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TDMA Tutorial

TDMA Tutorial. Outline of Presentation. Evolution of Technology AMPS to TDMA The TDMA Digital Control Channel Features and capabilities Technical description Services and design examples. TDMA Standards Overview. EIA 553 Analog AMPS-based technology platform IS-54B

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TDMA Tutorial

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  1. TDMA Tutorial

  2. Outline of Presentation • Evolution of Technology • AMPS to TDMA • The TDMA Digital Control Channel • Features and capabilities • Technical description • Services and design examples

  3. TDMA Standards Overview • EIA 553 • Analog AMPS-based technology platform • IS-54B • Introduces a TDMA digital traffic channel and a new feature set • authentication, calling number ID, message waiting indicator, and voice privacy.

  4. TDMA Standards Overview - cont. • TDMA • Backwards compatible to IS-54B and EIA 553. Includes a digital control channel and advanced features. • TDMA Rev A • Upbanded IS-136 for seamless cellular service between 800 MHz and 1900 MHz frequency bands, over the air activation and programming services developed. • TDMA Rev B • Introduces a range of new features (broadcast SMS, packet data etc.)

  5. Services Quality Capacity Coverage Cost TDMA B TDMA A plus EFRC IS-54 Adopted by TIA/CTIA TDMA Rev. 0 TDMA in Commercial Service TDMA Standards Process Begins 1994 1990 1992 1996 1988 1998 TDMA Standards Evolution

  6. 40 ms TDMA Frame Sync SACCH CDVCC Data RSVD Data TDMA Slot Format TDMA Traffic Channel Structure • Modulation • p /4 DQPSK - differential quadrature phase shift keying. • Across air bit rate = 48.6 Kbps. • Frame Structure • TDMA frame = 40mS. • Six 6.67 ms slots per frame, two slots used for full rate voice.

  7. TDMA Speech Coding • Speech and channel coding are important factors in good voice quality. Other factors include: • System planning (handoff, reuse, coverage, etc.) • Handset design • Echo suppression, audio balancing, … • Two speech codecs defined for TDMA • VSELP - Vector Sum Excited Linear Predictive • ACELP - Algebraic Code Excited Linear Predictive • VSELP • Originally defined for IS-54B - 80s Technology • ACELP • Newly defined for TDMA - 90s Technology - “state of the art” • Offers wireline voice quality in clean conditions

  8. 5 Tail bits 48 Most Perceptually Significant Bits 7-bit CRC Computation 7 216 208 260 260 Rate 1/2 Convolutional Coding 2-slot interleaver Puncturing 96 Voice Cipher Speech Coder (ACELP) Coded Class-1 bits Class-1 bits 52 Class-2 bits codec + channel coding = 7.4kbps + 5.6kbps = 13kbps codec 7.4kbps ACELP Channel Coding

  9. TDMA Voice Quality

  10. Mobile Assisted Handoff (MAHO) • System instructs mobile to measure neighbor channels. • Results reported back to system to aid handoff decision. • Designed to decrease dropped calls and improve handoffs. • TDMA supports any combination of handoff between digital and analog channels. • TDMA also supports handoff between 800 MHz and 1900 MHz cellular bands.

  11. Digital Control Channel Forward Channel (FDCCH) Reverse Channel (RDCCH) RACH SPACH BCCH SCF Reserved PCH F - BCCH ARCH E - BCCH SMSCH S - BCCH The Digital Control Channel

  12. Forward DCCH SYNC SCF DATA CSFP DATA RSVD SCF 28 12 130 12 130 10 2 Forward DTCH SYNC SACCH DATA CDVCC DATA RSVD CDL 28 12 130 12 130 1 11 Subfields Forward DCCH Slot Structure • SCF (Coded Superframe Phase) • Provides reverse DCCH access control • CSFP (Coded Superframe Phase) • Provides superframe phase • CDL (Coded Digital Locator) • Provides DCCH . • SYNC • Provides for slot synchronization • CDVCC • Coded digital verification color code • DATA • 1/2 convolutional coding with intraslot interleaving

  13. Superframe Formation TDMA Frame TDMA Block Time Time Time Time Time Time Time Time Time Time Time Time Time Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot Slot 1 2 3 4 5 6 1 2 3 4 5 6 1 SFP SFP SFP SFP SFP SFP SFP SFP SFP SFP SFP SFP = 0 = 1 = 2 = 3 = 4 = 5 = 6 = 7 = 8 = 9 = 30 = 31 Superframe - 32 slots (0.64 sec duration)

