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1. TABLE OF CONTENTSEXECUTIVE SUMMARY.............................................................................................................................. 2I. THE
GROWTH OF HSPA...................................................................................................................... 3II.
EVOLUTION OF VOICE SERVICE OVER 3GPP MOBILE NETWORKS
.............................................. 5 A. GSM CS VOICE.................................................................................................................................. 5 B.UMTS CS Voice
................................................................................................................................... 5 C.
Voice over HSPA................................................................................................................................. 6 D.
Voice over LTE
.................................................................................................................................... 8III.
BENEFITS OF VOICE OVER HSPA...................................................................................................... 9IV. VoHSPA
TECHNICAL OPTIONS
......................................................................................................... 11 A. IR.58 MinimumMandatory Feature Set ............................................................................................. 11 1.
Non-Radio features
......................................................................................................................... 11 2. Radio
(and related Packet Core) features .....................................................................................11 B. Additional features
............................................................................................................................. 14V.
STATUS OF VoHSPAREALIZATION.................................................................................................. 17VI.
CONCLUSION
......................................................................................................................................
19REFERENCES............................................................................................................................................
21ABBREVIATIONS
.......................................................................................................................................23ACKNOWLEDGEMENTS
........................................................................................................................... 25 Page 1
2. EXECUTIVE SUMMARYOver the next few years HSPA will be, based simply onsheer projected number of devices, theoverwhelming technology for delivering mobile
broadband technology to consumers. The consensus isthat this will continue to be the
case through the remainder of the decade, even as Long Term Evolution(LTE) begins
proliferating.As a result, the mobile industry is continually striving to improve HSPAtechnology. One important facetof this effort relates to the delivery of voice services. Up
to now, mobile voice services have beendelivered by service providers using traditional
circuit-switched (CS) technology. Largely absent havebeen the benefits to be derived
from leveraging packet-switched (PS) and Internet Protocol (IP) basedtechnologies byoperators. (This is in contrast to third party, over the top voice over IP [VoIP]
services.)The industry is poised, however, to introduce voice services using PS, IP-based
technologies. Oncedeployed, both mobile network operators and consumers stand tobenefit significantly from moreinnovative, robust and efficient services.This paper
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describes the technological features that are being developed to make Voice over
HSPA(VoHSPA) a reality. It describes the two potential options for VoHSPA. The first
option leverages IPMultimedia Subsystem (IMS) technology developed in conjunctionwith Long Term Evolution (LTE), and isreferred to as IMS Voice over HSPA or simply
IMS Voice. The other option delivers voice by modifyingexisting circuit-switch based
techniques so that those communications can be transmitted over an HSPAinfrastructure,and is referred to as CS Voice over HSPA (CSoHS).This paper reports on the status ofthe ecosystem for commercializing the needed technology featuresunder both options. As
detailed later in the paper, with one exception, all of the features considerednecessary for
a robust VoHSPA service are available now or will be available from vendors in 2012-2013for operator testing and validation.4G Americas hopes that this paper serves as a
catalyst for the development of these technologies,illuminating both the progress that has
been made as well as what remains to be achieved to makeVoHSPA a reality for
consumers. Page 2 3. I. THE GROWTH OF HSPAGlobally, as of February 1, there were 423 HSPA
networks in 160 countries in operation. And based onthe number of subscriptions, HSPA
stands as the predominant means of providing mobile broadbandservices globally. Overthe next several years, the gap between HSPA and other technologies will widen.As
