Hiperlan

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  • Notes: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...)
  • Notes:Maintaining a high data-rate (23.5 Mbit/s) is power consuming - problematic for mobile terminalspacket header with low bit-rate comprising receiver informationonly receiver(s) address by a packet continue receivingFrame structureLBR (Low Bit-Rate) header with 1.4 Mbit/s450 bit synchronizationminimum 1, maximum 47 frames with 496 bit eachfor higher velocities of the mobile terminal (> 1.4 m/s) the maximum number of frames has to be reducedModulationGMSK for high bit-rate, FSK for LBR header
  • NOTES:HIPERLAN/2 has a very high transmission rate up to 54 Mbit/s. This is achieved by making use of a modularization method called Orthogonal Frequency Digital Multiplexing (OFDM). OFDM is particularly efficient in time-dispersive environments, i.e. where the radio signals are reflected from many points, e.g. in offices. HIPERLAN/2 connections are time-division multiplexed and connection-oriented, either bidirectional point-to-point or unidirectional point-to-multipoint connections. There is also a dedicated broadcast channel through which the traffic from an AP reaches all terminals. Unlike other radio-based systems, the traffic on a LAN is inherently random and bursty. This may cause serious problems with respect to throughput, because the performance is one of the most important factors of wireless LANs. In HIPERLAN/2, each connection can be assigned either a simple relative priority level or a specific QoS in terms of bandwidth, delay, jitter, bit error rate, etc. The HIPERLAN/2 Access Points have a built-in support for automatic transmission frequency allocation within the AP's coverage area. This is performed by the Dynamic Frequency Selection (DFS) function. An appropriate radio channel is selected based on both what radio channels are already in use by other AP's and to minimize interference with the environment. Thus, there is no need for manual frequency planning as in cellular networks like GSM. The HIPERLAN/2 network supports authentication and encryption. Both the AP and the MT can authenticate each other to ensure authorized access to the network or to a valid network operator. The encryption can be used on established connections to protect against eaves-dropping and man-in-the-middle attacks. In HIPERLAN, each communicating node is given a HIPERLAN ID (HID) and a Node ID (NID). The combination of these two IDs uniquely identifies any station, and restricts the way it can connect to other HIPERLAN nodes. All nodes with the sama HID can communicate with each other using a dynamic routing mechanism denoted Intra-HIPERLAN Forwarding.The support for handover enables mobility of MTs. The handover scheme is MT initiated, i.e. the MT uses the AP with the best signal as measured for instance by S/N-ratio, and as the user moves around, all established connections move to the AP with the best radio transmission performance, while the MT stays associated to the HIPERLAN/2 network. The HIPERLAN/2 architecture is easily adapted and integrated with a variety of fixed networks. All applications running over a fixed infrastructure can also run over a HIPERLAN/2 network. The power save mechanism in HIPERLAN/2 is based on MT-initiated negotiation of sleep periods. The MT requests the AP for a low power state and a specific sleep period. At the expiration of the sleep period, the MT searches for a wake up indication from the AP, and in the absence of that sleeps the next period, and so forth. The MT receives any pending data as the sleep period expires. Different sleep periods are supported depending on the requirements.
  • Notes:3.1 Physical LayerThe channeling is implemented by Orthogonal Frequency Division Multiplexing (OFDM) due to its excellent performance on highly dispersive channels. The basic idea of OFDM is to transmit broadband, high data rate information by dividing the data into several interleaved, parallel bit streams, and let each bit stream modulate a separate subcarrier. The channel spacing is 20 MHz, which allows high bit rates per channel yet has reasonable number of channels: 52 subcarriers are used per channel (48 subcarriers for data, 4 subcarriers tracking the phase for coherent demodulation). The independent frequency subchannels are used for one transmission link between the AP and the MTs. OFDM provides flexibility considering the realization of different modulation alternatives. Seven different physical layer modes (PHY modes) are specified in table 1.3.2 Data Link Control LayerThe Data Link Control (DLC) layer includes functions for both medium access and transmission (user plane) as well as terminal/user and connection handling (controlplane) . It consists of the following sublayers (see Figure 3):Medium Access Control (MAC) protocolError Control (EC) protocol (or Logical Link Control, LLC )Radio Link Control (RLC) protocol (also known as RCP ) with the associated signalling entities:DLC Connection ControlRadio Resource Control (RCC)Association Control Function (ACF)3.3 Convergence LayerThe Convergence Layer (CL) adapts service request from higher layers to the service offered by the DLC and converts the higher layer packets (SDUs) into a fixed size used within the DLC. This function makes it possible to implement DLC and PHY that are independent of the fixed network to which the HIPERLAN/2 network is connected. There are currently two types of CLs defined: cell based and packet based. The former is intended for interconnection to ATM networks, the latter is used in a variety of configurations depending on fixed network type.
