NOVEL BIPHASE CODE -INTEGRATED SIDELOBE SUPPRESSION CODE

A kind of novel binary phase code named sidelobe suppression code is proposed in this paper. It is defined to be the code whose corresponding optimal sidelobe suppression filter outputs the minimum sidelobes. It is shown that there do exist sidelobe suppression codes better than the conventional optimal codes-Barker codes. For example, the sidelobe suppression code     

SAW MINIMUM PEAK SIDELOBE FILTER FOR 15-bit M-SEQUENCE PHASE CODE SIGNALS

This paper presents computation results of the minimum peak sidelohe filter (LP filter) forthe 15-bit M-sequence phase coded signal with feedback connection [4,3,0] and initial condition 1001.Thedesign of the filter resorts to the linear programming method.The peak sidelobe level is reduced to—21.47 dBby the LP filter of length 15,and is 7.49 dB lower than that by the matched filter.The LP filter can suppressthe peak sidelobe even more by increasing its length.The minimum peak sidelobe filter for the 15-bit M-sequence phase coded signal (initial condition 1001) has been implemented with a surface acoustic wave(SAW) device.Experiments show that the peak sidelobe level of the manufactured filter is—19 dB and,thus,only differs from the theoretical value of—21.47 dB by 2.47 dB.     

Optimal p-ary Codes from Constacyclic Codes over a Non-chain Ring R

This paper is devoted to the study of con- stacyclic codes over a non-chain ring R. The generator polynomials of all constacyclic codes over R are characterized and their dual codes are also determined. We also introduce a Gray map. It is proved that the image of a vconstacyclic code of length n over R under the Gray map is a cyclic code of length 2n over a field with p elements, where p is odd prime. Moreover, we obtain a substantial number of optimal p-ary linear （cyclic） codes, in terms of their parameters, via the Gray map.     

COMPUTER SIMULATION FOR AN ULTRA-LOW RANGE SIDELOBE PULSE COMPRESSION SCHEME

A canceling range sidelobes scheme has been suggested by Yang Guangzheng, et al.,(1997) this technology is based on the fact that all sidelobe of group correlation function of ideal sets are zero. At first, this paper gives the best ideal sets (i. e. the best biphase code sets whose maximal sidelobe not more than 2) for all code length N≤12, which have been obtained from binary sequences by means of the best codes sieving method suggested by Yang Guangzheng, et al.(1997) Computer simulation for group correlation property of best ideal sets for code length N=12 on various conditions is made. Simulation result shows that the sidelobe level of best ideal set with no weighting is zero, under condition of zero-Doppler shift and has ultra-low sidelobe on Doppler up to 5kHz with no weighting and whose tolerance of phase and amplitude distortion is bigger too.     

A Novel Wavenumber Domain SAR Imaging Algorithm Based on the Fractional Fourier Transform

The conventional Wavenumber domain algorithm （WDA） employs Fast Fourier transform （FFT） to implement matched filter. It is characterized by its high precision SAR imaging. Compared with FFT, Fractional Fourier transform （FrFT） can provide lower and narrower sidelobes when it is applied to compress chirp signals at the optimal transform. This paper proposed a novel SAR imaging algorithm, termed FrWDA which replaces FFT in WDA with FrFT. The FrWDA was derived and its implementation was presented. How to choose the optimal transformation order was given subsequently. The FrWDA preserves high precision focusing, and has better performance on sidelobe suppression. The FrWDA is more suitable for the high precision SAR imaging, especially in target detection and recognition. Simulation results demonstrate that FrWDA provides better performance on focusing and sidelobe suppression compared with the classical FFT-based WDA.     

Multiple-Symbol Interleaved RS Codes and Two-Pass Decoding Algorithm

For communication systems with heavy burst noise, an optimal Forward Error Correction(FEC) scheme is expected to have a large burst error correction capability while simultaneously owning moderate random error correction capability. This letter presents a new FEC scheme based on multiple-symbol interleaved Reed-Solomon codes and an associated two-pass decoding algorithm. It is shown that the proposed multi-symbol interleaved Reed-Solomon scheme can achieve nearly twice as much as the burst error correction capability of conventional single-symbol interleaved Reed-Solomon codes with the same code length and code rate.     

Erasure-Correction-Enhanced Iterative Decoding for LDPC-RS Product Codes

Low-density parity-check(LDPC)codes are widely used due to their significant errorcorrection capability and linear decoding complexity.However,it is not sufficient for LDPC codes to satisfy the ultra low bit error rate(BER)requirement of next-generation ultra-high-speed communications due to the error floor phenomenon.According to the residual error characteristics of LDPC codes,we consider using the high rate Reed-Solomon(RS)codes as the outer codes to construct LDPC-RS product codes to eliminate the error floor and propose the hybrid error-erasure-correction decoding algorithm for the outer code to exploit erasure-correction capability effectively.Furthermore,the overall performance of product codes is improved using iteration between outer and inner codes.Simulation results validate that BER of the product code with the proposed hybrid algorithm is lower than that of the product code with no erasure correction.Compared with other product codes using LDPC codes,the proposed LDPC-RS product code with the same code rate has much better performance and smaller rate loss attributed to the maximum distance separable(MDS)property and significant erasure-correction capability of RS codes.     

