Types of Splits:
We have three categories of splits
- High Layer Splits
- Low Layer Splits
- Double Splits
- High Layer Split: It consist of split 2,3,4 & 5.The benefits of opting this functional splits are drastically reduced bandwidth, latency tolerant i.e for long distances.
- Low Layer Split: It consists of split 6,7 &8. The benefits of opting this functional split are cost effective RRH, Ideal for COMP. It has High Bandwidth requirements and very tight latency requirements.
- Double Split: Double splits are the splits in which two splits have been considered between RAN i.e CU,DU & RU. Practically we have two double a) Option 2 & 6 , b) option 2 & 7.2.
Below figure represents the functional split:
Choosing a Functional Split:
When considering the functional split defining a fronthaul interface there are two competing interests:
a) There is a benefit in keeping an O-RU as simple as possible because size, weight, and power draw are primary deciding considerations and the more complex an O-RU, the larger, heavier and more power-hungry the O-RU tends to be.
b) There is a benefit in having the interface at a higher level which tends to reduce the interface throughput relative to a lower-level interface – but the higher-level the interface, the more complex the O-RU tends to be.
- To resolve this, O-RAN has selected a single split point, known as “7-2x” but allows a variation, with the precoding function to be located either “above” the interface in the O-DU or “below” the interface in the O-RU.
- O-RUs within which the precoding is not done are called “Category A” O-RUs while O-RUs within which the precoding is done are called 27 “Category B” O-RUs.
- When O-RU Category A is supported by O-DU it is mandatory to support a total number of precoded streams of up to 8. Support for more than 8 precoded streams is optional.
Stay tuned for more updates on Split option 7.2x which is an ORAN Split.