# Intelligent Transmission Control Scheme for 5G mmWave Networks Employing Hybrid Beamforming
## 4 Proposed Work
### Network Protocol
#### 4.1.2 Enhanced mmWave Scalable TCP Protocol  
Modifications were implemented to the Cwnd growth and reduction procedures in S-TCP to enhance stability and ensure high throughput in mmWave networks. The enhancement of the raise or lower approaches augments S-TCP's equity and stability in the mmWave network without compromising its throughput. Mathematical Analysis of cwnd Growth in mmS-TCP  
TCP's congestion window (cwnd) regulates how many packets may be sent before an acknowledgment. Traditional TCP congestion control methods, such as NewReno, halve cwnd when packet loss is detected, causing underutilization in low-latency, high-bandwidth mmWave networks. We suggest the following modified cwnd update rule:  
After seeing an ACK, cwnd boosts as follows:  
\[Cwnd-cwnd+1/b\]  
where \(b\) is incremented up to a threshold (e.g., 125). When packet loss is detected (apart from retransmission timeouts), cwnd decreases as follows:  
\[Cwnd-cwnd-0.125\times cwnd\]  
Instead of the traditional halving. The modified additive increase guarantees quicker recovery without being too aggressive in high-speed networks. The \(b\) parameter controls the growth rate dynamically so that there is gradual adaptation according to network conditions. In comparison to NewReno, which increases linearly (one segment per RTT), the proposed technique guarantees a higher throughput with improved stability in dynamic mmWave scenarios. The conventional TCP congestion control cuts cwnd by 50%, which, in high-speed networks can be too aggressive and results in excessive underutilization over the long term. The suggested 0.125\(\times\) reduction makes smoother adaptation possible and prevents sudden drops in throughput, allowing faster recovery and improved multi-user fairness. This mechanism is consistent with delay-based congestion control mechanisms and provides enhanced TCP fairness in multi-flow environments. Cwnd Raise the Mechanism of mm-Scalable TCP  
MmS-TCP can enhance TCP fairness by altering the cwnd increase mechanism. Upon receiving 100 ACKs, S-TCP increments the cwnd size by 1 packet. Receiving 100 ACKs when sending one packet consistently results in a quicker delivery rate compared to NewReno. On the other hand, a sudden rise in S-TCP could harm other TCP flows with different congestion controls. To reduce the aggressiveness of S-TCP and avoid a drop in quantity, we modified the growth rate of continuous cwnd as follows for whenever an ACK is established:  
\[cwnd\leftarrow\ 1/b \tag{9}\]  
where b is increased by 1 each time and ACK is received until it reaches 125. Whenever an ACK is established, the S-TCP value rises by 1/100; when 100 ACKs are established, the cwnd rises by one container. The growth rate and level of aggressiveness of S-TCP are dictated by the value of b of Equation (7). When the value of b is low, S-TCP will rise quickly, whereas when b is high, the cwnd will increase at a slower pace. cwnd Reduction Mechanism of mm-Scalable TCP  
The mmS-TCP cwnd reduction feature is designed to prevent high packet losses during the start of a connection and to improve network reliability. In all instances of packet loss, excluding \"Retransmission time-out (RTO)\", S-TCP reduces cwnd by 0.125, as illustrated in Equation (8). In the initial phase, the congestion window (cwnd) may exceed the connection's capacity due to the bottleneck buffer size; a decrement of 0.125 in cwnd could lead to additional retransmission timeouts (RTO) and initiate a recurrence of the delayed start phase. Multiple instances of a slow start phase may result in numerous packet losses during the initial stages of a TCP connection, impacting other flows that utilize the same connection. Although S-TCP's repeated slow-start phases resulted in numerous duplicated ACKs, mmS-TCP managed to greatly decrease the occurrence of duplicated ACKs during the initial connection, ultimately leading to enhanced network stability and a slight increase in throughput.