Scheduling in LTE is a process in which the resources on the
shared channel i.e. PDSCH and PUSCH are assigned to users on sub-frame basis. Scheduling done on the basis of below factors:
Users traffic demand, QOS requirements and estimated channel quality.
The scheduling is done by the Uplink and Downlink schedulers which both are situated in eNodeb.
The smallest time/frequency entity that the scheduler may assign is twelve sub carrier (180kHZ) in frequency domain and 1ms in time domain and this is called scheduling blocks.
Resources handled by scheduler in downlink are:
1.Physical resource blocks-PRB
2.PDCCH resource
3.DL power
4.TX Rank
5.Baseband module processing capability
Resources handled by scheduler in Uplink are:
1.PRB
2.PUCCH resources
3.Baseband module processing capability
Downlink scheduling process:
1.UE provides a CQI report
2. DL scheduler assigns resources per RB based on QOS and CQI
3.Resource allocation is transmitted in same TTI as data.
Uplink Scheduling process:
1.UE request UL transmission via scheduling request
2.Scheduler assigns initial resources without detailed knowledge of buffer count
3.More detailed BSR(Buffer status report) follow in connection with data
Transmission Channels priority in scheduling:- For every cell in every TTI(1ms), the Scheduler determines the UEs that are assigned resources. Each radio bearer is given a certain scheduling priority, based on algorithms which take the QCI (QoS Class Identifier) related parameters as input.The UE with the highest priority is selected first for transmission.The different transmissions are prioritized in the following order:
Downlink:-
1.Common channels
2.HARQ retransmission of DCCH
3.Initial transmission of DCCH
4.HARQ retransmission of DTCH
5.Initial transmission of DTCH
Uplink:-
1.Transmission of random access msg3
2.HARQ retransmission
3.Initial transmission of DCCH
4.Initial transmission of DTCH.
Types of scheduling Algorithms: Below are the major types of Scheduling Algorithms:
1.Round Robin
2.Proportional Fair
3.Max C/I
4.Semi-persistant
Will discuss in details about above scheduling algorithms in next blog.
Users traffic demand, QOS requirements and estimated channel quality.
The scheduling is done by the Uplink and Downlink schedulers which both are situated in eNodeb.
The smallest time/frequency entity that the scheduler may assign is twelve sub carrier (180kHZ) in frequency domain and 1ms in time domain and this is called scheduling blocks.
Resources handled by scheduler in downlink are:
1.Physical resource blocks-PRB
2.PDCCH resource
3.DL power
4.TX Rank
5.Baseband module processing capability
Resources handled by scheduler in Uplink are:
1.PRB
2.PUCCH resources
3.Baseband module processing capability
Downlink scheduling process:
1.UE provides a CQI report
2. DL scheduler assigns resources per RB based on QOS and CQI
3.Resource allocation is transmitted in same TTI as data.
Uplink Scheduling process:
1.UE request UL transmission via scheduling request
2.Scheduler assigns initial resources without detailed knowledge of buffer count
3.More detailed BSR(Buffer status report) follow in connection with data
Transmission Channels priority in scheduling:- For every cell in every TTI(1ms), the Scheduler determines the UEs that are assigned resources. Each radio bearer is given a certain scheduling priority, based on algorithms which take the QCI (QoS Class Identifier) related parameters as input.The UE with the highest priority is selected first for transmission.The different transmissions are prioritized in the following order:
Downlink:-
1.Common channels
2.HARQ retransmission of DCCH
3.Initial transmission of DCCH
4.HARQ retransmission of DTCH
5.Initial transmission of DTCH
Uplink:-
1.Transmission of random access msg3
2.HARQ retransmission
3.Initial transmission of DCCH
4.Initial transmission of DTCH.
Types of scheduling Algorithms: Below are the major types of Scheduling Algorithms:
1.Round Robin
2.Proportional Fair
3.Max C/I
4.Semi-persistant
Will discuss in details about above scheduling algorithms in next blog.
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