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Chris Wright, Marketing Manager, CBNL

Whether maximising the use of software defined networking, optimising transmission circuits, or introducing innovative new business cases – driving efficiencies in backhaul was centre stage at this year's Packet Microwave and Mobile Backhaul Forum.

With LTE and small cells often the backdrop, the event provided an insight as to how operators can exploit new solutions to cost effectively manage the rising tide of new applications traffic.

As event sponsors, CBNL played a leading role in discussions and have provided our event highlights on two short films.

Packet Microwave Forum 2013, Day 1: SDN for efficient backhaul and highlights

Packet Microwave Forum 2013: Day 2 highlights

Chris Wright, Marketing Manager, CBNL

Chris Wright, Marketing Manager, CBNL

Lionel Chmilewsky, CEO, CBNL
This week CBNL CEO Lionel Chmilewsky discussed the latest trends in mobile backhaul with Eurocomms and what the future holds.

Eurocomms.com: What key trends are impacting the business case of modern backhaul networks?

Lionel Chmilewsky: "There are two: increase in demand and raised consumer expectations.

We have recently seen a rapid and heavy surge in demand for connectivity. If you add all of the new methods of communication to a whole host of machine to machine communications, you end up with a situation where the capacity of networks have to scale greatly to meet this new demand.

The perfect example of this is that in an average house previously you would have had one internet connected device - a PC - now you have a smartphone for every person, a family tablet, a connected TV and a computer all demanding high speeds and high-quality content. Increasingly people have the same expectation of connectivity outside the home.

The reason all the content must be of a high quality reinforces the second trend we are seeing – an increase in customer expectations. Gone are the days when a customer would be happy waiting 30 seconds for an image to load, they have been sold the image of “superfast internet” and the ability to get what they want when they want it by operators.

Therefore, operators now have to scale infrastructure to meet the promise that they have made, whilst keeping costs at a manageable level.

How should operators adjust their backhaul strategies to ensure they deliver this?

The need for increased global capacity and connectivity will necessitate a change in operator strategy. This demand has caused the adoption of new technologies such as network specialised small cells to ensure that consumer expectations are met.

The cost of mobile backhaul is a paramount factor in running and launching services and there is a need from operators to run this at a much lower cost, achieving a higher ROI – especially at a time where revenues are under threat. There is no point in providing the best service in the country if the operating costs drive your business into the ground.

The three things that an operator requires are a high quality of service, quick time to market and a low Total Cost of Ownership (TCO). Luckily as the needs increase so does the technology that can address these needs. Point-to-Multipoint (PMP) technology, for example, can drive costs down and offer 50 per cent TCO savings over other forms of backhaul.

If things stay static, operators will lag behind their competitors. There needs to be an opportunity to upgrade the technology and continue to innovate, with cost savings obtained by increased efficiency and utilisation of resources rather than sacrificing performance or features.

You mentioned PMP; why should operators being looking at this technology rather than Point-to-Point (PTP) microwave systems?

Many companies already use and trust PTP systems, and, as with anything convincing people to embrace the next step in the evolution takes a bit of time and research.

PMP is easier to deploy as it requires less transmitters and instead concentrates traffic in a central hub which reduces initial outlay. Similarly, the evolution of PMP technology has reduced the skills and time needed for deployment, enabling operators to reduce costs and get their services to market quickly. Sector coverage provides the flexibility to backhaul new sites quickly by a single installation team, without a visit to the access point or the need for additional spectrum.

PMP can also reduce exorbitant spectrum rental expenditure by a reduction in the overall spectrum needed to deliver equivalent services to its old-style PTP counterpart. It can optimise spectral efficiency by 40 per cent over PTP, which leaves more capacity open for growth and can alleviate congestion in addition to the cost reduction.

This will only become more important as bandwidth and spectrum space becomes more and more precious to mobile operators trying to handle the heavy demands being placed upon them. It will also become more crowded and more expensive as more connected systems come online. Therefore over other forms of backhaul, PMP will enable operators to reduce churn by providing a consistent service as technology changes, maintain revenues and market strength and ultimately increase profitability.

