Doc.: IEEE 802.15-02/138r0 Submission March 2002 Steve Shellhammer, Symbol TechnologiesSlide 1 Steve Shellhammer, Nada Golmie, Robert Van Dyck, Jie Liang,
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March 2002
Steve Shellhammer, Symbol TechnologiesSlide 1
doc.: IEEE 802.15-02/138r0
Submission
Steve Shellhammer, Nada Golmie, Robert Van Dyck, Jie Liang, Y.C. Maa,
Anuj Batra, Jim Lansford, and Arun Arunachalam
Tutorial on 802.15.2 Draft
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 2
doc.: IEEE 802.15-02/138r0
Submission
Outline of 802.15.2 Draft• Interference Modeling
– Physical Layer Modeling– MAC Layer Modeling
• Collaborative Coexistence Mechanisms– AWMA– PTA
• Noncollaborative Coexistence Mechanisms – BT Packet Scheduling and Selection– BT Adaptive Frequency Hopping
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 3
doc.: IEEE 802.15-02/138r0
Submission
System Simulation Modeling
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 4
doc.: IEEE 802.15-02/138r0
Submission
• Additive White Gaussian Noise
• Path loss model
• Received power and SIR depend on topology and device parameters:
mdd
mddLp
8)8/log(335.58
85.0)log(202.40
PTR LPP IR PPSIR
Channel Modeling
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 5
doc.: IEEE 802.15-02/138r0
Submission
• DSP based implementation of transceivers• Design using typical parameters (goal is to
remain non-implementation specific)• Bluetooth
– Non-coherent Limiter Discriminator receiver
• IEEE 802.11– Direct Sequence Spread Spectrum (1 & 2 Mbits/s)– Complementary Code Keying (5.5 & 11 Mbits/s)– Frequency Hopping (1 Mbits/s)
Physical Layer Modeling
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 6
doc.: IEEE 802.15-02/138r0
Submission
• MAC behavioral implementation for Bluetooth and IEEE 802.11 (connection mode)
• Frequency hopping • Error detection and correction
– Different error correction schemes applied to packet segments (Bluetooth)
– FCS (802.11)
• Performance statistics collection– Access delay, packet loss, residual error, throughput
MAC Layer Modeling
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 7
doc.: IEEE 802.15-02/138r0
Submission
BluetoothData PacketsDM5, 2871 bitsOffered Load 50%SCO Packets HV1, 366 bitsTx Power 1 mW
802.11Data Rate 11 Mbits/s, 1 Mbits/sModes Direct Sequence, FHPacket Size 12000 bitsOffered Load 50%Tx Power 25 mW
Bluetooth Slave
Bluetooth Master
802.11 AP
802.11 Mobile d=1m
582.5Voice
4412Voice
9012Voice
132.3Data1 Mbit/s FH
1 Mbit/s DS
11 Mbit/s DS1518Data
3814Data
802.11BTBT Traffic802.11 Type
Percentage of Packet Loss
Typical Modeling Results
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 8
doc.: IEEE 802.15-02/138r0
Submission
Collaborative Coexistence Mechanisms
802.11MAC
802.15.1Link Manager
802.11 PLCP+ PHY
802.15.1Baseband
PTAControl
Status Status
Tx Confirm(status)
Tx Confirm(status)
Tx RequestTx Request
CollaborativeCoexistenceMechanism
802.11 Device 802.15.1 Device
AWMAMedium FreeGeneration
Medum Free
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 9
doc.: IEEE 802.15-02/138r0
Submission
Alternating Wireless Medium Access (AWMA)
• Collaborate Coexistence Mechanism for Collocated IEEE 802.11b and Bluetooth– Both in the same laptop or handheld
• Coordinated MAC Layer• Subdivide WLAN Beacon Interval
– WLAN Interval– WPAN Interval
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 10
doc.: IEEE 802.15-02/138r0
Submission
Alternating Wireless Medium Access
• Synchronization of all units connected to the same WLAN Access Point
• Eliminates WLAN/WPAN interference due to no temporal overlap
• Good for high-density of WLAN/WPAN units.
