Mobile communications chapter 7 wireless lans
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Mobile Communications Chapter 7: Wireless LANs. HIPERLAN HiperLAN2 (pages 257-263) QoS. HiperLAN2. Official name: BRAN HIPERLAN Type 2 High data rates for users up to 54 Mbps ! 5 GHz band (Europe: 5.15-5.35 GHz and 5.47-5.725 GHz license exempt bands) Connection oriented:

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Mobile Communications Chapter 7: Wireless LANs

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Mobile communications chapter 7 wireless lans

Mobile Communications Chapter 7: Wireless LANs

  • HIPERLAN

    • HiperLAN2 (pages 257-263)

    • QoS

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.1


Hiperlan2

HiperLAN2

Official name: BRAN HIPERLAN Type 2

  • High data rates for users up to 54 Mbps!

  • 5 GHz band (Europe: 5.15-5.35 GHz and 5.47-5.725 GHz license exempt bands)

  • Connection oriented:

    • Prior to data transmission HiperLAN2 networks establish logical connections between sender and receiver. Connection set up is used to negotiate QoS parameters.

    • All connections are TDMA with TDD for separation of up/downlink.

    • Point-to-point as well as point-to-multipoint connections are offered.

    • Additionally, a broadcast channel is available to reach all mobile devices in the transmission range of an access point

  • Quality of service support:

    • With the help of connections, support of QoS is much simpler.

    • Each connection has its own set of QoS parameters (bandwidth, delay, jitter, bit error rate, etc.)

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.2


Hiperlan21

HiperLAN2

Official name: BRAN HIPERLAN Type 2

  • Dynamic frequency selection:

  • HiperLAN2 does not require frequency planning like IEEE 802.11.

  • All access points have built in support which automatically selects an appropriate frequency within their coverage area.

  • All APs listen to neighboring APs as well as to other radio sources in the environment.

  • The best frequency is chosen depending on the current interference level and usage of radio channels.

  • Security support

  • Authentication as well as encryption are supported by HiperLAN2

  • Both, mobile terminal and access point can authenticate each other.

  • All user traffic can be encrypted to protect against eavesdropping or man-in-the-middle attacks.

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.3


Hiperlan22

HiperLAN2

Official name: BRAN HIPERLAN Type 2

  • Mobility support

  • Mobile terminals can move around while transmission always takes place between the terminal and the access point with the best radio signal.

  • Handover between access points is performed automatically.

  • If enough resources available, all connections including their QoS parameters will be supported by a new access point after handover.

  • However, some data may be lost during handover.

  • Network and application independent

  • APs can connect to many types of networks like Ethernet, Firewire, etc.

  • Interoperation with 3G networks, support for many home audio/video devices

  • Power save modes

  • Mobile terminals can negotiate certain wake-up patterns to save power.

  • Either short latency requirements or low power requirements can be supported.

  • Plug and Play

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.4


Hiperlan2 architecture infrastructure mode

HiperLAN2 architecture - Infrastructure mode

AP

Core

Network

(Ethernet,

Firewire,

ATM,

UMTS)

APT

APC

1

3

AP

APT

APC

2

APT

MT4

MT3

MT2

MT1

  • Two access points (AP) are shown

  • Core network, an Ethernet, Firewire,

  • ATM, 3G, etc

  • Each AP: an Access Point Controller

  • one or more access point tranceivers

  • An APT can comprise one or more sectors (shown as cells here)

  • MPs can move around in the cell

  • The system automatically assigns the APT/APC with the best transmission quality.

  • No frequency planning is needed.

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.5


Hiperlan2 three handover situations may occur

HiperLAN2 – three handover situations may occur

AP

Core

Network

(Ethernet,

Firewire,

ATM,

UMTS)

APT

APC

1

3

AP

APT

APC

2

APT

MT1

MT4

MT3

MT2

  • Sector handover – a new cell (See MT1 in the figure below)

  • Radio handover – different APTs but the same APC (See MT3 in the figure below)

  • Network handover – different APCs (See MT2 in the figure below) In this case the core network and higher layers are also involved. If not supported by the core network, a new association must take place.

