Wcdma Rnp Link Budget

WCDMA RNP Link Budget *WCDMA RNP Link Budget

Link Budget in WCDMA The link budget is used to calculate the maximum path loss to maintain a link between the transmitter and the receiver on a specific environment. Thus the corresponding cell range can be derived from the path loss with a propagation model.

Contents Introduction

Parameters of Link Budget

Example of Link Budget

Introduction Link Budget

Forward link :Difficult to assess: depends on the cell edge level of interference on the location of the mobile

Reverse link:Easy to assessLargely used in RND / RNO

IntroductionInterference

WCDMA is intrinsically Interference limited system

Coverage and capacity depend on the interference experimented by the receiver

IntroductionInterference on the Forward link

Primary source of interference: typically power broadcasted by surrounding cells

Secondary source of Interference: other links in the same cell serving other UE

IntroductionInterference on the Reverse link

Primary source of interference: other UE in the same cell

Secondary source of Interference: other UE outside the cell. These UE are not under the power control of the cell.

IntroductionInterference reduction during RNP

criticalNeed of thorough guidelines in order to:Reduce co-channel interference Reduce adjacent frequencies interferenceown networkNetwork of Competitors

Link Budget ParametersAnalysis Scenarios

Maximum Transmission Power of DCH

Cable Loss & Body Loss

Antenna Gain

EIRP(Equivalent isotropic Radiation Power)

Noise Figure

Required Eb/No

Sensitivity of receiver

Link Budget Parameters

Interference margin

Margin of Background Noise

Fast Fading Margin

Minimum Required Signal Strength

Penetration Loss

slow Fading Margin

Soft Handover Gain

Propagation Model

Analysis ScenariosMorphology

Generally, there are 5 types of planning area:Dense UrbanUrbanSuburbanRural AreaHighway

The type of area impacts:Mean penetration lossStandard deviation of slow fadingPropagation Model & the factor of path loss

Analysis ScenariosMorphology (Cont.)

Various planning strategies are applied according to the type of area. It is necessary to configure following parameters:Channel modelSectorizationIndoor coverageTarget service (seamless coverage)TMA and Diversity modeCell loadingAverage antenna heightCable loss

Analysis ScenariosChannel model

The channel model defines the number of signal path, relative path loss and delay variance to abstract the wireless channel.According to specifications of 3GPP R4(TR25.943 V4.0.0), typical channel models are used as following:Static: no multipathTU3: typical urban area, pedestrian, 3km/hTU50: typical urban area, vehicle, 50km/hTU120: typical urban area, vehicle, 120km/hRA120: rural area, vehicle, 120km/hRA250: rural area, vehicle, 250km/hHT120: high terrain, vehicle, 120km/h

Analysis ScenariosChannel model (Cont.)

Values of some parameters vary with the channel in the wireless environment. The variances are acquired generally by the link simulation.Link performance: required EbNo in both channelsDownlink interference margin: due to the variance of orthogonal factor in different channel environmentsFast fading margin (Power control headroom): due to different link performanceSoft handover gain over fast fading margin: due to different link performance

Analysis ScenariosSectorization

Three types of sectorization are commonly used:Omni 3-sector6-sectorThe item cause changes:Antenna gain: the antenna type is different with the sectorization. Cell loading: the area of cell coverage and thus soft handover overhead vary with sectorization.

Analysis ScenariosBearer Type

This is the bit rate that the user service requires.Generally in UMTS the following options are supported:4.75 kb/s5.15 kb/s5.9 kb/s6.7 kb/s

The requirements of EbNo are different with bearers or services.7.4 kb/s7.95 kb/s10.2 kb/s12.2 kb/s(AMR Voice Codec)64 kb/s LCD&UDD144 kb/s LCD&UDD384 kb/s LCD&UDD

Analysis ScenariosDiversity mode

The diversity in Node BUplink receive diversitytwo-antennafour-antennaDownlink transmit diversityNoneSTTD (Space Time Transmit Diversity)Closedloop-Mode1Closedloop-mode2The link performance, required EbNo, is improved by the diversity.

