IEEE 1588 over Wireless Local Area Networks

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IEEE 1588 over Wireless Local Area Networks

• The IEEE 1588 Precision Time Protocols (PTP)
  standard was developed to provide sub microsecond
  accuracy in system clock synchronization in 802.3
  Ethernet networks. However the synchronization
  accuracy achieved is dependent on the
  configuration of the network i.e. the type of
  network devices, the number of devices in the
  network, which contribute to the load in the
  network, the processing delays at the PTP server
  and client and lastly the point of time-stamping
  of the PTP frames at the PTP server and client.
  This joint project between RIT and Spectracom
  Rochester investigated in detail the effects of
  the above mentioned factors in both 802.3 based
  Ethernet and 802.11b WLANs. The study was
  extended to 802.11b based WLANs due to recent
  increased interest in Wireless Sensor Actuator
  Networks (WSAN) for industry control, where high
  accuracy in time synchronization is essential.
• Protocol and processing delays at the PTP server
  and client was incorporated, and tests conducted
  to study effects with and without these
  processing delays i.e. by time-stamping the PTP
  packets at the PTP layer, where the packets
  incurred delays due to PTP and MAC layer
  processing and just before they left the physical
  layer, where they do not incur any processing
  delays.

For the studies in both 802.3 based Ethernet and
802.11b based WLAN, test cases including
different types of network devices, varying
traffic loads and network configurations were
covered. Test cases especially to study the
effects of the contention based medium access,
collision and back-off effects, and where
applicable asymmetric traffic effects for both
types of networks were used. The investigative
studies gave a clear insight into the factors
affecting the synchronization accuracy achieved
between server and client and helped define the
application limitation of the PTP clock while
providing possible solutions to overcome the
limitations.
Year 2005 Funded CEIS, NYSTAR Nirmala Shenoy,
Spectracomcorp, Rochester