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RadioScape queries viability of DVB-H for mobile multimedia

Posted: 08 Jun 2005 ?? ?Print Version ?Bookmark and Share

Keywords:digital radio? radioscape? digital video broadcast-handheld? dvb-h? digital multimedia broadcasting?

By John Walko

EE Times

Digital radio specialist RadioScape has raised serious concerns about the technical and commercial viability of using Digital Video Broadcast-Handheld (DVB-H) technology for delivering multimedia services to mobile handsets, suggesting that the alternate Digital Multimedia Broadcasting (dmb) technology favored by carriers in the Far East is superior.

Addressing the GSPx Mobile Conference in Eindhoven, the Netherlands last month (May 17), Les Sabel, VP of technology for RadioScape outlined the results of the trials in Cambridge, England, that he says show that the design of DMB networks can proceed using essentially the same rules as for current DAB audio networks.

He stressed that DMB, unlike DVB-H, is based on proven DAB technology with spectrum, transmission towers and capacity already available for it in most countries.

Sabel noted during his presentation that DVB-H is a modification of Digital Video Broadcast-Terrestrial (DVB-T) for handheld devices but has spectrum allocation issues as many countries are currently using these frequencies for analogue television.

"DMB is viewed by many as the next logical step in the evolution of DAB," says Sabel. "More importantly, it could also represent the next step in the evolution of mobile phones delivering the vision of video and data on the move that 3G promised but cannot deliver in a cost effective and efficient manner. A one-to-many broadcast technology, such as DMB, provides a broadband pipe of multimedia services that the one-to-one approach of 3G can only provide in small numbers and expensively."

Despite the huge impetus building around DVB-H , Sabel says indications are that for that technology to work effectively in mobile and indoor environments it will need to use transmission parameters similar to DAB. This will eliminate any real capacity advantages and still leave DVB-H with the issue of transmission power requirements due to its larger bandwidth.

"Our field trials show that good DMB reception can be achieved with existing DAB transmitters that only use low amounts of power to cover a large footprint," says Sabel. He adds: "I have yet to see any comparative, quantitative evidence for DVB-H but, recent discussions indicate that for DVB-H to achieve the same footprint, network providers will typically require a five times greater density of transmitters."

According to Sabel, this will make DVB-H very expensive to establish and run let alone the possibility of public concerns over yet more transmission towers. "DMB clearly offers a much better, more cost effective solution for operators that can be implemented now as it based on proven DAB technology as can be evidenced by DMB pioneers in countries such as Korea and China where trial systems are already up and running."

He adds that recent studies of the power requirements suggest that reliable mobile operation is unlikely with DVB-H unless the network uses QSPK modulation. Coupled with the propagation issues this throws up, Sabel says a DVB-H network is likely to need a transmitter density that is at least five times that of DAB/DMB networks.

The WorldDAB organization has been enhancing the existing Eureka 147-based standard, notably adding an outer layer coding (OLC) scheme. Service based enhancements, such as Electronic Program Guides, conditional access and multimedia object transfer have also been added and are expected to be agreed and standardized within months.

RadioScape believes that these and the introduction of Enhanced Stream and Packet modes provide the additional error protection necessary for the robust delivery of multimedia content mobile operators are seeking.

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