by Platon Scheblykin
05/28/2008 | 10:08 PM
We’ve recently started a series of tests of Draft N wireless adapters, beginning it with a review of the Trendnet TEW-624UB. The device we are going to discuss today is another Wi-Fi adapter with a USB interface. It is manufactured by D-Link and called DWA-142.
D-Link’s Draft N products fall into three categories (in the order of lowering performance): Xtreme N, RangeBooster N, and Wireless N. The DWA-142 is a medium-performance product, belonging to the RangeBooster N category. You’ll see shortly how it differs from Xtreme N, for example.
So, let's get started and meet our today's hero.
First let's take a look at the official specifications of the D-Link adapter:
- IEEE 802.11n (draft)
- WEP (64/128bit)
2 integrated PIFA antennas (2dBi)
- OFDM (BPSK/QPSK/16 QAM/64-QAM)
2400 – 2483.5 MHz
Nominal data transfer rate
- 802.11g: 6/9/12/18/24/36/48/54 Mb/s
- 802.11b: 16dbm
11 for North America, 14 Japan,
USB 2.0, 1.1 Standard
From the USB port
- Transmitting: 270mA
97.33mm (diameter) x 19.3mm
The box contains standard accessories:
D-Link seems to have stepped up to a new level in design of its products after it started the production of Draft N equipment. The DWA-142 is a vivid example of this. A regular Wi-Fi adapter with a USB interface has a typical design that looks like a massive flash drive. The new network device from D-Link is completely different. Its case resembles a flying dish, or an external Wi-Fi antenna, or a hat – whatever you prefer. The top part of the round case of the DWA-142 is made from matte black plastic. A green activity indicator is located at its edge so that it could be viewed from both the top and the side. The bottom and sides of the case are made from translucent black plastic and you can take a look at the device’s PCB.
It’s hard to see any vent holes in this case at first sight, but there are actually quite a lot of them here. D-Link’s engineers made them in the top cap (in the round depression), in the side and in the bottom panel of the case. So, the DWA-142 is ventilated well and the ventilation system doesn’t spoil its appearance. The adapter has grooves in the bottom of the case to be mounted on a wall. It’s quite a rare thing for devices of this class.
We took the device’s cap off in order to see its internal design. To do this we unfastened two self-tapping screws hidden under two out of the three rubber feet at the bottom of the case.
The PCB occupies all the space inside the case. This is done to simplify the mounting of the components as well as to fix it securely in place because the PCB is not fastened to the case with any other means. Nearly all of the radio elements are installed on the top side of the PCB, half of them (including the radio module chip) being covered with a metallic screen. At the edges of the PCB you can see two antennas for transmitting data between the adapter and an access point.
The DWA-142 is based on Marvell’s Top Dog chipset supporting Draft N. The chipset consists of an 88W8362 MAC-controller and an 88W8006 RF-modulator. The latter is screened as we’ve mentioned above.
On the reverse side of the PCB there is a seat for a console but we can’t tell you what kind of a console it is because there is almost no public information about the Top Dog on the Web. It may be a seat for a JTAG connector as almost every controller is equipped with this interface today.
Following our habitual practice when testing a new device, we didn’t install the driver included with the DWA-142 but searched for the latest version at the D-Link website. It was version 1.30. The driver comes with a wireless connection manager that is meant to replace the standard Windows manager. D-Link’s version is not far superior in terms of functionality, though. In fact, it only has a nicer appearance and a friendlier interface.
When started up the program shows a Wireless Networks tab. This tab displays all the wireless networks found. You can connect to one of them or select a network from the list of connection profiles (My Wireless Networks). Also on this tab you can enable the Wi-Fi Protected Setup (WPS) to transfer settings in encrypted form from the router.
The program’s second screen, My Wireless Networks, is an extended version of the same-name list on the first tab. Particularly you can edit parameters of the connection profiles. You can also open a small Help system from the manager’s window that will give you instructions on how to start out about setting up a wireless network.
We didn’t have a router (or an access point) based on the Top Dog chipset at the time of our tests, so we could only see how Marvell’s chipset behaved with other developers’ chipsets. To be specific, we tested the D-Link DWA-142 with routers based on chipsets from Atheros, Broadcom and Ralink. These routers have already been tested in our labs, and we know their capabilities well enough. And we’ll check out the D-Link DWA-142 with a router based on the Marvell chipset as soon as we have such an opportunity.
We used the following hardware and software for the tests:
First we tested the speed of router-adapter (LAN-WLAN) and adapter-router (WLAN-LAN) connections using the High_Performance_Throughput scenario of the IxChariot program. The connection was established near the routers with WPA2-PSK encryption using the AES algorithm. This is the standard encryption for Draft N, and it is going to be such in the official 802.11n specification. We used the latest driver for the adapter and the latest firmware for the routers.
Below is the diagram for the TEW-624UB USB-adapter. It is not a comparison of the two devices (that’s why we publish two different diagrams) but rather an illustration of how the problem of compatibility between Wi-Fi chipsets from different brands is being steadily solved.
So, there are both positive and negative points. For example, the ASUS WL-500W defaulted from the test. The DWA-142 could establish a connection with it, but the connection didn’t work – the IxChariot test would abort with an error message. The connection status window would report a speed of 270Mbps at that. We can see the Atheros chipset is the leader in terms of performance after the driver and firmware have been improved. Currently, this chipset seems to deliver the highest quality, we guess.
Next we measured the WLAN coverage area using almost all possible combinations of routers (without the ASUS one) and wireless adapters. We measured the signal level of a LAN-WLAN connection in five points:
Point 1: Near the router
Point 2: At a distance of 4 meters without obstacles
Point 3: At a distance of 5 meters + two thin gypsum wallboards
Point 4: At a distance of 6 meters + one brick wall, about 30cm thick
Point 5: At a distance of 17 meters + one thin gypsum wallboard and one 50cm brick wall
Now we can see that the compatibility issues with Draft N chipsets are being solved, even though slowly. It would be better if we had lower but identical results for all the routers. With the current state of things, you have to be careful when choosing equipment for new-generation networks. As for the particular USB adapter, the DWA-142 is quite worthy of its price even though it does not deliver highest performance possible.
There is little that can be said about the DWA-142 adapter. We like it because of its original design. It is certainly different externally from other Wi-Fi adapters with a USB interface. We can note one serious drawback about it: the DWA-142 works poorly with the Intensify chipset. This adapter is going to be a perfect choice for a desktop PC because it can be oriented optimally in space, as opposed to PCI cards.