Decentralized Clustering Mechanism for 802.11aj (60GHz New Technique Proposal)

1. Decentralized Clustering Mechanism for 802.11aj (60GHz New Technique Proposal) Date: 2013-11-9 Presenter: Dejian Li

2. Author List Dejian Li

3. Abstract • This presentation is part and in support of the complete proposal described in IEEE 802.11-13-1301r0 (slides) • This document is to propose a MAC protocol amendment to support decentralized PCP/AP clustering for 802.11aj (60GHz) • The proposed MAC protocol supports the backward compatibility with 802.11ad legacy device Dejian Li

4. Background: Decentralized PCP/AP Clustering • In 11ad, PCP/AP clustering is used to improve spatial sharing and interference mitigation with other co-channel DMG BSSs. • S-PCP/S-AP provides synchronization and other services to a PCP/AP cluster. • A member PCP/AP shall transmit its DMG Beacon frame during one of the Beacon SPs. • Clustering: cluster formation, cluster maintenance and cluster report Dejian Li

5. Background: Channilization and DBC MAC protocol • Large band and small band channel • LB channel 2 are overlapping with SB channel 5 and 6 • Dynamic Bandwidth Coexistence (DBC) MAC[2] • Paring PCPs/APs: Channel 2 is split into Channel 5 and Channel 6, and two small band PCP/AP form a pair of synchronization PCPs/APs. • PCP/AP can starts up or operates in the small band, e.g., Channel 5. 2 3 5 6 7 8 Dejian Li

6. Clustering for DBC MAC (1/3) • Suppose PCP/AP 1 is operating on S5 and supports clustering, it can perform as S-PCP/S-AP on S5. • According to DBC MAC, to avoid interfering with other 802.11ad PCP/AP, PCP/AP 1 (S-PCP/S-AP) should transmit DMG Beacon in large band channel 2 in NP. • Besides Beacon SPs, PCP/AP 3 and PCP/AP 4 should also reserve SP for the NP of PCP/AP 1. • If there are none 802.11ad STAs in the BSS, small band PCP/AP can join the small band cluster as a cluster member without transmitting notification frame in NP. • Otherwise, if there is at least one 802.11ad STA in the BSS of PCP/AP 3, then PCP/AP 3 should retain NP after joining the cluster. Dejian Li

7. Clustering for DBC MAC (2/3) • Suppose the paring DBC PCP/AP 1 and PCP/AP 2 are operating in the small band S5 and S6 respectively, they can initiate to form a cluster on each small band channel . • Note that the maximum number of member PCPs/APs may be different in the two clusters. S-PCP/S-AP at Channel6 Member PCPs/APs at Chanel 6 S-PCP/S-AP at Channel 5 Member PCPs/APs at Channel5 Dejian Li

8. Clustering for DBC MAC (3/3) • If there exists 11ad STA(s) in the BSS of a small band PCP/AP, NP1 and NP2 must be retained to keep backward compatibility with the 11ad STA of the BSS. • Suppose PCP/AP 1 of paring small band DBC PCPs/APs intends to join the co-channel cluster, if NP must be retained for the paring DBC PCPs/APs, the rules for setting the VBI and SBBI are: • SBBI 1 of PCP/AP 1 should be set to BIcluster of the target cluster • VBI should be set to the integer times of both SBBI 1 and SBBI 2 Dejian Li

9. Joining large band cluster for DBC PCP/AP • Besides joining a co-channel small band cluster, small band DBC PCP/AP can also join a large band cluster, while its BSS still operates on the small band or switches to operate on the large band. Dejian Li

10. Problem of joining large band cluster for DBC PCP/AP • Due to operating on different channels, it is hard to detect the large band beacon for a small band DBC PCP/AP, resulting in difficult cluster joining or cluster merge . • The small band DBC PCP/AP may not be able to receive a large band DMG Beacon in its short time NP in passive way. • It is not feasible for a small band DBC PCP/AP to monitor the large band channel for a long time. Dejian Li

11. Active cluster probe in cluster formation (1/4) • Proposed active cluster probe scheme for efficient cluster discovery: • A small band PCP/AP transmits DMG Beacon/Probe Request frame including Cluster Probe IE on the large band channel in NP/DTI. • TheCluster Probe IE comprises timing informationfor when the feedback is transmit. • The small band PCP/AP can reserve a few randomly time located SPs in DTI to transmit the Cluster Probe IE. • The number of Probe Request frames for cluster probe should be limited. • Large band PCP/AP responds with a Probe Response frame including Extended Cluster Report element according to the timing requirement in Cluster Probe element. Dejian Li

