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Signal Processing of WiMAX Physical Layer Based on Low-Density Parity-Check Codes
Chawalit Benjangkaprasert,Torpong Inchan 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
WiMAX technology supports very high data rate, high capacity and high quality in mobile broadband wireless access system. The performance of the WiMAX system can be enhanced by incorporating a better channel coding technique. This paper presents the excellent performance channel coding known as low-density parity check (LDPC) codes which is a part of WiMAX system. A modified array code parity check matrix for LDPC encoder is used and the message passing (MP) algorithm for LDPC decoder is used, respectively. Both systems are modulated by the basic standard modulation scheme. The computer simulation results confirm that the bit error rate (BER) performance of the WiMAX system that incorporate with the powerful LDPC coding technique has been improved over the conventional standard WiMAX system. However, the computational complexity of the proposed WiMAX system is higher than the previous one.
Variable Forgetting Factor RLS Algorithm for Adaptive Echo Cancellation
Sethaphak Sukhumalchayaphong,Chawalit Benjangkaprasert 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
Adaptive algorithms are widely used for support a wide range of applications. The attractive one application is an echo canceller in the long distance telephone network. The performance improvement of the echo cancellers depends on the choice of the adaptive filtering algorithm. Therefore, in this paper the variable forgetting factor recursive least squares (RLS) algorithm for adaptive lattice structure filter for the echo canceller in telephone network is presented. The proposed echo canceller provides high performance and low misadjustment in steady state for all considered noise distributions.
Controllable Band-Notched Slot Antenna for UWB Communication Systems
Weerathep Kueathaweekun,Noppin Anantrasirichai,Chawalit Benjangkaprasert,Jintana Nakasuwan,Toshio Wakabayashi 한국전자통신연구원 2012 ETRI Journal Vol.34 No.5
We propose a slot antenna consisting of a rectangular slot on the ground plane, fed by a microstrip line with a rectangular-ring-shaped tuning stub that can be deployed in ultra-wideband (UWB) communication systems to avoid interference with wireless local area network (WLAN) communication. Our antenna can achieve a single band-notched property from the 5 GHz frequency to the 6 GHz frequency owing to a controllable band notch that uses L- and J-shaped parasitic elements. The antenna characteristics can be modified to tune the band-notched property (4 GHz to 5 GHz or 6 GHz to 7 GHz) and the bandwidth of the band notch (1 GHz to 2 GHz). Furthermore, the shifted notch with enhanced width of the band notch from 1 GHz to 1.5 GHz is described in this paper. The UWB slot antenna and L- and J-shaped parasitic elements also provide the band-rejection function for reference in the WiMAX (3.5 GHz) and WLAN (5 GHz to 6 GHz) regions of the spectrum. Experiment results evidence the return loss performance, radiation patterns, and antenna gains at different operational frequencies.
Performance Analysis of Channel Effective for Wireless LAN and Wireless Ad-Hoc Networks
Auttapon Pomsathit,Jintana Nakasuwan,Aekkarat Lorphichian,Chawalit Benjangkaprasert 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
Wireless local area networks (WLANs) provide mobility and convenience to users, the efficiency of today"s WLANs are still far from satisfactory. In this paper discusses the performance of WLANs and wireless Ad-Hoc networks, our main contribution is analyze several methods to compare the throughput performance on simulation and experimental results. We describe NS-2 (Network Simulation) implementations for fine-tuning WLAN and wireless Ad-Hoc network parameters such as the physical layer (IEEE802.11) datalink layer (MAC) and network layer (Routing Protocol) related parameters. Customizing these parameters oppose to using the values specified in the standards will increase throughput and channel utilization under fixed load conditions.
Performance Analysis of Space diversity for OFDM transmission
Aekkarat Lorphichian,Auttapon Pomsathit,Jintana Nakasuwan,Thanupong Srikalsin,Chawalit Benjangkaprasert 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10
This paper presents a simple space diversity scheme for orthogonal frequency-division multiplexing (OFDM) transmission. Using multiple antenna technology provides the same diversity order as maximal-ratio receiver combining (MRRC). It is also shown that the scheme may easily be generalized to M transmit antennas and M receive antennas to provide a diversity order of 2M. We examine feasibility of several types of OFDM transmitter diversity techniques and generate data for the third-generation wireless systems. In particular, single input single output (SISO), single input multiple output (SIMO), multiple input single output (MISO), and multiple input multiple output (MIMO) techniques are compared. We employ the long range AWGN channel to enable transmitter diversity.