Pre‐interference canceller for digital microwave radio systems

The authors discuss radar interference and the effect on digital microwave radio systems. Bit interleaving is proposed as a way of canceling radar interference. In particular, 3-GHz maritime radar interference to 5- or 6-GHz (16-QAM) (quadrature amplitude modulation) digital microwave radio systems is described. The magnetron oscillator performance is discussed. The construction of a bit interleaving circuit and experimental results are described, showing the positive effect of bit interleaving used as a radar interference canceler. Bit interleaving equipment being designed for a digital microwave system with 16 QAM is described. >

In conventional interference cancellers, an auxiliary antenna has been used to obtain only an interference signal whose amplitude and phase was then adjusted to cancel out the interference in the signal received by the main antenna. In fact, however, conditions under which an auxiliary antenna can be used to receive such an interference signal necessary for cancellation are limited; and in all other cases, interference cannot be cancelled.In the interference canceller proposed in this paper, a signal consisting of the desired and the interference signal is received by both the main antenna and the auxiliary antenna, and the interference signal is extracted from the received signal using both antennas; interference is then cancelled using this extracted signal.First, the theory behind the operation of this canceller is presented and its configuration is described. Then the results of an experiment using a 16‐QAM signal as the desired signal and an FM (CH 3600) signal as the interference signal are presented. An improvement of about 17 dB has been obtained with regard to interference which cannot be cancelled out by conventional cancellers, thereby validating the operational principles of the proposed canceller.

The interference cancellation can restrain the strong interference between high power transmitter and receiver. The main point is to make sure the time delay between interference signal and reference signal match. The paper researches on the influence of time delay to the interference cancellation system. When the interference signal is single frequency signal, the ICR is unrelated with the time delay. When the interference signal is wideband signal, the ICR is related with the time delay. The simulation analysis and experiment results explain that ICR decreases as time delay increases if the bandwidth of the interference signal is the same, and the ICR decreases as the bandwidth of the interference signal increases if the time delay is the same.

The capacity and performance of cellular mobile system are affected by cochannel interference (CCI) signals. Adaptive array antennas can be used in base stations to reject or attenuate the interference signals and reduce their effect on the desired signal. This Paper presents the ability of the adaptive array antenna to reduce co-channel interference. Also, the effect of number of interference signal on the adaptive antenna performance is studied. Simulation results show that the adaptive array antenna is capable of reducing the effect of co-channel interference signals and recovering the desired signal at the output of the antenna. Also, we simulate the effect of the number of antenna elements on the adaptive array antenna performance.

Recent studies have shown that trellis-coded modulation can achieve coding gains in the residual intersymbol interference environment that exists after adaptive equalization on terrestrial digital microwave radio (DMR) systems. Simulated system signatures for 140 Mb/s DMR systems incorporating trellis-coded 512-QAM modulation are presented and the results compared to the system signatures of equivalent uncoded 256-QAM systems. At a threshold bit-error rate (BER) of 10/sup -3/, the signature of the uncoded system can be degraded by the addition of coding. However, at a threshold BER of 10/sup -4/, it is found that trellis coding improves the system signature. Conditional probabilities of outage and the percentage of error-free seconds are also calculated for the coded and uncoded systems. >

When the wireless communication network is interfered, the communication effect will be affected. In order to improve the interference signal processing effect and the identification accuracy of the interference signal, a wireless communication network interference suppression algorithm based on joint estimation is proposed. Using the deep learning method to identify the interference signal, obtain the effective interference signal of wireless communication network, improve the accuracy of interference signal identification, and track and parameter modulation the identified signal; The node model of wireless communication network is established, and the joint estimation method is used to suppress the interference signal for the nodes in the model. The interference suppression of wireless communication network is realized through the state estimation of single tone interference and narrowband interference. The experimental results show that the proposed algorithm has a high accuracy of interference signal recognition, the highest value reaches 98%, and the wireless communication data packet loss rate is low, the highest value is only 0.37, which verifies its interference suppression effect.

