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LTE network fundamentals

sheytoon
Mayor / Maire

In response to the positive feedback on my first post about network sharing last weekend, I thought it would be a good idea to expand to other topics that people might be interested in learning about.

 

Here are the topics previously discussed:

 

These are the topics I am hoping to cover. If there is a preference for what you would like to see first, let me know!

 

  1. How do voice calls work? What is CSFB and VoLTE? Why does SMS work on LTE, but not voice?
  2. What is MIMO and how does it work?
  3. How can I achieve very fast speed test results?
  4. 3G vs 4G vs LTE. What is the difference? What are the paths to 1 Gbps, and how are peak network speeds calculated?
  5. What does a cell site look like in real life?
  6. Basics of LTE roaming and why I don't need to change my APN (disclaimer: This is not a strong point for me).
  7. How is a SIM card used to help a phone attach to the network?
  8. Who are the main players in providing network equipment for the cellular operators like Telus?

Additional topics:

 

NEW:

Additional 5G topics:

  1. What does the 5G icon mean?
38 REPLIES 38

@dust2dust yes I think it's still valid. VoLTE works on any and all LTE bands.

 

Edit: every band except B29, but you don't actually need to worry about that because a phone will never use B29 as a primary cell. As long as a phone is on LTE, VoLTE will work.

dust2dust
Mayor / Maire

Hi @sheytoon - Is this still all valid? I see you edited your other reference post.

Do you also know which exact bands/frequencies volte would use? Or does it simply just need lte working?

 

https://productioncommunity.publicmobile.ca/t5/Get-Support/LTE-network-fundamentals/m-p/134299/highl...

@CatCanyon what kind of information are you trying to find out?

 

Most people will not need NSG. It's an advanced tool for network engineers and enthusiasts.

 

You can still get the relevant readings on a Samsung phone by dialing *#0011#, no need for NSG or root.

 

Rooting means modifying an Android phone's software in order to have root level access. This gives the user/NSG app permission to read additional information from the phone's modem and diagnostic ports.

 

Rooting is risky if you are not careful with what you are doing. You can damage your phone by unintentionally changing system level software, or giving malicious apps elevated permissions. Proceed at your own risk.

Here is more information about rooting but there are risks involved and if you decide to do it to make sure to backup your phone first.

https://www.tunesbro.com/blog/root-samsung-galaxy-s10/

CatCanyon
Great Citizen / Super Citoyen

Would you be willing to explain the "rooted" phone reference. That is the language I got when I tried to use Signal Guru... my phone was not "rooted". I use a Samsung 10+. Is there a way to "root" the phone so I can get a reading from Signal Guru??

CatCanyon
Great Citizen / Super Citoyen

Hi... thanks for the information. I loaded Signal Guru and found that it was never to purchase the app in order to get a reading. Is this what I should expect... or is there a way to get a reading without a purchase? ?

airzonephoto
Good Citizen / Bon Citoyen

Thank you so much for this info.

Minimum recommended phone specs:

  • 3G UMTS/W-CDMA/HSPA: B2 (1900) and B5 (850)
  • 4G FDD-LTE: B66 and B12

 

Currently VoLTE is not available and voice calls are only on 3G.

VoLTE is now available as of February 2023. Voice calls, SMS and data can work on 3G or LTE. Fastest data speeds are on LTE.

 

For LTE, these are all of the available bands on the network: 2, 4, 5, 7, 12, 13, 17, 29, 30, 66. Some bands are available in some locations, others available elsewhere.

 

Any phone you are considering should ideally have LTE B66 (or B4) and B12 (or B17) for minimum coverage. If your phone does not have all recommended bands, you may have poor coverage / no service / slow data in some locations.

 

For LTE: B2, B7 will give you faster speeds. LTE B5 may give better indoor coverage in some downtown urban areas. The rest are not really necessary.

jpar
Model Citizen / Citoyen Modèle

That's a great explanation, sheytoon!

Topic #9: An in-depth look at exactly which frequencies/channels/bands are used for LTE by Public Mobile (TELUS), along with their performance limits and capacities?

This topic was requested by @Korth

 

It's important to remember that spectrum holdings are different across different cities and provinces.

