1
Throughput Enhancement in Throughput Enhancement in WiMax Mesh Network Using WiMax Mesh Network Using
Concurrent TransmissionConcurrent Transmission
Advisor: Dr. Kai-Wei Ke
Speaker: Jaw-Woei Ma
Date:03/28/2006
2
OutlineOutline
Introduction
1.WiMAX
2.Mesh NetworkSchedulingConcurrent TransmissionSimulation and AnalysisConclusionsReferences
3
WiMAXWiMAX
Worldwide Interoperability for Microwave Access(全球微波存取互通性 )
A wireless broadband network connection
technique. the last mile.Cost saving.Easy to employ
4
WiMAX versus WiFiWiMAX versus WiFi
WiFi Bandwidth:11Mbps (802.11b) , 54Mbps (802.11g)
Range:100m
WiMAX Bandwidth:134Mbps, 300kbps~2Mbps (末端用戶 )
Range:48kmWiMAX,WiFi和有線網路屬於”互補關係”
5
Mesh NetworkMesh Network
PMP ( point to multipoint ) The downlink, from the BS to the user,operates on a PM
P basis
Mesh Traffic can be routed through other SSs and can be occu
r directly between SSs
Subscriber station share uplink to the BS on a demand basis all above
6
Distributed Scheduling
Superiority of the Mesh BS, which effectively result in Centralized Scheduling
On a combination of both
Mesh Network (cont.)Mesh Network (cont.)
7
Scheduling in Mesh ModeScheduling in Mesh Mode
Distributed Scheduling
No clearly defined BS
a distributed manner like an ad-hoc network
8
Centralized Scheduling
BS determines slot allocation for all SSs
a centralize manner like PMP mode
traffics can be relayed by other SSs through a multi-hop route which is defferent from PMP mode
9
Combination
a hybrid of both can be adopted in Mesh mode
10
Two Control Message
MSH-CSCF(Mesh Centralized Scheduling Configuration)
deliver the information of channel configuration and routing tree
11
MSH-CSCH
(Mesh Centralized Scheduling)
deliver the information of bandwidth request and grant and updating of routing tree
Grant/Request Flag: 0 = Grant (downlink )
1 = Request ( uplink )
12
Each entry of Scheduling TreeEach entry of Scheduling Tree
NodeID
NumberOfChildren
ChildIndex (table)
Uplink/Downlink Burst Profile
13
The BS generates MSH-CSCF and broadcasts it to all its neighbors
BS -> SS (MSH-CSCF)
According to the routing tree in MSH-CSCF message, all the SSs maintain a routing tree whose root is BS and children are SSs
SS -> BS ( MSH-CSCH: Request )
BS can gather bandwidth requests from all the SSs, and assign spatial resource for SSs (put in MSH-CSCH: Grant message)
rebroadcast until all the SSs receive MSH-CSCH:Grant
SchedulingScheduling
14
After receiving a MSH-CSCH:Grant message, the SSs determine its actual uplink and downlink transmission time from MSH-CSCH:Grant by a common algorithm which divides the frame proportionally
Scheduling (cont.)Scheduling (cont.)
15
TDMATDMA
16
Concurrent TransmissionConcurrent Transmission
17
solid lines : directional links in the routing tree
dashed lines : connect the neighboring nodes in one-hop
the curves : the interference by an active link
Link InterferenceLink Interference
18
L(x,y) represent the link from x to y
the interfered links by L(4,6) are L(6,4), L(2,4), L(5,2), L(4,2),L(BS,2),L(BS,1),L(3,1)
i.e. when node 4 is transmitting data to node 6,The number of interfered links by L(x,y) is given by I(x,y), so I(4,6)=7
19
Py(x) = I(x,y) + I(y,x) + Pz(y).
for example, P4(6) = I(4,6) + I(6,4) + P2(4).
Constructing Routing TreeConstructing Routing Tree
20
network begins with only one BS
all the SSs enter the network one by one
all its neighbor nodes are eligible to be the father node of the entering SS
entering SS should select a father node with minimal interference
21
Father node is
where Neighbor(x) is a set of x’s neighbor nodes.
22
23
After SS5 entered the network
P2(4)=46,P5(4)=30
so the father node of SS4 is adjusted from SS2 to SS5
24
Concurrent Transmission Algorithm Concurrent Transmission Algorithm
The order of transmission time determination in uplink is the same as transmission order of MSH-CSCH: Request
25
The ideaThe idea
The transmission time should be as early as possible on condition that no collision would happen
The transmission time of an SS should not be earlier than any of its children’s
26
Algorithm (Uplink)Algorithm (Uplink)
27
Algorithm (Downlink)Algorithm (Downlink)
the algorithm in downlink is similar to that in uplink
28
SimulationSimulation
Simulation Scenario:
Random topology is generated in an L*L square.
( L = d √(n / 2) )
n is the number of SSs d is the maximal transmission range between tw
o nodes.
29
single channel network with no bit errors
all the SSs are immobile and working in half duplex
highest available rate (set to 50Mbps here)
regardless of the channel state
Every SS request 0.5Mbps
bandwidth for both uplink and downlink
30
ResultResult
show the overall end-to-end throughput
with different routing trees
The number of SSs increases from
20 to 120 with a step of 10
The throughput values are the average of simulations in 500 times
31
Results (Uplink)Results (Uplink)
32
Results (Downlink)Results (Downlink)
33
AnalysisAnalysis
Throughput:
(1). interference-based routing tree >
random routing tree
(2). adjusted interference based routing tree > non-adjusted interference-based routing tree
34
Analysis (cont.)Analysis (cont.)
This concurrency algorithm performs best when using an adjusted and interference-base routing tree.
35
ConclusionsConclusions
promote spatial resource reuse, which increases the overall end-to-end throughput
Simulation results indicate that different constructions of routing tree impact the performance of the concurrent
algorithm
36
Future WorkFuture Work
With rapid demands of mobility wireless access we need
Consider the scenario that SSs are mobile to improve our algorithm
37
ReferenceReference[1] Jian Tao, Fuqiang Liu, Zhihui Zeng, and Zhan
gxi Lin, “Throughput enhancement in WiMax mesh networks using concurrent transmission,” Proceedings of 2005 International Conference on Wireless Communications, Networking and Mobile Computing.
[2] Hung-yu Wei, Samrat Ganguly, Rauf Izmailov, and Zygmunt Haas,"Interference-Aware IEEE 802.16 WiMax Mesh Networks," The 61st
IEEE Vehicular Technology Conference (VTC Spring'05), May 2005.
[3] IEEE 802.16 standard
