Top PDF Noncoherent Block Detection in the Presence of DC Offset

Noncoherent Block Detection in the
Presence of DC Offset

Noncoherent Block Detection in the Presence of DC Offset

Noncoherent Block Detection in the Presence of DC Offset Char-Dir Chung, Senior Member, IEEE Abstract— In this paper, we deal with noncoherent detection of a digitally phasor block-modulated signal in the additive white Gaussian noise channel when a direct-current (DC) offset is present in the receiver baseband processing. By processing the received baseband signal block by block, a generalized linear transform is used to remove the offset prior to data detection, thereby releasing the succeeding detection process from the threat of DC offset. Operating on transform output blocks, a generalized maximum-likelihood scheme is developed for noncoherent data detection without a priori knowledge of channel amplitude and phase. When all the signaling blocks are confined within the space expanded by the basis vectors obtained from the offset-removal transform matrix, the proposed detection scheme can exploit the advantage of performing data detection and estimation on channel amplitude and phase jointly in the maximum-likelihood sense. It is analytically shown that the block detection scheme provides the bit error performance asymptotically approaching that of the corresponding ideal coherent phase-shift-keyed (PSK) detection in the absence of DC offset when the block length is increased. An iterative detection scheme is also modified from the block detection scheme to simplify the realization complexity. Both block and iterative detection schemes are shown to outperform the conventional training-sequence-aided PSK detection scheme under the same transmission throughput efficiency.
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Noncoherent block detection in the presence of DC offset

Noncoherent block detection in the presence of DC offset

Noncoherent Block Detection in the Presence of DC Offset Char-Dir Chung, Senior Member, IEEE Abstract— In this paper, we deal with noncoherent detection of a digitally phasor block-modulated signal in the additive white Gaussian noise channel when a direct-current (DC) offset is present in the receiver baseband processing. By processing the received baseband signal block by block, a generalized linear transform is used to remove the offset prior to data detection, thereby releasing the succeeding detection process from the threat of DC offset. Operating on transform output blocks, a generalized maximum-likelihood scheme is developed for noncoherent data detection without a priori knowledge of channel amplitude and phase. When all the signaling blocks are confined within the space expanded by the basis vectors obtained from the offset-removal transform matrix, the proposed detection scheme can exploit the advantage of performing data detection and estimation on channel amplitude and phase jointly in the maximum-likelihood sense. It is analytically shown that the block detection scheme provides the bit error performance asymptotically approaching that of the corresponding ideal coherent phase-shift-keyed (PSK) detection in the absence of DC offset when the block length is increased. An iterative detection scheme is also modified from the block detection scheme to simplify the realization complexity. Both block and iterative detection schemes are shown to outperform the conventional training-sequence-aided PSK detection scheme under the same transmission throughput efficiency.
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Maximum Likelihood Block Detection of Noncoherent Multi-h CPFSK 陳俊達、楊新雄

Maximum Likelihood Block Detection of Noncoherent Multi-h CPFSK 陳俊達、楊新雄

In this thesis, we examine maximum likelihood block detection (MLBD) of noncoherent continuous phase frequency shift keying signals with periodic modulation indexes (Multi-h CPFSK) in AWGN and flat Rayleigh fading channels. First, the maximum likelihood metric is introduced, and the bit error probability of the detection algorithm in an AWGN channel is derived. The noncoherent detector is shown to consist of a bank of matched filters followed by a sequence estimator. In the AWGN channel, the simulation results are consistent with theoretical results, and demodulation using MLBD with a four-symbol observation is compared with MLSD and one-bit differential detection (DD). MLBD has about 3 dB improvements over 1-bit DD, and have no more than 3-4 dB loss than MLSD. The performance of MLBD in a flat Rayleigh fading channel are obtained by computer simulation. When in slowly fading case, it is interesting to note that the performance of a three-symbol observation has 1 dB improvement over a two-symbol observation. However, when fading becomes fast, both the two- and three-symbol observations form an error floor, and the performance of the three-symbol observation is worse than the two-symbol observation at a high SNR. In the flat Rayleigh fading channel, the SNR about 30 dB is required by MLBD to yield a bit error rate of 0.001. Hence, we can conclude that the modulation scheme using the multi-h signal can be a practical one in the fading channel when MLBD is applied.
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A fully digital noncoherent and coherent GMSK receiver architecture with joint symbol timing error and frequency offset estimation

A fully digital noncoherent and coherent GMSK receiver architecture with joint symbol timing error and frequency offset estimation

