BASIC GSM RNP & RNO Training Department Course Contents Introduction to GSM network Mobile radio link Network planning procedure Advanced network planning Introduction to GSM Network 1. GSM system architecture 2. GSM bandwidth 3. Difference between GSM900 and GSM1800 4. GSM Logical channels GSM System Architecture VLR HLR Other MSC EIR AuC OMC Other BTS´s GSM Bandwidth GSM 900 : 890 915 935 960 Channel spacing 200kHz Duplex Spacing : 45 MHz GSM 1800 : Channel spacing 200kHz 1710 1785 1805 1880 Duplex Spacing : 95 MHz Difference Between GSM900 and GSM1800 GSM900 and GSM1800 are similar GSM 900 GSM 1800 Frequency band 890...960 MHz 1710...1880 MHz Number of channels 124 374 Channel spacing 200 kHz 200 kHz Access technique TDMA TDMA Mobile power 0.8 / 2 / 5 W 0.25 / 1 W There are no major differences between GSM 900 and GSM 1800 Logical Channels GSM900/GSM1800 logic channel architecture Logical Channels Common Channels Dedicated Channels (CCH) (DCH) Broadcast Control Common Control Traffic Channels Control Channels Channel (BCCH) Channel (CCCH) (TCH) FCH SCH BCCH PCH AGCH RACH SDCCH FACCH TCH/F TCH/H (Sys Info) SACCH TCH/9.6F TCH/ 4.8F, H TCH/ 2.4F, H Downlink Channels FCCH SCH Common BCCH BCCH Channels CCCH PCH AGCH SDCCH DCCH SACCH Dedicated FACCH Channels TCH TCH/F TCH/H Uplink Channels RACH CCCH Common Channels SDCCH DCCH SACCH FACCH Dedicated TCH/F Channels TCH TCH/H Use of Logical Channels “off” state Search for frequency correction burst FCCH Search for synchronization sequence SCH Read system information BCCH idle mode Listen paging message PCH Send access burst RACH Wait for signaling channel allocation AGCH dedicated Call setup SDCCH mode Assign traffic channel SDCCH Conversation TCH Call release FACCH idle mode Exercises 1. Write down the frequency used for uplink and downlink. Answer: GSM system uses different frequency for uplink and downlink. GSM900: Uplink: 935---960 Downlink: 890---915 GSM1800: Uplink: 1805--1880 Downlink: 1710--1785 Exercises 2. Write down the types of logical channels and the hierarchy Answer: Logical Channels Common Channels Dedicated Channels (CCH) (DCH) Broadcast Control Common Control Traffic Channels Control Channels Channel (BCCH) Channel (CCCH) (TCH) FCH SCH BCCH PCH AGCH RACH SDCCH FACCH TCH/F TCH/H (Sys Info) SACCH TCH/9.6F TCH/ 4.8F, H TCH/ 2.4F, H Course Contents Introduction to GSM network Mobile radio link Network planning procedure Advanced network planning Mobile Radio Link 1. Radio wave propagation 2. Propagation models 3. Antenna systems 4. Diversity technique 5. Interference and interference reduction 6. Link budget Radio Link Propagation Multi-path propagation Radio path is a complicated propagation medium Limited transmitting energy The service range is determined by the transmission power of mobiles Battery life-time Limited spectrum Set upper limitation for data rate (Shannon´s theorem) Additional effort needed for channel coding Frequency reused result in self- interference Radio Propagation Environment Multi-path propagation Shadowing Terrain Building Reflection Interference Reflections Strong echoes can cause excessive transmission delay No impact If the delay falls in the equalizer window Cause self-interference if the delay falls out of the equalizer window direct signal strong reflected signal amplitude long echoes, out of equalizer window: self-interference delay time equalizer window 16 s Fading(1) Slow fading (Lognormal Fading) Shadowing due to large obstacles on propagation direction Level (dB) Fast fading (Rayleigh fading) +10 Serious interference from multi-path 0 signals -10 -20 920 MHz v = 20 km/h -30 0 1 2 3 4 5m Fading(2) power Rayleigh fading +20 dB lognormal fading mean value - 20 dB 2 sec 4 sec 6 sec time Propagation Absorption Heavy amplitude attenuation A A - 5..30 dB Material determining phase shift Diffraction Wedge-model Knife edge Multiple knife edges Mobile Radio Link 1. Radio wave propagation 2. Propagation models 3. Antenna systems 4. Diversity technique 5. Interference and interference reduction 6. Link budget Propagation Model Historical CCIR- Model for Radio station Not very accurate nor serious Okumura- Hata Empirical model Measure and estimate additional attenuations Applied for larger distance estimation (range: 5 .. 