NAS:
The Non-Access Stratum is a set of protocols in the Evolved Packet System. The NAS is used to convey non-radio signalling
between the User Equipment (UE) and the Mobility Management Entity (MME) for an LTE/E-UTRAN access.
CQI: Channel Quality Indicator
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Indicates that how traffic should be handled on LTE network. QCI values indicate a certain priority level for traffic
on a network.
indicates different QoS performance characteristics of each IP packet.
 resource type (GBR or non-GBR)
 Priority
 Packet delay budget
 Packet error loss rate
QCI values seem to be mostly used by eNBs in controlling the priority of packets delivered over radio links.
Which Physical Channel Carriers CQI Value?
CQI is carried by PUCCH or PUSCH depending on the situation as follows.
 Carried by PUCCH: Periodic CQI
 Carried by PUSCH: Aperiodic CQI (and Periodic CQI)
GBR: Guaranteed Bit Rate
The default bearer is always a non-GBR bearer, with best effort data rates. Let’s look at non-GBR
bearers to understand the need for GBR bearers: As the Uu (Air) interface is shared between many
UEs, each can transfer data. Let’s take an example of a cell with two UEs in it and not much
bandwidth available. If UE1 and UE2 are both sending the same amount of data, it’ll be evenly split
between the two. But if UE1 starts sending a huge amount of data (high bit rate) this will impact on
the other UEs in the cells ability to send data over the air as it’s a shared resource. So, if UE2 needs
to send a stream of small but important data over the air interface, while UE2 is sending huge
amounts of data, we’d have a problem.
To address this, we introduce the concept of a Guaranteed Bit Rate. We tell the eNB that the bearer
carrying UE2’s small but important data needs a Guaranteed Bit Rate and it reserves blocks on the
air interface for UE2’s data. So now we’ve seen the need for GBR there’s the counter point – the
cost. While UE1 can still continue sending but the eNB will schedule fewer resource blocks to it as it’s
reserved some for UE2’s data flow. If we introduced more and more UEs each requiring GBR bearers,
eventually our non-GBR traffic would simply not get through, so GBR bearers must be used
sparingly.