Latency and Jitter impact in LTE Volte services

Latency and Jitter impact in LTE Volte services 


The jitter and latency are used as the metrics to measure the performance of the network. The main difference between the jitter and latency lies within their definition where latency is nothing but a delay through the network whereas the jitter is variation in the amount of the latency.

The jitter and Latency are the crucial metrics to monitor and measure the network performance. Latency is the period starting from the transmission of the packet from the sender to the reception of the packet at the receiver. On the other hand, the jitter is the difference between the forwarding delay of the two consecutive received packets in the same streams

Latency :-latency is simply a measured delay, the time it takes for a task to occur.

In term of VoIP ,LTE services 

Latency is defined as the average time between the transmission of packet and the reception of an acknowledgment.

Low latency is a key performance index for better user experience. 

• The delay between a person speaking, and the recipient on the other end of the phone hearing those words
• The time it takes for the VoIP solution to actually process and convert the voice information into data packets
• Time of ping test result (transmitted data and received response )
• latency is “the delay before a transfer of data begins following an instruction for its transfer.”

Impact of Latency :-

• Quality of phone call
• Slow data experience
• Poor browsing experience
• Long pause and overlapping noises or words 
• Loss of service at worst impact of high letency 

What increases Latency :-

• Hardware envolved on nodes for packet routings and some of them have limited capacity of routing packets in UL/DL
• Wireless interface with abnormal signal deviation /poor coverage 
• Distance between devices increase latency 
• High congestion in network 

Measurement of Latency and tolerable range 

• latency cannot be eliminated from existence , so it can be minimised and it's favour services as low it is.
• Latency is measured in milliseconds (Ms) usually
• C-Plane latency < 100ms best 
• U-Plane latency < 10ms best
• One way latency <150ms
• Two way latency < 300ms
• 

Jitter :-Cisco defines Jitter as “a variation in the delay of received packets,” meaning that Jitter is actually a differentiation within the latency (or delay) between each data packet.

jitter is the difference between the delays of the IP packets. In other words, when the delay of latency of the variate through the network it causes jitter. It can be explained with an example, assume four packets are sent at times 0, 1, 2, 3 and received at 10, 11, 12, 13, the delay between the packets are same in all packets which is 10 units of time. In the different case, if these packets arrive at 11, 13, 11, and 18, then the generated delay is 11, 12, 9, 15 which will be different from the above case.

Impact of Jitter :-

• Packets are sent “in a continuous stream with the packets spaced evenly apart.” However, due to network congestion, Cisco says that “this steady stream can become lumpy, or the delay between each packet can vary instead of remaining constant.”
• Congestion in the network can cause jitter while latency can be produced through propagation delay, switching, routing and buffering.