Background: Why WiMAX ?

WiMAX is expected to do more for Metropolitan Area Networks (MANs) and what Wi-Fi has done for local area networks (LANs)? WiMAX is not projected to replace Wi-Fi, but to complement it by connecting Wi-Fi networks to each other or the Internet through high-speed wireless links. You can therefore use WiMAX technology to extend the power and range of Wi-Fi and cellular networks. However, in developing countries, WiMAX may become the only wireless technology because Wi-Fi and cellular have not penetrated areas that can be reached with WiMAX technology. (Wimax.com, 2007)

Range

The wide range of the WiMAX technology depends on the height of the antennas, if they are installed at the suitable position from where there is no barrier between the transmitter and receiver, and then we can get better range and service from it. Even though the frequency for operation of WiMax is not definite, the most likely band at 3.5GHz is higher in frequency than the 3G bands at around 2.1 GHz. Range will, as a result, be lower, perhaps somewhere between 50% and 75% of the range of 3G. WiMAX can therefore support 30 to 50 kilometres distance with Line-of-Sight (LOS) links. As far as Non-line-of-sight (NLOS) links in concerned WiMax can support the broad range from 3 to 10 kilometres using advanced modulation algorithm that can overcome many interfering objects that Wi-Fi systems cannot pass through. (Tom Carpenter, 2006)

Data Rates

The technology used for WiMax is Orthogonal Frequency Division Multiplexing (OFDM), it is not appreciably more supernaturally efficient then the technology commonly used for 3G that is Wideband Code Division Multiple Access (WCDMA). However OFDM is coupled with a high channel bandwidth, that allows greater data rates. So, on average, for an equivalent spectrum allocation, users will see similar data rates. In specific simulations, where there are few users, it is possible that WiMax will provide a higher data rate than 3G. However, in commercial systems, such simulations are likely rare.

WiMAX Speed & Mobility Ratio

Fig 1: WiMax Speed & Mobility Ratio (Wikipedia)

Timing

It is normally believed that WiMax will enter into the market some five years after 3G is well established. This drawback in time is likely to be important since without a convincing advantage only a few service providers will choose to move from 3G to WiMAX. However, those yet to deploy a system may find the choice balanced between the two technologies.

Cost

The network costs of WiMax will be likely to be higher than for 3G because of the reduced range and hence the necessity to build more cells. The subscriber subsidy costs may be lower if WiMax is built into processor chips, although this may not apply if users wish to have WiMax handsets. (William Webb, 2007)

Quality of Service (QoS)

Excellent Quality Of service management donates from variety of WiMax features. Just as on a Wi-Fi network, WiMAX users share a data pipe and QoS can degrade as more users are added to the network. Using the QoS features of WiMAX, service providers can guarantee certain users specific bandwidth amounts by limiting the bandwidth consumption of other users.

Grant request mechanism for accessing to network is the first aspect of Quality of Service. The WiMAX functioning of disagreement allocates only a fixed amount of time to be given to these grant requests. Disagreement refers to the act of competing for access to the network. Because of the limited amount of time available, bandwidth cannot be consumed by contention requests. When a disagreement request comes into the network, the system compares the request with a service level agreement for the user making the request, and they are granted, or denied, access accordingly.

Link by link modulation schemes is another benefit of WiMax Quality of Service. In other words, the base station can use different modulation schemes for different links. The modulation scheme used is related directly to the distance of the link. Rather than all users' links being downgraded by the user farthest away, link by link modulation enables closer users to use higher data-rate modulation schemes.(Tom Carpenter,2006)