USE_OF_DSP_FOR_WIRELESSue_AND_MOBILE.ppt

Studymaterial

1. USE OF DSP FOR WIRELESS
AND MOBILE
COMMUNICATION
BY
RAJAT KUMAR
RISHABH SHRIVASTAVA
SACHIN KUMAR SINGH
SHIV MOHAN GUPTA
VINAY SONKER

2. 2
What is Signal Processing?
•Example of Signals:
–Analog: Speech, Music, Photos, Video, radar, sonar,
…
–Discrete-domain/Digital:
•digitized speech, digitized music, digitized images, digitized
video, digitized radar and sonar signals,…
•stock market data, daily max temperature data, ...
Processing
Signal in Signal out
Operation, Transformation
(Analog or Digital) (Analog or Digital)

3. 3
What is Digital Signal Processing?
•But what about analog signals?
Digital Processing
Digital Signal in Digital Signal out
Operation, Transformation performed
on digitalsignals (using a computer or
other special-purpose digital hardware)
Analog Signal
in
Analog-to-
Digital (A/D)
Conversion
Digital Processing
Digital-to-
Analog (D/A)
Conversion

4. 4
Signal Processing Examples
Why Go
Digital??

5. Digital Signal Processing And Its Benefits
Byasignalwemeananyvariablethatcarriesorcontainssomekindof
informationthatcanbeconveyed,displayedormanipulated.
Examplesofsignalsofparticularinterestare:
-speech,isencounteredintelephony,radio,andeverydaylife
-biomedicalsignals,(heartsignals,brainsignals)
-Soundandmusic,asreproducedbythecompactdiscplayer
-Videoandimage,
-Radarsignals,whichareusedtodeterminetherangeandbearing
ofdistanttargets

6. 6
Why Use DSP For Wireless
Communication?
•Wireless Systems requires more and more high
performance and higher bandwidth
2.5G
3G
2G
Bit Rate
Performance
~100MIPS
8-13 Kbps
~10,000MIPS
64-384 Kbps
~100,000MIPS
384-3000 Kbps
DSP performance
might not be
enough for
future
applications
4G
~1000,000MIPS
10 Mbps –100+ Mbps

7. 7
What are the alternatives
•High-performance GPPs with DSP enhancements.
–Eliminating the need of a DSP and GPP for many products and
thus reducing cost
–Example: Pentium 4
•Single Instruction Multiple Data (SIMD) instructions allowing
identical operations on multiple pieces of data in parallel.
•144 new special instructions providing advanced capabilities for
applications such as 3D graphics, video encoding/decoding, and
speech recognition.
•Several Data Types (floating/integer)
•Multi-Core DSPs
•Application Specific Integrated Circuits (ASIC)
•Field Programmable Gate Array (FPGA)

8. ASIC, FPGA
•Uses hard-wired logic with varied architectures
according to the application
•FPGA
•It is a network of reconfigurable hardware with
reconfigurable interconnect controlled by a
switching matrix

9. DSP aspects in Wirelesscommunication
•Source Coding (Speech coding)
•Detection and matched filtering
•Diversity and rake receivers
•Multi-user detection
•Error Correction

10. Speech coding for mobile
•To reduce the bit-rate required for transmitting telephone
quality speech, a new approach to speechcompression
is needed.
•Current mobile phones compress to about 13,000 b/s (bit
per second) and weaim to achieve 4,000 b/s and lower
using a method called 'DAP-STC'.
•Compression is generallyachieved by spectrally
analysing speech segments to derive a model of the
human speech process.
•DAP-STC is a new and potentially more accurate way of
doing this with a modified speech productionmodel.
•A variable bit-rate version achieves an average 2,400
b/s and is suitable for packetised speechas may be
transmitted over computer networks.

