SS Initialization Overview

Transcription

1 SS Initialization Overview Downlink Sync Auth. Key Xchange Get Uplink Parameters Setup Time Ranging Register Download Configuration File Capability Negotiation DHCP Setup connection and service flow (provisioned BE first) NCHU CSE WMAN - 1

2 Steps 1) Scan for downlink channel and establish synchronization with the BS (retrieve DL-MAP / DCD) 2) Obtain transmit parameters (from UCD message) (uplink channel descriptor) 3) Perform ranging (RNG-REQ and RNG-RSP) 4) Negotiate basic capabilities 5) Authorize SS and perform key exchange 6) Perform registration 7) Establish IP connectivity (DHCP) optional 8) Establish time of day optional 9) Transfer operational parameters (TFTP) optional 10) Set up connections Option : indicated by REG-REQ message NCHU CSE WMAN - 2

3 Message Flows BS Wireless channel Send DL/UL-MAP DL/UL-MAP SS SS power on Send UCD/DCD Send DL/UL-MAP UCD/DCD DL/UL-MAP The action of power on sequence complete Send DL/UL-MAP Send DCD Send DL/UL-MAP Send UCD Send DL/UL-MAP Send DL/UL-MAP DL/UL-MAP DCD DL/UL-MAP UCD DL/UL-MAP DL/UL-MAP Establish PHY synchronization Wait for UCD Obtain parameters for UL channel Extract slot info for uplink Wait for transmission opportunity to perform ranging Start ranging process NCHU CSE WMAN - 3

4 Transmit Parameters - Downlink(1/2) Achieve MAC synchronization. The SS achieves MAC synchronization once it has received at least one DL-MAP message. SS knows when BS broadcasts channel parameters from DL-MAP. Note that DL-MAP is encoded with well-known parameters. Obtain downlink parameters Retrieve parameters from the DCD messages.» Describe downlink channel character DCD messages contain:» Frame duration, TTG size, RTG size, downlink center frequency, BS ID, and so on.» Downlink burst profiles. Transmit/Receive Transition, TTG Receive /Transmit Transition, RTG NCHU CSE WMAN - 4

5 Transmit Parameters - Upwnlink (2/2) Obtain uplink parameters Retrieve parameters from the UCD messages.» Know uplink channel parameters. UCD messages contain:» Uplink center frequency, bandwidth request opportunity size, ranging request opportunity size, and other PHY specific parameters.» Uplink burst profiles. Receive the UL-MAP SS can perform initial ranging. Initial ranging opportunities (parameters). NCHU CSE WMAN - 5

6 OFDMA Frame Structure FCH (frame control header) Transmit/Receive Transition, TTG Receive /Transmit Transition, RTG NCHU CSE WMAN - 6

7 MAC Frame Architecture with TDD Mode DLFP(DL frame prefix) May be to different SSs To the same SS NCHU CSE WMAN - 7

8 The Content of MAC Frame The frame control head (FCH) provides the frame configuration information such as MAP message length, coding schemes, and available subchannels. DLFP(DL frame prefix) includes four information elements (IEs) which record the important information to SSs. Each IE includes four elements: receiver CID DIUC (Downlink Interval Usage Cod)» adopt modulation and code burst profile» the started time of burst profile increased synchronization NCHU CSE WMAN - 8

9 The Content of MAC Frame DL Burst1 includes DCD (downlink channel descriptor), UCD (uplink channel descriptor), DL-MAP and UL-MAP NCHU CSE WMAN - 9

10 Uplink Channel Descriptor (UCD) Message Configuration Change Count (page 10) Incremented by one (modulo 256) by the BS whenever any of the values of this channel descriptor change. This value is also referenced from the UL-MAP messages. Ranging Backoff Start Initial backoff window size for initial ranging contention Ranging Backoff End Final backoff window size for initial ranging contention Request Backoff Start Initial backoff window size for contention BW requests Request Backoff End Final backoff window size for contention BW requests All above parameters are expressed as a power of 2. Values of n range 0 15 the highest order bits shall be unused and set to 0 The Uplink_Burst_Profile is a compound TLV encoding that associates with a UIUC, TLV: Type-Length-Value UIUC(Uplink Interval Usage Code) NCHU CSE WMAN - 10

