Ajarn Dr.Prapun (อาจารย์ ดร.ประพันธ์ สุขสมปอง) is currently a faculty member at Sirindhorn International Institute of Technology (SIIT), Thammasat University. He was born and grown up in Bangkok, Thailand. After finishing high school there with a perfect 4.0/4.0 GPA, he won the King's Scholarship--arguably the most competitive and honorable scholarship for Thai high-school students--which granted him the financial support for his four-year undergrad study at Cornell university.

Prapun's undergraduate performance at Cornell's School of Electrical and Computer Engineering (ECE) was no less impressive than his high-school years. He topped the Cornell ECE class of 2002, with the highest GPA among all engineering students. Prapun joined Professor Toby Berger's group in 2003 and got his Ph.D. in 2008. His interest lies in the areas of communication theory, information theory, probability theory, and theoretical neuroscience. He also loves to draw picture on Microsoft Word.

Ajarn Prapun always highly values the teaching aspect of his career and his life. Many of his notes are available on his personal websites. In 2006, he received the Teaching Assistant of the Year Award from members of the Cornell IEEE Student Branch "for exemplary teaching in ECE". Recently, in 2010, he also received the Best Teaching Award from SIIT.

For more information, here is his CV. (Dowload pdf version.)

Current Research Projects

1. การวิเคราะห์ความสามารถในการส่งข้อมูลของเส้นประสาท (Capacity Analysis of Biological Neurons)
   
   • Our research interest is in the field of computational neuroscience. More specifically, our expertise is in the area of neuro-information theory where the ultimate goal is to understand how biological neurons work. This insight is the dream of any neuroscientist. We approach the issue from a communication engineering perspective. The goal is to construct theoretical models which are simple yet biologically realistic and provide insights into the neuron codes. We focus on the energy efficiency of the neurons. In particular, a crucial quantity for us is the information rate that can be conveyed per unit of energy (bits-per-joule). Our study involves ideas from probability theory, communication theory, information theory, the analysis of signal and noise, and, of course, neuroscience.
     
   • หากมนุษย์สามารถเข้าใจการทำงานของสมองของตนเองได้ องค์ความรู้นี้จะนำไปสู่การประยุกต์ใช้ในหลากหลายสาขาวิชา ซึ่งมิได้จำกัดอยู่แต่เพียงสาขาวิชาที่เกี่ยวข้องกับการศึกษาการทำงานของสมองโดยตรงอย่างประสาทวิทยาหรือวิทยาศาสตร์การแพทย์เท่านั้น สาขาวิชาอื่นยังสามารถนำเอาความเข้าใจพื้นฐานนี้ไปสร้างระบบอื่นที่ทำงานคล้ายสมองได้ ตัวอย่างเช่น งานวิจัยของเราพบว่าการส่งข้อมูลในสมองนั้น.ใช้พลังงานอย่างมีประสิทธิภาพ ซึ่งเป็นจุดมุ่งหมายหลักประการหนึ่งของวิศวกรรมไฟฟ้าสื่อสารเช่นกัน การศึกษาระบบที่บรรลุจุดประสงค์ดังกล่าวอยู่แล้วจึงอาจนำไปสู่การพัฒนาระบบสื่อสารยุคใหม่ได้ งานวิจัยนี้จึงเน้นศึกษาการส่งข้อมูลของเส้นประสาทในมุมมองของวิศรกรรมสื่อสาร โดยมุ่งวิเคราะห์ค่าความสามารถในการส่งข้อมูลต่อหน่วยพลังงาน (bits-per-joule).
   • References
     • Suksompong, P. and Berger, T., "Capacity Analysis for Integrate-and-Fire Neurons With Descending Action Potential Thresholds," Information Theory, IEEE Transactions on , vol.56, no.2, pp.838-851, Feb. 2010
     • Suksompong, P. and Berger, T., "Jitter Analysis of Timing Codes for Neurons with Descending Action Potential Thresholds," Information Theory, 2006 IEEE International Symposium on , vol., no., pp.650-654, 9-14 July 2006
     • P. Suksompong, “Capacity Analysis for NeuronsWith Descending Action Potential Thresholds,” Ph.D. dissertation, Cornell Univ., Ithaca, NY, 2008.
     • W. B. Levy and R. A. Baxter, “Energy efficient neural codes,” Neural Comput., vol. 8, no. 3, pp. 531–543, 1996.
     • W. B. Levy and R. A. Baxter, “Energy-efficient neuronal computation via quantal synaptic failures,” J. Neurosci., vol. 22, no. 11, pp. 4746–4755, Jun. 2002.
     • F. Rieke, D. Warland, R.D.R.V. Steveninck, and W. Bialek, Spikes: Exploring the Neural Code, The MIT Press, 1999.
       
