Transcript
Federal Department of the Environment, Transport, Energy, and Communication DETEC Federal Office of Communications OFCOM
Factsheet Wireless Local Area Networks (WLAN) & Radio Local Area Networks (RLAN)
Version 2.5c / 17. 03. 2006
Federal Office of Communications Zukunftstrasse 44, 2501 Biel Tel. +41 32 327 55 11, Fax +41 32 327 55 58 www.bakom.ch
Factsheet RLAN 2.5c
2
Contents 1.
INTRODUCTION.............................................................................................................................................. 3
2.
WHAT IS MEANT BY A RADIO LOCAL AREA NETWORK (RLAN)? ................................................. 3
3.
PRINCIPLE OF AN RLAN .............................................................................................................................. 3 3.1. 3.2. 3.3.
4.
SECURITY ......................................................................................................................................................... 5 4.1. 4.2.
5.
ACCESS POINT (AP) ..................................................................................................................................... 4 MOBILE TERMINAL (MT)............................................................................................................................. 4 SERVICES ..................................................................................................................................................... 5
CONFIDENTIALITY ........................................................................................................................................ 5 ELECTROMAGNETIC COMPATIBILITY AND THE ENVIRONMENT ..................................................................... 6
APPLIED STANDARDS................................................................................................................................... 6 5.1. DECT-BASED RLANS ................................................................................................................................. 6 5.2. RLAN IN THE 2.4 GHZ BAND ....................................................................................................................... 6 5.2.1. RLANs according to IEEE 802.11 ...................................................................................................... 6 5.2.2. RLANs according to IEEE 802.11b .................................................................................................... 7 5.2.3. RLANs according to IEEE 802.11g .................................................................................................... 7 5.2.4. HomeRF / SWAP ................................................................................................................................ 7 5.2.5. Bluetooth (future IEEE 802.15, WPAN) ............................................................................................. 7 5.3. RLAN IN THE 5 GHZ BAND .......................................................................................................................... 8 5.3.1. RLANs according to IEEE 802.11a .................................................................................................... 8 5.3.2. RLAN's according to IEEE 802.11h ................................................................................................... 8 5.3.3. HIPERLAN/1 ...................................................................................................................................... 8 5.3.4. HIPERLAN/2 ...................................................................................................................................... 8 5.3.5. Comparison of 802.11x, HIPERLAN/2 and HomeRF....................................................................... 10 5.3.6. HiSwan ............................................................................................................................................. 10
6.
STANDARDS, FREQUENCIES AND TRANSMITTING POWERS FOR RLANS IN SWITZERLAND .............................................................................................................................................. 11 6.1.
THE ERC/DEC(04)08 ON A VIEW .............................................................................................................. 12
7.
RLAN AIR INTERFACES ............................................................................................................................. 13
8.
LEGAL BASIS ................................................................................................................................................. 15
9.
APPENDIX ....................................................................................................................................................... 15 9.1. 9.2.
FURTHER SOURCES OF INFORMATION ......................................................................................................... 15 ABBREVIATIONS......................................................................................................................................... 16
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1. Introduction The RLAN factsheet provides an introduction and an overview of wireless networks for the interested public.
2. What is meant by a Radio Local Area Network (RLAN)? Nowadays, personal computers (PCs) in offices are generally networked. In most cases this networking is achieved by means of a cable which connects the PC with the network connection socket in the vicinity of the PC. Depending on the network and controller used, data transmission rates of 10 Mbit/s, 100 Mbit/s and up to 1 Gbit/s can be achieved. For some time, therefore, there has been a desire to liberate users from this cable. The advantages are obvious: no costly cabling work has to be carried out in offices and a PC or laptop can be used anywhere in the office. As a result of the possibilities of information technology and constant progress in semiconductor integration, it has now become possible to realise this desire. Wireless networks at prices affordable for everyone have recently become available. The terms Radio Local Area Network (RLAN) and Wireless Local Area Network (WLAN) mean the same thing.
3. Principle of an RLAN Internet
AP = Access Point Router
Server
Laserdrucker
MT = Mobile Terminal Ethernet
Laserdrucker = Laser printer
(a)
Access Point, AP
Access Point, AP
(a)
Mobile Terminal, MT
(b) Mobile Terminal, MT
By means of Radio LAN's, connections can be established between the Mobile Terminal and the Access Point (a). This makes the Mobile Terminal part of the Ethernet, and allows it to access all connected devices, such as printers, servers, internet access, etc. If no infrastructure exists, direct connections for data exchange (b) can be set up between multiple Mobile Terminals.
