1 Lte Radio Network Coverage Dimensioning Isuee 1.20

LTE Radio Network Coverage Dimensioning

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Before dimensioning some link budget parameters need to be prepared such as penetration loss, propagation model, fading margin and interference margin



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Before a network planning, we should firstly decide the planning targets, Which are important inputs for the planning

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The target service is the data service normally, the target quality of the data service is judged by the cell edge throughput. This throughput requirements are normally different in different target area, such as urban and rural.

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The coverage probability is according to the network deployment strategy, for different

region ,such as dense urban and rural, we may apply different coverage probability. 

Target load affects not only the cell capacity, but also the coverage, since in different load conditions, the interference at of cell border is different also.

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Before planning, we should collect as much information as possible, such as to confirm if the indoor areas’ coverage is required, if TMA is used or not ...



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The type of area will affect the pass loss during the link budget, including 

Channel mode

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Indoor penetration loss

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Standard deviation of shadow fading margin

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Path loss factor

Morphologies determines the propagation model formula using in cell radius calculation, as well as other parameters such as eNodeB antenna height and penetration loss

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Channel model has effect on the demodulation threshold and lead to difference cell radius

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ETU: Extended Typical Urban model

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EVA: Extended Vehicular A model



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Similar to other wireless communications systems, such as CDMA2000 EVDO, WiMAX and HSPA, the LTE features a rate layering feature. That is, the higher the required edge rate,

the smaller the cell coverage radius. The lower the required edge rate, the larger the cell coverage radius.



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Radio Network Dimensioning is a simplified analysis for radio network.

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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 eNodeB hardware, cell average throughput and cell edge throughput. 

Objective: 

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To obtain the network scale ( approximate eNodeB number and configuration)

Method: 

Select a proper propagation model, traffic model and subscriber distribution, and then estimate the eNodeB number, coverage radius, cell throughput, cell edge throughput and so on.



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Wireless network dimensioning intends to obtain the approximate EUTRAN 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 LTE 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 eNodeB quantity are adjusted to optimize the coverage. And then the system capacity is analyzed to check whether it meets the requirement.

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Plan implementation parameters, such as antenna type / azimuth / tilt / altitude / feeder type / length …

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Plan cell parameters, such as tracking area planning, PCI planning, Neighbor relation planning, PRACH configuration planning…





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The carrier bandwidth of LTE could be 6RBs, 12RBs, 25RBs, 50RBs, 100RBs , the number of RB affects the cell border throughput directly

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MIMO is normally the different configuration in LTE, it can improve the LTE coverage and capacity, we should consider the gain of MIMO in planning

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MCS : Modulation & Coding Scheme, which is a radio channel auto adaptive algorithm . With high order MCS, the throughput can be higher, but it is not suitable in poor channel

condition. So we have to select different MSC for different channel quality when calculating the coverage and capacity. 

3GPP define a number of bands for LTE, so the propagation model should be selected accordingly.







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Generally, LTE has the same dimensioning procedure as the other wireless system

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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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The following propagation models can be used for LTE link budget.Cost231-Hata, SPM and Cost231-Hata (Huawei) can be used for LTE band higher than 1500MHz. Okumura-

Hata and Okumura_Hata (Huawei)can be used for LTE band lower than 1500MHz. 

Cost231-Hata

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Cost231-Hata（Huawei）

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Okumura- Hata

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Okumura- Hata（Huawei）

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SPM



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Normally the link budget is limited by data channel, so in this course data channel link budget is discussed mostly.



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For

Channel Mode:  

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For

EPA is Extended Pedestrian A model. EPA 3 means the speed in the model is 3km/h. ETU is Extended Typical Urban. EUT 3, ETU 30, ETU 60 and ETU 120 means the speed in the model is 3km/h, 30km/h, 60km/h and 120km/h. EVA is Extended Vehicular A model. EVA 3, EVA 30, EVA 60 and EVA 120 means the speed in the model is 3km/h, 30km/h, 60km/h and 120km/h. HST is High Speed Train. HST 350 means the speed in the mode is 350km/h.

MIMO Scheme: 

SFBC is Space-Frequency Block Code.

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FSTD is Frequency Switched Transmit Diversity.

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MIMO can bring gain to LTE link budget. So MIMO scheme is considered in input parameters.



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Generally ,the max allowed path loss is calculated from the transmission power and the reception sensitivity.

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In the propagation, the Losses are normally static , such as penetration loss, body loss and cable loss.

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The gains (e.g. antenna gain, MIMO gain) can improve the max allowed path loss , since it enhances the signal strength or it can bring some compensation to the losses.

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The margins are reserved to ensure the coverage performance. With the margin revered , the coverage( calculated by link budget) can always satisfy the planning target even in case of the cell is loaded or in somewhere the slow fading is greater than the average value.





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EIRP is Equivalent Isotropic Radiated Power.

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Considering indoor coverage Penetration Loss is in the formula to calculate MAPL.

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Shadow fading indicates the fading brought by obstruction due to a building or a natural feature. Shadow fading changes slowly, and is thus called “slow fading”. Statistics repeatedly show that the median levels of received signals follow log-normal distribution with the time and location at a certain distance. Fading caused by location (mainly from

obstruction) far exceeds fading caused by time. Therefore, the major concern for shadow fading is those caused by location changes.







