3. WCDMA Radio Planning Fundamentals

download 3. WCDMA Radio Planning Fundamentals

of 60

  • date post

    27-Oct-2015
  • Category

    Documents

  • view

    35
  • download

    6

Embed Size (px)

description

JJ

Transcript of 3. WCDMA Radio Planning Fundamentals

Slide 1Customer Confidential
Customer Confidential
Customer Confidential
WCDMA Planning Process Overview
Nominal Planning Fundamentals
Customer Confidential
Customer Confidential
Packet Switched Core
Customer Confidential
marketing
business
plan
traffic
assumptions
transmission
plan
coverage
plan
Network
dimensioning
Customer Confidential
DEFINITION
PLEMENTATION
Customer Confidential
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Customer Confidential
This diagram shows when some cells are loaded
Cell-A
Cell-C
Cell-B
Customer Confidential
"actual" Loading, (ie from the traffic inputs defined in dimensioning)
This diagram shows a Fixed Uplink Load design
Results => No or Min Coverage Holes!
No (or minimum) coverage holes problems
More cells required
Traffic mobility taken into account. (Note: dimensioning assumes uniform traffic distribution)
eg. Actual UL load = 8%
eg. Fixed UL load = 30%
Cell-A
Cell-C
Cell-B
Cell-D
Cell-E
Cell-F
Cell-C
Cell-B
Cell-G
Cell-A
Cell-H
Customer Confidential
Traffic Density Map
QUALITY RELATED
MS Class
Indoor Coverage
Location Probability
Blocking Probability
Gives an Estimation of the Equipment Necessary to Meet the Network Requirements
Network Dimensioning Activities
Customer Confidential
CS data
PS data
Coverage area
m
m
m
m
Customer Confidential
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
* © Nokia Siemens Networks WCDMA Planning Fundamentals/Jan2008
Customer Confidential
Customer Confidential
Sites are expensive
Base station sites are valuable
long-term assets for the operator
Emphasise: - Field Planners' choice will influence the value of the investment
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Each site needs to be assessed on several grounds.
Radio
Transmission
Access
Power
Planning
Ideally every site option reported by the surveyor would pass in each of the areas listed above.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Donkeys - Low sites which provide very little coverage.
Donkeys carry so little traffic that they often never pay for themselves.
Boomers - High sites which propagate much further than is needed.
A boomer will cause localised interference and prevent capacity being added to some other sites in the area.
Small “Donkey” site
Large “Boomer” site
Customer Confidential
Good radio engineering practice doesn’t change much for UMTS.
It just becomes more important.
In UMTS
A “Donkey” will never pay for itself.
A “Boomer” will reduce the range and capacity of surrounding sites.
Two major factors determine whether a site is considered good, a “Donkey” or a “Boomer”, They are:
Site location.
Antenna height.
Other parameters can be used in an attempt to control booming sites but it is far better to avoid building them in the first place.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Importance of Controlling 'Little i'
WCDMA is an interference-limited network. I.e. capacity of the network is directly linked to how interference is maintained/controlled.
From the Radio Network Planning point of view, the "little i" - other-to-own cell interference- is the only thing that can really be influenced by the Planner during the site selection and planning stage. WCDMA RF planning is all about having good dominance in the desired coverage area.
Unlike in GSM, that there is no frequency plan to "play" with in order to minimise the effects of bad sites.
Uplink Load Equation
Downlink Load Equation
Emphasise: - try to convey the message that controlling INTERFERENCE is one of the biggest concerns, given that WCDMA is an interference-limited system
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Importance of Controlling 'Little i'
Planners have to select the sites diligently so that the other-to-own cell interference ratio is MINIMIZED by planning clear dominance areas during site selection / planning phase.
RESULT: Doubling of the "little i" will cause throughput to decrease to 70% of the original value
Emphasise: - try to convey the message that controlling INTERFERENCE is one of the biggest concerns, given that WCDMA is an interference-limited system
BTS TX power
0.2, 0.4, 0.6, 0.8
MS speed
3 km/h
MS/BTS NF
Customer Confidential
Some overlap is required to allow soft handover to occur
Need to control amount of interference since the network capacity is directly related to it.
Soft handover helps to reduce interference. (Soft HO Gain)
Too much overlap:
Increases Soft Handover overhead --> reduce capacity
i = Coverage Overlap
Emphasise: - try to convey the message that controlling INTERFERENCE is one of the biggest concerns, given that WCDMA is an interference-limited system
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
uncontrolled interference
interleaved coverage
interleaved coverage areas:
wanted cell
interferences
Emphasise: - try to convey the message that controlling INTERFERENCE is one of the biggest concerns, given that WCDMA is an interference-limited system
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
use hills/high rise buildings to separate cells
contiguous coverage area
well defined dominance areas
needs only low antenna heights if sites are slightly elevated above valley bottom
wanted cell
boundary
Emphasise: - SIGNAL CONFINEMENT is a major challenge, but with proper site selection we can get closer to that
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
It has good clearance,
overlooks the surrounding rooftops.
Bad site; blocked by neighbour building
Emphasise: - pay attention to distant obstacles, they can be turned into useful barriers for limiting signal coverage