illustrated below, by 2016 45 percent of all mobile subscriptions will be based on HSPA
technology, ascompared to 8 percent for LTE and 7 percent for CDMA. Figure 1. Global
Mobile Technology Forecast 2011-2016 (Source: Informa)This trend is also evident inthe Americas. For example, by the end of 2015 it is forecast that the totalnumber of
HSPA subscriptions will surpass the total number of GSM subscriptions in Latin
America. Thisis depicted in the graph below. Figure 2. Latin American TechnologyGrowth Forecast 2011-2016 (Source: Informa) Page 3
4. These trends have some important implications. One relates to the evolutionary pathfor mobile voicetelephony service, which has been one of, if not the most important
service provided over mobilenetworks, and up to the present, the main source of revenuesfor mobile operators. For example, willpreparations to deliver voice services over
emerging LTE networks be leveraged to improve mobile voiceservice over existing
mobile networks? And what provisions are being made so that legacy voice servicescancoexist and interoperate with newer voice services?The mobile industry is working to
address these questions. In order to better appreciate thesedevelopments, some
background is provided in the next section. Note that this information, and moregenerallythis paper, deals with the evolution of mobile voice telephony services in 3GPP based
mobilenetworks, that is, carrier grade telephony service provisioned by mobile operators,
in contrast to over thetop (OTT) VoIP service provided by third parties over the
operators network but without the involvementof the mobile operator itself in the serviceprovision. Page 4
5. II. EVOLUTION OF VOICE SERVICE OVER 3GPP MOBILE NETWORKS A.GSM CS VOICECellular service based on GSM technology was launched in the early
1990s. Based on digital CStechnology to provide full duplex (simultaneous two way)voice telephony. GSM employs a dedicatedtimeslot over the air interface to carry
individual voice communications from the Mobile Station (MS) to theBase Transceiver
Station (BTS), transiting on from there toward the core network using dedicatedtrunkresources. This method of providing radio resources is referred to as Time Division
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Multiple Access(TDMA), and it allows a frequency pair to carry either 8 (full rate) or 16
(half rate) time slots. The followingfigure illustrates the basic network elements for
carrying GSM CS voice. Figure 3. Illustration of network elements for providing GSMCS voice B. UMTS CS VOICEUniversal Mobile Telecommunications System (UMTS)
is a third generation mobile cellular technology fornetworks based on the GSM standard,
and was first launched in the early 2000s. UMTS employsWideband Code DivisionMultiple Access (W-CDMA) radio access technology to offer greater spectralefficiencyand bandwidth for both CS voice and PS data to mobile network operators than TDMA
radioaccess offered with GSM. The core network supporting UMTS CS voice does not
differ much from theone supporting GSM CS voice. This allows the UMTS and GSMradio access network to share a commoncore network as shown in the figure below. Page
5
6. GSM BTS PSTN A SS7 Abis BSC Air 2/3G (Um) MSC/ VLR Iu-cs NodeB RNC Air(Uu) Iub Figure 4. Illustration of network elements for providing both UMTS and GSMCS voice service C. VOICE OVER HSPAThe traditional mechanism of mapping the CS
voice connection over a Dedication Transport Channel(DCH) in the radio network has
been in place since the very first UMTS/W-CDMA standard was Aestablished in version3.0.0 of 3GPP Rel-99. An HSPA radio service was only later introduced,specifically
targeting high speed packet access, and thus only PS data could initially be mapped onto
it.Subsequently a number of voice related optimizations were introduced to HSPA,
enabling Voice overHSPA (VoHSPA), initially designed to carry digital CS voice trafficover the PS HSPA radio layer(CSoHS). This promised to be significantly more efficient
than the traditional CS voice over DCH service,both in terms of system capacity and UE
power consumption. From a radio perspective there is littledifference whether data bitsflow over a CS or PS connection. Thus, in order to be able to benefit fromvoice related
HSPA improvements, the limitation preventing CS connections from being mapped to
theHSPA radio layer was removed in the Rel-8 specifications. (Notably the feature
capability indication bitfor UE support of CSoHS was introduced in the Rel-7specifications, making it early implementable, thatis, a Rel-7 compliant UE is able to
support CSoHS even though the feature is technically part of Rel-8specifications.)The
graphic below depicts CSoHS implementation. Page 6 7. Scheduler prioritizes CS mapped to R99 or HSPA bearer AMR adaptation voice
packets depending on terminal capability possible Transport AMR queues etc adapt. CS
R99 IuCS HSPA scheduler HSPA Combined to one carrier IuPS PS R99 NodeB RNCFigure 5. Illustration of CSoHS ImplementationIn CSoHS, the already digitized voice
packets use HSPA channels for transport back to the existing CSinfrastructure