20km) Not suitable for small distance ( < 1km) Hata Model Model used for 900 MHz L A B log f 1382 log hb a (hm ) . (44.9 6.55 log hb ) log d Lmorpho with f frequency in MHz additional attenuation due h BS antenna height [m] to land usage classes a(h) function of MS antenna height d distance between BS and MS [km] and A= 69.55, B = 26.16 (for 150 .. 1000 MHz) A= 46.3 , B = 33.9 (for 1000 ..2000MHz) Mobil Radio Link 1. Radio wave propagation 2. Propagation model 3. Antenna system 4. Diversity technique 5. Interference and interference reduction 6. Link budget Antenna Characteristics Lobes Main lobes Side and Back lobes Front-to-Back ratio Half-power beam-width Antenna downtilt Polarization Frequency range Antenna impedance Mechanical size Coupling Between Antennas main lobe Horizontal separation Sufficient decoupling distance: 5-10λ Antenna patterns superimposed if distance too close 5 .. 10 Vertical separation Decoupling distance:1λ can provide good RX /TX decoupling Minimum coupling loss Installation Examples Recommended decoupling TX - TX: ~20dB 0,2m TX - RX: ~40dB Horizontal decoupling distance depends on Antenna gain Omni-directional.: 5 .. 20m directional : 1 ... 3m Horizontal rad. pattern Omni-directional antenna Use vertical separation for RX and TX Use vertical separation (“fork”) for RX and diversity RX Vertical decoupling is much more effective Installation Examples Directional antenna Antenna down tilt Improve hotspot coverage Reduce interference 5..8 deg Feeder Feeder parameter Type Diameter 1800MHz 900MHz (mm) dB/100m dB/100m 3/8” 10 14 10 5/8” 17 9 6 7/8” 25 6 4 1 5/8” 47 3 2 Use the short feeder whenever possible Distributed Antennas Leaking feeder Cables with very high loss per length unit “distributed antenna” often used for tunnel coverage. This kind of feeder is expensive Propagation loss: 4 ... 40 dB/100m 50 Ohm coupling loss: ~ 60 dB (at 1m dist.) Optic fiber distribution system Distribute RF signal radiate from discrete antenna points at remote locations via (very thin) optic fiber. Repeaters Repeater type Narrow-band Repeater Wide-band Repeater The Repeater is used to relay signal into shadowed area Behind hill Into valley Into building decoupling ~40 dB needed Note: The Repeater needs a host cell Mobile Radio Link 1. Radio wave propagation 2. Propagation models 3. Antenna systems 4. Diversity technique 5. Interference and interference reduction 6. Link budget Diversity Time diversity t Coding, interleaving Frequency diversity f Frequency hopping Space diversity Multiple antennas Polarization diversity Dual-polarized antennas Multi-path diversity Equalizer Benefit From Diversity Diversity gain depends on environment Antenna diversity 3dB gain More path loss acceptable in link budget Higher coverage range R(div) ~ 1,3 R A 1.7 A 70% more coverage per cell Needs, less cells in total R The above case can be satisfied only under ideal condition. That is the environment is infinitely large and flat Mobile Radio Link 1. Radio wave propagation 2. Propagation models 3. Antenna systems 4. Diversity technique 5. Interference and interference reduction 6. Link budget Interference Signal quality = sum of all expected signals carrier (C ) sum of all unexpected signal = interference (I) atmospheric expected signal noise other signals Notes: GSM specification : C / I >= 9 dB (Co-Channel) Effects of Interference Affect signal quality Cause bit error Repairable errors : channel coding, error correction Irreducible errors : phase distortions Interference situation is Non- reciprocal : uplink <> downlink Unsymmetrical : different situation at MS and BTS C/I Co-Channel C/I : 9dB Adjacent Channel C/I : -12dB Signal Quality in GSM RX Quality RXQUAL class : 0 ... 7 RXQUAL Mean BER BER range class (%) from... to 0 0.14 < 0.2% good 1 0.28 0.2 ... 0.4 % usable signal 2 0.57 0.4 ... 0.8 % 3 1.13 0.8 ... 1.6 % acceptable 4 2.26 1.6 ... 3.2 % 5 4.53 3.2 ... 6.4 % unusable 6 9.05 6.4 ... 