GSM Radio - 2 days

This course is designed to assist engineers involved in GSM network design and operations. Starting with the problem of the minimum C/I required for an adequate quality TCH, it leads to the measures provided by the GSM specifications and solutions within the control of the network designer. Propagation at 900 and 1800 MHz is and its effect upon the C/I experienced in real networks is examined . Path loss, fading and ISI models including Rayleigh and Rician fading, Hata and Okumura losses are covered in the context of macro, micro and pico cells. Co and adjacent channel interference from neighbour cells and unwanted mobiles is covered in the context of frequency reuse patterns and the GSM transmit mask. The concept of minimum coupling loss for micro and pico cells within a macro cell operational environment is covered. GSM specifications for a workable C/I in the harsh radio medium are considerd including GMSK, equalisation, interleaving, down and uplink power control, DTX and frequency hopping. The trade-off between improved C/I and traffic capacity is discussed. Diversity reception and attennas are covered with coupling methods for multiple TRX multiplexing to one antenna. Antenna tilt to set a cell radius, combined with BTS transmit power, and minimum receive level are covered by exercises.

Propagation at 900 and 180 MHz. Multi-path propagation. Rayleigh fading. Rician fading. Path loss. Time dispersion. Hata and Okumura models. 'Rules of thumb'. Calculations of required BTS transmit power for various cell sizes. Marginal receive levels. Working C/I.

Co and Adjacent channel interference. The 4/12 pattern and interferers. The capacity limitations of the 4/12 pattern. More efficient patterns - MRP and FR. The degradation in C/I of more efficient reuse patterns. The use of baseband and synthesiser hopping to regain a working C/I in more eficient reuse patterns. The GSM transmit mask. The effect of adjacent channels of the same frequency. The effect of adjacent channels of adjacent frequency. Minimum Coupling Loss. Practical considerations of MCL with micro and pico cell operations.

GSM specifications. GMSK. Equalisation - Time dispersion tolerance. Interleaving. DTX. Down and uplink power control. Frequency hopping - baseband, synthesiser, cyclic and pseudo random.

Minimum acceptable C/I. optimising the network for minimum acceptable C/I and maximum capacity.

BTS Antennas. Diversity reception. Coupling methods - passive couplers - tuned couplers - advantages and disadvantages. A typical BTS serving three sectored cells.BTS transmit specifications. Antenna gain. Antenna tilt. Cell radius.