Forward Link Performance Analysis in CDMA Distributed Antenna Systems with Imperfect Channel Estimation

1　Introduction　The Distributed Antenna (DA) system has been proposedas a promising antenna architecture for the future wirelesscommunication systems[1~10].　In the DA systems, with remote antennas, the presentcellular structure is removed and cells are not divided geo graphically, but according to the user needs. That is, ac cording to the channel estimates computed via pilot signals,the Processing Node (PN) continuously measures the chan nels between the mobiles and the remote ante…     

Performance Bound for LDPC Coded Unitary Space–Time Modulation

This paper is concerned with the bit error probability (BEP) of coded unitary space–time modulation systems based on finite-length low density parity check (LDPC) codes. The union bound on the BEP of the maximum likelihood (ML) decoding is derived for any code rate, unitary space–time constellation and mapping. The tightness of the bound is checked with simulation results of the ordered statistic decoding (OSD). Numerical and simulation results show that the union bound is also close to the error performance of the sum–product (SP) decoding at low BEP levels when Gray mapping is employed. The derived bound is useful to benchmark the error performance of finite-length coded unitary space–time modulation systems, especially for those that employ short-to-medium length LDPC codes.

Performance of Convolutionally Coded Multicarrier DS-CDMA System

A new convolutionally coded direct sequence （DS） CDMA system is proposed. The outputs of a convolutional encoder modulate multiple band-limited DS-CDMA waveforms. The receiver detects and combines signals for the desired user and feeds a soft-decision Viterbi decoder. The performance of this system is compared to that of a convolutionally coded single carrier DS CDMA system with a Rake receiver. At roughly equivalent receiver complexity, results will demonstrate superior performance of the coded multicarrier system.     

Analysis of Phased-Mission System Reliability and Importance with Imperfect Coverage

Accounting for static phased-mission systems (PMS) and imperfect coverage (IPC),generalized and integrated algorithm (GPMS-CPR) implemented a synthesis of several approaches into a single methodology whose advantages were in the low computational complexity, broad applicability,and easy implementation. The approach is extended into analysis of each phase in the whole mission.Based on Fussell-Vesely importance measure, a simple and efficient importance measure is presented to analyze component‘s importance of phased-mission systems considering imperfect coverage.     

Performance Analysis of Anti-Interference UWB-OFDM System

1Introduction Duetotherobustnesstomultipathfading,highrate,lowincostandsmallpowerconsumption,UWBcom municationisapromisingtechniqueforshortrang,high speedwirelessapplications[1-8].ButUWBsystem designhasmanychallenges.Oneofthemainchallenges isdealingwithal…     

Effect Investigation of Channel Estimation Deviation on STBC Performance in CDMA System

1　Introduction　Inrecentyears ,Space Timecode (STC) [3,8～ 11] hasattractedmuchattentionfrommanyscholarsinthefieldofwirelesscommunicationsasaneffectivetransmitdi versitytechniquecombatingfadinginwirelesscommuni cations.SpaceTimeBlockCode (STBC) [3] ,whichisproposedbyS .M .Alamoutiin 1998asasub optimaltransmitdiversitytechnique ,canobtain gainthroughemployingtwoantennasattransmitend .However,STBChastheassumptionofflatfadingchannelcondi tionthatlimitsitsuseonbroadbandwirelesscommuni cat…     

Performance Analysis of a DS-CDMA Cellular System with Effects of Soft Handoff in Log-Normal Shadowing Channels

Next generation wireless communication is based on a global system of fixed and wireless mobile services thatare transportable across different network back-bones,network service providers and network geographical boundaries.This paper presents an approach to investigate the effects of soft handover and perfect power control on the forward link ina DS-CDMA cellular system.Especially,the relationships between the size ofhandover zone and the capacity gain are e-valuated under the log-normal shadow channel.Then the optimization of maximum forward capacity is very necessary tobe done with the maximum size of soft handover zone to the various system characteristics.     

Performance Analysis of Joint Relay and Transmit–Receive Antenna Selection for Low Density Parity Check-Asynchronous Distributed Space Time Block Coded Cooperative Diversity System

In this work we propose a joint relay and transmit–receive antenna selection method for amplify and forward asynchronous distributed space time block coded (ADSTBC) system. To the LDPC coded signal received from the source at the relays, we apply linear dispersion codes which are optimized over the delay profile of the system to produce the ADSTBC. Selection of the best transmit–receive antenna pair between source and selected relays, and that of between the selected relays and destination is done on the basis of instantaneous signal to noise ratio (SNR) of the respective paths. The relays and transmit-receive antenna pairs are selected by maximizing the end-to-end instantaneous SNR. Performance analysis of the system is done on the basis of pair wise error probability and outage probability (P_out).     

