performance evaluation of multiple access protocols for ad hoc networks using directional antenna
DESCRIPTION
Performance Evaluation of Multiple Access Protocols for Ad hoc Networks Using Directional Antenna. Tamer ElBatt, Timothy Anderson, Bo Ryu WCNC 2003, March 2003 speaker : Chen-Chi Hsieh. Outline. Introduction System Model Channel Reservation Based on Directional Antennas Information - PowerPoint PPT PresentationTRANSCRIPT
Performance Evaluation of MPerformance Evaluation of Multiple Access Protocols for Aultiple Access Protocols for Ad hoc Networks Using Directid hoc Networks Using Directi
onal Antennaonal AntennaTamer ElBatt, Timothy Anderson, Bo RyTamer ElBatt, Timothy Anderson, Bo Ry
uu
WCNC 2003, March 2003 WCNC 2003, March 2003
speakerspeaker:: Chen-Chi HsiehChen-Chi Hsieh
OutlineOutline
IntroductionIntroduction System ModelSystem Model Channel Reservation Based on Channel Reservation Based on
Directional Antennas InformationDirectional Antennas Information Results and DiscussionResults and Discussion
IntroductionIntroduction
The broadcast nature of omni-The broadcast nature of omni-directional antenna directional antenna causes multi-user interferencecauses multi-user interference thus limit the spatial reusethus limit the spatial reuse
Introduction – Introduction – Related WorkRelated Work
Three schemesThree schemes Omni-directional reservation (802.11)Omni-directional reservation (802.11) Directional reservation (DRTS/DCTS) Directional reservation (DRTS/DCTS) Hybrid reservation (DMAC using Hybrid reservation (DMAC using
DRTS/OCTS)DRTS/OCTS) Decide whether to proceed with a Decide whether to proceed with a
transmission in a specific direction or transmission in a specific direction or notnot
Rely on hearing/not hearing a reservation Rely on hearing/not hearing a reservation messagemessage
Introduction – Introduction – Related Work Related Work (cont.)(cont.)
NeighborNeighbor N(x) N(x) :: Area covered by the radiation pattArea covered by the radiation patt
erns of all erns of all beams at node xbeams at node x Partition N(x) into Block-Neighbor BN(x) aPartition N(x) into Block-Neighbor BN(x) a
nd Unblock-Neighbor UBN(x)nd Unblock-Neighbor UBN(x) BN(x) BN(x) :: at least one of its beams is blocked frat least one of its beams is blocked fr
om transmissionom transmission UBN(x) UBN(x) :: not hear any reservation messagenot hear any reservation message
Cause collision to the ongoing transmissionCause collision to the ongoing transmission
Introduction – Introduction – Related Work Related Work (cont.)(cont.)
Omni-directional Omni-directional Reservation(802.11)Reservation(802.11)
All neighbors become aware of the ongoing All neighbors become aware of the ongoing transmissiontransmission
N(S)=N(S)= {{ 1,2,3,4,5,6,D1,2,3,4,5,6,D }} BN(S)=N(S) UNB(S)=ΦBN(S)=N(S) UNB(S)=Φ
N(D)=N(D)= {{ 1,4,5,6,7,8,9,S1,4,5,6,7,8,9,S }} BN(D)=N(D) UNB(D)=ΦBN(D)=N(D) UNB(D)=Φ
•AdvantageAdvantage ::•Minimize the possibility of coMinimize the possibility of collisionsllisions
•DrawbackDrawback ::•Too conservativeToo conservative
Introduction – Introduction – Related Work Related Work (cont.)(cont.)
Directional ReservationDirectional Reservation D-RTS/D-CTSD-RTS/D-CTS
•AdvantagesAdvantages ::•Initiates more simultaneousInitiates more simultaneous reservation attemptsreservation attempts•Trade-off between collisions and Trade-off between collisions and spatial reusespatial reuse
•DrawbacksDrawbacks ::•Unaware of each other Unaware of each other •Highly subject to collisionsHighly subject to collisions
N(S)=N(S)= {{ 1,2,3,4,5,6,D1,2,3,4,5,6,D }} BN(S)= { 4,5,6,D } UBN(S)= { 1,2,3}
N(D)=N(D)= {{ 1,4,5,6,7,8,9,S1,4,5,6,7,8,9,S }} BN(D)= { 4,5,S } UBN(D)= { 1,6,7,8,9 }
Introduction – Introduction – Related Work Related Work (cont.)(cont.)