Telus current LTE bands are (in order of band number):

  • B2 (1900 MHz or PCS)
  • B4/B66 (2100 MHz or 1700 MHz or AWS / AWS-1)
  • B5 (850 MHz or CELLULAR / CLR)
    • As of March 2021, B5 is no longer available in urban Manitoba (Winnipeg and Brandon)
  • B7 (2600 MHz or 2500 MHz or BRS)
  • B12/B17 (700 MHz)
  • B13 (700 MHz)
  • B29 (700 MHz), for downlink only (SCC for CA only)
  • B30 (2300 MHz or WCS), for TELUS only (not shared with Bell at this time)

Telus current 3G bands are:

  • B2 (1900 MHz or PCS)
  • B5 (850 MHz or CELLULAR / CLR)
    • As of March 2021, B5 is no longer available in urban Manitoba (Winnipeg and Brandon)

As previously mentioned in the Carrier Aggregation topic, wider channels give the best performance. Maximum bandwidth for a single LTE channel is 20 MHz (non-CA). The widest channel combination today for Telus with CA is 75 MHz (B2 20 MHz + B4 15 MHz + B7 20 MHz + B7 20 MHz).

 

Higher frequency bands like B7 are generally more abundant, so Telus and Bell tend to own more blocks of these bands. The downside of high frequencies is twofold:

  1. They don't propagate far in open air, so it's not good for long distance coverage or rural areas. This is why we will likely not see B7 in cottage country areas like the Kawarthas.
  2. They don't penetrate objects well, so it's not good for deep indoor / underground coverage.

Conversely, low frequency bands like B5 or B12/17/13 are great for rural and indoor coverage, but they tend to have narrow bandwidth (generally 5 MHz), so capacity is very limited on these bands. In addition, it's challenging to deploy these bands in urban areas because their excellent propagation characteristics make them interfere with neighbouring sites.

 

Back when Microcell (Fido) was an independent operator, they studied the effects of spectrum propagation. This study has been made public and is available here:

https://www.ic.gc.ca/eic/site/smt-gst.nsf/vwapj/microcellsch_e.pdf/$FILE/microcellsch_e.pdf

In summary, B2 requires 1.3x to 2x the number of sites to provide equal coverage to B5.

 

As you can appreciate, a combination of low and high frequency spectrum will result in the best of both worlds. Generally, operators will assign high priority to the higher frequency bands. Users who are within high frequency coverage will get better performance by using wider channels, and anyone outside of this coverage area will be on the lower frequency bands. If operators didn't do this, all phones would just stay on low frequencies permanently, resulting in congestion while high frequencies remained unused.

 

Due to this implementation, it's possible that your coverage may appear to get worse than before! For example, you might be in a good B2 coverage area and a few months later, Telus might deploy B7 which has fair coverage. Since B7 will have higher priority, your phone will choose it, and you will see less signal bars (RSRP). This doesn't mean B2 coverage has changed, but your particular experience might be worse, even though overall capacity for Telus users in your area has increased substantially.

 

Individual spectrum holdings can be viewed on Industry Canada's website. Spectrum licenses are sold in blocks for different service areas. Service areas can be small or large depending on the Tier defined in the auction's rules. Service areas in Tier 2 being large (province level), and Tier 4 being very small (town level):

http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/h_sf01627.html

 

Auction results are available here:

http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/h_sf01714.html

 

For spectrum ownership that isn't available from auctions, you will need to use the Spectrum Licence Browser on IC's website:

https://sms-sgs.ic.gc.ca/licenseSearch/searchSpectrumLicense?execution=e1s1

 

Unfortunately IC doesn't use band numbers, so you will need to translate the spectrum name accordingly.

MVP
Model Citizen / Citoyen Modèle

@sheytoon wrote:

 

 

As for throttling, I suspect there is some limit placed at the EPC (core). See HERE and HERE.

 

.


I was recently able to reach  82 Mbps down, 42 Mbps up in a random speedtest.

 

Very strong signal, full bars, SINR = 25 dB (measured by Network Signal Guru), LTE band 7. Basically standing in the parking lot near the  building with  Bell/Telus cellphone tower. Time - around 2pm, daytime. Location: London, ON

 

Topic #8: Who are the main players in providing network equipment for the cellular operators like Telus?

