Cpri And Obsai - Altera Cyclone V Device Handbook

4-30

CPRI and OBSAI

When you select this option, provide an input reference clock to the channel PLL that has the same frequency
as the low-speed parallel clock.
CPRI and OBSAI
Use the deterministic latency functional mode to implement protocols such as CPRI and OBSAI.
The CPRI interface defines a digital point-to-point interface between the Radio Equipment Control (REC)
and the Radio Equipment (RE), allowing flexibility in either co-locating the REC and the RE, or a remote
location of the RE.
Figure 4-29: CPRI Topologies
In most cases, CPRI links are between REC and RE modules or between two RE modules in a chain
configuration.
If the destination for the high-speed serial data that leaves the REC is the first RE, it is a single-hop connection.
If the serial data from the REC must traverse through multiple REs before reaching the destination RE, it is
a multi-hop connection.
Remotely locating the RF transceiver from the main base station introduces a complexity with overall system
delay. The CPRI specification requires that the accuracy of measurement of roundtrip delay on single-hop
and multi-hop connections be within ±16.276 ns to properly estimate the cable delay.
For a single-hop system, this allows a variation in roundtrip delay of up to ±16.276 ns. However, for multi-
hop systems, the allowed delay variation is divided among the number of hops in the connection—typically,
equal to ±16.276 ns/(the number of hops) but not always equally divided among the hops.
Deterministic latency on a CPRI link also enables highly accurate triangulation of the location of the caller.
OBSAI was established by several OEMs to develop a set of specifications that can be used for configuring
and connecting common modules into base transceiver stations (BTS).
The BTS has four main modules:
• Radio frequency (RF)
• Baseband
• Control
• Transport
In a typical BTS, the radio frequency module (RFM) receives signals using portable devices and converts
the signals to digital data. The baseband module processes the encoded signal and brings it back to the
baseband before transmitting it to the terrestrial network using the transport module. A control module
maintains the coordination between these three functions.
Altera Corporation
RE
RE
Ring
RE
REC
Radio Equipment
Control
RE
RE
Chain
RE
RE
Tree and Branch
RE
RE
Point-to-Point
RE
Transceiver Protocol Configurations in Cyclone V Devices
CV-53004
2013.10.17
Send Feedback