Senior DSP Engineer
Nvidia
مجموع سنوات الخبرة :18 years, 8 أشهر
LTE Modem, DSP algorithms design,
C++/Matlab
Filtering, equalizer, Coding/Decoding, MIMO, OFDM, Modulations...
DSP and RF Systems Engineer for the WiFi 802.11 a/b/g/n/ac.
5G Tx Chain Optimization. Integration in Samsung Mobility Platform. Galaxy S6 WiFi/BT Chipset Optimization.
- Optimization of EVM for different modulations (OFDM, CCK, BPSK) for 802.11n from analog RF settings. Optimizing PLL settings to reduce phase noise contribution.
- RF Calibration algorithms, Image and DCO compensation algorithms, optimizing Tx settings: Power Amplifier, Mixer, Baseband. Optimizing AM-AM, AM-PM, IM3, harmonics. frequency trimming.
- Pout and DPD. VSWR stability, temperature variation stability, skew lots, and supply voltage variation effect, Rx sensitivity, NF, EVM budget Analysis.
- RF chain analysis of Power, Gain, IP3, Noise Figure
- Study of 802.11af modem using Matlab model (scrambler, convolution encoder, puncturer, interleaver, mapper, IFFT, CP, Viterbi...).
- Digital signal processing: Signal Detection, Estimation, Digital Filtering, Channel Equalization, Coding, Decoding Optimization Algorithms, Adaptive Algorithms.
August 2011-July 2012
Cambridge Silicon Radio (CSR) (Sophia Antipolis)
DSP and RF Systems Engineer: Algorithms review and enhancement (Tx RF, power amplifier, DC Offset comp, image comp, mixer..) . Radio evaluation and calibration, RF issues, PHY and RF optimization.
- Evaluation and Characterization of the Tx Chain and the 5GHz Power Amplifier in particular.
- The transmit calibration including the following tasks : DC Offset Calibration, Image Calibration, Pout Calibration, Digital Predistortion : writing calibration algorithms using Matlab.
- Evaluation of VSWR stability, AM-AM, AM-PM, stability with temperature, skews stability.
- Optimization of Tx Settings (Mixer, Filter, DAC, PA, …), LB settings for DPD.
- Providing support for IEEE 802.11a/b/g/n standards (modulation schemes….).
- Familiar with the general equipments: Oscilloscope, spectrum analyzer, signal generator, load pull, multimeters, etc
- Familiar with high speed interface (USB, SPI)
- Thorough understanding of RF transceiver architecture and subsystems, such as LNA, PLL, Mixer, VCO, PA and Antenna.
- Power detectors, and basic analog building blocks.
- Familiar with transistor level RF circuit design, with one successful TSMC 40nm CMOS tapeout experience.
- Knowledge of RF relevant radio standards
- Knowledge of RF lab equipment including: spectrum analyzers, vector signal generators,
oscilloscopes, multimeters, power supplies, protocol analyzers, load pull….
Wireless Indoor Engineer: Radio, MAC & Phy Layers for the 802.11n, Updating test plans, Test and Validation, expertise on IEEE WLAN 802.11b/g/n
Wireless Indoor Engineer: Radio, MAC & Phy Layers for the 802.11n, Updating test plans, Test and Validation, expertise on IEEE WLAN 802.11.b/g and 802.11n.
- Writing specifications for the PHY/MAC layers for the future Livebox of France Telecom
( 802.11b/g/n).
