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A new method of RAKE reception for Impulse Radio Ultra Wideband (IR-UWB) systems in high mobile environments is described. The conventional multipath diversity reception method for UWB is RAKE receiver, which is usually applied under static environments. In high mobile environments, due to extremely wide bandwidth of UWB signals, frequency components are shifted differently and this makes the pulse-width...
In this paper we deal with the problem of minimizing the complexity of an IR-UWB system by the introduction of Time-Reversal, under a power constraint and fixing a reachable performance in terms of BER. An approximate trade-off in the choice of the number of taps at the transmitter and the number of fingers at the receiver is proposed.
In this paper, we present the bit error probability (BEP) of a relay network employing UWB links between its nodes. Since UWB systems can resolve many paths and are thus rich in multipath diversity, the use of the Rake diversity combining is very effective. However, because of the complexity, it is impractical in the scenarios with portable terminals or in the networks with multiple relays. Time-reversal...
In this work, a genetic algorithm (GA) based frequency domain equalization (FDE) scheme referred to as FDE-GA, which does not require any guard interval (GI),is proposed for direct sequence-ultra wideband (DS-UWB) wireless communication systems and is shown to significantly outperform the RAKE receiver. The proposed FDE-GA receiver also has a dramatic complexity reduction over the previous RAKE-GA...
The existing transmit diversity schemes for time domain synchronous OFDM (TDS-OFDM) is only suitable either for fast time-varying but weakly frequency-selective channels, or strongly frequency-selective but slow fading channels. In this paper, the space-time shifted constant amplitude zero autocorrelation (CAZAC) sequence based TDS-OFDM transmit diversity scheme is proposed for doubly selective channels...
A low complexity Parallel Interference Cancellation (PIC) technique is proposed to suppress Multi-Access Interference (MAI) and minimize near-far effect for multi-user communication using Direct-Sequence Code Division Multiple Access (DS-CDMA). Interference signal is estimated using a relationship between cyclic correlation of the received signal and user's code of the interferer without requiring...
A low-complexity architecture of a RAKE Receiver subsystem for a Direct Sequence Ultra-Wideband (DS-UWB) is presented, followed by FPGA implementation and system performance results. The proposed subsystem is composed of a Channel Estimator (CE) and a novel hybrid Partial/Selective (HPS) maximal ratio combining (MRC) RAKE Receiver (RR), which combines the benefits of both partial and selective RAKE...
In this paper, the design and implementation of a low complexity Direct Sequence Ultra-Wideband (DS-UWB) receiver subsystem which incorporates a Channel Estimator (CE) and a novel hybrid Partial/Selective (HPS) RAKE Receiver (RR) using maximal ratio combining (MRC) is presented. The proposed architecture demonstrates the tradeoff between energy capture, performance and receiver complexity by combining...
On of the main drawbacks of Orthogonal Frequency Division Multiplexing (OFDM) is the significant increase in the Peak-to-Average Power Ratio (PAPR), due to the large dynamic range of its symbol waveforms, which in turn requires a wide dynamic range of power amplification. To overcome this problem, a novel selected mapping (SLM) based technique named Orthogonal-SLM (OSLM) is proposed, where each candidate...
The performance of a space-time block coded orthogonal frequency-division multiplexing (STBC-OFDM) system often relies on the assumption of quasi-static channels. For the time-varying multipath channel, co-channel interference (CCI) and inter-carrier interference (ICI) occur and performance degrades seriously. In this paper, we propose an iterative interference cancellation scheme to reduce both CCI...
In this paper we investigate the trade-off between the number of fingers in the prefilter of a TR-IR-UWB system versus the number of fingers in the rake receiver. This allows studying the gain brought by time reversal when the complexity is switched from the receiver to the transmitter i.e. when the number of fingers is increased in the prefilter, while it is reduced in the rake receiver.
Convolutional spreading CDMA with cyclic prefix (CS-CDMA/CP) enables multiuser interference-free (MUI-free) transmission over multipath downlink channels with the use of zero correlation zone (ZCZ) codes. However, MUI-free transmission is guaranteed only when the data length D, channel delay L, and ZCZ length Z satisfy Z + 1 ges D + L, and the user population is constraint to be K les [N/(Z+1)], where...
This paper develops a novel framework for sharing secret keys using existing automatic repeat request (ARQ) protocols. Our approach exploits the multi-path nature of the wireless environment to hide the key from passive eavesdroppers. The proposed framework does not assume the availability of any prior channel state information (CSI) and exploits only the one bit ACK/NACK feedback from the legitimate...
In this paper, we propose an evolved partial response scheme capable of 256-QAM single carrier radio access. Rather than using such high order modulations as 64-QAM or 256-QAM, we employ aggregations of low order modulation signals whose transmission speeds are beyond the Nyquist rate. To detect these modulation signals, we use a semi-ring structure and reduced state methods in order to exploit the...
This paper presents a performance analysis of vector orthogonal frequency division multiplexing (VOFDM) in multipath fading channel to investigate its diversity gain, performance limitation and the choice of dimension in the vector block for the design of a low-complexity receiver. Based on the analytically derivation, it is first verified that VOFDM can realize the maximum diversity gain while the...
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...
We propose to use the Rake receiver to improve the system performance by collecting more signal power in an ultra-wideband (UWB) system precoded by the channel phase information, called the CPP-UWB system [1], in this work. The performance of the proposed system is determined by the selected channel taps and the corresponding combining schemes for those Rake fingers. Three combing schemes, Le., the...
For cellular mobile telecommunication, cell identification is an indispensable initial process to establish a communication link. Cell identification requires high computational complexity and accuracy in a short time, especially during the handover process. To achieve high-performance cell identification with low-complexity for the orthogonal frequency division multiplexing (OFDM) systems, this work...
In this paper, a differential code-shifted reference ultra-wideband (CSR UWB) transceiver has been proposed to reduce the power spent to transmit the reference pulse sequence so as to improve the bit-error rate performance of the systems. In the differential CSR UWB transceiver, by differentially encoding M information bits to be transmitted simultaneously, one data pulse sequence can be used as the...
It has been shown that relaying systems can offer spatial and multipath diversity in amplify-and-forward (AF) relay-assisted transmission over frequency-selective fading channels when trellis coded modulation (TCM) is applied as an outer code. However, the price for such advantages is the high decoding complexity. To overcome this disadvantage, the technique of subcarrier grouping is applied for orthogonal...
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