11 UCD Format NCHU CSE WMAN - 11

12 Uplink Map (UL-MAP) Message UCD Count (page 10) Matches the value of the Configuration Change Count of the UCD, which describes the uplink burst profiles that apply to this map. Allocation Start Time Effective start time of the uplink allocation defined by the UL-MAP units are PHY-specific (pp. 153)» minislots : SC and SCa PHY layers» symbols and subchannels : OFDM and OFDMA PHY layers The end of the last allocated burst is indicated by allocating an End of Map burst (CID = 0 and UIUC = 14). Map IEs The contents of a UL-MAP IE is PHY-specification dependent. NCHU CSE WMAN - 12

13 Uplink Map (UL-MAP) Message NCHU CSE WMAN - 13

14 Uplink_Burst_Profile NCHU CSE WMAN - 14

15 Uplink Interval Definition Request IE BS specifies an uplink interval for bandwidth requests The character of this IE changes depending on the type of CID used in the IE» Broadcast or multicast CID (poll) : an invitation for SSs to contend for requests.» Unicast CID (poll) : an invitation for a particular SS to request bandwidth» part of a QoS scheduling scheme that is vendor dependent For bandwidth request contention opportunities, the BS shall allocate a grant that is an integer multiple of the value of Bandwidth request opportunity size (in unit of PS) which shall be published in each UCD transmission. NCHU CSE WMAN - 15

16 Uplink Interval Definition Initial Ranging IE An interval is allocated in UL-MAPs» the maximum round-trip propagation delay plus the transmission time of the RNG-REQ message For ranging contention opportunities, the BS shall allocate a grant that is an integer multiple of the value of Ranging request opportunity size, (in unit of PS) which shall be published in each UCD transmission. Data Grant Burst Type IEs provide an opportunity for an SS to transmit one or more uplink PDUs. Start time (in units of symbol duration) : relative to the Allocation Start Time given in UL-MAP (may across to next frame) NCHU CSE WMAN - 16

17 Ranging Request (RNG-REQ) message What is ranging? Ranging is the process of acquiring the correct timing offset and power adjustments. Using RNG-REQ/RNG-RSP messages. transmitted by the SS at initialization : initial ranging Periodically: data grant intervals (16e-2005) when the MS is attempting to perform re-entry (wake-up), association (initial) or handover (roaming) To determine network delay To request power and/or downlink burst profile change. CID = Initial ranging CID if Joining network not yet registered CID = Basic CID If sent in a data grant interval NCHU CSE WMAN - 17

18 Ranging Request (RNG-REQ) message when the SS is attempting to join the network, two parameters are included in the RNG-REQ message Requested Downlink Burst Profile (1 byte)» Bits 0-3 : DIUC (Downlink Interval Usage Cod)» Bits 4-7 : 4 LSB of Configuration Change Count value SS MAC Address (initial) during initial ranging on the SS s Basic connection, the parameter MAC Version is provided 1 : : c-2002 and its predecessors 3 : a-2003 and its predecessors 4 : : and e-2005 (16e-2005 add) AAS broadcast capability may be included in the RNG-REQ message: Applied for SCa/OFDM/OFDMA NCHU CSE WMAN - 18

19 Ranging Request (RNG-REQ) message after the SS has received an RNG-RSP, two parameters are included in the following RNG-REQ (periodic) message : Requested Downlink Burst Profile (1 byte)» Bits 0-3 : DIUC» Bits 4-7 : 4 LSB of Configuration Change Count value Ranging Anomalies (1 byte) (periodic)» Bit #0 SS already at maximum power.» Bit #1 SS already at minimum power.» Bit #2 Sum of commanded timing adjustments is too large. If ranging was unsuccessful, the SS increases its power level and sends a new ranging message, continuing this process until success. NCHU CSE WMAN - 19