12.8 % signal 7 18.1 > 12.8 % Interference sources Multi-path (long echoes) Frequency reuse External interference Note : Interference has the same effect as poor coverage. Reduce the interference as possible. Methods for reducing Interference Frequency planning Suitable site location Antenna azimuth, downtilt and height bad location good location Methods for reducing Interference Frequency hopping A diversity technique, frequency diversity include: Less fading loss De-coding gain Interference averaging Power control based on quality Evaluate signal level and quality DTX Silent transmission in speech pauses Methods for reducing Interference Adaptive antenna According to subscriber distribution, concentrate signal energy to certain direction. Adaptive channel allocation Always assign the best available channel during call setup. Frequency Hopping Diversity technique Frequency diversity can reduce fast fading effects Useful for static or slow-moving mobiles Cyclic base-band hopping TRX hops cyclic between its allocated frequencies RF hopping Either cyclic or random hopping Needs wideband combiner Can use any frequency included in the MA Power Control Save battery life-time Minimize interference GSM : 15 steps and 2 dB for each Use power control in both uplink and downlink triggered by level or quality signal level target level e.g. -85 dm Power control isn‟t allowed on BCCH time DTX DTX (Discontinuous transmission) Switch transmitter off in speech pauses and silence periods, both sides transmit only silence updates (SID frames) comfort noise generated by transcoder. VAD: voice activity detection Transcoder is informed the use of DTX/ VAD Battery saving and interference reducing Mobile Radio Link 1. Radio wave propagation 2. Propagation models 3. Antenna systems 4. Diversity technique 5. Interference and interference reduction 6. Link budget Link Budget Calculation Why we need a link budget? Which will decide the coverage range? The coverage range is limited by the weaker one. Two-way communication needed link usually limited by mobile transmitting power Desired result: downlink = uplink Link budget should be balanced Exercises 1. Write down the diversity techniques. 2. Write down the antenna‟s main parameters. 3. Write down the method used to reduce interference. Answer 1.The diversity techniques are time diversity, frequency diversity, space diversity and polarization diversity. 2.The antenna‟s main parameters are lobes (main lobes, side/back lobes), front-to-back ratio, half-power beam- width ,antenna down tilt, polarization, frequency range, antenna impedance, mechanical size etc.. 3.The methods used to reduce interference are frequency hopping, DTX, power control based on quality, adaptive antenna, optimized channel allocation. Course Contents Introduction to GSM network Mobile radio link Network planning procedure Advanced network planning Network Planning Procedure 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection Network Planning Principle initial marketing dimensioning business plan transmission coverage plan plan traffic parameter estimate plan Frequency plan final topology Scope of Network Planning Operator‟s requirements External information Subscriber forecasts Terrain data Coverage requirements Network planning Population data Quality of service Data acquisition Site survey Bandwidth available Field measurement evaluation Recommended sites CW design and analysis Transmission plan Network design Network performance Number & configuration of BSC Gos Antenna specifications Margin calculations BSS topology Interference probabilities Frequency plan Quality observation Network evolution strategy Input Data Maps Main city Important road Location of mountain range Inhabited area Shore line Local knowledge Typical architecture Structure of city Demographic Data Statistical yearbook Largest town and city Population distribution Where are the expected subscribers 250 000 pop. Local knowledge Population migration route 400 000 pop. Traffic volume Subscriber concentration area 300 000 pop. Network Configuration Estimate number of BTS needed VERY rough initial estimation : total operator‟s bandwidth = average number of TRX allowed per cell planned freq. reuse rate number of BTS needed for traffic reasons Evaluate achievable cell coverage range =f (topography, requirements, signal levels, environment, ...) number of BTS needed for coverage reasons Finances Marketing Planning Network Planning 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection Network Topology Umbrella cell Macro cell Micro cell Pico cell Macro Cell Network Cost performance solution Suitable for covering large area Large cell range High antenna position Cell ranges 2 ..20km Used with low traffic volume Typically rural area Road coverage Normally Use omnidirectional antenna Exception: Use beamed antenna for road coverage Micro Cell Network Capacity oriented network Suitable for high traffic area Mostly used with beamed cell 0,5 .. 