Latest Advance in 802.11. Siti Nurul ShatillaAbstract-802.11 or The IEEE 802.11 workgroup is most widely used in Wireless Local Area Network (WLAN) designations. The IEEE 802.11 designates a physical and medium access layers by using spread spectrum techniques. There are different sets of physical layers in IEEE 802.11 which generally known by a non capital identification letter, such as 802.11a, 802.11g, etc. Provide wireless network connectivity to itinerant users that used portable devices such as laptops, pda, etc.
Index Terms-IEEE 802.11, wifi, wireless
INTRODUCTION
Wireless local area network (LAN) connects users on a particular floor of building. Provide connections to nomadic users with the portable devices to access thw world wide web. WLAN had been standardized to spread the use of its applications among users. Most of them reduced on the unlicensed band. In order to regulate the unlicensed band, two dominant approaches were used: one is an interoperable rule among all equipment, and spectrum etiquette. [1]
The IEEE 802.11 Wireless LAN working group were establish in 1987.[2] This working group was for the standardization of spread spectrum WLAN for use in the Industrial Scientific and Medical (ISM) bands. The European Telecommunication Standards Institute (ETSI) has defined a wireless standard called HIPERLAN to provide 23.5 Mbps in the 5-Mhz band, and the Federal Communication Commission (FCC) allocated 2.4GHz for IEEE 802.11 a/b/g./n[1]
Table 1
IEEE 802.11 standards
Standards
Carrier
(Frequency)
Data
(Rates)
IEEE 802.11 b
2.4GHz
10 Mbps
IEEE 802.11 a
5.8 GHz
20 Mbps
IEEE 802.11 g
2.4 GHz
20 Mbps
IEEE 802.11 n
5.8 GHz
100 Mbps
This paper is organized as following; in section II we have a glimpse about the wireless standard system for IEEE-based. That is we look at general overview for IEEE 802.11. Then in section III we have the IEEE 802.11 systems. That is, we have an overall view of the standard IEEE 802.11. There is also a little bit about the WiFi Alliance, a brief about the latest 802.11n wireless LAN technology also the pros and cons between four general 802.11 b/a/g/n. In section IV, is about the working group standards in 802.11 the existing and latest development on 802.11. Finally the conclusion.
II. WIRELESS STANDARD SYSTEMS FOR IEEE-BASED
General view for IEEE-based
IEEE wireless standards use both unlicensed and licensed bands to provide the last mile connection to wireless nomadic users also mobility services. IEEE 802.11 wireless-related working groups2−3 and their respective frequency bands are indicated as (1) 802.11 Wireless Local Area Network (WLAN) operates at unlicensed band, 2.4 GHz (2.4 to 2.4825 GHz) and 5 GHz (5.15 to 5.35 and 5.47 to 5.825 GHz; (2) 802.15 Wireless Personal Area Network (WPAN) operates at unlicensed band, 2.4 GHZ; (3) 802.16 BroadbandWireless Access(BWA) operates at licensed and unlicensed bands, 10 to 66 GHz for LMDS and 2 to 11 GHz for MMDS; and (4) 802.16e extends 802.16 to operate below 6 GHz for mobility; initially focus three bands, on 2.5 GHz and 3.5 GHz licensed bands and 5.7 GHz U.S. unlicensed band. The comparison of IEEE-based wireless standards with 2G and 3G is shown in Fig. 1
Fig 1: IEEE-based wireless standard versus cellular standards
III. IEEE 802.11 SYSTEMS
A. Overall
As shown in Fig 2 802.11 WLAN also known as Wi-Fi, is consist of a series of specifications (802.11, 802.11b, 802.11g, 802.11a and 802.11n). The main objective is to accommodate wireless LAN services that are consistent with 802.3 Ethernet network. The 802.11 specifications hierarchy is shown in Fig 3. In fig 3 shows that IEEE 802.11b specification operates in the 2.4 GHz band and has maximum data rate of 11Mbps with range about 100 meters. 802.11 operates in unlicensed band that is divided into four bands which supports up to 54Mbps. Dynamic Frequency Selection (DFS) and Transmit Power Control (TPC) are required among these four bands mentioned above.
Fig. 2: The IEEE wireless standards
802.11g operates in 2.4GHz band and can have backward compatibility with 802.11b. 802.11g can transmits up to 1 and 2 Mbps by using Barker codes and 5.5 and 11 Mbps using Complementary Code Keying (CCK).[3] For higher data rate, can use the Orthogonal Frequency Division Multiplexing (OFDM) for 6, 9, 12, 18, 24, 36, 47, and 54 Mbps.
