In recent years, high-definition video content such as YouTube and Netflix has become an integral part of our lives, increasing the demand for wireless transmission of 4 K and 8 K images with high quality. Consequently, many technical papers have proposed systems for high-quality video transmission. However, most of these systems extend international standards, making implementation difficult. Therefore, in this paper, we construct a system compliant with IEEE 802.11ac/ax/be standards using a multi-scalable image transmission system. The multi-scalable image transmission system enables high-quality image transmission by structuring packets so that layers ordered by their contribution to image quality in JPEG 2000 can be sent to Sub STAs with larger channel capacities. By configuring the receiver using multiple Sub STAs, data with different contributions to image quality can be transmitted using the multi-user functionality of IEEE 802.11ac/ax/be standards. As a result, the MIMO system using multi-scalable image transmission can achieve high-quality communication without extending the IEEE 802.11ac/ax/be standards.

Self-interference cancellation is an important technology to achieve full-duplex communication. The self-interference (SI) signal in IEEE 802.11 networks can be suppressed using Joint Transmission (JT) with null beamforming. This method requires a weight matrix that is obtained from the Channel State Information (CSI). However, JT requires very tight synchronization between multiple access points (APs). Since multiple APs run on different clock sources, offsets between APs might occur, making it difficult to cancel the SI signal. In this paper, we evaluate the SI cancellation of JT with null beamforming when an atomic clock is used in our simulation model. Our results show that SI cancellation with an atomic clock can have results similar to the ideal condition (i.e., the same external clock source is applied to all APs).

Recently, the Wi-Fi human activity recognition (HAR) system has attracted attention, using channel state information (CSI). CSI is a characteristic that indicates the radio propagation environment from transmitter to receiver, indoor environment. Therefore, sensing technology that predicts the indoor environment by calculating backward from the CSI is being considered. We first analyzed CSI in the time direction using singular value decomposition (SVD). In addition, a long short-term memory (LSTM) is applied to the obtained features to classify Absence/Presence. Furthermore, we implemented this system, where software-defined radio (SDR) receiver and common commercial wireless access point.

Rate adaptation algorithm has an important role in the Wi-Fi network. It ensures that the nodes transmit at a suitable transmission rate with minimum packet errors on the receiving side. However, there are cases when the existing algorithms fail to adapt to the changes in the communication environment. In this paper, we propose a rate adaptation algorithm using a Deep Q-network (DQN), in which the DQN agent controls the transmission rate of a node in response to the communication environment. We also evaluate the proposed algorithm using the field-programmable gate array (FPGA) and software-defined radio (SDR). The experimental result shows that the proposed algorithm can adaptively select the suitable MCS and maintain the throughput.

In this paper, an industrial wireless LAN including a Media Access Control (MAC) layer and a Physical (PHY) layer based on the industrial communication standard is described. The hardware implementation is processed on Software Defined Radio (SDR) platform which provides fast processing for the hardware and software co-design. The experimental results show that the proposed wireless system can control up to four motors with 500 us to 750 us per motor which has a lower transmission time compared to PROFINET wireless standard. On the other hand, the high reliability of this system is also considered in this paper. It is important to formulate the communication error rate because it takes a long time to verify by the simulation. We need to investigate a quantitative evaluation method from the formulation of the communication error rate and evaluate the reliability of the system. This paper shows the evaluation results that reliability can be guaranteed even after three years of operation by performing at least one re-transmission time of the system which is suitable to the industry wireless communication standard.

We demonstrate a self-interference (SI) cancellation in cooperative multiple-input multiple-output (Co-MIMO) for full-duplex (FD) wireless communication systems by applying the block diagonalization used in multi-user MIMO. The proposed method's implementation uses a field-programmable gate array (FPGA) and software-defined radio (SDR). In the experiment, a total of 33 [dB] SI can cancel with two cooperative APs and two antennas per AP in the IEEE 802.11 system.

In this paper, we propose self-interference (SI) cancellation in cooperative multiple-input multiple-output (Co-MIMO) for full-duplex (FD) wireless communication systems. This proposal solves SI by applying the block diagonalization used in multi-user MIMO. Therefore, there is no need for a radio frequency (RF) canceller, which has a large hardware (HW) size and is difficult to extend to MIMO. Furthermore, we can achieve higher throughput by applying Co-MIMO, in which multiple access points (APs) work together to communicate. The proposed method's implementation uses field-programmable gate array (FPGA) and software-defined radio (SDR). In the experiment, a total of 33 [dB] SI can cancel with two cooperative APs and two antennas per AP in the IEEE 802.11 system.

