A robust symbol-timing and carrier-frequency synchronization scheme applicable to orthogonal frequency-division-multiplexing systems is presented. The proposed method based on a training symbol specifically designed have steep rolloff timing metric. metric also provides sync detection capability. Both time domain frequency (FD) are investigated. For FD training, maintaining low peak-to-average power ratio of the was taken into consideration. channel estimation incorporated in system order...

Two timing offset estimation methods for orthogonal frequency division multiplexing (OFDM) systems as modifications to Schmidl and Cox's method (see IEEE Trans. Commun., vol.45, p.1613-21, 1997) are presented. The performances of the estimators in additive white Gaussian noise channel intersymbol interference compared terms estimator variance obtained by simulation. Both proposed have significantly smaller both conditions.

We have developed a low-cost, real-time sleep apnea monitoring system ''Apnea MedAssist" for recognizing obstructive episodes with high degree of accuracy both home and clinical care applications. The fully automated uses patient's single channel nocturnal ECG to extract feature sets, the support vector classifier (SVC) detect episodes. "Apnea is implemented on Android operating (OS) based smartphones, either general adult subject-independent SVC model or subject-dependent model, achieves...

To find an efficient and valid alternative of polysomnography (PSG), this paper investigates real-time sleep apnea hypopnea syndrome (SAHS) detection based on electrocardiograph (ECG) saturation peripheral oxygen (SpO(2)) signals, individually in combination. We include ten machine-learning algorithms our classification experiment. It is shown that proposed SpO (2) features outperform the ECG terms diagnostic ability. More importantly, we propose classifier combination to further enhance...

This paper presents general classes of optimal training signals for the estimation frequency-selective channels in MIMO OFDM systems. Basic properties discrete Fourier transform are used to derive which minimize channel mean square error. Both single and multiple symbols considered. Several pilot tone allocations across transmit antennas presented classified as frequency-division multiplexing, time-division code-division multiplexing frequency-domain, time-domain, combinations thereof. All...

A time-domain based channel estimation for OFDM system with pilot-data multiplexed scheme is investigated. As an approximation to linear minimum mean square estimator (LMMSE), a proposed where intra-symbol time-averaging and most significant taps selection are applied. The relation differences of the method DFT-based LMMSE methods discussed. performances method, Chini, Wu, El-Tanany Mahmoud (see IEEE Trans. on Broadcasting, vol.44, no.1, p.2-11, 1998) Yeh Lin vol.45, no.4, p.400-409, 1999)...

Massive multi-input multi-output (MIMO) systems require channel state information (CSI) at base stations. In multicell environments, adjacent cells using the same spectrum cause a pilot contamination problem and degrade CSI quality. Under such practical it is important to assess achievable rate of system for proper design. There exist bounds uplink (UL) in literature, but general closed-form downlink (DL) are not available yet. This paper studies massive MIMO DL with or without pilot-aided...

This letter proposes a simple channel estimator for multi-cell massive MIMO system with pilot contamination. Under moderate or strong contamination, the existing least square (LS) suffers from substantial performance degradation while minimum mean error (MMSE) offers much improved over LS estimator. However, MMSE assumes perfect knowledge of cross-cell large-scale coefficients and such an assumption is practically unjustifiable. The proposed overcomes issues both estimators provides...

A reduced complexity channel estimation for OFDM systems with transmit diversity is proposed by exploiting the correlation of adjacent subchannel responses. The sizes matrix inverse and FFTs required in at every data symbol are half existing method nonconstant modulus subcarrier symbols or constant some guard tones. reduction size multiplications still achieved no price a slight BER degradation channels small relative delay spreads, performance becomes quite comparable to method. An...

This letter addresses training-signal-based combined timing and frequency synchronization channel estimation for orthogonal frequency-division multiplexing systems. The proposed scheme consists of two stages. At the first stage, coarse frequency-offset estimates are obtained. Based on these estimates, a (coarse) response estimate is at second stage obtained by maximum-likelihood (ML) realization based sliding observation vector. Then ML performed. A means complexity reduction an adaptive...

In this paper, we derive exact closed form bit error rate (BER) or symbol (SER) expressions for orthogonal frequency division multiplexing (OFDM) systems with carrier offset (CFO). We consider the performance of an OFDM system subject to CFO in additive white Gaussian noise (AWGN), flat and selective Rayleigh fading channels. The BER/ SER performances BPSK QPSK modulation schemes are analyzed AWGN frequency-flat channels while is considered frequency-selective Our results can easily be...

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Direct conversion orthogonal frequency division multiplexing (OFDM) systems suffer from transmit and receive analog processing impairments such as in-phase/quadrature (I/Q) imbalance causing inter-carrier interference (ICI) among sub-carriers. Another source of performance-limiting ICI in OFDM is Doppler spread due to mobility. However, the nature each them quite different. Unlike previous work...

