Abstract
This paper analyzes and compares two time interpolators, i.e., time replica and time linear interpolator, for pilot aided channel estimation in orthogonal frequency division multiplexing (OFDM) systems. The mean square error (MSE) of two interpolators is theoretically derived for the general case. The equally spaced pilot arrangement is proposed as a special platform for these two time interpolators. Based on this proposed platform, the MSE of two time interpolators at the virtual pilot tones is derived analytically; moreover, the MSE of per channel estimator at the entire OFDM symbol based on per time interpolator is also derived. The effectiveness of the theoretical analysis is demonstrated by numerical simulation in both the time-invariant frequency-selective channel and the time varying frequency-selective channel.
Highlights
Orthogonal frequency division multiplexing (OFDM) [1,2,3] has been widely used in high-speed wireless communication systems, such as broadband wireless local area networks (WLANs) [4], wireless metropolitan area networks (WMANs) [5] and worldwide interoperability for microwave access (WIMAX) [6], due to its advantages of transforming frequency-selective fading channels into a set of parallel flat fading sub-channels and eliminating inter-symbol interference [7].Channel estimation is one of the most essential tasks in compensating distortion from channels and performing coherent detection in orthogonal frequency division multiplexing (OFDM) systems
Symbol. δm (k) denotes the variation of the Channel state information (CSI) of the kth tone from the mth OFDM symbol to the (m +1) th OFDM symbol. emR (k ) and emL (k ) are the channel estimation errors of the mth OFDM symbol at the kth tone where time replica or time linear interpolation are employed for CSI estimation at the virtual pilot tones, respectively
From (15), one can conclude that 1) in a timeinvariant frequency-selective channel, ξL is always lower than ξR by 3 dB; in a time-variant frequencyselective channel, the performance difference depends on the specific channel variation; 2) in most situations, as the general case in (9), ξR > ξL, i.e., time linear interpolation is better than time replica
Summary
Orthogonal frequency division multiplexing (OFDM) [1,2,3] has been widely used in high-speed wireless communication systems, such as broadband wireless local area networks (WLANs) [4], wireless metropolitan area networks (WMANs) [5] and worldwide interoperability for microwave access (WIMAX) [6], due to its advantages of transforming frequency-selective fading channels into a set of parallel flat fading sub-channels and eliminating inter-symbol interference [7]. To answer these questions above, this paper analyzes and compares the performances of time replica and time linear interpolator in both the time-invariant frequencyselective channel and the time varying frequency-selective channel. EmR (k ) and emL (k ) are the channel estimation errors of the mth OFDM symbol at the kth tone where time replica or time linear interpolation are employed for CSI estimation at the virtual pilot tones, respectively. We will analyze and compare the MSE performance of two time interpolators: time replica and time linear interpolator
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