YateUCNTM redundancy
The simplified architecture of YateBTS/YateENB-YateUCN networks is based on replacing the components’ functions and protocols with software on commodity hardware. This achieves redundancy by adding a new YateUCN server in the network, instead of providing back-up to each GSM/LTE core network component.
The YateBTS is the software implementation of the GSM/GPRS-specific protocols for the BTS (Base Transceiver Station) and BSC (Base Station Controller). When the SatSite base station is used in 2G mode, the YateBTS communicates directly with the YateUCN core over SIP/GTP protocols, without needing a BSC.
The YateBTS also integrates a part of the MSC, which enables the SatSite to connect to any YateUCN in the network, irrespective of its geographic location.
Any YateUCN node can be configured to take over extra-traffic from another YateUCN unit in case of network congestion or failure.
Because the YateUCN uses SIP to communicate with both the YateBTS and the YateENB, the same redundancy mechanism is provided for both GSM and LTE.
Each SatSite unit holds a list of all the YateUCN nodes in the network, where extra-traffic can be routed in case of failover; this is done without the device connecting to a different SatSite, and only the data connection from the previous YateUCN to the new one is changed.
If the mobile device remains connected to the same SatSite, registration to the Mobile Switching Center/Visitor Location Register/Serving GPRS Support Node in the new YateUCN is performed whenever the device communicates with the network for a voice or data service. Registration to the new YateUCN is also updated in the HLR.
If the device roams to an area served by a different SatSite, it will remain connected to the YateUCN currently serving it, and a new query in the HLR is not required. This reduces the load on the HLR and allows a higher subscriber capacity.
If a YateUCN core is not found in the list, the YateBTS looks up a new DNS address for a YateUCN core that can be used to offload the traffic.
MSC redundancy
Conventional GSM networks rely on special-purpose hardware destined to perform specific functions.
Redundancy in conventional GSM/GPRS networks implies each MSC node redirecting traffic to a specific MSC in case of network failure.
Because typical MSC/VLR in data centers are limited to serving a given number of BSCs in a geographical area, an additional MSC/VLR needs to be planned for each data center. This leads to increases in equipment and servicing expenses.
Traffic is offloaded to the back-up MSC and a new registration/authentication in the HLR is required for the subscriber.
In LTE, load traffic sharing is achieved by an eNodeB connecting to any other MME in the network when needed. This requires multiple MME nodes to be planned in the network.