Prediction of interference by modeling a radio interference meter

A method of predicting interference by modeling a radio-interference meter which satisfies the requirements of the CISPR is considered. The quasi-peak voltages of the radio interference is determined by analyzing the transmission of the interference signal through a channel consisting of a bandpass filter, a quasi-peak detector and an indicator instrument. The peak, mean and root mean square radio-interference voltages are calculated from the envelope at the output of the bandpass filter. Examples of the calculation of the radio-interference voltage for different forms of detectors in the measuring instrument are given.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 44–47, June, 1994.     

Detection and avoidance scheme for direct-sequence ultra-wideband system: a step towards cognitive radio

Detection and avoidance (DAA) is a soft-spectrum-based adaptation scheme proposed for multi-band ultra-wideband (MB-UWB) radio as a measure of co-existence between UWB devices and existing radio systems in overlapped bands. However, the principle of DAA in the direct-sequence UWB (DS-UWB) is very different from that in MB-UWB method. In DS-UWB, re-design of transmission pulses is required each time a new set of allowed bandwidths is discovered, as opposed to the turning-off-carrier-tone way in MB-UWB. Therefore the re-design of DS-UWB pulses in a cognitive radio environment must be easily reconfigurable. The problem of synthesising DS-UWB pulses conforming to arbitrary spectrum masks is addressed. In the proposed method, the masks are expanded by orthonormal functions chosen to be Hermite? Gaussian functions (HGFs). As the HGFs are eigenfunctions to the fractional Fourier transform, of which the inverse Fourier transform is a particular case, the set of the HGFs constitutes both a time-domain and a frequencydomain basis, that is, a co-basis, and therefore the transmission pulses can be easily obtained from the expansion of the specified spectrum masks. The co-basis-expansion-based DAA scheme for DS-UWB is evaluated through computer simulations.     

Unified method for bit error rate calculation of time-hopping and direct-sequence ultrawide band systems in the presence of multiple user interference and narrow-band interference

Time-hopping ultra wideband (TH-UWB) and direct-sequence ultra wideband (DS-UWB) systems are among the standards proposed for UWB communications scenarios. A general unified mathematical approach has been proposed for calculating the bit error rate (BER) for both TH-UWB and DS-UWB systems in the presence of multiple-user interference and a strong narrow-band interference in a multi-path scenario. Unlike many other mathematical models that provide upper or lower bounds for BER, this model calculates the exact values for BER in given scenarios. A partial rake receiver has been chosen as the receiving terminal. The modified Saleh-Valenzuela channel model has been used in this analysis. The model can asses the effect of any given narrow-band interfering systems. For the purpose of simulation, the narrow-band interfering system used is a Wi-Max transceiver based on IEEE 802.16-2004 standard. The validity of the model has been checked by comparing the mathematical results with numerical values achieved trough simulation. It is important to notice that this method can simultaneously be applied to both TH-UWB and DS-UWB.     

电阻加载偶极天线阻抗带宽及脉冲辐射特性研究

分析了偶极天线电阻加载方面的若干问题，包括不同电阻加载方式阻抗频率特性比较，连续与离散串联集中电阻加载脉冲辐射特性比较，证明其它加载方式具有与Wu-King电阻加载相似的特性，与未加载偶极天线相比，阻抗带宽较宽，辐射脉冲失真较小。     

Mesh模式下基于最小干扰流量的带宽调度算法

研究了干扰链路流量大小对IEEE802．16Mesh网络传输性能的影响,提出了一种通过计算用户站（SS）和基站（BS）的通信路径干扰的总流量来寻找总干扰流量最小的路由算法,并结合路由树给出了一种冲突避免调度的方法。该算法既考虑了干扰链路的数量,又考虑了干扰链路的实际通信强度,在建立路由树的过程中能够更快地使系统达到更佳的负载均衡状态,最大强度地避免调度中可能出现的带宽冲突。由于干扰流量的影响可以得到有效的控制,系统的吞吐量可以明显提高。仿真结果验证了该算法的有效性。     

Measurement of the spectral density of broadband radio interference

It is shown that the main characteristics of broadband radio inteference may be the voltage spectral density for pulsed interference and the power spectral density for both pulsed and smooth interference.Translated from Izmeritelnaya Tekhnika, No. 1, pp. 40–42, January, 2005.     

Performance of impulse radio direct sequence ultra-wideband system with variable-length spreading sequences

An adaptive transmission scheme using variable-length spreading sequences (VLSS) is proposed. The system is based on an impulse direct sequence ultra-wideband (DS-UWB) approach for wireless communication where the number of active users is variable. In contrast to the conventional DS-UWB system, which employs a fixed length spreading code, the proposed system changes the length of spreading code according to the system load adaptively, which is proven to be able to reduce the inter-chip interference, inter-symbol interference and multiple-access interference and thus improve the system performance in terms of bit error rate. The proposed system is simulated in multipath channels with a high level of multipath fragments, modelled by the standard IEEE 802.15.3a indoor channel model 1 (CM1) and channel model 2 (CM2). Numerical results demonstrate that when RAKE receivers are employed, the proposed VLSS DS-UWB system outperforms the conventional system by appropriately allocating the spreading sequences.     

