cdma2000 Overview

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Wireless Communications Engineering
Lecture 14 Wireless LAN (2) Prof. Mingbo
Xiao Jan. 4, 2005
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WLANs

• IEEE 802.11x
• ETSI BRAN HIPERLAN
• Bluetooth
• HomeRF Networking mobile data and voice devices
  to a PC anywhere in the home
• IrDA Wirelss data cable replacement for devices
  in line of sight

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BRAN Family
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HIPERLAN Type 1

• Provides a high-speed WLAN
• Access method elimination yieldnonpreemptive
  priority multiple access (EY-NPMA)
• Similar to CSMA/CA
• Three phases priority resolution, elimination,
  and yield

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HIPERLAN Type 2 Overview

• Spectrum 5 GHz
• Maximum physical rate 54 Mbps
• Maximum data rate, layer 3 32 Mbps
• MAC Central resource control/TDMA/ TDD
• Fixed network support IP/ATM/UMTS

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HIPERLAN Type 2

• Constituted by three layers PHY, DLC, and the
  convergence layer (CL)
• Each layer has a user plane and control plane
• User plane includes functions related to
  transmission of traffic over the established user
  connections
• Control plane includes functions related to the
  control, establishment, release, and modification
  of the connections

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Protocol Reference Model
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Physical Layer

• Provides a basic data transport function by a
  baseband modem and an RF part
• Transmission format on the PHY layer is a burst
  consisting of a preamble part and a data part
• Modulation scheme OFDM (achieving good
  performance on highly dispersive channels)

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(No Transcript)
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Data Link Layer Overview

• Represent the logical link between an AP and its
  associated MTs
• Implements QoS, channel quality, number of MTs,
  and MAC
• Operates on a per-connection basis, to maintain
  QoS on a virtual-circuit basis, using means such
  as FEC, ARQ, and flow pacing

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Data Link Layer

• Consists of the error control (EC), radio link
  control (RLC), and MAC functions
• Data transport handles data packets from higher
  layer via user service access point
• Control part radio resource control (RRC),
  association control function (ACF), and RLC,
  which provides a transport service to the DLC
  connection control (DCC)

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Convergence layer

• Data transport part provides adaptation of the
  user data to the DLC layer message format
  (DLC-SDU)
• If higher layer network protocol is not ATM, its
  common part (CP) provides segmentation and
  reassembly (SAR)
• Integrated HIPERLAN into fixed networks via
  Service specific convergence sublayer (SSCS)
• Control part of CL can use the control functions
  in the DLC

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System Architecture

• Structured in a centralized mode (CM), with two
  main entities MT and AP
• AP coordinates MTs in its area and can control
  one or more sectors
• Direct link mode (DM) established between MTs so
  that they can directly exchange information

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Centralized Architecture
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DLC channels

• Logical channel
• a generic term for any distinct data path
• defined by the type of information it conveys and
  the interpretation of the values in the
  corresponding messages
• mostly used when referring to the meaning of
  message contents
• Transport channels
• provide the basic elements for constructing
  protocol data units (PDUs)
• describe the format of the various messages

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Logic Channels

• 1. Broadcast control channel (BCCH) It conveys
  downlink broadcast control channel information
  concerning the whole radio cell.
• 2. Frame control channel (FCCH) Downlink, it
  describes the structure of the MAC frame. This
  structure is announced by resource grant messages
  (RGs).
• 3. Random access feedback channel (RFCH)
  Downlink, it informs the MTs that have used the
  RCH in the previous MAC frame about the result of
  their access attempts. It is transmitted once per
  MAC frame per sector.

