Updated RsMA Overview TR45.5.3.1/98.11.17.09 Updated RsMA Overview Submitted by: Hughes Network Systems & QUALCOMM Incorporated November 17, 1998 ©1998

Updated RsMA Overview TR45.5.3.1/98.11.17.09

Updated RsMA OverviewSubmitted by:

Hughes Network Systems

&

QUALCOMM Incorporated

November 17, 1998

©1998 Hughes Network Systems & ©1998 QUALCOMM Incorporated.

The information contained in this contribution is provided for the sole purpose of promoting discussion within the TIA and is not binding on the contributors. The contributors reserve the right to add to, amend or withdraw the statements contained herein.

The contributors grants a free, irrevocable license to the Telecommunications Industry Association (TIA) to incorporate text contained in this contribution and any modifications thereof in the creation of a TIA standards publication; to copyright in TIA's name any TIA standards publication even though it may include portions of this contribution; and at TIA's sole discretion to permit others to reproduce in whole or in part the resulting TIA standards publications.

Nothing contained herein shall be construed as conferring by implication, estoppel, or otherwise any license or right under any patent, whether or not the use of information herein necessarily employs an invention of any existing or later issued patent, or copyright. The contributors reserves the right to use all material submitted in this contribution for their own purposes, including republication and distribution to others.

2Updated RsMA Overview TR45.5.3.1/98.11.17.09

Motivation for Improved Access

• Existing access scheme has marginal performance, is wasteful of system resources, and is poorly suited for data applications.

• Improved call set-up reliability is needed.

• Data services require an access protocol that: – minimizes latency and maximizes throughput

– maximizes system capacity

• Protocol flexibility is critical to cdma2000– existing requirements:

» PSMM’s & MAC signalling (no dedicated channels active)

» SMS, meter reading, POS applications

– future data service requirements: » unknown --> flexibility desirable


Existing IS-95 A/B Access

• IS-95 A/B access scheme is based on a slotted aloha protocol

• Accessing mobiles send probes on R-ACH:– 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.

– Access slotting is typically 200 ms

– back-off delays (multiple of 200 ms)

– persistence delay (multiple of 200 ms)


Existing IS-95 A/B Access Scheme (cont.)

Access Channel

Page Channel

Preamble Message

~ 80 ms ~ 120 ms

Acknowledgement~ 240 ms

• Access channel performance– impact on capacity

» 95% success requires large probe power (6 dB to 10 dB greater than Eb/No)

» lower power --> greater probability of retransmission and increased latency

– throughput & delay» typical access times: ~620 ms.

» typical worst case: ~1340 ms.


Limitations of IS-95 A/B Access Scheme

• Detection and acquisition:– power required to detect is actually ~ 2% of what is typically transmitted

• Message error rate performance:– in order to get message through error free, mobile must transmit at high power

(> 8 db over operating Eb/No)

– if message error, retransmission at higher power and increased latency

• Latency performance:– long preamble typically used (base station constraint)

– data rate is low, so message duration is long

– protocol delays are large, with average access times > 620 ms.

• Impact on data services:– reduced system capacity

– low throughput and large delays

– no connectionless packet data service capability


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 and 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.)

– Increased call setup reliability


Overview of Proposed Approach• Reservation Multiple Access (RsMA) is really two distinct access

protocols– Improved Slotted Aloha mode:

» used for short messages (e.g. < 20 ms.)

» open loop power control only

– Reservation mode:» message duration: 20 ms < T_msg < 500 ms

» closed loop power control on RL

F-CACH

R-CCCH

F-PCCH

PreambleR-RACH

PreambleR-RACH Message

F-CCCHAcknowledgement~ 50 - 100 ms.

MWPilotAloha Mode:

Reservation Mode:

MW Hash IDPilot

Reservation Access Probe(5 m s)

CACH slot = 5 m s.

~ 50 ms

Channel Assignment Message Repeated Channel Assignment Message~ 20 ms~2.5 ms

Channel Est.Preamble

Message

2.5 ms

PILOT & PCCH Power Control Subchannel


Summary of Enhancements

• Slotted Aloha Mode:– Throughput (per channel):

» 40 msg/sec vs. 4 msg/sec (~10x over IS-95 A/B)

– Average latency (per message):» 100 ms vs. 620 ms (>6x over IS-95 A/B)

– System Capacity:» improvement of ~3 dB due to shorter preamble & 3 dB due to better

modulation/coding (4x over IS-95 A/B)

• Reservation Mode:– Throughput efficiency (per channel):

» 90% vs. 20% (~4.5x over IS-95 A/B)