Performance analysis of low average reporting bits cognitive radio schemes in bandwidth constraint control channels

Collaborative spectrum sensing is regarded as a key technology for tackling the challenges of the practical implementation of cognitive radio (CR). However, most of the proposed solutions require infinite bits or several bits exchanging per each CR to make the final decision to indicate the absence or presence of a primary user. It is well known that if N CRs employ energy detector with the same threshold and then send individual decision bits to a fusion centre, the OR-rule (1-out-of-N rule) will be optimal under Neyman-Pearson criterion. To decrease the average number of exchanging bits, we propose novel schemes while they perform as well as the OR-rule, our analytical and simulation results show that the proposed schemes has two important advantages over previously proposed schemes: (1) the average number of exchanging bits for N CRs always is 1/N bits per CR in perfect control channels; however, it is much higher than 1/N for the other proposed methods, e.g. it is 1 bit for the OR-rule and (2) the proposed method is very robust against the errors of imperfect control channels, specially, in low signal-to-noise ratio (SNR) regimes. Furthermore, the average number of reporting bits do not change considerably under the imperfect control channels.     

The effects of offset voltage on the amplitude and bandwidth ofkick-out pulses used in the nose-to-nose sampler impulse responsecharacterization method

The amplitude and bandwidth of kick-out pulses used in the nose-to-nose sampler impulse response characterization method were measured as a function of offset voltage. The measuring instrument was of similar bandwidth and its effects on the measurement were not removed. The amplitude is almost linear for offset voltages from -500 mV to 500 mV, except for values from about -50 mV to 50 mV. Slight changes in bandwidth were observed for offset voltages from -250 mV to 250 mV with significant bandwidth loss observed for offset voltages outside this range     

Effect of clock offset on an impulse radio ultra wideband ranging system with comparators

Impulse radio ultra wideband (IR-UWB) can achieve high resolution in ranging because it uses a very short pulse with a duration of less than 1 ns. In order to reduce cost and power consumption, a ranging system with high-speed comparators has been proposed. In this system, it is necessary to reduce noise power through averaging the comparator outputs. The authors evaluate the effect of clock offset on the averaging process, and a two-stage averaging scheme for the IR-UWB ranging system is proposed. Through computer simulation, it is proved that the proposed scheme can reduce the effect of the clock offset with appropriate numbers of initial averaging.     

Calculation of the mismatch error when checking instruments for measuring radio interference

The various methods of checking instruments for measuring radio interference are analyzed. Formulas are derived for calculating the mismatch error Translated from Izmeritel’naya Tekhnika, No. 7, pp. 63–65, July, 1999.     

Performance analysis of decision-feedback equalisation for cellular mobile radio with cochannel interference and fading

The error probability of minimum-mean-square-error decision-feedback equalisation (MMSE-DFE) is evaluated for digital cellular mobile radio systems in the presence of cochannel interference (CCI) and is compared with linear equalisation (LE). The main contribution of the paper is that this analysis accounts for pulse waveform, modulation and fading of the signal of interest, as well as the CCI. Quadrature-amplitude modulation (QAM) signalling in frequency-selective and quasi-static channels is considered. The CCI is treated as a stationary process, when caused by random phase and symbol-timing offsets relative to the signal of interest. Analysis includes techniques combining antenna diversity. The performance improvement as a function of taps in both feedforward and feedback filters is quantified. Owing to residual intersymbol interference (ISI) and CCI, the evaluation of the error probability is extremely complicated and time consuming in simulation. To overcome this issue, an efficient method based upon Gauss quadrature rules (GQR) is presented to compute the error probability. The method is not limited due to interference statistics and it yields remarkable advantages compared with other methods. The convergence of finite-length results to their infinite-length counterparts is also provided. Unlike the case of white noise, the simulations reveal that with the same finite length the DFE is unable to outperform the linear equaliser in a CCI-dominated channel if the feedback filter is of insufficient length.     

Co-channel interference suppression by time and range adaptive processing in bistatic high-frequency surface wave synthesis impulse and aperture radar

Intense co-channel interference (CCI) severely depresses the target detection in high-frequency surface wave radar (HFSWR). In this study, the CCI cancellation algorithm by time and range adaptive processing is proposed for a novel HFSWR ? bistatic HF surface wave synthesis impulse and aperture radar. With the real data, the interference is firstly modelled and then its features are investigated. The analyses show that the same interference prevails over a few but different bins through different channels, whereas the echoes are relatively weak and exist in all bins; in range domain, however, the interference takes over all the bins including positive and negative bins and will spread over the same and considerable Doppler area through different channels, whereas the echoes appear only in partially positive bins. On the basis of the features, the interference covariance matrix can be obtained by selecting the samples whose average power is much higher than that of the others in time domain and in range domain; the samples from either or both of beyond the detectable bins and negative bins can be selected for training. The interference can be cancelled by projecting the polluted data into the orthogonal subspace, constructing the projecting matrix with the eigenvectors associated with large eigenvalues of the covariance matrix. Finally, the segment handling and samples requirement are also discussed for reducing the computation burden. The experimental results are provided to demonstrate the performance of the method.     

Measurement of radio signal parameters based on spline approximation of the interference correlation function

On the basis of a spline-parabolic approximation for the envelope of a correlation function of Gaussian interference, an analytical expression is obtained for the required likelihood function that is a basis for constructing an evaluation algorithm for unknown radio signal parameters. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 9–10, December, 2007.