12. Active cluster probe in cluster formation (2/4) • Both the pairing DBC PCPs/APs joining an existed large band cluster • If PCP/AP 1 detects the presence of a large band PCP/AP cluster and meet the joining requirement, it should transmit an Cluster Switch Announcement IE to its peer DBC PCP/AP 2 during NP prior to joining the cluster. • Cluster Switch Announcement IE • Used to motivate and assist the peer DBC PCP/AP to join the large band cluster • Coordinate the joining sequence of the paring DBC PCP/AP • NP is canceled if one of the DBC pairing PCPs/APs transmits the Cluster Switch Announcement IE in its NP. Dejian Li

13. Active cluster probe in cluster formation (3/4) • 1.08/2.16 BSS Coexistence Information: Control field for the Cluster Probe element • Request Token: is set to a nonzero value chosen by the requester AP • SP Offset, SP Space, SP Duration, Repetition Count: together to define a number of SPs for transmitting and receiving Probe Response frame including the Extended Cluster Report IE. • Request token: used in decentralized clustering and copied from request token field in Cluster Probe element • Next BTI Offset: indicate the start time of the next DMG Beacon • Reported Clustering Control: Control information of the large band cluster Cluster Probe element format Extended Cluster Report IE format Dejian Li

14. Active cluster probe in cluster formation(4/4) • Keep compatibility with 11ad • For that 11ad devices can not identify the proposed Cluster Probe element, compatibility needs to be considered when the small band PCP/AP and the 802.11ad PCP/AP are performing cluster formation or cluster merge. • Resolution: • If the number of transmitting times of Cluster Probe IE reaches the upper limitation but the small band PCP/AP did not receive any response, then the PCP/AP may request its STA to monitor the large band channel, similar to DFS of 802.11. • The STA monitoring the large band channel can use cluster report to report the received cluster information. • The small band PCP/AP can reserve SPs to monitor the Beacon SPs in large band channel using the cluster information. Dejian Li

15. Cluster Maintenance • Problem in cluster maintenance • It is hard to implement cluster merge for a small band member PCP/AP, since the small band member PCP/AP may not find the large band cluster. • Resolution • If a PCP/AP discovers a cluster in another channel and intends to join it, it should transmit Cluster Switch Announcement IE to its member PCPs/APs prior to switching cluster. • The cluster members try to receive the DMG beacon of the target S-PCP/S-AP using the cluster information contained in the Cluster Switch Announcement IE. • If a cluster member receives the DMG beacon of S-PCP/S-AP of the new cluster, it should start performing the cluster formation steps; otherwise, it should complete the cluster maintenance steps according to 802.11ad. Cluster Switch Announcement IE format Dejian Li

16. Cluster Report • Show the cluster channel number in cluster report element • If a small band non-PCP/non-AP STA receives a DMG beacon of a large band cluster, it shall transmit a Cluster Report IE with a Cluster Channel Number field to its PCP/AP to report the interference information. • Cluster Channel Number: • set to 01 if the reported cluster is in the low frequency small band channel. • set to 10 if the reported cluster is in the high frequency small band channel. • set to 11 if the reported cluster is in the large band channel. Cluster Report Control field Dejian Li

17. Summary • The proposal provides a solution of decentralized PCP/AP clustering for 11aj • Cluster formation • An active probe method to find large band cluster for small band DBC PCP/AP. • Rules of adjusting VBI and SBBI for small band DBC pairing PCPs/APs. • Cluster maintenance • The PCP/AP that is switching cluster should include an announcement to make its cluster switching state clear to the cluster members, which can decrease the time desired by the cluster maintenance. • Cluster report • The cluster channel number is indicated by modifying Cluster Report IE. • Main modifications to 11ad: • 3 new elements are defined: Cluster Probe element, Extended Cluster Report element, Cluster Switch Announcement element • 1 element is modified: Cluster Report element Dejian Li

18. Reference [1] In the IEEE P802.11ad TM -2012 Standard “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications – Amendment 3: Enhancements for Very High Throughput in the 60 GHz band,” December 2012. [2] 11-13-0433r1 - MAC Protocol to Support Dynamic Bandwidth for 802.11aj (60GHz) Dejian Li