Development of Microwave Link for 8K Super Hi-Vision Program Contribution

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Hirokazu Kamoda, Kenji Murase, Naohiko Iai, Hiroyuki Hamazumi and Kazuhiko Shibuya*1 *1 NHK Engineering System, Inc.

As the satellite broadcasting of 4K/8K Super Hi-Vision is band is not strongly affected by rain and can be transmitted scheduled to start in 2018, the portable wireless contribution over distances up to 50 km, making efficient FPU operation links for program production, which are used for electronic possible. To maintain the same efficient operability with news gathering, outside broadcasting, etc., must be adapted FPUs used for 4K/8K reporting and production (4K/8K to the 4K/8K format. We upgraded a HD (2K) microwave FPUs), the FPUs must be upgraded to 4K/8K while still us- contribution link system particularly used for fixed and ing microwave band frequencies. line-of-sight transmissions to adapt it to 4K/8K operations There is also a need to introduce 4K/8K FPUs smoothly by increasing the transmission capacity. A 200-Mbps-class while maintaining the existing microwave band channel transmission capacity was achieved by enhancing the spec- allocations so that the operation of current HD FPUs can tral efficiency while keeping the conventional channel band- continue. Thus, technology is needed to increase spectral width (18 MHz). efficiency and dramatically increase transmission capacity To enhance the spectral efficiency, we employed dual- without changing allocated channel bandwidths. polarized MIMO (Multiple-Input Multiple-Output) using In earlier research on technologies to increase spectral both horizontal and vertical polarizations and OFDM (Or- efficiency for next-generation digital terrestrial broad- thogonal Frequency Division Multiplexing) with higher-order casting1)-3), dual-polarized multiple-input multiple-output modulation. We conducted outdoor experiments using a (MIMO) and orthogonal frequency division multiplex- preliminary prototype built halfway through the develop- ing (OFDM) with higher-order modulation were found to ment and proved the feasibility of the technologies by suc- be able to dramatically increase the transmission capacity cessful transmission of 8K video and audio signals over 50 while maintaining digital terrestrial television broadcasting km. bandwidths (6 MHz). From the perspective of increasing capacity, the application of this technology in FPUs is a promising option. 1. Introduction The authors have studied increasing the transmission ca- NHK has been conducting R&D on 4K/8K Super Hi- pacity by applying dual-polarized MIMO and OFDM with Vision, a television broadcasting service that will provide higher-order modulation to upgrade microwave-band FPUs highly realistic, ultrahigh-definition images. Test satellite to 4K/8K. This article discusses a microwave band 4K/8K broadcasting of 4K/8K Super Hi-Vision began in 2016, and FPU system that we have developed and reports on field preparation to begin regular service in 2018 is in progress. transmission tests performed to confirm its feasibility. This also generates a need to upgrade field pick-up units (FPUs) to 4K/8K. These are portable radio transmission devices that can quickly transmit live coverage or program 2. Microwave band 4K/8K FPU system materials for reporting or program production from venues around the country to the broadcast studio. Upgrading FPUs 2.1 Technical requirements for transmission capacity, to 4K/8K involves increasing their transmission capacity so frequency, and power that they can transmit 4K and 8K video and audio signals To transmit 4K/8K signals using limited frequency re- (4K/8K signals), which require more capacity than HD sig- sources, as with current HD systems, the compression cod- nals. ing of video and audio signals is unavoidable. Using H.265/ Microwave band (6-7 GHz) FPUs are used for most cur- HEVC (High Efficiency Video Coding), the latest video rent HD reporting and program production. This microwave compression encoding, a bit rate of between 100 and 300

