某机场塔康地面台移址技术分析

塔康地面台是某机场的主要导航设备,由于某种原因,原塔康地面台安装地点被迫拆除。因为飞行任务的需要,该设备需要重新选址。本文从设备原理简介、场地影响和移址场地选择等方面进行了深刻的技术分析,并对预选的3个站点进行了优势和对比分析,为塔康台新站点的最终选定,提供了理论依据。

涡河蒙城枢纽移址重建影响分析

蒙城枢纽是涡河上一座集防洪、排涝、蓄水灌溉、交通航运于一体的大型枢纽工程,由于涡河航道等级提高船闸需扩建,同时蒙城定位为生态城市对水环境和水景观有更高的需求,枢纽需移址重建。文章分析了枢纽移址重建,对防洪、排涝、灌溉、航运、环境、水资源等方面的影响及处理方案,提出枢纽移址重建技术上是可行的,符合流域总体规划要求,有利于促进区域经济的发展。

浅谈中波发射台选址

随着城市规模的扩大和房地产的蓬勃发展,笔者所在的中波台面临着需要择址搬迁的命运,笔者想结合自身实际情况聊聊中波台选址应注意的事情。

扬州市安墩闸站S形轴伸泵装置选择及应用

分析原安墩闸站运行资料,并结合移址改建后安墩闸站的设计运行管理要求,选择S形轴伸泵装置,排涝标准为20年一遇。土建工程量减小,工程运行耗能显著降低,每年节省电量约960MWh,闸站运行管理更加便捷。同时应用CFX对安墩闸站S形轴伸泵装置性能进行预测,结果显示S形轴伸泵装置内部流态平顺,水流运动十分合理。水泵叶片最佳安放角为-2°,最高运行效率可达76%,设计工况下运行效率可达75%。

A novel secure multicast scheme in mobile Internet

A novel multicast communication model using a RingNet hierarchy is proposed. The RingNet hierarchy consists of 4 tiers: border router tier, access gateway tier, access proxy tier and mobile host tier. Within the hierarchy, the upper 2 tiers are dynamically organized into logical rings with network entities. A novel hierarchical secure access control scheme on key management is proposed based on the RingNet model. Network entities within the multicast hierarchy belong to different privileged local groups. Network entities of the higher-privileged local groups have the right to derive the keys held by network entities of the lower-privileged local groups, and the reverse operation is not allowed. With the key management approach, any insertion and changing of local group key will not affect other local groups. The analytical result shows that the scheme has higher security than Lin’s.

PAPR reduction in mobile WiMAX:A new ZCMT precoded random interleaved OFDMA system

Mobile WiMAX(worldwide interoperability for microwave access) air interface adopts orthogonal frequency division multiple access(OFDMA) as multiple access technique for its uplink(UL) and downlink(DL) to improve the multipath performance.All OFDMA based networks,like mobile WiMAX,experience the problem of high peak-to-average power ratio(PAPR).The high PAPR increases the complexity of analog-to-digital(A/D) and digital-to-analog(D/A) convertors,and also reduces the efficiency of RF high-power-amplifier(HPA).In this work,a new zadoff-chu matrix transform(ZCMT) precoding based random interleaved orthogonal frequency division multiple access(OFDMA) system was proposed for PAPR reduction in mobile WiMAX system.The system is based on precoding the constellation symbols with the ZCMT precoder before subcarrier mapping.The PAPR of proposed system is analyzed with the root-raised-cosine(RRC) pulse shaping to keep out of band radiation low and meet the transmission spectrum mask requirement.Simulation results show that the proposed system has better PAPR gain than the hadamard transform(WHT) precoded random interleaved OFDMA systems and the conventional random interleaved OFDMA systems.Symbol-error-rate(SER) performance of the system is also better than the conventional random interleaved OFDMA systems and the random interleaved OFDMA systems with WHT.The good improvement in PAPR significantly reduces the cost and the complexity of the transmitter.

CHANNEL ESTIMATION OF MULTI-RATE DS-CDMA SIGNALS IN SLOW FADING MULTIPATH CHANNELS

In Direct-Sequence Code Division Multiple Access(DS-CDMA) mobile communi-cation systems, it is very important to obtain accurate estimation of the channel parameters,especially that of the propagation delay. But the near-far problem may make the estimationcomplicated and can degrade the estimation performance significantly. In this paper, an efficientMaximum Likelihood (ML) method is presented for channel parameter estimation of multi-rateDS-CDMA systems in slow fading multipath channels in a near-far scenario. The algorithmextended the ML approach to multi-rate DS-CDMA systems, and proposes decomposing a multi-dimensional optimization problem into a series of one-dimensional optimization and has improvedcomputational efficiency. Theoretical analysis and numerical examples show that the estimatorproposed is effective and near-far resistant.