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In this context, the range of the wireless link depends of several factors, such as:
transmitting power
interference (with other users, can be optimised by network design)
data transmission rate (type of modulation)
the environment (inside or outside the house, line of sight link).
The following conditions apply:
the higher the data transmission rate, the shorter the range
the more obstacles between the wireless users and the Access Points, the shorter the range
the more simultaneously active users, the lower the data transmission rate
This explains why the data transmission rate drops at greater distances, or when there is reciprocal interference. The data transmission rate, moreover, refers to the maximum data transmission rate in both directions. This data transmission rate is split between the individual users using this channel. The more users on this channel, the lower the data transmission rate for each individual user. In addition, overhead and access losses have to be taken into consideration, which lead to a reduced effective data transmission rate.
3.1.
Access Point (AP)
The Access Point is the switching point in the RLAN. The wireless users are connected via the Access Point to the world of fixed networks, i.e. the Access Point is normally connected to the Ethernet. In many cases, other functions are integrated in the Access Point, e.g.: •
ADSL / cable modem
•
10/100 MHz LAN link
•
Router
•
Print server
Additional software functions may also be provided by the Access Point, such as: •
Firewall
•
Access control
•
Password protection
•
Encryption.
3.2.
Mobile Terminal (MT)
Users with laptops are connected by a PCMCIA card and those with a desktop PC are connected by a separate PCI card or a PCI holder card, which in turn can take a PCMCIA card. For laptops, the size of PCMCIA card is normally Type 2. The subscriber connection communicates across the air interface with the Access Point, from where connections with the wirebound Ethernet are established. Ad hoc functions generally also provide the possibility of exchanging data directly, without an Access Point. The Mobile Terminal is actually “only” a portable terminal, since the systems are not designed for mobile operation. The various standards, however, permit without exception handover from one base station to the next. 17. 03. 2006
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The first roaming platforms between RLAN / GSM / UMTS are currently under development.
3.3.
Services
It is not possible to speak of actual services in the case of wireless LANs. Commercially available systems are used for wireless connection of PCs to the Ethernet. For the user, these systems are fully transparent, i.e. it makes no difference whether he or she is connected to the network via a cable or via a wireless link. Thus all applications and services (file transfer, access to printers, the internet, ...) which are available on the network are available without limitation (subject to the restricted data transmission rate). Current offerings are limited to LAN applications and internet access, with all its facilities. Other services, such as telephony, must be provided by a service provider. Systems are currently being developed which implement access control via a GSM SIM card, offering the possibility of billing the services concerned to a mobile telephone account.
4. Security 4.1.
Confidentiality
In the case of WLANs, security is a moot point, since access to the air interface is entirely possible without on-site access. The range is approx. 100 metres, or approx. 300 metres maximum. The encryption algorithms which are applied are described in chapter 5.3.5. However, it has recently been shown that the encryption can be broken – given appropriate effort. Software tools already exist to permit hacking into the encryption procedure. The encryption techniques work on individual or multiple layers of the OSI model, using different methods. There is a wide range of such methods. The widely used WEP (Wired Equivalent Privacy) encryption method, which uses the RC-4 algorithm, has proved to be insecure. The method uses a constant WEP key and a variable initialisation vector (IV) transmitted on the radio channel in clear text. This vector is only 24 bits long and is generated randomly. Consequently the same effective key occurs relatively frequently for different packets. Long-term monitoring and observation make it possible to determine the constant WEP key. Cracking tools exploit precisely this weakness. A further development of WEP, known as WEP2, uses a 128-bit initialisation vector and periodic renewal of the previously constant WEP key. This extension is considered to be not much more secure and has therefore already been rejected. WEPplus is a new, more secure but proprietary development. This encryption method is more robust in that a key generation algorithm is used which avoids weak keys. It is therefore more difficult to crack the key by monitoring the radio channel. Nonetheless, it is only a matter of time until a corresponding software tool becomes available. WEPplus is fully backward-compatible with earlier WEP-WLANs. Fast Packet Keying works on a similar principle and was developed by RC4's inventors, RSA Data Security. For each data packet, this algorithm generates a 104-bit packet key and a 24-bit initialisation vector. This avoids the repeated use of a key with the same initialisation vector, one of the principal problems with WEP. Fast Packet Keying is also designed for compatibility with existing WLAN hardware and can be retrofitted using driver and firmware upgrades. One of the most promising solutions currently is IPSec. IPSec is an encrypted TCP/IP protocol and requires data traffic on the network to use the IP protocol exclusively. In most cases this is not a problem, since TCP/IP is omnipresent because of the spread of the internet. IPSec is one of the most secure methods of encryption for RLANs, but requires careful and somewhat complex configuration. Unfortunately, of all the techniques, IPSec involves the greatest increase in overhead and consequent reduction in data transmission rate.
