computer science

Vehicular Reactive Routing protocol

Vehicular Reactive Routing protocol is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Vehicular Reactive Routing protocol rather than just read about it. In short: Vehicular Reactive Routing protocol (VRR) is a reactive routing protocol with geographical features which is specifically designed for Wireless Access for the Vehicular Environment (WAVE) standard in vehicular ad hoc networks (VANETs). The protocol takes advantages of the multichannel scheme defined in WAVE and uses the Control Channel (CCH) for signalling, and relies on one of the multiple Service Channels (SCHs) f…

Key takeaways

Vehicular Reactive Routing protocol belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Vehicular Reactive Routing protocol to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Vehicular Reactive Routing protocol from memory before moving on to harder problems.

Reference excerpt

Vehicular Reactive Routing protocol (VRR) is a reactive routing protocol with geographical features which is specifically designed for Wireless Access for the Vehicular Environment (WAVE) standard in vehicular ad hoc networks (VANETs). The protocol takes advantages of the multichannel scheme defined in WAVE and uses the Control Channel (CCH) for signalling, and relies on one of the multiple Service Channels (SCHs) for payload data dissemination.

Protocol design

The Vehicular Reactive Routing (VRR) protocol is integrated with the WAVE stack and is embedded at the Logic Link Control layer. VRR is a multi-channel protocol which exercises efficient route discovery, route maintenance and data deliver processes with the use of the Control Channel (CCH) and a Service Channel (SCH). Standard WSA messages are transmitted over CCH and IPv6 packets are transmitted over SCH. To obtain a current neighbour location the WSA frame is modified to carry position information (incurs an additional 4 Bytes). Route request and route reply demands are transmitted inside WSA frames (additional 40 Bytes) over the Control Channel and data acknowledgment and all application data (IPv6 packets) are sent over the Service Channel. Due to these modifications, a route is firstly established over the CCH and afterwards data are transmitted over the SCH.

VRR protocol messages The VRR protocol uses 3 signalling message types. Messages, route request (RREQ) and route reply (RREP) are broadcast on the CCH and acknowledgment (ACK) packets are transmitted on the SCH. Data packets are IPv6 packets and are transmitted after route discovery or route maintenance on one of SCHs. RREQ and RREP are situated inside the WRA field of WSA frame and on each hop the WSA frame is discarded and a new WSA frame created. Both messages are transmitted in the lowest Traffic Class (background).

VRR Broadcasting This algorithm is based on combination of three approaches

Neighbour elimination family: receiving nodes themselves decide to rebroadcast data or not on base of network coverage. If all nodes in transmit range of receiver node are covered by the information, then the receiver node does not rebroadcast. If some node is not covered by the information in transmit range of the node then the node prepares data to rebroadcast. Source-dependent dominating sets: The principle is that a sender determines for a small subset of neighbours which is called multipoint relay (MPR). Only nodes inside the subset can rebroadcast information from the source. Probability: where probability depending on the distance between a transmitter and a receiver. A Higher probability is chosen for node further from a source and vice versa with a lower probability for closer nodes. Principle of VRR Broadcasting simply like that: A transmitter sends a broadcast data.

If receiving node is chosen as MPR node by transmitter, it sets up shortest backoff time (waiting time before rebroadcasting). If receiving node is not chosen as MPR node by transmitter, it sets up backoff time depend on its mobility behaviour (distance from a transmitter, speed and vector of motion). If receiving node calculates that its neighbour's nodes are already covered by broadcast information, then the node doesn't rebroadcast. An advantage of VRR Broadcasting approach is that all receiving nodes have some opportunity to rebroadcast information (not only MPR nodes), but only a few nodes have the best opportunity (i.e. the shortest backoff time) for rebroadcasting. Another advantage is that in the case of the multipoint relay node not always receiving the broadcast due to collisions (in a dense busy network) then other nodes who overhear can transmit the information instead.

Route discovery technique The RREQ frames are broadcast by the VRR Broadcasting algorithm. If a node doesn't have a route to destination then the node rebroadcasts depend on the algorithm. If a node has a route to destination, it creates broadcast frame RREP and set up backoff time depend on mobility behaviour (distance from a transmitter, speed and vector of motion). If a RREP is transmitted by a transmitter, all neighbour's nodes received also the RREP and they discards own RREQ or RREP effort except node which is on a way to a source node. Principle of VRR Route Discovery handshake (without MPRs) (animation)

References

Worked examples

Example 1 — a first encounter with Vehicular Reactive Routing protocol

Start with the simplest possible case. Write down what Vehicular Reactive Routing protocol claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Vehicular Reactive Routing protocol before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Vehicular Reactive Routing protocol ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Vehicular Reactive Routing protocol

In research: Vehicular Reactive Routing protocol appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Vehicular Reactive Routing protocol in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Vehicular Reactive Routing protocol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ad hoc routing protocols, Routing algorithms, Routing protocols, so understanding it makes those chapters shorter.
In everyday life: Look for Vehicular Reactive Routing protocol outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Vehicular Reactive Routing protocol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vehicular Reactive Routing protocol means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Vehicular Reactive Routing protocol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vehicular Reactive Routing protocol in simple terms?

Why does Vehicular Reactive Routing protocol matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Vehicular Reactive Routing protocol?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Vehicular Reactive Routing protocol.