Research On Hybrid Multiple Access Technique Based On Interleave Division Multiple Access

OFDM has been become a major candidate for future mobile communicationstransmission standard since its outstanding advantages. However, OFDM systems havetwo technical problems， such as high peak-to-average power ratio (PAPR) andfrequency offset sensitivity. In recent years, Single Carrier Frequency Division MultipleAccess（SC-FDMA） is proposed for PAPR problem. SC-FDMA has the advantages ofmulti-carrier communications, it has single-carrier modulation structure and lowerPAPR. Therefore, SC-FDMA is fit for the uplink of wireless communication system. Interms of the study for carrier frequency offset, although it has been considerablecomplete, few researches on OFDM related to the evolution of technology is carried out.Moreover, in general the carrier synchronization algorithms for OFDM are notappropriate for other evolution systems. For each OFDM system will need specificsynchronization scheme. Therefore, the new systems related to OFDM were faced withnew carrier synchronization trouble.OFDM-CDMA system is the combination schemes of OFDM and CDMA.According to the paper PAPR problem in OFDM-CDMA systems, we propose thecombination of SC-FDMA instead of OFDM and CDMA, and calledSC-FDMA-CDMA. SC-FDMA-CDMA performs better than OFDM-CDMA in PAPRfor uplink, and its BER performance is close to OFDM-CDMA. In addition, thetechnology can also implement mixture of resource scheduling. Simulation resultsverify the above conclusions.OFDM-IDMA is a novel wireless communication scheme based on OFDM and interleave division multiple access (IDMA). OFDM-IDMA is proposed for somedisadvantages and difficulties related to OFDM-CDMA systems. The study of thisarticle focuses on two technical problems of OFDM-IDMA based on multi-carriertechnology program.According to OFDM-IDMA suffers a PAPR problem, in this paper, we propose ahybrid multiple access scheme for LTE uplink, which combines IDMA and SC-FDMA,named as SC-FDMA-IDMA. This hybrid multiple access scheme inherits manyattractive features of SC-FDMA and IDMA. We discuss the performance comparison ofSC-FDMA-IDMA and OFDM-IDMA. Theoretical analysis and simulation results showthat SC-FDMA-IDMA performs better than OFDM-IDMA in PAPR for LTE uplink, andits BER performance is close to OFDM-IDMA.For the carrier frequency offset present in multi-carrier system will bring outinter-carrier interference (ICI), resulting in multiuser interference (MUI), which is thesame as that of OFDM-IDMA systems. And ICI and MUI will damage the mechanismof chip-by-chip (CBC) iterative detection and degrade the system performance. In thispaper, we build the model of carrier frequency offset (CFO) for OFDM-IDMA andstudy the effect of CFO on the performance of OFDM-IDMA. When the users have thesame CFO, we research a carrier synchronization method based on CBC iterativedetection. This method employs the reconstructed signal of exterior information asvirtual training sequence to estimate the residual frequency offset in frequency domain,and compensate corresponding loss of performance in time domain. Theoretical analysisand simulation results show that OFDM-IDMA system can remain the performance ofno CFO in the case of smaller CFOt；The performance of OFDM-IDMA system withlarger CFOs employing carrier synchronization method based on CBC iterativedetection is close to that of OFDM-IDMA system without CFOs.