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At network access level, in addition to the encryption algorithms, the customary security mechanisms such as logon with user name and password, computer account (identification of a PC by its MAC address) and domain security features are active. All security systems, whether regarded individually or combined, do not offer 100% protection. Further information can be found on the internet1.
4.2.
Electromagnetic compatibility and the environment
The Decree on Protection from Non-ionising Radiation (Verordnung über den Schutz vor nichtionisierender Strahlung – NISV2) is in principle also applicable to wireless networks. Because of an RLAN's low transmitting power, no equipment values are laid down in the decree for these installations. Only the emission limits are in play. RLAN's, which are operated
according to the permitted maximum radiated power, comply with these limits from a range of about 15 cm from the antenna. The regulations of individual cantons must, however, be complied with.
5. Applied standards 5.1.
DECT-based RLANs
One simple solution is the application of the DECT standard to link wireless users. In this case, the Access Point is normally provided with an ISDN port, via which data is routed to the internet. Using ISDN trunking techniques, data transmission rates up to a maximum of 128 kbit/s from and to the internet can be achieved. DECT is a standard which has proved itself over some years; it is very robust, powerful and has since become inexpensive. It additionally supports handover between base stations, in so far as these are connected by a cable. The DPRS (DECT Packet Radio Service) protocol allows effective data transmission rates of up to 552 kbit/s by trunking twenty-three 24 kbit/s slots, which can be distributed asymmetrically to the up- and downlink. DPRS supports V.24, Ethernet and ad hoc sessions. Attempts are in progress to develop the DECT standard with data transmission rates up to 2 Mbit/s. DECT belongs to the IMT-2000 family, of which UMTS is also a member.
5.2.
RLAN in the 2.4 GHz band
5.2.1. RLANs according to IEEE 802.11 The IEEE established the IEEE 802.11 standard in 1997. It permits a data transmission rate of 1 or 2 Mbit/s and works in the ISM frequency band of 2.4 GHz. In this frequency range (2400 2483.5 MHz) 79 channels, each with 1 MHz bandwidth, are available. These channels are each occupied briefly (for a few ms) using the Frequency-Hopping-SpreadSpectrum System (FHSS); communication then takes place on a different channel. To achieve this, the transmitter and receiver must occupy the channels synchronously according to a preset table. The same standard also describes a method with a spread of signal bandwidth by a factor of 11. This so-called Direct-Sequence-Spread-Spectrum (DSSS) method distributes the energy used for the transmission of information over 22 MHz. Multiple connections can then take place simultaneously on the same channel. For this type of technique, there are 13 carrier frequencies channels with a 5 MHz channel arrangement available in the 2400 - 2483.5 MHz frequency range. 1
http://www.securityfocus.com , http://www.sans.org
2
http://www.admin.ch/ch/d/sr/c814_710.html 17. 03. 2006
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In order to ensure trouble-free operation of different RLANs on the same site, e.g. only channels 1, 7 and 13 should be occupied; otherwise the channels overlap. All subsequent IEEE 802.11 standards are based on the same MAC layer; only the data transmission rates or, additionally, the frequency range change.
5.2.2. RLANs according to IEEE 802.11b In 1999 the data transmission rate was increased to 5.5 or 11 Mbit/sec by modifying the type of modulation. The increase in data transmission rate is achieved by the use of CCK spread codes (Complementary Code Keying), a class of sophisticated spread codes. It is accompanied by a reduction in range. The data transmission rates defined in the IEEE 802.11 standard are also supported. The IEEE 802.11b standard works at the higher data transmission rates exclusively with DSSS. Radio LANs according to this standard are currently the most widespread. Products which are identified by the Wi-Fi3 Logo are compatible with other Wi-Fi devices, regardless of the manufacturer.
5.2.3. RLANs according to IEEE 802.11g An extension of the 802.11b standard was produced under this designation. With this standard it is expected to achieve a minimum 20 Mbit/s in the 2.4 GHz ISM band. The higher data rates are achieved by extending the air interface (PHY) by two modulations/coding types. The extension bears the name Extended-Rate-PHY (ERP). The following are the new modulations/coding types: •
ERP-PBCC: the user data are coded with the aid of a convolution coder with 256 states and then modulated using 8PSK. In addition the preamble and header are abbreviated in time, producing gross bit rates of 22 and 33 Mbit/s in this mode.
