1. New Code for RTS/ANP for Lower Probability of Collision
Month Year
doc.: IEEE yy/xxxxr0
November 2007
New Code for RTS/ANP for Lower Probability of Collision
IEEE P Wireless RANs Date:
Authors:
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Soo-Young Chang, Huawei Technologies
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
November 2007
Abstract
In the current TG1 draft, a code is being used for RTS and ACK/NACK codewords. However there can be only 15 codewords applied. Therefore when multiple SPDs select one of them for their RTS codeword, the probability to collide with RTS codewords for other SPDs will be relatively high.
In this document, to lower this probability of collision a new code is being introduced for the RTS and ACK/NACK codewords.
It improves probability of collision while it lowers processing complexity.
Soo-Young Chang, Huawei Technologies
John Doe, Some Company

3. CURRENT CODE November 2007 NPD NACK Go-On
Soo-Young Chang, Huawei Technologies

4. Received 16 bit RTS/ACK codeword
November 2007
NEW CODE DESIGN
Cascading two identical 8-bit orthogonal codes
Received data: divided into two subcodewords
Each subcodeword is compared with 8 8-bit codewords.
8x8=64 codewords realized
Among these codewords, three codewords are assigned to NPD, Go-On, and NACK.
Subcodeword 1
Subcodeword 2
Received 16 bit RTS/ACK codeword
Soo-Young Chang, Huawei Technologies

5. ORTHOGONAL 8 BIT CODE RTS/ANP index r0 r1 r2 r3 r4 r5 r6 r7 1 2 3 4 5
Month Year
doc.: IEEE yy/xxxxr0
November 2007
ORTHOGONAL 8 BIT CODE
RTS/ANP index r0 r1 r2 r3 r4 r5 r6 r7 1 2 3 4 5 6 7 8
Soo-Young Chang, Huawei Technologies
John Doe, Some Company

6. NEW CODE FOR 16 BITS For subcodeword 1 For subcodeword 2 1 2 3 4 5 6 7
Month Year
doc.: IEEE yy/xxxxr0
November 2007
NEW CODE FOR 16 BITS
For subcodeword 1
For subcodeword 2
RTS/ACK index r0 r1 r2 r3 r4 r5 r6 r7 1 2 3 4 5 6 7 8
RTS/ACK index r8 r9
r10
r11
r12
r13
r14
r15 1 2 3 4 5 6 7 8
Soo-Young Chang, Huawei Technologies
John Doe, Some Company

7. ASSIGNMENT OF A CODEWORD TO EACH SPD
November 2007
ASSIGNMENT OF A CODEWORD TO EACH SPD
Method 1
Assign a codeword to an SPD randomly
Still has a probability of collision
Method 2
Assign a codeword to an SPD corresponding to its subchannel number.
In this method the subchannel number means a subchannel in a TV channel where its lowest subchannel among subchannels it is protecting (or its protected devices cover) if it has multiple subchannels covered by itself.
This method can guarantee that in the next step no collision occurs.
Soo-Young Chang, Huawei Technologies

8. ADVANTAGES OVER CURRENT CODE
November 2007
ADVANTAGES OVER CURRENT CODE
New code Current code
Low complexity
a simpler look-up table required:
less memory needed
:needs 8 8-bit codewords :needs bit codewords
Computational complexity
:16 8-bit comparisons :15 16-bit comparisons
More codeword combinations
64 combinations 15 codewords
lower prob. of collision:1/62 higher prob. of collision:1/12
Soo-Young Chang, Huawei Technologies

9. DISADVANTAGE OVER CURRENT CODE
November 2007
DISADVANTAGE OVER CURRENT CODE
New code Current code
Less Hamming distance
Slightly lower error control capacity:
Hamming distance: 4+4=8 Hamming distance: 8
: error detection: up to 6 bits : up to 7 bits
: error correction: up to 2 bits : up to 3 bits
This can be interpreted as an Eb/N0 difference.
6/7 and 2/3 error control ratio can be < 0.5 dB Eb/No difference for the same error control capability.
With the (15, 7) linear code used, 1.5 dB dB Eb/No coding gain with distance of 5 (4 bit error detection cap) (02-053r1, Jan. 07).
1 bit error detection difference = 1.5 * 1/5 = 0.3 dB difference.
Soo-Young Chang, Huawei Technologies

10. November 2007
CONCLUSIONS
In the document, xxxx _Sensing_Beacons_Using_Short_Quiet_Periods, a new code is being proposed for RTS/ACK codewords.
With the new code design for RTS/ACK,
lower processing complexity and probability of collision can be achieved with the same length of codewords as that introduced in the 22.1 current draft.
To achieve the same error control capability, the new code needs a little bit higher Eb/No value than the current code by <0.5 dB.
Soo-Young Chang, Huawei Technologies

11. November 2007
References
xxxx _Sensing_Beacons_Using_Short_Quiet_Periods
Soo-Young Chang, Huawei Technologies