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by sixstringtheory
1001 days ago
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If I ran a company where someone tried to release a 19K page spec I'd keep firing people until someone could produce a spec that I could actually review and sign off on, that could also still be reproduced in working technology. How does this kind of thing fly at all? |
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When GSM was originally specified, there was serious doubt if it would work at all on the hardware available at the time.
A GSM call has a 3.62us send window, a 3x3.62us waiting period, and a 3.62us receive slot. That’s probably hard enough to achieve on a single cell, but factor in distance to the tower as well, and the handset has to do a lot of calculations.
Once you start considering handoff between cells things get even more interesting. The handset continuously reports a list of cell towers it can “see” along with the strength of their signals from the handsets position.
Once the cell tower decides that the handset is moving out of range, it propagates a handoff message to its upstream node, which repeats this process until a suitable downstream node is found, and each cell tower is then alerted that the handset with an ongoing call is switching from/to that cell, and finally the handset is informed. The handset has no say in this process other than the list of cell towers.
All of this took place in the late 1980s, it was finalized in 1987, and modern processors at the time would be the Intel 386DX running at 12 to 40 MHz. Obviously not handsets came with a 386 processor, and when I worked on mobile phones in the early 2000s, the norm would be something like an 8 to 12 MHz 16bit platform.
Since then the specification has been revised hundreds of times. In the original specification, messaging (SMS) was an afterthought, and a way of utilizing otherwise unused bandwidth, which was normally reserved for command and control. Turns out messaging was a hit with GenX, so many changes were made to that subsequently, like EMS[1], MMS[2] and RCS[3].
Likewise focus shifted from phone calls to data, which was 4G, and to IoT and always on devices, which is what 5G is about. 4G and 5G also has increased the number of active devices possible.
Add to that WiFi calling and all the other little enhancements, and I wouldn’t be the least bit surprised if the specification is closer to 50,000 pages today.
[1] https://en.wikipedia.org/wiki/Enhanced_Messaging_Service [2] https://en.wikipedia.org/wiki/Multimedia_Messaging_Service [3] https://en.wikipedia.org/wiki/Rich_Communication_Services