Effect of soft and softer handoffs on CDMA system capacity
Effect of soft and softer handoffs on CDMA system capacity
复制标题
软切换和更软切换对 CDMA 系统容量的影响
DOI：
--
复制
发表时间：
1998
期刊：
影响因子：
--
通讯作者：
R. Steele
中科院分区：
文献类型：
--
作者：
Chin‐Chun Lee;R. Steele
根据平均比特能量干扰功率谱密度来评估软切换和软切换对码分多址(CDMA)系统容量的影响，该平均比特能量干扰功率谱密度对应于10/sup-3/的误比特率。文中还考虑了不完全扇区划分对扇区划分效率的影响。在反向链路上，由于不需要额外的信道来执行软切换，因此没有容量损失，而软切换提供的宏分集可以改善反向链路的质量，扩大小区覆盖。在前向链路上，当在未扇区化的小区中采用软切换时，对于话音活动系数为3/8或1/2，由于在切换区域中分配给用户的两个业务信道而导致的容量损失分别为0.2%或1.1%。由于前向链路的容量高于反向链路的容量，这种小的容量损失不会影响系统容量。对于每个小区具有三个扇区的扇区小区，在扇区之间存在重叠覆盖区域，其中这些区域中的移动站受到同信道干扰的增加。对于重叠角为5/spl deg/的系统，反向链路和前向链路系统的扇区化效率分别为0.96和0.7。当采用软切换和软切换时，前向链路扇区划分效率提高到0.97。我们发现，软切换的应用不仅提高了前向链路的容量，而且提高了小区和扇区边界附近移动台的信干比(SIR)。
The effect of soft and softer handoffs on code-division multiple-access (CDMA) system capacity is evaluated for unsectorized and sectorized hexagonal cells according to an average bit energy-to-interference power spectral density, which corresponds to a bit-error rate (BER) of 10/sup -3/. The effect of imperfect sectorization on sectorization efficiency is also considered. On the reverse link, there is no capacity loss as no extra channels are needed to perform soft handoff, while the macrodiversity provided by soft handoff can improve the reverse-link quality and extend the cell coverage. On the forward link, when soft handoff is employed in unsectorized cells, the capacity loss due to two traffic channels assigned to a user in the handoff zone is 0.2% or 1.1% for a voice activity factor of 3/8 or 1/2, respectively. As the forward-link capacity is higher than that of the reverse link, this small capacity loss does not affect the system capacity. For sectorized cells having three sectors per cell, there are overlapping coverage areas between sectors, where mobiles in these areas are subjected to an increase in cochannel interference. For an overlapping angle of 5/spl deg/, the sectorization efficiency is 0.96 and 0.7 for the reverse-link and forward-link systems, respectively. When soft and softer handoffs are employed, the forward-link sectorization efficiency is improved to 0.97. We find the application of soft and softer handoff improves not only the forward-link capacity, but also the signal-to-interference ratio (SIR) for mobiles near the cell and sector boundaries.