5G(NR): UL Resource allocation


5G(NR): UL Resource allocation

Resource allocation in time domain:

             When the UE is scheduled to transmit a transport block and no CSI the report, or the UE is scheduled to transmit a transport block and a CSI report(s) on PUSCH by a DCI, the Time domain resource assignment field value m of the DCI provides a row index m + 1 to an allocated table.

           Indexed row defines slot offset K2, the start symbol S and the allocation length L, and the PUSCH mapping type to be applied in the PUSCH transmission.

        When the UE is scheduled to transmit a PUSCH with no transport block and with a CSI report(s) by a CSI request field on a DCI, the Time-domain resource assignment field value m of the DCI provides a row index m + 1 to an allocated table which is defined by the higher layer configured pusch-TimeDomainAllocationList in pusch-Config. 


=>  The slot where the UE shall transmit the PUSCH is determined by K2 as

=> where n is the slot with the scheduling DCI, K2 is based on the numerology of PUSCH,  and Mu PUSCH and Mu PDCCH are the subcarrier spacing configurations for PUSCH and PDCCH, respectively.

=> The starting symbol S relative to the start of the slot, and the number of consecutive symbols L counting from the symbol S allocated for the PUSCH are determined from the SLIV(start and length indicator value) of the indexed row:



  => The PUSCH mapping type is set to Type A or Type B as defined in Subclause 6.4.1.1.3 of [4, TS 38.211] as given by the indexed row.

The UE shall consider the S and L combinations defined in table 6.1.2.1-1 as valid PUSCH allocations



Determination of the resource allocation table to be used for PUSCH (6.1.2.1.1).                Table 6.1.2.1.1-1 defines which PUSCH time domain resource allocation configuration to apply. Either a default PUSCH time-domain allocation.









Default PUSCH time domain resource allocation A for normal CP: Table- 6.1.2.1.1-2: 

        According to table 6.1.2.1.1-2, is applied, or the higher layer configured pusch-TimeDomainAllocationList in either pusch-ConfigCommon or pusch-Config is applied. 

Row index
PUSCH mapping type
S
L
1
Type A
j
0
14
2
Type A
j
0
12
3
Type A
j
0
10
4
Type B
j
2
10
5
Type B
j
4
10
6
Type B
j
4
8
7
Type B
j
4
6
8
Type A
j+1
0
14
9
Type A
j+1
0
12
10
Type A
j+1
0
10
11
Type A
j+2
0
14
12
Type A
j+2
0
12
13
Type A
j+2
0
10
14
Type B
j
8
6
15
Type A
j+3
0
14
16
Type A
j+3
0
10

Definition of value j: Table 6.1.2.1.1-4: 

                  Table 6.1.2.1.1-4 defines the subcarrier spacing specific values j. j is used in the determination of in conjunction with table 6.1.2.1.1-2, for normal CP or table 6.1.2.1.1.-3 for extended CP, where is the subcarrier spacing configurations for PUSCH.           

µPUSCH
j
0
1
1
1
2
2
3
3

Definition of value Delta (Δ): Table 6.1.2.1.1-5: 

       Table 6.1.2.1.1-5 defines the additional subcarrier spacing specific slot delay value for the first transmission of MSG3 scheduled by the RAR. When the UE transmits an MSG3 scheduled by RAR, the Δ value specific to MSG3 subcarrier spacing µPUSCH is applied in addition to the K2 value. 

µPUSCH
Δ
0
2
1
3
2
4
3
6


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5G-NR: Channels

5G-NR: Channels

Introduction:
         In this blog, we will discuss all types of changes, their functionality, and channel mapping in short. Like LTE, NR channels are the same.


Mainly there are three types of channels :
1- Logical channels
2- Transport channels
3- Physical channels 




1- Logical Channels:
           Logical channels are functioning between RLC and MAC layers. There are 5 types of logical channels. Logical channels are further divided into two groups, Fist is control channels and second is traffic channels. below are the logical channels and their short description.

1- BCCH (Broadcast control channels)
2- PCCH (Paging control channels)
3- CCCH (Common control channels)
4- DCCH (Dedicated control channels)
5- DTCH (Dedicated traffic channels)  => Traffic channel


1- BCCH (Broadcast control channels):
             The network always transmits the BCCH over the air in the downlink. This is downlink broad channels.(gNB --> UEs).  it is used to transmit the system information messages like SIBs and MIB in the downlink. 