Assume that we first convert the received signal from radio frequency (RF) to baseband and the real and imaginary compo- nents of the base-band complex signal are and . These two signals are oversampled, digitally frequency discriminated, and low-pass filtered to obtain raw digital data. This data goes through an FFT for synchronization preamble bits detection. If detected, both frequency offset and sampling time error are es- timated from the FFT results. Symbol timing sychronization is done in a feedforward manner. Carrier frequency offset com- pensation is done in a hybrid manner. On one hand, frequency offset estimation is fed back to a VCO during the preamble pe- riod. On the other hand, this estimation can be used to change the decision threshold in a noncoherent detection mode or rotate the signal constellation in a coherent detection mode. After syn- chronization is finished, we obtain the demodulated data. The whole synchronization and data detection process can be un- derstood in more detail by examining the flowchart shown in Fig. 2.
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BLOCK COPOLYETHERESTERS .3. PREPARATION OF BLOCK COPOLYETHERESTERS BY A TEREPHTHALIC ACID PROCESS IN THE PRESENCE OF SALTS

BLOCK COPOLYETHERESTERS .3. PREPARATION OF BLOCK COPOLYETHERESTERS BY A TEREPHTHALIC ACID PROCESS IN THE PRESENCE OF SALTS

endotherm corresponding to the melting of the hard polyester segments was observed for the block copolyetheresters. Their thermal proper- ties were significantly affected b[r]

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Complete elimination of DC offset in current signals for relaying applications

Complete elimination of DC offset in current signals for relaying applications

This section proposes the algorithm of SDFT that estimates the DC offset, frequency, and phasor from a fault current signal.. Since there are several components in a fault curr[r]

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Spin-current generation and detection in the presence of an ac gate

Spin-current generation and detection in the presence of an ac gate

J chir 共t兲⫽关 具 J y x 共t兲 典 ⫺ 具 J x y 共t兲 典 兴/2. 共15兲 It is easily seen that this chiral projection has the same form as the expression 共4兲 for a 1D system, if n represents the electron density of the 2DEG. In Fig. 2 we illustrate the spin-current distribution for a circular gate which is marked as the gray area. The spin polarization at any point under the gate has two components parallel to the 2DEG. For any di- rection specified by the unit vector N ជ , the two spin-polarized fluxes with polarization directions parallel and antiparallel to N ជ will oscillate out of phase by the amount of ␲ along the direction perpendicular to N ជ . Such out of phase oscillation is schematically plotted in Fig. 2. The amplitude of the spin density flow in each of the opposite directions, as marked by the dashed-line arrows, is just J chir (t). In the 2DEG outside the gate area, the spin current can be supported only by spin diffusion. Therefore the chiral ac spin polarization is accu- mulated in the vicinity of the circumference of the gate, and from where diffuses away from the gate area. It can also diffuse under the gate. For small gates such back diffusion can diminish the efficiency of the spin generation. On the other hand, for large gates with the size larger than the spin- diffusion length the diffusion counterflow does not reduce much the total spin current.
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Noncoherent Detection of MDPSK in DS-CDMA 賴昱廷、楊新雄

Noncoherent Detection of MDPSK in DS-CDMA 賴昱廷、楊新雄

frequency-selective fading channel. We are now combining the MSDD and Rake receiver to be the signal demodulator. In conventional, there are two kinds of Rake receivers. One is coherent demodulator and another is noncoherent demodulator. For coherent demodulation, it needs to have channel estimation at each path. The advantage is that the performance will be improved. On the other hand, the disadvantage is complexity and operation will increase. On the contrast, for noncoherent demodulation, it is the performance degradation and complexity simplification. In this thesis, we suggest a multiple symbol differential detection on Rake receiver for DS-CDMA system. From out computer simulation, only for hard decision, the performance is improved and the improvement is proportional to the number of multipath and the number of the length of multiple symbol. This will not happen in conventional MDPSK. Moreover, we employee the technique of Viterbi-decoding differential detection to obtain additional improvement.
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Server Placement in the Presence of Competition

Server Placement in the Presence of Competition

of the same theoretical upper bound on average. 1 Introduction This paper considers a strategy for setting up servers to compete with existing ones. For example, we assume that there are originally a number of McDonald’s restaurants in a city, but no Kentucky Fried Chicken (KFC) restaurants. Now, if we decide to set up a number of KFC restaurants in the same city, where should we place them? We need to determine the locations for KFC so that they can compete with McDonald’s and maximize their profits. Due to heavy competition among business of similar nature, it is important to choose locations of new servers in the area where the competitors have deployed their servers.
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Control of the Surface Charges of Au?Ag Nanorods:  Selective Detection of Iron in the Presence of Poly(sodium 4-styrenesulfonate)