– Average latency (per message):» ~ 5x better for same conditions

– System capacity:» ~11 db improvement (i.e. ~3 dB modulation & coding + 8 dB closed loop

power control)


Required Changes to RTT

F-CPHCH(ForwardCom m onPhysicalChannel)

R -CPHCH(ReverseCom m onPhysicalChannel)

F-P ICH Forward P ilo t Channel

F-CAPICH Forward Com m on Auxiliary P ilo t Channel

F-CCHT(ForwardCom m onChannelType)

R-CCHT(ReverseCom m onChannelType)

F-PCH Forward Paging Channel

F-CCCH Forward Com m on Contro l Channel

R-ACH Reverse Access Channel

R-CCCH Reverse Com m on Contro l Channel

F-SYNC Forward Sync Channel

R-RACH Reverse Request Access Channel

F-PCCH Forward Power Contro l Channel

F-CACH Forward Channel Assignm ent Channel

• Forward Link:» Power Control Channel (F-PCCH)

» Channel Assignment Channel (F-CACH)

• Reverse Link:» Request Access Channel (R-RACH)


Level of Effort to Incorporate

• Physical Layer:– Draft baseline text for RsMA submitted in Burlington (10/98)

» no text exists for R-CCCH without RsMA, so incremental effort is negligible

– Incorporate RsMA into Phase 1

– Implications of pushing RsMA to Phase 2:

» Infrastructure & handset hardware changes REQUIRED

» Inferior access methodology

• Signaling Layer:– Draft baseline text not yet started (~1-2 months)

– Incorporate into Phase 1 (i.e. 1/99)

• MAC Layer:– Baseline text ready for Colorado Springs (11/98)

– Incorporate MAC layer support in Phase 1


Reverse Channel Overview • Reverse Reservation Access Channel (R-RACH)

– Slotted Aloha random access channel used in two modes:» Reservation Mode: reservation requests sent

» Aloha mode: short messages sent

– multiple R-RACH’s supported

• Reverse Common Control Channel (R-CCCH)– assigned dedicated access channel

– slotted operation

– Pilot sub-channel

• Modulation per IS-95C for R-CCCH and R-RACH (Aloha mode) – 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-RACH: » reservation access probe (RAP) = initial preamble + mode indicator + hash ID

» message access probe (MAP) = initial preamble + mode indicator + message

– R-CCCH: » packet = channel estimation preamble + message/pilot


Forward Channel Overview

• Forward Common Assignment Channel (F-CACH)– single Walsh code control channel supporting multiple R-RACH’s and R-CCCH’s

– multiple F-CACH’s supported

– used to carry channel assignments, and load control messaging

– F-DCCH format (modulation, coding, CRC’s, 9.6 kbps, 5 ms. frames)

• Forward Power control Control Channel (F-PCCH)– single Walsh code channel, divided into sub-channels

– multiple PC sub-channels per F-PCCH, each supporting a single R-CCCH

– PC rate and number of PC sub-channels is a system parameter (0, 200, 400, 800 bps)

• Modulation– Both F-CACH & F-PCCH are DTX

– When ON, F-CACH uses QPSK (same modulation/coding as F-DCCH)

– When ON, F-PCCH uses QPSK


Example Channel Structure

F-CACH

R-CCCH

F-PCCH

PreambleR-RACH

PreambleR-RACH Message

F-CCCHAcknowledgement~ 50 - 100 ms.

MWPilotAloha Mode:

Reservation Mode:

MW Hash IDPilot

Reservation Access Probe(5 m s)

CACH slot = 5 m s.

~ 50 ms

Channel Assignment Message Repeated Channel Assignment Message~ 20 ms~2.5 ms

Channel Est.Preamble

Message

2.5 ms

PILOT & PCCH Power Control Subchannel


Reverse Waveform Description• R-RACH:

– Initial preamble : integer number 1.25 ms. segments of unmodulated pilot

– Mode Word : 1.25 ms (4 bits each repeated 3x)

» Mode Indicator (1 bit) : RAP or MAP

» Rate/Frame Indicator (3 bits): data rate and frame duration

– Reservation Mode: 2.5 ms

» Hash ID : 16 bits, r=1/4, k=9 conv. Coded.

» The hash ID can be divided into 2 pools:• managed: distributed by the system

• random: selected by mobiles

– Aloha Mode:

» Short message: maximum duration is system parameter

• R-CCCH:– Channel estimation preamble : integer number 1.25 ms. segments of

unmodulated pilot

– Message portion (integer number of frames)

– Physical layer CRC’s per frame

– Pilot used to aid in coherent detection


Forward Waveform Description

• F-CACH:– fixed message duration (5 ms.)

