osc ne twork capacity-network costs

INTRODUCTION

Cellular operators are making the most of GSMcellular networks with good profit despite thenewer technologies available, and consequentlyGSM covers more than 90 percent of the world’spopulation (GSM Association, GSMA). Addi-tionally, the average selling prices for GSMhandsets are generally lower than for third/fourthgeneration (3G/4G) technologies, since GSMrequires low-cost hardware, and there are possi-bly less royalties associated with GSM. There-fore, there is still significant growth in emergingmarkets such as China, India, and EasternEurope. As speech services remain the mostimportant application for wireless networks andfallback from Long Term Evolution (LTE), it

magnifies the importance of continuous improve-ment in GSM technology and its standardizationefforts.

Cellular radio networks are based on thereuse of frequencies due to the scarcity of radiospectrum resources. As traffic increases, GSMoperators have to increase their hardware capa-bility, hence adopting tighter frequency reuses toaccommodate more subscribers and traffic.Additionally, operators need to decrease GSMspectrum to have more bandwidth for the newtechnologies. Both situations bring co-channelinterferers closer and cause the networks tooperate in more challenging interference condi-tions. Thus, increasing the spectral efficiency ofspeech services becomes a necessity, not only toaccommodate the growing voice traffic, but alsoto make room for increasing data traffic.

GERAN remains under continuous develop-ment in the Third Generation Partnership Pro-ject (3GPP). In the recent past, several newfeatures aimed at increasing system capacityhave been proposed, such as interference rejec-tion combining (IRC), single-antenna interfer-ence cancellation (SAIC), source-adaptive AMR(SA-AMR), and 8-phase shift keying (PSK)speech channels. In addition, network vendorsare continuously developing new radio resourcemanagement features such as dynamic frequencyand channel allocation (DFCA) [2] andenhanced power control algorithms.

One of the latest improvements proposed forGSM voice evolution was the orthogonal sub-channel (OSC) transmission technique [3], whichsimultaneously accommodates two users on thesame GSM radio resource by using orthogonalsubchannels. The OSC feature can provideincreased network capacity and reduce networkcosts through efficient usage of hardware andspectrum resources.

Applications of this technology can serve theincreased circuit switch (CS) traffic without theneed for installation of new transceivers (TRX),or increasing site density by adding new basetransceiver stations (BTSs). In this case, OSCwould reduce the interference experienced bythe network; hence, new traffic would be accom-modated with better expected quality as well. Ina second case, OSC may be applied when theoperator wants to share its licensed spectrumbetween GSM and 3G/4G technology [4].

IEEE Communications Magazine • December 201280 0163-6804/12/$25.00 © 2012 IEEE

ABSTRACT

The explosive growth of mobile communica-tions, and the overly crowded and expensivespectrum have pushed both system engineersand operators to make their systems as spectrallyefficient as possible in order to accommodatethe increasing traffic demand. This article is atutorial introduction to the orthogonal subchan-nel (OSC) technique. OSC was adopted toimprove the capacity of the GSM/EDGE radioaccess network GERAN, and it is a new conceptin which two users can simultaneously share thesame GSM radio resource (time slot and fre-quency) in both the downlink and in uplinkdirections. Potentially, OSC could not only pro-vide increased network capacity, but also reducenetwork-associated costs through more efficientusage of hardware and spectrum resources. Inaddition, this article presents some challengesrelated to this method, as well as solutions andtheir respective impact. The results providedherein may contribute to guidelines for networkdimensioning and optimization, as well as listpotential enhancements to the OSC radioresource management mechanisms needed tofurther exploit the benefits of OSC. Currently, inreal OSC network deployments a capacity gainof 50 percent has been achieved at the cell level.As an indication of the importance of OSC,GSMA awarded it (called Quad Rate) the BestTechnology Breakthrough award at MobileWorld Congress 2012 [1].

TOPICS IN RADIO COMMUNICATIONS

Rafael C. D. Paiva, Robson D. Vieira, Renato Iida, and Fernando M. Tavares, Nokia Institute of Technology

Mikko Säily, Jari Hulkkonen, Rauli Järvelä, and Kari Niemelä, Nokia Siemens Networks

GSM Voice EvolutionUsing Orthogonal Subchannels

Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next PageIEEE

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IEEE Communications Magazine • December 2012 81

Refarming of spectrum may then be appliedwhen LTE or HSPA systems are deployed [5, 6].