Control of the Surface Charges of Au?Ag Nanorods: Selective Detection of Iron in the Presence of Poly(sodium 4-styrenesulfonate)

Conclusions We have developed a colorimetric probe, based on CTAB- Au-Ag NRs in the presence of PSS, for the selective detection of Fe 2+ ions. The charge dependence of CTAB-Au-Ag NR agglomeration and the selectivity of the binding of PSS toward Fe 2+ ions are the two most important parameters determining the sensitivity and selectivity of this probe. Our reasoning is supported by TEM, ζ potential, and absorption data. The present probe was sensitive toward Fe 2+ (LOD ) 1.0 µM), with high selectivity over most interference metal ions in aqueous solution. Judging from these results, we foresee great practical potential for various shaped Au-Ag NRs that have outstanding optical properties, including strong and sharp longitudinal SPR absorption bands in the visible and near-infrared regions. To achieve the advantages of sensitivity, selectivity, and high throughput, bioconjugation of Au-Ag NRs is essential. In the future, we will focus on the preparation of various bioconjugated Au-Ag NRs, which we hope can be used practically for the simultaneous analysis of several analytes of interest, such as metal ions and proteins.
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The effect of friction reduction in the presence of in-plane vibrations

The effect of friction reduction in the presence of in-plane vibrations

Received: 12 June 2004 / Accepted: 9 August 2005 / Published online: 9 December 2005 © Springer-Verlag 2005 Abstract A reduction of friction by vibrations has been observed in various experiments. This effect can be applied to actively control frictional forces by modulating vibrations. Moreover, common methods of con- trolling friction rely on lubricants and suitable material combinations. The superimposition of vibrations can further reduce the friction force. This study presents a theoretical approach based on the Dahl friction model that describes the friction reduction observed in the presence of the tangential vibrations at an arbitrary angle.
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Kinetics of styrene emulsion polymerization in the presence of montmorillonite

Kinetics of styrene emulsion polymerization in the presence of montmorillonite

Chemistry Department, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.. and.[r]

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Catalytic properties of NiX zeolites in the presence of ceriumadditives

Catalytic properties of NiX zeolites in the presence of ceriumadditives

Owing to the electron-donating properties and the high polarizing field of Ce3+ cations, it is conceivable the Ce3+ ions modify the strength of the inter- action be[r]

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Structure of fast shocks in the presence of heat conduction

Structure of fast shocks in the presence of heat conduction

structure of various MHD shocks 15–18 and the structure of reconnection layer. 19–23 In our earlier studies, 15,16,23 we have examined the ef- fects of parallel heat conductivity K 储 on slow shocks and intermediate shocks by using one-dimensional 共1D兲 magne- tohydrodynamic 共MHD兲 numerical simulations. In the pres- ence of K 储 , a slow shock consists of two parts: the isothermal main shock and the foreshock. In this paper, we will focus on the heat conductivity effects on the fast shock structure and the evolution of the density jump across the main shock. At the main shock, most plasma and field quantifies make a jump in their values. The foreshock is a region immediate upstream of the main shock, in which some plasma and field quantifies are different from those in the far upstream region due to some physical processes taking place at the main shock. In the presence of heat conduction, the foreshock is formed due to the heat flux flowing from the high- temperature downstream region to the upstream region. Due to thermal diffusion, the width of foreshock region 共L d 兲 ini- tially expands toward upstream linearly with time. With the slowing down of the leading diffusion edge of foreshock at a later stage, L d tends to reach a constant value and the fore- shock structure reaches a steady state in the shock frame. In the steady state, the value of diffusion velocity V d in the foreshock is found to be nearly equal to the upstream con- vection velocity in the fast shock frame. The jumps of physi- cal quantities, such as density, pressure, velocity, and mag- netic field, across the main shock can be determined by the modified Rankine-Hugoniot 共RH兲 relations with heat flux. 15,16 The results show that the calculated density jump across the main shock with heat conduction can far exceed the maximum value of 4 without heat conduction, consistent with simulation results. We also study the time evolution of the foreshock structure under different set of initial upstream parameters 共 ␤ 1 , M A1 , ␪ 1 兲.
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Performance of Noncoherent Maximum-Likelihood Sequence Detection for Differential OFDM Systems With Diversity Reception

Performance of Noncoherent Maximum-Likelihood Sequence Detection for Differential OFDM Systems With Diversity Reception