What does the future hold?

The future will see a closing of the digital divide. There is a great demand for increased connectivity in the developing world and as we see this demand addressed the nature of the global telecoms market will change. Cisco recently predicted that by 2017 global mobile data traffic will reach 11.2 Exabytes per month, up from 885 Petabytes per month in 2012. Once these people have achieved that level of technological interaction, they will never want to go back, so the trend can only increase from there.

Read the interview and join the discussion on Eurocomms.com

 

Dr John Naylon, Chief Technology Officer, CBNL

We recently talked about how to choose between PMP and PTP from a technical perspective, so now let’s have a look at this choice from a financial standpoint.

The following slides work through a simplified version of the TCO model we use with new customers, detailing all the assumptions we make.

We believe the total cost of ownership is by far the best way to make a rational choice between different types of equipment. 

After all, it is no use having very low cost equipment if the spectrum rental to operate it is extortionately expensive. 

Likewise free spectrum sounds fantastic, but if the equipment that operates in that band is itself very expensive the overall solution cost is not likely to be optimal.

As shown on slide 10, PMP begins to show very significant TCO savings as soon as the average number of sites per backhaul hub increases beyond one or two. 

In networks we deploy today, this average is usually 5 or 6 links per hub, and this number is steadily rising as networks continue to densify.

For our bigger customers, the savings realised run into millions of dollars per annum!

Chris Wright, Marketing Manager, CBNL

Mary-Ann Russon, Deputy Editor at Mobile Europe, recently interviewed Dr John Naylon, CTO at CBNL, at the Small Cells World Summit to understand the latest trends in small cell backhaul.

Interview one focuses on small cell backhaul market status and the cost considerations service providers should be aware of when deployming backhaul networks.

 

 

Interview two looks at how small cell backhaul trends differ acoss developed and emerging markets and the effect this has on the technologies deployed.

Dr John Naylon, Chief Technology Officer, CBNL

One of the most common questions we’re asked by new customers is,

“How do I decide when to deploy point-to-multipoint (PMP) and when to deploy point-to-point (PTP) for my backhaul?”

This is a great question, because the two technologies are very complementary to each other. 

An engineering perspective

From an engineering perspective, in making the choice between PMP and PTP for a given link, we are seeking to maximise efficiency and utilisation of the equipment and the RF channel while satisfying a set of requirements for throughput, latency and link availability. 

In economic terms, this translates into choosing the technology which gives the lowest total cost of ownership while satisfying those requirements.

Traffic characteristics

An excellent way to make the choice between PMP and PTP is to look at the characteristics of the data traffic we want to carry. 

I’m going to consider mobile broadband backhaul traffic here, because that’s what the majority of our customers use our technology for today. 

In a future post I will talk about small cell backhaul traffic.

As ever, the NGMN has some useful information we can use, in the whitepaper Guidelines for LTE Backhaul Traffic Estimation.

This paper describes (§2.2) the initially counter-intuitive result that the peak throughput for an eNodeB actually occurs, not during busy hour, but during quiet time. This is because:

“During busy times, there are many UEs being served by each cell. The UEs have a range of spectrum efficiencies, depending on the quality of their radio links. Since there are many UEs, it is unlikely that they will all be good or all be bad, so the cell average spectral efficiency (and hence cell throughput) will be somewhere in the middle.

During quiet times however, there may only be one UE served by the cell. The cell spectrum efficiency (and throughput) will depend entirely on that of the served UE, and there may be significant variations … the scenario under which the highest UE and cell throughputs occur [is]: One UE with a good link has the entire cell’s spectrum to itself. This is the condition which represents the ‘headline’ figures for peak data rate”.

