Bluenet
a New Scatternet
Formation Scheme*
Huseyin Ozgur Tan
*Zifang Wang,Robert J.Thomas, Zygmunt
Haas
ECE Cornell Univ*
Outline
Introduction
 Bluenet Scheme
 Evaluation Methods
 Simulation Environment
 Simulation Results

Introduction

Performance issues for scatternet formation
 Waste

of capacity for bridge nodes
Resynchronization of radio from one piconet to another
 Cost
of some of network resources to maintain a
scatternet


Master-Slave relation
Tradeoff
 Decent
level of Connectivity
 Reserving enough network resources
Introduction
Other scatternet formation schemes
 At that time a few papers that address this
problem
 The most important one : Bluetree
 In this paper proposed Bluenet and
Bluetree algorithms are compared

Bluetree

Two modes of formation





Blueroot Grown Bluetree
Distributed Bluetree
All resulting scatternets: spanning
tree
Adv: spends the least of network
resources
Disadv:

Reliability


If one parent node is lost, scatternet
becomes disconnected
Efficiency

All traffic has to traverse the tree in
upward and downward direction
Bluenet Scheme

Background Information

Information exchange requires master slave relation


Visibility graph




Polling and coordinating the slaves
Bridge overhead


Network consisting of all the units and all the potential links
Scatternet is a small fraction of all the potential links
Scatternets are a subgraph of visibility graph
Intra piconet overhead


Try to construct the scatternet while forming master slave relations
Switching delay between different piconets
Standby -> Inquiry -> Page = master slave relation
Bluenet Algorithm

Goal: efficient scatternet



Reasonable good connectivity but preserves network resources
for communications.
The network resources should be spread as evenly as
possible to prevent bottlenecks
3 Rules



Rule 1: Avoid forming further piconets inside a piconet
Rule 2: For a bridge node, avoid setting up more than one
connections to the same piconet
Rule 3: Inside a piconet the master tries to acquire some number
of slaves
Bluenet

Rule 1:
 Since the traffic is well organized in a piconet
 can be achieved if the master sends the list of
its
slaves to all its slaves

Rule 2:
 To avoid excessive bridge overhead for the bridges
 can be achieved if the units are capable of sending
their piconet identity

Rule 3:
 Size
of the piconet effects final structure
Bluenet
Phase I: Initial piconets are formed
 Phase II: Separate Bluetooth node get
connected
 Phase III: Piconets get connected to form
a scatternet

Evaluation Methods

Average Shortest Path (ASP)
 Average
shortest path length among all 2-node pairs
in a Bluetooth network
 Only related with topology
 ASP0 = minimal ASP obtained from visibility graph
 ASPsct = actual ASP of the scatternet being evaluated
 R = ASPsct /ASP0
Evaluation Methods

Maximum Traffic Flows (MTF)
 Important
to learn about the information carrying
capacity of network
 MTF is based on maximum flow problem


 If
The maximum amount of information that can be transmitted
per unit time from source node s, to sink node t, without
violating the link and node capacity limits.
Ford-Fulkerson Algorithm
there is multiple sources and sinks problem of
maximizing becomes maximum multi-commodity
flows.
Evaluation Methods

Algorithm for approximating MTF
 A.
calculate all maximum flows for all commodities by
using Ford-Fulkerson method
 B. Select the commodity pair with the largest
maximum flow; then remove the commodity pair; and
decrease the corresponding link capacities
 C. repeat steps A&B until there is no commodity pair
left.
 The MFT is the sum of the largest maximum flows
obtained from each run of b
Simulation and Results




n, Bluetooth devices are randomly placed
Visibility graph is obtained
The scatternets are generated by Bluenet and Bluetree
Performance is evaluated
Simulation Results



On ASP
200 scatternet
samples are
generated
Mean ASP
 Bluenet
= 2.08
 Bluetree = 2.31
Simulation Results



On MTF
6 scatternets are
formed for both
schemes
6000 randomly
generated multicommodities are
used for
calculation
Conclusion

Advantages
 Easily
implementable on existing Bluetooth specs
 Fast topology construction


No further information collection
Disadvantages
 All
devices are assumed to be turned on
simultaneously
 No mobility support

Static nodes
Future Work

Must be compared with the new scatternet
formation methods
 Especially

with Law & Siu’s method
Future work can be done on mobility
support
 dynamicity
Thanks for patience
Questions & Answers