– 9600 bps, k=9, rate 1/2 coding with 16-bit frame CRC’s

– message types:

» Channel assignment messages

» Wait message (admissions/flow control)

» 2 reserved message types

• F-PCCH:– PC rate determines the number of PC sub-channels supported:

» 24 @ 800 bps, 48 @ 400 bps, 96 @ 200 bps.

– PC Sub-channel assignment implicit in F-CACH channel assignment msg.


System Timing Parameters• R-RACH Access Slot (n*1.25 ms)

– interval between permitted accesses on R-RACH

• F-CACH Slot– slotting used on F-CACH (5 ms, minimum)

• Min. Delay to Channel Assignment– minimum interval from request to earliest channel assignment message

– 5 ms, typical.

• Max. Delay to Channel Assignment– maximum interval from request to last channel assignment message

– 40 ms. typical

• Number of channel assignment message repeats– 1-2, typical

• Power Control Delay in RL closed loop PC bits– 1.25 ms, typical


Admission/flow Control

• Admission/flow control:– Slow Response Time (~ 200 ms, typical):

» access parameters conveyed on F-BCCH give current persistence parameters and delays

» these parameters control flow on the R-RACH(s)

» sent periodically with dynamic control possible

– 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-RACH and R-CCCH for reservation mode traffic

• system loading


e.g. F-CACH Messages• Messages are fixed length (5 msec):

– Overhead Bits (24 bits): Encoder Tail (8 bits) CRC (16 bits)

– Channel Assignment Message (24 bits): Message Type (2 bits) Mobile Hash ID (16 bits) R-CCCH/F-PCCH Channel Assignment (5 bits) Reserved (1 bit)

– Wait Message (24 bits): Message Type (2 bits) Mobile class mark threshold (4 bits) Max data rate for mobiles with class marks over the threshold (2 bits) Max data rate for mobiles with class marks under the threshold (2

bits) Minimum delay to retransmission for all reservation mode mobiles(10

bits) Reserved (4 bits)


Mobile Procedures

• Aloha Mode:– Mobile determines that aloha mode is best based on Tx. data rate and

message size

– If F-CACH is supported, mobile first monitors F-CACH to determine whether blocking condition prevails.

– If not blocking, mobile “randomly” selects from the corresponding R-RACH set and transmits a Message Access Probe (MAP)

– Aloha mode access channel protocol:» mobile uses persistence parameters to regulate access attempts

– After MAP transmitted on R-RACH, mobile monitors F-CCCH for acknowledgement:

» If no ACK within time out, retry at higher power


Mobile Procedures (cont.)• Reservation Mode:

– Mobile “randomly” selects a R-RACH and transmits a Reservation Access Probe (RAP) conditioned on:

» observed Ec/Io > T_rqst dB

» “current” persistence parameters and non-blocking condition

– Aloha access channel protocol:» mobile uses persistence parameters to regulate access attempts

– After initial RAP, mobile monitors corresponding F-CACH for:» Channel Assignment Message or Wait Message

– Conditions:» If no message within time-out, retransmit RAP at higher power

» If wait message sent, retransmit RAP 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


System Procedures• System monitors R-RACH’s for messages & requests on R-RACH

slot boundaries– search windows set to accommodate PN randomization (if not 0) + prop. delay +

multipath spread

• Aloha Mode:– If MAP detected on R-RACH, system:

» demodulates and decodes message

» send ACK back on F-CCCH

• Reservation Mode:– If RAP detected on R-RACH, system:

» decodes hash ID,

» queue’s channel assignment/access control message,

» transmits the message in the assigned F-CACH slot(s).

– If request granted:

» system monitors the assigned R-CCCH for channel estimation preamble

» If preamble detected system demodulates and power controls message portion

» Else if preamble not detected system releases R-CCCH for subsequent requests and ceases sending PC bits on F-PCCH after timeout


e.g. Channel Organization• R-RACH:

– up to 32

– may have 1 F-CACH associated with each R-RACH

• F-CACH:– no. of F-CACH’s supported (0 to 7)

• R-CCCH:– 24 per F-CACH (0 to 23)

• F-PCCH:– 24 sub-channels uniquely paired with R-CCCH @ 800 bps PC

– PC rate determines number of sub-channels per F-PCCH» 800 bps --> 24 subchannels

» 400 bps --> 48 subchannels

» 200 bps --> 96 subchannels

• Notes:– R-RACH’s can segregate RAP and MAP traffic, or mixed traffic

– 0 F-CACH’s can be supported (pure Aloha mode)

Documents

Updated RsMA Overview TR45.5.3.1/98.11.17.09 Updated RsMA Overview Submitted by: Hughes Network Systems & QUALCOMM Incorporated November 17, 1998 ©1998