Millimeter-wave large-scale antenna systems typically apply hybrid analog-digital precoders to reduce hardware complexity and power consumption. In this paper, we design for physical-layer security under two types of channel knowledge. With full knowledge at transmitter, provide sufficient conditions on the minimum number RF chains needed realize performance fully digital precoding. Then, precoder maximize secrecy rate. By maximizing average projection between precoder, propose a...

We derive conditions on the impulse response and input signal of a frequency-selective finite-impulse channel to be diagonalized by discrete cosine transform (DCT) into parallel, decoupled, memoryless subchannels. show how these can satisfied in practical multicarrier transceiver through novel design guard sequence front-end prefilter. This DCT-based results complete elimination interblock intercarrier interference without knowledge at transmitter same overhead, compared with DFT-based...

This paper addresses an optimal periodic training signal design for frequency offset estimation in frequency-selective multipath Rayleigh fading channels. For a fixed transmitted energy within fixed-length block, the structure (the locations of identical subblocks) and subblock are presented. The optimality is based on minimum Cramer-Rao bound (CRB) criterion. Based CRB joint channel, (optimality only estimation, not necessarily channel estimation) derived. obtained by using average...

This paper introduces a novel differential modulation scheme for two-user cooperative diversity system which does not require channel state information at either the users or destination. The performance of fixed decode-and-forward and selection relaying protocols is evaluated in both symmetric asymmetric interuser-channel cases. lower bound on protocol given, while exact bit-error probability thoroughly derived. achieves gain when signal-to-noise ratios interuser channels are sufficiently...

We develop robust mean-square error (MSE)-optimal training signal designs for multiple-input multiple-output orthogonal frequency-division multiplexing channel estimation with frequency offset and phase noise (PN), present analytical simulation results the frequency-offset PN effects on estimation. The proposed are more advantageous moderate-to-high values of signal-to-noise ratio (SNR), residual offset, level. At SNR = 10 dB, normalized MSE reductions our signals at |v|=0.1,0.5 about 9 19...

We present a new initial ranging method for OFDMA systems such as IEEE 802.16-2004. First, orthogonal signal design is proposed by which an efficient, low-complexity multi-user detection developed. Based on the detector results, power estimation detected subscriber stations performed. Then, utilizing together with redundancy introduced cyclic prefixes, iterative timing offset estimator presented. Compared existing methods CDMA-type codes (in frequency-domain) defined in 802.16-2004, achieves...

This paper addresses preamble-based low complexity synchronization, channel estimation and equalization for Zero-padded (ZP) MB-OFDM based UWB systems. The proposed synchronization method consists of sync detection, coarse timing estimation, fine oscillator frequency offset estimation. distinctive features systems the interplay between carrier hopping at receiver are judiciously incorporated in method. In order to apply one-tap frequency-domain equalizer, required circular convolution...

Interference alignment (IA) is known to significantly increase sum-throughput at high SNR in the presence of multiple interfering nodes, however, reliability IA little known, which subject this paper. We study error performance and compare it with conventional orthogonal transmission schemes. Since most algorithms require extensive channel state information (CSI), we also investigate impact CSI imperfection (uncertainty) on performance. Our results show that under identical rates, attains a...

In this paper, we consider a downlink orthogonal frequency division multiplexing system from base station to high-speed train equipped with fully/partly calibrated massive uniform linear antenna-array (ULA) in wireless environments abundant scatterers. Multiple Doppler off- sets (DFOs) stemming intensive propagation paths together transceiver oscillator offset (OFO) result fast time-varying frequency-selective channel. We develop an angle domain carrier (CFO, general designation for DFO and...

We address the initial ranging process in OFDMA systems such as IEEE 802.16a. The proposed method includes three main tasks - timing estimation, multi-user code detection, and power estimation. All are performed based on a bank of correlators corresponding to codes. estimation scheme is peak correlator outputs. detection outputs an adaptive threshold. A novel threshold setting proposed. simple user-power estimator derived adjustment at random access users also which brings significant...

In this letter, we propose a hybrid analog-digital precoder design to enhance the physical layer security of millimeter-wave (mmWave) multiple-input single-output (MISO) systems with partial channel knowledge. We derive closed-form expression for average signal-to-interference-and-noise ratio (SINR) eavesdropper (Eve) as function precoder. Using SINRs Eves, secrecy rate lower bound. Then, low-complexity artificial-noise-aided (AN-aided) maximize Numerical results show that proposed AN-aided...

Adaptive automatic repeat request (ARQ) schemes are quite effective for throughput enhancement in time-varying mobile channel environments. An ARQ scheme with adaptive error-correcting codes is considered. A robust sensing algorithm by making use of XOR-ing proposed link adaptation. With the estimation algorithm, an that adapts its according to conditions presented. The efficiency evaluated terms performance computer simulation a characterized Rayleigh fading and log-normal shadowing. As...