Wi-Fi is a type of wireless technology that uses radio waves to provide connectivity to a wired network or the Internet. At home, the office, or a cafe, Wi-Fi is responsible for providing connectivity to our wireless devices. This is a type of technology that many take for granted. This post is intended to help both beginner and intermediate-level readers understand wireless networking. Topics covered include:
- IEEE 802.11 Standards
- Additional IEEE 802.11 Standards
- Frequency Ranges
- 2.4GHz Frequency Band
- 5.0GHz Frequency Band
- Wireless Devices You Must Know
- Wireless NICs
- Wireless Access Points
- Wireless Routers
- Wireless Network Modes
- Infrastructure Mode
- Ad Hoc Mode
- Broadcasting and Transmission Methods
- Channel Sharing Technologies – CSMA/CA
- Wireless Security
- Summary of the 4-way WPA Handshake
- WPA2’s Inevitable Downfall
- WPA3 is on the Way
IEEE 802.11 Standards
To truly comprehend the operation and complexities of wireless networks, there must be a good foundation in IEEE 802.11. This is a family of layer 1 and layer 2 specifications for wireless networking standards. In other words, IEEE 802.11 defines how a wireless network operates. That being said, there are many IEEE 802.11 standards to cover; the most notable being 802.11b, 802.11a, 802.11g, 802.11n, and 802.11ac. Here is a helpful table that summarizes each IEEE 802.11 standard.
This table is useful for studying as it identifies the date that the standard was officially rolled out, the frequency range it operates in, the channels it uses, throughput, antenna configuration, maximum range in feet, spectrum, and any noteworthy details.
Despite it’s name, “IEEE 802.11b” actually came out just before IEEE 802.11a in 1999. However, 802.11b was the first to receive the Wi-Fi Seal of Approval. With a data throughput of up to 11 Mbps, it’s not that great; however, what it lacks in throughput, it more than makes up for in maximum distance. In the most suitable conditions, this standard can reach up to 300 feet; however, if there a lot of obstacles and concrete walls (which is usually the case), the distance is slightly limited. IEEE 802.11b networks operate in the 2.4GHz frequency band, and that’s what makes them good for distance.
There are only three non-overlapping channels in the 2.4GHz frequency band, which are channels 1, 6, and 11. The downside of 802.11b is that it uses “Direct Sequence Spread-Spectrum (DSSS)” as its broadcast method, making it more prone to interference. In addition, using the 2.4GHz frequency band can be a problem in modern wireless networks because many wireless devices are operating in this range. The term for this over-crowding is called “device saturation” or “device density.” And lastly, even though 802.11b is still used, it’s very old. This causes a lot of backwards compatibility problems for the newer 802.11 standards and wireless devices.
The primary difference between “IEEE 802.11a” and 802.11b is that the former operates in the 5.0GHz frequency band instead of the 2.4GHz frequency band, which reduces the chance of interference from other devices. This is because there are more than just 3 channels to configure wireless access points. The 5.0GHz frequency band includes 24 non-overlapping 20MHz channels and 12 non-overlapping 40MHz channels; therefore, device saturation shouldn’t be a problem. Additionally, IEEE 802.11a has a much higher throughput at 54 Mbps, but it lacks in the distance department. An 802.11a network has a maximum distance of about 150 feet, which is half the distance of 802.11b. Interestingly, IEEE 802.11a never gained much popularity, perhaps because it was expensive to implement and was incompatible with 802.11b networks since they operate on different frequencies. As for similarities, IEEE 802.11a also uses DSSS.
The third standard in the IEEE 802.11 family was developed in 2003. “IEEE 802.11g” supports a maximum throughput of 54 Mbps and a theoretical maximum distance of 300 feet. Similar to IEEE 802.11b, this standard operates in the 2.4GHz frequency band which means it only uses channels 1, 6, and 11. What makes IEEE 802.11g a better alternative is that it’s backwards compatible with 802.11b, meaning an 802.11g Wireless Access Point (WAP) or Wireless Router can support both 802.11g and 802.11b wireless client devices.
