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    Osc ne twork capacity-network costs Osc ne twork capacity-network costs Document Transcript

    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® TOPICS IN RADIO COMMUNICATIONS GSM Voice Evolution Using Orthogonal Subchannels 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 ABSTRACT magnifies the importance of continuous improve- ment in GSM technology and its standardization The explosive growth of mobile communica- efforts. tions, and the overly crowded and expensive Cellular radio networks are based on the spectrum have pushed both system engineers reuse of frequencies due to the scarcity of radio and operators to make their systems as spectrally spectrum resources. As traffic increases, GSM efficient as possible in order to accommodate operators have to increase their hardware capa- the increasing traffic demand. This article is a bility, hence adopting tighter frequency reuses to tutorial introduction to the orthogonal subchan- accommodate more subscribers and traffic. nel (OSC) technique. OSC was adopted to Additionally, operators need to decrease GSM improve the capacity of the GSM/EDGE radio spectrum to have more bandwidth for the new access network GERAN, and it is a new concept technologies. Both situations bring co-channel in which two users can simultaneously share the interferers closer and cause the networks to same GSM radio resource (time slot and fre- operate in more challenging interference condi- quency) in both the downlink and in uplink tions. Thus, increasing the spectral efficiency of directions. Potentially, OSC could not only pro- speech services becomes a necessity, not only to vide increased network capacity, but also reduce accommodate the growing voice traffic, but also network-associated costs through more efficient to make room for increasing data traffic. usage of hardware and spectrum resources. In GERAN remains under continuous develop- addition, this article presents some challenges ment in the Third Generation Partnership Pro- related to this method, as well as solutions and ject (3GPP). In the recent past, several new their respective impact. The results provided features aimed at increasing system capacity herein may contribute to guidelines for network have been proposed, such as interference rejec- dimensioning and optimization, as well as list tion combining (IRC), single-antenna interfer- potential enhancements to the OSC radio ence cancellation (SAIC), source-adaptive AMR resource management mechanisms needed to (SA-AMR), and 8-phase shift keying (PSK) further exploit the benefits of OSC. Currently, in speech channels. In addition, network vendors real OSC network deployments a capacity gain are continuously developing new radio resource of 50 percent has been achieved at the cell level. management features such as dynamic frequency As an indication of the importance of OSC, and channel allocation (DFCA) [2] and GSMA awarded it (called Quad Rate) the Best enhanced power control algorithms. Technology Breakthrough award at Mobile One of the latest improvements proposed for World Congress 2012 [1]. GSM voice evolution was the orthogonal sub- channel (OSC) transmission technique [3], which INTRODUCTION simultaneously accommodates two users on the same GSM radio resource by using orthogonal Cellular operators are making the most of GSM subchannels. The OSC feature can provide cellular networks with good profit despite the increased network capacity and reduce network newer technologies available, and consequently costs through efficient usage of hardware and GSM covers more than 90 percent of the world’s spectrum resources. population (GSM Association, GSMA). Addi- Applications of this technology can serve the tionally, the average selling prices for GSM increased circuit switch (CS) traffic without the handsets are generally lower than for third/fourth need for installation of new transceivers (TRX), generation (3G/4G) technologies, since GSM or increasing site density by adding new base requires low-cost hardware, and there are possi- transceiver stations (BTSs). In this case, OSC bly less royalties associated with GSM. There- would reduce the interference experienced by fore, there is still significant growth in emerging the network; hence, new traffic would be accom- markets such as China, India, and Eastern modated with better expected quality as well. In Europe. As speech services remain the most a second case, OSC may be applied when the important application for wireless networks and operator wants to share its licensed spectrum fallback from Long Term Evolution (LTE), it between GSM and 3G/4G technology [4]. 