     • W. Gerstner and W.M. Kistler, Spiking Neuron Models, Cambridge University Press, 2002.
     • P. Dayan and L. F. Abbott, Theoretical Neuroscience: Computational and Mathematical Modeling of Neural Systems, 1st ed. Cambridge, MA: MIT Press, 2001.
       
2. การวิเคราะห์และพัฒนาระบบเครือข่ายไร้สายโดยใช้เทคนิคการส่งและรับข้อมูลแบบหลายผู้ใช้ (Analysis and Improvement of Wireless Local Area Network with Multiuser Transmission Technique)
   • During the past decade, wireless LAN (WLAN) has gained mainstream acceptance. Some of us become heavy users of this technology without knowing what it is. In our offices, university campuses, hotels, or airports, the connection to the rest of the world is provided to us via WLAN. 802.11 is the widely accepted standard for WLAN. This standard has evolved over the years. Currently, 802.11b, 802.11a, and 802.11g enjoys huge share of the market. In the next couple months, a new standard, 802.11n, is expected to be ratified. Surprisingly, products utilizing 802.11n have already been put in the market. These products are based on the draft versions of the standard. In other words, the market demand for higher throughput (faster data rate) and better range (larger coverage area) have driven the utilization of 802.11n even when it is still not finalized. It is then important to study 802.11n. However, we should not stop there. Undoubtedly, the standard which comes after 802.11n would also be rushed to the market. In fact, there has already been an attempt to draft successors of 802.11n. One of the techniques being considered utilizes multiuser multiple-input multiple-output (MU-MIMO) transmission. We shall investigate and analyze this technique in detail so that we can cleverly apply it to the new standards.
   • ในช่วงเวลาหลายปีที่ผ่านมา ระบบเครือข่ายแบบไร้สาย (WLAN) ได้เข้ามามีบทบาทต่อชีวิตประจำวันของกลุ่มคนหลากหลายอาชีพ ไม่ว่าจะเป็นนักเรียน อาจารย์ นักวิจัย พนักงานสำนักงาน นักธุรกิจ ล้วนใช้ประโยชน์จาก WLAN ทั้งสิ้น ซึ่งมาตรฐานของ WLAN ที่ใช้กันแพร่หลายในปัจจุบันก็คือมาตรฐาน 802.11 ของ IEEE ซึ่งจนถึงวันนี้ ได้มีการเปลี่ยนแปลงและพัฒนาไปเป็น 802.11b, 802.11a, 802.11g และในอีกไม่กี่เดือนข้างหน้ามาตรฐาน 802.11n ก็น่าจะออกมาอย่างเป็นทางการ ทั้งนี้ เป็นที่น่าสังเกตว่า ได้มีการนำมาตรฐาน 802.11n มาใช้อย่างแพร่หลายในตลาดไปแล้วแม้ว่าจะยังไม่มีการรับรองอย่างเป็นทางการ เหตุผลก็คือตลาด WLAN ไม่สามารถรอได้อีกต่อไป ความต้องการเข้าถึงข้อมูลด้วยความเร็วสูงนั้นมีมากเกินกว่าความเสี่ยงที่จะนำเอามาตรฐานที่ยังไม่มีการรับรองอย่างเป็นทางการมาใช้ ดังนั้นจึงไม่เป็นที่สงสัยเลยว่ามาตรฐานใหม่ที่กำลังจะตาม 802.11n ออกมา จะเป็นที่จับตามองและมีการผลักดันให้ออกสู่ตลาดอย่างรวดเร็วเช่นกัน โดยในขณะนี้ได้มีการพยายามร่างมาตรฐาน WLAN ยุคใหม่ขึ้นมา เทคนิคหนึ่งซึ่งเชื่อกันว่าจะมีบทบาทสำคัญ ก็คือ การส่งข้อมูลแบบ multiuser multiple-input multiple-output (MU-MIMO) เราจะศึกษาและวิเคราะห์เทคนิค MU-MIMO อย่างละเอียด เพื่อนำไปสู่การประยุกต์ใช้กับมาตรฐาน 802.11 อย่างชาญฉลาด
