doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 1 Forwarding in mesh containing MPs in power save Date: Authors:

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 2 Abstract The current s draft 2.0 defines power save, routing and frame transmission rules These features have been independently developed –However these features should be coupled and they should interact This presentation provides means to link these features together

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 3 Background The target of the s is to define a single device class, Mesh Point (MP), implementing same services For mesh network frame forwarding is key service –Without frame forwarding connectivity through network is not achieved; and this leads to routing For handheld and other battery powered devices power save is a must –Consumers are expecting good performance and still have a long battery life from devices

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 4 Recap of s D2.0 The current power save mechanisms in s define mechanisms for power save –Frame exchange is initiated by the beaconing –The scheme works well for best effort traffic, but may not offer good QoS for real time applications Many comments in LB 126 were requesting clarifications for interoperation of forwarding and power save –Also routing needs to be considered in this context

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 5 Recap of s D2.0 Many presentations on the routing and power save have been made: –11-07/2181r0 shows that routing and power save are compatible, all MPs are capable to use default HWMP routing –11-07/2095r2 proposes enhancement to the routing that enables control are Path Requests issued only to active mode or all MPs Routing should use metrics which avoids using battery powered devices for frame forwarding –The battery powered devices should not be used as a first option for frame forwarding

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 6 Routing metric to characterize MP power principle The routing metric parameters should be able to characterize the power mode in which the MP operates For routing purposes it is important to know the MPs operating in active mode (for some time) and support battery powered devices –The ‘active mode only’ MP may change its power mode after it has explicitly indicated to other peer MPs that it will no longer operate only in active mode –The ‘mainly in deep sleep’ MP may change its power management mode, if needed, but the device is trying to avoid all data transmissions The updating of the routing metric requires frame exchange which introduces delays –Updating of the routing information takes longer time than change of the MP’s power management mode ~ 10 seconds for routing ~ 0.5 seconds for a link

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 7 Power management mode use in mesh MPs shall be able to adjust the used power management mode according to transmitted traffic to reduce power consumption –If there is no or moderate traffic load, peer service periods are used (i.e. there is time to operate in doze state) –If there is high traffic load the MP usually switches to active mode (i.e. no time to operate in doze state) –This is normal operation for battery powered devices The forwarding MPs should be conservative on the timing for power management mode change –Time limits for forwarding MP to change power management mode should be defined –The time limits avoid forwarding MP to switch power management mode too quickly which may cause poor QoS for forwarded traffic MP may have multiple links which all have independent power management modes –The MP needs to perform the power management mode transition for all links in mesh network to be able to operate in doze state

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 8 From route discovery to frames transmission After routing has discovered the route for the traffic, frames may be transmitted –The forwarding MPs may not have knowledge of the traffic characteristics –The forwarding MPs may measure the traffic characteristics when it forwards the frames, but the measurement results may be inaccurate and measurements may add implementation complexity to MPs A mechanism to describe the characteristics of the traffic, i.e. periodicity of the frames transmission is needed for: –Selecting the appropriate power mode –Peer service period triggering between active and PS MPs –MDA setup

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 9 Traffic Information passing The MPs which are sink or the source of the frames have good knowledge of the traffic generation periodicity –A mechanism for conveying QoS information through all MPs in transmission path is needed Traffic information is transmitted in unicast frames to the same path as the data frames The transmission of the traffic information is not controlled. Traffic information may be sent, if the path changes or the receiving MP notices poor QoS for the traffic

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 10 Frames forwarding in Mesh Each MP needs to select the coordination function (EDCA or MDA) and power management mode for frames it transmits –802.11s D2.0 does not specify or recommend how to select appropriate mechanisms s D2.0 provides limited amount of alternatives for power saving MPs that forward frames –The following slides introduces different frames forwarding schemas and describe briefly how they should be used

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 11 PS and frames forwarding interoperation The MP may continue to operate in power save mode and exchange the frames –This operation is suitable for situations when “small amount” of low AC (AC0 or AC1) frames are exchanged –If contiguous peer MPs in transmission path of high AC frames operate in power save mode, the traffic QoS is not in appropriate level Peer service periods may be triggered from power saving MP only after beacon transmission. Delays are likely in order of hundreds of ms, depending on the beacon transmission periodicity PS MP B Forwarding path PS MP APS MP C

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 12 PS and frames forwarding interoperation The MP may change itself to active mode –This should be preferred operation, if there is high traffic load or devices are not aware of the traffic information for the high AC traffic and long time operation in this forwarding scheme is possible if MP is not power constrained –This may be default operation for simple mains powered MPs like washing machines, TVs, media servers, etc that are not power constrained Forwarding path Active mode MP AActive mode MP C Active mode MP B

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 13 Some PS MPs may benefit from active mode MPs PS MP may transmit frames and trigger active mode MP at any time, similarly as terminals may transmit frames to AP at any time –If high AC frames are forwarded, the PS MP may periodically trigger peer service periods for frames transmission –Only the power save MP needs to coordinate peer service period triggering, no additional complexity for active mode MPs This scheme enables every second MP in the forwarding path to operate in power save mode Active mode MP B Forwarding path PS MP A PS MP C

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 14 Enabling PS for all MPs in forwarding path If both MPs are operating in power save mode, they need some common schedule for frames transmission. Mesh Deterministic Access (MDA) may be used for this service: –MDA enables real time (high AC) data transmission between two (power saving) MPs –MDA reservation mechanisms improve data transmission efficiency which reduces power consumption –This scheme enables all MPs in the forwarding path to operate in power save mode Presentation xxxx-r0 describes more details how power saving MPs use MDA PS MP B Forwarding path PS MP APS MP C

doc.: IEEE /0578r0 Submission 2008 May Jarkko Kneckt, NokiaSlide 15 Summary Forwarding path may contain power saving MPs –Rules and recommendations for selecting the appropriate power mode and coordination function should be included to s Routing should avoid power saving MPs use for frames forwarding