Conference Paper

Reduced-Rank Adaptive Least Bit Error-Rate Detection in Hybrid Direct-Sequence Time-Hopping Ultrawide Bandwidth Systems

Dept. of Electr. Eng., Nat. Univ. of Comput. & Emerging Sci., Islamabad, Pakistan
DOI: 10.1109/ICC.2009.5199402 Conference: Proceedings of IEEE International Conference on Communications, ICC 2009, Dresden, Germany, 14-18 June 2009
Source: DBLP


In this paper we consider the low-complexity detection in hybrid direct-sequence time-hopping ultrawide bandwidth (DS-TH UWB) systems. A reduced-rank adaptive LBER detector is proposed, which is operated in the least bit error-rate (LBER) principles within a detection subspace obtained with the aid of the principal component analysis (PCA)- assisted reduced-rank technique. Our reduced-rank adaptive LBER detec- tor is free from channel estimation and does not require the knowledge about the number of resolvable multipaths as well as that about the multipaths' strength. In this paper the bit error-rate (BER) performance of the hybrid DS-TH UWB system is investigated, when communicating over the UWB channels modelled by the Saleh-Valenzuela (S-V) channel model. Our study and simulation results show that this reduced-rank adaptive LBER detector constitutes a feasible detection scheme for deployment in practical pulse-based UWB systems. estimation. It achieves its near-optimum detection with the aid of a training sequence at the start of communication and then main- tains its near-optimum detection based on the decision-directed (DD) principles during the communication (9). The reduced-rank adaptive LBER detector does not require the knowledge about the number of resolvable multipaths as well as that about the locations of the strong resolvable multipaths; It only requires the knowledge (which is still not necessary accurate) about the maximum delay-spread of the UWB channels. Furthermore, the reduced-rank adaptive LBER detector is operated in a reduced-rank detection subspace obtained based on the principal component analysis (PCA) (10). The detection subspace usually has a rank that is significantly lower than that of the original observation space. Owing to the above-mentioned properties of the reduced-rank adaptive LBER detector, we can argue that it is a low-complexity detection scheme, which is feasible for practical

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    ABSTRACT: This paper investigates and compares the performance of wireless sensor networks where sensors operate on the principles of cooperative communications. We consider a scenario where the source transmits signals to the destination with the help of $L$ sensors. As the destination has the capacity of processing only $U$ out of these $L$ signals, the strongest $U$ signals are selected, while the remaining $(L$ –$U)$ signals are suppressed. A preprocessing block similar to channel shortening (CS) is proposed in this paper. However, this preprocessing block employs a rank-reduction technique instead of CS. By employing this preprocessing, we are able to decrease the computational complexity of the system without affecting the bit-error-rate (BER) performance. From our simulations, it can be shown that these schemes outperform the CS schemes in terms of computational complexity. In addition, the proposed schemes have a superior BER performance as compared with CS schemes when sensors employ fixed-gain amplification. However, for sensors that employ variable-gain amplification, a tradeoff exists in terms of BER performance between the CS scheme and these schemes. These schemes outperform the CS scheme for a lower signal-to-noise ratio.
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