TCP Performance in Wireless Networks: A Survey of Existing Solutions

1
TCP Performance in Wireless Networks A Survey
of Existing Solutions Modupe Omueti momueti_at_cs.sfu
.ca School of Engineering Science, Simon Fraser
University
Existing TCP Solutions for Wireless Networks
Standard TCP
Design-based

• TCP designed originally for wired networks
• Wired networks characterized by negligible random
  BER
• Congestion indicated by packet loss
• Congestion control algorithms invoked for packet
  loss

• Split connection
• Separates TCP into wired and wireless e.g.,
  I-TCP, M-TCP
• End-to-end connection
• Treats TCP as single connection e.g., TCP SACK,
  TCP Veno, TCP-Jersey, TCP Westwood

End-to-end TCP Connection
Split TCP Connection
Application-based

• Ad Hoc Application
• Frequent route changes and network partitions
  e.g., Ad hoc TCP

• Satellite Application
• Long propagation delay and high BER e.g.,
  TCP-Peach

• Cellular Application
• Frequent disconnection and reconnection e.g.,
  Freeze-TCP

Satellite
Peer (PDA)
TCP Congestion Control Algorithms
Mobile host
Fixed Host
peer
peer
Base Station
Earth Station
ISSUES
Wireless Networks
Layer-based

• Hard-state Transport Layer
• Splits TCP connection into wired and wireless
  e.g., I-TCP
• Pure Transport Layer
• Maintains state crucial to end-to-end connections
  e.g., TCP SACK

• Soft-state Cross Layer
• Makes TCP sender aware of wireless link e.g.,
  TCP multiple ACKs
• Soft-state Transport Layer
• Employs TCP-aware local loss recovery e.g.,
  TCP Snoop

• High BER and thus more packet losses
• TCP misinterprets packet losses
• TCP invokes congestion control algorithm
• TCP throughput decreases and performance degrades

• Pure Link Layer
• Hides wireless link errors from TCP e.g., AIRMAIL

RESOLUTION
Ideal Solution
Comparison of Existing Solutions with Ideal
Solution

• References
• R. Ludwig, A case for flow-adaptive wireless
  links, University of California, Berkeley, CA,
  Tech. Rep. UCB//CSD-99-1053, May 1999.
• Y. Tian, K. Xu, and N. Ansari, TCP in wireless
  environments problems and solutions, IEEE
  Commun. Mag., vol. 43, no. 3, pp. S27-S32, Mar.
  2005.