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Section 4: cdma2000 MAC

Section 4: cdma2000 MAC. What cdma2000 MAC Provides. The cdma2000 MAC sublayer provides: MAC Control States - procedures for controlling the access of data services (packet and circuit) to the physical layer;

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Section 4: cdma2000 MAC

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  1. Section 4:cdma2000 MAC

  2. What cdma2000 MAC Provides • The cdma2000 MAC sublayer provides: • MAC Control States - procedures for controlling the access of data services (packet and circuit) to the physical layer; • Best Effort Delivery - reasonably reliable transmission over the radio link with a Radio Link Protocol (RLP) that provides a “best effort” level of reliability; and • Multiplexing and QoS Control - enforcement of negotiated QoS levels by mediating conflicting requests from competing services and the appropriate prioritization of access requests. • Enhanced Access Procedures

  3. Channel Naming • Example: f-csch = Forward Common Signaling CHannel

  4. Logical Channels • Dedicated Traffic Channels (dtch) – • data channel dedicated to a single PLICF instance; • Common Traffic Channels (ctch) – • data channel with shared access among many mobile stations and/or PLICF instances; • Dedicated Signaling Channels (dsch) – • Upper Layer Signaling data dedicated to a single PLICF instance; and • Common Signaling Channels (csch) – • Upper Layer Signaling data with shared access among many mobile stations and/or PLICF instances.

  5. cdma2000 MAC State Transitions

  6. Packet Data States • Active State • Dedicated traffic channels (e.g., fundamental or supplemental) are allocated; • The Activity Timer starts when no traffic is exchanged and reset when there is traffic to be exchanged; • Traffic channel is released when the Activity Timer expires. • Control Hold State • A dedicated control channel is maintained on which MAC control commands (e.g., to begin a high speed data burst) can be transmitted. • Power control is also maintained so that high speed burst operation can begin with minimum delay. • Reverse pilot may be transmitted in a “gated” mode (i.e. with a duty cycle of less than one) to reduce interference and save power

  7. Packet Data States (cont’d) • Suspended State • No dedicated channels to or from the user are maintained • The state information for RLP is maintained • Active Set is stored by the BS so that if the Active Set is not changed the BS can instruct the MS to use the stored Active Set • Service Configuration Record is stored by the BS (to avoid Service Negotiation) • Mobile may continue monitoring the Paging Channel in the non-slotted mode for a shot time interval (~ 1-2 sec) after dropping the dedicated channels. This expedites a transition to the Active State shortly after the dedicated channels are released.

  8. Example of Packet Data State Transition

  9. State Transition Example

  10. cdma2000 Layered Structure

  11. Simplified Layered Architecture

  12. Functional Entity Definitions • Signaling • Performs Channel Assignment, Service Negotiation, Handoff, etc • Data Service PLICF • Interacts with the Resource Control and the Peer PLICF to coordinate state transitions between the MS and BS • DCR (Dedicated/Common Router) PLICF • Controls the behavior of the BS/MS when in Dormant State • MUX & QoS • realtime prioritization of the use of dedicated traffic resources • Mux/de-Muxing of the logical channels from/to different physical channels based on the Logical to Physical Mapping table (LPM)

  13. Resource Control • Locks and Unlocks resources and harmonizes state transition across multiple PLICFs • Maintains a database to control the operating configuration of the mobile, including • the current logical to physical channel mapping, and • the currently defined physical channel configuration (e.g., dedicated vs. common control operation; number of active SCHs; DCCH vs. FCH; etc.). 4 = Locked blank = unlocked sr_id = Service Reference ID

  14. State Transitions: Active State Active Control Hold

  15. Simplified State Transitions Active Control Hold Suspended

  16. Multiple Services • Multiple services with different characteristics may be connected simultaneously. • The Resource Control coordinates amongst multiple services • State transitions are synchronized (i.e. the RC assures that all the services make the state transition at the same time) • This synchronization is necessary because each state (e.g., Active, Suspended) has a certain set of attributes that correspond to the behavior of the BS/MS as a whole

  17. PLICF A Traffic... State Suspended Active Control Hold ... Allocate dmch, dtch Resource dmch, dtch dmch Confirm Release Indication dtch Unlock dtch Resource Control Allocate Indication dmch, dtch Release Indication dtch PLICF B Dragged to Active... PLICF B Dragged to Control Hold... PLICF B State Active Control Hold Suspended Resource dmch, dtch dmch Time Dragging Example • Service ‘A’ requests for a transition to Active from Suspended • Service ‘B’ gets dragged up to Active as well

