Improvements in speech services of GERAN

1
Improvements in speech services of GERAN
Masters Thesis presentation
Author Tommi Jokela Supervisor Prof.
Sven-Gustav Häggman Instructor M.Sc. Benoist
Sébire
2
Contents
Objectives and motivation Background Simulations R
esults Conclusion
3
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).
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GSM standardization
Phase 1-2
Phase 2
5
GERAN
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
6
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.

7
Flexible Layer One (2/2)
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Adaptive Multi-Rate codec (1/2)

• Provides various codec modes with different
  speech qualities.
• Key operation The codec mode adaptation (figure
  below).

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Adaptive Multi-Rate codec (2/2)

• Narrowband AMR (GERAN Rel98)
• 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 Rel5)
• 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.

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Circuit-switched speech versus VoIP

• CS speech
• Good speech quality and spectrum efficiency
• Quite inflexible
• VoIP
• Poor spectrum efficiency
• Good speech quality harder to achieve
• Very flexible

11
Simulations (1/2)

• Objectives
• Assess the performance of circuit-switched speech
  services and VoIP in GERAN Release 5.
• Determine suitable FLO configurations for
  circuit-switched speech services and VoIP in
  GERAN Release 6.
• Assess the performance of proposed FLO
  configurations.

12
Simulations (2/2)
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Results from the CS simulations (1/2)
CS speech performance in GERAN Releases 5 and 6

• Observations
• CS performance equal in GERAN Releases 5 and 6.
• FLO can be safely used to replace the logical
  channels of GERAN Release 5.

11.00
CIR_at_1FER (Rel'5)
10.00
CIR_at_1FER (Rel'6)
9.00
8.00
7.00
6.00
CIR dB
5.00
4.00
3.00
2.00
1.00
0.00
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
AMR-NB, GMSK
AMR-WB, GMSK
AMR-WB, 8PSK
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Results from the CS simulations (2/2)
Improvements on narrowband AMR
10.00

• 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!

CIR_at_1FER (NB/GMSK, Rel'5)
9.00
8.00
CIR_at_1FER (NB/8PSK, Rel'6)
7.00
6.00
CIR dB
5.00
4.00
3.00
2.00
1.00
0.00
12.2
10.2
7.4
5.9
4.75
Codec mode (AMR-NB)
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Results from the VoIP simulations (1/2)
VoIP performance in GERAN Release 5
26.00

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

CIR_at_1FER (CS Rel'5)
24.00
CIR_at_1FER (VoIP Rel'5)
22.00
20.00
18.00
16.00
14.00
CIR dB
12.00
10.00
8.00
6.00
4.00
2.00
0.00
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
AMR-NB, GMSK
AMR-WB, GMSK
AMR-WB, 8PSK
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Results from the VoIP simulations (2/2)
VoIP performance in GERAN Release 6
18.00

• 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.

17.00
CIR_at_1FER (Rel'5)
16.00
CIR_at_1FER (Rel'6, EEP/EED)
15.00
CIR_at_1FER (Rel'6, UEP/UED)
14.00
13.00
12.00
11.00
10.00
CIR dB
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
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
AMR-NB, GMSK
AMR-WB, GMSK
AMR-WB, 8PSK
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CS speech vs. VoIP (1/2)
Link level performance of AMR-NB 12.2 on GMSK
channels
100.00
10.00
FER
CS speech - Rel'5
1.00
CS speech - Rel'6
VoIP - Rel'5
VoIP - Rel'6 (EEP/EED)
VoIP - Rel'6 (UEP/UED)
0.10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
CIR dB
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CS speech vs. VoIP (2/2)
Link level performance of AMR-NB 12.2 on 8PSK
channels
100.00
10.00
FER
1.00
CS speech - Rel'6
VoIP - Rel'5
VoIP - Rel'6 (EEP/EED)
VoIP - Rel'6 (UEP/UED)
0.10
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CIR dB
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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.

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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.