Editing /usr/lib/pm-utils/power.d/wireless as described in https://bugs.launchpad.net/ubuntu/+source/linux/+bug/651008/comments/9 did indeed fix this permanently on my MacBook 4,1 with a Broadcom Corporation BCM4321 802.11a/b/g/n (rev 03) controller. WLAN throughput is now at normal levels (around 7 to 8 Mbit/s effective at 54 Mb/s nominal) even on battery power.
Editing /usr/lib/ pm-utils/ power.d/ wireless as described in https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/651008/ comments/ 9 did indeed fix this permanently on my MacBook 4,1 with a Broadcom Corporation BCM4321 802.11a/b/g/n (rev 03) controller. WLAN throughput is now at normal levels (around 7 to 8 Mbit/s effective at 54 Mb/s nominal) even on battery power.