Improvements in speech services of GERAN Master’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 1-2Phase 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 GERAN GSM/EDGE radio access network UTRAN UMTS terrestrial radio access network CN Core network BSC Base station controller BTS Base transceiver station RNC Radio network controller BSS Base station subsystem MS Mobile 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)

Adaptive Multi-Rate codec (1/2) Provides various codec modes with different speech qualities. Key operation: The codec mode adaptation (figure below).

Adaptive Multi-Rate codec (2/2) Narrowband AMR (GERAN Rel’98) Audio bandwidth equal to 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 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 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)

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 CIR [dB] (Rel'5) (Rel'6) AMR-NB, GMSKAMR-WB, GMSKAMR-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 Codec mode (AMR-NB) CIR [dB] (NB/GMSK, Rel'5) (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 CIR [dB] (CS Rel'5) (VoIP Rel'5) AMR-NB, GMSKAMR-WB, GMSKAMR-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 CIR [dB] (Rel'5) (Rel'6, EEP/EED) (Rel'6, UEP/UED) AMR-NB, GMSKAMR-WB, GMSKAMR-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% % CIR [dB] FER 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% % CIR [dB] FER 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.