USB Wi-Fi Adapter 101

Computers
  1. Introduction
  2. Wi-Fi Adapter Categories
  3. Wi-Fi Standards
  4. Wi-Fi 802.11ac
  5. Modern USB Wi-Fi Adapter Examples
  6. USB 2.0 Versus 3.0
  7. Anatomy Of A USB Wi-Fi Adapter
  8. External Versus Internal Antenna
  9. Software
  10. Extension Cable
  11. What To Look For
  12. Conclusion
  1. Introduction
  2. Wi-Fi Adapter Categories
  3. Wi-Fi Standards
  4. Wi-Fi 802.11ac
  5. Modern USB Wi-Fi Adapter Examples
  6. USB 2.0 Versus 3.0
  7. Anatomy Of A USB Wi-Fi Adapter
  8. External Versus Internal Antenna
  9. Software
  10. Extension Cable
  11. What To Look For
  12. Conclusion

Just as no man is an island, a computer needs to be connected to its network, and in turn the Internet, to be truly useful. While a wired Ethernet cable is preferable for many applications, the reality for many is that Wi-Fi is more convenient.

The wireless network starts with a broadband modem able to communicate with an Internet Service Provider (ISP), which facilitates your access to the Internet. Unless that modem has wireless functionality built-in, it’ll probably be attached to a wireless router through an Ethernet cable. Most Wi-Fi-enabled routers also give you a handful (in the neighborhood of four) Ethernet ports for wired devices close by. It’s what broadcasts your wireless signal.

In turn, the client devices connecting to the network (say, your workstation, tablet and smartphone) need to have wireless radios integrated and enabled in order to transmit and receive data over the network. If your PC doesn’t already have a wireless adapter, you have several options for adding one. Given the ubiquity of USB, many folks find that interface to be the easiest. The attached Wi-Fi adapter allows the computer to communicate wirelessly with the router, and in turn the modem.

Wi-Fi Adapter Categories

There are several different ways that Wi-Fi can be enabled on a computer, and each implementation has its own pros and cons that you should be aware of, including:

  • USB: USB Wi-Fi adapters are easy to install. Simply plug one into an available port and download its drivers (if your operating system doesn’t already include them). Of course, their external nature means that USB adapters consume at least one port; many are so large that they block others as well. And they stick out, which many enthusiasts disdain enough on their svelte PCs, much less their diminutive notebooks.
  • Desktop Motherboard:In some cases, the Wi-Fi adapter is either built into the motherboard itself or integrated as an add-on accessory. While this can be convenient, and does not take up any space you’d want for other peripherals, these adapters are in the middle of a metal case. Most include antennas that require routing outside of your chassis to avoid issues with signal strength and interference.
  • Integrated: In some cases, the Wi-Fi is built directly into the device, such as with smartphones and tablets. The advantage of this setup is obviously that you get functionality within a convenient form factor. Unfortunately, that makes upgrades difficult or impossible, limiting your ability to keep pace with wireless standards.
  • PCIe: PCIe stands for Peripheral Component Interconnect Express. Compatible cards fit into slots on your PC’s motherboard, and require access to the system’s internals. They frequently have antennas that protrude out the back of the card in order to maximize range. Notebooks typically have smaller slots on-board that accommodate mini-PCIe wireless cards. Typically, these slots come populated. But standardization makes it possible for an end-user to remove and upgrade to a faster Wi-Fi adapter down the road.

Wi-Fi Standards

802.11ac is the current Wi-Fi standard. It uses both the 2.4GHz band (like 802.11b and 802.11g) and the 5GHz band (like 802.11n). The next standard, 802.11ad, is reportedly due this fall and adds a third frequency to the mix (60GHz) and is designed for high bandwidth over short distances.

With 802.11ac as the current Wi-Fi standard, 802.11n-based gear is quite affordable. Naturally, you’ll ask yourself whether you should save some money on that older equipment. While you can certainly get acceptable performance from 802.11n, at this point I’d recommend springing for the more modern standard. Much of the early price premium is gone, and 802.11ac does offer some benefits, detailed below.