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Mbps would be needed to transmit a 4K/8K signal4). Cur- orthogonally polarized signal components can be canceled rent HD FPUs have a transmission capacity of approximate- using MIMO detection*1. ly 60 Mbps, so the transmission capacity must be increased OFDM with higher-order modulation increases the num- by a factor of 2 to 5. ber of modulation levels used for the quadrature amplitude To maintain the same operability of current FPUs, the modulation (QAM) of subcarriers from 64QAM, as used same channel bandwidth of 18 MHz in the C (6.425-6.570 by current FPUs (Fig. 1 (a)), to 1024QAM (Fig. 1 (b)) or GHz) and D (6.870-7.125 GHz) bands is preserved. Also, 4096QAM. This increases the number of bits transmitted to prevent new interference with existing radio systems, with each carrier symbol from 6 bits to 10 bits or 12 bits, including current FPUs, the maximum transmission power increasing the transmission capacity by a factor of 1.7 to 2. is set at 5 W, the same as for current FPUs (although it is The transmission capacity was further increased by in- set to 0.2 W if an analog FPU is operating in an adjacent creasing the number of points used for fast Fourier Trans- channel). The proposed system described below will use forms (FFTs) from the current 2,048 to 8,192, increasing the horizontal and vertical polarizations simultaneously, so the effective symbol length relative to the guard interval (GI) transmission power refers to the total power of both polar- length (Fig. 2), and by reducing the number of pilot signals. ized signals. The transmission capacity can be increased by a factor To summarize, the transmission capacity must be in- of 2 to 5 by combining the above technologies. Note that to creased by a factor of 2 to 5 while maintaining current regu- minimize the increase in the required carrier-to-noise ratio lations of bandwidth and transmission power. (C/N) as a result of increasing the number of modulation levels, instead of convolutional and Reed-Solomon concat- 2.2 Overview of technologies to increase spectral enated coding used in current FPUs, a low-density parity efficiency check (LDPC) and Bose-Chaudhuri-Hocquenghem (BCH) Technologies to increase spectral efficiency, including concatenated coding is used as the forward error correction dual-polarized MIMO and OFDM with higher-order modu- (FEC). lation, had already been developed for next-generation terrestrial broadcasting research and were employed for the *1 With MIMO, the multiple transmitted signals arrive at the 4K/8K FPU. receiver having interfered with each other along the propagation path. The process of reconstructing the originally trans- Dual-polarized MIMO is a technology that uses two mitted signals from multiple received signals is called MIMO orthogonally polarized waves to provide double the trans- detection. Generally, known signals are used to estimate the mission capacity of current FPUs, which use a single po- propagation path and the results are used to estimate the larization. Interference between the polarizations of the transmitted signals.

Carrier orthogonal component amplitude

Carrier in-phase component amplitude

64 (26) constellation points 1024 (210 ) constellation points

64QAM (Current HD FPU) 1024QAM

(a) (b) Figure 1: Increasing number of constellation points for subcarrier modulation

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Guard interval Effective symbol interval