20 Ranging and Power Control During initialization, the SS performs initial power leveling and ranging using ranging request (RNG- REQ) messages transmitted in initial maintenance windows. The adjustments to the SS s transmit time advance, as well as power adjustments, are returned to the SS in ranging response (RNG-RSP) messages. For ongoing ranging and power adjustments, the BS may transmit unsolicited RNG-RSP messages commanding the SS to adjust its power or timing. Burst profile is not included NCHU CSE WMAN - 20

21 Ranging response (RNG-RSP) transmitted by the BS in response to a received RNG-REQ when an initial or periodic ranging message based on code division multiple access (CDMA) is received,» use the initial ranging CID. (D5 add) may also be transmitted asynchronously to send corrections based on measurements that have been made on other received data or MAC messages NCHU CSE WMAN - 21

22 Ranging response (RNG-RSP) message (1/2) Ranging Status 1 = continue, 2 = abort, 3 = success (no re-range D5 remove) Timing Adjust Information (signed 32-bit) SS shall advance its burst transmission time if the value is negative and delay its burst transmission if the value is positive. Power Level Adjust Information (signed 8-bit, 0.25 db units) Offset Frequency Adjust Information (signed 32-bit, Hz units) fine-frequency adjustment within a channel Downlink Frequency Override Center frequency, in khz, SS redoes initial ranging. (ranging status = 2) Uplink Channel ID Override Licensed bands : (D5 remove) License-exempt bands: The Channel Nr where the SS should redo initial ranging. NCHU CSE WMAN - 22

23 Ranging response (RNG-RSP) message (2/2) Basic CID (2 bytes) A required parameter if the RNG-RSP message is being sent on the Initial Ranging CID in response to a RNG-REQ message that was sent on the Initial Ranging CID. Primary Management CID (2 bytes) A required parameter if the RNG-RSP message is being sent on the Initial Ranging CID in response to a RNG-REQ message that was sent on the Initial Ranging CID. SS MAC Address (48-bit) (successful case) A required parameter when the CID in the MAC header is the Initial Ranging CID. Downlink Operational Burst Profile (2 bytes) Byte 0: the least robust DIUC that may be used by the BS for transmissions to the SS. (well-known for SS) Byte 1: Configuration Change Count value of DCD defining the burst profile associated with DIUC. AAS broadcast permission NCHU CSE WMAN - 23

24 Ranging response (RNG-RSP) message WirelessMAN-OFDM PHY-specific parameter Ranging Subchannel WirelessMAN-OFDMA PHY when an initial ranging message based on code division multiple access (CDMA) is received, (w/ ranging subchannel) Ranging code attributes is transmitted from the BS (OFDMA time symbols reference, subchannel reference, and frame number) NCHU CSE WMAN - 25

25 Change Burst Profile (OFDMA) If downlink burst profile management is not applicable to OFDMA PHY. SS changes downlink operational profile by two methods SS uses an allocated data grant to send a DBPC-REQ» used to change to more or less robust profile SS uses the initial ranging interval to send a RNG-REQ» only be used to request to change to a more robust profile SS determines the optimal method. (out of spec.) Uplink periodic ranging For each SS, the BS maintains a T27 timer. At each timer expiration, BS shall grant bandwidth to the SS timer is restarted each time a unicast grant is made to the SS. When the status of the last RNG-RSP is continue, SS shall not use the data grant to service its uplink connections except to transmit a RNG-REQ message. Downlink Burst Profile Change Request (DBPC-REQ) NCHU CSE WMAN - 26

26 OFDMA-based ranging (1) WirelessMAN-OFDMA PHY specifies a Ranging Subchannel and a set of special pseudo noise Initial Ranging Codes and Periodic Ranging Codes Subsets of codes shall be allocated in the UCD Channel Encoding for (1) Initial Ranging, (2) Periodic Ranging and (3) Bandwidth Requests, such that the BS can determine the purpose of the received code by the subset to which the code belongs. For example, SS randomly select one code from initial ranging code subset, modulate it onto the Ranging Subchannel, and subsequently transmit in ranging slot randomly selected from the available ranging slots on the UL subframe. See NCHU CSE WMAN - 27

