Image Processing Reference
In-Depth Information
system technology continues to exist unchanged as a set of profiles within KNX, frequently referred
to as KNX/EIB.
The KNX specifications are maintained by Konnex Association, which is also responsible for
promotional activities (including a university cooperation program) and the certification of test
laboratories and training centers.
Regarding physical media, EIB already provided the choice of dedicated TP cabling and PL trans-
mission as well as a simple form of IP tunneling intended for remote access. RF communication and
advanced IP tunneling were added under the KNX umbrella (albeit are not yet published within the
context of []). []).The KNX specification also includes additional TP and PL variants which could be
used for future devices.
The main KNX/EIB medium is the TP cabling variant now known as KNX TP. The single TP
carries the signal as well as V DC link power. Data is transmitted using a balanced base band
signalwithbps.TPallowsfreetopologywiringwithuptomcablelengthperphysical
segment. Up to four segments can be concatenated using bridges (called
line repeaters
), forming a
line
.
CAN-like, medium access on TP is controlled using CSMA with bit-wise arbitration on message
priority and station address. Four priority levels are provided.
KNX RF uses a subband in the MHz frequency band reserved for short-range devices
(telecommand, telecontrol, telemetry, and alarms) by European regulatory bodies which is lim-
ited by a duty cycle requirement of less than %. Particular attention was given to minimizing
hardware requirements. To this end, KNX RF does not only support bidirectional communication,
but transmit-only devices as well. This reduces cost for simple sensors and switches without status
indicators. KNX RF devices communicate peer-to-peer.
EIBnet/IP (or KNXnet/IP, []) addresses tunneling over IP networks.
∗
Its core framework sup-
ports discovery and self-description of EIBnet/IP devices. It currently accommodates the specialized
“Service Protocols” Tunneling and Routing. Actually, both of them follow the tunneling principle,
but differ in their primary application focus. EIBnet/IP Tunneling is to provide remote maintenance
access to KNX installations in an easy-to-use manner and therefore restricted to point-to-point com-
munication. EIBnet/IP Routing allows the use of an IP backbone to connect multiple KNX (main)
lines. Routers using this protocol are designed to work “out-of-the-box” as far as possible. hey com-
municate using UDP multicast. Group management relies on IGMP. No central configuration server
is necessary.
As outlined above, the basic building block of a KNX network is the
line
,whichholdsupto
devices in free topology. Following a three-level tree structure, sublines are connected by main lines
via routers (termed
line couplers
) to form a zone. Zones can in turn be coupled by a backbone line.
Network partitions on open media are typically linked into the topology as a separate line or zone.
IP tunneling is typically used for main lines and the backbone, with EIBnet/IP routers acting as cou-
plers. Overall, the network can contain roughly , devices at maximum (not counting EIBnet/IP
specific address space extensions).
EverynodeinaKNXnetworkisassignedan
individual address
which corresponds to its posi-
tion within the topological structure of the network (zone/line/device). This address is exclusively
used for unicast communication. Reliable connections are possible. Multicast addressing is imple-
mented in the data link layer. For this purpose, nodes are assigned additional nonunique MAC
addresses (
group addresses
). he group addressing and propagation mechanism is thus very efficient.
Yet, acknowledgements are provided on layer (i.e., within an electrical segment) only. The entire
group answers at once, with negative acknowledgements overriding positive ones. his mechanism is
∗
EIBnet/IP supersedes “plain” EIBnet, which provided tunneling over Ethernet, and the legacy EIBlib/IP (iETS) point-
to-point IP tunneling protocol.