•
DSSS-OFDM: this type of modulation is a hybrid of DSSS and OFDM. A shortened preamble and header are modulated and spread as in standard IEEE802.11b BPSK. The user data are modulated by OFDM on 48 sub-carriers. Depending on the data rate, the sub-carriers BPSK, QPSK, 16QAM or 64QAM are modulated. Varying the subcarrier modulation type and the code rate (1/2, 2/3 or 3/4) produces gross bitrates of 6, 9, 12, 18, 24, 36, 48 or 54 Mbit/s.
The 11g standard is compatible with equipment to IEEE802.11 and 11b. In addition, the OFDM parameters are adapted to those of RLAN systems in the 5GHz band; this allows the manufacture of WLAN chipsets which support the 2.4 and 5 GHz band.
5.2.4. HomeRF / SWAP The HomeRF working group, with the aim of forming an alliance similar to WiFi, was wound up at the beginning of 2003.
5.2.5. Bluetooth (future IEEE 802.15, WPAN) Bluetooth (BT) is designed for bridging short distances (up to 10 metres at 0 dBm EIRP and up to 150 metres at 20 dBm EIRP) with data transmission rates up to 1 Mbit/s. There are three power classes of devices, 0, 4 and 20 dBm (1, 2.5 and 100 mW). Bluetooth devices are expected to be used typically in a Wireless Personal Area Network (WPAN). A WPAN embraces all the wirelessly connected devices (mobile telephone, organiser, laptop, printer, camera, multimedia projector, ...) in close proximity to a person. The goal is to simplify the connection of the above-mentioned devices.
3
http://www.wirelessethernet.org/ 17. 03. 2006
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Bluetooth connections are powerful and robust point-to-point links, with the possibility of operating several connections simultaneously. One possibility is even multi-hop connections, which extend the local spread of a PAN, using intermediate devices as repeaters. Unlike WLAN, which allows mobile access to the intranet or the internet, Bluetooth is designed as a universal wireless adapter (e.g. serial interface). The wirebound counterpart would be the USB interface. The first products are wireless headsets for mobile phones, plus printer and video camera connections to PCs and laptops. Bluetooth is especially optimised for low energy consumption. Since Bluetooth, like IEEE802.11 / IEEE802.11b, works in the 2.4 GHz ISM band, the systems may cause reciprocal interference. Capacity reduces as traffic increases. This is a disadvantage which must be taken into consideration in bands which are not subject to licensing.
5.3.
RLAN in the 5 GHz band
In the 5 GHz band it is permissible to operate radio LANs in Switzerland which comply with the EN 301 893 standard. Up-to-date information is provided at 4:
5.3.1. RLANs according to IEEE 802.11a Radio LAN's according to IEEE 802.11a work in the 5 GHz band. They offer data transmission rates of 6 Mbit/s to 24 Mbit/s and optionally up to 54 Mbit/s. The channel arrangement is 20 MHz. The standard provides for three frequency bands with different transmitting powers (see chapter 7). Unfortunately, RLANs according to IEEE 802.11a lack some features (e.g. automatic channel selection and transmitting power regulation). However, the use of systems to this standard is possible with certain restrictions. More detailed information is available from OFCOM4.
5.3.2. RLAN's according to IEEE 802.11h As a result of the revision of the IEEE 802.11a standard to include TPC and DFS, there is now nothing to prevent the use of these RLANs in Europe.
5.3.3. HIPERLAN/1 The Hiperlan/1 standard was published by ETSI in 1998 and represents a wireless replacement for the Ethernet. The 2 possible data transfer rates are 1.47 Mbit/s and 23.5294 Mbit/s. Despite various announcements, devices have never been produced for this standard.
5.3.4. HIPERLAN/2 HIPERLAN/2 was the successor to its unsuccessful predecessor, HIPERLAN/1. HIPERLAN/2 is orientated more towards the infrastructure and connections. This standard connects portable devices with broadband networks based on TCP/IP, ATM, Ethernet, FireWire, multimedia applications and, in future, UMTS. The Tunnelling Protocol PPP is also supported. As the HIPERLAN/2 standard supports Quality of Service (QoS) it therefore forms the important foundation for transport of protocols which require QoS (e.g. ATM). HIPERLAN/2 provides for two different network architectures: with Access Point, which corresponds to a cellular architecture, or as an ad hoc network, which allows point-to-point connections. The cellular structure is typically used in the professional sector and is permanently installed. In this mode data exchange always takes place via the Access Point. In ad hoc mode, one of the portable devices is dynamically selected as the Central Controller (CC), which above all offers the same QoS support as the Access Point. In this mode, data exchange between the portable devices takes place directly; the CC retains control.
