.
.
.
D-Link AirPro 5GHz 802.11a Wireless Network Solutions Review
Date : Tuesday, 5th November 2002
By: Stygian
Provided By: D-Link
Introduction
As we all know, home computing has been popular for quite some time now so it is fairly common to find that a home has a need for a computer network similar to one offered in a small business setting. Networking is not just something that is done for fun - rather it becomes very useful to share resources such as printers, drive space and other services, thereby cutting down on complexity and reducing costs, both of which are helpful to the home user or business owner. The only real obstacle to a small network can be the physical aspect of it - how to lay the CAT-5 cabling so that it is not too obtrusive. This can often be quite a task if one has to network computers on different floors of a building or even in adjacent rooms.
Enter wireless networking. The original specs were limited somewhere around 2Mbps, quite a drop from the rating of 100Mbps for 100baseTX. 802.11b, when it debuted, increased bandwidth ratings to 11Mbps but with WEP enabled the actual throughput dropped much lower. For many users, especially those with laptops/notebooks, this was adequate for most network services such as listening to MP3s from a shared drive or browsing the Internet, but for many people not interested in portable computing this kind of bandwidth drop was not worth the convenience of going wireless.
But some of you may have heard of 802.11a, one of the newer wireless standards. This standard specifies operation in the 5GHz frequency range, as opposed to 802.11b's 2.4GHz operation, and has a rated bandwidth of, get this, 54Mbps! However, there are some drawbacks. First of all, 802.11a is *not* backwards compatible with 802.11b, so if you have an existing wireless network and wish to upgrade to 802.11a, you'll have to upgrade every wireless device in your network. However, there will be some dual-mode products coming out soon, such as Access Points that support both 802.11b and 802.11a. In addition, you can expect the prices to be higher than those of 802.11b-only products, so keep that in mind.
Today, I'll be looking at D-Link's 802.11a offering in the form of three of their products: The AirPro 5GHz Wireless Access Point, the AirPro 5GHz Wireless PCI Adapter and the AirPro 5GHz Wireless CardBus Adapter. All of these products, when used together with each other, support up to 72Mbps of bandwidth using D-Link's proprietary "Turbo" mode, bringing this wireless network's bandwidth close to that of 100baseTX. When used with other 802.11a products they will only operate up to the specified 54Mbps rating.
Specifications
Because all of these products are made by D-Link and are 802.11a compliant, they share some common features listed below. In addition, it appears that all of these 802.11a products are driven by Atheros chipsets.
Common Features:
"Turbo mode will allow transmission on 2 channels, which will improve data rate (up to 72 Mbps). This is proprietary to D-Link products. This setting must be the same on the access point and clients or you will not be able to communicate with each other."Also, some info on OFDM:
"All products use OFDM: Orthogonal Frequency Division Multiplexing, an FDM modulation technique for transmitting large amounts of digital data over a radio wave. OFDM basically splits the radio signal into multiple smaller sub-signals that are then transmitted simultaneously at different frequencies to the receiver. OFDM reduces the amount of crosstalk in signal transmissions. 802.11a and the upcoming 802.11g WLAN technology uses OFDM."
The
DWL-5000AP
An Access Point will be the central part of your wireless network should you want to integrate it with an existing wired network. This means that when your wireless clients are operating in infrastructure mode, all wired communication will take place through the Access Point, as it serves as a sort of hub. This contrasts with Ad-Hoc mode, where an Access Point is not needed; in this mode of operation, wireless clients communicate directly with one another and this mode does not support integration with a wired network.
| . |
. |
. |
The DWL-5000AP comes well-packaged and is secured in its bubble wrap within a carton ensuring that it doesn't get bumped around during transportation, damaging its antennae (or antennas). Upon taking it out of the packaging I was surprised at how light it was; looking back on this I guess I shouldn't have, as many other networking devices with plastic cases are also very light. I would have liked it to have a metal case or at least a metal base as that would have given it a studier feel and also would have made it less prone to sliding around on a surface. On the other hand, feet are included that can be installed on the base to increase traction between it and the surface it is on.
 Indicator LEDs. |
 Console connector, RJ45 jack to wired network and DC input. |
 Feet, console cable and power cable. |
The unit itself is also unremarkable, with the requisite LEDs present on the front including power, wired network activity and wireless activity. On the back, is the connector for a console cable, an RJ-45 jack for connection to your wired LAN and the DC power input. It was very nice of D-Link to include the console cable, as if for some reason you cannot connect to the web-interface of the Access Point, you will have a backup option available without having to buy the cable. As a downside, a CAT5 cable for connection of this AP to your wired network was not included. Seeing as how D-Link included a console cable, I would've liked them to include a CAT5 cable as well.
