5 Advanced content production technology

Transcription

1 5 Advanced content production technology In preparation for the launch of 8K Super Hi- Vision (SHV) broadcasting in 2020, we are developing program contribution transmission equipment for producing high-quality content and performing high-capacity transmissions. We are also researching technologies to build contribution networks using Internet Protocol (IP) and enhancing Integrated Services Digital Broadcasting-Terrestrial (ISDB-T). In our research on wireless transmission of uncompressed SHV signals, we improved the temperature characteristics of 120-GHz-band Field Pick-up Units (FPUs) with polarization multiplexing. Field transmission experiments conducted under various conditions demonstrated the FPUs could operate in outdoor environments. In our research on bidirectional FPUs for highspeed wireless transmission of file-based video, we implemented a time-division duplex (TDD) scheme in hardware and experimentally evaluated the transmission characteristics. We also studied the packet structure of a hybrid automatic repeat request (HARQ) scheme combining forward error correction and automatic repeat request. The Japanese government has required that FPUs operating in the 700-MHz band be phased out in favor of ones that operate in the 1.2-GHz and 2.3-GHz bands. For this migration to the new bands, we have devised a multiple-input multiple-output (MIMO) transmission scheme using space-time trellis code that can stably transmit video at 35 Mbps rate in a mobile environment. We submitted a proposal on this scheme to the Information and Communications Council, and the Council later issued it as a technical standard for these frequency bands. In our research on radio microphones, which the government has also required to be migrated to white space between channels or the 1.2- GHz band, we conducted transmission experiments indoors and outdoors on transmitting uncompressed linear pulse code modulation (PCM) audio and a multi-channel operation method. The Association of Radio Industries and Businesses (ARIB) subsequently issued the technical specifications of these methods as a standard. In our work on millimeter-wave mobile cameras for studios and on-location reporting, we studied ways to reduce the amount of computations of the multiple-input multiple output (MIMO) transmission scheme and to equalize channel characteristics in the frequency domain by using a single carrier method. To improve the reception characteristics of the millimeter-wave mobile camera, we developed an elliptical horn antenna with improved horizontal gain by reducing the antenna s vertical half-value angle from 50 to 20. The camera was used in golf relay programs. We are researching technologies for Internet Protocol (IP) based contribution networks to enable faster and more reliable contribution transmissions. We developed a technology to transmit video stably even with wireless fading channels, such as wireless LAN, along with technologies to mitigate latency and simultaneously transmit multiple raw video footage using IP networks. In our research on enhanced ISDB-T, we are studying an Area One-Seg system that can provide urgent information to specific reception areas during disasters and other emergencies. In September, we conducted field experiments on a system that allows local governments and other organizations to provide urgent information in times of disaster by using service-area-limited broadcasting. The study was conducted at an experimental transmission station in Yatomi City, Aichi Prefecture. The results showed that the service area could be limited as designed, and the demonstration showed the effectiveness of the system. 5.1 Contribution transmission technology GHz-band FPU for uncompressed SHV We are continuing our research on a 120-GHz-band Field Pick-up Unit (FPU) for wireless transmission of uncompressed 8K Super Hi-Vision (SHV) signals using polarization multiplexing. In FY2013, we conducted wireless transmission experiments and improved the FPU. We evaluated the performance of the compact 120-GHzband radio frequency (RF) unit (No. 1) prototyped in FY 2012 and confirmed that it could transmit outdoors (1). We exhibited wireless transmission of uncompressed dual-green format SHV signals with the No. 1 unit and the FY 2011 prototype at the NHK STRL Open House. Based on the results of performance evaluations of the No. 1 unit, we prototyped a compact 120-GHz-band RF unit (No. 2) with improved temperature and frequency characteristics (2). We also built a baseband (BB) signal processing unit that multiplexes 16 HD-SDI signals transmitted with forward error correction; the unit outputs two 11-Gbps-class signals. The resulting FPU (Tx/Rx) consists of compact RF units (No. 1 and No. 2) and the BB signal processing unit (Figure 1) and can transmit uncompressed SHV signals. 28 NHK STRL ANNUAL REPORT 2013

