Research & Technology Innovation Centre Interactive Broadcasting Workshop (Brussels, 11 September 2002) Future Interactive Broadcasting Networks Alberto Morello
Digital TV and Radio for hand-held & vehicular receivers Current scenario While audio-walkmen (radio, cassette, CD players) are well established, hand-held TV sets have been a market flop so far Since 10 years DAB receiver market is not taking-off Digital Terrestrial Broadcasting will replace analogue TV. Nevertheless DVB-T services for fixed TV sets are independent from services for mobile/portable receivers: the channel capacity varies from 24 Mbps down to 6-9 Mbps per UHF channel Many European Projects propose a scenario where cellular phones (GSM, GPRS, ) include a DVB-T /DAB receiver, to allow for portable TV/Radio
Digital TV and Radio for hand-held & vehicular receivers Which perspective? The cellular phone is always with you. Would you like to use it also:.as a perfect audio-walkman.. and as a portable TV set? Probably YES, if: cheap Low extra-cost (say 10%) for the terminal Low extra-cost (say 0-10%) 0 for TV/Radio services satisfactory technical quality: A single, light, hand-held held set for many integrated services (Phone, Internet access, TV, Radio) Good service continuity, battery duration
: key technical characteristics Signal bandwidth: 4.8 MHz (5 MHz Channelling) Two-way connection (up-link & down-link): 5 MHz + 5 MHz (Freq. Division Duplexing) or 5 MHz (Time Division Duplexing) Wide-band spread spectrum + QPSK modulation + rate 1/3 or 1/2 convolutional or Turbo coding Suitable for mobile/portable reception (as DxB-T) Capacity per cell per channel : about 2 Mbps (1/3 code) or 3 Mbps (½ code) 2 Mbps 2 Mbps 384 kbps x 5 144 kbps x14 V < 50 km/h
Which audio & video services can be transported by? Good quality VIDEO coding for small displays (CIF or QCIF resolution) is feasible at 100-300 Kbps (MPEG-4, H26L, Media-player). High quality STEREO AUDIO coding is feasible at 32-64 kbps (e.g. MP3, AAC) will support the required protocols for: Audio and video download or streaming over IP IP Multicast Due to the high capacity required by video and audio, it is likely that only short clips will be economically downloadable (unicast) via.
Is TV and Radio broadcasting feasible via? From a technical point of view, yes: using multicast protocols on, spectrum efficiency is guaranteed on the radio link Palm computer technology is becoming mature in terms of display quality, processing speed, battery duration, weight, dimensions. but from an economical point of view, cellular networks are not suitable to implement cheap broadcasting services.. lets explain why
The Network Structure is imposed by the traffic type, rather than by the transmission constraints INTERACTIVE UNICAST TRAFFIC Spectrum efficiency Small cells Cellular Telephony (e.g.: ): the cell dimensions range from few hundred meters to some kilometres The base stations and the cellular phones transmit low power BROADCAST TRAFFIC Spectrum efficiency Costs reduce by enlarging cells Broadcasting: the cell dimensions range from some kilometres to more than one hundred of kilometres The stations transmit high power
Network structures: BROADCASTING Broadcast networks (satellite, terrestrial) are the cheapest way to convey the same programme to thousands of houses Conversely, over large coverage areas, their capacity for interactive services is low Cellular networks (GSM, ) are expensive, since they require a very large number of transmitters/base stations (tens of thousands), totally connected by a backbone network The difference of cost is of 1-2 orders of magnitude!!! but they can convey a huge interactive capacity (millions of phone calls at 10 kbps)
Possible synergies between Broadcasting & Traditional approach Digital broadcasting systems (DVB-T, DAB) and networks carry the wide-band broadcasting services (one-way); GSM / (run by Telecom Network Operators) may enhance the broadcasting services as return paths for interactivity (e-commerce, Internet). DVB is evaluating the needs to set-up a DVB-M group to enhance DVB-T for mobile applications (time interleaving, turbo-coding, introduction of H26L coding, receiver cyclic switch-off to reduce power consumption,...?????)
An alternative approach: why not over broadcast networks? BROADCAST CELLULAR
Two superimposed networks, two frequency bands, a single technology: Broadcast network operator BROADCAST FREQUENCY BAND UNIDIRECTIONAL FREQUENCY BAND Telecom network operator BI-DIRECTIONAL
Comparison between two scenarios DVB-T+DAB+ B-+ DVB-T (6-10 Mbps) DAB BROADCAST CELLULAR CELLULAR
Terminal complexity DVB-T+DAB+ versus B-+ Traditional approach B- approach DVB-T Tuner & dem DAB-T Tuner & dem Tuner & demod TX & mod Single B- Tuner/demod? Under Tunerstudy Tuner & demod & demod TX & mod MPEG2 video dec MPEG2 audio dec MPEG4 video dec MP3/AAC audio dec MPEG4 dec MP3/AAC dec Display Loud speakers Display Loud speakers API: MHP-MOBILE + MOT + MeXe API: MeXe Phone
Terminal power consumption & usage time DVB-T: the full bit-stream has to be decoded (FFT,FEC): For mobile applications, about 5-10 Mbit/s are demodulated/decoded and only about 1/10 of them are used (1 TV service) B-: after DS-SS, the processing speed ( turbo decoding, ) is at the service speed (e.g. at 200-500 kbit/s) Example: Assuming the following DVB-T receiver power budget: 20% tuner, 40% demodulator, 40% video decoder.. Reducing the demodulator power consumption by a factor of 10, the B- terminal usage time can be 1.5 times that of a DVB-T receiver (very rough estimation!!!!)
B- versus DVB-T / DAB Spectral efficiency for mobile services (high ruggedness DVB-T mode) DAB DVB-T B- Transmission ruggedness Spectral efficiency [audio progr. in 1 MHz] Spectral efficiency [TV progr. in 1 MHz] Comparable (using rate 1/2 code) W-CDMA & OFDM in a multipath channel? 6.7 5.8 9.4-1.3 1.4 Hypotheses: DAB: MPEG layer1 audio at 128 kbps per stereo; multimedia at 200 kbps DVB: MPEG layer1 audio at 128 kbps per stereo; MPEG2 video at 576 kbps, CIF; multimedia at 200 kbps B-: AAC audio at 64 kbps; MPEG4 video at 430 kbps, CIF; multimedia at 200 kbps (NB: using H26L, both DVB-T and B- may double their spectral efficiency)
Is a new standard necessary for B-? B- is a sub-set of the standard: only fine tuning of the protocols is needed (at SW/Firmware level, rather than at chip-set level) E.g., Standardisation is required on a Service Discovery channel (similar to DVB SI), delivering access information to the terminals Video server A Video server X Core network SI Conventional base station High Power TX SI
Conclusions (1) Two technical solutions are available to deliver digital radio, TV and interactive services to cellular phones and vehicular receivers: DVB-T and DAB (for broadcasting) + GPRS/ (for interactivity) B- (for broadcasting) + (for interactivity) This preliminary survey indicates that the technical performance of the two solutions may be comparable The key advantage of the B- solution is the lower complexity and power consumption in the receiver
Conclusions (2) The traditional technical approach seems to meet the highest level of consensus by broadcasters and telecom operators The technology walls (DVB-T for broadcasters and for Telecom) are still perceived as strong protections of the broadcast and telecom business areas. Legal Framework Wall Frequency-band Wall Technology Wall Telecom Centro Ricerche business e Innovazione area Tecnologica DVB-T Broadcast business area
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