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The 800 MHz frequency band is a portion of the electromagnetic spectrum, or frequency band, that encompasses 790–862 MHz. Being a part of the spectrum known as "UHF Bands IV and V" (i.e. 470MHz to 862MHz) it was allocated by the ITU to Broadcasting as the primary user in Region 1 and was used for analogue television broadcasting before changing to digital terrestrial television in many countries.〔The 'Mobile Service' in ITU terms, not to be confused with mobile phone operators, was allocated as a secondary user of the band〕 As such it is also referred to as "digital dividend" spectrum. In Europe and to some extent elsewhere, the band corresponds to UHF channel 61–69. In most territories the band was also used by Services Ancillary to Broadcasting (SAB) or Services Ancillary to Programme Making (SAP), both often now referred to as PMSE (Programme Making and Special Events) in the form of professional wireless microphones, radio talkback systems and wireless monitor systems. The European Parliament approved May 2010, the change of use of the 800 MHz band making it available for purposes other than broadcasting (television) – e.g. mobile broadband.〔(May 14th, 2010, intomobile.com: Europe’s 800 MHz band = America’s 700 MHz band; 4G has a long way to go ) Citat: "...Last week the European Commission announced that they’ve chosen 800 MHz as a standard to introduce mobile broadband across the continent..."〕 From the year 2013 the 800 MHz band can be used to deliver wireless broadband services, in Europe.〔(16 Feb 2012, techeye.net: EU demands freeing up 800 MHz spectrum by 2013 ) Quote: "...to ensure a comprehensive roll out of high speed mobile broadband..."〕 == Possible interference problems == Some claim that there have not been enough interference studies made in the EU.〔(15 November 11, computerworlduk.com: EU rules on radio spectrum ignore interference issues, group claims ) Quote: "...Under the RSPP, all EU countries must make the 800MHz band available for wireless broadband services by January 1, 2013...However, newcomers to the 800MHz band that "speaks loudly" could drown out other sorts of communications being executed by consumer equipment (such as television tuners or cable modems)..."〕〔(2 June, 2011, ispreview.co.uk: 760000 UK Households Could Lose Digital TV Due to Superfast Mobile Broadband ) Quote: "...Ofcom warns that some situations could be too difficult or costly to fix and suggests that it may be "preferable to maintain the consumers’ access to TV while accepting the loss of the DTT service". In other words, you'd (about 30,000 homes) have to fork out for a satellite or cable service..."〕 The reason for the interference problem is that the rf-chain in TV-equipment is designed to receive 470–862 MHz (EU channels 21–69) and therefore includes the range of frequencies which the new services are, or will be, using. Most TV receiving equipment in current use and currently on the market was not designed with the expectation that there would be anything but TV signals in the frequency range 470 MHz to 862 MHz. Due to the very limited guard band between the new services and the existing TV services in some cases the LTE 800 base station signals may cause interference to DTT particularly in EU channels 59 and 60. Strong LTE base station signals in 800 MHz band, may cause limiting or clipping, that is due to overdrive in antenna amplifiers and/or DTT tuners in e.g. flat panels, set top boxes, USB-tuners and digital video recorders. Depending on the dynamic range performance of the affected receiving equipment, the following may happen: * When forward error correction (FEC) is adequate, the TV reception will be unaffected * If the interference is sufficiently severe such that FEC cannot correct all of the errors, there will be pixelation in the picture and/or there will be sound drop-outs. * In severe cases of interference the error correction will not cope at all and this will result in a black TV-screen and / or complete loss of sound. Overload in the RF chain will not only affect one TV channel. All signals passing through the overloaded device will be affected for as long as the device remains overloaded. Essentially there are two types of interference sources in the 800 MHz band: The LTE base stations and the mobile terminals — handsets, tablets, dongles — which are sometimes close to TV equipment. Although the base stations may be relatively far away from the TV equipment they may be adjacent to the TV antenna, or if further away they may be in the 'beam' of the TV antenna, i.e. in the direction which the TV antenna points, and considerably closer than the TV transmitter which it is desired to receive resulting in a high level of interfering signal in the TV system. In the case of apartments, hotels, schools, colleges, offices, etc. with communal TV antenna systems the base station may be very close indeed, even on the same roof. For the time being there are not many terminals in the European market that use the LTE 800 frequency band but this is increasing rapidly. In the UK an organisation (Digital Mobile Spectrum Limited (DMSL), known as "at800") was set up specifically to mitigate any interference from the new LTE 800 services to TV reception in the UK.〔 https://at800.tv/find-out-more/about-us/〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「800 MHz frequency band」の詳細全文を読む スポンサード リンク
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