19.5.2000
Marja-Leena Lahti
Department of Electrical Engineering
Helsinki University of Technology
marja-leena.lahti@sonera.com
Abstract
This document introduces the IEEE standard 802.11 for Wireless Local
Area Network (WLAN). The document also makes a comparison to GSM cellular
network, where the cell size could be much larger. The paper discusses
the basis outlining the network planning process, such as frequency, scale
of mobility, transmission capacity needs and population variation. Finally
the total network planning process of a cellular network is introduced.
The question is how does the use of unlicensed frequency band affect the
WLAN network planning. Finally the study suggest what are the relevant
requirements for wireless communication with short range mobility. It also
suggests what GSM planning criteria can be omitted in the WLAN environment.
2 The Standards
2.1 Characteristics of GSM
and WLAN
2.1.1 Extent of Coverage
2.1.2 Services
2.1.3 Cellular and Non Cellular
-Networks
2.2 GSM Physical Layer
2.3 IEEE 802.11 Protocol
Layers
3 Basis for the
Network Planning Process
3.1 Frequency Range
3.2 Mobility
Aspects
3.2.1 Scale of Mobility
3.2.2 Speed of the Mobile
3.3 Transmission Capacity
Needs
3.4 Power Control
3.5 Population Variation
3.6 Timing Advance
4 Network Planning Process
4.1 Targets for the
Network Planning
4.2 Coverage Planning
4.3 Capacity Planning
4.4 Frequency Planning
4.5 Parameter
Planning and the Follow Up
4.6 Relevant Requirements
for IEEE 802.11
4.6.1 Infrastructure WLAN
4.6.2 Ad Hoc WLAN
In the first chapter the technologies, the cellular standard GSM and
WLAN are introduced. Then the aspects outlining the network planning process
- such as frequency, scale of mobility, transmission capacity needs, population
variation - are discussed. Finally the total network planning process of
a cellular network is introduced. An important question is how does the
use of unlicensed frequency band affect network planning in the WLAN environment.
Finally the study suggests what are the relevant requirements for wireless
communication with short range mobility. It also suggests what GSM planning
criteria can be omitted in the WLAN environment.
The GSM network is consisted of cells. The coverage area of each cell is different in different environments. Macro cells can be regarded as cells where the base station antenna is installed in a mast or a building above the average roof top level. However, small cells or micro cells are cells where the antenna height is under the average roof top level. Thus the cell radius can vary depending on the antenna height, antenna gain and propagation conditions from couple of hundred meters to several tens of kilometers. Officially 35 km is the longest distance GSM specification supports, though the specifications define an extended cell, where the cell radius could be double [8]. Also indoor coverage is supported by GSM. Indoor coverage can be built by using power splitters to deliver RF signal from the antenna outdoors to separate indoor antenna distribution system. When all the capacity of the cell is needed indoors, e.g. in shopping centers or airports etc., the indoor coverage can be built by using antennas only inside the building. In suburban areas the indoor coverage is usually origin by the inbuilding penetration of radio signal, not by a separate indoor antenna system.
WLAN is a standard offering a limited coverage for LAN users. Cell radius is usually from few tens of meters to some hundred meters. IEEE 802.11 wireless LAN is a locally situated network - a local area network. The coverage area is consisted of small islands and the purpose is certainly not to offer a large coverage network like GSM. The coverage area is often tailored according to the users own need and can also be temporary.
The specifications of wireless LAN outlines two possible modes of operations: client/server and ad hoc mode WLAN. [4] In the client/server WLAN - also often called as an infrastructure configuration - terminals communicate with base stations or access points (AP), which form the coverage area. The access points are further connected to the wired network. This document concentrates mainly on the infrastructure WLAN when discussing network planning issues. This is because a WLAN access point can comparable to a GSM base station, but in the ad hoc mode the same station acts both as an access point and as a station and needs therefore a different point of view.
The coverage area of the client/server type WLAN network is usually bordered upon a building or a campus and can therefore be comparable to a single GSM inside cell. The main difference between the GSM and WLAN technologies are, that to cover the whole building with the WLAN technology, there has to be several access points depending on the building architecture, wall materials etc. In the GSM solution the coverage area can be built with a single base station by distributing the signal into antennas locating in different rooms by using power splitters.
