No abstract

Fractional frequency reuse (FFR) and exploitation of the channel state information at the transmitter (CSIT) are effective approaches to improve the spectrum efficiency of the outer coverage region. When channels vary within a physical transmission frame, the above improvement is substantially suppressed. To remedy this, this paper develops new FFR patterns for multi-cell OFDMA systems with frequency or time division duplexing (FDD/TDD) in time-varying channels. Simulation results show notable performance gains of the proposed schemes over the existing ones.

Next generation wireless systems require much higher data rate supports and hence larger bandwidths than the existing systems. Due to the compatibility requirement with the existing legacy systems and the constraints on the availability of contiguous spectrum, bandwidth (or carrier) aggregation has recently emerged as a practical means for supporting high data rate requirement of next-generation systems. A practical issue associated with the bandwidth or carrier aggregation is the significant increase of the peak-to-average power ratio (PAPR) of the time-domain signal. This paper proposes a low-complexity PAPR reduction method for bandwidth aggregated systems with orthogonal frequency division multiplexing / multiple-access (OFDM/OFDMA) or single-carrier frequency division multiple access (SC-FDMA). The proposed approach adopts the existing selective mapping concept, but with some modifications for substantially reducing complexity and signaling overhead, while adapting to carrier-aggregated systems. Performance evaluation under 3GPP LTE-Advanced environment shows PAPR reduction advantage of the proposed method while not requiring any signaling overhead.

New generation wireless systems target to support much higher data rate which requires larger bandwidth than the existing systems. Lack of contiguous spectrum resources and the compatibility requirement with the legacy systems make the concept of carrier aggregation (CA) a practical means for supporting high data rate in next generation systems. One of the practical issues related to the CA is the dramatically increased peak-to-average power ratio of the time domain signal. This article proposes several low-complexity and no-overhead PAPR reduction methods for bandwidth aggregated systems with orthogonal frequency division multiplexing/multipleaccess or single-carrier frequency division multiple access in multi-in multi-out system configurations. For the proposed phase-rotation based PAPR reduction methods, a reliable phase rotation detector at the receiver is developed to maintain the receiver performance. Performance evaluation under 3GPP LTE-Advanced environment shows the advantage of the proposed methods while not requiring any signaling overhead.