An 802.11g wireless network that supports both 802.11g and 802.11b clients must be configured in “mixed mode.” On the other hand, if it’s an 802.11g network supporting purely 802.11g clients only, then the network should preferably be configured to “native mode.” Running an IEEE 802.11g network in mixed mode means the network must slow down in order to support the older 802.11b clients, which means the network’s max throughput can only be a maximum of 11 Mbps. As for its broadcasting method, 802.11g uses both DSSS and “Orthogonal Frequency-Division Multiplexing (OFDM).”
“IEEE 802.11n” came out in 2009 with a variety of new features. In addition to faster speeds (up to 100 to 600 Mbps), it came with a new antenna technology called “Multiple Input/Multiple Output (MIMO)” technology. This is opposed to 802.11b/a/g’s “Single In/Single Out (SISO)” technology. All 802.11n WAPs or wireless routers have to use multiple antennas for MIMO to work. Having multiple antennas enables multiple simultaneous connections, allowing the network to achieve amazing speeds. 802.11n WAPs use another feature called “transmit beamforming,” which is a multiple antenna technology that assists in eliminating dead spots. 802.11n also operates in BOTH the 2.4GHz frequency band and 5.0GHz frequency band. Some devices can operate in both of these frequency ranges, it eliminates the saturation issue in the 2.4GHz range. If using the 5.0GHz frequency band, 802.11n networks only use the 20MHz and 40MHz channels.
Like 802.11g, the new 802.11n is backwards compatible with 802.11b and 802.11g devices. Again, this requires different “modes” of operation to complete this feature. In “Greenfield mode,” the WAP only serves 802.11n devices. This allows the network to utilize 802.11n to its maximum potential, which is also why it’s called “High Throughput (HT)” mode. If the network is running “legacy” devices (e.g., 802.11b/g), the WAP uses “Legacy mode” to send out separate packets to these older wireless devices. This definitely slows down the network for the older devices to catch up, which is why it’s sometimes referred to as “Non-High Throughput (non-HT) mode.” The last mode, called “Mixed mode,” is used when running an 802.11b/g/n network simultaneously. Encapsulating 802.11n frames into 802.11b/g frames will lower the throughput. IEEE 802.11n uses OFDM.
Finally, “IEEE 802.11ac” was created in 2013 and it’s the latest installment in the IEEE 802.11 family of wireless standards. It has a maximum throughout of 1,000 Mbps (which is 1 Gbps) and has a maximum distance of 300 feet. Seeing as the 2.4GHz frequency band is becoming more and more saturated on modern wireless networks, 802.11ac solely uses the 5.0GHz frequency band. And, instead of using MIMO technology, it uses “Multi-User MIMO,” or “MU-MIMO” technology, which is a major improvement to MIMO. Like 802.11n, IEEE 802.11ac also uses a OFDM.
An optional feature for IEEE 802.11ac is to use the 80MHz and 160MHz channels in the 5.0GHz frequency band by using a process called “channel bonding“. In 2015, the FCC approved of these new channels, which were once previously prohibited.
Other 802.11 standards
There are other 802.11 standards that aren’t very popular. They’ve come out over the past decade and are not globally recognized standards.
For example, “IEEE 802.11ah” rolled out in 2016. It was praised for its increased range over 802.11b/g/n networks and its ability to use very low frequency 900MHz channels. This makes it great for Wi-Fi-enabled IoT devices that are located far from an access point. Furthermore, lower frequencies tend to penetrate through walls and other obstructions much better than the higher frequencies used in the other 802.11 standards.
“IEEE 802.11af” came out in 2014, but it never became popular because it had a lot of disadvantages depending on location. This standard used unused television frequencies between 54 MHz and 790 MHz. Depending on the location of the network, those channels may already be in use. But, what’s most notable is the broad range of channels, which would require expensive hardware in order to implement an 802.11af network.