The throughput of existing MIMO LANs is limited by the number of antennas on the AP. This paper shows how to overcome this limit. It presents interference alignment and cancellation (IAC), a new approach for decoding concurrent sender-receiver pairs in MIMO networks. IAC synthesizes two signal processing techniques, interference alignment and interference cancellation, showing that the combination applies to scenarios where neither interference alignment nor cancellation applies alone. We show analytically that IAC almost doubles the throughput of MIMO LANs. We also implement IAC in GNU-Radio, and experimentally demonstrate that for 2x2 MIMO LANs, IAC increases the average throughput by 1.5x on the downlink and 2x on the uplink.

Pulse wind tunnel aerodynamic tests are an important part of hypersonic aircraft design and development. With the development of hypersonic aircraft technology, the aircraft model in pulsed wind tunnels has gradually become large-scale and heavy-loaded. During the force measurement test, due to the influence of the increased size of the aircraft model, the real aerodynamic signal of the force measurement system is submerged by the interference signal. During the effective test time of several hundred milliseconds, it is impossible to obtain high-precision aerodynamic signals of the force measuring system using traditional signal-processing methods. Therefore, for the in-depth study of aerodynamic identification of short-time hypersonic pulsed wind tunnels, there is an urgent need for an identification algorithm that can adapt to the force measurement system of large-scale aircraft. In this paper, a new aerodynamic identification algorithm that combines a traditional signal-processing method and a deep neural network is proposed and applied to pulse combustion wind tunnels. The algorithm is mainly divided into signal preprocessing and deep learning. First, the original signal is decomposed into different sub-signals via variational modal decomposition (VMD), and then the real aerodynamic signal is obtained via convolutional neural network (CNN)-long short-term memory (LSTM) training. For different interference signals in the pulsed wind tunnel test, this algorithm innovatively designs VMD preprocessing and optimizes hyperparameters, to extract signal features for subsequent deep learning and to filter out interference components. To ensure the consistency between the validation and the application, the algorithm was verified using the suspension test bench during training, and satisfactory results were obtained. Finally, the algorithm is applied to the suspension force measurement system of a pulse combustion wind tunnel, and the aerodynamic identification results present satisfactory accuracy.

Outage in digital microwave radio systems during multipath fading is highly correlated with the channel amplitude dispersion. This characteristic is exploited in a new digital microwave radio system measurement technique which yields dispersion signatures. These dispersion signatures can be readily applied to assess the effects of time varying channels on digital radio equipment. Thus, dispersion signatures can be used for in-service monitoring of equipment operation during actual fading. Routine maintenance assessment and laboratory evaluation of digital microwave radio equipment can also be readily carried out. The laboratory evaluation results can be used for system design both with and without diversity.

Two block-coded modulation (BCM) families particularly suited for high-capacity digital microwave radio systems are presented. The first family is based on one-step partitioning, and the second family is based on two-step partitioning of the signal constellation. The alphabet expansion is a decreasing function of the block length, and the constellation is constructed in such a way as to minimize both the average and peak signal powers. Using short block lengths, specific modulation schemes are described that transmit 4, 6, and 8 information bits per symbol. The asymptotic coding gain is only on the order of 2 dB in the first family, and of 3 dB in the second family, but their detection simplicity makes the presented BCM schemes particularly attractive for high-speed applications where trellis-coded modulation (TCM) decoders may be difficult to implement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This paper presents a novel interference cancellation (IC) scheme for both synchronous and asynchronous direct-sequence code-division multiple-access (DS-CDMA) wireless channels. In the DS-CDMA system, the multiple access interference (MAI) and the near-far problem (NFP) are the two factors which reduce the capacity of the system. In this paper, we propose a new algorithm that is able to detect all interference signals as an individual MAI signal by maximum correlation detection. It is based on the discovery of all the unknowing spreading codes of the interference signals. Then, all possible MAI patterns so called replicas are generated as a summation of interference signals. And the true MAI pattern is found by taking correlation between the received signal and the replicas. Moreover, the receiver executes MAI cancellation in a successive manner, removing all interference signals by single-stage. Numerical results will show that the proposed IC strategy, which alleviates the detrimental effect of the MAI and the near-far problem, can significantly improve the system performance. Especially, we can obtain almost the same receiving characteristics as in the absense of interference for asynchrnous system when received powers are equal. Also, the same performances can be seen under any received power state for synchronous system.

