1. RTS_ANP sequence Design and Simulation
Jan 2007
doc.: IEEE /0xxxr0
June 2007
RTS_ANP sequence Design and Simulation
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Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

2. Jan 2007
doc.: IEEE /0xxxr0
June 2007
Abstract
As adopted in Montreal meeting, to decrease the probability of collision, the SPD should randomly select a RTS sequence from a given set whenever it sends RTS to PPD. Here we introduce the RTS sequence design and give the corresponding simulation results.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

3. Contents RTS_ANP Designs. Simulation Results. Conclusion June 2007
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Contents
RTS_ANP Designs.
Simulation Results.
Conclusion
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

4. Jan 2007
doc.: IEEE /0xxxr0
June 2007
RTS_ANP Design (1/4)
In the original Draft, when several SPDs send RTS sequence at the same RTS period, since there is only one RTS sequence, the PPD can’t distinguish which SPD send the RTS sequence and must send “NACK” back to the SPDs, thus none of the SPDs could send its beacon at this time, and we call this problem as RTS collision problem.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

5. Jan 2007
doc.: IEEE /0xxxr0
June 2007
RTS_ANP Design (2/4)
To resolve the problem mentioned above, we proposed：
whenever a SPD needs to send a RTS, it randomly select a RTS sequence from the pre-defined RTS set. Since different SPDs select the RTS sequence randomly and independently, the probability that these SPDs select the same RTS sequence will be very small, and therefore, reduce the RTS collision probability.
When the PPD receive multiple RTS sequences, it pick one of them and send it back as ANP.
SPDs compare the ANP sequence to the RTS sequence it had sent to the PPD. If they are the same, the SPD send its beacon in the next beacon superframe, otherwise, it should wait to randomly select and send RTS again.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

6. Jan 2007
doc.: IEEE /0xxxr0
June 2007
RTS_ANP Design (3/4)
We must design the RTS sequence set carefully so that the PPD can identify RTS sequences that had been transmitted by several SPDs. This means that RTS sequences in the RTS sequence set should have very low cross-correlation value. There are two kinds of sequences we may consider:
M-sequence: the cross-correlation value is always 1 and this is quite small compared to its self-correlation value which equals to the length of the m-sequence. Besides, the cross-correlation values are very small even these m-sequences are not aligned with each other. This is very useful in real communation system since the signals from different SPDs may arrive at the PPD at different time because of the different distance or different processing time, etc.
Hadamard sequence: the Hadamard sequences have the perfect cross-correlation value 0. However, when the sequences are not aligned with each other, some of the correlation values will not be as good as we want.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

7. Jan 2007
doc.: IEEE /0xxxr0
June 2007
RTS_ANP Design (4/4)
To make the system more robust for possible mis-alignment, we suggest to use 15-bit m-sequences. The RTS sequence set contains the sequence
{     } and any n<15 bit right cyclically shift of this sequence.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

8. Simulation Results (1/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (1/8)
In the following 3 slides, we give the simulation results of correlation value under the SNR of 20dB, 10dB, 0dB. In these figures, x-value is the m-sequence index, Here we use totally 15 m-sequences as the RTS sequence set. and two different m-sequences was transmitted (with index 3 and 7 in this simulation). y-value is the correlation value for every m-sequence.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

9. Simulation Results (2/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (2/8)
(a) The amplitude ratio between the two RTSs is 1:1
(b) The amplitude ratio between the two RTSs is 1:0.5
Figure 1: The Correlation Result When SNR=20dB, Two RTS sequences were transmitted.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

10. Simulation Results (3/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (3/8)
(a) The amplitude ratio between the two RTSs is 1:1
(b) The amplitude ratio between the two RTSs is 1:0.5
Figure 2: The Correlation Result When SNR=10dB, Two RTS sequences were transmitted.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

11. Simulation Results (4/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (4/8)
(a) The amplitude ratio between the two RTSs is 1:1
(b) The amplitude ratio between the two RTSs is 1:0.5
Figure 3: The Correlation Result When SNR=0dB, Two RTS sequences were transmitted.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

12. Simulation Results (5/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (5/8)
From figures on the previous 3 slides, we can see that for every 15 m-sequence, there are two peaks which corresponding to the two transmitted m-sequences. the PPD can pick these two peaks out and recognize which m-sequence was transmitted by SPDs, and then send corresponding ANP information. These figures are just a glance of the simulation result, we use it to give a raw judgement whether PPD can distinguish different RTSs or not by DQPSK modulation. It’s natural that if we can see corresponding peaks stand out of other correlation values “by eyes”, then it should be easy to indentify corresponding RTSs by some computer programs.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

13. Simulation Results (6/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (6/8)
To get more exact detection performance, we will count and calculate the probability of Failed detection by following methods: First, pick the one with largest absolute correlation value from the 15 correlation values, if this value is larger than the average value of other 14 absolute correlation values multiply with Threshold 2.5, we declare that a RTS was detected; The second RTS pick and judgement is just like the first one except that we remove the largest absolute correlation value that had been detected.
Figure 4: Simulation link for RTS sequence detection
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

14. Simulation Results (7/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (7/8)
Simulation Condition: 1) 15-bit m-sequences for the RTS/ANP sequence set; 2) Assume Perfect Symbol Synchronization; 3) DQPSK and Spreading as in the TG1 Draft; 4) 4-bit soft output by the DQPSK demodulator; 5) AWGN channel and Profile_A channle; 6) Statistic Length: 10,000 Frames
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

15. Simulation Results (8/8)
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Simulation Results (8/8)
Figure 5: The Failed Detect Probability under AWGN Channel and Profile A Channle, The amplitude ratio between the two RTS sequence is 1 : 0.5
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

16. Jan 2007
doc.: IEEE /0xxxr0
June 2007
Conclusions
From the simulation Results, we can see that under AWGN and Profile A channel:
The strongest RTS can be detected with high probability even under SNR as low as 0dB condition.
Because the small distance between SPD and PPD, the SNR is usually high (more than 15dB). With such a high SNR, the second strongest RTS (which is 6dB weaker than the strongest RTS) can be detected with high probability too.
So, we can conclude that with the m-sequence RTS set, the RTS collision problem in the Draft can be alleviated greatly.
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

17. And any comments or questions？
Jan 2007
doc.: IEEE /0xxxr0
June 2007
Questions?
Thank you！
And any comments or questions？
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi

18. References June 2007 《22-07-0011-00-0001_Huawei_SPD_RTS_Collision》
Jan 2007
doc.: IEEE /0xxxr0
June 2007
References
《 _Huawei_SPD_RTS_Collision》
《 _TG1_Preliminary_Draft》
Wu Yu-Chun, Huawei Hisi
Wu Yu-Chun, Huawei Hisi