  18. PLICF A Timeout... State Control Hold Suspended ... Unlock dmch Resource dmch Release Indication dmch Resource Control PLICF A Dangling... Release Indication dmch PLICF B Unlock dmch State Suspended Control Hold Resource dmch Timeout... Time Dangling Example • Service ‘A’ requests for a transition to Control Hold from Suspended • Service ‘A’ dangles in the Control Hold state until service ‘B’ is ready to make the transition

  19. PLICF_A PLICF_B • RC confirmation • RC confirmation [2] • Timer expires • Send Request for releasing dtch • Timer expires • Send Request for releasing dtch [4] Locked Unlocked Locked Unlocked • RC releases dtch • RC releases dtch [1] [3] [5] [5] • RC confirmation • RC confirmation • Timer expires • Send Request for releasing dmch • Timer expires • Send Request for releasing dmch [9] Locked [7] Unlocked Locked Unlocked • RC releases dmch • RC releases dmch [6] [8] [10] [10] Multiple Services: Releasing Resources and Dangling Active Control Hold Active State Control Hold State

  20. PLICF_A PLICF_B [4] • Has Data to Send • Send Request for locking dtch • RC Lock confirmation Locked Unlocked Locked Unlocked [3] Receives Confirmation for Allocation of dtch Receives Indication for Allocation of dtch [2] [2] • Have Data to Send • Send Request for Allocating dtch Locked Unlocked Locked Unlocked [1] Multiple Services: Allocating Resources and Dragging Control Hold Active Active State Control Hold State

  21. State Transition Procedure • A PLICF locking or unlocking a logical resource • The RC determines if the request leads to a release or allocation of a physical resource • If a physical resource needs to be release or allocated, then the RC instructs the L3-Signaling to allocate or release the physical resource

  22. Mux Sublayer • Mux Option: determines • max number of MuxPDUs on the SCH • Single-size or double-size MuxPDUs • Mux PDU Type • LTU: Logical Transmission unit: • 1, 2, 4, or 8 MuxPDUs that are protected by a CRC which is added at the MUX sublayer • Data block: A block of data that belongs to the same service or signaling • MuxPDU: MuxSDU + header • The header specifies the Signaling, Primary, or secondary • MuxPDU Type: determines • Rate Set (e.g., 1 or 2) • how to parse the MuxPDU

  23. PDU Types and New Mux Options • Example: • Mux Option 0x906: Maximum 1 double-size MuxPDU Type 3 • Mux Option 0x822: Maximum 4 single-size MuxPDU Type 3

  24. Resource Config. Database (RCD)

  25. RRC Messages • Extended Supplemental Channel Assignment Message (20 ms) • For each Supplemental Channel it specifies: • Units of Start Time • A list of Active Sets for F-SCH (PN codes, Walsh Codes, and Quasi-orthogonal functions) • Assignment • Forward Supplemental Channel Assignment Mini Message (5 ms) • Specifies the Supplemental Ch. ID, Start Time, Duration, and an index to the list Active sets

  26. RRC Messages (cont’d) • Reverse Supplemental Channel Assignment Mini Message (5 ms) • Specifies the Supplemental Ch. ID, Start Time, Duration, and Rate • Reverse Supplemental Channel Request Mini Message (5 ms) • Specifies the Supplemental Ch. ID, Requested Rate, and Requested Duration.

  27. MAC Messaging (cont’d) Reverse High-Rate Transmission Forward High-Rate Transmission

  28. Existing IS-95 A/B Access • IS-95 A/B access scheme is based on a slotted aloha protocol • access channel slots are non-overlapping • Accessing mobiles send probes on R-EACH: • probes consist of: • preamble portion (typically 80 ms) • message portion (typically 120 ms) • Acknowledgements are transmitted on the paging channel • acknowledgement time-out (typically 320 ms) • If no acknowledgement is received, mobile increases power and tries again (i.e. power ramping) • Access slotting is typically 200 ms • back-off delays (multiple of 200 ms) • persistence delay (multiple of 200 ms)

  29. IS-95A/B Access Procedure

  30. Requirements for Improved Access • Increase System Capacity • Minimize power required to service transactions • reduce power on preamble for detection • reduce power on message portion • minimize message retransmission probability • Facilitate better flow control and admissions policies • Increase Throughput & Reduce Delay • Minimize service transaction times • increased data rates (9.6, 19.2 and 38.4 kbps) • shortened preamble • reduce message error probability • reduce protocol latency (i.e. slot duration, ack. timeout, etc.)