This paper describes the interference suppression in wireless digital video communication networks. Wireless digital systems are significantly less sensitive to noise and interference. The frequency spectrum is used to introduce wireless digital video services. Wireless digital video systems may offer improved RF performance, can work in communication conditions where spectrum efficiency is not to high and sophisticated modulation and error correction techniques are adopted. Digital modulation and channel coding systems ensure frequency spectrum efficiency and ruggedness against noise and distortion.

For cellular networks, the increased cell density and decreased cell size will give rise to significant inter-cell interference. In this work, an adaptive antenna array and an iterative receiver are combined to facilitate inter-cell interference suppression and cancellation at the receiver end. Iterative receivers exchange soft information between different receiver modules, e.g., symbol detector and channel decoder. An adaptive antenna array is integrated within the iterative receiver, which performs interference suppression and successive interference cancellation. The beamforming weight vectors are updated in each iteration using interference rejection combing, which takes into account the soft information from the channel decoder and previously estimated interfering signals. The proposed algorithm can effectively suppress and cancel the interference signal with various signal-to-interference ratios under different channel models.

A low complexity Parallel Interference Cancellation (PIC) technique is proposed to suppress Multi-Access Interference (MAI) and minimize near-far effect for multi-user communication using Direct-Sequence Code Division Multiple Access (DS-CDMA). Interference signal is estimated using a relationship between cyclic correlation of the received signal and user's code of the interferer without requiring any knowledge of the channel condition. The user's codes for the multi-user DS-CDMA communication are constructed by using a set of m-sequences. The cyclic correlation is performed using Fast Walsh-Hadamard Transform (FWHT) which exhibits low computational complexity, i.e., it does not require any multiplication/division operations. In addition to low complexity, the proposed technique does not require complicated channel condition estimation and has no convergence issues. The uncoded Bit Error Rate (BER) performance of the proposed interference cancellation is calculated and compared with the conventional one over three different types of channels: AWGN, slow Rayleigh fading, and multipath channels.

Currently, due to the increasing complexity of navigation support for aircraft (A/C), with the growth of requirements for them, it is increasingly necessary to develop systems for integrated processing of navigation information. The facilities for radio engineering flights support and aeronautical telecommunications are the main source of collecting processing and presenting information about the air situation to the traffic control staff. They are also used to solve the number of navigation problems. At the same time, the level of flight safety, along with the capacity of air traffic control zones depending on the decision of the ATC unit, is largely specified by the reliability of the various input information provided. At another point, most sophisticated digital tools for radio engineering flights support and aeronautical telecommunications at the output of the receiving-analyzing route have a decision or threshold circuit, the actuation of which, as a result of exposure to a mixture of noise and interference signals, reduces the reliability of information due to bursts of signal distribution, provided that impulse interference affecting the equipment and mush of receivers are not correlated. The work provides an estimate of the average amount of signal bursts at the output of the decision circuit taking into consideration the analysis of the probabilistic characteristics of the signals under consideration. For noises subject to the Rayleigh distribution and narrow-band impulse interference with a zero-mean value, the mathematical expectations of the average response time and the average number of positive bursts of the estimated process are found. The case of interfacing two airway surveillance radars “Skala-M” and “ATCR-22”, which have virtually identical operating characteristics, is analyzed. The dependence of the burst duration is calculated for the situation when the “Skala-M” radar is a source of unintended EMI for the “ATCR-22” radar.