Independent Additive White Gaussian Noise Research Articles

Achievable Rate of Near-Field Communications Based on Physically Consistent Models

This paper introduces a novel information-theoretic approach for studying the effects of mutual coupling (MC), between the transmit and receive antennas, on the overall performance of single-input-single-output (SISO) near-field communications (NFC). By incorporating the finite antenna size constraint using Chu’s theory and under the assumption of canonical-minimum scattering (CMS), we derive the MC between two radiating volumes of fixed sizes. Expressions for the self and mutual impedances are obtained by the use of the reciprocity theorem. Based on a circuit-theoretic two-port model for SISO radio communication systems, we first establish its input-output relationship where the noise depends on the self/mutual impedances of the antennas, unlike the conventional assumption of independent additive white Gaussian noise. We then characterise the achievable data rate for a given pair of transmit and receive antenna sizes, thereby providing an upper bound on the system performance under physical size constraints. Through the lens of these findings, we shed new light on the influence of MC on the information-theoretic limits of near-field communications using compact antennas.

Evaluation Results of the Signal Decomposition Technique for OFDM Transmission which Achieves the Power‐Added Efficiency Improvement and the SNR Enhancement Using the Noise Elimination

SUMMARYThe authors have proposed the signal decomposition technique as one of the powerful solution to mitigate the large peak‐to‐average power ratio (PAPR) to be addressed in orthogonal frequency division multiplexing (OFDM) transmitters especially on mobile terminals. In order to enhance the receiver SNR, the simple noise elimination techniques working together with the signal decomposition technique have also been proposed that eliminates the noise added on the decomposed constant amplitude on‐off‐signals taking advantage of the knowledge of their constant amplitude at the receiver. In this paper, we discuss the parameter design issue of the proposed techniques and their optimization. Then, demonstrate the PAPR, the power‐added efficiency (PAE), and also the BER performances operating on the optimized parameters. It is confirmed that the proposed signal decomposition technique improves the PAPR by 4 dB and doubles the PAE at the complementary cumulative distribution function of 1%. It is also confirmed that the proposed noise elimination technique improves the receiver SNR by 3 dB at the BER of 10 to 3, which is nearly equal to that of conventional OFDM, under the conditions that the decomposed signals are transmitted over the independent additive white Gaussian noise channels. Furthermore, it is demonstrated that the proposed techniques work properly when the decomposed signals are transmitted over 2 × 2 multi‐input multi‐output.

Algorithms and Applications for Estimating the Standard Deviation of AWGN when Observations are not Signal-Free

Consider observations where random signals are randomly present or absent in independent and additive white Gaussian noise (AWGN). By using a recently established limit theorem, we introduce a new estimator for the estimation of the noise standard deviation when the signals are less present than absent and have unknown probability distributions. The bias, the consistency and the minimum attainable mean square estimation error of the estimator we propose are still unknown. However, the experimental results that are presented are very promising. First, when the Minimum- Probability-of-Error decision scheme for the non-coherent detection of modulated sinusoidal carriers in independent AWGN is tuned with the outcome of our estimator instead of the true value of the noise standard deviation, the Binary Error Rate tends to the optimal error probability when the number of observations is large enough. Second, given some speech signal corrupted by independent AWGN, our estimator can be used to estimate the noise standard deviation so as to adjust the standard Wiener filtering of the noisy speech. The objective performance measurements obtained by so proceeding are very close to those achieved when the Wiener filtering is tuned with the true value of the noise standard deviation.

Channel noise robust transmit power optimized linear precoder for ISI channel with minimal complexity equalizer

A special class of linear precoder-equalizer pair with equalizers formed by simple tapped delay lines is proposed. With this special equalizer structure, the equalizer of this system not only can enjoy the minimal implementation complexity, but also can avoid the noise amplification effect. Moreover, using nonmaximally decimated filterbank structure, this precoder-equalizer pair is proven to be able to guarantee intersymbol interference (ISI)-free communication by zero-forcing approach, even if spectral nulling exists in the physical channel. Another advantage of this system is that the length of the guard period introduced by the precoder can be any positive integer values, thus the guard period can be designed to maximize the spectral efficiency by selecting it to be as short as one symbol per block of transmitted signal. A systematic method for designing a minimal transmit power finite-impulse response (FIR) precoder under the proposed precoder-equalizer pair structure is presented. Under the ISI channel with independent additive white Gaussian noise, the design of this minimal transmit power FIR precoder is shown to be a minimum mean square error precoder design. Simulation results are presented to illustrate the performance of the proposed precoder-equalizer structure and that of the transmit power minimized precoder.

Near-Shannon/Slepian–Wolf Performance for Unknown Correlated Sources Over AWGN Channels

We consider the problem of joint source-channel coding of two correlated binary information sequences. Instead of compressing the information using source coding, both sequences are independently channel encoded and transmitted over two independent additive white Gaussian noise channels. No information about the correlation between the sources is required in the encoding process. The correlation between both sequences is exploited at the receiver, allowing reliable communications at signal-to-noise ratios very close to the theoretical limits established by the combination of Shannon and Slepian-Wolf theorems. This occurs even when the correlation between sources is not known at the decoder, since it can be estimated jointly with the iterative decoding process.

Eigenvector algorithm for blind MA system identification

We present a novel approach to the blind estimation of a linear time-invariant possibly mixed-phase moving average (MA) system (channel) based on second and fourth order statistics of the stationary received signal. As the algorithm incorporates the solution of an eigenvector problem, it is termed E igenV ector approach to blind I dentification (EVI). One of EVI’s main features is its ability to obtain reliable estimates of the channel’s MA parameters on the basis of very short records of received data samples. It is also robust with respect to an overestimation of the channel order. Furthermore, we demonstrate that, if independent additive white Gaussian noise is present, the degradation of the MA parameter estimates is minor even at low signal-to-noise ratios. By simulation results, we finally show the potential applicability of EVI to mobile radio communication channels under time-invariance conditions typically assumed in GSM receivers.

Error rate performance of digital FM mobile radio with postdetection diversity

An analysis of bit error rate (BER) in a binary digital FM system with postdetection diversity is presented. Expressions for the average BER due to additive white Gaussian noise (AWGN), random FM noise and delay-spread in the multipath channel are derived for reception using differential demodulation (DD), and frequency demodulation (FD) assuming independent fading signals. Calculated results for MSK show that the BER performance is strongly dependent on the RMS-delay/bit-duration ratio and that the delay-spectrum shape is of no importance when the receiver predetection filter product is optimized for the effect of AWGN. The effect of fading correlation on the diversity improvement is also analyzed for a two-branch case with multiplicative Rayleigh fading signals. Expressions for the average BER due to AWGN and random FM noise are derived. Calculated results are shown for the average BER due to random FM noise assuming a horizontally spaced antenna system at a mobile station. It is shown that the use of small antenna spacings leads to a diversity improvement greater than that obtainable for the case of independent AWGN. >