4
http://www.bakom.ch/themen/geraete/00568/01232/index.html?lang=en 17. 03. 2006
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The standard supports both a degree of user mobility within the local infrastructure and handover between adjacent cells. In an initial phase, the handover function will be limited to the architecture with Access Points. The HIPERLAN/2 standard specifies a total of 19 channels in a 20 MHz channel arrangement with a -20 dBc bandwidth of 22 MHz and is located in two frequency ranges, 5150 - 5350 MHz (8 channels) and 5470 MHz - 5725 MHz (11 channels). Data transmission rates of 6, 9, 12, 18, 27, 36 and 54 Mbit/s are available. Channel selection is dynamic, i.e. the system searches for an interference-free channel. The data transmission rate is adapted to the respective quality of the connection. If interference is detected, the channel is changed. Control over this is exercised by the Access Point or the CC. The decision to change the frequency channel or type of modulation (see details below) is based on monitoring of all devices participating in communication. As far as use of the devices in Switzerland is concerned, this means that channel selection has to be restricted to the lower three channels. Consequently, the efficiency of dynamic channel selection is considerably reduced. The physical layer of HIPERLAN/2 is based on the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme. The sub-carrier modulation types employed are, depending on the respective data transmission rate: BPSK, QPSK, 16QAM and 64QAM. This is dynamically adapted to the transmission quality (BER, PER) at the time. 64QAM is an optional type of modulation, as the data transmission rate of 54 Mbit/s is also optional. It is therefore up to the manufacturer to implement 64QAM in his equipment. All other modulation types on the other hand are prescribed by the standard. A summary of the types of modulation is provided in chapter 7. The error protection used in HIPERLAN/2 is based on an ARQ (Automatic Repeat Request) scheme. The receiver informs the transmitter which packets it has received correctly and which it has not. The transmitter repeats the packets not sent correctly, as long as these are within a maximum validity period. The validity period depends on the application. This ensures that transmission is not impeded by data which is no longer required. Efficient powersave modes are another feature of the HIPERLAN/2 standard. These take into account the fact that many RLAN cards are used in battery-powered devices. Regulation of transmitting power is also associated with this feature.
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5.3.5. Comparison of 802.11x, HIPERLAN/2 and HomeRF The following table compares the features of standards 802.11, 802.11b, 802.11g, 802.11a/h and HIPERLAN/2. The parameters of the air interface are given in chapter 7. Standard max. gross bitrate [Mbit/s] max. net bitrate [Mbit/s]
802.11
802.11b 802.11g
802.11 a/h
HIPERLAN/2
2
11
54
54
54
~1.2
~8
~30
~30
~30
QoS Support
Point Coordination Function (not ATM-compatible)
ATM/802.1p (ATMcompatible)
Authentication
with or without Shared Key Authentication
NAI/IEEE address/X.509
Encryption
WEP
DES, 3DES
Handover Support
no1)
no2)
Ethernet
Ethernet, IP, ATM, UMTS, FireWire
Compatibility
1) Yes in the case of signalling with IAPP or a proprietary protocol via a fixed network connection or wireless 2) Yes in the case of signalling is defined by HIPERLAN/2 Global Forum (H2GF) via a fixed network connection or wireless
5.3.6. HiSwan HiSwan is an abbreviation for “High Speed Wireless Access Network”. This is a Japanese standard for RLANs which should be compatible with Hiperlan/2. Equipment according to this standard has never appeared and the activities were stopped.
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6. Standards, frequencies and transmitting powers for RLANs in Switzerland Wireless networks which meet the following standards may be operated in Switzerland: •
DECT
•
In the 2.4 GHz band, all devices fulfilling the standard EN 300 328-2, such as IEEE 802.11, IEEE 802.11b and IEEE 802.11g.
