IRAT Strategies

This section describes the principles in terms of where the UEs should camp in Idle mode and the recommended strategy for CS and PS during a call. It is assumed in this document that an LTE or WCDMA system have back-up from another radio access technology (RAT) if coverage is lost. For LTE the back-up would be WCDMA or GSM, and for WCDMA, it is GSM.

The proposed strategies for RAT interworking aim at minimizing the number of system transitions and obtaining the highest possible throughput for packet-switched (PS) services. System transitions increase the probability of call drops, longer outage times for PS services, as well as lower throughput.

For circuit-switched (CS) voice calls, the general strategy is to keep the call in WCDMA as long as there is WCDMA coverage. Load issues in any of the systems could suggest certain deviation from this strategy. CS voice call in GSM should not do handover to WCDMA, except when GSM coverage is lost, for example when user goes into a building where there is only WCDMAcoverage.

For PS services, the general strategy is to use the RAT capable of providingthe highest bit rates to the largest extent possible. This results in prioritizing LTE for PS if LTE is available and terminal capability allows it, and WCDMA otherwise. Therefore, it is recommended to use priority-based cell reselection in Idle mode to move Idle mode UE in GSM to LTE and WCDMA and from WCDMA to LTE. Priority-based cell reselection only makes sure that the RAT with higher priority has adequate quality, and not comparing that to the quality of the current low-priority RAT.

Once being in LTE, a LTE capable terminals that want to perform CS servicescan be temporarily redirected to WCDMA (or GSM) using CS Fallback (CSFB). Non-LTE capable terminals should use WCDMA as the preferred RAT to camp on and initiate PS and CS services, conditioned on the adequate quality of WCDMA signal for Idle mode camping. The recommended parameter settings for LTE, WCDMA, and GSM support those strategies. Parameters and recommended values to implement the strategies are given further.

Overview of IRAT strategy

The strategy is implemented through parameters in GSM, WCDMA and LTE. Idle mode parameters cover users in the following states of the different RATs:

• WCDMA: IDLE, URA_PCH and CELL_FACH

• LTE: RRC_IDLE

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• GSM: Idle and Packet transfer mode Dedicated mode parameters cover users in the following states:

• WCDMA: CELL_DCH (CS and PS)

• LTE: RRC_CONNECTED

• GSM: CS voice call users

The handover (HO) or cell change (CC) is controlled by the network, based on measurement reports from UE, while cell reselection is controlled by UE, based on configuration parameters broadcast by the network. Figure 1 shows the possible IRAT transitions between the different states.

Mobility for a PS connection is controlled by idle mode parameters in GSM and dedicated mode parameters in WCDMA. Thus, the triggering thresholds for IRATHO/CC must be matched between GSM idle mode and WCDMA dedicated mode to avoid back and forth mobility between GSM and WCDMA (W2G and G2W ping-pong). Similarly, triggering thresholds controlling mobility

between WCDMA and LTE must be matched, in both Idle and Dedicated mode,

to avoid W2L and L2W ping-pong.

The following features are recommended when implementing the proposed strategy.

