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This paper describes low power architecture by using a dynamic wordlength technique in wireless orthogonal frequency division multiplexing (OFDM) system. The number of wordlength in digital signal processing (DSP) has to be carefully determined because wordlength affects system performance and hardware cost. Dynamic wordlength technique is applied to a fast Fourier transform (FFT) processor and a...
This paper presents a baseband and RF transceiver at 5.2-GHz band for wireless LAN systems. The baseband unit supports 2×2 MIMO-OFDM with an 80-MHz channel and provides the maximum data rate of 600 Mbps. The wider channel of 80 MHz is a candidate technology for the next WLAN standardization of IEEE802.11ac. OFDM tends to cause high peak PAPR for the wider channel and distort power amplifier performance...
This paper presents a new partial transmit sequence (PTS) technique. It is used to effectively reduce the peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) technology and is implemented to solve the PAPR problem in the multiple-input/multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) technology. To achieve better PAPR performance, a quite large...
The IEEE802.11ac task group has started to establish a next-generation WLAN standard. The wider channel of more than 80 MHz achieving over a 1-Gbps data rate is discussed. We have developed an experimental platform consisting of baseband and RF units in a 2×2 MIMO-OFDM system for the wider channel and evaluated its system performance in a field experiment. A MIMO-OFDM transceiver in the baseband unit...
Wordlength determination is a crucial task in digital hardware implementations for green computing because the wordlength affects power consumption and system performance. Digital hardware requires careful wordlength design for a sufficient dynamic range. Nevertheless, wordlength can be reduced during better conditions. We present a modeling approach for dynamic variable wordlength (DVW) in digital...
In this paper, we propose a new PAPR reduction using the hybrid of a partial transmit sequences (PTS) and cascade adaptive peak power reduction (CAPPR) methods with genetic algorithm (GA). These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average...
MIMO-OFDM performs signal detection on subcarrier-by-subcarrier basis and increases its computational complexity. A complete pipeline MMSE detector meeting requirements for a high throughput has been presented in our previous work, which provides real-time processing even for large numbers of subcarriers. However, it requires large circuit scale and tends to be excessive for small numbers of subcarriers...
The orthogonal frequency division multiplexing (OFDM) is one of the promising technologies to improve the spectral efficiency, enhance system capacity and mitigate inter-symbol interference in the wireless communication system. In this paper, we aim at the study on adaptive modulation and coding technologies for wireless system over frequency selective fading channel. This adaptive allocation algorithm...
This paper proposes a blind modulation detection technique for adaptive orthogonal frequency division multiplexing (adaptive OFDM) communications. Adaptive modulations are applied to improve communication performance in OFDM over complicated multi-path fading channels. This paper proposes a new method which reduces detection errors in blind modulation and improves communication throughput in adaptive...
In this paper, we propose a new PAPR reduction by using the hybrid of partial transmit sequences (PTS) and cascade adaptive peak power reduction (CAPPR) methods with coded side information (SI) technique design by genetic algorithm (GA). These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers...
This paper presents a new design method for reducing power dissipation of Viterbi decoder using variable wordlength architectures in wireless bit-interleaved coded modulation and orthogonal frequency division multiplexing (BICMOFDM) systems. The proposed method observes wireless communication quality and adjusts a wordlength in order to keep a desirable PER. Two types of the Viterbi decoder are used...
Digital circuit designs in sub-threshold region have been studied in recent years. Their works focus on special purpose for some digital applications in low frequency. This paper proposed modeling analysis of each CMOS logic cell operating at sub-threshold region. We explore the delays and power dissipation of logic cell and make scaled factors mapping from typical voltage to sub-threshold voltage...
In this paper, we propose a new PAPR reduction using the hybrid of a partial transmit sequences (PTS) and an adaptive peak power reduction (APPR) methods with genetic algorithm (GA). These methods are used in an Orthogonal Frequency Division Multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large Peak to Average Power...
VLSI implementation for a 4times4 multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) transceiver is described that targets 1-Gbps data transmission for next-generation wireless LAN systems. The IEEE802.11 Very High Throughput (VHT) Study Group concluded that a signal bandwidth of more than 80 MHz is needed to achieve 1-Gbps throughput in the MAC layer. The proposed...
The changes of surrounding wireless environments have impact on communication quality. Cognitive radio is an attractive technique to follow such changes while classical fixed radio suffers from differences between supposed and actual communication environments. This paper attempts a new concept in OFDM cognitive radio and proposes an environment-adaptive agent system that finds appropriate communication...
This paper presents a new study over logics circuit operation in subthreshold and threshold region. CMOS circuit model operation logic will make deep primary reference for this study. This new research presses low voltage features to circuit stated. By using profoundest results of the study, we will develop FFT processor designs as an example of digital wireless circuits. The FFT processor can operate...
In this paper, we propose a new PAPR reduction by using a partial transmit sequences (PTS) method with coded side information (SI) technique. These methods are used in an orthogonal frequency division multiplexing (OFDM) system. The OFDM employs orthogonal sub-carriers for data modulation. These sub-carriers unexpectedly present a large peak to average power ratio (PAPR) in some cases. In order to...
This paper presents a VLSI architecture of a 4 times 4 MIMO-OFDM transceiver for over 1-Gbps data transmission in forthcoming wireless LAN systems. The IEEE802.11n draft provides date rates of up to 600 Mbps. The IEEE802.11 VHT Study Group considers a signal bandwidth of more than 80 MHz to achieve 1-Gbps throughput in MAC layer. The presented architecture focuses on the VLSI implementation of these...
In this paper, the evaluation and the implementation of quasi-cyclic LDPC (QC-LDPC) codes in MIMO-OFDM systems are presented. QC-LDPC has comparative error correcting performance with random irregular LDPC and considerably reduces complexity. We evaluate communication performance of the QC-LDPC coded system based on the IEEE802.11n standard in a 4 times 4 MIMO scheme. In the LSI implementation, we...
This paper presents a VLSI architecture of MMSE detection in a 4 x 4 MIMO-OFDM receiver. Packet-based MIMO- OFDM imposes a considerable throughput requirement on the matrix inversion because of strict timing in frame structure and subcarrier-by-subcarrier basis processing. Pipeline processing oriented algorithms are preferable to tackle this issue. We adopt Strassen's algorithms of matrix inversion...
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