PHY Power Saving Features For 11ac July 2010 doc.: IEEE 802.11-10/0785r0 July 2010 PHY Power Saving Features For 11ac Date: 2010-07-13 Authors: Yujin Noh, LG Electronics Yujin Noh, LG Electronics

Abstract Useful Usage Model for efficient power consumption July 2010 doc.: IEEE 802.11-10/0785r0 July 2010 Abstract Useful Usage Model for efficient power consumption Consideration aspects for less-overhearing Potential signaling options for the Micro-Sleep Feature PHY ID for power saving in detail VHT-SIG field design aspect PHY ID compression methods CRC Fail of VHT-SIG-B Consideration of MAC ID for power saving Yujin Noh, LG Electronics Yujin Noh, LG Electronics

Multi-media Streaming at Networked Home July 2010 Multi-media Streaming at Networked Home Distributed Consumer Electronics(CE) around the AP More than one device of the networked home is likely to be communicated with one shared AP Direct data transmission between distributed CEs to support robust HD video streaming and surveillance (e.g. Direct Link Setup, WiFi Direct) Surveillance Camera HD Video Streaming Data Transfer DLS MU-MIMO Yujin Noh, LG Electronics

Previous features for power saving July 2010 Previous features for power saving With CSMA/CA based, each STA needs to be enforced to listen to the channel to know about the current status regardless of its own data communication with AP Some method for power saving to reduce the time required for STA to listen to the channel Basic power save mode switching between awake state and sleep state with PS-Poll frame from STAs APSD (Automatic Power Save Delivery) PSMP (Power Save Multi-Poll) In case of the high throughput to be supported, less chance to sleep due to a lasting awake state supporting reasonable QoS Consumer need for efficient power consumption even during awake state for the consumer electronics Yujin Noh, LG Electronics

Considerations for Power Save features in PHY July 2010 Considerations for Power Save features in PHY Information to indicate whether or not to listen and decode the data packet Data non-reception STAs can switch to sleep state after decoding VHT-SIG (VHT-SIGA or VHT-SIGB) Consideration aspects AP and STA have different required power efficiency at the transceiver Efficient power management of STA is typically more desirable Yujin Noh, LG Electronics

Use cases for Micro-Sleep during Active State July 2010 Use cases for Micro-Sleep during Active State Observation Data transmission can be categorized into 3 links Scenario 1 : STA-to-AP Scenario 2 : AP-to-STA Scenario 3 : STA-to-STA (DLS, Direct Link Setup) Yujin Noh, LG Electronics

Micro-Sleep during Active State (1/3) July 2010 Micro-Sleep during Active State (1/3) Consideration aspect 1 (STA-to-AP transmission, UL) Data reception at AP No need for all STAs to overhear UL data packet (not intended users) The power save information in VHT-SIG to allow Rx micro sleep for all STAs Yujin Noh, LG Electronics

Micro-Sleep during Active State (2/3) July 2010 Micro-Sleep during Active State (2/3) Consideration aspect 2 (AP-to-STA transmission , DL) Only a single/subset of STAs (SU-MIMO/MU-MIMO) in BSS require data reception STA(s) requires information on whether or not to demodulate and decode received signal from AP for power saving The PHY ID (e.g. Association ID) concept to indicate intended receiving STA(s) which allows Rx micro-sleep on subset of STAs Yujin Noh, LG Electronics