In this paper, we propose a hardware development of a high accuracy Precision Time Protocol (PTP) on Software Defined Radio (SDR) for Industrial WLAN systems. To increase the throughput of the transmission system, we propose a low overhead 3-frames exchange PTP instead of 4-frames transmission as IEEE 1588 PTP protocol. Besides, our hardware-software co-design of the full SoC MAC-PHY can select the PTP timestamp point to remove the random transmission jitters caused by higher layers and the imbalanced timing made by the rugged hardware designs between master and slave. In previous work, the PTP synchronization has been evaluated on the M820-ZYNQ platform with Dummy PHY. In this paper, the proposed PTP system is developed on the SDR platform with real PHY. The SDR platform can reduce the processing delay between software and hardware compared to the previous platform. The result of our demonstration experiments shows that an oscilloscope captures the time synchronization of the proposed system in high accuracy with the nano-second level, which is less than 200 ns.

The Markov chain based model by Bianchi for IEEE802.11 distributed controlled access is a highly accurate analytical tool for estimating the system throughput when a single Basic Service Set (BSS) network operates in isolation. However, with the increase of wireless LAN access points being deployed on the same area, an environment with multiple BSS interfering with each other has become the default network scenario. The purpose of this work is to extend the single BSS Markov chain model into a multi-BSS model by incorporating the influence of STAs' interference range and carrier sense range to their own transmission and collision probabilities. We verify the proposed multi-BSS analytical model using the latest version of the ns-3 simulator which has recently supported accurate PHY abstractions for multi-BSS simulation. We show that the proposed model has a high accuracy (within 1%) independent of the multi-BSS network topology.

In this paper, we propose a design of asynchronous communication for an industrial wireless LAN system. In our design, MAC is synchronous multi-user round-robin transmission protocol. Low overhead Packet Division Multiple Access scheme is utilized for Multi-user Downlink transmission up to 80 MHz, while Frequency Division Multiple Access is employed for the uplink transmission. The designed of PHY system is developed based on a fast and deterministic communication featuring the synchronous multi-user system. In this paper, the industrial robots are not only controlled by synchronous communication but also by asynchronous communication via our industrial WLAN (iWLAN) system. This paper presents the hardware and software cooperative design. In the verification, up to 10 motors can be controlled by our iWLAN system by asynchronous communication, and the delay of each robot measured is 188 μs on average. Besides, the time synchronization captured by oscilloscope is from 40 to 100 ns as in our target.

We demonstrate a precision time protocol (PTP) used to synchronize clocks in industrial wireless local area network (iWLAN) communication systems. The implementation of the system on FPGA boards for accurate verification and to test the feasibility of the system in a real environment. The result has been confirmed that time synchronization is high accuracy from 40 to 100 ns.

Currently, Global Positioning System (GPS) is widely used as a representative position estimation system. However, GPS suffers from poor position estimation accuracy in an indoor environment. Moreover, time synchronization between devices needs to be performed for position estimation which is a resource intensive process. In previous studies, an asynchronous protocol (i.e., no synchronization requirement) called Grid Search was proposed to handle this problem. However, this method also has high complexity and takes a lot of search time to estimate the position. In this paper, we propose a method to narrow the search range using intersecting chord under the condition that generated circles intersect with each other. The proposed position estimation method has low complexity but can achieve accuracy comparable to Grid Search, i.e., a maximum estimation error less than 2 meters with 80% of the trials are within 1 meter. In addition, the calculation time can be reduced up to 6 times compared to the Grid Search when the search range extends to 5 times.

Image and video transmission is highly expected to proliferate with the wide spread of Wi-Fi devices and the introduction of multiple-input multiple-output (MIMO) systems. This paper proposes a novel precoder for video transmission in overloaded MIMO systems, which is based on an eigenbeam space division multiplexing (E-SDM) technique. This paper also proposes a low complexity postcoder, which detects some of data symbols by a linear approach and the others by a prevoting vector cancellation (PVC) approach. It is shown from simulation results that the proposed precoder and postcoder achieve 40 dB in peak signal-to-noise ratio while reducing the computational complexity by over 61 compared to the conventional PVC-based detection when received signal-to-noise ratio is higher than 10 dB.

