07 01 RA41207EN60GLA0 Cell range

LTE FDD Coverage Planning - Cell Range

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Background

Accurate propagation modeling is fundamental to both the simulation based approach and the path loss based approach to LTE radio network planning. The key inputs to propagation modeling are the propagation model itself, the digital terrain map (DTM) and the site configuration data.

Radio network planning is often completed using a set of propagation models rather than a single propagation model. This may be necessary if propagation conditions vary from site to site. Different models may be tuned for specific antenna heights or specific cell ranges.

Digital terrain maps often become out- of-date and subsequently become a source of error. The site configuration data relies upon the accuracy of the antenna gain pattern as well as the antenna height, azimuth and tilt data.

Operators may have existing propagation models for their 2G and 3G radio networks. They may wish to use the same models for LTE radio network planning. In this case, their models should be compared with typical Nokia models to help identify any significant differences. It is reasonable to assume that a propagation model which has been used to plan a GSM 900 network can also be applied when planning an LTE 900 network.

When a project requires the definition of a new propagation model, the following tasks should be completed:

DTM specification, purchase and validation selection of propagation model type based upon requirements.

Planning and completion of drive survey.

RF measurement post-processing and propagation model calibration.

Propagation model validation and continuous auditing.


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DTM requirements should be specified in terms of resolution, format and the number of clutter categories. The resolution should be relatively high for urban and suburban areas but can be reduced for rural areas. It is typical to use a 20 m resolution for urban and suburban areas, whereas a 50 m resolution may be used for rural areas. If the resolution is too low, then the accuracy of the map and the subsequent propagation modeling suffers.

If the resolution is too high, then the DTM is likely to be expensive and the computer processing requirement may become excessive. Resolutions which are higher than 20 m may be appropriate for dense urban areas where cell ranges are particularly small. If microcells with below roof-top antennas are to be planned, then it may be necessary to purchase a map which includes building vectors.

Building vectors may have either two or three dimensions. Ray tracing can be used as a propagation modeling technique to take advantage of the increased resolution provided by building vectors. The format of the DTM should be specified to match the format used by the radio network planning tool.

If the required format is not available, then the purchased map will require post-processing prior to importing. The appropriate number of clutter categories depends upon the geographic area. It is typical to make use of about ten categories.

Some planning tools may have a maximum number of categories which can be imported. In this case, the DTM can be post-processed to merge similar categories.

If the number of categories is large, the propagation tuning exercise becomes more difficult. After the DTM has been purchased and imported into the radio network planning tool, a set of checks should be completed to help validate its accuracy.

Clutter types and vectors should be compared with those indicated on paper maps. Likewise, the ground height data should be compared with that indicated on paper maps.

After the digital terrain map has been validated, an initial selection of propagation models should be made. It may be necessary to change this selection if it is subsequently found to be inappropriate during the model tuning task.

The requirement for a set of different propagation models should be evaluated. In general, the type of propagation models which can be selected are limited to those which are supported by the radio network planning tool.


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Cost 231 model is an extension of the Okumura-Hata model to frequencies up to 2000 MHz while the Hata model is specified for ranges up to 1500 MHz (150 – 1500 MHz

Comments regarding the equation and the corrections:

The slope of the radio wave attenuation as a function of distance is called radio propagation slope and this parameter has a strong impact on the maximum distance between the BTS and the MS.

The propagation slope depends heavily on the propagation environment and also on the antenna height

The slope may be changed using the s factor. Please also note that there are 2 slopes for d< 1km

The first 2 terms are independent on the distance and they add some frequency corrections (A and B)

The city type environment affects the correction which is based on the mobile height (e.g. 1.5 m could not be accurate if the UE is placed in one building)

a(hMS) factor is used for this correction

a(hBS) factor is used for the BS antenna height correction. It is known that the OH model is suitable in cells that have the antennae well above the roof-top. If the antenna is close to the roof-tops then the correction factor is needed


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Cost 231 model is an extension of the Okumura-Hata model to frequencies up to 2000 MHz while the Hata model is specified for ranges up to 1500 MHz (150 – 1500 MHz

Comments regarding the equation and the corrections:

The slope of the radio wave attenuation as a function of distance is called radio propagation slope and this parameter has a strong impact on the maximum distance between the BTS and the MS.

The propagation slope depends heavily on the propagation environment and also on the antenna height

The slope may be changed using the s factor. Please also note that there are 2 slopes for d< 1km

The first 2 terms are independent on the distance and they add some frequency corrections (A and B)

The city type environment affects the correction which is based on the mobile height (e.g. 1.5 m could not be accurate if the UE is placed in one building)

a(hMS) factor is used for this correction

a(hBS) factor is used for the BS antenna height correction. It is known that the OH model is suitable in cells that have the antennae well above the roof-top. If the antenna is close to the roof-tops then the correction factor is needed


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It was mentioned in Scenarios and use cases that the most common deployment scenario for LTE will be the co-existence with existing 2G and 3G networks. This section presents a link budget comparison between the three different technologies to provide an indication of how feasible a site re-utilization can be for an existing operator


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As is commonly the case, uplink is the limiting factor for all technologies, and when looking only at MAPL, the LTE system allows for higher allowed path loses. However, the fact that LTE is deployed in a higher frequency (2600MHz vs. 2100 MHz and 1800 MHz) means that the signal will suffer more from the attenuation with the result of similar cell ranges to the other technologies.

To conclude, LTE2600 can be successfully deployed on the WCDMA2100 (Rel.99) grid when designed for CS64 service at the cell edge and on the GSM 1800 grid when designed for voice service at the cell edge. In that case, LTE deployment should provide at the cell edge1 Mbps in downlink and 64 kbps in uplink.

It is possible for an existing operator to deploy an LTE network re-utilizing the existing 2G or 3G site grid. The study above has been made under very specific conditions that may not apply to all existing operators. A detailed link budget comparison, taking into account the features of the existing network, should be created for each operator.


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Date post:	11-Jan-2016
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07 01 RA41207EN60GLA0 Cell range

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