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Wcdma for umts radio access for third genergation mobile communacations phần 9

ITU cho người đi bộ xe ITU Một bàn giao mềm hơn được con đường bằng, có nghĩa là thiệt hại cho cả hai thành phần mềm chuyển giao được, bình đẳng có nghĩa là con đường thiệt hại cho cả hai trạm cơ sở mềm bàn giao được, có nghĩa là con đường cao | Physical Layer Performance 355 Table 12.4. Soft and softer handover gains against fast fading ITU Pedestrian A ITU Vehicular A Softer handover gain equal mean path loss to both sectors 5.3 dB 3.1 dB Soft handover gain equal mean path loss to both base stations 4.0 dB 2.2 dB Soft handover gain 3 dB higher mean path loss to the worst receiving base stations 2.7 dB 0.8 dB handover gain is obtained. The soft handover gain for uplink coverage is shown in Table 12.4 for the case of 3 km h two receiving base stations and AMR speech. We assume here that the fast fading is uncorrelated between the base stations and sectors. Two cases are shown when the mean path losses to the two base stations are identical and when there is a 3 dB mean difference in the path loss. These two cases are illustrated on the upper row of Figure 12.9. The first case gives the highest soft handover gain. When the difference in mean path loss becomes large the soft handover gain vanishes and at a certain mean power difference the terminal will leave soft handover and only remain connected to the strongest base station. A typical value for the window drop is 2-4 dB see Chapter 9 for more details. The results show that the lower the multipath diversity the larger the soft handover gain. For equal mean path loss the soft handover gain is 4 dB for an ITU Pedestrian profile and 2.2 dB for an ITU Vehicular A profile. Soft handover equal path loss to both base stations path loss to 2nd base station No macro diversity reference case Softer handover Figure 12.9. Soft and softer handover cases for the soft handover gain evaluation Uplink soft handover uses selection combining in RNC based on a CRC check while in softer handover the uplink transmission from the mobile is received by two sectors of one Node B. In softer handover the signals from two sectors are maximal ratio combined in the 356 WCDMA for UMTS baseband Rake receiver unit of the base station see Section 3.6. The soft and softer handover gains .