LTE Network Planning

Transcription

1 LTE Network Planning

2 AGENDA LTE Network Planning Overview Frequency Planning Coverage Planning Capacity Planning End-user Demand Model

3 BASIC DESIGN PRINCIPLES OF RF SYSTEMS The coverage: area within which the RF signal has sufficient strength to meet QoS requirements. The capacity : ability of the system to support a given number of users. To improve coverage, capacity has to be sacrificed, while to improve capacity, coverage will have to be sacrificed The QoS (i.e. performance): ability to adequately provide the desired services in the RF system. With LTE, coverage, capacity, and QoS are all interrelated. To improve one of them, both the others (or at least one) have to be sacrificed. Coverage QoS Capacity

4 PLANNING & DESIGN PHASES High-level Planning: spreadsheet-based model of the RF link budget to estimate the cell count required to meet capacity & coverage requirements, per clutter type (i.e. urban, sub-urban, rural.) and for each planning period. It does not include terrain effects. Detailed Design: requires an RF propagation tool and terrain database to model the characteristics of the selected antenna, the terrain, and the land use and land clutter surrounding the site. Produces a more accurate determination of the number of sites required, as well as detailed equipment configuration. Deployment Optimization: may include such items as collecting drive data to be used to tune or calibrate the propagation prediction model, predicting the available data throughput at each site, fine tuning of parameter settings (e.g. antenna orientation, downtilting, frequency plan). This presentation covers the high-level planning phase.

5 High-Level Planning Frequency Planning Rural Suburban Urban Dense-Urban Number of LTE Subs Cell-Edge QoS BH Traffic per LTE Sub UL/DL Link Budget Cell Capacity Total BH Traffic Propagation Model Coverage Area Nbr Capacity Sites Nbr Coverage Sites Number of Sites End Planning Period 1

6 AGENDA LTE Network Planning Overview Frequency Planning Coverage Planning Capacity Planning End-user Demand Model

7 Frequency reuse mode 1*3*1 Advantages of 1*3*1 High frequency efficiency, High sector throughput Do not need complex scheduling algorithm, system Disadvantages of 1*3*1 Co-frequency interference is hard Low Cell edge data rate, difficulty for continuous coverage. S111 BTS Used in limit frequency band and discontinuous coverage scenario

8 SFR (Soft Frequency Reuse)1*3*1 SFR 1*3*1 with ICIC DL ICIC:cell center use 2/3 band,cell edge use 1/3 band;so, in cell edge, frequency reuse 3, different cell edge use different frequency. Tx power in cell center lower than cell edge Tx power to control interference. UL ICIC: cell center use 2/3 band,cell edge use 1/3 band, so, in cell edge, frequency reuse 3, different cell edge use different frequency. Cell users in same BTS transmit in the odd / even frame scheduling, respectively SFR 1*3*1 networking merit Lower down interference with ICIC High Frequency efficiency DL SFR 1*3*1 UL SFR 1*3*1 Note: S111 BTS Note: S111 BTS ICIC - Inter-Cell Interference Coordination

9 SFR 1*3*1 Vs FFR 1*3*1 FFR 1*3*1 DL&UL User in Cell center and cell edge within the cell separate by time domain,different site cell edge separate by frequency domain; SFR1*3*1 DL SFR1*3*1 UL DL cell center decrease Tx powe;ul in cell edge,different cell separate in frequency domain, User in Cell center and cell edge within the cell separate by time domain Similarities Separate by the frequency domain / time domain for interference cancellation Cell centers use more bandwidth resources, cell edge use of about 1 / 3 frequency bands, difference FFR use all the sub-carrier in cell center, SFR use 2/3 sub-carriers In DL/UL, FFR same reuse mode,, SFR use different mode DL Tx Power: SFR: cell center is lower than cell edge; FFR: cell center is same with cell edge UL frequency resource: FFR mode, in cell edge, fixed use 1/3 of the frequency band; In SFR mode, cell edge use partial band, normally near 1/3 of the frequency.