The specifications of WLAN defines also an ad hoc mode. In this mode
mobile terminals by themselves build the network. The coverage area is
built by the help of wireless adapters and is limited. [5, 13] In the ad
hoc mode the whole network is seen as movable, and it is independent of
any infrastructure unlike GSM or client/server type WLAN. It is also isolated,
because it has no interface to the wired network.
The services and therefore the users of WLAN are different from those in GSM network. Due to the versatile set of GSM services – voice, data, short message services etc. and the possibility of the large scale mobility GSM can be regarded as a competitor to the wired public network. However, WLAN supports only data communication and therefore can be seen as a potential alternative or an extension to the wired LAN. [11]
The standardization process of IEEE 802.11 begun from the need to connect wirelessly to the wired Ethernet based data communications network and thus to offer mobility for the LAN users within a rather small area. One of the main advantages of WLAN is that it provides LAN users an access to real time information anywhere in their organization. Further one aim was to reduce installation costs and thus achieve short and long term cost savings. Installing a wireless system can be fast and the need to pull cable through walls and ceilings can be eliminated. Wireless technology allows also the network go where the wire cannot go.
The specification work of the standard IEEE 802.11 was started in 1990
and completed in 1997 by the Institute of Electrical and Electronic Engineering
(IEEE) [13]. The first phase of the standard IEEE 802.11 supports only
1 Mbit/s and 2 Mbit/s data rates. The first phase standard was followed
by an extension IEEE 802.11b, which supports data rates up to 11 Mbit/s
with the radio frequency technology direct sequence spread spectrum. [6,
12] However, the user does not have to purchase the radio operator's license
in order to use the frequency band 2,4-2,483 GHz, which is dedicated to
WLAN use, but it is also known as an ISM band (band for the industrial,
scientific and medical use) [14]. This means that anyone who have access
to a WLAN can buy and install an access point. This is a very problematic
basis from the network planning point of view.
The non-cellular WLAN do not require an infrastructure when using ad
hoc mode of operation. Thus the complete system can be seen as movable.
The physical layer of GSM defines the modulation scheme used, which
can be considered as a combination of frequency division multiple access
(FDMA) and time division multiple access (TDMA) [8]. The spectrum available
for GSM use is first according to FDMA technique divided into channels,
each channel 200 kHz of bandwidth. One or more frequencies are then assigned
to each base station (BTS). Every 200 kHz channel is further divided into
8 time slots. Each user is then assigned to a time slot or to a set of
time slots. Transmission is possible only during this time slot, after
that the user has to wait until he receives another time slot.
The standard defines three different physical layer characteristics for WLAN: one infrared, and two RF transmission methods. This document concentrates only on the two RF methods: direct sequence spread spectrum (DSSS) and frequency hopping spread spectrum (FHSS). [12] However, due to the operation in an unlicensed RF band, the spread spectrum modulation must fulfill the requirements set by each country.
The chosen modulation techniques for the DSSS is Differential Bi and Quadrature Phase Shift Keying (DBPSK and DQPSK). However, the FHSS uses 2-4 level Gaussian Frequency Shift Keying (GFSK) as the modulation schemes. Depending on the modulation scheme used both direct sequence and frequency hopping spread spectrum supports data rates of 1 Mbit/s and 2 Mbit/s. As mentioned in chapter 2.1.2 also the data rates of 8 Mbit/s and 11 Mbit/s with the DSSS are possible to achieve while using WLAN that supports the standard IEEE 802.11b [6, 12]. The operation frequency of both RF methods is 2,4 GHz. [5, 13]
In order to wireless LAN devices to be interoperable, they have to have
the same physical layer standard. Therefore a DSSS equipment is not capable
of communicating with a FHSS based equipment.
As mentioned earlier the specified frequencies for GSM use lie in the 900 and 1800 MHz. However, both WLAN RF methods are planned to operate in the unlicensed 2,4 GHz frequency band occupying typically a bandwidth of 83 MHz between 2,4-2,483 GHz. The maximum allowed antenna gain is 6 dBi. Also different frequencies are approved in different countries. [4, 12]
The direct sequence spread spectrum generates a redundant bit pattern, length of eleven bits, which then multiplies each data bit to be transmitted. The bit pattern is also often referred to a chipping code. Only one chipping code is used [12] unlike in CDMA system, which has a set of codes. The receiver must be tuned into the right frequency in order to be able to receive the information being broadcast. Direct sequence spread spectrum is at the moment the one that most wireless spread spectrum WLANs uses [14].