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
BAD: In a urban/dense urban area,
too high a site is a bad site since it
will introduce too much interference
to other sites in the network
(remember the little i)
Uplink Load Equation
Downlink Load Equation
Customer Confidential
building
These situations can easily be avoided!!
Time consuming and costly to fix.
Emphasise: -examples taken from Hong Kong projects, must "adapt" them to local characteristics of the projects
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
roughly 10km = TOO FAR. There is a river
as well, so interference is enormous. Site
distance is about 700meters in this
phase!! Site was good in phase 1
when distance between sites was 4km!
Well shit happens … who could have known
that they were going to build this high building one year after installation ?!
Planners should
Examples of Bad Sites
Emphasise: - same as before
Customer Confidential
in the same direction! Installation problem.
Is this installation OK? The satellite dish is in
near field of the GSM900 antennas -> some
effects for sure. Definite interference to satellite
system. But could not be tested because the
satellite system was not in use!
Avoid installing antennas in close proximity to
other objects since its radiation pattern will
be altered.
Customer Confidential
Examples of GOOD Sites
Enough space between the two Tx/Rx and Rx Div., AND pointing in the same direction!
Site survey point of view: Provides clear dominance to the desired coverage area.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Summary of Site Selection Guidelines
The objective is to select a site location which covers the desired area but keeps emissions to a minimum.
The site should be located as close to the traffic source as possible.
The closer the site is to the traffic, the less output power will be required by the user equipment and node B. This will minimise the noise affecting other users on both the serving cell as well as other nearby cells.
The antenna height selected will depend largely on the type of environment in which the site is to be located. Eg Dense Urban, Urban, Suburban, Rural.
The key factor to be considered is how well can the emissions be controlled.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
You can "feel" the site only if you are there!
If one or more of these characteristics are not fulfilled by the examined site, the Field Planner should REJECT the site and choose another site
Be flexible, even creative! Try to think of all the possible implementation solutions that the site could support: different pole heights, split poles for different sectors, etc.
Always check neighbouring sites, to be sure your chosen candidate is "fitting" well into the surrounding, e.g. for coverage, SHO zones,etc.
Emphasise: - once again and for all, the Site Selection is the end result of a MUTUAL COLLABORATION between different departments: INFORMATION SHARING and a CLIMATE OF RECIPROCAL COOPERATION are the magical recipe for success !!!
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Using Existing Cellular Sites
Most UMTS networks will be built around an existing GSM network.
Many GSM networks were built around existing analogue sites.
In the early days of analogue cellular sites were often located to give maximum coverage. No thought was given to capacity issues.
Despite causing problems in high capacity networks, many of these high sites are still in operation today.
Most cellular networks contain these nightmare sites.
When rolling out UMTS around an existing network it is vital to avoid these sites.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
UMTS Configurations
Omni
Some solutions eliminate the need for RF plumbing.
Some require similar amounts of equipment to a GSM BTS.
Some increase the number of antennas on a site.
The configuration can be affected by the wide variety of UMTS antennas.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Co-locating a Node B at a GSM site
Isolation requirements between UMTS and GSM systems can be derived from UMTS and GSM specifications.
In many cases equipment performance will exceed the requirements in the specifications.
Each vendor should be able to provide information which can be used to improve the isolation requirements.
The isolation requirements will affect
Choice of antenna configuration
Filtering at both the GSM and UMTS sites.
Isolation is the attenuation from the output port of a transmitter to the input port of the receiver.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Interference Issues
Wideband Noise - unwanted emissions from modulation process and non-linearity of transmitter
Spurious Emissions - Harmonic, Parasitic, Inter-modulation products
Blocking - Transmitter carriers from another system
Inter-modulation Products - Spurious emission, specifications consider this in particular
Active: non-linearities of active components - can be filtered out by BTS
Passive: non-linearities of passive components - cannot be filtered out by BTS
Other EMC problems - feeders, antennas, transceivers and receivers
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Interference Issues
Nonlinear system transfer function can be expressed as a series expansion
In the case of one input frequency, vin = cos 1t, output will consist of harmonics, m1
Fundamental (m = 1) frequency is the desired one.
If m > 1, there are higher order harmonics in output => harmonic distortion.
Can be generated both inside an offender or a victim system.
In the case of two input frequencies, vin = cos 1t + cos 2t , output will consist of harmonics m1 + n2, where n and m are positive or negative integers.
Intermodulation is the process of generating an output signal containing frequency components not present in the input signal. Called intermodulation distortion (IMD).
Most harmful are 3rd order (|m| + |n| = 3) products.
