
• /
• pp.507-510
• /
• 2008

Electrical properties of multi-channel metal-induced unilaterally precrystallized polycrystalline silicon thin-film transistor (MIUP poly-Si TFT) devices and circuits were investigated. Although their structure was integrated into small area, reducing annealing process time for fuller crystallization than that of conventional crystal filtered MIUP poly-Si TFTs, the multi-channel MIUP poly-Si TFTs showed the effect of crystal filtering. The multi-channel MIUP poly-Si TFTs showed a higher carrier mobility of more than 1.5 times that of the conventional MIUP poly-Si TFTs. Moreover, PMOS inverters consisting of the multi-channel MIUP poly-Si TFTs showed high dynamic performance compared with inverters consisting of the conventional MIUP poly-Si TFTs.

• The KIPS Transactions:PartC
• /
• v.11C no.2
• /
• pp.203-212
• /
• 2004

There is a rapidly growing demand for wireless telecommunication. The restricted number of channels is a significant bottleneck for the capacity of mobile communication systems. Consequently, when assigning the channels to the different base stations, it is desirable to reuse the same channel af much as possible. It is then important to avoid any possible interference between different mobile users, while satisfying the given demand. The objective of this thesis is to develop a hybrid heuristic algorithm to find the channel assignment method for allocating the channels in an efficient way, which does not violate the compatibility constraints. We also show several benchmarking channel assignment problems using proposed channel assignment method for validation in this thesis.

• Journal of Communications and Networks
• /
• v.10 no.1
• /
• pp.28-37
• /
• 2008

In this paper, we investigate the problem of minimizing the average transmission power of users while guaranteeing the average delay constraints in time-varying uplink channels. We design a scheduler that selects a user for transmission and determines the transmission rate of the selected user based on the channel and backlog information of users. Since it requires prohibitively high computation complexity to determine an optimal scheduler for multi-user systems, we propose a low-complexity scheduling scheme that can achieve near-optimal performance. In this scheme, we reduce the complexity by decomposing the multiuser problem into multiple individual user problems. We arrange the probability of selecting each user such that it can be determined only by the information of the corresponding user and then optimize the transmission rate of each user independently. We solve the user problem by using a dynamic programming approach and analyze the upper and lower bounds of average transmission power and average delay, respectively. In addition, we investigate the effects of the user selection algorithm on the performance for different channel models. We show that a channel-adaptive user selection algorithm can improve the energy efficiency under uncorrelated channels but the gain is obtainable only for loose delay requirements in the case of correlated channels. Based on this, we propose a user selection algorithm that adapts itself to both the channel condition and the backlog level, which turns out to be energy-efficient over wide range of delay requirement regardless of the channel model.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37C no.11
• /
• pp.1112-1128
• /
• 2012

In cognitive radio networks, secondary users are allowed to utilize the channels currently not occupied by primary users opportunistically. Secondary users can communicate with each other using the commonly available channels (common channels) which may change dynamically based on the activity of the primary users. Even though many studies have dealt with cognitive radio behaviors, the detailed procedures for common channel configuration have not been paid much attention. In this paper, the fast and reliable dynamic common channel setup and reconstruction method for the point-to-point communications in military cognitive radio networks is proposed. The detailed time parameters are considered for common channel setup and reconstruction, such as the packet exchange time, channel request waiting time, and rendezvous time. Through numerical analyses, the delay and throughput performance of the proposed method is derived and evaluated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.1A
• /
• pp.58-64
• /
• 2009

In this paper, we propose an dynamic random channel allocation scheme increasing probability of channel acquisition and reducing delay by limiting the number of minimum RCHs(Random CHannels) as an optimal factor $\beta$. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD and MT(Mobile Terminal) can obtain chance of traffic transmission through channel competition in RCH period. And AP(Access Point) can dynamically schedule the number of RCHs based on the number of the collision in each RCH of the previous frame. Therefore, the proposed scheme increases a probability of channel acquisition and reduces delay by means of guaranteeing the number of minimum RCHs. With a practical Internet traffic, it is concluded that by the proposed scheme the delay reduction of the order of 19% and slightly better throughput are obtained compared to the conventional algorithm.

• Proceedings of the Korean Information Science Society Conference
• /
• 2012.06d
• /
• pp.262-264
• /
• 2012

Dynamic spectrum access and cognitive radio is a viable solution to solve congestion in ISM band. The dynamic environment of multi-channel wireless LAN is modeled by using continuous time Markov process. Bayes theorem is applied to infer channel access decisions dynamically to ensure current data transmission is switched to only likely candidate channels.

• Proceedings of the IEEK Conference
• /
• 2002.06d
• /
• pp.13-16
• /
• 2002

This paper presents a new baseband modulation system for the reception improvement of VSB system in dynamic multipath channel. By introducing the 1/2 Trellis Coded Modulation in baseband modulation, the TOV of proposed modulation is improved very much compared with 8-VSB modulation and better than the pseudo 2-VSB modulation of Philips which is the most robust modulation for VSB transmission system as far. Through the computer simulation, the performance of the proposed modulation is examined and the results are shown.