1. Khaled Hatem Almotairi and Xuemin (Sherman) Shen IEEE Globecom 2010 Speak: Huei-Rung, Tsai Symmetrical Power Control for Multi- channel Multi-hop Wireless Networks

2. Outline  Introduction  Problem description  Goals  System Model  Symmetrical TPC Protocol  Performance Evaluation  Conclusions

3. Outline  Introduction  Problem description  Goals  System Model  Symmetrical TPC Protocol  Performance Evaluation  Conclusions

4. Introduction  There are many schemes to improve the network capacity  Use the available orthogonal channels (Multi-channel)  Transmission power control (TPC) to increase the frequency reuse  It’s a promising approach to combine the two solutions  There are many studies about Multi-channel/TPC in past years  Multi-channel (MMAC, SSCH)  TPC (SSP)  Multi-channel + TPC  DCA-PC  Busy tones and power control

5. Introduction  DCA-PC (DCA with power control)  In DCA protocol, each node has two interfaces  One is fixed on the control transmitted RTS/CTS/RES packets  Other switches between data channel transmitted Data/ACK packets B A Data Channel 2 Control Channel B A RTS/CTS/RESData/ACK

6. Introduction  SSP  Divides time into slots  Each slot nodes turn their power to a fixed value  Does not utilize multiple channels  Busy tones and power control  Bandwidth is divided into 4 sub-channels:  Data channel  Control channel  Narrow-band transmit tone (BT t )  Narrow-band receive tone (BT r )  Tones indicate whether there is a transmission or reception

7. Problem description  Hidden power problem due to asymmetrical links  Transmit control packets at the maximum power over control channel  Data/ACK packets at minimum powers over any data channel A B C D Interference range ABCD Control Channel Channel 2 Time Channel 3 ABCDAB Channel 2 CD Control Channel Channel 2 Time Channel 3 ABCDAB

8. Problem description  Asymmetrical links will cause hidden power problem  Prove A packet is received correctly if SINR ≥ T SINR The receiving power at receiver is P: Transmission power G: Antenna gain h: antenna height d: distance k: path loss exponent Assume one interfering node with a distance r from the receivers presented The SINR receiver measured ≥ T SINR if <1, a)Cause collisions b)Result unfairness

9. Problem description  This paper assign different and maximum allowable powers to each data channel

10. Goals  Proposed a symmetrical power control for multi-channel multi- hop networks to resolve the hidden power terminal problem due to asymmetrical links in multi-channel networks

11. Outline  Introduction  Problem description  Goals  System Model  Symmetrical TPC Protocol  Performance Evaluation  Conclusions

12. System Model  There are M channels that have equal bandwidths  One channel is control channel  M−1 channels are data channels  Each node is equipped with two half-duplex transceivers  The two interfaces can operate simultaneously without interfering  Nodes transmit over the common control channel at P max  Symmetrical TPC protocol is similar to the DCA protocol, but also can be implemented using other principles

13.  Every nodes follow the principles  Transmit control packets at P max over control channel  Data/ACK packets at P i over data channel i Symmetrical TPC Protocol Node B Node A Channel 2 Node B Node C Time Node D Node A Control Channel RTS ACK RES(2) DIFS DATA CTS(2) SIFS DIFS NAV CAL[2], NAL[Node A] SIFS C D A B P max

14. Symmetrical TPC Protocol  Every maintain two lists  NAL (Node ID, duration, preChannel)  CAL (Channel number, duration) C D A B Control Channel RTS NAL[A].duration = T data +T CTS +T SIFS +  NAL[A]. preChanel = Ch 3 CAL[2].duration = NAL[A].duration B 1.Packet size L d 2.ACI from node A’s CAL B determine P min by T data =(L data +L ACK )/R d +T SIFS +2 

15. Symmetrical TPC Protocol  Every maintain two lists  NAL (Node ID, duration, preChannel)  CAL (Channel number, duration) C D A B Control Channel CTS(2) 1.Selected data channel (channel 2) 2.T data NAL[B].duration = T data NAL[B]. preChanel = Ch 3 CAL[2].duration = T data A NAL[B].duration = T data +  NAL[B]. preChanel = Ch 2 CAL[2].duration = T data +  D T rem =T data -T RES -T SIFS - 

16. Symmetrical TPC Protocol  Every maintain two lists  NAL (Node ID, duration, preChannel)  CAL (Channel number, duration) C D A B Control Channel RES(2) NAL[A].duration = T rem NAL[A]. preChanel = Ch 4 CAL[2].duration = T rem C 1.Selected channel 2.T rem

17. Outline  Introduction  Problem description  Goals  System Model  Symmetrical TPC Protocol  Performance Evaluation  Conclusions

18. Performance Evaluation  Compare with DCA-PC and 802.11 MAC implemented on ns-2  Maximum communication range is 250 meters  Carrier sensing range is 550 meters  50 wireless nodes placed randomly in a 1000x1000 m2 flat area  There are 4 Channel (250, 250, 167, and 127 meters)

19. Performance Evaluation

22. Conclusions  This protocol allocates different P max to each channel  In the symmetrical protocol, nodes select data channel based on the received power and transmit at the allowable power that is allocated to the selected data channel.