Figure 4, reproduced here, illustrates this point:

Illustration of cell throughput during busy and quiet times

The paper goes on to give the following peak and mean traffic figures for a number of LTE configurations:

Figure 5: Mean and peak (95%-ile) user plane traffic per cell for different LTE configurations

Understanding the peak-to-mean ratio

What we can immediately see from this figure is that the peak-to-mean ratios of the traffic in the dominant, downlink, direction are very large, ranging from about 4:1 to almost 6:1. 

This agrees well with measurements we see from real networks. 

For example, the following from a very busy HSPA+ network show the peak-to-mean ratio of the backhaul traffic for each node B (on the y-axis) plotted against the peak backhaul demand for that node B on the x-axis.

Peak Backhaul Demand (Mbps)

When traffic has a high peak-to-mean ratio like this, we call it “bursty”, as opposed to “smooth” when the peak-to-mean ratio is close to 1. 

Data traffic in general, for example on LANs and residential internet access connections as well as mobile networks, is bursty; and this presents a difficulty in carrying it efficiently on PTP links, as shown here:

Bursty traffic is hard to carry effeciently

The problem here is that a PTP link with a single traffic source (a ‘tail link’ in the backhaul network) needs to be dimensioned to carry the peak traffic, but there is only a single source of offered load. 

Therefore the utilisation of the link (or efficiency) is equal to the mean offered load divided by the capacity, or in other words the reciprocal of the peak-to-mean ratio of the traffic. 

So if my traffic has a peak-to-mean ratio of 4:1, the maximum utilisation of a PTP link carrying that traffic is ¼, or 25%. 

In the chart above, you can visualise this as all the white space below the red line being wasted bandwidth, which is provisioned but unused.

It’s important to say that this is not a failing in PTP systems in any way – it is simply that the characteristics of the traffic are not well suited to the static bandwidth provisioning that PTP provides.

The advantage of a PMP system is that it can serve multiple sources of offered load simultaneously. 

The bandwidth of the shared RF channel is dynamically allocated to different sources as required. 

Conceptually, then, the peaks and troughs from different traffic sources ‘cancel out’ to some extent, as we illustrate in the following live network example showing eight nodeBs being backhauled by a single VectaStar Gigabit sector.

Multipoint backhaul packet switched not circuit switched

Here we are also relying on another property of the traffic, namely that peak demands for different nodeBs do not occur at exactly the same time. 

We discuss this at greater length in The Effect of System Architecture on Net Spectral Efficiency for Fixed Services.

Liberating spectrum to meet growing capacity demands

A useful analogy here is to think about a bank with deposit accounts.

Banks operate a fractional reserve system, meaning that they are only able to repay a defined fraction of the total of deposits at any given time.

This therefore relies on the observation that, statistically, not everybody goes to the bank and withdraws all their savings at the same time.

When this assumption breaks down, there is a ‘run on the bank’.

In a similar way, we rely on the observation that, statistically, not every node B requires its theoretical peak backhaul throughput at the same time.

When this assumption breaks down, things are a bit less dramatic however – we simply discard some low priority traffic.

This is perceived (if at all) by users as a temporary reduction in internet browsing speed.

Crucially, we can dimension the system in such a way as to set the probability that this occurs to a value of our choosing.

The advantage of fractional reserve banking is that it liberates dormant capital for further investment and lending.

Likewise, the more efficient use of RF channels in PMP systems liberates dormant electromagnetic spectrum (provisioned but unused, as in the example above) for use addressing the ever-growing capacity demands of modern mobile networks.

Conclusion

In conclusion, then, some brief rules of thumb for when to deploy PTP and when to deploy PMP are as follows:

Deploy PTP…
… when traffic is smooth (voice dominated)
… when traffic has already been aggregated
… in the middle mile of backhaul
… for long distance links
… when spectrum is uncongested or inexpensive
Deploy PMP…
… when traffic is bursty (data dominated)
… to create an on-air traffic aggregation
… for tail links (last mile)
… for dense deployments
… when spectrum is congested or expensive