Mumbai University > Electronics and Telecommunication > Sem 7 > Mobile Communication

Marks: 10 M

QoS refers to the ability (or probability) of the network to provide a desired level of service for selected traffic on the network.

• Service levels are specified in terms of throughput, latency (delay), jitter (delay variation) and packet errors or loss.
• Different service levels are specified for different types or streams of traffic.
• To provide QoS, the network identifies or “classifies” different types or streams of traffic and processes these traffic classes differently to achieve (or attempt to achieve) the desired service level for each traffic class.
• The effectiveness of any QoS scheme can be measured based on its ability to achieve the desired service levels for a typical combination of traffic classes (“traffic profile”)

The QOS/queuing algorithms for LTE

The QoS level of granularity in the LTE evolved packet system (EPS) is bearer, which is a packet flow established between the packet data network gateway (PDN-GW) and the user terminal (UE or MS). The traffic running between a particular client application and a service can be differentiated into separate service data flows (SDFs).

SDFs mapped to the same bearer receive a common QoS treatment (e.g., scheduling policy, queue management policy, rate shaping policy, radio link control (RLC) configuration). A bearer is assigned a scalar value referred to as a QoS class identifier (QCI), which specifies the class to which the bearer belongs. QCI refers to a set of packet forwarding treatments (e.g., scheduling weights, admission thresholds, queue management thresholds, and link layer protocol configuration) preconfigured by the operator for each network element. The class-based method improves the scalability of the LTE QoS framework. The bearer management and control in LTE follows the network-initiated QoS control paradigm, and the network initiated establishment, modification, and deletion of the bearers.

LTE Bearers

1. Guaranteed Bit rate (GBR): Dedicated network resources related to a GBR value associated with the bearer are permanently allocated when a bearer becomes established or modified.

2. Non-guaranteed Bit rate(non-GBR) A service utilizing a non-GBR bearer may experience A non-GBR bearer is referred to as the default bearer, which is also used to establish IP connectivity, similar to the initial Service Flow in WiMAX. Any additional bearer(s) is referred to as a dedicated bearer and can be GBR or non-GBR.

The following are QoS attributes associated with the LTE bearer: