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In this paper, a precoding OFDMA uplink technique is proposed for the upcoming 4G cellular system. Such as IEEE 802.16m and 3GPP LTE, both of them are 4G candidates. We especially tackle the common carrier frequency offset (CFO) problem which brings the inter carrier interference (ICI) and multiple access interference (MAI). The main idea of this paper is the proposed QR dirty paper coding (QR-DPC) method, which is based on QR decomposition. Assisted with block diagonalization (BD) algorithm, we successfully utilize the precoding technique to eliminate the annoying MAI in a multiuser uplink system. Thus, the combination of BD and QR-DPC can significantly increase the BER performance as compared to conventional DPC. Moreover, we can further enhance the performance of QR-DPC by using the famous Water Pouring algorithm. Simulation results confirm that the proposed system can provide excellent performance under the ICI, MAI, and multipath interference environment.