  31. Improved Access Methods • Employ overlapped slotting • make long code a function of slot time to prevent hard collisions • Improve message error rate performance • closed loop power control • employ adjustable step sizes • Protocol Optimization: • reduce slot intervals, timeout params, etc. • for very short messages, closed loop PC provides little gain • closed loop PC can be used to correct gross inaccuracies in open loop estimate • longer messages can be moved to a dedicated channel • soft handoff can be used to improve access performance

  32. Overview of Proposed Approach • Reservation Multiple Access (RsMA) is composed of three distinct access protocols: • Basic Access Mode (slotted aloha): • best for very short messages (e.g. < 20 ms.) • open loop power control only • no soft handoff • Power Controlled Access Mode (PCA): • best for latency sensitive applications • closed loop power control on RL • no soft handoff • Reservation Mode (RsMA): • best for longer messages • closed loop power control on RL • soft handoff facilitated

  33. Access Channels • Forward Link: • Common Power Control Channel (F-CPCCH) • Channel Assignment Channel (F-CACH) • Common Control Channel (F-CCCH) • Reverse Link: • Reservation Access Channel (R-EACH) • Common Control Channel (R-CCCH)

  34. Reverse Reservation Access Channel • Reverse Enhanced Access Channel (R-EACH) • Slotted Aloha random access channels • multiple R-EACH’s per F-CCCH • R-EACH is operated in 3 primary modes: • BA Mode: short messages sent • PCA Mode: messages sent with closed loop PC • RsMA Mode: reservation requests sent • Data rates supported: • 9.6 kbps (20 ms frame),19.2 kbps (10, 20 ms frames), 38.4 kbps (5, 10, 20 ms frames) • R-EACH Probe Structure: • BA Mode: alohaaccess probe (AAP) = initial preamble + message • PCA Mode: message access probe (MAP) = initial preamble + mode request frame + message • Reservation Mode: reservation access probe (EAP) = initial preamble + mode requestframe

  35. Reverse Common Control Channel • Reverse Common Control Channel (R-CCCH) • Assigned dedicated access channels • Multiple R-CCCH’s supported • long code can be common or user specific (designated) • Data rates supported : • 9.6 kbps (20 ms frame),19.2 kbps (10, 20 ms frames), 38.4 kbps (5, 10, 20 ms frames) • Soft Handoff : • 2-way soft handoff can be accommodated on the R-CCCH • demod at 2 separate BTS’s • PC independently from 2 BTS’s

  36. Forward Common Assignment Channel • Forward Common Assignment Channel (F-CACH) • single Walsh code control channel supporting multiple R-EACH’s and R-CCCH’s • multiple F-CACH’s supported • Modulation format: • single 128-chip Walsh code channel • DTX, QPSK • fixed 9.6 kbps; k=9, rate 1/2 conv. code • fixed 5 ms message duration with CRC • Messages: • BTS-level channel assignments/acknowledgements • load & flow control (wait message)

  37. Forward Power Control Channel • Forward Power Control Channel (F-CPCCH) • multiple F-CPCCH’s supported • single Walsh code channel, divided into multiple sub-channels • Each F-CPCCH subchannel supports a single R-EACH or R-CCCH • Number of PC sub-channels per F-CPCCH • depends on PC rate which is a system parameter: • 800 bps PC --> 24 subchannels per F-CPCCH • 400 bps PC --> 48 subchannels per F-CPCCH • 200 bps PC --> 96 subchannels per F-CPCCH • Modulation format: • single 128-chip Walsh code channel • DTX, uncoded QPSK • fixed 9.6 kbps bit rate per I-Q phase branch • Step Sizes • Access channel specific up & down steps.

  38. R-EACH Waveform Description • Probe Preamble (sent in all modes): • integer number 1.25 ms. • preamble can be divided into multiple ‘on’ and ‘off’ pieces • Mode Request Frame (not sent in Basic Access Mode) • 5 ms frame, rate 1/2 coded message • Message Fields: • mode indicator (1 bit): indicates PCA vs. Reservation mode • Hash ID (16 bits):random or managed temporary mobile ID • rate word (3 bits): indicates data rate and frame length of message • neighbor PN (9 bits): PN offset of neighbor (set to 0 if no handoff requested) • CRC (8 bits) and Tail bits (8 bits) • reserved (3 bits) • Message Portion (not sent in Reservation mode) • max. message duration is system parameter • rate must be consistent with rate word in Mode Request Frame

  39. R-RCCCH Waveform Description • Channel Estimation Preamble: • integer number 1.25 ms. • preamble can be divided into multiple ‘on’ and ‘off’ pieces • Long Code • common long code mask • designated mode: user specific long code mask • Message portion: • message is an integer number of frames • max. duration is system parameter • data rate must be consistent with resource grant • CRC’s per frame

