SLIV

SLIV is the Start and Length Indicator for the time domain allocation for PDSCH. One of the big difference between LTE and NR scheduling is that NR schedules not only for slot but also the symbols within the scheduled slot, whereas in LTE the schedule is done only for subframe level (not for the symbol levels within the scheduled subframe).

SLIV defines the start symbol and the number of consecutive symbols for PDSCH and PUSCH allocation using Single Number. Often, SLIV is considered to be very confusing because you need to figure out two quantities(start and length) from the single value.

• How a single number SLIV value get interprented to start symbol and number of symbol ?
• How the SLIV value get configured into RRC message ?
• SLIV Mapping Table
• Sample Log
• Get the Test Procedure and Log / Amarisoft TechAcademy

How the single number(SLIV) can represent the two different quantity (i.e, start symbol and number of consecutive symbols) ? It is possible because SLIV is created by a specific rule as  defined in 38.214 5.1.2.1 Resource allocation in time domain as follows.

NOTE : With this formula, you can easily figure out SLIV value if you are given the start symbol and the number of symbols, but it is not that simple to figure out start and symbol length from a given SLIV.  To figure out start and length of symbols from a given SLIV value, it would be handy to use a lookup table in this page.

if (L-1) <= 7 then

      SLIV = 14 x (L-1) + S

else

      SLIV = 14 x (14-L+1) + (14-1-S)

          , where 0 < L <= 14 - S

                   S = Start Symbol Index

                   L = Number of Consecutive Symbols

According to the above equation, you can create a huge tables with the possible S and L values. But not all of the combinations are taken as valid.  Only the set of combinations meeting the condition in the following table is allowed. Following table is from Release 15 specfication.

< 38.214-Table 5.1.2.1-1: Valid S and L combinations >

< 38.214-Table 6.1.2.1-1: Valid S and L combinations >

NOTE : The above table has been changed as follows in Release 16.

< 38.214 V16.4.0 -Table 5.1.2.1-1: Valid S and L combinations >

< 38.214 V16.4.0 -Table 6.1.2.1-1: Valid S and L combinations >

How the SLIV value get configured into RRC message ?

PDSCH/PUSCH mapping type in the above table is specified in RRC message as shown below.

PDSCH-TimeDomainResourceAllocation ::=      SEQUENCE {

    k0                                  INTEGER (1..3)

    mappingType                         ENUMERATED {typeA, typeB},

    startSymbolAndLength                BIT STRING (SIZE (7)) // SLIV

}

PUSCH-TimeDomainResourceAllocation ::=  SEQUENCE {

    k2                                  INTEGER (0..7)                          

    mappingType                         ENUMERATED {typeA, typeB},

    startSymbolAndLength                BIT STRING (SIZE (7)) // SLIV

}

SLIV Mapping Table

Applying the equation shown above and  38.214-Table 5.1.2.1-1, I have created a big table as below.

Following is the SLIV values that I calculated according to the formnula described above. You can use SLIV value as a key value to find out a unique pair of (S, L) in a look-up table. (NOTE : If you clicked on the linked page, you will get an example of PDSCH scheduling for a specific SLIV that I created using Matlab 5G Toolbox)

Reference

[1]