Proxim WORP Protocol Description

WORP is a polling algorithm designed for wireless outdoor networks

Wireless Outdoor Router Protocol (WORP)
WORP is a newer revision of the Karlnet Turbocell, but it is not backward compatible.

WORP takes care of the performance degradation that happens when standards-based 802.11wireless LAN technology is used for outdoor building-to-building connectivity, incurred by the so-called “hidden-node” problem.

Benefitts:

• More effective use of bandwidth
  • Sustain more simultaneous users
• More concurrent subscribers (up to 250 depending on the Model)
  • Reduces Infrastructure investment per subscriber
• Asymmetric Bandwidth Control
  • Enables Service Provider to differentiate his service offering between i.e. business and residential customers
    

WORP Solves the Hidden Node Problem

The Hidden Node problem

• 802.11 radios use CSMA/CA (Collision Avoidance) for transmission
• Requires radios to hear each other
• RTS/CTS (Request to send/Clear to send) mechanism should have solved this problem
• However, multiple radios can still send an RTS when another radio is transmitting, and this will corrupt all data being sent degrading overall performance

WORP Solutions for the Hidden Node Problem

• WORP polling algorithm ensures that collisions cannot occur
• WORP increases the performance of the overall network significantly
• WORP polling dynamically adapts to the number of satellites that are active on the network and how much data they have queued up to send

WORP Details:

• WORP uses IEEE 802.11 radios in a modified way
• IEEE802.11 radios require unicast frames to be responded by ACK frame within 10 microseconds after transmission of the frame
  • This imposes a limit to the distance between stations, based on the speed of the transmission (speed of light = 2998 * 105 M/s)
  • The theoretical limit on the distance between two radios would then be approximately 1500 meters
  • Beyond that distance the ACK frames would not be in time
• WORP solves this issue by transmitting all information as multicast IEEE 802.11 frames (even when sending to a single destination):
  • Uses the unique MAC address of the destination radio with the multi-cast bit flipped on

• Network uses 2 strings for identification
  • Network Name: same for entire “roaming area”
  • Base Station Name: unique per BSU, so SU can be “locked”.
    • avoids customers relocating without contacting you
    • better bandwidth control.
• BSU to SU communication
  • Registered Subscriber Unit gets port number assigned
    • BSU’s bridge learn table shows WORP Satellites as ports 2, 3…251.
  • BSU is broadcasting the information listed above, but this broadcast stops when all configured SUs have registered and are active.
  • Registration: MD-5 authentication uses “Network Secret” string
  • De-registration: when BSU or SU has not seen its peer for 30 sec.
  • Bandwidth control per interface (SU/BSU, wireless/Ethernet) or Radius.