Can be generated both inside an offender or a victim system.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Interference from Other System
GSM spurious emissions and intermodulation results of GSM 1800 interfere WCDMA receiver sensitivity
WCDMA spurious emissions interfere GSM receiver sensitivity
GSM transmitter blocks WCDMA receiver
WCDMA transmitter blocks GSM receiver
GSM 1800 UL
GSM 1800 DL
Customer Confidential
M Distortion
from GSM1800 DL to WCDMA UL
GSM1800 IM3 (3rd order intermodulation) products hits into the WCDMA FDD UL RX band if:
1862.6 f2 1879.8 MHz
1805.2 f1 1839.6 MHz
For active elements IM
products levels are higher
than IM products produced
WCDMA
DL
WCDMA
UL
GSM1800
DL
GSM1800
UL
Customer Confidential
Harmonic distortion
Harmonic distortion can be a problem in the case of co-siting of GSM900 and WCDMA.
GSM900 DL frequencies are 935 - 960 MHz and second harmonics may fall into the WCDMA TDD band and into the lower end of the FDD band.
GSM900
1900 -1920 MHz
2nd harmonics can be filtered out at the output of GSM900 BTS.
f
Customer Confidential
Isolation Requirements
1710 MHz
1785 MHz
UMTS Rx
2110 MHz
2170 MHz
For example - To prevent UMTS BTS blocking: with transmit power = 43 dBm
Max level of interfering signal for blocking = -15 dBm in UMTS
Isolation required = 58 dBm
Customer Confidential
Isolation can be provided in a variety of different ways.
By antenna selection and positioning.
By filtering out the interfering signal.
By using diplexers and triplexers with shared feeder and multiband antennas.
UMTS
GSM
Filter
UMTS
GSM
Diplexer
UMTS
GSM
Customer Confidential
Difficult to calculate isolation between two antennas and measurements are required.
Best configurations - antennas pointing in different directions or where there is vertical separation between antennas
The following configurations will should all give 30dB isolation.
d
d
d
90º
120º
d
d
180º
d
Customer Confidential
Site sharing with third party systems
Some UMTS sites might be co-located with other non GSM operators.
PMR
Broadcast
Navigation
Some of these systems use older equipment which might be more vulnerable to EMC issues.
Need to define minimum antenna separations between systems
Better to avoid sites used for safety critical applications.
UMTS antennas
Other systems
Minimum separation
Customer Confidential
Rules of thumb:
h d/3, 10 < d < 20 m
h d/4, d > 30 m
Top view
Side view
h (meters)
d (meters)
Clearance angle
Customer Confidential
Antenna installation
Safety margin of 15 between the reflecting surface and the 3 dB lobe
d has to be >
Customer Confidential
Customer Confidential
Customer Confidential
A nominal plan is initially a hypothetical wireless network.
The nominal plan is the starting point for the cell rollout process and will evolve into the final network design.
As physical sites are identified and acquired, the nominal plan is amended.
Nominal Plan
Customer Confidential
Identifies the approximate number of sites required.
Identifies the approximate site radii required for:
Urban/Suburban/Rural areas
Voice/Data services
Typical cell radii estimates
Service supported
Customer Confidential
Create Nominal Plan
Position a hexagonal grid of sites over the desired coverage area.
The radius of each hexagon can be determined from the previous slide.
The capacity of the network can then be analyzed to detect:
Hot spots that require cell splits.
Under used cells that could be removed from the plan.
Example nominal plan for Jersey
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
The sites in a nominal plan are only imaginary.
To become a real network, physical sites are required.
A suitable physical site must be found for each nominal site.
A suitable physical site must amongst other things:
Give adequate radio coverage.
Be aesthetically and politically acceptable to the local community.
Have power nearby, good access and a co-operative owner.
A survey of each nominal site is normally carried out to identify possible site options which meet the above criteria.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Define Search Areas
Guidelines have to be given to the surveyor so the options give appropriate radio coverage.
The guideline is given in the form of a search area. Could be:
Radius from the nominal site.
One or more polygons following height contours.
Or
Customer Confidential
Surveyor visits each search area and identifies potential site options.
The first sites to be considered should be
Existing radio sites.
Sites offered from major site owners (MSO) E.g. Utilities & Railways.
All options should meet certain criteria to ensure that they are
Technically acceptable.
Build able
A good idea to consult with the planning/zoning authority during the survey.
Good training of surveyors will save time later in the build process.
* © Nokia Siemens Networks NetAct Simulation Procedure/Jan2008
Customer Confidential
Report will include:
Accurate grid reference.
Photographs of the site.
360º panoramic photos from site or if obstructed from nearby location/structure.
A
D
C
B
Customer Confidential
Site Selection
Quickly eliminate unsuitable options.
Nominate a preferred option and possibly a backup option.
A3rd
D1st
C2nd
Customer Confidential
Detailed Site Design
Prior to commencement of construction work, a detailed site design is required.
Includes
Equipment capacity requirements
Can’t be completed in isolation. Must take into account other sites.
60º
60º
180º
180º
300º
300º
Customer Confidential
Check that the coverage is in line with your expectations.
Adjust site locations and add additional sites if improvements to coverage is necessary.
Check for excessively high sites.
* © Nokia Siemens Networks WCDMA Planning Fundamentals/Jan2008
Customer Confidential
Thank You
b
e=b+c-d
g
l=10*log10(1/(1-(k/100)))
m=h+j
Information rate dBHz48.06
Soft Handoff Gain dB4.5
s
t
pl=e+f+q-g-p-r-s-t