  14. Superframe Composition One Superframe = 16 TDMA frames = 640ms SPACH F-BCCH E-BCCH S-BCCH ... ... ........... ... S S S F E S SFP 0 31 • F-BCCH “Fast Broadcast Channel” • Messages repeat every superframe • Messages contain information critical for service on DCCH • E-BCCH “Extended Broadcast Channel” • Messages extended over multiple superframes • Messages less time critical • SPACH “SMS, Paging, and Access Channel” • Used for sending Point-to-Point Messages • S-BCCH “SMS Broadcast Channel” • Reserved for Broadcast SMS (IS-136B)

  15. One Hyperframe = Two Superframes = 1.28s One Superframe One Superframe SPACH SPACH F-BCCH E-BCCH S-BCCH F-BCCH E-BCCH S-BCCH ... ........... ... ........... ... ... ... ... S S S S S S S S F E F E 0 31 0 31 Superframes and Hyperframes • The SPACH “SMS, Paging, and Access Channel” • Page messages (PCH) • PCH messages are always repeated in secondary superframe • Access Response Messages (ARCH) • ARCH messages are sent in idle SPACH slots (i.e. no page messages) • ARCH message may be sent over multiple superframes • Teleservices messages (SMSCH) • SMSCH message are sent in idle SPACH slots • SMSCH message may be sent over multiple superframes

  16. Sleepmode • Sleepmode allows for battery savings • Various level of sleepmode are supported • Level of sleepmode is determined at registration • Mobile assigned PCH slot is determined by hashing algorithm 1 2 3 4 5 6 7 8 9 10 11 13 14 Superframe 0 1 2 3 4 5 6 Hyperframe 12 Paging Frame Class 1 Paging Frame Class 2 Paging Frame Class 3 Paging Frame Classes 4 through 8 not shown

  17. . . . . . . . . . . . . . . . . . . SPACH SPACH F F E E S S F F E E S S F F E E S S Sleepmode Activities (1) If mobile is unable to read PCH in primary superframe, it must try reading assigned PCH in secondary superframe (2) If the system changes F-BCCH, the mobile is notified through system toggling of the BCN change flag in mobiles assigned PCH slot. (3) Changes in the E-BCCH are indicated by a change flag in the F-BCCH. Primary Superframe Secondary Superframe Next Hyperframe 3 1 2

  18. Reverse DCCH G R PREAM SYNC DATA SYNC+ DATA 24 6 6 16 28 122 122 Abbreviated Reverse DCCH G R PREAM SYNC DATA SYNC+ DATA R AG 6 6 16 28 122 24 78 6 38 Reverse DTC G R DATA SYNC DATA SACCH CDVCC DATA 6 6 16 28 122 12 12 122 Reverse DCCH Slot Structure • Two burst lengths are defined to accommodate both large and small cells • SYNC+ provides additional synchronization information to the base station. • PREAM aids base station automatic gain control to reduce signal distortion. • AG provides 38 bits of guard for the abbreviated burst. • G and R provides guard and ramp.

  19. TDMA frame 40 ms 1 2 3 4 5 6 1 2 DCCH Downlink Bursts 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 Phone checks slot availability Phones checks reception status First burst transmitted Additional bursts transmitted 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 1 Uplink RACH Subchannels time expended R-DCCH Multiple Access • Subchanneling allows for multiple uplink paths

  20. L3 Layer 3 Message L2 L3DATA L2 HDR CRC L3DATA L2 HDR CRC CSFP SCF L1 Sync DATA DATA Layer 3 - 2 - 1 Mapping

  21. DCCH Layer 3 Functionality • Call processing, registration, and paging • Mobile assisted channel allocation (MACA) • Identity structures • Cell selection • Cell reselection • Hierarchical cells • Tiered services • Private/public systems

  22. Call Processing • Origination uses the same call model as IS-54B • Phone sends origination message to system on reverse DCCH • Traffic channel designation sent in base station response • Paging on the DCCH • A phone is allocated a particular SPACH slot which is monitored for pages. • This allocation is based on the MIN of the phone • Authentication • Same algorithms as used in IS-54B

  23. Paging • TDMA Paging • No rescan on reverse access channel removes the traditional system border problems associated with analog. • Mobile responds to pages on the same DCCH as it receives pages on. • Page message combination supports higher paging capacity • Single word paging uses one L2 frame per page • Triple hard paging uses one L2 frame per three pages • Standard allows for even further paging capacity through use of 20 and 24 bit TMSIs • TDMA registration techniques allow for defining precise paging areas which can further increase messaging capacity.

