When eNodeB decides UEs for resources (RBs), including the number of resources (RBs) to be sent or given- this is scheduling. What is LTE Scheduling? When it comes to LTE, scheduling comes on at per subframe basis. Moreover, the entity that works for this is called the scheduler.
What Is LTE Scheduling?
As was stated at the outset, LTE scheduling is per subframe basis. Moreover, LTE schedulers do different functions for efficiency.
HARQ (ARQ + FEC)
This allows recovery. Recovery from residual errors. Moreover, this is done by link adaptation.
This controls the neighboring cells’ interference. In addition, this is responsible for providing the correct SINR level. This is crucial in coming up with an accurate data rate.
On the other hand, the packet scheduler arbitrates access to air interface resources.
Rate control does resource allocation. Moreover, this comes among radio bearers of the same UE. But this should be available at the eNB for DL. Also, with the UE for UL.
Moreover, this distributes air interface resources. This is on a per TTI basis for selected active users.
Another is the Link Adaptation. This selects the combination of parameters. Moreover, these parameters include modulation, transmit schemes, and channel coding.
Three Types Of Scheduling
LTE MAC supports three different types of scheduling. Namely, dynamic, persistent, and semi-persistent scheduling.
This type of scheduling can be done with different services. But this comes with the expense of the Control Signalling.
Moreover, in every TTI, MAC checks for UEs for scheduling. Also the availability of data for each UE for scheduling. Another is the UE feedback in channel conditions.
In addition, using these data and with the help of PDCCH. Scheduling of resources for UE is possible.
With persistent scheduling, Packets are scheduled on a fixed basis. Which is more similar to Circuit Switched. However, in this case, it does not depend on the condition of the channel. Plus, consistency for resource allocation is also observed throughout the call period.
This type of scheduling is a hybrid way. That is because this overcomes the lapses of both preceding schedules. Namely, persistent and dynamic scheduling.
Three Types Of Schedulers
Round Robin or the RR Scheduler
It speaks from its name. Because this works in a round-robin manner. This goes both in selecting and scheduling UEs. As a result, this produces a more equal resource share.
However, a disadvantage of this is that it reduces the overall cell throughput. This is because of the UEs with optimal CQI. These are distributed PRBs.
This scheduler selects the possible UE schedules. However, this is based on experienced CQI. Thus, the highest CQI’s become the possible scheduling. As a result, this increases the overall cell throughput.
On the other hand, this can also result in a lower user experience. That is because of the UEs’ lower CQI. These might result in denied scheduling instances and starves throughput.
Moreover, PFS performs by considering both resource fairness and maximum cell throughput.
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