Frequency Hopping

GSM and DCS both employ frequency hopping technique for two main advantages:

• To reduce Mulitpath Fading effect which is dependent in carrier frequency
• To randomize Co-Channel Interference (CCI)

The hopping algorithm is continuously broadcast on BCCH and MS/BTS transmits TDMA frames on different hopping carriers during a call on hopping TRX. Hopping is used on TCH, SDCCH and all Packet Data channels while BCCH and common control channels are not allowed to hop. Frequency hopping types are:

• Baseband Hopping (BBH)
• Synthesizer Hopping (SFH)
• Discrete Hopping

Sector Swap Issue in a Cellular Network

Sector Swap issue refers to the situation when cables of connected to wrong antennas, for example, sector 2 cables are connected with the sector 1 antenna and sector 1 cables are connected to sector 2 antenna. This issue can cause degraded quality, call drop, illogical hand over etc.

Power Control RxLev for GSM and DCS

The upper and lower bounds of Power Control RxLev for Downlink should be set such as signal strength is maintained slightly above the threshold of noise floor. This would provide for enough signal strength to maintain a good voice quality and keeping the interference level to the minimum. Thus, these values are kept more aggressive for DCS, being a clearer band than GSM, for instance, the upper and lower bounds for DCS are generally set to -80dBm and -90dBm as compared to GSM values of -75 dBm and -85 dBm.

GPRS and EGPRS

As per The European Telecommunications Standards Institute (ETSI), GPRS has 4 coding schemes namely CS-1, CS-2, CS-3 and CS-4. CS-1 offers lowest data rate with highest data protection whereas CS-4 has highest data rates with minimal protection of data. E-GPRS uses 8-PSK modulation (transmits 3 bits per symbol) scheme and consequently has 9 coding schemes MCS-1 to MCS-9 in order of highest to lowest data protection and lowest to highest data speeds.

Antenna Tilts

There are two types of antenna tilts used in telecom networks:

1. Electrical Tilt
2. Mechanical Tilt

Electrical Tilt has a uniform affect on the main lobe whereas Mechanical Tilt causes side lobe effect when it is given a down tilt. The effect can be demonstrated easily on Coverage Planning tools.

SMS Transfer during a Call

SACCH is also used for SMS delivery when a call is in progress.

Handover Optimization in GSM

Optimizing Handover procedures in a telecom network helps a great deal in decreasing call drop rate, increasing HSR and thus improving mobility and quality of the network. Handover parameters like RxQual thresholds at which handover should be triggered, timers that control the repetition of Handover requests to neighbour cells, penalty on source cells to curb the handover requests on congested cells are some of the areas that create a significantly positive impact on network KPIs.

Fast Drive Investigation (FDI)

Fast Drive Investigation (FDI) is a post processing tool developed by engineers of Pakistan. It is the only product in the field of  RF Optimization fully developed locally by a team of experienced engineers. The tool is in use by telecom operators in Pakistan and Afghanistan and has received tremendous appreciation and acclaim for its world-class algorithms and convenience. The features of the product include overshooters identification with footprints, quick neighbor audit feature, mesh analysis for multi-server environment, low-coverage zones depiction, graphical analysis of various KPIs etc with a standard comparable to international software. Other tools advantageous for Optimization engineers are also included in their product line. More on this can be read from their website. Trial version of the software is not available which needs to be developed to increase its propagation and usage worldwide.

More here: 360cellutions.com