10.03.2003presented by hasan sÖzer 1 jump mode a dynamic window-based scheduling framework for...

10.03.2003 presented by Hasan SÖZER 1

JUMP Mode

A Dynamic Window-based Scheduling Framework for Bluetooth Scatternets

Niklas Johansson

Fredrik Alriksson

Ulf Jönsson

Switch Lab, Ericsson Research


Outline

Introduction Rendezvous Window Distribution Signaling of Presence Scheduling Structure Clock-drift & Power Saving Issues Conclusion


Introduction ... motivation

PMP: Participant in Multiple Piconets PMP nodes have to switch in time-division bases;

inter-piconet scheduling (IPS) Effective scheduling is needed;

Present when needed Identify absent PMPs

Availability & performance constraints should be considered


Introduction (2) ... a tradeoff

Tradeoff concerning switching frequency Frequent: large switching overhead Infrequent: long delays


Introduction (3) ... Sniff mode

SNIFF Mode (a power save mode) often proposed for scatternet operations periodic reocurring pause in communication conflict-free Has drawbacks;

SNIFF parameters required throughout the scatternetNot flexibleChanging topology would lead to renegotiation


Introduction (4) ... Jump mode

JUMP Mode; an alternative mode Time is divided into time windows each of pseudo-

random length; rendezvous windows (RV) Avoids systematic collusions & starvation

Fully distributed Flexible Efficient Adaptible to different piconets and traffic conditions An alternative for power saving in Bluetooth


Introduction (5) ... Jump mode

Jump mode link PMP signals all concerned nodes when

“jumping” to another piconet PMP stands still during RV;

Communicates with the members of the piconet based on intra-piconet scheduling mechanism

A framework is defined, not a specific inter-piconet scheduling algorithm


Rendezvous Window Distribution ... usage

Jumping nodes schedule their activities using RVs of pseudo random length

Each node has its own unique sequence of RV fall into well-defined points; RV points

RV points are distributed in a random manner, based on some unique information of the node (So, others can calculate)

Randomness avoid systematic colliding RV points are used for signaling


Rendezvous Window Distribution (2) ... formation

Time is divided into intervals of Nsf frames In each interval one frame is pseudo randomly selected to

become a RV point Time interval fall between two selected frames constitute a

RV window


Rendezvous Window Distribution (3) ... formation

Galois fields & FHSS algorithm are proposed for generation of unique pseudo-random RV windows

Bluetooth MAC address (BD_ADDR) can be fed into the random generator as the unique identifier of the node


Signaling of Presence ... basics

Master Polls the jumping slave at its RV points. If it responds,

Master assumes that the slave will be present until its next RV point and vice versa

Slave Selects the piconet to be present in the upcoming RV

window, responds to the poll of the Master of the selected piconet in the corressponding RV point


Signaling of Presence (2) ... basics

A Master PMP node does not necessarily have to set up JUMP mode towards its regular, non-PMP slaves


Signaling of Presence (3) ... scenarios



LT2 acts as slave in all of its piconets At each RV point, LT2 responds to either Master LT2 is free to choose which piconet it wants to spend the

next RV window in



LT1 acts as Master in Piconet 2 and as slave in Piconet 1

LT1 does not have to set up JUMP mode in Piconet 2 since none of the slaves is a PMP node and therefore should listen all the time



If LT1 fail to signal its presence at a RV point in Piconet 1, it could directly go back and serve Piconet 2 without having to wait until the next RV point



Network Access Point (NAP) illustrates a Master having several jumping slaves

Intra-piconet scheduler is responsible for allocating the capacity among active units in the piconet



If RV points of two jumping slaves collide, Master chooses one of them to poll

Pseudo-randomness avoids systematic collisions Non-PMP slaves are not affected by the signaling

protocol, they continuously listen Non-PMP slaves do not receive poll messages when

Master is a PMP node and it jumps to the other piconet


Signaling of Presence (9) ... jumping slave signaling

Jumping slaves may set up a long-term schedule Advantages:

Reduced overhead Less fragmented intra-piconet schedule Improved robustness

Disadvantages Less flexible (traffic should be static)

Mixed long-term schedule can be used some RVs are fixed, some are processed with the basic

signaling scheme


Signaling of Presence (10) ... jumping Master signaling

Master can signal its presence and absence to its connected slaves. By this way; Peer node can act as jumping slave Slave can save power when Master is gone

Master can utilize its own RV points and broadcast its presence Broadcast message may not be received

A RV window can be reserved for each piconet through which Master’s schedule is transmitted


Signaling of Presence (11) ... connected jumping nodes


Signaling of Presence (12) ... connected jumping nodes

Jumping nodes may act as a Master towards the other jumping node

Jumping masters should not poll the jumping slaves when they are absent

Jumping slaves may arrange their RVs accordingly since, they know their Master’s schedule


Scheduling Structure

Scheduling may conceptually be divided into two: Inter-piconet scheduling Intra-piconet scheduling

Intra-piconet scheduler should consider the results of inter-piconet scheduling JUMP mode may inform about which slaves are

actually present and which are not


Clock-drift & Power Saving

Because of the clock-drifts, an offset has to be added to the frame numbers calculated PMP nodes can track the clocks in all piconets it

participates in and update required offsets accordingly (once every 30 seconds)

Jumping nodes can utilize JUMP mode for power saving


Conclusion

An efficient & flexible scheme Adaptible to different traffic conditions Missing RV points may cause defficiencies Intra-piconet scheduling is also important Just a framework is defined, no spesific

algorithms are given

10.03.2003presented by hasan sÖzer 1 jump mode a dynamic window-based scheduling framework for...

Documents

rv window slide

bluetooth slide

node slide

upcoming rv window

sniff mode sniff mode

hasan szer3 introduction

hasan szer11

hasan szer4 introduction