Wireless Technologies | CompTIA Network+ N10-007 | 1.6

In this video you will learn about wireless technologies such as:  802.11 standards, cellular technologies, WiFi frequencies, channel bandwidth, channel bonding, MIMO/MU-MIMO, unidirectional & omnidirectional, and wireless site surveys.

802.11 Standards

• 802.11a:  Maximum speed of 54Mbps using the 5GHz frequency band with a maximum indoor range of 35m.
• 802.11b:  Maximum speed of 11Mbps operating in the 2.4GHz frequency band with a maximum indoor range of 35m.
• 802.11g:  Maximum speed of 54Mbps operating in the 2.4GHz frequency band with a maximum indoor range of 45m.  It is backwards compatible with 802.11b.
• 802.11n:  Maximum speed of 150Mbps when using a single 20MHz channel, or it can run up to 300Mbps with channel bonding (40MHz channel).  Operates in the 2.4GHz frequency by default, but it can also support 5GHz frequencies as well.  802.11n has a maximum indoor range of 70m.  Supports MIMO (multiple input multiple output) antennas to improve performance and range, although not all devices include multiple antennas.
• 802.11ac:  Uses only the 5GHz band and supports up to 80MHz-wide channels compared to 20MHz for 802.11b/g and 40MHz for 802.11n using channel bonding.  Supports multi-user MIMO (MU-MIMO).  The speed of 802.11ac is up to 433Mbps per stream when 80MHz-wide channels are used.

Cellular

GSM (Global System for Mobile Communications)

The GSM is a standard developed by the European Telecommunications Standards Institute to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as mobile phones and tablets.  Its main task was to develop a single, consistent network for all of Europe and come up with a better and more efficient technical solution for wireless communication.  

The GSM standard operates on three different carrier frequencies:  the 900MHz band, which was used by the original GSM system; the 1800MHz band, which was added to support the swelling number of subscribers and the 1900MHz frequency, which is used mainly in the U.S.  One of the main advantages of the GSM standard is the ability to roam and switch carriers by using individual mobile units (if partner networks are located in their destination).

TDMA (Time-Division Multiple Access)

TDMA is a channel access method for shared-medium networks.  It allows several users to share the same frequency channel by dividing the signal into different time slots.  The users transmit in rapid succession, one after the other, each using its own time slot.  This allows multiple stations to share the same transmission medium (e.g. radio frequency channel) while using only a part of its channel capacity.  TDMA is used in most 2G cellular systems, while 3G systems are based on CDMA (code-division multiple access).

CDMA (Code-Division Multiple Access)

CDMA is a digital cellular network standard that utilizes spread-spectrum technology.  This technology does not constrict bandwidth’s digital signals or frequencies but spreads it over a fully-available spectrum or across multiple channels via division.  Thus, there is improved voice & data communication capability and a more secure and private line.  Essentially, CDMA offers more airspace capacity than time-division multiple access (TDMA) based Global System for Mobile Communications (GSM) standard.  Furthermore, CDMA uses less power.  The CDMA digital standard is a leading communications network standard in North America and parts of Asia.

Frequencies

Your wireless router uses radio frequencies to transmit internet to your WiFi-connected devices like smartphones, laptops, tablets, etc.  The difference between 2.4GHz and 5GHz frequencies comes down to 2 factors:  bandwidth (speed) and range.  A 2.4GHz connection travels farther at lower speeds, while 5GHz frequencies provide faster speeds at a shorter range.  Whether you choose 2.4GHz or 5GHz will depend on where and how you use your WiFi connection.  A lot of electronic devices & appliances use the 2.4GHz frequency, including microwave ovens, baby monitors, and garage door openers.  If you have many of these in your home, or if you live in apartments or condos surrounded by other people, that 2.4GHz band is likely to be congested, which can damage speed and signal quality.

2.4GHz Overview

• Pros:  larger coverage area; better at penetrating solid objects
• Cons:  lower data rate; more prone to interference; usually more devices using this frequency
• Max Connection Speed:  ~150Mbps
• Max Signal Range from Router:  ~410 ft

5GHz Overview

• Pros:  Higher data rate; less prone to interference; usually fewer devices using this frequency
• Cons:  smaller coverage area; worse at penetrating solid objects
• Max Connection Speed:  ~1Gbps
• Max Signal Range from Router:  ~410 ft amplified

Channel Bandwidth

Bandwidth is a broad term defined as the bit-rate measure of the transmission capacity over a network communication system.  Bandwidth is also described as the carrying capacity of a channel or the data transfer speed of that channel.  However, broadly defined, bandwidth is the capacity of a network.  Bandwidth exists in physical or wireless communication networks.

Channel Bonding

Channel bonding (also known as Ethernet bonding & NIC bonding) is when a cable modem combines multiple channels to increase the amount of traffic that it can comfortably support.  Channel bonding is a practice commonly used in 802.11 implementations in which two adjacent channels within a given frequency band are combined to increase throughput between two or more wireless devices.

MIMO (Multiple Input & Multiple Output)

MIMO is a method for multiplying the capacity of a radio link using multiple transmission & receiving antennas to exploit multipath propagation.  MIMO has become an essential element of wireless communication standards including IEEE 802.11n & 802.11ac.  Some smartphones and tablets simply use the term MIMO if they support two or more 802.11n or 802.11ac streams.  MIMO devices are available in the following configurations:

• 1×1:  one transmit, one receive antenna
• 2×2:  two transmit, two receive antennas
• 2×3:  two transmit, three receive antennas
• 3×2:  three transmit, two receive antennas
• 3×3:  three transmit, three receive antennas

The number of transmit antennas typically corresponds to the number of data streams (spatial streams) the device can support.  In the case of a router that supports both 2.4GHz and 5GHz signals, the specifications include this information for each band.  Devices that have different numbers of receiving antennas and sending antennas may be identified by the number of data streams it can send and receive.  For example, a device with a 2×3 antenna configuration can also be identified as having a 2×3:2 configuration (two send antennas, three receive antennas, and send/receive support for two data streams).

MU-MIMO (Multi-User Multiple Input & Multiple Output)

MU-MIMO allows a WiFi router to communicate with multiple devices simultaneously.  This decreases the time each device has to wait for a signal and dramatically speeds up your network.  Considering that the average household has upwards of eight devices battling for bandwidth simultaneously, MU-MIMO will increasingly improve a household’s WiFi experience (especially when it comes to streaming and gaming).

Unidirectional & Omnidirectional Antennas

Unidirectional antennas focus radio frequency (RF) energy in one or two directions which lowers the beam width and overall area covered, but increases the strength of the signal and distance covered in that direction.

An omnidirectional antenna is able to radiate or receive equally well in all directions.  From the locus, the signal is emitted in the 360 degree plane to cover a certain area.  Because the signal is not focused, the distance that it reaches is generally small relative to that of a unidirectional antenna.  Typical applications of these antennas include hotspots for WiFi either indoors or outdoors where multi-path environments exist.

Wireless Site Survey

A wireless site survey is the process of planning and designing a wireless network, to provide a wireless solution that will deliver the required wireless coverage, data rates, network capacity, roaming capability and quality of service (QoS).  The survey usually involves a site visit to test for RF (radio frequency) interference, and to identify optimum installation locations for access points.  This requires analysis of building floor plans, inspection of the facility, and use of site survey tools.  Feedback from IT managers and end users of the wireless network are also important in determining the design parameters for the wireless network.