Hello, everyone!
Today, I would like to share an intro on WiMAX.
WiMAX (Worldwide Interoperability for Microwave Access) is a standardized form of wireless metropolitan area network (WMAN) technology that has historically been based on proprietary solutions, such as MMDS and LMDS. The first version of the IEEE 802.16 standard was completed in October 2001 and defines the air interface and medium access control (MAC) protocol for a wireless metropolitan area network, intended to provide high-bandwidth wireless voice and data for residential and enterprise use.
This standard was followed by the 802.16a standard in early 2003. Both standards support peak data rates up to 75 Mbps and have a maximum range of about 50 km. Because WiMAX systems have the capability to address broad geographic areas without the costly infrastructure requirement to display cable links to individual sites, the technology may prove less expensive to expand and should lead to more ubiquitous broadband access.
Wireless broadband promises to bring high-speed data to multitudes of people in various geographical locations where wired transmission is too costly, inconvenient, or unavailable. The 802.16 standard uses Orthogonal Frequency Division Multiple Access (OFDMA), which is similar to OFDM in the way that it divides the carriers into multiple sub-carriers.
OFDMA, however, goes a step further by then grouping multiple sub-carriers into sub-channels. A single client or subscriber station might thus transmit using all of the sub-channels within the carrier space, or multiple clients might also transmit with each using a portion of the total number of sub-channels simultaneously. In the RF front-end, WiMAX uses OFDM, which is robust in adverse channel conditions and enables NLOS operation. This feature simplifies installation issues and improves coverage while maintaining a high level of spectral efficiency. Modulation and coding can be adapted per burst, ever striving to achieve a balance between robustness and efficiency in accordance with prevailing link conditions.
Service providers will operate WiMAX both on licensed and unlicensed frequencies. The technology enables long-distance wireless connections with speeds up to 75 Mbps. This can provide very high data rates and extended coverage. However:
75 Mbps capacity for the base station is achievable with a 20 MHz channel at best propagation conditions. But regulators will often allow only smaller channels (10 MHz or less) reducing the maximum bandwidth.
Even though 50 km is achievable under optimal conditions and with a reduced data rate (a few Mbps), the typical coverage will be around 5 km with indoor CPE (NLOS) and around 15 km with a CPE connected to an external antenna (LOS).
To keep from serving too many customers and thereby greatly reducing each user’s bandwidth, providers will want to serve no more than 500 subscribers per 802.16 base station.
One of the main advantages of this technology is the capacity to deploy broadband services in large areas without physical cables. These characteristics give telecommunication suppliers the capacity to implement new broadband telecommunication infrastructures very quickly, and with a lower cost than wired networks.
To sum up, the main advantages of the WiMAX technology in relation to other connection technologies are:
It does not need cable installation, which can solve the access problem to remote places;
It is rather quick to deploy. This technology could have an access velocity that is 30 times higher than basic ADSL technology. Besides frequency range is between 2 and 11 GHz, with the maximum range of 50 km from the base station, and data transmission to 70 Mbps. So, one BS sector can serve different businesses or many homes with DSL-rate connectivity.
Another advantage is the high capacity to service modulation (data and voice), to perform symmetric transmission (the same velocity to send and receive data), and the use of QoS.
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