There was also IEEE 802.11ad, which seemed desirable in theory, but didn’t have much use in modern wireless networks. This 2012 specification uses the 60GHz frequency band, which is ideal for very high data rate and short-range communications. Think very, very short distances and very high frequencies. These type of high frequencies will not easily penetrate through walls and would require wireless clients be fairly close to the access point or wireless router. And, because these are such high frequencies, an 802.11ad network would therefore require expensive equipment to implement.
As previously mentioned, the modern IEEE 802.11 standards are using either the 2.4GHz frequency band or the 5.0GHz frequency band. The 5.0GHz frequency band provides much higher bandwidth than the 2.4GHz frequency band, and therefore, has faster data connections. On the other hand, since the 2.4GHz frequency band uses lower frequencies, it will be able to penetrate walls and other obstructions much better than the 5.0GHz frequency band, making it a better alternative for farther distances.
2.4 GHz Frequency Band
So, it appears that the 2.4GHz frequency band is great for distance, but not as great for max data transfer. One other thing that should be mentioned once more is that 2.4GHz frequency band can easily become saturated with wireless devices since its used in the popular 802.11b/g/n networks and only uses 3 channels.
According to the diagram, the are many channels in the 2.4GHz frequency band and each are 20MHz wide; however, wireless networks should only use non-overlapping channels, which leaves only channels 1, 6, and 11. If wireless access points are in close-proximity of each other and use the same channel, this will eventually cause interference. For that reason, network administrators typically do not set up their wireless access points with overlapping channels.
5.0GHz Frequency Band
The 5.0GHz frequency band has much more room than the 2.4GHz frequency band. The newer IEEE 802.11 standards, such as 802.11n and 802.11ac, support this frequency range. Higher frequencies equates to higher throughput, but higher frequencies are directly proportional to attenuation. This means the higher the frequency used, the less signal strength.
Based on the above diagram, there are many 20MHz, 40MHz, 80MHz, and 160MHz channels. The larger the width of the channel, the less channels there will be available to use. This is due to something called “Channel Bonding.” For example, an 80MHz channel takes up four-20 MHz channels. Likewise, a 160MHz channel takes up eight-20MHz channels. While having many channels in the 5.0GHz frequency band is great, it will eventually run short, which is why the Wi-Fi Alliance is working to acquire additional channels to use.
Depending on the location of the network, a channel may also not be used. For example, in the U.S., it is acceptable to use channel 38. However, it is illegal to use channel 38 in Canada, Switzerland, Japan, and several other countries. Many countries have their own regulations regarding allowable channels and maximum power levels. In the U.S., the FCC makes these decisions on the radio frequency spectrum as to prevent interference with weather-radar, satellite, and military services. Each country has their own reasons.
Wireless Devices You Must Know
Before moving on, it’s important to understand the few wireless devices that really make up a wireless network. They are wireless NICs, WAPs, and wireless routers.
Wireless networks transmit radio waves at different frequencies using “Wireless Network Interface Cards (NICs).” Wireless NICs are the same as wired NICS, but instead of sending electrical pulses down a wire, they are transmitting radio waves through the air. Also, instead of following IEEE 802.3 standards, wireless NICs are following the specifications laid out in any one of the 802.11 standards that were discussed earlier.
A “WAP” is a “Wireless Access Point.” The WAP itself is a client of the wireless network. It acts as a bridge for wireless clients to access the wired network, hence the name “access point.” WAPs can also act as a Wi-Fi range extender, considering that they have a built-in transmitter and receiver. If a router does not have wireless capabilities, an access point can be connected to the router via an Ethernet cable to serve wireless clients.
