CDMA Network Planning by AWE Communications GmbH www.awe-com.com
Contents Motivation Overview Network Planning Module Air Interface Cell Load Interference Network Simulation Simulation Results by AWE Communications GmbH 2
Motivation Challenges in Radio Network Planning Characteristics of the WCDMA technique: DS-CDMA, FDD/TDD Rake reception, power control, soft and softer handover Different services (data rates, Eb/N0 requirements) Spreading / de-spreading different spreading gains Mutual influence of coverage and capacity Coverage limited by the uplink and capacity by the downlink Coverage uplink downlink Capacity by AWE Communications GmbH 3
Motivation Radio Network Planning of GSM Networks Only speech service (symmetric) Power control ~ 2 Hz Mobile power up to 2 W Constant cell capacity based on FDMA/TDMA channels Frequency planning modifications path loss prediction coverage network Separate planning of coverage and capacity capacity traffic modelling by AWE Communications GmbH 4
Motivation Radio Network Planning of UMTS Networks Different services (asymmetric) Fast transmit power control ~ 1.5 khz Mobile power up to 0.125 W (speech) Soft and softer handover Interference limited system (cell breathing / soft capacity) Capacity depends on instantaneous load situation (throughput and user locations) modifications coverage + capacity WCDMA simulation network traffic modelling path loss prediction Combined planning of coverage and capacity by AWE Communications GmbH 5
Overview Radio Network Planning of CDMA Networks Determination of transmitting power in UL and DL power budget (variable interference power) max. Tx power Tx antenna gain path loss Rx antenna gain spreading gain noise power noise rise due to interference P t0 P t0,max Antenna gain Transmitter loss EIRP Path loss Antenna gain Receiver loss CDMAsystem gain TX Channel Receiver Diversity gain Noise Rise / interference E b /N 0 P N by AWE Communications GmbH 6
Overview Radio Network Planning of CDMA Networks Coverage influenced by provided capacity (cell breathing) Regular cell structure Speech service Variable traffic density (cell load) Soft capacity Mutual influence of coverage and capacity by AWE Communications GmbH 7
Air Interface (1/5): Overview Multiple Access (CDMA/WCDMA/HSPA) UL / DL separation mode (FDD / TDD) Channel Bandwidth Carriers available in network Transmission Modes (MCS) - Spreading Factor - Modulation - Code Rate - Data Rate (DL/UL) Cell assignment - Highest received power (pilot subcarriers) in DL - Min. required SNIR and min. Required Rx power in DL Definition of air interface by AWE Communications GmbH 8
Air Interface (2/5): CDMA/WCDMA/HSPA Code Division Multiple Access Chip rate Orthogonality Factor (important for interference) Handover windows (soft/softer) Max. number of codes Pilot Channel Settings -Txpower backoff -Spreading Factor by AWE Communications GmbH 9
Air Interface (3/5): Carriers Carriers available in the network Bandwidth of carrier ( thermal noise) Multiple carriers in different frequency bands can be used in one project (same bandwidth for all carriers required) Arbitrary carriers can be assigned to a BS TDD or FDD mode can be selected (identical for all BS in whole network) TDD mode: Ratio between UL and DL (e.g.: 1:1 or 3:1) can be defined for whole network FDD mode: UL-DL carrier separation can be defined (identical for all carriers) Carrier definition by AWE Communications GmbH 10
Air Interface (4/5): Services Specification of an arbitrary number of transmission modes for DL and UL by definition of Modulation (BPSK/GMSK, QPSK, 8-PSK, 16-QAM, 32- QAM, 64-QAM) Coding Rate (1/2,1/4,.) Spreading Factor Overhead ratio Parallel used codes Data rate automatically computed Min. required Eb/N0 target at BS and MS Min. required received signal level Power Backoff at BS and MS Definition of MCS by AWE Communications GmbH 11
Air Interface (5/5): Duplex Mode Duplex Mode: FDD - Specification of carrier separation of UL and DL TDD - Specification of guard time to switch between UL and DL - Total Frame Length - Ratio between DL and UL (e.g. 1:1, 3:1, ) Options for settings of duplex mode Default: whole network i.e. all carriers and cells (BS) operating in same mode Specific simulation of TDD mode TDD simulated similar to FDD. But results (max. data rate, etc.) are scaled with DL:UL ratio by AWE Communications GmbH 12
Definition of Parallel Used Codes Definition of multiple codes for higher data rates (e.g. HSPA) Increase of own cell interference in addition to interference due to predefined cell load Required Tx power increased Limitations given by Eb/N0 target and the max. Tx power Results on transmission mode level consider only single code Throughput results consider the parallel used codes by AWE Communications GmbH 13
Definition of Cell Load (Interference) Definition of relative transmit power if no traffic is considered Interference (Eb/N0) calculation influenced by this parameter Value indicates how much of the data transmission power should be considered for the interference calculation 50% means 50% of the linear data transmission power (in Watts) Data transmission power is calculated based on total transmit power, the power split (data/pilot) and the power backoff value Cell load can be defined globally or individually for each transmitter Definition of noise rise in uplink by AWE Communications GmbH 14
Interference in CDMA networks CDMA signal orthogonality: ideal: no intra-cell interference (orthogonal codes) SNIR real: orthogonality is reduced e.g. due to multipath propagation intra-cell interference arises common practice in simulation: orthogonality factor used to scale intra-cell interference (constant for all UE) Effect of orthogonality for coverage: P own SF P user 1 Pothers Pnoise by AWE Communications GmbH 15
Simulation Results Cell assignment Cell area, site area, best server Max. number of received carriers/transmitters/sites (in downlink) Received power in mobile station Eb (energy per bit) and Ec (energy per chip) Signal to interference ratio: Eb/N0 after despreading (Eb includes spreading gain and own cell interference reduced by OF) and Ec/(N0+I0) with interference power independent of OF (own cell, neighboring cells and noise) Total received interference and noise power Overall Max. achievable data rate (DL and UL) Max. achievable throughput (DL and UL) For each transmission mode at each pixel Min. required Tx power at MS (UL) and BS (DL) Max. received Rx power at MS (DL) and BS (UL) Max. achievable Ec/N0 and Eb/N0 in downlink and uplink Reception probability in downlink and uplink by AWE Communications GmbH 16
Simulation Results Eb/N0 (DL) by AWE Communications GmbH 17
Simulation Results Max. throughput (DL) by AWE Communications GmbH 18
Further Information www.awe-com.com by AWE Communications GmbH 19