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Network sharing explained!

sheytoon
Mayor / Maire

Hi everyone, I have noticed that there is some misunderstanding about the network sharing between Bell and Telus. Hopefully this will help with some of the confusion. I've worked as a network engineer for operators and vendors and this is an area I am familiar with.

 

To begin with, let's start with a simple LTE network diagram:Network-diagram.jpg

 

  • UE is the phone.
  • E-UTRAN is the LTE radio access network, also known as RAN. In LTE, the RAN is only comprised of 1 element, this is the base station, also known as eNodeB. This is basically the "tower" that your phone talks to. In 3G networks, the RAN is made up of NodeB (tower) and RNC (controller).
  • EPC is the LTE core network (proper name is Evolved Packet Core), and this equipment is hosted in a few secure facilities across Canada. Data between RAN and core is carried via "backhaul" or transport network (not shown here).

 

Bell and Telus only share the RAN across Canada. They share 3G and LTE RANs. In some cities (Vancouver), Telus owns the RAN, and Bell users are allowed to use it. In other cities (Toronto), it's the other way around. This allows Bell and Telus to spend less money building out a network, while both benefiting from it. In a city like Toronto, there are only 3 RAN operators: Rogers, Bell, Shaw (Freedom Mobile/Wind). Any other company that sells service is really using the RAN of those 3 companies.

 

Bell and Telus have independent EPC and IMS networks (IMS is used for VoLTE among other things). The core network is what authenticates user SIM cards, tracks usage and billing, completes calls, delivers text messages, and connects data sessions to the internet. All Bell and Telus eNodeBs in Canada are connected to both Bell and Telus cores.

 

To make a phone call, or send/receive text, or use data, the whole network must be functional. The RAN cannot deliver any services on its own, and the core cannot directly talk to a phone. So if any of these parts go down, the user will not have service.

 

If there is ever an outage that only affects Telus subscribers, it's probably due to the core. If there is an outage that affect Bell and Telus subscribers simultaneously, it's probably due to the RAN.

 

Coverage is 100% due to eNodeB. Therefore, if you have good coverage with Bell or Virigin Mobile, you will have identical coverage with Telus, Koodo, or PM. It can be possible for coverage to be different if Bell and Telus didn't share all bands. However, they currently share all bands except Band 30 (2.3 GHz, which is high frequency and doesn't impact coverage). Band 30 is only for Telus at the moment.

 

UPDATE

As a result of Bell's 2017 acquisition of MTS, the situation in Manitoba is complicated. In Winnipeg and Brandon, Telus operates a new independent RAN, separate from the shared Bell/Rogers RAN. Coverage between Bell and Telus is different in these markets as a result.

/UPDATE

 

For a good map of NodeB (3G) and eNodeB (LTE) locations, refer to this link:

https://www.ertyu.org/steven_nikkel/cancellsites.html

After clicking on a site, refer to BW (bandwidth), this may give a clue to the technology being used.

  • 1.25 MHz is CDMA (old 2G network that is not used by modern phones) As of mid-2019, there is no longer any CDMA networks in operation in Canada.
  • 4.15 MHz is Bell 3G
  • 5 MHz can be 3G or LTE
  • 10 MHz or higher is LTE

 

Here is a specific example of how it works in Quebec City:

https://productioncommunity.publicmobile.ca/t5/Get-Support/Network-sharing-explained/m-p/148276/high...

 

If you have any questions, I'll do my best to help answer them!

 

Update: additional LTE topics explained here:

http://productioncommunity.publicmobile.ca/t5/Discussions/LTE-network-fundamentals/td-p/130581

 

Update 2: key information from this article was used in a 2020 post by Inside Towers, without crediting the original article here. 

81 REPLIES 81

sheytoon
Mayor / Maire

@srlawren

My pleasure!

One thing that I'm still trying to figure out is why there is a speed discrepancy.

