6 ms·

I've always wondered why cellular is affected by this, anyone have a link?

TrickyRick 9y ago
There's a limited amount of "space" in the air, ie not everyone can be transmitting at the same time. This is fixed using a few different techniques depending on the cell network but for GSM something called TDMA (Time division multiple access) is used. This basically gives your phone a certain amount of time to broadcast on before it should leave the airwaves for someone else to transmit on. Too many people in one location means not enough time for everyone to transmit.
- ghthor 9y ago
  This is the main reason yes. No amount of backhaul can change this. There are 2 solutions to this problem. 1) Distributing a web of much smaller cells, lower power so much less devices are connected per node. 2) DIDO pCell technology developed by Artemis. All antennas transmit and the waveforms from each broadcast interfere around each receiver to create a valid signal for that signal device. Both systems require loads of calculations by the broadcasters to either manage handoffs from each mini cell, or to calalate valid distributed broadcasts per each receiver. This type of event would have been a great opportunity for Artemis to show off their tech.
- vvanders 9y ago
  That's not really quite accurate on modern networks. Most of them use CDMA which allows many devices to transmit/receive at the same time, assuming that they can modulate their power with respect to distance from the tower/etc(which is a requirement for the "xor" to cancel out). That said there's still a bunch of other stuff you have to sort out if you want to support that many devices in a small space.
  - dboreham 9y ago
    "Many" is still not thousands or even hundreds.
  - TrickyRick 9y ago
    > Most of them use CDMA Really? I thought CDMA was something only Verizon used for their network. I tried looking into it a bit prior to writing the original answer but I couldn't find anything other than a mention on the TDMA Wiki [1] which has a [citation needed]. Do 3G/4G networks across the world use CDMA as well? Because I know that in Sweden carriers are buying up large chunks of frequency bands to be able to increase 4G coverage, that shouldn't be needed with CDMA, right? [1]: https://en.wikipedia.org/wiki/Time-division_multiple_access https://en.wikipedia.org/wiki/Time-division_multiple_access
mschuster91 9y ago
I believe it's the backhaul capacity that's the problem. Even assuming "only" 1 MBit/s constant traffic per customer, an uplink of 1 GBit/s can only handle a thousand clients tops. Cheap-ish providers are worse - they usually don't run fiber to every tower because laying fiber is expensive, but instead only to one tower which then distributes uplink via directional microwave to nearby towers. Once that link gets saturated or has issues, the whole area is screwed. Providers like Deutsche Telekom (or other former monopolists) usually have it easier as they have huuuge amounts of fiber and especially conduits in the ground, which means it's easier for them to wire up even small towers with real dedicated fiber uplink.
- MertsA 9y ago
  This is pretty off base. Backhaul is the "easy" part here. It's easy to get way more bandwidth available on a microwave link than the bandwidth available to clients.
foobaw 9y ago
Disclaimer: I worked at an OEM phone company. Cell towers get saturated pretty easily by crowds. Network providers probably did not account for the crowd, or even if they did, it wasn't enough. I would assume a company like Niantic asked network providers to install additional cell towers beforehand, so my best guess is they tried their best but still failed. The technical details are quite complex, and you would need to read up on GSM,UMTS,LTE,TDMA,CDMA, but the bottom-line is, the overall technology isn't good enough yet.
fencepost 9y ago
The technologies used and underlying principles have changed enormously from 2G/GSM to 3G/WCDMA to 4G/LTE/OFDMA but a lot of it comes down to questions of how many individual connections each tower can handle and the minimum amount of airtime communicating with each device requires. At one point (still?) there are also questions of how strongly each device and tower must be broadcasting to keep the received signal at each end within acceptable levels. Edit: Expanding on this a little while I still have time to edit, and all of this is from a non-telecom person so it's likely I have errors in here. Still, this should provide a starting point for the history and what to look for to get more current/accurate info. Most 2G was GSM which used TDMA (Time Division) - basically, each device connecting to the tower was assigned a "slice" of the available time and had to broadcast within that time slice. When the tower ran out of slices, some devices simply couldn't connect to it. Sprint and Verizon were the exceptions, they used CDMA which allowed many devices to broadcast at the same time and was able to decode data for/from each device based on the Code Division used to encode it. CDMA towers "breathed" which meant that their coverage area could vary based on how many devices were connected because the devices and towers had to keep broadcasts within particular power levels at the endpoints. CDMA allowed more devices, TDMA could allow larger coverage from each tower by reducing the number of time slices (which also reduced the number of devices that could connect). Notably, CDMA allowed devices to talk to multiple towers at once with reconciliation being handled by a smarter backend, while TDMA required more explicit handoffs between towers. Way back when this was why on GSM your call would simply drop, but on CDMA you'd simply develop a severe case of robot voice. 3G almost all moved to WCDMA, which I believe had many of the same advantages in density as CDMA. 4G moved to somethind different (OFDMA?), which I haven't read enough about to really understand but which is technically quite different from WCDMA. Most LTE uses yet another protocol. On T-Mobile, this was noticeable when T-Mo "refarmed" its network, converting a bunch of frequency bands from 4G to the newer higher-capacity but incompatible LTE. I know a few people who had 4G phones on T-Mobile and were offered free replacement phones because T-Mobile had basically yanked the actual 4G network out from under them. Basically, there's a lot out there, it has changed a LOT over the last 10-15 years, and many of the changes were actually complete replacements rather than incremental upgrades.
lnanek2 9y ago
What's to wonder about? Each tower can only handle a certain number of people, and the cell phone companies don't put the number of towers needed for an event like this in permanently.

