About IEEE Wireless Networks
802.11 Based Wireless Network
IEEE 802.11 has become the de-factor standard for wireless networking. The aim of the report is to present information about the IEEE 802.11 wireless networks. In the following sections of the report, different wireless networks belonging to the class of the IEE 802.11 have been discussed. It covers the major IEEE 802.11 amendments and updates, standards etc. along with discussion WiFi technology and many other aspects of the IEEE 802.11. There are many amendments of IEEE 802.11, all are not equally important and some have become obsolete. Those have been omitted.
IEEE 802.11 basically refers to a set of wireless data communication standards for wireless LANs or WLANs. There are many wireless networks based on the standard and it has become the de facto standard class for WLANs. The technology behind IEEE 802.11 is called Wi-Fi. It is managed and overseen by the IEEE or Institute of Electrical and Electronics Engineers 802 or IEEE LAN/MAN Standards Committee.
IEEE 802.11 contains a set of physical layer or PHY and medium access control or MAC layer specifications to implement wireless local area networks having communication with the frequency bands, 900 MHz, 2.4 GHz, 3.6 GHZ, 5 GHz, and 60 GHz. IEEE 802.11 forms the class of the most widely used wireless computer networking standards those are used at homes and offices and covers a wide array of devices like computers, laptops, printers, tablets, smartphones and smart objects used for PAN or personal area networks. It also support IoT or Internet of Things and M2M of Machine to Machine communication by allowing the devices to communicate with one another without any human intervention.
In 1997, the base version of the IEEE 802.11 was released. Then there were many subsequent amendments. These amendments along with the standard provides the basic building block of the wireless networking products and services that use the Wi Fi communication system. Currently, there is the only one standard, IEEE 802.11-2007 and many amendments. These amendments are for different types of wireless networks. Some examples of the amendments are, 802.11a, 802.11b, 802.11g, and 802.11n
The family of IEEE 802.11 includes a range of half duplex communication channels and over the air modulation techniques using the basic protocol IEEE 802.11- 1997. It was the first wireless networking standards added to the family of the IEEE 802.11 and was named as IEEE 802.11b. It was widely accepted and later on amendments released as IEEE 802.11a, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac. There are many other standards and service amendments. These are used for extending the scope of the existing standards or some correction over some previous standard.
The IEEE 802.11b and IEEE 802.11g uses 2.4 GHz ISM band and it is under operation in the United States under the federal rules and regulations. Because of the choice of the frequency band, IEEE 802.11b suffered from interference coming from Bluetooth devices, microwave oven, cordless telephones, and so on. Then IEEE 802.11b and IEEE 802.11g were updated to control the susceptibility to interference and interferences depending on the DSSS or Direct Sequence Spread Spectrum along with OFDM or Orthogonal Frequency Division Multiplexing signaling methods respectively. IEEE 802.11a uses the 5GHz frequency band with at least 23 non-overlapping channels compared to the 3 non-over lapping channels offered by the 2.4 GHz ISM frequency band. Depending on different environmental criteria. IEEE 802.11n uses any one of the 2.5 Ghz or the 5 GHz band. On the other hand, IEEE 802.11ac uses the 5GHz band.
Based on different countries, the spectrum and segment of radio frequency varies in different countries. For example, the operating license for the frequency for IEEE 802.11g is different from the same operating in the UK and so on.
Legacy System: IEEE 802.11
The IEEE 802.11- 1997 or the IEEE 802.11- 1999 are identified as the legacy IEEE 802.11 systems that operate on the initial standards of wireless networking that was released in 1997 and was clarified in details in 1999. These are rarely used these days (Gast 2011).
It used to work on the 1 to 2 Mbps data rate. Data were transferred via IR or Infrared signals using either DSSS or frequency hopping technique at the frequency band of 2.4 GHz. It used to use the CSMA/CA or carrier sense multiple access with collision avoidance technique for channel management. it led to the sacrifice of a significant amount of the channel capacity to make the data transmission more reliable under adverse and diverse environmental conditions (Gast 2011).
