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MediaFLO (branded in the U.S. as FLO TV) is Qualcomm's technology to transmit data to portable devices such as cell phones and PDAs, used for mobile TV. Broadcast data includes real-time audio and video streams, individual, non-realtime video and audio "clips", as well as Internet Protocol datacast application data such as stock market quotes, sports scores, and weather reports.[1] The "F-L-O" in MediaFLO stands for Forward Link Only,[2] meaning that the data transmission path is one-way, from the tower to the device. The MediaFLO system transmits data on a frequency separate from the frequencies used by current cellular networks. In the United States, the MediaFLO system uses frequency spectrum 716-722 MHz, which was previously allocated to UHF TV channel 55.[3][4] It is a competitor to the Korean T-DMB, the Japanese 1seg and the European DVB-H standards. Devices including MediaFLO were first introduced by LG and Samsung at CES 2006 in Las Vegas. On December 1, 2005 Verizon Wireless and Qualcomm announced partnership for the launch of the MediaFLO network, and Verizon launched the service commercially as part of its VCAST offering on March 1, 2007, marketing the MediaFLO-specific technology/service as "VCAST TV".[5] A similar announcement was made by AT&T Mobility in February 2007.[6] AT&T Mobility launched their MediaFLO service on May 4, 2008.[7] The first non-phone TV-only devices were released in late 2009.[8] Qualcomm is also conducting MediaFLO technical trials internationally, with the intention of forming partnerships with existing multi-channel content providers / service operators.
[edit] TechnologyThe protocol was developed because of the inherent spectral inefficiency of unicasting high-rate full-motion video to multiple subscribers. Additionally, traditional analog television and over-the-air digital television signals (DVB-T) were difficult to implement on mobile devices, due mostly to power consumption issues. ATSC, used only by the United States and its neighbors, also has difficulty even with fixed reception due to multipath, and ATSC-M/H (which is free-to-air from individual TV stations) was not finalized until 2008. In addition, the transmission need not convey as high a resolution as would be needed for a larger display. MediaFLO streams are only 200-250 kbit/s, which would be insufficient for a larger screen size.[9] [edit] Modulation and codingIn the current US implementation, FLO is transmitted by a network of high-power broadcast transmitters operating at effective radiated powers as high as 50 kilowatts. This allows for a coverage area of a transmitter to be as large as 30–40 km.[9] The activation of many of these transmitters were delayed due to the official end of analog TV broadcasting on channel 55 being delayed.[10] Immediately following the transition, the FLO network was expanded to several new markets, and coverage was enhanced in some existing ones.[11] The transmission is an encrypted OFDM set of QAM signals sent on a 5.55 MHz channel from 716-722 MHz (former UHF TV channel 55). The band was auctioned-off by the FCC and known as the Lower 700 MHz Block D.[12] Qualcomm also bought, in a later auction, the use of former analog UHF TV channel 56 (722-728 MHz) in Boston, Los Angeles, New York, Philadelphia and San Francisco for additional services. All of the transmitters send the same signal and use the same frequency, forming a single-frequency network. This allows the mobile to decode the signal from more than one transmitter in the same way that it might if it was a multipath-delayed version from the same transmitter.[9] All stations use callsign WPZA237, but each has an identifier indicating its group and number. For example, one station in the metro Atlanta media market is ATLAN6, while another is ATLA14. Some other operational parameters of MediaFLO are as follows:
All of the barrier (data) traffic occurs within an MLC using the 3500 non-overhead subcarriers. The protocol also contemplates a certain amount of inter-symbol time spacing, to allow for the effects of multi-path transmission and reception.
There is a window time TWGI included both before and after each OFDM symbol. However, since this window is shared between each two consecutive symbols, TS = TU + TWGI + TFGI. [edit] Commercial deploymentIn the U.S., all FLO television providers offer a set of 10 basic channels:
Additionally, the FLO Preview Channel is a free-to-view barker channel, available without subscription.[13] For conditional access, Verizon Wireless utilizes its EVDO network to authenticate mobile handsets and provide the decryption keys necessary to decode the programming. There are currently 12 TV channels being broadcast for Verizon.[14] The Verizon-specific channels are: AT&T has also launched its own MediaFLO-powered broadcast TV service with the following AT&T-specific channels:[15] [edit] References
[edit] See also
[edit] External links |
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