tailieunhanh - TEAM FLY WIRELESS NETWORK DEPLOYMENTS phần 8

Điều này là phiền hà do sự cần thiết phải đáp ứng các yêu cầu tương thích điện từ cụ thể. Hơn nữa, giai đoạn đầu vào cho PA, trong đó cung cấp các sản phẩm giả mạo sẽ góp phần khó khăn trong việc đáp ứng | Frequency Hopping in GSM Networks 179 used for indirectly adjusting cell parameters. The Dropped Call Ratio is an counter available f rom the Operations and Maintenance OMC for off-line processing of statistics. The Dropped Call Ratio has been traditionally used in the performance monitoring and optimization of cellular tystems. This indicator is also closely linked to the Radio Link Time-out which is determined bytlie decoding failure rate of the SACCH frames. Although widely used the indicator only indirectly represents the performance of the Traffic Channel TCII . Therefore in certain frequency reuse scenarios it aannot always provide accurate indication of the TCH quality. Both RXpUAL and FER can be measured simultaneously with Test M ilc equipment and at the BTS with A-bis . allTrace measurement facilities These are ispecial arnngements that are needed in the aptimization stages because the betavior of RXQUAL with Frequency Hopping is different to non-hopped systems. One way to show ihis is to plot the system reported Dropped Call Ratio ilgainst the number of eoents where the . exceeds a threshold level . RXQUAL greater than 5 in a cell. This gives an area-wide impression of the rail q ual i ty which involves many mobiles and reflects the true behavior for the RXQUAL parameter The cell parameters in GSM are defined oil a per cell basis and the RF optimization is perforated by qdjusting the thresholds for these parameters in terms of the reported parameters . RXQUAL and RXII X . The drive tests are useful bo build a detailed log of the behavior in known problem areas. The plot in Ftgrne 2 shows that the Dropped Call Ratio against the percentage of bad quality of calls defined the events where RXQI AI. exceeds 5. The observed data confirms that the Dropped Call Ratio does not have a strong dependence on bad quality defined by the RXQUAL threshold. This behsvior is due to the averaging effects of Jnterference in Frequency Hopping systems. .