• The WCDMA feature GSM Handover and Cell Reselection (FAJ 121 154) provides the support needed for the UE to perform cell reselection from WCDMA to GSM. See Idle Mode and Common Channel Behavior.
• The WCDMA feature LTE Cell Reselection (FAJ 121 1474) provides the support needed for the UE to perform cell reselection from WCDMA to LTE. See Idle Mode and Common Channel Behavior.
• The WCDMA feature LTE Cell Reselection Dedicated Priority (FAJ 1213588) prevents LTE cell reselection for UEs that are LTE-capable but has no LTE subscription with the operator. See LTE Cell Reselection Dedicated Priorities.
• The WCDMA feature Packet Switched Handover from LTE (FAJ 121 1611) enables the transfer of one or more already established PS connections from LTE to UTRAN. PSHO from LTE is only performed in connected mode. See Packet Switched Handover from LTE.
• The LTE features Coverage-triggered WCDMA Session Continuity (FAJ121 0493) and Coverage-triggered GERAN Session Continuity (FAJ 1210495) provide the support needed for the UE to perform Idle mode cell reselection from LTE to WCDMA and GSM. These features also allow redirection to WCDMA or GSM for ongoing PS connections in LTE when bad coverage is detected in LTE. In this latter case, the mechanism is Release-with-Redirect where the PS call is released in LTE and re-established in WCDMA. See Coverage-triggered WCDMA Session
• The LTE feature Coverage-Triggered WCDMA IRAT Handover (FAJ 1210897) that provides the support needed for the UE to perform a seamless handover from LTE to WCDMA in connected mode when bad coverage is detected in LTE. No interruption for the PS call is caused by handover as in Release-with-Redirect, which makes it a recommended feature to use. This feature, however, has the feature 'Coverage-triggered WCDMA Session Continuity' as a pre-requisite.
• The LTE feature Mobility Control at Poor Coverage (FAJ 121 3013) that provides improvement in the procedure to determine when an UE in LTE connected mode should start IRAT and Inter-frequency measurement and when it should perform IRAT or Inter-frequency handover or Release-with-Redirect. See Mobility Control at Poor Coverage, 
• The LTE feature CS Fallback to GERAN and UTRAN (FAJ 121 0856) releases the UE and redirects it to WCDMA or GSM when a CS voice call needs to be set up. The feature is recommended together with the WCDMA feature Release with redirect to LTE (FAJ 121 2174) that will return the device to LTE after a CS Fallback. See CS Fallback to GSM and WCDMA.
• The WCDMA feature CS Fallback from LTE (FAJ 121 1610) allows UTRAN to establish a CS speech call that is transferred from LTE based on Fallback mechanism.
• In GSM, from G10A onwards, the feature GSM-LTE Cell Reselection (FAJ123 155) is introduced and the feature GSM-UMTS Cell Reselection and Handover (FAJ 121 57) is updated to support priority-based cell reselection.
• The GSM feature Fast Return to WCDMA after Call Release (FAJ 123 149) is recommended to use to reduce the time in GSM where there is WCDMA coverage. Further, the feature Combined cell re-selection triggering GSM to WCDMA (FAJ 121 933) introduces network support for an improved GSM to WCDMA cell reselection algorithm, resulting in increased likelihood to be served in a WCDMA network.

Idle Mode IRAT strategy
The overall idle mode strategy is that the UEs should camp on the RAT providing the best possible packet data performance in accordance with the capability of the UE until coverage is lost. This means LTE capable terminals camp on LTE and terminals not capable of LTE camp on WCDMA. UEs only capable of GSM camp on GSM. It is recommended to use priority based cell reselection, with the priority order LTE, WCDMA and GSM where LTE has the highest priority. IRAT related features are used for moving the UE in case the requested service is not supported by the network the UE is camping on. Figure below shows the different transitions between the RATs involved in achieving the recommended idle mode priority based strategy.

• A: Cell reselection from WCDMA to LTE should be done as soon as the RSRP level is above the minimum criteria for cell reselection. A margin should be used to prevent ping-pong IRAT cell reselection back to WCDMA. In WCDMA border cells no neighbor relations to LTE should be defined.
• B: Cell reselection from LTE to WCDMA shall only be done when the signal strength or quality level are below the minimum criteria in LTE and above sufficient levels in WCDMA including a margin.
• C: Cell reselection from GSM to WCDMA should be done as soon as possible as the WCDMA cell is above the minimum criteria plus a margin to avoid ping-pong IRAT cell reselection. The UE will continuously search for higher priority WCDMA (and LTE) cells.
• D: Cell reselection from WCDMA to GSM shall only be done when the WCDMA cell becomes unsuitable for camping. Measurements on GSM should only start just before the WCDMA cells' minimum criteria. The Idle mode UEs in WCDMA should be kept there until camping is not allowed on WCDMA before cell reselection to GSM occurs.

URA_PCH IRAT mobility Strategy
Cell reselection in URA_PCH will follow the Idle mode strategy.

