Initial Ranging procedure in WiMAX standard
description
Transcript of Initial Ranging procedure in WiMAX standard
![Page 1: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/1.jpg)
Initial Ranging procedure in WiMAX standard
Student:Chung-ming Li
![Page 2: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/2.jpg)
Outline
Introduction WiMAX frame structure Down-link timing synchronization Initial ranging Timing offset System design conclusion
![Page 3: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/3.jpg)
Introduction
In OFDMA, it is required that all transmission from MS should arrive BS at the same time.
Imagine a cell size of 10Km, we have round trip time of 66.6 us.
UL data must arrive BS within 0 to 66.6 us.
The whole network synchronization refers to BS clock.
![Page 4: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/4.jpg)
Introduction
MSs are distributed all over the cell. A MS at cell edge receive data quite
late and transmits data very early , being compared with MS close to BS.
When a new MS is seeking entry into the network, the MS has no idea as to what time or power should be used for transmitting the initial signal.
![Page 5: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/5.jpg)
Introduction
This is the BS’s job to detect this new MS.
Find the misalignment between the new MS ,and then send response to correct it.
The following slides start with a brief description about how WiMAX handles this situation.
![Page 6: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/6.jpg)
WiMAX frame structure
TTG and RTG are 105.714 μs and 60 μs, respectively.
![Page 7: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/7.jpg)
WiMAX frame structure
![Page 8: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/8.jpg)
Down-link timing synchronization
DL UL
5ms
DL UL
5ms
DL UL
5ms
DL ULDL U
L
Initialization AGC Stage Normal AGC Stage
t
Power-on happens at a random time
Enable a 5ms counter
Measure power
Energy detection
AGC
Packet DetectionYes
Yes
YesSeveral tunes
Enable a 5ms counter
ED
AGCPKT
AGC
Power on
![Page 9: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/9.jpg)
Down-link timing synchronization
Oversampling
Mixer
4 Channel ADC 50Mhzto 44.8Mhz SRRC
LO PLL
9 62 2.5(10 ) 20(10 )j te
fA/D
4
44.850
AWGN
![Page 10: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/10.jpg)
Down-link timing synchronization
SRRC
)()()( fGfGfG RT
2
4[ ] 1 ,
2 2[(1 )sin( )] (1 cos( ))],4 42
( ) ( ) ( )sin[ (1 ) ] 4 cos[ (1 ) ]
( ) ( )[1 (4 ) ]
0,
g n
n k n k n kp p pn k n kp p
( ) 0for n k
( )4Pfor n k
( 1) 2Nfor n k
( 1) 2Nfor n k
![Page 11: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/11.jpg)
Down-link timing synchronization
![Page 12: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/12.jpg)
Down-link timing synchronization
21
0
0, ( interger)=0, otherwise
N j knN
n kk
k
s S e
ifk iM i
Sk
12 21
0 0
21
0
NN Mj kn j kMn
N Nn k kM
k k
Nj knM NM
kMk
n N n Nsn M
then
s S e X e
S e
S S S
must be integer !!sN
![Page 13: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/13.jpg)
Down-link timing synchronization
Packet detection by cyclic prefix
2 2 2 2
1
_0
12
_0
(( ) ( ))cov( , )
( ) ( ) ( ) ( )
CP
CP
X YXY
X Y
L
k i k i FFT sizeiL
k i FFT sizei
E X u Y uX Y
E X E X E Y E Y
r r
r
is the scanning sample offsetk
CP
CP
FFT_size
![Page 14: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/14.jpg)
Down-link timing synchronization
AWGN; theis ,1 to0 from profile-delay channel theis where
,1
0
knL
knkshkrL
1 1 1
0 0 0
1 1 1
0 0 0
,
where is the scanning sample offset,
W W L
w w
L W W
w w
r w k f w h s w k n w k f w
h s w k f w n w k f w
k
![Page 15: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/15.jpg)
Down-link timing synchronization
Matched filter is with an eye to maximizing SNR
1 1
1
1
0
1 1
1 1
1 1 1 1 1 1
1 1 10 0 0 0 0 0
1 1 2
0 0
then 0,
if ( ) for 0,
and E ( ) 0 for 0
then
W
w
L W - L W - L W -
w w wk k
L W -
wk
n w k f w
s w k f w k
s w k f w k
h s w k f w h s w k f w h s w k f w
h f w
1h k
![Page 16: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/16.jpg)
Down-link timing synchronization
1
2
1 1 2 221
0 0
1
,
where 0, , 1
L W -
wk
h f w h k
k L
![Page 17: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/17.jpg)
Initial ranging
In WiMAX, code division multiple access( CDMA) codes are used to detect new MS.
A new MS will transmit one CDMA code.
The BS is not only to detect the new MS but also to calculate its timing,frequency and power offset.
![Page 18: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/18.jpg)
Initial ranging
Code length=144, 256 sets, using BPSK modulation
![Page 19: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/19.jpg)
Timing offset
CyclicPrefix
FFT windowCyclicPrefix
Delay
BS clock
Receive data
020( ) ( )j n kDFTx n n e X k
![Page 20: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/20.jpg)
Timing offset
Signal in FFT
0( )x n n 02 ( )j n ke X k
12CDMA Code with phase shift ( )j n ke X k
1 02 ( ) ( ) ( )j n n ke X k X k
1 0
1442 ( )
1
( ) ( )j n n k
k
e X k X k
0For , ( ) ( ) ,k=1,2,.....144
We get a peak!n n and X k X k
![Page 21: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/21.jpg)
21without timing advance with timing advance
Timing offset
![Page 22: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/22.jpg)
System Design
6
8
(105 60) 1023 10
6.75 Km
air
air
d
d
![Page 23: Initial Ranging procedure in WiMAX standard](https://reader036.fdocuments.net/reader036/viewer/2022062315/5681637b550346895dd4598e/html5/thumbnails/23.jpg)
Conclusion
The BS detects the new MS and calculates the timing offset, then corrects MS transmitting parameters.
Taking the round trip time intoconsideration,the maximal cell size should be 6.75 Km.