Yuta Ida

Non-linear fast fading compensation for HTRCI-MIMO/OFDM with QRM-MLD and channel ranking

In multiple-input multiple-output orthogonal frequency division multiplexing (MIMO/OFDM) systems, large complexity is considerable work. To mitigate this problem, high time resolution carrier interferometry (HTRCI) for MIMO/OFDM applying QR decomposition with M algorithm maximum likelihood detection (QRM-MLD) and channel ranking has been proposed. In the fast fading environment, since many errors are occurred in the last part of the packet, the decision direct method has been proposed. However, it requires also large complexity. Therefore, in this paper, we propose the non-linear prediction method for a HTRCI-MIMO/OFDM with QRM-MLD and channel ranking.

Interference cancellation using replica signal for HTRCI-MIMO/OFDM in time-variant large delay spread longer than guard interval

Orthogonal frequency division multiplexing (OFDM) and multiple-input multiple-output (MIMO) are generally known as the effective techniques for high data rate services. In MIMO/OFDM systems, the channel estimation (CE) is very important to obtain an accurate channel state information (CSI). However, since the orthogonal pilot-based CE requires the large number of pilot symbols, the total transmission rate is degraded. To mitigate this problem, a high time resolution carrier interferometry (HTRCI) for MIMO/OFDM has been proposed. In wireless communication systems, if the maximum delay spread is longer than the guard interval (GI), the system performance is significantly degraded due to the intersymbol interference (ISI) and intercarrier interference (ICI). However, the conventional HTRCI-MIMO/OFDM does not consider the case with the time-variant large delay spread longer than the GI. In this paper, we propose the ISI and ICI compensation methods for a HTRCI-MIMO/OFDM in the time-variant large delay spread longer than the GI.

Performance evaluation for AF relay TFI-OFDM systems

Amplify-and-forward (AF) relay transmissions can achieve a low power long distance communication. The problem of the AF method is that the channel state information (CSI) between source-relay (SR) and relay-destination (RD) should be obtained simultaneously in the destination node. The pilot signal is inserted to obtain the CSI, and the time frequency interferometry (TFI) method can reduce the number of pilot signals and the channel estimation (CE) power. This paper proposes the low power CE for AF relay transmissions in an orthogonal frequency division multiplexing based on the TFI method.

Variable packet splitting transmission in multi-relay cooperative communications with DF and DAF for SC-FDMA

In recent years, cooperative communications are widely studied. Cooperative communications can obtain the space diversity as multiple-input multiple-output (MIMO) systems. In cooperative communications, the relay method is important as decode-and-forward (DF) and decode-amplify-forward (DAF). The multi-relay cooperative communications can improve the system performance. In the multi-relay cooperative communications, the optimum packet splitting method is effective. Moreover, the multi-relay cooperative communications can more improve the system performance by using the power allocation (PA). However, the PA method requires large feedback information (FBI). To solve this problem, in this article, we propose the optimum packet splitting method based on the time domain channel state information (CSI) in the multi-relay cooperative communication with DF and DAF.

Estimation based on weighted channel variance for HTRCI-MIMO/OFDM with QRM-MLD and channel ranking under fast fading Channel

To achieve more high-speed communication systems, multiple-input multiple-output orthogonal frequency division multiplexing (MIMO/OFDM) is adopted in several standardisations. On the other hand, the conventional MIMO/OFDM requires many pilot signals to estimate the channel state information (CSI). To achieve an accurate CSI with the small number of pilot signals, high time resolution carrier interferometry (HTRCI) for MIMO/OFDM has been proposed. Moreover, QR decomposition with M-algorithm maximum likelihood detection (QRM-MLD) and channel ranking has been proposed to achieve both the reducing complexity and the improving system performance. However, the conventional HTRCI-MIMO/OFDM with the QRM-MLD and channel ranking did not consider the problem of the fast fading channel. In the fast fading environment, many errors are caused in the last part of the packet. To overcome this problem, the decision-direct method has been proposed. However, it requires large complexity because of the iterative processing. Therefore, in this paper, we propose the non-linear prediction method for an HTRCI-MIMO/OFDM with the QRM-MLD and channel ranking. Copyright

On bent ZCZ codes

This paper discusses a set of sequences with a zero correlation zone such that their Fourier transform over GF(p) corresponding to the Hadamard transform over GF(p) takes only unit magnitude, called a bent ZCZ code. The constructions and properties of polyphase bent ZCZ codes of period pn including bi-phase and quadriphase ones are clarified.

Performance enhancement for AF relay MIMO/OFDM with complex HTRCI pilot signal

Recently, amplify-and-forward (AF) multiple-input multiple-output (MIMO) relay transmissions are studied to achieve high quality communications. On the other hand, they have to estimate all channels between the source-relay and relay-destination nodes in the receiver. In MIMO orthogonal frequency division multiplexing (OFDM) systems, high time resolution carrier interferometry (HTRCI) has been proposed to achieve an accurate channel estimation (CE) with a small number of pilot signals. However, the conventional HTRCI-MIMO/OFDM is not adopted in AF relay transmissions. Therefore, in this paper, we propose the complex HTRCI (C-HTRCI) pilot signal to achieve an accurate CE for AF relay MIMO/OFDM systems.

Mitigated deep faded channel with relay node allocation for MUDiv/OFDMA

In recent, to achieve several services with the information product, high speed and high quality systems of wireless communications are demanded. To achieve this demand, orthogonal frequency division multiple access (OFDMA) has been proposed. In a wireless network, the transmitted signal of each user has independent channel fluctuation characteristics. By using this characteristic, the multiuser diversity (MUDiv) effect can be obtained, and MUDiv/OFDMA has been proposed. Before now, we have proposed a low complexity MUDiv/OFDMA. However, it degrades the system performance compared with the conventional MUDiv/OFDMA in the channel as a Pyramid model. To solve this problem, in this paper, we propose the method to mitigate the deep faded channel for a low complexity MUDiv/OFDMA with the relay node allocation.

Interference compensation scheme using time domain replica signals for SP-MIMO/OFDM under large delay spread channel greater than GI

In mobile communications, MIMO-OFDM transmission performance suffers severe degradation caused by the large delay spread channel greater than guard interval (GI). This is because the excess delay results in considerable inter-symbol interference (ISI) between adjacent symbols and inter-carrier-interference (ICI) among subcarrier in the same symbol. In the case of scattered pilot (SP), the interference of pilot signals causes the deterioration of channel estimation. In this paper, we propose the interference compensation scheme using the time domain replica signals.We make the time domain replica signals from detected signals and the excess channel impulse responses over GI. After compensation of the time domain replica signals and the received signals, we recalculate the channel state information (CSI) and the CSI is updated. Finally, we carry out the channel compensation with updated CSI for obtaining an accurate compensated signals.

Three hop AF relay transmissions for OFDM applying real and imaginary TFI pilot signals

Multi-hop relay transmissions achieve high quality and vast area communications by using several relay nodes. For the relay method based on an amplify-and-forward (AF), channel estimation (CE) is only demanded in the destination node. In the single-hop AF relay transmission for orthogonal frequency division multiplexing (OFDM) systems, we have proposed the CE by using the pilot signal based on the time frequency interferometry (TFI). However, in the multi-hop AF relay transmission, the conventional TFI method degrades the system performance due to a null signal and the overlapped channel. To solve this problem, in this paper, we propose the CE based on the real and imaginary TFI pilot signals in the three hop AF relay transmission for OFDM systems.