Provisioning of Temporal QoS in Bluetooth Networks

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Provisioning of Temporal QoS in Bluetooth Networks

• Wei-Peng Chen and Jennifer C. Hou
• Dept. of Computer Science
• Univ. of Illinois at Urbana-Champaign

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Motivation

• Existing scheduling algorithms in Bluetooth
  Systems focus on throughput, fairness but not QoS
• Goals
• Fulfill temporal QoS requirements
• Compliance with the Bluetooth specification
• Handle dynamic establishment and termination of
  connections
• Based on distance-constrained task model
• Focus on intra-piconet scheduling in this paper

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Review of Intra-Piconet Scheduling

• Schedule is controlled by the master on a TDM
  basis.
• A slave is allowed to send a packet only when it
  is polled by the master.
• The master transmits a packet to a slave in an
  even slot and the slave sends back a packet to
  the master in the subsequent odd slot.

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QoS Signaling Mechanism

• quality of service msg is sent by a master to
  notify a slave of the pending traffic
• The slave must accept it in any case
• quality of service req msg is initiated by a
  slave
• can be accepted or rejected by the master.
• Parameters carried in msg specifying the QoS
  characteristics of connections
• Polling interval the max endurable spacing
  between two consecutive polls for a Master-Slave
  pair (MSP).

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Message Model (Ci ,Di)

• Connection Mi is expressed as (Ci ,Di)
• Ci max amount of msgs (in slots) can be sent
  from Mi within any period of Di
• Di the deadline for the messages in Mi
• if Mi arrives at time t, it must be sent by time
  tDi

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Static Intra-Piconet Scheduling Problem
Definition

• Given a set of connections
  , allocate slots to all msg. in Mi before its
  deadline Di
• Consider first
• static case connection set M is fixed
• uni-directional connection (either from master to
  slaves or from slaves to the master)

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Static Intra-Piconet Scheduling Step I
Specialization

• Transform given connection set M to M
• DD1,D2,,Dn consists solely of multiples
• Di ? Di (more restricted constraint)
• Specializing D(M) with respect to 2
• Examples (1,5),(2,9)? (1,4),(2,8)

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Static Intra-Piconet Scheduling Step II
SlotAllocator

• SlotAllocator assigns the current slot to the
  connection with the tightest deadline among all
  connections have not fulfilled the requirements
• Theorem 1 If Di divides Dj for all i lt j and
  ?(M) ? 1, SlotAllocator will allocate Ci slots to
  Mi in any time window of size Di slots, for all
  i.
• Total utility
• Schedulability check

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Dynamic Intra-Piconet Scheduling

• Extension to dynamic connection establishment and
  termination
• Only consider uni-directional connection
• Artificially add one null message stream ME
• Slots assigned to the null stream ME will be used
  to transmit regular, non-QoS-sensitive messages.

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Temporal Distance Constraint

• Decompose each Mi into a set of sub-connections,
  s.t.
• Ex (5,8) (1,2) (1,8)
• Schedule sub-connection Mij(1,Dij)
• Equivalent to two consecutive slots for Mij must
  be less than Dij
• ? Temporal distance constraint

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Connection Establishment and Termination
Request Mi
Release Mi
No
Admission controller
Relabel Mi to null stream
reject
Yes
found
No
If exists any other ME with same Di ?
Finish
Scheduler
Yes
No match
accept
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Extension to connections in both directions

• In Bluetooth two consecutive slots (an even slot
  and an odd slot) are assigned as a basic unit to
  a MSP.
• Search for empty slots from the allocated
  connections of the same MSP before using null
  streams
• Ex (1,4) for M?S2 can accommodate (1,8)(1,16)
  for S2 ?M
• Use Task Table to efficiently maintain connections

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An Example (t2, T11D2)
T01 1st conn. for null
T11 1st conn. for M?S1
dominant connection
T12 2nd conn. for S1?M
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An Example (t5, T12D4)
T12
T12 2nd conn. for S1?M
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An Example (t9, T13D8)
T13
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An Example (t11, T14D4)
S
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Simulation Scenarios

• Use IBM Bluehoc package in ns-2
• CBR/UDP for QoS-sensative
• FTP/TCP for non-QoS-sensative
• Two scenarios
• 2 FTP 5 CBR with rate 40, 20, 10, 5, 2.5kbps
  from master to 7 slaves
• 2 FTP(M?2S) 5 CBR(M?5S) 5 CBR(5S ?M) with
  rate 20, 10, 5, 2.5, 40kbps
• Compare with
• Deficit Round Robin (DRR), Adaptive Flow-based
  Polling (AFP), and Round Robin (RR)

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Simulation Results I (M?S)

• AFP favors TCP connections
• Why not 100??

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Simulation Results - II (M?S)

• FTP pkts (512byte) are segmented as DH5 pkts,
  compared with DH1 pkts for CBR pkts (25 byte)
• DH5(M?S) is sent as 5 consecutive slots(M?S) 1
  reverse slot
• Block opportunities for the QoS conn. in the
  following 4 slots
• DH5 has higher throughput because of longer
  payload

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Conclusion Future Works

• proposed intra-piconet scheduling algorithms to
  schedule connections with temporal QoS
  requirements in Bluetooth networks
• Consider more than a pair of slots as the basic
  scheduling unit in the future
• Extend to inter-piconet scheduling

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Provisioning of Temporal QoS in Bluetooth Networks

• Wei-Peng Chen and Jennifer C. Hou
• Dept. of Computer Science
• Univ. of Illinois at Urbana-Champaign