 => In 5G NSA(non-standalone mode), system information is not transmitted over BCCH channels. it is transmitted via master note i.s. LTE eNodeB.

 => in 5g SA(Standalone mode), system information(MIB and SIBs) transmitted through the BCCH channel.

2- PCCH (Paging control channels):
             PCCH is also a downlink channel and it is used for transmitting paging information from the network to devices. whenever the network needs to find out the devices, then the network uses the PCCH channel for paging information.
             It can also be used to transmit the system information change notification and an indication of ongoing PWS (public warning system) broadcast.

 => In 5G NSA(non-standalone mode): paging is not transmitted over PCCH channels. it is transmitted via master note i.s. LTE eNodeB.

 => in 5g SA(Standalone mode), paging transmitted through the PCCH channel.

3- CCCH (Common control channels):
             CCCH is used by a device to establish or re-establish an RRC(radio resource control) connection. this is referred to as SRB(Signaling radio bearer) 0.


4- DCCH (Dedicated control channels):
            This is a two-way channel for the transfer of control information when the device has an RRC connection. SRBs when DCCH is activated including 

SRB -1: This is used for RRC message
SRB -2: This is used for NAS(non-access stratum) messages and has a lower priority than SRB -1.
SRB -3: This is newly introduced in 5G NSA(non-standalone mode ). this is used to configure measurements, MAC, RLC, physical layer parameters as well as RLF(radio link failure) parameters.

5- DTCH (Dedicated traffic channels):
              This is a point to point channel that may exist in the uplink and downlink. It is a part of DRB(Data radio Bearer) assigned to the devices. this channel is mainely used for transfring the userdata


2-Transport channel:
           Transport channels are functioning between MAC layer and Physical layer. there are 5 types of Transport channels. 

1- BCH  (Broadcast channel)
            This is a broadcast channel that is a part of the SS(Synchronization signal) block. it includes the MIB.

 2- DL-SCH  (Downlink chared channel)
            This channel supports dynamic scheduling and dynamic link adaptation by varying the antenna mapping, modulation, coding scheme, and resources/power allocation. In addition, it supports HARQ (Hybrid automatic repeat request) operation to improve performance.

 3- PCH  (Paging Channel)
            This channel is used to carry the PCCH, It utilizes DRX(discontinuous reception) to improve the battery life.

 4- UL-SCH  (Uplink shared channel)
             This is similar to DL-SCH, it used for uplink data transmission. It also supports the DRX algorithems for device power saving.


5- RACH (Random access channel)
            This channel carries limited information and is used in configuration with physical channel and preamble to improve contention resolution procedure.

This channel is also defined in the transport channels, although it does not carry transport block.










3- Physical Channels:
      Physical channels are used to transmit the signals on the air. There are 6 types of Physical channels. in which three channels are downlink channels and the other three channels are uplink channels.
1-PBCH     (Physical broadcast channel)
2-PD-SCH  (Physical downlink shared channel)
3-PDCCH   (Physical downlink control channel)
4-PRACH   (Physical Random access channel)
5-PU-SCH  (Physical uplink shared channel)
6-PUCCH   (Physical uplink control channel)
1-PBCH(Physical broadcast channel)
            The network always transmits the BCCH over the air in the downlink. This is downlink broad channels.(gNB --> UEs).  it is used to transmit the system information messages like SIBs and MIB in the downlink. 

 => In 5G NSA(non-standalone mode), system information is not transmitted over BCCH channels. it is transmitted via master note i.s. LTE eNodeB.

 => in 5g SA(Standalone mode), system information(MIB and SIBs) transmitted through the BCCH channel.

2-PD-SCH(Physical downlink shared channel)
          This channel supports dynamic scheduling and dynamic link adaptation by varying the antenna mapping, modulation, coding scheme, and resources/power allocation. In addition, it supports HARQ (Hybrid automatic repeat request) operation to improve performance.
it is also used for--
- Unicast data transmission
- Random access responce message
- delevery part of System information messages

3-PDCCH(Physical downlink control channel)
            This channel is used for downlink control information(DCI). downlink control information is necessary for proper reception and decoding of downlink user data.

