Wifi as a Precious Resource

Although Wi-Fi technology is advancing every day, at its core it is still over-the-air technology, and is subject to certain limitations. In order to get the most out of your wifi it must be thought of as a finite, precious resource.  Here we will discuss the benefits of utilizing your ethernet LAN over your wireless LAN when possible. 

Wireless LAN will not be able to perform at the same speeds as an ethernet LAN. Ethernet is a full duplex technology which means that data can simultaneously be sent to and from the client. Wifi systems are half duplex, this means that data can only be sent in one direction at a time which will slow down the flow of data.  Using an ethernet LAN means that you have the advantage of per port switching. Each connection plugs into a port on the switch, this allows traffic to be received from many different clients at once. Clients using a wireless LAN all have to share the airspace. Say we have 3 clients on the WLAN all using one channel to send traffic to and from their workstations, all 3 clients will have to wait for each others traffic to move through the channel before it can transmit or receive data, while on your ethernet LAN each connection has its own wire with its own port and is able to transmit and receive immediately. 

In a test of 16 802.11g/n laptops all downloading a 1MB roaming desktop file, Ethernet LAN took 25 seconds and wireless took 2 minutes to complete the download. Because Wireless is a “shared medium,” The bandwidth resources are finite, so as you increase the number of clients in an area, the slower the network will perform for all clients.

In conjunction with the limitations put on wireless by the amount of clients using the systems the overhead of the 802.11 protocol can decrease the amount of throughput on the wireless system.  

The IEEE 802.11ac standard allows for multiple gigabit data throughput in the 5GHz band. Vendors selling 802.11ac compatible access points can claim gigabit speeds for their product. It is in theory possible for the product to reach these types of speeds, but it is often forgotten in the excitement of such high speeds that data rate is not the same thing as throughput, and the technical requirement needed to reach those speeds are often untenable in an enterprise environment. 

Throughput will never measure up to data rate. Data rate is the speed of transmission, or the number of bits per second that the device can carry during a single transmission. Throughput is the effective transmission rate experienced by applications. The difference between the data rate and throughput is explained by the 802.11 protocol overhead which takes into account contention mechanisms, frame acks, management packets, as well as the signal levels that are associated with a client's connection to the access point. 

We can think of the channels discussed earlier as the road used by the data (or cars on the road) to get from one place to another. these channel widths can stand on their own as 20MHz, or be widened to 40Mhz or 80Mhz. The problem with widening the road is that it takes up the space needed for second or third road. In a normal office environment, to maximize data rates you must use 40Mhz channels. Your expanded channel width now reduces the amount of non-overlapping channels you can reuse. In a high capacity environment channel utilization is key to allowing traffic to flow smoothly through the network. Less channels means you now have more clients per channel. causing WLAN performance to suffer. 

Before deploying a WLAN solution especially within an enterprise environment, it is important to take into consideration the limits of a WLAN network compared to an Ethernet LAN. When Modern Mechanic deploys WLAN solutions we highly recommend connecting all immobile work stations to an ethernet LAN, leaving the airspace clear for any mobile clients who do not have the option to wire up. 

Feel free to contact our WLAN specialists for more information on what Modern Mechanic can do to get your office set up with a professional wireless network. 

 Coleman, D., & Westcott, D. (2012). CWNA: Certified Wireless Network Administrator Official Study 

Guide Exam PW0-105. (3rd ed., pg 157). Indianapolis, IN: John Wiley.

 802.11 is a layer 1 and 2 protocol. While a user may truly only care for her layer 7 traffic, overhead in a 
WLAN is all traffic that is not layer 3 - 7.

Posted on June 25, 2014 .