UWB ranging
Ultra-wideband impulse radio ranging (or UWB-IR ranging) is a wireless positioning technology based on IEEE 802.15.4z standard,[1] which is a wireless communication protocol introduced by IEEE, for systems operating in unlicensed spectrum, equipped with extremely large bandwidth transceivers.
UWB enables very accurate ranging[2] (in the order of centimeters) without introducing significant interference with narrowband systems.
To achieve these stringent requirements, UWB-IR systems exploit the available bandwidth[3] (which exceeds 500 MHz for systems compliant to IEEE 802.15.4z protocol) that they support, which guarantees very accurate timing (and thus ranging) and robustness against multipath, especially in indoor environments.
[4] The available bandwidth also enables UWB systems to spread the signal power over a large spectrum[5] (this technology is thus called spread spectrum[6]), avoiding narrowband interference.
[7][8][9] UWB-IR relies on the low-power transmission of specific sequences of short-duration pulses.
The bands supported by the standard are the following ones: The primary time division in UWB systems is structured in frames.
Each frame is composed by the concatenation of 2 sequences: The further time subdivisions of the preamble and the PPDU are organized in different ways.
For localization purposes, only the preamble is employed (and described in detail later on), since it is specifically designed to perform accurate synchronization at receiver side.
where the additional parameters are defined as follows In order to associate the propagation delay to a distance, there must exists a LoS path between transmitter and receiver or, alternatively, a detailed map of the environment has to be known in order to perform localization based on the reflected rays.
In presence of multipath, the large bandwidth is of paramount importance to distinguish all the replicas, which otherwise would significantly overlap at receiver side, especially in indoor environments.
The propagation delay can be estimated through several algorithms, usually based on finding the peak of the cross-correlation between the received signal and the transmitted SHR waveform.
[12][13][14] The first one is based on the time of arrival (TOA) and it is called one-way ranging.
It requires a priori synchronization between the anchors and it consists in estimating the delay and computing the range as
The second method is based on the round-trip time (RTT) and it is called two-way ranging.
It consists in the following procedure: In this second case the distance between the 2 anchors can be computed as
