doc: add introduction + some more ideas
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@ -5,6 +5,14 @@ Thomas Kolb DL5TKL
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== Introduction
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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.
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The protocols defined here are inspired by the Packet Radio network and Bluetooth Low Energy.
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The protocols are designed primarily for centralized infrastructure as they were common in the Packet Radio network.
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Few base stations (_digipeaters_) provide wide coverage from exposed locations.
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Every user can connect to the base station, but they can not necessarily receive each other’s transmissions.
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Therefore, a star topology network where the base station coordinates transmissions is the primary goal.
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== General Notes
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All data is transmitted in network byte order (big endian = MSB first).
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@ -42,11 +50,10 @@ The PHY header describes how the following data symbols should be interpreted. I
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. Modulation/code combination ID (MODCOD): 4 bit
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. Number of data symbols: 12 bit
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. CRC8 of the previous 16 header bits: 8 bit
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Therefore the PHY header has as size of 24 bit, including CRC.
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Therefore the PHY header has as size of 16 bit.
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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.
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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.
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The PHY header is always modulated using QPSK.
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@ -222,7 +229,8 @@ Due to the long possible bursts, this system can achieve high throughput if ther
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To be defined:
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- connection establishment procedure (request, response)
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- when are new clients allowed to connect?
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- how do clients get an IP(v6) address? -> should be derived from the call sign
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- when are new clients allowed to connect? -> base station calls for any new stations in regular intervals
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- handling of packets from unknown clients that are not connection requests
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- signal quality handling
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