What is The Relation between eCPRI, Option 7, Option 7-2x and Split E?
April 4, 2023

The increase in data rates in 5G makes it impractical to continue with the conventional CPRI fronthaul implementation. Moving towards a higher layer split would relax the latency and bandwidth requirements, but then fewer processing functions can be centralized. It is thus critical that the new functional-split architecture takes into account technical and cost-effective trade-offs between throughput, latency, and functional centralization.

Several standards bodies have moved to identify different split points in the radio processing chain that allow for a substantial reduction of the transport capacities in RAN architectures compared to the current approach. So let’s define first the 4 group standards as below:

  1. 3GPP: The 3rd Generation Partnership Project is an umbrella term for a number of standard organizations that develop protocols for mobile telecommunications.
  2. CPRI: The Common Public Radio Interface (CPRI) standard defines an interface between Radio Equipment Control (REC) or DU and Radio Equipment (RE) or RRU. eCPRI is an evolved version of CPRI that targets the 5G data rates with its flexibility and it supports more efficient compression and decompression of data.
  3. SCF: Small Cell Forum is a global organization whose mission is to enable and accelerate the sustainable digital transformation of industry, enterprises, and communities. 
  4. ORAN Alliance: O-RAN ALLIANCE is a worldwide community of mobile operators, vendors, and research & academic institutions with the mission to reshape Radio Access Networks to be more intelligent, open, virtualized, and fully interoperable.

The choice of optimal 5G NR split points depends on specific deployment scenarios. In April 2017, 3GPP announced the selection of option 2 (PDCP/high RLC) as the high-layer split point (F1 Interface) [TS 38.470], while staying open for any of the low-layer split points (option 6 for MAC/PHY split or option 7 for intra-PHY split) [TR 38.816].

5G Functional Split Options

In fact, the option 7 split point has been further diversified by several groups, both in view of different modes of cooperation between multiple radio sites and in view of fixed network transport requirements. For split option 7 (intra-PHY), multiple sub-options have been defined (7.1, 7.2, and 7.3). The main difference between them the blocks are hosted in each option between DU and RU.

For more details about Why Option 7-2x is the best option for the fronthaul between DU and RRU?, you can read the below article:

Why 7.2x split is the Best Split Option?

Another question that may come to your mind is, Why we are using eCPRI in 5G and not CPRI?, actually, CPRI is one possible transport protocol for option 8, however, the answer to this question can read below article:

Why 5G needs moving from CPRI to eCPRI?

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