 

For the RAN, there are 3 large vendors:

  • Ericsson
  • Huawei
  • Nokia

Two smaller vendors are Samsung and ZTE. The 3 large vendors make up the majority of the global market share, and all 3 have excellent products. Telus uses Huawei, Bell uses Huawei and Nokia, Rogers uses Ericsson and Huawei, Freedom Mobile uses mostly Nokia (with some Huawei for a small part of 3G), Sasktel uses Huawei, Videotron uses Ericsson for LTE and Nokia for 3G, EastLink uses Ericsson.

 

There have been many mergers and acquisitions over the years, resulting in Nokia owning the wireless divisions of Siemens, Alcatel, Lucent (including AT&T Bell Labs) and Motorola. Ericsson owns the wireless division of Canada's Nortel. Huawei is essentially standalone.

 

For the core, there are 4 big vendors. This includes the same 3 companies above, as well as Cisco. In Canada, Cisco, Ericsson and Nokia EPCs are deployed.

@MVP wrote:

Thank you  again, Sheytoon for the interesting info! Let me note, that two main things the end user cares about are

(i) the download/upload speed

(ii) reliability of connection

 

So, the wider is the  frequency bandwidth,  the more info can pass through, the higher should be the download speed,

 


Yes to this part

 

 

 


@MVP wrote:

and this means that the  total power matters, not the power per channel, i.e. that older RSSI measure is still  better to judge the efficiency of the connection?

 

It sort of makes a  common sense,  transmitted information amount should be proportional to the signal power.

 


Channel is the wrong term here because there is only one shared channel for all users, but yes, the total power for all the LTE resources being assigned to the user is important. That's why in Topic #3 I explained the importance of SINR, which includes the power of the signal for the resources used, as well as the interference and noise on the same resources.

MVP
Model Citizen / Citoyen Modèle

@sheytoon wrote:

@MVP

LTE is quite robust, due to reasons like OFDM technology and MIMO. It's a complex topic that is too technical for this message board.

 

That article is awesome by the way! Reference Signals are sort of like "pilot" signals, used by phones to determine cell signal strength. There is no data or traffic carried on them, so they're always at a constant power (hence a reliable "reference"). The value RSRP is measuring this signal. The acronym RSRP stands for "Reference Signal Received Power".

 

Because LTE uses flexible channel sizes, it's not fair to measure total wideband power. 20 W on a 5 MHz channel is a far better signal than 20 W on a 20 MHz channel, since the same amount of power is spread across a narrower frequency range. LTE utilizes time-frequency resource blocks (RBs), and each RB has 12 subcarriers, therefore a 5 MHz channel (25 RB) will have 300 subcarriers as stated in the article. Larger channels will have more subcarriers. Reference Signals are always spaced every 3 subcarriers.

 

Not totally sure how SINR is measured on the phone, but my guess is the average of all RB SINRs.


 

Thank you  again, Sheytoon for the interesting info! Let me note, that two main things the end user cares about are

(i) the download/upload speed

(ii) reliability of connection

 

So, the wider is the  frequency bandwidth,  the more info can pass through, the higher should be the download speed, and this means that the  total power matters, not the power per channel, i.e. that older RSSI measure is still  better to judge the efficiency of the connection?

 

It sort of makes a  common sense,  transmitted information amount should be proportional to the signal power.

 

Topic #7: How is a SIM card used to help a phone attach to the network?


Disclaimer: This is mainly a core topic, and not my area of expertise. I am mostly confident in the information, but there may be some mistakes.

 

The main purpose of a SIM card is to identify and authenticate the user with the network. Among the many parameters on a SIM card, the following are especially important:

  • Ki (secret key)
  • IMSI (International Mobile Subscriber ID)
 
IMSI is a unique number similar to IMEI, but for the subscriber, not the phone. Only one IMSI is used on your SIM, and it doesn't change whether you are using 3G or LTE. From the network's point of view, this number identifies you with Public Mobile. On an Android phone, you can download an app like this to view your own IMSI (look for "SIM Subscriber ID"):
 
As you can see, the first 6 digits of your IMSI are always the same as the network ID (Fido being the notable exception).
Telus = 302220
Bell = 302610
Rogers = 302720
 
These numbers are known as PLMN, which are unique global network identifiers. A PLMN is further broken down into MCC (Mobile Country Code) and MNC (Mobile Network Code). Canada's MCC is 302. In North America, MNC is always 3 digits. For the rest of the world, MNC is 2 digits. The MNC identifies an operator in that country.
 