  • Three main control functionsAssociation control function (ACF): authentication, key management, association, disassociation, encryptionRadio resource control function (RRC): handover, dynamic frequency selection, mobile terminal alive/absent, power saving, power controlDLC user connection control function (DCC): setup and release of user connections, multicast and broadcastConnection-orientedAfter completing association, a mobile terminal may request one or several DLC connections, with one unique DLC address corresponding to each DLC connection, thus providing different QoS for each connection
  • Notes:The MAC protocol is used for access to the medium (the radio link). The control is centralized to the AP which inform the MTs, when they are allowed to send data. The air interface is based on time-division duplex (TDD) and dynamic time-division multiple access (TDMA), which allows for simultaneous communication in both downlink and uplink within the same time frame, i.e. the MAC frame. The MAC frame format consists of four elements: Broadcast Channel (BCH), Down Link (DL), Up Link (UL), and Random Access (RA) . Except for the broadcast control, the duration of the fields is dynamically adapted to the current traffic situation. The whole DLC is based on scheduling efficiently MAC frame . The MAC frame and the transport channels form the interface between the DLC and the PHY.BCH (broadcast channel): enables control of radio resourcesFCH (frequency channel): exact description of the allocation of resources within the current MAC frameACH (access feedback channel): conveys information on previous attempts at random accessMultibeam antennas (sectors) up to 8 beams supportedA connection-oriented approach, QoS guaranteed
  • HIPERLAN/2 comprises the following functional entities:NOTE 1: The entities are taken from the Common Reference Model (CRM) [2g], and in case of any differencesCRM takes precedence.- Access Points (APs), which are the interface points to core networks. The AP may be decomposed intoInterWorking Functions (IWFs) and an Access Point Controller (APC) controlling one or multiple Access PointTransceivers (APTs).ETSI24 TR 101 031 V2.2.1 (1999-01)- Access Point Controllers (APCs) which present network-specific interfaces to the core network viaInterWorking Functions (IWFs) which comply with appropriate standards. The APC provides methods tofacilitate intra-AP handover and to control the routing of traffic through the HIPERLAN/2 network.- InterWorking Functions (IWFs), which translate the internal (B.2) interface of the HIPERLAN/2 network intonetwork specific interfaces of the external core network and translate the internal (B.1) interface of theHIPERLAN/2 network to higher protocol layers within the wireless terminal.- Access Point Transceivers (APTs), distributed so as to be able to provide coverage throughout the service areaof the Broadband Radio Access Network. These communicate via the air interfaces (W.1) with RadioTerminations (RTs).- Terminal Adapter (TAs). A terminal adapter comprises an RT and an IWF, and it presents connections forcustomers’ terminal.- Radio Terminations (RTs) are the radio parts of the TAs.The reference model is intended to align with the ITU IMT2000 and ETSI UMTS models of the radio access networkand identifies the following reference points:Reference point WI.1: internal proprietary or standard interface of the terminal node that supports relevant corenetworks.Reference point B.1: a service interface which is defined in terms of abstract services and parameters for the User,Control and Management planes of the HIPERLAN/2 air interface protocol stack. This interface is expected to be acommon definition for HIPERLAN/2 systems and for those HIPERACCESS systems which define interoperation via acommon air interface. It may not actually exist, and is therefore not required to be present in any real implementation,but forms the basis for specification and testing.Reference point W.1: defines the radio interface between the Access Point Transceiver and the Radio Termination. It isan interoperability interface that includes a standardized air interface and can be used as a radio coexistence interface.Reference point B.2: a service interface which is defined in terms of abstract services and parameters for the User,Control and Management planes of the HIPERLAN/2 air interface protocol stack. This interface is expected to be acommon definition for HIPERLAN/2 and those HIPERACCESS systems which define interoperation via a common airinterface. It may not actually exist, and is therefore not required to be present in any real implementation, but forms thebasis for specification and testing.NOTE 2: The Access Point may be considered to comprise one or more Access Point Transceivers connected to asingle Access Point Controller. The interface between these two elements is not necessarily visible and isnot specified.Reference point W.2: the interface is the supported standard interface to the relevant core network. It is in principlepossible to specify interfaces for all core networks that BRAN systems support (see subclause 7.1.4).Reference point B.3: an interface over which are specified the mechanisms for communicating with the ElementManagement System, specific to the management of the radio access network.