immediately beyond the radio access network at the Radio Network Controller
(RNC).Only certain relatively straightforward changes are needed in the network and inthe UEs to enable PCSoHS, as will be explained further below.Another option for
moving voice traffic over these high-speed data channels has emerged more recently.This
approach will carry voice natively using IP (that is, VoIP) in conjunction with IP
MultimediaSubsystem (IMS) technology standardized in Rel-8. The graphic belowhighlights the distinctionsbetween traditional Rel-99 CS Voice, CSoHS and IMS Voice
approaches. voice over DCH Traditional CS DCH radio Iu-cs DCH flow UE BTS RNC
CS core Radio network Voice over IP over HSPA HSPA radio Iu-ps HSPA flow UE BTSRNC PS core Radio network over HSPA CS voice HSPA radio Iu-cs HSPA flow UE
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BTS RNC CS core Radio network Figure 6. Illustration of CSoHS relation to IMS Voice
and traditional CS voice (Note BTS synonymous with NodeB in HSPA) Page 7
8. IMS voice will allow operators to increase system capacity even further than withCSoHS, while permittingthe consolidation of their infrastructure on an IP based platform
and enabling innovative new applications B,Cthat combine voice with data functions in
the packet domain. D. VOICE OVER LTELong Term Evolution (LTE) consists of aradio access network called the Evolved UMTS Radio AccessNetwork (E-UTRAN), andpacket core network called Evolved Packet Core (EPC), together referred to asthe
Evolved Packet System (EPS). The principal drivers for LTE have been to provide higher
bandwidthat the radio interface, and better spectral efficiency (the information ratetransmitted over a givenbandwidth) and lower latency for packet data. LTE was first
standardized in the 3GPP Rel-8specifications.Support for voice in the EPS can be done
with IP Multimedia Subsystem (IMS) or CS Fallback (CSFB).CSFB allows the UE to
switch to GSM/HSPA CS services from LTE whenever voice services are needed.On theother hand, Voice over LTE (VoLTE) encompasses native support for voice telephony
over theLTE radio access, and is achieved via IMS functionality.IMS has many options
and capabilities. In order to define some level of interoperability between thecapabilitiesoffered by the device manufacturer and network vendors, GSMA established a profile in
IR 92 Dfor offering IMS voice (as well as SMS) over LTE. As will be described further
below, the effortsexpended to establish the IR 92 guidelines have also served as the
foundation for developing a similarset of guidelines for delivering an interoperable, IMSbased voice service over HSPA. Page 8
9. III. BENEFITS OF VOICE OVER HSPARecent simulations substantiate the benefitsanticipated from VoHSPA. Chief among these are increasesin the spectral efficiency ofmobile networks. Spectral efficiency is a measure of how much can bepacked into a
given unit of capacity for a given unit of time (and is typically measured in
bits/second/Hz).The logic is that if voice calls can be more efficiently delivered from a
spectral standpoint over PS ratherthan CS networks, then this frees up radio resources foradditional data.This is the case whether the technique deployed is CS voice over HSPA
or IMS Voice, as summarized inthe following graphic. E Figure 7. VoHSPA Frees Up
Resources for Data (Source: Qualcomm)Simulations involving HSDPA as well as Rel-7and Rel-8 systems support the potential for significantresource gains with VoHSPA. For
example: A 2011 simulation analyzing the capacity of CSoHS using an HSPA Rel-7system using discontinuous reception and transmission (described further on in this
paper) for best power consumption savings showed results of 190 users/cell with dual
antenna UEs, compared to 180 F users per cell when those features were not used. A
2010 simulation of CSoHS using an HSPA Rel-7/8 system showed significant in voice
capacity over Rel-99 CS voice under similar system conditions and voice quality, maxing
out at better than G triple the capacity when equalizers are used in UEs rather than RAKEreceivers. A 2010 evaluation of Rel-8 Enhanced Serving Cell Change functionality(described later in this paper) concluded that when implemented robust mobility for
VoHSPA can be achieved, Page 9
10. chronicling that under tough urban canyon conditions, significant gains are achievedcompared to H legacy procedures in call drop rates, packet drops, and duration of serving
cell changes.Earlier studies provide additional evidence of the prospects for battery life
gains when certain features Iare enabled in the UE. Page 10
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11. IV. VOHSPA TECHNICAL OPTIONS A. IR.58 MINIMUM MANDATORYFEATURE SETGSMA has recently completed a profile for devices and networks
offering IMS Voice in its IR 58 FPermanent Reference Document (PRD). This profilewas developed to complement to the GSMAsestablishment of a profile for the provisionof VoLTE in it IR 92 PRD. IR 58 was developed by a globalcross section from industry
to provide guidance on a minimum mandatory set of features defined inexisting Rel-8specifications that should be implemented in order to ensure an interoperable, highquality,IMS-based telephony service over an HSPA radio access layer.IR 58 serves as an