Number of FFT points: 2,048 100.14 µs

12.5 µs

Number of FFT 400.57 µs points: 8,192

12.5 µs 8.3% improvement

Time axis

Figure 2: Increased transmission efficiency by increasing number of FFT points

2.3 4K/8K upgraded microwave band FPU system in Fig. 3. Block diagrams for this system are shown in Fig. 4 A photograph of the microwave band 4K/8K FPU intro- and the transmission parameters and the realized transmis- ducing the advanced technologies discussed above is shown sion bit rates are given in Tables 1 and 2, respectively. This system is based on the standards used for current OFDM Table 1: Microwave band 4K/8K FPU transmission parameters FPUs, ARIB STD-B335) and STD-B576). The system is de- Item Specification scribed in this section in order of the signal flow. FFT size 2,048 8,192 Occupied bandwidth (MHz) 17.21 17.20 (1) Converting input signals to FEC blocks Carrier interval (kHz) 9.99 2.50 In Fig. 4 (a), the input signal is an MPEG-2 transport stream (TS), with video and audio compression encoding Total 1,723 6,889 Data carriers 1,428 6,426 Table 2: Microwave band 4K/8K FPU transmission rates Number of Pilot (CP/SP)*1 216/217 216/217 carriers Transmission rate (Mbps) *2 Subcarrier TMCC 16 64 Code rate modulation 2,048 FFT 8,192 FFT AC*3 62/61 182/181 points points 64QAM, 256QAM, Subcarrier modulation 1/2 76.5 93.8 1024QAM, 4096QAM 2/3 101.9 125.1 FFT sampling clock (MHz) 20.450743 64QAM 3/4 112.1 137.6 Effective symbol length (µs) 100.14 400.57 5/6 127.4 156.4 Guard interval length (µs) 12.52 12.52 1/2 101.9 125.1 Symbol length (µs) 112.66 413.09 2/3 135.9 166.8 Number of symbols/OFDM frame 440 440 256QAM 3/4 149.5 183.5 OFDM frame length (ms) 49.57 181.76 LDPC code 5/6 169.9 208.5 Inner code (Approx. code rates R 1/2 127.4 156.4 =1/2, 2/3, 3/4, 5/6) 2/3 169.9 208.5 Outer code BCH code 1024QAM 3/4 186.9 229.4 MIMO-supporting CP/SP SP: Horiz. (1,0), Vert. (0,1) carrier multiplication CP: Horiz. (1,1), Vert. (1,-1) 5/6 212.4 260.7 coefficient*4 1/2 152.9 187.7 *1 CP: Continual Pilot, SP: Scattered Pilot *2 Transmission Multiplexing Configuration and Control 2/3 203.9 250.2 4096QAM *3 Auxiliary Channel 3/4 224.3 275.2 *4 In parenthesis: (even-symbol multiplier, odd-symbol multiplier) 5/6 254.9 312.8

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using H.256/HEVC (or other) and multiplexing, so this Dual-polarized antennas TS is first converted to FEC blocks. The FEC block struc- Transmitter Receiver ture is shown in Fig. 5. The TS is a continuous stream radio-frequency head radio-frequency head of fixed-length, 188-byte packets (TS packets), which are stored in the payload part of the FEC block. They are stored in a similar way to that used in the transmission method for advanced wideband digital satellite broadcasting (ARIB STD-B447)), i.e., as a sequence of 187 bytes, excluding the synchronization byte (1 byte) at the beginning of the TS packet. The bits per field in the FEC Modulator Demodulator block structure are shown in Table 3. The number of TS

Figure 3: Microwave 4K/8K FPU

Modulator Time frame add GI OFDM IFFTand Radio Quadrature modulation composition inter-leaving frequency head

MPEG-2 Frequency/ TS Symbol polarization Pilot TMCC signal mapping interleaving signal, etc. antenna

input BCH coding LDPC coding Bit interleaving Dual-polarized Energy dispersal FECblock config. Radio Time frame add GI OFDM IFFTand frequency head Quadrature modulation composition inter-leaving

(a) Transmitter system

Demodulator

GI removal Time Radio FFT modulation Quadrature de-interleaving frequency head MPEG-2 TS signal Dual- Extract pilot MIMO output polarized signal, etc. detection antenna deinterleaving BCH decoding LDPC decoding LLR computation Bit de-interleaving Symbol demapping TS packet extraction Frequency/polarization Inverse energy dispersal GI removal Time Radio FFT modulation Quadrature de-interleaving frequency head

(b) Receiver system Figure 4: Microwave band 4K/8K FPU transmitter/receiver systems