In Europe there are 13 frequencies for DSSS use, the center frequencies and corresponding channel numbers are listed in the table 3.1. The channels are overlapping and the receiver adjacent channel rejection demand is 35 dB, which needs 30 MHz gap between the neighbouring channels. [4] The center frequencies are located in 5 MHz interval and according to the adjacent channel rejection requirement, there has to be five channels between, in order to avoid interference caused by neighbouring access points. This frequency reuse plan means also that an access point having six neighbours, alternate neighbour uses the same frequency as illustrated in figure 3.1. This frequency design demand has to be taken into account, when choosing operating frequency to the DSSS equipment. The problem is that there is no controlling organisation that follows the reuse of frequencies, like regulator and operators in the case of GSM.
Table 3.1. DSSS frequency plan used in Europe.[4]
Channel number Frequency 1 2412 MHz 2 2417 MHz 3 2422 MHz 4 2427 MHz 5 2432 MHz 6 2437 MHz 7 2442 MHz 8 2447 MHz 9 2452 MHz 10 2457 MHz 11 2462 MHz 12 2467 MHz 13 2472 MHz
Figure 3.1. An example of a frequency plan of an infrastructure network using DSSS.
In the frequency hopping spread spectrum the carrier changes the frequency used according to a pattern known both by the transmitter and the receiver. There are 79 non-overlapping channels specified, each channel occupying 1 MHz. 26 different pseudorandom hopping pattern are specified. [4] The hopping rate is specified by the regulator of each country. Therefore WLAN equipment must meet the requirements of the country where it is sold. [12] The user can choose the frequency hopping pattern used by a FHSS equipment.
The frequency hopping spread spectrum is a technique that enables coexistence of multiple networks or other devices in the same area. This is due to the resistant to multipath fading through the inherent frequency diversity system. Also the frequency hopping design criteria described in [1] have the desirable effect on the multipath fading resistant.
Certain differences can be found between the direct sequence and the frequency hopping spread spectrum. DSSS supports bigger data rates (up to 11 Mbit/s) and FHSS equipment are usually inexpensive compared to DSSS equipment. [6, 12, 14]. In a case where high throughput is needed and the interference is not a problem DSSS is the better choice.
The defined frequency band or the frequency channels available sets the practical limit for the capacity of a GSM network. However, this is rarely the case, typically the defined bandwidth is divided between numerous operators by the regulator of each country. Thus the regulator defines the maximum capacity of the network.
As stated the use of the ISM band requires no operator license. The
technology choice of spread spectrum is different from the one used in
GSM. Therefore the actual capacity limit is not defined according the available
bandwidth but the interference level. Further packet mode traffic, which
is used in WLAN, does not know the specification of congestion. Therefore
the available transmission capacity depends strongly on the interference
level. The problem of a WLAN is that there could be interference not only
caused by the other access points located in the own network, but also
caused by neighbouring WLAN or other equipment using the same frequency
band. There is not much to do with the interference level in the latter
case.
The main difference is that GSM network is consisted of cells and therefore
requires a handover mechanism. However, the specifications of WLAN do not
define a handover mechanism [13], therefore the roaming is transparent
to the MAC layer of IEEE 802.11. This means that in case of an Infrastructure
WLAN from the wired network point of view there seems to be two node's
having different IP addresses, but the IP addresses share the same domain
network name. In case of ac hoc WLAN the concepts of handover or adjacent
access point can not be found, because the stations act both as an access
point and as a station. As pointed out the whole system can then be seen
as movable.
In order to ensure the large scale of mobility, several functions has had to be designed. The mobility management of GSM is defined in the layer three specifications, and it is very complicated compared to that of a WLAN user. As stated the smallest unit of the radio network is a cell. Several cells build up a location area (LA). The concept of LA has been a necessity to define, in order to handle large scale mobility of the user. If a powered mobile station (MS) is having an incoming call, it is paged through the pacing (PAGCH) channel of a cell. It would be a waste of bandwidth if the paging has to be done in every incoming call through every cell of the network. Thus the network knows situation of each user in an accuracy of a location area. [9] The operator decides the size of the location areas in order to balance the signalling traffic of the network.
