My current research interests are MAC Layer Protocol Research for Wireless Networks, Space-time Coding & MIMO (Multiple Input Multiple Output) Antenna for Next-generation Wireless Networks, Vertical handover and mobility management in heterogeneous wireless networks (802.11/Bluetooth/802.20/HiperMAN), Adaptive transmission control for multimedia (voiceIP, audio,video & data traffics) over hybrid wireless/mobile neworks & Internet, TCP-friendly Congestion Control, Video Multicasting and IP DiffServ QoS. I was involved in the project of French National Research Network in Telecommunications (RNRT) -- VTHD++ (Performance analysis of communication protocols over a high speed network), working with Dr. Thierry Turletti and Dr. Walid Dabbous. You can download our ns-2 implementation codes for IEEE 802.11e QoS-enahnced wireless LAN here.

Research Contents

1. MAC layer protocol research for wireless networks (IEEE 802.11 a/b/e/g/n, IEEE 802.15 ultra-wide band (UWB) wireless LAN/MAN/PAN standardization activities)
  Since voice, audio, video and data flows have different quality of service (QoS) requirements, i.e., bandwidth, delay, jitter and packet error-tolerant performance, it's not efficient of current data link layer protocol (LLC/MAC) support in IEEE 802.11/IEEE 802.15 (802.11a/g OFDM & 802.11b HR, 802.11n MIMO, 802.15.1 Bluetooth, 802.15.3a UWB, 802.15.4 Senors). IP differentiated services (DiffServ) are sub-optimal without lower layers' support. We try to design and implement adaptive transmission protocols for multimedia (VoIP, audio, data and video) via wireless access networks accessing to DiffServ VTHD backbone. Both transport layer & data link layer (LLC/MAC) service differentiation & unequal error-protection schemes (Hybrid-ARQ) are in study to manage & support the different access demands of user and service classes. We participated the latest standardization works done at IEEE 802.11 WG, e.g. the upcoming 802.11E standard (TGe) and IEEE 802.11 n MIMO high-throughput wireless standard (TGN) to enhance the performance of all IEEE 802.11 MAC (DCF, PCF, EDCA, HCF) for MIMO/OFDM-based wireless PHY layers. We will test our enhanced protocols in both network simulator (Berkeley ns-2) environments and via our real network testbed. And I'm now supervising several students working on this sub-project of VTHD++ project. (see the following figure 1 and figure 2):

Research papers: 

