Technology whitepaper of 10G GPON Plus Enhanced Network
A new approach from GPON to 10G PON Plus
10G GPON Plus Network—10G IPVB Overlay GPON
Scale and Value of GPON
According to data released by the Ministry of Industry and Information Technology of China, the number of broadband access users of the three major telecom operators is steadily increasing, and the number of gigabit users is rapidly expanding.
The data show that the total number of Internet broadband access users of the three basic telecom operators reaches 545 million, among which, the users with access rates of 100Mbps or above reach 508 million, accounting for 93.2% of the total number of users, and the users with access rates of 1000Mbps or above reach 40.88 million. It is seen that although the scale of G/EPON fiber to the home network in China is huge, the gigabit users are less than 10%.
With the growth of 4K/8K ultra-high definition video, it is necessary to upgrade and expand the 100Mbps users to 1000Mbps. Therefore, how to reasonably and effectively upgrade and expand the existing 2.5G GPON network to a 10G PON network has very realistic and economic significance.
One upgrading approach is to simply replace GPON networks with 10G xGPON optical passive network technology, phasing out GPON networks in 2-3 years.
Herein, to prolong the GPON network life cycle, and effectively protect the original investment, this paper proposes a 10G IPVB Overlay GPON network architecture (10G GPON Plus network), which can upgrade the existing GPONs to a 10G optical network at much lower cost and in a more convenient way. The paper firstly analyzes the access services in the future and their demand for access bandwidth. Secondly, the paper discusses the transmission performance, reliability, and availability of live TV service, and the access performance of interactive service of the 10G GPON Plus network. It shows that the 10G GPON Plus network can guarantee the superior transmission performance of live TV service, with professional video technical standards. At the same time, the network enables strong reliability and availability, perfectly avoiding the weakness of traditional IPTV networks. Finally, two application scenarios of the GPON Plus network are presented. One application is the multi-terminal 10G expansion mode of the standard GPON network, the other is how the FTTH network of CATV evolves to a 10G all-IP service network.
Major access services of 10G PON network---UHD video
The main goal and motivation of the FTTH network are to increase bandwidth and access more kinds of video services with higher quality because video services represented by TV live broadcasts and video on demand have become the most important applications in peoples’ life, entertainment, and work. Telecom service providers firstly induced video services over their legend copper access networks, with very little market sharing. And later, with the widespread deployment of FTTH networks, they take the technology of IPTV service, an interactive ultra high definition video, as an opportunity to extend their video market successfully, in turn, driving the fast growth of the IPTV market.
In 2021, China's 4K UHD TV market has already accounted for more than 72%, but the base of IPTV UHD users is still a large quantity. Obviously, the H.264 video transmission of IPTV can not meet the viewing quality requirement of 4K UHD TV sets. And the 4K UHD TV sets require much higher quality video transmission services which demand higher bandwidth and lower bidirectional delay for multicast IPTV streams.
Fig. 1 4K/8K UHD Videos
As shown in figure 1, a standard 4K UHD video stream is between 36-57Mbps, and an 8K video is between 80-160Mbps. If transmitting 100 sets of 4K (4Gbps) and 20 sets of 8K (2.4Gbps) live TV programs, a total video stream bandwidth of 6.4Gbps is required.
In addition, the IP live TV service is highly sensitive to the packet loss/bit error rate of interactive IPTV systems. According to the relationship between packet loss rate and link bandwidth utilization rate given in Huawei's "Experience-Driven 4K Transmission Network White Paper", the packet loss rate can be ignored only when the link bandwidth utilization rate is much lower than 70%.
Fig. 2 Relationships between network buffer and packet loss rate at different link utilization rates
If considering the future transmission of 3R video services (VR, virtual reality, AR, augmented reality, and MR, mixed reality), the bandwidth consumption of downstream video services is even more amazing. Generally, a set of VR program bandwidth is around 300Mbps, AR around 500Mbps, and MR is even higher.
Therefore, the focus of 10G FTTH network bandwidth expansion is to transmit large-capacity, ultra-high-definition IP live-TV stream with high-quality QoS.
