invention relates to wireless communication systems, and more particularly to techniques for improving the downlink (DL) spectral efficiency of such systems. 2. Relevant Background Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems. These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies. When a wireless communication system employs multiple antennas at the transmit and receive ends, one way to increase the data rate and/or capacity for such a system is to use multiple-input multiple-output (MIMO) antenna technology to provide multiple parallel channels to the same user. The LTE downlink and LTE uplink use MIMO antenna technology with up to four transmit and four receive antennas to improve data rates and link quality. Uplink MIMO enables four channel streams to be simultaneously transmitted to a user on the same transmit time interval (TTI) by using an open loop transmit diversity scheme. This open loop scheme may be enabled by, for example, one bit per antenna transmission (or one bit per antenna per TTI) and the use of different pre-coding matrices at each transmit antenna. In order to achieve optimum performance with multi-antenna techniques, the precoding matrix design is critical. There are many known precoding algorithms. Two classes of precoding algorithms that are typically used in practice are the following. Pre-coded distributed feedback: The transmitter uses all the channel state information (CSI) available to it, i.e., the complete CSIT, to perform precoding (beam-forming). This method requires that the user equipment (UE) feedback the quantized channel information to the base station in time and frequency synchrony. Pre-coded limited feedback: The transmitter relies on limited UE feedback, based on which it performs quantization of the CSI. Typically, quantization is performed by using antenna selection, which includes the option of leaving out the index of one of the antennas from the feedback. The limited feedback methods differ based on the number of quantization bits and feedback timing (e.g., frequency-selective fading channel or frequency-flat fading channel). When a UE transmits data to a base station using multi-antenna transmission, the receiver should select a precoding matrix, which is the best match to the transmission channel properties. It is often called the precoding codebook. In LTE systems, a precoding codebook is specified in a downlink control channel (PDCCH) message to a UE for each downlink component carrier. These codebooks contain codewords that are used by the UE for channel estimation in the uplink (UL) while being used for downlink transmission. The detailed structure of the codebook depends on system bandwidth, modulation and coding scheme (MCS) and number of streams. For a given bandwidth, modulation scheme and MCS, the codewords are constructed by following a set of rules as listed in Table 1 below. The rule depends on the number of transmit antennas and the number of data streams. TABLE 1Number of datastreams:Number of transmit (Tx) antennas:Number of codewords: 1T (eNB-to-UE)2121211:T2 (eNB-to-UE)2424232:T3 (eNB-to-UE)3232323:T4 (eNB-to-UE)4142134:T6 (eNB-to-UE)616316 4:T9 (eNB-to-UE)9192191:T12 (eNB-to-UE)1212121:T18 (eNB-to-UE)1818181:T24 (eNB-to-UE)2424232:T36 (eNB-to-UE)3636363:T48 (eNB-to-UE)4848484:T6 (eNB-to-UE)614614 4:T72 (eNB-to-UE)7216316 4:T84 (eNB-to-UE)84192192:T96 (eNB-to-UE)96192192:T108 (eNB-to-UE)108108108:T120 (eNB-to-UE)120909101:T144 (eNB-to-UE)144144144:T150 (eNB-to-UE)150120150:T156 (eNB-to-UE)156156101:T168 (eNB-to-UE)168168168:T180 (eNB-to-UE)180181018:T192 (eNB-to-UE)192192192:T216 (eNB-to-UE)21618116101:T240 (eNB-to-UE)240180180:T252 (eNB-to-UE)252172172:T270 (eNB-to-UE)270270270:T288 (eNB-to-UE)280180280:T300 (eNB-to-UE)3018021101:T336 (eNB-to-UE)33618116101:T360 (eNB-to-UE)360360160:T384 (eNB-to-UE)384384384:T420 (eNB-to-UE)4204204204:T480 (eNB-to-UE)480306225:T504 (eNB-to-UE)504306325:T600 (eNB-to-UE)602361256:T648 (eNB-to-UE)648322456:T720 (eNB-to-UE)721482160:T768 (eNB-to-UE)768384384:T816 (eNB-to-UE)816384384:T864 (eNB-to-UE)864384384:T900 (eNB-to-UE)900900900:T960 (eNB-to-UE)960483648:T1008 (eNB-to-