Interleave division multiple access (IDMA) is a potential candidate for the future fifth generation (5G) systems. In this paper, we propose a novel architecture for IDMA system with low latency while maintaining low complexity. In the conventional architecture, the IDMA receiver sequentially processes deinterleaving, despreading, spreading and interleaving for multiuser detection. The proposed architecture, which is called the interleaved domain, can perform multi-user detection directly without deinterleaving the received frame. Because of this, the interleaving is no longer needed in the interference cancellation loop resulting in the decrease of latency by half and the increase of throughput by twice. In VLSI implementation results, the proposed architecture has reduced circuit area and power consumption by 53% and 58% compared to the conventional architecture on the same throughput condition.

This paper proposes a design of wireless communication system, particularly physical layer system (PHY) for Factory Automation (FA) system based on Wireless Local Area Network (WLAN) communication system. The designed PHY system is developed based on a fast and deterministic communication featuring a synchronous multi user round robin transmission protocol. Low overhead Packet Division Multiple Access (PDMA) scheme is utilized for Multi-user Downlink transmission, while the Frequency Division Multiple Access (FDMA) is employed for the uplink transmission. For efficient PHY implementation, several approaches on architectural aspects are also introduced. Implementation results show that the optimized design of transmitter and receiver have efficient logic resource while maintain required processing speed and error performance.

For the last decades, the advancement of system on chips complexity and size are driving the verification process of the digital designs to be much more complicated and time consuming. Moreover, nowadays, the verification process takes up to 80% of overall design development time. This paper emphasizes the importance of automatic testbench generator for industrial wireless local area network (iWLAN) for factory automation system (FA). The proposed generated testbench is written in SystemVerilog to represent the functions and to reduce the code size compared to traditional Verilog testbench. It is also supported by assertion-based method to simplify the code and to improve the observability in SoC verification. Experimental results show that our proposed method produces smaller code size and can improve the efficiency of the verification of SoC designs. Moreover, we shows the verified iWLAN system data transfer.

This paper proposes a 4×4 MU-MIMO channel emulator with automatic channel sounding feedback used for beam-forming and MU-MIMO precoding features of IEEE 802.11ac. The main contribution of this paper is the design of a MU-MIMO channel emulator capable of sending channel feedback automatically to the AP from the generated channel coefficients after a programmable time duration. This function helps to evaluate the precoding algorithms without channel estimation error and uses very minimal MAC features. The second contribution is the design of single path implementation with serial processing which plays an important role on reducing the hardware complexity. The design choice makes it possible to generate channel coefficients for very high sampling rate systems with little increase in complexity. In addition, single path implementation allows the addition of the feedback channel output with only few additional nonsequential elements which would otherwise double in a parallel implementation. To demonstrate the functionality of our MU-MIMO channel emulator, we present actual hardware emulator results of precoded receive signal constellation on oscilloscope.

In this work, an industrial Wireless Local Area Network (iWLAN) system used to control industrial robots (iRBs) in factory automation (FA) environments is addressed. For fast and deterministic communication, we propose a synchronous multi-user round-robin transmission protocol. To reduce the overhead caused by the conventional multiple downlink access, we also propose a low overhead Packet Division Multiple Access (PDMA) technique. The analysis and simulation results show that our proposals provide 100% and 300% better throughput than the conventional industrial Point Coordination Function (iPCF) and Space Division Multiple Access (SDMA) protocol schemes, respectively. In particular, with the control duration per iRB of being better than 100 μsec, the proposal completely satisfies the demand for fast control of FA systems. Furthermore, the hardware architecture of MAC layer of iWLAN system is also proposed and designed to successfully implement the proposed protocol.

Transceiver hardware impairments are the distortion noise sources that can degrade performances of wireless systems. In this paper, we analyze the impacts of hardware impairments on outage performance and throughput of the cognitive relay networks with amplify-and-forward (AF) and decode-and-forward (DF) relaying protocol under the transmit power limit constraint. We derive the exact expressions that quantify the impacts of transceiver hardware impairments on outage performance and throughput of the networks and corroborate the results by simulation. It is shown that the impacts of transceiver impairments are nonlinear and increase proportional to the increment of hardware impairment levels. Interestingly, we found that the cognitive relay networks with AF protocol is more susceptible to transceiver hardware impairments than the DF protocol. Consequently, the DF cognitive relay networks provide better outage performance and throughput than the AF cognitive networks in the same specific parameters.

