UMTS: WCDMA Air Interface
The UMTS air interface is based on CDMA - therefore planning tools for GSM/EDGE or any other Non-CDMA air interface cannot be re-used for UMTS.
The determination of the interference in a CDMA network (with or without MIMO) is a critical task due to the cell breathing and requires therefore highly accurate propagation models.
WinProp's ray-optical propagation models and the dominant path model (DPM) for rural, urban and indoor scenarios predict the signal level as well as the LOS/NLOS status and they consider additionally the polarization of the signals (especially important for MIMO antennas).
Parameters of WCDMA in WinProp
For UMTS FDD and TDD networks with 5 MHz bandwidth the properties of the UMTS WCDMA air interface are pre-defined in WinProp's CDMA module (for different frequency bands used for WCDMA around the world).
ProMan in combination with the PRO-C module is therefore ideally suited for the simulation of UMTS WCDMA networks.
The user can optionally modify the following parameters of the WCDMA settings to adapt the CDMA module to the properties of the actual network:
- Parameters related to the spreading
- Power backoffs for pilot, control, and data codes (either default for all cells or individually for each cell)
- Cell assignment mode and min. required thresholds for SNIR (Ec/N0) and signal level
- Transmission Modes
- MCS (modulation and coding)
- Number of parallel codes (HSPA)
- Min. required Eb/N0 (and optionally signal level)
- Tx power backoff
- 2x2, 2x4, 4x4, etc.
- Interference between the MIMO streams (depending on polarizations of MIMO streams, LOS/NLOS conditions, etc.)
- TDD properties (e.g. ratios between UL, DL, guard)
Simulation of UMTS Networks
Besides the classical cell assignment, WinProp's CDMA module provides the following simulation results:
- Cell assignment
- cell area
- max. number of received carriers/transmitters/sites (in downlink)
- received power in mobile station
- total received interference and noise
- Control channels
- Received signal level and SNIR for control channels
- For each transmission mode at each pixel:
- min. required Tx power at UE (UL) and Node B (DL)
- max. received Rx power at UE (DL) and Node B (UL)
- max. achievable Ec/N0 and Eb/N0 in downlink and uplink
- reception probability (DL and UL)
- For the mobile stations in the simulation area (i.e. for each pixel in the area):
- max. achievable data rate for a single user at the pixel (downlink and uplink) incl. gain due to MIMO
- max. achievable throughput (for multiple users) at the pixel incl. gain due to MIMO
- number of received MIMO streams (and their signal levels, SNIRs, etc.) in uplink and downlink
Consideration of MIMO
MIMO is an optional technology for the WCDMA air interface to increase data rates and throughput. WinProp's CDMA module considers MIMO in UMTS WCDMA network planning:
- The number of MIMO streams received in up- and downlink is predicted and for each of the MIMO streams the signal level and SNIR are visualized.
- Distributed MIMO is possible (the location of each Tx antenna radiating a MIMO stream is defined individually by the user => arbitrary locations are possible).
- The MIMO streams of a signal can be assigned to the Tx antennas individually. Multiple antennas can radiate the same MIMO stream (DAS).
- The interference between the MIMO streams depends on the LOS/NLOS conditions, the signal levels, and the polarizations of the signals (the polarization of each Tx antenna can be defined individually).