VI. C ONCLUSIONS In this paper, we review the NSD and its three special cases, namely, the CR, DR, and VR. Based on the estimator-detector structures, a hierarchical interpretation of the NSD and its spe- cial cases are also presented. Then the NSD and its special cases are applied to the differential OFDM systems with diversity re- ception. Moreover, assuming sufficient CP, we provide a simple closed-form BER expression for differential OFDM systems employing the CR with diversity reception in the time-varying multipath Rayleigh fading channels. Numerical results have revealed that, with multi-antenna diversity reception, the per- formance of the CR is improved significantly. However, when few receive antennas are available, the implementation of the DR or VR is necessary for achieving better and satisfactory performance.
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Impedance analysis of working PEMFCs in the presence of carbon monoxide

Impedance analysis of working PEMFCs in the presence of carbon monoxide

Figure 8b shows the dependence of the ohmic resistance in the catalytic layer 共R N 兲 on current density. The cathode resistance R N,c , was not affected significantly in the presence of CO in hydrogen. However, the anode resistance R N,a increased with the concentration of CO in hydrogen, which is a similar trend to R ct,a . This result should not be explained from the point of view of the Nafion poly- mer electrolyte in catalytic layer, because the concentration of CO was too low to affect the conductivity of the Nafion polymer elec- trolyte. A proper explanation can be based on the structure of the catalytic layer, which was porous. As a binder, the Nafion polymer electrolyte was distributed in the catalytic layer to form an electro- lyte net. Figure 6 is the equivalent circuit for the reaction behavior on a single active site. This equivalent circuit was successfully ap- plied to explain the reaction behavior of the electrode without CO poisoning. However, as the CO poisoning occurred, it failed to ex- plain the increase of ohmic resistance in the catalytic layer with current density. The reaction behavior of the electrode might be explained with the complex equivalent circuit in Fig. 10. In each Nafion polymer electrolyte channel in the catalytic layer, the ohmic resistance connected with the charge-transfer resistance in series, as shown in Fig. 10a. There were numerous Nafion polymer electrolyte channels in the catalytic layer. All of these electrolyte channels formed a proton conductive net with multiple channels and basically connected in parallel. R N and R ct in Fig. 6 may be considered the sums of the parallel connection for the ohmic and the charge- transfer resistances in each electrolyte channel in Fig. 10, respec- tively. As the CO poisoning occurred, many active sites adsorbed CO and became inactive. The Nafion polymer electrolyte connected to the inactive sites also became nonconductive, because the proton did not transport in this path to participate in any reaction. There- fore, parts of the parallel connections in the equivalent circuit dis- appeared due to the CO poisoning, as shown in Fig. 10b. Therefore, R N,a 共the sum of parallel connection for ohmic resistance in each electrolyte channel 兲 increased with R ct,a in the presence of CO, as shown in Fig. 8.
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Biodegradation of pyridine using aerobic granules in the presence of phenol

Biodegradation of pyridine using aerobic granules in the presence of phenol

The staining-CLSM test revealed that active microorganisms located at the granule surface while protein and some poly- saccharide comprised the granule core. The presence of phenol limited pyridine degradation rates by the granules. On the contrary, pyridine had minimal effect on the granules to degrade pyridine. The double reciprocal Lineweaver–Burk plot showed a competitive type of inhibition for phenol on pyridine degradation. The V max , K m and K I in the Michaelis–Menten kinetics were estimated as 63.7 mg/L/h, 827.8 and 1388.9 mg/L, respectively. The DGGE fingerprint pattern identified nine strains in the aerobic granules.
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Reaching strong consensus in the presence of mixed failure types

Reaching strong consensus in the presence of mixed failure types

Compared with the features of the existing protocols, the under- lying network topologies of the proposed protocol do not have to be fully connected, the mixed failure types can be to[r]

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Testing for Structural Changes in the Presence of Long Memory

Testing for Structural Changes in the Presence of Long Memory

We derive the limiting null distributions of the standard and OLS-based CUSUM- tests for a structural change of the coefficients of a linear regression model in the context of long-memory disturbances. We show that both tests behave fundamentally different in a long-memory environment, as compared to short memory, and that long memory is easily mistaken for structural change when standard critical values are employed.

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PATH PLANNING IN THE PRESENCE OF OBSTACLES BASED TASK REQUIREMENTS

PATH PLANNING IN THE PRESENCE OF OBSTACLES BASED TASK REQUIREMENTS

The constraint due to the presence of obstacles inside the robot workspace, which is usually identified as the geometrical con- straint, is met by planning collision-[r]

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