3G Network Roll-Out Vision, Challenge and Solution LS Telcom Summit 2005 June 8 th, 2005 Bernard Breton, Vice President Research & Development

Transcription

1 Network Performance for Profitability 3G Network Roll-Out Vision, Challenge and Solution LS Telcom Summit 2005 June 8 th, 2005 Bernard Breton, Vice President Research & Development 1 Design Optimize Business Improvement

2 Rolling Out 3G Networks Goal is to explain: - Review of 3G Roll-Out Philosophies - Preparing for initial commercial launch - Performing pre-launch optimization - Post-launch network optimization - Conclusion & Discussions 2

3 3G Roll-Out Philosophy: 1:1 Overlay 1:1 Overlay Approach For each GSM macro-cell, a WCDMA cell is deployed Advantages Easy to rollout (almost no rollout considerations) Easy to outsource (simple design criteria) Works reasonably well if there are no GSM capacity cells Disadvantages Higher initial CAPEX Lower performance levels Does not work with all sites some GSM sites just can t be reused More complex and expensive post-launch optimization Makes it difficult to have various coverage objectives (no control over it) 3

4 1:1 Rollout Process 1:1 Overlay Approach Install all Node B of a cluster For each GSM BTS for a given cluster, a WCDMA Node B is installed. If dual-band antennas are installed, then the existing antenna is replaced with a new dual band antenna Integrate all new Node B When a group of Node B (cluster) is enabled, various system parameters (GSM and WCDMA) must be updated. This is particularly true for the neighbor relations in order to provide good handover performance Coverage/Quality objectives are truly only dealt with during the optimization phase Drive test area Most vendors rely heavily on drive test to drive the manual optimization process in order to achieve agreed KPIs. Drive tests can also be utilized to improve predictions when using an automated network optimization solution (ACP) Optimize radio parameters Antenna configuration, power settings and neighbor relations can be optimized based on drive test and/or predictions. Automatic or manual techniques can be used 4

5 Link Budget Comparison 1:1 Overlay Approach GSM Link Budget UMTS Link Budget Bandwidth 200 khz Data rate: kbps Noise Density -174 dbm/hz Noise density: dbm/hz Noise -121 dbm Noise: dbm BS Noise Figure 4 db Processing gain: db Target C/N 12 db Target Eb/Nt: db Sensitivity -105 dbm BTS Sensitivity: dbm MS EIRP 24 dbm Service margin: db BS Antenna Gain Max. Path Loss 15 dbi 144 db Max. Path Loss: db (no loading) Voice DCS 1800 and UMTS 64/144 kbps link budgets are very similar 5

6 Excessive Pollution in 1:1 Re-use Model 1:1 Overlay Approach Large areas with a very low spectral efficiency and poor Ec/Io 6

7 Coverage & Capacity Considerations 1:1 Overlay Approach Given that the link budgets are reasonably compatible between DCS1800 and WCDMA, the average cell spacing will be adequate It remains a utopian concept to think that a simple 1:1 re-use is feasible Almost certainly, capacity cells do exist in urban areas (particularly true in 900) Excessive propagation can be solved in GSM with proper frequency planning. This is nowhere as easy in WCDMA In fact, hierarchical cell structures are often used to provide a trade-off between coverage and capacity Such structure does not work in WCDMA Key initial problem with a 1:1 re-use will be the presence of a small (but important) number of substantial polluters, leading to a lower capacity and quality 7

8 Coverage Considerations of a Loaded Network 1:1 Overlay Approach WCDMA link budget is very dependent upon the actual network load (i.e. cell breathing effect) During busy hours, the high-data rate coverage will therefore suffer quite substantially (E.g. 384kbps allowable path loss restricted to 132 db at 75% - about 10 db worst than GSM) Voice link budget remains better (or equal to) GSM even when loading is quite high ( > 75 % ) This translates to a network with solid voice coverage and fluctuating high data rate coverage Might make it difficult to sell the value of high-data rate services when they are only solid during the quiet times 8

9 Cell Breathing Impact on UMTS Coverage 10% Network Load 75% Network Load 1:1 Overlay Approach Probability of Service Voice > 99% > 95% > 90% > 50% 144 kbps 9

10 Cell Breathing Impact : Statistics Service Coverage Comparison Percentage of calls below to to to to to Voice 10% Voice 75% % % % % Service & Loading 10

11 Solving the Radio Pollution Reducing the amount of radio pollution is key to both coverage and capacity Spectral efficiency is directly linked to the dominance of the best serving sector (i.e. focus on in-cell noise rather than out of cell noise) With a 1:1 re-use model, physical antenna parameters are the only efficient mean to reduce radio pollution This translates into very significant post-design optimization efforts Given that the propagation characteristics can only be somewhat influenced by antenna parameters, it also means that the optimization process will not be able to improve performance as much as it could if initial sites where selected on the basis of their radio characteristics Ultimately, there are cases where the only way to correct major pilot pollution problems is to shut down the polluter. This is indeed something to avoid post rollout 11 1:1 Overlay Approach