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Logic Channels (Contd)

• 4. RLC broadcast channel (RBCH) Downlink, it
  conveys (when necessary) broadcast control
  information concerning the whole radio cell. The
  information transmitted by RBCH is classified as
• Broadcast RLC messages
• Assignment of MAC_ID to a nonassociated MT
• Convergence layer ID information
• Encryption seed.
• RBCH is transmitted only

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Logic Channels (Contd)

• 5. Dedicated control channel (DCCH) It
  transports RLC messages in the uplink direction.
  A DCCH is implicitly established during
  association of an MT.
• 6. User broadcast channel (UBCH) Downlink, it
  transmits user broadcast data from the CL. The
  UBCH transmits in repetition or unacknowledged
  mode and can be associated or unassociated to
  LCCHs.
• 7.User multicast channel (UMCH) Downlink, it is
  employed to transmit user point-to-multipoint
  user data. The UMCH is transmitted in
  unacknowledged mode.

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Logic Channels (Contd)

• 8. User data channel (UDCH) Bidirectional, it is
  employed to exchange data between APs and MTs in
  CM or between MTs in DM. The UDCH is associated
  or not to LCCHs.
• 9. Link control channel (LCCH) Bidirectional, it
  is employed to exchange ARQ feedback and discard
  messages both in CM and in DM. The LCCH is also
  used to transmit resource request messages (RRs)
  in the uplink direction (only in CM) and discard
  messages for a UBCH using repetition mode. LCCHs
  may or may not be associated with UDCHs/UBCHs.
• 10. Association control channel (ASCH) Uplink,
  in this case the MTs that are not associated to
  an AP transmit new association and handover
  requests.

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Transport Channels

• 1. Broadcast channel (BCH) Downlink, it contains
  15 bytes of radio cell information such as
  identification of the AP and its current
  transmitted power.
• 2. Frame channel (FCH) Downlink, its length is a
  multiple of 27 octets. It contains a description
  of the way resources have been allocated and can
  also contain an indication of the empty parts of
  a frame.
• 3. Access feedback channel (ACH) Downlink, its
  length is 9 octets. It contains information on
  access attempts made in the previous RCH.

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Transport Channels (Contd)

• 4. Long transport channel (LCH) Downlink and
  uplink, its length is 54 octets. It is used to
  transmit DLC user PDUs (U-PDUs of 54 bytes with
  48 bytes of payload).
• 5. Short transport channel (SCH) Downlink and
  uplink, its length is 9 octets. It is used to
  exchange DLC control PDUs (C-PDU of 9 bytes).
• 6. Random channel (RCH) Uplink, its length is 9
  octets. It is used for sending control info when
  no granted SCH is available. It carries RRs as
  well as ASCH and DCCH data.

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Mapping for Downlink
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Mapping for Uplink
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Mapping for Direct Link
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MAC Layer

• Based on TDMA/TDD, with frames period of 2 ms
• APs control the allocation of resources, and
  determine if two MTs can directly exchange
  information
• MTs may request resources using RRs, and can
  request fixed capacity allocation over multiple
  frames

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Basic MAC Frame
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MAC Operations

• A scheduler, centralized in the AP, to determine
  the composition of the MAC frame
• A process in APs and in MTs that receives and
  transmits PDUs
• A process that maps logical channels onto
  transport channels
• MAC entities that exchange control information

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Access to RCH

• Each MT maintains a contention window, CWa, to
  control the access to the RCH
• randomly chooses a number r between 1 and CWa and
  starts counting r RCHs
• can only access the rth RCH.
• if it receives the ACH with a positive feedback,
  it then resets a to 0.

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Other DLC Entities

• DLC connection control (DCC), signaling to
  establish or release a connection
• ACF supports functions related to the exchange of
  information about link capabilities and
  association of MT with AP
• Error control entity supports Acknowledged mode
  (selective repeat ARQ) Repetition mode
  (repeating the LCHs) Unacknowledged mode
• Radio resource control involves handover, dynamic
  frequency selection (DFS), MT alive, and
  power-save procedures

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Radio Resource Control

• DFS automatically assigns frequencies to each AP
  for communication
• MT alive enables AP to figure out if any
  associated MT is not transmitting
• Power-save procedure defines the appropriate
  signaling for transmitter power control and
  definition of sleeping mode of MTs