80 0163-6804/12/$25.00 © 2012 IEEE IEEE Communications Magazine • December 2012C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® Refarming of spectrum may then be applied OBJECTIVES when LTE or HSPA systems are deployed [5, 6]. The objectives The standardization of GSM voice evolution of ENHVAMOS STANDARDIZATION needs to consider several objectives of system feasibility, performance, and compatibility with enhancements are VAMOS IN 3GPP FROM RELEASE 9 TO 11 legacy voice and data services. The performance to improve the call The GSM Enhanced Data Rates for Global Evo- requirements of VAMOS not only guarantee the lution (EDGE) radio access network (GERAN) link performance, but also provide increased quality of paired in 3GPP has introduced OSC under a working spectral efficiency at the air interface and hard- mobiles and item named Multi-User Reusing One Slot ware capacity improvements of base stations non-paired mobiles, (MUROS) [7]. This first study item was pro- doubling the number of voice channels per posed to analyze several details and features transceiver. In order to allow VAMOS deploy- and utilize network related to enhancements to this technology such ment in most of the GSM/EDGE markets and to synchronization for as adaptive quadrature PSK (AQPSK), higher minimize the impact on existing networks, the order modulations, user diversity, and frequency perceived voice quality should not decrease. The intercell interference hopping schemes [8]. Soon after MUROS, the target is to support existing legacy downlink coordination and Voice over Adaptive Multi-User Channels on advanced receiver performance (DARP) phase 1 mitigation. One Slot (VAMOS) study item [9] was opened. mobile stations by including them in the OSC VAMOS is based on the concept of OSC extend- multiplexing scheme without impacting the ed with AQPSK modulation, where the transmit- mobile station hardware platform. The feasibility ter power can be adjusted between sub-channels, of including the non-DARP mobile stations into and shifted SACCH, to improve performance of the multiplexing is being investigated in 3GPP, the associated signaling channel. The main and, in principle, BTSs need to support new and objective of VAMOS working item was to serve legacy channels serving all kinds of legacy mobile as a way forward to accelerate standardization stations simultaneously. The impact on the process; hence it has streamlined a set of fea- resources dimensioning on the BTS-BSC inter- tures taken from MUROS, and it is focused on face (Abis) should be minimized. The target is the main principles of OSC concept in order to also to ensure that standardization of VAMOS maximize the system benefit with acceptable in 3GPP minimizes the impact on network plan- complexity. ning and frequency reuse. Along with high demand for advanced voice services, a number of enhancements were dis- COMMON WORKING ASSUMPTIONS cussed for standardization in 3GPP Release 10, In order to evaluate the performance of which further boost the spectral efficiency of VAMOS and its related features, GERAN has voice in GSM networks employing tight frequen- defined common simulation guidelines [11]. cy reuses. Examples of these enhancements These guidelines include the simulation scenar- include a optimized transmit pulse shaping filter, ios and all of its related parameters. All the sim- and improvements to the associated control ulation results shown in this article follow these channel signaling for sub-channels. guidelines using a modified MUROS 1 scenario 3GPP Release 11 currently works on a study with variable number of TRX and bandwidth item on VAMOS enhancements (ENHVAMOS) [11]. These simulations help to understand how [10], where the capacity gains are being the voice capacity can be increased by adding improved. The objectives of ENHVAMOS the OSC specific features. enhancements are to improve the call quality of paired mobiles and non-paired mobiles and uti- lize network synchronization for inter-cell inter- OSC CONCEPT DESCRIPTION ference coordination and mitigation. The OSC concept is capable of duplicating the voice capacity in GSM channels, where two users IMPACT TO SPECIFICATIONS can share the same physical radio resource The introduction of VAMOS has influenced sev- simultaneously. For proper separation of the eral 3GPP specifications. The main implications users’ signals, each user should use different are seen in the physical layer of a radio path in training sequences, which should be mutually the 45 series from 45.001 to 45.004, where chan- uncorrelated for optimum OSC performance. nel organization and configurations for traffic The GSM time slot structure for different and associated control channels were defined channel modes is shown in Fig. 1a. In the stan- along with new modulation, symbol rotation, dard GSM channel modes, one TRX can allo- burst format, training sequences, and mapping cate 8 and 16 users in the same frequency when of the associated control channels to the frame using full rate (FR) and half rate (HR) channel structure. The radio transmission and reception modes, respectively. Accordingly, if OSC is with performance requirements have been speci- applied for both FR and HR calls, 16 and 32 fied in 45.005 with new VAMOS test scenarios, users can be allocated to the same frequency modulation accuracy and power versus time with double full rate (DFR) and double half rate mask for AQPSK and radio performance (DHR), repectively. Therefore, multiplexing requirements for mobile stations and base sta- users significantly increase the circuit-switched tions. The specification of the radio subsystem traffic capacity in a network. link control in 45.008 deals with the power back- Figure 1b shows the theoretical maximum off for AQPSK modulation on a broadcast carri- OSC CS capacity for different number of traffic er and the subchannel-specific power control, channel (TCH) TRX. The capacity is calculated and considers the impacts on measurement for 2 percent blocking