CELL_FACH IRAT mobility strategy
It is recommended the that cell reselection in CELL_FACH should follow the strategy for CELL_DCH state. This means that GSM measurements on CELL_FACH should be turned off in WCDMA core cells. For more information of scenarios where there are border cells between different WCDMA frequency layers, see Additional WCDMA Carrier Deployment.

CELL_DCH IRAT mobility Strategy
The recommended IRAT strategy for UEs in WCDMA CELL_DCH state is to keep the UEs in WCDMA and to minimize unnecessary IRAT measurements. CS and multi-RABs containing CS could start IRAT measurements but only in border cells where the WCDMA coverage is limited. IRAT measurements for PS only RABs should be avoided because it is better to stay on WCDMA until the users have finished the PS data transfer before any IRAT measurements and transitions are initiated. Further there is an elevated risk of dropped calls during the IRAT process and the user packet throughput is usually much higher in WCDMA compared to GSM. The recommended IRAT HO strategy is below figure.

• A: PS HO, Single Radio Voice Call Continuity (SRVCC) and WCDMA session continuity from LTE to WCDMA should be done from LTE border cells only. 
• B: Handover should only be allowed for border cells. For WCDMA core cells all IRAT HO should be limited by setting the hoType to "NONE". For border cells IRATHO shall be allowed for CS Speech and Multi-RAB CS + PS, but not allowed for PS only. This is achieved by setting hoType to "GSM_PREFERRED". The IRATCC for PS can then be limited by using very low values for the parameters serviceOffset2dEcNo and serviceOffset2dRscp for all UeRc's that are serving PS only. When more than one WCDMA carrier is involved, see Additional WCDMA Carrier Deployment on how to set hoType.
• C: GSM packet transfer mode IRAT cell reselection should be allowed to WCDMA but not CS HO as long as there is GSM coverage. It is better to finish the CS call first and then do the IRAT cell reselection. The CS HO should be switched off using the parameters QSC, MSRL and ISHOLEV, 

Call Setup in LTE
For LTE terminals, the proposed strategy is to keep PS-only services in LTE. If CS service is not supported in LTE it can be set up in WCDMA (or GSM) using the feature “CS Fallback to GSM and WCDMA” (CSFB).


Call Setup in WCDMA
For non-LTE terminal, or in case LTE coverage is not available, the call (PS or CS) is set up in WCDMA.
CS Speech Call Setup in GSM
CS speech calls established in GSM should remain in GSM except when GSM coverage is lost, for example when user goes into a building where there is only WCDMA coverage. The reason is to minimize the number of IRATHOs.
High demand for CS Speech in combination with PS data could motivate diverging from this general recommendation where CS Speech+PS call in GSM can be moved to WCDMA Multi-RAB. In this case, the IRATHO for the CS Speech component from GSM to WCDMA should be allowed. However, the risks related to IRAT transitions should be balanced against the benefits of multi-RAB access. Furthermore, with the use of priority-based cell reselection together with the recommended GSM feature 'Fast return to WCDMA after CS call release', there will not be many UE in GSM that uses CS+PS.
Packet Call Setup in GSM
To maximize throughput for PS connections, calls in GSM Packet transfer mode should do IRAT cell change to WCDMA (or LTE, depending on UE capability) as soon as coverage and quality is acceptable. Connections in GSM idle mode and packet transfer mode are controlled by the same parameters, and the parameter setting must therefore consider the desired behavior in both idle and
packet transfer modes. However, with the use of priority-based cell reselection together with the recommended GSM feature 'Fast return to WCDMA after CS call release', there will not be many UEs in GSM that initiate PS services.

IRAT mobility strategy during state transitions
If the UE has been redirected to a lower priority RAT due to the setup of CS Speech, such as in the case of Circuit-switch Fall-back (CSFB) from LTE to WCDMA, the recommendation is to reselect back to higher priority RAT as soon as possible but only during a state transition, for example transition from CELL_DCH to CELL_FACH state.
It is therefore recommended to activate the WCDMA feature Release with redirect to LTE (FAJ 121 2174) to redirect the UE back to LTE after CSFB. Use this feature only from WCDMA cells where there is overlapping LTE coverage. It is recommended to use the feature Fast Return to WCDMA after Call Release (FAJ 123 149) if the UE has been redirected from WCDMA to GSM during a call set-up in an area where there is WCDMA coverage.