12 Dual-Band Antennas and Impact on Design When using multi-band antennas, it introduces additional design & optimization constraints for both WCDMA and GSM The antennas offer limited per-band adjustments (electrical tilt only) Unless dual or tri-band antennas are already installed, existing GSM antennas need to be replaced Typically, operators will want to deploy the WCDMA network without substantially impacting the GSM KPIs Over-the-years optimization of GSM parameters is leading to solid KPIs. Change in radiation characteristics can affect (often negatively) the network performance Performance of GSM1800 is more difficult to guarantee given that the only freedom for UMTS optimization is the electrical tilt, which is often shared with GSM :1 Overlay Approach

13 Optimization for Multi Band in a 1:1 Re-Use Despite the limitations, there are essentially three options: Optimize the WCDMA network and GSM1800 and possibly even GSM900 simultaneously (co-optimization) Requires very advanced software and makes the optimization process quite complex Makes the rollout of optimization changes more difficult (need to coordinate between two technologies) Optimize the WCDMA network and assess GSM performance to manage coverage impact This actually makes sense since in general, there is a reasonable correlation between the performance of a WCDMA network and a GSM network (i.e. making one work better leads to the other one working better) The primary factor to look for is downtilt since WCDMA optimization will typically lead to stronger downtilts than GSM would like (soft handover and need to reduce pilot pollution leads to more aggressive down-tilting in WCDMA) Optimize WCDMA layer with constraints on the optimization This indeed makes sense if dual-bands antennas are not used everywhere 13 1:1 Overlay Approach

14 3G Roll-Out Philosophy: Progressive Overlay Site selection & density is directly driven by coverage objectives Density is therefore as variable as are the coverage objectives Site selection and their parameters are based on their ability to contribute positively to the 3G network (i.e. doesn t assume a 2G site is a good 3G site) Advantages Lowest possible CAPEX/OPEX cost Worst polluters are inherently not re-used Allows for better control of the coverage objectives Provides a better mean to deal with site availability issues Can deal better with a dynamic environment (i.e. problems with site acquisition, optimization constraints ) Disadvantages More complex process almost certainly requires better tools Implies there is an acknowledgment that deploying a WCDMA network makes the design process even more dynamic 14 Progressive Overlay Approach

15 What is a Coverage Objective? Service Penetration (%) Voice Service Coverage Outdoor CPICH Coverage 144kbps Service Coverage Indoor CPICH Coverage Implicit coverage objective of a 1:1 re-use Number of sites 15

16 Progressive Overlay Rollout Process Define coverage objectives (Marketing) Service areas are defined with specific service objectives in mind by marketing (E.g. 90% 144 kbps indoor coverage for Paris Intra Muros) Possible candidate sites would typically be the existing GSM sites + other available sites Define initial likely configuration and constraints for all possible candidate sites Define list of potential candidate sites within service area (140 sites) Create nominal configuration for all candidate sites Verify availability of the most valuable sites Define new list of most valuable additional sites (20 more sites) Estimate CAPEX requirements (i.e. site count) to fulfill the coverage objectives while considering design constraints Based on the reference scenario, find out the 20 sites that provides the best overall coverage contribution Output: reference scenario Determine number of required sites (100 sites) Establish short list of most valuable sites (20 sites) Have we reached coverage objectives? Yes No Re-assess nominal plan and confirm sites required (which sites and how many) 16 1:1 Overlay Approach

17 Process Illustration Set of Possible Candidate Sites Possible candidate site (GSM site or other possibly available site) 17

18 Process Illustration Creation of initial reference scenario Site selected in initial reference scenario (which achieves the coverage objectives) 18

19 Process Illustration When a site is not available, update reference scenario New site required due to a site not being available Site is not required anymore 19 Site is not available anymore

20 Site Potential Analysis Site Importance (%) Priority (1-3) Coverage (Erlangs) Site Site Site Site Site Site Site Site Site

21 Overall UMTS Roll-Out Process 21 Progressive Overlay Approach

22 Pre/Post Launch Optimization During Pre-Launch Optimisation No traffic in the network, no subscribers Network typically tuned only based on drive test data Labour intensive with repeated drive test A combined measured/predictive solution is best suited to provide solid initial design and reduce manpower During Optimization Commercial traffic, subscribers using the network Statistics used to monitor network performance (KPIs) Drive testing just in case Post roll-out network optimization is an ongoing process, unlike prelaunch optimization 22

23 Pre/Post Design Optimization Network Quality Analysis Percentage of the area Initial GSM Roll-Out Planner Optimizer Progressive overlay 1:1 Re-Use to to to to -9-9 to 0 Ec/Io (db) 23

24 Conclusions Progressive Overlay Provides Substantial Advantages Better aligned with business objectives Ability to deploy a network with variable coverage objectives Lower initial CAPEX Ability to deploy equipment more progressively, as traffic load is raising Provides a better link between the site acquisition and design activities Easier to optimize network once loaded Software Solutions are a Enabler Progressive overlay increases the complexity of some tasks but automated solutions substantially reduce manpower required. Automated solutions can improve both time to market and quality of initial network. 24

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