Hybrid ReservationHybrid Reservation Use different combinations of omni-Use different combinations of omni-
directional and directional reservation directional and directional reservation messages (D-RTS/O-CTS)messages (D-RTS/O-CTS)
N(S)=N(S)= {{ 1,2,3,4,5,6,D1,2,3,4,5,6,D }} BN(S)= { 4,5,6,D } UBN(S)= { 1,2,3 }
N(D)=N(D)= {{ 1,4,5,6,7,8,9,S1,4,5,6,7,8,9,S }} BN(D)= { 1,4,5,6,7,8,9,S } UBN(D)=ΦΦ
Introduction – Introduction – Related works (cont.)Related works (cont.)
Hybrid ReservationHybrid Reservation ““Medium Access Control Protocols Using Medium Access Control Protocols Using
Directional Antennas in Ad Hoc Networks” IEEE Directional Antennas in Ad Hoc Networks” IEEE INFOCON 2000INFOCON 2000
A B C D E
DRTS(B)
OCTS(B,C)OCTS(B,C)
DATA
ACK
DRTS(D)
OCTS(D,E)
DATA
ACK
OCTS(D,E)
Exploit the spatial reuse but raise collision problem
Introduction – Introduction – Related works (cont.)Related works (cont.)
Hybrid Reservation (cont.)Hybrid Reservation (cont.)
DrawbacksDrawbacks Doesn’t strike a balance
minimizing control packet collisions May lead to further collisionsMay lead to further collisions
Introduction Introduction (cont.)(cont.)
New concepts in this paperNew concepts in this paper All neighbors of the source and the destinAll neighbors of the source and the destin
ation should ation should bebe aware of the intended traaware of the intended transmissionnsmission ,, if possibleif possible
Antenna blocking decisions should be basAntenna blocking decisions should be based on the information included ed on the information included in the RTSin the RTS/CTS packets/CTS packets
Introduction Introduction (cont.)(cont.)
The contributions of this paperThe contributions of this paper Balance the Balance the trade-offtrade-off
between omni-directional and directional between omni-directional and directional reservationsreservations
Resolve new type of Resolve new type of collisionscollisions ConceptConcept
Sending reservation packets carrying Sending reservation packets carrying ““directional antennas informationdirectional antennas information” to as ” to as many neighbors as possiblemany neighbors as possible
Knowing their locations relative to the Knowing their locations relative to the transmitter-receiver pairtransmitter-receiver pair
System Model - System Model - Antenna ModelAntenna Model
Antenna ModelAntenna Model Each nodeEach node
a fixed number (B)a fixed number (B) of switched beams of switched beams Each of width Each of width θθ == 2π/B2π/B radians radians
Transmitted energyTransmitted energy uniformly in a beam of width θuniformly in a beam of width θ
Nodes receive Nodes receive omni-directionallyomni-directionally Beams are non-overlappingBeams are non-overlapping
System Model System Model – – Network Network Assumptions (cont.)Assumptions (cont.)
Each node obtains neighboring Each node obtains neighboring information by a information by a node-discovery schemenode-discovery scheme
Information of each nodeInformation of each node The identities of all neighborsThe identities of all neighbors The identities of neighbors that lie within The identities of neighbors that lie within
the coverage of each beamthe coverage of each beam Location of a nodeLocation of a node
RS
A
not allowed to engage in any communicationsnot allowed to engage in any communications
A
transmit on any directional beam transmit on any directional beam except the one pointing towards the transmitterexcept the one pointing towards the transmitter
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
InformationInformation Balance the aforementioned trade-Balance the aforementioned trade-
offoff Send RTS/CTS packets over Send RTS/CTS packets over all all
unblockedunblocked beams beams Add two fields to the RTS/CTS Add two fields to the RTS/CTS
messagesmessages the index of the directional beam the index of the directional beam currently currently
being usedbeing used the index of the directional beam the index of the directional beam intended intended
to be usedto be used
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
Information Information (cont.)(cont.)
