移动通信讲.pptVIP

4.2 Power control4．2 功率控制 In introducing the cell concept in mobile wireless systems, we noted that this concept was motivated by the need to increase the capacity of these systems. 在介绍移动无线通信系统中的小区 概念时，注意到这个概念是由增大系统 容量的需要引发的。 Thus, system channels may be reused, allowing more mobile users to access the system, providing（只 要） cells using the same channels are not too close together. We specified（规定） the closeness“ by indicating（指点，指示，指出） that the total interference power from co-channel cells must be no more than the signal power within a given cell. 只要使用相同信道的小区不是“特别接 近”，就能使更多的用户接入系统，系统信 道从而得以复用。“接近度”的规定保证来自 同信道小区的总干扰功率不大于本小区内信 道功率。 We quantified this concept by introducing the signal-to-interference ratio SIR on a given channel as a measure of performance. Given a specified requirement for the SIR and the number of channels actually available, one can then determine the number of mobile users that may be accommodated within any given cell (and hence the entire mobile system). 通过对一给定信道引入信干比SIR来量 化这个概念，以作为性能的度量。给定了 SIR特定的要求和总的可用信道数目，就可 以确定任何一个给定小区中能够容纳的移 动台用户数目(从而得到整个移动系统)。 Critical to all of this is the maintenance of an appropriate SIR. This requires monitoring and controlling mobile power to ensure that the SIR in a given cell does not drop below a specified threshold. All mobile cellular systems incorporate（采用） means for monitoring mobile uplink power with base stations sending power control messages（信息，消息） to mobile units in their cells. 所有因素中最关键的是保持合适 的SIR。这需要监测和控制移动功率以 保证在一个给定小区内不低于一个确 定的阈值。所有的移动蜂窝系统采用 了在基站检测上行功率，再对其小区 内的移动单元发送功率控制信息的机 制。 For simplicity in describing the various algorithms, we focus on uplink power control. We thus assume the transmitters to be located at the mobiles and the receivers at the base stations. The SIR is thus measured at each of the base stations, for a given channel. 为简化各种方法的讨论，集中讨论 上行功率控制。假设发射机位于移动 台，接收机位于基站。这样每个基站对 给定信道的SIR值