Performance of the Production Band 3 receivers (84-116 GHz) for the Atacama Large Millimeter Array (ALMA)

This paper presents the performance of production Band 3 receivers (84-116 GHz) for the Atacama Large Millimeter Array (ALMA) that operate in Chile at 5000 m altitude. The fabrication, and testing of a total of 73 receivers necessitated stringent quality control during assembly and custom designed automated test set for accurate and reproducible measurement results. Interfaces to the ALMA receiver system are described in details. The average single side band noise temperature of band 3 production receivers is 33.2 K, with a minimum of 24.4 K and a maximum of 45.5 K. As for image rejection, the average is 18 dB, with a minimum at 12 dB and a maximum of 21 dB. Other performances with test methodology are described such as gain variation within the IF band, the gain and phase stability, gain compression, and beam patterns. This paper also describes the interfaces to the ALMA front end system, the testing methodology used, and the test results.     

低噪声自动测试及噪声源自动校准系统

本文介绍一个噪声自动测试系统。该系统主要完成两大类功能:测试低噪声器件的噪声温度和校准固态噪声源的超噪比。同时兼有测量被测件的电压驻波比和测量电子部件/器件及接收机的噪声系数等功能。测试/校准软件用于控制仪器的设置和测试流程;计算和补偿插入损耗;计算和修正失配影响;自动生成标准格式的原始记录和证书报告(包括曲线)。该系统为同轴、宽频段、全面开展无线电噪声参数测试/校准的自动测试系统。     

Erasure insertion in frequency-hop communications with fading andpartial-band interference

The use of block coding and errors-and-erasures decoding can enhance performance substantially in frequency-hop communication systems, provided that a good scheme is employed to determine which symbols to erase. In this paper, methods for determining erasures derived from Bayesian decision theory are applied to the mitigation of fading and partial-band interference. The performance of receivers using the Bayesian technique is compared with that of receivers that make erasure decisions using Viterbi's (1982) ratio-threshold test. The performance of hard-decision demodulation and the theoretical performance of receivers with access to perfect side information are also compared. It is found that the Bayesian receiver provides the best performance, and that error probabilities for the Bayesian receiver are lower than those for hard-decision demodulation by as much as six orders of magnitude     

Bayesian methods for erasure insertion in frequency-hopcommunication systems with partial-band interference

The erasure of unreliable symbols improves the performance of most types of error-control coding if a good method is used to decide which symbols should be erased. Bayesian decision theory is employed to obtain such a method for use in frequency-hop communications with Reed-Solomon coding and errors-and-erasures decoding. The performance of frequency-hop communications with Bayesian erasure insertion is analyzed for channels with both partial-band and wideband Gaussian noise. The Bayesian technique is compared with Viterbi's ratio-threshold test, and these are compared to receivers that do not erase and use errors-only decoding. Comparisons are also made with receivers that erase all the symbols that are affected by the partial-band interference. When interference is strong, large coding gains result from the Bayesian method, and error probabilities are reduced by several orders of magnitude     

Prediction Techniques for Cavity-Crystal Receivers

A technique is presented for the reliable prediction of spurious response and intermodulation interference characteristics for microwave receivers of the cavity-crystal type. Calculation procedures, data collection, and simplification measures are given. The results of a test prediction using a typical microwave communication receiver are presented.     

“AQUA”: A New Audio Quality Monitoring Algorithm for the Performance of DRM Receivers in Fading Channels

This paper presents a new Audio QUAlity monitoring algorithm: “AQUA” for assessing the performance of Digital Radio Mondiale (DRM) receivers. AQUA targets performance evaluation of consumer grade receivers in fading channels objectively. Consumer grade DRM receivers do not generally possess a Receiver Status and Control Interface (RSCI), which prohibits the possibility of analysing digitally decoded audio bit stream after reception. AQUA relies on the analysis of the received analog audio output signal instead. The paper describes the development of the AQUA algorithm and the measurement system used for receiver audio quality testing. The performance of AQUA is compared to conventional RSCI derived metrics like Bit Error Rate (BER) and Frame Error Rate (FER) of the decoded audio data. A series of tests are conducted in a variety of propagation conditions using a DRM dedicated testing system with a fading channel emulator. It is shown that FER estimates using AQUA are in good agreement with conventional FER figures derived from RSCI in different fading channel scenarios. This allows AQUA to be used as a reliable alternative to conventional FER performance analysis for automated objective testing of DRM receivers.      