Several cells are connected to Base Station Controllers (BSC) and further BSCs are connected to Mobile Switching Centers (MSC). The number of BSC and MSC is a matter of the vendor but also a matter of optimisation and maximizing the reliability of the network and therefore not discussed here. When the MS moves from cell to cell, and from a location area to another area, additionally two subsequent registers – HLR (home location register) and VLR (visitor location register) – are required.
Radio Resource Management, which controls the call setup, maintenance and termination, as well as it also handles the signalling used in handovers. Different types of handovers are supported. Intra cell handover, which can occur within a cell or within a frequency from time slot to another time slot. This is normally done in case of interference. The other type is a handover between different cells. The cells can be situated in different BSCs and/or different MSC. This of course affects the signalling need in handover. This type of a handover is the way to move within the network. Despite of the ability to move within the network by handovers, handovers can be used to control the traffic load of the cells.
The MS measures the RX level of the surrounding BTSs according to the neighbouring list and reports the measurements to the BSC, where the handover decision is done. The suitable choices of handover and power control parameters makes the BSC to keep the connection alive by the help of power control. The handover attempt is not done until the user really is in the border of the cell.
---
On the other hand the mobility concept of WLAN is slightly simplier. Typical users of WLAN infrastructure mode can be e.g. doctors seeing his patient, the patient information can be written straight to the patient register in the laptop by the help of WLAN. Also students at the universities or people participating conferences could use their laptops as a notebook by the help WLAN. Ac hoc WLAN offers no access to the wired network, instead of that the stations can share files, which could be useful e.g. in confrerences. These are indoor solutions, but the specifications tell no reason why WLAN coverage can not be built outdoors as well. Anyway in cases like this it could be supposed that the WLAN users do not need to move within the network in that extent what the user is expected to move in GSM network. This is perhaps because WLAN does not support speech transmission and data service users are not expected to move in a large scale. Thus it could be assumed that a typical WLAN user would be a user that moves from location to location, but uses the WLAN equipment only at a fixed location. Therefore no complex mobility scenario is needed. Next the basic services supporting mobility are shortly described.
Association is a basic service that enables the connection between the station (STA) and the access point (AP) in an infrastructure WLAN. An access point is basically a radio base station that covers an area of about 30…300 m depending on the environment. An access point and its associated clients form all together a Basic Service Set (BSS). [13] Though no handover mechanism is specified in the standard, the standard introduces a service called reassociation, which is related to the roaming from one BSS to another. Two adjoining BSS form together an Extended Service Set (ESS) if they share the same ESS identity (ESSID). This is the case when roaming is possible. [4] Thus the parameter ESSID can be referred to the concept of neighbouring cell in GSM network.
An Independent Basic Service Set (ad hoc mode, IBSS) is the most basic
type of IEEE 802.11 WLAN. At the minimum it is consisted of two stations.
The network is often formed without pre-planning is alive until either
station is moved away from the others coverage area. [4]
It is assumed the N to be 100. The velocity v' can now
be calculated to be one tenth of the velocity v. Thus the speed
of the mobile is more crucial issue to the user of a wireless local area
network than to a mobile phone moving within a network covering larger
entities. Thus the aim of the WLAN coverage planning is often to maximise
the coverage area of an individual WLAN access point.
In case of data services the estimated need of capacity is not as straight forward. It is not possible to measure the amount of capacity needed from the used application. If we know that the www-application would demand say 40 kbit/s from the GPRS service, this does not take into account how unexpectedly the user can behave. He can suddenly found some interesting link transmitting e.g. video picture and thus the demand for transmission capacity still increases. However, this kind of a phenomena does not take into account that the behave of one user affects also to the behaves of the other users. Let us think about the www-surfer, that has found an interesting video picture. As his transmission capacity need increases, the transmission capacity of other www-surfers in the same cell decreases. So the behaving scheme of a data user can be regarded as a very complex mathematical model and thus this theme is suggested to a subject of further study.
It can also be stated the packet data user - e.g. GPRS or WLAN user
- does not experience the congestion in the way that the circuit switched
user (e.g. GSM voice) does. The congestion of a packet data transmission
is experienced as the transmission rate of the service becomes slower.
So practically there is always room for another user using packet service.
Only the speed of the service can not be quaranteed.
