## 2 Network Scenarios and Problems  
In this section, we first explain the underlying background of IEEE 802.11_ay_ in detail, then discuss throughput observations of various cases of TCP and MPTCP with four bonded channels and explain the problems of MPTCP packet scheduling from the transport layer and the TCP design issues. In particular, we explain several fundamental assumptions inherent in stochastic TCP models that are challenged by the improved data traffic dynamics of IEEE 802.11_ay_ networks.
fields); (ii) EDMG portion, comprising of the fields recognized by EDMG Stations (STAs), such as their STF and CEF fields, as well as the new headers A and B. IEEE 802.11_ay_ supports three types of frames: Control (DMG beacons, Beamforming Training, etc.), Single Carrier (SC), and Orthogonal Frequency Division Multiplexing (OFDM). For data networking, we can EDMG SC (1-21 modulation and codings, maximum of 8085 Mbit/s) or EDMG OFDM (20 modulations and coding, maximum of 8316 Mbit/s).  
A high-level view of the considered multipath data networking scenario in the Internet of Drones using IEEE 802.11_ay_ is shown in Figure 3. Channel configuration of IEEE 802.11_ay_ allows 8 (2.16 GHz) channels in operations. It facilitates the bonding of a continuous group of channels to enhance the transmission rate significantly. Bonding a maximum of four channels results width of 8.64 GHz, and the standard entails using two bonded channels.  
For the beam refinement protocol (BRP) introduced in the 802.11 ad and its switching time limitations (36 ns), IEEE 802.11_ay_ redesigned the training field to adapt to the device heterogeneity and the flexibility of switching times. The training field consists of a configurable number of units, and each unit includes several subfields, including six Golay sequences. IEEE 802.11_ay_ adds a variable Golay sequence flexibly set by the user and, in the case of channel bonding, is also dependent on the number of continuous channels. They have strong correlation characteristics, making them ideal for estimation and beamforming. To assist the estimation and beamforming for MIMO communication, for each space-time stream, IEEE 802.11_ay_ enables a uniquely identified orthogonal set of these sequences.  
IEEE 802.11_ay_ has two types of MIMO: (i) SU-MIMO is a single-user MIMO that enables two devices to broadcast and receive various spatial streaming (up to eight); (ii) MU-MIMO is a multi-user MIMO for downlinks which enables an AP to send distinct spatial streaming to several devices (up to 8) at the same time. In particular, 802.11_ay_ supports MIMO for multifold improvement in throughput. It allows simultaneous transmission and receipt of up to eight spatial streams at the same frequency and time. In addition, for the MIMO transmission, the standard requires the capability of analog RF precoding.  
Phased antenna arrays can synthesize a narrow beam pattern in this mode to establish a spatial channel for each stream; however, depending on the quality of the phase shifters and the arrangement, it is often not plausible to generate pencil beams with low inter-stream interference. This explains the need for the collaborative design of beamforming and channel allocation at lower layers while performing performance-oriented MPTCP congestion control and scheduling from the TRA layer. As illustrated in Figure 3, it is worth noting that our main focus in this paper is to _develop a complete understanding of the dynamics  
Figure 3: A high-level view of the considered MPTCP data networking scenario in the Internet of Drones using multiple APs of IEEE 802.11_ay_. Our _main focus in this paper_ is to develop a complete understanding of such dynamics of MPTCP over 802.11_ay_ WiFi to identify and ameliorate the MPTCP design issues at the transport layer.  
Figure 2: Enhanced directional multi-gigabit (EDMG) fields of 802.11_ay_.  
of MPTCP over IEEE 802.11 ay networks to identify and ameliorate the MPTCP design issues, which is still lacking, and this is a highly challenging task.