The good architecture specifications provide a frame work which is rearward compatible in which future service add-ons and enlargement of system capablenesss without loss of backward compatibility and besides supports bequest engineering. Based on this IEEE 802.20 ‘s ( Mobile Broadband Wireless Access ) frame work is done. It is consistent with operator demand and equipment. It provides a model for rapid development of cost effectual, multi-vendor, interoperable, broadband, Mobile, wireless entree. This compatibility criterion is used in broad assortment of frequence sets.
OFDMA ( Orthogonal frequence divison multiple entree ) technique is used in wideband manner and this is designed to run clip divison semidetached house ( TDD ) and freuency division semidetached house ( FDD ) bandwidths from 5 MHz to 20 MHz. For other system holding more than 20MHz other multicarrier that can take usage of larger bandwidth are defined on wideband manner.
AIR INTERFACE INTRODUCTION:
The air interface was designed in beds and each bed was defined with interfaces, every bit good as with each protocols. One or more protocols can besides be specified for beds for carry throughing their cardinal map. The beds of IEEE 802.20 are grouped into PHYSICAL and MAC Layers. This signifier good defined and enables compatibility with broad scope of upper bed architecture and application.
AIR INTERFACE INTRODUCTION:
Multi-route criterions are defined by the MBWA Wideband manner in which each path has a alone way to web with an independently runing but indistinguishable protocol stack to it. For frontward nexus ( FL ) and rearward nexus ( RL ) at a given clip merely one path can be used. To enable rapid and efficient transportation of control and informations between entree webs, systems deploying wideband manner supports a web based route-tunnelling which has capableness of keeping and making practical connexions between two entree webs. Inter Route Tunnelling Protocol ( IRTP ) supports air interface of such web architecture.
The below figure depicts the layering architecture for each path of air interface in wideband manner. Each sublayer consists of different protocols that perform map of sublayer.
IEEE 802.20 Physical Layer: In Wideband Mode.
By and large IEEE 802.20 ‘s PHY bed provides the following for frontward and change by reversal nexus. They are:
Power end product
The physical ( PHY ) bed of 802.20 comprises of
Two duplex manners:
Time Division Duplex ( TDD )
Frequency Division Duplex ( FDD )
Two forward nexus skiping manners:
Symbol Rate Hopping
Two synchronism manners:
Two multi-carrier manners:
Transition uses OFDM with QPSK, 8PSK, 16QAM, and 64QAM transition formats.
In wideband manner PHY bed supports both FDD and TDD deployments thereby using similar baseband wave form for both.
FDD manner is provided for sweetening of backward compatibility on mated spectrum.
TDD manner supports emerging odd spectrum.
For both frontward and change by reversal nexus to better throughput it ‘s specification provides transition signal up to 64 QAM with Synchronous Hybrid Automatic Repeat Request ( HARQ ) . It supports different coding strategies like whirl codifications, turbo codifications and a low-density para cheque ( LDPC ) in different environments.
The PHY Layer in contrary nexus has a particular and alone characteristic that is a part of signalling from Access Terminal ( AT ) to Access Network ( AT ) occur over a CDMA ( code division multiple entree ) controls a section embedded in endorser of OFDMA although it is based on Orthogonal frequence division multiplexing. Therefore techniques developed for CDMA and soft handoff techniques can be made used by uninterrupted signalling from AT to AN. The Access Network ( AN ) makes easy broadband measurings required for improved interfaces because CDMA section is hopped over full broadband channel.
IEEE 802.20 MAC LAYER: In wideband manner
The MAC bed of 802.20 consists session, convergence, security, and lower MAC maps. The lower MAC sub bed controls operations of informations channels: Forward Traffic Channel and Reverse Traffic Channel. Radio nexus sublayer which has protocols provides many services as follows:
Reliable and insequence bringing of application sublayer packages.
Quality of service ( QoS )
Multiplexing of application sublayer packages.
The air interface support MAC protocols On, Hold and Sleep provinces with fast passages among them.
In the On province, client uses the system resources actively to convey and have informations.
In order to acquire higher system efficiency, the Hold province should be initiated whenever the client does n’t utilize the system.
The sleep province is initiated when the user is wholly inactive.
To convey the user from sleep province to ON province Paging mechanism is used to wake up. This mechanism allows a nomadic station to conserve energy with the aid of Sleep province and still allows for the nomadic station to have incoming packages.
MBWA air interface should direct paging signals one time every 100ms to cut down hold associated with waking a user up.
Conveyance of required information from Access Network ( AN ) and the Access Terminal ( AN ) are supported by multiple application protocol provided by the application sublayer. For transit of packages to or from other configured paths over the in usage path is done by IRTP which is specified by application bed. Extensile Authentication Protocol ( EAP ) which is support protocol is besides included in application sublayer for security maps such as for privateness, hallmark and mandate for services subscribed. Interfaces to IP ( IPv4 or IPv6 ) , to protocols for transporting packages from other air interfaces or webs and to Robust Header Compression ( RoHC ) support protocol are all besides supported by application bed to back up user informations transmittal.
Air link connexion constitution and care service are provided by The Connection Control Plane.
