Nagarjuna Gandrothu
M.E (Electronics Engineering)
Summary: Over 14 years of extensive experience in design and development of DSP based products, including 4 years of managing a team of technical talent that is a mix of DSP, Systems and Network Engineering. Broad experience in DSP algorithm/Software development for real-time communication systems such as Modems, Codecs, Voice/ Data / Fax, VoIP and Video Telephony solutions that run on real-time embedded, multi-threaded platforms for TMS320C54x, TMS320C3x, ADSP21xx, ADSP2106x, ADSP BF535 & BF561 targets.
Education:
1989-1991 Madras Institute of Technology,
Master of Engineering (Electronics Engineering)
Specialization in DSP and Communications.
Thesis: A TMS320C25 based DQPSK Modem Design & Implementation.
1984-1988 Andhra University,
Bachelor of Engineering (Electronics & Communications Engineering)
Thesis: Data Modem for Differential Phase Shift Keying.
Standards/Protocols:
Ø ITU Speech Codecs G.7xx (G.726, G.728, G.723.1, G.729AB, G.722.1 etc),
Ø Modem Technologies ITU V.22, V.32, V.34, V.90, V.27ter fax modems etc,
Ø BellCore GR-317, IEEE-743, ANSI T1.201
Ø Good know-how on ITU G.167, G.168 Echo cancellers, H.323, SIP etc.
Languages/Tools:
Ø C, DSP Assembly languages (Analog Devices Blackfin BF535, BF561, TMS320C3x, TMS320C54x, TMS320C6x, ADSP21xx, ADSP2106x, ADSP21xx)
Ø MATLAB, Hyperception, QEDesign
Ø TI DSP/BIOS, Code Composer
Ø Analog Devices VisualDSP tools
Ø A variety of DSP Simulation & Emulation tools, Signal Analyzers, Logic Analyzers, Telephone Network Emulators, MOS/PESQ Test Equipment, Ethereal, LanForge Network Simulators etc.
Professional Experience:
April, 2002 - Present:
Independent Consultant (DSP & Embedded Systems)
Analog
Devices, Inc.,
Consultant - Group Head / Technical Manager @IPDC
I was instrumental and successful in
setting-up the group for SST’s Videophone product line at
Some of the accomplishments are as following:
Ø The Blackfin BF561 based uClinux Videophone development is the latest ongoing project and pretty much most of the features that are present on NetKernel based Videophone have come on the latest platform. The team is mainly classified in to two - Kernel Team and Application Team. The application team works out of IPDC, who take the responsibility of designing the uClinux based applications plus audio/speech activities. The main activities include managing the TotalTeam to bring all the deliverables together and make a successful release as per the committed date. With the help of Kernel team, the project is poised to become a clear bread winner for the division in the coming future J.
Ø Designed and implemented a true dual core architecture for the Videophone, with Core A of BF561 performing major activities like the Kernel, Network stacks, Audio/Video drivers, different speech codec’s (G.7xx); while Core B is completely used for video algorithms (H.263/H.264). The total system architecture has been revamped as a part of making a true dual core videophone, with improved memory reorganization, employing a suitable cache mechanism etc. More or less, single-handedly, this new design and development has been carried out on the Bravo2.1 platform. With the help of audio and video teams, the total system has been built successfully, and this code base became mother of the new activity – uClinux based videophone.
Ø Single handedly, completed porting of the dual core BF561 based videophone from the legacy BF535 solution (with Core B containing almost all code, except the PPI drivers). This solution is aimed at porting and validating the entire videophone on the new Bravo2.1 platform with BF561. Although both cores are being used, this is not a true dual core structural design.
Ø
Managed the team in moving the existing speech
codecs, SmartBravo features etc on to BF561 on NetKernel, as well as uClinux
environment. All of the SST’s speech codecs adhere to ITU norms, and work in
packet loss environments. MOS/PESQ scores are optimal in the industry* (as per tests performed at
Ø Designed and developed SmartBravo mechanism, which can be effectively used in systems having memory limitation and those that do not use cache mechanism. Primarily this has been designed for BF535 based Panview 1.x Videophone system, to manage the G.723.1 (dual rates) and G.729AB codecs to automatically come up and work in real-time on a need basis. The user can statically bring up a speech codec of the choice at the originating side. The end point after successful negotiation dynamically brings up the code of speech codec that is negotiated for (incase if the code corresponding to the codec does not exist already).
Ø Performed architectural modifications for enhancing and maintaining the audio drivers - AD1886 on Panview 1.x and AD1985 Panview2.x platforms respectively.
Ø Worked and subsequently directed the team on porting and integrating various speech codecs (G.723.1 6.3kbps and 5.3kbps, G.729A/B/AB, G.711 a-law & u-law, GSM-AMR), various Acoustic Echo Cancellation (AEC) systems in to the system.
Ø
Designed and developed a Gen
Jul, 1997 - Mar,2002:
3Com
Corporation,
Senior DSP Engineer
Performed architectural design, development, testing and debugging of algorithms and real-time, multi-tasking, embedded software for 3Com TotalControl™ HiPerDSP product used in Remote Access Systems. Coded multi-threaded software in TMS320C54x DSP assembly. Designed simulations using Matlab and "C" languages.
