A Multi-link Based Seamless Handoff Scheme for Next Generation Wi-Fi Networks
基于多链路的下一代 Wi-Fi 网络无缝切换方案

I. Introduction  I. 引言

1. We design a seamless handoff scheme based on multilink technology and power control technology, which can ensure that at least one link is available for communication throughout the entire AP handoff process;
   我们设计了一种基于多链路技术和功率控制技术的无缝切换方案，能够确保在整个 AP 切换过程中至少有一个链路可用于通信；
2. Comprehensively taking throughput, energy consumption, and OBSS interference into consideration, we design a DPA algorithm to determine the optimal period of power adjustment and power levels for seamless handoff process;
   综合考虑吞吐量、能耗和 OBSS 干扰，我们设计了一种 DPA 算法，以确定无缝切换过程中的最佳功率调整周期和功率水平；
3. We evaluate the proposed scheme based on three performance metrics, including throughput, energy consumption, and area of OBSS interference. Compared to traditional AP handoff scheme, our proposed scheme effec-
   我们根据三个性能指标评估所提出的方案，包括吞吐量、能耗和 OBSS 干扰的面积。与传统的 AP 切换方案相比，我们提出的方案有效地
   tively enhances throughput and reduces communication interruptions. In contrast to seamless handoff schemes without using DPA algorithm, our proposed scheme alleviates energy consumption and OBSS interference issues.
   有效地提高了吞吐量并减少了通信中断。与不使用 DPA 算法的无缝切换方案相比，我们提出的方案缓解了能耗和 OBSS 干扰问题。
   The rest of this paper is organized as follows. In Section II, we introduce the proposed AP handoff scheme and the DPA algorithm. We evaluate the performances of throughput, energy consumption, and OBSS interference of different schemes in Section III. Finally, we conclude our work in Section IV.
   本文的其余部分组织如下。在第二节中，我们介绍了提出的 AP 切换方案和 DPA 算法。在第三节中，我们评估了不同方案在吞吐量、能耗和 OBSS 干扰方面的性能。最后，我们在第四节中总结了我们的工作。

II. Proposed Seamless Handoff Scheme
II. 提议的无缝切换方案

A. Seamless handoff scheme
A. 无缝切换方案

Different from the traditional AP handoff process, as shown in Fig. 1, our proposed scheme increases the transmit power of target AP on a new frequency band, which enables STAs to establish a new connection with the target AP before disconnecting from the source AP. Consequently, in our scheme, there is consistently at least one available link throughout the entire process of AP handoff, guaranteeing the transmission reliability. For instance, as shown in Fig. 1, during the handoff, the STA keeps a connection with the source AP in the 2.4 GHz band and concurrently establishes a new connection with the target AP in the 5 GHz band.
不同于传统的 AP 切换过程，如图 1 所示，我们提出的方案在新的频段上增加目标 AP 的发射功率，这使得 STA 能够在与源 AP 断开之前与目标 AP 建立新的连接。因此，在我们的方案中，在整个 AP 切换过程中始终至少有一个可用链接，保证了传输的可靠性。例如，如图 1 所示，在切换过程中，STA 保持与 2.4 GHz 频段的源 AP 的连接，同时在 5 GHz 频段与目标 AP 建立新的连接。