2 5 Advanced content production technology 5.1 Contribution transmission technology Compact 120-GHz-band RF unit set on a camera tripod Baseband signal processing unit Figure GHz-band FPU structure for uncompressed SHV (Receiver side) We conducted wireless transmission experiments in the field using this FPU. We confirmed stable wireless transmission of an uncompressed SHV signal over a distance of 250 m under heavy rainfall conditions (60 mm/h) (3). (1) J. Tsumochi, F. Suginoshita, S. Okabe: 120-GHz-band FPU for SHV Signal Transmission, ITE Technical Report, Vol. 37, No. 34, pp , (2013) (in Japanese) (2) S. Okabe, J. Tsumochi, F. Suginoshita: Temperature Characteristics of 120-GHz-band Wireless Link, IEICE General Conference, No. B-5-119, (2014) (in Japanese) (3) J. Tsumochi, S. Okabe, F. Suginoshita, J. Takeuchi, H. Takahashi, A. Hirata: Field Experiments on Super Hi-Vision Signal Transmission using 120-GHz-band FPU, IEICE General Conference, No. C-2-111, (2014) (in Japanese) Bidirectional Field Pick-up Unit (FPU) transmission technology We are researching bidirectional FPUs for high-speed wireless transmission of file-based video. In FY 2013, we studied the time-division duplex (TDD) scheme, implemented it in hardware, and experimentally evaluated its transmission characteristics. Bidirectional FPU experimental equipment prototype and evaluation We evaluated the performance of the experimental microwave-band (6 to 7 GHz) bidirectional FPU prototyped in FY 2012 (Figure 1) and improved its functions. Using a propagation delay generator, we verified that the proposed TDD method operates with the maximum time use efficiency without being affected by fluctuations in the transmission delay. We also conducted wireless transmission tests using a dual-polarized parabolic antenna with a splash plate in a radio wave anechoic chamber and confirmed the feasibility of one-way transmission at up to 180 Mbps over a distance of 50 km (1). We improved the transmission and reception characteristics of the radio frequency (RF) unit and implemented a high-precision automatic frequency control (AFC) function and an adaptive modulation function. Media Access Control (MAC) layer packet structure We have been studying Type-II hybrid automatic repeat request (HARQ) since FY HARQ is an automatic repeat request scheme combining with forward error correction codes. Type-II means that a transmitter retransmits different parity bits from the first transmission. In FY 2013, we confirmed through computer calculations that transmitting efficiency does not decrease significantly even if the retransmission packet size is 1/4 of the first transmission and the packet control field is included (2). We also implemented the HARQ scheme in hardware. (1) K. Mitsuyama, N. Kogo, F. Uzawa, N. Iai: Prototyping and performance evaluation of TDD-based 2x2 MIMO-OFDM transceiver, IEEE RWW2014, MO3D-1, pp (Jan. 2014) (2) F. Uzawa, K. Mitsuyama, K. Aoki, T. Hiraguri: An Evaluation on HARQ Scheme for Bi-directional FPU with Consideration of Packet Control Information, IEICE General Conference 2014, No. B-5-134(2014) (in Japanese) reception control unit 1 TRC1 reception RF unit 1 V TRH1 H Bidirectional 2 2 MIMO using dual-polarization Dual-polarized transmission/reception antenna reception RF unit 2 V TRH2 H reception control unit 2 TRC2 reception RF unit (TRH1) reception control unit (TRC1) Dual-polarized parabolic antenna with a splash plate (60cm in diameter, 30 dbi gain) Figure 1. Bidirectional FPU experimental equipment prototype MHz-band frequency migration In response to the Ministry of Internal Affairs and Communications action plan for spectrum reallocation, NHK STRL is preparing to change the frequencies used by our FPUs and wireless microphones. In particular, we want to achieve a smooth migration away from the 700-MHz band to the 1.2- and 2.3-GHz bands. NHK STRL ANNUAL REPORT