This TotalControl WAN HUB with HiPerDSP product is the most successfully deployed product all around the world with large penetration in RAS market segment.
Ø Lead Engineer on Universal Port project based on TotalControl™ platform, a system that is capable of terminating data, fax or voice calls on the same dial port by utilizing state-of-the-art technologies.
Ø Designed and implemented the RAS lower modulations on HiPerDSP HDM (High Density Modem) - V.32/V.32bis/ V.32ter, V.22/V.22bis, V.21 & V.23; each as an independent application on the new kernel based DSP architecture.
Ø Designed and implemented Modem Detection Application that performs the originate/answer Call progress & Automode processing.
Ø Implemented on bringing up the modem upper modulations (V.34, X.2 & V.90) with Probe & V.34 overlay mechanisms into the system. Also tweaked different parameters in tuning this new system to emulate similar results as that of the legacy system.
Ø Designed and implemented new DSP sub-overlays (V.34, Probe and V.22 overlays) to gain more DSP memory space that can be used to add more features and instrumentation code.
Ø Implemented various features - IBM Bisync support, Native fast connect, SS7 feature support such as Dual Continuity Tone Test, 102-type Milliwatt test (ANSI T1.207).
Ø Implemented V.27ter fax modem on C54x platform on current OS as well as unified architecture.
Ø Implemented V.22/V.22bis Fast Training and Auto Detect features on the HDM platform for HiperTRAX transaction processing system.
Ø Involved in implementing and enhancing the Interpolating filters.
Ø Implemented and supported Ring Detection feature for Dynatron project.
Ø Involved in various stages in enhancing the HDM DSP system including debugging, tweaking & testing of various kinds of problems.
Jun, 1996 - Jun, 1997
RadiSys
Corporation,
DSP Software Engineer
Worked on Voice Compression Engine project which includes ADPCM speech codecs, echo chancellor, fax and modem capabilities all embedded on a single VLIW DSP processor.
Ø Developed a TMS320C6x based G.726 codec during this period.
Ø Designed and developed an Emergency Alert System (EAS) using TMS320C32 processor. This is a stand alone system employing Audio Frequency Shift Keying modulation/ demodulation for transmitting and receiving data along with real-time audio play back. Certified by FCC, this system is used to broadcast emergency alert messages issued by the US National Weather Services.
Ø
Developed a gen
Ø Debugged and enhanced the performance of a TMS320C32 based EEG Monitoring system.
Sep,1991 - Apr,1996
Signion Systems Pvt. Ltd.,
Signal Processing Engineer.
Ø Developed a GMSK demodulator for GSM applications using ADSP2171 DSP processor. The design is based on matched filtering the received signal with a suitable prototype filter and using Viterbi algorithm for optimum data decision.
Ø
Designed and developed a low-cost Universal Software Radio Modem on
Analog Devices ADSP2171 processor to facilitate modulation, demodulation for
various phase modulation schemes such as BPSK, QPSK, OQPSK and MSK. The design
and technology was transferred to
Ø Developed a 256 kbps MSK modem on a single low-cost DSP ADSP-2171, including an innovative table driven modulation scheme and novel quadrature IF heterodyne. The system uses a Direct Digital Synthesizer to correct the carrier frequency offsets. A Host interface is also developed to upload/ download data and programs on to this stand-alone board. The performance of the modem in the presence of additive white gaussian noise and with frequency offsets is well with in the theoretical optimum.
Ø
Optimized and ported modules of C-Sound, a complex and versatile music
synthesis system (developed by researchers at Media Research Laboratories,
Ø Designed and developed MBC (Meteor Burst Communications) adaptive variable data rate modem based on Texas Instruments TMS320C30 processors. The modem adapts to one of the four data rates (2400, 4800, 9600 and 19200 bps) depending upon the channel conditions. The key features of the modem are spectrally efficient MSK modulation, digital matched filtering, bit timing synchronization, coherent detection, BCH encoding/ decoding, differential encoding/decoding, automatic data rate detection, carrier acquisition/ tracking and signal-to-noise ratio estimation/ prediction. This system was developed for DEAL (Defense Electronics Applications Laboratories), Dehradun, Government of India.
Ø Implemented a TMS320C30 based 17 kbps continuous mode MSK modem and encapsulated the main DSP modules in to a library.
Ø
Involved in the development of 17kbps/64 kbps VSAT modem DSP sub-system based on
TMS320C30 DSP processor. This has been developed for C-Dot (Center for Development of Telematics,
Publications:
• Universal Software Radio Modem, Proceeding
of National Conference on Communications, Indian Institute of Technology,
• Novel Techniques in High Speed Modem Implementation using Programmable DSPs, Proceedings of SPCOM-95, Indian Institute of Sciences, Bangalore, India, August 1995. (Also published in the "Indian Academy of Sciences" magazine as best paper during 1995).
• High Speed VSAT Modem, VIII National
Conference on In-House R&D in Industry,
• Adaptive Data Rate Modem for Meteor Burst Channel, VII National Conference in In-House R&D in Industry, New Delhi, India, Nov,1993.
Interests:
• DSP, Digital Communications, Computer Communications & Networking
• Design and Analysis of Algorithms.
References:
Available upon Request.