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Wireless networks in difficult conditions of signal receiving are characterized by a high level of burst data losses, at which a large number of data fragments can be lost in a row. In this case, to recover the lost data, the use of forward error correction methods (FEC) in most cases does not give a sufficient effect. The use of standard data loss recovery methods based on automatic retransmission request (ARQ) at the data link and transport layers of the OSI model can lead to significant delays, which is often unacceptable for real-time streaming services. In such a case, it may be preferable to skip the piece of data rather than delay waiting for the piece to be delivered on retransmissions. The use of ARQ-based techniques on application layer of OSI model for data streaming allows for a more efficient recovery of lost data chunks in wireless networks with a high level of burst losses. The known models of a discrete channel for wireless networks allow for analytically assessing the probability of data loss, however, they do not take into account cases with retransmission of lost data. The study proposes a mathematical model of data transmission in a wireless communication channel based on the Gilbert model, which takes into account the loss recovery by the ARQ method and allows you to calculate the data loss ratio. To check the adequacy of the proposed model, a software was developed that ensures the transmission of data streaming in a wireless communication network with recovery of fragment losses at the application level, and a corresponding experimental study was carried out. It is shown that the mathematical model takes into account the burstiness of transmitted data losses and their recovery by the ARQ method.

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The article presents methods for relaying Multi-Stream data at the application layer of OSI model through a relay node in UAV networks - MS-AL-ARQ Relaying methods. MS-AL-ARQ method is taken as the principal one. One of the basic operating principles of Application Layer ARQ-based Multi-Streaming (MS-AL-ARQ) is to determine a lost fragment from one of the source nodes based on a sequence number with an IP address ID. After determination of the lost data fragment, a negative non-acknowledgment NACK is sent to the source node. A round trip time RTT is set, after each NACK to schedule the requesting process. This action is performed until data fragment is received or the data fragment timeout RTO expires. The main difference between MS-AL-ARQ and MS-AL-ARQ Relaying is that MS-AL-ARQ Relaying works with buffers on the source and destination nodes as well as working with a buffer on the relay node. To describe the methods, the definition of a leading/priority source node with sending video priority, was introduced. The core metrics for determination of the leading node is the packet delivery ratio (counter PDR), which calculates the value at the relay node in a given interval and only then transmits data to the recipient node. There are several options to define the leading/priority source node: default, static, and dynamic definition. In this case, the situation with the flying relay node and the ground relay node is considered separately. The choice of relay node position is related to the characteristics of the node. Thus, a ground-based relay node could be a laptop, where the computing resources are often higher and the memory capacity can allow storing incoming data for longer time periods and a flying relay node is represented by a UAV with limited productive resources. The final part presents a test bench for further laboratory testing of the MS-AL-ARQ Relaying method and the results of laboratory tests confirming the relevance of developing algorithms based on MS-AL-ARQ Relaying methods.