View
20
Download
1
Category
Preview:
DESCRIPTION
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: - PowerPoint PPT Presentation
Citation preview
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.1
Mobile Communications Chapter 7: Wireless LANs
HIPERLANHiperLAN2 (pages 257-263) QoS
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.2
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 SS02 7.3
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 SS02 7.4
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 SS02 7.5
HiperLAN2 architecture - Infrastructure mode
2
3
1
AP
APT APC CoreNetwork
(Ethernet,Firewire,
ATM,UMTS)APT
APT
APC
AP
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 SS02 7.6
HiperLAN2 – three handover situations may occur
2
3
1
AP
APT APC CoreNetwork
(Ethernet,Firewire,
ATM,UMTS)APT
APT
APC
AP
MT4
MT3
MT2
MT1
• 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 SS02 7.7
Centralized vs. direct mode
MT1
AP/CCAP
MT2
data
control control
MT1 MT2
data
control
Centralized mode: Infrastructure modeAll APs are connected to the core networkMTs are associated with APsEven if two MTs share the same cell, all data is transferred via the AP.This mode is mandatoryThe AP takes complete control of everything
Direct mode: Ad Hoc modeData 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.
MT1 MT2 +CCdata
control
HiperLAN2 – The physical layer
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.8
• 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 SS02 7.9
Operating channels of HiperLAN2 in Europe
5150 [MHz]5180 53505200
36 44
16.6 MHz
center frequency = 5000 + 5*channel number [MHz]
channel40 48 52 56 60 64
5220 5240 5260 5280 5300 5320
5470
[MHz]
5500 57255520
100 108
16.6 MHz
channel104 112 116 120 124 128
5540 5560 5580 5600 5620 5640
132 136 140
5660 5680 5700
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.10
Basic structure of HiperLAN2 MAC frames
MAC frame MAC frame MAC frame MAC frame
2 ms 2 ms 2 ms 2 ms
broadcast phase downlink phase uplink phaserandom
access phase
. . .
TDD, 500 OFDMsymbolsper frame
variable variable variable
MAC: creates frames of 2 ms durationEach 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)
HiperLAN2 – Convergence Layer
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.11
• 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.
End
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.12
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 SS02 7.13
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 SS02 7.14
Prof. Dr.-Ing. Jochen Schiller, http://www.jochenschiller.de/ MC SS02 7.15
HiperLAN2 protocol stack
Higher layers
Convergence layer
Data link control - basic data
transport functionScope of HiperLAN2standards
DLC controlSAP
DLC userSAP
Radio link control sublayer
Physical layer
Radioresourcecontrol
Assoc.control
DLCconn.
controlError
controlRadio link control
Medium access control
Recommended