  24. Registration Types • DCCH-based registration conditions are defined according to the following order of priority: • Test registration New to TDMA • Power down • Deregistration New to TDMA • Power up • System transition condition Enhanced in TDMA • Location area (VMLA) New to TDMA • Periodic registration Enhanced in TDMA • ACC to DCCH transition New to TDMA • The system broadcasts which forms of registration are supported on F-BCCH.

  25. 4 9 1 5 1 10 4 9 4 5 4 9 10 5 9 4 10 5 9 10 8 9 8 10 8 8 VMLA Registration 1 RNUM broadcast by cell. RNUM list sent to mobiles at registration. Mobile must register when unknown RNUM received.

  26. Aspects of TDMA Registration • TDMA-Based Registration • Several new registration types are added in TDMA • Mobiles indicate the registration type they are responding to. • The nuisance registrations can be reduced • The registration defined to fully support private, public, and residential systems. • VMLA-based registration • increases system control over paging load by tracking mobiles based on location. • eliminates the ping-pong registration problem by defining overlapping areas. Through a proper configuration, a TDMA system can result in reduced registration traffic with greater paging efficiency.

  27. Mobile Assisted Channel Allocation (MACA) • MACA allows the mobile to provide the base station with a channel quality report upon access. • Channel Quality Report • Long-term measurement - on serving DCCH: a running average over 32 frames of RSS, WER, and BER. • Short-term measurement - on up to 15 channels specified by base: RSS based on 4 measurements. • The base station indicates the specific access types that the mobile is to provide a channel quality report. • The MACA report can be used by the base station for enhanced channel assignment.

  28. DCCH Selection • Digital control channels can be placed on any channel within an operating band • DCCH “pointers” • Coded DCCH Locator (CDL): • The is sent within every forward digital traffic channel burst • The CDL points to a location of a DCCH within a block channels. • Control Channel Information Word (CCI): • The CCI word is sent as part of the ACCH overhead message. • The CCI contains a pointer to a single DCCH, the pointer includes the channel number, DVCC, and hyperband of a DCCH. • DCCH pointers are provided upon call release from both DTCs and AVCs. • Probabilistic DCCH assignments may also be used.

  29. Scan history channels for last used DCCH Scan analog control channels for DCCH pointer Scan probability blocks for DCCH or DTC with locator field DCCH Selection Process • Exact DCCH selection procedures are mobile vender specific.

  30. Cell Reselection Procedures • TDMA cell reselection procedures are executed by mobiles while a mobile is in the idle state (i.e., sleepmode). • Parameters broadcast by the base station gracefully steer mobiles to cells based on: • Mobility • Cell type (underlay or overlay) • Relative and absolute RF thresholds • Received signal strength • Private, public, residential

  31. DCCH Neighbor Lists • The DCCH neighbor list is central to the cell reselection process. • Every DCCH broadcasts a neighbor list. • The DCCH neighbor list provides mobiles with reselection parameters on all neighbor cells and sectors. • Mobiles use this information to choose the appropriate cell based mobility, desired network type, etc. • The neighbor list provides the mobile with all neighbor parameters needed for selection. • There is no need for a mobile to sync up and read neighbor cells prior to reselection • An additional neighbor list may also be broadcast for alternate band (i.e. 800, or 1900MHz)

  32. Signal Strength Measurements • While in the idle state, the mobile maintain two sets of signal strength measurements. • Long_RSS • Long_RSS is a running average of 5 measurements maintained for the serving DCCH in addition to all neighbor DCCHs. • Short_RSS is a running average 2 RSSI measurements • Short_RSS is a running average of 2 measurements maintained for the serving DCCH only. • Signal strength measurements are taken at a periodicity set by the base station. With TDMA, there’s no need to sync up and demodulate neighbor channels in order to take a power measurement.

  33. Neighbor Cell 1 Neighbor Cell 2 Neighbor Cell 3 Neighbor Cell 24 The Neighbor List Message Neighbor List Message

  34. Key Reselection Parameters • RSS_ACC_MIN • Minimum signal strength required for a phone to access a cell. • RESEL_OFFSET • A hysteresis value used for adjacent cell reselection (i.e. cell type regular). • SS_SUFF • The signal strength deemed sufficient for a phone to reselect a preferred or regular cell. • MS_ACC_PWR • Maximum power a phone can use to access a particular cell.