Within modern 802.11n and 802.11ac Wi-Fi adapters, there are several different speed tiers:

Type 2.4GHz Mb/s 5GHz Mb/s
N150 150 N/A
N300 300 N/A
N600 300 300
N900 450 450
AC600 150 433
AC1000 300 650
AC1200 300 867
AC1900 600 1300

Notice that adding throughput from the 2.4GHz and 5GHz bands gives you the equivalent nomenclature. For example, N600 is precisely the sum of 300 and 300. However, the math is not as clean for AC1200 since 300 and 867 give us a sum of 1176. This gets rounded to a nice even AC1200, which is easier to remember.

Wi-Fi 802.11ac

802.11ac introduces other innovations and advancements to Wi-Fi. These include:

  • Dedicated 5GHz bandwidth. While the range of 5GHz is typically less than 2.4GHz, the 5GHz band is significantly less congested and faster – two advantages that make it worth using.
  • While 802.11n channel bonding maxed out at 40MHz, 802.11ac offers this at 80 and even 160MHz. Recall that bonding is the method by which a single 20MHz channel can be combined with other channels to create a multilane highway to enhance data transmission speeds.
  • 802.11n used 64 QAM (quadrature amplitude modulation); 802.11ac increases this to 256 QAM, which is 33% more efficient.
  • 802.11n MIMO (multiple in/multiple out) maxed out at four spatial streams, while 802.11ac doubles this to eight, doubling data throughput.

Modern USB Wi-Fi Adapter Examples

Some examples of current USB Wi-Fi adapters include:

An entry-level N150 USB Wi-Fi adapter, which is quite affordable and can be found for around $10. The Trendnet TEW-649UB is an example of this. However, it tops out at 150 Mb/s over 2.4GHz and cannot access the 5GHz band. For basic use and slower Internet connections, you may find this more than adequate, however.

The fastest USB adapters are rated for AC1200 speeds, and they’re available from most manufacturers. An example is Netgear’s AC1200 WiFi USB 3.0 Adapter (A6210). It features a high-gain antenna that flips up to increase signal strength. It purportedly achieves speeds of 300 Mb/s over 2.4GHz and 900 Mb/s on 5GHz. You’ll find it priced around $50.

The D-Link AC1900 Wi-Fi USB adapter is an upcoming product that should enable even greater performance. It is due out this spring, and promises a speedy 600 Mb/s over 2.4GHz and a blistering 1300 Mb/s on the 5GHz band. The D-Link AC1900 Wi-Fi USB adapter expected this spring will feature even faster speeds than what are currently available.

USB 2.0 Versus 3.0

It is no surprise that current 802.11ac adapters utilize USB 3.0. The USB 2.0 standard, so called “Hi Speed,” theoretically maxes out at 480 Mb/s (60 MB/s), and USB 3.0 standard, also known as “Super Speed,” increases that to 5 Gb/s (625 MB/s). Of course, real-world throughput is usually quite a bit lower.

With 802.11ac’s peak data rates exceeding what USB 2.0 is capable of over the 2.4GHz and, even more dramatically, the 5GHz frequencies, the use of USB 3.0 becomes mandatory for the necessary throughput.

Anatomy Of A USB Wi-Fi Adapter

A USB Wi-Fi adapter packs a lot of technology into a compact form factor, just take a look at a disassembled example below:

We can see that it has a USB connector, of course, which is soldered onto the green circuit board hosting the necessary electronics. Much of the adapter is covered by that large interference shield. Still, it all fits into the plastic clam shell case that we’re accustomed to plugging in to the back of our PCs.

External Versus Internal Antenna

USB Wi-Fi adapters can be categorized based on their antennas, which can be omnidirectional (transmitting and receiving in all directions) or directional (focusing the transmission in only one direction). The strength of an antenna gets expressed in decibels (dB) relative to a standard reference antenna. Because this standard reference antenna is isotropic, that metric gets expressed as dBi, meaning decibels relative to the isotropic antenna. While this spec is not consistently available for USB Wi-Fi adapters, in cases when it is, this allows a more direct comparison of the expected signal strength for the adapter.

One differentiating factor of USB adapters is an external antenna, or a slimmer profile with an internal antenna. Both have their advantages, disadvantages and applications.

In situations where the signal strength is less than optimal, whether due to router location, interfering obstacles like walls and/or floors, and when there are multiple Wi-Fi networks nearby, a USB-based Wi-Fi adapter with an external antenna is preferred. Also, in the situation where a 5GHz signal is chosen for the Wi-Fi connection, but it is not strong, an adapter with an external antenna can make it usable (keeping in mind that 5GHz penetrates obstacles like walls or floors less than 2.4GHz). An adapter with an external antenna that can be adjusted and positioned to optimize signal strength is particularly ideal for these situations.

