5.12 MIMO operation of HS-DSCH

25.2243GPPPhysical layer procedures (TDD)TS

5.12.1 General procedure

This section applies only when a UE is configured in MIMO mode.

The general transmitter structure to support MIMO operation of HS-PDSCH transmission is shown in figure 11A. Channel coding, interleaving and spreading are done the same as in non-MIMO mode. The Node B scheduler can decide to transmit one or two transport blocks to a UE in one TTI. The spread complex valued signals are fed to both TX antenna branches, and weighted with precoding weights.

If the UTRAN schedules a single transport block to a UE in one TTI, it uses EBB (Eigenvector Based Beam-forming) or antenna selection for transmission of that transport block on the HS-PDSCH sub-frame. If the UTRAN schedules two transport blocks to a UE in one TTI, it uses two orthogonal precoding vectors to transmit the two transport blocks. The precoding vectors are generated by SVD (Singular Value Decomposition) of the channel matrix or grouped beam-forming to form the two beams. The PARC with two transmit antennas can be viewed as a special case, where the stream per antenna is transmitted independently.

Figure 11A: The generic downlink transmitter structure to support MIMO operation for HS-PDSCH transmission.

The Node B estimates the uplink channels seen from each antenna by uplink physical channels or standalone midamble channel. The Node B scheduler decides whether to schedule one or two transport blocks to a UE in one TTI and what transport block size(s) and modulation scheme(s) to use for each of them. The Node B determines the precoding vectors applied on the HS-PDSCH sub-frame and forms the beams to the UE. The associated HS-SCCH type for single or dual stream HS-DSCH transmission is signaled to the UE. The UE transmits the CQI report and ACK/NACK of each stream to the Node B via the associated HS-SICH.

5.12.2 Identification of MIMO dual stream

When the UE is configured in MIMO mode and the dual stream transmission is adopted, the two streams are called stream1 and stream2 respectively. According to the special default midamble allocation scheme, the Node B shall allocate the pattern1 to stream1, and the pattern2 to stream2. The UE identifies and detects two transport blocks in one TTI according to the different patterns.

5.12.3 UE antennas time switched transmission

When the UE is configured in MIMO mode, uplink time switched transmission at the UE with two antennas for uplink physical channels, i.e. HS-SICH, E-PUCH, DPCH and standalone midamble channel if configured by higher layers, is used for uplink channel estimation.

The UE switches the two antennas to transmit the uplink physical channels HS-SICH, E-PUCH, and DPCH and standalone midamble channel among the uplink timeslots which may belong to one TTI or multiple TTIs allocated by UTRAN. The downlink signaling HCSN and ECSN are used to guarantee the identification of the two UE antennas and the exact update of the two channel estimation vectors at Node B. Note that time switched transmission is not applied to the random access uplink physical channel.

If the standalone midamble channel is not configured, the UE antennas time switched transmission procedures for uplink physical channels are described below.

– If the allocated resource for the UE includes multiple uplink timeslots in one TTI, the UE shall transmit the uplink physical channels in every timeslot by using the antenna selected according to the received downlink signaling value and the predefined relationship between UE and Node B. The details are as follows:

– If there is an HS-SICH in this TTI, the Node B implicitly informs the UE by HCSN on HS-SCCH which antenna shall be used to transmit HS-SICH. The UE shall use the antenna indicated by the parity of HCSN decimal value to transmit HS-SICH. Based on the reference antenna carrying HS-SICH, the UE switches the transmit antennas in turn for the consequent uplink transmission in this TTI;

– Else if there is no HS-SICH but scheduled E-PUCH in this TTI, the Node B implicitly informs UE by ECSN on E-AGCH which antenna shall be used to transmit the first timeslot of E-PUCH. UE shall use the antenna indicated by the parity of ECSN decimal value to transmit first timeslot of E-PUCH. And based on the reference antenna carrying the first timeslot of E-PUCH, the UE switches the transmit antennas in turn for the consequent uplink transmission in this TTI;

– Else, the UE shall take the antenna used to transmit the uplink channel in the first timeslot of this TTI as reference and switch the transmit antennas in turn in the consequent uplink timeslots in this TTI. The reference antenna is the other antenna different from the one used last time for this transmission type which may be non-scheduled transmission, semi-persistent transmission and RDI E-PUCH transmission.

– Else, the allocated resource for the UE just include one uplink timeslot in one TTI, the UE shall select the antenna according to the different uplink channel.

– If there is an HS-SICH in this uplink timeslot, the UE shall select the antenna indicated by the parity of HCSN decimal value on the associated HS-SCCH;

– Else if there is no HS-SICH but scheduled E-PUCH in this uplink timeslot, the UE shall select the antenna indicated by the parity of ECSN decimal value on E-AGCH;

– Else, the UE shall select the other antenna different from the one used last time for this transmission type which may be non-scheduled transmission, semi-persistent transmission and RDI E-PUCH transmission.

If the standalone midamble channel is configured, the UE antennas time switched transmission procedures for uplink physical channels are described below.

If the UE needs to transmit an HS-SICH, the UE shall use a different antenna from the one used for HS-SICH to transmit the associated standalone midamble channel in the other uplink timeslot of the same subframe configured by higher layers.

If there is other uplink physical channel(s) besides HS-SICH in subframe for the UE to transmit, the standalone midamble channel shall be omitted.