cmpe 257: wireless and mobile networking
DESCRIPTION
CMPE 257: Wireless and Mobile Networking. Spring 2005 Bluetooth. Announcements. Today. Bluetooth. Simulation Results. Experimental Setup. Qualnet simulator 802.11 MAC with 371m radio range. 50 nodes in a 1500x1500 area. Random node placement. - PowerPoint PPT PresentationTRANSCRIPT
CMPE 257 Spring 2003 1
CMPE 257: Wireless and Mobile Networking
Spring 2005Bluetooth
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Announcements
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Today Bluetooth.
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Simulation Results
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Experimental Setup Qualnet simulator 802.11 MAC with 371m radio range. 50 nodes in a 1500x1500 area. Random node placement. Two different underlying multicast
routing protocols (MAODV and ODMRP).
Application data size 512 bytes. 5 sources and 10 group members.
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Reliable Delivery Ratio over MAODV
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Reliable Delivery Ratio over ODMRP
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Average Goodput - MAODV
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Average Goodput - ODMRP
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Bluetooth
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Cable Replacement
1 Mb/s. Range ~10 meters. PANs Single chip radio.
Low power & low cost.
Why not use Wireless LANs?- power- cost
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Applications: Synchronization
Automatic synchronization of calendars, address books, business cards.
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Applications: Cordless Headset
Multiple device access.
Hands-free operation.
Cordlessheadset
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More applications… Conference table. Cordless computer. Instant photo transmission. Cordless phone.
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Features Cost20 dBm (~100 m)
Point-to-multipoint
No Scatternet
ApplicationsFile Transfer,
Dial-Up Networking
LAN access, Fax, …
169 $
---
200 $
0 dBm (~10 m)
Point-to-multipoint
No Scatternet
File Transfer,
Dial-Up Networking
LAN access, Fax, …169 $
---
CompanyToshiba,
Motorola,
Digianswer
IBM, TDK
3COM
10 m user-user;
100 m user-Base Station
Point-to-multipoint
SW- & FW-upgradeable
File Transfer,
Dial-Up Networking
LAN access, Fax, E-mail
Unconscious connection
149 $
Nokia
10 m user-user;
Point-to-point
Connectivity Battery
for the cell phone
File Transfer,
Dial-Up Networking
LAN access, Fax, E-mail
Unconscious connection
149 $
Ericsson,
Sigma
10 m user-user;
Point-to-point;
ARM processor;
USB; RFCOMM ports
Basic BT Radio stack
Embedded or Host stack
Programmable
500 $
1500$
Bluetooth on the market:Bluetooth on the market:PC cards, Cell phones, Head sets, Chip sets,…
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Bluetooth WG History May 1998: Bluetooth SIG is formed.
Promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba.
Goal: develop license-free technology for universal wireless connectivity.
Target: handheld market. Bluetooth spec: defines RF wireless
communication interface and protocols.
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Bluetooth WG History May 1998: Public announcement of
Bluetooth SIG. July 1999: 1.0A spec (>1,500 pages)
published. December 1999: version 1.0B released. December 1999: promoters increases to
9. 3Com, Lucent, Microsoft, Motorola
February 2000: 1,800+ adopters. February 2001: version 1.1 out.
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More History… Recently, IEEE 803.15.1 standard
for Wireless PANs (WPANs) Only MAC and PHY.
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Goals Low cost. Power efficiency. Single-chip implementation. (early implementations are double-
chip)These goals defined: Link speed. Communication range. Transmit power.
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Bluetooth Protocol Stack
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Single chip with RS-232,USB, or PC card interface
Applications
Link Controller
Host Controller Interface
Radio+partof baseband=Physical layer
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Radio Band Public, i.e., no need for licenses. Available worldwide. Industrial, Scientific, Medical (ISM)
band. Unlicensed, globally available. Centered around 2.4 GHz.
Frequency hopping. Range: 10cm to 10m.
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Unlicensed Radio Spectrum
902 Mhz
928 Mhz
26 Mhz 83.5 Mhz 125 Mhz
2.4 Ghz
2.4835 Ghz5.725 Ghz
5.785 Ghz
cordless phonesbaby monitorsWireless LANs
802.11BluetoothMicrowave oven
unused
33cm 12cm 5cm
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Bluetooth Radio Link
MA scheme: Frequency hopping spread spectrum. 2.402 GHz + k MHz, k=0, …, 78 1,600 hops per second. 1 Mb/s data rate.
Number of hopping sequences defined. Master node defines sequence to be used. Slave units use master id to pick sequence.
. . .
1Mhz
1 2 3 79
83.5 Mhz
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BT Radio Link (Cont’d) Time-division duplex (TDD)
Separation of Xmission and reception in time: one-chip implementation.
Units alternately transmits and receives. Gaussian Frequency Shift Keying (G-
FSK) modulation. ‘1’s as positive frequency deviations
from carrier frequency; ‘0’s as negative deviations.
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Multiple Access BT targets large number of independent
communications active in the same area at the same time.
Single FH channel: 1 Mb/s. Each 1Mb/s channel shared by limited number
of participants. In target user scenarios, it’s unlikely that all units in-
range will share data among all of them. 1 MB/s is reasonable. (is it?)
