Thursday, July 7, 2011

Basic concepts of WiMAX

WiMAX means Worldwide Interoperability for Microwave Access



  • WiMAX based on the IEEE802.16 protocol is a broadband wireless technology applied to the Metropolitan Area Network (MAN).
  • It complies the "Broadband + Wireless" trend. WiMAX features the Orthogonal Frequency Division Multiplex Access (OFDMA), Multiple Input Multiple Output (MIMO), and other advancedtechnologies to maintaain its broadband advantage.
  • It is called 3.5G or 4G technology. In October of 2007,it has become the 4th standard of 3G technology.
Protocols:

WiMAX is based on the 802.16 protocol that has two standards:
  • 802.16d Fixed Broadband radio access standard: It specifies the air interface layer between the fixed access terminals and the BTS.
  • 802.16e Mobile Broadband radio access standard: It supports the mobile stations. Moreover it supports both the fixed broadband radio access system and mobile broadband radio access system.
Technical Benefits of WiMAX:

1. Advanced technical functions:
  • It incorporates multiple technologies including OFDMA, MIMO, AMC, HARQ etc.
2. Wide coverage and high throughput:
  • The maximum coverage distance of a BS is 50km. The typical coverage distance is 6km to 10km.
  • The maximum throughput of each sector is 75Mbit/s.
3. Easy to Expand:
  • It is easy to add new sectors.
  • It is easy to plan the channel bandwidth.
4. Low risks of overhead and investment
5. Broadband access

Technical Specifications of WiMAX:

802.16d standard:

Bandwidth (MHz): 1.75-20
Frequency (GHz): 2-11
Mobility: Fixed or Roaming
Transmission technology: Multi carrier, OFDM
Multiple access: OFDMA
Spectrum Assignment Unit: Sub-channel
Duplex mode: TDD,FDD
Peak rate (Mbit/s): 75 Mbps (20MHz)
Modulation mode:DL:BPSK,QPSK,16QAM,64QAM; UL:bpsk,qpsk,16QAM
Inter-cell handovers: No
Enhanced Technology: Intelligent antenna, MIMO, HARQ,AMC
Access control: The BS periodically allocates bandwidths to the MS and provides opportunities for periodic unicast polling. The MSs access the network based on priority.
QoS: Supporting five QoS class standards including UGS,ERtPS,RtPS,NrtPS and BE.
Battery saving mode: No

802.16e standard:

Bandwidth (MHz): 1.25-20
Frequency (GHz): 2-6
Mobility: Middle-rate mobile station (<120km/h)
Transmission technology: Multi carrier,OFDMA
Multiple access: OFDMA
Spectrum Assignment Unit: Sub-channel
Duplex mode: TDD,FDD
Peak rate (Mbit/s): 15 Mbps (5MHz), 30 MHbps (10MHz)
Modulation mode:DL:BPSK,QPSK,16QAM,64QAM; UL:bpsk,qpsk,16QAM
Inter-cell handovers: Yes
Enhanced Technology: Intelligent antenna, MIMO, HARQ,AMC
Access control: The BS periodically allocates bandwidths to the MS and provides opportunities for periodic unicast polling. The MSs access the network based on priority.
QoS: Supporting five QoS class standards including UGS,ERtPS,RtPS,NrtPS and BE.
Battery saving mode: Supporting idle and sleep modes

Global Spectrum Distribution of WiMAX:

Primary frequency bands:
  • 2.3G: 2.3 - 2.4 GHz
  • 2.5G: 2.496 - 2.690 GHz
  • 3.5G: 3.4 - 3.6 GHz
QoS - Based Services:
  • Unsolicited Grant Service(UGS): VoIP (without silence suppression)
  • Extended Real-time Polling Service(ertPS): VoIP (with silence suppression)
  • Real-time Polling Service(rtPS): MPEG video
  • Non-Real-time Polling Service(nrtPS): FTP service
  • Best Effort(BE): Network browse, e-mail
Network Elements of WiMAX:
  • MSS (Mobile Subscriber Station)
  • ASN (Access Service Network): The ASN consists of the Base Station (BS) and the Access Service Network-Gateway(ACN-GW). The ASN manages the IEEE802.16e air interface and enables the MS to access multiple CSNs.
  • CSN (Connect Service Network): The CSN is connected to the internet, ASP, PLMN, and other networks. It provides Authentication, Authorization and Accounting (AAA), roaming between different NSPs (Network Service Providers), IP address management, location management, mobility management, connection for multiple services, policy management, and QoS management.
  • NAP (Network Access Provider)
  • NSP (Network Service Provider)
Networking features of WiMAX:
  • Independent networking
  • Hybrid networking with 2G/3G
  • Easy to construct the network
  • Low cost

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