There's a limited amount of "space" in the air, ie not everyone can be transmitting at the same time. This is fixed using a few different techniques depending on the cell network but for GSM something called TDMA (Time division multiple access) is used. This basically gives your phone a certain amount of time to broadcast on before it should leave the airwaves for someone else to transmit on. Too many people in one location means not enough time for everyone to transmit.

ghthor 9y ago
This is the main reason yes. No amount of backhaul can change this. There are 2 solutions to this problem. 1) Distributing a web of much smaller cells, lower power so much less devices are connected per node. 2) DIDO pCell technology developed by Artemis. All antennas transmit and the waveforms from each broadcast interfere around each receiver to create a valid signal for that signal device. Both systems require loads of calculations by the broadcasters to either manage handoffs from each mini cell, or to calalate valid distributed broadcasts per each receiver. This type of event would have been a great opportunity for Artemis to show off their tech.
vvanders 9y ago
That's not really quite accurate on modern networks. Most of them use CDMA which allows many devices to transmit/receive at the same time, assuming that they can modulate their power with respect to distance from the tower/etc(which is a requirement for the "xor" to cancel out). That said there's still a bunch of other stuff you have to sort out if you want to support that many devices in a small space.
- dboreham 9y ago
  "Many" is still not thousands or even hundreds.
- TrickyRick 9y ago
  > Most of them use CDMA Really? I thought CDMA was something only Verizon used for their network. I tried looking into it a bit prior to writing the original answer but I couldn't find anything other than a mention on the TDMA Wiki [1] which has a [citation needed]. Do 3G/4G networks across the world use CDMA as well? Because I know that in Sweden carriers are buying up large chunks of frequency bands to be able to increase 4G coverage, that shouldn't be needed with CDMA, right? [1]: https://en.wikipedia.org/wiki/Time-division_multiple_access https://en.wikipedia.org/wiki/Time-division_multiple_access

mschuster91 9y ago

I believe it's the backhaul capacity that's the problem. Even assuming "only" 1 MBit/s constant traffic per customer, an uplink of 1 GBit/s can only handle a thousand clients tops. Cheap-ish providers are worse - they usually don't run fiber to every tower because laying fiber is expensive, but instead only to one tower which then distributes uplink via directional microwave to nearby towers. Once that link gets saturated or has issues, the whole area is screwed. Providers like Deutsche Telekom (or other former monopolists) usually have it easier as they have huuuge amounts of fiber and especially conduits in the ground, which means it's easier for them to wire up even small towers with real dedicated fiber uplink.

MertsA 9y ago
This is pretty off base. Backhaul is the "easy" part here. It's easy to get way more bandwidth available on a microwave link than the bandwidth available to clients.

foobaw 9y ago

Disclaimer: I worked at an OEM phone company. Cell towers get saturated pretty easily by crowds. Network providers probably did not account for the crowd, or even if they did, it wasn't enough. I would assume a company like Niantic asked network providers to install additional cell towers beforehand, so my best guess is they tried their best but still failed. The technical details are quite complex, and you would need to read up on GSM,UMTS,LTE,TDMA,CDMA, but the bottom-line is, the overall technology isn't good enough yet.

fencepost 9y ago

The technologies used and underlying principles have changed enormously from 2G/GSM to 3G/WCDMA to 4G/LTE/OFDMA but a lot of it comes down to questions of how many individual connections each tower can handle and the minimum amount of airtime communicating with each device requires. At one point (still?) there are also questions of how strongly each device and tower must be broadcasting to keep the received signal at each end within acceptable levels. Edit: Expanding on this a little while I still have time to edit, and all of this is from a non-telecom person so it's likely I have errors in here. Still, this should provide a starting point for the history and what to look for to get more current/accurate info. Most 2G was GSM which used TDMA (Time Division) - basically, each device connecting to the tower was assigned a "slice" of the available time and had to broadcast within that time slice. When the tower ran out of slices, some devices simply couldn't connect to it. Sprint and Verizon were the exceptions, they used CDMA which allowed many devices to broadcast at the same time and was able to decode data for/from each device based on the Code Division used to encode it. CDMA towers "breathed" which meant that their coverage area could vary based on how many devices were connected because the devices and towers had to keep broadcasts within particular power levels at the endpoints. CDMA allowed more devices, TDMA could allow larger coverage from each tower by reducing the number of time slices (which also reduced the number of devices that could connect). Notably, CDMA allowed devices to talk to multiple towers at once with reconciliation being handled by a smarter backend, while TDMA required more explicit handoffs between towers. Way back when this was why on GSM your call would simply drop, but on CDMA you'd simply develop a severe case of robot voice. 3G almost all moved to WCDMA, which I believe had many of the same advantages in density as CDMA. 4G moved to somethind different (OFDMA?), which I haven't read enough about to really understand but which is technically quite different from WCDMA. Most LTE uses yet another protocol. On T-Mobile, this was noticeable when T-Mo "refarmed" its network, converting a bunch of frequency bands from 4G to the newer higher-capacity but incompatible LTE. I know a few people who had 4G phones on T-Mobile and were offered free replacement phones because T-Mobile had basically yanked the actual 4G network out from under them. Basically, there's a lot out there, it has changed a LOT over the last 10-15 years, and many of the changes were actually complete replacements rather than incremental upgrades.

lnanek2 9y ago

What's to wonder about? Each tower can only handle a certain number of people, and the cell phone companies don't put the number of towers needed for an event like this in permanently.