2km Cost performance solution Usage of available site‟s equipment Typical application Medium town Suburb Typical coverage range: 0.5 .. 2km Cell coverage range Achievable cell coverage depend on Frequency band (450, 900, 1800 MHz) Surroundings and environment Link budget figure Antenna type Antenna direction Minimum required signal level Hexagons and Cells Three cells ( three hexagons) Network Planning Procedure 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection 7. Transmission planning Traffic Estimation Estimate number of subscribers Long-term prediction Forecast Subscribers Expected traffic load per subscriber Particular habits of subscribers Busy hour conditions Busy hour of the day Traffic patterns Traffic Planning Estimation of expected traffic Number of subscribers in area Traffic load per subscriber Coverage ==> traffic per sq.km ==> traffic per cell ==> number of TRX needed per BTS Allow extra capacity for roamer and busy hour traffic Transmission should not be the bottleneck of the system Traffic Patterns Traffic varies between different hours, estimated traffic must be able to satisfy the peak loads. Busy hour traffic is typically twice that of the average. 100 % 90 peak hour 80 off-peak 70 60 50 40 30 20 10 0 0 2 4 6 8 10 12 14 16 18 20 22 24 hr Network Planning Procedure 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection Coverage Requirements Rollout phases and time schedules Coverage requirement Agree on min. level for outdoor coverage phase 1 CW launch Loss requirement Indoor coverage area Mobile classes Operator‟s cell deployment strategies rollout Omni-cell site in rural area rollout phase 3 phase 2 Directional site in urban area Coverage Planning Loss Due to coverage Due to interference Full coverage of an area can hardly be guaranteed ! common values: 90~95% Network planning 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection 7. Transmission planning Frequency Planning Why we reuse the frequency? 8 MHz = 40 channels * 8 timeslots = 320 users ==> max. 320 simultaneous calls!!! Limited bandwidth Interference are unavoidable Minimize total interference in network Use calculated propagation prediction for frequency allocation Frequency Planning Target Find solution to minimize interferences in the network Traditional method Hexagonal cell patterns Regular grid Cluster sizes D Frequency reuse distance: D = R *sqrt(3*cluster-size) R Frequency Planning Frequency planning always consider the following case Actual situation is different. Power control, actual traffic and distribution of subscribers. Average frequency reuse rate is a criteria for good allocation scheme: physical practical limit limit 0 10 20 safe, but uneconomical Frequency Reuse Reuse frequency as often as possible Increase network capacity But maybe cause some interference f2 f6 f3 f3 f5 Consideration for frequency reuse f5 f4 f7 f4 f7 f2 f7 f2 f6 f2 f6 f3 Interference matrix calculation R f3 f5 f3 f4 f5 f5 f4 D Propagation model tuning f4 f7 f2 f2 f6 f6 f3 Minimize total interference in network f3 f5 f4 f5 f4 Multiple Reuse Rate Frequency reuse rate measurement criteria for effectiveness of frequency plan Co-relationship : effectiveness interferences Interaction with coverage planning Multiple reuse rate increase effectiveness of freq. plan 1 3 6 9 12 15 18 21 same frequency tight reuse planning safe planning in every cell (tight layer) (BCCH layer) (spread spectrum) normal planning (TCH macro layer) Multiple reuse rate Capacity increase with multiple reuse rate e.g. network with 300 cells BWi bandwidth : 8 MHz (40 radio channels) cap. N re use i Single reuse (4X3) Network capacity = 40/12 * 300 = 1000 TRX Multiple reuse: BCCH layer: reuse =14, (14 freq.) normal TCH: reuse =10, (20 freq.) tight TCH layer: reuse = 6, (6 freq.) ==> Network capacity = (1 +2 +1)* 300 = 1200 TRX Network Planning Procedure 1. Cellular planning principle 