# Adaptive TCP Transmission Adjustment for UAV Network Infrastructure
## 2 Related Work  
This section lists several related work focusing on TCP performance enhancement in ad hoc network. There is some research about modifying TCP for ad hoc networks or wireless networks. [PERSON] et al. [14] suggested new congestion control algorithm for better performance in wireless networks. They argued that the major problem of random segment loss in the wireless networks is the bit error. Therefore, the arrival of duplicate acknowledgement or even the retransmission timeout is not enough to denote actual reason of congestion. They provided fast transmission solution by adjusting CWND size according to count of timeouts, 3 dup ACKs and timeout interval of the retransmission timer. However, this algorithm was only implemented for TCP-NewReno and was not considered about any other TCP protocols. [PERSON] et al. [15] provided a solution named AFStart which acts like a slow-start algorithm for the network environment with long-distance and high end-to-end latency. They proposed a solution that finds available bandwidth to set the _sstthresh_ and adjust the congestion window. To estimate the available bandwidth, they used ImTCP [16] which derives the available bandwidth based on round trip time (RTT). If there is enough bandwidth to be used, this algorithm ramps up CWND aggressively which is faster than traditional slow-start algorithm for fast transmission. [PERSON] et al. [17] said that TCP performs poorly under Vehicular Ad hoc Network (VANET) due to its high mobility and wireless errors such as transmission path change (fading) and interferences that lead to unpredicted packet drop. Therefore, they analyzed various TCP such as Vegas, Compound, Westwood, NewReno, BIC and CUBIC under vehicular environment for variable speed and traffic. They argued that TCP-CUBIC is the best algorithm in the aspect of throughput and TCP-Vegas has strong aspects of delay control. Although improvement of the algorithm was not included, they showed that various aspects of congestion avoidance should be considered in the wireless environment with mobility. [PERSON] et al. [18] suggested High speed TCP to improve the performance of TCP connections with large congestion windows for Ad hoc environment with no guaranteed bandwidth and node mobility. This algorithm was based on the relation between an average congestion window and packet drop rate. The characteristic of HSTCP algorithm is increasing and decreasing CWND abruptly to improve the retransmission time and to avoid congestion in dynamic conditions where node mobility is completely random. Using CWND increase and decrease factor seems flexible and suitable for an unstable ad hoc network. However, they implemented in experiment with assumed value of CWND increase factor and decrease factor with lack of explaining. Also, their evaluation study was performed with fixed CWND increase and decrease factors, which cannot satisfy the various network environments. Also, there is some research about TCP-CUBIC for an ad hoc network. [PERSON] et al. [19] presented an algorithm that solves a problem of significant packet losses due to small buffer size in Linux TCP. This problem especially occurs when small memory devices (such as digital cameras and digital camcorders) upload photos or movies via long distance network. The proposed solution analyzed the shape of the throughput curve of TCP-CUBIC in order to decide whether or not to increase the sender buffer. [PERSON] et al. [20] proposed a Markovian model to determine the steady state throughput of TCP-CUBIC in wireless environment. The proposed model considered both congestion loss and random packet loss due to fading. Also, they proposed a solution which increases the throughput performance of TCP-CUBIC by moderately increasing the window growth factor and the multiplicative decrease factor. However, they presented normalized throughput only, but they did not show the total throughput or comparison with original TCP-CUBIC. Evaluation of normalized throughput showed that throughput is improved by the reduced packet loss.