Demodulation Reference Signal Based Channel State Information Feedback in Ofdm-Mimo Systems

1. A wireless transmit/receive unit (WTRU) comprising: at least one antenna; and a processor, operatively coupled to the antenna, configured to receive from an eNodeB information designating a first plurality of sub-bands; wherein the designated first plurality of sub-bands include a demodulation reference signal (DM-RS) for use by a plurality of WTRUs; wherein a second plurality of sub-bands include data for a single WTRU; wherein the DM-RS for the plurality of WTRUs is transmitted over an antenna port; wherein the antenna port has a selected precoding; and wherein the processor is further configured to utilize the DM-RS to estimate a channel of the designated first plurality of sub-bands; wherein the eNodeB transmits the DM-RS in the first plurality of sub-bands and the data for the single WTRU in the second plurality of sub-bands in a same transmission time interval (TTI).

2. The WTRU of claim 1 wherein the processor is further configured to receive a scrambling indication associated with the DM-RS.

3. The WTRU of claim 1 wherein a plurality of DM-RSs are used to estimate a channel for a plurality of antenna ports of the eNodeB.

4. The WTRU of claim 1 wherein the processor is further configured to receive a channel state information reference signal (CSI-RS) and to estimate a channel using the CSI-RS.

5. A method comprising: receiving, by a wireless transmit/receive unit (WTRU), information designating a first plurality of sub-bands; wherein the designated first plurality of sub-bands include a demodulation reference signal (DM-RS) for use by a plurality of WTRUs; wherein a second plurality of sub-bands include data for a single WTRU; wherein the DM-RS for the plurality of WTRUs is transmitted over an antenna port; wherein the antenna port has a selected precoding; and utilizing, by the WTRU, the DM-RS to estimate a channel of the designated first plurality of sub-bands; wherein an eNodeB transmits the DM-RS in the first plurality of sub-bands and the data for the single WTRU in the second plurality of sub-bands in a same transmission time interval (TTI).

6. The method of claim 5 further comprising receiving, by the WTRU, a scrambling indication associated with the DM-RS.

7. The method of claim 5 wherein a plurality of DM-RSs are used to estimate a channel for a plurality of antenna ports of an eNodeB.

8. The method of claim 5 further comprising receiving a channel state information reference signal (CSI-RS) and to estimate a channel using the CSI-RS.

9. An eNodeB comprising: at least one antenna port; and a processor, operatively coupled to the antenna port, configured to transmit to each of a plurality of wireless transmit/receive units (WTRUs) information designating a first plurality of sub-bands; wherein the processor is further configured to transmit a demodulation reference signal (DM-RS) in the designated first plurality of sub-bands for use by the plurality of WTRUs to estimate a channel of the designated first plurality of sub-bands; and wherein a second plurality of sub-bands include data for a single WTRU; wherein the DM-RS for the plurality of WTRUs is transmitted over an antenna port; wherein the antenna port has a selected precoding; wherein the DM-RS in the first plurality of sub-bands and the data for the single WTRU in the second plurality of sub-bands is transmitted in a same transmission time interval (TTI).

10. The eNodeB of claim 9 wherein the processor is further configured to transmit a scrambling indication associated with the DM-RS.

11. The eNodeB of claim 9 wherein the processor is further configured to transmit a channel state information reference signal (CSI-RS) to the plurality of WTRUs.