STANDARDIZATION

VAMOS IN 3GPP FROM RELEASE 9 TO 11The GSM Enhanced Data Rates for Global Evo-lution (EDGE) radio access network (GERAN)in 3GPP has introduced OSC under a workingitem named Multi-User Reusing One Slot(MUROS) [7]. This first study item was pro-posed to analyze several details and featuresrelated to enhancements to this technology suchas adaptive quadrature PSK (AQPSK), higherorder modulations, user diversity, and frequencyhopping schemes [8]. Soon after MUROS, theVoice over Adaptive Multi-User Channels onOne Slot (VAMOS) study item [9] was opened.VAMOS is based on the concept of OSC extend-ed with AQPSK modulation, where the transmit-ter power can be adjusted between sub-channels,and shifted SACCH, to improve performance ofthe associated signaling channel. The mainobjective of VAMOS working item was to serveas a way forward to accelerate standardizationprocess; hence it has streamlined a set of fea-tures taken from MUROS, and it is focused onthe main principles of OSC concept in order tomaximize the system benefit with acceptablecomplexity.

Along with high demand for advanced voiceservices, a number of enhancements were dis-cussed for standardization in 3GPP Release 10,which further boost the spectral efficiency ofvoice in GSM networks employing tight frequen-cy reuses. Examples of these enhancementsinclude a optimized transmit pulse shaping filter,and improvements to the associated controlchannel signaling for sub-channels.

3GPP Release 11 currently works on a studyitem on VAMOS enhancements (ENHVAMOS)[10], where the capacity gains are beingimproved. The objectives of ENHVAMOSenhancements are to improve the call quality ofpaired mobiles and non-paired mobiles and uti-lize network synchronization for inter-cell inter-ference coordination and mitigation.

IMPACT TO SPECIFICATIONSThe introduction of VAMOS has influenced sev-eral 3GPP specifications. The main implicationsare seen in the physical layer of a radio path inthe 45 series from 45.001 to 45.004, where chan-nel organization and configurations for trafficand associated control channels were definedalong with new modulation, symbol rotation,burst format, training sequences, and mappingof the associated control channels to the framestructure. The radio transmission and receptionwith performance requirements have been speci-fied in 45.005 with new VAMOS test scenarios,modulation accuracy and power versus timemask for AQPSK and radio performancerequirements for mobile stations and base sta-tions. The specification of the radio subsystemlink control in 45.008 deals with the power back-off for AQPSK modulation on a broadcast carri-er and the subchannel-specific power control,and considers the impacts on measurementquantities for AQPSK.

OBJECTIVES

The standardization of GSM voice evolutionneeds to consider several objectives of systemfeasibility, performance, and compatibility withlegacy voice and data services. The performancerequirements of VAMOS not only guarantee thelink performance, but also provide increasedspectral efficiency at the air interface and hard-ware capacity improvements of base stationsdoubling the number of voice channels pertransceiver. In order to allow VAMOS deploy-ment in most of the GSM/EDGE markets and tominimize the impact on existing networks, theperceived voice quality should not decrease. Thetarget is to support existing legacy downlinkadvanced receiver performance (DARP) phase 1mobile stations by including them in the OSCmultiplexing scheme without impacting themobile station hardware platform. The feasibilityof including the non-DARP mobile stations intothe multiplexing is being investigated in 3GPP,and, in principle, BTSs need to support new andlegacy channels serving all kinds of legacy mobilestations simultaneously. The impact on theresources dimensioning on the BTS-BSC inter-face (Abis) should be minimized. The target isalso to ensure that standardization of VAMOSin 3GPP minimizes the impact on network plan-ning and frequency reuse.

COMMON WORKING ASSUMPTIONSIn order to evaluate the performance ofVAMOS and its related features, GERAN hasdefined common simulation guidelines [11].These guidelines include the simulation scenar-ios and all of its related parameters. All the sim-ulation results shown in this article follow theseguidelines using a modified MUROS 1 scenariowith variable number of TRX and bandwidth[11]. These simulations help to understand howthe voice capacity can be increased by addingthe OSC specific features.