This paper proposes a hardware architecture of K-best-based 4 × 4 MIMO decoder that supports up to 256-QAM. The novelties such as Direct Expansion, and 2D Sorter play important roles on reducing the complexity of the decoder. In addition, the most complex operators such as divider and multiplier are eliminated in this design. As compared to the previous works, the proposed decoder achieves the highest throughput (up to 2.7 Gbps), consumes the least power (56 mW), and obtains the best hardware efficiency(15.2 Mbps/Kgate).

Designing an efficient MIMO decoder for higher order MIMO system such as 8×8 is a big challenge. The Group Detection (GD) method has been considered as a good choice because it balances well the trade-off between detection accuracy and computational complexity. This method converts the higher order MIMO channel matrix into several lower order matrices and then decodes these lower order matrices separately. In another aspect, a Multi-User MIMO (MU-MIMO) system commonly requires a pre-coding such as Block Diagonalization (BD) to eliminate the inter-user interference (IUI). In this paper, we show that a MU-MIMO system can reuse the BD pre-coding at the transmitter to perform the GD at the receiver for reducing the complexity. To improve the performance, a Group Selection (GS) method should be used before doing GD. While the optimal GS method achieves high performance, its complexity is too high for real applications. For balancing the complexity-performance trade-off, we propose an Averaged Log Likelihood Ratio Group Detection (A-LLR-GD) in this paper. The packet error rate (PER) and Bit Error Rate (BER) simulation results on IEEE 802.11ac simulator show that our proposed one achieves higher performance with low increase in computational complexity as compared to the conventional works.

Although the K-best algorithm is well-known as an efficient suboptimal version of the maximum likelihood detection (MLD), its complexity is still significantly affected by the constellation size W. Especially, its sorting task is known as the major bottleneck. In this paper we propose a two dimensional (2D) sorter-based K-best algorithm, whose complexity is negligibly affected by W. Instead of considering all of the constellation nodes as the full K-best does, our algorithm specifies the best nodes directly and processes these nodes only. In addition, the notion of 2D sorter is introduced to simplify the sorting task. The paper shows that the complexity of our algorithm is 87 times less than that of the full K-best. It is also less complex than the conventional works. In terms of BER performance, our algorithm outperforms the BLAST MMSE, LRA-MMSE, and is close to the full K-best.

Sampling frequency offset (SFO) that occurs due to a sampling frequency mismatch between the transmitter and receiver oscillators is one of the main problem in the orthogonal frequency division multiplexing (OFDM) based digital terrestrial television (DTTV) system. The SFO can cause an intersymbol interference and an intercarrier interference that may degrade the performance of an OFDM system and result in high bit error rate. Since the value of SFO is usually very low (part per million scale), the SFO estimation is very susceptible to a noise. In this paper, we propose the estimation method that can minimize the influence of the noise in SFO estimation and also minimize the computational complexity. The performance of the proposed method has been verified with computer simulation. The computer simulation results show that the proposed sampling frequency offset estimation is more efficient in computational complexity compared to the conventional method to achieve the similar performance.

In this paper, we propose a hardware architecture of high-speed sorted QR decomposition for a 4×4 MMSE-MIMO decoder. A QR decomposition (QRD) is commonly used in many MIMO detection algorithms. In particular, a sorted QR decomposition (SQRD) is a advanced algorithm to improve a MIMO detection performance. The proposed architecture can decompose an augmented channel matrix for MMSE detection by using modified Gram-Schmidt algorithm with pipelining and resource sharing processing. This architecture can be applied in a high-throughput MIMO-OFDM system such as IEEE802.11n which supports data throughput of up to 600Mbps. We implement the proposed architecture with 334k gates in 90nm CMOS technology. The proposed design can achieve a high performance of up to 50.0 million 4×4 SQRD operations per second with the maximum operating frequency of 300 MHz.

In this paper, we present an efficient and high throughput hardware implementation of the RC4 algorithm. The main idea of the proposed architecture is the utilization of a tri-port RAM to reduce the memory resource and to increase throughput. The proposed design requires two clock cycles for generating one byte of ciphering key and uses only a block of 256 bytes RAM. These result in 50% increment of system throughput and three times reduction of RAM resource compared to the recent architectures. The proposed implementation supports variable key length from 8 to 128 bits and achieves 80 MB/s throughput at 160 MHz operating frequency. It aims to support the WEP security in the MAC layer of 600 Mbps 4×4 MIMO wireless LAN system based on IEEE 802.11n standard.

