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Wireless internet routing. Philippe Jacquet. Internet and networking. Internet User plurality connected to Sources plurality. Wireless architectures. Three main architectures Point to point Base station Mesh. Signal processing complexity in ground wireless networks. - PowerPoint PPT Presentation
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Wireless internet routing
Philippe Jacquet
Internet and networking
• Internet– User plurality connected to– Sources plurality
Wireless architectures
• Three main architectures– Point to point
– Base station
– Mesh
Signal processing complexity in ground wireless networks
• Diagram Capacity-Range
GSMUMTS
WavelanIEEE 802.11
Hiperlan1&2IEEE802.11a
UMTS pico-cell UMTS
micro-cell
Capacityin bit/s
distance in m
bluetooth
Mobile ad hoc networks
• Mesh and mobile
6
• DARPA’s proposal for LANdroids
2. Wireless network capabilities required
7
2. Which wireless networks?
MANET VANET wireless sensors
Wireless community network
Wireless networks
Mobile ad hoc networks– Mobility makes link failure a necessity
• Refresh period 1 second• Automatic self-healing
– Local neighborhood is local space• Unlimited neighborhood size
– Stadium network: N=10,000, with average degree 1,000
• BGP needs 1014 links exchange per refresh time• BGP fails on Wifi networks with 20 users at
walking speed.• Heavy density kills link state management.
Wireless internetMobile ad hoc routing
• Mobile Ad hoc NETworks– Two protocol classes:
• Proactive class• Reactive class
Proactive class
• Link state protocols– Full internet legacy– Topology compression– Periodic control traffic– Permanent routing tables– OLSR
Reactive class
• Distance vector based– Partial internet legacy– Path limited topology– On demand route discovery– Temporary routing tables– AODV
Optimized Link State Routing protocol
• Topology compression– Run light and fast, only on best routes
• Carry a subset of the local table • Stay on selected links
Topology compression graph(V,E)
• Optimized Link State Routing (OLSR) – A mobile network can be very dense (ex:
|V|=104,|E|=107)– Instead advertizing all links, a node advertizes only its
multipoint relays.– The multipoint relay set much smaller than neighbor
set |)(| EoEE r =→
)|(||| 2VOE =
Multipoint relay sets
Multipoint relay set of a terminal :Neighbor subset that covers the two hop neighbors
Goal: find the smallest posible multipoint relay set
Multipoint relay links
Multipoint relay set
• Local computation– Need to know two-hop neighborhood– Optimal is NP hard– Greedy algorithm is optimal to factor
• Good enough for performance
€
logV
Multipoint relay set
• Greedy selection algorithm
• On node AIntialize N2 N2(A), Er(A) .
While (N2) do
Find y in N(A) which maximizes |N2N(y)|
Add Ay to Er(A)
N2 N2- N(y)
Return Er(A)
Topology compression
• In Erdös-Rényi random graph models:
• In unit disk random graph model:
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τ r =E rE
=Ologn
n
⎛
⎝ ⎜
⎞
⎠ ⎟
€
τ r =O n−
2
3 ⎛
⎝ ⎜
⎞
⎠ ⎟
BA
Topology compression
• The union of multipoint relay link sets is a remote-spanner– Nodes compute their routing tables with the
remote-spanner and their local table.
• Topology compression is lossless.– Optimal routes in tables also optimal in genuine
topology.
Route optimality proof
• By recursion: if D is at distance k from A in G(V,E) there exists a route of length k in G(V,E(A)+Er) from A to D– true for k=1: (A,D)E(A).– If true for k, then if D at distance k+1, let the chain F-H-D
with d(A,F)=k-1 and d(A,H)=k. Node F is a two hop neighbor of node D.
– Let M the multipoint relay of D which covers F.– M is at distance k from A, thus there exists a route L of
length k in G(V,E(A)+Er) from A to M.– (M,D) Er, thus L+(M,D) is in G(V,E(A)+Er) and is of length
k+1.A DF H
M
Control traffic reduction
• Topology reduction– Topology compression
• Dissemination reduction– Information about topology move only on
multipoint relay links
• Further dissemination reduction– Wireless flooding
• Total reduction
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τ r
€
τ r
€
V
E
€
τ r2 V
E
Wireless flooding
• A single transmission per node– broadcast emission – Instead of a copy per link
Dissemination reduction
• link flooding (cost |E|) packet P node AP←reception();If !(P==null) then
if!(P received) theninsert P in received;B←last_emitter(P);for each C N(A) do
if(C≠B) then send(P,C);• broadcast flooding (cost |V|)
P←reception();If !(P==null) then
if!(P received) theninsert P in received;broadcast(P);
Multipoint relay flooding
• Only multipoint relays flood the information (reduction factor |Er|/|E|) P←reception();If !(P==null) thenif!(P received) then
insert P in received;B←last_emitter(P);
if(BA Er) then
broadcast(P);
Multipoint relay flooding
• Packet P dissemination from node S. Any arbitrary A– Closest emitter of P to A: distance k– Prove that k≤1
Multipoint relay flooding
A
FG
H
€
k
G’
€
k −1
€
k − 2
OLSR neighbor sensing
• Partial Link control on network layer
• Periodic broadcast of hello message– Contain list of heared neighbors– Two way check
MPR selection
• Collect the 2-way neighbor lists of neighbor nodes
• Run the selection algorithm.
• Advertize MPR set in hello