The GSM specifications specifies both downlink and uplink power control. The downlink power control mainly decreases the interference level of the network and thus improves the quality of the network. BTS power control is not obligatory and thus it is up to the decision of the operator. On the other hand the uplink power control improves the battery lifetime of a mobile phone. The GSM power control is controlled by BSC and it is based on the measurements done by the BTS and MS. The measurements are done in 480 ms interval. If the average result of the measurement exceeds the threshold, the power change is done in 2 dB steps, each step takes 60 ms. The power control range of a GSM mobile phone in the 900 MHz band is from the 13 dBm (20 mW) to the maximum specified 39 dBm (8 W). [8]
WLAN is a symmetrical system, which can be noticed from the stations ability to act as an access point in the ad hoc mode. Thus the power control functions similarly from the stations and the access points of view. In the DSSS WLAN the maximum transmission power is specified to be 100 mW (EIRP), whereas the minimum power level shall be no less than 1 mW. Four different power levels are defined. For example in an infrastructure network the station selects it's power management mode by a parameter, by which the station informs the access point through a successful frame exchange. In a case when there is nothing to be received or transmitted the station is able to fall into a sleep mode and then consumes very low power. In this mode the station is not able to transmit or receive any data. However, in a low power mode the station listens periodically beacons sent by the access point. In this way the access point is announcing the stations of it's existence. [4]
In the FHSS WLAN the power level are specified as follows. The EIRP of the maximum transmission power is 100 mW and the smallest transmission level is 10 mW. [4] The specified power levels are regulated by local regulators and are different from continent to continent. The values presented here are the values used in Europe.
It could be assumed that the speed of the mobile also affects the users
ability to recover from the fading point. Thus the mobile station moving
at high speed recovers from the fading caused by the multipath propagation
more quickly than the slow moving mobile. Thus the power control can regarded
more critical to the slow moving user.
In case of WLAN user or packet data user, the capacity planning can
be omitted, because there is always room for another packet data user,
only the offered transmission rate decreases when the amount of users increases.
So the document suggests, that the population variation does not have to
take into account when planning a WLAN network. On the other hand in a
case where are several hundreds of concurrent users and a certain level
of data rate must be quaranteed, the use of several access point instead
of one should be considered, although sufficient coverage area could be
created with one access point.
The resolution of the parameter timing advance (0,55 km) is bigger than
the specified maximum range of Wireless LAN. Therefore no timing advance
parameter is needed in short range communication system like WLAN.
Network planning is a ongoing process, which has to be optimised economically.
However, one target is also to take into account the possible capacity
need in the future right from the beginning. The different steps of the
planning process are illustrated in the figure 4.1.
Figure 4.1. The network planning is a ongoing process,
which is consisted of various steps and affected by various parameters.
In the capacity planning two different schemes can be distinguished:
capacity planning of a certain area entity and capacity planning of an
individual cell. The capacity of a GSM cell is consisted of TRX's. One
TRX contains 8 channels or timeslots, and TRX can carry 4 Erlangs traffic
with 2 % time congestion. Thus accepted congestion level affects the capacity
planning. Some level of congestion can be acceptable e.g. in the city areas
where cell overlapping can be found in a great extent. However, the offered
capacity is not only a matter of excisting channels, the operator can affect
the amount of needed channels by the help of various parameters by which
the operator can share the offered load between neigbouring cells.
Now in case of infrasructure WLAN the situation is that the user who have access to the LAN and wants to make that wirelessly, buys an access point and installes it. The user makes a coverage plan by simply installing the equipment e.g. to the wall and if the place is not optimised he probably tries another place. Further the user makes a frequency plan by selecting randomly the channel, if there are lot of interference he will probably change it. So the coverage planning and frequency planning steps can be found in WLAN planning "process". However, the planning step of capacity can be omitted in the WLAN environment. As stated previously this is from the reason, that there is always room for another WLAN packet user. The information is transmitted in packet mode, therefore the user does not experience any congestion, only the transmission rate varies. However, as stated previously if a certain transmission data rate is to be quaranteed and there are e.g. several hundreds of concurrent users there might be a need for using several access points instead of one, although sufficient coverage area could be created with one access point. Overall it can be stated that a distinctive capacity design principle can be found from the GSM world but cannot be found from the WLAN environment.