  • Hiperlan

    1. 1. Company LOGO HIPERLAN
    2. 2. Index Introduction Motivation Standards Reference Model Types HIPERLAN/1 HIPERLAN/2 HIPERACCESS HIPERLINK Comparison Between Types Failure Web references
    3. 3. What is HIPERLAN ? Hiperlan – High Performance Radio Lan WLAN Standard. It was initiated by the RES-10 group of the ETSI as a pan- European standard for high-speed wireless local networks. In ETSI the standards are defined by the BRAN project (Broadband Radio Access Networks).
    4. 4. Motivation for HIPERLAN Massive Growth in wireless and mobile communications. Emergence of multimedia applications Demands for high-speed Internet access Deregulation of the telecommunications industry
    5. 5. Standard Of HIPERLAN HIPERLAN is a European family of standards on digital high speed wireless communication. Spectrum : 5.15-5.3 GHz and the 17.1-17.3 GHz. Ensure the possible interoperability between different manufacturers. Defines a common air interface including the physical layer for wireless communications tools
    6. 6. HIPERLAN Reference Model
    7. 7. Proposed Types HIPERLAN 1 HIPERLAN 2 HIPERACCESS HIPERLINK
    8. 8. HIPERLAN /1 Characteristics Data transmission  point-to-point, point-to-multipoint, connectionless  23.5 Mbit/s, 1 W power, 2383 byte max. packet size Services  asynchronous and time-bounded services with hierarchical priorities  compatible with ISO MAC Topology  infrastructure or ad-hoc networks  transmission range can be larger then coverage of a single node (“forwarding“ integrated in mobile terminals) Further mechanism  power saving, encryption, checksums
    9. 9. HIPERLAN layers, services, and protocols MSAP HCSAP MSAP HCSAP HM-entity HC-entity HM-entity HC-entity MAC layer CAC layer PHY layerHP-entity HP-entity LLC layer HMPDU HCPDU data bursts MAC protocol CAC protocol PHY protocol MAC service CAC service PHY service MSDU MSDU HCSDUHCSDU
    10. 10. HIPERLAN /1 - Services and protocols CAC service  definition of communication services over a shared medium  specification of access priorities  abstraction of media characteristics MAC protocol  MAC service, compatible with ISO MAC and ISO MAC bridges  uses HIPERLAN CAC CAC protocol  provides a CAC service, uses the PHY layer, specifies hierarchical access mechanisms for one or several channels Physical protocol  send and receive mechanisms, synchronization, FEC, modulation, signal strength
    11. 11. HIPERLAN/1 Physical Layer Functions  modulation, demodulation, bit and frame synchronization  forward error correction mechanisms  measurements of signal strength  channel sensing Channels  3 mandatory and 2 optional channels (with their carrier frequencies)  mandatory • channel 0: 5.1764680 GHz • channel 1: 5.1999974 GHz • channel 2: 5.2235268 GHz  optional (not allowed in all countries) • channel 3: 5.2470562 GHz • channel 4: 5.2705856 GHz
    12. 12. HIPERLAN 1 - Physical layer frames LBR synchronization data0 data1 datam-1 . . . HBR
    13. 13. HIPERLAN 1 - CAC sublayer Channel Access Control (CAC)  assure that terminal does not access forbidden channels  priority scheme Priorities  5 priority levels for QoS support  QoS is mapped onto a priority level with the help of the packet lifetime (set by an application) • if packet lifetime = 0 it makes no sense to forward the packet to the receiver any longer • standard start value 500ms, maximum 16000ms • if a terminal cannot send the packet due to its current priority, waiting time is permanently subtracted from lifetime • based on packet lifetime, waiting time in a sender and number of hops to the receiver, the packet is assigned to one out of five priorities • the priority of waiting packets, therefore, rises automatically
    14. 14. HIPERLAN /1 MAC Layer Compatible to ISO MAC Supports time-bounded services via a priority scheme Packet forwarding  support of directed (point-to-point) forwarding and broadcast forwarding (if no path information is available)  support of QoS while forwarding Encryption mechanisms  mechanisms integrated, but without key management Power conservation mechanisms  mobile terminals can agree upon awake patterns (e.g., periodic wake-ups to receive data)  additionally, some nodes in the networks must be able to buffer data for sleeping terminals and to forward them at the right time (so called stores)
    15. 15. HIPERLAN/2 Features High speed transmission (54 Mbit/s) Connection-oriented Quality-of-Service (QoS) support Automatic frequency allocation Security support Mobility support Network & application independent Power save
    16. 16. HIPERLAN/2 Reference Model
    17. 17. Table 1: PHY modes defined for HIPERLAN/2.
