This document discusses adaptive modulation and coding (AMC) techniques in wireless communications. It provides an introduction to AMC and describes how it allows matching modulation, coding, and other signal parameters to radio link conditions. The document then outlines the development roadmap for broadband wireless access (BWA) and WiMAX, including added support for mobility, advanced antennas, and modulation/coding schemes. It discusses the advantages of AMC in improving transmission rates and bit error rates by exploiting channel state information. Finally, it notes challenges around AMC being sensitive to measurement errors and delay in selecting the appropriate modulation.

1. Adaptive Modulation
&
Coding Technique

2. A s h r a f u r R a h m a n
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S a y e d u r R a h a m a n F a r u q i e
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3.  Introduction
 Development Roadmap
 Modulation techniques
 Evolution of broadband
Wireless technology
 Advantages
 Challenges
Overview

4. Link adaptation, or adaptive
coding and modulation
(ACM), is a term used in
wireless communications to
denote the matching of the
modulation, coding and other
signal and protocol
parameters to the conditions
on the radio link
The pathloss, the
interference due to signals
coming from other
transmitters, the
sensitivity of the receiver,
the available transmitter
power margin, etc.
Introduction

5. BWA
DEVELOPMENT
ROADMAP
The current WiMAX revision is based upon IEEE802.16e-
2005, approved in December 2005.
• Adding support for mobility
• Scaling of the Fast Fourier transform (FFT) to the
channel bandwidth in order to keep the carrier
spacing constant across different channel bandwidths
(typically 1.25 MHz, 5 MHz, 10 MHz or 20
MHz
• Advanced antenna diversity schemes, and hybrid
automatic repeat-request (HARQ)
• Adaptive Antenna Systems (AAS) and MIMO
technology
• Denser sub-channelization, thereby improving indoor
penetration
• Introducing Turbo Coding and Low-Density Parity
Check (LDPC)
• Introducing downlink sub-channelization, allowing
administrators to trade coverage for capacity
or vice versa
• Adding an extra QoS class for real time applications

6. MODULATION
TECHNIQUES Both QAM and QPSK are modulation techniques used in IEEE (Wi-
Fi*), IEEE(WiMAX*) and 3G (WCDMA/HSDPA)wireless
technologies.
The modulated signals are then demodulated at the receiver
where the original digital message can be recovered.
The use of adaptive modulation allows wireless technologies to
optimize throughput, yielding higher throughputs while also
covering long distances.

7. EVOLUTION
OF
BROADBAND
WIRELESS
TECHNOLOGY

8. SYSTEM DESIGN
MODULATION/CODING SCHEMES
SUPPORTED BY WIMAX

9. System Architecture
Fig. 3. BWA System Components
1. Basic Wimax

10. System Architecture
Fig. Cognitive Mechanism
2. Cognitive Engin

11. ADAPTIVE
COMMUNICATION
SYSTEM
1. AMC Architecture
2. AMC System Performance
1. Channel Quality Estimation
2. Parameter adaptation
3. Feedback Mechanism

12. ADVANTAGES
Adaptive modulation systems improve rate of
transmission, and/or bit error rates, by exploiting the
channel state information that is present at the
transmitter.
Especially over fading channels which model wireless
propagation environments, adaptive modulation
systems exhibit great performance enhancements
compared to systems that do not exploit channel
knowledge at the transmitter.
.

13. CHALLENGES
AMC is sensitive to measurement error and
delay. In order to select the appropriate
modulation, the scheduler must be aware of
the channel quality
Errors in the channel estimate will cause the
scheduler to select the wrong data rate and either
transmit at too high a power, wasting system
capacity, or too low a power, raising the block error
rate.
.

14. QUESTIONS?
?
.

15. THANK YOU