Yasuhiro Hamaguchi

A spectrum-overlapped resource management in dynamic spectrum control technique

This paper proposes a spectrum-overlapped resource management (SORM) technique using a dynamic spectrum control (DSC) and turbo equalizer for flexible frequency domain resource management under multiuser conditions. In the proposed technique, discrete spectrum of the transmitted signal is mapped onto spectrum components having the highest channel gain in the system band while accepting partial spectrum overlapping between users, and a frequency domain soft-canceller with minimum mean square error (FD-SC/MMSE) turbo equalizer is applied as the signal detection scheme for multiuser detection (MUD) in order to cancel not only inter-symbol interference (ISI) but also inter-user interference (IUI). Computer simulation including extrinsic information transfer (EXIT) analysis confirms that the proposed scheme can achieve high frequency selection diversity and realize flexible frequency domain resource management.

A Frequency Domain Scheduling for Uplink Single Carrier Non-Orthogonal Multiple Access with Iterative Interference Cancellation

This paper proposes a frequency-domain (FD) scheduling for an uplink single carrier non-orthogonal multiple access (SC-NOMA) with the assistance of iterative interference cancellation (IC). In the SC-NOMA, an evolved Node B (eNB) with an iterative IC receiver is capable of allocating overlapped spectra to plural intra-cell user equipments (UEs) exceeding the number of receive antennas. As a result, the SC-NOMA can enhance the spectral efficiency owing to the non-orthogonal multiplexing. However, when the subband (SB) criterion scheduling, that assigns an SB to a UE on the basis of the metric only on an SB, is applied, this scheduling is not suitable in the SC-NOMA. This is because the throughput in single carrier transmission depends on all the allocated SBs. Therefore, we propose a novel FD scheduling based on the expected value of cell throughput which is calculated by both the SB selected by the metric as a candidate and the previously allocated SBs. The eNB assigns the candidate SB if the expected cell throughput increases after allocating the candidate SB. Computer simulations confirm that the proposal can improve throughput performances compared to the SB criterion scheduling in the SC-NOMA.

A Design Criterion of Error Correcting Codes for Spectrum-Overlapped Resource Managements

In this paper, we propose a new criterion for the extrinsic information transfer (EXIT) analysis in the spectrum-overlapped resource management (SORM) for a broadband single carrier transmission. In the SORM technique, each user can ideally obtain a maximum channel gain by allowing overlapped allocation, assuming the soft canceller with minimum mean square error (SC/MMSE) turbo equalization for multi-user detection. When the interference is not completely removed by SC/MMSE turbo equalization, frame error rate (FER) remarkably degrades. To solve this problem, we proposed a new criterion which is used for design of error correcting code in order to improve convergence property of SC/MMSE turbo equalization without large redundancy of channel code. In the proposed criterion, we design the decoder so that the decoders EXIT property is fitted to the upper bound of equalizers property and the channel code sharply improves mutual information (MI) in the lower amount of input MI. This paper evaluates FER performance with the irregular low-density parity-check (LDPC) codes designed based on this criterion. As a result, this paper shows that the irregular LDPC code designed based on the proposed criterion for the SORM outperforms conventional codes.

New Virtual Sub-Carrier Allocation Method for CI Multiplexed Channel Estimation Signals on MIMO-OFDMA

In a MIMO-OFDMA system, carrier interferometry multiplexed (CIM) signals with the discrete Fourier transform based channel estimation (CIM/DFT-CE) have been proposed. Using CIM/DFT-CE, high channel estimation accuracy is realized with a small number of symbols under ideal conditions. In this paper we indicate that the channel estimation accuracy of the sub-channel at the edge in the active band is significantly degraded under real conditions. To improve this degradation, we propose a new virtual sub-carrier allocation method, taking the periodic property of the CIM signals in the receiver into consideration. We use computer simulation to demonstrate that the channel estimation accuracy of the sub-channel at the edge is improved by the proposed method under real conditions.