diff --git a/doc/hamnet70.adoc b/doc/hamnet70.adoc
index 598738d..e7b8397 100644
--- a/doc/hamnet70.adoc
+++ b/doc/hamnet70.adoc
@@ -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