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Cable Based All IP Solution

Time : 2021-10-26Source : 数码科技

1. Background

In order to provide better user experience and improve the operation efficiency at the same time, there is a trend of all IP for cable operators. Generally, all IP means the IP transmission of all the services, such as Live, VOD, Voice, and Internet.

Why need all IP for cable operators?

Cable operators are changing more and more programs from SD to HD or 4K/8K to provide better user experience. Considering the fact that typical bandwidth of a single frequency in cable is around 38Mbps, in which one 4K/8K program is impossible to carry, so it is necessary to solve the bottleneck of spectrum resources for cable operators to evolve to the new 4K/8K era.

Meanwhile, because of the fierce competition, cable operators are more and more caring about improvement of operation efficiency for existing platforms, which can be achieved through better integration of various platforms (live, VOD, OTT, etc. ).


2. Cable Based All IP Solution

2.1 Solution Diagram

For the all IP trend of different services, the following diagram shows the typical way of achieving the target.

2.2 Solution Introduction

The key of cable based all IP solution is the IP transmission of all services for the terminals, which mainly includes Internet data services, VOD services, live services and VoIP services.

  • Internet data services. It includes uplink and downlink data transmission.

For the traditional DVB network, it is impossible to provide the Internet service, while through DOCSIS/PON network (the bidirectional network), cable operators can provide the full IP transmission for data services.

  • VOD services. It includes the return (uplink) of VOD programs control signaling and the transmission (downlink) of VOD programs.

The characteristic of VOD program is individuation. The VOD program required by each subscriber is different. Considering the current network conditions of cable operator, the traditional way is to provide the VOD through EQAM (or IPQAM) system, which means STB returns the VOD control signaling through the uplink channel of data, and the video stream is pushed to STB through the frequencies of EQAM. So in conclusion, this is a DVB based VOD solution and it should be changed. Until now, many operators have solved this issue by the deployment of OTT system.

  • Live services. It includes SD, HD, 4K/8K, etc.

There are several characteristics of live services:

a)Similarity. Many subscribers would watch the same program at the same time.

b)Program viewing dispersion is very large. 80% of subscribers usually watch 20% of the popular programs, while 80% of non-popular programs are not likely to be watched.

c)More and more bandwidth is occupied by live programs. With the continuous upgrading of program quality (HD / 4K / 8K), the bitrate is doubled or tripled, and the bandwidth occupied by live video will be even more in the future.

The traditional way of live programs transmission is through DVB, which uses RF transmission and STB will demodulate RF signal to decode the programs. The typical bandwidth of a single frequency is 38Mbps, which usually support to carry around six HD (MPEG-4) programs before, and now only one 4K program can be carried through one single frequency. No matter whether someone is watching or not, all live programs will occupy the spectrum resources. With the increase of the bitrate of live programs, the existing frequency resources will gradually be unable to carry the future large bitrate video. At the same time, the frequency resources of cable operators are nearly saturated, so it is impossible to solve this problem by increasing more frequencies.

The solution is to change the live program transmitted through DVB way on RF to IP way by multicast. The advantages of the IP way include:

a)Multicast provides the same services similar to DVB "broadcast". For subscribers that watching the same program, only one program stream is transmitted, so it will not increase the bandwidth pressure.

b)Available on demand. For programs that are not watched by subscribers, they will not be transmitted over the network. In this way, a large number of "saved" frequencies / bandwidth can be used for broadband services and live broadcast of "hot" high bitrate programs.

c) Service expansion is smoother. In DVB way, if you want to add 4K programs, you need to adjust the frequency planning. This work is very complex and easy to affect the existing services. If IP way is adopted, as long as the bandwidth is guaranteed, it is very easy to add / change programs, and the actual bandwidth consumption will not be greatly increased.

  • Voice service(mainly VoIP). Under the current network conditions, need the terminals (ONU / CM) to support it and add voice server in head-end switch room. Besides, all IP transmission link should be used.Firstly, the SDI signal is digitized to form a media data segment, and then a data block file and an FEC error correction coded data block based on the SDI signal coded data block are formed according to SMPTE ST2022-6 and SMPTE ST2022-5, and then the two types of data blocks Encapsulated into IP data packets, transmitted via Ethernet. At the receiving end, perform IP unpacking, FEC decoding, data verification and error correction, data file serialization, etc., and finally complete the SDI signal recovery output.

2.3 All IP Network Upgrade

2.3.1 Head-end system upgrade

Considering all IP upgrade of the head-end, it mainly includes VOD system upgrade and live broadcasting system upgrade.

For VOD system upgrade, need to upgrade the VOD system to IPTV/OTT system, while for the live broadcasting system, need to upgrade from DVB based to IP based, which can be achieved by increasing stream media gateway to adapt to the IPTV/OTT system.

2.3.2 Cable access network upgrade

Spectrum planning

At present, because live broadcasting (SD/HD) and VOD services occupy the majority of spectrum planning, spectrum resources are under great pressure. Therefore, all IP evolution needs to sort out and optimize the existing spectrum resources.

Sorting out existing spectrum resources:

  1. Are there too many frequencies used for analog programs?
  2. Are there too many frequencies used for VOD programs?
  3. Are there idle or unused frequencies?
  4. Does the network support 750/860/1000MHz?

Optimization of existing spectrum resources:

  1. QAM64→QAM256
  2. Reduce the frequencies of analog programs
  3. IP channel carries non popular live programs
  4. IP channel carries non popular live programs

2.3.2 Network terminal upgrade

For the CM: DOCSIS 3.0 CM is adopted for all IP solution deployment, which supports at least 8 * DS + 4 * US (optional supports 16 * DS + 8 * US). Besides, channel-binding technology is used to provide sufficient access bandwidth.

For the STB: Need to deploy the IPTV STB gradually.


2. Cable Based All IP Solution

In recent years, cable operators are facing fierce competition from both other operators and online video providers. In order to keep the market share and revenue, it is necessary to provide better user experience to attract the subscribers and improve the operation efficiency at the same time.

Cable based all IP solution solved all the above-mentioned challenges perfectly. Besides, it could bring many benefits to cable operators:

1. Solve the problem of insufficient spectrum and bandwidth fundamentally.

2. Make the future development direction of system and business more clearly.

3. Maximize the use of existing assets and continuously accumulate brand value.

4. The future network evolution is clearer.

What’s more, with the development of DOCSIS 3.1 and DOCSIS 4.0, cable network could provide 1Gbps or even more broadband access (especially with higher upstream speeds), which is the key of many applications in the future, such as interactive video conferencing, remote learning and health care applications, IoT and virtual reality, etc.

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