10 Frequency reuse mode 1*3*3 Advantage of 1*3*3 F3 F3 Low co-frequency interference, good coverage High sector throughput F3 F2 F3 F2 F3 F2 F2 F2 Disadvantage of 1*3*3 F3 F3 Low frequency efficiency More frequency resource required F2 F2 S111 BTS Used in rich frequency resource and discontinuous frequency band coverage

11 Frequency Planning Advantages of 1*3*1 High spectral efficiency and high sector throughput and capacity No frequency planning required Do not need complex scheduling algorithm Disdvantages of 1*3*1 Co-frequency inter-cell interference at the celledge can be alleviated by frequency scheduling and the ICIC S111 enodeb Most LTE deployments (if not all) are using frequency reuse of 1 i.e. 1*3*1

12 Frequency Reuse Comparison Cell 1 Cell 2 Cell 3 Power Power Power Hard Frequency Reuse Frequency Frequency Frequency Cell 1 Cell 2 Cell 3 Power Power Power Fractional Frequency Reuse Frequency Frequency Frequency Cell 1 Cell 2 Cell 3 Power Power Power Soft Frequency Reuse Frequency Frequency Frequency

13 Hard Frequency Reuse Cell 1 Cell 2 Cell 3 Power Power Power Frequency Frequency Frequency Hard Frequency Reuse Sub-carriers are divided into disjoint sets Neighbouring cells don't use the same set of frequencies/sub-carriers User interference at cell edge is maximally reduced The spectrum efficiency drops by a factor equal to the reuse factor

14 Fractional Frequency Reuse Cell 1 Cell 2 Cell 3 Power Power Power Frequency Frequency Frequency Fractional Frequency Reuse Cell space is divided into 2 regions: inner region & outer region (edge users) One section of the system spectrum is used in all cells Edge users are given orthogonal sub-bands SINR is significantly increased The bandwith is not fully used within one cell This scheme is particularly useful in the uplink

15 Soft Frequency Reuse Cell 1 Cell 2 Cell 3 Power Power Power Soft Frequency Reuse Frequency Frequency Frequency Cell space is divided into 2 regions: inner region & outer region (edge users) Non-uniform power spectrum: edge users are given more power SINR is increased The bandwith is fully used within one cell This scheme is particularly useful in the downlink

16 AGENDA LTE Network Planning Overview Frequency Planning Coverage Planning Capacity Planning End-user Demand Model

17 Cell-edge QoS : SNR vs Bitrate Source: 3GPP TS

18 Link Budget Define all the gains and losses along the RF path between the base station and the subscriber device (e.g. vehicle loss, building loss, ambient noise, transmit powers, receive sensitivities, antenna gains). Estimate a maximum allowable pathloss i.e. MAPL. With the MAPL, the propagation model can estimate site coverage, i.e. the number of sites required for adequate system RF signal coverage The Rx Sensitivity and Tx Power can be expressed on either a per sub-carrier basis or per composite sub-carriers basis; but both parameters must share the same reference.

19 Link Budget The Link Budget is the accounting of all the losses and gains during a transmission inside the medium, antennas, cable etc. Basically the way to calculate the link budget is : Received Power = Transmitted Power + Gains Losses. Estimate s a maximum allowable pathloss i.e. MAPL. With the MAPL, the propagation model can estimate site coverage, i.e. the number of sites required for adequate system RF signal coverage

20 Conventional LTE Link Budget The purpose of link budget in LTE network planning is: To use such factors as building penetration loss, feeder loss, antenna gain, and the interference Margin of radio links to calculate all gains and losses that will affect the final cell coverage To estimate the maximum link loss allowed based on the maximum transmit power of the terminal and enodeb transmit power allocation. Coverage radius of a base station can be obtained according to the maximum link loss allowance under a certain propagation model. The radius can be used in subsequent design.