10G GPON Plus Network---10G IPVB Overlay GPON
In view of the fact that the main purpose of bandwidth expansion is to provide IPTV live broadcast service, this paper proposes a solution for this by superimposing a 10G IP broadcast system (ITU-T J.1210 IPVB protocol) and GPON system to build a two-channel GPON Plus network, as shown in figure 3.
Fig. 3 Architecture of 10G GPON Plus network
In the 10G GPON Plus network, the live IPTV stream is transmitted completely through the optical broadcast channel of 1550nm by following the IP broadcast protocol, ensuring the desired QoS of no delay, no jitter, and low bit error for live IPTV stream.
The 10G IP Gateway in the 10G GPON Plus network is functionally composed of an ONU module and a 10G IP receiving module (IP Tuner), and connected with two fibers respectively. One fiber is connected to the BoSA of the ONU module, and the other fiber is connected to the 10G IP Tuner module. The 10G IP Gateway may be connected to single fiber with three wavelength channels (1550/1490/1310nm) through a built-in WDM.
The 10G IP stream Distribution Line Terminal (DLT) performs the function of service convergence of live IPTV, VOD, OTT TV, and local IP video stream. According to operation strategies, DLT can dynamically allocate the IP streams of Internet services to the 10G broadcast channel or to the 1490nm GPON downstream channel, thus expanding the bandwidth of the downstream channel of the system up to 12.5Gbps.
The 10G GPON Plus network is similar to the biplane architecture of the viaduct bridge, that is, a 10G bandwidth broadcast channel is superimposed on the GPON network to evolve into an asymmetric bidirectional broadband access network.
Fig. 4 10G GPON Plus Network—10G IPVB Overlay GPON
The features of the 10G GPON Plus network are：
* IP broadcast channel - provides 10G downstream at a low cost, supporting 4k/8K UHD TV and VR video broadcast.
* Dual-channel asymmetric broadband access: 12.5Gbps downstream and 1.25Gbps upstream.
* Supporting all IP services——Live TV, SDV (Switch Digital Video), VOD or Interactive IPTV, OTT TV, and Internet services.
Performance analysis of 10G GPON Plus network
Transmission quality capability of 10G GPON Plus network for live IPTV broadcast service
For live TV broadcast service, the reason why IP broadcast has super high video transmission quality is that it broadcasts all TV data simultaneously to every home rather than switches data to exclusive homes individually. Thus there is no switching delay and jitter, and as long as the receiving optical power exceeds the receiving sensitivity threshold, the packet loss will be small. The switched and Non-switched modes of IP video broadcast are illustrated in figure 5.
Fig. 5 ALL IP networks supporting switched and non-switched IP Videos
In the one-way broadcast mode (no Switched Digital Video), all TV programs are distributed to all users in the network. Users can select any one of the TV programs to watch by using the IP Tuner.TV programs with the one-way broadcast mode have the characteristics of high QoS, no delay, no jitter, and good user experience (QoE).
SDV (Switched Digital Video) two-way broadcast mode means that the TV programs are only transmitted on the demand of users, thus, saving the downstream bandwidth. And if one user orders and receives a TV program stream on demand, all other users in the network are allowed to share the same TV program stream. The SDV broadcast mode not only performs the bandwidth utilization as high as that of traditional IPTV but also does not need complex protocols (such as IGMP protocol). The switching strategy of the TV program stream in the SDV system is simple and fast, and it has the advantages of high QoS, no delay, no jitter, and a good QoE user experience.
According to the statistical law of users' habit of watching live TV, 80% of users watch 20% of the TV programs and the remaining 20% choose to watch the remaining 80% of TV programs. Thus, the 10G GPON Plus network can perform optimal dynamical bandwidth allocation by broadcasting the most popular 20% of TV programs through the one-way broadcasting mode and delivering 80% of the programs through the two-way SDV broadcasting mode. It is estimated that 60% of the broadcast bandwidth of live TV streaming services can be saved.