Analysis ScenariosTower Mounted Amplifier (TMA)

TMA will boost signal strength to overcome the effect of noise in the first amplifier on the receiver. It can be very useful when the feeder loss is so large.The noise figure of the receiver will be improved if TMA is used.

Analysis ScenariosIndoor coverage

Whether indoor coverage is available depends on the intention of the operator.The penetration loss and the standard deviation of slow fading are subject to the requirement for indoor coverage.

Maximum Transmission Power of TCHUplink TX Power

For a UE, the maximum transmission power of DCH is the same as its nominal maximum output power.The UE is assumed to transmit the maximum power in the link budget. According to 3GPP TS 25.101 V3.7.0, four classes of output power are specified for UE:

Power Class

Nominal maximum output power

Tolerance

1

+33 dBm

+1/-3 dB

2

+27 dBm

+1/-3 dB

3

+24 dBm

+1/-3 dB

4

+21 dBm

2 dB

Maximum Transmission Power of TCHDownlink TX Power

The maximum transmission power for a TCH in the downlink is determined by the RNC and varies with the service. In the link budget, it can be configured according to the service type, capacity requirement and concern of link balance.

Cable Loss

The cable between the cabinet and the antenna or TMA often introduces loss of signal power.

The cable loss impacts:Noise Figure of the receiver in the uplinkEIRP in the downlink

For the 7/8 cable, the loss is about to be 6dB per hundred- meter length in 2G frequency band. Besides, the loss of jumper and connector should be included.

Body LossIntroduces the effect of the human being handling the terminal in the link budget.

And depends on the operational conditions.

Typical values are about 3dB for voice service and 0dB for data service.

Antenna GainAccounts for the gain at the antennas of the mobile terminal and Base Station

Typical values for the Mobile station are 0dBi .

Base station antennas gains are dependant on configuration.

EIRPEquivalent Isotropic Radiation Power (EIRP) is defined as follows in Link Budget:

Noise FigureUETypical value for UE receiver is 7dBBSDefine the cable connector of the antenna as the reference point for NF calculation to accommodate the cases of with and without TMA In the case of without TMA and 3 dB for cable loss, according to the following diagram and the formula of NF calculation,

the noise figure can be calculated as follows:

Cable

NodeB

NF

Gain

XdB

NF at this port: 2.72 dB

-XdB

Noise FigureBS (Cont.)In the case of with TMA and 3dB for cable loss,

similarly the noise figure can be calculated as follows:

Note: the NFCabinetTop is a variable parameter because of gain adjustment to compensate gain variance and maintain a constant RF channel gain.

Cable

TMA

NodeB

NF at this port is Channel Gain related, See Table Below

NF

Gain

XdB

-XdB

Jumper before TMA

2.0dB

12dB

0.5dB

-0.5dB

Required EbNoNeeded by the user service to maintain the link with acceptable quality.

Output from Link-level Simulation according to the following factors:Channel type Mobile speedQoSReceiver implementation

Sensitivity of the ReceiverMinimum signal power on the cable connector of antenna needed by the receiver to demodulate signal with specific BER or BLER target.In the Link Budget, the sensitivity of receiver is determined by performance of BS or UE itself and required Eb/No.Diversity, service and channel-related impacts on the sensitivity of receiver are included in the relevant required Eb/No K: Koltzmann constant T: temperatures in degrees Kelvin W: receiver bandwidth NF: Noise Figure of the receiver on the cable connector of antenna EbNo: required demodulation threshold Rb: bit rate of service

Sensitivity of the ReceiverNote that the concept of sensitivity of the receiver is different from that defined in the specification of 3GPP TS25.104 V3.7.0 in the following aspects:Reference point: it is the cable connector of the antenna whether a TMA is available in the link budget; comparatively in the protocol it is defined as where the figure indicates:

Diversity mode: it is assumed a receiver with available diversity in the link budget; but none for the requirements in the protocol.Channel model: only static channel is assumed in the specification requirements.

From

antenna connector

(

External LNA

(if any)

External diplexer

or

RX filter

(if any)

Test port B

Test port A

BS

cabinet

Interference MarginThe interference margin is used to account for the increase in the interference level within the cell due to other users.

