基于DCT-SC-FDMA的混合子载波映射方法

Hybrid Subcarrier Mapping Method Based on DCT-SC-FDMA

LTE-A中上行采用单载波频分多址(SC-FDMA)技术,下行采用正交频分多址(OFDMA)技术。本文主要研究上行SC-FDMA技术,利用离散余弦变换(DCT)代替离散傅里叶变换(DFT),并基于DCT-SC-FDMA系统,提出了一种不同于传统的交织式映射(IFDMA)和集中式映射(LFDMA)的混合子载波映射(HFDMA)方法。仿真结果表明,在峰均比(PAPR)性能与LFDMA相似的情况下,本文提出的DCT-HFDMA方法在误比特率(BER)方面性能有一定的提高。

Single carrier frequency division multiple access(SC-FDMA)technology and orthogonal frequency division multiple access(OFDMA)technology are adopted in the LTE-A uplink and downlink,respectively.Because the characteristic of the user equipment transmission power is limited,the uplink multiple access method with lower PAPR,termed as SC-FDMA access method,is proposed in the protocol of3GPP.It has the advantages of both single and multicarrier scheme,and the structure and properties are similar to OFDMA.SC-FDMA access method has low PAPR of the transmitted signal power and can cover a larger area.In this paper,we shall consider the problem of uplink SC-FDMA and use discrete cosine transform(DCT)instead of discrete Fourier transform(DFT)to improve the performance of BER.This proposed method can attain better spectral energy compression performance and can make the energy be concentrated in the low frequency part such that the ISI can be reduced obviously.Moreover,DCT uses a real number operation which is different from the DFT complex operation.This proposed method can reduce the processing complexity and phase imbalance of the signal.Besides,this paper also proposes hybrid subcarrier mapping(HFDMA)method based on DCT-SC-FDMA system,which is different from the traditional interleaved mapping(IFDMA)and localized mapping(LFDMA).The proposed method is structurally spread over the whole frequency resource and there are some continuous subcarrier blocks at the same time.This allocation method can improve the robustness of the system to frequency offset.Simulation results show that the proposed DCT-HFDMA method can effectively improve the performance of BER under the situation that the peak to average ratio(PAPR)performance is similar to that of LFDMA.