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Handover

• Mainly MT initiated
• there is an AP-initiated capability for handover
  in case an AP wants to decrease its load
• MT handover sector handover, radio (intra-AP)
  handover , and network handover

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Radio and Network Handover
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Bluetooth Overview

• Introduction
• Ad Hoc Radio Connectivity
• Bluetooth Radio System Architecture
• Applications of Bluetooth Technology
• Conclusions
• References

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Introduction

• In May 1998, a Bluetooth Special Interest
  Group(SIG)was formed by Ericsson, Nokia, IBM,
  Toshiba, and Intel to promote the Bluetooth
  concept and establish an industry standard
• Bluetooth is a short range radio technology that
  operates in the Industrial-Scientific-Medical(ISM)
  band from 2,402MHz to 2,480MHz

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Introduction(cont.)

• The aim was to eliminate cables between mobile
  phones and PC cards, headset and desktop devices,
  etc.
• Version 1.0 of the specification was first
  published in July 1999
• Version 1.1 of the spec. was then published at
  Feb. 22 2001
• Bluetooth data rate can achieve about 1Mbit/s

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Usage Scenarios
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Technology Characteristics

• Low-cost,
• Low-power,
• Small-sized,
• Short-range,
• Robust wireless technology

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General Characteristics

• Universal wireless interface
• Ad-hoc networking architecture
• 80 Mhz in unlicenced ISM band at 2.45 Ghz
• Gross bitrate 1 Mbps
• Simultaneous voice and high speed data support
• Evolves from cable replacement - gt networking
  solution

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Scatternets

• Each piconet has one master and up to 7 slaves
• Master determines hopping sequence, slaves have
  to synchronize
• Participation in a piconet synchronization to
  hopping sequence
• Communication between piconets devices jumping
  back and forth between the piconets

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Piconet
Slave 1
Master
Slave 2
Slave 3
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Piconets and Scatternets
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Protocol Stack Component
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Bluetooth System Architecture
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Radio Spectrum

• Must be open to the public without the need for
  licenses and must be available worldwide
  (2400MHz to 2483.5MHz)
• Bluetooth is based on FH-CDMA
• High speed of hops in the frequency spectrum
  makes the connection very robust to interference
• Code-division multiple access offers the best
  properties for ad hoc radio systems
• In the 2.45GHz ISM band, a set of 79 hop carriers
  have been defined at a 1MHz spacing

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Baseband Layers

• Provide a mapping of logical channels onto
  physical channels
• Determine the Bluetooth air-interface.
• Define the process by which devices search for
  other devices and how they connect to them.
• Define the master and slave roles for device.
• Define how synchronous and asynchronous traffic
  can share the air-interface.

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2.4 GHz, FHSS (CDMA), TDD
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FHSS Pattern Synchronization
The slaves synchronize themselves to the Master
Clock
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Frequency Selection
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Modulation Scheme

• Bluetooth uses Gaussian-shaped frequency shift
  keying(FSK)modulation with a nominal modulation
  index of k 0.3
• This modulation scheme allows the implementation
  of low-cost radio units

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Medium Access Control

• Bluetooth has been designed to allow a large
  number of independent channels, each channel
  serving only a limited number of participants
• Theoretically, the spectrum with 79 carriers can
  support 79Mb/s
• Different channels have different masters and
  therefore also different hopping sequences and
  phases

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Medium Access Control (Contd)

• By definition, the unit that establishes the
  piconet becomes the master
• In Bluetooth, the master implements centralized
  control only communication between the master
  and one or more slaves is possible
• Master unit schedules the traffic in both the
  uplink and downlink

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Link Manager Layer

• Link managers in each device negotiate the
  properties of the Bluetooth air-interface between
  them using the link manager protocol (LMP).
• The properties includes bandwidth allocation and
  periodic bandwidth reservation to support audio
  traffic.
• Supervise device pairing and encryption of the
  data flowing over the air-interface.

