Mobile Adhoc Networks
- Wi-Fi
IEEE 802.11, the Wi-Fi standard, denotes a set of Wireless LAN/WLAN standards developed by working group 11 of the IEEE LAN/MAN Standards Committee (IEEE 802). wireless fidelity(IEEE 802.11) is a family of 802.11b, 802.11a, 802.11g etc. The term is promulgated by the Wi-Fi Alliance.
The term 802.11x is also used to denote this set of standards and is not to be mistaken for any one of its elements. There is no single 802.11x standard. The term IEEE 802.11 is also used to refer to the original 802.11.
Protocols
Protocol / Release Date / Op. Frequency / Data Rate (Typ) / Data Rate (Max) / Range (Indoor)802.11a / 1999 / 5.15-5.35/5.47-5.725/5.725-5.875 GHz / 25 Mbit/s / 54 Mbit/s / ~30 meters
802.11b / 1999 / 2.4-2.5 GHz / 6.5 Mbit/s / 11 Mbit/s / ~100 meters
802.11g / 2003 / 2.4-2.5 GHz / 25 Mbit/s / 54 Mbit/s / ~30 meters
802.11n / 2006 / 2.4 GHz or 5 GHz / 200 Mbit / 540 Mbit/ / ~50 meters
802.11 legacy
The original version of the standard IEEE 802.11 released in 1997 specifies two raw data rates of 1 and 2 megabits per second (Mbit/s) to be transmitted via infrared (IR) signals or by either Frequency hopping or Direct-sequence spread spectrum in the Industrial Scientific Medical frequency band at 2.4 GHz. IR remains a part of the standard but has no actual implementations.
The original standard also defines Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) as the medium access method. A significant percentage of the available raw channel capacity is sacrificed (via the CSMA/CA mechanisms) in order to improve the reliability of data transmissions under diverse and adverse environmental conditions.
Standards
802.11a
Release Date / Op. Frequency / Data Rate (Typ) / Data Rate (Max) / Range (Indoor)1999 / 5 GHz / 25 Mbit/s / 54 Mbit/s / ~30 meters
The 802.11a standard uses the same core protocol as the original standard, operates in 5 GHz band, and uses a 52-subcarrier orthogonal frequency-division multiplexing (OFDM) with a maximum raw data rate of 54 Mbit/s, which yields realistic net achievable throughput in the mid-20 Mbit/s. Since the 2.4 GHz band is heavily used, using the 5 GHz band gives 802.11a the advantage of less interference. However, this high carrier frequency also brings disadvantages. It restricts the use of 802.11a to almost line of sight, necessitating the use of more access points; it also means that 802.11a cannot penetrate as far as 802.11b since it is absorbed more readily, other things (such as power) being equal.
802.11b
Release Date / Op. Frequency / Data Rate (Typ) / Data Rate (Max) / Range (Indoor)1999 / 2.4 GHz / 6.5 Mbit/s / 11 Mbit/s / ~50 meters
802.11b has a maximum raw data rate of 11 Mbit/s and uses the same CSMA/CA media access method defined in the original standard. Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s using TCP and 7.1 Mbit/s using UDP.
802.11b is usually used in a point-to-multipoint configuration, wherein an access point communicates via an omni-directional antenna with one or more clients that are located in a coverage area around the access point. Typical indoor range is 30 m (100 ft) at 11 Mbit/s and 90 m (300 ft) at 1 Mbit/s. With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to 8 kilometers (5 miles) although some report success at ranges up to 80–120 km (50–75 miles) where line of sight can be established. This is usually done in place of costly leased lines or very cumbersome microwave communications equipment. Designers of such installations who wish to remain within the law must however be careful about legal limitations on effective radiated power.
802.11g
Release Date / Op. Frequency / Data Rate (Typ) / Data Rate (Max) / Range (Indoor)June 2003 / 2.4 GHz / 25 Mbit/s / 54 Mbit/s / ~30 meters
802.11g. This flavor works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s, or about 24.7 Mbit/s net throughput (like 802.11a). 802.11g hardware work with 802.11b hardware. Details of making b and g work well
together occupied much of the lingering technical process. In older networks, however, the presence of an 802.11b participant significantly reduces the speed of an 802.11g network. Even though 802.11g operates in the same frequency band as 802.11b, it can achieve higher data rates because of its similarities to 802.11a. The maximum range of 802.11g devices is slightly greater than that of 802.11b devices, but the range in which a client can achieve full (54 Mbit/s) data rate speed is much shorter than that of 802.11b.