It introduces in the Link Budget a way for accounting for the loading of the cell.

The more loading is allowed the larger margin is needed.

Typical values for the interference margin are between 1-3dB corresponding to 20%-50% loading in the uplink.

Uplink LoadingThe loading factor can be defined as:

Where Rj is the bit rate of the j-th link in the cellj is the user activity factori is the other to own cell interference ratioEbN0 is the target for the j-th link in the cellW is the chip rate

Uplink Interference MarginThe uplink interference margin should be equal to the maximum planned noise rise in BS receiver:

Downlink LoadingIn the Downlink the loading factor can be expressed as

Where j is the orthogonality factor in the downlinkRj is the bit rate of the j-th link in the cellj is the user activity factor ij is the other to own cell interference ratio of j-th linkEb/N0 is the target for the j-th link in the cellW is the chip rate

Downlink Interference MarginThe downlink interference margin should be equal to the planned maximum noise rise in the receiver of UE on cell edge. For a user j on cell edge:

Downlink Interference MarginWhere j is the orthogonality factor in the downlinkRj is the bit rate of the j-th link in the cellj is the user activity factor ij is the other to own cell interference ratioEb/N0 is the target for the j-th link in the cellW is the chip ratePCCH is the common channel power transmitted by the BSPN is the noise floor of UECLj is the coupling loss, which is the loss between the antenna connectors of BS cabinet and UE receiver for j-th link

Downlink Interference MarginAssuming there are enough users in the cell and demodulation performance is irrelevant to location, such approximation can be supposed:

Downlink Interference MarginSo the downlink interference margin can be written as:

Note: mean values without subscript j refer to averaging over all users in the cell; mean values with subscript j refer to averaging over users on the cell edge.

Interference Margin (IM) vs. Load FactorAn example of downlink interference margin vs. downlink loading with balanced links is depicted as:

Interference Margin vs. Load FactorIt indicates a nonlinear relationship between downlink interference margin and load factor. While downlink load factor approaches unit, the system reaches its pole capacity and the noise rise over thermal goes to infinity.Because of common channel power, the noise rise over thermal is a non-zero value while no user accesses to the cell. It is different from that of uplink.

IM vs. Load Factor vs. Coupling LossAccording to the following figure, it should be noticed that the variation of coupling loss on the cell edge will impact the noise rise of UE there.

Total Transmission Power vs. Load FactorIn the downlink, it is important to estimate the total amount of BS transmission power required.

Total Transmission Power vs. Load FactorStarting from the same point where load factor is zero, power requirements reach the maximum limited by the power amplifier in different rates, and with different downlink loading.

And the figure also presents that the larger the cell range, the faster the increase rate and the less load factor while hitting the limit. It means that for a large cell, the BS should allocate more power for compensating path loss instead of more links than the BS of a small cell does.

Optimal Design with PA and CapacityGenerally, the larger maximum transmission power , the more available capacity. But regarding the issue of cost-performance ratio, there is a optimal design with capacity and maximum transmission power, which determines the cost of the power amplifier, the most valuable component of BS hardware.

Another Definition of DL Load & IMDue to the limit of transmission power in downlink, the loading can be estimated by:

Accordingly, the interference margin in downlink is:Note that mean values of j, ij and CLj are caculated by averaging over users on the cell edge.

Another Definition of DL Load & IMWith given j, ij, CLj and maximum transmission power, the interference margin changes linearly with the load in the DL. Due to an intuitive linear relationship, together with the concern of the link between transmission power and capacity in the downlink, this definition of DL load and interference margin is applied in the link budget.

Margin of Background NoiseAccounts for the environmental noise above the thermal noise of the receiver.

The background noise is introduced by other systems, human beings and so on.

