82BSSPAR Handover Control and Adjacencies.docx

1、82BSSPAR Handover Control and AdjacenciesBSSPARHandover Control & AdjacenciesTraining DocumentThe information in this document is subject to change without notice and describes only the product defined in the introduction of this documentation. This document is intended for the use of Nokia Networks

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3、onnel, and the customer assumes full responsibility when using it. Nokia Networks welcomes customer comments as part of the process of continuous development and improvement of the documentation. The information or statements given in this document concerning the suitability, capacity, or performanc

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6、IS DOCUMENT OR FOR ANY DAMAGES, INCIDENTAL OR CONSEQUENTIAL (INCLUDING MONETARY LOSSES), that might arise from the use of this document or the information in it.This document and the product it describes are considered protected by copyright according to the applicable laws.NOKIA logo is a registere

7、d trademark of Nokia Corporation.Other product names mentioned in this document may be trademarks of their respective companies, and they are mentioned for identification purposes only.Copyright Nokia Oyj 2003. All rights reserved.Contents1 Module Objectives 52 Introduction to the Handover Process 6

8、3 Handover Decisions 74 Handover Timers 95 Target Cell Evaluation Process 115.1 Decision Algorithms 125.2 C/I Based Handover Candidate Evaluation 146 Radio Resource Handovers 166.1 Power Budget Handover 176.2 Umbrella Handover 206.3 Combined Umbrella and Power Budget 246.3.1 Fast Moving MS (FMMS) Ha

9、ndling In Macro Cell 276.3.2 MS Speed Detection and Variable Window Size 276.4 Handover due to Quality or Signal Level 326.4.1 Handover due to Quality 326.4.2 Handover due to Signal Level 356.5 Handover Due to Interference 377 Imperative Handovers 397.1 MS BTS Distance 407.2 Rapid Field Drop and Enh

10、anced Rapid Field Drop 417.2.1 Chained Adjacent Cells In Rapid Field Drop 427.2.2 Turn-Around-Corner MS 438 Traffic Reason Handovers 488.1 MSC-Controlled Traffic Reason Handover 488.2 BSC Initiated Traffic Reason Handover (Advanced Multilayer Handling) 498.2.1 Interactions with other Features 519 Lo

11、ad control between layers: Advanced Multilayer Handling (AMH) 529.1 IUO Load Control 529.2 Multilayer (Dual Band/Micro Cellular) Network Load Control 539.3 Parameters Involved in AMH feature activation 5310 Direct Access to Desired Layer/Band (DADL/B) 5510.1 DADL/B interactions with other features 5

12、611 Handover Parameter List 5812 Adjacent Cell Parameter List 6413 Practical Examples of Handovers 6814 Handover Control Exercise 6915 Handover Exercise 7016 Key Learning Points 7117 Review Questions 781 Module ObjectivesAt the end of this module, the participant will be able to: List ten types of h

13、andovers, in the order in which they are prioritised. State the parameters defining the minimum intervals between handovers, and between handover attempts. Discuss the target cell evaluation process. Explain the parameters associated with power budget handovers. Name the parameters used to control u

14、mbrella handovers. List the parameters associated with MS speed detection and handovers. Discuss the mechanism and parameters for handover due to signal level or quality. State the various types of imperative handovers and their associated parameters. Explain the Advanced Multilayer Handling (AMH) c

15、oncept and parameters.2 Introduction to the Handover ProcessHandover decisions are made by Radio Resource Management in the BSC.They are based on the DL & UL measurement results reported by the MS & BTS, which are then processed according to parameter settings for each cell, and then processed by th

16、e Handover Control Algorithm, producing a decision. Target cell evaluation is also part of the handover process. Handovers are triggered by threshold comparison, or by periodic comparison.Why are handovers needed?1. Call continuity: to ensure a call can be maintained as an MS moves in geographical l

17、ocation, from the coverage area of one cell to another.2. Call quality - to ensure that if an MS moves into an area of poor quality or poor coverage, the call can be moved from the serving cell to a neighbouring cell (with better quality) without dropping the call.3. Traffic Reasons - to ensure that