21 Link budget parameters are grouped as follows: Propagation (Transmission) related parameters, such as the penetration loss, body loss, feeder loss, and background noise Equipment dependent parameters, such as the transmit power, receiver sensitivity, and antenna gain LTE-specific parameters, such as the pilot power boosting gain, Multiple Input Multiple Output (MIMO) gain, edge coverage rate, repeated coding gain, interference margin, and fast fading margin System reliability parameters, such as slow fading margin Specific features that will affect the final path gain

22 Link Budget Model: Uplink Other Gain Slow fading margin UE Antenna Gain Interference margin UE Transmit RF Power Body Loss Penetration Loss Uplink Budget Gain Margin Loss Path Loss Path Loss enodeb Antenna Gain enodeb Cable Loss enodeb receive sensitivity

23 Link Budget Model: Downlink Other Gain Slow fading margin enodeb Transmit Power Cable Loss NodeB Antenna Gain Interference margin Path Loss Downlink Budget Gain Margin Loss Path Loss Penetration Loss Body Loss UE Antenna Gain UE receive sensitivity

24 Transmitter EIRP Example

25 Receiver Gains & Losses

26 Propagation Gains & Losses PARAMETER VALUE DL UL Tx EIRP (db) a Rx EFS (dbm) b Body, Vehicle, Foliage, or Building Loss (db) c Interference Margin (db) d 2 2 Log Normal Margin (slow fade) (db) e Maximum Allowable Pathloss (db) f = a b - c d e

27 RF Propagation Models HATA Model COST-231 HATA Model Erceg-Greenstein Model

28 Coverage HATA Model Frequency (f): 150 MHz to 1500 MHz Mobile Station Height (Hm): between 1 m and 10 m Base Station Antenna Height (Hb): between 30 m and 200 m Link distance (d): between 1 km and 20 km.

29 COST-231 HATA Model Coverage Frequency (f): 1.5 GHz to 2 GHz Mobile Station Antenna Height (Hm): 1 up to 10m Base Station Antenna Height (Hb): 30m to 300m Link Distance (d): 1 up to 20 km

30 Erceg-Greenstein Model T errain A Hilly terrain with moderate-to-heavy tree densities T errain B Intermediate pathloss condition T errain C Mostly flat terrain with light tree densities Base Station Height (Hb) 10 to 80 m Mobile Height (Hm) 2 to 10 m

31 Cell Count vs Link Budget Any improvement in the link budget increases the cell size, and decrease the number sites required to cover a given area.

32 Tools in the Planning Process Link Level Simulator System settings/environment: System BW Channel (CIR, CFR) Number of Antennas PAPR, Synchronization, Channel estimation algorithms, etc Inputs User allocations MCS MIMO operation User/control data Input data System settings Channel coding/modulation Link Level Simulator Outputs Performance of channel coding/ber EVM Performance of algorithms Visualization (Time and frequency plots, BER curves, MCS curves: throughput vs SNIR) Example: Frequency response Radio Channel Sync/Estim Output. Output. Provides the possibility to adjust/evaluate: - algorithms of sync, channel estimation, - application in various channel conditions, - RF emission, filtering Channel decoding Output.

33 Tools in the Planning Process RNP Tool System settings/environment: Chosen and tuned propagation models Chosen and tuned traffic models Geographical data digital map (elevation, land usage, ) Inputs Site locations and configuration Antenna models (patterns) Available frequencies and BWs Spectrum reuse method MCS mapping (from Link Level) Map Network parameters RNP Tool Outputs Coverage (field strength, Rx power level, best server) Capacity (interference, SNIR, data rates) Visualization (coverage/capacity maps, statistics) Example: SINR map Pathloss Output. Rx_Lev Best server C/I Output. Output. Output. Usually Static Simulations Provides the possibility to adjust/evaluate: -Site locations, powers, spectrum reuse methods, frequency planning, - parameter configuration. MCS mapping Bit/rates Output.

34 Tools in the Planning Process System Level Simulator System settings/environment: System BW System parameters configuration (CellIDs, frequencies) Channel, traffic, user distribution models, etc Inputs Coverage (from RNP tool) Capacity (from RNP tool) Site location (from RNP tool) QoS User positions RRM algorithms Traffic demands/qos Input from RNP System Level Simulator Outputs Utilization of resources Dynamic/Semi-static coverage/snir/bitrates Blocked users Visualization (SNIR/Spectral efficiency, resource utilization) Mobility performance Example: Spectral efficiency UE position Position adjustment Random fading Conn. Est. Power/datarate RRM alg. Output. Usually Dynamic Simulations Provides the possibility to adjust/evaluate: - different RRM algorithms, - power control algorithms - traffic shaping methods, - interference management schemes - fade margins, UE power margins Interference Output.

