A description about IEEE 802.16 Standard based on the text book "Ad Hoc Wireless Networks: Architectures and Protocols" by C. Siva Ram Murthy and B. S. Manoj.

1. IEEE 802.16 STANDARD
Lakshmi. M. B
Sr. No. 9219708
S3, MTech CSE
Sahrdaya College of Engineering and Technology, Kodakara
September 29, 2020
Lakshmi. M. B IEEE 802.16 Standard 1/25

2. Metropolitan Area Network (MAN)
Networks that span several kilometers.
Much larger in size than LANs.
Their functionalities differ from those of LANs.
Often connect large buildings.
Usage of broadband wireless access (BWA) led to the
requirement of a standard.
Lakshmi. M. B IEEE 802.16 Standard 2/25

3. IEEE 802.16 Standard
Officially known as air interface for fixed broadband
wireless access systems.
Based on OSI model.
Specifies the air interface of fixed point-to-multipoint BWA
systems.
DLL is capable of supporting multiple physical layer
specifications.
Lakshmi. M. B IEEE 802.16 Standard 3/25

4. BSs are connected to public networks.
BS serves several SSs, which in turn serve buildings.
Thus, BS provides SS with a last-mile (or first-mile) access to
public networks.
BSs and SSs are stationary.
Challenge – to provide support for multiple services with
different QoS requirements and priorities.
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5. Differences Between IEEE 802.11 and IEEE 802.16
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6. IEEE 802.16 Protocol Stack
Lakshmi. M. B IEEE 802.16 Standard 6/25

7. Physical Layer
Uses traditional narrow-band radio (10-66 GHz) with
conventional modulation schemes for transmission.
Convergence sublayer hides the transmission technology from
the DLL.
2 new protocols are added at the physical layer – IEEE
802.16a and IEEE 802.16b
IEEE 802.16a operates at 2-11 GHz frequency range.
IEEE 802.16b operates at 5 GHz ISM band.
Lakshmi. M. B IEEE 802.16 Standard 7/25

8. Signal strength of millimeter waves falls off with distance from
BS resulting in reduction of SNR.
3 modulation schemes are used, namely,
1. QAM-64
2. QAM-16
3. QPSK
Lakshmi. M. B IEEE 802.16 Standard 8/25

9. 1. QAM-64
Offers 6 bits/baud data rate.
Used by subscribers that are located near BS.
2. QAM-16
Offers 4 bits/baud data rate.
Used by subscribers that are located at intermediate distance
from BS.
3. QPSK
Offers 2 bits/baud data rate.
Used by subscribers that are located far away from BS.
Lakshmi. M. B IEEE 802.16 Standard 9/25

10. Assume 30 MHz of spectrum.
Subscribers that are far away get lower data rates.
Millimeter waves travel in straight lines unlike microwaves.
High error rates associated with millimeter waves have called
for the usage of Hamming codes.
Other networks uses checksums to detect errors and request
transmission of frames that have errors.
Lakshmi. M. B IEEE 802.16 Standard 10/25

11. Physical layer can pack multiple MAC frames in a single
physical transmission to gain improved spectral efficiency.
Voice traffic is generally symmetric whereas Internet access
have more downstream traffic than upstream traffic.
To accommodate them, IEEE 802.16 uses FDD and TDD.
Bandwidth can be changed dynamically to match the traffic in
the corresponding direction.
Lakshmi. M. B IEEE 802.16 Standard 11/25

12. Data Link Layer
Designed for wireless environment.
Broadband services call for very high uplink and downlink bit
rates, and a range of QoS requirements.
Preferred to be a protocol-independent engine.
DLL of IEEE 802.16 was designed to meet all these
requirements.
Lakshmi. M. B IEEE 802.16 Standard 12/25

13. Subdivided into three sublayers:
1. Security sublayer
2. MAC sublayer common part
3. Server specific convergence sublayer
Lakshmi. M. B IEEE 802.16 Standard 13/25

14. 1. Security Sublayer
Bottom-most sublayer.
Deals with privacy and security.
Crucial for public outdoor networks.
Manages encryption, decryption, and key management.
Lakshmi. M. B IEEE 802.16 Standard 14/25

15. 2. MAC sublayer common part
Protocol-independent core.
MAC frames are integral multiples of physical layer time slots.
Each frame contains downstream and upstream maps.
Strikes a trade-off between stability of contention-less
operation and efficiency of contention-based operation.
Lakshmi. M. B IEEE 802.16 Standard 15/25

16. Downlink – data to SS is multiplexed using TDM.
Uplink – medium is shared by SS using TDMA.
All services offered by IEEE 802.16 are connection-oriented.
4 classes of service:
0.1 Constant bit rate service
0.2 Real-time variable bit rate service
0.3 Non-real-time variable bit rate service
0.4 Best effort service
Lakshmi. M. B IEEE 802.16 Standard 16/25

17. (i) Constant bit rate service
Intended for transmitting uncompressed voice.
Certain time slots are dedicated to each connection of this
type.
Available automatically without explicit request.
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18. (ii) Real-time variable bit rate service
Intended for compressed multimedia and soft real-time
applications.
To accommodate them, BS polls SS periodically.
Category of real-time traffic — where the missing of
deadlines results in non-catastrophic events.
Lakshmi. M. B IEEE 802.16 Standard 18/25

19. (iii) Non-real-time variable bit rate service
Intended for large file transfers and other transmissions that
are not real-time.
To accommodate them, BS polls SS often.
Lakshmi. M. B IEEE 802.16 Standard 19/25

20. (iv) Best effort service
Intended for all other applications.
Polling is absent and SS contend by sending requests for
bandwidth in time slots marked in the upstream map .
Collisions are reduced by using the binary exponential back-off
algorithm.
Lakshmi. M. B IEEE 802.16 Standard 20/25

21. 3. Server specific convergence sublayer
Topmost sublayer.
Function – to interface to the Network layer.
IEEE 802.16 - designed to integrate seamlessly with both
connection-less protocols and connection-oriented protocols.
Mapping ATM connections to IEEE 802.16 is quite
straightforward.
Mapping packets to IEEE 802.16 is done in a judicious
manner.
Lakshmi. M. B IEEE 802.16 Standard 21/25

22. Request/grant scheme is used for handling bandwidth
allocation.
Bandwidth requests are always per connection.
Bandwidth grants may be grants per connection (GPC) or
grants per SS (GPSS).
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23. Bandwidth GPSS
Suitable if there are many connections per SS.
Offloads the responsibilities of the BS.
Allows sophisticated QoS guarantees and a low overhead.
Needs complex SSs.
Lakshmi. M. B IEEE 802.16 Standard 23/25

24. Bandwidth GPC
suitable if there are only a few users per SS.
BS grants bandwidth to each connection.
Incurs a higher overhead.
Allows a simpler SS.
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25. Lakshmi. M. B IEEE 802.16 Standard 25/25