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WCDMA Radio Network Coverage Planning Confidential Information of Huawei. No Spreading Without Permission N-1
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1-OWP112010 WCDMA Radio Network Coverage Dimensioning ISSUE1.21

Jul 16, 2016

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OWP112010 WCDMA Radio Network Coverage Dimensioning ISSUE1.21

  • WCDMA Radio Network Coverage Planning

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    Capacitycoverage (typical case: downlink load balance)

    Capacityquality (typical case: lowering BLER through outer loop power control)

    Coveragequality (typical case: lowering the data rate of the connections with

    much path loss through AMRC)

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    3G radio network planning can be divided into three phases. They are shown in

    above figure, and consist of dimensioning, pre-planning and cell planning.

    According to the above figure, the output result of radio network dimensioning

    stage serves as the input condition of the pre-planning, and the pre-planning is

    based on the network dimensioning and also checks the network dimensioning

    result. The site quantity can be adjusted according to the pre-planning result in

    order to obtain the reasonable sites. If the existing sites are considered in the

    selection of theoretical sites during the pre-planning, the pre-planning result will

    be more practical, thus facilitating the cell planning.

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    Radio Network Dimensioning is a simplified analysis for radio network

    Dimensioning provides the first and most rapid evaluation of the network element

    number as well as the associated capacity of those elements. The target of

    dimensioning phase is to estimate the required site density and site configurations

    for the area of interest. Dimensioning activities include radio link budget and

    coverage analysis, capacity evaluation and final estimation of the amount of

    NodeB hardware and E1, cell average throughput and cell edge throughput.

    Objective:

    To obtain the network scale ( approximate NodeB number and

    configuration)

    Method:

    Select a proper propagation model, traffic model and subscriber

    distribution, and then estimate the NodeB number, coverage radius, E1

    number per site, cell throughput, cell edge throughput and so on.

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    The service distribution, traffic density, traffic growth estimates and QoS

    requirements are already essential elements in dimensioning phase. Quality is

    taken into account here in terms of blocking and coverage probability.

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    Wireless network dimensioning intends to obtain the approximate UTRAN scale.

    Based on the network dimensioning, geography and traffic distribution, the

    network is pre-planned in detail by using planning software and digital map.

    Based on the network dimensioning and site information, the initially selected

    WCDMA site is imported into the planning software, and coverage is estimated by

    parameters setting. Then an analysis is made to check whether the coverage of

    the system meet the requirements. If necessary, the height and tilt of the antenna

    and the NodeB quantity are adjusted to optimize the coverage. And then the

    system capacity is analyzed to check whether it meets the requirement.

    Implementation parameters, such as antenna type / azimuth / tilt / altitude /

    feeder type / length

    Cell parameters, such as transmission power of traffic channel and common

    channel, orthogonal factor, primary scrambling code

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    Based on the network dimensioning and site information, the initially selected

    WCDMA BS is imported into the planning software, and coverage is estimated by

    setting the cell parameters and engineering parameters. Then an analysis is made

    to check whether the coverage of the system meet the requirements. Then the

    system capacity is analyzed to check whether it meets the requirement. If

    necessary, the height and tilt angle of the antenna and the BS quality are adjusted

    to optimize the coverage.

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    These graphs are prediction results of Huawei planning tool: U-Net

    For the result of coverage prediction, focus on the distribution of best servers and

    pilot level. For the small areas with unqualified level, adjust the azimuth and

    down tilt to improve the coverage. For the large areas with weak coverage,

    analyze whether the site distance is over large:

    If yes, add sites to improve coverage.

    If no, check whether the configuration of parameters related to coverage

    prediction is correct.

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    We should consider other factors when we select the backup sites

    Commercial factor: rent

    Radio propagation factor: situation / height / surrounding /

    Implementation factor: space / antenna installation / transmission / power

    supply

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    Simulation is oriented to simulate the running situation of networks under the

    current network configuration so as to facilitate decision-making adjustment.

    Now there are two system simulation classes: static simulation and dynamic

    simulation.

    Static simulation focus on user behavior such as browsing Internet, call. It would

    gain the performance of radio network based on snapshot.

