CPRI TOPOLOGY 1
Star topology
- Advantage
Transmission reliability is high. When an RRU or an optical cable is faulty, only the related sector is affected.
Networking mode is simple and installation and maintenance are easy.
- Disadvantage
RRUs cannot be cascaded when the star topology is used.
Chain topology
- Advantage
The chain topology reduces the cost for optical fibers.
- Disadvantage
Faults in an upper-level RRU may affect lower-level RRUs.
CPRI TOPOLOGY 2
If the physical bandwidth of a CPRI port is insufficient to support a cell, using load sharing within one LBBP, and the RRU can be connected to two CPRI ports on one LBBP for sufficient bandwidth.
For multi-carrier RRUs, inter-board load sharing topology can be used. The RRU is connected to CPRI interfaces of the two LBBPs and each CPRI link transmits data for one carrier. The OM channel can only be set up on one of the two CPRI links for transmitting OM signaling.
Load-sharing networking mode
Advantage
The transmission reliability is improved.
Wider transmission bandwidth can be achieved with two optical fibers.
Disadvantage
Two optical fibers must be connected to one RRU.
The inter-board load-sharing topology requires two BBP boards.
RRUs cannot be cascaded when the load-sharing topology is used.
CPRI TOPOLOGY 3
In an intra-board cold backup ring topology
If the baseband processing board is faulty, services carried by all RRUs on the ring are interrupted and cannot be restored.
If a CPRI port or CPRI link that transmits services on the ring is faulty, the RRU services are interrupted and then return to normal after the services are switched to the other cable.
If a CPRI port or CPRI link that does not transmit services is faulty, services on the RRUs are not affected.
In an inter-board cold backup ring topology
If a baseband processing board that transmits services is faulty, services on all RRUs on the ring are interrupted and then return to normal after the RRUs establish communications with another baseband processing board.
If a baseband processing board that does not transmit services is faulty, services on the RRUs are not affected.
If a CPRI port or CPRI link that transmits services on the ring is faulty, the RRU services are interrupted and then return to normal after the services are switched to the other cable.
If a CPRI port or CPRI link that does not transmit services is faulty, services on the RRUs are not affected.
In the hot backup ring topology, two CPRI links transmit identical service data and the BBP and RRU process service data on one link only.
If a baseband processing board that establishes an OM channel with an RRU on the ring is faulty, services on the RRU are interrupted and then return to normal after the RRU establishes communications with another baseband processing board.
If a baseband processing board that does not establish an OM channel with an RRU is faulty, services on the RRU are not affected.
If a CPRI port or CPRI link that carries the OM channel is faulty, services on the RRU are quickly switched to another cable and return to normal.
If a CPRI port or CPRI link that does not carry the OM channel is faulty, services on the RRU are not affected.
Hot backup ring topologies are more reliable than cold backup ring topologies.