27 Example of Ranging Channel in OFDMA frame structure NCHU CSE WMAN - 28

28 OFDMA-based ranging (2) After acquiring downlink synchronization and uplink transmission parameters, SS transmits RNG-REQ (encoded by one Initial Ranging Code) on one ranging slot When BS successfully receives a CDMA Ranging Code, it can not determine which SS (unknow SS), So BS broadcasts a RNG-RSP that advertises the received Ranging Code as well as the ranging slot (such as OFDMA symbol number, subchannel, etc) The RNG-RSP contains» needed adjustment : time, power, possibly frequency corrections, and» status notification. When Ranging Response message with continue status, SS continues the ranging process with further ranging codes randomly chosen from the Initial Ranging domain (not periodic) Initial ranging process is over after receiving RNG-RSP message which includes a valid Basic CID NCHU CSE WMAN - 29

29 OFDMA-based ranging (1) BS SS Initial ranging Sending Code only Use initial ranging code Not success yet Still in initial ranging Use initial ranging code NCHU CSE WMAN - 30

30 OFDMA-based ranging (2) BS SS Still initial ranging Sending code again In periodic region Use initial ranging code Allocate Bandwidth Send RNG-REQ Ps. Enter periodic ranging When RNG-RSP with CID NCHU CSE WMAN - 31

31 Registration request (REG-REQ) (1) The process by which SS is allowed entry into the network. Include parameter: Primary Management CID (in the generic MAC header) The CID in the generic MAC header is the Primary Management CID for this SS, as assigned in the RNG-RSP message. NCHU CSE WMAN - 32

32 Registration request (REG-REQ) (2) The REG-REQ shall contain the following TLVs: Hashed Message Authentication Code (HMAC) Tuple» Shall be final attribute in the message s TLV attribute list.» In Mesh Mode, message digest is calculated using HMAC_KEY_U. IP Version SS Capabilities Encodings Vendor ID Encoding Vendor-specific information Convergence Sublayer Capabilities ARQ Parameters For PMP operation, the REG-REQ shall contain the following TLVs: Uplink CID Support» The number of uplink CID supported in SS three for managed SSs and two for unmanaged SSs SS management support» w/ or w/o secondary management connection IP management mode NCHU CSE WMAN - 33

33 Registration response (REG-RSP) (1) Include parameter: Primary Management CID (in the generic MAC header) Response» 0 = OK» 1 = Message authentication failure NCHU CSE WMAN - 34

34 Registration response (REG-RSP) (2) The REG-RSP shall contain the following TLVs SS Capabilities Encodings» Response to the capabilities of the requester provided in the REG-REQ.» indicates whether or not the capabilities may be used. IP Version Vendor ID Encoding Vendor-specific information ARQ Parameters» ARQ and fragmentation parameters specified by the BS to complete ARQ parameter negotiation for the secondary management connection. IP management mode» Response to REG-REQ indication of whether or not the requester wishes to accept IP-based traffic on the Secondary Management Connection, once the initialization process has completed. NCHU CSE WMAN - 35

35 Contention resolution Collisions may occur during Initial Ranging and Request intervals. After a contention transmission, waits for a RNG-RSP message (1. initial ranging) the SS waits for a Data Grant Burst Type IE in a subsequent map (2. bandwidth request) truncated binary exponential backoff with the initial backoff window and the maximum backoff window are controlled by the BS are specified as part of the UCD message and represent a power-of-two value. Request IEs or Initial Ranging IEs allocate contention intervals in the UL-MAP messages Random backoff (in slots) may across multiple intervals assigned in IEs. NCHU CSE WMAN - 36

36 Contention resolution retry when range timeout (200ms no range response) data grant timeout (10ms no data grant depend on service QoS) Until reaches the maximum number of retries if SS receives a unicast Request IE or Data Grant Burst Type IE, it shall stop the contention resolution process BS may set up the Request (or Ranging) Backoff Start and Request (or Ranging) Backoff End to emulate an Ethernet-style backoff by setting Request (or Ranging) Backoff Start = 0 and Request (or Ranging) Backoff End = 10 in the UCD message Open issue for optimize window (beyond the scope of standard) similar to HiperLAN Type II NCHU CSE WMAN - 37

