1. inside a vehicle that will interconnect various

1.      
INTRODUCTION

In-Vehicle Networking is a
communication bus inside a vehicle that will interconnect various control
systems.  The main driving forces for the
development of vehicle network technology have been the advances made in the
electronics industry in general. The need for in-vehicle networking is obvious
that it will substantially reduce the harnesses inside the vehicle, can
efficiently share the sensors inside the vehicle, sharing of information
between systems and enabling diagnostics of systems through a common backbone
network that gives easy serviceability and maintainability. Control systems
typically consist of control of automotive power train, body electronics, and
steering, braking, drive by wire, fuel measurement system, battery monitoring
system etc…

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2.      
In VEHICLE
NETWORKING

There are several
network types and protocols used in vehicles by various manufactures. Many
companies are encouraging a standard communication protocol

Some of the common
vehicle buses protocols include:

CAN , CAN FDLIN FlexRay  IDB-1394AFDXMIL STD 1553ByteflightARINC 429Keyword Protocol 2000 (KWP2000) MOST

In the OSI model for the networking which represents
the 7 layer model for open system interconnection. Layers 1-4 are dealing with
lower layer which basically does the
data movement where as the layers 5-7 are higher layers dealing with
application level processing. Most of the networking protocols use some of the
layers whereas a very few like Ethernet will be using all the layers.

In the
in-vehicle networking each communication protocol will support different
topologies or a combination of topologies. Some of the common topologies are
point to point, star, ring, bus, hybrid topologies. Each topology has its own
merits and demerits. Like in point to point which is simplest and fastest but
addition of nodes will not be feasible. Bus topologies have the flexibility to
add nodes but each node will be sharing the bus backbone network and arbitrate
while performing the communication. Star topology is faster and having
flexibility to add nodes but additional hardware like hub, switches are
externally required to communicate with the nodes and it becomes the single
point failure. Hence the protocol which supports hybrid networking will be
successful in catering to future communication needs.

There are two
types of communication methodology in the bus network. Event triggered and time
triggered.

In event triggered communication
the message is transferred based on the event occurrence and the communication
will be asynchronous. This saves lot of bandwidth but the latency of the
message delivery is based on the size of the message and the bus traffic at
that instant of time.

 In time triggered protocol, the total message
cycle is divided in slots dedicated to the nodes and messages and each node
will send the message in dedicated slots monitored by the Master of the bus.
This provides the determinism required for a vehicle networking. This requires
more bandwidth, configuration of network and messages prior to implementation.
When additional nodes are added, the network to be reconfigured or put it in
reserved spaces.

The key bus parameters to be considered
for any vehicle network are

a)      
Throughput

b)      
Data Latency

c)      
Bus loading

d)      
Error Recovery

e)      
Fault tolerance

f)       
Dynamic Switching

g)      
Initialization time during switching,

h)      
Interoperability

i)        
Fault confinement.

j)       
Low cost

k)      
Immunity from external noise

l)        
Ability to operate in harsh environments

m)    Overall robustness and reliability