Experience 

Senior & Principal Member of Technical Staff 

                            April 1998 to present

AT&T Labs – Research, NJ, USA

Mobile Wireless Network Research Group

Led and Participated in many Successful Projects on 802.16 / WiMAX, 802.11 / Wi-Fi, 3G Cellular Networks, and Mobile Networking, as well as Business Projects in support of various AT&T business units, and internal AT&T IT organizations. Represented AT&T in and made technical contributions to IEEE 802.11/16/20/21/22 Working Groups, Wi-Fi Alliance, and WiMAX Forum.  

802.16 / WiMAX / 3GPP / 4G Cellular:

• Developed and analyzed various alternatives for next generation mobile cellular network architecture for packet data transport for WiMAX, 3GPP LTE SAE EPC.

• Analyzed sessions statistics to understand the impact of Push applications to the scalability of 3G and LTE SAE EPC networks
• Instrumented the power consumption of cellular base stations, including its support systems such as air conditioning. Developed models to understand the overall power consumption to discover the most cost-effective way of improving power efficiency.
• Proposed and analyzed a novel and practical Infrastructure Mesh architecture for broadband wireless access networks that substantially improves coverage and throughput performance.
• Analyzed coverage, capacity of multi-cell WiMAX systems under various conditions and 802.16 PHY/MAC for performance comparisons
• Analyzed & contributed various proposals and components of mobile WiMAX network architecture, especially in mobility management, security, multiple host support & radio resource management
• Devised and proposed a new distributed and open network architecture for WiMAX based on Ethernet transport
• Developed new practical approaches & analysis for mesh networking for 802.16 to reduce deployment cost,  improve capacity & coverage
• Represented AT&T and Contributed to IEEE 802.16 WG and WiMAX forum, especially to the 802.16 Multihop Relay Study/Task Group (also instrumental in its formation), WiMAX Service Provider Working Group and Network Working Group. Instrumental in AT&T becoming a WiMAX Board member
• Developed and compared techno-economic models for Mesh vs. traditional wireless access network topologies for WiMAX deployment
• Led Security Architecture development for AT&T’s WiMAX trials

802.11 / WiFi :

• Initiated and led Radio Resource Management (RRM), Large-Scale Deployment (Both using Large-Scale simulations and modeling), and WLAN User Location Tracking Projects and supported AT&T Business Services on the subjects. Thanks to my advocacy, RRM for WLAN has emerged as an important subject in the industry as large WLAN deployments become common.
• Contributed to IEEE 802.11 (TGi) and Wi-Fi Alliance on Public WLAN Security issues, and started the 802.11 Task Group k for Radio Resource Measurement/Management and co-authored major portions of the specification.
• Architected and led the deployment of Secure WLAN networks for Enterprise and Public Networks for external customers and AT&T’s internal use, with VPN-based Security, 802.1x/WPA/802.11i Security, policy establishment, threat assessment, advanced access control, guest access, backend infrastructure integration, process control and user support. This architecture serves as the blueprint for ongoing deployment of secure WLAN across AT&T.
• Conducted Research on and provided solutions to AT&T's Public WLAN services regarding Security, Threat Assessment, Authentication (WPA, 802.11i, EAP/1x, and mixed security support), and 3G Internetworking (EAP-SIM/AKA, SS7 & Transport Interworking).
  

Internet Roaming:

• iCard: Initiated and led the development of a secure multi-interface mobility manager implemented on a PC card form-factor Linux network node. All Mobility and Security functions are handled in iCard, hidden from host platform. Demonstrated at Mobicom’03.
• Devised and Prototyped in software a method for Mobility Support for IPsec Tunnel Mode. For corporate remote access applications, this enables mobility across multiple subnets with minimal modifications and no additional overhead without compromising compatibility and existing security afforded by IPsec tunnels.
• Led the Internet Roaming Project, an Enterprise-Oriented Secure Mobility Architecture, which enables corporate employees in the field to gain secure intranet access via a wide variety of access technologies, including cellular and public WLAN. This research project yielded more than a dozen patents (granted or pending)

3G Wireless Networks :

• Wireless Channel Information Services: Developed & prototyped an architecture for feedback of network-based information on radio link conditions, thus enabling real-time adaptation of mobile applications to optimize performance. Suitable for incremental deployment and server-based applications in existing networks.
• Research on EDGE/GPRS adaptive modulation, and wireless QoS for VoIP over EDGE. GPRS Core network QoS, QoS/Call signaling, and mobility. All-IP implementation issues for 3G.
• Led a project team for measurement and modeling of PDA and smart-phone traffic characteristics and user-perceived performance over an emulated 3^rd generation mobile cellular network.
• Authored several AT&T Internal Policies for Secure Mobile Remote Access.

Broadband Fixed Wireless Access Field Trial :

Possibly the first deployment of two-way broadband fixed wireless system (in ’97), involving commercial cable modem, radio, and data equipment. Led the team that deployed and operated a 13 site fixed wireless network for friendly customers with automatic remote management systems for obtaining Operational Experience, Propagation Measurements, and User Adoption Issues. (Refer to IEEE Comm. Magazine, Oct. 1999)

Distributed CMTS System : 

Developed advanced DOCSIS-based cable modem network architecture for AT&T Broadband (now Comcast) next generation cable plant, and related Video on Demand systems. This architecture enables vastly higher network capacity and scalability by pushing digital transmission down to mini Fiber nodes and reusing RF channels independently for smaller groups of users.

System Analyst / Consultant

June 1996 to June 1997

Spectrum Wireless, Mountainview, CA

• Modeled and analyzed System and Physical Link performance for GSM.
• Evaluated options for Signal Processing for Macro Diversity for Cellular systems.
• Built Large-Scale Channel Models and Simulators.
• Consulted on Network Planning, Automatic Site Placement, Field Measurements

Research Assistant

April 1994 to February 1998

Stanford Wireless Personal Communications Research Group

• Conducted research on Wireless System Modeling, Capacity
• and Coverage issues, Dynamic Channel Allocation, Complexity, Signal Processing (equalization, synchronization, MLSE) for various cellular systems such as PACS, PHS, GSM, IS-54/136, IS-95, DECT.
• Research on Blind Equalization, Blind Sequence Estimation, Blind Diversity Combining, Short Burst Wireless Receivers, involving Large-Scale Computer Simulations.
• Developed new simulation models for various wireless Channel and Propagation Environments.

Teaching Assistant

 September 1996 to December 1996

Stanford University, Electrical Engineering 

• High Frequency Laboratory Class at Stanford, EE dept. for graduate students on constructing and testing high frequency RF circuits.

Professional Associations :

Member of   

IEEE, IEEE Standards Association, Sigma Xi Scientific Society

Formerly Voting member of IEEE 802.11, 802.16, 802.20, 802.21, 802.22.