07 RA41207EN20GLA0 LTE Radio Planning Capacity v03
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Radio Planning Capacity
LTE RPESS Radio Planning Capacity
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Radio Planning Capacity
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Radio Planning Capacity
Module Objectives After completing this module, the participant should be able to:
• Understand basic traffic modelling • Evaluate the cell capacity • Understand the main factors impacting the cell capacity • Review the baseband dimensioning
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Radio Planning Capacity
Radio Planning Capacity Capacity Dimensioning Cell Capacity (Throughput) Baseband Dimensioning
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Radio Planning Capacity
Capacity Dimensioning Process – Overview Site Area
Area Size
Subscribers
Subscribers Density
Traffic Model
Site Capacity
Subscriber Data Volume in BH
Total Offered Traffic
# Coverage Sites
# Capacity Sites Max BH = Busy Hour # Sites
• Outputs: • Site count for capacity and coverage • The final number of sites is the bigger number from capacity and coverage point of view • The calculation could be done for each clutter type and for different phases (for example years) 5
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Radio Planning Capacity
The Number of Sites due to Coverage Site Area
Area Size
Subscribers
Subscribers Density
Traffic Model
Site Capacity
Subscriber Data Volume in BH
Total Offered Traffic
# Coverage Sites
# Capacity Sites Max
BH = Busy Hour 6
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Radio Planning Capacity
The Number of Sites due to Coverage Area Size (Km²) • this is the planned area • typically defined for each clutter type • the customer may provide this value
Site Area (Km²) • this is the site area calculated from the link budget and using the propagation model • depends on the number of cells per site (typical 3 cells per site)
Number of sites due to coverage: # Sites due to Coverage = Roundup (Area Size / Site Area) Example: • Planned area is 100 Km² • Site Area is 10 Km² • The number of sites due to coverage is 100 Km²/ 10 Km² = 10
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Radio Planning Capacity
The Number of Sites due to Capacity Site Area
Area Size
Subscribers
Subscribers Density
Traffic Model
Site Capacity
Subscriber Data Volume in BH
Total Offered Traffic
# Coverage Sites
# Capacity Sites Max
BH = Busy Hour 8
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Radio Planning Capacity
The Number of Sites due to Capacity Operator subscriber density depends on: • Population density • Mobile phone penetration • Operator market share
The subscriber density & subscriber traffic profile are the main requirements for capacity dimensioning Traffic forecast should be done by analysing the offered Busy Hour traffic per subscriber for different services in each rollout phase Traffic data: • Voice: • Erlang per subscriber during busy hour of the network • Codec bit rate, Voice activity
•Video call : •Erlang per subscriber during busy hour of the network •Service bit rates
• NRT data : • Average throughput (kbps) per subscriber during busy hour of the network • Target bit rates
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Radio Planning Capacity
Traffic Model Typical Subscriber’s Profile:
session length or session size
• Subscriber traffic profile from traffic model • The main purpose of traffic model is to describe the average subscriber behaviour during the most loaded day period (the Busy Hour)
• One example is the NSN LTE traffic model – The traffic model defines an application mix consisting of 5 services (VoIP, Video, Streaming, Web browsing & FTP) – There are 3 subscriber profiles each one mapped onto an application mix: Voice Dominant Data Dominant Voice/Data FTP = File Transfer Protocol BHCA = Busy Hour Call Attempts
NSN Traffic Model (TM) 10
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Data Dominant: If customer is mainly interested in a data oriented deployment (data hotspot, wireless xDSL…)
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Radio Planning Capacity
Total Offered Traffic – Example • Number of Subcribers = 10,000 • Average Data Volume per Subscriber per Busy Hour (BH) from the NSN Traffic Model assuming the data dominant scenario: 10.24 MByte
