Effect Of Doppler Frequency Research Articles

Performance analysis for low-complexity detection of MIMO V2V communication systems

In Vehicle-to-Vehicle (V2V) communication, the rapid movement of vehicles brings fast attenuation of signal propagation and serious shift effect of Doppler frequency, leading to serious transmission performance deterioration. Multiple-Input Multiple-Output (MIMO) technique can be well applied in V2V communication by exploiting diversity and multiplexing gain to improve the system reliability and increase the data rate. In an MIMO system, the achieved diversity and multiplexing gain is closely related to its detection method. Integer-Forcing (IF) detection is one of the linear detections proposed in recent years. Compared to the traditional linear and Maximum Likelihood (ML) detection, IF has a good tradeoff between the complexity and system performance. In this paper, considering its good detection performance, IF is applied to the detection of a MIMO V2V communication system and the performance is further analyzed theoretically by employing Alamouti code at the transmitters. The diversity gain proves to be full and is confirmed by the simulation results.

Direction of Arrival Estimation Accuracy Enhancement via Using Displacement Invariance Technique

A new algorithm for improving Direction of Arrival Estimation (DOAE) accuracy has been carried out. Two contributions are introduced. First, Doppler frequency shift that resulted from the target movement is estimated using the displacement invariance technique (DIT). Second, the effect of Doppler frequency is modeled and incorporated into ESPRIT algorithm in order to increase the estimation accuracy. It is worth mentioning that the subspace approach has been employed into ESPRIT and DIT methods to reduce the computational complexity and the model’s nonlinearity effect. The DOAE accuracy has been verified by closed-form Cramér-Rao bound (CRB). The simulation results of the proposed algorithm are better than those of the previous estimation techniques leading to the estimator performance enhancement.

Channels estimation in OFDM system over Rician fading channel based on comb-type pilots arrangement

Orthogonal frequency-division multiplexing (OFDM) is a transmission technique that is based on many orthogonal carriers that are transmitted simultaneously. Channel estimation techniques for OFDM systems, based on comb-type pilot arrangement, over frequency-selective Rician and time-varying fading channel are investigated. The advantage of comb-type pilot arrangement, in channel estimation, is the ability to track the variation in the channel, which is the main reason for inter-carrier interference modelled as an additive white Gaussian noise, leading to an increase in the noise level. The estimation of the channel at the pilot frequencies is based on least-square (LS) method. Several interpolation methods have been used to estimate the channel response at the data frequency. In this study, simulation results for Rician channel model were examined and bit error rate/signal-to-noise ratio performance, for various conditions, were considered, and the pilot arrangement was used with the LS estimation and low-pass interpolation techniques, leading to a reduction in the effect of Doppler frequency.

A circular passive synthetic array: an inverse problem approach

Based on the general concept of the inverse acoustic radiation problem, the temporal scanning of a stationary acoustic field along a closed contour is used to simplify the measurement approach for obtaining information on source directionality. The mathematical formulation is derived from a model of the two-dimensional acoustic field. The formulation of the inverse problem is also investigated to establish a methodology for improving the angular resolution of the array processing. The fundamental relationship between the sound sources and the circular passive synthetic array is explored, utilizing existing mathematical methods, in order to develop the processing algorithm. Other subjects of practical interest, such as directional ambiguity, effect of Doppler frequency, interference noise, and processing gain are discussed. It is concluded that the results can be used to establish guidelines for engineering design and deployment of this type of synthetic array, and to further exploit the new array signal processing technique. >