Wi-Fi based on IEEE 802.11 which is a set of standards for wireless local area network (WLAN) computer communication, developed by the IEEE LAN/MAN Standards Committee (IEEE 802) in the 5 GHz and 2.4 GHz public spectrum bands. Although the terms 802.11 and Wi-Fi are often used interchangeably, the Wi-Fi Alliance uses the term "Wi-Fi" to define a slightly different set of overlapping standards. Actually, the WiMAX Forum is keen to present 802.16 as complementary to the local area IEEE standard, 802.11 or Wi-Fi. However, according to there different applications and characteristics, these two should be used in different concrete situation. Following words will give there comparison in some special aspects.
WiMAX
Spectrum license: uses licensed spectrum typically; it’s also possible to use unlicensed spectrum.
Coverage: Optimized for outdoor non-line of sight; supports mesh networks; supports advanced smart antenna.
Range: long-range system; covers many kilometers; optimized up to 50km; point to multipoint (or multipoint to multipoint); handles many users widely spread out, tolerant of greater multipath delay spread up to 10ms; PHY and MAC designed for multimile range.
QoS: uses a mechanism based on setting up connections between the Base Station and the user device, each connection is based on specific scheduling algorithms which means that QoS parameters can be guaranteed for each flow; grant request MAC; designed to support voice and video from the start; supports differentiated service level; TDD/FDD/HFDD – symmetric or asymmetric; centrally enforced QoS.
Performance: Bandwidth 10/20 MHz, 1.75/3.5/7/14 Hz, 3/6 MHz; maximum data rate 70Mbps; Maximum 5 bps/Hz
Scalability: highly scalable from what are called “femto”-scale remote stations to multi-sector 'maxi' scale base that handle complex task of management and mobile handoff functions and include MIMO-AAS smart antenna susystems; channel bandwidths can be chosen by operator for sectorization; scalable independent of bandwidth with 1.5 MHz to 20 MHz width channels; MAC supports thousands of users.
Wi-Fi
Spectrum license: uses license-exempt (unlicensed) spectrum only to provide access to a network.
Coverage: typically covers only the network operator’s own property, be used by an end user to access their own network which may or may not be connected to the internet; optimized for indoor use; no mesh support within standards; smart antenna support proprietary.
Range: shorter range system, typically hundreds of meters, optimized for 100 meters (now is more than 100m); point to point; No ’near-far’ compensation; designed for indoor multipath delay spread up to 0.8ms; PHY and MAC optimized for 100m range; range can be extended but then MAC non-standard
QoS: introduced a QoS mechanism similar to fixed Ethernet where packets can receive different priorities based on their tags which means that QoS is relative between packets/flows as opposed to guaranteed; contention-based MAC; standard can not guarantee latency for voice or video; no allowance for differentiated levels of service on a per user basis; TDD only-asymmetric.
Performance: bandwidth 20 MHz; maximum data rate 54 Mbps; maximum 2.7 bps/Hz.
Scalability: wide 20 MHz channels; MAC supports tens of users
WiMAX is a serious threat to 3G because of its broadband capabilities, distance capabilities and ability to support voice effectively with full Qos. This makes it an alternative to cellular in a way that Wi-Fi can never be, so that while operators are integrating Wi-Fi into their offerings with some alacrity, looking to control both the licensed spectrum and the unlicensed hotspots, they will have more problems accommodating WiMAX. But as with Wi-Fi, it will be better for them to cannibalize their own network than let independents do it for them, especially as economics and performance demands force them to incorporate IP into their systems. Handset makers such as Nokia will be banking on this as they develop smartphones that support WiMAX as well as 3G. A standards-based long distance technology will avoid many of the problems of high upfront costs, lack of roaming and unreliability that those ahead of their time pioneers encountered, but it will still need to gain market share rapidly before 3G takes an unassailable hold. Given the current slow progress of 3G, especially in Europe, and the unusually streamlined process of commercialising WiMAX, the carriers are indulging in wishful thinking when they say nothing can catch up with cellular.
Due to the ease and low cost with which Wi-Fi can be deployed, it is sometimes used to provide Internet access to third parties within a single room or building available to the provider, often informally, and sometimes as part of a business relationship. For example, many coffee shops, hotels, and transportation hubs contain Wi-Fi access points providing access to the Internet for customers.
Although we just focus on the comparison between WiMAX and Wi-Fi because the comparison of these two is most considerable, we can also connect WiMAX (802.16) with other standards such as 802.15 (Bluetooth), 802.20 WAN, RFID, etc. The figure (source: [1]) below indicates the comparison and relationship of these standards.
The first figure above shows the two directions of PAN to WAN, ETSI HiperMAN is a competing standards to WiMAX and details of such these kinds of competing standards will be discuss combine with WiMAX in the next section of blog.
References:
[1] Dr. Mohammad Shakouri, "The Impact of 802.16 Technology Will Enable Ubiquitous Delivery of Broadband Wireless Services", WiMAX Forum.
No comments:
Post a Comment