The very first time a SIM is used on a network, the IMSI is sent to eNodeB to identify the user. This information is not encrypted, so it is minimized to avoid eavesdropping. The IMSI includes the PLMN as mentioned above, as well as the subscriber ID. This way, the network knows exactly who is trying to attach, and which operator they claim to be from. Authentication is required to prove the user is legitimately from that operator (this is explained further below). Once the user is attached, the core network will remember the IMSI and assign a temporary IMSI (TMSI) to the user to be used for future attach requests. In subsequent attach requests, the phone will send its TMSI, and the network should remember this user. If there is ever a problem, the network can always ask for the IMSI again, but this is not common.
 
The secret key (Ki) is a very important number used for authentication. The exact same key is stored on the operator's core network, inside the HSS. During the LTE attach procedure, the MME will ask the HSS for a challenge question and expected response. It will forward the challenge question to the phone (via eNodeB), but will hold on to the expected response.
 
When eNodeB asks the phone to respond to the challenge, the SIM card uses its key to come up with the response. The response is passed on to MME (via eNodeB). The MME compares the response to the expected response, and if they match, the user is accepted. If not, user is rejected (though allowed to make emergency calls).
 
For an excellent overview of the authentication procedure, refer to this video:
 
As you can imagine, the key is a critical piece of this process, and it's not shared with anyone, not even the MME, which is the powerful "brains" of the LTE network.
 
In a roaming scenario, the visited MME will exchange information with the home HSS to complete authentication. This avoids sharing keys between operators.
lte_roaming_architecture.jpg
 
The big exception with authentication is emergency calls. In fact, calling 911 doesn't even require the phone to have a SIM card. Even though the phone may show no signal bars, it will say "emergency calls only". The phone will be talking to the network in the background and is permitted to only make emergency calls. All other service requests are denied.
 
Please note that sometimes during activations, people will require a new SIM card to get their accounts set up correctly. This is not due to incorrect key or IMSI values, but maybe the wrong IMSI is linked to a user's account number internally at the operator's billing system. These provisioning steps are separate from what I have discussed here, and I am not familiar with those processes.

@MVP

LTE is quite robust, due to reasons like OFDM technology and MIMO. It's a complex topic that is too technical for this message board.

 

That article is awesome by the way! Reference Signals are sort of like "pilot" signals, used by phones to determine cell signal strength. There is no data or traffic carried on them, so they're always at a constant power (hence a reliable "reference"). The value RSRP is measuring this signal. The acronym RSRP stands for "Reference Signal Received Power".

 

Because LTE uses flexible channel sizes, it's not fair to measure total wideband power. 20 W on a 5 MHz channel is a far better signal than 20 W on a 20 MHz channel, since the same amount of power is spread across a narrower frequency range. LTE utilizes time-frequency resource blocks (RBs), and each RB has 12 subcarriers, therefore a 5 MHz channel (25 RB) will have 300 subcarriers as stated in the article. Larger channels will have more subcarriers. Reference Signals are always spaced every 3 subcarriers.

 

Not totally sure how SINR is measured on the phone, but my guess is the average of all RB SINRs.

MVP
Model Citizen / Citoyen Modèle

**bleep** forum does not let me post the link !

Please search for LTE RSSI vs RSRP, the website is s4gru . com 

MVP
Model Citizen / Citoyen Modèle

@sheytoon wrote:

Test server locations can absolutely affect network speeds, but I made sure to use the same servers. Not sure what you mean by APN location. APN is just a profile. I think you mean the routing from PGW to internet, or maybe how location is determined from the operator's connection point to the internet?

 

You're right though, there could even be other factors besides the core. What would help narrow down the problem is having a Telus SIM on hand, which I do not!


Hi, sheytoon, yes, i meant how the signal is rooted after the PGW  thing (in your pic above). 

