Wireless Network

Wi-Fi: Is 5 Ghz better than 2.4 Ghz for larger wireless networks?

Even though many Wi-Fi networks operate primarily over the 2.4 Ghz band, there are distinct advantages of using the 5 Ghz band especially with the increasing popularity of 802.11n.

Have you ever thought of creating an exclusive 5 Ghz Wi-Fi network? It’s no more an impractical idea, especially since the 2.4 Ghz spectrum is getting over crowded and 5 Ghz is the better option for channel bonding, which is key to higher 802.11 n performance. If you build a 5 Ghz network, your neighbors will love you 🙂

But practically, building a Wi-Fi network exclusively on the 5 Ghz band may not be possible because in larger wireless networks, there are so many wireless clients that may not have 5 Ghz capable wireless adapters. High end laptops and ipad may come with it by default, but most other devices like Wi-Fi enabled cell phones, Wi-Fi printers, etc may not.

Another hurdle to building a 5 Ghz network is its cost. 5 Ghz capable Access Points and Wi-Fi adapters are more expensive than their 2.4 Ghz counterparts. But as the popularity of 802.11n networks increase, we can expect more and more 5 Ghz capable clients and access points to be dual band enabled and cost lesser.

2.4 Ghz, being a lower frequency band offers a higher range (distance coverage) than 5 Ghz. But this can also be an issue in large networks/dense networks as multiple access points within a certain range can cause more interference.

But in-spite of these limitations, 5 Ghz Wi-Fi networks are popular because of the following advantages.

Wi-Fi: Advantages of 5 Ghz Network Vs 2.5 Ghz Network

Depending on the country and use of channel bonding, 2.4 Ghz spectrum has 1 – 4 non over lapping channels and 5 Ghz spectrum has 8 – 24 non over lapping channels. Data in Wi-Fi is transmitted on non-overlapping channels in order to avoid interference and the resulting packet collisions/packet loss. With so many non-over lapping channels, 5 Ghz band is the best choice for larger networks as it can avoid interference from other AP’s in the vicinity, much better than 2.4 Ghz band.

5 Ghz spectrum is capable of transmitting at a higher data rate (higher bandwidth) due to a technique called ‘Channel bonding’ used in 802.11n. In this technique, two 20 Mhz channels are combined to form one 40 Mhz channel and hence the bandwidth capacity is almost doubled. But, use of channel bonding cuts the number of available channels into half and hence it can be more practically implemented in the 5 Ghz band.

The 2.4 Ghz spectrum has a lot of interference not only from neighboring access points in the same floor (and the ones on the top floor/below floor), but also from other devices/wireless standards operating in the same frequency. For example, Bluetooth, cordless phones, wireless speakers, microwave ovens, baby monitors, etc could interfere with Wi-Fi signals. This results in reduced efficiency as packets lost due to collision need to be retransmitted/recreated. There are no such problems with the cleaner 5 Ghz band which is mostly free from interference.

Certain vendors claim that 5 Ghz radio is better as it can reflect more and scatters better. So, these waves can travel around obstructions (through reflections from neighboring surfaces). But there are other vendors who claim just the opposite of this, that 2.4 Ghz spectrum can travel through obstructions better. I am not sure which one is true and the reader can comment if they have a better idea on this topic.

5 Ghz seems is a better choice with larger wireless networks because of the additional non-overlapping channels present in it. It is possible for network managers to carefully plan the frequency of operation of adjacent access points (and the ones on the top floor, bottom floor) so that they don’t interfere with each other.

Dual band Wi-Fi implementations:

Practically, the best option available for network administrators is to go for a dual-band Wi-Fi implementation. This is because there will always be some legacy clients that do not support 5 Ghz and guests visiting the campus may not have 5 Ghz adapters on their laptops. Dual band implementations are generally planned for 2.4 Ghz with an overlay of 5 Ghz network.

In order to increase the efficiency of dual band networks,

Devices that can operate in 5 Ghz can be forcefully made to operate in 5 Ghz (both AP’s and clients can be set to operate only in 5 Ghz) (or) the controller/access points can push them over to 5 Ghz in order to free the available bandwidth in the 2.4 Ghz band for other devices. The second technique is called band steering and certain controllers can automatically do it when a higher number of devices start connecting in 2.4 Ghz.

Some access points allow software selection of frequency bands in individual radios and this could be very useful as the frequency of operation of each radio could be decided based on the load/capability of devices, at any point of time.

One more technique used by administrators is to lower the transmit power of 2.4 Ghz radios, so that dual band enabled wireless clients will automatically connect to the high power 5 Ghz radios.

802.11 ac is the next (new) wireless standard that is coming up and it primarily operates in the 5 Ghz spectrum. This should encourage more companies to migrate to 5 Ghz gradually. It is to be seen if 2.4 Ghz is supported with it, as well.


One Comment