Reduced-rank adaptive multiuser detection in hybrid direct-sequence time-hopping ultrawide bandwidth systems

Abstract

In this paper a range of reduced-rank adaptive multiuser detectors (MUDs) are proposed and investigated for the hybrid direct-sequence time-hopping ultrawide bandwidth (DS-TH UWB) systems. The adaptive MUDs are operated based on the recursive least square (RLS) principles. Three types of reduced-rank techniques are investigated, which are the principal component (PC), cross-spectral metric (CSM) and Taylor polynomial approximation (TPA). These reduced-rank adaptive techniques are beneficial to achieving low-complexity, high spectral-efficiency and robust detection in hybrid DS-TH UWB systems. In this contribution bit error rate (BER) performance of the hybrid DS-TH UWB systems using proposed reduced-rank adaptive MUDs is investigated by simulations, when communicating over UWB channels modelled by the SalehValenzuela (S-V) channel model. Our simulation results show that, given a sufficiently high rank of the detection subspace, the reduced-rank adaptive MUDs are capable of achieving a similar BER performance as that of the full-rank ideal minimum meansquare error MUD (MMSE-MUD) but with significantly lower detection complexity. Furthermore, the TPA-based reduced-rank adaptive MUD is capable of yielding a better BER performance than the PC-or CSM-based reduced-rank adaptive MUD, when the same but relatively low rank detection subspace is assumed.Index Terms-Ultrawide bandwidth, hybrid direct-sequence time-hopping, adaptive detection, reduced-rank detection, recursive least square.

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

“…Finally, as an example, in Table I, we compare the performance and complexity of the proposed algorithm with the correlation detector, MMSE detector, full-rank LMS adaptive detector, full-rank RLS adaptive detector, and reduced-rank RLS adaptive detector when K = 5, N c = 16, N ψ = 4, g = 1, L = 15, and E b /N 0 = 10 dB. The principles of these related detectors can be found in [6], [7], and [14]- [16].…”

“…In [7] and [14], the full-rank adaptive detection has been considered, where the adaptive detector is operated based on the NLMS [7] or LMS [14] algorithm. Furthermore, in [15] and [16], the reduced-rank adaptive detection in hybrid DS-TH UWB systems has been investigated, where the reduced-rank adaptive detectors are operated in the principles of NLMS [15] or RLS [16]. In the following discussion, we provide a brief description of the hybrid DS-TH UWB system model.…”

“…Compared with the PCA-assisted reduced-rank adaptive RLS-MUD in [16], the reduced-rank adaptive LBER-MUD has a significantly lower complexity. This case is because the adaptive LBER-MUD has a complexity similar to the adaptive LMS-MUD [9], [10].…”

“…Furthermore, as analyzed in [9], [10], the LBER algorithm can provide higher flexibility for system design compared with the nLMS algorithm. Furthermore, note that, in [15] and [16], the performance of hybrid DS-TH UWB systems that employ reduced-rank adaptive detection has been investigated, where the reduced-rank adaptive detectors are operated in the principles of normalized least mean square (NLMS) [15] or recursive least square (RLS) [16]. Those interested in the details of these reduced-rank adaptive detectors are referred to the aforementioned references.…”

Th-Uwb Receiver Based on Two PDFS Approximation in Multiuser Systems

“…A user in the system can select its own TH sequence and exchanges it with the other users or there is a central controller which assigns and distributes TH sequences to the users. Thus each user knows the TH sequences of all the users in the system, which is the assumption also made by [14,21,22]. With the assumptions above, each user knows the arriving time of the pulses sent by other users, i.e., the receiver knows whether or not the pulse of the desired user is collided.…”