A Technical Comparison of 802.11n to 802.11g

A Technical Comparison of 802.11n to 802.11g Abstract 802.11n was developed to address issues of distance and speed. These were issues with wireless g and especially big issues with legacy devices that were used previously. Wireless N devices allow for a wider range by using multiple-input multiple-out and multiplexing allowing more data to be sent at a given time than before in previous a/g devices. It also allows for better communication between the radios and receivers to modify the signal so that noise becomes less of an issue and getting the best signal to the receiver is more of the issue. This 802.11n development led to a faster more evolved internet solution and will lead us to even faster solutions and even great distances spanned due to the distances already accomplished by this top of line, high-speed solution. It accomplishes all of this while still maintaining a high-level of security and not compromises on speed or power consumption.

A Technical Comparison of 802.11n to 802.11g

In less than a decade, wireless LANs have evolved from an interesting idea to an indispensable technology for millions of businesses and consumers. So it is just a matter of what technology to use. Currently there are two heavily used technologies which are wireless g and wireless n. This will be explained in full detail below as we look at the breakdown between both of these. Wireless g was created to increase a powerful tool for increasing the mobility and productivity of users, and have unlocked a new generation of wireless-enabled applications. Its characteristics are depicted in the table below.

Frequency Spread Spectrum Technology 2.4GHz ISM band ERP; ERP-OFDM , ERP-DSSS/CCK are mandatory ERP-DSSS/CCK:1,2,5.5 and 11Mbps Data Rates ERP-OFDM:6,12,24Mbps Also supported: 9,18,36,48 and 54Mbps Backwards Compatibility Date Ratified 802.11 HR-DSSS and DSSS 2003 802.11g Characteristics Wireless G is still used today but is no longer the most popular or preferred wireless technology since Wireless N has been developed and is in use today. Wireless N is a much faster and more reliable technology that can be used over larger distances than its wireless G predecessor. It uses MIMO, multiple-input multiple-output, which is simply the using several different antenna to have a larger coverage area. It uses multiple radio chains, which is the radio itself and its antennas including any converters and amplifiers. This

A Technical Comparison of 802.11n to 802.11g allows for more data to be sent and transmitted by the use of spatial multiplexing. Spatial multiplexing, which works in a way like a highway that allows different streams of data to be transmitted and working like the lanes on a highway, in that having their own path that does not cross into the other but all streams can be put back together at the receiving end for an output. They are considered to be spatial diverse due to them having their own streams, whereas older radios before 802.11n used switched diversity. Switched diversity used only one antenna and multiple signals were received and it picked the best signal and used it. 802.11n has an optional capability called transmit beamforming (TxBF), which is simply an array of antennas set up in a linear-phased array. There are two other types of antenna arrays to talk about. One is a switched antenna array, which is an antenna array that only has a set number of patterns it can beam. An adaptive antenna array moves the beam towards the receiver.

If the receiver location is known then using this technology the phase can be adjusted and allowing multipath to result in upfade rather than affecting the signal in a negative way. Transmit beamforming relies upon both implied and explicit feedback. Implied feedback is when the receiver and the transmitter work together determining the MIMO channel to figure out what needs to be done to get the best signal by using phase modulation. Explicit feedback is when it does practically the same thing except the beamformer uses that information to transmit. The transmitter is considered the beamformer, while the receiver is considered the beamformee. Transmitters (beamformer) that us beamforming adjust the phase based on feedback from the receiver (beamformee). This is called sounding frames. 802.11n uses both 20 MHz and 40 MHz channels for operations. For digital signals this data is put on a carrier signal in bits and that is referred to as symbols. Wireless a/g radios use an 800 nanosecond guard interval between these symbols whereas n radios also has this 800 ns

A Technical Comparison of 802.11n to 802.11g interval but has an option 400ns guard interval. Guard interval is the amount of time that is waited before sending the next symbol. The data rates in 802.11n are set by the modulation and coding scheme, which is a variation of modulation, number of spatial streams, channel size, and guard interval. There are 77 schemes for the 20MHz and 40 MHz HT channels. Also included in 802.11n is a revised power management. A method known as spatial multiplexing power save was developed which allows a wireless n device to power down all but one of its radios in order to save power and conserve energy when not in use. Wireless N devices are high-throughput (HT) devices, which is in a simplified form the same the definition of the 802.11n standard. High throughput is defined as speeds of 100Mbps or greater.

There are four different protection modes which are 0-3. Since all devices have to backwards compatible older devices would be able to signal the high throughput device and signal when to use the modes. The first mode is mode 0, Greenfield mode, and only HT devices can be in use for this mode to be used as well as all clients must have the same capabilities. The second mode is mode 1, nonmember protection mode, and all stations must be in HT stations. If a nonmember is heard inside the BSS then protection mechanisms begin. The third is mode2, HT 20 MHz protection mode, is used for compatibility so that not only the 20 MHz station is the only one transmitting all the time and so that the 40MHz stations have security. The fourth mode is mode3, HT mixed mode, is used when there are more than one non-HT device that is associating with the HT access point. 802.11n was developed to address issues of distance and speed. These were issues with wireless g and especially big issues with legacy devices that were used previously. Wireless N devices allow for a wider range by using multiple-input multiple-out and multiplexing allowing more data to be sent at a given time than before in previous a/g devices. It also allows for better

A Technical Comparison of 802.11n to 802.11g communication between the radios and receivers to modify the signal so that noise becomes less of an issue and getting the best signal to the receiver is more of the issue. This 802.11n development led to a faster more evolved internet solution and will lead us to even faster solutions and even great distances spanned due to the distances already accomplished by this top of line, high-speed solution. It accomplishes all of this while still maintaining a high-level of security and not compromises on speed or power consumption. While 802.11g served as the baseline for a while and is still in use, but the best is 802.11n.

References

Coleman, D. D., & Westcott, D. A. (2009). Certified Wireless Network Administrator Official Study Guide. Indianapolis, IN: Wiley Publishing, Inc.