OSC CONCEPT DESCRIPTIONThe OSC concept is capable of duplicating thevoice capacity in GSM channels, where two userscan share the same physical radio resourcesimultaneously. For proper separation of theusers’ signals, each user should use differenttraining sequences, which should be mutuallyuncorrelated for optimum OSC performance.

The GSM time slot structure for differentchannel modes is shown in Fig. 1a. In the stan-dard GSM channel modes, one TRX can allo-cate 8 and 16 users in the same frequency whenusing full rate (FR) and half rate (HR) channelmodes, respectively. Accordingly, if OSC isapplied for both FR and HR calls, 16 and 32users can be allocated to the same frequencywith double full rate (DFR) and double half rate(DHR), repectively. Therefore, multiplexingusers significantly increase the circuit-switchedtraffic capacity in a network.

Figure 1b shows the theoretical maximumOSC CS capacity for different number of trafficchannel (TCH) TRX. The capacity is calculatedfor 2 percent blocking probability and takinginto account BCCH TRX so that the x-axis 0

The objectives

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IEEE Communications Magazine • December 201282

refers to the BCCH only case. It should be notedthat interference estimation is not included inthis calculation. It can be seen that the capacitygain potential is very high. DHR will more thandouble the network capacity in the HR case.

In the downlink direction, a base stationsends for both OSC users a single QPSK modu-lated signal, which may be a subset of the 8-PSKEGPRS constellation as shown in Fig. 2a, wherethe most significant bit contains the informationfor the user on sub-channel 0 while the least sig-nificant bit contains the signal for the user onsub-channel 1 (Fig. 3). Another possible inter-pretation of this concept is that the informationfor users on subchannels 0 and 1 are containedin the in-phase and quadrature components,respectively. Therefore, a single composite signalcarries two information flows using orthogonalchannels in the same radio frequency resource.

At the MS side, legacy receivers are able todecode this composite signal as an ordinaryGMSK modulated signal. However, due to themultipath propagation, the orthogonal proper-ties among the training sequences are reducedby inter-symbol interference between the twosignals. Multi-user detection techniques can beused for cancelling or suppressing interferenceamong the signals. One example is single-anten-na interference cancellation (SAIC) [2], whichcancels the dominant interferer by means of sig-nal processing. This technique is extremely ade-quate in mobile terminals since it is a challengeto adopt multiple antennas in low-cost GSMdevices.

Downlink discontinuous transmission (DTX)can also be supported with OSC. When an OSCuser is in DTX mode in downlink the other usercan fully occupy the radio channel, and the basestation transmission can use GMSK since thereis no information to be sent to the user in DTX.Hence, lower frame erasure rate (FER) andhigher speech quality is observed to the activeuser.

In the uplink direction each mobile using

OSC transmits using a GMSK modulated signal.The BTS receives signals from both subchannelsand applies interference rejection (e.g., interfer-ence rejection combining, successive interferencecancellation, or joint detection), together withthe knowledge of both training sequences to sep-arate the signals and decode the symbols peruser.

RADIO RESOURCE MANAGEMENTOSC poses some new challenges for radioresource management (RRM) algorithms, whichhave to deal with the signal quality of two userssimultaneously. In the downlink direction, thepower control algorithm is limited, since onlyone carrier is used to transmit for both users, sothe transmitted power is the same for them.Thus, RRM algorithms should try to multiplexusers with similar radio conditions, requiringapproximately the same transmitted power. Oth-erwise, it is likely that the transmitted power willbe unnecessarily higher, creating more interfer-ence in the network. In the uplink direction, thebase station will experience different receivedpowers, which may cause some challenges inreception. As both users transmit at the sametime, if one signal is stronger than the other, theBTS may not be able to detect the weaker sig-nal, causing strong degradation on this user.Intelligent radio resource management shouldbe performed to prioritize the allocation of usersin sufficient radio conditions into OSC channels.

BASIC RRM ALGORITHMSRadio resource management concentrates someimportant efforts in GSM since it is responsiblefor choosing the most suitable channel to newconnections. The channel allocation can be con-sidered as a natural solution to reduce interfer-ence. For instance, channel allocation may bebased on the interference level of each channel,in addition to path loss difference between usersto be multiplexed in OSC channels. The path

Figure 1. GSM voice evolution using OSC.

