Wireless Local Area
Networks: Standardization Aspects
Contributed by Torben Rune, Netplan(
1999, updates 2004).
The need for bandwidth in LAN based comunication equipment has been constantly
rising. New user-friendly technology such as graphics based documents and program-
interfaces have strained many existing LAN infrastructures and the emergence
of real time high definition video transmissions are sure to strain these infrastructures
further. The new wireless technology must be able to meet tomorrow’s needs
for bandwidth.
With the need for bandwidth in
wireless communications also come the need to address the
problems of quality of the transmission service. Especially video
signals are very prone to drastic reductions of quality once the
bandwidth drops even if only momentarily. Once the bandwidth
drops, the video frame can freeze and the sound and the video
signals might loose its synchronization.
The clear winner for wireless standards is the IEEE
802.11 series of standards.
- In recognition of the importance and
potential of using DECT for wireless LAN access, the DECT
standards committee established a working party in August 1993,
RES-03/DATA, to develop the DECT Data Services Profiles. The
first standard in this family of profiles contains interworking
conventions to Ethernet and Token Ring. This standard will be the
first pan-European wireless LAN standard that caters for
interoperability of different manufacturers equipment. It
supports net throughput data rates of up to 552 kbit/s using a
single radio. The standard was finalized in February 1994 and is
expected to be approved in mid 1995. Other standards are expected
to cover interworking with services such as Fax, Modem, RS-232
and File Transfer.
- Another standardization effort within ETSI
is HIPERLAN (High Performance Radio Local Area Network). The
committee responsible for HIPERLAN is RES-10 which has been
working on the standard since November 1991. CEPT has allocated
two frequency bands for HIPERLAN, one band between 5.15 and 5.30
GHz and one band between 17.1 and 17.3 GHz. The standard for the
5 GHz band was finalized in January 1995 and is expected to be
approved in the beginning of 1996. Work on the 17 GHz standard
has recently started.
The 5 GHz HIPERLAN standard has specified a
raw bit rate of approximately 24 Mbit/s using a MAC protocol
supporting multi-media communication. The 17 GHz version is
expected to offer an ATM 155 Mbit/s compatible bit rate. Both
standards will cater for interoperability of different
manufacturers' equipment and are aimed to work efficiently with
ATM cell transfer. Products compliant to the HIPERLAN 5 GHz
standard shall be possible to implement on a PCMCIA Type III card
and should be available on the market 1997.
Seen from the perspective of the
data communications industry, HIPERLAN is the most interesting of
the coming standardized wireless technologies. HIPERLAN has the
highest data rate, and its design allows for a variety of
applications.
- Within IEEE, the 802.11 committee is set the
standard for wireless LAN products using the 2400-2483.5 MHz frequency band.
This standard are also used in Europe since its European version applies to
the ETS 300 328 standard. The IEEE 802.11 standard also caters for interoperability
of different manufacturers' equipment offering a raw bit rate of 1 or 2 Mbit/s.
The first drafts appeared in 1995.
- A different but interesting approach is the ISM band regulation. Very little is being standardized
but entrepreneurs can to a large extent experiment with proprietary solutions.
The Global Picture
One of the major problems
concerning this technology is standardization. The problems
concerning standardization are among other things making the best
use of a scarce resource - the radio spectrum while at the same
time making the standard attractive enough to use so the market
can grow.
A number of global and national
standardization initiatives have taken place in wireless
technology.
-
The global organization IEEE has
been working 6 years on the 802.11 standard, which is almost ready to be adopted. The 802.11
standard accommodates both infra-red and spread-spectrum radio
with a protocol CSMA/CA (carrier-sense multiple access/collision
avoidance) similar to CSMA/CD used in the Ethernet.
- In the US a new standard called
NII/SUPERnet has been introduced concerning wireless
communications in the 5.150-5.350 GHz and 5.725- 5.875 GHz band.
- JAPAN has introduced the SPDCS
standard ("Small Power Data Communication System), which
operates at 2.4 GHz. JAPAN has also introduced standards in the
19 GHz spectrum - Light Wireless Communications System (LWCS) and
in the 30-300 GHz spectrum - Millimeter Wave Wireless LAN (MWWL).
- Europe has introduced the
Digital European Cordless Telecommunications (DECT) standard
(which is not a LAN standard) and has just introduced the
HIPERLAN standard after several years of work.
- The networking industry itself
has taken an important initiative under the name of WLANA,
(members are 3Com, Aironet Wireless Communications, AMD, Digital,
Harris Semiconductor, IBM, Lucent Technologies, Norand, Proxim,
Raytheon Electronics, Symbol Technologies, Windata and Xircom).
WLANA promises 'to promote increased awareness and knowledge of
wireless LANs among potential customers, independent software
vendors and systems integrators'.
Frequency Regulations
The Netherlands (1995)
Three categories are being distinguished:
- For non-critical services with bit rates up to 250 kbit/s, CEPT has allocated frequencies in the 2.4 - 2.4835 GHz ISM band in recommendation T/R 10-01.
ETSI published standard ETS 300 328.
the output power is restricted to 100 mW e.i.r.p.
A type approval is required.
Initially, radio LAN's had to be used indoors only.
Radio LANs in the 2452-2470 MHz band are allowed outdoors as well,
but require a user license.
Particularly the radiation in vertical direction has to be reduced, by using an appropriate antenna diagram.
- For reliable services with bit rates up to 2 Mbit/s DECT standards are recommended
in 1.8 - 1.9 GHz band.
Relevant Common Technical Regulations (CTR) of the European Commission are
CTR 6, CTR 10 and CTR 11, all addressing DECT.
- HIPERLAN: Advanced computer applications with rates up to 20 Mbit/s in the 5, 17 and 61 GHz bands. ETSI issued Technical Report ETR 069 (Service and Facilities)
and ETR 133 (HIPERLAN System Definitions).