3 5 Advanced content production technology 5.1 Contribution transmission technology FPU transmission technology We are researching multiple-input multiple-output (MIMO) transmission schemes using space-time trellis codes (STTCs) for FPUs used in mobile reporting to increase the transmission capacity beyond that of current schemes. In FY 2013, we developed 2 4 STTC-MIMO transmission equipment capable of diversity reception using four reception antennas to deal with long delay waves and propagation loss in the 1.2- and 2.3-GHz bands. We conducted transmission experiments using the new frequencies in Kyoto, Hiroshima, and on the Lake Biwa road race course, and obtained data to make preparations for the frequency migration, such as the MIMO reception characteristics for a dual-polarized Yagi-Uda antenna. We also contributed to standardization activities at the Association of Radio Industries and Businesses (ARIB); the STTC-MIMO scheme we have been studying was incorporated in one of its standards (1). This standard enables stable transmission at the 35-Mbps video bit rate recommended by ITU, even in a mobile environment. To support large-scale reporting using many reception base stations, such as is done in covering road races, we developed transmission equipment using the 2 (16,4) STTC-MIMO scheme, which selects for demodulation the four most appropriate reception signals from a maximum of 16 reception signals (Figure 1). Figure 1. 2 (16,4) STTC-MIMO transmission equipment Radio microphone transmission technology The frequencies used by specified radio microphones, i.e., those subject to the Radio Law in Japan, will be migrated to the 1.2-GHz band or the white space of terrestrial TV broadcasting. The 1.2-GHz band is available throughout Japan, but it is used for radiolocation (radar). In order to share this band, the new microphones will need a digital method resistant to interference. Current radio microphones use a single carrier QPSK scheme with audio latency of 1 to 3 ms (occupied bandwidth: 288 khz (Two-piece model) Figure 2. OFDM digital radio microphone prototype (Hand-held model) receiver or 192 khz). We are researching the use of orthogonal frequency division multiplexing as a way to provide stable transmissions resistant to interference and multipath as well as low latency. An OFDM digital system with an occupied bandwidth of 600 khz can transmit uncompressed linear PCM audio at a latency of under 1 ms. In FY 2013, we performed transmission experiments in the studio and outdoors, on OFDM digital radio microphones with a 600-kHz occupied bandwidth. We also built hand-held and two-piece models (Figure 2). These prototypes can operate for about four hours on two AA batteries, and they show the feasibility of reducing the power consumption of the OFDM digital system. At the same time, we verified the operation of prototype OFDM digital systems with occupied bandwidths of 288 khz and 192 khz and using various transmission parameters as a way to enable multi-channel operation. The OFDM digital systems with occupied bandwidths of 600 khz, 288 khz, and 192 khz were incorporated in an ARIB standard (2) on transmission schemes for specified radio microphones. (1) ARIB: 1.2GHz / 2.3GHz-band Portable OFDM Digital Transmission System for Television Program Contribution, STD-B57 ver. 2.0 (in Japanese) (2) ARIB: Specified Radio Microphone for Land Mobile Radio Station (TV White Space Band, 1.2GHz Band, STD-T112 ver.1.2 (in Japanese) Wireless contribution link technology For the next generation of contribution links supporting 8K Super Hi-Vision (SHV), we are developing reliable large-capacity wireless cameras and FPUs. To this end, in FY2013, we studied multiple-input multiple-output (MIMO) transmission technology and single carrier-frequency domain equalization (SC-FDE) and improved the performance of our millimeterwave mobile camera. MIMO transmission technology To reduce the volume of computations used to detect MIMO signals, we devised a maximum-likelihood decoding method that suppresses the number of computations as the number of MIMO transmission antennas and modulation order increase (1). This method orthogonalizes the propagation channel matrix for the transmission and reception antennas of smaller block matrices and selects transmission signal point candidates by using Manhattan metric in each block matrix. It reduces the computation volume by 96.1% from that of the conventional maximum-likelihood decoding method when quadrature phase shift keying (QPSK) modulation is used for 4 4 MIMO multiplex transmission. Computer simulations also showed that the method achieves the same level of transmission characteristics as ordinary maximum-likelihood decoding even with high-correlation MIMO channels (channel correlation value: 0.8). We also conducted 42-GHz transmission experiments based on software defined decoding and demonstrated the effectiveness of our method. Single Carrier-Frequency Domain Equalization (SC-FDE) We studied technologies for the SC-FDE method in order to identify the transmission characteristics of the SC-FDE method when using the amplifier in the non-linear range and compared the level of improvement relative to the OFDM method. We op- 30 NHK STRL ANNUAL REPORT 2013