I'll have to check my results to make sure CA was active on PM. I thought it was, but need to double check. Will update the other thread when I have some free time. Hopefully I didn't make any mistakes during my testing.

srlawren
Retired Oracle / Oracle Retraité

@sheytoon once again, thank you for that excellent technical explanation!  


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@echf

CA shouldn't be the cause of speed difference. I'm skeptical of that reasoning. Both Bell and Telus subscribers should be able to use all CA combinations today. Both operators usually have excellent backhaul and core networks, but since the experience is different between Bell and PM, I'm suspecting it might be due to the core.

 

The Telus press release is a bit confusing with regards to Toronto. Telus doesn't really own any RAN in the GTA, but they do own many sites in Windsor and Ottawa, which might be part of the Ontario wireless upgrades they mentioned.

@srlawren

I'll provide a bit of background before I answer your question.

 

Wireless networks use spectrum that each operator has licensed from the government to broadcast.

 

LTE specifications allow flexible channel sizes to be deployed with the following bandwidths: 1.4, 3, 5, 10, 15, or 20 MHz. Wider channels provide faster speeds. The spectrum itself is not related to speeds. For example, 20 MHz of 700 MHz spectrum (Band 12 or 17) would be faster than 10 MHz of 2600 MHz spectrum (Band 7). But nobody owns 20 MHz of 700 MHz, so they usually own wider bandwidths at higher frequencies. That's why people generally say higher frequency spectrum is for capacity, while lower frequency spectrum is for coverage.

 

A company like Freedom Mobile might have 10 MHz of spectrum in Band 4, so they can deploy a single 10 MHz LTE channel or 2 separate 5 MHz channels (1 for 3G and 1 for LTE). Generally, everyone deploys the widest bandwidth possible at all times.

 

Example, for Band 4 in Toronto, Bell owns 10 MHz of block F and Telus owns the adjacent 5 MHz of block E.

B4 Block F owners: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf09011.html

B4 block E owners: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf09010.html

 

Since these blocks are contiguous (there is no gap between them), if someone owned both blocks E and F, they would own 15 MHz, which they could deploy as a single 15 MHz LTE channel, even though it's technically 2 blocks of government licensed spectrum. Bell and Telus were given permission by Industry Canada to use each other's Band 4 spectrum, so they own 15 MHz of Band 4 in most of the country, but not everywhere. That's why you don't see a 15 MHz channel for Band 4 in Halifax (Mainland Nova Scotia spectrum tier) on Bell / Telus.

 

As LTE traffic increases, congestion occurs and more capacity is needed to serve customer demand. There are load-balancing techniques that can be used, but another option is Carrier Aggregation (CA). This allows an operator like Bell or Telus to combine multiple channels into one logical channel.

 

The specifications allow up to 5 channels to be combined, and as mentioned, each channel can be up to 20 MHz wide. In an ideal scenario, this means someone can deploy 100 MHz CA with 5 carriers.

0116_CTE_Qorvo_F1.gif

UPDATE

As of 3GPP Release-13, up to 32 carriers can be aggregated for a total of 640 MHz of spectrum:

http://www.3gpp.org/news-events/3gpp-news/1628-rel13

/UPDATE

 

In reality, operators don't own so much spectrum, so they still want to combine what they have into CA combinations. For Bell, a good example in Toronto is Band 2 (20 MHz) + Band 4 (15 MHz) + Band 29 (10 MHz). This is 3-CA or 3-carrier CA or tri-band CA, using 45 MHz of aggregated spectrum, resulting in peak download speeds of 335 Mbps.

 

In technical terms, the main band is called the Primary Component Carrier (PCC), and the additional bands are added as Secondary Component Carriers (SCC). You can have 1 PCC and up to 4 SCCs at one time being used. For Samsung phones, dial *#0011# and you can see the status of CA during a download session. Here you can see B2 PCC and B4 SCC1 and B29 SCC2. Channel sizes are shown as well. In this example, B2 is 15 MHz because this is in Calgary, not Toronto.