•
In the 5 GHz band, all devices fulfilling the standard EN 301 893 and falling under the framework of ERC/DEC(04)085 (see Decides 1.-6. and chapter 6.1). This includes for instance IEEE 802.11h and Hiperlan/2, and with certain measures also IEEE 802.11a and Hiperlan/1 (see chapter 7)
•
Bluetooth
The licence-free frequency ranges released for RLAN systems are in the 2.4 GHz- and 5 GHz frequency band. In these bands there is no protection from interference. The following frequency ranges and transmitting powers are available in Switzerland for RLAN systems:
Frequency band
Frequency range
max. EIRP [mW]
2.4 GHz band (ISM band)
2400 - 2483.5 MHz
100
5 GHz band
5150 - 5350 MHz a)
200
5-GHz-band
5470 – 5725 MHz
1000
a) RLAN according to standard EN 301 893 and restricted to indoor applications (indoor use) The technical interface requirements define one of the conditions for market access for radio equipment. They describe the frequency characteristics and the radio parameters, as well as the permitted measurement procedures. The technical interface requirements RIR10106 are legally binding for RLANs. Antennas with directional effect for RLANs are available on the market or in some cases are self-manufactured. Such antennas may be used to reduce reciprocal interference between different systems or neighbouring cells, as a result of which the range or data transfer rate increases. Operation of equipment with such an antenna is permissible, however, only if the maximum EIRP transmitting power does not exceed the values indicated in the table above. The equipment user is responsible for compliance with the regulations in force (EIRP, in-house for 5 GHz, etc.). In practice this means that the transmitting power must be reduced if a directional antenna is used.
5
http://www.ero.dk/documentation/docs/doccategory.asp?catid=1&catname=ECC/ERC/ECTRA%20Decisions
6
http://www.ofcomnet.ch/cgi-bin/rir.pl?lg=en 17. 03. 2006
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6.1. The ERC/DEC(04)08 on a view The following table contains the requirements of the European decision ERC/DEC(04)08 on RLAN equipment. Frequency range
5150 – 5250 MHz
5250 – 5350 MHz
5470 – 5725 MHz
Indoor or Outdoor use
Indoor only
Indoor only
Indoor and Outdoor
Max. mean e.i.r.p
200 mW
200 mW
1000 mW
Max. mean e.i.r.p. density
0.25 mW in any 25 kHz
10 mW in any 1 MHz
50 mW in any 1 MHz
Required standard compliance
EN 801 893
EN 801 893
EN 801 893
TPC or 3dB reduction required
no
yes
yes
DFS complying with ITU-R M.1652 Annex 1
no
yes
yes
Uniform random channel selection
yes
yes
yes
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7. RLAN air interfaces The following table provides an overview of the air interfaces of RLAN systems. Systems and frequencies which are not allowed in Switzerland are shown in italic. Standard
DECT Bluetooth
IEEE 802.11
No. of channels range (GHz) (CH) Frequency
PHY data transmission rate (MBit/s)
Modulation method
Spreading
Channel access
max. Radio Link Range (m) Transmitting quality power control (mW EIRP)
10
1.728
0.864 (3dB)
1.152
GFSK (B⋅T=0.5)
kein
TDMA/FDM
250
keine
...300
2.4 - 2.4835
79
1
1
1
GFSK
FHSS
TDD/FH
1 / 2.5 / 100
ja
2...100
79
1
1
1
2-level-GFSK
1
2
4-level-GFSK
22
1
DBPSK
CSMA/CA
100
keine
30...300
22
2
DQPSK
22
1
DBPSK
22
2
DQPSK
CSMA/CA
100 keine
10...100
22
5.5, 11
DBPSK / CCK / PBCC
22
1
DBPSK
22
2
DQPSK
22
5.5, 11
DQPSK / CCK / PBCC
22
22, 33
8PSK / ER-PBCC
keine
10…100
22
6, 9
BPSK
22
12, 18
QPSK
22
24, 36
16QAM
22
48, 54
64QAM
2.4 – 2.4835
2.4 – 2.4835
13
13 IEEE 802.11g