Pilot Pollution Problem Analysis

Pilot Pollution Definition and Judgment Standards

Definition

The pilot pollution is that excessive strong pilots exist in a point but no primary pilot is strong enough.

Judgment Standards

Pilot pollution exists if all the following conditions are met:

l   The number of pilots that meet the following condition is more than Th_N
CPICH_RSCP > Th_{RSCP_Absolute}

l   (CPICH_RSCP_1st - CPICH_RSCP_{(ThN +1)th})< Th_{RSCP_Relative}

Assume that Th_{RSCP_Absolute} = –100 dBm, Th_N = 3, and Th_{RSCP_Relative} = 5 dB, and then pilot pollution exists if all the following conditions are met:

l   More than three pilots meet the following condition
CPICH_RSCP > –100 dBm.

l   (CPICH_RSCP_1st - CPICH_RSCP_4th) < 5 dB

Causes and Influence Analysis

Causes Analysis

Ideally the signals in a cell is restricted within its planned range. However the signals cannot reach the ideal state due to the following factors of radio environment:

l   Landform

l   Building distribution

l   Street distribution

l   Waters

Pilot pollution is the result of interaction among multiple NodeBs, so it occurs in urban areas where NodeBs are densely constructed. Normally typical areas where pilot pollution occurs easily include:

l   High buildings

l   Wide streets

l   Overhead structure

l   Crossroad

l   Areas round waters

I. Improper Cell Distribution

Due to restriction to site location and complex geographic environment, cell distribution might be improper. Improper cell distribution causes weak coverage of some areas and coverage by multiple strong pilots in same areas.

II. Over High NodeB or Highly-mounted Antenna

If a NodeB is constructed in a position higher than around buildings, most areas will be with in the line-of sight range. Therefore signals are widely transmitted. Over high site cause difficult control of cross-cell coverage, which causes pilot pollution.

III. Improper Antenna Azimuth

In a network with multiple NodeBs, the antenna azimuth must be adjusted according to the following factors:

l   NodeB distribution of the entire network

l   Coverage requirements

l   Traffic volume distribution

The sector azimuth of each antenna is set to cooperate with each other. If the azimuth is improperly set:

l   Some factors might cover the same area. This causes excessive pilot pollution.

l   Weak coverage exist in some areas without primary pilot.

The previous two situations might lead to pilot pollution. Therefore you must adjust the antenna according to actual propagation.

IV. Improper Antenna Down Tilt

Setting antenna down tilt depends on the following factors:

l   Relative height to around environment

l   Coverage range requirements

l   Antenna types

If the antenna down tilt is improper, signals are received in the areas which are covered by this site. Therefore interferences to other areas causes pilot pollution. Even worse, interferences might cause call drop.

V. Improper PICH Power

When the NodeBs are densely distributed with a small planned coverage rang and the PICH power is over high, the pilot covers an area larger than the planned area. This causes pilot pollution.

VI. Ambient Factors

The signals cannot reach the planned state due to the following factors of radio environment:

l   Landform

l   Building distribution

l   Street distribution

l   Waters

The ambient factors include:

l   High buildings or mountains block signals from spreading
The signals of a NodeB to cover a target area are blocked by high buildings or mountains, so the target area will have no primary pilot. This causes pilot pollution.

l   Streets or waters influences signals
When the antenna direction is pointing a street, the coverage range is expanded by the street. When the coverage range of a NodeB overlaps with the coverage range of other NodeBs, pilot pollution occurs.

l   High buildings reflect signals
When high glassed buildings stand near a NodeB, they will reflect signals to the coverage range of other NodeBs. This causes pilot pollution.

Influence Analysis

Pilot pollution causes the following network problems.

I. Ec/Io Deterioration

Multiple strong pilots interferes useful functional signals, so Io increases, Ec/Io decreases, BLER increases, and network quality declines.

II. Call Drop Due to Handover

More than three strong pilots or no primary pilot exists in multiple pilots, frequent handover occurs among these pilots. This might cause call drop.

