NHK is conducting research on the next generation of digital terrestrial broadcasting to enable large-volume content services such as Super Hi-Vision. In dual polarized MIMO transmission, we applied LDPC (Low Density Parity Check) code to FEC (Forward Error Correction), and previously reported a multi-dimensional interleaving scheme that reduces deterioration caused by the difference of channel responses of two polarizations. We developed the bit interleaving scheme that is applied in multi-dimensional interleaving and dual polarized MIMO transmission, and this paper reports the result of computer simulation.
Superposed multicarrier transmission scheme is known to improve frequency utilization efficiency where several wireless systems share spectrum. In superposed multicarrier transmission scheme froward error correction (FEC) coding is applied over subcarriers so that the effects of interference caused by superposition is mitigated by interleaving effects. When the interference power is large, the effects of FEC become smaller particularly owing to the mis-setting of initial log likelihood ratio (LLR). To solve this problem, FEC metric masking is proposed where initial LLRs for interfered subcarriers are replaced by neutral value in the receiver followed by decoding. Since the knowledge of interfered band had been considered as pre-known in early studies, we proposed interfered band detection technique based on packet error rate (PER) by using FEC metric masking. In this technique the subcarriers where FEC metric masking is applied are changed and PER is measured. Based on the masked subcarriers corresponding to the minimum PER, we can detect the interfered band. In this report we alter the estimation scheme of interfered band for the detection technique proposed. Altered estimation scheme is based on the gradients of PER instead of minimum PER. We evaluate the detection technique by computer simulation and show that it can detect the interfered band with higher probability when E_b/N_0 is low and superposed rate is high.
We have developed a wireless Hi-Vision TV (HDTV) camera, called the "Millimeter-wave Mobile Camera", which can transmit HDTV pictures with high-capacity and low delay. For this development, a realization of bi-directional transmission between HDTV camera and control room is essential and we developed a 42GHz-band STBC transmission system for return link with 4 transmitting and 1 receiving antennas, which can transmit HDTV pictures for camera man with low delay, including HDTV camera precise remote control and so on. In this paper, the outdoor transmission performance of the STBC transmission system was measured and compared with the result of computer simulation.
In this report, we propose the improvement method of MIMO channel capacity using tunable transmit-array antenna. This method is effective in improving the channel capacity for the situation where keyhole effect exists. The transmit-array is placed at the aperture between two enclosed rooms. The numerical analysis based on the raytracing method showed the 10 % value of the channel capacity can be improved by 10 Bits/s/Hz and this result supports the effectiveness of the proposed method for reducing the dead zone in wireless communication systems.
The 21GHz-band satellite broadcasting system is studied for transmission channels to deliver ultra high definition TV, 3D television and so on. The 21GHz-band suffers from severe fading due to rain, a fading mitigation technique forming a boosted beam with an array-fed reflector is effective for the 21GHz-band satellite system. Therefore, we designed and manufactured an experimental model of an array-fed imaging reflector antenna for the 21GHz-band broadcasting satellite system. We verified the characteristics by measurement. A 7dB boosted beam has been successfully obtained.
Recently, MIMO transmission system is in practical use for realizing high speed and reliable wireless communications. However, the effectiveness of MIMO transmission is not fully obtained when the multiple antennas are arrayed in a compact mobile terminal because of the shorten distance between the antennas. In order to alleviate the drawbacks, we have proposed a distributed MIMO antenna system which distributes the multiple antennas onto some substrates. This paper shows the effectiveness of the distributed antennas by comparing the antenna performance of the single substrate with four antennas and 2 substrates with 2 antennas in free space and environment around human body, respectively, through the computer simulation.
During live outside broadcasting (OB) of road races, such as marathons and ekiden, video images are taken using cameras on moving OB vans and the signals of the video images are transmitted by FPU in 700 MHz band. The FPU is mounted on the OB vans and the transmitted power of FPU is 5 W; however, few studies have been performed concerning the SAR on the human body due to the FPU. In this report, we designed a transmission antenna and an OB van and calculated SAR with a numerical model of the human body. From the results, we found that the peak of 10g average SAR on human body is lower than 0.02 [W/kg] when the transmission antenna is set on the OB van in the usual operation.