• Qiang Ni, Lamia Romdhani, and Thierry Turletti. "A Survey of QoS Enhancements for IEEE 802.11 Wireless LAN". Wiley Journal of Wireless Communication and Mobile Computing (JWCMC), John Wiley and Sons Ltd., 2004; Volume 4, Issue 5: 547-566. (.pdf)
• Qiang Ni, and Thierry Turletti. "QoS Support for IEEE 802.11 WLAN", (To appear in a book soon), Nova Science Publishers, New York, USA, 2004. (.pdf)
• Gion R. Cantieni, Qiang Ni, Chadi Barakat, Thierry Turletti, "Performance Analysis of Finite Load Sources in 802.11b Multirate Environments", To appear in Elsevier Computer Communications Journal, special issue on Performance Issues of Wireless LANs, PANs, and Ad Hoc Networks, 2004. (.pdf)
• Imad Aad, Qiang Ni, Chadi Barakat, and Thierry Turletti. "Enhancing IEEE 802.11 MAC in Congested Environments", IEEE applications and services in wireless networks workshop (ASWN), Boston, August 2004. (.pdf)
• Pierre Ansel, Qiang Ni, and Thierry Turletti. "An Efficient Scheduling Scheme for IEEE 802.11e". Accepted to appear in proceedings of WiOpt (Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks), Cambridge, UK, March 2004. (.pdf)
• Mohammad Malli, Qiang Ni, Thierry Turletti, and Chadi Barakat. "Adaptive Fair Channel Allocation for QoS Enhancement in IEEE 802.11 Wireless LANs". Accepted to appear in IEEE ICC 2004 (International Conference on Communications), Paris, France, June 2004. (.pdf)
• Qiang Ni, Imad Aad, Chadi Barakat, and Thierry Turletti, "Modeling and Analysis of Slow CW Decrease for IEEE 802.11 WLAN". Proceedings of IEEE PIMRC (International Symposium on Personnel, Indoor and Mobile Radio Communications), Beijing, China, Septembre 2003. (.pdf)
• Lamia Romdhani, Qiang Ni, and Thierry Turletti. "Adaptive EDCF: Enhanced Service Differentiation for IEEE 802.11 Wireless Ad Hoc Networks". IEEE WCNC'03 (Wireless Communications and Networking Conference), New Orleans, Louisiana, USA, March 16-20, 2003. (.pdf)
• Gion R. Cantieni, Qiang Ni, Chadi Barakat and Thierry Turletti. "Performance Analysis of Finite Load Sources in 802.11b Multirate Environments". INRIA Research Report No. 4881, Jul. 2003. (.pdf)
• Pierre Ansel, Qiang Ni, and Thierry Turletti. "FHCF: A Fair Scheduling Scheme for 802.11e WLAN". INRIA Research Report No. 4883, Jul. 2003. (.pdf)
• Imad Aad, Qiang Ni, Chadi Barakat, and Thierry Turletti. "Enhancing IEEE 802.11 MAC in congested environments". INRIA Research Report No. 4879, Jul. 2003. (.pdf)
• Qiang Ni, Lamia Romdhani, Thierry Turletti and Imad Aad. "QoS Issues and Enhancements for IEEE 802.11 Wireless LAN". INRIA Research Report No. 4612, Nov. 2002. (.pdf)
• Imad Aad, Qiang Ni, Claude Castelluccia, and Thierry Turletti. "Enhancing IEEE 802.11 Performance with Slow CW Decrease". IEEE 802.11e working group document 802.11-02/674r0, November 11, 2002. (.pdf)
• Lamia Romdhani's Master Thesis supervised by me and Thierry. "Adaptive service differentiation for QoS enhancement in IEEE 802.11 wireless LANs", July 1, 2002. (.pdf)
• Lamia Romdhani, Qiang Ni, and Thierry Turletti. "AEDCF: enhanced service differentiation for IEEE 802.11 wireless ad-hoc networks", INRIA Research Report No. 4544, 2002. (.ps)

Related Links
Imad Aad's 802.11 WLAN Homepage (my friend & colleague) 
 

2. Space-time coding & MIMO (Multiple Input Multiple Output) antenna design for next-generation wireless networks

Research papers: 

• Zhonglin Chen, Wei Cai, Qiang Ni and Guangxi Zhu. "Differential space-time block-coded OFDMA for frequency selective channel". IEEE PIMRC 2003 (IEEE International Symposium on Personal, Indoor and Mobile Radio Communications), Beijing, China, Sept., 2003, pp 2171 - 2175. (.pdf)

3. Vertical handover and mobility management in heterogeneous wireless networks (IEEE 802.11/Bluetooth/IEEE 802.20 MBWA/ETSI HiperMAN)

Research papers: 

• Kaouthar Sethom, Hossam Afifi, and Qiang Ni. "Adaptation Interface for Seamless Handover between IEEE 802.20 MBWA/802.11/802.15". IEEE 802.20 Mobile Broadband Wireless Access Working Group Document 802.20-03-104, Nov. 12, 2003. (.pdf)