IEEE 802.11b is an amendment on the legacy IEEE 802.11 specifications of wireless networking. It gives the throughput of the 11 Mbps using the same 2.4 GHz frequency band. It supports and controls various data transmission methods in wireless networking. These are commonly recognised as IEEE 802.11a, IEEE 802.11g, IEEE 802.11n and IEEE 802.11ac. These are used to provide seamless wireless networking connectivity at home and offices (O'Hara & Petrick 2011).
It supports the CSMA/CA medium access protocol as defined in the actual protocol standard. But there is an overhead due to the use of the CSMA protocol. That reduces the throughput. On TCP protocol it gives 5.9 Mbps and using UDP, it gives 7.1 Mbps instead of 11 Mbps (Gast 2011).
The first mainstream computer that was sold with the support of IEEE 802.11b, was Apple iBook. Technically, the IEEE 802.11 standards uses the CCK or Complementary Code Keying technique for modulation. It helps to increase the throughput significantly. It also helped to reduce the price. And it became the first IEEE 802.11 standard to be used for the wireless LAN technologies around the globe (O'Hara & Petrick 2011).
However, the devices supported by the IEEE 802.11b, also suffers from the interference issues coming from other devices working with the 2.4 GHz band, prominently the microwave devices and the Bluetooth devices.
IEEE 802.11b supports P2P or Point to point configurations. An access point communicates with another mobile device by using an omnidirectional antenna connected to mobile clients belonging to the coverage area of the access point. The range of an access point depends on the environment, sensitivity of the receiver, and output power.
IEEE 802.11g was the amendment made on the IEEE 802.11 in 2003. The specification added to this amendment made the throughput much higher. The data rate became 54Mbps using the same frequency band like IEEE 802.11b. Under the name of WiFi, the specification implemented globally. IEEE 802.11g has become the clause 19 in the current version of IEEE 802.11-2007.
IEEE 802.11g is the 3rd modulation standard for the WLNAs. It uses CSMA/CA based data transmission scheme. The maximum throughput possible for it is 54 Mbps for a data packet of 1500 bytes. Smaller packets offer lesser throughput (O'Hara & Petrick 2011).
The hardware supported by the IEEE 802.11g is also backward compatible with IEEE 802.11b hardware. It helps to make IEEE 802.11b and IEEE 802.11g work together seamlessly. IEEE 802.11g uses OFDM or orthogonal frequency-division multiplexing that offers data rates ranging between 6 Mbps to 54Mbps. It also supports DSSS, DBPSK, and DQPSK schemes (Tsao & Huang 2011).
IEEE 802.11n is the amendment made to the IEEE 802.11-2007 in 2009. In this specification, it added the support to use multiple antennas to improve the data rates from the previous amendments. It is also referred as MIMO or Multiple Input Multiple Output. The primary purpose of the amendment was to improve the maximum net data rate from 54 Mbps to 600 Mbps. However, the implementation of error detection schemes lowers the data rate slightly. It uses four spatial streams of data with a 40 MHz channel (Geier 2015). It also offers frame aggregation, data encoding services and many security improvements. It operates within the frequency range from 2.4GHz to 5GHz.
In the MIMO technology, multiple antennas are coherently used for resolving more information than it was possible to resolve with a single antenna. It can be achieved by using SDM or Spatial Division Multiplexing. In SDM, multiple independent data streams are multiplexed simultaneously within a single and higher bandwidth based spectral channel. MIMO SDM is used to improve the throughput significantly. Each of the spatial data stream takes on antenna for data reception and transmission. It also requires a separate chain of radio frequency and an AD or Analog to Digital converter. Hence, it is expensive to implement.
