Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ Anti-blocking Mechanism by PNC] Date Submitted: [May 15, 2008] Source: Hyoungjin Kwon, Jinkyeong Kim, Seungeun Hong, Yongsun Kim, Kyeongpyo Kim, Wooyong Lee Company: [Electronics and Telecommunications Research Institute (ETRI)] Address: [ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon, 305-700, Republic of Korea] Voice: [], FAX: [], E-Mail: kwonjin@etri.re.kr , jkkim@etri.re.kr, iptvguru@etri.re.kr, doori@etri.re.kr, kpkim@etri.re.kr, wylee@etri.re.kr Re: [] Abstract: [In order to avoid blocking in line-of-sight, anti-blocking mechanism via PNC is introduced.] Purpose: [To be considered in IEEE 802.15.3c standard] Notice:This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release:The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. ETRI

2. Contents • Human Blocking • Previous Approaches • Anti-blocking Mechanism by PNC • Link Setup • Normal Data Transmission via PNC • Blocking Detection and Avoidance • Recovery of Blocked Link • Amplify and Forward Operation • Conclusion ETRI

3. Human Blocking In general, a device uses single (direct) link. If there is a (human) blocking, the direct link is cut off. May, 2008 Slide 3 ETRI

4. Previous approaches To overcome the human blocking, there is a beam steering mechanism. However, once the steered signal is reflected, its power is degraded more than 20dBs. In addition, there can be no medium to reflect beams. DEVs exchange data directly or via the PNC. However, in case of passing through PNC, transmission time will be at least doubled compared to the time via direct link, because the data packet received at PNC should be decoded and then forwarded to destination DEV. May, 2008 Slide 4 ETRI

5. Anti-blocking by PNC • In order to meet delay constraint as well as avoid blocking, we introduce new functionality of PNC. It is the capability to relay packets from one DEV to another DEV. • Assumptions of PNC for anti-blocking mechanism • Amplify and forward (AF) on RF level • Have at least two RF chains for receiving signal and at the same time, sending it • Switch the mode of two RF chains, (Rx->Tx and Tx->Rx) • Beam forming capability is preferable. ETRI

6. Link setup • A pair of devices set up 2 relay links with a Relay-PNC. • If there is a Relay-PNC, a pair of devices request association to Relay-PNC. • If the Relay-PNC grants access to its use, then do beam-forming sequentially with a pair of devices in CAP. • Do beam-forming inbetween a pair of devices in CTA, if necessary. • Then, two DEVs and Relay-PNC move to CTA together for data transmission. Relay-PNC Relay link Relay link Destination Source Direct link [Configuration of a pair of devices and PNC] ETRI

7. Normal Data Transmission via PNC • Then, two devices can use a direct link and relay links via PNC for data transmission. • In this “example”, we assume data transmission uses two links alternatively for easy explanation of our proposed scheme. • The source DEV transmits its data and receives acknowledgment in response to the data. • Then, the a pair of devices switch their transmission path and exchange data again. Relay links Direct link ETRI

8. Blocking Detection and Avoidance • If there is no acknowledgement frame in response to data frame sent from chosen link, a source device considers the link blocked. • Then, the device should use another link to avoid the blocking. • The pair of devices move to detour link and exchange data via the detour link. Relay links Direct link ETRI

9. Recovery of the Blocked Link • Sometimes later (or periodically), the device can check whether the blocked link is available or not because the human blocking may be temporary. • If it is still impossible to exchange data through the direct link, the device use only the relay links for data transmission and repeat checking the availability of the direct link. • Otherwise, the source device can send data via the recovered direct link. Relay links Direct link ETRI

10. AF operation of Relay-PNC • During beacon period and CAP, the relay-PNC is operating as normal PNC. So, both antennas are being operated in the same Rx mode or Tx mode. • In CTA, the relay-PNC does amplify-and-forward. • Thus, a source-sided antenna is being operated in Rx mode and the other one is in Tx mode first. • Anti-blocking mechanism is based on ACK frame. Therefore, after relaying from source to destination, the antenna mode of relay-PNC should be switched in order to relay ACK frame from destination to source. ETRI

11. Conclusion • Advantages of introduced anti-blocking mechanism based on ACK via PNC • When the human blocking occurs, seamless communication can be achieved by detour link via PNC. • Simple blocking avoidance mechanism • Power efficient solution compared to beam steering technology ETRI

12. Backup slide May, 2008 Slide 12 ETRI

13. Alternating Link vs Single Link Transmission Alternating Link Transmission When there is a blocking, one of the links is still available and some of the data can be received. Antennas of the Relay-PNC are already set for the current data transmission and the relay-PNC doesn't require any antenna mode switching time. Good for AV streaming application Single Link Transmission When blocking occurs, the relay-PNC needs to switch the mode of either antenna from RX to Tx which requires switching time and there can be packet loss due to this latency. Good for file transfer application May, 2008 Slide 13 ETRI