sep. 18, 2003chung-hsien hsu a dynamic slot assignment scheme for slave-to-slave and multicast-like...

Sep. 18, 2003 Chung-Hsien Hsu

A Dynamic Slot Assignment Scheme for Slave-to-Slave and Multicast-like Communication

in Bluetooth Personal Area Networks

C. M. Cordeiro, S. Abhyankar, and D. P. Agrawal

OBR Center for Distributed and Mobile Computing

Department of ECECS, University of Cincinnati

To Appear in IEEE Globecom 2003 and ACM/IFIP PWC 2003

Reporter: Chung-Hsien Hsu


Outline

Introduction The Dynamic Slot Assignment (DSA) Scheme

Connection Request Connection Release Slot Scheduling and Assignment Example Scenario

Simulation Conclusion


Introduction – Bluetooth Overview

Two link types: Synchronous Connection Oriented (SCO)

Circuit-switched. To use for audio applications. Strict QoS requirement. Packet type: HV1,2,3

Asynchronous Connectionless Link (ACL) Packet-switched. To use in data applications. No such strict requirement on end-to-end delay. Packet type: DH 1, 3,5 and DM 1, 3,5


Introduction – Motivation

The Master/Slave paradigm of Bluetooth should not be adopted in its current form

Bandwidth is wasted by forwarding through the master. End-to-end packet delay increases. Power consumption is significantly increased at the master unit.

Communication with one device Communication with more than one device


Dynamic Slot Assignment (DSA)

Basic idea: To appropriately manage the polling cycle conducted by the

master of the piconet.

As devices initiate or terminate communication with each other

Master restructure the piconet polling cycle

Propagating the resulting schedule to the members of the piconet

Slaves communicate directly


Dynamic Slot Assignment (DSA) – Connection Request

CONNECTION_REQ Destination(s) Baseband packet type Desired transmission rate Acceptable transmission rate

M

S1

S2 S3

S4

CONNECTION_REQ(S3, DH5, 30, 50)CONNECTION_REJ SLOT_SCHED

Connection ID = C1,3


Dynamic Slot Assignment (DSA) – Connection Release

CONNECTION_REL Connection identifier

M

S1

S2 S3

S4

Connection ID = C1,3

CONNECTION_REL(C1,3)SLOT_SCHED


Dynamic Slot Assignment (DSA) – Slot Scheduling and Assignment

Master computes a new schedule for devices when it receives either a connection request or termination.

Which slot(s) belong to which device. In which slot(s) a given slave needs to listen.

Using broadcast method to inform all devices. Broadcasting the same message three tiemes.


Dynamic Slot Assignment (DSA) – Slot Scheduling and Assignment (cont.)

Providing both unicast and multicast-like communication within a piconet by using this single message format.

SCO connections are treated differently Which have a fixed scheduling.

SLOT_SCHED

Header New Connection Info.

New and Existing ACL Connections Info.


Dynamic Slot Assignment (DSA) – Slot Scheduling Message Format



# ACL Conn.# DestinationsSCO/ACL

1 3 4

… New Conn. Number# Slots AssignedDest. i Add.Source Add.

33*(# Destinations)

2 4

TxSlot Slot-Cycle…Conn. # i

4*(# ACLConn.)

8 8

Slot-Cycle is always a multiple of 6.

Assumption CONNthres = 16


Dynamic Slot Assignment (DSA) – Example Scenario

M

S1

S2 S3

S4

CONNECTION_REQ(S2, DH5, 30, 50)

Slot-Cycle = 6

Polling



M

S1

S2 S3

S4

C1,2 Polling ( priority is given to those devices currently without open connections. )

1 1 1 1 2 5 C1,2 C1,2 1 12

CONNECTION_REQ(S2, DH5, 30, 50) SLOT_SCHED

Slot-Cycle = 6



M

S1

S2 S3

S4


C1,2

Slot-Cycle = 12

Polling



M

S1

S2 S3

S4

1 1 2 3 4 3 C3,4 C1,2 , C3,4 1 18


SLOT_SCHED

C1,2

Slot-Cycle = 18

PollingC3,4

Slots = ( polling_cycle * index_in_list ) + TxSlot


Simulation

Environment Simulator: BlueHoc Device: 8 (using a single piconet) Region: 7m x 7m Radio range: 10m Channel capacity: 1Mbps Compare with the existing Bluetooth


Simulation (cont.)

Comparing metrics: Aggregate Throughput Delay Overhead Power Consumption

Traffic scenarios: Scenario A:

3 FTP connections are initiated consecutively in different points in time. Scenario B:

2 SCO connections are initiated consecutively in different points in time. Scenario C:

3 connections (SCO, Telnet, FTP) are initiated consecutively.


Simulation (cont.) – Aggregate Throughput


Simulation (cont.) – Delay


Simulation (cont.) – Overhead


Simulation (cont.) – Power Consumption


Conclusions

Proposing a dynamic scheduling scheme Implementation of direct communication between any two slaves

within a piconet. Support for multicast-like transmissions for group communication.

DSA outperform existing Bluetooth Providing optimal bandwidth usage Lower delay Low overhead


Compare with Time-Slot leasing approach

Similarity: Master allocate slots to slave for direct communication.

Differences: SCO connection. Provide for multicast-like communication. Dynamically adjusts the slot cycle so as to meet traffic needs.


Dynamic Slot Assignment (DSA) – Slot Scheduling Message Format



# ACL Conn.# DestinationsSCO/ACL

1 3 4

… New Conn. Number# Slots AssignedDest. i Add.Source Add.

33*(# Destinations)

2 4

TxSlot Slot-Cycle…Conn. # i

4*(# ACLConn.)

8 8

sep. 18, 2003chung-hsien hsu a dynamic slot assignment scheme for slave-to-slave and multicast-like...

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