2. Network topology 3. Traffic estimation 4. Coverage planning 5. Frequency planning 6. Site selection Site Location Cell performance has a close relationship with site location Site is long-term investment Site acquisition is a slow process Hundreds of sites needed per network Site is a valuable long-term asset for the operator Bad Site Location Avoid hill-top location for site Uncontrollable interference Cross coverage Bad handover behavior wanted cell uncontrolled, strong boundary interferences cross coverage areas: Good Site Location Prefer site off the hill-top Use hill to separate cell Contiguous coverage area Need only low antenna height if site are slightly elevated above valley bottom wanted cell boundary Site Selection Criteria Radio criteria Non-radio criteria Good view in main beam Space for equipment direction Availability of leased transmission No obstacles line or microwave link Good visibility of terrain Power supply Antenna installation situation Access restrictions LOS to next microwave site House owner Short feeder length Rental costs Course Contents Introduction to GSM network Mobile radio link Network planning procedure Advanced network planning Advanced Network Planning 1. Network evolution 2. Indoor coverage 3. Tunnel coverage 4. Parameters Cell Evolution Umbrella Cell Macro Cell Micro Cell Pico Cell 5-50Km 1-5Km 100m-1Km 10m-100m Early 80‟s Mid-end 80‟s Mid 90‟s Mid-end 90‟s Macro Cell Layered Network Layered Network High layer station Middle layer station Middle layer station Low layer station Low layer station Low layer station Low layer station Indoor station Indoors station Indoors station Indoors station Network Capacity evolution Measure for network spectrum efficiency Directed Erl/ (MHz * sq.km) Retry A function of Load HO Power Control Bandwidth Half-rate Frequency efficiency of technology code DTX Frequency reuse multiple cell Cell size coverage Load distribution Frq. hopping Advanced Network Planning 1. Network evolution 2. Indoor coverage 3. Tunnel coverage 4. Parameters Why Indoors Indoor coverage become the main competition between operators Subscribers expect continuous coverage and better quality Outdoor cell can‟t provide sufficient indoor coverage Good Quality! INDOOR SOLUTION Benefits Continuous Coverage Low Transmission Powers (BTS/MS) Dedicated Indoor Solution Subscriber expectation Office Equipment Continuous Service Less Interference Good Quality Safety MS Battery Life-time Building Penetration Loss Signal level in building is estimated by using a building penetration loss margin Big differences between rooms with window and without window(10~15 dB) signal level increases with floor number :~1.5 dB/floor (for 1st ..10th floor) Pindoor = -3 ...-15 dB Pref = 0 dB Pindoor = -7 ...-18 dB rear side : -18 ...-30 dB -15 ...-25 dB no coverage Building Penetration Loss Signal loss for penetration varies between different building materials, e.g.: mean value reinforced concrete wall, windows 17 dB concrete wall, no windows 30 dB concrete wall within building 10 dB brick wall 9 dB armed glass 8 dB wood or plaster wall 6 dB window glass 2 dB Total building loss = median values + superimpose standard deviations + (lognormal) margin for higher probabilities In-Building Path Loss Simple path loss model for in-building environment Outdoor loss: Okumura„s formula Lout Lout = 42,6 + 20 log( f ) + 26 .. 35 log( d ) Wall loss Lwall = f (material; angle) Lwall Indoor loss: linear model For Pico-Cells Lin Lin = L0 + d d building type loss application example old house 0,7 dB/m (urban l) commercial type 0,5 dB/m (modern offices) open room, atrium 0,2 dB/m (museum, train station) Indoor Coverage Solutions Small BTS Antennas Mini BTS Distribute antenna Leaky cable Repeater Signal distribution Active Power splitter Passive Optical fiber Optical Indoor Planning Single cell approach Multi-Cell approach t f1..f6 f5 f3 f1 f1..f6 f6 f4 f2 f1..f6 f5 f3 f1 Example1: Example2: 1.2 MHz allocation 1.2 MHz allocation 50 mErl/subscriber, GOS=2% 50 mErl/subscriber , GOS=2% no frequency reuse: reuse per two floor, separate frequencies within one floor: a) three floors a) three floors 36 Erl=> 720 subscribers 27 Erl => 540 subs b) ten floors b) ten floors 36 Erl => 720 subscribers 90 Erl => 1800 