    Dynamic simulation focus on detail of user behavior such as duration and data

    rate of browsing. It would gain the performance of radio network based on

    analysis of mobile subscribers. But it requires higher precision of e-map.

    At present, Static simulation is in common use. Monte Carlo simulation is one

    type of static simulation.

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    Some UEs or terminals are distributed based on a certain rule (such as random

    even distribution) at each snapshot

    It is required to consider the possibility of multiple connection failure

    (uplink/downlink traffic channel maximum transmit power, unavailable channels,

    low Ec/Io and uplink/downlink interference

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    These graphs are prediction results (based on simulation) of Huawei planning tool:

    U-Net

    The previous predictions (Coverage by transmitter, Coverage by signal level,

    Overlapping zones) are based on coverage, the predictions in this slide are based

    on simulation.

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    In the coverage dimensioning, the link is estimated according to elements such as

    planned area, network capacity, and equipment performance in order to obtain

    the allowed maximum path loss. The maximum cell radius is obtained according

    to the radio propagation model and allowed maximum path loss. And then the

    site coverage area is calculated. Finally, the site quantity is calculated. Of course,

    the site quality is only for the ideal cell status, and some additional sites will be

    needed in actual terrain environment.

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    Link dimensioning intends to estimate the system coverage by analyzing the

    factors of the propagation channels of the uplink signal and downlink signal. It is

    the link analysis model.

    If the parameters such as transmit signal power, gain and loss of the transmitter

    and receiver, and quality threshold of received signal are known or estimated, the

    allowed maximum path loss used for ensuring the quality of received signal can

    be calculated.

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    In network planning, the value should be set according to the UE capacity with

    lowest power grade in the commercial network of the operator.

    Note that it is possible that a UE supporting high-speed uplink data service

    (higher than 64kbps) has a higher power grade than a UE supporting only voice

    and low-speed data services, for example, power grade 3dBm 24dBm.

    With a higher maximum power rating, the maximum path loss is increased accordingly.

    This allows the operator to plan cells with a relatively larger coverage.

    The UE cable loss, connector loss, and combiner loss are quite negligible, hence a

    0 dB loss is assumed here

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    The 0 dBi antenna gain is considered here with respect to the internal antenna of

    mobile phones.

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    The penetration loss is related to building type, incidence angle of

    the radio wave and so on. In the link budget, assume that the

    penetration loss obey the Log-Normal distribution. The penetration

    loss is related to mean value of penetration loss and standard

    deviation

    When indoor coverage is required to coverage by outdoor macro NodeBs,

    building penetration loss needs to be considered. Building penetration loss is

    related to such factors as incidence angle of the radio wave, the building

    construction (the construction materials and number and size of windows), the

    internal building layout and frequency. Building penetration loss is highly

    dependent on specific environment and morphology and varies greatly. For

    instance, the wall thickness in Siberian tends to be larger than that of Singapore

    in order to resist coldness and hence the formers building penetration loss is

    correspondingly larger.

    In addition, sometimes vehicular coverage may be required and consequently

    vehicular penetration loss also needs to be included in link budget process. typical

    vehicular penetration loss is around 8dB.

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    Antenna gain: It refers to the ratio of the square of the actual field of an antenna

    at a point in the space to the square of the field of an ideal radiation unit at the

    same point in the space, namely power ratio. It is the gain in the main transmit

    direction. In general, the gain is related to the antenna pattern. If the central lobe

    is narrow and the back lobe and side lobe are small, the gain is high. If the

    transmit direction is centralized, the antenna gain is high. For an omnidirectional

    antenna, the gain in all the directions is the same.

    Front-to-back ratio: It refers to the ratio of the maximum gain in the principal

    direction to the gain in the reverse direction. It describes the directing feature. If

    it is high, the directed receive performance of the antenna is high.

    Beam width: It refers to the separation angle between the main transmit direction

    of the power and the point with 3 dB of transmit power reduced, and the area is

    called an antenna lobe. Tilt: It refers to the tilt angle of a directional plate

    antennal. It is used to control interference and improve coverage.

    Polarization: The vector direction of the electrical field in the direction with the

    highest radiation. A dual polarized antenna can provide diversity over a single

    antenna, thus saving one antenna.

