AJIT C. WARRIER ajit.warrier@gmail.com http://ajitwarrier.org
Visa Status: US Permanent Resident
3439 Mentone Ave., #5
Los Angeles, CA – 90034.
Phone – (1) 919 389-9737
Education PhD, Computer Science, GPA: 3.87/4.0 (August 2004 – August 2008),
North Carolina State University, Raleigh, USA.
MS, Computer Science, GPA: 4.0/4.0 (August 2002 – August 2004),
North Carolina State University, Raleigh, USA.
BE, Computer Engineering, GPA: 3.92/4.0 (June 1998 – May 2002),
Nirma Institute of Technology (Gujarat University), India.
Computer Skills
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Languages/Libraries : C/C++ (STL, Boost), NesC, Core Java, Python, Shell (Bash, Tcl), Visual
Basic.
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Networking Software : Multi-hop routing software (OLSRD, Click router), MAC (ZigBeebased Radios - CC1000/CC2420, 802.11a/b/g - MadWifi-NG), TCP/IP Network Stack (Linux
2.6.x), TinyOS Network Stack, IPerf, Tcpdump/Wireshark.
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Software Profiling/Debugging Tools : GDB/DDD, Gprof, Objdump, Valgrind, Linux kernel debugging with UML/Qemu virtualization.
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Embedded Systems : U-Boot, Linux Kernel Network Stack (v2.6.x), Linux Kernel Device
Driver and Kernel Module Development.
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Miscellaneous : TCP/IP Sockets Programming, Pthreads, Network Simulator (ns), TinyOS development.
Work Experience
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Embedded Software Engineer: Silvus Technologies, Los Angeles, CA., September 2008present – Embedded software development for Linux/PowerPC architecture, developing MAC kernel modules for the Silvus MIMO radio, MAC ARQ algorithm design and implementation, multi-hop wireless routing support, and link adaptation for the Silvus MIMO radio.
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Graduate Research Assistant: North Carolina State University (Advisor: Dr. Injong Rhee),
August 2004-August 2008 – involved in research on MAC, routing and transport protocols for wireless ad-hoc networks.
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Undergraduate Internship: Tata Consultancy Services (TCS), January 2002-May 2002.
Involved in the design, analysis and implementation of a billing system for telecom companies.
Visual Basic was used for the front-end, and Oracle PL/SQL and shell scripts for the back-end.
Projects (R&D)
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WiSeNet: ZigBee and Mesh (802.11a/b/g) Test-bed at North Carolina State University
Lead member of the team responsible for the setup of a wireless research test-bed: o 120 ZigBee-based MicaZ devices. o 70 802.11a/b/g-based Soekris devices. o All nodes are remotely powered using PoE. o Soekris nodes remotely mount file systems using NFS.
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Network Test-bed Management Tools
Created a library of Python scripts for network test-bed management. Functionality included: o Remote command execution and process status monitoring. o Centralized logging of system/kernel messages from test-bed nodes using netconsole kernel module. o Automated topology/scenario generation and routing setup and breakdown. o Extensive performance monitoring, including network and data link layer buffer sizes and overflows.
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Transparent TCP-Proxy Server

Implemented a TCP-proxy server. The server sits at the Internet gateway and intercepts outgoing
TCP connections, terminates them and relays data to the final destination using a new TCP connection. This allows separation of TCP algorithms within a network/test-bed and the outside
Internet.

ECN-enabled TFRC Congestion Control
Modified the TFRC congestion control algorithm to react to ECN-bit. Implemented a kernel module to monitor the network buffer size and set the ECN bit on outgoing packets.

Performance Comparison/Testing of TCP-variants
Performed comprehensive testing of different TCP-variants, TCP-NewReno, TCP-Veno, TCP-
Westwood+, TCP-FeW on a multi-hop wireless test-bed. Results showed that all TCP-variants face comprehensive unfairness/starvation issues in wireless environments.

DiffQ: Congestion Control for 802.11a/b/g Mesh Networks
Implemented a congestion control algorithm in the Linux kernel for wireless mesh networks: o Source rate control performed at application layer. o Linux kernel module intercepts packets at intermediate nodes using NETFILTER routines and performs hop-by-hop rate control. o MadWifi-NG MAC driver was modified to support 8 priority levels.
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QoS MAC for ZigBee-based Mesh Networks
Designed and implemented Siren – a QoS MAC for wireless mesh networks for the CC2420
ZigBee radio in the MicaZ sensor device on the TinyOS platform. Siren allows prioritized packet transmissions for different application QoS requirements such as best effort, real-time, etc.
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TDMA MAC for Mesh Networks
Designed and implemented Z-MAC– a TDMA-based MAC protocol for the CC1000 radio in the
Mica2 sensor device on the TinyOS platform. TDMA slots are assigned based on a distributed algorithm – DRAND.
Publications
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Conference o DiffQ: Differential Backlog Congestion Control for Multi-hop Wireless Networks ,
A. Warrier, S. Janakiraman, P. Wason, S. Ha and I. Rhee, INFOCOM 2009. o Experimental Evaluation of MAC Protocols for Fairness and QoS Support in
Wireless Networks , A. Warrier, I. Rhee and J. Kim, ICNP 2008. o Cross-Layer Optimization Made Practical , A. Warrier, L. Lee and I. Rhee,
Broadnets 2007 (Invited Paper). o DRAND: Distributed Randomized TDMA Scheduling for Wireless Ad-hoc
Networks , I. Rhee, A. Warrier, J. Min and L. Xu, MobiHoc 2006. o Mitigating Starvation in Wireless Sensor Networks, A. Warrier, J. Min and I. Rhee,
MILCOM 2006. o Z-MAC: a Hybrid MAC for Wireless Sensor Networks , I. Rhee, A. Warrier, M. Aia
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Journal and J. Min, Sensys 2005. o DRAND: Distributed Randomized TDMA Scheduling for Wireless Ad-hoc
Networks , I. Rhee, A. Warrier, J. Min and L. Xu, IEEE Transactions on Mobile
Computing, 2009. o Z-MAC: a Hybrid MAC for Wireless Sensor Networks , I. Rhee, A. Warrier, M. Aia and J. Min, IEEE Transactions on Networking, 2008. o How Much Energy Saving Does Topology Control Offer For Wireless Sensor
Networks ? – a Practical Study , A. Warrier, S. Park, J. Min and I. Rhee, Elsevier
Computer Communications Journal.
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Posters/Demos: o DiffQ: Differential Backlog Congestion Control for Multi-hop Wireless Networks,
A. Warrier, S. Ha, P. Wason and I. Rhee, SECON 2008. o TCP Performance Problems in Wireless Multi-hop Networks, A. Warrier, S. Ha and
I. Rhee, Stanford Clean Slate Program, 2008.

o Z-MAC: a Hybrid MAC for Wireless Sensor Networks, A. Warrier, J. Min and I.
Rhee, SIGCOMM 2005.
Societies and Honors
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Member, Honor Society of Phi Kappa Phi
In recognition of having the GPA in the top 1% of NC State graduates.
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Outstanding Graduate Teaching Assistant Award for academic year 2004-2005.
References (available on request).