20/04/2024
Moving from optical components in RAN to optical components for RAN
Since the second mobile systems generation in the 1990s, the RAN capacity has grown exponentially [1]. Moving from 4G to 5G, this trend shows no sign of slowing down: peak data rate (maximum download speed) increased more than 60 times and traffic demand (data load on networks) increased 10 times. In particular, the fifth-generation mobile networks introduced several improvements from previous generations, including higher data rates enabled by much wider spectrum allocations. As an example, while the maximum spectrum width for LTE is 20 MHz, 5G NR can achieve up to 100 MHz in mid-band, and up to 800 MHz in high bands. The race for the spectrum allocations in the fifth-generation mobile systems goes in parallel with that for the rollouts of 5G networks: by 2027, it is expected that 5G networks will carry 62 percent of total mobile data traffic [2]. The increase in traffic is not the only aspect that differentiates 5G from previous mobile system generations. In highly populated cities, densification of the network (traffic load per square kilometer) is as important as the capability to deal with a high concentration of users. Analysts say that big cities will be served with 1 or 2 petabytes per square kilometer by 2025 [3]. Consequently, the mobile transport network follows a similar evolution in capacity and density. All this results in a need for increasingly high data rates in the transport network, pointing to the growing importance of optical solutions in mobile networks. Another way to illustrate the growing importance of optics in RAN is depicted in Figure 1, where the total bill of material (BoM) cost for a radio unit (RU) is shown with the pluggable optics cost portion for three different mobile generations (3G WCDMA in 2009, 4G LTE in 2014, and 5G NR in 2022). As can be seen, the relative cost portion of the optics has roughly doubled with 5G NR.