37 Transmission opportunities The size of an individual transmission opportunity for each type of contention IE shall be published in each transmitted UCD message. The BS shall always allocate bandwidth for contention IEs in integer multiples of these published values. WirelessMAN-SC system for example,» frame duration =1 ms,» each minislot = 2 PSs, each PS = 4 symbols (1minislot = 8 symbols)» uplink preamble =16 symbols = 2 minislots,» SS transition gap (SSTG) = 24 symbols = 3 minislots.» For QPSK, each transmission opportunity requires 8 minislots: 3 for the SSTG, 2 for the preamble, and 3 for the bandwidth request message.» This payload requirement would be specified as a value of 16 (pp. 167) assigned to the UCD TLV Bandwidth request opportunity size NCHU CSE WMAN - 38

38 Transmission opportunities One Request IE with 24 minislots indicates there will be three transmission opportunities NCHU CSE WMAN - 39

39 Sleep-mode for mobility-supporting MS Sleep Mode is intended to minimize MS power usage decrease usage of Serving BS air interface resources. Implementation of sleep-mode is optional for the MS mandatory for the BS Defines Power Saving Class a group of connections, which have common demand properties, use one power saving class may be repeatedly activated and deactivated activated class : start sleep/listening windows sequence associated Algorithm of choosing Power Saving Class type for certain connections (service) is outside of the scope of the standard. NCHU CSE WMAN - 40

40 Sleep-mode for mobility-supporting MS Three types of Power Saving Classes (I, II, III) Terms : Unavailability interval is a time interval that does not overlap with any listening window of any active Power Saving Class (overlap with sleeping window) Availability interval is a time interval that does not overlap with any Unavailability interval During Unavailability interval, BS shall not transmit to the MS, and buffer/drop SDUs MS power down transceiver or perform another activities:» scanning neighbor BSs» associating with neighbor BSs etc., During Availability interval, MS receives all DL transmissions as normal mode MS examines DCD/UCD change counts and the frame number of the DL-MAP to verify synchronization with the BS. Upon detecting a changed DCD and/or UCD count, 1. using the Broadcast Control Pointer IE for tracking and updating DCD and/or UCD changes 2. the MS shall continue reception until receiving the corresponding updated message. NCHU CSE WMAN - 41

41 Sleep-mode for mobility-supporting MS During handover, MS sends RNG-REQ which may include Power_Saving_Class_Parameters BS shall transmit unsolicited MOB_SLP-RSP message to the MS after handover (BS commands MS) In MOB_TRF-IND message with negative indication for the MS, the BS may include an updated SLPID for a MS by appending SLPID_Update TLV in the MOB_TRF-IND message. if the MS s current SLPID matches the Old_SLPID, update it MS in Sleep Mode may participate in periodic ranging Serving BS allocates UL transmission opportunity for periodic ranging MS transmits RNG-REQ message and waits RNG-RSP NCHU CSE WMAN - 42

42 Sleep-mode for mobility-supporting MS MS in Sleep Mode may maintain triggers to perform event-based actions for CINR, RSSI, and RTD trigger (defined in DCD message) Neighbor BS CINR and Neighbor BS RSSI trigger (defined in MOB_NBR-ADV message) Actions-trigger negotiation MS requests to associate specific actions with certain triggers by using Enabled-Action-Triggered TLV in RNG-REQ or MOB_SLP- REQ message. BS replies RNG-RSP or MOB_SLP-RSP message including Enabled-Action-Triggered TLV provided that it allows to activate the requested type of Power Saving Class. Serving BS may verify MS exit from Sleep Mode by making an UL allocation for MS at any time subsequent to supposed wakening event (e.g. positive indication in MOB_TRF-IND message) by transmitting at least BR message» if there is no data to transmit, BR field of the BR PDU shall be set to 0 RTD (Round Trip Delay) NCHU CSE WMAN - 43

43 Example of Power Saving two Power Saving Classes Class A contains connections of BE and NRT-VR types» BS allocates sequence of listening window of constant size and doubling sleep window. Class B contains single connection of UGS type» BS allocates sequence of listening window of constant size and sleep window of constant size. NCHU CSE WMAN - 44