DS-OCDMA Receivers Based on Parallel Interference Cancellation and Hard Limiters

In an incoherent direct-sequence optical code-division multiple-access (DS-OCDMA) system, multiple-access interference (MAI) is one of the principal limitations. To mitigate MAI, the parallel interference cancellation (PIC) technique can be used to remove nondesired users' contribution. In this paper, we study four DS-OCDMA receivers based on the PIC technique with hard limiters placed before the nondesired users or before the desired user receiver, or both. We develop, for the ideal synchronous case, the theoretical upper bound of the error probability for the four receivers. Significant performance improvement is obtained by comparison with conventional receivers in the case of optical orthogonal codes. The paper highlights that the number of active users with null error probability is doubled, compared with conventional receivers. Finally, we show that, thanks to their good performances, the PIC structures permit considerably reducing the minimal code length required to have 30 users with bit-error rate$≪10^-9$. So, the hardware constraints are relaxed for realistic application.     

Interference-Robust Air Interface for 5G Ultra-dense Small Cells

An ultra-dense deployment of small cells is foreseen as the solution to cope with the exponential increase of the data rate demand targeted by the 5^th Generation (5G) radio access technology. In this article, we propose an interference-robust air interface built upon the usage of advanced receivers as main interference mitigation technique. Both Interference Rejection Combining (IRC) and Successive Interference Cancellation (SIC) principles are considered. An efficient usage of such receivers is ensured by a proper frame structure design and system assumptions. Different approaches for the rank adaptation are also investigated. Simulation results show that proposed air interface built upon advanced receiver can be a feasible alternative to traditional solutions based on frequency reuse planning. Open issues and further challenges are also addressed.     

Performance Analysis of a Pre-BLAST-DFE Technique for MISO Channels With Decentralized Receivers

The performance of a pre-Bell Laboratories Layered Space-Time Architecture (BLAST)-decision feedback equalization (DFE) technique with Tomlinson-Harashima precoding and decentralized receivers, operating over multiple-input single-output (MISO) frequency-selective fading channels, is evaluated. First, we derive the probability of symbol error for Tomlinson-Harashima precoding operating over single-input single-output channels with intersymbol interference. We then generalize this result to MISO frequency-selective fading channels with decentralized receivers by using the QR decomposition technique. The effect of optimal ordering of the decentralized receivers, which minimizes the total transmit energy, is investigated. We obtain a closed-form expression for the probability density function of the squared diagonal elements of the upper right triangular matrix belonging to the optimal QR decomposition when two transmit antennas and two receivers are used. We also provide simulations to corroborate the analytical results.     

等效模型在干扰功率控制技术中的应用

研究干扰系统功率控制等效模型的原理及应用，达到提高干扰测试系统试验能力、满足新体制雷达干扰试验更高要求的目的。详细论述了功率控制等效模型基本原理，举例说明了等效模型在功率控制中的应用，总结了实际应用结果和应用价值。     

GPS接收机Z跟踪技术抗干扰性能分析

Z跟踪技术是民用GPS接收机为消除或减弱AS（Anti—Spoofing）政策影响,实施精密测距和高精度导航定位的一种有效方法。通过分析Z跟踪技术载波相位测量的基本原理,研究了GPS接收机Z跟踪技术的抗压制干扰、抗欺骗干扰性能。结果表明：采用Z跟踪技术的GPS接收机与C／A码接收机的抗压制干扰基本相同;其在信号捕获状态下的抗欺骗干扰能力取决于欺骗干扰信号与GPS信号的相关程度,而在信号跟踪状态下抗欺骗干扰能力则等同于抗伪随机噪声码干扰能力。     