Tomlinson Harashima Precoding (THP) for Multi-User Multiple Input Multiple Output (MU-MIMO) system has been proposed as an effective way to achieve near capacity to the theoretical limit in MU-MIMO channels. In order to achieve better performance, other THP methods such as minimum mean square error (MMSE) THP and lattice reduction aided (LRA) THP are proposed. Those methods outperform the conventional THP, however, the computational complexity also increases. In this paper, we propose a modified THP by new approach using square root with less increase of computational complexity. Computer simulation shows that proposed method can achieve better trade-off between bit error rate and computational complexity than MMSE THP and LRA THP.

In a soft decision Viterbi decoder, the log-likelihood ratio (LLR) metric is used to improve the performance of the error correction. On linear systems under additive white gaussian noise channel, this is straightforward as the error distribution at the input of the Viterbi decoder is also gaussian. In non-linear systems such as the M-ary non-coherent non-orthogonal frequency shift keying (FSK), this is generally not true. However, non-orthogonal non-coherent FSK LLR has not yet been proposed in literature. In this paper we derived the LLR for the M-ary non-orthogonal FSK mathematically and verified it using simulations.

The combination between a two dimensional (2D) filter with a non-rectangular spectrum and the 3- points diagonal averaging method is proposed in this paper as a channel estimation method for a 2×2 MIMO DVB-T2 system. The 3-points diagonal averaging method can shorten the distance between reference pilot along frequency direction before interpolation; consequently, it will optimize the performance of an interpolation filter. The two stages implementation of a 2D nonrectangular filter is also proposed in this paper to reduce the complexity of the channel estimation method. Simulation results show the robustness of the proposed method in very high speed mobile environment.

We propose a packet delayed lattice reduction aided MIMO detection for 802.11n system. Lattice reduction algorithms are iterative in nature that results in long latency. In high throughput systems like 802.11n, reduction of latency via parallelization causes high hardware complexity. Without parallelization, the receiver needs to buffer the incoming data until the lattice reduction finishes. Depending on the latency of the lattice reduction, this buffering may cause deep memory requirements as well as missed interframe space deadline requirement. In this paper, we resolve this problem by foregoing buffering of incoming data for the current packet and use the output of lattice reduction to the next packet after the computation is finished. We show that lattice aided MIMO detection can be delayed for as much as 15ms with negligible effect on performance.

In this paper, we propose a HDTV transmission over IEEE802.3ac 4 × 5 MIMO WLAN System. The proposed system employs the next generation wireless LAN system based on IEEE802.3ac specification. It reaches more than 33 meter propagation distance by using 80 MHz of bandwidth on the 5 GHz band. In this system, video data is compressed by JPEG 2000 with error resilience tools. These tools improve error performance against wireless channel, and enable very high throughput communication. Computer simulations are used to evaluate the bit error performance's influences to the video quality. Finally, we present RTL design results of the proposed wireless LAN system.

In mobile environment, decode quality is largely influenced by multipath fading and Doppler shift. In this paper, we reported improvement of mobile reception for high-definition television (HDTV) of integrated services digital broadcasting - terrestrial (ISDB-T) by using maximum ratio combining (MRC) diversity and using two-dimensional (2D) filter in channel estimation. From computer simulations, we show that the bit error rate (BER) of the proposed method is improved compared to that of conventional systems. Finally, we verify reception quality of a received movie signal using our proposed system via computer simulation.

Long Term Evolution (LTE) physical layer identity can be recognized either in frequency domain or time domain. In this paper we serve some comparisons in term of complexity, latency, and recognition probability. As a result, frequency domain detection has superiority on performance for SNR higher than 3dB on all channel models, as well as lower latency than time domain scheme one. However, it requires huge computation resources that might meet difficulty for mobile devices implementation.

We propose a 4K digital cinema wireless transmission over 1.2 Gbps wireless LAN system. The proposed system employs next generation wireless LAN system based on IEEE802.11TGac. It uses 80 MHz of bandwidth on 5 GHz band. In this system, video data is compressed by JPEG 2000 with added error resilience tools to improve error performance against wireless channel. Computer simulations are used to evaluate the bit error performance's influences to the video quality.