  35. Reselection Parameters, Cont. • Delay • Specifies the minimum time for which a candidate cell must be seen at adequate signal • CELLTYPE • Specifies a

  36. Macrocell (regular) Macrocell (regular) A B + - (RESEL_OFFSET ) (RESEL_OFFSET ) B B Cell Boundary AB Cell Reselection - Adjacent Cells Example – Adjacent Cells Suggested Settings: CELLTYPEB = REGULAR DELAYB = 0 RESEL_OFFSETB = -3dB RESEL_OFFSET provides hysteresis between two adjacent cells

  37. DELAY m Cell Reselection - Delay NL Delay – Microcells A Macrocell (overlay) B mobile direction Microcell RSS_ACC_MIN C D Suggested Settings: CELLTYPEB = Preferred DELAYB = 1 or more hyperframes; Delay should be set high enough to keep high mobility mobiles off microcell

  38. Macrocell (non-preferred) A Microcell (preferred) B -7 2 d Bm SS_SUFF -8 2 d Bm B Reselection - Underlay SS_SUFF Example – Underlaid Microcell Assumptions: HandoffBA = -85 dBm Suggested Settings: CELLTYPEB = PREFERRED SS_SUFFB = -82 dB DELAYB = 1 or higher

  39. Capacity Seamless TDMA Private/Public Systems Flexibility Hierarchical Cells Total System Integration Cell Reselection

  40. Hierarchical Cells • Hierarchical cell structures • Low power microcells overlaid by high power macrocells • Why hierarchical cells ? • Flexible system growth/ increased capacity • Low mobility traffic • In building • Hot spots/ cold stops • Tiered services • Private and residential systems • Capacity when and where you need it. • Extended mobile talk time With TDMA, there’s no cumbersome power control issues involved in setting up low power underlayed cells.

  41. Cold Spot: Economic Remote Coverage Capacity: In Building Application Capacity: Traffic Relief A Capacity Tool - Hierarchical Cells Cold Spot: Fill-in Capacity: Cell Split Alternative Due to hierarchical deployment, TDMA offers the best long-term RF capacity story

  42. Workplace Public Mall/ Airport, etc. Residential Tiered Services

  43. Public WPBX Tiered Service Regions Residential Types of Private Systems • Virtual private systems • Semi-private systems • Airport, mall, convention center • Private only systems • Office parks • Residential systems • Neighborhoods, suburbs • Autonomous systems • Wireless PBX • Companion microcell

  44. Basic Capabilities • Capabilities provided through TDMA include: • Seamless system transition between private and public systems • Differentiated charging • Alphanumeric display of serving system • Underlays and in building support • Private only or semi-private • Possible to define multiple private systems off a single DCCH Due to TDMA cell reselection and hierarchical deployment, TDMA offers strongest tiered services story.

  45. The Mechanics of Tiered Services • Cell Reselection Algorithms: • Seamless DCCH transition between public and private systems. • Registration Procedures: • Assign and remove subscribers from system • Remove risk of nuisance registrations. • System Identities: • Private and residential system IDs uniquely identify a system • Network type (3 bit map on the DCCH) defines a cell as public, private, residential, or semiprivate. • Alpha Tags: • Identify systems to subscribers by alphanumeric name. • System Priorities: • Users rank private, residential, or public systems according to preference.

  46. TDMA - Digital PCS TDMA Scorecard Dual-Band Standard ¦ PCS at 800 & 1900 MHz Terminals ¦ Dual-band, cost effective Voice Quality ¦EFRC MOS - wireline equivalent Capacity ¦N=5/4 reuse and underlays Enhanced Services ¦SMS, Over-the-Air Activation, Sleepmode, IS-41C, ... In-building Services ¦Hierarchical cell structure for underlays and WPBX Data ¦Circuit switched using IS-135 High speed data evolution path Roaming ¦1900 / 800MHz TDMA & AMPS Intelligent directed roaming Fixed & Mixed ¦Mobility, fixed, & mixed

  47. Services and Design Examples • Short message service features and examples • Over-the-air activation • Wireless office design example • Circuit switched data service • TDMA summary

  48. Larry: the meeting is canceled e-mail Larry: the meeting is canceled . . . . . . center Cellular Messaging • Enables alphanumeric messages to be exchanged between the network and a DCCH capable phone. • Message delivery is acknowledged. • Message attributes dictate phone behavior. • Includes two way messaging and in-call delivery. Larry: the meeting is canceled .. . . . . . . . . . . . . . . . . . . TAP TNPP Larry: the meeting is canceled IS-41 message base station Voice MSC

  49. Messaging Examples • One-way information services • News, stock quotes, sports scores. • Broadcast services • Traffic, weather, etc. • E-mail notifications • Containing “from,” “subject” and first part of message. • Paging • Both one- and two-way paging with responses and acknowledgments. • Platform for integrated messaging solutions • Voice mail, etc.

  50. On-Air Activation • Enables delivery of NAM information and updates to the phone over the air. • Simplifies the activation process for both the subscriber and service provider. • Provides a flexible download capability. • Provides a secure mechanism for A-key updates.

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