- WiFi Feature Testing: SSID, auto channel select feature, signal power, Beacon Period, Data Beacon Rate, AP discovery, and client association, WiFi Multimedia (802.11e), Wireless QoS, WiFi Security (WPA, WPA2 support, Testing with AES, TKIP, WEP encryption), Compliance of WiFi APs to DFS regulations (Radar pulses defined by FCC, ETSI, Detection Probability Test), Voice and Video Testing ( loss, jitter measurement, voice and video MOS measurement, VoIP roaming test, VoIP QoS service capacity test ), Interoperability Testing (Interoperability between different types of WiFi client (a/b/g/n) equipment like laptops, and smart phones from different manufacturers, running different OS (Windows, Linux...)). Performance and Scalability Testing (UDP throughput - upstream, downstream, and bidirectional traffic, different packet sizes, multiple clients, open and secure clients, 802.11n downstream aggregation efficiency, and penalty for security encryption). Physical layer features (Central Frequencies, transmit spectrum, 3dB bandwidth, Emitting Power, spurious, out of band interferer, EVM, observation in span 0 mode, OFDM features, MIMO features, Beamforming, STBC…), WiFi MAC layer ( Association, A-MPDU and A-MSDU aggregations, protection mechanism, bit rates selection algorithms, EIFS...). Interference, coverage, sensitivity (link budget analysis). WiFi jamming regarding other technologies (DECT, GSM, UMTS..). The Use of the Azimuth Channel Emulator (ACE) to emulate MIMO channels ( TGN, Butler, Gaussian...). Familiar with Ixchariot and Iperf to generate traffic, omnipeek and wireshark ( with airpcap) for sniffing. Fully automatic functional tests (using TCL to command the ACE and Ixchariot, VB for the R&S signal generator and python for the testbed). Carry out many WiFi Studies ( Video over Wifi, Wifi Direct, impact of DFS in 5GHz band, MAC layer convergence for future WLAN and WPAN Wireless Systems ..). Partners with leading WiFi chipset companies to provide rich set of novel and high-performance WiFi solutions ( Atheros, Broadcom, Ralink, Qualcomm, Quantenna, Lantiq..)
- Provide thorough Analysis of test results/defects of software, hardware and embedded firmware and be able to help determine root cause and provide debugging information
- Isolate defects, help developers reproduce errors, and ensure that defects are fixed
DSP Modem Algorithms for 802.16e . Digital Communications Engineer, Optimization of MIMO Decoding Algorithms.
R&D Digital Communications Engineer, optimization of MIMO Decoding Algorithms.
- Study of the recent developments in space-time coding and signal processing techniques appropriate for MIMO communication systems Review of the information theory results on the capacities of wireless systems employing multiple transmit and receive antennas. - Study of structures of MIMO decoders and some well-known pre-processing techniques with a focus on the diversity Multiplexing Tradeoff of MIMO decoders.
- Proposing a new ML sequential decoding algorithm (Spherical Bound-Stack decoder combining the Depth-First-Search strategy and the Best-First-Search strategy).
- Proposing a new soft output MIMO decoder exploiting the suitable structure of the stack decoder algorithm to provide a soft output, required when STBC are concatenated with error correcting codes (internal nodes still stored in the stack at the end of hard decoding process to calculate the Log-Likelihood Ratio (LLR))
- Reducing the complexity of the stack decoding algorithm using different techniques (the use of parallel processing, the child-sibling strategy and the complex strategy (decoding over complex symbol alphabets)).
- Suggesting a solution to the problem of the increase in decoder complexity in the case of severe channels. Indeed, these decoders seem to be converted to exhaustive search decoders visiting all constellation points. Thus, we introduce time and complexity constraints and we propose to finish the stack decoding by a ZF-DFE decoding for hard decoding and a K-Best decoding for soft outputs.
- Concatenation of MIMO STBC with OFDM, and channel coding (BCC, LDPC, Turbo Code).
September 2006 Master's internship at France Telecom Issy-les-Moulineaux,
Subject: Channel Imperfections and its Effect on Performances of Space-Time Codes,
(Application to 3G Model)
. A. Salah, A. Saadani, and G. Rekaya Ben-Othman ”On the linear precoding of non-orthogonal STBC for MIMO systems”, IEEE International Symposium on Personal Indoor and Mobile Radio Communications (PIMRC), Athens, Greece, September 2007.
July-August 2005 NSS engineer at ZTE Corporation, Tunisia, Installation and Configuration of CDMA2000 Network.
Graduation project at Eurecom Institute, Nice Sophia Antipolis,
Subject: Channel Estimation for Mobile Terminal Localization in Cellular Systems.
M.Triki, A.Salah and D.T.M Slock ” Interference cancellation with bayesian channel models and application to TDOA/IPDL mobile positioning”, ISSPA 2005, International Symposium on Signal Processing
Engineering Internship at ZTE Corporation, Tunisia,
Subject: UMTS Network Performance Simulation, Planning & Installation.
Ph.D. in Digital Communication, Communications & Electronics Department TELECOM ParisTech., France, Advisor: Prof. J-C.Belfiore; co-advisor: Dr. G-R. Ben Othman. Title: Low Complexity Decoding Schemes for MIMO Systems