4.2.12 Physical channel mapping

25.2123GPPMultiplexing and channel coding (FDD)Release 17TS

The PhCH for both uplink and downlink is defined in [2]. The bits input to the physical channel mapping are denoted by , where p is the PhCH number and U is the number of bits in one radio frame for one PhCH. The bits v_p,k are mapped to the PhCHs so that the bits for each PhCH are transmitted over the air in ascending order with respect to k.

In compressed mode, no bits are mapped to certain slots of the PhCH(s). If N_first + TGL  15, no bits are mapped to slots N_first to N_last. If N_first + TGL > 15, i.e. the transmission gap spans two consecutive radio frames, the mapping is as follows:

– In the first radio frame, no bits are mapped to slots N_first, N_first+1, N_first+2, …, 14.

– In the second radio frame, no bits are mapped to the slots 0, 1, 2, …, N_last.

TGL, N_first, and N_last are defined in subclause 4.4.

4.2.12.1 Uplink

When UL_DPCH_10ms_Mode is configured, uplink physical channel mapping depends on whether a compressed-mode transmission gap overlaps with the first radio frame in 20ms CI. A distinction is made between the following cases:

4.2.12.1.1 UL_DPCH_10ms_Mode is not configured by higher layers, or, no compressed-mode transmission gap overlaps with the first radio frame in the 20ms CI

In uplink, the PhCHs used during a radio frame are either completely filled with bits that are transmitted over the air or not used at all. The only exception is when the UE is in compressed mode. The transmission can then be turned off during consecutive slots of the radio frame.

4.2.12.1.2 UL_DPCH_10ms_Mode is configured by higher layers, and, a compressed-mode transmission gap overlaps with the first radio frame in 20ms CI

In this case, physical channel mapping is performed over 20ms Compression Intervals (20m CI). Note that as a consequence of radio frame segmentation procedure in Subclause 4.2.6, there are no bit inputs to the second radio frame in one 20ms CI. Denote the bit inputs to the physical channel mapping in a 20ms CI by , where p is the PhCH number and U is the number of bits in one radio frame for one PhCH. Then, the 15 slots used to map the bits are the first 15 slots in the 20ms CI excluding slots in the compressed-mode transmission gap. In other words,

if N_first + TGL  15, i.e., the transmission gap spans only one radio frame, and the mapping is as follows

The 15 slots used for mapping are slots 0 to N_first – 1 in the first 10ms radio frame in the 20ms CI, slots N_last + 1 to slot 14 in in the first 10ms radio frame in the 20ms CI, and slots 0 to TGL – 1 in the second radio frame of the 20ms CI.

Else if N_first + TGL > 15, i.e., the transmission gap spans two consecutive radio frames, the mapping is as follows:

If the transmission gap occurs at the beginning of the first radio frame of the 20ms CI, then the 15 slots used for mapping are slots N_last + 1 to slot 14 of the first radio frame of the 20ms CI and slots 0 to N_last of the second radio frame of the 20ms CI;

Else, if the transmission gap occurs at the end of the first radio frame of the 20ms CI, then the 15 slots used for mapping are slots 0 to N_first – 1 of the first radio frame of the 20ms CI and slots N_last + 1 to N_last + 15 – N_first of the second radio frame of the 20ms CI.

4.2.12.2 Downlink

In downlink, the PhCHs do not need to be completely filled with bits that are transmitted over the air. Values v_p,k {0, 1} correspond to DTX indicators, which are mapped to the DPCCH/DPDCH fields but are not transmitted over the air.

In compressed mode when DL_DCH_FET_Config is configured by higher layers, the mapping of data bits onto the slots of the PhCH is the same as normal mode, with a difference that the data bits that are mapped to slots in a transmission gap are not transmitted over the air.

During compressed mode by reducing the spreading factor by 2, the data bits are always mapped into 7.5 slots within a compressed frame. No bits are mapped to the DPDCH field as follows:

If N_first + TGL  15, i.e. the transmission gap spans one radio frame,

if N_first + 7  14

no bits are mapped to slots N_first,N_first + 1, N_first +2,…, N_first+6

no bits are mapped to the first (N_Data1+ N_Data2)/2 bit positions of slot N_first+7

else

no bits are mapped to slots N_first, N_first + 1, N_first + 2,…, 14

no bits are mapped to slots N_first – 1, N_first – 2, N_first – 3, …, 8

no bits are mapped to the last (N_Data1+ N_Data2)/2 bit positions of slot 7

end if

If N_first + TGL > 15, i.e. the transmission gap spans two consecutive radio frames,

In the first radio frame, no bits are mapped to last (N_Data1+ N_Data2)/2 bit positions in slot 7 as well as to slots 8, 9, 10, …, 14.

In the second radio frame, no bits are mapped to slots 0, 1, 2, …, 6 as well as to first (N_Data1+ N_Data2)/2 bit positions in slot 7.

N_Data1and N_Data2 are defined in [2].