SIMULATED-ANNEALING-BASED SELECTION OF BINARY CODES

Binary code signals have been widely used in various radars due to their simpleimplementation,but the selection of the binary codes with high comporession ratio and lowsidelobes is not solved well,because of the difficult processing in mathmatics and expensivecalculation cost.In this paper,neural computing is introduced into the field of the selection ofbinary codes and a new method based'on simulated annealing(SA)is proposed.The experimentsshow that the proposed method is able to select the optimal binary codes with much less timecost than the known methods,furhtermore the optimization selection of the binary codes versusthe calculation cost tradeoff is easier.     

Performance analysis of channel estimation for LDPC-coded OFDM system in multipath fading channel

In this paper, the channel estimation techniques for Orthogonal Frequency Division Multiplexing （OFDM） systems based on pilot arrangement are studied and we apply Low Density Parity Check （LDPC） codes to the system of IEEE 802.16a with OFDM modulation. First investigated is the influence of channel cstimation schemes on LDPC-code based OFDM system in static and multipath fading channels. According to the different propagation environments in 802.16a system, a dynamic channel estimation scheme is proposed. A good irregular LDPC code is designed with code rate of 1/2 and code length of 1200. Simulation results show that the performance of LDPC coded OFDM system proposed in this paper is better than that of the convolution Turbo coded OFDM system proposed in IEEE standard 802.16a.     

Construction and performance research on variable-length codes for multirate OCDMA multimedia networks

A new kind of variable-length codes with good correlation properties for the multirate asynchronous optical code divi- sion multiple access （OCDMA） multimedia networks is proposed, called non-repetition interval （NRI） codes. The NRI codes can be constructed by structuring the interval-sets with no repetition, and the code length depends on the number of users and the code weight. According to the structural characteristics of NRI codes, the formula of bit error rate （BER） is derived. Compared with other variable-length codes, the NRI codes have lower BER. A multirate OCDMA multimedia simulation system is designed and built, the longer codes are assigned to the users who need slow speed, while the shorter codes are assigned to the users who need high speed. It can be obtained by analyzing the eye diagram that the user with slower speed has lower BER, and the conclusion is the same as the actual demand in multimedia data transport.     

Improved FEC Code Based on Concatenated Code for Optical Transmission Systems

The improved three novel schemes of the super forward error correction(super-FEC) concatenated codes are proposed after the development trend of long-haul optical transmission systems and the defects of the existing FEC codes have been analyzed. The performance simulation of the Reed-Solomon(RS)+Bose-Chaudhuri-Hocguenghem(BCH) inner-outer serial concatenated code is implemented and the conceptions of encoding/decoding the parallel-concatenated code are presented. Furthermore, the simulation results for the RS(255,239)+RS(255,239) code and the RS(255,239)+RS(255,223) code show that the two consecutive concatenated codes are a superior coding scheme with such advantages as the better error correction, moderate redundancy and easy realization compared to the classic RS(255,239) code and other codes, and their signal to noise ratio gains are respectively 2～3dB more than that of the RS(255,239)code at the bit error rate of 1×10 -13 . Finally, the frame structure of the novel consecutive concatenated code is arranged to lay a firm foundation in designing its hardware.     

A VERTICAL LAYERED SPACE—TIME CODE AND ITS CLOSED—FORM BLIND SYMBOL DETECTION

Vertical layered space-time codes have demonstrated the snormous potential to accommodate rapid flow data.Thus far,vertical layered space-time codes assumed that perfect estimates of current channel fading conditions are available at the receiver.However,increasing the number of transmit antennas increases the required training interval and reduces the available time in which data may be transmitted before the fading coefficients change.In this paper,a vertical layered space-time code is proposed.By applying the subupace method to the layered space-time code,the symbols can be detected without training symbols and channel estimates at the transmitter or the receiver.Monte Carlo simulations show that performance can approach that of the detection method with the knowledge of the channel.     

A novel concatenated code based on the improved SCG-LDPC code for optical transmission systems

Based on the optimization and improvement for the construction method of systematically constructed Gallager (SCG) (4, k) code, a novel SCG low density parity check (SCG-LDPC)(3969, 3720) code to be suitable for optical transmission systems is constructed. The novel SCG-LDPC (6561,6240) code with code rate of 95.1% is constructed by increasing the length of SCG-LDPC (3969,3720) code, and in a way, the code rate of LDPC codes can better meet the high requirements of optical transmission systems. And then the novel concatenated code is constructed by concatenating SCG-LDPC(6561,6240) code and BCH(127,120) code with code rate of 94.5%. The simulation results and analyses show that the net coding gain (NCG) of BCH(127,120)+SCG-LDPC(6561,6240) concatenated code is respectively 2.28 dB and 0.48 dB more than those of the classic RS(255,239) code and SCG-LDPC(6561,6240) code at the bit error rate (BER) of 10 -7 .     

