Transcript
Hybrid Wireless Network Protocols
Prepared by :- Mohammad Abdelhadi Mohammad Mustafa
Khaled Melhem
Outline :-
● Introduction.
● What is Hybrid Wireless Network.
● Proposed Protocols.● One hop Direct transmission.● Two hop Direct transmission.● Handoff Procedures.
● Simulation Results.
Introduction.● Wireless networks are of two types :-
● Base station-Oriented Wireless Network.○ Single-hop that requires fixed Base Station.○ Better performance.○ More Reliable.
● Ad Hoc Wireless Network.
○ Doesn't have any centralized administration.○ MHs depend on each other for communication.○ Low cost.○ High flexibility.○ Bandwidth usage and battery power consumption are
more efficient.
Introduction● Problems in BS-oriented wireless network.
○ BS failure problem
Introduction● Problems in Ad Hoc Wireless Networks:-
○ Rerouting caused by mobility. ● Disrupted Connection.
What is the Hybrid Wireless Network?
● Hybrid Wireless Network can act as a bs-oriented or ad hoc network at any given time according to the environment conditions.
● Made by adding Base stations to Ad hoc Network.● Has the advantages of both Ad-hoc and Base stations.● Mobile nodes communicate with each other using Ad Hoc
mode when they are in range, and use basestation to communicate when they are out of range.
● More efficient and reliable.● Flexible with seamless handover.
What is the Hybrid Wireless Network?
Proposed Protocols
● The Protocol for One-Hop Direct Transmission.
● The Protocol for Two-Hop Direct Transmission.
Direct Transmission
● Is the situation where two MHs communicate directly or use a third MH as a relay without the help of base station.
● The sender broadcasts the connection request message.● All devices within the sender's signal covering area would
receive this message ( including the BS).● Each MH receiving the message will check the destination
ID.● If the destination ID matches itself, The transmission
procedure begins.● When the destination moves out of the covering area, the
BS would have to take over (BS-Oriented Mode)
The Protocol for One-Hop Direct Transmission.
● Sender broadcast a SEARCH message.● If the receiver is within the range and finds out the
destination is itself, it responds with ACK message to the sender.
● The BS also receives the SEARCH message and it sends the SETUP message to the destination.
● if the destination sends the DIRECT message to the BS, the communication will be direct between MHs.
● Otherwise, if the destination sends an ACCEPT message to the BS, the communication will be BS-oriented mod.
● The Continuity of the communication of the two modes depends on the distance between the communicating pair.
One-hop direct transmission mode
The BS-oriented mode
Handoff Procedure
● Direct transmission mode:○ if the destination detects that the signal strength is less
than the threshold value, handoff must be executed.○ The destination sends the CHANGE message to its
sender.○ The sender receives the CHANGE message and it sends
the SEARCH message again, then BS-oriented mode will be used or two-hop mode.
Handoff Procedure
● BS to One-hop direct transmission:○ If the receiver detects that it is within the coverage region
of the sender's signal and the signal is strong enough, it has the option to switch from the BS-oriented.
○ The receiver sends the CHANGE request to the sender.○ The sender sends the SEARCH message out.....Direct
transmission steps.○ After the sender receives the ACCEPT message from the
receiver, it sends a TearDown message to the BS and breaks the connection.
BS-oriented handoff
Protocols for Two-Hop Direct Transmission Mode
● Cover wider area than the one-hop.● allow two MHs to communicate through a third MH acting as
a relay.● Each MH must implement a Neighbor Database.● A disrupted connection could occur.● Two is the optimal number for hops to avoid the routing
problems that could occur with more than two hops.
Two-Hop Direct Transmission Mode
● This situation happens when the communicating pair are both within an intermediate's coverage area.
● The sender transmits data to the receiver through an intermediate MH.
● If a MH is in the sender range there are two cases:○ When it is the receiver, it sends ACCEPT message back
(One-hop direct transmission).○ If it is NOT the receiver, it will check the neighbor data
base, if the destination is in its data base, it forward the SETUP message, and sends ACCEPT back to the sender if the connection is accepted.
Two-Hop Direct Transmission Mode
● The destination only accept one copy of the SETUP message.
● At the same time, the BS would receive the SEARCH
message. It queries the MH and sends the SETUP message to the destination. For direct transmission, the destination receives the SETUP message and sends the DIRECT message to its BS. Otherwise, the destination would accept the connection from the base station.
Two-Hop Direct Transmission Mode
Handoff Procedure
● if the destination or the intermediate node finds that the strength of the signal is less than a critical value, the handoff procedure is requested and executed at this time. The system will try to find another direct transmission path.
● If a direct transmission path is not found, the BS-oriented mode will take over. The handoff procedures are listed as follows.○ The destination or intermediate node sends the
CHANGE message to the sender for changing connection.
○ As the sender received theCHANGE request, it re-initiates the connection by sending out SEARCH. The next several steps are the same as in the initial connection setup.
Simulation Results
Simulation Results
Thank you for listening!Any Questions?
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