The problem of the WLAN planning is also that the user is not necessarily familiar with technical equipment. In a case the user installes an access point and tries to make a wireless connection to the LAN, but does not get it, he probably does not know what the problem is. Is the used frequency too interfered or perhaps the installation place for the access point is not good enough? Further what is making the interference? However, the writer does not have experience of testing a live connection in WLAN, but assumes that the biggest problem at the moment is the interference caused by other equipment (not WLAN) using same frequency band. Micro owens, Blue Tooth equipment or different electronical equipment using 2,4 GHz (e.g. door opening equipment) could cause interference.
Relevant requirement for the IEEE 802.11 infrastucture network planning
would be that the intelligence of the frequency planning should be in the
equipment itself. In this way the level of interference would be minimised.
The other demand could be that there would be a larger frequency band dedicated
to the WLAN use than available today, so the interference would be spread
into a larger area and thus the average interference level would be lower.
Both demands suggested in the document are taken into account in the next
generation WLAN called HiperLAN2, which uses higher frequency (5 GHz) and
supports also interfunction with third generation cellular standard UMTS.
In HiperLAN2 the access point automatically selects an appropriate channel
and dynamically changes it according to the level of interference [6].
Generally the problems an ad hoc WLAN is facing could be the same as in the infrastructure mode. The used frequency is perhaps interferred or the coverage area is not large enough etc. However, the writer assumes that the coverage is not a usual problem in an ad hoc mode. This is because it is assumed that the users have decided to meet each other in some conference room and the only demand for the coverage is that the stations can hear each other in that specific room. So the network is typically created spontaneously and is alive until a station has moved out of the coverage area of other stations.
The question of the network planning in an ad hoc mode is irrelevant.
No network planning process of an ad hoc WLAN can be addressed. So rather
than discussing the problem of network planning of an ad hoc WLAN, the
more suitable question is that how the stations configure themselves to
act both as an access point and as a station. The ad hoc WLAN is using
a certain frequency and thus a station that wants to be a member of the
network should use the same frequency. So can an accidental WLAN station
be a member of any ad hoc WLAN it has founded? Further, if the used frequency
is too interferred and the connection between stations is poor, an interesting
question is that what happens if one of the stations suddenly decides to
the try another frequency? Is this somehow possible or are the frequency
selection and the possibly frequency change a common decision of all the
members of ad hocWLAN ? These are questions that are left under further
study.
The standard IEEE 802.11 WLAN defines to the LAN user (e.g. laptop) a mean to connect wirelessly the Ethernet based LAN. Also wireless connection (ad hoc mode) between stations are defined. The main advantages of WLAN is to offer mobility for the LAN users though within a rather small area. Cell radius is usually from few tens of meters to some hundred meters. WLAN provides LAN users an access to real time information anywhere in their organization. Further one aim was to reduce installation costs and thus achieve short- and long-term cost savings. Installing a wireless system can be fast and the need to pull cable through walls and ceilings can be eliminated. Wireless technology allows also the network go where the wire cannot go.
The document has compared various parameters - such as frequency range, mobility aspects, transmission capacity needs, power control, population variation and timing advance - outlining the network planning of GSM and WLAN. The coverage area of a WLAN is usually very limited, usually bordered upon a building or a campus and can therefore be comparable to a single GSM inside cell. Because of the limited coverage the speed of the mobile is stated to be crucial to WLAN user, as well as the power control. The documents handles the transmission capacity need of a user using data communication. It is stated that the behaving of an individual data user affects the behaving of the other data users sharing the resources of the same cell. The conclusion is that it is difficult to estimate the need for transmission capacity from the used application. Because of WLAN data communication uses packet mode communication instead of GSM's circuit switch mode, the WLAN user does not experience congestion in the same way as the circuit switch user. Only the offered transmission rate varies. This is the reason why there is no need to take the population variation of WLAN into account. Further it was stated that no timing advance parameter is needed in short range wireless communication like WLAN.
The targets of the GSM network planning are depending on the offered services, the user needs and therefore expected traffic load. Also the frequency band available and the chosen infrastucture outlines the structure of the network. The main targets of the network planning is to quarantee service with a quality good enough and to offer capacity with a sufficient low congestion. The GSM network planning process is consisted of three phases: coverage, capacity and frequency planning. The phases are strongly dependent on and affected by each other.
