This is an extension to WIFI called as WIMAX we attained this using low power correlator

1. Low-Power Correlation for
IEEE 802.16 OFDM Synchronization
on FPGA
By
S.M.Brundha (10G21A0455)
D.Navajyothi (10G21A0426)
I.Akkil (10G21A0438)
MC.Chaithanya(10G21A0419) ASCET

2. • Aim
• Objective
• Motive
• Existing system
• Proposed system
• Implementation flow
• Operational flow
• Simulation and synthesis report
• Applications
• Conclusion

3. To implement a low-power correlator for
IEEE 802.16 OFDM synchronization on
FPGA

5. MOTIVE
• Here IEEE 802.16 refers to the wireless Metropolitan area
network(WMAN)or wireless microwave access(WIMAX)
and the multiplexing technology we use is OFDM
• It is necessary to have timing synchronization for the
transmitted signal so we use cross correlation technique for the
received samples and filter coefficients.
• Initially it is implemented with the multipliers later multiplier
less also in the multiplier less we replace the adders with the
low power one

6. WIMAX
• where as WLAN (IEEE 802.11) restricted to smaller area(100m)
• It has lower data rate(54Mbps)
• WLAN referred to as WIFI provides low quality of service
• IEEE 802.16d used here refers to the fixed microwave access used for
broadband internet access
• Broadband refers to larger channel band width provided for
larger data rate (100Mbps)
• WIMAX technology can be extended for larger area (10Km)
•By using a single base station in an area we can serve many users in
different areas.

7. WLAN Service
WMAN service

8. OFDM TECHNOLOGY
• It is an extension for FDM
• we can serve more number of customers using a single channel
where as in FDM a single channel will render service to one
customer.
• Efficient channel usage in OFDM with no guard band by
making signals to be orthogonal
Cylic prefixing

9. CORRELATION
• Here we use cross correlation this happens between the
received samples and between the coefficients
• This is applied to find whether there is timing synchronization
for the received signal i.e whether the signal reached receiver
on time
• Generally correlation is done to attain the original signal from
the noise effected one’s based with the preamble symbols

10. Multiplier based cross correlation
• In the previous cases multiplier based correlation is
used and It is complex to implement .
• Correlation is similar to FIR filter implementation we
go in similar to DSP implementation
As in general we have for FIR filters
output=ax(n)+bx(n-1)+cx(n-2)+dx(n-3)+…..

11. Similarly for correlators after Z transform
Output = Pr [63] Ri + z−1( Pr [62] Ri + z−1( Pr [61] Ri + · · ·)
Transpose direct form of the
correlator
Eg:
Rin*pr[63]=[1010]*[0]=0000
Rin*pr[62]=[1010]*[1]=1010 and
so on

12. •In the multiplier less based technology we are going to use the shift and add
technique initially the input along with the preamble samples are being shift and
added
•The out put will be of 2 types with carry or without carry which is provided to
the multiplexar based on the preamble symbol which acts as a selection line the
required output is attained and it is is given to the adder
•
• Atlast all the output of the adder are added and then we attain the required
correlation for timing synchronisation
Eg:
Rin=1110
If preamble bit is 0 then

13. Multiplier less Implementation
•In the multiplier less based technology we are going to use the shift and add
technique initially the input along with the preamble samples are being shift and
added
•The out put will be of 2 types with carry or without carry which is provided to
the multiplexar based on the preamble symbol which acts as a selection line the
required output is attained and it is is given to the adder
• Atlast all the output of the adder are added and then we attain the required
correlation for timing synchronisation•

14. • In the existing technology of WIMAX we have used the carry
save adder for the correlation operation for timing
synchronization which may consume more area as we have a
separate block for storing the carry which consumes more
power and area.