   • References
     • Thanakorn Bamrungkitjaroen, Prapun Suksompong, Chalie Charoenlarpnopparut, Keattisak Sripimanwat, and Kazuhiko Fukawa, "Application of Pipelining Technique in Concatenated Tomlinson Harashima Precoder for Downlink MIMO Systems", Proceedings of the Asia SImulation Conference 2011 (AsiaSim 2011), Seoul, Korea, November 16-18, 2011 [TRLG, NRU, TARG]
     • P. Kanjanavirojkul, K. Keeratishananond, and P. Suksompong, "Implementation of SU-MIMO and MU-MIMO GTD-System under Imperfect CSI Knowledge", Proceedings of the International Conference on Signal Processing, Communications and Networking (ICSPCN 2011), Venice, Italy, April 27-29, 2011. [NRU, TARG, TRLG]
     • P. Kanjanavirojkul, K. Keeratishananond, P. Suksompong, "Implementation and Performance of Generalized Triangular Decomposition in Multi-user MIMO", Proceedings of the International Conference on Information and Communication Technology for Embedded Systems 2011 (ICICTES 2011), Pattaya, Thailand, January 27-29, 2011. [TARG, TRLG]
     • Ying Jun Zhang; Peng Xuan Zheng; Soung Chang Liew, "How Does Multiple-Packet Reception Capability Scale the Performance of Wireless Local Area Networks?," Mobile Computing, IEEE Transactions on , vol.8, no.7, pp.923-935, July 2009
     • Douglas S. Chan, Prapun Suksompong, Jun Chen and Toby Berger, "Improving IEEE 802.11 Performance with Cross-Layer Design and Multipacket Reception via Multiuser Iterative Decoding," IEEE 802.11-05/0946r0, 2005.
     • Douglas S. Chan, "Technologies Delivering Multiuser Transmission for Next-Generation IEEE 802.11 Wireless Networks," Nov 5, 2007.
3. PAPR Reduction for OFDM system
   • Orthogonal Frequency Division Multiplexing (OFDM) also known as discrete multitone (DMT), has becomes a widely-accepted communication technique for broadband wireless communication. The key idea is to transmit a high-rate data stream by splitting it into a large number of lower-rate substreams, each modulating an individual subcarrier; hence OFDM is one of multicarrier modulation (MCM) techniques. Subcarriers in OFDM system are closely packed in the frequency domain such that the modulated signals are still mutually orthogonal even though they overlap, making OFDM system bandwidth-efficient. Moreover, the low data rate on the subcarriers mitigates the effect of the multipath problem in wireless environment. Another advantage of OFDM system is that it can be implemented via (inverse) fast Fourier transform ((I)FFT) which make it fast and efficient.
     