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loss criterion becomes important when usershave significant differences in radio conditions,since it is likely that the user demanding morepower from BTS will create increased interfer-ence in the network. These challenges are typi-cally addressed with improved power controlschemes and interference diversity techniques.

The channel mode adaptation algorithm(CHMA) is another important feature used tomaintain minimum voice quality and increasednetwork capacity. Although it would be desirableto have as many users in OSC channels as possi-ble in order to take full advantage of hardwareimprovements, it is important to guarantee thatusers with poor radio conditions are not multi-plexed into OSC channels. Hence, a simpleRRM implementation can be based on the net-work load, quality, and signal level measure-ments, when the network needs to choose thebest channel mode to be applied for each con-nection.

In GSM networks a power control algorithmis usually applied to guarantee minimum signallevel and voice quality, while maximizing thebattery life and minimizing the interferencetoward other cells. In the downlink direction thesame transmitting power is used for both OSCpaired users; thus, the power control has to becontrolled by the weaker link. Therefore, theincreased power will also impact the other OSCuser, even if power increase was not demandedby it. Additionally, power reduction can be doneonly when it is applicable to both of the OSCpaired users simultaneously. In the uplink direc-tion power control is independent for each OSCpaired user, but still the received uplink signalpowers should not be too different for properreceiver performance.

OSC system simulation results for 900 MHzband assuming 100 percent of SAIC receiversare shown in Fig. 4. Network voice traffic capaci-ty was determined based on blocked call rate(BCR) and bad quality call rate (BQC), where abad quality call was assumed for calls with aver-age frame erasure rate below 3 percent. HR andDHR cases were evaluated for a 4 TRX configu-ration, and HR also for a 6 TRX configuration,to study the impact of the number of TRXs onhigher voice capacity and bandwidth.

In the 4 TRX case with HR, network capacityis limited by hardware, and therefore increasedbandwidth does not increase voice capacity.Once OSC is applied, there is double the amount

of voice channels available, and the networkcapacity becomes limited by interference. Hence,network voice capacity in the DHR case increas-es as a function of bandwidth. For example, 29percent capacity gain is achieved in the 7 MHzcase and 51 percent gain in the 10 MHz case.Comparison between DHR with 4 TRX and HRwith 6 TRX shows that it is possible to reducethe number of TRXs by two when applying OSCwith approximately 9 MHz bandwidth.

These example simulations show that OSCcan be used efficiently for reducing hardwarerequirements in a cellular network, since TRXreduction can be applied without compromisingthe overall network capacity. Thus, OSC may beused as a means for reducing both implementa-tion and operational costs, since fewer TRXswould probably also lead to reduction of mainte-nance and energy costs.

Additional improvements using OSC couldbe obtained by substituting HR channel modewith DFR. Although DFR does not providehardware efficiency improvements over legacyHR channel mode, it has a higher raw bit rate,which enables usage of codecs with either higherrobustness or improved perceptual speech quali-ty. Additionally, wideband AMR (AMR WB)codecs [12] were only standardized for FR chan-nel modes in GSM, which means that DFR canfurther benefit from the improved perceptualvoice quality offered by those codecs [13].

Figure 3. OSC symbols used on subchannel 0 and subchannel 1.

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Figure 2. a) 8PSK constellation symbols used on OSC, and 8-PSK symbols used for subchannel powerimbalance with b) subchannel 0 attenuated; c) subchannel 1 attenuated.

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ADVANCED POWER CONTROL

Normal power control in the downlink offers fewcontrol possibilities for OSC calls, since trans-mitted power is controlled by the user in theworst radio condition. Hence, some OSC-specif-ic power control features arise by modifying theconstellation used for transmitting OSC symbolsin downlink shown in Fig. 2a. One possibility isthe application of the AQPSK feature, in whichthe transmitted constellation can be linearlymodified to apply a power imbalance betweenusers sharing a channel [14].