Cross-layer in MIMO-OFDM System with Adaptive Modulation and Coding：Design and Analysis

The queuing performance of the cross-layer system with Space-time block code （STBC） over Multi- input-multi-output （MIMO） channel is analyzed. The Adaptive modulation and coding （AMC） in physical layer and finite length of buffer in data-link layer are combined with this model. A simple cross-layer design and the queue state process are proposed based on finite state 1V[arkov channel model~ which is to solve the service process. The proposed cross-layer design is also incorporated with STBC to further improve the system performance. Simulation results illustrate the dependence of system performance on various parameters, and quantify the performance gain due to cross-layer optimization. The adjustment of target packet loss rate of adaptive modulation coding in physi- cal layer can maximize average throughput of the system, meanwhile a significant improvement of the system perfor- mance is brought.     

Performance Analysis of RF Spiral Inductor with Gradually Changed Metal Width and Space

To decrease the metal losses of RF spiral inductor,a novel layout structure with gradually reduced metal line width and space from outside to inside is presented.This gradual changed inductor has less eddy-current effect than the conventional inductor of fixed metal width and space.So the series resistance can be reduced and the quality (Q) factor of the inductor relating to metal losses is increased.The obtained experimental results corroborate the validity of the proposed method.For a 6nH inductor on high-resistivity silicon at 2.46GHz,Q factor of 14.25 is 11.3% higher than the conventional inductor with the same layout size.This inductor can be integrated with radio frequency integrated circuits to gain better performance in RF front end of a wireless communication system.     

Performance Analysis of a Sectorized Distributed Antenna System with Reduced Co-Channel Interference

1IntroductionThe next generation mobile communication systemissupposedto provide high data rate services such as Inter-net access and multi media applications whichare morelikelyto be affected by Inter-Symbol-Interference(ISI)inwireless multi-path fading …     

Optimization of MQAM Modulation Schemes in Mobile Communications(Ⅰ)——Analysis of MQAM BER Performance in AGWN Channel Based on Signal Space

Based on signal space concepts, a transmission error code performance for MPSK, square MQAM and star MQAM modulation schemes on the AGWN channel is analyzed. The corresponding BER formulas and computer aided numeric results are also given. Therefore it provides a theoretical basis for choosing MQAM modulation schemes in mobile communications.     

Simplified Semi-Blind Channel Estimation for Space–Time Coded MIMO-OFDM Systems

The combination of Space–Time Coded Multiple Input Multiple Output systems (STC-MIMO) with Orthogonal Frequency Division Multiplexing (OFDM) is recently being investigated as an effective means of providing high-speed data transmission over dispersive wireless channels. The strengths of the two techniques coalesce and render MIMO-OFDM systems robust to ISI and IBI. However, the decoding and demodulation of STC-OFDM needs reliable channel knowledge at the receiver, unless differential modulation techniques are used. Semi-blind methods for channel estimation are seen to provide the best trade-off in terms of bandwidth overhead, computational complexity and latency. The conventional Expectation-Maximization (EM) algorithm for semi-blind channel estimation improves a pilot-based estimate with a two step process; however, it is computationally complex to implement. In this paper, we propose a variant of the EM method, referred to as ML-EM, for semi-blind estimation of doubly dispersive channels in space–time coded MIMO-OFDM systems. Here, the conventional EM algorithm is coupled with the ML decoder for space time block codes (STBCs). The technique shows good performance, even in highly correlated antenna arrays, and is computationally simpler than conventional EM. The method incurs a training overhead of less than 1%, and performs close to exact CSI through iterative processing at the receiver.     

Optimization of MQAM Modulation Schemes in Mobile Communications（I）—Analysis of MQAM BER Performance in AGWN Channel Based on Signal Space

Based on signal space concepts, a transmission error code performance for MPSK, square MQAM and star MQAM modulation schemes on the AGWN channel is analyzed.The corresponding BER formulas and computer aided numeric results are also given.Therefore it provides a theoretical basis for choosing MQAM modulation schemes in mobile communications.     