6342d5df3e62ec17bdf656657eb5fd38.jpg

 

One thing to keep in mind is that the total aggregated bandwidth is very important. A single 20 MHz LTE channel (non-CA) will be faster than 3-CA of 5 MHz each (total aggregated bandwidth = 15 MHz).

 

The eNodeB can configure many different CA combinations very easily, and Bell or Telus can configure 5-CA today if they wanted to, but the problem is that phones are built with very specific CA combinations. Just because a phone supports B2 and B4 in non-CA (regular) mode, it doesn't mean it supports B2 + B4 CA with those specific channel bandwidths. So, you can appreciate why this is a very difficult task for operators. They need to work with phone manufacturers to build devices with very specific CA combinations. This is difficult for Canadian operators, because they are small on the global stage. Samsung and Apple are not going to build customized phones with certain CA capabilities just for Bell or Telus or Rogers. This is one of the reasons why you always see Industry Canada (IC or ISED) follow the USA spectrum regulations (FCC). This gives us a better chance to use phones designed for the USA market, which has a stronger "ecosystem".

 

To answer your question, CA is entirely a RAN feature, and as long as certain bands are shared by both Bell and Telus (which they are, except B30), then they can all use CA the same way.

 

Update: Bell / Telus now has quad-band or 4-CA with B2 (20 MHz) + B4 (15 MHz) + B7 (20 MHz) + B7 (20 MHz), for a total of 75 MHz aggregated bandwidth. They have also enabled higher-order modulation, called 256 QAM, which enables total peak download speeds close to 750 Mbps.

@fathom

Not sure exactly what the high cost is due to. I don't work on the business side, just engineering.

 

To recap: backhaul is the connection from the eNodeB's baseband unit (BBU) to the core network. There's 2 main types of backhaul connections for modern networks: fiber and microwave.

 

Bell and Telus have invested heavily in fiber, and most of their sites, especially in urban and suburban areas use fiber directly to eNodeB locations. Rural sites use microwave, and extreme rural sites use satellite backhaul, but that introduces massive latency (delay).

 

Rogers has fiber as well, but more microwave than Bell or Telus. Part of the reason for this is RAN sharing allows Bell/Telus to focus on building half the country with the same amount of money, so they can deploy fiber more quickly and easily.

 

Wind Mobile has a lot of microwave due to being a new player. Microwave is much easier and cheaper to deploy, but it doesn't provide the same capacity or reliability as fiber.

 

A microwave antenna looks like this. You can spot one easily on a site:

 Class 4 antenna.jpg

As we start to see massive throughput increases with LTE-Advanced and 5G, we will start to see limitations in microwave backhaul and companies like Rogers and Wind will need to catch up.

echf
Model Citizen / Citoyen Modèle

Same question! So the speed different between Bell and Telus/PM is mainly because the carrier aggregation (bandwidth) and their backbone network?

 

I heard Telus is investing in GTA (http://about.telus.com/community/english/news_centre/news_releases/blog/2015/05/08/telus-investing-1...). Is this going to significantly improve Telus network performance vs Bell.

 

Thank you so much for sharing!

@youbme

Wireline networks are quite different from wireless, but as a very high level analogy, it is similar to what you described. Though I would say the cable/DSL modem would be the "access" part of the network, not the router.

 

Certainly the CMTS/DSLAM and customer modem must both be working in order to get service.

srlawren
Retired Oracle / Oracle Retraité

@sheytoon how does carrier aggregation factor into the picture?


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fathom
Model Citizen / Citoyen Modèle

Thanks for sharing and explaining.

That was a good sunday morning coffee read 🙂

 

Is the high cost of cellular in Canada partly due to its size (loooong cables required for the transport network between the various RAN and core and the large number of towers (eNodeB, might as well try to learn the terms) required to service all Canadian, esp in rural areas?

@Jeremy_M Please consider this for the knowledge base. Assuming there are no egregious errors of course!


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youbme
Deputy Mayor / Adjoint au Maire

Thank you @sheytoon forbreaking down network sharing for those of us who didn't study in your field.

