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Performance Evaluation Study for HiperLan WLAN Protocol - PowerPoint PPT Presentation

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Performance Evaluation Study for HiperLan WLAN Protocol. Omar A. Elprince Student#220510. Agenda. What is HIPERLAN? Origin of HIPERLAN HIPERLAN MAC Mechanism HIPERLAN Family Features of HiperLAN/2 MAC Frame Structure Transport Channels The Channel Access Mechanism

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Performance Evaluation Study for HiperLan WLAN Protocol

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Presentation Transcript
  • What is HIPERLAN?
  • Origin of HIPERLAN
  • Mechanism
  • HIPERLAN Family
  • Features of HiperLAN/2
  • MAC Frame Structure
  • Transport Channels
  • The Channel Access Mechanism
  • Signaling and Control
  • Error Control
  • Simulation Results
what is hiperlan
  • HIPERLAN - HIgh PErformance Radio LAN
  • HIPERLAN is a new standard for Radio LANs developed in Europe by ETSI
  • HIPERLAN is an interoperability standard which specifies a common air interface MAC and PHY layers in OSI model
  • HIPERLAN will be a family of standards
origin of hiperlan
Origin of HIPERLAN
  • Early wireless LANs operating in the ISM bands (900MHz and 2.45GHz)
  • Low data rate (~1Mbps) - an indirect result of the FCC spread spectrum rules part 15.247.
  • Severe interference environment - from unlike wireless LANs and other ISM band systems.
  • Lack of standards - IEEE 802.11 was initiated to satisfy this need but it was taking time to develop.
  • ETSI set up RES10 group to develop a standard that would be equal in performance to wired LANs such as Ethernet.
hiperlan mac
  • Concept:
    • Fully distributed MAC networks with and without infrastructure permits multi-hop relaying via neighbors based on LBT (Listen before talk)
    • Channel Access Mechanism is based on channel sensing and a contention resolution scheme called EY-NPMA - Elimination Yield Non-pre-emptive Priority Multiple Access using listen-talk contention resolution and using talk-listen Immediate packet acknowledgment.
    • It defines a priority scheme and a life time for each packet which facilitate the control of QoS.
    • In addition to routing it handles the encryption and power conservation.
hiperlan mac cont d the channel access mechanism
HIPERLAN MAC (Cont’d)The Channel Access Mechanism
  • The channel access cycle consists of three phases: the prioritization phase, the contention phase and the transmission phase.
  • The aim of the prioritization phase is to allow only nodes with the highest channel access priority frame to participate in the next phase.
  • The contention phase starts immediately after the transmission of the prioritization burst, and it further consists of two phases: the elimination phase and the yield phase.
  • The transmission phase begins if the channel is sensed idle during the yield listening interval.

PhasesPrioritization Phase1-5 slots of 168bits (talk)Contentions PhaseElimination - 0-12 slots of 212bits (talk),1 slot of 256bits (listen), prob(talk-listen) = 0.5Yield - 0-9 slots of 168bits (listen), prob(n) = 0.1Tx to Rx turn around time 6s256 contenders, 3.5% collision probabilityTotal of 0-5152bits (0-219s) MAC header



Previous simulations show that the HIPERLAN MAC can simultaneuosly support25 audio links @ 32kbit/s, 10ms delivery 25 audio links @ 16kbit/s, 20ms delivery1 video link @ 2Mbit/s, 100ms deliveryAsynch file transfer @ 13.4Mbit/s



hiperlan 1 mac cont d priority is a function of lifetime and user priority
HIPERLAN 1 MAC (Cont’d)Priority is a function of lifetime and user priority
  • NRL < 10ms
  • 0
  • 1
  • 10ms < NRL< 20ms
  • 1
  • 2
  • 20ms < NRL < 40ms
  • 2
  • 3
  • 40ms < NRL < 80ms
  • 3
  • 4
  • NRL > 80ms
  • 4
  • 4
hiperlan mechanism
HIPERLAN Mechanism
  • MT initially requests resources (RR) to the AP, the MT

may use the RCH to send the RR msg to AP.

  • If collision occurs then the MT is informed in the ACH of

the next MAC frame. The MAC uses a new back off


  • After the successful resource request, the MT goes into

the contention free mode- where the AP schedules the

MT for transmission.

  • Scheduling is done by the centralized control in the
  • AP->QoS increases
hiperlan mac cont d mac frame structure
HIPERLAN MAC (Cont’d)MAC Frame Structure:
  • The basic MAC frame structure on the air interface has a fixed duration of 2 ms and comprises transport channels for broadcast control, frame control, access control, downlink (DL) and uplink (UL) data transmission and random access.
  • The MAC frame and the transport channels form the interface between DLC and the physical layer.
transport channels
Transport Channels
  • The access feedback channel (ACH, downlink only) conveys information on previous access attempts made in the RCH.
  • The broadcast channel (BCH, downlink only) contains control information that is sent in every MAC frame and reaches all the MTs. The BCH provides information (not exhaustive) about transmission power levels, starting point and length of the FCH and the RCH,
  • The frame control channel (FCH, downlink only) contains an exact description of how resources have been allocated within the current MAC frame in the DL- and UL-phase and for the RCH.
  • The C-PDUs are referred to as the short transport channel (SCH), and the U-PDUs are referred to as the long transport channel (LCH).
  • The random access channel (RCH, uplink only) is used by the MTs to request transmission resources for the DL- and UL-phase in upcoming MAC frames, and to convey some RLC signalling messages.
features of hiperlan 2
Features of HiperLAN/2
  • High-Speed Transmission up to 54Mpbs
    • Using the OFDM
  • Connection-oriented
    • Data is transmitted on a connection between the AP and the MT, that has been established prior to transmission using the signaling functions.
  • QoS
    • Each connection can be assigned a special type of QoS eg: bandwidth, delay, BER
    • To virtually support any type of service like multimedia, VoIP and real time video
signaling and control
Signaling and Control

Radio Link Control (RLC ) gives a transport service for signaling entities:

– Association Control Function (ACF)

– Radio Resource Control Function (RRC)

– DLC user Connection Control Function (DCC)

signaling and control contd
Signaling and Control (Contd)
  • Association Control Function (ACF)
    • Authentication
    • Association/Disassociation
    • Encryption
  • Radio Resource Control (RRC)
    • Handover
    • Dynamic Frequency Selection
    • Power saving
error control
Error Control
  • Acknowledge:
    • Based on Selective Repeat (SR)
    • Provides reliable transmission
  • Repetition
    • Reliable Retransmission by repeating the DLC PDUs
    • Transmitter arbitrarily retransmits the PDUs, but the receivers accepts only in a sequential order
  • Unacknowledge
    • Unreliable Transmission
    • Transmitter sends the PDUs in increased sequential order, and the receiver will deliver the received ones to the Convergence Layer (CL)
centralized direct mode used by hiperlan 2
Centralized/Direct Mode used byHiperLAN/2
  • AP Cell: consists of many MTs and an AP
  • AP Cell has a centralized control (logical function)which

decides when the AP or the MT can access the medium

  • Geographical Area:
    • Outdoor: 100m- 150m
    • Indoor: 30m
  • AP is connected to the Backbone Network (BN)
  • BN provide different services to the MT eg:Internet
  • APs are interconnected through the BN, thus increasing the coverage
  • Handover mechanism helps in the mobility of the MTs.