Localization based on standard wireless LAN infrastructure using MIMO-OFDM channel state information

Abstract

An indoor localization method using multiple input, multiple output orthogonal frequency division multiplexing (MIMO-OFDM) channel state information (CSI) is proposed as a method that can be implemented on wireless local area networks of a current standard without affecting their protocol structures and that does not require a training process for adaptation to indoor environments. In the proposed method, the CSI obtained by the MIMO-OFDM receivers of all access points upon successful reception of a data packet from a mobile terminal (MT) is processed in order to determine the location of the MT. The proposed method analyzes the multipath effect that appears in the CSI as multiple complex sinusoids by using the matrix pencil method in order to extract only terms that are contributed by direct paths from the MT to the access points. Localization is achieved using the direct-path terms on the basis of the maximum likelihood principle.

Endpoints-Clipping CSI Amplitude for SVM-Based Indoor Localization

“…Current WLAN technologies, such as 802.11n, employ OFDM and Multiple-Input Multiple-Output (MIMO) technologies [28,29]; CSI is divided into different subcarrier groups. Under the bandwidth of 40 MHz, the number of subcarriers is 114, then the CSI matrix H can be expressed as H=[]H11H12⋯H1qH21H22⋯H2q⋮⋮⋱⋮Hp1Hp2⋯Hpq where p and q represent the number of transmitting antennas and the number of receiving antennas, respectively, and m=p×q is the number of pairs of antennas.…”

Performance limit of AOA-based localization using MIMO-OFDM channel state information

“…Reducing the cost of sending the downlink CSI to the processor may be done with a chunk-based scheme [16][17][18], where an average magnitude of CFR for a block of contiguous subcarriers is sent instead of the complex values of the CFR of all subcarriers within the block. However, AOA-based localization requires the CFR in complex form [9]. Therefore, strictly following [16][17][18] may not be appropriate for our problem.…”

“…Assume that each BS employs an array of antennas, with the spacing between them on the order of half wavelength. Then, the CFR for the q-th BS respecting the k-th subcarrier and m-th antenna can be expressed by [9] …”

“…Recently, it has been shown that multipleinput multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) channel state information (CSI) may be used as the observation data for localization based on AOA [9]. For localization based on AOA, it generally requires that direct radio paths between the MD and the base stations (BSs) are available sufficiently for triangulation.…”

“…A few localization methods requiring hardware of just an existing wireless network have been proposed in the literature [6][7][8][9] and implemented commercially. Most of them [6][7][8] adopt fingerprint matching as the basic scheme of location determination.…”