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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

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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 &

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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

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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