133637039 Mobile Access Training for UMTS

RF Design CourseMobileAccess Student Manual

MobileAccess Confidential 1

Upon Successful Completion of this lesson you will be able to:

Understand the basic wireless voice technologies and frequency bands

Comprehend the factors that affect a link budget

Develop a comprehensive RF design document for the customer



Wireless Technologies at a Glance

Note: For simplicity, only one block is shown although there are corresponding pairs of

uplink and downlink channels.

iDEN/SMR and analog channels occupy 25 or 30 kHz discreet channels that repeat in

blocks. Analog allows for 1 traffic channel per discreet channel. iDEN/SMR allow for 1 to 6

time/traffic slots per channel, depending on BTS type. The power level per channel is fixed.

TDMA uses 30 kHz channels that repeat in blocks with 2-3 traffic slots in each channel (2 in

control channels, 3 in all other channels). GSM uses 200 kHz channels that repeat in blocks

with 8 time slots in each channel (1 control, 7 traffic). The total power level of the channel is

constant.

CDMA uses 1.25 MHz channels (also known as CDMA carriers) that can theoretically carry 64 independent traffic slots. The actual number is dependent on the amount of noise

affecting the site. The total power in a CDMA carrier is dependent on the number of traffic

channels in use and their relative power requirements. MobileAccess uses the following

rules of thumb for CDMA: -3 dB backoff for BDA (half the traffic for the DAS, half for the outside world) and -6 dB for BTS application (everything for the DAS).

UMTS or W-CDMA operates very similar to CDMA but uses a 5 MHz channel. The back-off

factor for UMTS is -8 to -10 dB.



PCS Frequencies

This table displays the uplink and downlink blocks for PCS services.

C-Block has been divided up into 3 sections and re-auctioned.

The G-block was provided to Nextel (now Sprint) by the FCC as part of their re-banding plan

for 800 MHz Public Safety.

Wireless Service Providers (WSPs) have also sold and/or exchanged portions of their full

licensed blocks so the actual frequencies to be covered need to be verified for every

network.



Cellular Low Band Frequencies

Cellular band is broken into non-contiguous blocks.



Low Band Frequencies

This table displays the low band services.

iDEN is also known as 800 SMR and 2-way radio.

SMR is also known as 900 SMR and 2-way radio.

Public Safety frequencies are located at 821-824 MHz UL and 866-869 MHz DL.

E-GSM and GSM are typical terms used for the European low band licensed frequencies.



The FCCs rules require winning bidders for CMA (B Block) and EA (A and E Block) licenses, to build out service and offer signal coverage to 35% of their geographic license

area within four years from the end of the DTV transition (four years from Feb. 2009), and

70% of the license area by the end of the license term, which is 10 years in length, Zufolo stated. For larger license areas in the C Block a population-based buildout requirement is applied and must provide signal coverage to 40% of the population of each [economic

area] in its license area within four years of the license term; and at least 75% of the

population of each EA in its license area by the end of the license term.



Typical Combinations:

These are the typical frequency bands and technologies that will be included in a multi-

operator network, but they should be confirmed on a market-by-market basis.

The exact licensed bands and desired capacity for each wireless service provider should

also be known prior to developing a RF design for an area so that the best combination of

remote hub units and MA1200 Add-ons can be used.



Frequencies Supported

The table above lists the supported MobileAccess frequencies.



Wireless Voice Applications

Voice Coverage Requirements are generally set by the customer. Applications that do not

require wireless internet generally are designed for a coverage pattern of -85 dBm over 90%

of the building. Stairways and elevators benefit from residual coverage but are usually not

covered at those same signal levels since its generally against building fire code to install antennas in those locations, but permission can be granted with the fire marshals and building owners/managers cooperation and approval.



WLAN Applications

This table provides some general design guidelines for WLAN coverage. The healthcare

targets are higher in order to help to ensure that the system can be upgraded to WMTS

later.

It is imperative to perform an RF site survey to verify the required RSSI targets can be met

with the proposed antenna spacing.

Also, buildings may have competing Wi-Fi networks that may require a change in your RF

design assumptions. The installation of one blue tooth device near your coverage area may

completely jam the Wi-Fi network so its especially important to locate any existing radiating sources in the coverage area and identify their uses.



Limiting Factors Order of Precedence

The above graph displays the typical limiting factors. Capacity requirements or higher

mobile RSSI levels might dictate denser spacing for particular technologies and change this

order of preference.



Link Budget Analysis Uplink

The table shown above lists the typical factors taken into account when analyzing the uplink

path from the mobile to the MobileAccess remote hub unit. The calculations above include

accounting for 32 RHUs connected to a single radio equipment sector since this is the

maximum number of RHUs that can be connected to a MobileAccess RIU. It also includes

the coaxial cable loss and antenna gain to determine the maximum allowable uplink path

loss.