We propose a new least squares based estimation algorithm for carrier frequency offset and frequency dependent I/Q imbalance compensation with very low complexity for direct conversion receivers. Compared to conventional algorithms, our proposed estimation has considerably lesser computation due to a reduced order least squares step. Simulation results show that the proposed algorithm has about 1.5dB better accuracy in CFO estimation compared to conventional algorithms and it can completely eliminate I/Q imbalance based on BER performance results. We also showed that the proposed algorithm needs only a minimum 3rdorder FIR filter to effectively remove an infinite impulse response modeled I/Q imbalance.

This paper discusses about RTL design of time domain auto-correlation architecture for two recent standards, i.e.Worldwide Interoperability for Microwave Access Orthogonal Frequency Division Multiple Access (WiMAX OFDMA) and 3rd Generation Partnership Project Long Term Evolution (3GPP LTE). We introduce time domain auto-correlation function to recognize WiMAX preamble and LTE primary synchronization channel (PSC) at the same time. To distinguish them from interference, we consider peak period as unique property of WiMAX's preamble and LTE's PSC. As a result, for SNR 0 dB in extended pedestrian A (EPA) and ITU pedestrian B channel models, more than 90% WiMAX's preamble as well as LTE's PSC can be detected correctly. From complexity point of view, our scheme requires 183k LUT when implemented into Xilinx4 xc4vlx200.

This paper presents our investigation on performance enhancement due to the implementation of low density parity check (LDPC) codes on IEEE 802.11n system and its Application Specific Integrated Circuit design. Simulation result shows that in higher coding rate, LDPC codes gives 6 dB better performance compared to binary convolutional codes. Logic synthesis is succesfully done on 0.13 mum CMOS technology with low-power standard cell library.

This paper introduces a novel algorithm for jointly estimating carrier frequency offset and I/Q imbalance for OFDM systems. The new algorithm is a closed form solution to obtain the frequency offset and I/Q imbalance parameters in the absence of noise. In the presence of noise, the proposed algorithm uses the least squares algorithm to accurately estimate the parameters. The proposed algorithm is thus very scalable in terms of complexity. While the target system is OFDM, the proposed algorithm applies to any system as long as two identical data blocks are received in the receiver. Simulation results show that given a suitable amount of CFO, the high estimation accuracy of the proposed algorithm makes its BER performance comparable to a system without CFO and I/Q imbalance.

This paper deals with our work in designing a 1.2 Gbps WLAN system. It reaches 33 meter propagation distance by using 80 MHz bandwidth on 5 GHz band. The proposed preamble has backward compatibility with IEEE802.11n system, allows band sharing and avoids collision within 5 GHz band. The proposed preamble has comparable PAPR and preamble efficiency with IEEE802.11n system. The 4 × 5 MIMO configuration contributes 2nd-order diversity gain and maintains both the throughput and performance. Run test for transmitting 90 frames of 4 K digital cinema under in-door channel model demonstrates the excellent performance of the proposed system.

This paper proposes a simple algorithm for joint estimation of carrier frequency offset and I/Q imbalance. The reduced complexity algorithm is derived from a closed form solution of the carrier frequency offset and I/Q imbalance parameters given two identical training blocks. The proposed algorithm also uses the least squares algorithm to give accurate estimate in the presence of noise. It was shown that for as little as 10 samples each from two identical OFDM symbols, the proposed algorithm can produce accurate estimate of CFO and I/Q imbalance. While the target system is OFDM, the proposed algorithm applies to any system as long as two identical data blocks are received in the receiver. Simulation results show that performance of the proposed algorithm that uses only 10 samples for complexity reduction is only ldB below a system without CFO nor I/Q imbalance degradation.

Group layered space-time can attain a better tradeoff between data rate and diversity gain. In this paper, we propose a generalized detection that is an ordered successive detection employing an extended Gaussian elimination algorithm. The detection algorithm can reduce computational complexity, as low as O(Nt2Nr) per symbol interval, by using the characteristics of the channel matrix. Nt and Nr are the number of transmitter and receiver antennas, respectively. Simulation results show that the proposed detector can achieve low-complexity and better performance over linear MMSE ones. In addition, the effect of spatial correlation in GLST systems is discussed from the BER performance.

