###### Abstract
However, it requires separating signals from the ANs into different frequency bands [17], which occupies a large bandwidth, consumes more energy, and increases the complexity of the RF front-end design. CD allows multiple ANs to share the same frequency band using unique codes to spread their signals to UN, but it is susceptible to the near-far effect [18]. In contrast to FD and CD, the TD scheme does not suffer from the above issues, albeit generating sequential TOA measurements would require a longer temporal duration for the ANs to finish their signal transmission [11]. Multiple signal transmissions may consume more energy, but this consumption is minimal compared to emitting a large bandwidth signal in the FD scheme. Additionally, FD is constrained by RF spectrum resources and sensitivity, not to mention the complexity of the RF front-end design. Therefore, the TD scheme offers significant advantages for practical applications. The TD broadcasting system allows the UN to obtain sequential one-way TOA measurements, facilitating JLAS without the need to send signals back to the ANs, thereby enhancing the security of UNs. The comparison between FD, CD, and TD technologies is tabulated in Table 1. Due to the advantages of using sequential TOA, a significant amount of research work has been emerging on developing methods to address the JLAS problem [7; 8; 19; 20; 21; 22; 23; 24]. \begin{table}
\begin{tabular}{p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt} p{56.9 pt}} \hline \hline
**Commun. Tech.** & \begin{tabular}{c} **Bandwidth** \\ **Occupation** \\ \end{tabular} & **Commun. Mode** & **Short Comings** & **Advantages** & **TOA Measurements** \\ \hline Frequency division & Large & Simultaneous & Energy-consuming, complex RF design & \begin{tabular}{c} Obtain TOAs \\ after one \\ communication round \\ \end{tabular} & Non-sequential \\ Code division & Small & Simultaneous & Near-far effect & \begin{tabular}{c} Obtain TOAs \\ after one \\ communication round \\ \end{tabular} & Non-sequential \\ Time division & Small & \begin{tabular}{c} One pair \\ by one pair \\ \end{tabular} & \
\begin{tabular}{c} Longer temporal \\ duration \\ \end{tabular} &
\begin{tabular}{c} Energy-saving, frequency \\ spectrum resource-saving, simple design \\ \end{tabular} & Sequential \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparisons between different communication technologies. In recent years, research focused on localization based on the TD broadcast sequential TOA measurements has received considerable attention, as shown in Table 2. Two-way TOA ranging relaxes the synchronization between nodes, making it more practical in WSN applications. The research in [20] addressed the cooperative localization problem for distributed nodes in wireless networks using shared transmission scheduling. The author's approach has low complexity and does not require node synchronization. The proposed weighted least squares (WLS) and iterative WLS estimator can attain the Cramer-Rao Lower Bound (CRLB). In underwater WSNs, where AN positions are perfectly known but their clocks are asynchronous, [PERSON]. [23] leveraged sequential transmission protocols and the broadcasting characteristics of underwater acoustic media to obtain a set of measurements. However, solving the optimization problem for finding the position of the UN is based on an exhaustive search and a multi-grid search, which lacks practicality in engineering applications, although it achieves the CRLB. To improve the computational efficiency, [PERSON]. [25] addressed JLAS by proposing a closed-form solution. The recent work in [26] tackled the two-way TOA JLAS problem using semidefinite relaxation, which relaxes the original problem into a convex one, a semidefinite programming (SDP) problem. The proposed SDP consistently converges to a globally optimal solution, reducing the localization error by over 40%. Additionally, the performance of this method is not affected by the speed of the UN.