Download Recent Advances in Wireless Networks

Chapter 14: Recent Advances in
Wireless Networks
 Introduction
 Ultra-Wide-Band Radio
Communication (UWB) and
WiMedia
 Wireless Fidelity System
(WiFi) and WiMax
 Optical Wireless Networks
 Advances in 802.11
 The Meghadoot Architecture
1
Ultra-Wide-Band Radio Communication
 UWB is a technology developed to transfer large amounts of data
wirelessly over short distances over a very wide spectrum of
frequencies in a short period of time.
• The amount of spectrum occupied by a UWB signal, i.e. the bandwidth of
the UWB signal is at least 25% of the center frequency. For example, a
UWB signal centered at 2 GHz would have a minimum bandwidth of 500
MHz and the minimum bandwidth of a UWB signal centered at 4 GHz
would be 1 GHz. The most common technique for generating a UWB signal
is to transmit pulses with durations less than 1 nanosecond.
• UWB technology has the capacity to handle the very high bandwidths
required to transport multiple audio and video streams.
• UWB will be ideally suited for transmitting data between consumer
electronics (CE), PC peripherals, and mobile devices within short range at
very high speeds while consuming little power.
• This technology operates at a level that most systems interpret as noise and,
as a result, does not cause interference to other radios such as cell phones,
cordless phones or broadcast television sets.
2
Ultra-Wide-Band Radio Communication
3
UWB Advantages
 Extremely Difficult to Intercept - LPI/LPD. Wideband pulsed
radar spreads the signal and allows more users access to a limited
amount of scarce frequency spectrum.
 Multipath Immunity - A low path loss and low energy density
minimizes interference to other services. UWB is very tolerant of
interference, enabling operation within buildings, urban areas, and
forests.
 Precision Network-wide timing - Real-time, continuous position
location down to a centimeter of resolution results in precision
geolocation systems.
 Low Cost - Requires minimal components resulting in small size
and weight
 Low Power - Typical consumption is in microwatts
4
UWB Applications
 Communications - High Speed WLANs, Mobile Ad-Hoc wireless
networks, Groundwave Communications, Handheld and Network
Radios, Intra-home and Intra-office communication. Stealthy
communications provide significant potential for military, law
enforcement, and commercial applications.
 Sensor Networks - Ground penetrating Radar that detects and
identifies targets hidden in foliage, buildings or beneath the
ground. Intrusion Detection Radars, Obstacle Avoidance Radars,
and Short-range motion sensing.
 Tracking/Positioning - Precision Geolocation Systems and highresolution imaging. Indoor and outdoor tracking down to less than
a centimeter. Good for emergency services, inventory tracking,
and asset safety and security.
5
WiMedia
 WiMedia refers to high data-rate, wireless multimedia networking
applications operating in a wireless personal area network
(WPAN).
 The WiMedia brand is defined and supported by the WiMedia
Alliance.
 The initial WiMedia radio technology will be based on
ultrawideband (UWB) as defined by the MultiBand OFDM
Alliance (MBOA) SIG's PHY and MAC specifications.
 The primary goals of the WiMedia Alliance are
• to enable coexistence of multi-protocol applications (UWB, 1394 and
TCP/IP among others) and
• to enable true multi-vendor interoperability by establishing procedures for
ensuring devices from different manufacturers coexist within the common
UWB radio platform.
6
UWB Standards
 802.15.3a is a group working on UWB standards but could not
decide between the two approaches – multiband OFDM
(MOFDM) from the TI/Intel-led MBOA group, or direct sequence
code division multiple access (DS-CDMA) from Motorola.
 Multiband OFDM Alliance SIG (MBOA-SIG) and WiMedia
Alliance have merged to create UWB industry specifications and
certification programs for consumer electronics, mobile and PC
applications.
 Advantages of the MultiBand OFDM proposal:
•
•
•
•
•
based on proven OFDM technology: used in IEEE 802.11a and 802.11g
Achieves data rates of 53 to 480 Mbps
Support for 4 to 16 simultaneous piconets
Spectrum easily sculpted for international regulatory domain compliance
easily extensible for future range/rate improvements
 Refer to MBOA at http://www.multibandofdm.org/.
7
Objectives of MBOA
 To develop, publish, and promote the best overall solution for
global UWB standardization
• As a formal SIG, publish detailed system specification in May 2004
 To support the development of a robust UWB ecosystem
• Support industry efforts to develop upper layer protocols and interfaces
• Provide a forum for vendors of antennas, RF modules, and test and
measurement equipment
• Work in harmony with IEEE, WiMedia, CEA, 1394-TA, Wireless-USB WG
 To ensure the standardization of UWB solutions with the best
coexistence characteristics possible and to continue work with
worldwide regulatory agencies to provide education and seek
specific approval of MBOA-based technology
 To enable a single worldwide standard for high bit rate UWB
applications with optimum time-to-market and maximum benefit
to the broadest number of end consumers
8
Wireless Fidelity Systems (WiFi)
 Wireless Fidelity (WiFi) is the standard for the high-speed wireless
LAN.