4. Adaptive control for voice, audio, video & data over hybrid wireless/mobile networks, PSTN & VTHD backbone
  In this project, VTHD deployed a broadband DiffServ-based IP test platform for next generation Internet, and IEEE 802.11/IPAQ PDA supports a seamless mobile accessing to users. The problem is, the network heterogeneity (high-speed error-free VTHD backbone vs. time-varying lossy WLAN) makes it difficult to transmit hybrid real-time voice,audio,video and data applications over such a heterogeous network. It's well known that the wireless channel characteristics highly change in several ways (interference, AGWN, multipath and the movement of the mobile host). In addition,voice,audio,video and data traffic have different quality of service & error-tolerant requirements.We want to study an effective mechanism for carrying multimedia applications over hybrid 802.11 WLAN & VTHD backbone. Now We have created a real heterogeous network testbed (see our VTHD network testbed figure) and tested two kinds of real-time multimedia applications: (1).H.323-based multimedia conference application (Netmeeting,Openh323); (2).SIP-based multimedia conference application (SDP, SIP, RAT, VIC) and some non-realtime data applications (FTP, email, Telnet/TCP) as backgroumd competing traffics. And we can easily communicate between mobile laptop, fixed Windows PC & Linux PC and ordinary telephone. We try to analyze the characteristics of both real-time voice, audio, video streams and bursty wireless channels.

Research papers

• Qiang Ni, Thierry Turletti and Wei Fu. "Simulation-based Analysis of TCP Behavior over Hybrid Wireless & Wired Networks". The 1st International Workshop on Wired/Wireless Internet Communications (WWIC 2002), Las Vegas, Nevada, U.S.A., June 24-27, 2002. (.pdf) (.ppt)   (WWIC'02 Conference Webpage Link)
• Abdramane Diallo, Qiang Ni, and Thierry Turletti. "Testbed-based performance evaluation of VoIP over wireless & wired LANs", June 2002. (.pdf)

5. TCP-friendly Rate Control

Research drafts: 

• Qiang Ni, et al. "Towards Enhancing Throughput Performance of TCP-friendly Multimedia Congestion Control Protocol". Dec. 2001. (.pdf)

6. Sender-adaptive & Receiver-driven Layer Multicast for Video Streaming (SARLM) over the Internet
  I worked on a SARLM architecture when I did my visiting internship at Wireless & Networking Group of Microsoft Research Asia (Beijing). We introduce a novel architecture, called the Sender-Adaptive and Receiver-driven Layered Multicasting (SARLM), for layered/scalable video multicast over the Internet. It is in the application layer and does not require any changes in network routers. In this architecture, a sender first compresses a video sequence into multiple data streams by using scalable coding with FEC (Forward Error Correction) and then sends each stream to a separate multicast group. Receivers dynamically estimate their available bandwidths using the packet-pair approach. They then join or leave multicast groups according to network conditions. At the same time, the receivers also transmit to the sender sparse feedbacks containing statistical information about the network conditions. Based on analysis of the feedback information, the sender adjusts the transmission parameters for each multicast group. You can know more about my previous work on SARLM in my papers.

Research papers: 

• Qiang Ni, Qian Zhang, Wenwu Zhu. "SARLM: Sender-adaptive and Receiver-driven Layered Multicast for Scalable Video". IEEE ICME 2001(IEEE International Conference on Multimedia and Expo), Japan,Aug. 22-25,2001. (.pdf)
• Qian Zhang, QuJi Guo, Qiang Ni, Wenwu Zhu and Ya-Qin Zhang. "Sender-adaptive and Receiver-driven Layered Multicasting for Scalable Video over the Internet". To appear in IEEE Transactions on Circuits and System for Video Technology (CSVT), 2004. (.pdf)

Research Tools

1. Our contributions on NS simulation source codes

  @Note: You can download our IEEE 802.11e enhancement NS simulation codes freely for academic use, but please cite our work when you use them:

•    ns-802.11e EDCF for IEEE 802.11e Wireless LAN 
•    Our ns-802.11e Adaptive EDCF (AEDCF) implementation webpage
•    Our ns-802.11e HCF/FHCF implementation webpage
•    Our ns-802.11e Adaptive Fair EDCF implementation webpage

Contact Info: qiang.ni@ieee.org or qiang.ni@may.ie or qiang.ni@sophia.inria.fr

Links to other people's NS code contributions

•    TKN Group's codes for EDCF and CFB simulations, TU-Berlin

•    Our 802.11 a/b/e/g WLAN driver
•    Ethereal Network Analyzer
•    TCPDump Network Analysis Tools
•    IPerf Traffic Generator