KTH WP4d Activity Report

1
KTH WP4d Activity Report

• Karl H. Johansson
• Department of Signals, Sensors and Systems
• Royal Institute of Technology
• Stockholm, Sweden

2
KTH WP4d Group

• Faculty
• Anders Forsgren, Håkan Hjalmarsson, Karl H.
  Johansson, Mikael Johansson, Gunnar Karlsson,
  Mikael Skoglund
• PhD students
• Lei Bao, Oscar Flärdh, Krister Jacobsson, Björn
  Johansson, Henrik Lundqvist, Niels Möller,
  Alberto Speranzon
• Industrial Collaborators
• Ericsson
• ABB
• Scania

3
KTH Contribution in WP4d

• Control of networks
• Dynamic control of end-to-end communication
  quality
• Estimation and control of QoS parameters (loss,
  delay etc.) for packet-switched networks
• TCP-friendly design of wireless access links
  (with UAQ)
• Optimal network-wide resource allocation (with
  UNISI)
• Demand estimation
• Control over networks
• Integrated control and coding
• Distributed control with quantized information

4
Wireless Internet

• Integration of Internet and cellular networks
  hard due to radio link variations
• When used over wireless links, TCP cannot ensure
  a high link utilization
• Packet drops, bandwidth and delay variations in
  radio link erroneously indicate network
  congestion to TCP
• How do interactions affect TCP throughput?
• Can we make the radio link and the cellular
  system TCP friendly?

5
Modeling and Control of IP Transport over
Cellular Radio Links

• UAQ-KTH Collaboration
• C. Fischione, F. Graziosi, H. Hjalmarsson,
• K. H. Johansson, N. Möller, C. Rinaldi,
• F. Santucci
• Research visits
• Joint publications Fischione et al., Möller et
  al.
• Results
• Radio link transforms losses into random delays
• Key dynamics from cascaded feedback control loops
• Inner and outer power controls
• Link-layer retransmission
• TCP
• Increased probability of spurious timeout ?
  reduced TCP throughput
• Adjust link layer properties to optimize TCP
  throughput

6
New Feedback Protocols for Wireless Internet

• Improved TCP throughput through new radio network
  feedback protocol
• Proxy between cellular system and Internet adapt
  sending rate to radio bandwidth variations
  obtained from radio network controller (RNC)

7
Proxy Solution Based on Radio Network Feedback

• Improved user experience of wireless Internet
• Substantially decreased time-to-serve-user and
  increased link utilization compared to
  traditional end-to-end TCP
• Better slow start, outage recovery, bandwidth
  adaptation, RNC utilization
• Collaboration with Å. Arvidsson, J. Petersson, R.
  Skog (Ericsson AB)

8
Distributed Cross-layer Coordination of
Congestion Control and Resource Allocation in
S-TDMA Wireless Networks

• UNISI-KTH Collaboration
• A. Arbrado, A. Bemporad, M. Johansson, S.
  Loretti, P. Soldati
• Research visits M. Johansson gave intensive
  course on Convex optimization of communication
  systems at UNISI P. Soldati visiting KTH until
  June 2005
• Joint publications Loretti et al., Soldati et
  al.
• Research Project
• Joint congestion control and spatial-reuse TDMA
  (S-TDMA) scheduling
• extends congestion control for fixed networks to
  systems with variable-capacity links
• S-TDMA is collision-free medium access protocol,
  dictated by schedule
• Distributed congestion control and resource
  allocation
• Aligns end-to-end rate selection, scheduling,
  power and rate adaptation
• Distributed organization, maintenance and
  updating of schedule

9
Proposed Solution and Results

• Two time-scale solution
• TCP/AQM on fast time-scale
• Incremental schedule updates on slow time-scale
• Formally proven to converge in ideal case
• Realistic protocols necessarily suboptimal
• Structured and transparent design procedure
• Isolated and quantifies performance losses in
  each step
• Continued activities
• Back-pressure driven resource allocation in
  wireless systems
• Network-wide resource allocation
• Cross-layer issues in sensor networks

10
WP4d-Related Links to Other Projects

• RUNES Reconfigurable ubiquitous networked
  embedded systems
• Integrated Project, FP6, coordinated by Ericsson
  AB
• Develop and exploit technology platform for
  wireless networked systems with emphasis on
  middleware
• WP4d-related collaboration with UNIPI and UPAT
• Euro-NGI Design and Engineering of the Next
  Generation Internet
• Network of Excellence, FP6, within the EC
  objective Broadband for All
• Provide required innovative traffic engineering
  architectures adapted to the new requirements and
  develop corresponding quantitative methods
• RECSYS Real-time embedded control of mobile
  systems with distributed sensing
• Shared-cost RTD, FP5
• Control and filtering under networked constraints
• WP4d-related collaboration with UNIPI

11
KTH Contribution in WP4d

• Control of networks
• Dynamic control of end-to-end communication
  quality
• Estimation and control of QoS parameters (loss,
  delay etc.) for packet-switched networks
• TCP-friendly design of wireless access links
  (with UAQ)
• Optimal network-wide resource allocation (with
  UNISI)
• Demand estimation
• Control over networks
• Integrated control and coding
• Distributed control with quantized information