Training sequence based channel estimation for indoor visible light communication system

Abstract

Channel estimation is a key technology in indoor wireless visible light communications (VLCs). Using the training sequence (TS), this paper investigates the channel estimation in indoor wireless visible light communications. Based on the propagation and signal modulation characteristics of visible light, a link model for the indoor wireless visible light communications is established. Using the model, three channel estimation methods, i.e., the correlation method, the least square (LS) method and the minimum mean square error (MMSE) method, are proposed. Moreover, the performances of the proposed three methods are evaluated by computer simulation. The results show that the performance of the correlation method is the worst, the LS method is suitable for higher signal to noise ratio (SNR), and the MMSE method obtains the best performance at the expense of highest complexity.The indoor visible light communiation (VLC) systems [1][2][3] still have many critical issues. Generally speaking, the indoor VLC environment is a confined space and LED is not only used as a lighting device, but also to be used as a communication device. The optical signals of LED travel via different paths and arrive at the receiver at different instances in time [4] . Experimental results have shown that the multipath propagation may cause the inter-symbol-interference (ISI), which will degrade the VLC system performance significantly when the original data rate is high [5] . In order to eliminate the effects of ISI, the instantaneous channel impulse response must be obtained before the recovery of the transmitted information. Obviously, the channel estimation plays a critical role in VLC systems. Refs.[6,7] described an iterative method for infrared channel estimation. However, the effect of the irregular shape of the objects and the human's activity were ignored, which makes the results not suitable for real indoor communication systems. As far as we know, no similar results for channel estimation in VLC systems are available.Since the optical propagation environment is complicated and time-varying, this paper proposes a training sequence (TS)-based channel estimation for indoor VLC systems. Considering the propagation property of light and the characteristics of optical modulation, a mathematical channel model for indoor VLC systems is established. Further, based on the established link model, three channel estimation methods, i.e., the correlation method, the least square (LS) method and the minimum mean square error (MMSE) method, are proposed and evaluated.The intensity modulation and direct detection (IM/DD) modulation is considered for indoor VLC systems, in which the desired waveform is modulated onto the instantaneous power of the carrier and a photo-detector produces a current proportional to the received instantaneous power. The binary information is modulated into "0" and "1". As illustrated in Fig.1, the received signal of the indoor VLC systems is given by [1] OPTOELECTRONICS LETTERS

OFDM Performance of Ultra Wideband in Wireless Body Area Network Channel

“…(7). The output of the filter is interpolated by nearest, linear, pchip, and spline interpolation methods to estimate the channel at data subcarriers [9]. The interpolation for the pilot data can be realized with different methods.…”

“…(10). The constant are defined in [9] according to model types Figure 3 shows the channel delay profile that was used in the simulations. Channel Model Four with 0…”

Efficient frequency‐domain channel equalisation methods for OFDM visible light communications

“…In addition, the correlation method, the LS and the minimum mean square error (MMSE) methods based on the training sequence were also investigated for OFDM-VLC [18]. However, these above works were mainly simulation based with no experimental verifications.…”

Training sequence based frequency-domain channel estimation for indoor diffuse wireless optical communications

“…As a typical channel estimation method, TD channel estimation has been discussed extensively for conventional radio communications [9,10]. However, http://jwcn.eurasipjournals.com/content/2012/1/326 LED LED only a few works have been done for the channel estimation for diffused WOC systems [11][12][13]. In [11], TS-based channel estimation for WOC systems has been investigated, and the optimal TSs for a better channel estimation performance have been found by computer search in [12].…”

“…However, http://jwcn.eurasipjournals.com/content/2012/1/326 LED LED only a few works have been done for the channel estimation for diffused WOC systems [11][12][13]. In [11], TS-based channel estimation for WOC systems has been investigated, and the optimal TSs for a better channel estimation performance have been found by computer search in [12]. Based on the "two-sided" channel estimation, Wang et al [13] focuses on the complementary sets of sequences for estimating a channel impulse response in WOC systems.…”