5G represents a new stage in the evolution of mobile communications history. Above all, it will revolutionize mobile data transfer by providing higher capacities within individual mobile radio cells. However, the new features of 5G are not limited to enabling better use of mobile data. The 5G network also offers a range of other possibilities. The future of broadband for consumers and businesses such as autonomous cars, smart communities, AI & IoT and even to immersive education will all rely on the speed and reliability 5G carries out.

5G is the answer to increasing data traffic:

Data traffic continues to grow unceasingly around the world. Network operators face the immense challenge of meeting demand for fast, ubiquitous data links by providing faster, larger wireless networks.

A communications standard, not a wireless standard:

The digital connections between people and machines are evolving at breakneck speed. This calls for powerful networks and an appropriate infrastructure. Increasing data volumes require faster data transfer.

Flexible provision of network infrastructure:

5G will set new standards. It will meet future requirements for data speed, network capacity, latency, and data security

Centralized/Cloud-RAN and CPRI

The C-RAN approach advocates for the separation of the radio elements of the base station (called remote radio heads, RRHs) from the elements processing the baseband signal (so called baseband units, BBUs), which are centralized in a single location or even virtualized into the cloud. This approach benefits from simpler radio equipment at the network edge, easier operation, and cheaper maintenance, while the main RAN intelligence (BBUs) is centralized in the operator-controlled premises. The challenge of C-RAN deployments is that such a functional split requires these two elements to be connected through a high-speed, low-latency, and accurately synchronized network, the so-called fronthaul. 5G networks will move towards centralizing the radio function using an eCPRI based fronthaul. The main objective here is to limit the electronics needed at the antenna site. This lowers cost as air conditioning is not needed at the antenna site.

Splitting the 5G RAN

  • Connects the 4G/5G core to the CU.
  • A latency of ~40ms may be tolerable on this link.
  • The 5G core may be up to 200 km away from the CU
  • Connects the CU with the DU.
  • The latency on the link should be around 1ms.
  • A centralized CU may be controlling DUs in an 80 km radius.
  • Fronthaul latency is constrained to 100 microseconds.
  • A DU may be serving RUs up to 10 km away.
Table 1. Radio access sites and functions

Physical Layer Network Variants at C-RAN & Pros/Cons

Physical Layer Connect PROs CONs
Dark Fiber Run Simple Lowest Latency Fiber Cost No Network Monitoring
Passive WDM Cost-effective, Low Bandwidth at Fronthaul Fiber Cost, No Network Monitoring
Active WDM Fiber Cost Save, OAM & Network Reliability High Hardware Cost
NG-PON2 Cost-effectiveness, Latency No OAM, Optics Cost
Wireless (mmWave, FSO) Fast & Agile Network, Fiber-free Limited Network Reach
Table 2. C-RAN Architecture Options

LIGHTRON is a primary contributor of Korea 5G NR Deployment which started as of the end of 2018. A wide range of optical transceiver products implement the advancements tailored to diverse roles and benefits of different 5G networks by different CSP (communication service provider) in Korean market.

O-band over C-band at Optics Selection

LIGHTRON optics portfolio for 5G NR technically aims for fiber-line efficiency and reduced OPEX by using quality-proven short-wavelength optics. Low dispersion in O-band allows simple 25G NRZ transmission without need for dispersion compensation. On the other hand, long wavelength (C/L-band) benefits still exist but are not compelling enough to offset the loss and cost from high dispersion.

Band C-band O-band
Dispersion High Low
Loss Low Insignificant in application
FEC Yes & Costly (Optional)
Reach 10km at 25G 40km at 25G
Cost High Low
Delivery Long Manageable
Table 3. Comparison of C-band and O-band Optical Spectrum