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Avsolute Grants

• Absolute Grants
  • Only the serving Node-B can issue an absolute grant
  • An absolute grant is addressed to a specific UE (like HS-SCCH)
  • Max rate (pointer in the E-TFC set) is explicitly signaled to the UE
  • Useful to rapidly ramp up or down the rate of an E-DCH
  • Each grant contains
    • E-RNTI to uniquely identify the UE
    • Granted rate
    • SingleProcess flag
  • The SingleProcess flag specifies whether the absolute grant applies to only one HARQ process or all HARQ processes
  • Upon reception, UE sets its max E-TFCI pointer to the value specified in the grant
  • Absolute grant is sent over the E-AGCH shared downlink physical channel

Index	Absolute Grant Value
31	(168/15)2x6
30	(150/15)2x6
29	(168/15)2x4
28	(150/15)2x4
27	(134/15)2x4
26	(119/15)2x4
25	(150/15)2x2
24	(95/15)2x4
23	(168/15)2
22	(150/15)2
21	(134/15)2
20	(119/15)2
19	(106/15)2
18	(95/15)2
17	(84/15)2
16	(75/15)2
15	(67/15)2
14	(60/15)2
13	(53/15)2
12	(47/15)2
11	(42/15)2
10	(38/15)2
9	(34/15)2
8	(30/15)2
7	(27/15)2
6	(24/15)2
5	(19/15)2
4	(15/15)2
3	(11/15)2
2	(7/15)2
1	ZERO_GRANT*
0	INACTIVE*

Relative Grants

• Relative Grants
  • Relative grants are a slower but less expensive way to control the max E-TFCI
  • The serving cell issues an UP, DOWN or HOLD relative grant
  • A non-serving cell issues HOLD or DOWN relative grant
  • Relative grants are transmitted over the E-RGCH downlink signaling channel
  • Relative rate control commands can be dedicated to a UE, common to a group of UEs, or common to all UEs in the cell, depending on which E-RGCH channels are specified for monitoring by the UEs
  • Non-primary cells can issue relative rate grants to users in SHO for adjacent-cell interference mitigation
• How the Serving Grant work ?
  • NodeB controls the UE bit rate by Serving Grants. A Serving Grant defines the power offset between E-DPDCH and DPCCH physical channels and there is 38 power offset values defined.
  • RNC signals a set of reference power offsets, that define a E-TFCI and the corresponding power offset, eight references at maximum.
  • NodeB and UE calculates the rest of E-TFCI and power offset mappings from the reference power offsets by formulas. The result gives a mapping table where each power offset value defines a certain transport block size.
  • Absolute grant command explicitly defines a certain power offset value from the power offset table. There is only 31 different values available with absolute grant command, so not all serving grants can be denoted. The blue ones in the example table are the ones available with AG.

Index	Scheduled Grant/ DPDCH power offset	E-TFCI (TB index)	TB size
37	(168/15)2*6	NoValue	NoValue
36	(150/15)2*6	NoValue	NoValue
35	(168/15)2*4	120	19950
34	(150/15)2*4	110	16572
33	(134/15)2*4	80	11514
32	(119/15)2*4	76	10824
31	(150/15)2*2	72	10152
		??
13	(27/15)2	8	708
12	(24/15)2	6	540
11	(21/15)2	5	522
10	(19/15)2	3	354
9	(17/15)2	NoValue	NoValue
8	(15/15)2	NoValue	NoValue
7	(13/15)2	1	186
6	(12/15)2	NoValue	NoValue
5	(11/15)2	NoValue	NoValue
4	(9/15)2	NoValue	NoValue
3	(8/15)2	NoValue	NoValue
2	(7/15)2	NoValue	NoValue
1	(6/15)2	NoValue	NoValue
0	(5/15)2	0	18

A relative grant command defines UP or DOWN step in the serving grant table, so it is not usable as such but it needs a reference power offset from where to make the UP/DOWN step. The reference power offset is NOT the serving grant that the NodeB has previously indicated to the UE, but it is a power offset value that UE has used in past transmission. Which transmission is used as a reference is defined by a strict timing, that is equal to HARQ acknowledgement timing on E-HICH channel. The Serving Grant Update procedure shall be applied at every TTI boundary and shall take into account the Absolute Grant message, Serving Relative Grant and non-serving Relative Grants that apply to the TTI.

PO index	AG index	PO_str	PO_val	SgToEtfci(i)
37	31	(168)^2*6	169344	54
36	30	(150)^2*6	135000	54
35	29	(168)^2*4	112896	54
34	28	(150)^2*4	90000	54
33	27	(134)^2*4	71824	54
32	26	(119)^2*4	56644	54
31	25	(150)^2*2	45000	54
30	24	(95)^2*4	36100	54
29	23	(168)^2	28224	54
28	22	(150)^2	22500	54
27	21	(134)^2	17956	54
26	20	(119)^2	14161	54
25	19	(106)^2	11236	54
24	18	(95)^2	9025	52
23	17	(84)^2	7056	44
22	16	(75)^2	5625	38
21	15	(67)^2	4489	32
20	14	(60)^2	3600	28
19	13	(53)^2	2809	24
18	12	(47)^2	2209	20
17	11	(42)^2	1764	18
16	10	(38)^2	1444	14
15	9	(34)^2	1156	12
14	8	(30)^2	900	9
13	7	(27)^2	729	8
12	6	(24)^2	576	4
11	-	(21)^2	441	4
10	5	(19)^2	361	0
9	-	(17)^2	289	0
8	4	(15)^2	225	0
7	-	(13)^2	169	0
6	-	(12)^2	144	0
5	3	(11)^2	121	0
4	-	(9)^2	81	0
3	-	(8)^2	64	0
2	2	(7)^2	49	0
1	-	(6)^2	36	0
0	-	(5)^2	25	0