Improvements in speech services of GERANMaster’s Thesis presentation

Author: Tommi Jokela

Supervisor: Prof. Sven-Gustav Häggman

Instructor: M.Sc. Benoist Sébire

Contents

Objectives and motivation

Background

Simulations

Results

Conclusion

Objectives and motivation

1. Assess the link level performance of speech services in GSM/EDGE radio access network (GERAN) Release 5.

2. Find out whether the performance of these services can be improved in GERAN Release 6.

3. Compare the performance of circuit-switched and packet-switched speech services of GERAN and state reasons for the possible differences.

The work was carried out for Nokia Research Center.

The results were contributed to the ongoing GERAN standardization that occurs on third generation partnership project (3GPP).

GSM standardization

Phase 1-2 Phase 2+

1996

Rel’96: High speech circuit-switched data (HSCSD)

1997

Rel’97: General packet-radio service (GPRS)

1998

Rel’98: Adaptive multi-rate codec (AMR)

1999

Rel’99: Enhanced data rates for GSM evolution (EDGE)

2002

Rel’5: GSM/EDGE radio access network (GERAN)

2003?

Rel’6: Flexible layer one (FLO)

GERAN

BSC

BTS

BSS

GERAN

MS

MS BTS

UTRAN

RNC

CN

UMTS multi-radio network

Um A

Gb

Iu

Iur

Iur-g

Iu

BSS

GERAN GSM/EDGE radio access

network

UTRANUMTS terrestrial radio

access network

CNCore network

BSCBase station controller

BTSBase transceiver station

RNCRadio network controller

BSSBase station subsystem

MSMobile station

Flexible Layer One (1/2)

The problem at GERAN Release 5:

• The spectrum efficiency of real-time packet-switched applications is relatively bad.

• The problem is largely due to the inflexible radio bearers, whose properties cannot be negotiated at call setup.

The solution at GERAN Release 6:

• Introduce a new physical layer concept that is based on the physical layer of UTRAN.

• The main advantage of FLO is that the properties of radio bearers can be negotiated at call setup in a flexible manner.

Flexible Layer One (2/2)

CRCattachment

Basic physical subchannels

Logical channel

Convolutionalcoding

Modulation

Interleaving Interleaving

CRCattachment

CRCattachment

CRCattachment

Convolutionalcoding

Convolutionalcoding

Convolutionalcoding

Ratematching

Ratematching

Ratematching

Basic physical subchannels

TrCH 1 TrCH nTrCH 2

Modulation

Adaptive Multi-Rate codec (1/2)

• Provides various codec modes with different speech qualities.

• Key operation: The codec mode adaptation (figure below).S

peec

h qu

ality

Channel quality

Codec mode 1

Codec mode 2

Codec mode 3

Switchingthreshold A

Switchingthreshold B

Adaptive Multi-Rate codec (2/2)

Narrowband AMR (GERAN Rel’98)

• Audio bandwidth equal to 300-3400 Hz.

• Speech quality lower than the quality of wireline communications.

• Most spectrum efficient codec among the speech codecs of GSM.

Wideband AMR (GERAN Rel’5)

• Audio bandwidth extended to 50-7000 Hz.

• The extension improves intelligibility and naturalness of speech.

• The quality of the highest codec modes exceeds the quality of 64 kbit/s PCM speech.

• High quality means more bits and reduced network capacity.

Circuit-switched speech versus VoIP

Spectrum efficiency

Voice quality

Service flexibility

Circuit-switchedspeech

VoIP

Ideal

CS speech

• Good speech quality and spectrum efficiency

• Quite inflexible

VoIP

• Poor spectrum efficiency

• Good speech quality harder to achieve

• Very flexible

Simulations (1/2)

Objectives

1. Assess the performance of circuit-switched speech services and VoIP in GERAN Release 5.

2. Determine suitable FLO configurations for circuit-switched speech services and VoIP in GERAN Release 6.

3. Assess the performance of proposed FLO configurations.

Simulations (2/2)

SourceChannelcoding

InterleavingBurst

formattingModulation

Propagationmodel

Noise InterferenceEstimation/detection

Impairments

Inner receiver Channel

Transmitter

Channeldecoding

deinterleaving

Outer receiver

Errorestimates

Results from the CS simulations (1/2)

Observations

• CS performance equal in GERAN Releases 5 and 6.