Link Budget Analysis Downlink

The table above illustrates the downlink path from the RHU to the handset. It takes into

account the same factors as the uplink path.

Comparing the maximum allowable uplink and downlink path losses shows that the system

is downlink limited for up to 32 RHUs. By designing the system to be balanced or downlink-

limited, it ensures that the mobile (the weakest device in the system) will be able to

overcome the noisy environment to speak with the radio equipment to place calls. If the system were uplink-limited, then the output power of the RHUs would need to be reduced

until the system is balanced (uplink loss equals downlink loss) or downlink-limited.

Most of the MobileAccess networks will be downlink-limited. The exception to that

assumption is when MA330 links are used. Please see the next slide.



Link Budget Calculations with MA330 Links

MA330 links have a higher noise figure than the RHUs (42 dB vs. 20 dB). They are the

greatest noise contributor when included in a network, but that is generally a small price to

pay for extending services to remote buildings in a campus environment or overcoming high

fiber losses.

The spreadsheet calculations shown above are based on the Friis formula that calculates

the effects of noise on multiple amplifiers installed in a chain. The resulting Noise Figure

can then be used in the previously shown uplink and downlink link budget calculations to

determine the effect of adding MA330s to a single radio sector.

For this example, there is one MA330 link used to service 32 RHUs installed in MRC

cabinets. The MA330 remote connects to the Base Units (BUs) that drive the 32 RHUs.



For this example, there are 4 MA330 links used to service 8 MRC cabinets within each

building. The campus noise figure calculates the cumulative effective of all 4 buildings being

served by a singe sector.



Link Budget Calculations with MA330 Links- Uplink

Notice that the Total Remote Unit Noise Figure From Noise Spreadsheet field has been updated with the new noise figure of 46.49 (46.5) dB for the 4 MA330 links feeding 32 RHUs

each (128 RHUs total). This change reduced the Maximum Allowable Uplink Path Loss to

99 dB from 111 dB (for 850 MHz) in the example with 32 RHUs but no MA330 links.



Link Budget Calculations with MA330 Links- Downlink

Using the new value of 99 dB for Maximum Allowable Uplink Path Loss and no change in

the downlink path except for the -101 dBm mobile RSSI level, the system is now uplink-

limited. Uplink-limited means that the mobile cant effectively communicate with the radio equipment even though the mobile is showing full bars on its strength indicator.

However this example shows the system operating to its extreme limits with respect to receiver sensitivity of the devices. A better example would be to show the effect of the

additional noise on a system designed for a target mobile receive level (full bars vs. minimal strength).



Link Budget Calculations with MA330 Links- Downlink

Changing the Minimum Signal Level at Handset from -101 dBm to -85 dBm (typical full bars strength indicator) changes the uplink vs. downlink comparison. The new minimum signal level results in the system being downlink limited by 5 dB for this example using GSM

phones in the 850 MHz band. Some WLAN devices transmit even less power.

In conclusion, the design engineer needs to continually review the link budget to ensure that

the system always has a balanced path to meet the customers requirements for service. In general, the MobileAccess networks are designed to be slightly downlink-limited.



Link Budget Calculations Downlink only

Most DAS networks are downlink-limited so were going to concentrate on the factors that affect the downlink patch.

This analysis will take into account the power output for the frequency and technology used,

RF splitter/combiner losses, coaxial cable losses, antenna gain, and environmental losses

within a pre-defined coverage area.

Each particular item will be addressed in the following slides.



Link Budget Calculations

The maximum power output for each radio is input into the field RHU output. This figure can be derived from the data sheet or by taking the maximum composite power output of the

device and subtracting 10*LOG(number of carriers) for greater than 12 channels.




In this case, 6 CDMA carriers is between 4 and 8 carriers, which have 14 dBm and 11 dBm

power per carrier respectively. Since 6 is exactly halfway between 4 and 8, the power levels

for 6 carriers is exactly halfway between their power levels as well at 12.5 dBm.

Note: Remember that the column titled GSM represents 900 MHz frequencies used in Europe (not the GSM technology used in the US).




To share power between multiple WSPs or technologies in the same amplifier, generally

each one gets half the available power. After determining the power per channel for each

WSP, you subtract 3 dB to get the power per channel when sharing with another WSP or

technology.



Link Budget Calculations Splitter Losses

Splitters are also known as power dividers. Examples with typical losses are shown on the

next two slides.



Link Budget Calculations RF Splitters

The next step in this link budget analysis is to consider the insertion losses associated with

using passive RF splitter/combiners, such as the two types shown above. Check the

manufacturers data sheet for exact splitting and insertion losses as these do vary slightly.

