Mobile Network Operators (MNOs) require substantial data capacities for core and trunking services, much of which uses fibre/cable.
The fibre/cable is susceptible to reliability issues. For rural areas, microwave/satellite is typically used for backhaul. Satellite links can be a highly reliable backup, but can be expensive.
Fibre restoral requires the transfer of traffic to satellite link(s) for fibre outages. The satellite link OPEX can be reduced by using a bandwidth on-demand technology. The scale matters; the more circuits backed up, provides more favourable OPEX. Let’s examine a system level approach for cost-effective satellite-based restoral.
Dimension Bandwidth Pool Capacity
If a restoral service exists, there can be multiple satellite operators, multiple contacts per operator, multiple transponders across bandwidth segments with linear and circular polarisation, and partial and full transponders. The objective is to optimise capacity; not all of it may be required to provide restoral services.
In greenfield designs, capacity must be located on satellites that cover the areas with the fibre nodes. With large service areas, locating satellite capacity can be challenging. Available satellite footprints may not fully cover the service area. The bandwidth must meet the minimum system availability metric, which is usually 99.9%.
Proper dimensioning is largely based on the benefits realised by pooling satellite bandwidth resources. When resources are shared, statistical probability can be used as an “oversubscription” model where creating a bandwidth pool maximises the number of fibre node restoral sites on the same satellite resources.
Locate Satellite Capacity
Satellites with footprints covering all or most restoral sites are preferred. This is key to a good design, since the parameters of the ground equipment will be selected to match the satellite footprints with the goal of OPEX reduction.
Spectrally Efficient Hardware
The best utilisation of satellite capacity requires efficient ground equipment. Proper design is performed using tools and hardware to maximise spectral efficiency.
Bandwidth optimisation techniques can be packet-based, using layer 2 or 3, such as IP header and payload compression, or the physical layer, with the transmission waveform. These techniques include ACM to reduce static link margin; advanced coding and modulation; carrier overlay (sometimes called carrier in carrier); and dynamic bandwidth management.
Automate Capacity Usage
Next, the operational criteria is established – automated or with a person in the decision path.
When a person is in the decision path, the event series typically involves the NOC personnel getting a call or alarm that a terrestrial link is down. The operator accesses the NMS, informs the network about the outage, and makes the hardware element changes to accommodate the outage sites with the most effective use of satellite capacity.
For automated outage recovery, the machine-to-machine connection detects/declares that a cable/fibre is down. The satellite backup network elements are activated without intervention by NOC personnel.
Frederick Morris is the Vice President of Product Marketing at Comtech EF Data.