important point of departure for elaborating on the two technical options forimplementing
VoHSPA. Below we outline the non-radio and radio features in IR 58 necessary forIMSVoice. Immediately following, we build on that work to outline certain additional
features we advise forensuring a robust VoHSPA service, based on either IMS Voice or
CSoHS techniques.1. NON-RADIO FEATURESIR 58 outlines a number of non-radio
features that should implemented in providing IMS Voice. Theseare included in Sections
2, 3 and 5 of the PRD, and include the following basic features: Generic IMS features
(SIP registration, Authentication, Call establishment and termination, etc.) IMS Media
Other Functionalities (IPv4/IPv6,, Emergency Services, Roaming, etc.)More details areprovided in the relevant sections of IR 58.2. RADIO (AND RELATED PACKET CORE)
FEATURES Section 4 of IR 58 describes the minimum radio and relevant packet core
features required forIMS Voice. The key feature sets are described below. Robust
Header Compression (RoHC) RTP/UDP/IP headers add significant overhead to VoIP
payloads. (The AMR 12.2 full rate frame size, for example, is 244 bits; RTP/UDP/IPv6headers are 480 bits). Thus, it is essential to use a header compression scheme such as
RoHC. RoHC provides a high degree of compression while still being very robust to
packet drops. With VoIP headers, RoHC is able to compress the RTP/UDP/IP headers
down to 3 or 4 bytes a large H percentage of the time. HSPA Radio Capabilities Radio Bearers Page 11
12. The data information in a voice call is split in two parts, signaling information and thecontent of the voice communication. These have different Quality of Service (QoS)requirements. While signaling information represents a small fraction of the totalpayload, it is sensitive to data loss. On the other hand, voice content can cope with data
loss, but is highly sensitive to delay. Due to these varying requirements, signaling
information and voice payload are transported over separate Packet Data Protocol (PDP)contexts, and ultimately different radio bearers with special transport and priority
settings, according to their profiles. Given that voice payload is highly sensitive to delay
but can accommodate a certain error rate without significant degradation, the transport of
voice packets makes use of a special configuration of the Radio Link Control (RLC)protocolunacknowledged mode (UM)and certain QoS priorities to ensure timely
delivery. The use of RLC UM improves the delivery speed by eliminating retransmissionof packets with errors with which the human ear can cope relatively well (up to a certain
error rate). Furthermore, the use of the highest QoS priority (Conversational) ensuresthat packet schedulers will consider the delay sensitivity of the packets and will transmit
these in a timely manner even in cases of network congestion. On the other hand, the
signaling information required to perform call control functions (such as establishing andterminating the call) is carried over a transport bearer in RLC acknowledged mode (AM),
to ensure an error-free delivery of the signaling messages. As speed of delivery is not as
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critical here, the chosen QoS Traffic Class (TC) is Interactive, with Traffic Handling
Priority (THP) of 1, which provides for medium prioritization. UE Discontinuous
Reception (DRX) and Discontinuous Transmission (DTX); Fractional DPCH (F-DPCH)UE DTX and DRX allow dynamically switching the UEs transmitter off whenever thereis no actual data traffic to be sent in the uplink (UL). These modes also allow
dynamically turning the UEs receiver off whenever there is no data traffic or UL powercontrol to be received in the downlink (DL). The obvious benefit of turning offtransmitters and receivers consists of UE battery conservation, yielding improved
talk/stand-by times. A not-so-obvious benefit from turning off the transmitter is to reduce
interference from pilot and control-channel-only transmissions, which reduce the UL
capacity needed to support a voice user. This, in turn, allows for supporting either agreater number of voice users, or for a greater portion of UL capacity to be available for
best efforts data users while serving the same number of voice users. UE DTX and DRX
can be used when the UL data traffic is mapped onto HSUPA and the DL data traffic on
HSDPA. It was specifically designed with VoHSPA in mind, to provide for efficient UEtransmitter and receiver activity management during periods of speech inactivity, as well
as even enabling the transmitter to be turned off in between UL voice packets during anactive speech phase. UE DTX and DRX are Rel-7 features, introduced under theContinuous Packet Connectivity (CPC) umbrella. J, K Page 12
13. Fractional DPCH (F-DPCH) is a prerequisite for UE DTX & DRX operation,providing improved UE battery life (better talk/stand-by times and increased systemcapacity) when operated together with VoHSPA. The F-DPCH code resource is time-
shared, thus several users can share the same code space for power control information.