Research on Translation Gateway for IPv4/IPv6

In this paper, a model of translation gateway is proposed. The communications between IPv4 network and IPv6 network are realized by using the Microsoft intermediate driver technology in environment of Windows 2000.

A Semi-blind Adaptive Beamforming Algorithm for Wideband Coherent CDMA

This paper presented a novel semi blind adaptive beamforming algorithm specially designed for wideband coherent CDMA mobile communication systems with multiplexd control and data channels. The presented algorithm uses a parallel structure to exploit not only the desired user’s pseudo noise sequence but also the information from multiplexed pilot and data symbols, thus help achieve faster convergence and lower bit error rate. Monte Carlo simulation results verified the performance improvement in terms of BER.

ITERATIVE "ONE-SHOT" DECORRELATION IN DS-CDMA SYSTEMS

In this paper, an iterative 'one-shot' decorrelator for asynchronous code Division Multiple Access(CDMA) systems is proposed. This decorrelator feedbacks the decorrelated symbols of interfering users before decision to mitigate their interferences. As a result, this decorrelator is a linear detector and does not need any amplitude information of users as in decision-feedback detectors. Compared with existing 'one-shot' decorrelator, it has reduced complexity and provided better performance while eliminating all Multiple Access Interference(MAI). The performance of this decorrelator is analyzed thoeritically, and analytical result is given. Numerical results show near-far resistant capability of this decorrelator in both AWGN and fading channel.

Multiple phase detector of M-ary phase shift keying symbols in code division multiple access systems

A novel iterative technique, the phase descent search detection was proposed. This technique constrained the solution （PDS） algorithm, for M-ary phase shift keying （M-PSK） symbols to have a unit magnitude and it was based on coordinate descent iterations where coordinates were the unknown symbol phases. The PDS algorithm, together with a descent local search （also implemented as a version of the PDS algorithm）, was used multiple times with different initializations in a proposed multiple phase detector; the solution with the minimum cost was then chosen as the final solution. The simulation results show that for highly loaded multiuser scenarios, the proposed technique has a detection performance that is close to the single-user bound. The results also show that the multiple phase detector allows detection in highly overloaded scenarios and it exhibits near-far resistance. In particular, the detector has a performance that is significantly better, and complexity that is significantly lower, than that of the detector based on semi-definite relaxation.

On-demand multicast routing protocol based on node classification in MANET

An improved on-demand multicast routing protocol(ODMRP), node classification on-demand multicast routing protocol(NC-ODMRP), which is based on node classification in mobile ad hoc networks was proposed. NC-ODMRP classifies nodes into such three categories as ordinary node, forwarding group(FG) node, neighbor node of FG node according to their history forwarding information. The categories are distinguished with different weights by a weight table in the nodes. NC-ODMRP chooses the node with the highest weight as an FG node during the setup of forwarding group, which reduces a lot of redundant FG nodes by sharing more FG nodes between different sender and receiver pairs. The simulation results show that NC-ODMRP can reduce more than 20% FG number of ODMRP, thus enhances nearly 14% data forwarding efficiency and 12% energy consumption efficiency when the number of multicast senders is more than 5.

A Survey: Several Technologies of Non-Orthogonal Transmission for 5G

One key advantage of 4G OFDM system is the relatively simple receiver implementation due to the orthogonal resource allocation.However,from sum-capacity and spectral efficiency points of view,orthogonal systems are never the achieving schemes.With the rapid development of mobile communication systems,a novel concept of non-orthogonal transmission for 5G mobile communications has attracted researches all around the world.In this trend,many new multiple access schemes and waveform modulation technologies were proposed.In this paper,some promising ones of them were discussed which include Non-orthogonal Multiple Access(NOMA),Sparse Code Multiple Access(SCMA),Multi-user Shared Access(MUSA),Pattern Division Multiple Access(PDMA)and some main new waveforms including Filter-bank based Multicarrier(FBMC),Universal Filtered Multi-Carrier(UFMC),Generalized Frequency Division Multiplexing(GFDM).By analyzing and comparing features of these technologies,a research direction of guiding on future 5G multiple access and waveform are given.

