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Wireless Networks - MAC layer. - Bluetooth. What is Bluetooth?. Cable replacement technology primarily

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what is bluetooth
What is Bluetooth?
  • Cable replacement technology primarily
  • Bluetooth wireless technology is an open specification for a low-cost, low-power, short-range radio technology for ad-hoc wireless communication of voice and data anywhere in the world.
  • Where does the name come from?
    • To honor a 10th century king Bluetooth in Denmark who united that country and established Christianity
bluetooth
Bluetooth
  • Bluetooth Piconet: a polling/TDMA scheme
  • Bluetooth working group history
    • February 1998: The Bluetooth SIG is formed
    • promoter company group: Ericsson, IBM, Intel, Nokia, Toshiba
    • + 3Com, Lucent, Microsoft, Motorola
  • Bluetooth uses a frequency-hopping scheme in the unlicensed band at 2.4 GHz.
  • The major goal is to allow relatively cheap electronic devices to communicate directly in an ad-hoc fashion, Moreover, the Bluetooth equipped devices can also form networks– such a network of personal devices is often referred to as a personal area network (PAN).
what does bluetooth do for you

Landline

Data/Voice Access Points

…and combinations!

Personal Ad-hoc Networks

What does Bluetooth do for you?

Cable Replacement

- Synchronization

- Cordless Headset

It is reported that more than two billion Bluetooth-ready devices were shipped during 2012 – over 50 millions every day.

bluetooth technical features
Bluetooth Technical Features:
  • 2.4 GHz ISM Open Band
    • Globally free available frequency
    • 79 channels (2400-2483.5 MHz ISM band)
    • Frequency Hopping & Time Division Duplex (1600 hops/second typically)
  • 10-100 Meter Range
    • Class I – 100 meter (300 feet)
    • Class II – 20 meter (60 feet)
    • Class III – 10 meter (30 feet)
  • Link Rate : 1 Mbps
  • Simultaneous Voice/Data Capable
    • SCO (Synchronous connection oriented) for voice
    • ACL (Asynchronous connectionless link) for data
frequency hopping
Frequency Hopping

1Mhz

79

83.5 Mhz

  • Divide Frequency band into 1 MHz hop

channels

  • Radio hops from one channel to another in a

pseudo-random manner as dictated by a hop sequence

slide8

Frequency Hopping Map

  • Wireless channel is divided into time slots of 625μs
  • Frequency hopping sequence is defined by a pseudorandom number generator known to both transmitter and receiver
  • Packet transmission is aligned with the start of time slot
bluetooth network topology
Bluetooth Network Topology
  • PICONET —— Bluetooth LAN
    • Collection of devices connected in an ad hoc fashion
  • One unit acts as master and the others as slaves for the lifetime of the piconet
    • Master – device that initiates a data exchange
    • Slave – device that responds to the master
  • Master determines hopping pattern, slaves have to synchronize
    • There is one only one pattern in one piconet
    • 1600hops/sec
    • Devices in a piconet are synchronized to the same clock defined by master
bluetooth network topology1

m

s

m

s

s

s

Bluetooth Network Topology
  • Point to point link
    • master - slave relationship
    • radios can function as masters or slaves
  • Assigning address
    • If (node -> node address==0)
          • MASTER
    • else
          • SLAVE
  • Piconet
    • Master can connect to 7 slaves
    • hopping pattern is determined by the master
connection setup
Connection Setup
  • Inquiry(查询消息)
    • Master 查找附近的蓝牙设备,以便通过收集来自从节点响应查询消息中得到该节点的设备地址(48b)和时钟
  • Inquiry – scan(查询扫描)
    • Slave设备周期地监听来自其他设备的查询消息,以便自己能被发现,并在监听到后发送它的地址和时钟信息。
connection setup1

Master

Active Slave

  • Parked Slave
  • Connected
  • Not in Pico

Standby

Connection Setup
  • Page (寻呼)
    • Master 通过在不同的跳频序列发送消息,来激活一个从节点, 并建立连接。调频序列由slaver的地址码计算出
  • Page – scan(寻呼扫描)
    • Slaver 周期性地在扫描窗间隔时间内唤醒自己,并监听自己的访问码, Slaver节点每隔1.28s在这个扫描窗上根据寻呼跳频序列选择一个扫描频率
packet types
Packet Types

Data/voice

packets

Control

packets

Voice

data

ID*

Null

Poll

FHS

DM1

HV1

HV2

HV3

DV

DH1

DH3

DH5

DM1

DM3

DM5

FHS – Frequency Hop Synchronization

DM – Data Medium rate

HV – High quality Voice

DV – Data Voice

DH – Data High rate

packet format
Packet Format

54 bits

72 bits

0 - 2744 bits

  • Access code
    • used for timing synchronization, offset compensation, paging, and inquiry

