Back To That Mesh Thing… [GiTO]

Let’s talk a little tech.

The Mesh was built by combining several already-extant pre-Collapse technologies. The first is digital radio.

Analog radio (your AM’s and FM’s) suffers from signal attenuation: the further you are from the source, the weaker the broadcast (the harder it is to perceive). This isn’t a linear relationship: most of the drop-off happens very quickly. It also suffers from interference (which you can hear as static).

Digital radio compensates for both. Attenuation is pretty much inverse: the signal stays relatively constant until very nearly the edge of the range, then drops off suddenly. It’s also fault tolerant; very little static.

The second tech is software defined radio. All Mesh nodes are software defined radios. An SDR replaces radio hardware (mixers, amplifiers, etc.) with software; the only piece of equipment you actually need is an antenna, everything else happens in the computer.

SDR has numerous benefits over hardware radios. It can use multiple protocols (and switch between them at will), it can adjust broadcast strength to the minimum required on-the-fly (reducing interference with other nodes on the same channel), and it can more easily detect faint signals (a critical advantage for the shortwave Mesh).

The last technology is the modem, the modulator-demodulator. Digital signals are encoded so they can be transmitted, and received signals are decoded back into digital information. (In the Mesh, this is a piece of software, not hardware.)

Taken together, these three technologies form the telecom aspect of the Mesh. Then there are the protocols: rules as to how the network will operate.

The Mesh divides up the shortwave frequencies into 50 separate channels. One node broadcasts on one channel, and receives on the other 49. (Mesh networking means all signals are sent to, and received by, every node at the same time. This is necessitated by the physical nature of radio itself.)

A root node has a specific and reserved channel, all other nodes get what space is available, top to bottom, first-come-first-served. Because North America only has 30 operating nodes, that means the bottom 20 channels are usually unused by standard Mesh traffic.

Some nodes reserve and use them for additional transmissions (doubling their bandwidth), some for duplicate transmissions (to ensure critical information is received), some for non-node Mesh transmissions (from groups out in the Outlaw), and some by pirate radio operators for actual voice transmissions. (Everybody hates those guys.) All of these uses are on a contingency-only basis; if standard Mesh traffic ever needed the space, they’d be displaced.

[Note: That paragraph packs a bunch of interesting setting info in a very tight space. Pirate radio and non-node Mesh traffic have interesting consequences, and interesting uses, and I hope to get back to them at some point.]

Of the 30 nodes in North America, eight are root nodes: one each for the four Fed states, plus the FDNY, Texas, Xiyatu, and Vancouver. Eastern Canada, Alaska, and Mexico have all applied for root licenses, but haven’t been granted them yet. They each have nodes, just not certified root nodes. (It doesn’t help that the three polities are generally untrusted, having reputations for unsavory dealings. Unjustly so in Mexico’s case.)

As with the economic details, these technical details won’t appear in the final writeup. They’re useful to define the scope and nature of the Mesh for my purposes, but players and GM’s will never have to understand what they mean other than: it’s slow and flaky, and the powerful, connected, or rich have dibs. (I’m sorry. “Priority.” Suck-ups and cronies have “priority”.)

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