No abstract

During recent years usage of Wi-Fi communications were increasing rapidly not only in commercial areas but also in private households. With increasing number of Wi-Fi devices a new kind of problems appeared, mostly related to poor Wi-Fi throughput or communication problems. In this paper an investigation on Wi-Fi networks in Vilnius City and it's surrounding is presented, covering the main problems of Wi-Fi network saturation and load during day. Also an investigation on dependence of Wi-Fi saturation on noise levels was made, showing the impact of neighbor AP to SNR. Ill. 7, bibl. 7 (in English; abstracts in English and Lithuanian).

Paper investigates transport control protocol (TCP) acknowledgment (ACK) optimization in low power or embedded devices to improve their performance on high-speed links by limiting the ACK rate. Today the dominant protocol for interconnecting network devices is the TCP and it has a great influence on the entire network operation if the processing power of network devices is exhausted to the processing data from the TCP stack. Therefore, on high-speed not congested networks the bottleneck is no longer the network link but low-processing power network devices. A new ACK optimization algorithm has been developed and implemented in the Linux kernel. Proposed TCP stack modification minimizes the unneeded technical expenditure from TCP flow by reducing the number of ACKs. The results of performed experiments show that TCP ACK rate limiting leads to the noticeable decrease of CPU utilization on low power devices and an increase of TCP session throughput but does not impact other TCP QoS parameters, such as session stability, flow control, connection management, congestion control or compromises link security. Therefore, more resources of the low-power network devices could be allocated for high-speed data transfer.

Disertacija rengta 2010-2017 metais Vilniaus Gedimino technikos universitete. Vadovas prof. dr. Šarūnas PAULIKAS (Vilniaus Gedimino technikos universitetas, elektros ir elektronikos inžinerija-01T). Vilniaus Gedimino technikos universiteto Elektros ir elektronikos inžinerijos mokslo krypties disertacijos gynimo taryba: Pirmininkas prof. dr. Dalius NAVAKAUSKAS (Vilniaus Gedimino technikos universitetas, elektros ir elektronikos inžinerija-01T). Nariai: doc. dr. Lina NARBUTAITĖ (Kauno technologijos universitetas, elektros ir elektronikos inžinerija-01T), doc. dr. Nerijus PAULAUSKAS (Vilniaus Gedimino technikos universitetas, elektros ir elektronikos inžinerija-01T), prof. habil. dr. Valeri SKLIAROV (Aveiro universitetas, Portugalija, elektros ir elektronikos inžinerija-01T), prof. dr. Vytautas URBANAVIČIUS (Vilniaus Gedimino technikos universitetas, elektros ir elektronikos inžinerija-01T). Disertacija bus ginama viešame Elektros ir elektronikos inžinerijos mokslo krypties disertacijos gynimo tarybos posėdyje 2017 m. rugpjūčio 29 d. 10 val. Vilniaus Gedimino technikos universiteto senato posėdžių salėje.