35 LTE Link Budget General Rules TX Pt Pr P_sens RX SNIR GAINS, LOSSES, MARGINS Link budget Pr = Pt + GAINS - LOSSES - MARGINS Question: what is the cell edge criterion? Distance d - Max throughput at the cell edge - Basic connectivity (i.e., lowest possible MCS) - Ref RX sensitivity requirement SNIR_min

36 LTE Link Budget Example Link Budget in Downlink Parameter Value Comment A Max enb TX power 46 dbm B Cable loss 3 db C CP loss 1 db D enb antenna gain max 19 dbi E EIRP max 61 dbm = A B C + D enb TX BW_RX 1.8 MHz F Noise power -102 dbm G SNIR_min 5 db From MCS tables H UE antenna gain 0 dbi I Min required RX power -97 dbm = F + G - H UE RX J total path loss 158 dbm = E I K Other gains, losses, margins - 10 db Shadowing, fast fading, multiantenna L Maximum Allowed Propagation Loss 148 dbm = J + K Cell range 3.5 km

37 LTE Coverage Site Coverage Area and Inter-Site Distance After determiation of cell range (radius) d we can estimate the site coverage area * Omni 2-sectors 3-sectors Site_area 2.6 * d * d * d 2 Intersite_distance 0.87 * d 2* d 1.5 * d #sites = deployment_area / site_area GRID to be entered into the RF Planning tool for verification * Source: J. Laiho, A. Wacker, T. Novosad, Radio Network Planning and Optimization for UMTS, W iley, 2002, pp 83

38 Link Budget Procedure Input Data Start Calculate UL/DL MAPL Calculate UL cell radius Calculate DL cell radius Balance cell radius Calculate site coverage area Calculate site number End

39 Link Budget Model: Uplink UE Transmit Power Other Gain UE Antenna Gain Slow fading margin Interference margin Body Loss Uplink Budget Gain Margin Loss Path Loss Antenna Gain Penetration Loss Path Loss Cable Loss Penetration Loss enodeb Antenna Gain enodeb Cable Loss enodeb receive sensitivity UE transmit power enodeb receive sensitivity

40 Link Budget Model: Downlink Downlink Budget enodeb Transmit Power Cable Loss Other Gain NodeB Antenna Gain Slow fading margin Interference margin Gain Margin Loss Path Loss Path Loss Antenna Gain Cable Loss Penetration Loss Penetration Loss UE receive sensitivity Body Loss UE Antenna Gain enodeb transmit power UE receive sensitivity

41 Link Budget Principle Link budget is aim to calculate the cell radius. Cell radius can be calculated by MAPL with using propagation model Two keys factors: MAPL Propagation Model Lu MAPL: Maximum Allowed Path Loss EIRP: Effective Isotropic Radiated Power MSSR: Minimum Signal Strength Required MAPL = EIRP - Minimum Signal Strength Required+ Gain - Loss - Margin EIRP = Max Tx Power - Cable Loss - Body Loss + Antenna Gain MSSR = Rx Sensitivity - Antenna Gain + Cable Loss + Body Loss + Interference Margin Cost231-Hata Model Total = Lu a( H UE ) + Cm = lg( f ) lg( H ) + ( lg( H )) lg( d) BS BS a( H ) = (1.1 lg( f ) 0.7) H (1.56 lg( f ) 0.8) UE UE

42 AGENDA LTE Network Planning Overview Frequency Planning Coverage Planning Capacity Planning End-user Demand Model

43 Site Capacity Spectral Efficiency Downlink Spectral Efficiency Based on Spectral Efficiency (*) Simulation takes into account Signaling Overhead UE mobility Slow/fast fading Power control Scheduling Results available Per spectrum bands Per channel bandwiths Per inter-site distance (*) figures obtained from dynamic system level simulations (vendor-specific) Uplink Spectral Efficiency SE figures can be interpolated for specific ISD and bands, and additional scaling factors applied

