Notes: a. Up to 12 cdma2000 downlink carriers theoretically planned; b. TDD permits unequal total physical uplink vs. downlink data rates.
Frequency Division Duplex Frequency Division Duplex or Time Division Duplex (TDD) b Uplink/Downlink Use Transmitters can be shared; new receivers required No: new base transceivers required. Share previous technology base radio equipment? Packet Switched; uses Internet infrastructure Packet Switched; uses Internet infrastructure Data Format and Infrastructure Up to 2 Mb/s Up to 2 Mb/s Data Rates supported Required Not required, but superior handover when used Base Station Synchronization 850 Hz sampling rate closed loop, uplink 1500 Hz sampling rate closed loop, up/downlink Power Control to remedy “near-far” problem of cdma 1.2288 Mc/s each 1.25 MHz carrier; 3.6846 Mc/s on uplink carrier 3.84 Mc/s (changed from 4.096 after “discussions” with cdma2000 proponents) Pseudo-random code (CHIP) rate 1.25 MHz. Downlink uses three carriers a ; Uplink uses 1 carrier w/ 3.75 MHz b.w. 5 MHz up/downlink Carrier spacing Easier to upgrade from IS-95 Easier to upgrade from GSM Evolution plan cdma2000 W-CDMA Aspect
The rivalry between long-time CDMA and TDMA opponents led to two different CDMA-based 3G designs
cdma2000 proponents accused their opponents of offering an incompatible 3G CDMA design for the primary purpose of having a standard not backward compatible with existing IS-95 CDMA... Viewed as an attempt to pre-empt the inventor’s own invention!
But, CDMA in the field has yet to fulfill high-capacity promises although it has several beneficial properties
Result is still two incompatible CDMA-based 3G air interface standards .
ETSI did modify the 3GPP CDMA “chip” rate to make backward compatibility with IS-95 easier to design, but mainly different 3G planners only could agree to disagree.
Notes: a. Sharing same carrier and base transceiver is economically important; b. Announced strategy of major US IS-136 carriers vacillates between this strategy (so-called EDGE COMPACT) and a straight-to-3G strategy.
Install new EDGE base transceivers with existing IS-136 base transceivers b Not planned. Evolution from IS-136 TDMA Mix GPRS with GSM on same carrier frequency a Mix GPRS with GSM on same carrier frequency a Share GSM time slots? Frequency Division Duplex Frequency Division Duplex Uplink/Downlink Use IP (Internet Protocol) and X.25 IP (Internet Protocol) and X.25 Packet Formats Supported Up to 56 kb/s per time slot; up to 384 kb/s per carrier. Up to 14.4 kb/s per time slot; up to 128 kb/s per carrier Data Rates Supported 8PSK (triple GSM bit rate) GMSK (exactly like GSM) Radio Modulation Little or no GSM base radio upgrade; requires packet switching infrastructure Little or no GSM base radio upgrade; requires packet switching infrastructure Evolution from GSM EDGE GPRS Aspect
EDGE Compact, UWC136+ CDMA IS-95 IS-136 GSM GPRS WCDMA CDMA 2000 CDMA one 3GPP2 3GPP 1G=Analog cellular EDGE X X X X X Earlier plan to gradually phase in EDGE Compact in the 850 MHz band was later abandoned and replaced by migration of IS-136 to GSM, GPRS and EDGE (AT&T Wireless and Cingular)
Module names are those for GPRS (likely earliest) implementation
MSC Serves GSM Voice users. GGSN- (Gateway GPRS Support Node) SGSN- Serving GPRS Support Node Real system has multiple SGSNs, multiple BSS:BSC-BTS installations, not shown. U u to PSTN MS/UE BSS (other BSS installations not shown) to Public Internet } This “private IP network” is called the “ Backbone” IP network. It carries IP Packets to/from the Public IP net and the SGSN. IP packets, to/from the Public Internet, “tunnel” inside of “ envelope” IP packets. In small 3G systems, the GGSN and the SGSN are the same switch. BSC BTS
IP packets are routed from Internet to SGSN via a GGSN Gateway Node, then encapsulated in an IP Packet “Forwarding Envelope” for the trip via the SGSN to the mobile unit.
so mobile station appears to have a fixed Internet address for duration of session, despite physical mobility and even possible handover from one SGSN to another.
GPRS-EDGE can segment and re-assemble packets into blocks sized for radio channel transmission
Net radio block size is dynamically adjusted from moment to moment, based on radio channel quality. Different modulation and error protection coding schemes give different useable net bit rate with same time slot duration.
USF RLC/MACHdr. HCS FBI Data: 74 octets=592 bits BCS TB 1392 bits total will be distributed over 4 bursts (GPRS Block) via interleaving (requires 8PSK modulation: EDGE) 36 bits 102 bits 1836 bits SB=4 36 bits 102 bits 1250 bits Puncturing used to reduce data bit field length, not USF or RLC bit fields. Rate 1/3 convolutional code USF=Uplink State Flag RLC/MAC Hdr.= Radio Link Control/Media Access Control Header HCS=Header Check Sum FBI=Final Block Indicator BCS=Block Check Sum TB=Tail Bits SB=Which MCS indicator USF is block encoded rate 1/12 to ensure accuracy. USF value in downlink controls which of 7 mobiles can trans- mit on uplink on that time slot.
Any slot may use this schedule except those devoted to setup-related stuff
Downlink (full rate)
Alternate (two half rate conversations)
Uplink (full rate) (half rate not shown)
0123 … 0123 … 23 24 25 0123 … 23 24 25 23 24 25 Key to Colors Red:Conversation 1 on full rate TCH(22.8 kb/s gross), or Conversation 1 on 1/2 rate TCH (11.4 kb/s). Blue: Conversation 2 on half rate TCH Yellow: SACCH for Conversation 1, Idle for 2 White: Idle time slot Green: SACCH for Conversation 2 In half-rate situations, the SACCH for one is the Idle slot for the other. 120 ms TCH=Traffic Channel; SACCH=Slow Associated Channel (call processing control signals)
May be used on any slot not assigned to 51-frame multiframes. GPRS and voice may use different slots on the same frequency.
Block 0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 Key to Colors Several colors represent packets from different subscribers. Note that the order and appearance is dynamically controlled by the amount of traffic, not by pre-assignment. Corresponding up/down blocks not used by same subscriber. Gold: PTCCH White: Idle time slot Block 0 B1 B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 240 ms
One (or more) time slot per frame is used for communication service.
“ Idle” time slots (including some of the other 7 slots not used for service) are used by frequency-agile mobile Rx to measure signals from nearby cell base station Tx units, to gather data for Mobile Assisted HandOver (MAHO)
Commands (downlink) and measurement reports for MAHO, etc.(uplink) transmitted via SACCH (for voice), or via PTCCH (for packets)