HIPERLAN

HIPERLAN is the generic term for the standards HIPERLAN / 1, HIPERLAN / 2, HIPERACCESS (formerly HIPERLAN / 3) and HIPERLINK (formerly HIPERLAN / 4). The standards describe an alternative technology for the IEEE 802.11 standard to establish radio networks between computers. They were defined by the Working Group Broadband Radio Access Network ( BRAN) ETSI ( European Telecommunications Standards Institute ) from 1996.

HIPERLAN is an acronym and stands for High Performance Radio Local Area Network.

The standards build on each other and are each further developments.

The standards have not been able to put on the market, even though they contain interesting technical concepts. In contrast to the IEEE 802.11 standard HIPERLAN does not use signaling in the unprotected ISM band at 2.45 GHz and used in the development phase the frequency range from efficient. The lower layer were taken to a large part in IEEE 802.11a.

• 2.1 Radio Link Control
• 2.2 Error Control
• 2.3 MAC
• 2.4 Convergence Layer
• 2.5 Interaction with other networks

HIPERLAN / 1

HIPERLAN / 1 was completed in 1996 by the BRAN working group. It looks Data transfer rates up to 23.5 Mbit / s at 5 GHz (specifically 5120-5300 MHz), where among other devices are operated by the WLAN standard IEEE 802.11a. It reaches distances in typical office environments of about 50 meters, but implements a method, via the node (network) can forward data packets to cover larger areas.

For mobile use, are ideal for wireless networks, power saving mechanisms have been implemented.

HIPERLAN / 1 shares its frequency range in 5 channels.

The structure is modeled on the ISO OSI reference model, but the data link layer (data link layer ) is divided into two sublayers: the MAC layer (Medium Access Control, not to be confused with the MAC address) and the CAC - layer (Channel Access Control).

MAC layer

The MAC layer provides next service primitives to send and receive data and functions to encrypt and energy saving features. It can be assigned to data packets five priorities. For this priority, the backoff time is calculated, which is serviced during shipment of the package.

CAC layer

CAC layer controls the access to the radio channel. She uses the EY- NPMA method ( Elimination Yield Non- Preemptive Priority Multiple Access):

With a free channel for random time to wait. If in time the medium is not busy, the station sent. If the channel is occupied, however, in an existing three -phase process, the next station is selected:

Prioritization phase

The prioritization phase, a burst frame is after a constant waiting time, which was multiplied by the priority of the packet sent. All transmitters whose packets have a lower priority, so switched off.

Contention - phase

Because this allows multiple transmitters can remain, more stations are in the two- part phase contention phase initially screened via an elimination bursting. In this case, each remaining station waits a random time, and then transmits a burst of. The stations that were involved in the recent burst, then compete in a yield Listening: Who first emits a burst there may transfer data.

Transmission phase

The transfer itself takes place in the transmission phase. Is a unicast packet transmitted thereby, a part of the transmission stage and the reception confirmation.

Theoretically, it is conceivable that also occur due to this complicated process collisions on the media. However, it is practically very unlikely.

Hidden terminal

Under a Hidden terminal refers to a station that is part of the transmitter in the dead spot in radio networks. This problem is solved in the IEEE 802.11 standard through the RTS / CTS method. HIPERLAN takes a different approach: On the one hand, the header of the HIPERLAN packets that are transmitted at a lower data rate, even outside the actual radio range are still to be determined, on the other hand recognize stations themselves that they are a "hidden terminal " when they in the contention phase lose to another station, but not noticed the subsequent data transmission. For the "hidden terminal ", the waiting times are then raised to prevent collisions.

Forwarding data packets

In HIPERLAN / 1 stations can be marked as " forwarders " and "Non - Forwarders". Forwarders pass data packets for other stations that are in the dead spot of the transmitter, but within easy reach of the station. Manage The stations each for a list of " Forwarders ", which are responsible for a goal. For multicast or broadcast packets only a smaller amount of " Forwarders " are responsible, called multipoint relays.

Power saving method

There are two methods to choose from: On the one hand, a receiver can turn off its transmitter and reduce the received power. Because headers are sent at a reduced data rate, the recipient can still decrypt and know whether he is meant. If so, the Doze mode is terminated.

Alternatively, a defined station, the answer " p- supporter ", also known packages for a disabled beneficiary, "p -Saver ". p- supporter and p- Saver synchronize themselves with respect to their waking hours in which the p- supporter forwards the data packets.

HIPERLAN / 2

The successor of HIPERLAN / 1 was adopted in 2000. The major extensions were added features that make it a wireless access network for wide area networks can be used. Among other things, a coupling to UMTS and Wireless ATM (Wireless ATM) has been thought. Quality of service parameters can be defined for the use of multimedia applications.

HIPERLAN / 2 can use the same frequencies as HIPERLAN / 1 and in addition the range 5470-5725 MHz. It supports data rates up to 54 Mbit / s (similar to IEEE 802.11a ). The ranges are similar: 30 meters inside buildings and up to 150 meters outside.

For HIPERLAN / 2 a centralized was additionally fashion, corresponding to the infrastructure mode in the 802.11 standard and a direct mode that corresponds to the ad- hoc mode, defined.

HIPERLAN/2-Standard in another layer model as in HIPERLAN / 1 is used. The physical layer is the same, however, the data link layer to a MAC layer, the Radio Link Control layer (RLC ), and the error control layer ( EC ) are arranged in parallel, divided. Above these layers, a Convergence Layer is defined.

Radio Link Control

The radio link control layer defines encryption method, handover mechanisms, so the handoff from one base station to another, power management functions and service primitives for opening and closing connections and to send broadcast and multicast messages.

Error Control

The error control layer ensures error-free data transmission. This is the so-called ARQ ( Automatic Repeat Request) resorted, in which a notice is required whenever an error occurs.

MAC

The structure of the MAC layer is described above.

Convergence layer

The Convergence Layer handles the fragmentation of large data packets into smaller ones for transportation and provides two transmission method is: the cell-based and packet-based transmission. The former transmits analogous to the ATM packets of fixed length, the latter packets of different size and is therefore compatible with Ethernet.

Interaction with other networks

HIPERLAN / 2 is called interconnection networks between different HIPERLAN networks Core Network. A core network is usually a wide area network.

Alternative: HIPERACCESS

HIPERACCESS represents an alternative to wired method to bridge the last mile of a wide area network to a local loop. It provides data rates of 23 Mbit / s and a range of up to 5 kilometers.

HIPERLINK

About HIPERLINK fixed point-to- point connections with data rates up to 155 Mbit / s and a range of up to 150 meters can be set up.