hiper lan (high performance radio lan)
Post on 18-Jan-2016
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HIPER LAN(High Performance Radio LAN)
Two main standards families for Wireless Lan: IEEE 802.11 (802.11b, 802.11a, 802.11g...) ETSI Hiperlan (Hiperlan Type 1, Type 2,
HiperAccess, HiperLink...)
HiperLAN Family
Hiperlan 1 Hiperlan2 HiperAccess HiperLinkDescription Wireless
EthernetWireless ATM Wireless Local
LoopWireless Point-
to-PointFreq. Range 5GHz 5GHz 5GHz 17GHz
PHY Bit Rate 23.5Mbps 6~54Mbps ~25Mbps
(data rate)
~155Mbps
(data rate)
Motivation of HiperLAN
Massive Growth in wireless and mobile communications
Emergence of multimedia applications
Demands for high-speed Internet access
Deregulation of the telecommunications industry
The History, Present and Future HiperLAN Type 1
Developed by ETSI during 1991 to 1996
Goal: to achieve higher data rate than IEEE 802.11 data rates: 1~2 Mbps, and to be used in ad hoc networking of portable devices
Support asynchronous data transfer, carrier-sense multiple access multiple access with collision avoidance (CSMA/CA), no QoS guaranteed.
HiperLAN Type 2
Goal: Providing high-speed (raw bit rate ~54Mbps) communications access to different broadband core networks and moving terminals
Features: connection-oriented, QoS guaranteed, security mechanism, highly flexibility
HiperAccess and HiperLink
In parallel to developing the HIPERLAN Type 2 standards, ETSI BRAN has started work on standards complementary to HIPERLAN Type 2
MAC
CAC
PHY
HiperLAN Type 1 Reference ModelPHY
MAC
ECACF DCC
RLC
DLC
CL
HiperLAN Type 2 Reference Model
Control Plane User Plane
MAC: Medium Access Sublayer EC: Error ControlCAC: Channel Access Control Sublayer RLC: Radio Link ControlPHY: Physical Layer RRC: Radio Resource ControlDLC: Data Link Control Layer ACF: Association Control FunctionCL: Convergence Layer DCC: DLC Connection Control
Architecture
RRC
CAC: Channel Access Control Sublayer
This sub layer deals with the access request to the channels.
The accomplishing of the request is dependent on the usage of the channel and the priority request.
HIPERLAN2 Protocol Stack
DLC: MAC Sublayer The medium access control creates frames of 2 ms duration as
shown in Figure. With a constant symbol length of four μs this results in 500 OFDM symbols.
Each MAC frame is further sub-divided into four phases with variable boundaries:
Broadcast phase: The AP of a cell broadcasts the content of the current frame plus information about the cell (identification, status, resources).
Downlink phase: Transmission of user data from an AP to the MTs.
Uplink phase: Transmission of user data from MTs to an AP.
Random access phase: Capacity requests from already registered MTs and access requests from non-registered MTs.
HiperLAN2 defines six different so-called transport channels for data transfer in the above listed phases. These transport channels describe the basic message format within a MAC frame.
Broadcast channel (BCH): This channel conveys basic information for the radio cell to all MTs. This comprises the identification and current transmission power of the AP. The length is 15 bytes.
Frame channel (FCH): This channel contains a directory of the downlink and uplink phases (LCHs, SCHs, and empty parts). This also comprises the PHY mode used. The length is a multiple of 27 bytes.
Access feedback channel (ACH): This channel gives feedback to MTs regarding the random access during the RCH of the previous frame. The length is 9 bytes.
Long transport channel (LCH): This channel transports user and control data for downlinks and uplinks. The length is 54 bytes.
Short transport channel (SCH): This channel transports control data for downlinks and uplinks. The length is 9 bytes.
Random channel (RCH): This channel is needed to give an MT the opportunity to send information to the AP/CC even without a granted SCH. The length is 9 bytes.
DLC: Error Control
Acknowledged mode: selective-repeat ARQ
Repetition mode: typically used for broadcast
Unacknowledged mode: unreliable, low latency
DLC: other features
Radio network functions: Dynamic frequency selection; handover; link adaptation; multibeam antennas; power control
QoS support: Appropriate error control mode selected; Scheduling performed at MAC level; link adaptation; internal functions (admission, congestion control, and dropping mechanisms) for avoiding overload
Radio Link Control Sublayer
It offers connection oriented systems ,offering QoS.
Three main control functions Association control function (ACF): authentication, key
management, association, disassociation, encryption
Radio resource control function (RRC): handover, dynamic frequency selection, mobile terminal alive/absent, power saving, power control
DLC user connection control function (DCC): setup and release of user connections, multicast and broadcast
Convergence Layer
HiperLAN2 supports two different types of CLs: cell-based and packet-based.
cell-based CL expects data packets of fixed size (cells, e.g., ATM cells).
packet-based CL handles packets that are variable in size (e.g., Ethernet )
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