Effect of a New Channel Assignment Strategy on Multihop Wir

eless Networks

Futoshi Tasaki, Fumito Uta, Hiroshi Tamura, Masakazu Sengoku, and Shoji Shinoda

IEICE Transaction on Communication, May 2004Special Section on Mobile Multimedia Communications

Outline

• Introduction• Preliminaries• Channel assignment strategies

– Strong edge coloring– Edge coloring based on degree of

interference

• Simulation and considerations• Conclusions

Introduction

• In the multihop wireless network, each terminal communicates to other terminals using– Time slot (TDMA)– Carrier (FDMA)– Code (CDMA)

• Cochannel interference may occur, channels cannot assigned randomly

Preliminaries

• Preconditions– No obstacle– Only light-of-sight links– Non-directed antenna– The same transmission power– GPS

Preliminaries

• Definitions terminal

Communication edge

Interference edge

Strong Edge Coloring

• Every two edges of distance at most two receive different colors

5 colors is needed

Edge Coloring Based on Degree of Interference

yx II

C

Signal strength

Signal strength oftwo interferences

Edge Coloring Based on Degree of Interference

Strict Interference Model

41

40

1

1

d

d

I

CCIR

42

40

1

1

d

d

I

CCIR

43

40

1

1

d

d

I

CCIR

44

40

1

1

d

d

I

CCIR

Strict Interference Model

• Because d1 is the smallest in d1, d2, d3 and d4, C1/I1 is the smallest value in the four CIR– Other three CIRs can be neglected

Strict Interference Model

Simple Interference ModelRM: the maximum distance between 2 terminals which can communicate

D: two terminal pairs should be away when using a same channel

Simple Interference Model

The distance between two adjacent terminals

is 1 unit

After inserting the interference edges

Simulations

• Mesh network–

– The ratio of rasgn means the efficiency of a channel assignment, a smaller rasgn is effective

Simulations

Simulations

• General mesh network (random topology)

Simulations

Consideration of Channel Assignment Algorithm

Consideration of the Number of Channels

Conclusion

• Strict Interference Model is more effective

• Edge-length selection algorithm is effective than random ordering

• Issues of mobility should be considered in the future

Thank you!!