Micro-Sleep during Active State (3/3) July 2010 Micro-Sleep during Active State (3/3) Consideration aspect 3 (STA-to-STA, DLS) STA1 and STA2 are paired for DLS operation It is assumed that STA1 transmits data packet to STA2 directly STA2 requires information on whether or not to demodulate and decode the received signal for power saving Possibility of indicate PHY ID for DLS Note : current specification does not support Association ID for DLS Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (1/7) July 2010 Signaling for the Micro-Sleep Feature (1/7) Link differentiation between DL and UL Simple and efficient signaling to solve half of the active reception processing waste 1 bit in VHT-SIG-A or 1 state taken from Group ID field Introduce the PHY ID in VHT-SIG Solves the other half of the active reception processing wastes simply The potential candidate : Group ID and AID (11bits) of STA(s) Receiver Behavior Procedure CRC Fail of VHT-SIG-B Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (2/7) July 2010 Signaling for the Micro-Sleep Feature (2/7) Use of Group ID as PHY ID Simple and efficient way to use Group ID included in VHT-SIG-A Depending on the definition, number of data non-RX STAs with sleep mode might be small than expected Extend PHY Group ID with (logical) MAC Grouping Same Group ID is allocated to multiple grouping of STAs Useful to allow giving possibility for AP to allocate and manage more combination of STAs Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (3/7) July 2010 Signaling for the Micro-Sleep Feature (3/7) Example of Group ID STA A, STA B, etc can correspond to MAC Address, Associated ID or some other unique identifier Refer to the corresponding document dealing with STA Group Management for MU-MIMO from LG Electronics for more details In that sense, AID signaling might be helpful to assist power saving of MU-MIMO Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (4/7) July 2010 Signaling for the Micro-Sleep Feature (4/7) To support Association ID for DLS Even though AID field is included in VHT-SIG, there is no way for Tx DLS STA to know AID of Rx DLS STA add a new field in DLS Action frame for power saving Example of DLS request frame Order Information 1 Category 2 Action 3 Destination MAC Address 4 Source MAC Address 5 Capability Information 6 DLS Timeout Value 7 Supported rates 8 Extended Supported Rates 9 Destination PHY ID Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (5/7) July 2010 Signaling for the Micro-Sleep Feature (5/7) Use of BSSID part of PHY ID It may help PHY ID ambiguity potentially in case of OBSS scenario In a typical OBSS circumstance, each AP assigns AID with 11 bits randomly The benefits of BSSID inclusion to PHY ID will be limited Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (6/7) July 2010 Signaling for the Micro-Sleep Feature (6/7) CRC Fail of VHT-SIG-B VHT-SIG-B is precoded (beamformed) in MU-MIMO transmission Reception SINR for non-intended STA is expected to be low This may cause CRC FAIL of VHT-SIG-B for non-intended STA regardless of AID inclusion in VHT-SIG-B Receiver behavior when CRC FAIL of VHT-SIG-B VHT-SIG-B contains MCS, [FEC] information which is necessary for decoding of received packet. STAs with decoded L-SIG & VHT-SIG-A correctly already has Channel Sense of busy information. STAs with CRC FAIL of VHT-SIG-B may go into RX micro-sleep Yujin Noh, LG Electronics

Signaling for the Micro-Sleep Feature (7/7) July 2010 Signaling for the Micro-Sleep Feature (7/7) Example of Receiver Behavior Procedure Yujin Noh, LG Electronics

VHT-SIG design aspects for PHY ID (1/2) July 2010 VHT-SIG design aspects for PHY ID (1/2) AID in VHT-SIG-A STAs can start micro sleep as early as possible Possibility of reinterpreting portions of NSTS field for AID in SU-MIMO transmission Impossible to signal multiple AID for MU-MIMO (4 time 11 bits is already 44 bits, where SIG-A has 48 bit limitation) AID in VHT-SIG-B Easier to support AID for each STA in MU-MIMO STAs can start micro sleep before actual data demodulation & decoding AID in VHT-SIG-B can be an unified solution for SU-MIMO and MU-MIMO Yujin Noh, LG Electronics

VHT-SIG design aspects for PHY ID (2/2) July 2010 VHT-SIG design aspects for PHY ID (2/2) Bit width restrictions in VHT-SIG-B VHT-SIG-B (26bits) may contain following fields MCS : 3~4bits [FEC : 1bit] (whether or not to include this is TBD) CRC : 8 bits Tail : 6 bits Having full 11 bits as PHY ID may not be possible if other bits are included in VHT-SIG-B Yujin Noh, LG Electronics

