Start of Transmission from Skytree —Part 3: Relocation Measures—

AkiraChief Engineer Oka TetsuyaEngineering Tokue Center Engineering Administration Department TV TOKYO Corporation Japan Broadcasting Corporation (NHK)

1. Relocation measures 4. Optimization of transmission results for each building. Furthermore, in delay time areas where there were inferred to be new At 9 am on 31 May 2013, the master concentrations of facilities in the shadow station used for terrestrial digital TV To minimize SFN failures caused by of other buildings, a C/N continuous broadcasting in Tokyo by NHK and five exceeding the guard interval around the measurement system incorporating a car- private broadcasting companies (with a reach time of the relocation, an optimal delay mounted TV tuner and GPS device was used of some 15 million households) was relocated time was determined for each relay station, to confirm the changes in reception status from the Tokyo to the Tokyo Skytree. and advance modifications were made at from both , and measurements were This relocation took place during normal 65 of these (approximately one third of the performed individually if necessary. Based on broadcasting without changing channels, total number of relay stations). This made the results of these measurements, advance and proceeded smoothly and without major it possible to greatly reduce the number of measures were implemented where necessary. incident due to the prior application of diverse households affected by interference in the studies, safeguard measures and common Kanto region. 7. Measures implemented based knowledge to ensure that signals could be on monitor surveys and received from both stations. 5. Launch of experimental test reception confirmation tests station 2. Deployment of Monitor tests were performed centered countermeasures An effective way of studying the effects around large-scale apartment blocks where of relocation is to perform measurements in the relocation was expected to have a To ensure the relocation went smoothly, which test waves are actually transmitted. large effect. These tests involved checking six companies in the Kanto region set up the However, considering the effects on broadcast nighttime test broadcasts and implementing Tokyo Skytree Transition Center (T-SAPO) radio waves in the same area and in other advance measures at facilities that were in July 2011. This center liaised with call regions, we were somewhat constrained judged to be inadequate. Next, we performed centers, general market researchers and by having to confine these emissions to reception confirmation tests to elicit industries to promote various studies and periods when other broadcasts are off the statements from households experiencing countermeasures. air. We therefore launched an experimental poor reception when switching over to the test station for the purpose of estimating Tokyo Skytree during broadcasting. These 3. Advance simulation the behavior of OFDM waves emitted from started in early morning time slots, and the Tokyo Skytree as low-power single were gradually shifted towards time slots Although the network for transmissions carrier waves (CW) in the intervals between with higher viewing figures. The tests were from the is currently complete, transmitted signals (OFDM waves). This performed 128 times before the cutover, differences in electric field values arose due to enabled us to figure out if there would be any and a series of measures was implemented at differences in the transmitter specifications effects by using estimated values calculated facilities where reports had been made. and differences in lag times due to the from the CW measurement values, even A call center was opened at about effect of the relocation on the positional during ordinary broadcast time slots. the same time as the initial test wave relationships of relay stations. transmissions. This call center was staffed by These relocation effects were estimated in 6. Preliminary survey measures up to 260 operators at peak times around the a simulation. First, the study area was divided time of the migration. into a mesh of approximately 1 km square In places that were expected to be affected Knowledge of the reception confirmation blocks, and a radio propagation simulator by the relocation, we first surveyed the tests became widespread due to publicity in was used to calculate the field strength of reception patterns so as to exclude areas using broadcast programs, websites, newspapers, all transmitting stations. A single frequency other means of reception such as CATV, train advertising and the like, with the result network (SFN) was then used to study the and we adjusted the measurement points that a questionnaire conducted at the end effects of all the stations in each area, and the accordingly. In the survey, we measured the of March found that approximately 75% of effects of transmissions in the same channels desired station, broadcast waves from the respondents had viewed these tests. by other stations outside the broadcast Tokyo Tower, and a CW signal from the region. The effects of boosters installed on Tokyo Skytree. In cases where it was not 8. Post cut-over support receiver equipment were also studied in a possible to estimate the propagation effects simulator. Furthermore, in the vicinity of the with a CW signal alone due to multipath On 31st May, the relocation went ahead as transmitter where there is a strong electric effects, measurements were performed by planned. At its peak, the work to implement field, we simulated the effects of adding or emitting OFDM test waveforms at nighttime countermeasures was being carried out by removing obstacles for all buildings in the during inactive periods in order to determine 1,000 crews, and was completed without any area, using data on the shape and height of in advance the measures required. major disruption. buildings. A measurement survey was performed We are currently conducting long-term for each facility where it was found that radio wave measurements at 16 locations in the electric field increased or decreased Tokyo and the surrounding regions, and are significantly according to the simulation implementing anti-fading measures.

18 New Breeze Winter 2014