Asia Pacific is moving quickly in terms of 5G development. According to the latest GSMA’s study, 5G connections across the region are expected to reach 670 million by 2025, accounting for just under 60 percent of global 5G connections. Therefore, mobile operators in Asia-Pacific preparing to support Gigabit LTE and ultimately 5G must make their networks significantly denser to deliver high-throughput, low-latency services.
Densification involves deploying small cells every few hundred feet throughout the radio access network (RAN), or splitting existing macro cell site sectors to add capacity, among other options. The C in C-RAN can stand for either “centralized” or “cloud” RAN. C-RAN is an enabling architecture for the RAN—both for small cells and macro sites—that lays the foundation for 5G.
Today, C-RAN is a major trend in the wireless industry. Chinese operators, alongside their Japanese and South Korean counterparts, are leading the way in C-RAN-related 5G research and development initiatives, delivering more agility, flexibility and efficiency to mobile networks while generating massive energy savings. China Mobile has been at the forefront of this network architectural change, deploying it for the last few years across 2,000 sites in three Chinese cities and a province. Other network operators are actively deploying C-RAN now, especially in the Asia Pacific region, where Chinese and Japanese network operators are aggressively rolling out advanced new C-RAN architecture.
The C-RAN advantage
C-RAN provides a more elegant and efficient alternative. By leveraging fiber’s huge signal-carrying capacity for fronthaul, operators can centralize multiple BBUs in one location, either at a cell site or at a centralized baseband units (BBUs) pool location. Centralizing multiple BBUs simplifies the amount of equipment needed at each individual cell site and presents a host of other key advantages, such as lower latency.
The ultimate end-game of C-RAN, is to have network functions be virtualized in “the cloud.” Once the BBUs are centralized, commercial off-the-shelf servers can handle much of the routine processing. This means the BBUs can be redesigned and scaled back to focus on the complex or proprietary processing. Centralizing base station processing with Cloud-based RAN simplifies network management and enables resource pooling and coordination of radio resources.
In addition to saving on hardware costs, the C-RAN model can create significant savings in terms of power, cooling and site leasing costs. In Asia, the first region to successfully deploy C-RAN commercially, operators have seen operating expenditures drop 30% to 50%. C-RAN is also enabling operators to access some interesting hidden features o LTE-Advanced (LTE-A) that can increase capacity without costing more money.
The future belongs to fiber
By centralizing the BBUs at a C-RAN hub, a new layer is introduced into the network known as fronthaul. Fronthaul is the link between the BBU pool and the remote radio heads at the cell site or the small cell location. While fiber is the best fronthaul option as it delivers more bandwidth, there will always be a place for microwave links, depending on the location. Some network operators are utilizing their existing fiber assets, such as a fiber-to-the-home (FTTH) network, with a technique called fiber network convergence, given the cost and challenge in laying new fiber and their desire to maximize existing resources.
Fiber network convergence refers to the combination of multiple services within a single access network. In other words, a single pipe is used to deliver all or multiple forms of communication services. Through fiber network convergence, a service provider could deliver a wider range of services, adopt new business models, offer innovative services and enter new markets. The process of fiber network convergence is primarily driven by the development of enabling technologies, user demand, and the service providers’ capabilities.
FTTH networks have an extensive footprint that is perfect for supporting fast-growing mobile applications such as distributed antenna system (DAS), small cell and Wi-Fi backhaul and/or C-RAN fronthaul. To get maximum usage out of their existing fiber assets, operators are using wave division multiplexing (WDM) over existing fiber to get 8, 16, or even 40 channels over a single fiber. The more channels that run over a fiber, the lower the overall costs.
WDM is a method of combining or separating multiple wavelengths of light in (MUX) or out (DE-MUX) of a single strand of fiber, with each wavelength of light carrying a different signal. The incorporation of passive WDM devices reduces the amount of fiber in the network, decreasing both the footprint and investment cost of network roll-outs. In existing networks, these components allow capacity upgrades at a relatively low cost without additional construction works.
Service providers can use the same fiber strand but keep cell site traffic and residential GPON traffic on different wavelengths. Passive C/DWDM modules are put at both ends of the fiber to combine/separate the different wavelengths. Alternatively, traffic on separate fiber strands can be kept; connectivity at the hubs can be designed and closures to appropriately route the traffic.
Overall, the C-RAN architecture is the future of the wireless network and should be seen as a precursor to 5G. It is expected to see it continue to grow and ultimately dominate the way cell sites are deployed.
Navin Vohra is VP, service provider, Asia Pacific for CommScope