In LTE, the cell selection and handover process is based on a technology called “Carrier Aggregation” (CA). CA allows multiple carriers to be aggregated together to increase the data rates and capacity of the network. The user equipment (UE) can be connected to one or more carriers depending on the available frequency bands and their capabilities.

On the other hand, in 5G NSA (Non-Standalone) mode, the cell selection and handover process is based on a technology called “Dual Connectivity” (DC). DC allows the UE to be connected to both 4G and 5G networks simultaneously, with the 4G network serving as the anchor and the 5G network providing additional capacity and speed. This enables a smoother transition from 4G to 5G as more 5G networks become available.

In summary, CA in LTE allows multiple carriers to be aggregated together to increase capacity and data rates, while DC in 5G NSA allows the UE to be simultaneously connected to both 4G and 5G networks, providing additional capacity and speed.

let’s look at an example to better understand the differences between Carrier Aggregation (CA) in LTE and Dual Connectivity (DC) in 5G NSA.

Suppose a UE is connected to an LTE network that supports CA. The network has two carriers, Carrier A and Carrier B, with Carrier A operating at a frequency of 1800 MHz and Carrier B operating at a frequency of 2600 MHz. The UE supports both carriers and is capable of aggregating them to increase its data rate.

When the UE needs to transmit a large amount of data, it can be assigned to both carriers, and the data will be split between them. The UE will receive signals from both carriers, and it will use a process called “Multiplexing” to combine the data transmitted over both carriers into a single stream. This results in higher data rates and increased capacity.

Now let’s consider a 5G NSA network that supports DC. Suppose the UE is connected to a 4G LTE network that serves as the anchor, and it is also connected to a 5G NR (New Radio) network for additional capacity and speed. When the UE is in an area with 5G coverage, it can connect to the 5G network and use its additional capacity to increase data rates.

The UE will receive data from both the 4G and 5G networks, and it will use a process called “Multiplexing” to combine the data transmitted over both networks into a single stream. This results in higher data rates and increased capacity.

However, unlike CA in LTE, DC in 5G NSA does not aggregate carriers from the same frequency band. Instead, it uses two separate networks with different frequency bands to provide additional capacity and speed.

In summary, CA in LTE allows carriers from the same frequency band to be aggregated to increase capacity and data rates, while DC in 5G NSA allows the UE to be simultaneously connected to both 4G and 5G networks, providing additional capacity and speed by using two separate frequency bands.

points to consider:

• In LTE, CA is typically used when there are multiple carriers available in the same frequency band, which is common in many LTE deployments. The UE can aggregate up to five carriers in LTE-A, depending on the UE’s capabilities and the network’s configuration.

• In 5G NSA, DC is used when 5G coverage is limited, and the UE needs to fall back to the 4G network to maintain connectivity. DC can also be used to take advantage of the additional capacity and speed provided by the 5G network when it is available.

• In 5G SA (Standalone) mode, DC is replaced by a technology called “Splitting” or “Split Session Handling,” which allows the UE to establish separate connections to both the 4G and 5G networks without relying on the 4G network as an anchor. This enables a more seamless transition from 4G to 5G and supports new 5G use cases that require low latency and high reliability.

• Both CA in LTE and DC in 5G NSA require additional signalling and processing overhead to manage the multiple connections and carriers. This can impact battery life and network performance, especially in high-mobility scenarios.

• As more 5G networks become available and 5G coverage expands, DC is expected to become less important and eventually phased out as 5G SA becomes the dominant mode of operation for 5G networks.

• In LTE, Carrier Aggregation (CA) can be used to increase the data rates and capacity of the network. For example, if a UE is capable of receiving two carriers simultaneously, it can receive data from both carriers and combine them to achieve higher data rates.

• In 5G NSA, Dual Connectivity (DC) can be used to provide additional capacity and speed by simultaneously connecting the UE to both 4G and 5G networks. The 4G network serves as the anchor, while the 5G network provides additional capacity and speed.

• DC in 5G NSA can also be used to support advanced features like Ultra-Reliable Low-Latency Communication (URLLC) and Enhanced Mobile Broadband (eMBB), which require low latency and high throughput.

• Both CA in LTE and DC in 5G NSA require UE and network support, and the actual data rates and capacity improvements depend on various factors, such as the number and quality of carriers, UE capabilities, network congestion, and signal strength.

• In 5G SA, carrier aggregation is still used to increase the data rates and capacity of the network. However, DC is replaced by a technology called “dual connectivity with control plane separation” (DC-CP), which allows the UE to establish separate connections to both the 4G and 5G networks without relying on the 4G network as an anchor.

• DC-CP in 5G SA enables faster handovers between the 4G and 5G networks, which is important for supporting new 5G use cases like autonomous vehicles and industrial automation that require seamless connectivity and low latency.

• Both CA in LTE and DC in 5G NSA/SA are important technologies that enable higher data rates, increased capacity, and support for new use cases in mobile networks. As 5G networks continue to evolve, these technologies are likely to play an important role in delivering the full potential of 5G.