WIRELESS ACCESS POINT: D-Link DWL-1000AP+

A wireless access point extends your wired LAN to wireless users, but this access point from D-Link does much more than that. The device can provide five functionalities. The first is the most basic one, that of an access point. Second, it can work as a wireless repeater to increase the range of your wireless network. Third, as a wireless bridge between two different wireless networks. Fourth, as a multi-point wireless bridge between more than two different wireless networks. And, fifth, in wireless client mode wherein it works as a client of some other wireless network. But, you can use only one of these functions at a time. 

When working as an access point, it has an enhanced mode of operation wherein if it’s used in conjunction with other enhanced D-Link wireless products, it will work at double the speed of regular 802.11b products, ie 22 Mbps (other 802.11b products work at 11 Mbps only). 

All the above-mentioned features are also present in the device’s younger cousin, D-Link DWL-900AP+. However, D-Link DWL-1000AP+ differs by offering load balancing and redundancy features. It can be used with other DWL-1000AP+ devices to create a load balanced wireless network. In this, all access points will share the wireless traffic amongst themselves as the number of wireless users increase. This way a particular access point will not run out of bandwidth once the wireless user base in your organization grows beyond a single device’s capability. Redundancy feature works such that it can be used as a backup access point for another DWL-1000AP+. So if the primary access point fails, the second one will take over. The backup and primary access points connect to each other via an additional Ethernet link provided on the devices. These features can be useful when implementing a wireless network in a large enterprise.

Coming to performance, we tested the throughput (raw data transfer rate), response time and streaming data rate between a wireless client and wired host, with the access point working as the communication link between the two. The wireless client was a laptop containing an internal mini-PCI 802.11b card. We also tested the access point with a D-Link 650+ Air Plus 802.11b PCMCIA card to check the enhanced wireless mode, which promises to double the transfer rate. The wired client was connected to the access point via a 100 Mbps switch. We used NeIQ Endpoint, Ixia Chariot Console, and NetIQ Qcheck for the tests. We tested at two wireless signal strength levels. First, at high signal strength, which was between 90-100%, and then at low signal strength, which was between 15-20%. Low signal strength obviously yielded lower performance as compared to high signal. The high signal strength was done keeping the clients in line of sight of the access point, while there were obstructions in the low signal test.

With a non D-Link wireless card, at high signal strength, the maximum and average throughputs achieved were 5 Mbps and 4.3 Mbps, respectively. With the D-Link Air Plus card these increased to 7.6 Mbps and 7.0 Mbps, respectively. So, while you would expect to achieve the theoretically possible transfer rates, in real world usage, what you get is much less. But still the D-Link wireless card managed a 50% improvement over the normal card, which can be attributed to the enhanced mode of operation available in some D-Link products.

Next, comes the response time which measures the latency in the network. The average response time between the wireless laptop and wired desktop was 3 millisecs, which is fairly good. It even improved to 2 millisecs with the D-Link wireless card 



Finally, we have the streaming test, which checks the network’s ability to transfer a continuous stream of data at a particular rate. This is useful for applications such as video conferencing and audio and video streaming. In the UDP streaming test, the maximum achieved streaming data rate was 490 kbps, which is also on the lower side but good enough for most streaming applications. With the D-Link card it went up to 590 kbps. 

After this we moved the laptop away from the aAccess point to a distance where the signal strength dropped to 15-20%. With the regular wireless card, the maximum and average throughputs achieved here were 0.983 Mbps and 0.360 Mbps. So the data transfer rate decreased significantly with the decrease in the signal strength. The response time also increased to move between 20-25 millisecs, which means increased latency in the network. The maximum streaming rate here was 246 kbps, which surprisingly is not very bad. Overall, an access point with features suitable for enterprise needs and is also priced well.

Anoop Mangla