F-DPCH allows organizing all DL traffic on HSDPA in a code-efficient way by replacingthe existing DL DPCCH code dedicated for each UE with a 2-bit slot carrying the UL
power control commands. Each user receives an F-DPCH channel having one symbol per
slot only, for providing uplink power control commands, while ignoring the other nine
symbols in each slot. These remaining symbols are consequently allocated to providepower control commands to other users. F-DPCH is especially useful in conjunction with
VoHSPA in that it allows for efficiently supporting a large number of simultaneous voice
users in the cell in a code-efficient manner. F-DPCH is a Rel-6 feature, with additional
improvements for soft handover support introduced in Rel-7. Conversational TrafficClass Handling To ensure the quality of real-time services like VoIP under conditions of
network congestion, the network must be able to support a special QoS TC
(Conversational) that provides certain bitrate and delay guarantees. In HSPA, theseparameters are indicated in the PDP context with the Guaranteed Bitrate (GBR) and
Transmission Delay parameters, which are mapped down to the NodeB parameters GBR
and Discard Timer, respectively. In networks supporting the Conversational TC, the
Node-B scheduler has a special function to monitor the current connection throughputand packet delay, and perform expedited transmission of voice packets in case these
parameters are not being met. In cases of network overload, the NodeB may decide to
drop voice packets that have not been transmitted in time. The value of the GBRparameter should be set according to the bitrate requirements of the Adaptive Multi-Rate
(AMR) codec used (for instance, 23.84 kbps for AMR Wideband (AMR- WB), 12.2 kbps
for regular AMR Narrowband (AMR-NB) or 5.9 kbps for lower codec modes). The
Transmission Delay is measured between the UE and the edge of the network, and it
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should be set to ensure a low enough mouth-to-ear delay (on the order of 100ms or
lower). Note that the use of GBR and delay sensitive schedulers, while necessary for a
quality delivery of voice and other real-time services, results in a certain capacity loss in
the system as compared to schedulers that work in best-effort mode. BearerManagement In order to assure the requisite QoS for IMS Voice, radio access bearers
having the appropriate characteristics must be established. For SIP signaling, the UEmust establish a Packet Data Network (PDN) connection by activating a PDP contextwith the Interactive TC with THP setting of 1. For voice calls utilizing Conversational
TC handling, the network must establish a PDP context, using interaction with dynamic
Policy Control & Charging (PCC) functionality. Page 13
14. P-CSCF The UE and the packet core must support the procedures for Proxy-CallSession Control Function (P-CSCF) discovery via GSM and UMTS radio access
networks, as described in the M relevant 3GPP specifications. Inter-RAT Mobility Ifthe UE supports both HSPA and LTE, and both the HSPA and LTE networks support
IMS Voice, then the UE and the network shall support inter-Radio Access Technology(inter-RAT) PS handovers to and from LTE. PS handover allows extended usage of IMS
Voice over the larger coverage provided by the LTE and HSPA layers, and minimizes theuse of Single Radio-Voice Call Continuity (SR-VCC).B. ADDITIONAL FEATURES4G
Americas advises implementation of the following additional features b for VoHSPA.These featuresare over and above the minimum mandatory features in IR 58, and unless
otherwise noted, are advisablefor both IMS Voice and CSoHS. The basic motivations for
these recommendations are to furtherminimize packet losses and variations in packet
arrival times that can impair the quality of voicecommunications.Required De-Jitter
Buffer (CSoHS only) A de-jitter buffer at the RNC is required for the CSoHS approach.
This is because voice packets may arrive at the RNC from a UE with jitter on the UL,
which means that the inter-arrival times of packets is not constant. Jitter can also occur insoft-handover situations where the transmission delay from each NodeB to a particular
RNC varies. The RNC will use information in the packet headers to identify the correctorder and timing of the voice frames. The RNC transmits the output of the de-jitter bufferto the MSC synchronously over the IuCS interface, as is done for a CS call. The UE also
implements the de-jitter buffer to remove jitter on the DL, which can result from G
factors such as network loading.Recommended Bicasting In HSDPA operation, duringthe Serving Cell Change (SCC) procedure from an old to a new serving High-SpeedDownlink Shared Channel (HS-DSCH) cell, all packets residing on the old serving HS-
DSCH cell are dropped for RLC UM bearers. In Rel-6, in order to optimize HSDPA Page
14 15. operation for real-time traffic, a feature was introduced that allows bicasting of RLC
UM PacketData Units (PDUs) from the RNC to both the old and the new HS-DSCH
serving cells whenneeded.This feature minimizes the amount of packet loss during theSCC procedure, and is particularlyimportant for real-time traffic such as voice, which is
transported over RLC UM and hence cannotbe recovered. Such packet losses can createaudible impairments during HS-DSCH SCCprocedures. Note, however, that in severe
urban canyon scenarios, bicasting alone cannotrecover all dropped packets, and in these
cases, an Enhanced SCC (E-SCC) procedure is Hrecommended. Enhanced Serving CellChangeIn the Enhanced-SCC (E-SCC) procedure standardized in Rel-8, a High Speed