  40. F-CACH Waveform Description • fixed messages duration (5 ms.) • Single 128-chip Walsh Code channel, • QPSK modulation with r=1/2, k=9 conv. Coding • Channel is DTX • no message --> no power • Message types: • Channel assignment message fields: • Wait message (admissions/flow control) • 2 reserved message types

  41. F-CPCCH Waveform Description • PC rate determines the number of PC sub-channels supported: • 24 @ 800 bps, 48 @ 400 bps, 96 @ 200 bps. • The power control sub-channel id for each F-CPCCH is partitioned as follows:

  42. Admission/Flow Control • Admission/flow control: • Slow Response Time (~ 200 ms, typical): • access parameters conveyed on F-BCCH give current persistence parameters and time-out values • Moderate Response Time ( 5 ms): • “wait message” is used to affect mobiles already accessing • sent when “overload” or “all busy” condition is near or prevailing • parameters affect: • flow on both the R-EACH and R-CCCH for reservation mode traffic • system loading • Inhibit Sense mode can be invoked: • mobiles required to examine F-CACH prior to transmitting • behavior is ISMA-like

  43. Channel Organization • R-EACH: • up to 32 per F-CCCH • F-CACH: • up to 7 F-CACH’s supported • R-CCCH: • up to 24 supported • F-CPCCH: • up to 7 supported • PC rate determines number of sub-channels per F-CPCCH

  44. Pure Aloha Procedures • mobile “randomly” selects from the corresponding R-EACH set and transmits a Enhanced Access Probe (EAP) • mobile uses persistence parameters to regulate access attempts • After EAP transmitted on R-EACH, mobile monitors F-CCCH for acknowledgement: • If no ACK within time out, retry at higher power

  45. Basic Access Mode

  46. PCA Procedures • Mobile “randomly” selects a R-EACH and transmits a Message Access Probe (MAP) conditioned on: • observed Ec/Io > T_rqst dB • “current” persistence parameters and non-blocking condition • Mobile uses persistence parameters to regulate access attempts • After initial MAP, mobile monitors both F-CPCCH and F-CACH: • Closed loop power control begins after parameterized delay value • Mobile looks for Channel Assignment Message containing its hash ID as confirmation of acquisition • Conditions: • If no Channel Assn. Message within time-out, mobile ceases transmission of current MAP and retransmits MAP at higher power some time later • If wait message sent, cease and reretransmit MAP later • Stop transmission if either: • Ec/Io falls below T_fade for T1 seconds • Ec/Io exceeds T_good and Ec/Io of PC bits is below T_bad for L PC bits

  47. Power Control Access Mode

  48. Reservation Procedure (no SHO) • Mobile “randomly” selects a R-EACH and transmits a Enhanced Access Probe (EAP) conditioned on: • observed Ec/Io > T_rqst dB • “current” persistence parameters and non-blocking condition • Mobile uses persistence parameters to regulate access attempts • After initial EAP, mobile monitors corresponding F-CACH for: • Early Ack. And Channel Assignment Message (EACAM) or Wait Message • Conditions: • If no message within time-out, retransmit EAP at higher power • If wait message sent, retransmit EAP later • If channel assignment rcvd., transmit message on assigned R-CCCH at next access slot and begin closed loop power control. • Stop transmission if either: • Ec/Io falls below T_fade for T1 seconds • Ec/Io exceeds T_good and Ec/Io of PC bits is below T_bad for L PC bits

  49. Reservation Access Mode (no SHO)

  50. RsMA Procedure (SHO) • Mobile “randomly” selects a R-EACH and transmits a Enhanced Access Probe (EAP) conditioned on: • observed Ec/Io > T_rqst dB • “current” persistence parameters and non-blocking condition • Mobile uses persistence parameters to regulate access attempts • After initial EAP, mobile monitors corresponding F-CCCH / F-CACH for: • EACAM Power Control Channel Assignment Message (PCCAM) to get Common PC channel and sub-channel corresponding to the neighbor BS • Conditions: • If no PCCAM message within time-out, retransmit EAP at higher power • If PCCAM rcvd., transmit message on assigned R-CCCH at next access slot and begin closed loop power control using F-CPCCH subchannels indicated in PCCAM. • Stop transmission if either: • Ec/Io falls below T_fade for T1 seconds • Ec/Io exceeds T_good and Ec/Io of both PC bit streams falls below T_bad for L PC bits

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