• The Average Data Rate per Subcriber could be calculated as: = Average Data Volume per Subscriber per BH [bit] / 3600 s = 22.75 Kbps
• The Total Offered Traffic could be calculated as: = Number of Subscribers * Average Data Rate per Subscriber = 10,000 * 22.75 Kbps = 227.5 Mbps
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Radio Planning Capacity
Capacity Dimensioning Process – Overview Site Area
Area Size
Subscribers
Subscribers Density
Traffic Model
Site Capacity
Subscriber Data Volume in BH
Total Offered Traffic
# Coverage Sites
# Capacity Sites
Max # Sites 12
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Radio Planning Capacity
The Number of Sites due to Capacity •
Site Capacity – The site capacity could be derived from the cell capacity: Site capacity = Cell Capacity * Number of Cells per Site
– The cell capacity is defined as the overall cell throughput (average cell capacity) – Calculation of an average cell throughput in LTE is based on system level simulations
– Details are provided on the next section of this chapter
• The number of sites due to capacity: # Sites due to Capacity = Roundup (Total Offered Traffic / Site Capacity) Example: – Site Capacity is 10 Mbps – Total Offered Traffic is 100 Mbps – The number of sites due to capacity is 100 Mbps/ 10Mbps = 10
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Radio Planning Capacity
Radio Planning Capacity Capacity Dimensioning Cell Capacity (Throughput) Baseband Dimensioning
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Radio Planning Capacity
Cell Throughput Calculation Methodology • DL & UL Capacity are calculated based on system level simulations • Algorithm calculates the Average Cell Throughput (capacity) for a single cell • During the system level simulations effects like UE mobility, slow/ fast fading, scheduling, power control, admission control, handovers have been considered
• The basic principle of these simulations is that for a given cell area a certain (evenly distributed) subscriber density is assumed and for each subscriber particular SINR conditions apply which depend on the location of the subscriber in the cell • Capacity Simulations Results: • Calculation of an average cell throughput is based on a method which calculates the spectral efficiency • 4 representative site grids (defined by the Inter-Site Distance (ISD): 500m, 1732m, 3000m, 9000m) have been simulated in dynamic system level environment • UL & DL spectral efficiency figures have been gathered for all available channel bandwidth configurations (1.4MHz, 3MHz, 5 MHz, 10MHz, 15MHz & 20 MHz)
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Radio Planning Capacity
Simulation Assumptions Parameter/Feature
UL
DL
Operating Band
2100 MHz
2100 MHz
Transmission power per PRB
Open loop power control; max UE power 23dBm
0.8 W (for every bandwidth configuration)
Antenna Scheme
Number of TX antenna = 1 Number of RX antenna = 2
Number of TX antenna = 1 Number of RX antenna = 2
Hexagonal layout
3 sector layout, 7 sites, 21 cells
3 sector layout, 7 sites, 21 cells
Scheduling
Channel unaware with Round Robin strategy
Channel aware with Proportional Fairness
Mean number of users per sector
10 UEs (ISD = 500m) 30 UEs (ISD = 1732m) 60 UEs (ISD = 3000m) 164 UEs (ISD = 9000m)
10 UEs per sector 210 UEs per area
Number of users per TTI
1 (1.4 MHz) 3 (3 MHz) 7 (5 MHz) 10 (10 MHz) 20 (15 & 20 MHz)
1 (1.4 MHz) 3 (3 MHz) 7 (5 MHz) 10 (10 MHz) 20 (15 & 20 MHz)
UE speed
3Km/h
3Km/h
Traffic model
Full buffer *
Full buffer *
Propagation model
3GPP TR 25.814 (macro cell)
3GPP TR 25.814 (macro cell)
*Full Buffer indicates the cell load is always 100% independent on the number of subscribers in the cell or their position in the cell
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Full Buffer Traffic Model assumes that for all subscribers there are full transmission buffers (UL & DL) at any point in time. Therefore there is always data waiting for the transmission. Thus, the situation that the cell resources (the physical resource blocks) remain unused in a certain TTI does not exist. Therefore the cell load is 100% independent on the number of subscribers in the cell or their position in the cell
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Radio Planning Capacity
UL/DL Spectral Efficiency
Spectral Efficiency (Kbps/KHz)