15. • In the carry save adder addition initially all the bits are added
we attain a carry and sum at each addition from right to left
the carry attained is not added with the next addition
instead stored and at last for all the sum bits we add the carry
bits

16. There is one CSA unit per bit
• Every CSA has a c output and an s output
• Doing this way, addition can be implemented in log m sums
• It is necessary to implement one final Adder
All these consumes extra area for the register used for carry saving and consumes
more power for the operation

17. • Hence we are going to replace the existing technology
correlator’s carry save adder with the ripple carry adder
hence thereby the power consumed decreases and the area
occupied also decreases

18. Ripple carry adder
In the previous case the carry save adder’s drawback is overcame by using the ripple carry added
it doesn’t require any extra register for the storage of the carry bits
The carry bit is directly added with the sum bit of the next addition
The layout of ripple carry adder is simple, which allows for fast design time
however, the ripple carry adder is relatively slow, since each full adder must wait for the carry
bit to be calculated from the previous full adder. The gate delay can easily be calculated by
inspection of the full adder circuit.

19. IMPLEMENTATION FLOW
Implementing it on FPGA
Simulating and synthesising the net list
Devoloping the code for different modules
registers,adders,,multiplexers

20. 1 1

21. 1

22. Softwares Utilised
• we require the usage of 2 softwares
Modelsim and Xilinx ISE
 Code is written on xilinx ISE 10.1 editor
window
 The simulation is being done by using
Modelsim 6.4b

25. Spartan3e
-xc3s250
LUT SLICES DELAY Power
CSA 4404 2353 8.545ns 6.128 W
RCA 3425 1869 6.800ns 5.962 W

26. The code is being dumped in to the FPGA SPARTAN 6
 FPGA are reprogrammable they use HDL for
programming
 These are flexible we can use it for digital signal
processing, as a microcontroller ,micro processor by
programming the device to achieve the required
operation
 CLB Contains look up tables refers to
group of logic gates forming an boolean
equation, flipflops, multiplexars .
The CLB’S are connected to any of the wire
segment similarly I/O blocks
I/O Blocks are used for read and write
operation

27. • Wimax used for broadband internet access for over
larger distance and with high speed
• consumers, businesses, and government agencies
alike will discover a whole new broadband paradigm,
which will significantly enhance their ability to
conduct their business

28. CONCLUSION
Over the multiplier based implementation multiplier less consumes less
power also replacing carry save adders with the ripple carry adders we
can attain less power usage .
An additional benefit of multiplierless correlation is that it can be used on
any FPGA architecture.In this RCA implementaion we can achieve less
delay overall than with CSA

29. REFERENCES
• IEEE Xplore Abstract - Low-Power Correlation for IEEE 802.16 OFDM Synchronization
on FPGA - http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6295680#
• Intel® My WiFi Technology –http://www.youtube.com/watch?v=5DHBFrPBNc8
• WiFi Vs WiMax -http://www.youtube.com/watch?v=Y7ydkmFaP7E
• EEVblog #496 - What Is An FPGA? –http://www.youtube.com/watch?v=gUsHwi4M4xE
• Finite impulse response --http://en.wikipedia.org/wiki/Finite_impulse_response
• Understanding and Using Correlation Analysis TradeStation Labs-
https://www.tradestation.com/education/labs/analysis-concepts/understanding-and-using-
correlation-analysis
• BBC - GCSE Bitesize: Communicating with waves: radio waves and microwaves-
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/waves/soundandlightrev3.shtml
• SSCE-Shift-Mult.pdf-http://users.utcluj.ro/~baruch/book_ssce/SSCE-Shift-Mult.pdf
• Inter Carrier Interference (ICI) in OFDM-http://www.dsplog.com/2009/08/08/effect-of-ici-
in-ofdm/
• What is difference between OFDM and FDM-
http://www.edaboard.com/thread169470.html
• Orthogonal frequency-division multiplexing - Wikipedia, the free encyclopedia-
http://en.wikipedia.org/wiki/Orthogonal_frequency-division_multiplexing#Orthogonality
• Cross-correlation – ALGLIB-http://www.alglib.net/fasttransforms/crosscorrelation.php
• Cyclic prefix - Wikipedia, the free encyclopedia
• Carry save addition-people.clarkson.edu/~linh/algorithms/carry%20save%20addition.pdf
• Ripple carry adders-www.engr.uky.edu/~jel/misc/d481/info/adders/adders.html