 

Would it be fair to compare the diagram you presented to a home network accessing internet where the router is the RAN, but the actual access to internet is controlled offsite from the ISP? I realize there are several variables as well for accessing internet, but that seems similar as there are multiple layers of control, each must be functioning for the end user to receive the service.

@computergeek541

 

WPS is strictly for 2G networks. This is mentioned in your link:

Handsets must have access to your service provider's 2G network. At this time, 3G networks do not support WPS.

sheytoon
Mayor / Maire

@MVP, @Indexx:
Prioritization can be done at RAN or core, but in different ways. RAN doesn't have a lot of granularity, so you could reserve a certain portion of spectrum for all Telus subscribers and no Bell subscribers. There is no way to distinguish a Telus subscriber from Koodo or PM. Having said that, Bell and Telus do not do this. Everything is dynamic based on usage and there is no discrimination at the RAN. The only exception is VoLTE and ViLTE, which are standardized protocols and need GBR (guaranteed bit rate) service. This is a form of QoS to ensure a quality VoLTE experience during congestion. But again, Telus and Bell VoLTE are treated equally by the RAN (they're just treated better than internet data). Regular data is always "best effort" or non-GBR.

The core has a lot more control over individual profiles. I'm not a core engineer so it's hard to know if/how something is being done at the core level.

From the RAN's point of view, there are 2 operators: Bell (302-610) and Telus (302-220). Creating a virtual operator using different APNs (PM or Koodo) is 100% under the control of the core network.

willph
Great Citizen / Super Citoyen

IF.....and I use the word IF strongly.

 

IF Telus is prioritizing Telus / Koodo / PM customers, then it would happen at the core network side (EPC).

It would not happen at the tower side as the agreements between Bell and Telus to share the towers equally.  FIFO (first in, first out) or first come first serve basis.  A Bell owned tower doesn't give priority to bell customers before Telus.  

 

ALSO, before switching my Telus number to PM, I ran a Telus sim and PM sim at the same time and did calls and speed tests all over Halifax, NS, Bedford, NS, and Dartmouth NS (my local areas) and it demonstrated equal service and speeds within a few kb/s of each other (resonable margin).  less than 25kb/s difference.

 

 

srlawren
Retired Oracle / Oracle Retraité

@sheytoon thanks for the detailed and yet easily understandable breakdown of how we get our services.  That was an enjoyable read!


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@Indexx wrote:

Where does prioritization/throttling happen, and can there be discrimination between providers happening at the tower?


The carriers likely have the ability to prioritize any subcriber they see fit over another.  Whether they actually practice this to normal cusotmers during every-day use is a matter that they're not telling us about.

 

From what I'm reading, some cell phone companies do give priority access to certain customers under a protocal called Wireless Priority Service.  Some members of emercency response teams, government, and other essentially/critical services are given the ability to dial a code that forces the network to give the prioty user the next available slot on the network to place a call.  The document that I was looking at specifically only meantion 2G netowrk ability, so the information may be a bit out-of- date,  but clearly, some carriers do at least the ability to priotize voice calls.

 

At the time of the infromation at http://www.ic.gc.ca/eic/site/et-tdu.nsf/eng/h_wj00016.html , only Rogers 2g and MTS cdma networks were providing WPS services,  but that information was as of 2011.

Indexx
Good Citizen / Bon Citoyen

Can there not be any prioritization happening at the tower?

I think the main concern/question is the throttling happening for PM customers.

 

Where does prioritization/throttling happen, and can there be discrimination between providers happening at the tower?

Vickel
Model Citizen / Citoyen Modèle

Good stuff, thanks for sharing

ShawnC13
Oracle
Oracle

Great post I think this should be kept in teh knowledge base for future reference for those saying their coverage isn't as good now with PM

 


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MVP
Model Citizen / Citoyen Modèle

Thank you for  interesting info.

 

So, in case Public Mobile traffic is throttled/prioritized, by Telus, at which of the above units does it occur?

eazybelle
Great Citizen / Super Citoyen

Cool, thanks for sharing that!

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