    18. 18. Data Link Layer Functions
    19. 19. Data Link Layer Functions
    20. 20. MAC frame structure
    21. 21. Convergence Layer
    22. 22. Generic Model
    23. 23. HIPERACCESS HIPERACCESS provides outdoor, high speed (25 Mbit/s typical data rate) radio access, it provides fixed radio connections to customer premises and is capable of supporting multimedia applications. Other technologies such as HIPERLAN/2 might be used for distribution within the premises. HIPERACCESS will provide the wide area broadband access network connections to residential households and small businesses.
    24. 24. HIPERLINK Interconnecting high data rate sources such as (access) networks requires high bit rates and large channel capacities. HIPERLINK provides point-to-point interconnection at very high data rates, e.g. up to 155 Mbit/s over distances up to 150m.
    25. 25. Comparison Between Types HIPERLAN 1 HIPERLAN 2 HIPERLAN 3 HIPERLAN 4 Application wireless LAN access to ATM fixed networks wireless local loop point-to-point wireless ATM connections Frequency 5.1-5.3GHz 17.2-17.3GHz Topology decentralized ad- hoc/infrastructure cellular, centralized point-to- multipoint point-to-point Antenna omni-directional directional Range 50 m 50-100 m 5000 m 150 m QoS statistical ATM traffic classes (VBR, CBR, ABR, UBR) Mobility <10m/s stationary Interface conventional LAN ATM networks Data rate 23.5 Mbit/s >20 Mbit/s 155 Mbit/s Power conservation yes not necessary
    26. 26. Comparison Between 802.11 and HIPERLAN/2 802.11 802.11b 802.11a HiperLAN2 Spectrum (GHz) 2.4 2.4 5 5 Max PHY rate (Mbps) 2 11 54 54 Max data rate, layer 3 (Mbps) 1.2 5 32 32 MAC CS CSMA/CA Central resource control/TDMA/TDD Connectivity Conn.-less Conn.-less Conn.- less Conn.-oriented Multicast Yes Yes Yes Yes QoS PCF (Point Control Function) PCF PCF ATM/802.1p/RSVP/Diff Serv (full control) Frequency selection Frequency-hopping or DSSS DSSS Single carrier Single carrier with Dynamic Frequency Selection Authentication No No No NAI/IEEE address/X.509
    27. 27. Comparison Between 802.11 and HIPERLAN/2 802.11 802.11b 802.11a HiperLAN2 Encryption 40-bit RC4 40-bit RC4 40-bit RC4 DES, 3DES Handover support No No No To be specified by H2GF Fixed Network Support Ethernet Ethernet Ethernet Ethernet, IP, ATM, UMTS, FireWire (IEEE 1394), PPP Management 802.11 MIB 802.11 MIB 802.11 MIB HiperLAN/2 MIB Radio link quality control No No No Link adaptation
    28. 28. Failure Due to competition from IEEE 802.11, which was simpler to implement and made it faster to the market. No Support of packets and frames with different size, and detection of the data frame type to be sent. No proper Generation of the appropriate sequence of control messages.
    29. 29. Web References http://en.wikipedia.org/wiki/HiperLAN http://www.cwins.wpi.edu/wlans96/documents/wsh96_wil kinson.pdf http://www.wirelesscommunication.nl/reference/chaptr01 /wrlslans/hiperlan.htm http://www.comlab.hut.fi/opetus/Summer_School_2004/ material/HIPERLAN.pdf http://www.ustudy.in/node/1738
    30. 30. Company LOGO

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