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Some resources are for common use e.g. synchronisation signals, PBCH(MIB), System information,
RACH message(preamble), RAR message, DL/UL allocation information, cell specific reference signals,
so on.
Some resources are for dedicated use e.g. UE dedicated allocations to carry SRB/DRB loads
(including HARQ retransmissions), signalling (scheduling requests, power control, timing adjustments,
HARQ acknowledgements), UE specific reference signals, DL CSI measurement reporting, so on.
Transport block is basically data along with PDCP/RLC/MAC headers.
After FEC coding (Phy/DSP function) of a transport block , we get a codeword.
PDCCH, PUCCH, PRACH, Synchronisation signals, and Reference signals (both common and UE specific) would
fall under control information.
PDSCH and PUSCH would hold codeword.
We already mentioned that at each TTI, scheduler need to decide resource allocation.
This automatically brings time separation between resources.
Also, we may choose different RBs or resource elements for different allocations, indicating frequency separation.
However, with techniques like CDMA, Multi-user diversity (pre-coding based MU-MIMO),
and beam forming , it is possible to have multiple allocations in same frequency and time region.
This effectively increase the amount of resources for allocations.
Below perspectives mainly cover selection criteria (that could be used by scheduling algorithm).
UE selection require selection of DL/UL resource either for DL/UL signalling (including reference signals)
and/or for transfer of DL/UL transport block or codeword.
Question here is: how to select a UE - in round robin fashion, random order, based on its age in the queue,
based on its buffer volume, or based on some other non-radio parameters.
Idea is to not to let starve or ignore any UE.
RR method is of course the simplest algorithm.
It possibly most fair, but not necessarily most efficient.
Users, even with poor conditions or smaller payloads get to use the resources,
but do not add much to system capacity
(assuming only certain number of UEs are processed in a TTI time).
Each bearer type (SRB or DRB or Common bearer) and their allocated QoS parameters are to be honoured during selection process.
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