The next device to know about are “wireless routers.” All wireless routers are WAPs because they have a built-in WAP. However, not all WAPs are wireless routers. A wireless router has extra features. Sure, it can also bridge wireless clients to a wired network, but it also provides access to the Internet or WAN, it can have a built-in network switch, DHCP features, NAT, firewalls, and it serves out important TCP/IP settings, such as DNS settings.
Wireless Network Modes
A wireless network can operate in one of two modes: Infrastructure mode or Ad Hoc mode. Let’s start with Infrastructure mode.
In “Infrastructure mode,” wireless nodes connect to one or more WAPs or a wireless router to create a star topology. From a security perspective, Infrastructure mode allows for more management and control of wireless nodes. A WAP that services an area of wireless nodes is called a “Basic Service Set (BSS).”
However, if more WAPs are added to extend the coverage area, this is called an “Extended Service Set (ESS).” Wireless networks that are using Infrastructure mode take a little more strategy to set up and configure. They require the network administrator to choose the correct 802.11 standard and ensure the proper wireless coverage. Infrastructure mode is much more common than Ad Hoc networks.
In Infrastructure mode, the wireless nodes need a way to identify the network or BSS. This ensures that wireless traffic is both received and transmitted on the correct wireless network and not some other overlapping wireless network. The solution is to use a “Basic Service Set Identifier (BSSID).” The BSSID is the 48-bit MAC address of the WAP or wireless router. With the BSSID, wireless clients can identify the network to connect to.
There is also something called the “Service Set Identifier (SSID).” This is simply the name of the network, such as “HOME-WiFi,” “Corporate_WiFi_2.4,” or “Cafe_Wireless.” This is great because if wireless users were to initially make a connection to the wireless network, they would have to enter the BSSID instead, and nobody wants to remember a 48-bit MAC address over a simple network name, right? WAPs broadcast the SSID out according to a specified time interval.
If there is more than one WAP on the wireless network, then the SSID becomes an “Extended Service Set Identifier (ESSID).” If the wireless network is going to enable roaming, then all WAPs should share the same ESSID in order to identify the ESS. “Roaming” is a neat feature that allows wireless users to walk around to different areas on the network and remain connected to the same ESS by seamlessly changing WAP connections that are in close-proximity.
Ad Hoc Mode
“Ad Hoc mode” is a type of peer-to-peer mode whereby every wireless node is in direct contact with each other wireless node. This topology looks like a mesh because there is no intermediary device, such as a wireless router or a WAP. Instead, the wireless nodes just communicate with each other. Wireless nodes that are using using Ad Hoc mode create an area called an “Independent Basic Service Set (IBSS).” These Ad Hoc wireless networks aren’t typically used that often unless it’s for something temporary, such as a study group or a business meeting that requires file-sharing.
In Ad Hoc mode, there is no WAP, so there cannot be a MAC address to use. Instead, the wireless nodes create their own, random 48-bit MAC address that acts as a BSSID.
802.11 wireless networks can use several different spread-spectrum broadcasting methods. There are three different broadcasting methods identified in 802.11 specifications: DSSS, FHSS, and OFDM.
The first transmission technology is “Direct Sequence Spread-Spectrum (DSSS),” and it’s used on the earlier 802.11 networks, such as 802.11b. DSSS is a little complex to understand because it uses a chipping rate and different modulation techniques, such as Quadrature Phase-Shift Keying (QPSK), Binary Phase-Shift Keying (BPSK), and so forth. But, the important thing to know is that DSSS sends out huge broadcasts on several different frequencies at once, which takes up a lot of bandwidth. For that reason, the IEEE moved away from DSSS in the later 802.11 standards.
“Frequency-Hopping Spread-Spectrum (FHSS)” works similarly to DSSS, but it’s better in that it can “hop” to different frequencies constantly to avoid other overcrowded frequencies. FHSS is also less prone to interference than DSSS.
The latest transmission technology is “Orthogonal Frequency-Division Multiplexing (OFDM),” seen on 802.11n and 802.11ac networks. OFDM splits a radio signal into smaller subsignals and puts them on separate orthogonal channels at different frequencies. It makes efficient use of the available spectrum and is less prone to interference.