44 Types of Power Saving Classes Type I : for connections of BE, NRT-VR types varying sleep window during listening window, no Tx/Rx SDU (only MOB_TRF- IND) Type II : for connections of UGS, RT-VR types fixed sleep window During listening window, may Tx/Rx SDU/fragments/ACKs Type III : for multicast and management connections One time sleeping NCHU CSE WMAN - 45

45 Power Saving Classes Type 1 Type I for connections of BE, NRT-VR type. relevant parameters Initial-sleep window Final-sleep window base Listening window Final-sleep window exponent Start frame number for first sleep window Traffic triggered wakening flag NCHU CSE WMAN - 46

46 Power Saving Classes Type 1 SleepWin = min (2 prevsleepwin, finalsleepwinbase 2 ^ (finalslpwinexp)) sleepwin is the sleep window, prevsleepwin is the previous sleep window, finalsleepwinbase is the Final-sleep window base, and finalslpwinexp is the Final-sleep window exponent A traffic indication (MOB_TRF-IND) message is sent by the BS on broadcast CID Sleep mode multicast CID during listening window NCHU CSE WMAN - 47

47 Power Saving Classes Type 1 Power saving deactivated by MOB_SLP-REQ (MS request) Bandwidth Request and Uplink Sleep Control (MS request) MOB_SLP-RSP (BS reply) DL Sleep Control Extended Subheader messages header (BS command) (pp 32 in slide) BS transmits a MAC SDU or fragment during availability window BS transmits RNG-RSP message MS receives MOB_TRF-IND message If TRF-IND_Required flag was set in MOB_SLP-REQ, Power Saving Class shall be deactivated if MS failed to receive MOB_TRF-IND message during availability window. Repeatedly checking MOB_TRF-IND message NCHU CSE WMAN - 48

48 Power Saving Classes Type 2 Type II for connections of UGS, RT-VR types relevant parameters Initial-sleep window Listening window Start frame number for first sleep window Power Saving Classes of this type are defined/activated/deactivated by MOB_SLP-REQ MOB_SLP-RSP Bandwidth request and uplink sleep control header DL Sleep control extended subheader RNG-REQ RNG-RSP NCHU CSE WMAN - 49

49 Power Saving Classes Type 2 All sleep windows are of the same size as initial window BS may send unsolicited MOB_SLP-RSP or DL Sleep control extended subheader to active/deactivate Power Saving Class during listening windows the MS may send or receive any MAC SDUs or their fragments at connections as well as ACKs to them. NCHU CSE WMAN - 50

50 Power Saving Classes Type 3 Type III for multicast connections as well as for management operations Ex. Periodic Ranging, DSx operations, MOB_ NBR-ADV etc. Power Saving Classes of this type are defined/activated/deactivated by MOB_SLP-REQ MOB_SLP-RSP Bandwidth request and uplink sleep control header DL Sleep control extended subheader RNG-RSP relevant parameters: Final-sleep window base Final-sleep window exponent Start frame number for sleep window NCHU CSE WMAN - 51

51 Power Saving Classes Type 3 Deactivation of Power Saving Class occurs automatically after expiration of sleep window. If Next Periodic Ranging TLV encoding is included in MOB_SLP-RSP, this activates Power Saving Class of type III for periodic ranging BS can continue to activate the Power Saving Class using Next Periodic Ranging TLV encoding in RNG- RSP message with ranging status set to success. NCHU CSE WMAN - 52

52 Power Mgmt -Sleep Mode NCHU CSE WMAN - 53

53 Association procedure optional initial ranging procedure enable the MS to acquire and record ranging parameters and service availability information of BS There are 3 levels of association Association Level 0: Scan / Association without coordination Association Level 1: Association with coordination Association Level 2: Network assisted association reporting During initial-range, if the RNG-RSP message contains a Service Level Prediction parameter set to 2, MS may mark the BS as Associated in its MS local Association table» and sets an appropriate aging timer (ASC-AGING-TIMER) NCHU CSE WMAN - 54

54 MAC Design NCHU CSE WMAN - 55