无线网络信号强度

Question

我使用 iwlist 检查本地网络的信号强度。我使用的实际命令是

 sudo iwlist wlan0 scan

为了使这里的视图更简单一些（过滤掉不相关的内容），我将使用

 sudo iwlist wlan0 scan | egrep '(Address: |ESSID:|Channel:|Frequency:|Quality=)'

当我在 Raspberry Pi 上运行此命令时，我得到的输出如下：

      Cell 01 - Address: 1C:**:**:**:**:**
                Channel:6
                Frequency:2.437 GHz (Channel 6)
                Quality=58/70  Signal level=-52 dBm  
                ESSID:"MOTOROLA-*****"
      Cell 02 - Address: 00:**:**:*:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=48/70  Signal level=-62 dBm  
                ESSID:"NSASA"
      Cell 03 - Address: 02:**:**:**:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=47/70  Signal level=-63 dBm  
                ESSID:"BroadbandHamnet-20-v3"
      Cell 04 - Address: BC:**:**:**:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=21/70  Signal level=-89 dBm  
                ESSID:"BillWhyTheScienceFi"
      Cell 05 - Address: C8:**:**:**:**:**
                Channel:3
                Frequency:2.422 GHz (Channel 3)
                Quality=20/70  Signal level=-90 dBm  
                ESSID:"Pepperland"

但在 Ubuntu 上我得到：

      Cell 01 - Address: 1C:**:**:**:**:**
                Channel:6
                Frequency:2.437 GHz (Channel 6)
                Quality=15/100  Signal level=15/100  
                ESSID:"MOTOROLA-*****"
      Cell 02 - Address: 00:**:**:*:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=15/100  Signal level=15/100  
                ESSID:"NSASA"
      Cell 03 - Address: 02:**:**:**:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=15/100  Signal level=15/100  
                ESSID:"BroadbandHamnet-20-v3"
      Cell 04 - Address: BC:**:**:**:**:**
                Channel:1
                Frequency:2.412 GHz (Channel 1)
                Quality=15/100  Signal level=15/100  
                ESSID:"BillWhyTheScienceFi"
      Cell 05 - Address: C8:**:**:**:**:**
                Channel:3
                Frequency:2.422 GHz (Channel 3)
                Quality=15/100  Signal level=15/100  
                ESSID:"Pepperland"

请注意，所有信号强度都列为“15/100”，并且没有显示信号强度（dBm）。

是我缺少某个设置还是 Ubuntu 无法提取这些信息？