subs Leaky cable Coaxial cable with perforated leads Radiating loss 10~40 dB per 100m Coupling loss typically 55 dB (at 1m) Produce constant field-strength along cable runs Work at wide-band Radiating loss become higher with high frequency Very large bending radius Formerly often used for tunnel coverage Expensive Indoor Coverage Examples With Repeater Relay outdoor signal into target building Need donor cell, add coverage but not capacity With indoor BTS and distributed antenna Heavy loss bring by power splitting and cable Outdoor Antenna 50m -50 dBm Gain: 18 dBi 1:1 4th floor 50m 7/8'' Cable 1:1 50m Loss: 4dB / 50m 4th Floor 1:1 3rd floor Cable length : 25m 50m 3rd Floor 1:1 50m 1:1 2nd floor 2nd Floor 50m 50m 1st Floor 1st floor 1:1:1 1:1 50m Ground Floor 50m Indoor Antenna 1:1 ground floor Gain: 9dBi 50m Target Indoor Coverage Building Repeater Types of Repeater According to operating frequency needs Wide-band Repeater decoupling > amplification Narrow-band Repeater According to working method Passive Repeater Needs strong external signal, useful only with very short cables and seldom used Active Repeater Amplify and re-transmits all received signals Repeater Application examples Coverage for low traffic area Remote valley Tunnel Underground coverage The Bulb Principles ... is better than ... Several smaller sites provide more indoor coverage area than a single large site Newspaper Principles The newspaper-principle Indoor coverage may be expected in locations where there is no enough daylight to read a newspaper comfortably Advanced Network Planning 1. Network evolution 2. Indoor coverage 3. Tunnel coverage 4. Parameters Wave Propagation in Tunnels Ideal antenna position: center of cross-section Distance to walls: min. 2λ Tunnel cross-section shape unimportant, if λ > 10 Time dispersion decreases with distance Install antenna 50~100m before tunnel entrance Good signal coupling between successive tunnels Tunnels are very suitable environment for radio wave propagation Tunnel Cross-Section Filling factor determines propagation condition Typical range for filling factors Road tunnels: 10% Metro: 60~90% filling factor =---------- Advanced Network Planning 1. Network evolution 2. Indoor coverage 3. Tunnel coverage 4. Parameters BSS Parameters BSS Relevant Parameter for Network Planning Frequency allocation plan Logical radio configuration Transmitting power Definition of neighboring cells Definition of location areas Handover parameters Power control parameters Cell selection parameters Radio link time-out counter Topology of BSC- BTS network Handover Types Intra-cell same cell but different carrier or timeslot Inter-cell different cells (normal case) Inter-BSC different BSC Inter-MSC different MSC Inter-PLMN (technically feasible, not supported) Intra-cell Inte-rcell inter-BSC Handover Criteria 1. Interference, UL and DL 9. MS Speed 2. Bad C/I ratio 10. Power Budget 3. Uplink Quality 11. Good C/I ratio 4. Downlink Quality 12. PC: Lower quality/level 5. Uplink Level thresholds (DL/UL) 6. Downlink Level 13. PC: Upper quality/level thresholds (DL/UL) 7. Distance 8. Rapid Signal Drop Location Area Design Location update affects all mobiles in network Location update in idle mode Location update after call completion Location update brings extra burden to the network Good location area design should avoid ping-pong location update major road Location area 2 Location area 1 Paging VS Location update Traffic signaling traffic function of user density, function of cell size, call arrival rate ... user mobility Paging Location update optimum number # of cells in Loc. area of cells in Loc. area minimize signaling traffic optimum varies with network evolution Exercises 1. Write down the network evolution process. 2. Write down solution and equipment for indoor coverage. 3. Write down the types of handover. Answer 1.The network evolution process is: Umbrella cell-> Macro cell - >Micro cell->Picro cell 2. The solution and equipment for indoor coverage are: Mini BTS, Repeater, antennas( distribute antenna, leaky cable), signal distribution( power splitter, optical fiber). 3.The handover types are: Inter BSC, Intra BSC, Intra cell, Inter cell, Inter MSC and Intra MSC.
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