Fig. 6 Statistical law of users' habit of watching live TV
Therefore, the 10G GPON Plus network, which superimposes a 10Gbps broadcast channel on the GPON network, will provide sufficient bandwidth and excellent transmission performance to meet the massive growth of IP live TV programs in the future, to prolong the life cycle of GPON networks, and to ensure economic benefits to operators.
Generally, the technical standard for broadcast TV video requires a bit error rate（BER）of 10-11, which is much higher than the BER requirement of 10-3 in IPTV systems according to the Ministry of Industry and Information Technology of china. Thus, in GPON Plus networks, the quality of live IPTV can be greatly improved to the same level as the technical standard for broadcast TV video.
Reliability and Availability of IPTV broadcast services in 10G GPON Plus networks
The IP broadcast link and GPON system can also work independently. In this case, live IPTV broadcast service and Internet access service are carried out independently over the two systems. In other words, GPON networks can extend their IPTV broadcast service with high reliability and high availability by simply adding an independently working one-way broadcast link.
First of all, as the result of the addition of the independent IP broadcast system, the viewing quality of live IPTV service no matter the number of users, that is the concurrency rate of users will not impair the viewing quality of IPTV service even in the extreme cases of viewing peak.
Secondly, the IP broadcast backup system can adopt a physical switching operation with a short switching time of a microsecond level, and it is too fast to be noticed by users, thus without impairing the quality of experience (QoE) of the service. This performance proves the availability and reliability of the GPON Plus network.
Finally, in 10G GPON Plus networks, the IP broadcast channel, and two-way GPON network can work fully in physical isolation mode. In the extreme circumstances where the two-way GPON network is attacked by harmful information and intrusion, resulting in the halt of the network, the independent IP broadcast channel can stay working independently and provide reliable IP broadcast television transmission. There is no risk of a shutdown of live IPTV services, and this meets the requirements of network availability standards.
Access performance of two-way interactive service in 10G GPON Plus networks
In 10G GPON Plus enhanced networks, the two-way access capability of the network consists of two parts, one is the two-way access bandwidth of the GPON network, and the other is the remaining downlink bandwidth after the 10G broadcast channel is allocated to the IPTV live broadcast service.
In GPON networks in China, generally, each PON-port of OLT serves 32 homes. Correspondingly, the static downstream/upstream bidirectional bandwidth for each household is about 78/39Mbps.
In the view of the assessment of upstream bandwidth capacity, for residential users, the services occupying the largest upstream bandwidth are video phone and home monitoring, each taking upstream bandwidth of 4Mbps and two taking 8Mbps in total. The current average upstream bandwidth of 39 Mbps in the GPON network is sufficient, that is this upstream bandwidth will be sufficient for GPON Plus networks.
As to the downstream bandwidth, in GPON Plus networks, there is no need to allocate 40% of the 2.5Gbps downstream bandwidth provided in the GPON subnet for live IPTV streaming services. And all the average static bandwidth of 78Mbps to each household can be fully used for Internet access services. Basically, this bandwidth can support each household watching two 4K Internet videos at the same time.
As the 10G IP broadcast channel is integrated with the GPON network, part of its downstream bandwidth can be allocated to deliver interactive services such as OTT/TV Internet video service and IPTV on demand, as shown in figure7:
Fig. 7 Integration of IPVB channels and GPON
The bandwidth of the 10G IP broadcast channel is usually divided into two parts: the bandwidth of 6Gbps is used for live IPTV services and the transmission of massive TV programs, such as 100 standard 4K TVs (3.6Gbps) and 20 standard 8K TVs (2.4Gbps). The rest bandwidth of 4Gbps can serve 1024 households, providing each household with a minimum static downstream bandwidth of 4Mbps (the dynamic bandwidth of 4x√ (1024/32) =22.4Mbps), or service 40 users, for them to watch 8K OTT video (100Mbps) simultaneously.
It is seen that the two-way access capability of interactive services is greatly improved in 10G GPON Plus networks. The minimum static bandwidth downstream for a user is as high as 78+4Mbps, which is full enough to meet the access demand of asymmetric two-way broadband services in the next 10 years, including 8K, VR, and other super-bandwidth video streaming interactive services.