Linear Direct-Detection Fiber-Optic Receiver Optimization in the Presence of Intersymbol Interference

A technique is developed for optimizing communication receivers by minimizing a Chernoff bound (CB) on the Bayes cost function. Being couched in terms of moment generating functions, the procedure is well suited to optical systems. Optimal CB receivers are derived and shown to coincide exactly with known minimum cost Bayes receivers for certain special cases of both electrical and optical communications for which closed form analytic solutions are possible. This provides endorsement for the method, which is then applied to more complex practical cases of linear optical fiber receivers in which both colored Gaussian noise and intersymbol interference play a part. The CB receivers are shown to offer some improvement compared with a zero forcing raised cosine equalizing receiver such as is commonly adopted, and all the evidence suggests that CB receivers achieve performance very close to the best possible with a linear receiver.     

Analysis of Tomlinson–Harashima Precoding in Multiuser MIMO Systems With Imperfect Channel State Information

Tomlinson–Harashima precoding (THP) is a successive pre-equalization technique that arranges all the receivers into a group of layers and then suppresses the interlayer interference in sequence at the transmitter. There are two basic THP structures according to the positions of the diagonal weighted filter—decentralized at the receivers or centralized at the transmitter—which are denoted dTHP or cTHP, respectively. In this paper, the investigation of THP in downlink multiuser multiple-input–multiple-output (MIMO) systems with imperfect channel state information (CSI) is performed. The interference power caused by imperfect CSI is first derived, and then, the comparison between the two basic THP structures and the linear zero-forcing (ZF) precoding is carried out in terms of the interference power and the system capacity. Furthermore, the cases with different CSI errors among users are considered, through which the independence of the interference power among layers or subchannels is presented, including the cases with single-antenna and multiantenna receivers. Analytical and simulation results indicate that with imperfect CSI, THP leads to less interference power than linear-ZF, and dTHP leads to larger system capacity than cTHP and linear-ZF.      

用于罗兰C接收机天波识别的IFFT频谱相除技术探讨

罗兰C无线电导航接收机所接收的是带有天波干扰的地波信号。为了有效的将天波分离，给出了一种简单但是有效的IFFT的频谱相除技术，应用于罗兰c接收机中采样点的适应性调节，并给出了一种会影响到整体性能的全面、综合的参数分析。仿真结果表明，运算能够在极高噪声环境下成功运行。     

Adaptive Multiuser Detection Based on RBF Networks in Impulsive Noise CDMA Channels

With increasing need for capacity in mobilecellular communications, code division multiple accesshas been viewed as the technique to meet this goal.However, the conventional receiver suffers frommultiuser interference and the near-far effect. Toalleviate this problem, various multiuser receivers havebeen proposed. They have been shown to enhance theperformance of the conventional receiver with respect to capacity and interference rejection. Butthese receivers, intended for Gaussian noise channels,can fail in other environments such as impulsive noiseconditions. A possible solution is to exploit the advantages of neural networks. A neuralnetwork's ability to reject non-Gaussian noise can beutilized to implement multiuser receivers that rejectboth impulsive noise and multiuser interference.Following this logic, this paper considers nonadaptivemultiuser receiver and adaptive multiuser receiver basedon radial basis function neural networks. Simulations ofthese receivers show results that are superior to previously studied multiuser receivers, withrespect to practicality and performance.     

多级生成的自动化测试框架的中心技术研究与实现

本文通过研究各种自动化测试框架,并经过实际自动化测试项目的实践检验,提出一个更为先进的自动化测试框架概念,这个框架的中心思想是多级生成机制.采用该机制,解决了测试工作中业务分析难的问题,把这个主观因素很强的部分变得客观化,变得有依据,变得可以自动化.框架后半部分整合了前人的成熟经验,使用数据驱动的测试框架原理做了数据自动生成与添加工作,直到测试用例的自动生成,将测试的一套过程全部自动化,并且这一过程也有很好的可回归性.     

