Tuesday 25 November 2014

21:48 - No comments

MAC Scheduler - by developer point of view

MAC scheduler:
The MAC scheduler is part of MAC from a logical view and the MAC scheduler should be independent from the PHY interface.
The interface is defined as a service access point offered by the MAC scheduler to the remaining MAC functionality, as shown in below Figure. A _REQ primitive is from MAC to the MAC scheduler. A _IND/_CNF primitives are from the MAC scheduler to the MAC.


Figure shows the functionality split between the MAC scheduler and the remaining MAC. For the purposes of describing the MAC scheduler interface the MAC consists of a control block and a subframe block, which uses the CSCHED and SCHED SAP respectively. The subframe block triggers the MAC scheduler every TTI and receives the scheduler results. The control block forwards control information to the MAC scheduler as necessary. The scheduler consists of the following blocks:
UL Is responsible for scheduling of the PUSCH resources.
DL Is responsible for scheduling of the PDSCH resources.
PDCCH/RACH Is responsible for shared resources between UL and DL.
HARQ Is responsible for handling HARQ retransmissions, keeping track of the number of retransmissions and redundancy versions.
Cell Cfg Stores the UE configuration needed by the MAC scheduler.
UE Cfg Stores the UE configuration needed by the MAC scheduler. LC Cfg Stores the logical channel configuration needed by the MAC scheduler. Sched Cfg Stores the scheduler-specific configuration needed by the MAC scheduler.

CSCHED – MAC Scheduler Control SAP:

CSCHED_CELL_CONFIG_REQ/CNF: 
CSCHED_UE_CONFIG_REQ/CNF:
CSCHED_LC_CONFIG_REQ/CNF:
CSCHED_LC_RELEASE_REQ/CNF:
CSCHED_UE_RELEASE_REQ/CNF:
CSCHED_CELL_CONFIG_UPDATE_IND:
CSCHED_UE_CONFIG_UPDATE_IND:

SCHED - MAC Scheduler SAP:

DL
SCHED_DL_RLC_BUFFER_REQ:
SCHED_DL_PAGING_BUFFER_REQ:
SCHED_DL_MAC_BUFFER_REQ:
SCHED_DL_TRIGGER_REQ:
SCHED_DL_RACH_INFO_REQ:
SCHED_DL_CQI_INFO_REQ:
SCHED_DL_CONFIG_IND:

UL
SCHED_UL_TRIGGER_REQ:
SCHED_UL_NOISE_INTERFERENCE_REQ:
SCHED_UL_SR_INFO_REQ:
SCHED_UL_MAC_CTRL_INFO_REQ:
SCHED_UL_MAC_CTRL_INFO_REQ:
SCHED_UL_CONFIG_IND

Tuesday 11 November 2014

21:39 - 2 comments

LTE RBs and their mapping between PDCP RLC MAC

LTE Radio Bearer



Query:
One UE can have the maximum 11 RB's ( 3 SRB and 8 DRB) as per the 36.331. I have referred like there is a one to one mapping between the RB's and LCID's at MAC level. But we have only LCID's 1 - 10. LCID 1 & 2 for SRB1,SRB2, rest are for DRB's. In this case how can we map among them.

Ans:
if you look closely you will find SRB0 is on CCCH and all others are on DCCH and DTCH . 

And all the data goes through as MAC PDU isn't it and it has a MAC header ,you might have gone through the MAC header which is something like this 
|R |R |E | LCID | 

now LCID has value of 00000 for CCCH which is for SRB0 and the missing DRB which you were not able to map. 

for all other values 00001 to 01010 identity of the logical channels starting from SRB1 till the others.