I-RNTI (inactive RNTI)

Last updated on 17 Apr 2023

The Radio Network Temporary Identifier (RNTI) is a unique identifier used by the 4G and 5G cellular networks to identify and manage the communication between the User Equipment (UE) and the Base Station (BS). RNTI plays a vital role in resource allocation, scheduling, and mobility management. In this context, an Inactive RNTI (I-RNTI) is a type of RNTI that is temporarily not in use by the UE.

In this article, we will delve into the concept of I-RNTI, its significance, and its role in 4G and 5G networks.

Background

Before we dive into I-RNTI, it is essential to understand the basics of RNTI. As mentioned earlier, RNTI is a unique identifier used in the 4G and 5G cellular networks to identify and manage the communication between the UE and the BS. RNTI consists of two parts: C-RNTI (Cell Radio Network Temporary Identifier) and U-RNTI (UE Radio Network Temporary Identifier).

C-RNTI is assigned by the BS to the UE to identify the UE within the cell. On the other hand, U-RNTI is assigned by the Radio Resource Control (RRC) protocol to the UE to identify the UE for the purpose of radio resource allocation and scheduling.

In the 4G and 5G networks, the UE can have multiple RNTIs assigned to it simultaneously. For example, the UE can have one C-RNTI and multiple U-RNTIs. The UE can switch between these RNTIs based on the communication requirements and network conditions.

What is I-RNTI?

Now that we have understood the basics of RNTI let us move on to I-RNTI. I-RNTI is a type of RNTI that is temporarily not in use by the UE. The UE can request the BS to assign an I-RNTI to it when it does not have any active communication with the BS.

There are several scenarios when the UE may not have any active communication with the BS. For example, the UE may be in a dormant state, where it is not actively transmitting or receiving any data. In this case, the UE can request the BS to assign an I-RNTI to it.

Similarly, the UE may be in an idle state, where it is not actively using any data services. In this case, the UE can request the BS to assign an I-RNTI to it. The BS can assign an I-RNTI to the UE, and the UE can use it to request resources from the BS when it needs to use data services.

Significance of I-RNTI

I-RNTI plays a crucial role in resource allocation, scheduling, and mobility management in 4G and 5G networks. When the UE requests an I-RNTI from the BS, the BS assigns a unique I-RNTI to the UE, which is not in use by any other UE in the cell. The UE can use this I-RNTI to request resources from the BS when it needs to use data services.

When the UE requests resources from the BS, it uses the I-RNTI to identify itself to the BS. The BS uses the I-RNTI to locate the UE in its database and allocate resources to the UE. Since the I-RNTI is unique to the UE, the BS can easily identify the UE and allocate resources to it.

I-RNTI also plays a crucial role in mobility management. When the UE moves from one cell to another, it needs to inform the new BS of its presence. The UE uses the I-RNTI to inform the new BS of its presence. The new BS then uses the I-RNTI to locate the UE in its database and establish a connection with the UE. This helps in seamless handover and reduces the latency in the handover process.

Another significant advantage of I-RNTI is that it allows the UE to conserve power. When the UE is not actively transmitting or receiving any data, it can request the BS to assign an I-RNTI to it. This helps in conserving the UE's battery, as the UE does not need to continuously monitor the radio interface for any incoming data. The UE can simply use the I-RNTI to request resources from the BS when it needs to use data services.

Moreover, I-RNTI allows the network to manage its resources more efficiently. When the UE requests an I-RNTI, the BS can allocate fewer resources to the UE as it is not actively using any data services. This helps in optimizing the network resources and reducing the network congestion.

I-RNTI in 4G and 5G Networks

In the 4G network, the UE can request an I-RNTI from the BS when it is in the RRC_IDLE state. In this state, the UE is not actively using any data services and is waiting for any incoming data. The BS can assign an I-RNTI to the UE, and the UE can use it to request resources from the BS when it needs to use data services.

In the 5G network, the concept of I-RNTI is extended to support the new network architecture. The UE can request an I-RNTI from the BS when it is in the RRC_INACTIVE state. In this state, the UE is not actively using any data services and is waiting for any incoming data. The BS can assign an I-RNTI to the UE, and the UE can use it to request resources from the BS when it needs to use data services.

In the 5G network, the I-RNTI is used in conjunction with the new concept of Radio Resource Control (RRC) inactive state. When the UE is in the RRC_INACTIVE state, it is not actively using any data services, and its context is stored in the BS. The UE can request the BS to assign an I-RNTI to it, which can be used to activate the UE when it needs to use data services. When the UE needs to use data services, it sends a request to the BS with the I-RNTI, and the BS activates the UE and assigns an active RNTI to it.

Conclusion

In conclusion, I-RNTI is a crucial component of 4G and 5G cellular networks. It allows the UE to conserve power, optimizes network resources, and enables seamless mobility management. The concept of I-RNTI is extended in the 5G network to support the new network architecture and the concept of RRC inactive state. I-RNTI is expected to play an even more significant role in the 5G network, where the focus is on low latency, high data rates, and massive connectivity.