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Cdma
- 1. 1 CDMA inOperation CDMA Networks • Cell Site Components • Network Components • CDMA Performance • Call Processing • Power Control • Operation • Administration • Maintenance CDMA Standards Theory Practice Voiice Data • IS-95 A/B • IS-2000 (1X/3X) • HDR CDMA in Operation Cell Site Components •Controller/Facility Interface •Channel Card/Modem •Baseband Radio •Amplifier •Filter •Antenna Interface
- 2. 2 CDMA inOperation Network Components • Public Switched Telephone Network • Mobile Switching Center/VoCoders • Executive Cellular Processor • Subscriber Data Base • Home/Visitor Location Register • Operational Data Bases • Base Station Controller • Base Station • Mobile Station PSTN ECP MSC BSC BSC BS BSC BS BS BS M S CDMA in Operation CDMA Performance • Performance/Interference Limited (Primarily Uplink) • Compare to AMPS/TDMA - Channel Limited • Replace 42 30KHz Channels with 1.25MHz Channel (With 7X Reuse, 6 AMPS Radios/Cell or 2/Sector) • 1X Frequency Reuse - Differentiate by PN Offset • Rake Receiver to handle multi-pathing • Encode 18-24 Voice Channels/Carrier • Each Channel Encoded by Unique Walsh Code • Voice Coding Reduces Number of Bits Sent • Voice Activity Factor (near 50%) Increases Capacity • Soft Handoff Improves Voice Quality Near Cell Borders
- 3. 3 CDMA inOperation CDMA Performance - Power Control •Downlink - All Channels Fade Equally • Uplink - Near Mobiles Must Transmit at Lower power than Distant Ones to Balance Link • Lockout of “Rogue” Mobiles • Round Trip Delay can also interfere with Bit Alignment BS M S M S CDMA Standards - IS95 Network Layer Overhead Channels and Messages Call Processing and Voice Channel Assignment Power and Overload Control Control Mobile Station Lockout, etc. Data Link Layer 20ms Data Frames Acknowledgement and Error Recovery Physical Layer Transmission of Raw Data Bits Encoding, Modulation, etc.
- 4. 4 CDMA inOperation - IS95 Air Interface Channels • Pilot Channel • Sync Channel • Paging Channel(s) • Access Channel(s) • Voice Channels Call Processing • Acquisition/Registration • Call Origination • Call Termination • Hand Off (Soft, Semi-, Hard) Power Control • Balance Power Level on Uplink • Cell Instructs Mobile to Adjust Power Up or Down based on FER • Overload Control Adjusts Overall Level CDMA in Operation System Acquisition • Mobile Reads Pilot For Timing • Sync Channel Message Gives Paging Carrier List • Mobile Hashes to Paging Channel and Retunes • Mobile Registers on Access Channel, Enters Idle State • Mobile Monitors Paging Channel until: • Idle Handoff • Page Received • Origination Message • Voice Channel Assigned on Call Origination/Termination • Call Disconnect or Drop, Mobile Rehashes and Returns to Idle
- 5. 5 CDMA inOperation Soft Handoff • Acquire Second Pilot (Up to 6) • Voice Channel Assigned on Secondary Cell/Sector • Uses Same Vocoder/Frame Handler • Select Best on Each Packet • Primary Transfer as Primary Signal Weakens • Softer Handoff between Sectors of a Cell - Share Modem and Backhaul Facility Soft Softer BS M S BS M S BS CDMA in Operation Operation, Administration & Maintenance (OA&M) • Provisioning (Subscribers, Equipment) • Billing and Accounting • Service Measurement • Status Display and Technician Interface • Fault Isolation and Recovery (Automated and Manual) • RF Optimization and Testing • Growth and Upgrade Procedures
- 6. 6 CDMA 2000 •Defines “3G” Evolution from IS-95A/B •RIT 2000 Framework covers 1.25-15MHz Carriers •Initial Standard for “3G-1X” Published 1999 •First Revision (Rev A) Just Approved •Production Systems Announced for Mid 2001 •Further Capabilities Proposed •HDR (High Data Rate) •1Xtreme •Standard for “3G-3X” Under Development •More to Come CDMA 2000 IS-95 Compatibility • Pilot, Sync, Page, Access Channel • Voice -> Fundamental Channel 2G or 3G • Dual Mode Mobiles/Channel Cards New Voice Capabilities • Quick Page Channel Extends Mobile Battery Life • 50-100% Capacity Increase Due To: • Reverse Pilot Channel • Faster Power Control • Orthogonal Transmit Diversity
- 7. 7 CDMA WirelessData Evolution Wireless Data Applications •Initially Simple IP Interface •Mobile IP Standard Under Development •Short Messages (Enhanced Pager) •Special Web Applications (Low Bandwidth) •Weather/Newsbriefs •Travel Reservations •Full Web/e-mail Access (Road Warrior) •ISP (without MSC) PSTN ECP MSC IWF IP Router BSC BSC BS BSC BS BS BS CDMA 2000 Data Implementation Fundamental Channel •9.6 Kb bi-directional •Data and Signaling •Used to Request Burst as Needed Supplemental Channel •Uni-directional Variable Size •Forward Burst From Primary Only •Reverse on all SHO Legs PSTN ECP MSC IWF IP Router BSC BSC BS BSC BS BS BS
- 8. 8 CDMA WirelessData Evolution Data Call Scenario •Normal System Acquisition and Fundamental Channel Assignment •Data Transmission in either direction at 9.6Kb •Data Backlog (Mobile or IWF) Initiates Burst Request •Burst May be granted at 19.2, 38.4, 76.8, 153.6 (Fixed Duration) •Data Stream (Burst Direction) goes to Supplemental •Messaging and Idle on Fundamental in Burst Direction •Fundamental Still Active In Other Direction •Burst Terminates and Data Stream Returns to Fundamental at 9.6 •No Data for 10 Seconds, Call Goes Dormant CDMA Wireless Data Evolution IS-95A - Voice Only IS-95B - Fundamental Channel for Circuit Data at 9.6 Kb •Cell Operation Same as Voice Circuit •IP Network Interface (bypass Vocoder) IS-2000 1X to 144Kb •Supplemental Channels - 1 Way Short Duration •Use Variable Length Walsh Codes •Dormancy to Ensure Cell Resource Utilization HDR to 2Mb •Downlink use TDM on full width carrier to achieve High Rates •Pilot and Page in Reserved Time Slots •Uplink like IS-2000 1X, plus reports momentary burst capability IS-2000 1Xtreme - to 5Mb? IS-2000 3X to ?