Theoretically, total bandwidth is 79 Mb/s. In practice, < 79 Mb/s since codes are non-
orthogonal.
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Baseband
Carries out MACfunctions.
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Control end of baseband+link controller=Data link layer
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Piconets BT communication takes place over
piconets. Piconet formation initiated by master. All other participants are slaves. Number of participants limited to 8 (1
master and 7 slaves). Channel capacity and addressing overhead. Each slave assigned a locally unique ID.
Master/slave role last for the duration of the piconet.
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Piconets: considerations Most target applications involve
local communication among small group of devices.
Piconets with up to 8 nods match well.
If many groups of devices active simultaneously, each group as separate piconet.
Overlapping piconets can coexist.
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Contention-Free MA Master and slaves. Master performs medium access control.
Schedules traffic through polling. Time slots alternate between master and
slave transmission. Master-slave: master includes slave address. Slave-master: only slave chosen by master in
previous master-slave slot allowed to transmit. If master has data to send to a slave, slave
polled implicitly; otherwise, explicit poll.
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BT StatesStandby
Inquiry Page
Transmit Connected
Park Hold Sniff
Unconnected
Connecting
Active
Low power
. Initially, all nodes in standby.. Node (master) can begininquiry to find nearbydevices.. Piconet is then formed.. Devices join by paging.
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Inquiry
Device discovery Listeners respond with their address.
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Paging Master
Active Slave
Parked Slave
Standby
Device enters paging to invite others to join its piconet.
Establishes links with nodes in proximity. Paging message unicast to selected
receiver. Receiver sends ACK. Sender becomes master, receiver slave.
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Piconet New Node Admission Master can actively try to discover
new nodes or wait (in scan/listen mode) to be discovered.
Communication in the current piconet suspended.
Admission latency versus piconet capacity tradeoff.
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Bluetooth Link Formation
Point-to-point link: Master-slave relationship.
m s
ss
m
s
Piconet: 8 units: channel capacity. Master (establishes piconet) can connect to up to 7 slaves. Master/slave relationship lasts while link/piconet lasts. No slave-to-slave communication.
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Link Types 2 types of links:
Synchronous (SCO) links: Point-to-point between master and slave. Link established by reserving slots in either
direction periodically. Used to carry real-time traffic (voice).
Asynchronous (ACL) links: Point-to-multipoint between master and slaves. Use remaining slots on channel. Traffic scheduled by master.
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Error Control Supports both FEC and retransmission. FEC for SCO packets. ARQ for ACL traffic.
If no ACKs, retransmit. Stop-and-wait ARQ.
Fast-ARQ: ACK included in RX slot immediately following the TX slot in which packet was sent.
CRC to check for errors.
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Packet Format72 bits 54 bits 0 - 2744 bitsAccess code
Header Payload
DataVoice CRCNo CRCNo retries
625 µs
master
slave
header
ARQFEC (optional)
FEC (optional)
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Access Code
Address of piconet master.
Access code
Header Payload
72 bits
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Packet Header
Addressing (3) Packet type (4) Flow control (1) 1-bit ARQ (1) Sequencing (1) HEC (8)
Access code
Header Payload
54 bits
Purpose
Broadcast packets are not ACKed
For filtering retransmitted packets
18 bitstotal
ss
m
s
16 packet types (some unused)
Max 7 active slaves
Verify header integrity
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Multiple Piconets Piconets may overlap in space and
time. They can work independently.
Each with its own hopping sequence. Packets with different access codes.
Or they can overlap, i.e., nodes can participate in more than 1 piconet. “Time sharing”.
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Scatternets Interconnection of multiple
piconets.
Master
Slave
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Scatternets (cont’d…) Interconnection by bridge nodes.
Bridge nodes are members of piconets they interconnect.
Bridge node “stay” in a piconet for some time, then switch to another piconet by changing hop sequence.
Do this for all member piconets. Send and receive in each piconet. Forward from one piconet to another.
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Link Manager Protocol
. Main functions: powermanagement and security.
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
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Power Management Low-power modes: prolong battery
life. Devices can be turned-off when idle. Devices wake up periodically to
send/receive data.
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Low-Power Operation 3 modes:
Hold: node sleeps for specified interval. Master can put slaves in hold while searching for new
members, attending another piconet, etc. No ACL packets.
Sniff: slave low-duty cycle mode. Slave wakes up periodically to talk to master. Fixed “sniff” intervals.
Park: Very low power state. Used to admit more than 7 slaves in piconet.
Slave gives up its active member address. Receives “parked” member address.
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Security Authentication and encryption.. Authentication using challenge-
response mechanism based on shared secret key
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Host Controller Interface
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
Optional interface layerbetween higher and lower layers of the BT stack.
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L2CAP
Logical Link Control andAdaptation Protocol=
Session Layer.
L2CAP provides• Protocol multiplexing• Quality of service negotiationRF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller Interface
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RFCOMM/SDP
RF
Baseband
Link Manager
L2CAP
RFCOMM/SDP
Applications
Link Controller
Host Controller InterfaceService discovery, interoperability with IR applications, serial port interface.
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References: Bluetooth papers in reading list. Johansson and Gerla’s Bluetooth
Tutorial at Mobicom 2001. Bluetooth 1.1: Connect Without
Cables, Bray and Sturman.