PHY ID compression methods (1/2) July 2010 PHY ID compression methods (1/2) Partial AID with N bits (where N < 11) The practical number of STA associated with a single AP will be limited Compressing AID may not help power save utilization in OBSS cases Example : AP transmits data packets to STA3 STA1 & 2 switch into micro sleeps after decoding of the partial AID STA 3 keeps decoding data packet STA3: AID = 1075 Partial AID =51* Partial AID = 51 STA2: AID = 1052 STA1: AID = 1054 Partial AID =28 Partial AID =30 Yujin Noh, LG Electronics

PHY ID compression methods (2/2) July 2010 PHY ID compression methods (2/2) AID compression by utilizing CRC field space Partial AID with N bits and CRC with (11-N) bits in VHT-SIG-B CRC masking with the last (11-N) bits of AID STAs with different AID will result in CRC value mismatch and FAIL of CRC checking Yujin Noh, LG Electronics

Problems with MAC ID power saving July 2010 Problems with MAC ID power saving MAC ID in MAC header Considering AP transmitting A-MPDU to STA(s) More long receiver processing time with active state for non-intended STAs Data non-reception STAs can start micro sleep only after decoding the first MPDU In case of the first MPDU with error , data non- reception STAs keep receiver processing until they can identify the MAC ID of next MPDU It is safe and beneficial to use PHY ID in VHT-SIG with the low data rate such as (Q)BPSK It might be beneficial for MAC ID to assist power saving feature as the last stage Yujin Noh, LG Electronics

Potential information for power saving July 2010 Summary In general, support of power saving during active state seems important. Potential PHY power saving features in different circumstance 1 bit or 1 state information in VHT-SIG-A is preferred for an efficient way to solve half of the active reception processing waste Additional consideration to support potential power saving CRC checking receiver behavior procedure Type Potential information for power saving UL 1 bit or 1 state indication in VHT-SIG A DL MU-MIMO Group ID and (partial) AID in VHT-SIG B DL SU-MIMO (partial) AID in VHT-SIG B DLS Yujin Noh, LG Electronics

July 2010 doc.: IEEE 802.11-10/0785r0 July 2010 Strawpoll Do you support adopting Link differentiation information (e.g. UL and DL) in VHT-SIG-A field as described in slide 10 and adding the following item into the specification framework document, 11-09/0992? R3.2.1.H: VHT-SIG-A includes the fields listed in Table 1. Field Bits Description Bandwidth TBD STBC 1 [10/382r2] Group ID [10/0582r1] A value of zero indicates [10/0382r2]: A single user transmission A transmission where the group membership has not yet been established A transmission that needs to bypass a group (e.g. broadcast) NSTS [10/0582r1] Link differentiation Yujin Noh, LG Electronics Yujin Noh, LG Electronics

Annex July 2010 July 2010 doc.: IEEE 802.11-10/0785r0 Yujin Noh, LG Electronics Yujin Noh, LG Electronics

Annex. CRC masking (1/2) CRC Match July 2010 Annex. CRC masking (1/2) CRC Match Partial AID with N bits and CRC with (11-N) bits in VHT-SIG-B CRC masking with the last (11-N) bits of AID 1 1 1 0 1 0 0 0 1 0 1 CRC Field AID MSB Field 1 0 1 0 1 1 1 1 1 0 1 XOR 1 0 0 1 0 1 0 1 0 0 0 || AID Always 000 CRC CRC Match (PASS) TX RX Yujin Noh, LG Electronics

Annex. CRC masking (2/2) CRC Mismatch July 2010 Annex. CRC masking (2/2) CRC Mismatch STAs with different AID will result in CRC value mismatch and FAIL of CRC checking 1 1 1 0 1 0 0 0 1 0 1 CRC Field AID MSB Field 1 0 1 0 1 1 1 1 1 0 1 XOR 1 0 0 1 0 1 0 1 0 0 0 || 0 1 1 1 0 0 1 0 1 1 1 0 1 1 1 1 1 1 1 1 1 0 AID Always 000 CRC CRC Mismatch (FAIL) TX RX Yujin Noh, LG Electronics