• FLO can be safely used to replace the logical channels of GERAN Release 5.

CS speech performance in GERAN Releases 5 and 6

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

11.00

12.2 10.2 7.4 5.9 4.75 12.65 8.85 6.6 23.85 15.85 12.65 8.85 6.6

CIR

[d

B]

CIR@1%FER (Rel'5)

CIR@1%FER (Rel'6)

AMR-NB, GMSK AMR-WB, GMSK AMR-WB, 8PSK

Results from the CS simulations (2/2)

Observations

• The link level performance of the current narrowband AMR service can be significantly improved in GERAN Release 6 with the 8PSK modulation.

• However, it is important to note that this link level gain may not translate directly on a system level gain!

Improvements on narrowband AMR

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

10.00

12.2 10.2 7.4 5.9 4.75Codec mode (AMR-NB)

CIR

[d

B]

CIR@1%FER (NB/GMSK, Rel'5)

CIR@1%FER (NB/8PSK, Rel'6)

Results from the VoIP simulations (1/2)

Observations

• The link level performance of VoIP services is very poor in GERAN Release 5.

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

22.00

24.00

26.00

12.2 10.2 7.4 5.9 4.75 12.65 8.85 6.6 23.85 15.85 12.65 8.85 6.6

CIR

[d

B]

CIR@1%FER (CS Rel'5)

CIR@1%FER (VoIP Rel'5)

AMR-NB, GMSK AMR-WB, GMSK AMR-WB, 8PSK

VoIP performance in GERAN Release 5

Results from the VoIP simulations (2/2)

Observations

• VoIP performance is significantly improved in GERAN Release 6.

• VoIP performance is still remarkably lower than the performance of CS speech.

• The EEP/EED schme outperforms the UEP/UED scheme.

VoIP performance in GERAN Release 6

0.00

1.002.003.00

4.005.006.00

7.008.009.00

10.0011.0012.00

13.0014.0015.0016.00

17.0018.00

12.2 10.2 7.4 5.9 4.75 12.65 8.85 6.6 23.85 15.85 12.65 8.85 6.6

CIR

[d

B]

CIR@1%FER (Rel'5)

CIR@1%FER (Rel'6, EEP/EED)

CIR@1%FER (Rel'6, UEP/UED)

AMR-NB, GMSK AMR-WB, GMSK AMR-WB, 8PSK

CS speech vs. VoIP (1/2)

Link level performance of AMR-NB 12.2 on GMSK channels

0.10%

1.00%

10.00%

100.00%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

CIR [dB]

FE

R

CS speech - Rel'5

CS speech - Rel'6

VoIP - Rel'5

VoIP - Rel'6 (EEP/EED)

VoIP - Rel'6 (UEP/UED)

CS speech vs. VoIP (2/2)Link level performance of AMR-NB 12.2 on 8PSK channels

0.10%

1.00%

10.00%

100.00%

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

CIR [dB]

FE

R

CS speech - Rel'6

VoIP - Rel'5

VoIP - Rel'6 (EEP/EED)

VoIP - Rel'6 (UEP/UED)

Conclusion (1/2)

Circuit-switched speech

• The circuit-switched speech channels of GERAN Release 5 can be replaced with FLO in GERAN Release 6. The link level performance remains unchanged.

• The link level performance of narrowband AMR can be improved in GERAN Release 6 with the 8PSK modulation.

• In addition to the direct improvements in link level performance, FLO also provides a possibility to reduce the complexity of CS speech by offering radio bearers that can be configured at call setup.

Conclusion (2/2)

Packet-switched speech (VoIP)

• The link level performance of VoIP over EGPRS is very poor.

• The link level performance of VoIP can be improved in GERAN Release 6, although the performance remains still well below the performance of CS speech.

• The EEP/EED scheme should be preferred over UEP/UED in channel coding.