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packets that can be stored in the payload depends on the polarizations. This distributes errors so that the error cor- code rate of the error correction code used. rection performance can be obtained at the receiver, even if The parity for the outer code, BCH, computed from the there is frequency-selective fading due to multipath signals header and payload is added. Stuff bits (6 bits) are also or differences in received power between the two polariza- added, and energy dispersal is applied so that not too many tions. Then, time interleaving is performed in the time di- consecutive 0 or 1 bits occur. The parity for the inner code, rection, giving a different delay to each carrier. This distrib- LDPC, is added to compose the 44,880-bit FEC block. utes errors due to fading, which causes the received power Current FPUs5)6) use a convolutional code for the inner to drop momentarily. code, so after error correction coding, it is a continuous, uninterrupted bit stream. Conversely, with the new FPU, a (4) OFDM frame composition block code is used for the inner code, so processing can be Next, pilot signals, transmission and multiplexing con- carried out in FEC blocks as shown in Fig. 5. Thus, error figuration control (TMCC) signals, and auxiliary channel correction coding and decoding can be performed in paral- (AC) signals are added to compose OFDM frames. OFDM lel, making it relatively easy to increase throughput. frames are composed for both the horizontally and vertically polarized signals. (2) Bit interleaving and subcarrier modulation The TMCC signal includes a synchronization signal for To increase the performance of LDPC decoding, bit in- OFDM frames and informs the receiver of the subcarrier terleaving is carried out on FEC blocks in accordance with modulation scheme used and other information. The AC the subcarrier modulation scheme. Then symbol mapping*2 signal is used to transmit information added by the user. The in accordance with the subcarrier modulation scheme is pilot signal is a signal known to the receiver, which is used

applied to the bit sequence to obtain 44,880/log2M carrier to estimate the propagation channel. Sending a sequence of symbols per FEC block (M is the number of modulation orthogonal pilot signals on the horizontally and vertically levels). polarized signals enables the receiver to perform MIMO detection. (3) Frequency/polarization interleaving and time inter- The number of data carriers and the number of frame leaving symbols are chosen such that FEC blocks fit in an OFDM The carrier symbols are lined up along the frequency axis frame without waste for all subcarrier modulation schemes. (carrier direction) and interleaved between subcarriers and Thus, Number of data carriers × Number of frame symbols ×

log2M = n × 44,880 (for integer n). (1) *2 The process of assigning a bit pattern to a constellation point. Therefore, OFDM frame synchronization enables immedi-

BCH code Stuff Header Payload LDPC code parity parity bits

Energy dispersal scope

Figure 5: FEC block structure

Table 3: FEC block structure bits

LDPC code rate Header Pilot BCH Stuff LDPC Total (Approx. code rate R) code parity bits code parity length 61/120 (1/2) 176 22,440 192 6 22,066 44,880 81/120 (2/3) 176 29,920 192 6 14,586 44,880 89/120 (3/4) 176 32,912 192 6 11,594 44,880 101/120 (5/6) 176 37,400 192 6 7,106 44,880

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ate start of error correction decoding and TS packet extrac- 3. Field transmission testing tion. To test the feasibility of the microwave-band 4K/8K FPU, With current FPUs, a superframe is composed of eight we conducted long-range transmission field tests. These OFDM frames5)6). Because of this, it is necessary to receive tests were conducted while the R&D was still in progress, up to eight OFDM frames before the extraction of TS pack- using basic test equipment with slightly different modula- ets can begin. With the new FPU, the FFT size is increased tor and demodulator specifications from those of the system to 8,192 points, increasing the symbol length and frame described in the previous sections. length, but the start of every OFDM frame always coincides with the start of a TS packet, so TS packet extraction can 3.1 Test equipment specifications begin after about the same duration as for current FPUs. The specifications of the basic test equipment used in these tests are given in Table 4. (5) Transformation to time-domain signal and radio- The OFDM carrier arrangement was based on the carrier frequency head arrangement in ISDB-T (used for digital terrestrial televi- The OFDM frame composed in the previous step is con- sion broadcasting)10) mode 3 (8,192 FFT points), with pilot verted to time-domain signals one symbol at a time by an signals modified for MIMO detection and other changes inverse FFT (IFFT), and the GI is added. Then, quadrature such as the total number of carriers. For subcarrier modu- modulation is performed to obtain intermediate-frequency lation, 64QAM to 4096QAM higher-order modulation was signals for horizontally and vertically polarized signals. In the radio-frequency head, the intermediate-frequency sig- *4 An index of the degree of discrimination between two or- nals are converted to microwave-band-radio-frequency sig- thogonally polarized signals. For example, when receiving a horizontally polarized signal, it is the ratio of the received nals and transmitted as horizontally and vertically polarized power of the horizontally polarized component to the re- signals from the dual-polarized antenna. ceived power of the vertically polarized component that has A high-efficiency dual-polarized splash-plate feed*3 para- leaked in. bolic antenna is used. This antenna is able to send and re- *5 In this case, the MIMO propagation channel is expressed as a 2×2 matrix, and the transmitted signals are found by mul- ceive both horizontally and vertically polarized signals us- tiplying the two received signals by the inverse of this matrix. ing a polarization separator. We were able to improve the This requires the least computation among the MIMO detec- antenna efficiency while using the same parabolic reflector tion methods. 6 A value expressing the log of the ratio of the probability that as for earlier antennas8). * the received bit is a zero to the probability that it is a one.