Test server locations can absolutely affect network speeds, but I made sure to use the same servers. Not sure what you mean by APN location. APN is just a profile. I think you mean the routing from PGW to internet, or maybe how location is determined from the operator's connection point to the internet?

 

You're right though, there could even be other factors besides the core. What would help narrow down the problem is having a Telus SIM on hand, which I do not!

MVP
Model Citizen / Citoyen Modèle

@sheytoon wrote:

@MVP

Negative SINR is a perfectly valid value, as it's a logarithmic scale. A value corresponding to zero SINR on a linear scale would be (negative infinity) dB.

 

As for throttling, I suspect there is some limit placed at the EPC (core). See pages 7 and 8 for more info on my tests:

http://productioncommunity.publicmobile.ca/t5/Discussions/Is-Public-Mobile-s-LTE-throttled-vs-Telus-...

 

* Seems I lost the ability to link to direct posts with the new layout of the forums.


 

Thank you again , Sheytoon! yes of course negative SNIR is perfectly valid mathematically, but it would probably require a  pretty tricky filtering to get a useful signal out of that. Also, we do not really know how exactly  Network Signal Guru app mesures SINR, so the number  may just be bogus...

 

The info you provide wrt throttling seems veryconvincing, however, i have a devil's advocate question: could it be possible that the speed difference/bottleneck occurs after EPC (e.g. related to the geographical/network locations of  APNs vs testing servers)?

Topic #6: Basics of LTE roaming and why I don't need to change my APN

Disclaimer: This is mainly a core topic, and not my area of expertise. I am mostly confident in the information, but there may be some mistakes.

Previously I described the LTE network with the simple diagram shown below.
Network-diagram.jpg
LTE roaming can be achieved in 2 ways:

  1. Home routed (traditional)
  2. Local breakout


Before any roaming takes place, the home operator and the visited operator must come to an agreement and connect to each other's core networks. If the user doesn't have a valid account at home, which allows roaming in the visited country, then the visited core network will reject the phone from attaching to the network.

With traditional roaming, the local SGW is used, but the home PGW is used. With local breakout, the local SGW and PGW are used.

lte_roaming_architecture.jpg

 

Let's look at an example:

A Telus user travels to the US and roams on AT&T. Once the AT&T core network authenticates the user's SIM card (see next topic for more info), the user is allowed to attach to the network to receive service. All of this takes place in a matter of seconds, and you may notice this short delay when you first disable airplane mode upon landing, until you have service.

With traditional roaming, the user's data is routed from AT&T's SGW to Telus's PGW in Canada, and then to the internet from there. Since the PGW is in charge of APNs, there is no need for a new APN. This is an ok approach for nearby countries, but what if the Telus user goes to Australia and is roaming on Telstra? Having to connect from Telstra's SGW to Telus's PGW will introduce noticeable delays and the LTE experience of the customer could suffer. This is especially true if he/she is trying to browse local Australian websites, which means the data travels from the phone to the RAN to Telstra's SGW, to Telus PGW, to internet, where it is finally routed back to the local Aussie web server.

In this scenario, Telus might have preferred to implement local breakout. One thing I'm not sure about here is how the APN would be configured. I believe the PGW can assign an APN to the phone via the MME during the attach procedure.

As far as I know, Telus does not implement local breakout as it is more challenging to rely on the foreign operator to keep track of data usage and other things that are more easily handled by Telus's own PGW.

@MVP

Negative SINR is a perfectly valid value, as it's a logarithmic scale. A value corresponding to zero SINR on a linear scale would be (negative infinity) dB.

 

As for throttling, I suspect there is some limit placed at the EPC (core). See HERE and HERE.

 

As for LTE having 100 channels, I don't really understand what is meant by that statement. LTE channels are made up of resource blocks, which increase proportionally with channel bandwidth, up to 100 RB for a 20 MHz channel.

 

Network Signal Guru is amazing! I use it too. It's great for rooted phones with Qualcomm chipsets.

MVP
Model Citizen / Citoyen Modèle

P.S. Just tested Public Mobile at a different spot with SNIR 15 to 20 dB, 

and immediately got  50d / 15u  Mbps!

 

Thanks for clarifying  OP!  Now it seems to me that  Public Pobile is NOT throttled.

