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Monthly Archives: July 2016

[Wireless Network] Introduction to Multipath TCP (MPTCP)

MPTCP is an evolution of TCP that allows a concurrent use of multiple interfaces for a single TCP session. If the both sides of a TCP connection are MPTCP-capable (otherwise a legacy TCP will be used between them), multiple subflows are established over different data paths, i.e., multiple network interfaces, and the MPTCP sender spreads TCP segments over the subflows. Spreading data over subflows is enabled by defining and managing separate congestion windows for individual subflows. TCP’s congestion control mechanism then distributes traffic based on the congestion condition of each data path. When a high congestion condition is detected in a data path, the amount of traffic on it is reduced and other less congested paths convey more. Thus MPTCP accomplishes dynamic load balancing between interfaces.

The detail explanation about MPTCP can be read below.

[Wireless Network] 802.11e QoS and Rate Adaptation

As the follow up from Wi-Fi Introduction, other requirements called Quality of Service and Rate Adaptation for WLAN were introduced to understand its channel access (EDCA and HCCA). The detail presentation can be seen below.

[Wireless Network] Basics of Wi-Fi

Once in 2015, I was requested by my former supervisor to present this Wi-Fi Introduction in Mobile Computing class for M.S degree students in Department of Electrical and Information Engineering, Seoul National University of Science and Technology. Check it out for the detail presentation below.

[JKIICE Korea Journal 2015] Performance Analysis of Adaptive Radio Activation in Dual-Radio Aggregation System

Today’s smartphones and user devices are equipped with multiple radio interfaces increasingly. Aggregating theses multiple radio interfaces and using them concurrently will increase a user’s communication speed immediately, but at the expense of increased power consumption. In this paper, we develop a mathematical performance model of an adaptive radio activation scheme by which a radio interface is activated only when needed for performance increase and deactivated otherwise. The developed model shows that the adaptive scheme reduces delay significantly and almost halves power consumption below a certain level of traffic input.

You can buy the journal article HERE.

[IEIE Korea Journal 2014] A Comparative Study of Aggregation Schemes for Concurrent Transmission over Multiple WLAN Interfaces

To increase wireless capacity, the concurrent use of multiple wireless interfaces on different frequency bands, called aggregation, can be considered. In this paper, we focus on aggregation of multiple Wi-Fi interfaces with packet-level traffic spreading between the interfaces. Two aggregation schemes, link bonding and multipath TCP (MPTCP), are tested and compared in a dualband Wi-Fi radio system with their Linux implementation. Various test conditions such as traffic types, network delay, locations, interface failures and configuration parameters are considered. Experimental results show that aggregation increases throughput performance significantly over the use of a single interface. Link bonding achieves lower throughput than MPTCP due to duplicate TCP acknowledgements (ACKs) resulting from packet reordering and filtering such duplicate ACKs out is considered as a possible solution. However, link bonding is fast responsive to links’ status changes such as a link failure. It is shown that different combinations of interface weights for packet spread in link bonding result in different throughput performance, envisioning a spatio-temporal adaptation of the weights. We also develop a mathematical model of power consumption and compare the power efficiency of the schemes applying different power consumption profiles.

You can buy the journal article HERE.

[APWCS 2013 International Conference] Where to Aggregate?: A Comparative Study of Aggregation Strategies in Multi-Radio System

To increase wireless capacity, the concurrent use of multiple wireless interfaces, called aggregation, can be considered. In this paper, we focus on using multiple WiFi interfaces between an access point and a client, and packet-level traffic spreading between interfaces. Two aggregation strategies, link bonding and multipath TCP (MPTCP), are tested and compared in a multi-WiFi radio system with their Linux implementation. Various test conditions such as traffic types, network delay, locations, interface failures, and configuration parameters are considered. Experiment results show that aggregation increases throughput performance significantly over the use of a single interface. Link bonding achieves lower throughput than MPTCP due to duplicate TCP acknowledgements (ACKs) generated by packet reorderings. However, link bonding is better under long network delay and interface failures since it is fast responsive to links’ status changes. It is shown that different combinations of interface weights for packet spread in link bonding result in different throughput performance, envisioning a spatio-temporal adaptation of the weights. Two solutions, delayed ACK and filtering duplicate ACKs, are discussed for further enhancement of link bonding.

Academic Schedule UGM 2016/2017

The new Fall semester 2016 for students in Universitas Gadjah Mada will begin very soon.

Here you need to prepare your required stuffs to comply with Academic Schedule from university.

You can donwload the official copy/scan of academic schedule for 2016/2017 HERE