4 5 Advanced content production technology 5.1 Contribution transmission technology 5.2 IP technologies for IP based contribution networks timized the noise parameter of minimum mean square error (MMSE) equalization in the frequency domain and implemented technologies including 16 amplitude and phase shift keying (APSK) modulation that is unaffected by the non-linearity of amplifier, error correction, and interleaving. The results of laboratory experiments showed the carrier to noise ratio (CNR) versus bit error rate (BER) characteristics were similar to those of computer simulations. The results will be the basis for implementing the SC-FDE method in hardware. We also found that the implementation complexity of the SC-FDE method is less than half that of the OFDM method for the modulator and twice that for the demodulator and verified the transmission characteristics of the SC-FDE method when using the amplifier in the non-linear range. Improving the performance of millimeter-wave mobile camera For more stable Hi-Vision transmissions, we developed an elliptical horn antenna which improved the horizontal (in the 0 degree direction) gain by reducing the antenna s vertical halfvalue angle from 50 to 20 (Figure 1). As a result, the gain of this antenna in the 0 degree direction was improved by 3.4 db compared with that of conventional conical horn antennas (2). We also developed a function to avoid the degradation in transmission performance caused by delayed reception of intermediate frequency (IF) signals beyond the guard interval due to differences in camera cable length and multiplexed tally signals with camera control signals to support various cameras. We developed a practical demodulator with a link-quality monitoring function compliant with 2 4 MIMO transmission and began a study on compact and low-cost millimeter-wave transmission modules. This millimeter-wave mobile camera was used for shooting programs such as the NHK Trophy and All Japan Tournament in gymnastics, the Japan Women s Open and the Japan Open Golf Championship, and Music Japan, the Kouhaku year end music show, and charity concerts (Figure 2). (1) S. Suzuki, N. Kogo, H. Hamazumi, K. Fukawa, H. Suzuki: Complexity-reduced MLD with Block QR Decomposition for Super Hi-Vision Television Wireless Transmission System, ITE Journal, Vol. 67, No. 12, pp. J488-J496 (2013) (in Japanese) (2) F. Ito, S. Suzuki, N. Kogo, H. Hamazumi: Development and Propagation Experiments of Elliptical Horn Antenna for a Wireless Camera in 42-GHz Band, ITE Technical Report Vol. 38, No. 8, pp (2014) (in Japanese) Conical horn antenna (conventional) Aperture: 9.4 mm <Antennas> Elliptical horn antenna (proposed) Long axis: 30 mm <3D directivity calculation value> Figure 1. Conical horn antenna and elliptical horn antenna Short axis: 8 mm Figure 2. In operation at the Japan Women's Open Golf Championship 5.2 IP technologies for IP based contribution networks We are studying IP technologies for Internet Protocol (IP) based contribution networks to enable more flexible operations and swift transmission of program contributions through the use of various IP networks. Contribution transmission technology using various IP network Wireless IP networks, such as wireless Local Area Networks (LANs) and mobile broadband networks, are prone to changes in link speed due to adaptive modulation and excessive delays due to buffers. To solve this problem affecting live transmissions, we studied a technology that can deal with link speed variations and file transmission technology that can mitigate excessive delays. Stable live transmissions through a variable-speed network requires a transmission rate control function to prevent packet losses due to excessive speed and a function for recovering lost packets. To deal with the speed changes affecting wireless LANs, we developed a streaming device that controls the transmission rate by using the link speed information from the wireless LAN device (1). We are also studying visible-light wireless IP transmission technology to make it possible to conduct underwater live broadcasts. Unlike the case of wireless LANs, the link speed of this system is constant but its communication is frequently interrupted by bubbles and particles suspended in the water. To deal with these problems, we studied the propagation characteristics of visible-light communication and designed a method to avoid such interruptions by using retransmission and redundant data transmission. When large files are transferred over a mobile broadband network, packets can remain for a long time in large-capacity buffers of wireless devices. This can increase the transmission NHK STRL ANNUAL REPORT

