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doc: add introduction + some more ideas

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Thomas Kolb 2024-06-08 11:49:43 +02:00
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doc/hamnet70.adoc
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@ -5,6 +5,14 @@ Thomas Kolb DL5TKL
== Introduction
Hamnet70 intends to provide a network system in the 70 cm amateur radio band that can transfer Internet Protocol (IP) packets at a high speed.
The protocols defined here are inspired by the Packet Radio network and Bluetooth Low Energy.
The protocols are designed primarily for centralized infrastructure as they were common in the Packet Radio network.
Few base stations (_digipeaters_) provide wide coverage from exposed locations.
Every user can connect to the base station, but they can not necessarily receive each other’s transmissions.
Therefore, a star topology network where the base station coordinates transmissions is the primary goal.
== General Notes
All data is transmitted in network byte order (big endian = MSB first).
@ -42,11 +50,10 @@ The PHY header describes how the following data symbols should be interpreted. I
. Modulation/code combination ID (MODCOD): 4 bit
. Number of data symbols: 12 bit
. CRC8 of the previous 16 header bits: 8 bit
Therefore the PHY header has as size of 24 bit, including CRC.
Therefore the PHY header has as size of 16 bit.
For additional protection, the header is encoded using a [8,4] Hamming code, which can reliably correct single-bit errors and detect double-bit errors in every block of four bits.
For additional protection, the header is encoded using a [12,8] Hamming code, which can reliably correct single-bit errors and detect double-bit errors in every block of eight bits.
The PHY header is always modulated using QPSK.
@ -222,7 +229,8 @@ Due to the long possible bursts, this system can achieve high throughput if ther
To be defined:
- connection establishment procedure (request, response)
- when are new clients allowed to connect?
- how do clients get an IP(v6) address? -> should be derived from the call sign
- when are new clients allowed to connect? -> base station calls for any new stations in regular intervals
- handling of packets from unknown clients that are not connection requests
- signal quality handling