Mesh Network

1
Mesh Network

• EE 548
• Adv. Topics in Comm. Systems
• Shen Wan

2
What is Mesh Network?

• A network that employs one of two connection
  arrangements, full mesh topology or partial mesh
  topology.

3
Features and Facts

• Recently, mesh ad hoc
• Do not need to be dynamic.
• Self management
• Scalability
• Self routing
• Mostly used for WLAN (and now WiMAX)

4
Protocols

• AODV - Ad hoc On demand Distance Vector
• Mobile Mesh
• TBRPF - Topology Broadcast based on Reverse-Path
  Forwarding (proactive)
• OSPF - Open Shortest Path First

5
Implementations

• MIT Roofnet
• Nortel wireless mesh network solutions

6
Mesh/Relay Networkingin WiMAX

• EE 548
• Adv. Topics in Comm. Systems
• Shen Wan

7
Background

• High frequency band such as 2-6 GHz has wide
  frequency bandwidth and enables to obtain higher
  throughput.
• The higher frequency, the more difficult NLOS
  communication.
• To cover NLOS area, simple Relay Station (RS) is
  more efficient than BS.

8
Different Mesh/Relay Schemes
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Benefits of Relay

• Coverage extension

10
Benefits of Relay

• Throughput enhancement

11
Types of Relay Stations
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Advantages of Mesh

• Capacity
• Scalability
• Infrastructure costs
• Range and NLOS
• Robustness
• Efficiencies

13
Challenges of Mesh

• Delay
• Cost
• Interference
• Bottleneck
• Synchronization

14
Realizations
15
Pros and Cons

• Logical Mesh
• Lower C/I and spectral efficiency
• High reuse factor
• Intra network interference needs protocol
  support
• Significant impact of external interference on
  large parts of the network
• Supporting a rich mesh can be difficult with few
  frequencies due to high reuse factor requirements

• Physical Mesh
• Significantly improved C/I and high spectral
  efficiency
• Low frequency reuse
• More expensive antenna systems
• Complex environment sensing with mechanical
  antennas

16
Interference-aware Routing
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Interference-aware Scheduling

• Seeks to maximize the number of concurrent
  transmissions, without creating exceeding
  interference for other simultaneous transmission.

18
Mesh vs. Relay
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Current status

• Mesh
• Logical Mesh in 802.16-2004
• New group Mobile Multi-hop Mesh Networking
  launched on May 2005.
• 802.16h study group
• Relay
• Technique Group will launch on May 2006.
• Drafting standard October 2006 (maybe)