very slow wireless connection ath9k driver

My wireless internet connection has been extremely slow for my desktop wireless N PCIe card. (A wired connection is simply not an option given where I am living.) When the connection is first made, I get average speeds (~100kB/s), but after a minute, the speeds drop to 5Kb/s, and then even lower. Furthermore, the connection will completely disconnect after about an hour. I have had this problem with Ubuntu 10.10, Ubuntu 11.04, and Ubuntu 11.10.

I do not believe my router to be the issue because my laptop connects just fine. (If it is relevant, the wireless network is configured with 802.11n as well as WPA2 encryption.)
I also do not suspect the kernel, because I have tried this driver on the default kernels for 10.10, 11.04, and 11.10.
Furthermore, solutions like "options ath9k nohwcrypt=1" or disabling IPv6 haven't worked either.
Finally, I have tried compiling the compat-wireless drivers from source and again, no success.

Here are the relevant specs:
lspci
00:00.0 Host bridge: Intel Corporation 2nd Generation Core Processor Family DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Xeon E3-1200/2nd Generation Core Processor Family PCI Express Root Port (rev 09)
00:16.0 Communication controller: Intel Corporation 6 Series/C200 Series Chipset Family MEI Controller #1 (rev 04)
00:1a.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2 (rev 05)
00:1b.0 Audio device: Intel Corporation 6 Series/C200 Series Chipset Family High Definition Audio Controller (rev 05)
00:1c.0 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 1 (rev b5)
00:1c.1 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 2 (rev b5)
00:1c.3 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 4 (rev b5)
00:1c.4 PCI bridge: Intel Corporation 82801 PCI Bridge (rev b5)
00:1c.5 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 6 (rev b5)
00:1c.6 PCI bridge: Intel Corporation 6 Series/C200 Series Chipset Family PCI Express Root Port 7 (rev b5)
00:1d.0 USB Controller: Intel Corporation 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1 (rev 05)
00:1f.0 ISA bridge: Intel Corporation P67 Express Chipset Family LPC Controller (rev 05)
00:1f.2 IDE interface: Intel Corporation 6 Series/C200 Series Chipset Family 4 port SATA IDE Controller (rev 05)
00:1f.3 SMBus: Intel Corporation 6 Series/C200 Series Chipset Family SMBus Controller (rev 05)
00:1f.5 IDE interface: Intel Corporation 6 Series/C200 Series Chipset Family 2 port SATA IDE Controller (rev 05)
01:00.0 VGA compatible controller: nVidia Corporation GF116 [GeForce GTX 550 Ti] (rev a1)
01:00.1 Audio device: nVidia Corporation Device 0bee (rev a1)
03:00.0 Network controller: Atheros Communications Inc. AR9285 Wireless Network Adapter (PCI-Express) (rev 01)
04:00.0 USB Controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 04)
05:00.0 PCI bridge: ASMedia Technology Inc. Device 1080 (rev 01)
06:02.0 FireWire (IEEE 1394): VIA Technologies, Inc. VT6306/7/8 [Fire II(M)] IEEE 1394 OHCI Controller (rev c0)
07:00.0 USB Controller: NEC Corporation uPD720200 USB 3.0 Host Controller (rev 04)
08:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)

sudo lshw -C network
  *-network
       description: Wireless interface
       product: AR9285 Wireless Network Adapter (PCI-Express)
       vendor: Atheros Communications Inc.
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: wlan0
       version: 01
       serial: f4:ec:38:e3:77:b2
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=ath9k driverversion=3.0.0-15-generic firmware=N/A ip=192.168.1.56 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
       resources: irq:17 memory:fa400000-fa40ffff
  *-network
       description: Ethernet interface
       product: RTL8111/8168B PCI Express Gigabit Ethernet controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:08:00.0
       logical name: eth0
       version: 06
       serial: 6c:62:6d:44:9c:a5
       size: 10Mbit/s
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half firmware=rtl_nic/rtl8168e-2.fw latency=0 link=no multicast=yes port=MII speed=10Mbit/s
       resources: irq:49 ioport:c000(size=256) memory:dc104000-dc104fff memory:dc100000-dc103fff