Mobile-TV,
Mobile WEB Access, and M-Commerce are amongst the new applications
enabled by the deployment of 3G networks. Realizing that current
applications as well as next generation applications are to be data
oriented applications, mobile service providers were amongst
the
first to migrate their existing Radio Access Networks
(RAN) to Ethernet/IP/MPLS
packet networks.
Migrating to Ethernet/IP/MPLS networks allowing the mobile service
providers to
support new
applications but to keep their CapEx and OpEx at controllable cost
while
being able to provide new competitive services. This is why Circuit
Emulation Services (CES) is considered an essential technology
for
the mobile service provider as it allows a moderate migration of the
base stations to IP based base stations as data applications usage is
ramping up. New base stations with IP interfaces will use the IEEE1588
Precision Timing Protocol for recovering the clock from the incoming
packet stream.
A
successful handover is dependent upon the level of synchronization
achieved at the base stations. In order to guarantee a smooth handover
between base stations, the clock synchronization performance must
meet the ITU-T G.823 and ITU-T G.824 clock
synchronization standards and it must meet the ETSI TS 145.010, ETSI TS
125.104 (FDD), and ETSI TS 125.105 (TDD) cellular standards (FFOFF). However, it was found
that the inherent packet network impairments severely
degrades the
clock synchronization performance to the level it may cause a
disconnect during handover. Packet
network impairments include:
A
new approach for clock synchronization over packet is required to
handle the inherent Ethernet/IP/MPLS packet network impairments in
order to meet both clock synchronization performance defined by the
ITU-T standards as well as the frequency accuracy requirement defined
in the ETSI standards to enable smooth hand over.
