• Proceedings of the Korean Information Science Society Conference
• /
• 2003.10c
• /
• pp.106-108
• /
• 2003

기존 TCP 기술은 높은 대역폭(High­Bandwidth) 및 큰 전송지연(High Delay)을 가진 통신에는 적합하지 못하다. TCP 기술의 성능향상을 위한 방법으로 TCP 제어 알고리즘을 수정하는 방법과 TCP Tuning 방법이 있다. 본 논문에서는 TCP Buffer Tuning 기술에 초점을 맞춰 통신망 상황에 따른 응용프로그램별로 자동화된 Buffer Tuning 기법을 제공하는 기술을 제안한다. ATBT(Automatic TCP Buffer Tuning) 에서는 송신측의 Buffer 크기를 조절하여 성능향상을 나타냈고, DRS(Dynamic Right Sizing)에서는 수신측의 Buffer 크기를 조절하여 성능향상을 도모하였다. 본 논문에서는 ATBT와 DRS의 장점을 접목하여 구현함으로써 보다 나은 성능향상을 나타내고 각 송.수신측의 모든 연결에 대해서는 Buffer를 공평하게 할당하여 메모리 사용의 효율을 높이고자 한다.

• The KIPS Transactions:PartC
• /
• v.12C no.1 s.97
• /
• pp.121-128
• /
• 2005

Tho existing TCP(Transmission Control Protocol) is known to be unsuitable for a network with the characteristics of high RDP(Bandwidth-Delay Product) because of the fixed small or large buffer size at the TCP sender and receiver. Thus, some trial cases of adjusting the buffer sizes automatically with respect to network condition have been proposed to improve the end-to-end TCP throughput. ATBT(Automatic TCP fluffer Tuning) attempts to assure the buffer size of TCP sender according to its current congestion window size but the ATBT assumes that the buffer size of TCP receiver is maximum value that operating system defines. In DRS(Dynamic Right Sizing), by estimating the TCP arrival data of two times the amount TCP data received previously, the TCP receiver simply reserves the buffer size for the next arrival, accordingly. However, we do not need to reserve exactly two times of buffer size because of the possibility of TCP segment loss. We propose an efficient TCP buffer tuning technique(called TBT-PLR: TCP buffer tuning algorithm based on packet loss ratio) since we adopt the ATBT mechanism and the TBT-PLR mechanism for the TCP sender and the TCP receiver, respectively. For the purpose of testing the actual TCP performance, we implemented our TBT-PLR by modifying the linux kernel version 2.4.18 and evaluated the TCP performance by comparing TBT-PLR with the TCP schemes of the fixed buffer size. As a result, more balanced usage among TCP connections was obtained.

• Journal of Internet Computing and Services
• /
• v.8 no.1
• /
• pp.15-23
• /
• 2007

Wireless LAN (IEEE 802.11) uses traditional TCP for reliable data transmission, But it brings the unintentional packet loss which is not congestion loss caused by handoff, interference, and fading in wireless LAN. In wireless LAN, TCP experiences performance degradation because it consumes that the cause of packet loss is congestion, and it decrease the sending rate by activating congestion control algorithm. This paper analyzes that correlation of throughput and buffer size for wireless buffer tuning. We find MBT (Maximum Buffer Threshold) which does not increase the throughput through the analysis, For calculation of MBT, we experiment the throughput by using high volume music data which is creased by real-time performance of piano. The experiment results is shown that buffer tuing based on MBT shows 20.3%, 21.4%, and 45.4% throughput improvement under 5ms RTT, 10ms RTT, and 20ms RTT, respectively, comparing with the throughput of operation system default buffer size, In addition, we describe that The setting of TCP buffer size by exceeding MBT does not have an effect on the performance of TCP.

• Journal of Internet Computing and Services
• /
• v.10 no.4
• /
• pp.199-211
• /
• 2009

Recent advancements in wireless networks have enabled support for mobile applications to transfer data over heterogeneous wireless paths in parallel using data striping technique [2]. Traditionally, high performance data transfer requires tuning of multiple TCP sockets, at sender's end, based on bandwidth delay product (BDP). Moreover, traditional techniques like Automatic TCP Buffer Tuning (ATBT), which balance memory and fulfill network demand, is designed for wired infrastructure assuming single flow on a single socket. Hence, in this paper we propose a buffer tuning technique at senders end designed to ensure high performance data transfer by striping data at transport layer across heterogeneous wireless paths. Our mechanism has the capability to become a resource management system for transport layer connections running on multi-homed mobile host supporting features for wireless link i.e. mobility, bandwidth fluctuations, link level losses. We show that our proposed mechanism performs better than ATBT, in efficiently utilizing memory and achieving aggregate throughput.

