Broadcasting, broadcasting and television, developing interactive TV services, can fully rely on the advantages of the HFC network to carry out broadcasting, on-demand and other switching services. In some cities, radio and television have built a small number of LAN communities. In these places, the same technical model of telecommunications IPTV can also be adopted, and multicast switches can be used to carry out services. Luo Feng of Wuxi Digital TV Co., Ltd. discussed several main technical modes including IPTV and interactive TV, and conducted a preliminary comparative analysis.
1. DVB for broadcasting, DVB+CM mode of CableModem for on-demand and interactive use
DVB transmits a large number of TV broadcast programs, has the advantages of maturity, reliability, and low price, and can enter millions of households with the translation of digital TV. Use CableModem for on-demand and interactive services, and the on-demand program stream is transmitted through the CableModem downlink channel. The DVB+CM mode realizes a complete interactive TV program. The CableModem module is best integrated in the DVB set-top box, which can reduce costs and improve reliability, and only use one device to improve the entire service to users. At present, some chip manufacturers have introduced a single chip solution with DVB+CableModem function.
Because DVB adopts MPEG-2 encoding, and CableModem system generally adopts MPEG-4, H.264 or AVS encoding format due to the limited bandwidth, so the DVB set-top box needs to add at least one of MPEG-4, H.264 or AVS encoding. Format support. Otherwise, there are only interactive functions, and VOD services cannot be realized. When Cable Modem system adopts 64QAM modulation mode, the downlink rate of each head end is 38Mbps, and when 256QAM modulation mode is adopted, the downlink rate of each head end is 51Mbps. In a very good quality HFC network, 256QAM modulation can be used. However, most HFC networks currently use 664QAM modulation, so that each video stream averages 1.5Mbps, and each headend supports up to 25 simultaneous on-demand broadcasts. The 10% simultaneous on-demand rate calculation means that each headend can develop up to 250 interactive TV users.
If the head-end purchases a single small device, each unit is about 130,000 yuan, plus the cost of the CableModem terminal, the cost per line reaches about 900 yuan, which does not include DVB set-top boxes, authentication billing gateways, and two-way HFC networks And so on. If you purchase a centralized big headend, the cost per line will reach about 1,200 yuan. According to the ARPU value of 40 yuan per month for each on-demand user, it will take 2-2.5 years to recover the line cost. It can be seen that the price of the DVB+CM model is too high to be suitable for large-scale commercial applications. It is only suitable for small-scale applications at the initial stage of business development and situations that require rapid business development.
2. DVB+LAN mode for broadcasting, on-demand and interactive LAN
This mode is basically the same as the DVB+CM mode, except that the Cable Modem two-way channel is changed to a LAN channel. The on-demand program flow is changed to the LAN channel formed by the switch, while the broadcast program still uses the traditional DVB system. LAN access has the advantage of sufficient bandwidth. The bandwidth to each corridor switch can reach 100M, and the uplink rate of the community aggregation switch can reach 1000M. Therefore, it can fully meet the video-on-demand requirements of each user, and there is enough bandwidth to ensure the needs of Internet services. In a 500-household community, if the number of on-demand users is 20%, and the on-demand rate is 60% at the same time, when each video stream averages 1.5Mbps, the occupied bandwidth is only 90M.
It is precisely because of the rich bandwidth that the encoding format can be MPEG-2 in addition to MPEG-4, H.264 or AVS. Also take the above cell as an example, when each MPEG-2 video stream averages 4Mbps, the total bandwidth of the cell is 240M, and it needs the support of a gigabit link. After adopting the same MPEG-2 encoding format as DVB broadcasting, the decompression algorithm of the set-top box can be simplified and the cost of the set-top box can be reduced. But at the same time, it has higher requirements on the bandwidth of the backbone network and a larger library storage system. Since broadcasting has been done through DVB, this mode is different from the telecom LAN access mode. The switch does not need to support multicast, and a simpler switch can be used. A LAN network that can be managed and focused on operations, when the network access rate is about 20%, the cost per line is about 700-1000 yuan, which is slightly lower than the DVB+CM model. Therefore, it is suitable for large-scale applications when the network access rate is high, or when there are many LAN cells.
3. Broadcast and on-demand use the same DVB IPQAM mode
Digital TV can transmit hundreds of program streams. If you divide the connection area and use dozens or even one or two hundred program streams for VOD service in each sub-area, you can provide complete broadcasting and on-demand services. , This is the basic idea of IPQAM mode. The sub-area can be composed of several or even dozens of optical nodes, covering about 20,000 to 50,000 users, and one or more IPQAM devices are placed in each sub-area. Each sub-area is actually each sub-center of the HFC network. IPQAM equipment is a device that multiplexes and up-converts the DVB/IP video stream and outputs it as an RF signal. The different RF signals output by IPQAM will be mixed with the broadcast signal from the total front-end respectively, and the mixed signals will be sent to different optical transmitter modules (optical contacts) and then directly transmitted to the final access network. The "channel resource spatial multiplexing" technology will be adopted in the way of network frequency resource allocation. Therefore, the entire VOD system will only need a few analog channels to realize large-scale VOD applications.
Each IPQAM modulator generally has 16 or 24 RF ports. When each RF port outputs a 64QAM modulated signal, the total code rate reaches 608M (16 ports). Each video stream adopts MPEG-2 format and requires a rate of about 4M, so that a 16-port IPQAM can support 150 concurrent on-demand requests. Calculated based on the 10% simultaneous on-demand rate, 1,500 interactive TV users can be developed. Such a sub-area of 30,000 households only needs two IPQAM devices to support when the interactive TV user access rate is 10%.