NEW METHOD TO RECOVER INTERNET PACKET LOSSES USING（2，1，m）SYSTEMATIC CONVOLUTIONAL CODES

A new method to recover packet losses using (2,1,m)convolutional codes is proposed.The erasure correcting decoding algorithm and the decoding determinant theorem is presented.It is also proved that the codes with optimal distance profile have also optimal delay characteristic.Simulation results show that the proposed method can recover the packet losses more efficiently than RS codes over different decoding delay conditions and thus suits for different packet network delay conditions.     

Low sidelobe aperture distribution of multistep amplitude quantization with pedestal

A low sidelobe aperture design method of multi-step amplitude quantization with pedestal is proposed, and general analysis and formulas are described. The computation results compared with our previous method "Multi-Step Amplitude Quantization(MSAQ)" on peak side-lobe level, aperture efficiency, normalized input power and sidelobe degradation with tolerance are given. It is shown that, under the same conditions, the method presented in this paper is better than the MSAQ.     

DETECTION PERFORMANCE OF DIGITAL POLARITY SAMPLED PHASE REVERSAL CODED PULSE COMPRESSORS

The nonparametic constant false alarm rate(CFAR)property of digital polarity sampled phasereversal coded pulse compressors is described.The detection performance in Gaussian and non-Gaussiannoise is determined.It is shown that the loss in signal-to-noise ratio of the processor relative to the incoherentmatched filter decreases as the code length increases.The asymptotic loss in Gaussian noise is 1.96 dB,and theloss in Weibull noise decreases with the shape parameter of the Weibull distribution and can even become again.     

SPATIAL-TEMPORAL JOINT FILTERP ROCESSING APPROACH FOR PHASED ARRAY AIRBORNE EARLY WARNING RADARS

To suppress the ground clutter for airborne early warning (AEW) radars is the key technique in radar signal processing. In this paper, a spatial-temporal nonadaptive joint filter processing approach is proposed to suppress the clutter for AEW radars, which can significantly reduce the computation compared with other optimal or suboptimal methods. The performance of this approach is better than that of the conventional cascaded nonadaptive processing, especially.     

SPC-APPM coded modulation for deep-space optical communications

A coded modulation scheme for deep-space optical communications is proposed,which is composed of an outer singleparity-check(SPC)-based product code,an interleaver,a bit-accumulator and a pulse-position modulation(PPM).It is referred as SPC-APPM code,which is decoded with an iterative demodulator-decoder using standard turbo-decoding techniques.Investigations show that the scheme has the advantages of low encoding and decoding complexities,good performance and flexible code rate for all rates above 1/2.Meanwhile,simulation results demonstrate that the SPC-APPM provides the performance similar to the low-density parity-check-APPM(LDPC-APPM),superior to the LDPC-PPM and product accumulate code-PPM(PA-PPM),although inferior to serially concatenated PPM(SCPPM).At the bit error rate(BER) of 10-5,the performance of SPC-APPM is about 0.7 dB better than LDPC-PPM and 1.2 dB better than PA-PPM.     

DECODING BEYOND THE BOUND OF THE COMPLEX-ROTARY CODE AND ITS DUAL CODE

The capabilities of decoding beyond the bound of the Complex-Rotary code (CRcodes) and its dual code are analyzed. It is obtained that the CR codes with normal error-correcting ability t = (p+1)/2 can correct (t+1)-errors up to C_(p~2+p(p+1))~(t+1)-p~(2Ct)_(2t+1) and itsdual code can correct (t_1+1)-errors up to C_(p~2+2tp)~(t_1+1)-2tpC_(p+1)~(t_1+1) where t_1=(p+1)/2-1 and pis a prime.     

Design of Raptor Design of Raptor-Like Rate Compatible SC Like Rate Compatible SC-LDPC Codes

This paper proposes a family of raptor-like rate-compatible spatially coupled low-density parity-check(RL-RC-SC-LDPC)codes from RL-RC-LDPC block codes.There are two important keys.One is the performance of the base matrix.RL-LDPC codes have been adopted in the technical specification of 5G new radio(5G-NR).We use the 5G NR LDPC code as the base matrix.The other is the edge coupling design.In this regard,we have designed a rate-compatible coupling algorithm,which can improve performance under multiple code rates.The constructed RL-RC-SC-LDPC code property requires a large coupling length L and thus we improved the reciprocal channel approximation(RCA)algorithm and proposed a sliding window RCA algorithm.It can provide lower com-plexity and latency than RCA algorithm.The code family shows improved thresholds close to the Shannon limit and finite-length performance compared with 5G NR LDPC codes for the additive white Gaussian noise(AWGN)channel.