ISD: Inter-Site Distance
UL Spectral Efficiency
DL Spectral Efficiency
Note: The simulation setup refers to SIMO mode, and focuses on realistic assumptions rather than on an idealized configuration. 17
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Uplink spectral efficiency simulation based on conditions of: 2.3 GHz, 3-sector hexagonal layout, Open Loop Power Control with adjusted P0/alpha settings, 1TX at UE, 2RX at eNB (MRC), EPA05, NSN RRM specific scheduler, 10% BLER target, full buffer (100% load), RF parameters according to [3GPP TR25.814] Downlink spectral efficiency simulation based on conditions of: 2.3 GHz, 3-sector hexagonal layout, 0.8W per PRB, 1TX at eNB, 2RX at UE (MRC), EPA05, NSN RRM specific scheduler, 10% BLER target, 10 UEs per sector (full buffer; 100% load), RF parameters according to [3GPP TR25.814]
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Radio Planning Capacity
UL/DL Cell Capacity
UL Average Cell Throughput (C100%)
DL Average Cell Throughput (C100%)
ISD: Inter-Site Distance 18
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Radio Planning Capacity
Cell Throughput Interpolation • In real planning scenarios the Inter Site Distance (ISD) obtained from the Link Budget Calculation is not equal to the ISDs that have been simulated • Therefore, additional interpolation is required to adapt to the results from the Link Budget • One interpolation example could be seen below:
Purple bars obtained from simulations. Yellow bars have been interpolated based on simulation results.
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Radio Planning Capacity
Factors Affecting the Cell Capacity •
The LTE Cell Capacity (Throughput) depends on:
• Cell Range (Pathloss) – Considered as a variation of the Inter Site Distance (ISD) – The effect of larger ISD has been presented in the previous slides – The SINR distribution is bad in larger cells which becomes more & more noise limited • Channel Bandwidth (1.4 MHz ... 20 MHz) – The best capacity performance can be achieved with wide channel bandwidth due to the maximum frequency diversity gain
– Small Bandwidth configuration are characterized by high system overhead
• Cell Load – The values presented so far are for 100% cell load – The impact of cell load is based on simulation results • LTE Features: – MIMO (Multiple Input Multiple Output) – Scheduling: Proportional Fair or Round Robin See next slides for details
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Radio Planning Capacity
DL
Impact of Cell Range on Cell Capacity
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Radio Planning Capacity
Impact of Channel Bandwidth on Cell Capacity LTE maintains high efficiency with bandwidth down to 5 MHz The differences between bandwidths come from frequency scheduling gain and different overheads
Spectral Efficiency Relative to 10 MHz 120 %
-40%
-13%
Downlink Uplink
Reference
100 % 80 % 60 % 40 % 20 % 0% 1.4 MHz 22
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3 MHz
5 MHz
10 MHz
20 MHz
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Radio Planning Capacity
Impact of Cell Load on Cell Capacity (1/3) • Simulated spectral efficiency (SE) figures are calculated for 100% load in all cells: – Best case from the resource utilization point of view (all resources -PRBs- are utilized) – Worse case from the interference point of view
• Additional simulations are available to investigate the impact of the cell load – The simulation scenario is shown in the figure below – The centre cell which is fully loaded all the time is the victim for which the overall cell throughput is measured – Surrounding cells impact the victim by inter-cell interference which depends on the neighbor cell load
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Radio Planning Capacity
Impact of Cell Load on Cell Capacity (2/3) • The figure below shows the relation between the victim cell throughput & the neighbour cell load • The victim cell throughput has been normalised to 1 in the figure, the value of 1 meaning 100% neighbor cell load • It has to be noticed that when the neighbour cell load is decreasing the cell throughput is increasing as expected • The most sensitive to interference is the case ISD = 500m
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Radio Planning Capacity