An infrastructure WLAN does not need a multi phased network planning process like used in GSM cellular system. This can be argued with the costs of the network planning. Also there is not going to be an organisator who would supervise the frequency reuse as the frequencies lie in the unlicenced frequency band. The steps of coverage planning and frequency planning can be found in WLAN planning "process". However, the planning step of capacity can be omitted in the WLAN environment for the same reason which was mentioned when defined the rules for the population varation. It was also stated that the question of the network planning process in an ad hoc WLAN is irrelevant.
Relevant requirement for the IEEE 802.11 infrastucture WLAN planning
would be that the intelligence of the frequency planning should be in the
equipment itself. Also the more channels are available for WLAN use the
lower the interference level would be. Both demands suggested in the document
are taken into account in the next generation WLAN called HiperLAN2, it
also supports interfunction with third generation cellular standard UMTS.
[1] Chayat Naftali, BreezeCom, Frequency Hopping Spread Spectrum
PHY of the 802.11 Wireless LAN Standard, IEEE 802.11 Tutorials, 1996. [referred
10.3.2000]
<http://grouper.ieee.org/groups/802/11/Tutorial/FH.pdf>
[2] Glas Jacobus Petrus Franciscus, Non Cellular Wireless Communication
Systems, Delft University of Technology, Delft, 1996. [referred 3.2.2000]
<http://cobalt.et.tudelft.nl/~glas/thesis/main-text.html>
[3] Hämäläinen Jari & Kari Hannu H., Proposed Operation of GSM Packet Radio Networks, PIMRC '95, September 27-29 1995.
[4] Institute of Electrical and Electronics Engineers, Inc., IEEE standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications, 1997, IEEE, 445 p.
[5] Institute of Electrical and Electronics Engineers, Inc., Short Description
of the Standard, 1999. [referred 11.3.2000]
<http://grouper.ieee.org/groups/802/11/main.html>
[6] Johnson Martin, HiperLAN/2 - The Broadband Radio Transmission Technology
Operating in the 5 GHz Frequency Band, White Paper, HiperLAN/2 Global Forum,
1999. [referred 24.3.2000]
<http://www.hiperlan2.com/site/specific/whitepaper.pdf>
[7] Nations Daniel, Wireless Local Area Networks, 1999. [referred 4.2.2000]
<http://www.ac.wwu.edu/~n9649918/wlans.html>
[8] Penttinen Jyrki, GSM-tekniikka, Järjestelmän toiminta, palvelut ja suunnittelu. Porvoo 1999, WSOY. 349 pages
[9] Scourias John, Overview of the Global System for Mobile Communiactions,
1997. [referred 9.2.2000]
<http://ccnga.uwaterloo.ca/~jscouria/GSM/gsmreport.html>
[10] Weckström Marja-Leena, Solukkosuunnittelu DCS1800 -matkaviestinjärjestelmässä, Master's Thesis, Helsinki University of Technology, Department of Electrical Engineering, Espoo 1996, 105 p.
[11] The Wireless LAN Association, What is a Wireless LAN?, Introduction
to Wireless LANs. [referred 9.2.2000]
<http://www.wlana.com/intro/index.html>
[12] The Wireless LAN Association, What is a Wireless LAN?, The IEEE
802.11 Wireless LAN Standard. [referred 9.2.2000]
<http://www.wlana.com/intro/standard/index.html>
[13] The Wireless LAN, Interoperability Forum, What is the IEEE 802.11
Wireless LAN Standard?, Technical Background [referred 9.2.2000]
<http://www.wlif.com/tech/wp_80211.html>
[14] Wood Joel B, The Wireless LANs Page, 1995. [referred 18.2.2000]
<ftp://ftp.netlab.ohio-state.edu/pub/jain/courses/cis788-95/wireless_lan/index.html>
Johnson Martin, Hyping Up the Wireless LAN, Telecommunications Magazine,
2000, Jan 2000
LaMaire Richard O. & Krishna Arwind & Bhagwat, Pravin &
Panian James, Wireless LANs and Mobile Networking: Standards and Future
Directions, 1996.
<http://www.comsoc.org/livepubs/comsoc/private/1996/aug/lamaire.html>
Skellern David J. & Lee L.H. Charles & McDermott Tom & Weste Neil H.E & Dalton John & Graham Jeffrey & Wong Tan F. & Myles Andrew F., A High-Speed Wireless LAN, IEEE micro, 1997, vol. 17, No 1 January/February 1997.
