3 ms·

Your cell phone company knows the tower you are talking to and probably which (directional) antenna you are talking to. Antennas are in the process of getting a

Your cell phone company knows the tower you are talking to and probably which (directional) antenna you are talking to. Antennas are in the process of getting a lot more directional with 5G, so they'll soon go from trivially being able to track you within a block or two to within a meter or two. It's not great.

PeterisP 5y ago
The core records of a cell phone company are at a cell level, which often are configured in a 120-degree sectors from a tower. If they really want, they can see the distance from the tower because that's a requirement for the communications protocol to work (LTE at least expects to account for lightspeed delay in allocating transmission slots) and gets measured during the communications, so the operator should be able to see that distance to the granularity of something like 100m (or is it less nowadays?); but AFAIK that's usually not stored unless you're in a 911 call or perhaps with some tracing warrant.
- eurasiantiger 5y ago
  These newfangled beamforming systems can alter the direction of transmission to optimize signal quality for your phone. How can they do that if the system cannot locate a handset with great accuracy?
  - iamstupidsimple 5y ago
    Beams don't have to be that accurate to boost signal quality. This is also speculation on my part but I'd suspect they're targeting specific clusters of devices in an area and using multiplexing than having dozens of radios on one tower.
  - PeterisP 5y ago
    I have no idea about what information the (5G?) beamforming protocols use; perhaps they have figured out a way for some "angle discovery" as part of the protocol handshake or perhaps they just require the device send GPS data for that adjustment (and in the absence of that data would just skip beamforming, getting worse rates); but the distance information for the 4G/LTE timing system would be an inherent part of the protocol even if the device does not have GPS enabled and is based on literally measuring the round-trip timing.
    - eurasiantiger 5y ago
      From Wikipedia/MIMO: ”To correctly form a beam, the transmitter needs to understand the characteristics of the channel. This process is called channel sounding or channel estimation. A known signal is sent to the mobile device that enables it to build a picture of the channel environment. The mobile device sends back the channel characteristics to the transmitter. The transmitter can then apply the correct phase and amplitude adjustments to form a beam directed at the mobile device. This is called a closed-loop MIMO system.”
SamBam 5y ago
As far as we know, though, the police haven't (yet) been able to demand Verizon turn over the records of everyone who sent near a crime scene at 2pm, though, have they? I feel like Google's location history is basically built for that kind of thing.

PeterisP 5y ago

The core records of a cell phone company are at a cell level, which often are configured in a 120-degree sectors from a tower. If they really want, they can see the distance from the tower because that's a requirement for the communications protocol to work (LTE at least expects to account for lightspeed delay in allocating transmission slots) and gets measured during the communications, so the operator should be able to see that distance to the granularity of something like 100m (or is it less nowadays?); but AFAIK that's usually not stored unless you're in a 911 call or perhaps with some tracing warrant.

eurasiantiger 5y ago
These newfangled beamforming systems can alter the direction of transmission to optimize signal quality for your phone. How can they do that if the system cannot locate a handset with great accuracy?
- iamstupidsimple 5y ago
  Beams don't have to be that accurate to boost signal quality. This is also speculation on my part but I'd suspect they're targeting specific clusters of devices in an area and using multiplexing than having dozens of radios on one tower.
- PeterisP 5y ago
  I have no idea about what information the (5G?) beamforming protocols use; perhaps they have figured out a way for some "angle discovery" as part of the protocol handshake or perhaps they just require the device send GPS data for that adjustment (and in the absence of that data would just skip beamforming, getting worse rates); but the distance information for the 4G/LTE timing system would be an inherent part of the protocol even if the device does not have GPS enabled and is based on literally measuring the round-trip timing.
  - eurasiantiger 5y ago
    From Wikipedia/MIMO: ”To correctly form a beam, the transmitter needs to understand the characteristics of the channel. This process is called channel sounding or channel estimation. A known signal is sent to the mobile device that enables it to build a picture of the channel environment. The mobile device sends back the channel characteristics to the transmitter. The transmitter can then apply the correct phase and amplitude adjustments to form a beam directed at the mobile device. This is called a closed-loop MIMO system.”

SamBam 5y ago

As far as we know, though, the police haven't (yet) been able to demand Verizon turn over the records of everyone who sent near a crime scene at 2pm, though, have they? I feel like Google's location history is basically built for that kind of thing.