Impact of Cell Load on Cell Capacity (3/3) The impact of the cell load on the cell throughput can be summarized by applying scaling factor for different ISDs and different cell load:
The Capacity C considering the Scaling factor is: C = C100% x load x scaling_factor(load) Example: ISD = 500m Cell Load is 50% the Capacity C is: C = C100% * 0,5 * 1.36 = 0.68 C100%
C100%: Capacity, when all cells are loaded to 100%
ISD: Inter-Site Distance 25
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Radio Planning Capacity
Impact of MIMO on Cell Capacity (1/3) RL 20 supports 2 transmit antennas at the eNodeB Transmit diversity (Tx diversity) • results in coverage improvement • therefore, it is more suitable to be used at the cell edge Open / Closed Loop Spatial Multiplexing • Spatial multiplexing on the other hand doubles the user data rate The mechanism of Adaptive MIMO Mode Control assures CQI dependent switching between Transmit Diversity and Spatial Multiplexing (see next slide) The average cell capacity is then determined by: • the ratio of the dual-stream transmissions (how much Tx diversity & how much spatial multiplexing) for one connection in average • The number of users out of total cell users which are using either Tx diversity or spatial multiplexing
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Radio Planning Capacity
Impact of MIMO on Cell Capacity (2/3)
Simulation Results (Source 4GMAX) 27
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Tx Div: Transmit Diversity SM or SpMux: Spatial Multiplexing OL MIMO: Open Loop MIMO SNIR: Signal to Noise + Interference Ratio
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Radio Planning Capacity
Impact of MIMO on Cell Capacity (3/3) • The highest gain could be seen for smaller ISD (higher SINR values over the cell so higher probability to be dominated by spatial multiplexing)
• The lowest gain is for bigger ISD (lower SINR values more likely so the cell is dominated by transmit diversity)
Recommended Adaptive MIMO Mode Control Capacity Gain The gain values in % are relative to the original spectral efficiency (without MIMO) 4 ISDs (Inter Site Distances) = 500m, 1732m, 3000m, 9000m 28
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Radio Planning Capacity
Impact of Scheduling on Cell Capacity (1/3) • In RL 20 two scheduling strategies for DL FDPS* are supported: • Round Robin RR (default) • Proportional Fair PF (license) • From the average cell throughput point of view there is some gain when Proportional Fair (PF) is used versus Round Robin (RR)
• The main reason for the gain is coming from the fact that the SINR distribution in the cell is improved when Proportional Fair is used
• The gain is dependent on the number of users that are scheduled together in the same TTI (1ms): the higher the number of scheduled users per TTI the higher the average cell throughput gain when Proportional Fair is in use
• 2 examples coming from simulations are shown in the next slides: • 3 scheduled users per TTI • 10 scheduled users per TTI * FDPS: frequency domain packetscheduling 29
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Radio Planning Capacity
Impact of Scheduling on Cell Capacity (2/3) Case 1: 3 simultaneous Users per TTI
RR PF RR PF
CDF (Cumulative Distribution Function) of SINR
Average Sector Throughput [Mbps]
*Assumptions: Operating Band 2GHz, Channel Bandwidth 10MHz, Total Power of the eNodeB shared among the PRBs, Antenna Scheme is 1Tx – 2RX, Full Buffer traffic model, random uniform distribution of users 30
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Radio Planning Capacity
Impact of Scheduling on Cell Capacity (3/3) Case 2: 10 simultaneous Users per TTI
PF RR
RR PF
CDF (Cumulative Distribution Function) of SINR
Average Sector Throughput [Mbps]
*Assumptions: Operating Band 2GHz, Channel Bandwidth 10MHz, Total Power of the eNodeB shared among the PRBs, Antenna Scheme is 1Tx – 2RX, Full Buffer traffic model, random uniform distribution of users 31
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Radio Planning Capacity