 

N.B. I'm still able to get 15d/0.2u even at NEGATIVE SNIR = -6 dB, (RSRP = -116 dBm), 

whicl is WEIRD, but I refer to this: http://s4gru.com/index.php?/blog/1/entry-308-rssi-vs-rsrp-a-brief-lte-signal-strength-primer/ saying that LTE has 100 channels, so effectively the signal is 20 dB stronger!  So, out of those 100 channels there are some with positive SNIR.

 

MVP
Model Citizen / Citoyen Modèle

@sheytoon wrote:

Topic #3: How can I achieve very fast speed test results?

 

In order to get peak download speeds on your phone, you need to make sure your signal is good and the network is not congested.
 
The main indicator for a good signal for download speeds is your phone's Signal to Noise (and Interference) Ratio, more commonly known as SNR (or SINR). This shows the cell's power relative to every other signal at the same frequency / channel in decibels (dB). The higher your SINR, the higher speeds you can expect to see. An excellent value for SINR would be 25 - 30 dB.
 
Number of bars are not related to SINR. You could have full bars with a poor SINR. The bars are showing a different measurement, which doesn't take interference into account. This value is known as RSRP, or the Reference Signal Received Power. RSRP is used for performing handovers, among other things.
 
For uplink, there's no way to check the SINR at the eNodeB, so the next best indicator would be RSRP. It's not perfect, but it's the best indicator available. An excellent value for RSRP would be -85 dBm or higher (Note: higher means less negative, and -75 dBm would be an example of a higher value).
  
 

Thank you, OP, for  the illuminating presentations!

 

With Public Mobile I have RSRP -  -100 dBm or less at home, SINR = 10 dB or less (often  even goes below zero 🙂 ), and still am able  to achieve 20d/5u  Mbps speed.

 

With Fido I have  SINR  = 20 dB, and can reach the speeds of 100d/20u.

 

So, it does make sense to speed test only of SINR > 20 dB.   

I use Network Signal Guru app  that shows a lot of info (SINR, RSRP, CA  etc), sometimes even difficult to digest. Will try to test PM in  a different spot, with higher SINR, to see what it gives.. 

 

 

sportymi
Model Citizen / Citoyen Modèle

You can almost write a textbook for these things. lol~ Thanks for the info!

Watoko
Deputy Mayor / Adjoint au Maire

Very interesting! Thanks for putting this together. It may not be for the average PM customer, but I certainly learned a lot!

 

Great work!

Topic #5: What does a cell site look like in real life?

 

A cell site (base station) is generally made up of a few essential parts:
  • Transport router to connect to backhaul network (backhaul can be microwave, fiber, satellite, etc)
  • Baseband unit for processing
  • Radio unit to transmit/receive RF signal
  • Antenna

With 2G networks, the Baseband and Radio units were located in a weatherproof cabinet or small shelter at the base of the tower (or on the roof of a building). Long RF cabling was used to connect to antennas. RF cabling is expensive, bulky, results in signal attenuation, and it wasn't the best way to design a network.

 

With modern 3G and 4G networks, the Radio units have been weatherproofed and mounted outdoors, directly beside the antennas, making the RF cabling very short. Now instead we have long fiber cables to connect the Remote Radio Units (RRU) to the Baseband Units (BBU). Fiber is practically lossless for this type of transmission. RRUs are generally built to support one band per radio, but can usually support multiple technologies.For example, a Band 2 radio (1900 MHz) can usually be used for UMTS (3G), LTE, or both at the same time!

 

base station.png

 

 

In Topic #2, I talked about MIMO and how it requires multiple antennas. It's important to note that multiple antenna elements can be manufactured in a single antenna panel. Here is a picture of an antenna with four ports (four internal antennas). This one antenna can be used to provide 4x4 MIMO:

t006_r10516_v5.jpg

 

Here's an example of a Sprint USA rooftop site where you can see the RRUs mounted to the back of the antenna pole:

roof.jpg

 

Rooftop cabinets housing BBU, power equipment, cooling equipment, and transport router:

roof-cabinet.jpg

 

All of the pictures I am sharing from Canadian sites are from public Google searches.

