## 1 Introduction
A lower SINR may result in a slower _modulation and coding scheme (MCS)_ that  
Figure 1: WLAN for an IoT system. will cause lower throughput. The wider bandwidth of the CB link may also cause the _hidden terminal problem_. A dual interface at an AP using \(11n\) and \(11 ac\) at \(2.4~{}GHz\) and \(5~{}GHz\) frequency bands is an efficient approach to enhance the network's performance while avoiding interference. It can reduce the number of active APs, which can further reduce the interference. Therefore, we have studied the _active AP configuration algorithm_ considering the _dual interface_[33] of a _Raspberry Pi_[34] AP adopting an external USB interface Archer T4U [35]. In this dual interface, the embedded one is used for \(11\)n, and the external one is for \(11\)ac. However, the previous algorithm limits the _non-channel bonding (non-CB)_. Thus, it should be extended to consider the CB. In addition, the algorithm selects the active APs and their host associations by estimating the throughput of a host using the _throughput estimation model_, where the estimation accuracy of the model is critical to determine the network performance. Thus, it should be improved under higher interference by the CB. In this paper, we study the _active AP configuration algorithm_ for the _dual interface_ with _channel bonding (CB)_ at the same AP. The goal of this algorithm is to find the AP configuration that minimizes the number of active APs in the WLAN under the minimum host throughput constraint for every host. The _dual interfaces_ at the AP will operate at different frequency bands, which allows the AP to communicate with two hosts simultaneously without any interference between them. As a result, the _dual interface_ can reduce interference between neighboring APs in the network and can solve the abovementioned problems in the CB. The main contributions of this paper are summarized as follows:  
1. We investigate the protocol selection at each Wi-Fi interface in a _WLAN_ to make the best use of them in the proposed access point (AP) with the _dual interfaces_ in the testbed system. From experiments, we show that the selection of \(11n\) at \(2.4~{}GHz\) at the embedded interface of _Raspberry Pi_ and of \(11 ac\) at \(5~{}GHz\) for the external USB interface _Archer T4U_ has better performances. 2. We present the modification of the _active AP configuration algorithm_ to take into account the use of the _dual interfaces_ and the _channel bonding (CB)_, where the interfaces operate at different frequency bands with IEEE 802.11n and 11 ac protocols, and the AP can communicate with two hosts simultaneously without any interference between them. 3. We incorporate the _throughput reduction factor_ into the _throughput estimation model_ to improve the estimation accuracy when multiple hosts are associated with the same AP. 4. We evaluated the proposal through both simulations using the _WIMENT simulator_[36] and experiments using the testbed system in real fields. The testbed system involved a _Raspberry Pi_ with an external _Archer T4U_ for the AP and _Linux PCs_ for the hosts. The rest of this paper is organized as follows: Section 2 presents related works in the literature. Section 3 reviews our previous works. Section 4 discusses the interface selection through experiments. Section 5 presents modifications of the active AP configuration algorithm. Section 6 evaluates the proposal through simulations and experiments. Finally, Section 7 provides concluding remarks with future works.