High frequency Bandwidth (MHz)
1.88-1.90
13
IEEE 802.11b
Channel arrangement (MHz)
5
5
5
2.4 – 2.4835
3 / 7e)
30 / 10
FHSS DSSS DSSS DSSS
CSMA/CA
100
CSMA/CA
100
DSSS
DSSS / OFDM
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Factsheet RLAN 2.5c
Standard
No. of Frequency range (GHz) channels (CH)
Hiperlan/1 5.15 - 5.25 a) (no equipment available)
5 GHz RLAN according to EN 301 893 (Hiperlan/2, IEEE802.11h)
IEEE 802.11a
14
0 c) e)
5.15 - 5.25 a)
4 a)
5.25 – 5.35 5.47 – 5.725
0 c) e)
23.5294
20
22 (-20dBc)
PHY data transmission rate (MBit/s)
11
22 (-20dBc)
Modulation method
Spreading
Channel access
1.47 / 23.5294
OFDM
EY-NPMA
like IEEE 802.11h
like IEEE 802.11h
OFDM, 52 subcarriers
CSMA/CA / TDMA/TDD
6, 9b)
BPSK
b)
QPSK
b)
24, 36
16-QAM
48b), 54b)
64-QAM b)
6, 9
b)
BPSK
12, 18b) b)
24, 36 b)
48 , 54
b)
max. Radio Link Range (m) Transmitting quality power control (mW EIRP) 200a)
FSK / GMSK (B⋅T=0.3)
12, 18
8 a) 20
5.47 – 5.725
High frequency Bandwidth (MHz)
4 a)
5.25 – 5.35 5.47 – 5.725
5.15 - 5.35 a)
Channel arrangement (MHz)
0
c) e)
200 a) 0
c) e)
Link adaptation
10...100
Link adaptation
10...100
Link adaptation
10...100
200 OFDM, 52 subcarriers
CSMA/CA / TDMA/TDD
1000
QPSK 16-QAM 64-QAM b)
a) Indoor operation only allowed b) Optional c) Because of missing TPC, DFS / Mitigation technique (according to ERC/DEC(04)08, Decides 1.-6. respectively EN 301 893) in all of Europe d) Overlapping e) Not allowed
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8. Legal basis The frequency bands for RLAN’s are allocated to class 3. These are so-called group frequencies, which are available for an unlimited number of users. In this class there is no protection from interference due to other systems7. According to art. 22 para. 1 LTC8 any use of the frequency spectrum is subject to licensing. OFCOM, pursuant to art. 8a FKV in the decree on frequency management and radio licences9 (art. 2 para.1 e) has excluded the radio equipment of a wireless network (RLAN) from the licensing obligation. Such installations therefore do not require a radio licence for use of the frequency spectrum. However, no radio licences can therefore be issued for these frequency ranges either, i.e. these installations are not allowed to operate at a radiated power higher than that prescribed. If RLAN equipment is used for operating a telecommunications network, with which a provider provides telecommunications services (e.g. speech transmission, data transmission services,...)10 for third parties (subscribers or other telecommunication services providers), a service licence according to art. 4 para. 1 LTC6 is required. In this context it is irrelevant whether the RLAN is used for the subscriber connection or for networking telecommunications equipment. The procedure for granting of a licence does not differ from the usual procedure for the granting of a service licence. The guide11 and application forms can be consulted on the OFCOM website.
9. Appendix 9.1.
Further sources of information
IEEE 802 LAN/MAN Standards Committee
http://www.ieee802.org
ETSI, EP BRAN
http://www.etsi.org http://pda.etsi.org/pda/queryform.asp
OFCOM
7
http://www.ofcomnet.ch/cgi-bin/rir.pl?lg=en
8
http://www.admin.ch/ch/d/sr/c784_10.html
9
http://www.admin.ch/ch/d/sr/c784_102_1.html
http://www.bakom.ch
10
Anyone subject to the exceptions according to art. 2 DTS (http://www.admin.ch/ch/d/sr/c784_101_1.html) does not provide a telecommunications service.
11
http://www.bakom.admin.ch/themen/telekom/00462/00797/index.html?lang=en 17. 03. 2006
Factsheet RLAN 2.5c
9.2.
