Limitations of TDoA Calculation and ORBRO's Structural Response

TDoA (Time Difference of Arrival) is a method of estimating the transmission location by analyzing the difference in time a single transmitted signal reaches multiple receivers. Because it does not require separate response processing from the terminal and calculations are performed only on the receiver side, it is simple in structure and capable of large-scale expansion, making it widely used as a high-precision location estimation technology in various industrial environments. However, this method guarantees consistent performance only under ideal conditions. Realistic variables such as reflections from indoor structures, clock discrepancies between receivers, and multipath reception distort the arrival time of signals and accumulate errors during the time difference calculation process. Additionally, TDoA is mathematically a non-linear optimization problem; if the initial estimation is inaccurate or there are no solution space constraints, the calculation may diverge or converge to a local minimum. These structural constraints can be summarized into three main issues: · Clock errors of just a few nanoseconds are amplified into location errors of several dozen centimeters. · Signal distortion occurring in reflection or NLOS (Non-Line-of-Sight) conditions is included in the time difference calculation, hindering accuracy. · If initial estimations or spatial constraints are inaccurate, the calculation may converge to physically invalid coordinates or fail to derive a solution. ORBRO solved these limitations not through simple filtering or post-processing, but through a redesign of the entire TDoA computational structure. We divided the entire flow from signal reception to coordinate output into a structure of collection, initialization, optimization, and quality verification, and inserted modules capable of quantitative control at each stage to ensure consistent convergence stability and result quality in real environments. This structural response is not just an algorithmic improvement, but the result of a system structure that has refined the entire TDoA calculation into a designable framework. The ORBRO TDoA calculation described hereafter consists of four core structural units, each performing an independent function to stably maintain real-time calculation quality.

6-Step Computational Flow for Precise Positioning: From Signal to Coordinates, How ORBRO TDoA Works

ORBRO's TDoA system goes beyond a simple RTT calculation structure and is designed as a multi-stage signal processing structure to secure the reliability of distance measurement and calculation quality. The technical response methods described in Chapter 2 are implemented within the actual system through the following six stages. Each stage is configured to quantitatively evaluate the quality of received signals and stably control the entire flow until a distance value is output.

Optimized Computational Structure Makes a Difference in Real-World Performance

Location calculation in a high-precision RTLS system is not just about outputting coordinates. Position values are comprehensively evaluated by various quality factors such as real-time performance, convergence speed, and consistency regarding environmental changes. In particular, since the TDoA (Time Difference of Arrival) method is calculated based on the time difference between receivers, a time difference error of just a few nanoseconds can be amplified into a coordinate deviation of several dozen centimeters, and performance differences become stark depending on the computational structure and initial condition settings. Indoor spaces make it difficult to maintain ideal signal quality due to reflections, multipath reception, and structural shielding. Therefore, the stability and reproducibility of calculations act as key factors determining the practical performance of an RTLS system rather than simple precision figures. ORBRO has maximized the reliability of calculations by inserting quality control at each stage and optimization algorithms based on a computational system that structurally reflects these conditions. In this chapter, we summarize how structural differentiation leads to quantitative results through the performance figures achieved by the ORBRO TDoA system in actual environments.

1. Accuracy

The prerequisite for TDoA calculation is that the clocks of all receivers (anchors) must be synchronized to the same standard. ORBRO periodically exchanges reference signals through high-speed communication between receivers and compensates for each receiver's clock drift in real-time at the hardware level. This maintains high-precision time alignment in nanoseconds (ns) without post-filtering, securing reliable raw time data required for real-time calculation.

2. Repeatability

Repeatability is an indicator that evaluates how consistently coordinates are output when measured repeatedly under the same conditions. Even if the measurement environment is constant, coordinates will fluctuate if there are signal reflections, clock deviations, or computational variances. ORBRO has realized a low variance value of approximately 4cm on average through designs such as clock compensation, convergence quality-based correction, and Z-axis constraints. This performance is particularly important in environments where fixed-position tags must maintain their location for long periods or act as fixed reference points.

3. Coordinate Jitter Rate

The coordinate jitter rate represents the frequency of abnormally large changes occurring between consecutively output position coordinates. This indicator reflects not only the consistency of signal quality in a real-time location system but also the stability of the calculation and exception-handling capabilities. ORBRO adopts a structural stabilization strategy that identifies and removes error signals in advance within the calculation structure rather than a simple filtering method, maintaining a jitter rate of less than 1% and increasing the reliability of the overall location flow.

4. Time to First Fix

Convergence time refers to the time it takes for the system to output the first valid coordinate after a tag transmits a signal. This indicator, which determines the real-time nature of the location system, is greatly influenced by the initial value setting and calculation convergence speed. ORBRO secured a convergence speed of less than 0.5 seconds on average by combining WLS-based initial estimation and Taylor expansion correction algorithms. This allows the location to be tracked as soon as the tag starts moving, providing users with a fast and intuitive response.

5. Signal Loss Recovery Rate

Recovery rate refers to how quickly the system can normalize location calculations when signals are temporarily not received from some receivers. This indicator reflects the overall reliability design, including calculation continuity, exception detection logic, and multi-convergence structures. ORBRO continues calculations based on remaining signals and previous convergence values even if some receivers do not respond, achieving rapid coordinate re-output of over 95% through recovery algorithms.

6. Location Stability in Complex Environments

Location systems must maintain stable coordinate calculations even amidst complex variables such as structural reflections, radio interference, and open space structures. ORBRO structurally controls the possibility of calculation failure through Z-axis constraints, receiver distance-based correction, and local solution avoidance algorithms, achieving a convergence rate of over 98% even in metal-dense areas or spaces where visibility is difficult to secure. This signifies responsiveness to environmental changes and the resilience of the computational structure beyond simple calculation success rates.

Precision Positioning is Completed by Structure – The Standard for TDoA Computation Redesigned by ORBRO

TDoA is not just a simple location estimation algorithm. Its computational structure must be composed of sophisticated layers—from receiver clock alignment and time difference interpretation to optimization convergence conditions and quality verification of final coordinates—to guarantee stable results. ORBRO follows the basic principles of TDoA but has redesigned its structure into a controllable system unit encompassing all key elements of location estimation, such as signal interpretation, calculation initialization, spatial constraints, and convergence evaluation. In this process, we have created a foundation to technically control the entire 'flow' of the calculation, rather than simply reducing errors. Even if signal quality varies or the environment becomes complex, ORBRO TDoA is configured to respond to exceptional situations and output accurate positions. TDoA is already a well-known technology, but precision, stability, and scalability differ completely depending on how the structure is designed. ORBRO's approach is the closest to the essence of this technology, representing a structural evolution that has elevated TDoA to a highly reliable, product-level real-time location system.