Rogers (left) and Bell (right) towers side by side in Toronto:side-by-side.PNG

 

 

Sometimes operators will share towers to save space. Tower owner will put their equipment higher up for better coverage and lease the lower spots to competitors.

 

Inside of a shelter will have the same equipment as the cabinets, but more spaced out. Here's an example of a site not in Canada (though they are all similar):

inside-shelter.jpg

 

In the last few years, operators have been getting creative in hiding RRU and antenna equipment in order to keep the sites looking clean. Sometimes these sites will be disguised as flagpoles, or simply "empty" poles that have a cover hiding the equipment. Here are some examples:

 

Rogers-flag.JPGsh-monopole.jpg

 

What if we combine the antenna and RRU into a single product? That could reduce RF cabling even more and increase efficiency. In fact, the major vendors are already doing this with integrated antenna products. For upcoming 5G products that utilize massive MIMO, the radios and antennas will always be integrated.


Ericsson's AIR:

AIR.jpg

 

Nokia's RAS:

RAS.jpg

 

Huawei's AAU:

AAU.JPG

 

What about micro / pico cells? These are just smaller base stations (eNodeB for LTE), with less power and capacity, and a combined RRU + BBU. Here's an example of a pair of Telus outdoor microcells:

micro8.jpg

 

Microcells can be installed indoors or outdoors.

Picocells are smaller versions of microcells, and are mainly installed indoors. They look similar to public WiFi access points.

 

Femtocells are even smaller versions of picocells, purchased directly by end customers to install in their homes/small offices for improved cellular coverage. They use the customer's own internet to route traffic to the operator's network via a secure tunnel. Femtocells are currently not offered by any operators in Canada.

Topic #4: 3G vs 4G vs LTE. What is the difference? What are the paths to 1 Gbps, and how are peak network speeds calculated?

 

The most popular 3G technology globally is known as UMTS. It was a new technology developed to increase efficiency and data capacity relative to older 2G GSM networks. UMTS uses the same core network as GSM, but the RAN is new. UMTS allowed RAN sharing to be implemented for the first time, so Bell and Telus cooperated in building a RAN to catch up with Rogers.
 
Similar to LTE, UMTS has 2 different implementations. Most operators use FDD, also known as W-CDMA (wideband CDMA), but China Mobile uses TDD, also known as TD-SCDMA. The 2 systems are generally incompatible with each other and phones will usually support one or the other, not both. See here for a quick overview of FDD and TDD.
 
HSPA+ is an evolution of the data part of UMTS, which allows faster data speeds than basic UMTS. HSPA+ and UMTS are both 3G technologies, though they are incorrectly identified as 4G.
 
The confusion began when Verizon was launching 4G (LTE) in the US and T-Mobile USA didn't want to be seen as having an inferior 3G (HSPA+) network. They decided to call their existing network 4G, and eventually other operators followed along. The United Nations International Telecommunication Union (ITU) normally defines what technologies can be called 3G, 4G, etc, and many in the technical industry were surprised when ITU allowed UMTS/HSPA+ to be called 4G. True 4G is a technology that can provide 1 Gbps (1000 Mbps), and even today we are only starting to see commercial networks offer these speeds.
 
So depending on what network you're on, and what software your phone has, you might see 3G, H+ or 4G for a UMTS/W-CDMA/HSPA+ network. For LTE, you might see 4G, LTE or 4G LTE.
 
Some manufacturers like Samsung have started displaying LTE+ when a Secondary Component Carrier (SCC) for CA is added and total aggregated bandwidth is greater than 20 MHz. There is no universally defined technology that is known as LTE+.
 
As mentioned above, 1 Gbps is one of the main goals of true 4G networks. This can be achieved through a combination of these enhancements:
  • CA up to 100 MHz bandwidth
  • 4x4 or higher MIMO
  • 256 QAM
 
Peak throughput values are defined as follows for SISO and 64 QAM:
  • 18 Mbps for 5 MHz bandwidth
  • 36 Mbps for 10 MHz bandwidth
  • 55 Mbps for 15 MHz bandwidth
  • 75 Mbps for 20 MHz bandwidth
 
For 2x2 MIMO, double the above values. For 4x4 MIMO, quadruple the above values. For 256 QAM, increase the peak throughput by ~33%.
 
