Wimax standards and Security The Wimax



Download 2,02 Mb.
bet20/186
Sana29.05.2022
Hajmi2,02 Mb.
#619147
1   ...   16   17   18   19   20   21   22   23   ...   186
Bog'liq
CRC - WiMAX.Standards.and.Security

Other Features

The PHY layer also has other features, some of them are mandatory and the others are optional. These features empower the performance of the technol- ogy to provide for robust performance over a wide range of frequencies and under different channel conditions.



          • Adaptive antenna system (AAS): uses multiple antennas at both the receiver and the transmitter ends (MIMO system) to increase channel capacity by steering the antenna beams toward multiple users to achieve in-cell frequency reuse. MIMO system is also benefi- cial in increasing the signal-to-interference ratio through coherently combining multiple signals. Another benefit of AAS is the decre- ment of required power due to utilizing beams formed of adaptive antennas.

          • Adaptive modulation: 802.16-2004 allows for different modulation schemes in the down- and uplink communication, i.e., BPSK, QPSK, 16QAM, 64QAM, and 256QAM. The 802.16 standard defines differ- ent combinations of the aforementioned modulation schemes and coding rates, providing for a wide range of trade-offs of data rate and robustness depending on channel conditions. Although 802.11a/g standard uses similar modulation schemes as 802.16, there is one dif- ference between them, 802.16 uses Reed–Solomon block code with an inner convolution code or Turbo coding. The latter is left as an optional feature.

          • Space time coding: is an optional feature of 802.16 that can be used in the downlink communication to provide for space trans- mit diversity. Space time coding assumes that the base station is

using two transmit antennas and the subscriber station uses one transmit antenna.





      1. MAC Layer

The MAC layer supports the different PHY specifications by using time divi- sion multiplexing, where users are assigned time slots to access the channel. The uplink communication is based on time division multiple access (TDMA). TDMA facilitates different levels of QoS and bounded delay communication through a predetermined service level agreement. This can be achieved by allocating bandwidth based on a request/grant mechanism. The standard 802.16-2004 supports both TDD and FDD, full and half duplex.

Link layer control (LLC)



Convergence sublayer (CS)



Common part sublayer (CPS)



Privacy sublayer (PS)



Transmission convergence sublayer



QPSK


16QAM


64QAM


256QAM




802.16-2004 is designed to carry any present or future higher-layer protocol such as IP versions 4 and 6, packetized voice-over-IP (VoIP), Ethernet, ATM, and virtual LAN (VLAN) services. 802.16 accomplishes this by dividing its MAC layer into separate sublayers that handle different services as follows:
MAC
layer
PHY
layer




        1. Download 2,02 Mb.

          Do'stlaringiz bilan baham:
1   ...   16   17   18   19   20   21   22   23   ...   186




Ma'lumotlar bazasi mualliflik huquqi bilan himoyalangan ©hozir.org 2024
ma'muriyatiga murojaat qiling

kiriting | ro'yxatdan o'tish
    Bosh sahifa
юртда тантана
Боғда битган
Бугун юртда
Эшитганлар жилманглар
Эшитмадим деманглар
битган бодомлар
Yangiariq tumani
qitish marakazi
Raqamli texnologiyalar
ilishida muhokamadan
tasdiqqa tavsiya
tavsiya etilgan
iqtisodiyot kafedrasi
steiermarkischen landesregierung
asarlaringizni yuboring
o'zingizning asarlaringizni
Iltimos faqat
faqat o'zingizning
steierm rkischen
landesregierung fachabteilung
rkischen landesregierung
hamshira loyihasi
loyihasi mavsum
faolyatining oqibatlari
asosiy adabiyotlar
fakulteti ahborot
ahborot havfsizligi
havfsizligi kafedrasi
fanidan bo’yicha
fakulteti iqtisodiyot
boshqaruv fakulteti
chiqarishda boshqaruv
ishlab chiqarishda
iqtisodiyot fakultet
multiservis tarmoqlari
fanidan asosiy
Uzbek fanidan
mavzulari potok
asosidagi multiservis
'aliyyil a'ziym
billahil 'aliyyil
illaa billahil
quvvata illaa
falah' deganida
Kompyuter savodxonligi
bo’yicha mustaqil
'alal falah'
Hayya 'alal
'alas soloh
Hayya 'alas
mavsum boyicha


yuklab olish