Channel Sharing Technologies – CDMA/CA
Wireless networks are half-duplex. For that reason, a wireless networkacts like a hub, which isn’t good because every wireless device connected to the WAP is in its own collision domain. Half-duplex wired Ethernet networks use “Carrier-Sense Multiple Access with Collision Detection (CSMA/CD)” to share the wire and detect frame collisions. But, since there is no way to detect collisions in the air, wireless networks cannot use CSMA/CD. Instead, they use “Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA).” There are other channel sharing technologies, but CSMA/CA is a very popular one.
CSMA/CA works by using “Distributed Coordination Function (DCF)” to specify how data will be sent out onto the airwaves. Prior to transmitting, the wireless node “listens” for wireless signals on the network to determine if other wireless nodes are currently transmitting, but they still cannot detect collisions. If the wireless network is busy, DCF defines a random backoff period before it can try to transmit again. Also, some wireless networks use Request to Send (RTS) and Clear to Send (CTS) exchange messages to assist with channel sharing. For example, if a WAP sends a CTS to a node, then that node may transmit data. However, the addition of RTS and CTS exchange messages does create additional overhead; thus, RTS/CTS is limited on 802.11 networks.
If the wireless network is clear, the node may transmit data to the WAP or wireless router. The node waits a reasonable amount of time for an acknowledgement from the receiver before it attempts to retransmit. If the acknowledgement does not arrive in time, the wireless node will assume the data collided with another transmission. Therefore, the wireless node will attempt to retransmit. This is the gist of how CSMA/CA works. It’s not perfect, but it does assist with collision avoidance.
Wireless networks are protected by encrypting the data during transmission. There are several ways to encrypt wireless networks, such as WEP, WPA, and WPA2. Right now, most wireless networks are using WPA2.
“Wired Equivalent Privacy (WEP)” was created back in 1999, but was deprecated by the Wi-Fi Alliance after it was exposed by a serious vulnerability involving the resuse of keys. Since each Initialization Vector (IV) was only 24-bits in length, an attacker could capture already-used IVs. The important thing to remember here is that WEP is no longer secure. Since WEP uses a symmetric stream cipher (RC4), it’s extremely important to never reuse keys; otherwise, security is compromised. In modern times, it’s rare to see WEP-protected wireless networks, but they are still out there. There are many automated tools that crack these networks using specific WEP cracking attacks (e.g., fragmentation, Cafe-Latte, ChopChop, and so on).
When WEP was cracked in 2001, there was an immediate need for a new authentication scheme to keep wireless networks protected. IEEE 802.11i, or “Wi-Fi Protected Access (WPA),” was a suitable and temporary fix for WEP in the meantime until researchers could perfect it. WPA has two basic modes: WPA-PSK and WPA-Enterprise.
“WPA-PSK” stands for “WPA-Pre-Shared Key.” It’s also known as “WPA-Personal” because it’s used on personal, home Wi-Fi networks. WPA uses Rivest Cipher 4 (RC4) symmetric stream encryption with “Temporal Key Integrity Protocol (TKIP).” The addition of TKIP made WPA better at managing the encryption keys than WEP.
“WPA-Enterprise” uses 802.11x, which requires the use of EAP and a RADIUS server. This is often used in conjunction with centralized wireless controllers along with Lightweight Access Point Protocol (LWAPP) for easier management and configuration of access points. This form of network access control is very secure and expensive to implement; therefore, it is typically reserved for enterprise wireless networks.