    In general, there are two or more lobes in an antenna pattern. The largest lobe is

    the central lobe, and others are side lobes. The separation angle between the two

    half-power points of the central lobe is the lobe width of the antenna pattern,

    namely, half-power (angle) lobe width. If the central lobe is narrow, the directivity

    is high, and the anti-interference capability is high.

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    Radio propagation in the land mobile channel is characterized by multiple

    reflections, diffractions and attenuation of the signal energy. These are caused by

    natural obstacles such as buildings, hills, and so on, resulting in so-called multi-

    path propagation. Furthermore, with the moving of a mobile station, the signal

    amplitude, delay and phase on various transmission paths vary with time and

    place. Therefore, the levels of received signals are fluctuating and unstable and

    these multi-path signals, if overlaid, will lead to fading i.e. short term fading. The

    mid-value field strength of Rayleigh fading has relatively gentle change and is

    called Slow fading i.e. long term fading. And it conforms to lognormal

    distribution.

    Long term fading the variation of signal level is slow and smooth.

    Short term fading the variation of signal level is fast and poignant

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    Slow Fading --- Signal levels obey Log-Normal distribution

    Propagation models predict only mean values of signal strength , the mean value of

    signal strength fluctuates. The deviation of the mean values has a nearly normal

    distribution in dB, The variation in mean values is called log-normal fading.

    Probability that the real signal strength will exceed the average one on the cell border is

    around 50%,for higher than 50% coverage probability an additional margin has to be

    introduced. The margin is called slow fading margin.

    Slow Fading Margin (SFM) is related with coverage probability in cell edge and standard

    deviation of slow fading. The equation is described as following:

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    Soft Handover --- handover between different NodeBs

    Softer Handover --- handover between cells in a NodeB

    SHO gain over slow fading is also known as the Multi-Cell gain because in soft

    handover more than 1 branch exists and hence the coverage probability increases

    which would result in the decreasing of required slow fading margin.

    Suppose that soft handover has 2 branches, and the orthogonality of the two

    radio link branches on slow fading is 50%. We can calculate the slow fading

    margin required with soft handovers based on the former assumptions, and

    compare it with the slow fading margin required without soft handover to get the

    SHO gain over slow fading.

    SHO gain over slow fading is dependent on the required area coverage probability,

    the propagation path loss slope and the STD. The following table gives the

    calculated SHO gain over slow fading and the propagation path loss slope equals

    to 3.59.

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    Fast power control

    to enhance weak signal caused by Rayleigh fading

    to mitigate interference and enhance the capacity

    to promote power utilization efficiency

    In WCDMA, user signals should be received at the NodeB with equal power all the

    time and for downlink the transmitted TCH power should be as small as possible

    while maintaining the required Qos. This implies that fast fading are compensated

    by the power control algorithm, which requires additional headroom at both UE

    and NodeB in order to let UE and NodeB following the power control commands

    at cell edge.

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    Because of the macro diversity combination, the soft handover reduces the

    required Eb/No by a single radio link, which results in additional macro diversity

    gain.

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    Interference margin is the required margin in the link budget due to the noise rise

    caused by system load (the noise rise due to other subscribers). The higher the

    system load is, the larger the interference margin should be.

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    If the W=1Hz, Nth=-174dBm/Hz

    If the W=200kHz, Nth=-121dBm/200kHz

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    Typical noises are: external sky and electric noise, vehicle start-up noise, heat

    noise from inside systems, scattered noise of transistor during operation,

    intermodulation product of signal and noise.

    Noise figure is used for measuring the processing capability of the RF component

    for small signals, and is usually defined as: output SNR divided by unit input SNR.

    NF

    Si

    Ni

    So

    No

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    For common services, the bit rate of voice call is 12.2kbps, the bit rate of video

    phone is 64kbps, and the highest packet service bit rate is 384kbps(R99). After

    the spreading, the chip rate of different service all become 3.84Mcps.