RF Splitters are also known as combiners and power dividers. Couplers may also be known

as unequal power dividers since the coupled and thru-put ports have different losses. Equal

power dividers have the same losses on all ports.



Link Budget Calculations MA860/WCE WLAN Module Losses

When WLAN is added to the DAS using the MA860 and WCE modules, then the cellular

services will be affected by the combining losses for those services. The WLAN services

are not affected though since the purpose of the MA860 & WCE is to replicate the AP on the ceiling behavior.



Link Budget Calculations Cable Losses

Another major factor to consider in the link budget analysis is the coaxial cable losses. The

insertion loss varies according to frequency.

The connector losses are included above as part of the total coaxial cable losses.

As always, check the manufacturers data sheet for the exact specifications to use.



Link Budget Calculations Antennas

The gain and pattern of the antenna play a major factor in the system design. Make sure to

check the manufacturers data sheet for their specifications before developing your link budget.



Link Budget Calculations Omni Antennas

Note: The CellMax antenna has a built-in jumper cable, which makes it cost effective where

802.11a is NOT required since it doesnt cover to 6 GHz.

The MobileAccess and Mars antenna both require jumper cables but cover from 450 MHz to

6 GHz, including 700 MHz.



Link Budget Calculations Panel Antennas

Panel antennas may also be used to provide a more controlled coverage area. They are

typically mounted against a wall or post.

The CellMax Panel antenna includes a jumper cable but only covers from 700 MHz to 2.5

GHz. The Mars antenna covers covers the same frequency range but requires a jumper

cable. The European Antennas panel covers from 700 MHz to 6 GHz and also requires a

jumper cable.



Link Budget Calculations Path Loss

The following slide shows the formula used in the free space calculation for Path Loss.



Body Losses

Body losses are generally accepted to be 2 dB. They may need to be higher for some public

safety solutions to account for radios under thick layers of protective coverings.



Wall/Clutter Losses

The number and composition of the walls between the antenna and pre-defined coverage

area radius should be calculated to determine the Total Wall/Clutter Losses in the link

budget.



Wall/Clutter Losses

Losses for typical environments are listed above. Actual losses should be verified during the

detailed RF site survey as materials and installation standards can vary widely.



Path Loss

The MobileAccess link budget method is reflective of the red line shown above for path loss.

This line shows free space path loss with each major obstacle (wall/clutter) reducing the

signal level.



Fade Margins

Choosing a fade margin factor is based on statistical analysis to increase the probability that

the received signal level will be equal to or better than the target RSSI level. Fade margin

can also be used to account for environmental factors, such as shadowing and diffraction.



Fade Margins

The numbers shown above are used by MobileAccess for most designs, and each designer

must choose the fade margin for his/her designs.



CDMA and UMTS/WCDMA Traffic Loading

See the next slide for the backoff factors used for CDMA and UMTS/WCDMA to account for

traffic loading.



Link Budget Review



Please refer to the data sheet for more details on this product.



Note the requirements for combining the UHF uplink and downlink into a common antenna.

The total bandwidth for the channels can not exceed 1.5 MHz and must have 2.5 MHz

separation to allow for 50 dB isolation between the uplink and downlink paths. If these

requirements cant be met, then separate uplink and downlink antennas are required.



When combining UHF services with the WSP services (either simplex or duplex for UHF),

remember to take into account the losses associated with the crossband couplers. These

are usually 3-4 dB for all services.



Some enterprise customers may not have access within tenant spaces to install antennas so

panel/directional antennas in the hallway may be the only option.

Strong mobile RSSI levels (> -70 dBm) are sometimes more easily achievable with panel

antennas on the outer edges of the building facing in.

Generally speaking, most systems are designed with omni antennas in the corridors.



Headend and Fiber Management

The diagram above illustrates the standard approaches MobileAccess uses to manage fiber

cabling at the headend, RHU, and intermediate distribution fiber (IDF) closets.

Fiber jumpers are used at the headend patch panel since this is where future capacity

upgrades will occur.

Pigtails are used to connect the fiber backbone directly to the RHUs and lateral fiber runs to

reduce fiber losses.

A couple of additional notes for multi-mode fiber (MMF) networks:

1. The type of MMF (62.5/125 or 50/125) used must be the same throughout the entire run

between the BU and RHU.

2. The maximum length for MMF is 300 meters between the BU and RHU.



MA1000/1200 Installation

The diagrams shown above illustrate the components and connector types used for a

MA1000 installation both with and without the MA1200 PCS Add-on. The MA860 and WCE

WLAN modules are not shown but could also be included in this installation.

Please note that the NEMA enclosure must have sufficient passive ventilation to allow the

modules to effective dissipate heat.