(6) Reception process Table 4: Main specifications of basic test equipment The reception process is basically the reverse of the trans- Item Specification mission process. The propagation channel is estimated from Transmit power 0.1 W (both polarizations; H, V) the received pilot signals, and through MIMO detection, Frequency bands C, D bands any cross-polarization interference occurring on the propa- Dual-polarized MIMO-OFDM, gation path is canceled, and the symbols transmitted on hor- Transmission format simplex transmission izontally and vertically polarized signals are estimated. It is Number of carriers 6,865 (both polarizations; H, V) assumed that the system will be used in line-of-sight envi- Number of FFT points 8,192 ronments where cross-polarization discrimination*4 will not Eﬀective symbol length 400.6μs degrade much, so a zero-forcing method,9)*5 which requires Guard interval length 12.5 μs (guard interval ratio: 1/32) less computation, is used for MIMO detection. In the demapping of the received symbols, the log-likelihood ratio Carrier modulation 64QAM, 256QAM, 1024QAM, 4096QAM (LLR)*6 is computed as the soft decision value for LDPC Inner code: LDPC code decoding. Error correction coding (Code rates: 1/2, 3/4, 5/6) Outer code: BCH code

*3 A feed with an emitter that has a structure with a metal plate Dual-polarized parabolic antenna Antenna at the end of a waveguide separated by a dielectric material. (Diameter φ: 0.6 m, 0.9 m)

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Table 5: Basic test equipment transmission rates those of current microwave-band FPUs. Transmission For the antenna, the emitter used with the current FPUs Carrier modulation LDPC code rate rate (Mbps) was replaced with a splash-plate feed emitter to create dual-

1/2 72.5 polarized parabolic antennas (with diameters of 0.6 m and 0.9 m)8). 64QAM 3/4 108.9 5/6 121.1 3.2 Test description and systems 1/2 96.6 An overview of the test systems is shown in Fig. 6. 256QAM 3/4 145.2 The transmission distance was set to be farther than 5/6 161.5 the standard link distance of 50 km set in the current 1/2 120.8 FPU requirements5). The transmitter was located at the 1024QAM 3/4 181.5 Dodaira Observatory in Tokigawa Town, Hiki District, 5/6 201.9 Saitama Prefecture, and the receiver was approximately 1/2 144.9 59 km away at the NHK Broadcast Center in Shibuya 4096QAM 3/4 217.8 Ward, Tokyo. Transmission was in the D band and the 5/6 242.2 antenna power was 0.2W (0.1 W per polarization). At the receiver, a variable attenuator was placed between the antenna and the radio-frequency head, enabling us used. The LDPC and BCH codes used were different from to measure the relationship between the reception power those described in the previous section but had very simi- and bit error rate. A codec supporting H.265/HEVC was lar performance. The LDPC code (code length 64,800 bits) not available at the time of these tests, so we inputted a and BCH code from the DVB-T2 standard11) were used. The 180 Mbps MPEG-2 TS 8K signal compressed using an transmission rates achieved with these transmission param- H.264/AVC (Advanced Video Coding) encoder into the eters are shown in Table 5. modulator, transmitted it, and used an H.264/AVC de- In order to support higher-order modulation, improve- coder for the output from the demodulator at the receiver ments were made to the radio-frequency head to obtain bet- to check the video on a monitor. We also recorded the ter frequency stability and phase noise characteristics than received intermediate-frequency signals with a wave-

