LENOVO的Y430P筆記本無線網卡BCM43142在ubuntu 14.04系統WIF上網不穩定

LENOVO的Y430P筆記本，網卡顯示以下：

$ 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，無線網卡BCM43142在ubuntu 14.04系統WIF上網不穩定，WIFI的信號強度在－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

當WIFI還正常連網時，tcpdump -nei wlan0卻顯示ARP-Request得不到網關的迴應數據:

17:07:20.014725 ARP, Request who-has 192.168.1.1 tell 192.168.1.11, length 46

可是一樣的電腦， 從安裝的WINDOWS 7系統鏈接一樣的WIFI，信號強度同樣，卻一直正常訪問。難道是在LINUX下的驅動有問題？