In start with Channel Acquisition process when the

In a time of expanding technologies raise the new era of
communication the Worldwide Interoperability for Microwave Access (WiMAX), it
is the newest wireless technology approved by the IEEE 802.16 group. The WiMAX
standard for Point to Multipoint wireless network. Giving a solution for
portability and higher speeds with affordable rates, even it is the best
solution to serve rural areas. The report will explain the main operation of
WiMAX and its major type, discussing the transmission rates and protocol used,
then finding what in physical and logical channel and finishing with the
security of WiMAX.

WiMAX Stand for Worldwide Interoperability for Microwave
Access, the name created by the WiMAX forums a group of organizations manage
the standardization of the technology, WiMAX hold the standard IEEE 802.16.
This new technology works similar to Wi-Fi but with enhanced capabilities.
WiMAX basic operation consist of 2 main steps. The process start with Channel
Acquisition process when the subscriber device start scanning the available
WiMAX frequencies, and sync with channel to acquire packets that hold the
downlink channel descriptor (DCD) and uplink channel descriptor (UCD) messages
which determine how to access the system. After this steps the subscriber
device send Initial ranging request and receive Timing Adjustment information
allowing both device to utilize the channel and either authorize the connection
or drop it.(Figure1) (Operation, 2009)

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WiMAX technology have Fixed and Mobile type, both have
different requirement, needs and usage. The Fixed WiMAX usually have a fixed
antenna and it operate between 2 to 11GHZ with speed varying between 75Mbps in
area of 10km, it has simpler modulation technique and higher throughput, and
Mobile WiMAX where it is similar to fixed but uses a lower frequency band,
operate at 2-6GHZ frequency and ranging the speed between 30Mbps in area of
3.5km, features getting a mobile device which can connect wirelessly Standing,
Walking, driving a car.(Brain&Grabianowski-2002),(Fili, 2005)

As for the structure of WiMAX protocol it contains many
layers, Protocol Layers are hierarchical model the network, and they are
referred to levels which each level does its own task. The WiMAX system has
four layers, staring from MAC Convergence is a functional process within
communication system that adapt a data packet to another road such as
ATM(Asynchronous Transfer Mode) or IPv4, secondly it passes through the MAC
Layer where it uses to coordinate the communication channel between devices and
communication medium and it only communicate availability and priority
schedules for device that users want to access to. Next MAC Privacy layer, it’s
the layer associated to encrypt information and authenticate over the link,
arriving to the last layer Security Sub-Layer, at this layer its where the
system performs access control and validating identity and encrypt data. (Figure2)(Kumar, Adhikary and Vaid, 2013)











Physical channels in WiMAX are radio-channels connected
between the transmitter and the receivers. It has many types of physical radio
frequency channels which can be in WiMAX system in a single carrier, or
orthogonal carriers and even multiple division access using orthogonal
carriers. Channel bandwidth differ from lower to upper frequency, WiMAX can be
setup to use different channel bandwidth by objectives of WiMAX and the
equipment used. the key characteristics is the channel band width for example
in 20MHz-25MHz-28MHz Radio frequency channel size(figure3).









And logical channels are part of physical channel that
created for a specific logical communication purpose. And every physical
channel has up to 65535 logical channel connection where every connection
multiple service flows in association with it.

And Logical channels are a portion of a physical
communications channel that issued for a particular (logical) communications
purpose. The physical channel can have logical channels up to 65,535
connections and each connection can multiple service flows associated with it.(Kalaichelvan and Harte, 2005)

And as for security, WiMAX have more sublayers in protocol
stack, and WiMAX contain many security sections. Data link layer security is
where the layer implements the exchange of the secure key and do the encryption
of traffic. basic WiMAX security contain of the following. (P.Ahuja and Collier, 2010)

Authentication: WiMAX
network use Privacy key management protocol which use RSA based authentication.

Authorization: user
authentication must be met to start authorization process

Encryption: WiMAX use 3DES
and AES encryption for data transfer over network.


technology expanding rapidly and it is a revolutionary technology, with many
benefits solving many daily life issues, it is best to research more about how
to enhance such technology, and make better data transmission in the channel,
keeping in mind security and how to achieve maximum security in such way not to
effect the connection, wireless organizations are always one step ahead to
thinking of the future of WiMAX.