18、 the traffic within the network is optimally distributed between the different layers or bands of a network.3 Handover DecisionsThere are numerous causes for a handover decision to be made, based on comparisons of measurements with thresholds. The HO threshold comparison includes the evaluation of t

19、he uplink and downlink level, quality, and interference. Other criteria also considered are: MS-BS distance evaluation, the evaluation of a rapid field drop, the detection of a fast or slow-moving MS, the detection of a turn-around-corner MS, power budget evaluation, and umbrella handover evaluation

20、.Figure 1 Handover CausesIf two or more criteria for a handover are present simultaneously, their order of priority is as follows:1. Interference (uplink or downlink)2. Uplink quality3. Downlink quality4. Uplink level5. Downlink level6. MS-BS distance (maximum or minimum)7. Turn-around-corner MS8. R

21、apid field drop9. Fast/Slow-moving MS10. Better cell (Power budget or Umbrella)11. PC due to Lower quality thresholds (uplink and downlink)12. PC due to Lower level thresholds (uplink and downlink)13. PC due to Upper quality thresholds (uplink and downlink)14. PC due to Upper level thresholds (uplin

22、k and downlink).When two or more of the above indicated criteria (from 1. to 9.) are present simultaneously, for example Uplink quality and Uplink level, the BSC performs target cell evaluation, only according to the criterion which has the highest priority. So, out of Uplink quality and Uplink leve

23、l, that would be Uplink quality. If no adjacent cell is good enough for a handover caused by this criterion, then the BSC proceeds to the next HO threshold comparison (10. Better cell), and then to the PC threshold comparisons (11. to 14.).4 Handover TimersThe BSC normally controls the intervals bet

24、ween handovers and handover attempts by the use of the following parameters:minIntBetweenHoReq (MIH)(HOC)(ZEHO)(0.31s)(5s), andminIntBetweenUnsuccHoAttempt (MIU)(HOC)(ZEHO)(0.31s)(3s)The first parameter (MIH) prevents repetitive handovers for the same MS, by using a timer that sets the minimum inter

25、val between handovers related to the same connection.The latter parameter (MIU) defines the minimum time that the MS must wait after a handover attempt fails, before it can try a handover attempt again.The MML default values are (5s) and (3s) as noted above, and the recommended values for these para

26、meters are the same as the defaults.The measurement averaging and the HO Threshold comparison do not stop during these intervals, although handovers are not possible.Figure 2 Handover TimersFigure 3 Handover Failure TimerFigure 4 Guard Period for back-handover5 Target Cell Evaluation ProcessTarget c

27、ell evaluation is made in Radio Resource Management in the BSC.The purpose of the process is to find the best target cell to satisfy the cause for the handover.Evaluation of the preferred list of target cells is based on:1. the radio link measurements2. threshold comparison3. the priority levels of

28、the neighbouring cells4. the load of those neighbouring cells which belong to the same BSC as the serving cell5. RX level comparison if it is neededTo be on the target cell candidate list, the neighbouring cells must, of course, be defined as Adjacencies in the outgoing direction from the serving ce

29、ll. The BTS sends the list of best candidates to the BSC. First the BSC defines and selects those cells which meet the requirements for the radiolink properties.RR Management can handle up to 32 of the best candidates for target cell evaluation.The loads of the traffic channels in these candidate ce

30、lls are checked by the parameter:btsLoadThreshold (BLT)(BTS)(ZEQO)(0.100%)(70%)If one of these candidate cells is already overloaded, (that is loaded above the threshold, which is a soft limit), then the priority that has already been set for that cell by the parameter:hoLevPriority (PRI)(ADJC)(ZEAO

31、)(0.7)(3)is decreased by the value of the parameter:hoLoadFactor (OF)(ADJC)(ZEAO)(0.7)(1)After the load check of each candidate, a comparison between priorities of each candidate cell is made, and the candidate with the highest priority will be selected as a target cell. If there are many cells with

32、 equally high priorities, the cell with the best received signal strength will be selected.Note: Parameter OF must NOT be set to be greater than PRI.With the BLT parameter, we define which proportion of reserved or unavailable channels, in all channels, is acceptable. BLT is one of the key parameters used in the handover control process. If this threshold is exceeded, the BTS (= cell, = sector) is considered to be