1. IEEE 802.15.3 High Rate WPAN - MAC functionalities & Power Save Mode - 2004. Mobile Network Lab. 정상수, 한정애

2. Contents Introduction – General description MAC – Medium Access Control –Piconet Management –Association & Disassociation –Channel Access & Channel Time Management –Synchronization & Acknowledgement –Power Management

3. Introduction(1) Highrate WPAN overview –Goals Ad hoc networks Fast connection time QoS support Dynamic membership Efficient data transfer Power managemnet

4. Introduction(2) –PNC (Piconet Coordinator) manages piconet –Timing is based on the superframe Beacon CAP CFP –2.4 GHz PHY 4 channels (high density) or 3 channels (with 802.11b) modes are available Supports 5 data rates –11Mbps(QPSK), 22Mbps(DQPSK without coding), 33Mbps(16QAM), 44Mbps(32QAM), 55Mbps(64QAM)

5. Piconet Management Starting a Piconet –DEV uses passive scanning to detect piconet –To start a piconet, DEV chooses the channel and broadcasts its beacon

6. Association DEV initiates association request during CAP or association MCTA PNC responds with DEVID –If association is denied, sends a responds with a reason code DEV sends second association request using newly assigned DEVID PNC broadcasts beacon containing DEV association information DEVID (Device ID) –Assigned in sequence –One associated DEV : One DEVID except PNC

7. Disassociation PNC sends a disassociation request to DEV with the reason code All DEVs should send frames to the PNC often enough to assure that the Association Timeout Period(ATP) is not reached If DEV cannot receive beacon for longer than ATP, the DEV shall consider itself disassociated

8. Channel Access Channel time is divided into superframe with –Beacon Contains piconet synchronization parameter and IE (Information Element)s –CAP (Contention Access Period) Optional. For command frames and non-stream data. Using CSMA/CA with backoff scheme –CFP (Contention Free Period) For data stream. PNC assigns to DEV with each CTA (Channel Time Allocation)

9. Contention based access –To minimize collision, first sense that medium is idle for a random length time (backoff) –When backoff counter is zero, DEV shall check whether there is enough time remaining in the CAP –CCA(Clear Channel Assessment) of PHY is used to detect the channel Backoff procedure –The DEV first waits a BIFS duration –Choose the random integer [0, (7, 15, 31, 63)] –Backoff counter is decreased only when the medium is idle for the pBackOffSlot duration –Whenever channel is busy, counter is suspended –Backoff counter shall be suspended outside of the CAP and superframe –If transmission fails, backoff counter shall be increased

10. Contention Free Access –To enable power saving and QoS –CTA Private CTA – for dependent piconet Dynamic CTA – scheduled on a superframe by superframe basis Pseudo-Static CTA – only for isochronous stream. Allowed to transmit during CTA as long as the number of consecutive lost beacon is less then mMaxLostBeacons Channel time usage –DEV uses CTR(Channel Time Request) message to change their CTA –PNC remember CTR until another CTR is received from the DEV –Source DEV is expected to estimate the channel time to send a frame and SIFS (+ ACK + SIFS time if ACK is used) –If a DEV did not receive the beacon, it can’t use CAP or MCTA or dynamic CTA except pseudo-static CTA –PNC must respond to a CTR DEV use information to adjust its parameter

11. Management CTA –PNC can use MCTAs instead of CAP for command frames –Open MCTA SrcID is BcstID. Any DEV can attempt to send a command frame to PNC –Association MCTA SrcID is UnassocID. Any DEV not associated to the piconet can attempt to send a association request to PNC –Access mechanism Assigned MCTA - TDMA basis Open & Association MCTA - Slotted ALOHA

12. Synchronization & Fragmentation Synchronization –All DEV within a piconet must be synchronized to the PNC clock –Each DEV resets its superframe clock to zero at the beginning of beacon preamble Fragmentation –All fragments shall be equal size except last fragment –Fragment number field incremented by one –If no-ACK policy is used, all fragment is discarded when a fragment is missing –If Dly-ACK policy is used, it is responsibility of the destination DEV to deliver the frame in correct order to upper layer

13. Acknowledgement No-ACK –Assumes that the frame is successful –Used with broadcast and multicast frame Immediate ACK –If intended recipient correctly receives the frame, it sends the ACK frame Delayed ACK –With the negotiation between DEVs Source DEV sends frame with Dly-ACK request bit Dest DEV sends Dly-ACK with setting max burst field –If dest DEV want to decline the use of Dly-ACK, it shall reply with the Imm-ACK –If the max burst value is 0, source DEV stops to transmission and reopen the Dly-ACK mechanism –If Dly-ACK is not received when requested, the last data frame is repeated until the ACK frame is received.

14. During the CAP, follows the backoff procedure During the CFP, when an ACK is expected but is not received during RIFS, retransmit the frame at the end of RIFS If retransmission occurred, there must be enough channel time Retransmission

15. Power management DEV state –AWAKE, SLEEP DEV mode –ACTIVE, HIBERNATE, PSPS, SPS

16. Power management - PSPS mode System wake beacon –Announced by the PNC, determined by the PNC –PNC shall announce the system wake beacon in the next wake beacon field PS set index equal to one PNC allocates MCTAs –For PSPS DEV may need to send command to the PNC

17. SPS mode SPS mode device –DEV may use SPS set determined by other DEV or determines the beacon interval –Other DEVs may use the information in PS status IE in beacon to learn when to transmit to an SPS DEV –SPS mode allows synchronized data transfer of DEVs PNC shall create one PS status IE in the beacon for each SPS set

18. SPS CTR

19. HIBERNATE mode –allows a DEV to conserve power for extended periods until DEV choose to listen for a beacon –So, DEV may loose it’s synchronization of piconet –To avoid being disassociated from the piconet, all DEVs in HIBERNTE mode must send at least one ACK frame to the PNC during their ATP

20. Reference IEEE 802, Part 15.3: Wireless Medium Access Control (MAC) and Physical Layer (PHY) Specification for High Rate Wireless Personal Area Networks (WPAN)