Cell Capacity Calculation Example Step 1: To obtain the Spectral Efficiency (SE) figures for specific ISD (Inter-site distance) and channel bandwidth interpolation is needed: SE = interpolate_SE (ISD, channel_bandwidth) Step 2: Calculate the cell throughput (C) from the spectral efficiency (SE) taking into account the cell bandwidth: C = SE x channel_bandwidth Step 3: MIMO gain is applied in case of 2 TX antennas at eNB C = C x (1 + MIMO_gain(ISD)) Step 4: Spectral efficiency figures have been simulated for 100% load case. It is needed to scale them according to the resource utilization and inter-cell interference level C = C x load x scaling_factor(load) Example for ISD=500m, 10MHz, 2x2 MIMO, 50% load
Step 1: interpolate_SE(500m, 10MHz) = 1.19bps/Hz Step 2: C = 1.19bps/Hz x 10MHz = 11.9Mbps Step 3: C = 11.9Mbps x (1+20%) = 14.28Mbps Step 4: C = 14.28Mbps x 50% x 1.37 = 9.8Mbps 32
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Radio Planning Capacity
LTE Capacity: RL20 & RL30 features Voice over LTE
Single Radio Voice Call Continuity (SR-VCC)
LTE VoIP
LTE VoIP
3G CS voice
3G CS voice
3G CS voice
3G CS voice
Options for voice call continuity when running out of LTE coverage (RL30): • 1) Handover from LTE VoIP to 3G CS voice – Voice handover from LTE VoIP to WCDMA CS voice is called SR-VCC – No VoIP needed in 3G • 2) Handover from LTE VoIP to 3G VoIP – VoIP support implemented in 3G LTE VoIP available in RL20
15 x more users per MHz with 3GPP LTE than with GSM EFR! 33
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Radio Planning Capacity
Radio Planning Capacity Capacity Dimensioning Cell Capacity (Throughput) Baseband Dimensioning
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Radio Planning Capacity
Baseband Dimensioning Target of Baseband Dimensioning: • Target of Baseband Dimensioning: Allow to estimate HOW many sites are required taking into account the HW (System Module) Limitations
• The approach presented so far in this chapter to calculate the number of sites from the capacity point of view (site throughput) only takes into account Physical Layer and/or RRM features into account (e.g. Channel bandwidth, transmit power, scheduler type, etc...)
System Module options: • FSME: high capacity system module • Note: FSME is the only one supported by RL10 and by RL20.
Input of the dimensioning: • Total Number of subscribers • Number of active subscribers (per Site) • Share of active subscribers
Output of the dimensioning: • Number of sites from baseband point of view 35
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Radio Planning Capacity
Baseband Dimensioning Input for the Dimensioning Active Subscribers • Flexi SM processing power has a strict limitation for the number of active UEs which can be handled*
• UE in E-UTRAN RRC_Connected and with DRB (Data Radio Bearer) established but with or without data to be transmitted in the buffer i.e. smartphones with always on applications like IM and mail
Share of active Subscribers • Percentage of active subscribers which should be handled by the eNB
• Share of Active Subscriber values have been calculated for each of NSN Traffic Models: – Voice Dominant: 11% – Data Dominant: 40% – Voice & Data Mix: 30% • Typical assumption is 30% Share of Active Subscribers for RL20 dimensioning *Note that in LTE the System Module capabilities depend strictly on the number of the included DSP modules. The 3G specific notation of system module capacity by means of Channel Elements (CEs) is not anymore valid 36
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The term refers to the terminals actively using applications as well as those which do not need to be considered for scheduling; Smartphones with always on applications like internet messaging (IM) or email
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Radio Planning Capacity
Baseband Dimensioning Output of the dimensioning Number of Sites (Baseband) • Number of Sites required based on the number of active users: #Sites =
Subscribers x ShareOfActiveSubscribers #MaxActiveSubscribers x NoOfCellsPerSite
• • • •
Example: Assume 10000 subscribers in the area System bandwidth is 10MHz There are 480 active users per cell with FSME in RL20 • 3 sectors per site • Share of active subscribers is 30%
Active UEs per cell
Active UEs per Site
# FSME
Site type
1 FSME
Omni
1 FSME
3-sector site
Up to 400
1200
1 FSME
6-sector site
N/A w 1 FSME
N/A w 1 FSME
Up to 400 Up to 400
2 6-sector FSME(*) site (3 2400 ( 2 x Up to 400 (2 BTS sectors x 1200) per site) FSME)
• #Sites (Baseband) = (10000*0,3)/(480*3) ≈ 2 *Note that system module extension is not supported in RL20 37
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