Wednesday, 7. June 2006, 02:49:29
My group choses 802.11 as the research topic. Why don't we have a look at 802.16 and UWB?
Wi-Fi: 802.11 may be not the best way for last mile connection. The use of 802.11-based hardware for metropolitan-sized networks decreases costs, but 802.11 has performance limitations when supporting larger numbers of users needing guaranteed bandwidth. In addition, RF interference is often a significant problem with 802.11 when covering large areas due to license free operation. A competitor may install an 802.11 network which interferes with yours, and users will suffer due to sporadic, poor performance. There's really nothing you can do about that because there are no legal grounds to remedy the situation. I summary it as follows: 802.11 is a free frequency, it is not controled by govenment and orgination. As we get the free service, we have to endure all the private activities. We need a method to make users of 802.11 keep friendly with each other. Maybe cognitive network is a good start.
WiMAX: 802.16 is on its way. 802.16 supports point-to-multipoint architecture in the 10-66 GHz range, transmitting at data rates up to 120Mbps. At those frequencies, transmission requires line-of-site, and roofs of buildings provide the best mounting locations for base and subscriber stations. The base station connects to a wired backbone and can transmit wirelessly up to 30 miles to a large number of stationary subscriber stations, possibly hundreds.
To accommodate non-line-of-site access over lower frequencies, IEEE published 802.16a in January 2003, which includes support for mesh architecture. 802.16a operates in the licensed and unlicensed frequencies between 2GHz and 11GHz using orthogonal frequency division multiplexing (OFDM), which is similar to 802.11a and 802.11g.
The 802.16 medium access control (MAC) layer (define) supports many different physical layer specifications, both licensed and unlicensed. Through the 802.16 MAC, every base station dynamically distributes uplink and downlink bandwidth to subscriber stations using time-division multiple access (TDMA). This is a dramatic difference from the 802.11 MAC, with current implementations operating through the use of carrier sensing mechanisms that don't provide effective bandwidth control over the radio link.
However, there is not any good product for you to set up a long range 802.16 WiMAX network.
UWB: 802.15 provide higher performance for short range transmission. Ultra-Wideband (UWB) technology brings the convenience and mobility of wireless communications to high-speed interconnects in devices throughout the digital home and office. Designed for short-range, wireless personal area networks (WPANs), UWB is the leading technology for freeing people from wires, enabling wireless connection of multiple devices for transmission of video, audio and other high-bandwidth data.
UWB, short-range radio technology, complements other longer range radio technologies such as Wi-Fi*, WiMAX, and cellular wide area communications. It is used to relay data from a host device to other devices in the immediate area (up to 10 meters, or 30 feet).
How UWB Works?
A traditional UWB transmitter works by sending billions of pulses across a very wide spectrum of frequencies several GHz in bandwidth. The corresponding receiver then translates the pulses into data by listening for a familiar pulse sequence sent by the transmitter. Specifically, UWB is defined as any radio technology having a spectrum that occupies a bandwidth greater than 20 percent of the center frequency, or a bandwidth of at least 500 MHz.
Modern UWB systems use other modulation techniques, such as Orthogonal Frequency Division Multiplexing (OFDM), to occupy these extremely wide bandwidths. In addition, the use of multiple bands in combination with OFDM modulation can provide significant advantages to traditional UWB systems.
UWB's combination of broader spectrum and lower power improves speed and reduces interference with other wireless spectra. In the United States, the Federal Communications Commission (FCC) has mandated that UWB radio transmissions can legally operate in the range from 3.1 GHz up to 10.6 GHz, at a limited transmit power of -41dBm/MHz. Consequently, UWB provides dramatic channel capacity at short range that limits interference.
Today, most computer and consumer electronic devices—everything from a digital camcorder and DVD player to a mobile PC and a high-definition TV (HDTV)—require wires to record, play or exchange data. UWB will eliminate these wires, allowing people to "unwire" their lives in new and unexpected ways. Through UWB:
1, An office worker could put a mobile PC on a desk and instantly be connected to a printer, scanner and Voice over IP (VoIP) headset.
2, All the components for an entire home entertainment center could be set up and connected to each other without a single wire.
3, A digital camcorder could play a just-recorded video on a friend's HDTV without anyone having to fiddle with wires.
4, A portable MP3 player could stream audio to high-quality surround-sound speakers anywhere in the room.
5, A mobile computer user could wirelessly connect to a digital projector in a conference room to deliver a presentation. 6, Digital pictures could be transferred to a photo print kiosk for instant printing without the need of a cable.
Conclude If we take a look into all these three technologies, it will be easy for us to find that they are different in transmission range, rate, and they work for different situation. Is it possible to melt all these technologies into one mesh architecture. A Harmonious, Heterogeneous, High Performance mesh network should be the ultimate goal.
WIDGETIZE