III. Capacity Decline

The interference of the areas with pilot pollution increases, the system capacity declines.

Solutions to Pilot Pollution

Antenna Adjustment

According to the test, change pilot signal strength of an area with pilot pollution by adjusting antenna down tilt and azimuth. This changes the distribution of pilot signals in the area. The principle for adjustment is enhancing primary pilot and weakening other pilots.

To enhance pilot coverage of an area, adjust the antenna azimuth pointing the area. To weakening pilot coverage of an area, adjust the antenna azimuth pointing the opposite direction of the area. Adjusting down tilt is similar. You can increase the cell coverage range by reducing antenna down tilt and reduce cell coverage range by increasing antenna down tilt.

Adjusting antennas is restricted to a range. If the down tilt is over small, you might enhance cell coverage but causes cross-cell coverage. If the down tilt is over large, you might weaken cell coverage but you might change the antenna pattern.

Figure shows the pilot pollution due to improper antenna azimuth.

In Figure, the area marked in black encounters pilot pollution due to improper azimuth of the antenna of SC100 sector (scramble No. is 100). The SC100 sector covers the area with an antenna azimuth of 90°, so the coverage is poor with weak signals and no primary pilot, which cause pilot pollution.

After adjustment of the antenna azimuth from 90° to 170°, the primary pilot signals become stronger and pilot pollution is eliminated.

Figure 6-2 shows the pilot pollution due to improper antenna down tilt.

In Figure the area marked in blacked encounters pilot pollution due to improper antenna down tilt. The down tilt of SC360 cell is 2°, so the coverage area is large, cross-cell coverage is difficult to control, and interferences to other areas form.

After adjustment of antenna down tilt of SC360 cell from 2° to 7°, the cross-cell coverage by SC360 cell is eliminated and pilot pollution is eliminated.

Some areas with pilot pollution is inapplicable to the previous adjustment. You can use the following methods based on actual situation:

l   Change the antenna to a different type

l   Add reflection device or isolation device

l   Adjust installation position of antenna

l   Adjust NodeB location

PICH Power Adjustment

Pilot pollution is caused by the coverage by multiple pilots. A direct method to solve the problem is to form a primary pilot by increasing the power of a cell and decreasing the power of other cells.

An over large down tilt causes aberration of antenna pattern. To reduce coverage range by pilot, you can decrease PICH power. Over small down tilt causes cross-cell coverage. To increase coverage range by pilot, you can increase PICH power. Adjusting power and adjusting antenna must cooperate.

Figure, shows the pilot pollution due to improper distribution of cells.

In Figure,

l   The distance between NodeB A and NodeB B is 1260 meters.

l   The distance between NodeB A and NodeB C is 2820 meters.

l   The distance between NodeB B and NodeB C is 2360 meters.

The distances is unbalanced, so the pilot pollution is difficult to eliminate.

The optimization is to reduce weak pilot strength and eliminate pilot pollution, detailed as below:

l   Ensure seamless coverage between cells by not adjusting transmit power of SC20 and SC30 cells.

l   Decrease the PICH power of SC10, SC40, and SC50 cells by 3 dB. These cells have little impact on seamless coverage.

Using RRU or Micro Cells

If adjusting power and antenna is not effective to solving pilot pollution, use RRU or micro cells.

Using RRU or micro cells aims to bring a strong-signal coverage in the area with pilot pollution, so the relative strength of other signals decreases.

When a network expansion is necessary or more requirements is on network quality, using RRU or micro cells is recommended. Micro cells are used in traffic hot spot areas, they support multiple carriers. Micro cells are used if large capacity is needed. Compared with using RRU, using micro cells is more expansive.

Figure,shows pilot pollution due to ambient factors.

The area marked in black encounters pilot pollution due to ambient factors. The area is covered by SC60 cell of NodeB A, SC110 cell or NodeB B, and SC130 cell of NodeB C. However, shown in Figure, hills prevent NodeB A from transmitting signals, high buildings prevent NodeB B and NodeB C from transmitting signals, so the signals from NodeB A, NodeB B, and NodeB C are weak. On the contrary, SC240 and SC250 cells of NodeB D have good propagation conditions in this direction. Therefore the cross-cell coverage is serious and pilot pollution occurs.