Protocol dialogue and protocol constellation services are provided by Session Control Plane. Besides configurable internal parametric quantity required by AT and AN are established by this session control plane.
An interface to enable OAM ( operation, disposal and care ) systems is provided by MAC and PHY direction information base ( MIB ) for unicast conveyance. This system gathers statistics from all protocols and direction planes like bytes successfully transferred, entree efforts, dropped connexions, and so on. Such information makes required maps in big and complex web to be performed by web direction system.
625k-Multicarrier Manner: ( 625k-MC ) :
This manner was developed to acquire maximal addition from adaptative multiple antenna signal processing. This is Time Division Duplex ( TDD ) air interface. Multiple TDD RF bearers are supported by this manner to increase peak informations rates available on a per user footing. It is enhancement to iBurst system as given by High Capacity Spatial Division Multiple Access ( HC-SDMA ) . Based on HC-SDMA specifications on commercially deployed system it is to the full backward compatible.
The transportation of IP traffic, including broadband IP information is enabled by 625-MC manner which is designed around multiple aerials with spacial processing and SDMA. Spatial preparation and correlated uplink and downlink intervention are provided by physical facet of protocol. Fast brand before brake, low operating expense and inter cell handover all are besides supported.
Baseline Features of HC-SDMA:
The Layer 1 ( L1 ) of HC-SDMA which is corresponded by physical bed of 625k-MC manner is characterised by TDD or TDMA construction with 5ms frames. These each frame contains 3 uplinks and three downlink explosions. Many facets of L1 are designed to back up the effectual usage of adaptative aerial arrays to supply high spectral efficiency. Spatial channel is a basic physical resource in the system. This spacial channel consists of a bearer, uplink and downlink clip slot brace and a spacial channel index.
The L2 and L3 functional specifications of the HC-SDMA system defines characteristics MAC and PHY which are encompassed in informations link bed of 625k-MC manner. Logical Sessionss for the efficient conveyance of IP packages are created by L3 of HC-SDMA. Specifications for dependable transmittal including MAC, RLC and logical channel construction are defined by L2 of HC-SDMA. Control maps and dynamic entree direction to map and transport logical channels onto PHY bed explosions are provided by the L2 MAC sublayer. To organize the power control and associate version required to keep an RF link the logical connexion and enrollment direction maps are defined by L3 protocol of HC-SDMA. With hallmark and air interface confidentiality the L3 protocol besides ensures a robust security substructure. Harmonizing to the ISO/International Electrotechnical Commission ( IEC ) 9796 standard hallmark for both BS and UT is based on utilizing digital certifications signed utilizing RSA algorithm ( Revist Shamir Adelman ) as signature primitive.
PHY LAYER ENHANCEMNET OF 625-MC:
The 625-MC manner defines excess transition techniques like 32QAM and 64QAM, mistake control coding for higher throughput rescue with peak uplink informations rates of 571.2kb/s and a peak downlink informations rates of 1.493 Mb/s. To back up extra transition classes extra RF specifications are provided by 625-MC manner.
Data Link bed ( MAC and LLC ) Enhancements:
For efficient voice over IP ( VoIP ) package transmittals and to back up the enhanced cell coverage there are extra MAC and RLC specifications.
To present short message broadcast services and multicast cyclosis services extra protocols are defined by 625-MC manner.
Three categories of QoS matching to guarantee forwarding ( AF ) , expedited forwarding ( EF ) , and best attempt ( BE ) are defined by 625-MC manner air interface. To command the watercourse shutdown timing each Sessionss QoS is exchanged by BS and UT.
AES advanced encryption criterion is used for security intent in this system.
Power preservation for the UT in slumber or idle manner is enabled by Sleep manner control which is offered by five paging activities defined by 625k-MC manner.
MIB is defined by 625k-MC manner to supply Radio web quality monitoring and control functionality. It is comprised of properties, actions, managed objectsand presentments required for pull offing a BS.
625k-MC Support for Adaptive Antenna Arrays:
For each downlink transmittal, current spacial preparation informations is provided by uolink slots predating the downlink in a frame as shown in above figure. Downlink slot is paired with each uplink slot. This coupling ensures that intervention environments will be extremely correlated. To forestall channel status from degrading the continuance is little between uplink and downlink. The public presentation of the adaptative aerial array is degraded by this. Low complexness multi antenna signal processing algorithms are enabled by bearer bandwidth which is comparatively narrow about 625 KHz.
Unique preparation sequence is assigned to each user on a given bearer clip slot brace. Of the propagating channel for suitably accurate appraisal is designed by developing sequence. A alone preparation sequence is used by coventional channel via SDMA which portions each UT from a selected set with good correlativity belongingss. Between the preparation sequences the kos correlativity belongings is really low. For the non nothing slowdown of the preparation sequence the autocorrelation belongings is really low.
625k-MC Mode Air Interface Handover:
UT directs the brand before interruption handover strategy of the air interface. Based on signal power and many other factors the broadcast channels from environing BSs and rank campaigners is monitored by each UT. While interchanging traffic channel information with its current helping BS a UT performs this type of measurings. It besides registers with new campaigner helping BS. Make before brake is manus over for the user informations. In this after successful enrollment the traffic channel redirects to new functioning BS.