In the technology of 10G xGPON networks, the average household bandwidth is 156Mbps in the case of each PON-port of 10G OLTs serving 64 users. Considering IPTV live services which occupy 40% of the total bandwidth, the actual effective available downstream bandwidth is only 93Mbps for two-way Internet services. Compared with the downstream bandwidth of 82 Mbps in the 10G GPON Plus network, the effective interactive bandwidth in the 10G xGPON network increases only by 11.8%. However, the average additional cost of 10G xGPON for one user is as high as USD100, which is about 3.2 times the cost of using 10G GPON Plus networks. Therefore, the approach of 10G xGPON networks has lower investment benefits and a lower performance-to-price ratio than the scheme of the 10G GPON Plus network.
In particular, in the case of each PON port of GPON OLT serving 64 users, the downstream and upstream bandwidths of each user in the 10G GPON Plus network are 39+4Mbps and 19.5Mbps, respectively, which basically meet the access requirements of interactive services for a long time in the future.
Application scenarios of 10G GPON Plus networks
Several application models of 10G GPON Plus enhanced networks are proposed, depending on the tiered billing of users and the operational requirements of business:
10G FTTH network with multiple access terminals——the evolution of GPON to 10G PON plus network
In order to reduce the initial investment and protect actual investment, and rapidly increase the number of users, in the first stage, the users of the 10G one-way system and of the GPON system can coexist in the same network. In the network, different service access terminals, including GPON ONU,10G IP Gateway, and 10G IP optical receiver (IP Tuner) are accessed in four combination forms for flexibly and economically adapting to different service situations and different user charging classifications, as shown in figure 8.
Fig. 8 10G GPON Plus network with multiple access terminals
For example, in a network where 50% of normal users have no upgrading plan temporarily, and prefer to keep the original ONU terminal and to remain the previous access services and access bandwidth. There are 20% of the high-end users in the network, who agree to be upgraded to 10G users, and enjoy at least 500Mbps bidirectional access bandwidth and 4K/8K ultra-high-definition video and interactive VOD. For these users, their expand broadband capacity can be satisfied by simply adding one 10G IP tuner to the network.
If 10% of the network users are new users, operators are advised to configure a 10G IP Gateway (built-in ONU+10G IP Tuner) for the users.
If the rest 20% of users in the network are TV-only users, a 10G IP Tuner can be configured to provide large capacity and ultra-high definition live IPTV, thus satisfying the appeal of these users at the lowest cost.
In the second stage, all the existing GPON ONU users in the network will be upgraded to 10G access by adding one 10G IP Tuner. The newly added users are configured with a 10G IP gateway (built-in ONU+10G IP receiver), and the TV-only users will be configured with one 10G IP Tuner, as shown in figure9.
Fig. 9 Evolution of GPON to a 10G PON plus network
In the third stage, OLT and ONU in the 2.5G GPON network are replaced by 10G xGPON devices, and the network is upgraded to 20Gbps/2.5Gbps upstream and downstream asymmetric super-bandwidth access network, comprehensively surpassing 10G xGPON. An enhanced 10G xGPON Plus network is constructed by superimposing a 10G IPVB broadcast channel on a 10G xGPON network.
Evolution of CATV network to 10G all IP network---Compatible with DVB-C digital TV broadcasting service
All IP is the final solution of FTTH networks. The 10G IPVB video broadcast technology can be adopted in the CATV network to transmit TS streams of DVB-C digital TV by TS Over IP to achieve all IP services access, as shown in figure10.
Fig. 10 A 10G FTTH network compatible with all IP and DVB-C
At the CATV Headend, the TS program stream of DVB-C TV is also sent to the DLT of the 10G IPVB system, the WDM system then multiplexes the IPVB stream (1530nm), DVB-C signal (1550nm), and GPON downstream (1490nm) and launches them into the ODN network of the FTTH network.
The 1530nm light carrying IPVB stream is split just before the fiber cable enters the user's home by using an optical filter（CWDM）, and the two optical fibers are both laid into the user’s home. The fiber carrying 1530nm light is connected to a 10G IP Tuner, and the other optical fiber (carrying 1550/1490/1310nm lights) is connected to the original ONU, and the 10G IP Tuner and the ONU are connected by a CAT5/6UTP cable, thus we complete the upgrade of a 10G all IP network.