102
3
1
5
46
7
8
9
11
S DO-RTSO-CTS
Node 5 : not engage in any communications
Node 2 : (1)block only the beam pointing towards node S (2)can initiate a transmission with node 10
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
Information Information (cont.)(cont.) New types of collisionsNew types of collisions
A neighbor may miss reservation A neighbor may miss reservation messages due to messages due to lying in the coverage lying in the coverage of a blocked beamof a blocked beam
A
RTSRTS
S DNode A : it may be active or inactive , May cause collision later
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
Information Information (cont.)(cont.) Solution of collisionSolution of collision
Use Use auxiliary channelauxiliary channel to transmit to transmit specialspecial reservation packets on reservation packets on blocked blocked beamsbeams
Suffering collisions from active Suffering collisions from active usersusers
Special reservation packetsRTS
S DA : inactive
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
Information Information (cont.)(cont.) Two solutions for solving collision prTwo solutions for solving collision pr
oblemoblem Use Use auxiliary channel(s)auxiliary channel(s) to transmit to transmit specspec
ialial reservation packets on reservation packets on blocked blocked beam beamss
Suffering collisions from active usersSuffering collisions from active users Send “Send “pending” RTS/CTSpending” RTS/CTS packets once packets once
the blocked beam becomes unblockedthe blocked beam becomes unblocked Involves synchronization complexityInvolves synchronization complexity
D1
S2Special RTS/CTS
S1RTS
RTS
DATA
S1 : unaware the ongoing transmission
DATA
D2
S2 D1
S1RTS
Pending RTS/CTS
Channel Reservation Based Channel Reservation Based on Directional Antennas on Directional Antennas
Information Information (cont.)(cont.) Solution of collisionSolution of collision
Use Use auxiliary channel(s)auxiliary channel(s) to transmit to transmit specspecialial reservation packets on reservation packets on blocked blocked beams beams
Suffering collisions from active usersSuffering collisions from active users Send “Send “pending” RTS/CTSpending” RTS/CTS packets once packets once
the blocked beam becomes unblockedthe blocked beam becomes unblocked Involves synchronization complexityInvolves synchronization complexity
Transmit different packets on multiple bTransmit different packets on multiple beams at the same timeeams at the same time
Results and DiscussionResults and Discussion NS-2 simulatorNS-2 simulator Under a wide variety of network Under a wide variety of network
loadsloads SchemesSchemes
omni-directional reservationomni-directional reservation directional reservationdirectional reservation hybrid reservationhybrid reservation
Results and Discussion – Results and Discussion – Simulation SetupSimulation Setup
Small networksSmall networks :: n = 50 nodesn = 50 nodes A rectangular areaA rectangular area :: 500 meters x 500 500 meters x 500
metersmeters Data packet sizeData packet size :: 500 bytes500 bytes No mobilityNo mobility B = 6 switched beams per node
Each of 600 width duration : 900 sec.
Results and Discussion – Results and Discussion – Simulation ResultsSimulation Results
Packet arrival rate/node λ(packets/sec)
Ave
rage
num
ber
of d
ata
pack
ets
tran
smitt
ed/s
ec
Results and Discussion – Results and Discussion – Simulation Results Simulation Results (cont.)(cont.)
Packet arrival rate/node λ(packets/sec)
Ave
rage
num
ber
of d
ata
pack
ets
colli
sion
s/se
c
Results and Discussion – Results and Discussion – Simulation Results Simulation Results (cont.)(cont.)
Packet arrival rate/node λ(packets/sec)
MA
C t
hrou
ghpu
t (K
bps)
Results and Discussion – Results and Discussion – Simulation Results Simulation Results (cont.)(cont.)
MA
C t
hrou
ghpu
t (K
bps)
Number of beams/node (B)
Results and Discussion – Results and Discussion – Simulation Results Simulation Results (cont.)(cont.)
DrawbacksDrawbacks Real switched beam antennas experience soReal switched beam antennas experience so
me overlappingme overlapping SolutionsSolutions
minimizes beam overlap minimizes beam overlap Physical layer algorithms “captures” the Physical layer algorithms “captures” the ss
trongest signaltrongest signal from interference in the ove from interference in the overlapped areasrlapped areas
Carrying out reservations in a Carrying out reservations in a round-robinround-robin f fashion over the course of K phasesashion over the course of K phases ,, where where K may take values between 2 and BK may take values between 2 and B
ConclusionsConclusions
Incorporating aggressiveness in the Incorporating aggressiveness in the reservation schemereservation scheme
Modifying the channel occupancy Modifying the channel occupancy criterion to depend on information criterion to depend on information carried by the RTS/CTS messagescarried by the RTS/CTS messages
Candidate solutions for combating Candidate solutions for combating new types of collisions inherent to new types of collisions inherent to directional antennasdirectional antennas