High buildings or hills blocks the area, so no strong pilot is present in the area. For this problem, adjusting antenna down tilt has little effect on eliminating pilot pollution. Instead adding RRU helps solve the problem.

Process for Analyzing Pilot Pollution Problem

The process for analyzing pilot pollution problem proceeds as below:

1)      Start Assistant. Analyze scanner-based RSCP for 1st Best ServiceCell and EcIo for 1st Best ServiceCell. Select the areas with high RSCP and poor EcIo as candidate areas with pilot pollution.

2)      Analyze scanner-based Whole PP. Select the areas corresponding to candidate areas as the key areas with pilot pollution.

3)      Locate the cells that cause pilot pollution of the key areas.

4)      Based on RSCP for 1st Best ServiceCell, judge whether the pilot pollution is caused by existence of multiple strong pilots or lack of a strong pilot. For the former cause, you can solve the problem by weakening other strong pilots. For the latter cause, you can solve the problem by strengthening some strong pilot.

5)      Analyze the RSCP and Ec/Io distribution of areas related to pilot pollution and confirm the cells that need eliminating the coverage of an area and that need enhancing the coverage of an area. Based on the actual environment, analyze the specific causes to pilot pollution (for analyzing causes, see 6.2.1  ). For specific causes, provide solutions to pilot pollution (for solution, see 6.3  ). While eliminating pilot pollution in an area, consider the influence to other areas and avoid causing pilot pollution or coverage voids to other areas.

6)      Retest after adjustment. Analyze RSCP, Ec/Io and Whole PP. If they cannot meet KPI requirements, re-optimize the network by selecting new key areas until KPI requirements are met.

RF Optimization

Once all the sites are installed and verification is complete, RF optimization starts. In some situations for a tight schedule, RF optimization might start after the construction of partial sites is complete. RF optimization is usually performed after 80% of total sites in a cluster are constructed.

RF optimization stage is one major stage of RNO. It aims at the following aspects:

l   Optimizing signal coverage

l   Control pilot pollution

l   Control SHO Factor based on DT

RF optimization also involves optimizing list of neighbor cells.

When the indexes like DT and traffic measurement after RF adjustment meets KPI requirements, RF optimization stage ends. Otherwise you must reanalyze data and adjust parameters repeatedly until all KPI requirements are met. After RF optimization, RNO comes to parameter optimization stage.

Process of RF Optimization

RF optimization includes the following four parts:

l   Test preparations

l   Data collection

l   Problem analysis

l   Parameter adjustment

Deciding Optimization Goal

The key of RF optimization is to solve problems as below:

l   Weak coverage

l   Pilot pollution

l   High SHO Factor based on DT

Actually, different operators might have different standards on KPI requirements, index definition, and attention. Therefore the RF optimization goal is to meet the coverage and handover KPI requirements in the contract (commercial deployment offices) or planning report (trial offices).

Define the indexes as required by contract as below:

The index definition is the percentage ratio of the sampling points with the index (such as CPICH Ec/Io) greater than the reference value in all sampling points.

List of RF optimization goals

Index	Reference	Remarks
Coverage rate	≥ 95%	Test on the acceptance route The planned continuous coverage service: l  CPICH Ec/Io ≥ –12 dB l  CPICH RSCP ≥ –95 dBm
CPICH Ec/Io ≥ –12dB	≥ 95%	Test result by scanner in outdoor unloaded conditions
CPICH RSCP ≥ –95dBm	≥ 95%	Test result by scanner in outdoor unloaded conditions
SHO Factor based on DT	30%–40%	The SHO Factor based on DT should be 5% to 10% lower than the goal, because the following optimizations cause the soft handover factor to increase
Pilot pollution ratio	≤ 5%	–

1.2  Dividing Clusters

According to the features of UMTS technologies, the coverage and capacity are interactional and the frequency reuse factor is 1. Therefore RF optimization must be performed on a group of or a cluster of NodeBs at the same time instead of performing RF optimization on single site one by one. This ensures that interference from intra-frequency neighbor cells are considered during optimization. Analyze the impact of the adjustment of an index on other sites before adjustment.