Transmitter: Dodaira Observatory Receiver: NHK Broadcasting Center (Saitama Prefecture) (Shibuya Ward, Tokyo)

4K/8K FPU (transmitter) 4K/8K FPU (receiver) Dual-polarized Dual-polarized parabolic parabolic antenna Bit error rate tester antenna 59km

Radio Radio Video TS player Modulator frequency frequency Demodulator decoder Monitor head (H,V) H,V VATT head (H,V) polarization

Waveform recorder

VATT: Variable attenuator H, V: horizontal/vertical polarizations

Figure 6: Systems for field test using basic test equipment

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form recorder so that we could analyze the propagation over 59 km is possible for parameters permitting transmis- channel. sion near 200 Mbps (1024QAM, R=5/6) with transmission margins of approximately 2.5 dB when using the 0.6 m an- 3.3 Test results tenna and 5.5 dB when using the 0.9 m antenna. Note that We first measured the received power with the variable the 0.9 m antenna was still under development when these attenuator set to 0 dB. During the test, the weather was clear experiments were performed, and the gain of this antenna and we measured values of -65 dBm when using the 0.6 m can be increased, meaning that the transmission margin can antenna and -62 dBm when using the 0.9 m antenna. These also be increased. values are approximately 1.5 dB lower than the values esti- We also transmitted an actual 8K signal from the TS play- mated by link budgets assuming free space propagation but er and confirmed that 8K video could be properly received are appropriate considering factors such as the systematic on the monitor at the receiver, verifying the operation of the error in the measurement system, losses due to the error in 4K/8K FPU. the antenna direction, the plastic dome placed over the re- To check the propagation channel state using both hor- ceiver, and signals reflected off the ground. izontally and vertically polarized signals, we extracted We then measured the bit error rates while the attenuator the OFDM pilot signals from the received and recorded setting was changed. These measurements and the results intermediate-frequency signals and computed the chan- of prior laboratory tests are shown together in Fig. 7. For nel response for each subcarrier. The results are shown in simplicity, Fig. 7 only shows the results for three sets of Fig. 8 (a). To cancel the characteristics of devices such as transmission parameters having transmission rates near 200 the radio-frequency head, we performed a calibration with Mbps*7. The field test results show a degradation of approxi- the principal-polarization components*8 obtained in the mately 1 dB compared with the lab results, but this differ- laboratory tests. Figure 8 (a) shows the propagation channel ence can be accounted for by considering the error due to responses for 5,617 of the 6,865 carriers, for which a valid differences in the measurement systems (in the lab, the error propagation channel could be estimated, with lower carrier was measured by adding noise, while in the field, the input numbers corresponding to lower frequencies. From Fig 8 (a), power was attenuated) and the effects of the propagation we can see that the principal-polarization components (H- channel, including the antenna. H, V-V) have gently sloped response, but there is almost The measured results in Fig. 7 show that transmission no difference between horizontally and vertically polarized signals. We consider that this frequency response is due to the characteristics of the antenna and polarization separator. φ0.6m φ0.9m The cross-polarization components (H-V, V-H) were in the Parabolic Parabolic range of -20 to -25 dB, but the cross-polarization discrimi- reception reception 10 0 power power nation of the antenna itself is approximately 30 dB, so there (VATT=0dB) (VATT=0dB) may also have been some mismatch in the alignment of the 10-1 facing transmit and receive antennas. 10-2 The condition numbers*9 for each subcarrier, calculated