5 5 Advanced content production technology 5.2 IP technologies for IP based contribution networks 5.3 Enhanced ISDB-T delay to several seconds and increase the delays of other communications as well. We developed a new congestion control method for Transmission Control Protocol (TCP) so that a buffer will not be filled up with packets. The results of experiments using an actual mobile broadband network showed that the method can reduce delays while maintaining throughput performance (2). Use of IP network for multiple contribution transmissions Raw video footage is transferred between broadcast stations using a digital leased line reserved for each piece of raw video footage. If multiple pieces of such footage could be transmitted simultaneously, the total transmission time will be shortened and immediate transmission of additional raw video footage will be possible. Structuring video transmission lines as an IP network instead of digital leased line can enable this sort of transmission, but it is necessary to manage the transmission rate for each piece of footage. We developed a system consisting of network traffic visualizer and transmission rate controller. For example, this system makes it possible to assign a high bit rate to high-priority raw video footage so that it can be delivered to the broadcast station as soon as possible. It is also possible to improve the picture quality of video being aired by decreasing the bit rate of the file transmission or monitoring video. (1) S. Oda, M. Kurozumi, Y. Endo: Development of mobile video transmitter for wireless LAN network, ITE Winter Annual Conference 2013, 12-8, (2013) (in Japanese) (2) T. Koyama, K. Aoki, Y. Endo, Delay-based TCP Considering the Latency by Data Link Layer Delay of Mobile Broadband Network, 2013Globecom, CQRM-8-02, pp , Enhanced ISDB-T Field experiments on service-area-limited One- Seg service for disaster areas The FY 2012 revision to Japanese government regulations has allowed municipal governments, universities and corporations to provide broadcasting services to a limited service area by using unoccupied UHF-band frequencies in the area, called white space, on the condition of their not affecting reception of existing digital terrestrial television broadcasting. In FY 2012, we developed an Area One-Seg system with such limited coverage so that areas affected by disasters could receive urgent information from local governments and other organizations (Figure 1). The system consists of portable content production and information gathering equipment for One-Seg services and transmission equipment. We conducted field experiments on the system in September of FY 2013 at a transmission station in Yatomi City, Aichi Prefecture (Figure 2) (1)(2). We recorded the reception status of mock area-limited broadcasting in case of disaster on multiple One- Seg receivers and confirmed that radio waves were delivered within the designed service area. The results of verification tests also showed that information directing people to evacuation centers and other lifelines would be received by One-Seg devices correctly, thereby demonstrating the system s effectiveness at providing emergency information. (1) H. Sanei, M. Nakamura, Y. Narikiyo, M. Takada: Development of a useful information collection and transmission system for disaster area via service-area-limited One-Seg broadcasting, IEICE General Conference, B-15-15, pp. 644 (Mar. 2013) (in Japanese) (2) H. Sanei, H. Miyasaka, Y. Narikiyo, M. Nakamura, N. Nakamura, M. Transmission antenna Reception display Video Data broadcasting Figure 2. Verification experiments Takada: Field trial on service-area-limited broadcasting services for disaster relief, ITE Winter Annual Convention, 12-6 (Dec. 2013) (in Japanese) Camera Information gathering system One-Seg transmission equipment Direct input Disaster related information input terminal Information gathering Data broadcasting content generation H.264 encoder Multiplexing Modulation and output One-Seg transmitter Figure 1. Service-area-limited One-Seg system for disasters 32 NHK STRL ANNUAL REPORT 2013