Resource Allocation Type 1 uses the same
number of RA bits as in Resource Allocation Type 0 but allows Resource
Allocation on an individual RB level even for larger bandwidths.
The Resource Allocation Information
consists of NRBG bits which will indicate the UE about a set of VRBs
(Localized Type) from one of the P
RBG subsets. The number of RBG subsets (P)
is same as RBG size (P) in RA Type 0
which is as given below:
In an RBG subset number p, where 0 ≤ p < P, it is possible to allocate every Pth RB starting from pth
RB and this allocation can be done using a bitmap.
A total of ⎾NRBDL/P⏋bits are required
for resource allocation as in RA Type 0. Resource Block assignment consists of
3 fields.
The First field with ⎾log2 (P)⏋ bits used to indicate the selected
RBG subset number among P RBG
subsets.
The second field with one bit is used
to indicate a shift of the resource allocation span within a subset. A bit
value of 1 indicates shift is triggered. Shift is not triggered otherwise
The third field indicates a bitmap,
where each bit of the bitmap addresses a single VRB in the selected RBG subset.
The VRB is allocated to the UE if the corresponding bit value in the bit field
is 1, the VRB is not allocated to the UE otherwise. The portion of the bitmap used to
address VRBs in a selected RBG subset has size NRBTYPE1
and is defined as:
NRBTYPE1 = ⎾NRBDL/P⏋—
⎾log2 (P)⏋ — 1
The addressable VRB numbers of a
selected RBG subset start from an offset, ∆shift(p) to the
smallest VRB number within the selected RBG subset, which is mapped to the MSB
of the bitmap. The offset is in terms of the number of VRBs and is done within
the selected RBG subset. If the value of the bit in the second field for shift
of the resource allocation span is set to 0, the offset for
RBG subset p is given by ∆shift(p)
= 0. Otherwise, the offset
for RBG subset p is given by ∆shift(p)
= NRBRBGsubset(p) — NRBType1,
where the LSB of the bitmap is justified with the highest VRB
number within the selected RBG subset. NRBRBGsubset(p) is the number of VRBs in RBG subset p and can be calculated by the following
equation,
Consequently, when RBG subset p is indicated, bit i for i = 0, 1, …, NRBType1
— 1 in the bitmap field indicates VRB number
Example:
Example:
Let us consider NRBDL
= 15. From the above table, number of RBG subsets (P) is 2. In this case, 1-bit (log2
(2)) is required to indicate the RBG subset number. One more bit is used to indicate
whether a shift is used or not. NRBTYPE1
= 8-1-1 = 6 bits are used for actual resource allocation bitmap. The resource allocation
is illustrated below:
Let the resource allocation bits are 00110011. MSB
indicates RBG subset number, second bit indicates if shift is enabled or not.
Remaining 6 bits indicate the bitmap of resource allocation of PRBs. In this
case, RBG subset 0 is chosen without a shift. Using the remaining 6 bits
110011, RB numbers 0, 1, 8, and 9 are allocated to the UE. Similarly, if
resource allocation bits are 11110011 ⇨ RB numbers 3, 6, 11, and 14 are
allocated to the UE.
Reference: 3GPP TS 36.213
