Abstract
This paper addresses pilot-assisted estimation offrequency-selective time-invariant channels in multicarrier Code Division Multiple Access communications systems (MC CDMA and MC DS-CDMA). Performance in terms of normalised mean square error (NMSE) is derived for two discrete channel frequency response estimators: a conventional estimator based on the minimum mean square error criterion, and an improved estimator exploiting subspace relationships between the frequency and impulse responses of the discrete channel. For MC DS-CDMA, NMSE performances of both estimators result in closed-form solutions. For MC CDMA, a closed-form solution is derived for the NMSE of the conventional estimator; upper and lower bounds are provided for the NMSE of the improved estimator. Furthermore, for the particular case of identically distributed discrete channels with common arbitrary power delay profile and uncorrelated weights, a closed-form expression for the NMSE of the improved estimator is also obtained. Numerical results illustrate the accuracy of the proposed NMSE expressions.
Highlights
The fantastic growth of wireless services and multiuser communications and the increasing demand for higher data rates during the last decade have boosted the research on broadband communications systems
This paper focuses on multicarrier CDMA (MC CDMA) (Multicarrier Code Division Multiple Access) [9] and MC DS-CDMA (Multicarrier Direct Sequence Code Division Multiple Access) [10] systems incorporating Cyclic Prefix (CP) guard interval, an elegant solution which enjoys detection devoid of interblock interference (IBI) [14]
This paper addresses the problem of pilot-assisted estimation of time-invariant channels in MC CDMA and MC DS-CDMA based wireless communications systems
Summary
The fantastic growth of wireless services and multiuser communications and the increasing demand for higher data rates during the last decade have boosted the research on broadband communications systems. MC CDMA divides the available bandwidth into a large number of narrow orthogonal subchannels and spreads each user’s data symbol in the frequency domain by transmitting all the chips of a spread symbol, at the same time, over the available subchannels [15], [16] using an OFDM-like transmission. In this context, the gain of each subchannel is different from the others. This paper addresses the problem of pilot-assisted estimation of time-invariant channels in MC CDMA and MC DS-CDMA based wireless communications systems. The operator E [·] stands for ensemble averaging, and IM denotes the M × M identity matrix
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