An ultra-wide bandwidth (UWB) signal propagation experiment is performed in a typical modern laboratory/office building. The bandwidth of the signal used in this experiment is in excess of 1 GHz, ...which results in a differential path delay resolution of less than a nanosecond, without special processing. Based on the experimental results, a characterization of the propagation channel from a communications theoretic view point is described, and its implications for the design of a UWB radio receiver are presented. Robustness of the UWB signal to multipath fading is quantified through histograms and cumulative distributions. The all RAKE (ARAKE) receiver and maximum-energy-capture selective RAKE (SRAKE) receiver are introduced. The ARAKE receiver serves as the best case (bench mark) for RAKE receiver design and lower bounds the performance degradation caused by multipath. Multipath components of measured waveforms are detected using a maximum-likelihood detector. Energy capture as a function of the number of single-path signal correlators used in UWB SRAKE receiver provides a complexity versus performance tradeoff. Bit-error-probability performance of a UWB SRAKE receiver, based on measured channels, is given as a function of the signal-to-noise ratio and the number of correlators implemented in the receiver.
This paper proposes a space-time selective RAKE (SRAKE) receiver with maximum signal-to-interference-plus-noise ratio (MSINR) for direct-sequence ultra-wideband (UWB) communications in the presence ...of narrowband interference (NBI) and multiple-access interference. For effectively extracting a fixed number of the UWB signal components (fingers) from numerous resolvable paths, four finger selection strategies (FSSs) are considered for the proposed space-time SRAKE receiver, including the optimum FSS (with MSINR), which is not very computationally feasible, and three feasible FSSs: an energy-based FSS (EB-FSS), a constrained energy-based FSS (CEB-FSS), and a hybrid energy-based FSS, which is also a combination of the EB-FSS and CEB-FSS. Through a performance analysis, we show that the performance of the proposed receiver in the presence of NBI not only depends on the power ratio, bandwidth ratio, and relative spectrum location of NBI with respect to the UWB signal, but also on the FSS used. Some simulation results are then presented to show that the proposed space-time MSINR-SRAKE receiver with the preceding FSSs used can provide a larger system capacity and better immunity to strong NBI than the existing time-only SRAKE receivers and space-time SRAKE receivers.
This paper investigates the performance of two direct sequence ultra wideband (DS-UWB) communication systems over multipath fading channels. The first system is the classic DS-UWB system and the ...second is obtained by adding a forward error control code (FEC), convolutional code. For the two systems, bipolar pulse amplitude modulation (BPAM) is applied. In the receiver end, the selective diversity combining receiver-SRake receiver is used as a feasible receiver. In the proposed coded scheme, we use soft output Viterbi algorithm (SOVA). The analysis shows that the coded DS-UWB system outperforms the conventional DS-UWB system significantly with the increase of the SRake fingers. The effective order of processing gains achieved by the coded scheme is the product of the number of SRake branches and the free distance of the code applied.
A study on Rake Receivers Umadevi, V.; Easwaran, P.
2017 IEEE International Conference on Electrical, Instrumentation and Communication Engineering (ICEICE),
2017-April
Conference Proceeding
The design of highly efficient receivers with a good balance in both performance and ramification is a major challenge. WCDMA Systems are reducing their ramification by using Rake Receivers. The ...probe work acts upon of the broadcasting bandwidth on the system performance using several types of Rake receivers such as All-RAKE (ARake), Selective-RAKE (SRake), Partial-RAKE (PRake), Adaptive Selective Rake (ASRake), Reduced Ramification RAKE (RC-Rake), A FlexRake, G-Rake and LMMSE Rake Receiver. Even more substitute Rake executions that focus to minimize the count of the calculated and aggregated paths, in Rake receivers of the previous category the picked out branches may be unneeded too many, although a adequate calibre of communication could be maybe achieved with low, particularly in environments with strong multipath. likewise, the Rake receivers of the second category could go on adding imperfect paths in an effort to attain the biased threshold, although a bit less collectible or the same execution could be accomplished by aggregating only the secure branches. The rake prescribed receiver accumulates dissimilar multipath propagated signal basics and coherently blends these in order to form a all over repro of a beamed signal. There subsist dissimilar complication rake receivers.
IEEE 802.15.4a impulse radio-time hopping ultra wide band (IR-TH UWB) physical layer (PHY) is robust against dense multipath fading. However, scattering and reflections in industrial surroundings, ...render plenty of resolvable multipath components (MPCs), for which coherent Rake reception suffers serious complexity. We propose an addition of an adaptive noise canceler (ANC) at the front end of conventional Srake in dense IEEE 802.15.4a industrial non line of sight (NLOS) environment. The performance of ANC is assessed and an equivalent orthogonal set for the generated biorthogonal signals is employed. In addition, we evaluate the error performance of the proposed adaptive Srake in comparison with conventional Srake and additive white Gaussian noise (AWGN) correlation receivers. Our simulation results show that the proposed architecture offers significant improvement with much reduced intricacy.
In ultra-wideband impulse radio (UWB-IR) system, Rake receiver can take advantage of the high degree of diversity that results from a large number of multipath components (MPCs). In this paper, we ...propose a reduced-complexity selective Rake (RC-SRake) receiver scheme under ultra-wideband multipath channels. It employs a convolution based finger estimation algorithm, which has minimal complexity that does not require precise channel information. We derive a closed-form expression for symbol error probability (SEP) of the proposed Rake receiver in term of the combined fingers and impulse noise. We evaluate these expressions numerically under various IEEE 802.15.4a channel models. It is observed that a similar ability of energy capture can be obtained with less than 10 fingers as compared to the ideal SRake. More importantly, as the number of combined fingers increases, the performance of our RC-SRake receiver improves in general despite occasional degradation due to the estimation error of impulse noise.
This work pays attention to the performance analysis of the conventional and encoded time hopping binary phase shift keying modulation (TH-BPSK) ultra wideband systems over multipath fading channels. ...In order to resist the multipath effects, selective diversity combining Rake (SRake) receiver is employed. The encoded TH-BPSK UWB system is obtained by substituting a convolutional encoder for the repetition encoder. Soft output Viterbi algorithm (SOVA) and Viterbi algorithm (VA) are employed as the decoding methods. The performance analysis shows that the coded TH-BPSK system outperforms the uncoded scheme significantly with the increase of the SRake receiver fingers. The effective order of processing gains achieved by the coded scheme is the product of the number of SRake branches and the free distance of the convolutional code.
The carrier direct-sequence spread based ultrawide-band (DS-UWB) is challenging for serious inter-symbol interference (ISI) problem, which is resulted from the dense multipath with a long ...root-mean-square (RMS) delay spread.We adopt a RAKE-decision feedback equalizer (RAKE-DFE) receiver in this paper to cancel the ISI. Different from the conventional selective RAKE (SRAKE), we proposed the optimum SRAKE for the receiver to select rays. The theoretical analysis and simulation results show that the proposed SRAKE scheme is the optimum, and the proposed receiver can get good performance, which is better than conventional SRAKE based RAKE-DFE receiver.
In this paper, we present the space time block codes (STBC) based M-ary code-selected modulation scheme of direct sequence bipolar pulse amplitude modulation (DSBPAM) ultra wideband (UWB) system with ...selective Rake (SRake) receiver and maximum ratio combining (MRC) over multipath channels in order to improve the system performance and transmission rate of the conventional DS UWB system. The system bit error probability is derived and the signal processing algorithm is provided. Simulation is performed with different SRake receiver fingers over multipath channels. The results show the efficiency of the M-ary STBC based DS-BPAM UWB scheme in both system performance and transmission rate.
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