A simplification of the AQPSK technique isachieved with subchannel-specific power control(SCPC), which uses an 8-PSK-like constellationas shown in Figs. 2b and 2c, and hence has theclear advantage of requiring simpler hardware.With this feature, the separation of constellationsymbols for one user is increased, yielding anequivalently higher power, while it is decreasedfor the other. As an example, SCPC is a way toequalize channel conditions when users experi-ence different radio conditions or are equippedwith different kinds of receiver capabilities.Additional steps of subchannel power imbalanceratio (SCPIR) are obtained by modification,burst by burst, of the transmitted constellationwithin the interleaving period of a voice frame.Applications of this technique include enablingmobile stations with non-SAIC receivers to bemultiplexed with SAIC receivers, where higherSCPIR would be delivered to non-SAIC users.When both mobile stations share the samereceiver capability, it is possible to increaseSCPIR for the benefit of the user in weakerradio conditions without increasing the transmit-ted power.

In Fig. 5 it is possible to observe simulationresults of SCPC on a scenario with 7 MHz band-width. This scenario includes one BCCH andthree TCH TRXs, in 900 MHz band, where 50

percent of the users are non-SAIC users. In thisscenario there is a high improvement on BQC,which has decreased by 50 percent in most cases.This result demonstrates that SCPC is a goodalternative for enabling non-SAIC receivers inOSC channels. On the other hand, this gain willbe worn out when old non-SAIC receivers, cur-rently only 40 percent, disappear.

INTERFERENCE DIVERSITY SPECIFIC FEATURESUser diversity (UD) can be used to improveinterference diversity capability for OSC calls. InOSC DHR setup, up to four users may be allo-cated to the same time slot. In Fig. 1a users aregrouped in pairs of two so that they do not inter-fere with each other. When UD is enabled in thenetwork, frame structure shall be modified sothat the transmission positions of selected usersare changed. This modification makes the pairedusers change pairs from burst to burst. There-fore, the transmission is not always synchronizedwith other half-rate users, and interferencediversity is achieved. One example is shown inthe bottom of Fig. 1a where user 1 is paired withuser 3 in the first burst and with user 4 in thesecond burst. Additionally, UD has a majoradvantage in a DTX enabled network, where theDTX silent periods are distributed among allusers applying UD. Therefore, UD would be afeature that is able to increase interferencediversity, and also to spread DTX gains over callperiods for OSC users. This in turn will decreaseFER and improve voice quality. UD may lead toan improvement of 35 percent in BQC [8].

SIGNALING ENHANCEMENTSOSC has also posed some new challenges forsignaling. Once a user is using an OSC channel,the decreased interference robustness may alsoaffect signaling messages, which could cause thecall to drop or either degrade measurement mes-sages, reducing RRM algorithms’ performance.For this reason, special signaling features weredeveloped to protect those messages.

The first proposed feature was the FACCHdouble stealing. Fast associated control channel(FACCH) is a message that may occur at anytime, and during a normal GSM voice connec-tion it steals the voice traffic blocks to be trans-mitted; hence, it naturally causes a smalldegradation in voice quality for a user transmit-ting it. When OSC is enabled, the interferencecaused by the user carrying normal traffic mayincrease the FACCH erasure probability, caus-ing this user to drop or retransmit an FACCHblock. To minimize interference during FACCHblocks, FACCH double-stealing was proposed,in which the normal voice radio blocks from thepaired user are stolen as well; that is, no infor-mation is sent for a user with normal traffic,and the user transmitting FACCH holds thechannel alone. This improves FACCH erasurerate while causing a small degradation for thesecond user.

Another approach to this problem is FACCHsoft stealing, where unequal SCPI is applied todecrease FACCH error probability while causingsmaller degradation on the second OSC usercompared to the double stealing technique.

Figure 4. Simulated system capacity results for BQC < 5 percent, BCR < 2percent in 900 MHz.

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Thus, this approach leads to a good compromisebetween signaling performance and voice quali-ty. Techniques for FACCH enhancement havealready shown a possible improvement of 20–30percent in dropped calls while increasing BQCby 6–10 percent [8].

Signaling can also be improved in slow associ-ated control channels (SACCHs). SACCH isused to send radio measurements required byRRM algorithms such as handover and powercontrol. The SACCH positions in the normalOSC frame structure are the same for pairedusers. If one OSC user is in DTX state, theSACCH blocks of its paired user will continue tosuffer from interference because SACCH blocksare transmitted regardless of the DTX state. Forimproving SACCH robustness, shifted SACCHsfor OSC were adopted in VAMOS, in which theSACCH position for each paired user is not thesame. Hence, while one user is transmitting anSACCH, the other is transmitting a normal TCHburst. The advantage of this feature is that thereis a probability of SACCH being transmittedwhen an OSC pair is in DTX mode, which pro-vides an SACCH FER improvement.