One thing to note is that this AP is only 802.11a compatible, so it will only work with 802.11a network adapters. 802.11b wireless devices will *not* work with this AP. Because of this, buying this AP only makes sense if you're building a new wireless network based on 802.11a. However, D-Link has released a dual-protocol AP, the DWL-6000AP, that does support both 802.11a and 802.11b clients simultaneously.
 Power supply. |
 Manual, quick install guide and video and documentation CDs. |
 |
 |
Another nice detail is that the power supply or AC-DC adapter is not in the plug that connects to the outlet. Instead, a regular power cable runs from the power supply to the outlet, preventing a cumbersome block from blocking access to outlets. I would also surmise that this allows for easier usage with other AC voltages as the power supply can accept different voltages should one change the type of power cable used. Also included was an extensive manual with many coloured screenshots to show the user exactly how to setup this Access Point for use in their network. It was very well written and easy to understand. For those of us who can skip the verbose explanations and prefer only the bare minimum details needed to get this unit running, a quick-install guide is provided with all the necessary info. Also included is a CD with documentation and a CD with a video demonstration of installation. I definitely have to commend D-Link on their documentation here, as they've appealed to users on all levels, making sure that those new to networking get all the instruction they need, and those experienced are not slowed down by one manual that is too wordy.
The
DWL-A520 PCI Adapter
As with all the other 802.11a devices in this review, the PCI adapter will support a transfer rate of up to 72Mbps, as claimed by D-Link, when used with other D-Link supporting "Turbo Mode" 802.11a devices. As it is designed for use with a desktop system, its antenna should provide better transfer speeds as compared to the Cardbus adapter. The antenna can also be set straight so that you can properly position the card into a PCI slot and screw it down. (Otherwise, it would be hard to get the bent antenna through the slot in your case.)
 . |
 . |
 . |
The antenna at the back can be positioned to face up when you install it in a tower case or a desktop case. As with the AP, excellent documentation, both a verbose manual and a quick-guide, is included. A CD with documentation, drivers and the D-Link's LinkMon software for helping the user access the status of a wireless connection is included as well.
 . |
 . |
 . |
 . |
The
DWL-A650 Cardbus Adapter
The Cardbus adapters represents the ideal usage for a wireless network. It is often cumbersome to use a notebook with a wired network unless you've designed your office very well for LAN usage. This adapter supports the same features as the PCI adapter. It plugs into a Type II slot in your laptop, and comes in a nice case in its packaging.
 . |
 . |
 . |
Setting a trend here, extensive documentation is yet again included along with the CD containing documentation, drivers and the LinkMon software. Because of the lack of antenna on the cardbus adapter and the optional use of power saving (ideal for portables), the range and transfer speeds of the cardbus adapter are likely to be less than those of its PCI brother.
 . |
 . |
 . |
Installation
Installation of the Access Point is pretty straightforward. All you need to do is provide power to the unit and then plug it into an ethernet port on a switch or hub in your existing network using a straight-through cable. You can then enter the default IP address of 192.168.0.50 into your browser's address bar to gain access to the web-based configuration of the Access Point. You can change the username and password required to gain entry to these configuration pages at a later time, and this would be advisable. Also, if you wish you can plug this Access Point straight into the ethernet port of a NIC in your computer, but you will have to use a crossover cable. Again, it would have been nice if a CAT-5 cable had been provided.
 A listing of associated wireless devices and their MAC addresses. |
 Main configuration page. |
 Advanced configuration. |
As mentioned, all configuration is done through the easy-to-use web interface. The IP address and subnet mask can be modified to suit your network's logical addressing in addition to the ability to change such basic things as the SSID and setting the encryption options. The firmware of the AP is also upgradeable through this interface. Overall, the interface is not hard to use and offers all the options you'd need, except I found one quirky option.
 WEP keys must be entered randomly; they're not generated. |
 The AP's firmware is upgradeable. |
If you enable encryption, you'll have to enter the keys, (which are in hex), manually. This can be a bit tedious as with the highest level of encryption, the key length is 152-bit! (24-bit IV + 128-bit). Having to enter all of these keys into every client and the AP would become a bit tiring. I've seen some other wireless encryption solutions that have you enter a keyword and then use some sort of alogrithm to generate the WEP keys from that keyword. Not a more secure system, but this would make it easier to enable WEP on your wireless network.
Even though these 802.11a devices offer 152-bit WEP encryption, there is some doubt over its viability and improvements over the 128-bit WEP being offered by most 802.11b devices. Because these system still uses the 24-bit IV, it is still susceptible to many of the attacks that can allow a malicious person to figure out the WEP key. (See this excellent article from Arstechnica for more information about IV-based attacks.) However, in a future firmware upgrade D-Link has stated that they will add 802.1x authentication and key management as a feature to the DWL-5000 AP. 802.1x will involve the use of software on a computer that acts as an authentication server, and software on the client wireless computers, but the AP will still have to support the pass-through of the 802.1x messages involving authentication. Expect 802.1x to become a standard soon. Lastly, this AP does support access control through MAC-address filtering, and this can be an excellent idea for small SOHO wireless networks where there are few clients. However, it is not foolproof as MAC addresses aren't encrypted in frames that can be sniffed, and once a "trusted" MAC address is known, it can be spoofed.
