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Three MIMO Wireless Access Points

Wireless networking technology is getting better all the time. Although the fabled Wireless Gigabit to the Desktop (wGTTD) isn't available to consumers yet, the latest technologies transmit faster and further than access points of just a few years ago. The technology currently driving faster wireless speeds for the consumer market is called Multiple Input/Multiple Output. MIMO refers to access points that use multiple antennas to detect wireless signals and aggregate multiple output or LAN connections. Vendors report that MIMO access points are as much as eight times faster at distances up to three times farther than 802.11g standard, which operates at a theoretical maximum speed of 54Mbps.

The next wireless standard, 802.11n, will use MIMO technology for theoretical maximum speeds of more than 100 Mbps. Many vendors have already released products that use MIMO technology, even though the IEEE P802.11 Task Group N hasn't voted to approve a final draft of the 802.11n standard. Without the standard, these products require both an access point and wireless network card that uses each vendor's proprietary technology to get the best performance. I couldn't help wondering whether the performance improvements these products offer would be worth the investment. Should I buy a non-standard product now, or wait for the new standard to be released? To answer the question, I tested three wireless-access products-from Linksys, Belkin, and Buffalo Technologies-to see what speed and distance improvements are already available.

I tested the three access points in a field adjacent to my back yard. I started by marking five points at 15, 100, 200, 250 and 300 feet away from the desk where I set up the products. The only obstructions between the access points and my wireless client were a glass door and a fence. I tested each access point by pinging a client 100 times with 65,000-byte packets. I also transferred 3.4MB and 34MB files three times each. (Figure 1 and Figure 2 show the results of these file-transfer tests.) I performed an initial test with both clients connected to the wired interface of the access point to confirm that factors such as cabling or disk speed wouldn't be a bottleneck. Then, I connected one client through the vendor-supplied PCMCIA wireless network card and performed the test again at each distance. Although I was able to ping my wired host at 300 feet during some trials, I was unable to successfully transfer even the 3.4 MB file at that distance with any of the products, so I excluded the 300-foot trial from the final results. In addition to the products reviewed, I performed the test with an 802.11g-compliant network card and access point as a control.

Because interference from various sources can affect performance, I repeated this procedure on three different days. Just before each day's test, I also used NetStumbler to detect other access points in the area. On all three days, NetStumbler reported that the only access point using channel 11 was my own, which I disabled. I configured each access point to use channel 11, except for the Linksys product, which has an automatic channel setting; I let it choose it's own channel.

I got similar results for both distance and speed for all three MIMO access points. The tests I performed were unable to distinguish between the products, but all three showed great improvements over my 802.11g access point. My 802.11g access point was unable to maintain a connection at much farther than 100 feet, but all three MIMO products completed file transfers at 250 feet. Although this isn't quite the advertised three times the distance, I highly recommend any of the products reviewed here if you have a large house or yard and can't get a network connection with your 802.11g access point.

Although I didn't get eight times the speed at any of the distances I tested, I imagine that at some point between 100 and 200 feet, the 802.11g access point would have one eighth the data rate of the MIMO products. In my tests, the MIMO access points were about three times faster than my 802.11g access point at 15 feet and 6 times faster at 100 feet, so you really do see more benefit at greater distances.

All three access points also get better data-transfer rates with larger files at all distances. As Table 1 shows, although the results of the ping test were inconsistent even with 100 65,000-byte packets, the 34MB file-transfer test that Figure 1 shows revealed a fairly clear trend in the decline of the transfer rate. The transfer rate of all three products declined rapidly between 15 feet and 100 feet, but didn't change much between 100 and 200 feet. It declined again between 200 and 250 feet.

Linksys Wireless: G Broadband Router with SRX
Linksys' MIMO technology is called Speed and Range eXpansion (SRX). In addition to the 802.11b- and 802.11g-compatible access point, the G Broadband Router with SRX model WRT54GX has four FastEthernet ports for an internal network and a fifth Ethernet port for a connection to an external network or the Internet. It is also a stateful packet inspection (SPI) firewall, a DHCP server, and supports WPA for wireless security.

Belkin Wireless Pre-N Router
The Belkin Wireless Pre-N Router was one of the first MIMO access points available on the market and is the only product I tried that uses the pre-n designation. But don't be misled by the name; Belkin uses pre-n to indicate that the device gets better speed and performance. The name doesn't imply compatibility with the 802.11n standard. However, the Belkin Wireless Pre-N Router is 802.11b and 802.11g compliant. Like the Linksys WRT54GX, the Belkin Wireless Pre-N Router has four FastEthernet ports for wired operation, a fifth for external networks, DHCP, an SPI firewall, and WPA wireless encryption.

Buffalo Technologies AirStation MIMO Wireless Cable/DSL Router
Like the other products I tested, Buffalo Technologies' AirStation MIMO Wireless Cable/DSL Router has four wired FastEthernet ports, an Ethernet port for external networks or the Internet, an SPI firewall, DHCP server, and WPA wireless security. It's also 802.11b and 802.11g compatible. The AirStation MIMO had slightly better performance than the other two products I tested with large-file transfer at 15, 200, and 250 feet, but the differences weren't great enough to warrant a recommendation over the other two.

Waiting for the Standard
Though wireless technology hasn't yet caught up to its copper-based counterpart, the technology is improving rapidly. MIMO access points will likely improve with the 802.11n standard, but the current proprietary technologies may reach just far enough to cover that extra distance in your house. If your Wi-Fi network isn't reliable, I recommend trying any of the products in this review rather than waiting for products that use the coming standard.

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