ÍNDICE DE TABLAS
CAPÍTULO 2. INTRODUCCIÓN
2.2 PSICOLOGÍA DEL ESTRÉS
2.2.4 El estrés y otros constructos psicológicos en el ámbito sanitario
The definition of the handover event detection failure in this guideline is that the network side fails to receive the measurement report when the UE enters (or leaves) the desired (or undesired) cell coverage area.
8.30.1 Symptoms
From the drive test, following symptoms will be observed by using TEMS and UETR:
- The UE sends “measurement reports” to the UTRAN; however, the UTRAN does not receive them or
- The UE does not generate “measurement reports” even if it enters the desired cell coverage area or
- The UE does not generate “measurement reports” even if it leaves the undesired cell coverage area.
Note: The coverage area of the desired (or undesired) cell can be verified by using pilot scanner.
8.30.2 Reason 1 – poor uplink quality
If the UE sends “measurement reports” to the UTRAN; however, the UTRAN does not receive them, it implies the quality of the uplink may be no good.
Solution
Please read chapter 8.60.
8.30.3 Reason 2 – incorrect handover series
The UE might handover to wrong cells, i.e. incorrect cells in the active set at the problematic area, and these active set cells do not have neighboring relationship with the desired cell. As a result, even though the UE enters the desired cell coverage area according to the original plan, handover event is not detected.
Handover series could be messed up because:
- Handover function failure or
- Too many unnecessary handover relationships or - Unwanted cell overshooting
Solution 1
If the problem is due to handover function failure, please read chapter 8.31.
Solution 2
If the problem is due to too many unnecessary handover relationships, the engineer should carefully justify the usefulness of the handover relationships and remove the unnecessary ones.
Note: If the necessary relationship is mistakenly deleted, more connection drops and high downlink interference may happen due to missing handover
relationship.
Solution 3
If the problem is due to overshooting of the unwanted cell, the engineer should check why the cell is overshooting.
- If the pilot power of the unwanted cell is too high, the engineer should reduce its pilot power back to a suitable level.
- If the pilot power of the unwanted cell is normal, please employ solution 2 and 3 in chapter 8.1.3 to overcome the overshooting problem.
8.30.4 Reason 3 - missing neighboring relationship
The possible reason why the handover event detection fails is because of missing neighboring cell relationship. In the drive test, the engineer can monitor the neighboring cell window to check if the desired cell is included in the monitored set.
Solution
The direct solution is to add the desired cell into the neighboring cell lists of the cells in the active set. However, it should be noted that too many neighboring cell relationships might slow down the search for the pilot channels in the UE.
8.30.5 Reason 4 – pilot pollution in dedicated mode
Pilot pollution can lead failure in the handover event detection. Please read chapter 8.4 for the descriptions and solutions about pilot pollution.
8.30.6 Reason 5 - too long intra-frequency neighboring cells list
According to 3GPP standardization, the maximum number of UE measured cells is 32 for the currently used frequency. Therefore, if the total number of cells in active set and preliminary intra-frequency monitored subset is more than 32, the preliminary intra-frequency monitored subset has to be reduced. Due to this reduction, the desired cell might be removed in the handover algorithm and handover event detection fails.Note:
- The cells in active set are the cells involved in soft or softer handover.
- The cells in the preliminary intra-frequency monitored subset are the cells taken from the union of the currently used frequency cells in the neighboring cell lists of the active set cells and then deleting the cells that are in the active set. For example (please see Table 11), if there are three cells in the active set – cell A, cell B and cell C, the preliminary intra-frequency monitored subset will contain Cell A1, Cell A2, Cell A3, Cell A4, Cell B1, Cell B2, Cell B3, Cell C1 and Cell C2.
Table 11. An example to illustrate the preliminary intra-frequency monitored subset
Active set cells Intra-frequency neighboring cell lists
Cell A Cell B, Cell C, Cell A1, Cell A2, Cell A3, Cell
A4
Cell B Cell A, Cell C, Cell B1, Cell B2, Cell B3
Cell C Cell A, Cell B, Cell C1, Cell C2
- Regarding the reduction in the preliminary intra-frequency monitored subset, the handover algorithm will select and then remove a number of cells from the neighboring cell lists in each active set cell respectively in order to be sure that each active set cell can contribute its neighboring cells for
monitoring. The removed neighboring cells are normally at the bottom of the neighboring cell lists.
Solution 1
If there are too many unnecessary handover relationships, the engineer should carefully justify the usefulness of the handover relationships and remove the unnecessary ones.
Note: If the necessary relationship is mistakenly deleted, more connection drops and high downlink interference may happen due to missing handover
relationship.
Solution 2
The engineer should put the neighboring cells in a desired order so the highest ranked cells appear in the top of the list.
8.30.7 Reason 6 – improper cell individual offset setting
If the cell individual offset Cell individual offset of the desired cell is too negative, handover event detection might fail.Solution
The Cell individual offset should be changed to not too large negative. If the performance of load shifting becomes no good after the change, new site must be added instead of using Cell individual offset to shift the load.
8.30.8 Reason 7 – slow searching or fast UE
Handover events are probably overlooked because:- There are many cells in the monitored set, the process for searching pilot channel might become very slow.
- The UE is in fast moving.
Solution
The engineer should carefully justify the usefulness of the handover relationships and remove the unnecessary ones.
Note: If the necessary relationship is mistakenly deleted, more connection drops and high downlink interference may happen due to missing handover
relationship.
8.30.9 Reason 8 – small soft handover area
Due to radio propagation, the soft handover area between two cells might be very small, e.g. corner effect. Then, a handover event is probably overlooked.
Solution 1
Giving a positive value to the cell individual offset Cell individual offset of the target cell can enlarge the soft handover area.
Solution 2
The engineer can change the antenna configuration or re-locate the sites so that the cell overlapping and soft handover area becomes larger. Obviously, it is a cost and time-consuming solution.