IQ imbalance compensation for IFDMA systems

摘要

Interleaved frequency division multiple access (IFDMA) has drawn much attention and is standardized for uplink physical layer protocol in 3GPP LTE. IFDMA combines the advantages of single-carrier and multi-carrier solutions, i.e., it provides a low PAPR as well as low complexity for user separation. However, IFDMA is closely related to multi carrier transmission and hence, it is also expected to be sensitive to In-phase/Quadrature-phase (IQ) imbalance caused by the frequency conversion at the transceiver. In this report, first, we analyze the effect of transmitter (Tx) IQ imbalance at the received signal and show that the Tx IQ imbalance causes a serious interference at the received signal only between a certain pair of users. Making use of this fact, we propose a joint pairwise Tx IQ imbalance compensation and channel equalization scheme for IFDMA receivers. Linear receivers based on zero-forcing and minimum mean-square error criterion are proposed and both of them can be efficiently implemented in discrete frequency domain.