A Comparison of Frequency-Domain Block MIMO Transmission Systems

Block transmission techniques, with appropriate cyclic prefix and frequency-domain processing schemes, have been shown to be excellent candidates for digital transmission over severely time-dispersive channels, allowing good performance with implementation complexity that is much lower than traditional time-domain processing schemes. Orthogonal frequency-division multiplexing (OFDM) modulation is the most popular block transmission technique. Single-carrier (SC) modulation using frequency-domain equalization (FDE) is an attractive alternative approach based on this principle. In this paper, we propose two new receiver structures for multiple-input-multiple-output (MIMO) channels employing SC (MIMO-SC) modulation and FDE schemes. These receivers have a hybrid structure with frequency-domain feedforward and time-domain feedback filters for intersymbol interference (ISI) and interference cancellation. The proposed schemes are compared with different MIMO systems employing OFDM modulation (MIMO-OFDM) receivers in terms of performance [bit error rate (BER) and throughput] and complexity. Our performance results show the superiority of MIMO-SC approaches relative to MIMO-OFDM in terms of the BER performance for the simulated scenarios. Also, the simulation results show that the proposed hybrid MIMO-SC receivers yield a higher throughput than a MIMO-OFDM system.     

Cross-Modulation Interference and Mitigation Technique for Ultrawideband PPM Signaling

The detection issues of ultrawideband (UWB) signals depend on the type of modulation scheme that is used during the transmission. Cross-modulation interference (CMI) is a problem that is specific to UWB pulse-position-modulation (PPM) signaling. In this paper, the effects of CMI on the performance of noncoherent UWB receivers are analyzed. The probabilities of error for transmitted-reference (TR) and energy detector (ED) receivers in the presence and absence of CMI are derived. Optimal and suboptimal CMI avoidance algorithms, which are based on novel acquisition techniques, are proposed for Rake receivers. The results show that the performance degradation in both receivers, which is due to the CMI effects, can be significant, depending on the modulation index. TR receivers still can be functional in the presence of CMI, and the target performance level determines the modulation index to be used. It is unlikely that effects of CMI on the performance of ED receivers in the presence of CMI are more severe relative to TR receivers, and the performance level is not acceptable. As a result, PPM signaling is not an appropriate modulation technique for ED receivers that are operating in the CMI region, unless CMI mitigation algorithms can be developed. Furthermore, the proposed optimal and suboptimal algorithms are two promising schemes for avoiding the CMI effects and, consequently, for improving the performance of Rake receivers operating in the CMI region.     

NGB终端中间件API接口测试用例的设计与实现

根据NGB终端中间件标准有关Java API和JS API的接口定义和要求,以及NGB的业务需求,制定了API接口测试用例的设计原则和设计方案,方案包括自动化和手动两种方式,两类测试相互补充。通过以频道搜索和媒体处理两个典型测试单元为例,介绍了这两类测试用例的软件设计流程和具体实现方法。该方案设计已经过验证,并应用于NGB中间件的标准符合性测试中。     

Performance analysis of LRT/GLRT-based array receivers for the detection of a known real-valued signal corrupted by noncircular interferences

A performance analysis of likelihood ratio test (LRT)-based and generalized likelihood ratio test (GLRT)-based array receivers for the detection of a known real-valued signal corrupted by a potentially noncircular interference is considered in this paper. The distribution of the decision statistics associated with the LRT and GLRT is studied. This allows us to give exact closed-form expressions of the probability of detection (P_D) and false alarm (P_FA) for two LRT-based receivers. Then, asymptotic (with respect to the data length) closed-form expressions are given for P_D and P_FA for four GLRT-based receivers. Finally, in order to strengthen the obtained results, some illustrative examples are presented.