Installation of the PCI adapter is also pretty straightforward, especially for those of use who have ever put together our own computers. Simply install the adapter into a PCI slot, screw it down, and then position the antenna so that it is pointed up when your case is in place. Installation of the cardbus adapter is even easier; you just need to push it into place in any Type-II compatible slot in your portable. Upon booting into Windows, you'll be prompted for the drivers that are on the CD; these installed without any problem. If you are running Win98SE as opposed to ME, 2000 or XP, you'll have to install the WMI (Windows Management Instrumentation) update before installing either the Cardbus or PCI adapter. However, this is clearly documented in the manual and instructions are provided on how to install this update.
 72Mbps will only be attainable under the best conditions. |
 Cardbus Adapter settings. |
 Different wireless profiles can be created. |
All the basic configuration options are provided through the driver control panel such as enabling of "Turbo" mode (for use with other D-Link 802.11a devices) and WEP configuration. As with the AP, you'll have to manually enter the WEP keys in hex for all of your clients as well as with the AP. Different wireless profiles can be created and saved so that you can change the configuration easily for different wireless setups, if by chance you use your notebook with different wireless LANs. Both the Cardbus and PCI adapters can be used in either Ad-Hoc mode (peer-to-peer without the use of an AP) or Infrastructure mode. (With the use of an AP to communicate and interface with a wired network.)
 Wireless setup configuration. |
 Again, WEP keys must be entered manually. |
 D-link's LinkMon software. |
D-Link's LinkMon software provides additional information about the wireless connection, such as transmit and receive rates, frame stats and other useful information should you run into trouble while configuring a client. It's not necessary to install this but it's recommended.
Testing
While the "Turbo" mode of these 802.11a devices claimed up to a 72Mbps data rate, I found that negotiating this data rate came only under the most ideal of circumstances, such as with the PCI adapter installed in a computer in the same room as the AP. This would almost defeat the purpose of a wireless network as one could easily setup a wired network in that same room for much less, and a wired network would have more bandwidth and be more reliable. However, these devices are not without merit, and I'll be the first to admit that the previous comparison was a bit extreme, but I just wanted to make the point that wireless, while extremely handy for portables, will not replace wired network in terms of pure bandwidth.
I used NetIQ's QCheck program for pure bandwidth tests, and under these ideal conditions, (PCI adapter installed in the same room as the AP about 8 feet away), I was able to acheive an average data rate of 26Mbps using the TCP packet test with a size of 1000KB. A 120MB file transfer test took 42.3s under these conditions as well. The response time was not any higher than 100-baseTX tests, as it was consistently 1ms. Not bad at all, and these number seem to indicate better performance than a 10-baseT network. Please keep in mind there was no other traffic on the network, and no other wireless activity from other devices at the time.
However, with the Cardbus Adapter at a distance of only about 40 feet and three walls separating the adapter from the AP, transfer rates dropped to an average of 5.5Mbps. Response times were not adversely affected, only rising to about 3ms, but occasionally there would be spikes of >100ms that would seriously affect realtime applications or games relying on latency.
Conclusion
For short distances, 802.11a's bandwidth can't be beat in terms of its wireless capability. It is certainly the fastest consumer-available wireless solution, but its incompatibility with existing 802.11b devices sour its features. I would only suggest that you buy these D-Link 802.11a devices if you are setting up a new wireless network. For close distances, such as within the same room or between adjacent rooms, the bandwidth, while still considerably less than that of 100-baseTX, will be a big improvement over 802.11b's bandwidth. However, as the distance increases, the bandwidth drops as well, down to the point where it is often less than that of 10-baseT. Latency spikes will also affect network performance to some degree, but as stated above, this problem sets in when distance becomes large or there are many walls in between the wireless client and AP. Specific to D-Link's products, the pros were the superb manuals and documentation plus the ease-of-installation for all of their products. The AP was easy to configure as the web-based interface was very intuitive. Even newcomers to wireless will have no problem configuring these devices to work together. For the future, the AP is firmware upgradeable so it can be made to support new security features as they emerge and are finalized. The only gripe I had was with the manual entry of WEP hex keys, which can be tedious given that you must enter the same keys into the AP and each client. I would have liked the ability to choose a keyword/passphrase that was then used by an alogrithm to generate the WEP keys for you, because this would have made enabling encryption easier.
Pros
Cons
Thank you to D-Link for getting these wireless devices out to me for testing, and for being patient with me! This review wouldn't have been possible without their help. Thanks guys!