1. Initially, we assume that the STA has established a multilink connection with the source AP $(2.4\mathrm{GHz}$$(2.4\mathrm{GHz}$(2.4GHz(2.4 \mathrm{GHz} and 5 GHz$)$$)$)). As the STA progressively moves away from the source AP, it will first disconnect the link on the 5 GHz band, since 5 GHz signals experience severe propagation loss. As the STA continues to move, the seamless handoff process will be initiated to maintain the communicational quality.
   最初，我们假设 STA 已经与源 AP $(2.4\mathrm{GHz}$$(2.4\mathrm{GHz}$(2.4GHz(2.4 \mathrm{GHz} 建立了多链路连接，并且在 5 GHz $)$$)$)) 上。随着 STA 逐渐远离源 AP，它将首先断开 5 GHz 频段的连接，因为 5 GHz 信号会经历严重的传播损失。随着 STA 继续移动，将启动无缝切换过程以保持通信质量。
2. The seamless handoff process is illustrated in Fig. 2. The STA selects a suitable AP as the target AP based on RSSI values. Then, the STA employs the DPA algorithm proposed in this paper to determine the optimal period of power adjustment and power levels $\{P{t}_s,P{t}_a,d_e,d_r\}$$\left\{P{t}_s,P{t}_a,d_e,d_r\right\}${Pt_(s),Pt_(a),d_(e),d_(r)}\left\{P t_{s}, P t_{a}, d_{e}, d_{r}\right\}. $P{t}_s$$P{t}_s$Pt_(s)P t_{s} and $P{t}_a$$P{t}_a$Pt_(a)P t_{a} respectively represent the transmit power of STA and AP during the period of power adjustment, while $d_e$$d_e$d_(e)d_{e} and $d_r$$d_r$d_(r)d_{r} respectively represent the distance between the STA and the target AP at the beginning and end of the power adjustment period.
   无缝切换过程如图 2 所示。STA 根据 RSSI 值选择合适的 AP 作为目标 AP。然后，STA 采用本文提出的 DPA 算法来确定最佳的功率调整周期和功率水平 $\{P{t}_s,P{t}_a,d_e,d_r\}$$\left\{P{t}_s,P{t}_a,d_e,d_r\right\}${Pt_(s),Pt_(a),d_(e),d_(r)}\left\{P t_{s}, P t_{a}, d_{e}, d_{r}\right\} 。 $P{t}_s$$P{t}_s$Pt_(s)P t_{s} 和 $P{t}_a$$P{t}_a$Pt_(a)P t_{a} 分别表示功率调整期间 STA 和 AP 的发射功率，而 $d_e$$d_e$d_(e)d_{e} 和 $d_r$$d_r$d_(r)d_{r} 分别表示功率调整开始和结束时 STA 与目标 AP 之间的距离。
3. When the distance $d$$d$dd between the STA and the target AP satisfies the condition $d_r<d<d_e$$d_r<d<d_e$d_(r) < d < d_(e)d_{r}<d<d_{e}, the transmit power of both STA and AP are increased. The STA adjusts its transmit power to $P{t}_s$$P{t}_s$Pt_(s)P t_{s}. The source AP sends a power adjustment request to the target AP during the period of power adjustment, and adjusts the transmit power of the target AP to $P{t}_a$$P{t}_a$Pt_(a)P t_{a}. Then, the STA establishes a connection with the target AP on the 5 GHz band in advance.
   当 STA 与目标 AP 之间的距离 $d$$d$dd 满足条件 $d_r<d<d_e$$d_r<d<d_e$d_(r) < d < d_(e)d_{r}<d<d_{e} 时，STA 和 AP 的发射功率都会增加。STA 将其发射功率调整为 $P{t}_s$$P{t}_s$Pt_(s)P t_{s} 。源 AP 在功率调整期间向目标 AP 发送功率调整请求，并将目标 AP 的发射功率调整为 $P{t}_a$$P{t}_a$Pt_(a)P t_{a} 。然后，STA 提前在 5 GHz 频段与目标 AP 建立连接。
4. The STA maintains a connection with the source AP on the 2.4 GHz band while simultaneously establishing a connection with the target AP on the 5 GHz band. Upon leaving the 2.4 GHz coverage of the source AP, the 2.4 GHz link with the source AP is broken. However, communication remains uninterrupted due to the remaining link with the target AP.
   STA 在 2.4 GHz 频段与源 AP 保持连接，同时在 5 GHz 频段与目标 AP 建立连接。当离开源 AP 的 2.4 GHz 覆盖范围时，与源 AP 的 2.4 GHz 链接被断开。然而，由于与目标 AP 的链接仍然存在，通信保持不间断。
5. When $d<d_r$$d<d_r$d < d_(r)d<d_{r}, the transmit power of the target AP in the 5 GHz band is restored to the original level. The STA terminates the link with the target AP in the 5 GHz band.
   当 $d<d_r$$d<d_r$d < d_(r)d<d_{r} 时，目标 AP 在 5 GHz 频段的发射功率恢复到原始水平。STA 与目标 AP 在 5 GHz 频段的链接终止。
6. When the STA enters the coverage of restored 5 GHz band, it reconnects with the target AP in the 5 GHz band.
   当 STA 进入恢复的 5 GHz 频段覆盖范围时，它会在 5 GHz 频段与目标 AP 重新连接。
   

   

B. DPA algorithm  B. DPA 算法