This isn’t exactly an encryption mechanism, but is inherently a part of wireless security. In WPA networks, there used to be “Wi-Fi Protected Setup (WPS).” On a WAP or wireless router, there could be a WPS 6-digit pin burned into the software. All a wireless user had to do was type the WPS pin that was printed on the router or WAP into the device making the connection to the network and, voila, the device was now paired. There was also sometimes a WPS button on the router or AP itself. Users could press that button to turn on a temporary discovery period for new devices in the vicinity, which would then provide the user 60 seconds to pair the device to the network. WPS was proven inherently insecure 2011, and the Wi-Fi alliance has since then urged everyone to disable WPS.
WPA2 was developed in 2004 as replacement for WPA. It is currently the most secure wireless authentication standard and it also uses WPA-PSK and WPA-Enterprise modes.
The difference is that WPA2 uses stronger cryptography than WEP and WPA. Instead of TKIP and RC4, it uses the “Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP)” and it also allows for the use of the “Advanced Encryption Standard (AES).” According to the NSA, AES is one of the strongest encryption algorithms and it creates at least 128-bit keys.
When connecting a wireless client to a Wi-Fi network using WPA2-PSK, a password (or a Pre-Shared Key [PSK]) must be used for authentication. When authenticating clients onto a wireless network, the following terms are used:
- The Supplicant: This is the wireless device making the connection (e.g., you phone, laptop, desktop, tablet, etc.). The device is running Supplicant software that assists with connecting to the network.
- The AP or Authenticator: This is the Wireless Access Point (WAP), which is the same thing as an “Access Point (AP).” The AP is likely a wireless router. The AP is responsible for giving Supplicants access to the wireless or wired network.
When connecting a supplicant to an AP, a “Four-Way Handshake” takes place.
In Step 1, the AP sends an ANonce to the Supplicant. A “nonce” is a value that can only be used once and it will be used to create the Pairwise Transient Key (PTK). The “A” stands for “Authenticator.” The ANonce is also sent with a Key Replay Counter to help discard replayed messages.
In Step 2, the Supplicant constructs the PTK. In order to create the PTK, the supplicant uses its own SNonce (Supplicant nonce), the PMK, the ANonce from Step 1, it’s own MAC address, and the Authenticator’s MAC address (which it already knows since it’s being broadcasted via beaconing).
Therefore, PTK = PMK + ANonce + SNonce + Supplicant MAC address + Authenticator MAC address. This information is put through a psuedo-random function to create the PTK.
The Authenticator also needs the SNonce used by the Supplicant; therefore, it sends the SNonce in plaintext and uses HMAC-SHA1 as an authenticity check or Message Integrity Code (MIC). It also sends the Key Replay Counter back to the Authenticator.
In Step 3, the Authenticator acknowledges and verifies the message received from the Supplicant during Step 2 by checking the MIC. It then uses the SNonce and the other required parameters it already knows to create the same PTK. It notifies the Supplicant that the PTK is installed, creates a Groupwise Temporal Key (GTK), and sends it over to the Supplicant with another MIC. The GTK is used for broadcast and multicast frames on the network. All clients use this same GTK.
In Step 4, the Supplicant acknowledges and verifies the message received from the Authenticator in Step 3 by checking the MIC. It acknowledges that the PTK and GTK were installed, and from then on, encrypted unicast and broad/multicast traffic can commence. The PTK and GTK will be divided into separate keys depending on which encryption protocols are being used.
Summary of the WPA 4-Way Handshake
To summarize, the client and the AP have to prove they both know the PMK without ever passing it through the air. This is done by exchanging cryptographic keys in a cleverly designed process. The PTK is never actually passed between the client and the AP. Instead, it is derived from information that the client and the AP share. Every time a client associates with an AP, new keys are created. This makes every session completely unique from the next. The WPA 4-Way handshake is not encrypted until after step 4 is completed.
This does not prevent attackers from eavesdropping because it is very common to capture the WPA 4-Way handshake and analyze it in a .pcap file. However, because the PTK and the PMK are never transmitted, attackers have to take extra steps to make any use of it. For example, an attacker can generate his own key and use the ANonce, SNonce, MAC addresses, and MIC from any WPA handshake capture to verify if it matches. Thus, a brute force or dictionary attack is possible if the Wi-Fi password is weak.