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.6


Centralized vs direct mode

Centralized vs. direct mode

MT1

MT1

MT2

MT2

MT2 +CC

MT1

  • Centralized mode: Infrastructure mode

  • All APs are connected to the core network

  • MTs are associated with APs

  • Even if two MTs share the same cell, all data is transferred via the AP.

  • This mode is mandatory

  • The AP takes complete control of everything

  • Direct mode: Ad Hoc mode

  • Data is directly exchanged between MTs if they can receive each other, but the network still has to be controlled:

  • This can be done either via an AP that contains a central controller (CC) anyway or via an MT that contains the CC functionality.

  • There is no difference between an AP and a CC besides the fact that APs are always connected to an infrastructure but here only the CC functionality is needed.

AP

AP/CC

control

control

data

control

data

control

data

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.7


Hiperlan2 the physical layer

HiperLAN2 – The physical layer

  • Many functions and features of HiperLAN2 physical layer served as example for IEEE 802.11a. It is not suprising that both standars offer similar data rates and use identical modulation schemes.

  • OFDM

  • BPSK, QPSK, 16-QAM and 64-QAM

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.8


Operating channels of hiperlan2 in europe

Operating channels of HiperLAN2 in Europe

channel

36

40

44

48

52

56

60

64

5150

5180

5200

5220

5240

5260

5280

5300

5320

5350

[MHz]

16.6 MHz

100

104

108

112

116

120

124

128

132

136

140

channel

5660

5680

5700

5470

5500

5520

5540

5560

5580

5600

5620

5640

5725

[MHz]

16.6 MHz

center frequency =

5000 + 5*channel number [MHz]

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.9


Basic structure of hiperlan2 mac frames

Basic structure of HiperLAN2 MAC frames

2 ms

2 ms

2 ms

2 ms

TDD,

500 OFDM

symbols

per frame

MAC frame

MAC frame

MAC frame

MAC frame

. . .

broadcast phase

downlink phase

uplink phase

random

access phase

variable

variable

variable

MAC: creates frames of 2 ms duration

Each MAC frame is further sub-divided into four phases

  • broadcast phase: The AP sends inf of the current frame

  • downlink phase: AP to MTs

  • uplink phase: MTs to AP

  • random access phase: for registered MTs – capacity requests

  • for new MTs access requests (slotted ahloha)

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.10


Hiperlan2 convergence layer

HiperLAN2 – Convergence Layer

  • The physical layer and the data link layer are independent of specific core network protocols.

  • A special convergence layer (CL) is needed to adapt to the special features of these network protocols.

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.11


Mobile communications chapter 7 wireless lans

End

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.12


Connection oriented

Connection oriented

  • Prior to data transmission, HiperLAN2 networks establish a logical connection between a sender and a receiver (e.g. A mobile device and an access point).

  • Connection set-up is used to negotiate QoS-parameters.

  • All connections are time-division-multiplexed over the air interface (TDMA with TDD for separation of up/downlinks).

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.13


Qos support

QoS support

With the help of ”connections”, support of QoS is much simpler!

Can handle time sensitive data transfers!

Each connection has its own set of QoS parameters:

  • Bandwidth

  • Delay

  • Jitter

  • Bit error rate

  • Etc

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.14


Hiperlan2 protocol stack

HiperLAN2 protocol stack

Higher layers

Convergence layer

DLC control

SAP

DLC user

SAP

Data link control -

basic data

transport function

Radio link control sublayer

Radio

resource

control

Assoc.

control

DLC

conn.

control

Scope of

HiperLAN2

standards

Error

control

Radio link control

Medium access control

Physical layer

Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/MC SS027.15


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