Precoding and postcoding techniques are used by the transmitter and receiver respectively in order to get the capacity of a MIMO link. Precoding does special coding and spatial beamforming. Spatial coding improves the data throughput by using spatial multiplexing, uses spatial diversity to increase the range and by using other techniques like Alamouti coding (Geier 2015). On the other hand, spatial beamforming helps in improving the quality of some received signal during the decoding stage.
Number of Antennas
The total number of simultaneous data streams must be limited by the minimum number of antennas operating on both sides of a communication link. Individual radios are also another limiting factor.
An IEEE 802.11n network can reach up to the 72 Mbps data rate over a single 20 MHz channel having one antenna and the guard interval is 1ns. With more antennas and different favorable conditions, it can reach up to 600 Mbps. The standard defines multiple coding rates and modulation schemes. These are represented by using an index called MCS or Modulation and Coding Scheme (Geier 2015).
There is a mismatch between the data rates offered by the PHY level and the user level. Because some of the throughout is wasted due to overhead from protocols, contention process, headers, interframe spacing and for sending and receiving ACK frames. Aggregation is a primary feature of MAC layer. It offers improvement of performance of wireless networks implemented based on the standards. There are two types of frame aggregation. Those are (Tsao & Huang 2011),
- Aggregation of the service data units of MAC
- Aggregation of protocol data units of MAC.
Frame aggregation is a process to pack multiple service and/or protocol data units together. It reduces the overhead and increases the data rate.
It is compatible with IEEE 802.11a, IEEE 802.11b and IEEE 802.11g. It follows various levels of protection such as,
- PHY level protection in mixed mode format
- MAC level protection based on CTS/RTS exchange
- PHY level protection in CTS format
IEEE 802.11ac is popular in the name of Gigabit WiFi. It facilitates high definition video streaming simultaneously to multiple users for home and business wireless networks. It offers faster wireless network synchronisation and in taking backup of large files. The specification supports data transfer rate up to 433 Mbps for each spatial stream and up to 1.3 Gbps per with three antennas and three data streams. It is also called as 5G Wifi because it operates on 5 GHz frequency band only. This band currently has very less chances of interference (Ong et al. 2011). Compares to IEEE 802.11n, that operates at a frequency range between 2.5 GHz to 5GHz, IEEE 802.11ac operates only on 5GHz.
IEEE 802.11ac is also backward compatible with the IEEE 802.11b, IEEE 802.11g, and IEEE 802.11n.
Beamforming is an important part of the IEEE 802.11ac specifications. It does not throw spatial signals in all directions, rather it detects the location of the devices and sends intense signals to the directions of the devices only (Ong et al. 2011).
Wi Fi technology is used with IEEE 802.11 networks for wireless local area networking. The devices must comply with the IEEE 802.11 standards to implement the WiFi technology. The WiFi alliance is the committee that controls and monitor the usage and implementation of the WiFi technology. WiFi is the trademark of it. It is used to understand the interoperability and compliance of the devices that supports WiFi. The devices that are compatible with the WiFi technology, can use WLANs working on the IEEE 802.11 standards to get connected to a wireless network access point and eventually can access the Internet. Hotspots operate within a range upto 20 meters indoor and longer range outdoor. However, the coverage can be restricted by various factors, like walls that blocks radio waves, or longer distance and so on. There can be overlapping access points to extend the coverage of WiFi ranges. WiFi signals work good on line-of-sight and with lesser interferences. However, under favourable circumstances, it can work upto data rate of 1 Gbps.
WiFi is very much vulnerable to Eavesdropping attacks when compared to the wired networks. There is a WiFi technology family built to protect the user’s information. WiFi is also used to create mobile hotspots to share the mobile network with others through wireless LAN connectivity.
QoS in IEEE 802.11 Networks
IEEE 802.11e address the issues with the QoS in IEEE 802.11 networks. WiFi technology is the core to the IEEE 802.11 networks. There are issues like slowing down the network connectivity and data rate, small delays in communication are common for the IEEE 802.11 networks. For normal data usage, that may not be a problem, however, on a large scale, such delays may lead to losses for businesses. Hence, the QoS implementation is required to ensure the quality of the services offered by the IEEE 802.11 networks (Roebuck 2011).
