**6.1. Conclusions**

 A new topology control algorithm for multi-radio WMNs, *Select x for less than x*, is proposed. It controls the network topology by selecting the nearest neighbors for each node in the network.

Channel Assignment Using Topology Control Based on Power Control in Wireless Mesh Networks 73

Following are some aspects of this work which can be extended in future.

**[11]** 

required Required Not

Not required

Ensured by the CA scheme

 Since TICA uses the new approach of building the interference level for all the frequency channels, it can be enhanced to model and account for the interference from co-

 Other algorithms for building the tree topology, such as Prim's algorithm [30] and Kruskal's algorithm [31], can be used for building the minimum power based tree,

**CA control** Centralized Centralized Centralized Centralized Distributed Distributed

**BFS-CA [20]** 

Periodic channel switching required

Fixed Fixed Fixed

Ensured by common control radio

No No No

**Failure recovery** Yes No No No Yes No

**Power control** Yes No No No No No

**MesTiC [14]** 

Not required

Ensured by common control radio

required Required Required Not

**D-HYA [17]** 

Required as CA changes with traffic

Topology defined by spanning tree

Ensured by the CA scheme

Performed by the CA scheme

**HMCP [18]** 

required

Per-packet channel switching required

Topology changing due to channel switching

Ensured by channel switching

No

which may lead to a further enhancement in the overall network throughput.

**6.2. Future work** 

located wireless networks.

**Feature TICA C-HYA** 

Not

Required for failure recovery

Topology controlled using TCA

Ensured by common control radio, ensured by the CA scheme

Performed by the CA scheme

**Table 3.** Features' comparison of related CA schemes

**Scheme**

**Knowledge of traffic load** 

**Channel switching** 

**Topology** 

**Connectivity** 

**Routing** 

 A new channel assignment algorithm for MRMC IEEE 802.11a-based WMNs, TICA, is proposed, which is based on topology control. As verified by a comprehensive performance evaluation, the improvement in the overall network throughput with TICA is significantly higher than the CCA scheme but is much higher than SRSC scheme in all three topologies. This is due to the fact that topology control based on power control results in an efficient frequency reuse during CA, which leads to an overall improvement in the network throughput.

In the CCA and SRSC schemes, which are two commonly-used benchmark schemes, MRs do not control their power, transmit with maximum power, and use AODV routing protocol as their routing agent. TICA, on the other hand, uses topology control by selecting the nearest neighbors for each mesh node in the network, which reduces the interference among the mesh routers. It uses the minimum power as the link weight when building the SPT with the required node degree as less power translates to less interference among the mesh routers. It uses a scheme to build the IL for all the frequency channels if all the available frequency channels have already been assigned within the interference range of a link. It assigns a LIC to a link if all the available frequency channels have already been assigned within the interference range of that link. LIC is the channel with the minimum IL, which means that assigning this channel to the link would result in minimum interference in the network. In TICA, from the information in the received CARM, each mesh router applies power control and adjusts its transmission power accordingly, based on the channel assigned to that mesh router to communicate with a neighbor and its distance to that neighbor.


## **6.2. Future work**

72 Wireless Mesh Networks – Efficient Link Scheduling, Channel Assignment and Network Planning Strategies

 A new topology control algorithm for multi-radio WMNs, *Select x for less than x*, is proposed. It controls the network topology by selecting the nearest neighbors for each node

 A new channel assignment algorithm for MRMC IEEE 802.11a-based WMNs, TICA, is proposed, which is based on topology control. As verified by a comprehensive performance evaluation, the improvement in the overall network throughput with TICA is significantly higher than the CCA scheme but is much higher than SRSC scheme in all three topologies. This is due to the fact that topology control based on power control results in an efficient frequency reuse during CA, which leads to an overall improvement