802.11n
Release Date / Op. Frequency / Data Rate (Typ) / Data Rate (Max) / Range (Indoor)December 2006 (draft) / 2.4 GHz or 5 GHz / 200 Mbit/s / 540 Mbit/s / ~50 meters (~165 ft)
In January 2004 IEEE announced that it had formed a new 802.11 Task Group (TGn) to develop a new amendment to the 802.11 standard for wireless local-area networks. The real data throughput is estimated to reach a theoretical 540 Mbit/s (which may require an even higher raw data rate at the physical layer), and should be up to 50 times faster than 802.11b, and up to 10 times faster than 802.11a or 802.11g.
Certification
Because the IEEE only sets specifications but does not test equipment for compliance with them, a trade group called the Wi-Fi Alliance runs a certification program that members pay to participate in. Virtually all companies selling 802.11 equipment are members. The Wi-Fi trademark, owned by the group and usable only on compliant equipment, is intended to guarantee interoperability.
Wi-MAX
WiMAX is defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum, to promote conformance and interoperability of the IEEE 802.16 standard, officially known as WirelessMAN. The Forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".
Advantages over Wi-Fi
- The WiMAX specification provides symmetrical bandwidth over many kilometers and range with stronger encryption (3DES or AES) and typically less interference. Wi-Fi is short range (approximately 10's of meters) has WEP or WPA encryption and suffers from interference as in metropolitan areas where there are many users.
- Wi-Fi Hotspots are typically backhauled over ADSL in most coffee shops therefore Wi-Fi access is typically highly contended and has poor upload speeds between the router and the internet.
- It provides connectivity between network endpoints without the need for direct line of sight in favorable circumstances. The non-line-of-sight propagation (NLOS) performance requires the .16d or .16e revisions, since the lower frequencies are needed. It relies upon multi-path signals, somewhat in the manner of 802.11n.
Technical info
WiMAX is another name of IEEE 802.16 wireless networks, in a rather similar way to Wi-Fi being interoperable implementations of the IEEE 802.11 Wireless LAN standard.
MAC layer
In Wi-Fi the media access controller (MAC) uses contention access in which all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis.
Physical layer
The original WiMAX standard (IEEE 802.16) specified WiMAX for the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004 (also known as 802.16d), added specification for the 2 to 11 GHz range. 802.16d (also known as "fixed WiMAX") was updated to 802.16e in 2005 (known as "mobile WiMAX"). and uses scalable orthogonal frequency-division multiplexing (OFDM) as opposed to the OFDM version with 256 sub-carriers used in 802.16d
Standards
IEEE 802.16e
IEEE 802.16e (Mobile WiMAX) provides an improvement on the modulation schemes stipulated in the original WiMAX standard.
- IEEE 802.16d
On the other hand, 802.16 (fixed WiMAX) offers the benefit of available commercial products and implementations optimized for fixed access. Fixed WiMAX is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment.
Associations
WiMAX Forum
he WiMAX Forum is "the exclusive organization dedicated to certifying the interoperability of its products, the WiMAX Forum defines and conducts conformance and interoperability testing to ensure that different vendor systems work seamlessly with one another."
WiMAX Spectrum Owners Alliance - WiSOA
WiSOA is the first global organization composed exclusively of owners of WiMAX spectrum. WiSOA is focussed on the regulation, commercialisation, and deployment of WiMAX spectrum in the 2.3–2.5 GHz and the 3.4–3.5 GHz ranges.
APPLICATIONS
- Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
- Providing a wireless alternative to cable and DSL for last mile (last km) broadband access.
- Providing high-speed mobile data and telecommunications services (4G).
- Providing a diverse source of Internet connectivity as part of a business continuity plan. Providing Nomadic connectivity.
- Comparison
Comparison of Mobile Internet Access methods
Standard / Family / Primary Use / Radio Tech / Downlink (Mbps) / Uplink (Mbps) / Notes
802.16e / WiMAX / Mobile Internet / SOFDMA / 70 / 70 / Quoted speeds only achievable at very short ranges, more practically 10Mbps at 10Km.