IEEE 802.11e enhances the specifications of the IEEE 802.11b networks. The QoS features are applicable to prioritizing the data, voice, and video transmission. It enhances the MAC layer by coordinating it with TDM or Time Division Multiple accesses construction and error correction mechanism for applications sensitive to delays (Tsao & Huang 2011).
Backward compatibility is offered with the point coordination and distributed coordination functions. These functions are known as HCF or Hybrid Coordination Function and EDCF or Enhanced Distribution Coordination Function. The access stations working under IEEE 802.11e are known as enhanced stations. These can work either as centralized controller for rest of the stations or these can work as hybrid coordinators (Roebuck 2011). The hybrid coordination function provides deterministic access to channels and policies using hybrid coordinators. The HCF model gives guaranteed services that have higher probability. Admission control is done using a signaling protocol with service rate requirement specification.
Advantages of IEEE 802.11
There are several benefits of the IEEE 802.11. These are,
- It is widely accepted, so it is easy to install and implement
- It offers higher range of frequencies for wireless LANs to operate
- It contains specifications for various coding techniques for data encoding (Roebuck 2011)
- It is cost effective
- It allows simultaneous use of different devices.
Disadvantages of IEEE 802.11
- There are interference issues
- There are network security issues with IEEE 802.11 based WLANs
- It needs high maintenance
- Prone to attacks like frame spoofing, session hijacking and unauthorized use.
The growth of IoT networks are highly supported by the IEEE 802.11 standards. There is another dedicated standard IEEE P2413, for the architectural framework of IoT. It helps to form working IoT groups based on the IoT architecture meeting various verticals. In future, more amendments can be made on the IEEE 802.11 standards to make it more secure and more suitable for IoT networks and personal area networks or PANs (Xiao & Pan 2012).
IEEE 802.11 standards have gained popularity for the emergence of wireless local area networks or WLANs. In recent years, these networks have offered more ease of use, flexibility and mobility. It has also reduced the cost of implementation, installation, and maintenance. The result is massive adaption of WLANs for business and personal usage.
In geographically limited areas, where it is not possible to offer wired LAN services, WLANs has become the saviours. The emergence of mobile networks and mobile WiFi hotspot based services have extended the reach of communication networks to remote places. In future, IEEE 802.11 must focus on making amendments that will support IoT and will focus on improving user experience.
The report covers detailed discussion on the IEEE 802.11 networks. It covers major networks and amendments. It also covers WiFi technology, advantages and disadvantages of IEEE 802.11 and its future perspectives. Readers will be able to understand what IEEE 802.11 is and how it has changed the domain of wireless LANs.
IEEE 802.11 has become the default standard for wireless local area networks. Starting from the basic IEEE 802.11a standard there have been number of amendments. Each amendment contains specifications to improve performance and quality of the services provides by the previous versions of the standards. Some of the amendment are backward compatible and seamlessly work with other standards previously implemented.
IEEE 802.11n not only improves bit rate but it also offers various techniques to improve the quality of services, like frame aggregation, data encoding and so on. IEEE 802.11ac or the gigabit network is suitable for large file transfer and HD streaming over the networks and over the wireless LANs. Currently, it’s being used in most of the devices and for different applications. It works on the 5GHz band and suffers from lesser interferences.
WiFi is the technology that helps to implement IEEE 802.11 standards. It is not any standard. It is the trademark to ensure that the devices are using the WiFi technology and comply with the IEEE 802.11 standard. There are various advantages like cost effectiveness, easy to implement, widespread acceptance of the standards and so on. However, there are issues like security issues, like frame spoofing, session hijacking etc.
In future, IoT can grow substantially and that will require more amendment to cater the requirements of the IoT networks. Other than that, it needs to improve the quality of services and must focus on improving user experience.