Shared ControlChannel (HS-SCCH) order from the target cell is used for indicating an
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SCC to the UE. In thisprocedure, for a short period of time the UE has to monitor the HS-
SCCH channel from the targetcell while also simultaneously monitoring the HS-SCCH
channel and decoding data from thesource cell.In the E-SCC procedure, the network pre-configures the UE with serving cell related information.In the legacy SCC procedure, by
contrast, such information is received only as part of the RLCreconfiguration message
that prompts an SCC, and whose reception in urban canyon scenarioscan be unreliable.The pre-configured information at the UE also includes the particular HS-SCCH channel(i.e., channelization code) that the UE needs to monitor for the target cell. At
theappropriate time, the target cell will send an indication of its readiness on the HS-
SCCH channelbeing monitored by the UE. Upon receiving this indication, the UEchanges its serving cell to the Htarget cell, and applies the pre-configured information
stored for the target cell. HS-SCCH-less operationIn typical HSDPA operation, thenetwork indicates to the UE that there is a packet for it using HS-SCCH, while the actual
packet is sent over the HS-PDSCH data channel(s). For relatively smallpackets, such as
with voice, the overhead from the HS-SCCH can take a significant portion of theoveralltransmit power needed to deliver that packet. In addition, for large numbers
ofsimultaneous VoHSPA users, the HS-SCCH channel utilization in the cell will be veryhighcompared to delivering the equivalent amount of data to high data rate (non-voice)users. Thisincreased ratio of HS-SCCH usage per bits delivered for voice may lead the
cell occasionally todeplete its HS-SCCH capacity.HS-SCCH-less operation allows for
transmitting a voice packet without the HS-SCCH indication,eliminating the overheadfrom the initial packet transmission attempt completely. The UE willcontinue receiving
on the assigned HS-PDSCH data channel if there is a voice packet for it,without the aid
of HS-SCCH indicating when it is there. Higher data rates or retransmissions ofmissedvoice packets are still scheduled with HS-SCCH. This feature is referred to ReducedLcomplexity HS-SCCH-less operation in the 3GPP specifications. Page 15
16. Voice Call Continuity (IMS Voice only) For IMS Voice, an operator mayencounter deployment scenarios where its IMS Voice capable radio coverage may not becoextensive with its concurrent CS radio coverage. In such scenarios, complementingIMS Voice coverage with CS capable coverage may prove advisable. The Single-Radio
Voice Call Continuity (VCC) procedures provided in the 3GPP specifications define N,O
procedures for IMS Voice handovers between HSPA and UMTS/GSM CS coverage.Aconcluding note applies for both CSoHS and IMS Voice, and relates less to the specific
featureidentified above, but is a more general observation about the scheduler
enhancements needed at theRNC to ensure robust mobility. Preserving seamlessconnections during mobility, and mapping voiceand control signaling to HSDPA entail
tighter requirements for SCC performance than with traditionalconfigurations of voice
and signaling. As discussed in several places earlier in this paper, the RNCscheduler
needs to be QoS aware in order to properly manage the special conversationalTCrequirements. In addition, the scheduler needs to apply a special TC handling to the
signaling messagesin order to guarantee that for example the commands ordering the UE
to change its serving cell arereceived with very high reliability and minimal latency.Furthermore, the network algorithms related toSCC procedures may require adjusting, as
more aggressive approaches to deciding on the serving cell,minimizing the execution
time and eliminating related connection breaks on the cell change may berequired with a
voice connection than what is permissible for more delay tolerant services. Page 16
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17. V. STATUS OF VOHSPA REALIZATIONAs part of 4G Americas efforts tocomplete this report, vendors provided information about whenVoHSPA features would
be available from them. Availability in this case means when these featuresareavailable to mobile network operators for testing and validation. Vendor responses were
aggregatedin order to arrive at the timelines given in the Feature Availability Matrix
below.The features listed parallel those described in the prior section of the paper. In thefirst grouping, the IR58 minimum mandatory features necessary for IMS Voice are listed.The second grouping consists of theadditional features that 4G Americas recommends for
a high quality VoHSPA service (whether based onCSoHS or IMS Voice). Corresponding
references to IR 58 are provided as appropriate in the last column. Table 1. FeatureAvailability Matrix Availability Feature CSoHS IMS Voice IR 58 ReferenceIR 58
MinimumMandatory FeaturesNon-Radio FeaturesA. Generic IMS features (SIP A. N/A
A. 1Q2012 A. Sec. 2registration, authentication, callestablishment and termination, etc.)
B. N/A B. 1Q2012 B. Sec. 3B. IMS Media C. N/A C. 1Q2012 C. Sec. 5C. Otherfunctionalities (IPv4 & v6,Emergency Services, Roaming, etc.)Radio (& related packet
core) featuresA. RoHC (IMS Voice only) A. N/A A. 2Q2012-EY2013 A. Sec. 4.1B.
HSPA Radio Capabilities B. 1Q2012- B. 1Q2012-EY2012 B. Sec. 4.2 Page 17 18. C. Bearer Management EY2013 C. 2H2012 C. Sec. 4.3D. P-CSF Discovery C.
2H2012 D. 1Q2012 D. Sec. 4.4E. Inter-RAT Mobility D. N/A E. 2H2012-EY2013 E.