probability and taking quantities for AQPSK. into account BCCH TRX so that the x-axis 0 IEEE Communications Magazine • December 2012 81C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® Time slot TDMA frame 300 Full rate FR 0 12 3 45 67 HR DHR 250 CS capacity for 2% blocking (erlang) Half rate 200 OSC full rate 150 100 OSC half rate 50 OSC half rate with user diversity 0 0 1 2 3 4 5 6 7 8 Number of TCH TRX User 1 User 2 User 3 User 4 Figure 1. GSM voice evolution using OSC. refers to the BCCH only case. It should be noted OSC transmits using a GMSK modulated signal. that interference estimation is not included in The BTS receives signals from both subchannels this calculation. It can be seen that the capacity and applies interference rejection (e.g., interfer- gain potential is very high. DHR will more than ence rejection combining, successive interference double the network capacity in the HR case. cancellation, or joint detection), together with In the downlink direction, a base station the knowledge of both training sequences to sep- sends for both OSC users a single QPSK modu- arate the signals and decode the symbols per lated signal, which may be a subset of the 8-PSK user. EGPRS constellation as shown in Fig. 2a, where the most significant bit contains the information for the user on sub-channel 0 while the least sig- RADIO RESOURCE MANAGEMENT nificant bit contains the signal for the user on OSC poses some new challenges for radio sub-channel 1 (Fig. 3). Another possible inter- resource management (RRM) algorithms, which pretation of this concept is that the information have to deal with the signal quality of two users for users on subchannels 0 and 1 are contained simultaneously. In the downlink direction, the in the in-phase and quadrature components, power control algorithm is limited, since only respectively. Therefore, a single composite signal one carrier is used to transmit for both users, so carries two information flows using orthogonal the transmitted power is the same for them. channels in the same radio frequency resource. Thus, RRM algorithms should try to multiplex At the MS side, legacy receivers are able to users with similar radio conditions, requiring decode this composite signal as an ordinary approximately the same transmitted power. Oth- GMSK modulated signal. However, due to the erwise, it is likely that the transmitted power will multipath propagation, the orthogonal proper- be unnecessarily higher, creating more interfer- ties among the training sequences are reduced ence in the network. In the uplink direction, the by inter-symbol interference between the two base station will experience different received signals. Multi-user detection techniques can be powers, which may cause some challenges in used for cancelling or suppressing interference reception. As both users transmit at the same among the signals. One example is single-anten- time, if one signal is stronger than the other, the na interference cancellation (SAIC) [2], which BTS may not be able to detect the weaker sig- cancels the dominant interferer by means of sig- nal, causing strong degradation on this user. nal processing. This technique is extremely ade- Intelligent radio resource management should quate in mobile terminals since it is a challenge be performed to prioritize the allocation of users to adopt multiple antennas in low-cost GSM in sufficient radio conditions into OSC channels. devices. Downlink discontinuous transmission (DTX) BASIC RRM ALGORITHMS can also be supported with OSC. When an OSC Radio resource management concentrates some user is in DTX mode in downlink the other user important efforts in GSM since it is responsible can fully occupy the radio channel, and the base for choosing the most suitable channel to new station transmission can use GMSK since there connections. The channel allocation can be con- is no information to be sent to the user in DTX. sidered as a natural solution to reduce interfer- Hence, lower frame erasure rate (FER) and ence. For instance, channel allocation may be higher speech quality is observed to the active based on the interference level of each channel, user. in addition to path loss difference between users In the uplink direction each mobile using to be multiplexed in OSC channels. The path 82 IEEE Communications Magazine • December 2012C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® Q Q Q (n.a.) (1,1) (n.a.) (0,1) (1,1) (0,1) (n.a.) (n.a.) (1,1) (n.a.) (n.a.) (n.a.) (n.a.) (0,1) (1,0) I I I (0,0) (1,0) (n.a.) (1,0) (0,0) (n.a.) (n.a.) (0,0) (n.a.) (sub-ch 0, sub-ch 1) (sub-ch 0, sub-ch 1) (sub-ch 0, sub-ch 1) a) b) c) Figure 2. a) 8PSK constellation symbols used on OSC, and 8-PSK symbols used for subchannel power imbalance with b) subchannel 0 attenuated; c) subchannel 1 attenuated. loss criterion becomes important when users have significant differences in radio conditions, Subchannel 0 since it is likely that the user demanding more power from BTS will create increased interfer- ence in the network. These challenges are typi- cally addressed with improved power control 0 1 schemes and interference diversity techniques. The channel mode adaptation algorithm (CHMA) is another important feature used to maintain minimum voice quality and increased Subchannel 1 network capacity. Although it would be desirable to