Note: if you use a N-M directly to the splitter, then youll need to adjust the connector count accordingly in the Bill of Materials.



MA2000 Lite Installation

The diagram shown above illustrate the components and connector types used for a

MA2000 Lite installation. The RHUs and filter module can be installed against a wood

backplane or in rack shelves. The MA1200 PCS Add-on and MA860 and WCE WLAN

modules are not shown but can be included as required.



MA2000 MRC Installation

The diagram shown above illustrate the components and connector types used for a

MA2000 MRC installation. The MRC can be installed against a wood backplane, drywall

with support anchors, or in a 19 rack. The MA1200 PCS Add-on and MA860 and WCE WLAN modules are not shown but can be added as required.



MA860 WLAN Installation

The diagram above shows the MA860 WLAN module connector types.



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MobileAccess Power

In this picture we see two separate power supplies which are available for use within the

system. Both of these power sources are designed to be attached directly into 115 volts AC

distribution through a standard power cord. Which power source will be required will depend

on the load of the individual equipment. All products operate on 24-48 VDC.

The 66 Watt supply is used for a single remote unit and the 100 W is used for a remote with

a PCs add on unit. Notice, the 100 Watt supply has 2 DC connectors

20% Reserve

Any 24-48 VDC supply may be used and the DC connectors can be daisy chained. Ideally

leave about 20% reserve in watts for temperature variation.



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Remote Powering Option

In this diagram the elegance of distributed power is displayed. A single power source can

be used to power a number of remote units within a single building. If all of the elements are

powered through the use of remote power tied to battery backup the system remains

available for considerable length of time during power interruptions.

Each pair of electrical conductors is limited to 100 W.

Using 18 gauge wire (18 AWG) the maximum distance between the power source and the

load must not exceed 1000 Ft.

If greater distance is required, then 16 or 14 gauge wire may be used since it offers less

impedance.



The DC power supply system approach that we have developed for the MobileAccess projects was taken in order to achieve compliance with the National Electrical Code (NEC) and building code requirements, for installations where there is plenum-rated open wiring above suspended ceilings.

Other considerations:

All plenum-rated cables are rated for 300 volts maximum, which limits us to NEC Class 2 wiring as defined by the NEC, which must be supplied by power supplies UL listed as Class 2, in order to comply with NEC requirements.

The basic requirement for a power supply that is UL listed as Class 2 is that it can not exceed 100VA (or 100 watts for DC systems), which is 2.1 amps at 48 VDC. The power supply must be inherently current-limiting using its electronics; you can not put a 2A fuse on a 1000W power supply and consider it Class 2. The Class 2 UL listing must show on the UL sticker, so an electrical inspector can readily verify the provision.

Putting the cabling in conduit is generally not desired for cost reasons. If the cabling is in conduit, then the wiring can be classified as Class 1, and the NEC Class 2 wiring limitations do not apply. However, the installed system cost goes up substantially.

As you can see, the NEC requirements on this are not as straightforward as they could be, thus the confusion in the industry. If you have an installation with open wiring fed by power supplies that are not UL listed Class 2, then:

(A) The electrical inspector can disapprove the installation, requiring replacement of wiring or power supplies, and/or

(b) The installing organization is liable if there is any subsequent damage to the property by fire or injury to personnel by shock.

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Basic Elements

These are the basic elements that MobileAccess includes in its design documents.

Responses to particular RFP/RFQs or customer requirements may include additional

elements, such as project plans, additional specifics on the equipment installations, and/or

capability statements, for example.



Sample Design Plan

The design plan or conceptual drawing is used to provide a customer with a one-page

overview of what the system will look like. It can be presented in many creative ways as

long as the designer, installer, and end customer can understand it.



Sample Floorplans

The floorplan above shows the proposed antenna locations and cable routing, including

between the floors. It also includes a key for the cable types used and unique identifiers for

all components. The individual cable run lengths are not shown but could also be included.



OET65 Overview

OET65 was developed to provided guidelines for limiting human exposure to radio

frequency electromagnetic fields for all wireless technologies.

The maximum near field limit is calculated for up to 1500 MHz and is a static 1 mW/cm2 up

to 100,000 MHz. The power density limits shown above are for general

population/uncontrolled exposure.

There are two different limits for exposure: general population/uncontrolled exposure and

occupational/controlled exposure.

The calculations shown above are for the worst case scenario for in-building networks.



850 MHz Example

The graph above shows how power density (blue line) would decay rapidly as the distance

from the antenna increased. The red line indicates the maximum exposure limit for the

frequency used.



OET65 WLAN Guidelines

2.4 GHz WLAN is evaluated using Supplement C to OET65 Bulletin.

133637039 Mobile Access Training for UMTS

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