• Does not support Bluetooth SCO link
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 11
doc.: IEEE 802.15-02/138r0
Submission
Packet Traffic Arbitration
This proposal does not address PHY or antenna issues
BluetoothBluetoothBasebandBaseband(up to HCI)(up to HCI)
802.11b MAC802.11b MAC
Bluetooth Bluetooth RadioRadio 802.11b PHY802.11b PHY
PTAPTA
BT TrafficBT Traffic 802.11 traffic802.11 trafficPTA-802.11 PTA-802.11
InterfaceInterface
PTA-PTA-Bluetooth Bluetooth InterfaceInterface
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 12
doc.: IEEE 802.15-02/138r0
Submission
Packet Traffic Arbitration
• Collaborative techniques define rules in advance for traffic management by direct communication between systems…no learning• Traffic light (TDMA) totally prevents
collisions• Yield, 4-way stop, etc. are also valid
rules• Maximizes traffic while avoiding
collisions
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 13
doc.: IEEE 802.15-02/138r0
Submission
Packet Traffic Arbitration
• Dynamic algorithm schedules traffic• Knowledge of time-frequency collisions is key
– Simultaneous transmission or reception allowed– Tx simultaneous with Rx allowed if not in-band
(requires good LNA and REALLY good channel filters)
– Critical for SCO operation-WLAN can work around in-band collisions
• This figure does not show polls/nulls, which often dominates Bluetooth traffic
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 14
doc.: IEEE 802.15-02/138r0
Submission
Packet Traffic Arbitration• Assumed MAC structure
– At most one message pending for BT– At most two messages pending for WLAN
PTAEngine
FrequencyCollision
Map
WLAN Stack
WLAN FIFO2
WLAN FIFO1
WLANModem
WLANModem
DecisionLogic
DecisionLogic
Bluetooth Stack
Backoff &CCA
TxEvent
Enable
Enable
SwitchMatrix
Bluetooth FIFO
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 15
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Packet Selection• Bluetooth provides a wide range of packet
types to select from: payload length, FEC options
• DM1, DM3, DM5, DH1, DH3, DH5,AUX1
– Guidelines:– range limited situation: use DM packet for its FEC– interference
• Adaptive packet payload length selection: – Adaptive fragmentation
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 16
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Packet Scheduling
• Interference Estimation • Maintain a Frequency Usage Table at
master and slave nodes.• Slave updates master’s Frequency Usage
Table every update interval.
• Master Scheduling Policy• Use “good” frequencies for master / slave
transmission (upstream and downstream)
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 17
doc.: IEEE 802.15-02/138r0
Submission
Channel Classification
• Draft provides an example algorithm for determining the quality of the channels. Actual implementation is left to the vendor.
• Metrics that could be used by the vendors include:– RSSI, PER, Carrier Sensing, and Packet ACK.
• Measurements can be made using:– Batch (block) techniques.– Online or offline techniques.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 18
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Packet Scheduling
Advantages:• It does not require changes to the Bluetooth
specifications.• It conforms to FCC rules. • It saves power since no transmission is
wasted in bad channels• It is neighbor-friendly and mitigates
interference on other systems.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 19
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Packet Scheduling
FrequencyOffset
Frequency Status
01 23...