have as many users in OSC channels as possi- ble in order to take full advantage of hardware 1 improvements, it is important to guarantee that users with poor radio conditions are not multi- plexed into OSC channels. Hence, a simple 0 RRM implementation can be based on the net- work load, quality, and signal level measure- ments, when the network needs to choose the best channel mode to be applied for each con- Figure 3. OSC symbols used on subchannel 0 and subchannel 1. nection. In GSM networks a power control algorithm is usually applied to guarantee minimum signal of voice channels available, and the network level and voice quality, while maximizing the capacity becomes limited by interference. Hence, battery life and minimizing the interference network voice capacity in the DHR case increas- toward other cells. In the downlink direction the es as a function of bandwidth. For example, 29 same transmitting power is used for both OSC percent capacity gain is achieved in the 7 MHz paired users; thus, the power control has to be case and 51 percent gain in the 10 MHz case. controlled by the weaker link. Therefore, the Comparison between DHR with 4 TRX and HR increased power will also impact the other OSC with 6 TRX shows that it is possible to reduce user, even if power increase was not demanded the number of TRXs by two when applying OSC by it. Additionally, power reduction can be done with approximately 9 MHz bandwidth. only when it is applicable to both of the OSC These example simulations show that OSC paired users simultaneously. In the uplink direc- can be used efficiently for reducing hardware tion power control is independent for each OSC requirements in a cellular network, since TRX paired user, but still the received uplink signal reduction can be applied without compromising powers should not be too different for proper the overall network capacity. Thus, OSC may be receiver performance. used as a means for reducing both implementa- OSC system simulation results for 900 MHz tion and operational costs, since fewer TRXs band assuming 100 percent of SAIC receivers would probably also lead to reduction of mainte- are shown in Fig. 4. Network voice traffic capaci- nance and energy costs. ty was determined based on blocked call rate Additional improvements using OSC could (BCR) and bad quality call rate (BQC), where a be obtained by substituting HR channel mode bad quality call was assumed for calls with aver- with DFR. Although DFR does not provide age frame erasure rate below 3 percent. HR and hardware efficiency improvements over legacy DHR cases were evaluated for a 4 TRX configu- HR channel mode, it has a higher raw bit rate, ration, and HR also for a 6 TRX configuration, which enables usage of codecs with either higher to study the impact of the number of TRXs on robustness or improved perceptual speech quali- higher voice capacity and bandwidth. ty. Additionally, wideband AMR (AMR WB) In the 4 TRX case with HR, network capacity codecs [12] were only standardized for FR chan- is limited by hardware, and therefore increased nel modes in GSM, which means that DFR can bandwidth does not increase voice capacity. further benefit from the improved perceptual Once OSC is applied, there is double the amount voice quality offered by those codecs [13]. IEEE Communications Magazine • December 2012 83C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® percent of the users are non-SAIC users. In this 100 scenario there is a high improvement on BQC, 4 TRX HR which has decreased by 50 percent in most cases. 4 TRX DHR 6 TRX HR This result demonstrates that SCPC is a good alternative for enabling non-SAIC receivers in 90 OSC channels. On the other hand, this gain will be worn out when old non-SAIC receivers, cur- rently only 40 percent, disappear. Voice capacity (erlang) 80 INTERFERENCE DIVERSITY SPECIFIC FEATURES User diversity (UD) can be used to improve interference diversity capability for OSC calls. In OSC DHR setup, up to four users may be allo- 70 cated to the same time slot. In Fig. 1a users are grouped in pairs of two so that they do not inter- fere with each other. When UD is enabled in the network, frame structure shall be modified so 60 that the transmission positions of selected users are changed. This modification makes the paired users change pairs from burst to burst. There- fore, the transmission is not always synchronized 50 with other half-rate users, and interference 5 6 7 8 9 10 diversity is achieved. One example is shown in Bandwidth (MHz) the bottom of Fig. 1a where user 1 is paired with user 3 in the first burst and with user 4 in the Figure 4. Simulated system capacity results for BQC < 5 percent, BCR < 2 second burst. Additionally, UD has a major percent in 900 MHz. advantage in a DTX enabled network, where the DTX silent periods are distributed among all users applying UD. Therefore, UD would be a ADVANCED POWER CONTROL feature that is able to increase interference Normal power control in the downlink offers few diversity, and also to spread DTX gains over call control possibilities for OSC calls, since trans- periods for OSC users. This in turn will decrease mitted power is controlled by the user in the FER and improve voice quality. UD may lead to worst radio condition. Hence, some OSC-specif- an improvement of 35 percent in BQC [8]. ic power