Because on-demand also uses the same MPEG-2 encoding format as DVB broadcasting, it simplifies the set-top box decompression algorithm and reduces the cost of the set-top box. Since the domestic IPOAM modulator costs about 4,000 yuan per frequency point, which does not include the backbone network and set-top box, when the CableModem method is used for backhaul, the cost per line of the access network is about 400 yuan. Users who don’t need Internet service but only need to order service can also use mobile phone short message back transmission. At this time, the cost per line of access network is about 200 yuan, which is the lowest of the above several technical models.
Through the above analysis of the mainstream technology models of IPTV and interactive TV, we can see that both IPTV and interactive TV will have their own focus on business models. IPTV focuses on the development of VOD on-demand services, while using multicast technology to implement broadcast services, and will vigorously develop other Internet-based interactive services. Radio and TV’s interactive TV also focuses on broadcasting services and on-demand services, and will increase the popularity of broadcasting services through the development of on-demand services. With different technology models of interactive TV, Internet-based interactive services can also enter millions of households.
Several technical models have obvious differences mainly in the following points:
(1) Broadcasting service-broadcasting service that satisfies the needs of the masses. IPTV adopts controllable multicast technology and needs to solve a series of new problems, and it is still in the trial operation stage; while interactive TV adopts mature DVB solution, many cities have been successfully operated for many years. Therefore, it is difficult for IPTV to catch up in the broadcasting business.
(2) On-demand services-IPTV reflects its own characteristics and advantages in on-demand services that meet individual needs. ADSL point-to-point connection and high bandwidth of LAN access can all be well developed. The way of on-demand by Cable Modem in interactive TV is limited by the head-end bandwidth and equipment price, and it is difficult to meet the requirements of large-scale on-demand business. The IPQAM mode enables radio and television to give full play to the advantages of the HFC network, especially after the digital TV is fully translated, a large amount of frequency resources are freed up, which is more conducive to the development of on-demand services.
(3) Video coding standards-In terms of video coding standards, IPTV is troubled by which standards are adopted. There are multiple standard branches in MPEG-4, and the issue of mutual compatibility needs to be considered; the H.264 industry chain is not mature enough, and there is still a problem of patent fees. The IPQAM mode of broadcasting interactive TV only adopts the MPEG-2 standard, the technology is mature, the chip price is low, and the cost of the set-top box is also low, which is conducive to large-scale promotion.
(4) On high-definition TV-because high-definition TV requires a larger video stream, IPTV can hardly support this well. The interactive TV of the radio and television is very easy to achieve, and this will be the strong point of the radio and television in the long term.
(5) Access cost-ADSL access in IPTV and IPQAM mode in interactive TV both have lower construction costs, so this competitiveness is close. The cost of LAN access in IPTV and the DVB+CM mode and DVB+LAN mode in interactive TV are relatively high.
In addition, each branch technique mode has some small problems. For example, ADSL access has issues with number selection rate and overall QoS guarantee; LAN access has security issues, multicast capability issues, and so on. The interactive TV also has some problems, such as the reverse noise problem when the Cable Modem is connected. But these will be resolved in operation, and will not have a great impact on the overall plan.
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How far(long) the transmitter cover?
The transmission range depends on many factors. The true distance is based on the antenna installing height , antenna gain, using environment like building and other obstructions , sensitivity of the receiver, antenna of the receiver . Installing antenna more high and using in the countryside , the distance will much more far.
EXAMPLE 5W FM Transmitter use in the city and hometown:
I have a USA customer use 5W fm transmitter with GP antenna in his hometown ,and he test it with a car, it cover 10km(6.21mile).
I test the 5W fm transmitter with GP antenna in my hometown ,it cover about 2km(1.24mile).
I test the 5W fm transmitter with GP antenna in Guangzhou city ,it cover about only 300meter(984ft).
Below are the approximate range of different power FM Transmitters. ( The range is diameter )
0.1W ~ 5W FM Transmitter ：100M ~1KM
5W ~15W FM Ttransmitter : 1KM ~ 3KM
15W ~ 80W FM Transmitter : 3KM ~10KM
80W ~500W FM Transmitter : 10KM ~30KM
500W ~1000W FM Transmitter : 30KM ~ 50KM
1KW ~ 2KW FM Transmitter : 50KM ~100KM
2KW ~5KW FM Transmitter : 100KM ~150KM
5KW ~10KW FM Transmitter : 150KM ~200KM
How to contact us for the transmitter?
Call me +8618078869184 OR
Email me [email protected]
1.How far you want to cover in diameter ?
2.How tall of you tower ?
3.Where are you from ?
And we will give you more professional advice.
About Us
FMUSER.ORG is a system integration company focusing on RF wireless transmission / studio video audio equipment / streaming and data processing .We are providing everything from advice and consultancy through rack integration to installation, commissioning and training.
We offer FM Transmitter, Analog TV Transmitter, Digital TV transmitter, VHF UHF Transmitter, Antennas, Coaxial Cable Connectors, STL, On Air Processing, Broadcast Products for the Studio, RF Signal Monitoring, RDS Encoders, Audio Processors and Remote Site Control Units, IPTV Products, Video / Audio Encoder / Decoder, designed to meet the needs of both large international broadcast networks and small private stations alike.
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We have customers of public and commercial broadcasters, telecom operators and regulation authorities , and we also offer solution and products to many hundreds of smaller, local and community broadcasters .
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