Sec. 4.5 E. 2H2012- EY2013Additional FeaturesMandatoryA. De-jitter Buffer(CSoHS
only) A. 1Q2012- A. N/A A. N/A EY2013RecommendedA. Bicasting A. No plans A. Noplans A. N/AB. E-SCC B. 2Q2013- B.2Q2013-EY2013 B. N/A EY2013 C. 2013C.
HSSCCH-less operation C. 2013 C. N/A D. 2013D. VCC (IMS Voice only) D. N/A D.
N/AAs outlined above, vendors have indicated that the minimum mandatory featuresneeded for IMS Voiceare either available at the present time, or will be available later
this year or in 2013. In addition, many ofthe additional features recommended by 4G
Americas either are or will be available along the sametimescales, with the notable
exception of bicasting enhancements.The time estimates listed above are best-estimatesummary information, and should not be construed ascontractual information or specific
to any commercial arrangement. Each individual vendor within 4GAmericas and the
industry as a whole will have their own specific availability dates for the listedfeatures.The timeframes above are intended to provide an overall sense for feature
readiness. Page 18
19. VI. CONCLUSIONIn general, it should be apparent that that full realization ofVoHSPA will involve a number of interrelateddependencies. These include important
initiatives in the following areas: Standardization developments Terminal
enhancements Radio access infrastructure enhancements Interworking with legacy
CS networks and technologies Coexistence and roaming with emerging LTE networks
Maturation of the IMS ecosystem
Continued diffusion of HSPA technologyThegraphic below encapsulates these considerations. LTE coexistence and roaming HSPAInterworking technology with legacy CS diffusion technology Standards VoHSPA IMS
ecosystem development maturation Terminal Infrastructure enhancements enhancements
Figure 8. Key Interrelated Dependencies for VoHSPAA key finding in this paper is thatvirtually all of the features believed necessary for a robust VoHSPAservice are either
presently available or will be available from vendors later this year or in 2013 for
testingand validation. The sole exception pertains to bicasting. Page 19
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20. Further, the industry will continue to remain mindful of the need to ensure that certaincritical featuresremain fully functional. For example, IR 58 contains provisions defining
the IMS Emergency Servicefeatures that will enable emergency calling services expectedby consumers.Finally, with respect to the important work concluded by GSMA in IR 58,
further efforts will need to bepursued within GSMA to ensure the effective cross-
operation of those guidelines with other GSMA PRDs P,Qsuch as IR.64 IMS CentralizedServices (ICS) and IR.65 IMS Roaming. Page 20 21. REFERENCESA. 3GPP TSG Service and Systems Aspects, 3rd Generation Mobile
System Release 1999Specifications, 3G TS 21.101 V3.0.0 (2000-
03)http://www.3gpp.org/ftp/tsg_sa/WG3_Security/_Specs/33908-300.pdfB. 4GAmericas, Evolution of HSPA
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%20Evolution%20of%20HSPA_October%202011x.pdfC. 4G Americas, Mobile
Broadband Explosion(2011)http://www.4gamericas.org/documents/Mobile%20Broadband%20Explosion_Rysa
vy_Sept2011.pdfD. IMS profile for Voice and SMS (GSMA permanent reference
document IR 92.1.0)http://www.gsma.com/go/download/?file=ir.92.pdfE. Qualcomm,How to Meet Data Demand
(2011)http://www.qualcomm.com/media/documents/files/how-to-meet-data-demand-
.pdfF. Qualcomm, CSoHS Voice Capacity in HSPA Networks
(2011)http://www.qualcomm.com/media/documents/files/csohs-voice-capacity-in-hspa-networks-with-realistic-overhead-channel-modeling.pdfG. Qualcomm, Circuit-Switched
Voice Services over HSPA (2010)http://www.qualcomm.com/documents/circuit-
switched-cs-voice-services-over-hspaH. Qualcomm, Enhanced HSDPA MobilityPerformance (2010)http://www.qualcomm.com/documents/enhanced-hsdpa-mobility-
performance-quality-and-robustness-voip-service)I. Tapia et al, HSPA Performance &
Evolution, Wiley (2009)J. IMS Profile for Voice over HSPA (GSMA permanent
