WI-MAX
Worldwide Interoperability for
Microwave Access (WiMAX) is the common name associated to the IEEE
802.16a/REVd/e standards. These standards are issued by the IEEE802.16 subgroup
that originally covered the Wireless Local Loop (WLL)
technologies with radio spectrum
from 10 to 66 GHz. Recently,these specifications were extended below 10GHz.
Harmonize standards and certify interoperability between equipment from different
vendors. Standardized Interoperable solutions will result in mass volume and
bring down costs, promote and establish a brand for the technology.
Wi-Fi style access will be
limited to a 4-to-6 mile radius (perhaps 25 square miles or65 square km of
coverage, which is similar in range to a cell-phone zone). Through the stronger
line-ofsight antennas, the Wi-MAX transmitting station would send data to
WiMAX-enabled computers or routers set up within the transmitter’s 30-mile
radius (3,600 square miles or 9,300 square km of coverage). This is what allows
Wi-MAX to achieve its maximum range.
Working Principle Used in
Gi-Fi:
In this we will use time division
duplex for both transmission and receiving. Here data files are up converted
from IF range to RF60Ghz range by using 2 mixers and we will feed this to a
power amplifier, which feeds millimeter wave antenna.The incoming RF signal is
first down converted to an IF signal cantered at 5 GHz and then to normal data
ranges. Here we will use heterodyne construction for this process to avoid
leakages due to direct conversion and due to availability of 7 GHz spectrum the
total data will be will be transferred within seconds.
Time -Division Duplex
Time-Division Duplex (TDD) is the
application of time-division multiplexing to separate outward and return
signals. It emulates full duplex communication over a half duplex communication
link.As uplink traffic increases, more channel capacity can dynamically be
allocated to that, and as it shrinks it can be taken away.Time division duplex
(TDD) refers to duplex communication links where uplink is separated from
downlink by the allocation of different time slots in the same frequency band.
It is a transmission scheme that allows asymmetric flow for uplink and downlink
data transmission. Users are allocated time slots for uplink and downlink
transmission.This method is highly advantageous in case there is an asymmetry
of uplink and downlink data rates. TDD divides a data stream into frames and
assigns different time slots to forward and reverse transmissions, thereby
allowing both types of transmissions to share the same transmission medium.
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