WiMAX is an advanced technology solution based on an open standard, designed to meet the need for very high speed wide area Internet access, and to do so in a low-cost, flexible way. It aims to provide business and consumer broadband service on the scale of the metropolitan area network (MAN). WiMAX networks are designed for high-speed data and will spur innovation in services, content, and new mobile devices. WiMAX is optimized for IP-based high-speed wireless broadband which will provide for a better mobile wireless broadband Internet experience.
The WiMAX product certifi cation program ensures interoperability between WiMAX equipment from vendors worldwide. The certifi cation program also considers interoperability with (HIPERMAN), the European telecommunication standards institute’s MAN standard.
With its large range and high transmission rate, WiMAX can serve as a backbone for 802.11 hotspots for connecting to the Internet. Alternatively, users can connect mobile devices such as laptops and handsets directly to WiMAX base stations without using 802.11. Mobile devices connected directly can achieve a range of four to six miles, because mobility makes links vulnerable. The WiMAX technology can also provide fast and cheap broadband access to markets that lack infrastructure (fi ber optics or copper wire), such as rural areas and unwired countries. WiMAX can be used in disaster recovery scenes where the wired networks have broken down. It can be used as backup links for broken wired links.
WiMAX can typically support data rates from 500 kbps to 2 Mbps. WiMAX also has clearly defi ned QoS classes for applications with different requirements such as VoIP, real-time video streaming, file transfer, and web traffic. A cellular architecture similar to that of mobile phone systems can be used with a central base station controlling downlink/uplink traffic.
WiMAX is a family of technologies based on IEEE 802.16 standards. There are two main types of WiMAX today: fi xed WiMAX (IEEE 802.16d — 2004) and mobile WiMAX (IEEE 802.16e — 2005). Fixed WiMAX is a point-to-multipoint technology, whereas mobile WiMAX is a multipoint-to-multipoint technology, similar to that of a cellular infrastructure. Both solutions are engineered to deliver ubiquitous high-throughput broadband wireless service at a low cost. Mobile WiMAX uses orthogonal frequency division multiple access (OFDMA) technology which has inherent advantages in latency, spectral efficiency, advanced antenna performance, and improved multipath performance in an NLOS environment. Scalable OFDMA (SOFDMA) has been introduced in IEEE 802.16e to support scalable channel bandwidths from 1.25 to 20 MHz. Release 1 of mobile WiMAX will cover 5, 7, 8.75, and 10 MHz channel bandwidths for licensed worldwide spectrum allocations in 2.3, 2.5, 3.3, and 3.5 GHz frequency bands. Also, next generation 4G wireless technologies are evolving toward OFDMA and IP-based networks as they are ideal for delivering cost-effective highspeed wireless data services.
The WiMAX specifi cation improves upon many of the limitations of the Wi-Fi standard (802.11b) by providing increased bandwidth and stronger encryption.
The 802.16 standard was designed mainly for point-to-multipoint topologies, in which a base station distributes traffic to many subscriber stations that are mounted on rooftops. The pointto-multipoint confi guration uses a scheduling mechanism that yields high efficiency because stations transmit in their scheduled slots and do not contend with one another. WiMAX does not require stations to listen to one another because they encompass a larger area. This scheduling design suits WiMAX networks because subscriber stations might aggregate traffic from several computers and have steady traffic, unlike terminals in 802.11 hotspots, which usually have bursty traffi c. The 802.16 also supports a mesh mode, where subscriber stations can communicate directly with one another. The mesh mode can help relax the LOS requirement and ease the deployment costs for high-frequency bands by allowing subscriber stations to relay traffi c to one another. In this case, a station that does not have LOS with the
base station can get its traffi c from another station. Mobile WiMAX systems offer scalability in both radio access technology and network architecture, thus providing a great deal of flexibility in network deployment options and service offerings. Some of the salient features supported by WiMAX are:
● High data rates: The inclusion of MIMO antenna techniques along with flexible subchannelization schemes, advanced coding, and modulation all enable the mobile WiMAX technology to support peak downlink data rates of 63 Mbps per sector and peak uplink data rates of up to 28 Mbps per sector in a 10 MHz channel.
● QoS: The fundamental premise of the IEEE 802.16 MAC architecture is QoS. It defines service fl ows which can map to DiffServ code points or MPLS flow labels that enable end-to-end IP-based QoS. Additionally, sub-channelization and MAP-based signaling schemes provide a flexible mechanism for optimal scheduling of space, frequency, and time resources over the air interface on a frame-by-frame basis.
● Scalability: Mobile WiMAX is designed to be able to scale to work in different channelization from 1.25 to 20 MHz to comply with varied worldwide requirements as efforts proceed to achieve spectrum harmonization in the longer term.
● Security: Support for a diverse set of user credentials exists including SIM/USIM cards, smart cards, digital certifi cates, and user name/password schemes based on the relevant extensible authentication protocol (EAP) methods for the credential type.
● Mobility: Mobile WiMAX supports optimized handoff schemes with latencies less than 50 ms to ensure that real-time applications such as VoIP can be performed without service degradation. Flexible key management schemes assure that security is maintained during handoff.
Source of Information : Elsevier Wireless Networking Complete
No comments:
Post a Comment