By Jim Geier

January 14, 2003

The debate continues as companies choose between using 2.4GHz and 5GHz wireless LANs. Gain a better understanding of what you should take into account when deciding on which one to deploy.

When deploying a wireless LAN, companies must make a decision on whether to use network interface cards (NICs) and access points designed to operate in the 2.4GHz or 5GHz band (or both). Not too long ago the choice of frequency band was easy, when only 2.4GHz (i.e., 802.11b) products were available. Now, 802.11b and 802.11g products are both available that operate in the 2.4GHz band, while 802.11a use the 5GHz band. This can cause confusion when designing a WLAN, so let’s take a look at what you need to consider when making this critical resolution.

Refer to Solid Requirements

When assessing the pros and cons of 2.4GHz and 5GHz systems, be sure to first define requirements. This provides a solid basis for defining all design elements. Without firm requirements, you’ll be making the choice on flimsy ground.

The following are requirements that you should consider when deciding on whether to deploy 2.4GH or 5GHz solutions:

• Geographical Location. Before getting to far, consider the geographical location of where the WLAN will operate. 2.4GHz WLANs have regulatory acceptance throughout most of the World; however, the use of 5GHz for WLANs is somewhat limited. For example, the U.S. allows operation of 5GHz WLANs, but other countries (e.g., China) do not. Your location may require you to use the 2.4GHz band regardless of other requirements.
• Performance. The 5GHz bands have much greater spectrum available. In this band there are 12 non-overlapping channels, each with 20MHz of bandwidth. This means significantly better performance as compared to the 2.4GHz band. The entire 2.4GHz band is 80MHz wide, which only allows three non-overlapping channels. If high performance is an important requirement, then lean toward the 5GHz band.
• Facility Size. As frequency increases, range generally decreases. As a result, 5GHz systems generally have less range than ones operating in the 2.4GHz band. The selection of a 5GHz WLAN could require a greater number of access points, which can result in higher costs. As a result, you may benefit by deploying 2.4GHz systems in larger facilities unless high performance is critical. Keep in mind, however, that 5GHz systems may have equal or even better range in some situations.
• Radio Frequency (RF) Interference. 2.4GHzWLANs can experience interference from cordless phones, microwaves, and other WLANs. The interfering signals degrade the performance of an 802.11b WLAN by periodically blocking users and access points from accessing the shared air medium. If it’s not possible to reduce potential interference to an acceptable level, then consider deploying a 5GHz system, which is relatively free from interfering sources.

• Interoperability. 2.4GHz and 5GHz systems are not directly compatible, and very few users (not to mention access points) today operate in the 5GHz band. Consequently, it may be best to deploy a 2.4GHz solution if you have very little control over the NICs that users have in their PDAs and laptops. This applies mostly to universities and public WLAN hotspots. Your application may require you to definitely implement 2.4GHz to support the more common 802.11b-equipped users. 
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• Vendors, however, have begun offering dual-band radio NICs and access points, which reduces interoperability problems. Someone equipped with a dual-band radio NIC can associate with either a 2.4GHz (802.11b/g) or 5GHz (802.11a) access point. As a greater number of users begin equipping their devices with the dual-band radio NICs over the next couple years, then the interoperability issue will diminish.
• Security. Security of the WLAN is of great concern to most companies. By minimizing the propagation of radio waves outside the physically controlled area of a facility, a wireless network is more secure because of the reduction of the potential for eavesdropping and denial of service attacks. As a result, 5GHz systems can provide enhanced security over 2.4GHz systems because of less range.
• Costs. 5GHz productscurrently cost 20 to 30 percent more than 2.4GHz counterparts — even over the brand new 2.4GHz 802.11g products. In addition, the lesser range the 5GHz offers increases the number of access points you’ll need for coverage. Think about whether the use of a 5GHz WLAN offers enough additional benefits (e.g., higher performance, less interference, etc.) to be worth the extra expense.

Final Thoughts

In most cases, you’ll probably determine that 2.4GHz is the way to go for common office applications. 2.4GHz products are certainly inexpensive and capable of supporting most application requirements. There will be some situations, however, that will strongly benefit from the use of 5GHz, such as densely-populated environments and multi-media applications.

Jim Geier provides independent consulting services to companies developing and deploying wireless network solutions. He is the author of the book, Wireless LANs and offers computer-based training (CBT) courses on wireless LANs.