Let's look at an example. Using a combination of these advancements, an operator can deploy 3-CA with 55 MHz of spectrum (20 + 20 + 15), 4x4 MIMO on all 3 bands and 256 QAM on all 3 bands. This would reach peak speeds of 1 Gbps. The calculation is:
3-CA = 75 + 75 + 55 = 205 Mbps
4x4 MIMO = 205 x 4 = 820 Mbps
256 QAM = 820 x 1.33 = 1091 Mbps
 
Once the network is ready, a compatible phone must be available to take advantage of all of the enhancements. Upcoming flagship phones are only starting to support 4x4 MIMO or 256 QAM for certain bands. They will not be able to do 3-CA and 4x4 MIMO and 256 QAM at the same time on all bands. It will take some time before we see phones on the market that can achieve 1 Gbps.

Topic #3: How can I achieve very fast speed test results?

 

In order to get peak download speeds on your phone, you need to make sure your signal is good and the network is not congested.
 
The main indicator for a good signal for download speeds is your phone's Signal to Noise (and Interference) Ratio, more commonly known as SNR (or SINR). This shows the cell's power relative to every other signal at the same frequency / channel in decibels (dB). The higher your SINR, the higher speeds you can expect to see. An excellent value for SINR would be 25 - 30 dB.
 
Number of bars are not related to SINR. You could have full bars with a poor SINR. The bars are showing a different measurement, which doesn't take interference into account. This value is known as RSRP, or the Reference Signal Received Power. RSRP is used for performing handovers, among other things.
 
For uplink, there's no way to check the SINR at the eNodeB, so the next best indicator would be RSRP. It's not perfect, but it's the best indicator available. An excellent value for RSRP would be -85 dBm or higher (Note: higher means less negative, and -75 dBm would be an example of a higher value).
 
In terms of network congestion, the Big 3 operators all have excellent core and backhaul networks, so it would be safe to assume there is no limitation there. The only limitation would be at the RAN, but again there's no way to measure this from the phone. As a rule of thumb, networks will be very close to zero utilization after midnight.
 
Here's an example of some tests I did last year in Toronto on Bell using a Samsung phone. B2 + B4 CA with a total aggregated bandwidth of 35 MHz (20 + 15), using 2x2 MIMO. Peak network capability is 260 Mbps. My results would have been even better after midnight.
Screenshot_2016-04-17-18-44-35.jpg
 
 
For comparison, here are the results from a lab environment, where 260 Mbps is the MAC layer limit. Application layer limit seems to be 249 Mbps.
Lab.png
 
From what I have seen using a Public Mobile SIM, there appears to be some limit imposed from the core network. See HERE and HERE for more info. Koodo users are not impacted:
 
UPDATE: As of May 26, 2017, Telus has resolved the speed issues at the core network and Public Mobile customers on "4G speed" plans are no longer limited in speed. See HERE and HERE.

Other upper limits also exist.  Maybe there's no limit to how many active antenna can get stuffed into each phone; maybe people won't mind hauling around ever-larger devices, maybe engineers will always invent ways to decrease component sizes and increase technological densities.

 

But (FCC) regulatory limits cannot be circumvented.  Useable portions of the EM spectrum are limited, and allowable portions even moreso.  Allowable transmission power is strictly limited, so mobile data can't just multiply and multiplex across more and more antenna elements without consequence.  And every Watt (well, milliWatt) of transmitted power has to come from an electrical power source - mobile batteries impose fundamental limits on how much energy they can store and on how much energy they can (safely) discharge - batteries in today's "ultra-power-efficient" devices can already get surprisingly (almost dangerously) hot and run charges down "into the red" after short activity sessions.

 

Many people and many organizations already protest radio noise for a variety of health, safety, aesthetic, and technical reasons.  It's increasingly difficult for a ham radio operator to erect a radio tower without being shut down by concerned neighbours.  People already campaign (sometimes successfully!) to shut down cellphone towers/repeaters in their neighbourhoods, and I'm sure that more antenna arrays to service more frequencies would attract even more attention as "dangerous" "noisy" "eyesores".

 

Just saying that many "real" limits are not technical, they're entirely different arenas - legal, financial, social, political, etc.

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