The latest IEEE standard, that is 802.11n can handle data rate in excess of 100Mbps [4] will be referred to 802.11n High Throughput (HT). The physical layer is OFDM including advanced antenna techniques. It is the improvement for 802.11g in terms of the amount bandwidth supported by utilizing multiple wireless signal and antennas (called Multiple In Multiple Out or MIMO technology) instead of one.[5]. These 802.11a, 802.11b, 802.11g and 802.11n are known as Wi-Fi technologies which will be explain later.
There are four different physical layers for four different transmission technologies that supported the 802.11 standards. There are Infrared(IR), Frequency Hopping Spread Spectrum (FHSS), Direct Sequence Spread Spectrum (DSSS), and OFDM. 802.11g are a recent expansion of 802.11b uses OFDM, 802.11a uses OFDM and 802.11b uses DSSS.
Fig. 3: 802.11 specifications hierarchy. (IAPP: interaccess point protocol)
B. Physical Layers and Available Bandwidth For Specific Systems (802.11 b/a/g)
802.11 is consist of several alternative physical layers (802.11 b/a/g/n) (shown in Fig. 4)
Fig. 4: Comparison of all 802.11 standards
1. 802.11 b/g
The available bandwidth for 802.11b and g is 83.5MHz shown in Fig. 5. Both b and g supports 14 overlappng channels. For 802.11a, there is 300MHz bandwidth available and up to 12 channel are available.
Fig. 5: Available bandwidth and channels for 802.11.
C. Wi-Fi
The Wi-Fi (Wireless Fidelity) Alliance [6] is a nonprofit international association formed in 1999 to certify interoperability of wireless Local Area Network products based on IEEE 802.11 specifications. Currently the WiFi Alliance has over 300 members companies from around the world, and over 6000 products certifications have been done since it began in March 2000.
New wireless standards are constantly being introduced. This includes 802.11, 802.11a, 802.11b, 802.11g, 802.1X, WPA, WPA2, 802.11i, 802.11n, etcetera. The major standards bodies introducing these WLAN standards are the IEEE, the Wi-Fi Alliance (formerly WECA), and the IETF. Working in concert with the IEEE, the Wi-Fi Alliance is concerned with
the practical implementation of IEEE WLAN standards, which was managed through an interoperability testing and certification process for vendor hardware solutions. The current certification includes WMM (Wi-Fi Multi Media), WPA2 (Wi-Fi Protected Access 2), 11g, 11d, and 11a. The Wi-Fi Process flow is shown in Fig. 6.
.
Fig. 6: Wi-Fi Certification flows
In order to produce secure, fast wireless connectivity and security Wi-Fi networks use radio technologies called 802.11. In the mid-1990s, working together with IEEE to developed industry standards and out of that cooperation, the Wi-Fi Alliance was born and has taken those standards and developed test labs around the world to test and certify that products meet the standards of interoperability and security.
Wi-Fi products are identified as 802.11, and are then further identified by a lower case letter that identifies which specific technology is in operation, such as 802.11g. Each certification set is defined by a set of features that relate to frequency, bandwidth and performance. Each generation also furthers security enhancements and may include other features that manufacturers may decide to implement.
Table 2
Wi-Fi Generation
Wi-Fi Technology
Frequency Band
Bandwidth
802.11a
5GHz
54 Mbps
802.11b
2.4GHz
11 Mbps
802.11g
2.4GHz
54 Mbps
802.11n
2.4GHz, 5GHz,
2.4 or 5 GHz (selectable),or
2.4 and 5 GHz (concurrent)
450 Mbps
Previous generation of Wi-Fi products that operate in the same frequency band will work with the tested Wi-Fi CERTIFIED products.
This Wi-Fi Alliance has 13 independent test labs in North America, Europe, Taiwan, Japan, Spain, Korea, Germany, China and India conduct the testing. This is to certify that the member products of Wi-Fi Alliance is interoperability with each other in Wi-Fi Certified.
Current Wi-Fi labs include:
1. Agilent Lab http://www.agilentcsg.timetrade.com in San Jose, CA; Melbourne, FL;
Taipei, Taiwan; Tokyo, Japan; Edinburgh, UK.