We investigated channel estimation with scattered pilots (SPs) in digital terrestrial television broadcasting (DTTB) and the performance of a receiver with a two-dimensional (2D) filter. High-accuracy interpolation is necessary because we perform channel equalization with SPs, which are inserted in transmit signals nonrectangularly. This interpolation is performed with a 2D filter that has a nonrectangular spectrum. However, the generation of the 2D filter involves heavy computational complexity. We propose a method of reducing the computational complexity by designing separable 2D filters. In addition, we present simulation results that compare our method with some conventional methods and show its effectiveness.

This paper presents an OFDM transceiver for wireless LAN systems and its baseband transceiver architecture. We study the optimum parameters about DFT size, guard interval, symbol duration, and number of subcarriers in an 80-MHz bandwidth by extending the IEEE 802.11a standard. The proposed transceiver has a maximum 300-Mbps transmit rate and achieves 600 Mbps by use of a 4times2 MIMO system. We have designed the SISO-OFDM transceiver in a 0.25-mum CMOS technology. The transceiver consumes about 800 mW at 2.5-V power supply and 80-MHz clock frequency. For verification, the architecture has been implemented to a FPGA prototype. We describe the parameters of our proposal and the TGn Sync optional proposal by comparison

In the current high-speed mobile communication, it is essential to have a technology for high-speed equalization of signals which have been distorted by multipath fading. However, in the traditional equalizer, adaptive direct form FIR filter, which uses the LMS algorithm has been used widely. Due to the low throughput associated with an FIR having a large number of coefficients, several pipe lined architecture, and their corresponding correction factor have been investigated for the LMS algorithm [4][5]. In this paper, we propose a pipelining architecture for the FIR portion of the Multilevel Modified Constant Modulus Algorithm (MMCMA). We also provide the correction factor associated with this architecture. The proposed pipeline method uses modules with 6 filter coefficients, resulting in an overall latency of a single sampling period, along the main transmission line. This is confirmed by computer simulation.

We propose an architecture for pipelined FIR ADF based on the CMA (constant modulus algorithm), which is a kind of blind equalizer. One of the features of proposed architecture, is its latency, which is independent of the number of taps of coefficients, and whose value is always fixed to a single clocking period. As of the critical path, the proposed method has a shorter path in comparison with conventional CMA using the direct form FIR ADF. Thus, an improvement in the processing speed and a lower power consumption can be attained. Some computer simulation are shown to verify the effectiveness of the proposed method.

We propose a subband adaptive digital filter (SBADF) for an orthogonal frequency division multiplexing (OFDM) system. The proposed SBADF is able to carry out the exact system identification without the degradation effect of both the aliasing and the cross terms even under critical sub-sampling. The inverse transfer function of the channel can be directly implemented after the system identification. The advantage of the proposed SBADF based equalizer is that it is not necessary to take account of the delay in terms of the transmission path because of the frequency-domain equalization. Some simulation results show the efficiency of the proposed SBADF for an OFDM system.

In this paper, we show a new blind identification algorithm which is based on second order statistics and exploits a single-input double-output (SIDO) model. It is suitable for a real-time processing system because of lower operation and high-speed convergence. The proposed blind identification algorithm is superior to conventional algorithms in view of simple structure and the uniqueness of solution. We also verify its efficiency by computer simulation.

A novel second-order statistics-based blind deconvolution and equalizer technique is proposed. This technique makes use of a two-channel perfect reconstruction filter bank derived from a two-component polyphase decomposition of the transmission channel in order to make exact system identifications possible. The proposed blind deconvolution algorithm is superior to conventional algorithms in view of the simple structure and the uniqueness of the solution. In order to verify the effectiveness of this method, several computer simulations including a 256 QAM signal equalizer and a blurred image recovery have been shown.

The over-sampling subband ADFs are in high demand because of shortening the convergence of adaptation algorithms and being able to avoid aliasing. However, the conventional methods must use the complex coefficient filter banks, which require a lot of computation compared to the real filter banks. The aim of this correspondence is to develop a new oversampling subband ADF which does not require complex coefficient filter banks but real filter banks. The filter banks are optimized such that the mean square error can be minimized. It turns out that the proposed scheme can minimize the aliasing effect due to decimation.