FUTURE ENHANCEMENTSOSC significantly increases the hardware capaci-ty of GSM networks, and when serving more andmore users the networks tend to become limitedby signal quality. This is caused by the increasedinterference coming from users in OSC chan-nels. Therefore, it is important to consider futureimprovements of OSC features to further exploitinterference robustness for OSC calls.

One possible improvement for OSC is todevelop new receivers specially designed forreceiving OSC transmission. These new receiversare aware of the constellation structure of Fig. 2and can properly cancel the interference of theother subchannel sharing the same radioresource. This improvement may significantlyincrease OSC performance, since it would makereceivers more robust to interference. Addition-ally, it would also allow non-SAIC receivers tobe multiplexed into OSC channels, when largeSCPI ratios can be used improve the legacyreceiver performance.

It is also important to develop network-levelinterference management features optimizedespecially for OSC when the challenging inter-ference conditions are limiting OSC gains inhigh traffic density networks. One example is thedynamic frequency and channel allocation(DFCA) [2] feature, which dynamically opti-mizes network performance by adapting to thenetwork load and interference conditions, and byallocation of the best available radio resource intime and frequency.

CONCLUDING REMARKSGSM networks, after two decades of operation,still have an important role in the telecommuni-cations market even though new wireless tech-nologies, like 3G and LTE/4G, are emerging;therefore, further enhancements are still neces-sary. In this context, OSC has proven to be animportant feature to optimize the resources

needed to carry GSM voice and data traffic. Thisarticle shows the feasibility of the OSC concept,as well as the potential spectrum and hardwaresavings. On the other hand, more efficient spec-trum resource usage would enable moreresources for new evolving technologies in spec-trum refarming to drastically increase the mobilebroadband traffic volumes. The main OSC fea-tures were introduced, and their applicability todifferent kinds of scenarios and capability wasdemonstrated to improve network performancein typical deployment cases. Further evolutionsteps are still desirable for taking full advantageof OSC. Standardization in 3GPP is workingtoward that direction, and looking for potentialresearch and development areas related to RRMand OSC concept improvements.

REFERENCES[1] Global Mobile Awards 2012, http://www.globalmo-

bileawards.com/awards-2013/winners-2012/, visited on27 Sept. 2012.

[2] A.N. Barreto, L.G.U. Garcia, and E. Souza, “GERAN Evo-lution for Increased Speech Capacity,” IEEE VTC ’07-Spring, Apr. 2007, pp. 1287–91.

[3] GP-070214, Voice Capacity Evolution with OrthogonalSub Channel; 3GPP TSG GERAN#33, Seoul, Korea, Feb.2007.

[4] R. D. Vieira et al., “GSM Evolution Importance in Re-farming 900MHz Band,” IEEE VTC ’10-Fall, Sept. 2010.

[5] H. Holma et al., “High-Speed Packet Access Evolution in3GPP Release 7 [Topics in Radio Communications],”IEEE Commun. Mag., vol. 45, no. 12, Dec. 2007, pp.29–35.

[6] D. Astely et al., “LTE: The Evolution of Mobile Broad-band,” IEEE Commun. Mag., vol. 47, no. 4, April 2009,pp. 44–51.

[7] GP-072027, WID on MUROS; 3GPP TSG GERAN#36,Vancouver, Canada, Nov. 2007.

[8] M. Säily et al., “Orthogonal Subchannel with AMR/SAICChapter,” M. Säily, G. Sebire, and E. P. Riddington,Eds., GSM/EDGE: Evolution and Performance, Wiley,2010.

[9] GP-081309, New WID on Voice Services over AdaptiveMultiuser Orthogonal Subchannels (VAMOS); 3GPP TSGGERAN#39, Florence, Italy, Aug. 2008.

[10] GP-110991, Study on VAMOS Enhancements (ENHVA-MOS); 3GPP TSG GERAN#50, Dallas, TX, May 2011.

Figure 5. Simulation results for SCPC with 50 percent non-SAIC users.

