Channel estimation techniques based on pilot arrangement in OFDM systems

TLDR

The study investigates OFDM channel estimation techniques that rely on pilot arrangements. The authors evaluate comb‑type pilot arrangements using LS and LMS estimation at pilot tones followed by multiple interpolation schemes—including linear, second‑order, low‑pass, cubic spline, and time‑domain IDFT/DFT—while also testing block‑type pilots that transmit pilots on every sub‑channel and applying a decision‑feedback equalizer with periodic block pilots. Bit‑error‑rate measurements across 16QAM, QPSK, DQPSK, and BPSK under Rayleigh and AR fading channels reveal the relative effectiveness of the tested estimation and interpolation schemes.

Abstract

Channel estimation techniques for OFDM systems based on a pilot arrangement are investigated. Channel estimation based on a comb type pilot arrangement is studied through different algorithms for both estimating the channel at pilot frequencies and interpolating the channel. Channel estimation at pilot frequencies is based on LS and LMS methods while channel interpolation is done using linear interpolation, second order interpolation, low-pass interpolation, spline cubic interpolation, and time domain interpolation. Time-domain interpolation is obtained by passing to the time domain by means of IDFT (inverse discrete Fourier transform), zero padding and going back to the frequency domain by DFT (discrete Fourier transform). In addition, channel estimation based on a block type pilot arrangement is performed by sending pilots in every sub-channel and using this estimation for a specific number of following symbols. We have also implemented a decision feedback equalizer for all sub-channels followed by periodic block-type pilots. We have compared the performances of all schemes by measuring bit error rates with 16QAM, QPSK, DQPSK and BPSK as modulation schemes, and multipath Rayleigh fading and AR based fading channels as channel models.