LENOVO的Y430P笔记本，网卡显示如下：
$ lspci
07:00.0 Ethernet controller: Qualcomm Atheros QCA8171 Gigabit Ethernet (rev 10)
08:00.0 Network controller: Broadcom Corporation BCM43142 802.11b/g/n (rev 01)
其中，无线网卡BCM43142在ubuntu 14.04系统WIF上网不稳定，WIFI的信号强度在－80DB左右:
user@xubu:~$ sudo iwconfig
[sudo] password for user:
wlan0 IEEE 802.11abg ESSID:"abc"
Mode:Managed Frequency:2.452 GHz Access Point: C8:4A:55:01:A2:73
Bit Rate=48 Mb/s Tx-Power=13 dBm
Retry long limit:7 RTS thr:off Fragment thr:off
Encryption key:off
Power Management:off
Link Quality=38/70 Signal level=-72 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:4 Invalid misc:214 Missed beacon:0
当WIFI还正常连网时，tcpdump -nei wlan0却显示ARP-Request得不到网关的回应数据:
17:07:20.014725 ARP, Request who-has 192.168.1.1 tell 192.168.1.11, length 46
但是同样的电脑， 从安装的WINDOWS 7系统连接同样的WIFI，信号强度一样，却一直正常访问。难道是在LINUX下的驱动有问题？