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[11] TR 45.914 V10.1.0, Circuit Switched Voice CapacityEvolution for GSM/EDGE Radio Access Network (GERAN)(Release 10): 3GPP, Nov. 2011.

[12] P. Ojala et al., “The Adaptive Multi-rate WidebandSpeech Codec: System Characteristics, Quality Advances,and Deployment Strategies,” IEEE Commun. Mag., vol.44, no. 5, May 2006, pp. 59–65.

[13] R. C. D. Paiva et al., “Improving the Speech Qualitywith OSC: Double full-rate Performance Assessment,”IEEE VTC ’10-Fall, 2010.

[14] TS 45.008 V10.4.0, Radio Subsystem Link Control(GERAN) (Release 10): 3GPP, Mar. 2011.

BIOGRAPHIESRAFAEL CAUDURO DIAS DE PAIVA ([email protected]) is aresearcher at Nokia Institute of Technology (INdT), Manaus,Brazil, since 2008 and is a doctoral student at the AaltoUniversity School of Electrical Engineering, Espoo, Finland.He obtained his Bachelor’s degree in electrical engineeringfrom UFSM in 2005, and his Master’s degree in signal pro-cessing from UFRJ in 2008. Among his research interests arereal-time models of nonlinear analog audio systems, newtechnologies, and standardization of wireless networks.

ROBSON DOMINGOS VIEIRA received M.Sc. and Ph.D. degreesin electrical engineering from the Catholic University of Riode Janeiro, Brazil, in 2001 and 2005, respectively. During2005 to 2010, he was working with white space concepts,and supporting some GERAN and 802.16m standardizationactivities focused on system performance evaluation atINdT. Since 2010, he is an R&D technical manager at INdT.His research interests include Wi-Fi Evolution, B4G, andcognitive radio networks.

MIKKO SÄILY graduated from Raahe School of Engineeringand Business with a Bachelor’s degree in embedded sys-tems and computer engineering. He joined Nokia in 1994and worked as a senior specialist in the areas of algo-rithms, digital signal processing, and radio performance.He has been involved in 3GPP standards and radio perfor-mance evolution. Currently he works as a research manag-er at Nokia Siemens Networks (NSN). He holds multiplepatents and has published several conference papers.

RENATO FARIA IIDA received his Telecom Engineer and M.Sc.degrees from the University of Brasília (UnB), Brazil, in2002 and 2006, respectively. He is a researcher at INdT,Brazil, since 2008. He worked in GSM/EDGE research andradio resource management using the OSC technology,TCP/IP networking and Location based services. Currentresearch topic is development of drivers and applicationsfor Windows phone 7 and 8.

FERNANDO M. L. TAVARES received his Electrical Engineer andM.Sc. degrees from UnB) in 2005 and 2009, respectively.He worked at INdT as a researcher for four years. He is cur-rently working toward a Ph.D. degree at Aalborg Universi-ty, Denmark, in close cooperation with NSN. His currentresearch interests are mostly related to interference man-agement concepts for beyond 4G networks.

JARI HULKKONEN graduated in 1999 (M.Sc.EE) from Oulu Uni-versity, Finland. Since 1996 he has worked with Nokia andlater with NSN. During 1996–2007 he was working inGSM/EDGE research and standardization projects, and hisstudies focused on radio resource management methodsand system performance evaluation. In 2006 he started tolead a radio research team in Oulu with focus on LTE andbeyond radio research and standardization. He has pub-lished several conference papers on wireless communica-tions and holds multiple patents.

RAULI JÄRVELÄ graduated in 1998 with an M.Sc. in appliedmathematics from Oulu University, Finland. He has beenworking with Nokia and NSN since 1998. He has beeninvolved in various GSM research and standardization pro-jects during his research career as a senior specialist andproject manager. Currently he works as a senior specialistin DSP SW integration.

KARI NIEMELÄ received his B.Sc degree in electrical engineer-ing from Helsinki Polytechnic in 1986. Currently he is aproduct manager in NSN in Oulu, Finland, and has workedwith radio communication since 1988. He holds 29 U.S.patents and has pioneered several enhancements, includ-ing OSC, and contributed in 3GPP. He still aims for furtherenhancements. He co-received a best paper award atICWMC 2010.


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