11. Source filter model
•Fig.

12. The Matched Filter Principle
•The optimum receiver for any signal
–in Additive white Gaussian Noise
–over a Linear Time-Invariant Channel
•is ‘a matched filter’:
Integrate
S
Locally stored reference
copy of transmit signal
Channel Noise
Transmit
Signal

13. The Matched Filter Principle
Integrate
S
Locally stored reference
copy of transmit signal for “1”
Channel Noise
Transmit Signal,
either S
0(t) for “0”
or S
1(t) for “1”
Integrate
S
Locally stored reference
copy of transmit signal for “0”
S
1(t)
S
0(t)
Select
largest

14. Fundamentals of Diversity
Reception
•What is diversity?
•Diversity is a technique to combine several copies
of the same message received over different
channels.
•Why diversity?
•To improve link performance

15. Methods for obtaining multiple
replicas
•Site Diversity
•Frequency Diversity
•Time Diversity
•Polarization Diversity
•AngleDiversity

16. Site (or macro) diversity
•Receiving antennas are located at different sites.
–Example: at the different corners of hexagonal cell.
•Advantage: multipath fading, shadowing, path loss and interference all
become "independent“

17. Frequencydiversity, Timediversity, Anglediversity
•Frequency diversity:
Each message is transmitted at different carrier
frequencies .
Time diversity:
Each message is transmitted more than once.
Useful for moving terminals.
Angle diversity:
• Waves from different angles of arrival are
combined optimally, rather than with random phase
•Directional antennas receive only a fraction of all scattered energy.

18. Low power implementation of DSP in
Mobile Communication
•The requirement for extended battery life, reduced size and low
electromagnetic interference for mobile communication equipment
has led to the development of a novel asynchronous DSP device
known as CADRE.
•Compiler support for the new device is needed to avoid manual
assembly-level programming.
•Apart from maximising speed and minimising code size, the
compiler is required to produce code which exploits the special
features of CADRE to minimise energy consumption.

19. Source: “Mobile data feels pressure from the need for speed”, Network News, 2 June 1998 (CAP Gemini, September 1999)
Mobile Communications Networks
First Generation
•Analogue
•Basic voice
telephony
•Low capacity
•Limited local and
regional coverage
•E.g. NMT, AMPS,
TACS, C-net
•Digital:
–Circuit switched
•Voice plus basic
data applications:
–Fax
–SMS (small message
services)
–Circuit-switched data
•Low data speed
•Regional coverage,
with trans-national
roaming
•E.g. GSM, D-AMPS,
PDC, IS 95 CDMA
•Digital:
–Packet and circuit
switched
•Advanced data —
i.e. multimedia
applications
•Fast data access
•Global coverage
•E.g. UMTS
(WCDMA,
TD/CDMA), IMT-
2000
Second Generation Third Generation
Wireless data already be introduced in second generation mobile
Development of mobile
communications

20. A FUNCTIONAL BLOCK DIAGRAM OF GSM
PHONE

21. The baseband processor’s signal
chain.

22. MIPS requirement for signal processing in
GSM

23. 23
DSP Targets: Cell Phone
-Speech Coders
-Speech Recognition
-Equalizers
-Antenna noise cancellation
-Image enhancement techniques
DSP
Chip
RF
Codec
Voice
Codec
RF
Receiver
Microprocessor
Chip
Cell
Peripherals
Controlled by Power Management Unit

24. 24
DSP Targets: Voice Over IP
DSP
Chip
Voice
Codec
Memory
(Card or
Chip)
Audio Coders
-MP3
-AC3
-AAC
Peripherals
Micro
processor

25. Attraction of DSPcomes from key advantagessuch as :
*Guaranteedaccuracy:(accuracyisonlydeterminedbythenumberofbitsused)
*PerfectReproducibility:Identicalperformancefromunittounit
ie.Adigitalrecordingcanbecopiedorreproducedseveraltimeswithno
lossinsignalquality
*Nodriftinperformancewithtemperatureandage
* Uses advances in semiconductor technology to achieve:
(i) smaller size
(ii) lower cost
(iii) low power consumption
(iv) higher operating speed
* Greater flexibility: Reprogrammable , no need to modify the hardware
* Superior performance
ie. linear phase response can be achieved
complex adaptive filtering becomes possible

26. CONCLUSION
•Designers of 3G base stations will make use of
the DSPs in order to achieve the high
performance and flexibility needed for
tomorrow’s voice and data applications.
•Speech coding is an essential application of
digital signal processing in modern day
telephony and mobile communications, which
employ high data compression ratios.