4-PRACH(Physical Random access channel)
          This channel carries limited information and is used in configuration with physical channel and preamble to improve contention resolution procedure.
            This channel is also defined in the transport channels, although it does not carry transport block.

5-PU-SCH(Physical uplink shared channel)
        This is similar to DL-SCH, it used for uplink data transmission. It also supports the DRX algorithms for device power saving.


6-PUCCH(Physical uplink control channel)
                      This channel is used for uplink control information(DCI). uplink control information is necessary for scheduling and HARQ procedure.
 Channel Mapping:









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5G-NR: Carrier Aggregation (CA)



5G-NR: Carrier Aggregation (CA)

Description:

        when there is no CA in the picture,  UE will receive and transmit data on a single carrier, this carrier is called primary component carrier and the corresponding cell is called a primary serving cell. In case of carrier aggregation, one or more component carriers are aggregated with the primary component carrier in order to support wider transmission bandwidth. 

Carrier Aggregation:

       Carrier Aggregation feature is introduced in the initial version of Release-15 of 3GPP Specifications. 5G New Radio uses carrier aggregation of multiple Component Carriers (CCs) to achieve high-bandwidth transmission (and hence high data rate). 

In LTE, you can aggregate a maximum up to five carriers that is one primary component carrier and four secondary component carriers. But in 5G NR supports aggregation of up to 16 components carriers.

    Carrier aggregation is designed to support aggregation of a variety of different arrangements of CCs, including CCs of the same or different bandwidths, adjacent or non-adjacent CCs in the same frequency band, including CCs of the same or different numerologies and CCs in different frequency bands. Each CC can take any of the transmission bandwidths, namely (5, 10, 15, 20, 25, 30, 40, 50, 60, 80, 90, 100) MHz for FR1 & (50, 100, 200, 400) MHz for FR2 respectively.




 A UE that is configured for carrier aggregation connects to one Primary Serving Cell (known as the ‘PCell’ in MCG or ‘PSCell’ in SCG) and one or more Secondary Serving Cell (known as ‘SCell’).
All RRC connections and Broadcast signalings are handled by the Primary serving cell. The primary Serving cell is the master of the whole procedure. Primary serving cell decides that which serving cell need to be aggregated or added and deleted from the Aggregation.

      
Now we will look into the role of Primary serving cell and secondary serving cell in terms of carrier aggregation.

 1- Role of Primary serving cell: followings are the role of primary serving cell.

=> Dynamically add or remove the secondary component carriers.
=> Dynamically activate and deactivate the secondary cell.
=> Handle all RRC(Radio resource control) and NAS(non-access stratum) procedures.
=> Receive measurement reports and control mobility of UE.

Note: Primary serving cell can be changed only at the time of handover.
2- role of Secondary serving cell: followings are the role of secondary serving cell.
=> An UE can aggregate maximum up to 16 component carrier where 1 is primary component carrier and 15 are secondary component carrier. (In case of LTE it is 1PCC and 4 SCC).
=>Actual number of secondary serving cell that can be allocated to UE is dependents on UE capability.

 Note: It is not possible to configure an UE with more UL CCs than DL CCs, while revere of this can be possible.

 ==================================================================
There are mainly three ways by which component carriers can be allocated.

 1- Intra Band Contiguous:
 In this Primary component carrier and secondary component carrier is configured with same band but they are contiguous.



2- Intra Band Non-Contiguous:

   In this Primary component carrier and secondary component carrier is configured with same band but they are not contiguous.



3-inter band Contiguous:

 In this Primary component carrier and secondary component carrier  are allocated on two frequency band.





By using the above configuration, infinite combinations are possible. But 3GPP has defined allowed combinations

Denoting Band combination:
CA_X:
        Denotes intra band contiguous CA
        e.g CA_10(band)

CA_X-X:
        Denotes intra band non-contiguous CA
        e.g CA_10-10

CA_X-Y:
        Denotes inter band contiguous CA
        e.g CA_10-20

Precondition for CA:
     UE can be configured CA only when it is capable to support CA. UE informs its  capability to the network during registration procedure in "UE capability information" message to network.




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