ViaLite Communications are regularly asked to comment on the disruption and evolution of the satellite communication industry, and the emergence of technologies that aim to offer virtualisation of the ground segment. In recent years, there has been considerable investment in, and promotion of technologies that might support this shift, including RF over Internet Protocol (RFoIP), virtualised modem, baseband processing, and network management products.
As a manufacturer of RF over Fibre (RFoF) technology solutions, RFoIP is an area of interest for ViaLite Communications. The promotion in the marketplace, and the interest in the concept to date, has led to an expectation from customers that a line of RFoIP products should be developed; however, the adoption of this new approach is not universally accepted, and significant questions and challenges do, and will, remain.
RFoF vs RFoIP
With any technology introduction there will always be a tendency to focus on the benefits associated with that technology and the features that claim to deliver them. However, it is critical that both the benefits and drawbacks are fully understood and appreciated to ensure that the correct technology selection is made for each individual requirement. To help prospective and existing customers make the right decision when considering RFoIP and RFoF solutions, there are some simple points to consider that can help determine which technology will be the best choice.
1. Latency
RFoIP solutions suffer substantial latency, because of the sampling and packetisation processes involved. Most RFoIP systems use a fixed buffer to compensate for this delay, which is caused by packets of information being received out of order, or even some packets being dropped entirely. This can be a huge disadvantage for RFoIP as IF processing equipment typically requires information to be received complete, in order and without delays; otherwise modem time-outs, reboots, and transmission failures can occur.
In contrast, RFoF has an extremely low level of latency and any calculated delay is always fixed and synchronised to pinpoint accuracy.
2. Infrastructure and Broadband
The ultimate aim of RFoIP is to use IP connections rather than the dark fibre network that would be used by an RFoF system. In regions such as Asia, satcom companies are often unable to procure the huge IP capacities that are needed from the local service providers, or find the IP networks with the high speed (100 GbE) connectivity required, resulting in RFoIP systems still using dark fiber.
To put this into context, the transportation of a typical full link bandwidth of a 6 GHz IF signal requires 120 Gbps of throughput. Some early real-world investigations have shown that there may only be 100 Mbps available, and that RFoIP Long Distance Link (LDL) applications have been limited to transport distances of only 100 km and not the vast distances promised. To date, RFoIP implementation has proved to be difficult, and the performance has been variable and often unacceptable.
3. Security and resilience
For satellite telecommunication, security and resilience are crucial for maintaining reliable and secure global communication networks, especially for critical services utilised by Government and Defence users. Given that RFoIP products use IP networks to transmit data and aim to employ cloud services for network function virtualisation, there are genuine concerns regarding the security aspects of this type of system. Unauthorised access and data breach instances continue to increase globally both in the physical and cyber domain, requiring enhanced security protocols at the network edge.
As RFoF technology does not rely upon IP networks for signal transportation, signal interception is extremely difficult; therefore, it has a huge advantage over RFoIP when security is paramount.
4. Costs
To fully reap the benefits of RFoIP, ground segment operators will need to replace existing infrastructure and teleport hardware, which will have been the result of a substantial historical investment that may not yet have been fully maximised. There is evidence to suggest that in the face of rising component prices due to global trade disruption, equivalent replacement hardware could be more expensive in the future. If this is not considered, when added to the increased operating costs due to the higher power consumption of RFoIP hardware, the true costs of switching may not be fully realised.
In addition, currently available RFoIP hardware specs offer lower operating temperature thresholds than an equivalent RFoF solution. In tropical regions, where very high temperatures and humidity are normal, the additional purchase and operating costs of running the required HVAC systems also needs to be considered. With an order of magnitude lower power consumption, an RFoF system provides high performance and flexibility at a fraction of the cost of an RFoIP system, without constraining network design improvements.
Conclusion
There is no doubt that software defined networks are credible concepts and will continue to be developed as a solution for upgrading ground segment infrastructure in the future. However, there is no evidence that the proposed RFoIP approach will replace RFoF within the satellite communications domain. RFoF technology continues to be used for successful IF signal transportation in the ground segment and there is widespread belief that it will be for some time to come, especially for critical communications applications.
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