16
Abbreviations
ADSL
Asymmetrical Digital Subscriber Line
AP
Access Point
ARQ
Automatic Repeat Request
ATM
Asynchronous Transfer Mode
BB
Baseband
BER
Bit Error Rate
BPSK
Binary Phase Shift Keying
BSS
Basic Service Set (means also infrastructure BSS)
BT
Bluetooth
CAC
Channel Access Control
CC
Central Controller
CCK
Complementary Code Keying
CDMA a)
Code Division Multiple Access
CEPT
European Conference of Postal and Telecommunications Administrations
CSMA/CA
Carrier Sense Multiple Access with Collision Avoidance
CSMA/CD
Carrier Sense Multiple Access with Collision Detection
dB
Decibel(s)
dBc
dB relative to the carrier power
dBm
dB referenced to one milliwatt
DBPSK
Differential Binary Phase Shift Keying
DCA
Dynamic Channel Allocation
DCS
Dynamic Channel Selection
DES
Data Encryption Standard
DPRS
DECT Packet Radio Service
DQPSK
Differential Quadrature Phase Shift Keying
DQPSK
Differential Quadrature Phase Shift Keying
DS
Direct Sequence
DSSS
Direct Sequence Spread Spectrum
EC
Error Correction
EIRP
Equivalent Isotropic Radiated Power
ERO
European Radiocommunications Office
ERP
Extended-Rate-PHY (i.e. IEEE802.11g)
ERP
Effective Radiated Power
ER-PBCC
Extended Packet Binary Convolutional Coding
ESS
Extended-Rate-PHY (IEEE802.11g) Extended Service Set (=union of BSS's)
ETSI
European Telecommunications Standards Institute
EY-NPMA
Elimination Yield Non-Preemtive Priority Multiple Access
FCC
Federal Communications Commission 17. 03. 2006
Factsheet RLAN 2.5c
FDD FDMA
17
Frequency Division Duplex b)
Frequency Division Multiple Access
FEC
Forward Error Correction
FH
Frequency Hopping
FHSS
Frequency Hopping Spread Spectrum
FSK
Frequency Shift Keying (4FSK = 4 Level FSK)
FTP
File Transfer Protocol
GFSK
Gaussian Frequency Shift Keying
GHz
Gigahertz (109 Hertz)
GMSK
Gaussian Minimum Shift Keying
GSM
Global System for Mobile Communication
HF
High Frequency
HL/2
Hiperlan Type 2
HR
High Rate
IAPP
Inter-Access Point Protocol
IBSS
Independent Basic Service Set (=Ad Hoc network), (not infrastructure BSS)
IEC
International Electrical Commission
IEEE
Institute of Electrical and Electronics Engineers
IMT-2000
International Mobile Telecommunications of the Year 2000
IP
Internet Protocol
ISDN
Integrated Services Digital Network
ISM
Industrial, Scientific and Medical
ITU
International Telecommunication Union
IV
Initialisation Vector
LAN
Local Area Network
MAC
Media Access Control (OSI Layer 2)
MAN
Metropolitan Area Network
MBit/s
Megabit (106 Bit) per second
MHz
Megahertz (106 Hertz)
m-PSK
Phase Shift Keying with m-phase states
mW
Milliwatt
OFDM
Orthogonal Frequency Division Multiplexing
OSI
Open Systems Interconnection
PAN
Personal Area Network
PBCC
Packet Binary Convolutional Coding
PC
Personal Computer
PER
Packet Error Rate
PHY
Physical Layer Interface (OSI Layer 1)
17. 03. 2006
Factsheet RLAN 2.5c
18
PLCP
Physical Layer Convergence Procedure
PMD
Physical Medium Dependent
PMP
Point to Multipoint
PP
Point to Point
PPP
Point to Point Protocol
m-PSK
Phase Shift Keying with m-phase states
PSTN
Public Switched Telephone Network
QAM
Quadrature Amplitude Modulation (16QAM = 16 Levels; 64QAM = 64 Levels)
QoS
Quality of Service
QPSK
Quadrature Phase Shift Keying
RF
Radio Frequency
RLAN
Radio Local Area Network
SHA
Secure Hash Algorithm
SWAP
Shared Wireless Access Protocol
TCP/IP
Transmission Control Protocol / Internet Protocol
TDD
Time Division Duplex
TDMA
c)
Time Division Multiple Access
UMTS
Universal Mobile Telecommunications System
USB
Universal Serial Bus
VLAN
Virtual LAN
W
Watt - unit of power
WAN
Wide Area Network
WARC
World Administration Radio Conference
WECA
Wireless Ethernet Compatibility Alliance
WEP
Wired Equivalent Privacy
WiFi
Wireless Fidelity
WLAN
Wireless Local Area Network
WLL
Wireless Local Loop
WPAN
Wireless Personal Area Network
a) Code Division Multiple Access (CDMA); in this method, the individual users are assigned codes. The signal to be transmitted is spread by means of this code and transmitted. In the receiver, the signal is unspread using the same code, restoring the original signal. The bandwidth of the signal to be transmitted can be selected by allocating corresponding codes. In this procedure, the central stations and subscriber stations transmit continuously, with the transmission signal being kept slightly above the absolutely essential minimum. b) Frequency Division Multiple Access (FDMA); in this method, the individual calls are carried on separate frequencies. The bandwidth of the individual connections can be adapted dynamically depending on traffic. In this procedure, the central station and the subscriber stations transmit continuously throughout the duration of the call. c) Time Division Multiple Access (TDMA); in this method, the individual subscribers are provided with time slots during which they transmit their data. For higher data transmission 17. 03. 2006
Factsheet RLAN 2.5c
19
rates, multiple slots can be combined. In this procedure, the central station normally sends continuously; the subscriber station sends during the slots allocated to it. In addition to the above access methods, there are also combinations such as CDMA with TDMA.
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