While an adapter with an external antenna is ideal from the standpoint of signal strength, they also tend to be bulky and protrude from the USB port. While less of an issue with a desktop, this can be a particular problem in a notebook, especially when they can get hit, and the USB port potentially damaged. In situations where the signal strength is strong, a smaller USB Wi-Fi adapter with an internal antenna and slim profile becomes the preferred choice.

In the never-ending quest for tiny electronics, a class of USB Wi-Fi adapters has emerged that can be described as “nano,” with the adapter only slightly larger than the USB port itself. While devices like this can certainly offer performance in a smaller package, keep in mind that a strong signal from a router is necessary for such a device to maintain a fast connection.

Software

A USB Wi-Fi adapter is a computer peripheral, and as such requires a software driver to function. This is why, when you plug the adapter into a USB port, it doesn’t always start up automatically.

This can be a frustrating challenge if Wi-Fi is the only available technology for getting your system online. Thankfully, most (but not all) Wi-Fi adapters come with software on a CD. Even this can be a limitation though, as an increasing number of laptops and desktops do not have optical drives. The other issue is that the software on the CD is often not the latest version of the driver. It is best to always check for newer builds on the Wi-Fi adapter manufacturer’s website. Consider the version provided in the package only as a starter to get you up and running.

Workarounds for the initial download of the software on a system with no optical drive and no other Internet access include downloading it to another system and copying it to a flash drive, moving the machine in question to a location where it can be plugged into a wired connection or using an external USB optical drive.

Extension Cable

A USB Wi-Fi adapter will only work as well as the signal it receives from the router. With the metal cases that surround most desktops, and the myriad of wires that supply power and data between the devices of a typical desktop, it is quite common for the available USB port that will accommodate the adapter to not be in an optimal location for maximizing signal strength. Add in the additional interference from nearby Wi-Fi networks and, in situations where the router is not in the same room as the computer, some signal strength optimization is often required.

Thankfully, there is a simple fix for this. A short (24” often works well) USB extension cable can allow a rear USB port to be utilized for the Wi-Fi adapter, while allowing the adapter to be positioned far enough away from the case, and in the direction of the router to gain signal strength. Such cables are available inexpensively, and can be indispensable to optimize the location of the antenna in relation to the router. 

What To Look For

Ultimately, several aspects need to be considered when choosing a USB Wi-Fi adapter. The first one is the adapter’s maximum data rate. In other words, for the home user of Google Fiber at 1 Gb/s, an AC1200 adapter can be easily justified. But for the user with 10 Mb/s DSL, any N150 USB Wi-Fi adapter will easily outperform the connection. Faster hardware isn’t necessary, since it can’t be utilized for improving Internet performance. On the other hand, for tech enthusiasts who use their home networks for more than just Web browsing, faster Wi-Fi adapters will accelerate file transfers across the LAN if the other network interfaces are up for the challenge. Look for a USB 3.0 adapter (as opposed to USB 2.0) for its higher transfer rate.

The next aspect is the need for an antenna. Gone are the days of the DIY Pringles cantenna; premade solutions are readily available now. If your USB Wi-Fi adapter is going to be used in the same room as the router, than any compact adapter should have enough signal strength. However, in cases where the USB Wi-Fi adapter is used farther away, especially with walls or floors in between, than an adapter with a high-gain antenna is called for. This needs to be balanced against any physical constraints, particularly when a bulky adapter will compromise a notebook’s portability. Also, some adapters come with a dock for ease of placement, which can be useful.

Make sure that your USB Wi-Fi adapter supports all of the 128-bit security standards, including WEP, WPA and WPA2. Also, certain manufacturers provide more complete software packages that are easy to configure. Many manage the Wi-Fi connection, replacing Windows’ built-in interface. Look to see if your vendor of choice has released software updates for its previous products as a sign of commitment to long-term support. Finally, look at the warranty period, which can vary from 90 days to the product’s lifetime.

Conclusion

The USB Wi-Fi adapter has several advantages, including ease of installation, affordable price points and compliance with the latest standards. These all contribute to making them a popular method to connect a computer wirelessly to the network. Understanding these devices will allow the user to purchase the best solution for their needs.

[Source : http://www.tomshardware.com/reviews/usb-wifi-adapter-guide,4108.html]