Iterative Decoding and Soft Interference Cancellation in Fast Frequency Hopping Multiuser System Using Clipped Combining

Iterative decoding (ID) aided fast frequency hopping (FFH), M-ary frequency shift keying (MFSK) using clipped combining in multiple access (MA) channels is investigated. All users’ data are convolutionally encoded and the encoded bits are interleaved and converted to M-ary symbols, which are transmitted using FFH-MFSK modulation. The soft metrics to be passed from the demodulator to the decoder are derived assuming a Rayleigh fading channel. We also propose a novel multiuser detection (MUD) scheme which employs joint soft decoding as well as successive interference cancellation (SIC), the receiver exploiting the soft information fed back by the decoder to the demodulator in order to cancel the interference imposed by reliable symbols. Our simulation results show that the proposed scheme is capable of combatting multiuser interference and outperforms the conventional ID by about 3dB

Variable Length Space Time Coded Modulation

A Variable Length Space Time Coded Modulation (VL-STCM) scheme capable of simultaneously providing coding, multiplexing and diversity gains is proposed. The scheme advocated achieves its best performance for correlated sources, where the source symbols exhibit a nonuniform probability of occurrence. The source symbols are encoded using an optimal trellis encoder into variablelength modulated signals and mapped to both the spatial and time domains. More explicitly, the proposed VL-STCM arrangement is a jointly designed source coding, channel coding, modulation and spatial diversity/multiplexing scheme. It is shown that the higher the source correlation, the higher the achievable performance gain of the scheme. Furthermore, the performance of the VL-STCM scheme is about 6 dB better than that of the Fixed Length STCM (FL-STCM) benchmarker at a source symbol error ratio of 10?4

Jointly optimised iterative source-coding, channel-coding and modulation for transmission over wireless channels

Joint source-coding, channel-coding and modulation schemes based on Variable Length Codes (VLCs), Trellis Coded Modulation (TCM), Turbo TCM (TTCM), Bit-Interleaved Coded Modulation (BICM) and iteratively decoded BICM (BICM-ID) schemes are proposed. A significant coding gain is achieved without bandwidth expansion, when exchanging information between the VLC and the coded modulation decoders with the advent of iterative decoding. With the aid of using independent interleavers for the In-phase and Quadrature phase components of the complex-valued constellation, further diversity gain may be achieved. The performance of the proposed schemes is evaluated over both AWGN and Rayleigh fading channels. Explicitly, at BER = 10-5 most of the proposed schemes have BER curves less than one-dB away from the channel capacity limit

Performance Analysis of Iteratively Decoded Variable-Length Space-Time Coded Modulation

It is demonstrated that iteratively Decoded Variable Length Space Time Coded Modulation (VL-STCM-ID) schemes are capable of simultaneously providing both coding gain as well as multiplexing and diversity gain. The VL-STCM-ID arrangement is a jointly designed iteratively decoded scheme combining source coding, channel coding, modulation as well as spatial diversity/multiplexing. In this contribution, we analyse the iterative decoding convergence of the VL-STCM-ID scheme using symbol-based three-dimensional EXIT charts. The performance of the VL-STCM-ID scheme is shown to be about 14.6 dB better than that of the Fixed Length STCM (FL-STCM) benchmarker at a source symbol error ratio of 10?4, when communicating over uncorrelated Rayleigh fading channels. The performance of the VL-STCM-ID scheme when communicating over correlated Rayleigh fading channels using imperfect channel state information is also studied

Comparative Study of TCM, TTCM, BICM and BICM-ID Schemes

Coded modulation is a bandwidth efficient scheme that combines the functions of coding and modulation. In this contribution, a comparative study of Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) and Iterative Decoding assisted BICM (BICM-ID) schemes over Gaussian and uncorrelated narrowband Rayleigh fading channels is presented in the context of 8-level Phase Shift Keying (8PSK), 16-level Quadrature Amplitude Modulation (16QAM) and 64QAM. We comparatively study the associated decoding complexity, block length and bandwidth efficiency. It is shown that TTCM constitutes the best compromise scheme, followed by BICM-ID

Near-capacity three-stage MMSE turbo equalization using irregular convolutional codes

Traditional Turbo EQualization (TEQ) schemes suffer from residual bit errors due to the non-recursive nature of the channel imposing Inter-Symbol-Interference (ISI). The performance of the traditional TEQ scheme may, however, be improved if an intermediate recursive channel codec is invoked, which results in a three-stage serially concatenated system. This intermediate code is necessary, especially when the inner module cannot be rendered recursive, for example, when a Minimum Mean Square Error (MMSE) equalizer is invoked. Our EXtrinsic Information Transfer (EXIT) chart analysis explicitly explains the performance gain, and based on this explanation IRregular Convolutional Codes (IRCCs) are constructed to be used as the outer code for the sake of achieving near capacity performance. Furthermore, the proposed analysis and design procedure may be applied in the context of diverse iterative receivers employing multiple soft-in/soft-out (SISO) modules

A REAL TIME MONITORING MODEL OF THE CALCIUM CARBONATE FOULING INDUCTION PERIOD BASED ON THE CONDUCTANCE TITRATION

A new method has been developed to monitor the calcium carbonate fouling induction period (CCFIP) in real time. Based on the conductance titration, this paper investigated the forming process of CCFIP by a staticdynamic combined simulation experiment unit. With the help of titration analysis (that is titrimetry), an accurate definition of CCFIP and the corresponding real time monitoring model were built up. The investigation results show that the proposed model applies not only to measure the CCFIP in real time, but also applies to an investigation of the influence of various factors on the CCFIP

Anomalous Crossing Frequency in Odd Proton Nuclei

A generic explanation for the recently observed anomalous crossing frequencies in odd proton rare earth nuclei is given. As an example, the proton ${1\over 2} [541]$ band in $^{175}$Ta is discussed in detail by using the angular momentum projection theory. It is shown that the quadrupole pairing interaction is decisive in delaying the crossing point and the changes in crossing frequency along the isotope chain are due to the different neutron shell fillings

Automatic Path Planning for Unmanned Ground Vehicle Using UAV Imagery

Field machines play an important role in the management of agricultural environments. Increasing use of automated machines in precision agriculture has gained significant attention of farmers and industries to minimize human work load to perform tasks such as land preparation, seeding, fertilizing, plant health monitoring and harvesting. Path planning is considered as a fundamental step for agricultural machines equipped with autonomous navigation system. For mountain vineyards, path planning is a big challenge due to terrain morphology and unstructured vineyards. This paper proposes a workflow to generate an automatic coverage path plan for unmanned ground vehicles (UGVs) using georeferenced imagery taken by an unmanned aerial vehicle (UAV). First, image acquisition is performed over a vineyard to generate an orthomosaic and a digital surface model, which are then used to identify the vine rows and inter-row terrain. This information is then used by the algorithm to generate a path plan for UGV