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    For instance:

    Service BLER Channel Model Uplink Eb/N0 Downlink Eb/N0

    AMR12.2k 1.00% TU3 5.4dB 7.8 dB

    RA120 4.5 dB 8.3 dB

    CS64k 0.10% TU3 2.8 dB 6.3 dB

    RA120 2.8 dB 6.8 dB

    CS64k 1.00% TU3 2.5 dB 5.4 dB

    RA120 2.3 dB 6 dB

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    In case of multi-path propagation, certain energy will be detected by the

    RAKE receiver, and become interference signals. We define the orthogonal

    factor to describe this phenomenon. It is obtained through simulation, and

    related to environment type and cell radius.

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    Continuous coverage target service requirement with specific coverage probability

    should be given for R99

    Cell edge throughput requirement with specific coverage requirement should be

    given for HSDPA

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    The cell total transmit power is the constant resources. The DL power consists of

    the following three parts:

    Power of the HSPA DL physical channel (HS-PDSCH, and HS-SCCH)

    Common channel power

    DPCH power

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    Fast power control

    For R99, power control margin should be considered

    For HSDPA, the maximum transmission power for HS-PDSCH is the

    remaining power excluding R99 power and power margin, and no power

    control margin

    SHO gain

    For R99, SHO gain should be considered

    For HSDPA, only hard handover, no SHO gain

    HSDPA related parameters should be configured when simulation

    Max number of HS-PDSCH channel

    Min number of HS-PDSCH channel

    HSDPA power allocation, dynamic or fixed

    HS-SCCH power allocation, dynamic or fixed

    Max number of HSDPA users

    Scheduling Algorithm

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    Single carrier for HSDPA and R99

    Advantages

    Maximum resource utilization efficiency

    Save cost

    Disadvantages

    Handover between HSDPA cell and R99 cell

    Two carriers for HSDPA and R99

    Advantages

    Fewer inter-frequency handover for HSDPA user

    Disadvantages

    High cost

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    If operator wants to upgrade HSDPA from R99, R99 should be met first, and

    HSDPA should not affect the R99.

    If operator setups R99 and HSDPA directly, R99 and HSDPA requirement should

    be met at the same time.

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    DL Coupling Loss :

    PL_DL: Downlink path loss

    Lf_BS: cable loss of NodeB

    Ga_antenna: Gain of UE antenna and NodeB antenna

    Lb: Body loss

    SFMNSHO: Slow fading margin without soft handover

    Lp: Penetration loss

    Cell edge Ec/No:

    PHS-DSCH : total power of HS-DSCH channel

    : non-orthogonality factor

    : neighbor cell interference factor

    : downlink load factor including R99 and HSDPA service

    Pmax : max transmission power of downlink

    Nt : thermal noise power spectral density , typical value is -108.16dB

    NF : receiver noise figure of UE, typical value is 7dB

    f

    DL

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    The theoretical maximum throughput is decided by the number of HSDPA codes.

    For HSDPA , soft handover gain and fast fading margin should not be considered

    in link budget , since neither power control nor soft handover in HS-PDSCH

    channel

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    The step is present below:

    According to the Cell Radius comes from R99 dimensioning, the Downlink

    Path Loss can be calculated

    According to the Downlink Path Loss , the Downlink Coupling Loss can be

    calculated

    According to the Downlink Coupling Loss and HS-DSCH Power, Cell Edge

    Ec/No can be calculated

    According to the Cell Edge Ec/No and simulation result, Cell Edge

    Throughput can be calculated

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    The step is present below:

    According to the Cell Edge Throughput and simulation result, Cell Edge

    Ec/No can be calculated

    According to the Cell Edge Ec/No and HS-DSCH Power, the Downlink

    Coupling Loss can be calculated

    According to the Downlink Coupling Loss, the Downlink Path Loss can be

    calculated

    According to the Downlink Path Loss and and Propagation Model, HSDPA

    Cell radius can be calculated

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    The step is present below:

    According to the Cell Radius comes from R99 dimensioning, the Downlink

    Path Loss can be calculated

    According to the Downlink Path Loss , the Downlink Coupling Loss can be

    calculated

    According to the Cell Edge Throughput and simulation result, Cell Edge

    Ec/No can be calculated

    According to the Downlink Coupling Loss and Cell Edge Ec/No , HS-DSCH

    Power can be calculated

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