     Unfortunately, due to the superposition of a large number of individual subchannels, the amplitude of the transmitted OFDM signal generally suffers from high peak-to-average power ratio (PAPR). This fact complicates implementation of the analog radio frequency (RF) frontend. When the PAPR is high, the digital-to-analog converter (DAC) and power amplifier (PA) of the transmitter require high dynamic ranges to avoid amplitude clipping. Such high dynamic range increases complexity, reduces efficiency, and increases cost of the components. On the other hand, if the dynamic range is too low, there would be substantial amount of signal distortion which in turn will raise the amount of bit error rate (BER). Furthermore, the distortion would cause unwanted out-of-band radiation.
     
     Tone reservation (TR) is a well-known technique to reduce PAPR. Its advantages include no side information and no distortion on the data-bearing carriers. Direct implementation of TR can be complicated and therefore several approximation algorithms were developed. One such algorithm is the iterative clipping and filtering (ICF) under TR constraint. We improve the performance of ICF by introducing the use of deep clipping. Simulation results confirm that the modified algorithm can significantly improve the performance of ICF. We also found that the simple use of deep clipping under one TR filtering could achieve acceptable level of PAPR reduction and therefore provide an inexpensive PAPR reduction.
   • References:
     • T. Chanpokapaiboon, P. Puttawanchai, and P. Suksompong, "Enhancing PAPR Performance of MIMO-OFDM Systems Using SLM Technique with Centering Phase Sequence Matrix", Proceedings of the 8th Annual International Conference on Electrical Engineering/Electronics, Computer, Telecommunications, and Information Technology (ECTI-CON 2011), Khon Kaen, Thailand, May 17-19, 2011 [TRLG, NRU]
     • S. Suppitux, S. Tangkachavana, T. Vinichhayakul, and P. Suksompong, "Enhancing PAPR reduction for Tone Reservation Algorithms by Deep Clipping", Proceedings of the 7th Annual International Conference on Electrical Engineering/Electronics, Computer, Telecommunications, and Information Technology (ECTI-CON 2010), Chiang Mai, Thailand, May 19-21, 2010.
     • Seung Hee Han and Jae Hong Lee, "An overview of peak-to-average power ratio reduction techniques for multicarrier transmission," Wireless Communications, IEEE , vol.12, no.2, pp. 56- 65, April 2005
     • Luqing Wang; Tellambura, C., "Analysis of Clipping Noise and Tone-Reservation Algorithms for Peak Reduction in OFDM Systems," Vehicular Technology, IEEE Transactions on , vol.57, no.3, pp.1675-1694, May 2008
     • Kimura, S., Nakamura, T., Saito, M., and Okada, M., "PAR reduction for OFDM signals based on deep Clipping," Communications, Control and Signal Processing, 2008. ISCCSP 2008. 3rd International Symposium on , vol., no., pp.911-916, 12-14 March 2008
     • Tellambura, C., "Computation of the continuous-time PAR of an OFDM signal with BPSK subcarriers," Communications Letters, IEEE , vol.5, no.5, pp.185-187, May 2001

Teaching

• For 2/2011, he teaches
  • ECS204 (Basic Electrical Engineering Laboratory) (For non-major students)
  • ECS455 (Mobile Communications)
  • IES302 (Engineering Statistics)
• For 1/2011, he taught
  • ECS315 (Probability and Random Processes)
  • ECS332 (Principles of Communications)
  • 3.2 Wireless Communication Engineering (as a co-lecturer)
  • TU130: A lecture on "Next-Generation Wireless Communication Systems"
• For 2/2010, he taught
  • ECS210 (Basic Electrical Engineering Laboratory)
  • ECS204 (Basic Electrical Engineering Laboratory) (For non-major students)
  • Lab C2 (Digital Communications II) for ECS450 (Signal Processing and Communication Laboratory)
  • ECS455 (Mobile Communications)
• In 2010, Dr.Prapun received the Best Teaching Award from SIIT.
• For 1/2010, he taught
  • ECS203 (Basic Electrical Engineering) (For non-major students)
  • ECS315 (Probability and Random Processes)
  • ECS395 (Seminar)
  • 3.2 Wireless Communication Engineering (as a co-lecturer)
• For 2/2009, he taught
  • TCS455 (Mobile Communications)
  • ECS304 (Basic Electrical Engineering Laboratory) (For non-major students)
  • ECS303 (Basic Electrical Engineering) (For non-major students)
  • Lab C2 (Digital Communications II) for ECS450 (Signal Processing and Communication Laboratory)
• For 1/2009, he taught ECS371 (Digital Circuits)
  • He is also a co-lecturer for 3.2 Wireless Communication Engineering.
• For Summer/2008, he taught MAS116 (Mathematics I: Calculus)
• For 2/2008, he taught ECS304 (Basic Electrical Engineering Laboratory)
• In 2006, Prapun received the Teaching Assistant of the Year Award from members of the Cornell IEEE Student Branch "for exemplary teaching in ECE".
• Prapun worked as a teaching assistant (TA) for numerous courses in the ECE department at Cornell including ENGRD 230 (Introduction to Digital Logic Design), ECE 310 (Introduction to Probability & Random Signals), ECE 320 (Networks and Systems), ECE 445 and 545 (Computer Networks & Telecom), ECE 467 (Digital Communication Receiver Design), ECE 488 (Radio Frequency Circuits & Systems), and ECE 521 (Theory of Linear Systems).

Research Area

• Wireless communication (การสื่อสารไร้สาย), digital communication theory (ทฤษฎีการสื่อสารแบบดิจิตอล), neuro-informational theory (ประสาทวิทยาศาสตร์เชิงทฤษฎีข้อมูล), Poisson process and Poisson convergence (การลู่เข้าสู่กระบวนการสุ่มแบบปัวส์ซอง), computation neuroscience (ประสาทวิทยาศาสตร์เชิงการคำนวณ), probability theory (ทฤษฎีความน่าจะเป็น).

Research Interest

• Energy-efficient coding; capacity per unit cost of input
  
• Neuron code; point process models as a framework for representing neural spike trains; quantal synaptic failure
  
• Poisson convergence via relative entropy
• Multi-user detection