A non-zero margin of background noise means:Reduced cell range of the networkReduced capacity of the network

Fast Fading MarginIn the link budget, the required EbNo is estimated by the link-level simulation with the assumption of perfect power control.The assumption will be invalid If a terminal transmits with maximum power on the cell edge and subsequently suffers from fast fading. It is because the terminal cannot respond to the power increase command issued by power control algorithm from RNC.The fast fading margin, or PC headroom, is included to account for the additional headroom needed in the mobile station transmission power to maintain adequate power.Consequently, fast fading margin can be calculated as:

Minimum Required Signal StrengthOn the base of sensitivity of the receiver, together with gains, losses and margins, the minimum signal strength required for achieving link quality can be estimated by:For the uplink

For the downlink

Penetration LossIf indoor coverage is guaranteed, penetration loss should be included in the link budget.Angles of incidence, building structures and material are among the factors determining penetration loss.It is assumed that penetration loss is log-normal distributed and described with standard deviation and mean value.In the link budget, the standard deviation of penetration loss combine with that of path loss to calculate the standard deviation of indoor loss according to the following formula:

Slow Fading MarginIf the Transmitter cannot increase its output power and compensate the path loss to ensure minimum required signal strength on the Receiver, the link will be failed and outage occurs.

In order to ensure the coverage probability, or keep a certain link outage probability, the Slow Fading Margin must be considered.

Slow Fading Margin is relative to the coverage probability, slop of path loss and Std Dev of slow fading.

Slow Fading MarginThe outage probability is:

It is obvious that when a UE is located on the cell edge, it is of most possibility for a outage to occurs. Where , it represents the difference between maximum permitted path loss and average path loss at a location with the distance of r.

Slow Fading MarginWith given standard variation of slow fading and maximum outage probability on the cell edge, the cell range can be deduced by following diagram:

slow fading margin and reserved in the calculation of path loss to ensure the coverage reliability.More common than outage probability, minimum edge coverage probability or area coverage probability are used in the target of network planning.

123123Reverse path loss function specified by Propagation Model

Slow Fading MarginConsidering the following expression:

It is assumed Smin is unrelated to the location. It is true for the uplink.Because the interference margin in the downlink is subject to the location, the assumption is somewhat invalid. But for the purpose of simplification, the slow fading margin in both directions are supposed to be the same.

Soft Handover GainSoft handover gain accounts for the diversity gain achieved during soft handover conditions . In link Budget, we divide it into two parts as follows: SHO gain over fast fading (Macro Diversity Combining Gain)Reduce the requirement for EbNo on the cell edgeEstimated in different circumstances by the link-level simulation

Soft Handover GainSHO gain over slow fading (Multicell Gain)More uncorrelated paths available to reduce the outage probabilityThe outage probability on the cell edge in SHO area is estimated by:

The gain can be resulted from:

Propagation ModelWith the path loss calculated in the link budget, the cell range for the specific analysis scenario can be figured out by using propagation modelCOST231-Hata, Asset standard macrocell,

COST231-Hata model:

Propagation Model

Asset Standard Macro model is specified as following:

Scenario of Link Budget

Uplink BudgetPL_UL: maximum Path Loss in uplinkPout_UE: maximum transmission power for traffic channel of UELc_BS: cable loss in BSLf_BS: feeder loss in BSGa_BS: antenna gain in BSGa_UE: antenna gain in UEMf: margin of fast fading (TPC headroom) G_Mf: SHO gain over fast fadingMs: margin of slow fading (slow fading)G_Ms: SHO gain over slow fadingMI_UL: margin of interference in uplinkMBn: margin of background noiseLp: mean value of penetration lossLb: body lossS_BS: sensitivity of BS receiver

Downlink BudgetPL_DL: maximum Path Loss in downlinkPout_BS: maximum transmission power for traffic channel of BSLc_BS: cable loss in BSLf_BS: feeder loss in BSGa_BS: antenna gain in BSGa_UE: antenna gain in UEMf: margin of fast fading (TPC headroom)G_Mf: SHO gain over fast fadingMs: margin of slow fading (slow fading)G_Ms: SHO gain over slow fadingMI_DL: margin of interferenceMBn: margin of background noiseLp: mean value of penetration lossLb: body lossS_UE: sensitivity of UE receiver

Cell Coverage CalculationThe coverage area for one site is a hexagonal configuration, which is estimated fromS: coverage areaK: constant accounting for sector configurationr: maximum cell range

Sheet1

Site configurationOmni2-sectored3-sectored6-sectored

Value of K2.61.31.952.6

Wcdma Rnp Link Budget

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