787776
Master Slave
Update Messagefrom Slave
Frequency Hopping Pattern
f1 f2
Slave Rx Master Rx
f3 f4
Slave Rx Master Rx
Delay PacketTransmission
Packet to Transmit
good good
bad bad
bad good
bad bad
good bad
good
good bad
bad
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 20
doc.: IEEE 802.15-02/138r0
Submission
Simulation Results
• Bluetooth Performance
0.25
0.2
0.15
0.1
0.05
0
BT Slave Pr [ Packet Loss]
0 1 2 3 4 5
Distance between Bluetooth Slave and 802.11 Mobile (meters)
No Scheduling, DM1
Scheduling, DM1, DM3, DM5
No Scheduling, DM3
No Scheduling, DM5
0 1 2 3 4 5
Distance between Bluetooth Slave and 802.11 Mobile (meters)
BT Slave Mean Access Delay (seconds)0.008
0.006
0.004
0.002
0
Scheduling, DM1
No Scheduling, DM1
Scheduling, DM5
No Scheduling, DM5
Scheduling, DM3No Scheduling, DM3
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 21
doc.: IEEE 802.15-02/138r0
Submission
Simulation Results• IEEE 802.11 Performance
0.05
0.04
0.03
0.02
0.01
0
802.11 Mobile Pr [ Packet Loss]
0 1 2 3 4 5
Distance between Bluetooth Slave and 802.11 Mobile (meters)
No Scheduling, DM1
Scheduling, DM1, DM3, DM5
No Scheduling, DM3
No Scheduling, DM5
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 22
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping• Adaptive frequency hopping (AFH) is a non-
collaborative mechanism that enables the coexistence of IEEE 802.15.1 devices with frequency static devices in the 2.4 GHz ISM band such as IEEE 802.11b.
• This mechanism dynamically changes the frequency hopping sequence in order to avoid or mitigate the interference seen by both 802.11b and the 802.15.1 device.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 23
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping• There are 4 main elements of Adaptive Hopping:
– AFH Capability Discovery– Channel Classification– Channel Quality Information Exchange– Adaptive Hopping Mechanism
• Channel classification is a mechanism for determining the quality of a channel. The channel is classified as either good or bad based on predefined metrics.– Used by both AFH and packet scheduling.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 24
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping
min
min
when }1,0{
when 1
NN
NN
G
G
UAP/LAP
PartitionSequenceGenerator
Traffic type(ACL or SCO)
LegacyHop
KernelCLK
FrequencyRe-mapper
p(k)
fhopfadp
Channel Conditions(SG, SBK, NG, NBK)
CLKAM_ADDR
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 25
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping
• The legacy hop kernel generates the hopping sequence defined in the IEEE 802.15.1 standard. This hopping sequence is referred to as the original hopping sequence.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 26
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping
• Partition sequence generator imposes a structure on the original hopping sequence without changing pseudo-random properties.– For SCO+ACL, good slots are first assigned to
voice slots.– For ACL only, good and bad channels are grouped
together. Reduces the effects of transitions from good-to-bad channels (retransmissions) and bad-to-good channels (idle slots). Maximizes throughput.
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 27
doc.: IEEE 802.15-02/138r0
Submission
Adaptive Frequency Hopping• The frequency re-mapping function
uses the partition sequence to generate the new hopping sequence. If necessary, this block uniformly re-maps the original hopping channel onto the set defined by the partition sequence.– When p(k) = 1, the re-mapping function
only hops over the good channels (reduced frequency hopping).
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 28
doc.: IEEE 802.15-02/138r0
Submission
LMP Commands
• The following LMP commands are needed for the AFH mechanism:
Check to ensure that device is using the correct hopping sequence
LMP_AFH_check_req/res
Forces device back to regular hopping setLMP_regular_hopping_req
Forces device to start adaptive hoppingLMP_AFH_start
Request and Return of Slave’s Classification
LMP_channel_metrics_req/res
Identifies AFH-capable devicesLMP_features_req/res
DescriptionLMP Command
March 2002
Steve Shellhammer, Symbol TechnologiesSlide 29
doc.: IEEE 802.15-02/138r0
Submission
Summary
• Draft D05 will be available on the server by Thursday AM.
• Motion to go to letter ballot on 802.11 and 802.15 on Friday AM.
• 40 day letter ballot to start no later than March 22, 2002.
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