Access

code

Header

Payload

header

Data

Voice

CRC

No CRC

No retries

ARQ

FEC (optional)

FEC (optional)

625 µs

master

slave

packet header

m

Max 7 active slaves

s

s

s

Packet Header

54 bits

  • Addressing (3)
  • Packet type (4)
  • Flow control (1)
  • 1-bit ARQ (1)
  • Sequencing (1)
  • HEC (8)

Access

code

Payload

Header

Purpose

16 packet types (some unused)

Broadcast packets are not ACKed

For filtering retransmitted packets

Verify header integrity

total

18 bits

Encode with 1/3 FEC to get 54 bits

inter piconet communication

Cordless

headset

mouse

Cell phone

Inter piconet communication

Cordless

headset

Cell phone

Cell phone

Cordless

headset

scatternet gateway node participates in more than one piconet on a time division basis
Scatternet- Gateway node participates in more than one piconet on a time-division basis

Not implemented in COTS equipment

scatternet scenario 2
Scatternet, scenario 2

How to schedule presence in two piconets?

Forwarding delay ?

Missed traffic?

Not implemented in COTS equipment

bluetooth protocol stack

Applications

IP

SDP

RFCOMM

Control

Data

Audio

L2CAP

Link Manager

Baseband

RF

Bluetooth Protocol Stack

Composed of protocols to allow Bluetooth devices to locate each other and to create, configure and manage both physical and logical links that allow higher layer protocols and applications to pass data through these transport protocols

Transport Protocol Group

bluetooth protocol stack1

Applications

IP

SDP

RFCOMM

Control

Data

Audio

L2CAP

Link Manager

Baseband

RF

Bluetooth Protocol Stack

Additional transport protocols to allow existing and new applications to operate over Bluetooth. Packet based telephony control signaling protocol also present. Also includes Service Discovery Protocol.

Middleware Protocol Group

bluetooth protocol stack2

Applications

IP

SDP

RFCOMM

Control

Data

Audio

L2CAP

Link Manager

Baseband

RF

Bluetooth Protocol Stack

Consists of Bluetooth aware as well as un-aware applications.

Application Group

l ink m anager p rotocol

Applications

IP

SDP

RFCOMM

Control

Data

Audio

L2CAP

LMP

Link Manager

Baseband

RF

Link Manager Protocol
  • Setup and management
  • of Baseband connections
    • Piconet Management
    • Link Configuration
    • Security
l2cap

IP

L2CAP

Applications

L2CAP - Logical Link Control

and Adaptation Protocol

SDP

RFCOMM

Data

  • L2CAP provides
    • Protocol multiplexing
    • Segmentation and
    • Re-assembly
    • Quality of service negotiation

Audio

L2CAP

Link Manager

Baseband

RF

rfcomm r adio f requency comm unication serial port emulation using rfcomm

IP

RFCOMM (Radio Frequency Communication)-- Serial Port Emulation using RFCOMM

Applications

SDP

Serial Port

RFCOMM

Data

  • Serial Port emulation on top of a packet oriented link
  • Similar to HDLC (High level
  • Data Link Control protocol)
    • RS232
  • For supporting legacy apps

Audio

L2CAP

Link Manager

Baseband

RF

ip over bluetooth v 1 0

IP

IP over Bluetooth V 1.0
  • Internet access using cell phones
  • Connect PDA devices & laptop computers to the Internet via LAN access points

Applications

SDP

GOALS

RFCOMM

Data

Audio

L2CAP

Link Manager

Baseband

RF

bluetooth personal area networks ad hoc and extend to mesh
Bluetooth Personal Area Networks- Ad Hoc and extend to Mesh
  • PANs extend the Internet to the user personal domain
  • 3G (2.5G) networks will give Internet access to PANs
  • PANs will generate more traffic than a single device
  • Utilize an aggregate of access networks (WLAN, 3G, DSL)
ip bluetooth networking conclusions
IP Bluetooth Networking - Conclusions

Bluetooth IP networking opens up new possibilities ---- Mesh networks

  • Enables spontaneous Ad Hocnetworking
    • Between people,
    • Between machines,
  • Mainly small, short range ad-hoc networks
    • Solves your “personal problems”...
    • Limited complexity and security risks
    • Sharing 3G traffic in current mobile internet????
  • The enabler for PANs!
    • Gives a natural extension of Internet into the PAN via 3G
    • Enables stepwise upgrading of devices -- not tied to one multimedia terminal!
    • Makes use of the 3G bandwidth immediately
  • QoS ~ Bluetooth ?