-3 1024QAM from the propagation channel responses, are also shown 10 R=3/4 with the laboratory test values in Fig. 8 (b). For most of 10-4 1024QAM the subcarriers, the field test values were slightly degraded 10-5 R=5/6 Bit error rate Field test 4096QAM 10-6 Lab test R=3/4 *7 For Fig. 7, the variable attenuator could only be adjusted in 1 dB intervals, but the bit error rate dropped sharply with only 10-7 a small increase in the reception power. For this reason, at -3 10-8 reception power settings with bit error rates below 10 , errors -80 -75 -70 -65 -60 were not detected and an estimation of the line is shown. Reception power [dBm] *8 Of the signals transmitted with a horizontally (or vertically) polarized wave, the signal component received with the hori- Figure 7: Reception power and bit error rate measurement results zontally (or vertically) polarized wave.

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1 0 Field test Lab test 0.8 -5 H-H H-V V-H -10 V-V 0.6

-15 0.4 -20 Condition number (dB) 0.2 -25 Propagation channel response (dB)

-30 0 0 0 1,000 2,000 3,000 4,000 5,000 1,000 2,000 3,000 4,000 5,000 Carrier number Carrier number

(a) Propagation channel response (b) Condition number

Figure 8: Per-carrier propagation channel responses and condition number

from the laboratory results, but the values were below 0.6 wave band. In order to introduce 4K/8K FPUs smoothly dB. This shows that polarization separation with almost no without changing these channel allocations, we have im- degradation due to noise accentuation was possible, even proved spectral efficiency to increase the transmission using the zero-forcing method, which is a simple MIMO capacity, so that 4K/8K video and audio signals can be detection method. transmitted while maintaining the current 18 MHz chan- We performed a computer simulation using the measured nel bandwidth. We introduced dual-polarized MIMO and channel responses to estimate the degradation in the bit error OFDM with higher-order modulation technologies to in- rate characteristics and found that the field test characteris- crease spectral efficiency, achieving a transmission capacity tics were degraded by approximately 0.4 dB (1024QAM, of up to 300 Mbps. We also verified the ability to transmit R=5/6) compared with the laboratory test characteristics. 8K video and audio signals with a transmission power of 0.2 Thus, the degradation of approximately 1 dB in Fig. 7 can W at distances over 50 km in field transmission tests. be considered reasonable. We will continue to develop practical devices, so that op- These results suggest that there was no significant deg- eration can begin in time for the full-scale dissemination of radation in cross-polarization discrimination for the clear 4K/8K broadcasting services expected in 2020. weather propagation in these tests. It will be necessary to take further measurements in the future to clarify the effects of factors such as rainy weather and long term changes. Acknowledgements We offer thanks to the Town of Tokigawa, Hiki District, Saitama Prefecture for willingly 4. Summary allowing the use of the Dodaira Observatory as the To enrich 4K/8K Super Hi-Vision broadcast programs, transmitter location for these field tests and to all persons we have developed a portable microwave band field pickup involved. unit (FPU) supporting 4K/8K. Currently, each broadcaster operates HD FPUs using different channels in the micro- This article was revised and amended on the basis of the following report appearing in ITE Technical Report. H. Kamoda, T. Kumagai, T. Koyama, S. Okabe, K. Shibuya, 9 This refers to the ratio between the larger and smaller eigen- * N. Iai, H. Hamazumi: “Long-haul transmission experiments of values of the 2×2 matrix representing the MIMO propagation channel. The smaller this ratio, the less susceptible the chan- a microwave link system for Super Hi-Vision,” ITE Technical nel is to noise. Report, Vol. 40, No. 4, BCT2016-28, pp. 45-48 (2016).

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