WiBro / WiBro / MobileInternet / OFDM / 50 / 50 / Short range (<500m)
iBurst / iBurst 802.20 / MobileInternet / HC-SDMA / 64 / 64 / 3-12 km
UMTS W-CDMA
HSDPA+HSUPA / UMTS/3GSM / Mobile phone / CDMA/FDD / .384
3.6 / .384
5.76 / HSDPA downlink widely deployed. Roadmap shows HSDPA up to 28.8Mbps downstream in the future.
Competing technologies
Within the marketplace, WiMAX's main competition comes from widely deployed wireless systems with overlapping functionality such as UMTS and CDMA2000.
- Bluetooth
Bluetooth is an industrial specification for wireless personal area networks (PANs). Bluetooth provides a way to connect and exchange information between devices such as mobile phones, laptops, PCs, printers, digital cameras and video game consoles .
Technical information
Communication & connection
A Bluetooth device playing the role of the "master" can communicate with up to 7 devices playing the role of the "slave". This network "group of up to 8 devices" (1 master and 7 slaves) is called a piconet. A piconet is an ad-hoc computer network of devices using Bluetooth technology protocols to allow one master device to interconnect with up to seven active slave devices . Up to 255 further slave devices can be inactive, or parked, which the master device can bring into active status at any time.
Setting up connections
Any Bluetooth device will transmit the following sets of information on demand:
- Device Name
- Device Class
- List of services
Air interface
The protocol operates in the license-free ISM band at 2.45 GHz. In order to avoid interfering with other protocols which use the 2.45 GHz band, the Bluetooth protocol divides the band into 79 channels (each 1 MHz wide) and changes channels up to 1600 times per second. Implementations with versions 1.1 and 1.2 reach speeds of 723.1 kbit/s. Version 2.0 implementations feature Bluetooth Enhanced Data Rate (EDR), and thus reach 2.1 Mbit/s. Technically version 2.0 devices have a higher power consumption, but the three times faster rate reduces the transmission times, effectively reducing consumption to half that of 1.x devices (assuming equal traffic load).
Security
Bluetooth uses the SAFER+ algorithm for authentication and key generation. The initialisation key and master key are generated using the E22 algorithm. The E0 stream cipher is used for encrypting packets. This makes eavesdropping on Bluetooth-enabled devices more difficult.
Specifications and Features
Bluetooth is also known as IEEE 802.15.1.
Bluetooth 1.0 and 1.0B
Versions 1.0 and 1.0B had many problems and the various manufacturers had great difficulties in making their products interoperable.
Bluetooth 1.1
- Many errors found in the 1.0B specifications were fixed.
- Added support for non-encrypted channels.
- Received Signal Strength Indicator (RSSI)
Bluetooth 1.2
- Adaptive Frequency-hopping spread spectrum (AFH), which improves resistance to radio frequency interference by avoiding the use of crowded frequencies in the hopping sequence
- Higher transmission speeds in practice
- Host Controller Interface (HCI) support for 3-wire UART
- HCI access to timing information for Bluetooth applications
Bluetooth 2.0
- 3 times faster transmission speed—up to 10 times in certain cases (up to 2.1 Mbit/s).
- 100 meter range (Depends on the class of the device)
- Lower power consumption through a reduced duty cycle.
Uses
A typical Bluetooth mobile phoneheadset A typical Bluetooth USB adapter
Bluetooth is a radio standard and communications protocol primarily designed for low power consumption, with a short range (power class dependent: 1 metre, 10 metres, 100 metres) based around low-cost transceivermicrochips in each device.
Class / Maximum Permitted Power(mW) / Maximum Permitted Power
(dBm) / Range
(approximate)
Class 1 / 100mW / 20dBm / ~100 meters
Class 2 / 2.5mW / 4dBm / ~10 meters
Class 3 / 1mW / 0dBm / ~1 meter
Applications
- Wireless control of and communication between a cell phone and a hands freeheadset or car kit. This was one of the earliest applications to become popular.
- Wireless networking between PCs in a confined space and where little bandwidth is required.
- Wireless communications with PC input and output devices, the most common being the mouse, keyboard and printer.
- Transfer of files between devices via OBEX.
- Transfer of contact details, calendar appointments, and reminders between devices via OBEX.
- Replacement of traditional wired serial communications in test equipment, GPS receivers and medical equipment.
- For controls where infrared was traditionally used.