Dividing clusters involves approval by the operator. The following factors must be considered upon dividing clusters:

l   According to experiences, the number of NodeBs in a cluster depends on the actual situation. 15–25 NodeBs in a cluster is recommended. Too many or few NodeBs in a cluster is improper.

l   A cluster must not cover different areas of test (planning) full coverage services.

l   Refer to the divided clusters for network project maintenance of the operator.

l   Landform factor
Landforms affect signal propagation. Mountains block signal propagation, so they are natural borders for dividing clusters. Rivers causes a longer propagation distance, so they affect dividing clusters in various aspects. If a river is narrow, the signals along two banks will interact. If the transportation between two banks allows, divide sites along the two banks in the same cluster. If a river is wide, the upstream and downstream will interact. In this situation, the transportation between two banks is inconvenient, dividing clusters by the bank according to actual situation.

l   A cell-like cluster is much usual than a strip-like cluster.

l   Administrative areas
When the coverage area involves several administrative areas, divide clusters according to administrative areas. This is easily acceptable by the operator.

l   DT workload
The DT must be performed within a day for a cluster. A DT takes about four hours.

Deciding Test Route

Confirm the KPI DT acceptance route with the operator before DT. If the operator already has a decided DT acceptance route, you must consider this upon deciding the KPI DT acceptance route. If the objective factors like network layout cannot fully meet the coverage requirements of decided test route by the operator, you must point this out.

The KPI DT acceptance route is the core route of RF optimization test routes. Its optimization is the core of RF optimization. The following tasks, such as parameter optimization and acceptance, is based on KPI DT acceptance route. The KPI DT acceptance route must cover major streets, important location, VIP, and VIC. The DT route should cover all cells as possible. The initial test and final test must cover all cells. If time is enough, cover all streets in the planned area. Use the same DT route in every test to compare performances more accurately. Round-trip DT is performed if possible.

Consider actual factors like lanes and left-turn restriction while deciding test route. Before negotiating with the operator, communicate these factors with local drivers for whether the route is acceptable.

1.4  Preparing Tools and Data

Prepare necessary software (listed in Table 3-2), hardware (listed in Table 3-3), and various data (listed in Table 3-4), because the following test and analysis are based on them.

1.4.1  Preparing Software

Table 3-2 lists the recommended software for RF optimization

Table 1-2 Recommended software for RF optimization

No.	Software	Function	Remarks
1	Genex Probe	DT	–
2	Genex Assistant	Analyzing DT data and checking neighbor cells	–
3	Genex Nastar	Analyzing performance, checking health, and locating problems	–
4	Mapinfo	Displaying maps and generating route data	–

Preparing Hardware

list of the recommended hardware for RF optimization

Recommended hardware for RF optimization

No.	Device	Specification	Remarks
1	Scanner	DTI Scanner	–
2	Test terminal and data line	U626, Qualcomm, and so on	At least two test terminals
3	Laptop computer	PM1.3G/512M/20G/USB/COM/PRN	–
4	Vehicle mounted inverter	DC to AC, over 300W	–

Preparing Data

lists the data to be collected before optimization

Data to be collected before optimization

No.	Needed data	Whether is necessary	Remarks
1	List of engineering parameters	Yes	–
2	Map	Yes	By Mapinfo or in paper
3	KPI requirements	Yes	–
4	Network configuration parameters	Yes	–
5	Survey report	No	–
6	Single site verification checklist	No	–
7	Floor plan of the target buildings	Yes	For indoor test

Data Collection

During RF optimization stage, the key is the optimization of radio signals distribution, with the major means of DT and indoor test. Before test, confirm with the customer care engineers the following aspects:

l   Whether the target NodeBs, RNCs, and related CN are abnormal due to being disabled, blocked, congested, and transmission alarms.

l   Whether the alarms have negative impact on the validity of test result data.
If the alarms exist, solve the problems before test.

DT is a major test. Collect scanner and UE data of radio signals by DT test. The data is applicable in analyzing coverage, handover, and pilot pollution problems.

