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Due to aggressive goals for future communication systems, direct-conversion receivers are an attractive option in terms of compactness and power dissipation. However, the price to pay is an additional impairment introduced by IQ imbalance, which might be compensated by appropriately designed DSP algorithms. In this context, joint recovery of carrier phase and IQ gain/phase imbalance has been presented...
Theoretical research on coordinated multi-point (CoMP) in the cellular uplink claims large improvements in spectral efficiency and fairness. However, the real-world implementation of CoMP is linked with major challenges such as multi-cell synchronization and multi-cell channel estimation, which have to be addressed to make sure that CoMP finds its way into next generation cellular systems (e.g. LTE-Advanced)...
Underlay ultra wideband (UWB) systems have to be able to detect the presence of primary systems operating in the same band for detect-and-avoid (DAA) operation. In this paper, the performances of joint and independent detection of multiple primary systems are investigated assuming that the primary systems are potentially dependent (e.g., frequency division duplex uplink-downlink communications). Joint...
In this paper, the loop-delay analysis and the complexity consideration of the joint carrier synchronization and equalization algorithm for OFDM systems are presented. As a result, the loop-delay induces an additional phase lag and further gives rise to instability for the dual-loop carrier synchronization loop. In addition, the complexity consideration shows that the presented algorithm definitely...
A two-hop relaying system where a source communicates with its destination through multiple relay nodes is studied for capacity maximization. Amplify-and-forward (AF) relaying is adopted for its simplicity. Taking the independent channel transfer function of different subcarriers and links into consideration, we formulate a resource allocation optimization problem for joint subcarrier assignment,...
In OFDMA cellular system, the inter-cell interference is the main interference of the system, which greatly degrades the system performance. In order to enhance cell average throughput and the cell-edge user's peak bit rate, a hybrid inter-cell interference mitigation scheme is proposed. The hybrid scheme combines the fractional frequency reuse scheme and the frequency hopping scheme, in which cell-edge...
In OFDM-based systems, data symbols are usually transmitted together with pilots, which are used for channel estimation or prediction. More pilots in use can further improve the accuracy of channel estimation or prediction. However, this can also result in the efficiency loss of channel gain allocated for data transmission. In this paper, we investigate the joint pilot and data adaptation regarding...
In this paper, a joint carrier synchronization and equalization algorithm is proposed for OFDM systems in the tracking stage. Significantly, the carrier synchronization scheme is a dual-loop, which is composed of an outer and an inner loops, with the multirate processing to eliminate the carrier frequency offset and the channel phase variation. In addition, the gain equalization loop is employed to...
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