00:00Hi.
00:01In the last session, we talked about the spectrum allocation
00:04in 5G NR.
00:05We also discussed about some of the concepts in 5G NR,
00:09like carrier aggregation, bandwidth part,
00:12which are important for optimizing the 5G performance
00:15and network efficiency.
00:17Now, in this session, we will be talking about dual connectivity
00:21concept in 5G NR.
00:23Dual connectivity is a feature that
00:26enhances the performance and the reliability
00:28of the modern wireless networks.
00:31Consider a scenario where a 4G eNB
00:34is providing the main coverage for a user device.
00:37And at the same time, the UE can also
00:40connect to a nearby 5G gNB coverage.
00:44If the UE only connects to the 4G eNB,
00:48then it can have the benefit of better coverage.
00:51But the data rates would be relatively low.
00:54And if the UE only connects to the 5G gNB,
00:58then it can enjoy the faster data rates.
01:00But at the same time, it may experience weaker coverage
01:04or frequent handovers due to more limited coverage
01:07of 5G signals, especially on the higher bands.
01:10Now, if you look at the protocol stack,
01:13then you will notice two type of data barriers,
01:15the MCG barrier from the primary node
01:18and the SCG barrier from the secondary node.
01:21MCG stands for master cell group.
01:24And SCG refers to the secondary cell group.
01:28Another important concept is a split barrier.
01:31In case of a split barrier, one of the nodes
01:33forwards the data plane packets to another node
01:36over to the X2 entropy.
01:39And later, the data is combined at the PDCP layer
01:42before it reaches to the core network.
01:45The split barriers can be terminated
01:47at either the primary node or secondary node.
01:50It depends on the network configuration.
01:53It is important to note that for split barriers,
01:56it is generally preferred and recommended
01:59that the primary node and the secondary node
02:01are co-located because there would
02:04be a significant amount of data transfer needs to be routed
02:07over the X2 interface.
02:10If you remember, we discussed about the option 3
02:12during the 5G deployment option session.
02:15So option 3 refers to the dual connectivity
02:18between 5G NR and 4G LTE using a 4G core network.
02:23You can see this in the center architecture
02:25in this picture here.
02:27Now, if the user plane data is split between the MCG and SCG,
02:32then it is known as option 3A.
02:35If the user plane is handled only through the MCG,
02:38this configuration is referred as option 3.
02:42And if the user plane data is managed by the SCG,
02:45this identifies as option 3X.
02:49So you can see in the center architecture for option 3,
02:53user plane data is routed from EPC to E node B.
02:57And then a portion of data is routed to G node B.
03:01And then both E node B and G node B
03:04sends this user plane data to the UE simultaneously.
03:08And later, UE will combine this all data
03:11received from different nodes.
03:12So this is option 3.
03:15Now coming to the option 3A in the left architecture.
03:19This is option 3A.
03:21So here, control plane data is handled by E node B.
03:25But user plane data is directly routed to the G node B
03:29from SCG.
03:31Now, it is not routed by the E node B.
03:34So one stream coming directly from EPC to E node B.
03:38And second stream directly coming from EPC to G node B.
03:42Then they are sending data to the UE
03:44simultaneously over the air.
03:47Now coming to the option 3X in the right architecture.
03:52So this is similar to the option 3.
03:54But here is a small difference.
03:56Now, first, the user plane data is routed from EPC to G node B.
04:01And then one stream is transmitted to the UE
04:05from this G node B. And second stream
04:07is routed to the E node B. And then E node B
04:10will transmit that stream towards the UE.
04:13Dual connectivity offers multiple benefits
04:16to improve network performance and user experience.
04:20With dual connectivity, the UE connects to both nodes
04:24at the same time.
04:25So it has fast and efficient load balancing
04:28across the network.
04:30And our coverage from the millimeter wave bands
04:32may be inconsistent due to its bad propagation characteristics.
04:36So in such scenarios, dual connectivity
04:39can enhance the mobility and robustness of the network
04:43and can ensure more stable connections,
04:45even in challenging environments.
04:48In addition, dual connectivity can
04:50help to accomplish higher data rates and per user throughput
04:54because it can use both the radio access
04:57technologies at the same time.
04:59OK, so that's it for today.
05:01I hope you are pretty much familiar now
05:02with the dual connectivity concept.
05:04In the next session, we will be talking
05:06about 5G flexible numerology.
05:09So stay tuned for the updates.
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