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In downlink the total power is distributed evenly over all subcarriers of the whole bandwidth.



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AWS band: 

UL: 1710MHz – 1755MHz, DL:2110MHz – 2155MHz





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Thermal noise per subcarrier is: 

Thermal noise per subcarrier = 10*lg(K*T*W) = -132.2dBm 

K is Boltzman constant. It is equal to 1.38*10-23.

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T is temperature in Kelvin. Normally it is 290.

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W is the signal bandwidth. Here W is 15KHz (one subcarrier in LTE).



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Target MCS, MIMO scheme, channel mode and etc. are input parameters for SINR simulation.

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Allocated RB number can be calculated by target cell edge rate and target MCS.





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The interference margin in practice depends heavily on the planned capacity so there is a tradeoff between capacity and coverage just like other cellular technologies.



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Penetration Loss indicates the fading of radio signals from an indoor terminal to a base station due to obstruction by a building. It is related to the incident angle, building

materials, terrain, and working frequency.



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The shadow fading margin is related to the area coverage probability requirement and the standard deviation of fading. The standard deviation of slow fading shows the distribution

of the radio signal strength at different test points at similar distances from the transmitter. The standard deviation of slow fading varies with the geological form. In plain areas, such as rural areas and open areas, the standard deviation of slow fading is lower than that in suburban and urban areas. Standard deviations requirement in Dense Urban area with highly integrated building layout and deeper indoor coverage requirement is even higher than typical urban environment.



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Higher the area coverage probability requirement is, more shadow fading margin is required.

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Higher the standard deviation is, more shadow fading margin is required.





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The parameters with zero value are not shown in the table.





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3GPP defines that maximum Tx power of LTE UE is 23dBm.





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Thermal noise per subcarrier is: 

Thermal noise per subcarrier = 10*lg(K*T*W) = -132.2dBm 

K is Boltzman constant. It is equal to 1.38*10-23.

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T is temperature in Kelvin. Normally it is 290.

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W is the signal bandwidth. Here W is 15KHz (one subcarrier in LTE).



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AWS band: 

UL: 1710MHz – 1755MHz, DL:2110MHz – 2155MHz







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The parameters with zero value are not shown in the table.





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By repeating the same uplink information, lower SINR will be required by the receivers at the eNodeB. The application of this feature is ideal for lower data rate applications such as

VoIP and Packet data services requiring slower rate. At least 4 dB gain can be achieved through this data repetition. 

TTI bundling Gain is included as part of SINR in link budget estimation.



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The concept of Interference Rejection Combining (IRC) is to regenerate the transmitted signal based on the estimated data from the previous receptions, emulate the distortion

occurring from the multi-path channels and, finally subtract all regenerated interfering signals from the uplink received signals to obtain more reliable estimation of original user’s data. This feature utilizes the spatial separation and characteristics of inter-cell interference to determine the power of the interfering UE which belongs to another cell. Once the pattern and power level is determined, the victim cell can then remove the interferer from the received signals. 

In comparison, Maximum ratio combining (MRC) do not make use of the spatial characteristics of the interference when calculating antenna weighting. So in cases where there are only a small number of dominating interfering sources, IRC can provide more improvement than MRC especially when there are a reasonable number of receive antennae for IRC to execute the compensation. Conversely, if there are a large number of equal power signals arriving at the receive antennae, the gain of IRC over MRC is not as significant.

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MRC is more applicable for the scenario with white noise while IRC is more applicable for the scenario with colored noise.









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D:Downlink subframe

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U:Uplink subframe

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S:Special subframe



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Multiple antennas in LTE may also be used to transmit the same signal appropriately weighted for each antenna element such that the effect is to focus the transmitted beam

in the direction of the receiver and away from interference, thereby improving the received SINR. The beam-forming weight vector should increase the antenna gain in the direction of the desired user while simultaneously minimizing the gain in the directions of interferers. Beam-forming can provide significant improvement in the coverage range, capacity, and reliability. To perform transmit beam-forming, the transmitter needs to have accurate knowledge of the channel, which in the case of TDD is easily available owing to channel reciprocity but for FDD requires a feedback channel to learn the channel characteristics so it is not implemented in LTE Release 8 or 9 yet. As of today, beam forming is specific only to LTE TDD and can operate either under 4x4 or 8x2 configurations. 

Currently, beam forming is only applicable for TDD version of LTE. The time synchronous version of LTE TDD on uplink and downlink also makes the implementation of beam forming more attractive than in LTE FDD.









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RND is used for coverage dimensioning and capacity dimensioning.

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GENEX U-NET is used for coverage prediction and capacity simulation during nominal

planning and detailed planning. GENEX-NET can also be used for LTE cell planning



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Before dimensioning some common input parameters need to be set.





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During dimensioning, RND can calculate or simulate some parameters based on input parameters.





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The figure is the result of best server prediction.



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The figure is the result of downlink RSRP prediction.



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The figure is the result of downlink RS SINR prediction.



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The figure is the result of handover area prediction.



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The figure is the result of PUSCH SINR prediction.




1 Lte Radio Network Coverage Dimensioning Isuee 1.20

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