44 Overhead Channels - DL Physical Downlink Shared Channel (PDSCH) Carries DL data and higher layer signalling. The PDSCH is allocated to different UEs usually every 1ms. PDSCH channel coding, modulation and sub-carrier allocation is dynamically controlled by the PDCCH (uses QPSK, 16QAM and 64QAM); Physical Downlink Control Channel (PDCCH) Informs UE about resource allocation for PCH and DL-SCH, plus the HARQ information relating to the DL-SCH. Also controls UL-SCH scheduling grants and indicates the UE identity (uses QPSK); Physical Broadcast Channel (PBCH) - DL channel that carries system broadcast traffic (uses QPSK), Physical Control Format Indicator Channel (PCFICH) Transmitted every sub-frame to inform the UE about the number of OFDM symbols used for the PDCCH channel (uses QPSK); Physical Hybrid ARQ Indicator Channel (PHICH) - Carries hybrid ARQ (HARQ) ACKs or NACKs for UL transmissions on the PUSCH (uses BPSK); and Physical Multicast Channel (PMCH) Carries the MBMS data and control if the cell supports MBMS functionality (uses QPSK, 16QAM and 64QAM).

45 Overhead Channels - UL Physical Random Access Channel (PRACH) Carries random access preambles used when the UE makes initial contact with the network; Physical Uplink Shared Channel (PUSCH) Carries uplink data and higher layer signalling. PUSCH is a shared channel allocated to different UEs usually every 1ms. The channel coding, modulation and sub-carrier allocation is dynamically controlled by the PDCCH (uses QPSK, 16QAM and 64QAM) and Physical Uplink Control Channel (PUCCH) Carries UL control information for a UE including CQI, HARQ, ACKs and NACKs, and UL scheduling requests (depending on format, PUCCH may use BPSK or QPSK).

46 Overhead Channels UL & DL

47 Average Cell Throughput for LTE

48 Coverage & Capacity Baseline Scenario Cell Radius UL edge 64~512kbps Avg. Cell Throughput DL/UL BW 2.6GHz 2.1GHz AWS 700MHz 2.6GHz 2.1GHz AWS 700MHz Dense Urban 0.21~ ~ ~ ~ / / / / Urban 0.39~ ~ ~ ~ / / / / SubUrban 1.47~ ~ ~ ~ / / / / Rural 3.16~ ~ ~ ~ / / / / 10.67

49 Throughput Calculation Example - PDSCH No of RB MCS I_TBS TBS SISO 2X2 MIMO From TS Table From TS Table TBS : Transport Block Size (bits) Channel Bitrate (Mbps) = TBS * 1000 / (1024*1024)

50 AGENDA LTE Network Planning Overview Frequency Planning Coverage Planning Capacity Planning End-user Demand Model

51 Traffic Models Changing with LTE Increased bandwidth leads to a more demanding user: GB per month = (Mbps link speed) 0.7 x 1.2 Daily distribution of data traffic is flatter than that of voice traffic 7% of daily volume The Internet has become more and more symmetric between downlink and uplink now is approximately 55%/45% downlink/uplink

52 Volume per Day (3G vs LTE)

53 Traffic Variations : OS & Device

54 Traffic Variations : apps & data plan

55 UL/DL Daily Pattern vs Apps Source : Ericsson 2012

56 Monthly Traffic (MB/Month) DEVICE Smartphone ,100 PC 2,000 2,500 8,000 Tablet ,200 Fixed Broadband 35,000 50, ,000

57 LTE Device Categories UE Category Peak Datarate (Mbps) Modulation Max RF Bandwith (MHz) MIMO (Max) DL UL DL UL DL DL QPSK, 16QAM, 64QAM QPSK, 16QAM 20 1X QPSK, 16QAM, 64QAM QPSK, 16QAM 20 2X QPSK, 16QAM, 64QAM QPSK, 16QAM 20 2X QPSK, 16QAM, 64QAM QPSK, 16QAM 20 2X QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM 20 4x QPSK, 16QAM, 64QAM QPSK, 16QAM x QPSK, 16QAM, 64QAM QPSK, 16QAM x QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM X8 Release-10 Categories Source: 3GPP TS

58 Applicable Standards 3GPP TS : User Equipment (UE) radio transmission and reception 3GPP TS : Physical layer procedures 3GPP TS : User Equipment (UE) radio access capabilities

59 THANK YOU