2. ADT Lab http://www.adt.com.tw in Taoyuan, Taiwan.
3. CETECOM Lab http://www.cetecom.es/web/en/pag/0.htm in Malaga, Spain.
4. NSTL Lab http://edata.nstl.com.tw/wifi main.htm Labs located in Taipei, Taiwan, Blue
Bell, Pennsylvania.
5. SGS Lab http://www.sgs.com/ in Taipei, Taiwan; Yokohama, Japan; Seoul, Korea.
6. TUV Lab http://www.us.tuv.com/product testing/wifi/index.html in Cologne, Germany;
Yokohama, Japan; Pleasanton, CA.
D. 802.11n IEEE Wi-Fi
Latest standard in the Wi-Fi that already made into the general market is the 802.11n. It was made to improve network throughput and also the reliability over previous standards a/b/g. Theoretically the 802.11n standard can operate at bandwidths up to 600 Mbit/s due to the TCP/IP protocol. It was create to enhance the performance as compared to the 802.11g standard. This is due to the multiple wireless signals and antennas instead of one. (Spatial multiplexing and antenna diversity) and channel bonding that is bonding two communication layers.
Utilizing multiple wireless signals and antennas is known as MIMO. In multipath signal, signal travels from the wireless access point to the wireless client and get reflected from windows, walls, and other objects. The MIMO technology uses the multipath signal variations to increase a receiver ability to recover the message information from the signal. Meanwhile channel-bonding in the 802.11 n significantly increase the amount of data that can be transmitted.
802.11n standard is the evolution in its concepts and better in all aspects. Produce much better bandwidth and less prone to interference. Its equipment should be backward compatible with older 802.11g devices.[7]
E. Advantages and Disadvantages between 802.11b/a/g/n
Table 3
802.11b
802.11a
802.11g
802.11n
Advantages
Posseses the lowest cost;signal range is good and not easily block
Fast maximum speed; regulated frequencies prevent signal interferences from other devices
Fast maximum speed; signal range is better and not easily interfere
Fast maximum speed and have the best signal range; more resistant to signal interference from outside sources
Disadvantages
Slowest maximum speed; home appliances may interfere on the unregulated frequency band
Highest cost; shorter range signal that is more easily obstructed
Cost more than 802.11b; appliance may interfere on the unregulated signal frequency
Cost more than 802.11b/g based networks.
IV. IEEE 802.11 WORKING GROUP STANDARDS ASIDE FROM 802.11 a/b/g/n
Nevertheless, there are also others related to this 802.11 technologies exist which there are the derivations of this Wi-Fi technologies for specific purpose. Listed below are the existing IEEE 802.11 standards exist or are in development to help or to enhance the creation of technologies for wireless local area networking based on the Official IEEE 802.11 Working Group Project Timelines -16 September 2010 [8],[9] :
Table 4
IEEE 802.11 Standard exist/in development
IEEE802.11 Standards
Description or Project Authorization Request
802.11c
Media Access Control(MAC) Bridges- Supplement that Support by IEEE 802.11
802.11d
Operation in additional regulatory. Worldwide compliance together with regulation for use of wireless signal spectrum in the year of 2001
802.11e
Support for the Quality of Service (but not yet rectified)
802.11F
The Inter-Access Point Protocol references for communication between access points to support roaming client in the year 2003,but suspended or withdrawn
802.11h
This is enhanced version of 802.11a to support the European regulatory requirements (2003).
802.11i
security advance for the 802.11 family (2004)
802.11j
enhancements to 5 GHz signaling to support Japan regulatory requirements (2004)
802.11k
Wireless LAN system management-this is in progress
802.11l
Was ignore to prevent confusion with the 802.11i
802.11m
upkeep of 802.11 family documentation
802.11p
Wireless Access for the Vehicular Environment
802.11r
fast roaming support via Basic Service Set transitions
802.11s
ESS mesh networking for access points
802.11T
Wireless Performance Prediction - reference for testing standards and metrics
802.11u
internetworking with 3G / cellular and other forms of external networks
802.11v
wireless network management / device configuration
802.11w
security enhancement for Protected Management Frames
802.11y
Contention Based Protocol for interference avoidance
V. CONCLUSION
802.11 has been developed rapidly and standardized; IEEE 802.11. Like most, technology advance in IEEE 802.11 occur mainly through a process of steady evolution. Therefore a good understanding of this system requires an understanding of what has come before.