• Journal of Internet Computing and Services
• /
• v.7 no.1
• /
• pp.131-141
• /
• 2006

Recently, many researchers have been studied several high performance data transmission techniques such as TCP buffer Tuning, XCP and Parallel Sockets. The Parallel Sockets is an application level library for parallel data transfer, while TCP tuning, XCP and DRS are developed on kernel level. However, parallel socket is not analyzed in detail yet and need more enhancements, In this paper, we verify performance of parallel transfer technique through several experiments and analyze character of traffic interference among socket connections. In order to enhance parallel transfer management mechanism, we predict the number of socket connections to obtain SLA of the network resource and at the same time, affected network bandwidth of existing connections is measured mathematically due to the interference of other parallel transmission. Our analytical scheme predicts very well network bandwidth for applications using the parallel socket only with 8% error.

• Journal of KIISE:Computer Systems and Theory
• /
• v.33 no.7
• /
• pp.363-369
• /
• 2006

It is aware that Bandwidth management with dramatically increasing traffic on account of frequent and large file transmission in a data grid environment is one of essential needs. A this paper we propose new method which guarantees QoS (Quality of Service) by being in control of resources in TCP layer based on existing studies that manage bandwidth over TCP buffer tuning. General QoS solutions manage network resources subsequent to observing them in IP or link layer, but the scheme in the paper is able to control network resources in TCP layer that is network upper layer. Consequently, bandwidth allocation to each user can be efficiently controlled depending on an authority each user is given so that users could be use different bandwidth. It is expected that a new paradigm is supposed in network resource management and the method of levies for users' bandwidth uses.

• The KIPS Transactions:PartD
• /
• v.11D no.4
• /
• pp.747-754
• /
• 2004

Database administrators should be aware of performance characteristics of database systems in order to manage database system effectively. The usages of system resources in database systems could be quite different under database workloads. The objective of this paper is to identify and analyze performance characteristics of database systems in different workloads, which could help database tuners tune database systems Under the TPC-C and TPC-W workloads, which represent typical workloads of online transaction processing and electronic commerce respectively, we investigated usage types of resource that are determined by fourteen performance indicator, and are behaved in response to changes of four tuning parameters (data buffer, private memory, I/O process, shared memory). Eight out of the fourteen performance indicators cleary show the performance differences under the workloads. Changes of data buffer parameter give a influences to database system. The tuning parameter that affects the system performance significantly is the database buffer size in the both workloads.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.15 no.4
• /
• pp.437-444
• /
• 2015

A high output power voltage controlled oscillator (VCO) in the U-band was implemented using a 65 nm CMOS process. The proposed VCO used a transmission line to increase output voltage swing and overcome the limitations of CMOS technologies. Two varactor banks were used for fine tuning with a 5% frequency tuning range. The proposed VCO showed small variation in output voltage and operated at 51.55-54.18 GHz. The measured phase noises were -51.53 dBc/Hz, -91.84 dBc/Hz, and -101.07 dBc/Hz at offset frequencies of 10 kHz, 1 MHz, and 10 MHz, respectively, with stable output power. The chip area, including the output buffer, is $0.16{\times}0.16mm^2$ and the maximum output power was -0.11 dBm. The power consumption was 33.4 mW with a supply voltage of 1.2-V. The measured $FOM_P$ was -190.8 dBc/Hz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.3
• /
• pp.399-405
• /
• 2011

In this paper, we present the design of Q-band LC VCO and injection locking buffer for 77 GHz automotive radar sensor using 130 nm RF CMOS process. To improve the phase noise characteristic of LC tank, the transmission line is used. The negative resistance by the active device cross-coupled pair of buffer is used for high output power, with or without oscillation of buffer. The measured phase noise is -102 dBc/Hz at 1 MHz offset frequency and tuning range is 34.53~35.07 GHz. The output power is higher than 4.1 dBm over entire tuning range. The fabricated chip size is $510{\times}130\;um^2$. The power consumption of LC VCO is 10.8 mW and injection locking buffer is 50.4 mW from 1.2 V supply.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.417-418
• /
• 2008

A quadrature voltage controlled oscillator(QVCO) with MOS-varactors has been fabricated for X-band applications. The QVCO consists of two cross -coupled differential cores and buffer amplifiers, which has fabricated in TSMC $0.18{\mu}m$ CMOS process. The QVCO exhibits a frequency tuning range from 8.38 GHz to 10.62 GHz. The phase noise is -88 dBc/Hz at 1 MHz-offset frequency. The total bias current is 25 mA including four buffer amplifiers.