Explain Latency in 4G and its impact on users?


#1

Can anyone please explain Latency in 4G and its impact on users?


#2

Simply time interval between services request and response.


#3

The LTE latency is described as the sum of controlplane (C-plane) and user-plane (U-plane) delays.

The C-plane latency is defined as the transition time between two states, from either RRC_IDLE or DRX (Discontinuous Reception) to RRC_CONNECTED. In LTE, the transition time from RRC_IDLE to RRC_CONNECTED should be less than 100 ms, while the transition from DRX to RRC_CONNECTED
depends on the DRX cycle period.

The U-plane latency, also known as the transport delay, is defined as the one-way transit
time between a packet available at the IP layer of a sender and the availability of the packet at the IP layer of a receiver.

Benifits is if latency is low,we achieve higher throughput, but drawback is ,it consume more power for the processing.

That’s the reason DRX came in LTE.

In LTE, the latency is different in DL and UL directions. In the downlink direction, resource allocation is done in every sub-frame (1 ms).In the uplink direction, when a UE doesn’t have PUSCH (Physical Uplink Shared Channel) resource, the UE has to send a Scheduling Request (SR) to the eNodeB when it wants to send data. The UE is allowed to send SR in PUCCH (Physical Uplink Control Channel) only within a certain interval in a sub-frame, which can be in the same SR cycle, or the UE has to wait for another cycle. In SR, the UE only sends a request for resource to send data in the uplink direction. It
doesn’t contain any information about the amount of data.