reference document IR. 58.1.0) http://www.gsma.com/documents/ir-58-1-0-ims-profile-for-voice-over-hspa/21986K. Qualcomm, Performance of VoIP Services over 3GPP
WCDMA Networks (2008)http://www.qualcomm.com/documents/performance-voip-
services-over-3gpp-wcdma-networksL. 3GPP, TR25.903 -Technical Specification GroupRadio Access Network; Continuous connectivity forpacket data users (Release 7)
http://www.3gpp.org/ftp/Specs/archive/25_series/25.903/25903-700.zipM. 3GPP, TS
24.229 - IP multimedia call control protocol based on Session Initiation Protocol (SIP)andSession Description Protocol (SDP); Stage
3http://www.3gpp.org/ftp/Specs/archive/24_series/24.229/24229-930.zipN. 3GPP, TS
23.216 - Single Radio Voice Call Continuity (SRVCC); Stage
2http://www.3gpp.org/ftp/Specs/archive/23_series/23.216/23216-870.zipO. 3GPP, TS23.237 - IP Multimedia Subsystem (IMS) Service Continuity; Stage
2http://www.3gpp.org/ftp/Specs/archive/23_series/23.237/23237-870.zip Page 21
22. P. GSMA, IR.64.20- IMS Service Centralization and ContinuityGuidelineshttp://www.gsma.com/go/download/?file=ir6420.pdfQ. GSMA, IR 65.5.0 -IMS Roaming and Interworking
Guidelineshttp://www.gsma.com/go/download/?file=ir6550.pdf Page 22
23. ABBREVIATIONS3GPP 3rd Generation Partnership ProjectAM AcknowledgedModeAMR Adaptive Multi-RateAMR-NB AMR NarrowbandAMR-WB AMR
-
7/29/2019 VoHS
11/11
WidebandAPN Access Point NameBTS Base Transceiver StationCDMA Code Division
Multiple AccessCPC Continuous Packet ConnectivityCS Circuit-SwitchedCSFB CS
FallbackCSoHS CS Voice over HSPADCH Dedicated Transport ChannelDLDownlinkDRX Discontinuous ReceptionDTX Discontinuous TransmissionEPC
Enhanced Packet CoreEPS Enhanced Packet System (i.e., LTE + EPC)E-SCC Enhanced
Service Cell ChangeE-UTRAN Enhanced UMTS Radio Access Network (a/k/a LTE)F-DPCH Fractional Dedicated Physical ChannelGBR Guaranteed Bit RateGSM GlobalSystem for Mobile CommunicationsGSMA Global organization for 3GPP technologies,
f/k/a GSM AssociationHS-DSCH High-Speed Downlink Shared ChannelHS-SCCH
High-Speed Shared Control ChannelHSDPA High-Speed Downlink Packet AccessHSPAHigh-Speed Packet AccessHSUPA High-Speed Uplink Packet AccessIMS IP Multimedia
SubsystemIP Internet ProtocolIPv4 IP version 4IPv6 IP version 6IR International
Roaming (a GSMA document citation tool)LTE Long Term EvolutionMS Mobile
StationNodeB Base Station in HSPA networksPCC Policy and Charging ControlP-CSCFProxy - Call Session Control FunctionPDN Packet Data NetworkPDP Packet Data
ProtocolPDU Packet Data UnitPRD Permanent Reference Document (a GSMA
document citation tool)PS Packet-SwitchedQoS Quality of ServiceRAB Radio AccessBearerRAT Radio Access TechnologyRLC Radio Link ControlRoHC Robust Header
Compression Page 23
24. RRC Radio Resource ControlRTCP RTP Control ProtocolRTP Real-TimeProtocolSCC Serving Cell ChangeSIP Session Initiation ProtocolSR-VCC Single RadioVoice Call ContinuityTDMA Time Division Multiple AccessTHP Traffic Handling
PriorityUDP User Datagram ProtocolUE User EquipmentUL UplinkUM
Unacknowledged ModeUMTS Universal Mobile Telecommunications SystemUTRANUMTS Terrestrial Radio Access NetworkVoHSPA Voice over HSPA (using either
Circuit-Switched or IMS approaches)VoIP Voice Over IP (typically refers in this paper to
IMS Voice over HSPA)W-CDMA Wideband CDMA Page 24 25. ACKNOWLEDGEMENTSThe mission of 4G Americas is to promote, facilitate and
advocate for the deployment and adoption of the3GPP family of technologies throughout
the Americas. 4G Americas Board of Governor members includeAlcatel-Lucent,
Amrica Mvil, AT&T, Cable & Wireless, CommScope, Ericsson, Gemalto, HP,Huawei,Nokia Siemens Networks, Openwave, Powerwave, Qualcomm, Research In
Motion (RIM), Rogers, T-Mobile USA and Telefnica.4G Americas would like to
recognize the significant project leadership and important contributions of BobCalaff ofT-Mobile USA, as well as the contributions of Etienne Chaponniere of Qualcomm, and
KarriRanta-Aho and Curt Wong of Nokia Siemens Networks, as well as representatives
from the othermember companies on 4G Americas Board of Governors who participated
in the development of thiswhite paper. Page 25