Two-dimensional (2-D) adaptive digital filters (ADFs) for 2-D signal processing have become a fascinating area of the adaptive signal processing. However, conventional 2-D FIR ADFs require a lot of computations. For example, the TDLMS requires 2N/sup 2/ multiplications per pixel. We propose a new 2-D adaptive filter using FFTs. The proposed adaptive filter carries out fast convolution using the overlap-save method, and has a parallel structure. Thus, we can reduce the computational complexity to O(log/sub 2/N) per pixel.

Conventional subband adaptive digital filters (ADFs) using filter banks have shown degradation in its performance because of the non-ideal nature of analysis filters. For this problem, we propose a new class of subband ADF which has two kinds of analysis filter banks. We first claim that subband ADFs with the optimum analysis filter bank, which can minimize the least squares error at each bin, can be designed in accordance with the statistics of the signals. We also propose a practical type of subband ADF which requires no a priori knowledge of the statistics regarding the signals. Several computer simulations are also given in order to show the efficiency of the proposed subband adaptive digital filter.

Conventional subband ADFs (adaptive digital filters) using filter banks have shown degradation in performance because of the non-ideal nature of filters. For this problem, we propose a new type of subband ADF incorporating two types of analysis filter bank. In this paper, we show that we can design the optimum filter bank which minimizes the LMSE (least mean squared error). In other words, we can design a subband ADF with less MSE than that of conventional subband ADFs.

An alias free parallel structure for system identification is proposed. The method utilizes the properties of a DFT filter bank in conjunction with accumulators which form a zooming mechanism on alias free points in the frequency domain. This method is very ideal for identifying long impulse responses under very adverse input coloring.>

The poly-phase structure (PPS) adaptive filter is an alias free structure whose update law obeys least square error minimization. This algorithm, in addition to fast identification of long impulse responses in stationary environment, exhibits remarkable tracking capabilities under adverse input conditions. The performance of PPS is unmatched even by the LMS based algorithms. With its fast transient response, the PPS is ideal for echo cancellation and echo suppression.>

An alias free parallel structure for adaptive digital filters (ADF's) is considered. We propose a new cost function for parallel ADF's. The limiting value analysis of system identification using proposed cost function is given in stochastic sense. The cost function is defined in each bin; accordingly, it enables the parallel processing of ADF's.>

Conventional subband adaptive filters (ADF) using filter banks have shown degradation in performance because of the nonideal nature of filter banks. For this problem, the authors propose an alias free subband structure for adaptive filtering using polyphase frequency sampling filter (FSF) banks. As a preliminary, they make it clear that the conventional polyphase discrete Fourier transform (DFT) bank is equivalent to a class of the FSF bank. Then, they propose a new class of ADF using the FSF banks based on the frequency sampling theorem. As a result, the proposed technique enables subband adaptive filtering without the degradation effect of both the aliasing and cross terms, even if one chooses critical subsampling.>

A new universal binary code for the positive integers is proposed as a modified version of M. Wang's (see ibid., vol.34, p.324-6, Mar. 1988) flag encoding scheme. The codeword length of the new scheme is shorter than Wang's, on an average, for large initial segments of the positive integers. The performance of the new scheme is also compared with that of other universal schemes. Furthermore, it is shown that an asymptotically optimal code can be achieved by modifying the new flag scheme such that the flag length varies dynamically.>

This paper proposes an adaptive dithering method, which can reproduce grey levels with good character quality. It also proposes dither threshold patterns with long run-length, which are able to obtain a compression ratio of about 3 or 4 when using modified Huffman coding schemes. The method presented here is applicable to facsimile equipment for transmitting pictures, including both continuoustone pictures and characters, using CCITT standard black and white picture coding.

This paper outlines a newly developed high-speed facsimile apparatus for satellite communication. An ISO A4 size document can be transmitted in about 3 s at a transmission rate of 1.536 Mbits/s using the apparatus. In the transmitter, a CCD linear image sensor and a fluorescent lamp are used for photoelectric conversion. In the receiver, an electrostatic recording technique using a multistylus electrode is applied. Furthermore, this apparatus applies a new tone-reproduction technique involving electrostatic recording, which makes it possible to reproduce documents, such as photographs, that have gray-level information without reducing the character quality. A facsimile control procedure which takes into consideration satellite communication circuit characteristics is established. The transmitter sends all documents to be sent continuously, receiving the message confirmation response for one document while transmitting the next one. The results of message transmission tests over experimental satellite communication circuits are described.