 A Wi-Fi network can be used to connect computers to each other,
to the Internet, and to wired networks (which use IEEE 802.3 or
Ethernet).
 Wi-Fi networks operate in the unlicensed 2.4 and 5 GHz radio
bands, with an 11/54 Mbps (802.11b/g) or 54 Mbps (802.11a) data
rate Any Wi-Fi product uses the same radio frequency (for
example, 2.4GHz for 802.11b/g, 5GHz for 802.11a).
 The Wi-Fi Alliance (http://www.wi-fi.org/)
• A global, non-profit industry association of more than 200 member
companies devoted to promoting the growth of wireless Local Area
Networks (WLANs).
• With the aim of enhancing the user experience for mobile wireless devices,
the Wi-Fi Alliance's testing and certification programs ensure the
9
interoperability of WLAN products based on the IEEE 802.11 specification.
WiMax
 WiMAX is an acronym that stands for Worldwide Interoperability
for Microwave Access.
 The WiMAX Forum is an industry-led, non-profit corporation
formed to promote and certify compatibility and interoperability of
broadband wireless products.
 The WiMax forum supports the industry-wide acceptance of the
IEEE 802.16 and ETSI HiperMAN wireless MAN standards.
10
Optical Wireless Networks
 Optical wireless communication enables communication using
infrared ray.
 Operates outdoor up to 5 Km and indoor a few meters.
 Advantages:
•
•
•
•
•
•
Abundance of unregulated bandwidth: 200 THz in the 700 – 1500 nm range
No multipath fading: Intensity modulation and direct detection
Higher capacity per unit volume
Cost effective at rates near 100 Mbps
Small cell size
At 800 – 890 nm and 1550 nm absorption effects are minimal.
 Disadvantages:
•
•
•
•
•
•
Multipath dispersion
Limited range
Difficult to operate outdoor
High power requirement
SNR can vary significantly with the distance
costly
11
Advances in IEEE 802.11
 Multimode 802.11 enables dynamically to use 802.11a/b/g.
 The 802.11e defined an extension of the 802.11 standard for
quality of service (QoS).
 The 802.11f developed specifications for implementing access
points and distribution systems.
 The 802.11h developed the MAC layer standard that comply with
European regulations for 5 GHz wireless LAN.
 The 802.11i group is working on mechanisms for enhancing
security in the 802.11 standard.
 The 802.11j task group is working on mechanisms for enhancing
security in the 802.11 MAC physical layer protocols to
additionally operate in the newly available Japanese 4.9 GHz and
5 GHz bands.
 The 802.11n defines standardized modifications to the 802.1112
MAC and physical layers to allows at least 100 Mbps.
Meghadoot
 The meghadoot architecture is a packet-based wireless network
architecture for low-cost rural community networks.
 The major goals of the Meghadoot project are
• Develop a fully distributed packet-based hybrid wireless network that can
carry voice and data traffic
• Provide a low-cost communication system in the rural regions
• Provide a low-cost communication network for urban environment
 Meghadoot uses a routing protocol called infrastructure-based ad
hoc routing protocol (IBAR).
 The end user equipment in Meghadoot is an IEEE 802.11 enabled
device.
 Meghadoot is aimed at deploying an 802.11 phone in rural areas,
using Voice over Wireless IP (VoWIP) that promises to free them
from their telephone handsets.
 VoWIP is an emerging technology that enables IP voice to be sent
13
over an 802.11 wireless LAN.
Final Thoughts
 Wireless networks are widespread in our daily life.
 Fourth generation (4G) WWAN communications systems that are
characterized by high-speed data rates at 20+ Mbps, suitable for
high-resolution movies and television. It describes two different
but overlapping ideas.
• High-speed wireless access with a very high data transmission speed, of the
same order of magnitude as a local area network connection (20 Mbps and
up). It can integrate wireless LAN technologies like Wi-Fi, as well as other
potential successors of the current 3G mobile telephone standards.
• Pervasive networks. A user is simultaneously connected to several wireless
access technologies and can seamlessly move between them. These access
technologies can be Wi-Fi, UMTS, EDGE or any other future access
technology. Included in this concept is also smart-radio technology to
efficiently manage spectrum use and transmission power as well as the use
of mesh routing protocols to create a pervasive network .
 A cell phone could be an integral part of all wireless standards.14