Performance Analysis of Combined mMCSK–mMFSK Modulation in AWGN and Rayleigh Fading Channel

As there are many use cases considered for robotics communications, the data rate variation may be very large. Some sensor applications may require very low data rate, telemetry data may require low-to-medium data rates and e.g. video application will require high data rates. On the other hand, robots may have to operate in very difficult radio propagation environments such as nuclear power plants or industrial facilities. To combat difficult propagation characteristics, an often used and well known mechanism is to use spread spectrum signal structures. Thus in this paper a novel modulation method is considered which offers the inherent signal structure and processing opportunities of spread spectrum signal and at the same time offers an easy mechanism to adapt the data rate from low to high depending on the requirement at hand thus addressing two important communication requirements for robotics. The introduction of $m$ MFSK generated the idea of applying the given approach to other modulation methods. To further enlarge the modulation alphabet sizes (with the price of larger spectrum usage) it was realized that combining the $m$ MFSK and $m$ MCSK would be an interesting choice. The $m$ MCSK– $m$ MFSK modulation is hence considered. A method to analyze this two-component modulation is developed and the performance analyses give results for $m$ MCSK– $m$ MFSK modulation in AWGN and flat Rayleigh fading channels for both coherent and non-coherent receivers. The performance was also assessed with orthogonal and non-orthogonal code constructs for coherent receiver.     

Feasibility Analysis of Applying Beidou Satellite Navigation System Ⅱ in Space TT&C Ship

通过建模理论分析和数值计算分析了“北斗”二代导航系统的定位性能及其对测量船应用的影响,论证了其应用的可行性.对其定位性能的仿真计算表明:“北斗”二代导航系统比GPS最大定位误差增大约12 m.推导了船位误差与定位精度的关系,计算分析了船位误差对测量船引导数据精度和外测精度的影响,得出在该导航系统主要覆盖区域,其定位性能能够满足使用测量船需求的结论.     

Capacity Analysis of Adaptive Transmission with Space–Time Block Codes in Spatially Correlated MIMO Nakagami-m Fading Channels

In this paper we investigate the impacts of spatial fading correlation on channel capacity of orthogonal space–time block codes (STBCs) over multiple-input multiple-output Nakagami- \(m\) fading under different power and rate allocation policy. This paper presents the single-input single-output equivalency of STBC which is equivalent to scalar additive white Gaussian noise channel, with a channel gain proportional to the Frobenius norm of the matrix channel. We derive the characteristic function (c.f.) of the signal-to-noise ratio at the output of the STBC decoder, when spatial fading correlation is assumed. The c.f. turns out to be a linear combination of Laplace transforms weighted by the eigenvalues of the channel correlation matrix, where each element corresponds to an elementary Gamma probability density function. Based on this approach, and using the linearity of the Laplace transform, the capacity expressions are derived for STBC under different adaptive transmission policy. Numerical results illustrate the impact of fading correlation and fading severity on the channel capacity and outline the performance differences between the distinctive adaptation policies.     

Performance Analysis and Optimal Power Allocation for Space–Time and Amplify-and-Forward Cooperative System

In this paper, we consider a space?Ctime and amplify-and-forward (ST-AF) cooperative system which consists of two-antenna source, single-antenna relay and destination. Source transmits Alamouti space?Ctime coding symbols to destination with cooperation of relay which adopts AF strategy. Closed-form symbol error rate (SER) is derived for the ST-AF system with PSK signals. Moreover, a SER approximation is developed to show the asymptotic performance of the ST-AF cooperative system in medium and high SNR regimes. For comparison, the SER approximation of another cooperative space?Ctime coding (C-STC) scheme is also derived. Theoretical analysis shows that the ST-AF can obtain more diversity gain and achieve higher diversity order than C-STC. Statistical optimal power allocation (OPA) algorithm for the ST-AF cooperative system is presented based on the SER performance. It turns out the OPA only depends on the channel links related to the relay, not depend on the direct link between source and destination. Finally, numerical simulations validate the theoretical analysis.     

Adaptive Modulation with Channel Estimation in High-Speed Packet-Based OFDM Communication Systems

1　Introduction　TherapidgrowthofInternetandmobilecommu nicationssuggestthatwirelesshigh speeddataser viceswillbeingreatdemand .Beyond 3Gsystemsaimingatdataratesupto 2 0Mbpsorevenhigherareunderintensivestudy[1～ 3] .Butprovidinghighdataratesinadversewirelesschannelsischalleng ing .OFDMhasbeenconsideredthemostpromisingsolutionforbeyond 3GbecauseofitsrobustnesstoInter SymbolInterference (ISI)andhighspectrumefficiency[4] .　OFDMhasanumberofapplications,includingAsymmetricDigitalSubscriber…