As working with DVB-C broadcast systems, the 10G IPVB broadcast channel transmits the same SPTS or MPTS video streams and CA-encrypted signals in the 10G all-IP network. Therefore, the DVB-C digital TV service platform and its CA encryption platform work in the same way as before, as shown in figure 10. In the network, the un-upgraded DVB-C users can continue using their CATV optical receivers to watch DVB-C TV programs based on RF QAM modulation, whereas the upgraded all-IP users can use the 10G IP Tuner to watch IP broadcast TV stream or use the original CATV optical receiver to watch DVB-C TV.
The two-mode STB can be used for DVB-C users and all-IP users in the 10G FTTH network. Because it is equipped with both RF and IP input ports, it can decode the TS TV stream from the two signal modes to the HDMI signal and sends the HDMI signal to TV sets.
In the legacy DVB-C based on QAM RF modulation technology, due to the limited transmission ability of each RF channel （38Mbps@64QAM@8MHz or 54Mbps@256QAM@8MHz）, it is hardly possible for a DVB-C TV broadcast system to transmit a set of 8K UHD TV stream in one RF channel. And also, due to the limitation of the number of RF channels, it is difficult for the system to support a large number of 4K TV streams.
On the contrary, the 10G IPVB channel is able to provide sufficient bandwidth for massive 4K /8K TV streams. Therefore, the 10G IPVB technology has the potential to pave a smooth way for the RF broadcasting systems of DVB-C TV in CATV networks to be upgraded to IPTV broadcasting and evolve into all-IP networks.
Equipment of 10G GPON Plus network
IP Distribution Line Terminal (DLT）WID6648
DLT is a core device that responds to the function of integrating the IP broadcasting channel and GPON channel. It aggregates the live TV, local TV, interactive IPTV or VOD, and OTT TV service streams, and it allocates different service streams to the 10G broadcast channel (1550 nm) or the GPON downlink channel (1490nm) according to the business strategy of operators.
10G full-service convergence platform I-CAP2000
CAP2000 is designed in 2RU or 1RU chassis platform, which is plug and play, and can be inserted into the IP DLT module, EDFA module, IP Repeater module, Network Management module, power module, etc.
10G GPON Plus Access terminal series WIG6200
HD DVB+IP Set Top Box —WIC6111
Two-mode HD DVB+IP Set Top Box —WIC6111
* HD DVB+IP Set Top Box compliant with MPEG4&H.265
* Support USB PVR
* EPG & DVB Teletext & DVB Subtitles
* Auto & Manual search function for DVB & IP
* Support smart CAS
* Support VOD & Mobile Screen Projection
Using the combination of GPON +10G IP broadcast channel, operators can develop more options to build FTTH networks as they take full consideration of the actual situations and competition patterns of their networks and find the optimal solution for developing a 10G all-IP optical network, and obtain the best investment reward and cost-effective network performance.
The essence of the 10G GPON Plus network is to return IP live TV from IP multicast switching mode to the natural property of IP broadcasting, so as to achieve a very high performance-to-price ratio so that the network can better meet the professional quality standards of live TV video and the availability requirements of reliable broadcasting. This kind of optical fiber access network has a stronger competitive advantage, so as to avoid the construction of a homogeneous IPTV optical fiber network.
In GPON networks, the overlay of IP broadcast channels is not only technological innovation but also a business model innovation. The enhanced GPON Plus network can not only carry the live IPTV service of the operator by broadcasting mode but also provide a dedicated transmission line for the OTT Internet video market. This provides a new OTT TV access scheme and creates brand new market space for the rich and colorful Internet live broadcasting service.
Finally, in order to make GPON Plus Network permanently maintain the technological leadership of more than one generation and its competitive advantage at the lowest cost, the overlay IP broadcast channel can be extended from the current 10G bandwidth to 25G or 50G bandwidth channel, and then build 25 or 50Gbps two-way asymmetric broadband FTTH access network.