Indoor test involves the following areas:

l   Indoor coverage areas
Indoor coverage areas include inside buildings, department stores, and subways.

l   Inside areas of important facilities
Inside areas of important facilities include gymnasiums and government offices.

l   Areas required by the operator
Areas required by the operator include VIC and VIP.

Test the previous areas to locate, analyze, and solve the RF problems.

Indoor test also involves in optimizing handover of indoor and outdoor intra-frequency, inter-frequency, and inter-system.

The DT and indoor test during RF optimization stage is based on VP service. According to the contract (commercial deployment offices) and planning report (trial offices), if seamless coverage by VP service is impossible in areas, such as, suburban areas and rural areas, the test is based on voice services. For areas with seamless coverage by PS384K service required by the contract (commercial deployment office) or planning report (trial office), such as office buildings, press centers, and hot spot areas, the test is based on PS384K service.

Drive Test

DT Types

According to different full coverage services in the planned areas, DT might be one of the following:

l   3G ONLY continuous talk test by using scanner + unloaded VP
According to simulation result and experiences, if the test result meets requirements on VP service coverage, the test result will also meet identical coverage requirements of PS144K, PS128K, and PS64K services.

l   3G ONLY continuous talk test by using scanner + unloaded voice service

l   3G ONLY continuous talk test by using scanner + unloaded PS384K

Setting DT Indexes

The following paragraphs take VP service for example.

Setting DT indexes proceeds as below:

1)      Start Genex Probe 1.3 software

2)      Select Configuration > System Config > Test Plan

For setting DT, see the following table.

Index	Meaning
Enable	Whether to implement this index. True for implementation. False for non-implementation. The recommended value is True.
Call Number	Called number. Whether the called terminal supports VP must be confirmed.
Setup Time (s)	The maximum time for setting up calls. It ranges from 20–30s. The recommended value is 25s.
Calling Time (s)	The time for a single call from call start to normal end of call. Set it great enough according to actual DT route. The recommended value is 99999s.
Idle Time (s)	Call internal time. The recommended value is 10s.
Call Count	Total call times. Set it great enough according to actual DT route. The recommended value is 999 times.

Collect call data tracing at RNC side while performing drive test. This help to locate and analyze problems.

Data to be collected includes:

l   Traced signaling messages of single subscriber

Indoor Test

GPS signals are unobtainable in door test. Obtain the plan of the target area before test.

Indoor test consists of walking test and vertical test. Perform walking test to obtain horizontal signals distribution inside buildings by selecting Indoor Measurement > Walking Test. Perform vertical test to obtain vertical signals distribution by selecting Indoor Measurement > Vertical Test. For the detailed method, see WCDMA Test Guide 3.0.

Indoor test services are services by seamless coverage required in the contract (commercial deployment office) or planning report (trial office). The method for indoor test and requirements on collecting call tracing data are the same as DT.

Collecting RNC Configuration Data

During RF optimization stage, collect neighbor cell data of network optimization and other data configured in RNC database. In addition, check whether the configured data is consistent with the previously checked/planned data.

While checking configured data, feed back the improperly configured data (if found) to product support engineers. During checking, pay special attention to handover reselection parameters and power setting parameters, as listed in Table 4-1.

Configured parameters to be checked

Type	Content to be checked
Handover reselection parameter	IntraFreqNCell (intra-frequency neighbor cell) InterFreqNCell (inter-frequency neighbor cell) InterRATNCell (inter-system neighbor cell)
Power configuration parameter	MaxAllowedULTxPower (maximum uplink transmit power of UE) PCPICHPower (PCPICH transmit power)

For handover reselection parameters, check list of neighbor cells, including intra-frequency, inter-frequency, and inter-system neighbor cells.

Output an updated Radio Parameter Configuration Data Table and parameter revision records. This is useful in problem analysis and following optimization stages.

Collecting data proceeds as below:

4)      Start RNC LMT

5)      Collect MML scripts

6)      Convert neighbor cell configuration data in MML scripts to Excel files by using Nastar

7)      Save the data in the format in which the data can be imported to Assistant.