Techniques for indoor positioning systems (IPSs) can be categorised as range-based or range-free. Range-based methods rely on geometric mappings to approximate a location given the calculated distances or angles from multiple reference points. In contrast, range-free strategies utilise fingerprinting, wherein an acquired fingerprint data is compared to a pre-collected dataset to identify the best position estimate. Among these, fingerprinting of channel state information (CSI) is preferred over other information such as received signal strength indicator as the former can exploit the effect of multipath propagation and is robust against non-line-of-sight channels. CSI has the potential to achieve cm-level positioning accuracy with a single reference point only. In this study, the authors survey CSI fingerprinting-based indoor positioning and mobility tracking systems. The process of fingerprinting that includes site surveying and signal preprocessing is discussed in detail. They determine the potential challenges of such systems and propose remedies to improve positioning accuracy. In general, spatial diversity, such as multiple-input multiple-output antennas and wireless sensor networks, or frequency diversity (e.g. high subcarrier count, frequency hopping mechanism) are exploited to achieve high positioning resolution. Such IPS can also be enhanced via additional sensors or spatial graphs for motion detection and tracking.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-spr.2020.0028

Survey of CSI fingerprinting-based indoor positioning and mobility tracking systems

This paper investigates the performance of coded orthogonal frequency division multiplexing (OFDM) in underwater optical wireless communications (UWOWC). Low density parity check (LDPC) and turbo code are used in conjunction with a 16 quadrature amplitude modulation (16-QAM) scheme. The channel impulse response (CIR) is simulated via the Monte Carlo modelling of light (MCML) approach using the Henyey-Greenstein model of scattering phase function. A clean seawater environment, and two types of realistic turbidity for coastal and harbour waters are considered. A one-tap minimum mean squared error frequency domain equalizer (MMSE-FDE) is used for equalization. Its coefficients are designed using a comb-type channel estimation (CE) arrangement and interpolation. The bit error rate (BER) performances obtained via simulation demonstrate that turbo code with the Max-Log Map decoder outperform LDPC with an SPA decoder, with improvements ranging between 2 to 4 dB at a 10−3 BER for three water types. It is also clear that the coded system provides a noteworthy performance improvement compared to the uncoded case, thus enhancing the reliability of UWOWC links at high data rates.

Coded OFDM over short range underwater optical wireless channels using LED

This work presents a blind fine synchronization scheme, which estimates and compensates residual carrier-frequency offset (RCFO) and symbol timing offset (STO) , for single-carrier frequency-domain equalization (SC-FDE) systems. Existing fine synchronization schemes for SC-FDE systems rely on time-domain unique words (UW) sequences as reference signals to assure the estimation accuracy, at the cost of decreased system throughput. The proposed technique, named simplified weighted least-square method for single-carrier systems (SWLS-SC), combines the decision feedback structure and SWLS estimator for OFDM systems. Together with specifically derived weighting factors, it has much better estimation accuracy than the well-known linear least-square (LLS) method for SC-FDE systems, and its BER performance can approach that of the ideal synchronization condition. The proposed technique is more effective than existing techniques, in terms of both performance and throughput. Theoretical estimation bounds are also derived to verify the effectiveness of the proposed method.

https://ir.nctu.edu.tw:443/bitstream/11536/23873/1/000330622000025.pdf

A Blind Fine Synchronization Scheme for SC-FDE Systems

. This paper investigates the performance of the 60 GHz IEEE 802.15.3c physical layer (PHY) specification in terms of bit error rate (BER) against signal to noise ratio. Two PHY modes of the standard have been implemented and simulated, i.e., Single Carrier and High Speed Interface. The first mode uses single carrier (SC) block transmission and the second mode uses orthogonal frequency division multiplexing (OFDM). One of the main issues in the new 60 GHz standards is multipath propagation, which plays an important role in the link quality. Thus, we have tested the PHY with the IEEE standard channel model, ray tracing simulations and real 60 GHz measurements.

/pdf/physical-layer-simulation-results-for-ieee-802-15-3c-with-3l3bdl3c7l.pdf

Physical layer simulation results for IEEE 802.15.3c with different channel models

A present technology relates to a transmission device, a transmission method, a reception device, a reception method, and a program that can improve reception performance of a frame to which a preamble is added. A transmission device of one aspect of the present technology generates a preamble including a sequence [d d . . . d −d] having iteration of a sequence d that is one of sequences a and b that are Golay complementary sequences, followed by an inverted sequence of the sequence d, and including a signal sequence in which a maximum value of an absolute value of a side lobe level of cross correlation between a sequence [d d −d] and a sequence [d −d] is 25 or less. The generated preamble is added to data to be transmitted in units of frames. The present technology can be applied to a device that transmits and receives data via a wireless transmission path.

Transmission device, transmission method, reception device, reception method, and program

The single-carrier block transmission (SCBT), a.k.a. single-carrier frequency-domain equalization (SC-FDE), is being considered as an option technique for the wireless personal area network (WPAN) operating at 60-GHz. To combat the inter-symbol interference (ISI) in non-line-of-sight (NLOS) environments, the frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion is much more effective than the one based on the zero forcing (ZF) criterion. However, MMSE-FDE needs the estimation of both the channel frequency response (CFR) and the signal-to-noise ratio (SNR). In this work, we estimated CFR and SNR based on the complementary Golay sequences whose sum auto-correlation has a unique peak and zero sidelobe. Through simulations, we proved that the proposed CFR and SNR estimation methods are very effective for SCBT system using MMSE-FDE.

https://download.intel.com/pressroom/pdf/innovation/60-GHz_WPAN_Paper.pdf

Ming Lei

Papers

CFR and SNR Estimation Based on Complementary Golay Sequences for Single-Carrier Block Transmission in 60-GHz WPAN