WPA2’s Inevitable DownFall
Although WPA2 is the securest encryption in use, it is far from perfect. It too has its own disadvantages.
Other than brute force and dictionary attacks, Mathy Vanhoef of imec-DistriNet, KU Leuven, and his partners, recently discovered how to crack WPA2. They call it “Key Re-installation Attacks,” or “KRACK attacks,” for short. Although this wasn’t the first weakness discovered in WPA2, it is by far the most serious. The KRACK attack does not rely on password guessing and it works against all modern Wi-Fi networks. All Wi-Fi supported devices, including Android, Linux, Apple, Windows, OpenBSD, MediaTek, Linksys, and others, are all affected by some variant of the attack. The KRACK attack has 10 CVE identifiers, which you can see here. I covered KRACK attacks in an earlier post back in June.
WPA3 is on the Way
In June 2018, the Wi-Fi Alliance announced the long-awaited, next generation in Wi-Fi security, WPA3. After 15 years, WPA3 will now begin to replace the existing WPA2 protocol, which is currently used by billions of wireless devices every day.
Just like WPA2, the new WPA3 will also include WPA-PSK and WPA-Enterprise. However, WPA3 will include several new security features, including protection from brute force attacks and dictionary attacks. It will also include perfect forward secrecy, protection on Open wireless networks, improved encryption, and a new replacement for WPS, called “Wi-Fi Easy-Connect.”
All WAPs, wireless routers, and wireless NICs have antennas, either built-in or sticking out of them. These antennas are responsible for transmitting and receiving 802.11 frames. The type of antenna and its placement ultimately depends on the network administrator’s preference. There are a variety of different antennas that suit different functions. Here are a few notable antennas commonly used on wireless networks.
“Omni-Directional antennas” radiate outwards from the device in all directions. For that reason, this type of antenna typically serves as a main antenna on a WAP to distribute the signal to other wireless nodes.
The example shown here is clearly an additional antenna with more power than the default Rubber Duck antenna on the access point, which is also a type of omni-directional antenna.
“Dipole antennas” have two radiating elements that radiate out into a “donut” shape. They do not do much radiating above or below, which means the signal wont bleed onto other floors in the building. Below are some outdoor dipole antennas.
Interestingly, some of the rubber-ducky looking antenna that are seen on WAPs and wireless NICs are actually dipole antennas. They may look like omni-directional antennas, but they have two radiating elements inside the antenna.
“Parabolic antennas” are a type of unidirectional antenna. They typically contain a dish of some sort to catch or receive the radio signals from far away and reflect it onto the central point.
These antennas are often used for satellite communication.
The “Yagi antenna” is a unidirectional antenna developed in Japan. They too can be used to extend the range of 802.11 networks, such as point-to-multi-point connections that connect buildings together.
Yagi antennas can transmit super-focused radio waves miles away, hence they are often called “beam” antennas.
A “Back-fire antenna” is a smaller type of unidirectional antenna that look similar to the parabolic antennas.
These antennas are often used in point-to-point connections and targeting specific areas without overextending its reach.
Wi-Fi Will Be Around For A Long Time
Wireless development is far from over as we’ll see with WPA3. Likewise, there will be future technologies, such as IEEE 1901 and IEEE 1905.1 that will perhaps compete with standalone 802.11 networks, as we saw with IEEE 802.16 (WiMAX), or even complement them.
Lammle, T. (2016). CCNA: Routing and Switching. Complete Study Guide. John Wiley & Sons: Indianapolis, IN.
Meyers, M. (2015). All in One CompTIA Network+ Certification Exam N10-006. McGraw-Hill Education: New York, NY.
Parsi, N. (2012). WLAN most common terms. Retrieved from http://ilovewifi.blogspot.com/2012/07/wlan-most-common-terms.html