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Aug 14 2017

What’s the point of point-to-point?

Introduction

In the fixed access world, there is always a lot of debate about technologies. Up until a few years ago, the industry was still arguing whether there was a place for point-to-point (P2P) fiber or whether passive optical networks (PON) would render it redundant. Thankfully, a consensus has been reached: today, it is agreed that both PON and P2P have their merits.

P2P has primarily found favor in business and low density residential FTTH deployments. However, the arrival of 10G next-generation technologies presents operators with new opportunities for better services, reducing costs or creating new revenue streams. Operators deploying a PON network or upgrading their legacy residential copper networks can benefit from using P2P as a complementary technology. We shall explore some of these opportunities in this article.

Comparing PON and P2P

PON is a point-to-multipoint technology where the access node connects a number of users over the same shared medium, using one transmitter. This means that the total available bandwidth is shared between all users, with a splitter used to divide the signal between users. This makes it a cost-effective way to provide high-speed broadband services to a large number of subscribers, particularly in densely populated areas.

In contrast, fiber point-to-point technology provides a direct and dedicated connection from the access node to each household or business. This has several benefits:

  • Bandwidth is fully dedicated to a single point of connection at all times
  • The simplicity of point-to-point connectivity makes for easier network protection, troubleshooting and service management.

These advantages come at a higher cost-to-connect per user than PON, so it is the specific application and corresponding return on investment that determine which technology is better suited.

It’s important to note that 10G fiber technologies, such as XGS-PON and 10G P2P, can coexist in the same infrastructure, helping operators get more from their investments. For example, the Nokia 7360 Intelligent Services Access Manager (ISAM) FX can simultaneously support multiple PON technologies and high-density point-to-point services thanks to its non-blocking backplane architecture, high switching and uplink capacity.

In this article, we will look at use cases other than residential FTTH where P2P can be deployed on an existing access network and platform to provide the best services for customers, reduce costs or create new revenue streams.

Use case 1: pre-aggregation

Many fixed network operators are pursuing deep fiber strategies, bringing fiber closer to end-users to provide higher bandwidth and premium services. This means deploying increasing numbers of small nodes supporting, for example, G.fast, VDSL2 vectoring, DOCSIS 3.1 or even small fiber nodes. These nodes must be backhauled and aggregated with sufficient capacity so as not to compromise the quality of service.

Nodes do not have to be connected directly to service routers, but can instead be pre-aggregated by existing access equipment in the field. It is more cost-efficient to pre-aggregate traffic from a large number of small remote nodes before bringing it to the network routers.

The choice of backhaul technology is a question of bandwidth and cost. The total backhaul capacity is a factor of the number of nodes, the number of users served by each node and the bandwidth offering to each user. A remote node serving 100 customers clearly needs a higher capacity connection than a node serving 16 customers. Current generation GPON and P2P may soon run out of capacity to backhaul increasing traffic. This opens the door to 10G technologies, either XGS-PON or 10G P2P.

In our analysis based on typical deployments, taking into consideration CAPEX costs for equipment and deployment, we have found that a split factor of 4 tends to be the tipping point: more than 4 access points favors XGS-PON, otherwise 10G P2P provides a better business case.

Use case 2: business services

P2P business services are mainly deployed for large organizations or business parks that demand high bandwidth, resilience and service availability. Although PON has features that enable high reliability, P2P goes further in guaranteeing resilience, albeit at a higher cost due to increased floor space in the central office and additional fiber connections.

However, most commercial customers can be served either through PON or P2P. Fixed operators who deploy PON networks in residential neighborhoods should consider offering services to small and medium businesses located in the same area. Our analyses show that adding business services on the existing residential PON network can increase the return on investment (ROI) by 15% and accelerate network monetization.

The density of customers and the required quality of service (capacity, resilience, etc.) are the determining factors to choose between PON and P2P.

Use case 3: mobile backhaul

As operators deploy 4G and prepare for the arrival of 5G services, their backhaul networks are under pressure to support significantly higher bandwidths and lower latencies from a higher number of small cells.

For mobile transport, the key considerations are capacity, latency and resilience. For macro-cells, the resilience is important, because a large number of users are impacted, while for small cells this requirement may not be so strong. Multiple P2P links provide the highest level of resilience for sites serving large numbers of users or in key strategic locations. In urban areas, where small cells are typically deployed, the proximity to existing residential access networks makes PON a perfect match for backhauling this traffic.

In terms of the business case, our initial investigations show that the cost drivers reach a tipping point at around 20 mobile sites per km². Less than 20 mobile sites per km² favors P2P, above this threshold there is a strong argument for using PON. Current 4G networks only reach more than 20 sites per km² in very densely populated urban locations. However, 5G networks using mm-Wave cells will likely have densities greater than 100 sites per km², even in suburban locations.

Use case 4: virtual unbundled local access

Virtual unbundled local access (VULA) is one of various bitstream methods. The difference between bitstream methods is the point of the interconnection.

In general, the point of interconnection between access seeker and access provider can be anywhere between the local access node and the regional or national aggregation server. In VULA, the interconnection happens just behind the local access node.

This means that an access seeker doesn’t need to own and operate access nodes, which lowers the barriers to new entrants. It also means that access seekers will need to own the part of the network beyond the access node, typically service routers, BNG, BRAS and similar, getting more control of the quality of service.

10G P2P allows access seekers to connect to a network provider’s access node. However, in this case the P2P card is used in a “reverse” direction: instead of connecting users, the ports on the card are used to connect access seekers in the upstream. There could be up to 36 access seekers with a 1 Gb/s connection, or 16 with a 10G connection. One access seeker can use more than one port on the card, depending on the bandwidth capacity it needs to deliver services to end users.

Figure 1: VULA – virtual unbundled access network

Summary

The ability for P2P to be deployed reusing the existing investment in infrastructure and OSS, makes it relatively simple for operators to use P2P for various applications that can enhance the operators’ business.

Using P2P as a complementary technology to copper or coax, or aggregate traffic from small nodes or radio sites, helps operators to streamline operations. At the same time, P2P helps unlock new revenue opportunities, either through wholesale offerings or higher tier business services, where superior levels of resilience and availability justify a premium price point.

About Ivana Despotovic
Ivana Despotovic is a marketing manager for Fixed Networks in Nokia. Ivana has international telecom and biomedical engineering experience, having held various positions in R&D and pre-sales. Ivana holds a PhD in Biomedical Engineering/Computer Science from Ghent University in Belgium.