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L2CAP Layer

• L2CAP Logical Link control and adaptation
• protocol layer.
• Traffic form data applications is first routed
  through the L2CAP layer.
• L2CAP also enables segmentation of large packets
  used by higher layers into smaller packets for
  baseband transmission.
• The ability of the corresponding reassembly of
  segmented packets by the receiving device.

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Remarks

• Note that the concept of master and slave devices
  does not propagate higher than the link manager.
• At the L2CAP layer and above, communication is
  based upon a peer-to-peer model and no special
  provisions are made for different actions in a
  master device or in a slave device.

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Middleware Protocol Group

• The middleware protocols make use of the
  underlying transport protocols.
• Present to the application layers defines a
  standard interfaces that may be used for
  communicating across the transports .

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Middleware Protocol Group
Audio
Control
SDP
TCS-BIN
UDP
TCP
IrMC
TCS-AT
IP
OBEX
PPP
RFCOMM
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RFCOMM Layer

• Bluetooth wireless communication is aimed at
  replacing cables,so support for serial
  communications and related application is an
  important feature.
• RFCOMMa virtual serial port to applications.
• RFCOMM is a serial port abstraction.

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SDP Layer

• For Bluetooth, traditional static configuration
  network is not sufficient.
• SDP Bluetooth service discovery
  protocol
• SDP defines a standard method for Bluetooth
  devices to discover and learn about the services
  offered by other device.

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Networking Layers

• Bluetooth allows connecting to large networks
  through a dial-up connection or via a network
  access point.
• WAP(Wireless Application Protocol) is for
  wireless networking.
• Once a dial-up connection to an IP network is
  established, standard Internet Protocols such as
  TCP, UDP, HTTP will be used.

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Audio

• Audio traffic is isochroous.
• Voice traffic traffic typically is routed
  directly to and from the baseband layer.
• SCOSynchronous Connection-Oriented
• SCO packets are defined for use with typical
  audio traffic.
• Bluetooth allows for up to 3 audio channels at
  one time.

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Type of Trasmission

• Synchronous Connection-Oriented (SCO) Link
• Circuit switched typically used for voice
• Symmetric, synchronous service
• Slot reservation at fixed intervals
• Point-to-point
• Asynchronous connectionless(ACL)link
• Packet switched
• Symmetric or asymmetric, asynchronous service
• Polling mechanism between master and slave(s)
• Point-to-point and point-to-multipoint

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ACL data rates
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ACL Polling Scheme
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SCO Data Rates
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Voice and Data Transmission
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Capacity of Piconet
One ACL link (432 kbps symmetric or 721/56 kbps
asymetric) or Three simultaneous SCO links (64
kbps) or A combination of voice/data
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States of a Bluetooth device
STANDBY
unconnected
inquiry
page
connecting
connected
transmit
active
PARK
HOLD
SNIFF
low power
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Connection Setup in a Piconet
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Packet structure of Bluetooth

• BB_PDU ( Baseband packet data unit)
• Access Code Header Payload

Inside Access Code
Sync Word64 bits
Preamble 4-bits
Trailer 4-bits
Preamble offer DC offsetSync Word Created from
LAP
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Header Structure
18 bits
1/3 FEC encoding
54 bits
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Error Correction

• Packet header
• 1/3 rate FEC
• SCO payload
• 1/3 rate FEC
• 2/3 FEC
• no FEC
• ACL payload
• ARQN using payload CRC (except AUX packet)
• 2/3 rate FEC optional

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Security

• Four different entities are used for maintaining
  security at the link layer

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Bluetooth Products

• Ericsson T39mc (Bluetooth chip embedded)
• Bluetooth earphone from Ericsson
• PC2PC-Bluetooth Motherboard from MSI
• HP DeskJet 995c Printer
• PDA, Packet PC and other IA products

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Where Bluetooth Fits In