In the CCA and SRSC schemes, which are two commonly-used benchmark schemes, MRs do not control their power, transmit with maximum power, and use AODV routing protocol as their routing agent. TICA, on the other hand, uses topology control by selecting the nearest neighbors for each mesh node in the network, which reduces the interference among the mesh routers. It uses the minimum power as the link weight when building the SPT with the required node degree as less power translates to less interference among the mesh routers. It uses a scheme to build the IL for all the frequency channels if all the available frequency channels have already been assigned within the interference range of a link. It assigns a LIC to a link if all the available frequency channels have already been assigned within the interference range of that link. LIC is the channel with the minimum IL, which means that assigning this channel to the link would result in minimum interference in the network. In TICA, from the information in the received CARM, each mesh router applies power control and adjusts its transmission power accordingly, based on the channel assigned to that mesh router to communicate with a neighbor and its

 As per the specification of the IEEE 802.11s standard for wireless mesh networks, the mesh routing protocol has to reside in the MAC layer. TICA not only performs channel assignment but performs routing as well by providing each node with the next hop information to reach the gateway node and hence, conforms to the requirements of IEEE

 A centralized Failure Recovery Mechanism for TICA is proposed, which supports automatic and fast failure recovery. In case of node failure, after detecting the failed node, deleting the MPNT of the failed node and deleting it from the MPNT of its neighbors, the gateway runs the TCA and builds the MPSPT. Based on the new MPSPT, the gateway calculates the link rankings and the channel assignments. The new channel assignments are communicated to the mesh nodes by the gateway via a new CARM using

 The proposed CA algorithm, TICA, does not require modifications to the MAC protocol and therefore, can work with existing IEEE 802.11a-based interface hardware.

**6.1. Conclusions** 

in the network.

in the network throughput.

distance to that neighbor.

the control radio over the control channel.

802.11s.

Following are some aspects of this work which can be extended in future.



**Table 3.** Features' comparison of related CA schemes

	- Other schemes for building the tree topology with the required node degree, such as the one proposed in [32], can be used which may lead to a better performance.

Channel Assignment Using Topology Control Based on Power Control in Wireless Mesh Networks 75

FRM Failure Recovery Mechanism

HMCP Hybrid Multi-Channel Protocol

MMAC Multi-channel Medium Access Control

MPSPT Minimum Power-based Shortest Path Tree

MPNT Maximum Power Neighbor Table

MesTiC Mesh-based Traffic and interference-aware Channel-assignment

TICA Topology-controlled Interference-aware Channel-assignment Algorithm

[1] N. Nandiraju, D. Nandiraju, L. Santhanam, B. He, J. Wang, and D.P. Agrawal, "Wireless Mesh Networks: Current Challenges and Future Directions of Web-in-the-Sky," *IEEE* 

[2] A. U. Chaudhry, R. H. M. Hafez, O. Aboul-Magd, and S. A. Mahmoud, "Throughput Improvement in Multi-Radio Multi-Channel 802.11a-based Wireless Mesh Networks,"

[3] A. U. Chaudhry, R. H. M. Hafez, O. Aboul-Magd, and S. A. Mahmoud, "Fault-Tolerant and Scalable Channel Assignment for Multi-Radio Multi-Channel IEEE 802.11a-based Wireless Mesh Networks," *Proceedings of IEEE Globecom 2010 Work-*

*Wireless Communications Magazine*, Vol. 14(4), pp. 79–89, August 2007.

*Proceedings of IEEE Globecom 2010*, December 2010.

LIC Least Interfering Channel MAC Medium Access Control MANET Mobile Ad hoc Network MCG Multi-Radio Conflict Graph

MND Maximum Node Degree

MRMC Multi-Radio Multi-Channel NS2 Network Simulator Version 2

SRSC Single-Radio Single-Channel

TCA Topology Control Algorithm

VCA Varying Channel Assignment WLAN Wireless Local Area Network WMN Wireless Mesh Network WSN Wireless Sensor Network

MR Mesh Router

PHY Physical Layer RT Random Topology SPT Shortest Path Tree

TC Topology Control

**7. References** 

GT Grid Topology GW Gateway

IL Interference Level