AN SVAD ALGORITHM BASED ON FNNKD METHOD

The capacity of mobile communication system is improved by using Voice Activity Detection (VAD) technology. In this letter, a novel VAD algorithm, SVAD algorithm based on Fuzzy Neural Network Knowledge Discovery (FNNKD) method is proposed. The performance of SVAD algorithm is discussed and compared with traditional algorithm recommended by ITU G.729B in different situations. The simulation results show that the SVAD algorithm performs better.

Technology Trends and Architecture Research for Future Mobile Internet

With the rapid development of wireless transmission technologies and the proliferation of mobile terminals, the mobile Internet has experienced exponential growth in recent years. However, at the same time, it is also facing more challenges, particularly regarding bandwidth, address space, security, mobility, and energy. In this article, we analyse the five abovementioned challenges and then survey related technology trends. We also describe the progress of architecture research aimed at the future mobile Internet. We reach the conclusion that a single technology cannot solve all the problems of mobile Internet, and future research should focus more on how to make architectures and technologies work together more effectively.

DPLL implementation in carrier acquisition and tracking for burst DS-CDMA receivers

This paper presents the architectures, algorithms, and implementation considerations of the digital phase locked loop (DPLL) used for burst-mode packet DS-CDMA receivers. As we know, carrier offset is a rather challenging problem in CDMA system. According to different applications, different DPLL forms should be adopted to correct different maximum carrier offset in CDMA systems. One classical DPLL and two novel DPLL forms are discussed in the paper. The acquisition range of carrier offset can be widened by using the two novel DPLL forms without any performance degradation such as longer acquisition time or larger variance of the phase error. The maximum acquisition range is 1/(4T), where T is the symbol period. The design can be implemented by FPGA directly.

An LFSR-based address generator using optimized address partition for low power memory BIST

Power consumption in test mode is much higher than that in normal mode,which is prone to causing circuit damage and reducing the yield of chips.To reduce the power dissipation efficiently,a modified linear feedback shift register(LFSR)is designed to decrease switching activity dramatically during the generation of address sequences for memory built-in self-test(MBIST).The address models are generated by a blend of two address generators with an optimized address partition and two distinct controlled clock signals.An address generator circuit for MBIST of 64 k×32 static random access memory(SRAM)is designed to illustrate the proposed scheme.Experimental results show that when the address bus size is 16 bits,compared with the traditional LFSR,the proposed LFSR can reduce the switching activity and dynamic power by 71.1%and 68.2%,respectively,with low area overhead.

PROXY-BASED PATCHING STREAM TRANSMISSION STRATEGY IN MOBILE STREAMING MEDIA SYSTEM

A mobile transmission strategy, PMPatching (Proxy-based Mobile Patching) transmission strat-egy is proposed, it applies to the proxy-based mobile streaming media system in Wideband Code Division Multiple Access (WCDMA) network. Performance of the whole system can be improved by using patching stream to transmit anterior part of the suffix that had been played back, and by batching all the demands for the suffix arrived in prefix period and patching stream transmission threshold period. Experimental results show that this strategy can efficiently reduce average network transmission cost and number of channels consumed in central streaming media server.

Carrier frequency offset estimation for a generalized OFDMA uplink

A residual carrier frequency offset （CFO） estimation scheme is proposed for the uplink of orthogonal frequency division multiple access （OFDMA） systems. Multiple access interference caused by CFOs in the uplink is investigated, as it severely affects the performance of a classical maximum likelihood （ML） frequency estimator. By the use of the estimated CFOs of the active users, the linear maximum mean square error （LMMSE） equalization is performed before the ML frequency estimator for the interference cancellation, which can help to sufficiently improve the estimation accuracy for the residual CFO of the incoming user. Analysis and simulations show that the modified ML estimator provides a tradeoff between estimation accuracy and computational complexity caused by the LMMSE interference cancellation, and the proposed method allows OFDMA systems flexibly allocating subcarriers to users.

王引河芒山闸除险加固可行性研究

永城市王引河芒山节制闸始建于1959年,1975年进行扩建。自扩建以来已连续运行40多年,虽经多次维修,目前仍存在许多安全隐患。经河南省水利厅核查,该水闸安全级别为四类,按相关规定的要求应当拆除重建,但由于下游海漫段被现有省道桥梁占用,在原址重建已不具备条件。因此,文章对该闸目前存在的各类问题进行总结,并对该闸除险加固的必要性及移址重建的可行性进行分析,以期为该闸移址重建提供相应参考。