control features arise by modifying the constellation used for transmitting OSC symbols in downlink shown in Fig. 2a. One possibility is SIGNALING ENHANCEMENTS the application of the AQPSK feature, in which OSC has also posed some new challenges for the transmitted constellation can be linearly signaling. Once a user is using an OSC channel, modified to apply a power imbalance between the decreased interference robustness may also users sharing a channel [14]. affect signaling messages, which could cause the A simplification of the AQPSK technique is call to drop or either degrade measurement mes- achieved with subchannel-specific power control sages, reducing RRM algorithms’ performance. (SCPC), which uses an 8-PSK-like constellation For this reason, special signaling features were as shown in Figs. 2b and 2c, and hence has the developed to protect those messages. clear advantage of requiring simpler hardware. The first proposed feature was the FACCH With this feature, the separation of constellation double stealing. Fast associated control channel symbols for one user is increased, yielding an (FACCH) is a message that may occur at any equivalently higher power, while it is decreased time, and during a normal GSM voice connec- for the other. As an example, SCPC is a way to tion it steals the voice traffic blocks to be trans- equalize channel conditions when users experi- mitted; hence, it naturally causes a small ence different radio conditions or are equipped degradation in voice quality for a user transmit- with different kinds of receiver capabilities. ting it. When OSC is enabled, the interference Additional steps of subchannel power imbalance caused by the user carrying normal traffic may ratio (SCPIR) are obtained by modification, increase the FACCH erasure probability, caus- burst by burst, of the transmitted constellation ing this user to drop or retransmit an FACCH within the interleaving period of a voice frame. block. To minimize interference during FACCH Applications of this technique include enabling blocks, FACCH double-stealing was proposed, mobile stations with non-SAIC receivers to be in which the normal voice radio blocks from the multiplexed with SAIC receivers, where higher paired user are stolen as well; that is, no infor- SCPIR would be delivered to non-SAIC users. mation is sent for a user with normal traffic, When both mobile stations share the same and the user transmitting FACCH holds the receiver capability, it is possible to increase channel alone. This improves FACCH erasure SCPIR for the benefit of the user in weaker rate while causing a small degradation for the radio conditions without increasing the transmit- second user. ted power. Another approach to this problem is FACCH In Fig. 5 it is possible to observe simulation soft stealing, where unequal SCPI is applied to results of SCPC on a scenario with 7 MHz band- decrease FACCH error probability while causing width. This scenario includes one BCCH and smaller degradation on the second OSC user three TCH TRXs, in 900 MHz band, where 50 compared to the double stealing technique. 84 IEEE Communications Magazine • December 2012C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® Thus, this approach leads to a good compromise between signaling performance and voice quali- 40 ty. Techniques for FACCH enhancement have Normal PC SCPC already shown a possible improvement of 20–30 percent in dropped calls while increasing BQC by 6–10 percent [8]. Percentage of calls with FER > 3% Signaling can also be improved in slow associ- 30 ated control channels (SACCHs). SACCH is used to send radio measurements required by RRM algorithms such as handover and power control. The SACCH positions in the normal OSC frame structure are the same for paired 20 users. If one OSC user is in DTX state, the SACCH blocks of its paired user will continue to suffer from interference because SACCH blocks are transmitted regardless of the DTX state. For improving SACCH robustness, shifted SACCHs 10 for OSC were adopted in VAMOS, in which the SACCH position for each paired user is not the same. Hence, while one user is transmitting an SACCH, the other is transmitting a normal TCH 0 burst. The advantage of this feature is that there 30 40 50 60 is a probability of SACCH being transmitted Erlang when an OSC pair is in DTX mode, which pro- vides an SACCH FER improvement. Figure 5. Simulation results for SCPC with 50 percent non-SAIC users. FUTURE ENHANCEMENTS needed to carry GSM voice and data traffic. This OSC significantly increases the hardware capaci- article shows the feasibility of the OSC concept, ty of GSM networks, and when serving more and as well as the potential spectrum and hardware more users the networks tend to become limited savings. On the other hand, more efficient spec- by signal quality. This is caused by the increased trum resource usage would enable more interference coming from users in OSC chan- resources for new evolving technologies in spec- nels. Therefore, it is important to consider future trum refarming to drastically increase the mobile improvements of OSC features to further exploit broadband traffic volumes. The main OSC fea- interference robustness for OSC calls. tures were introduced, and their applicability to One possible improvement for OSC is to different kinds of scenarios and capability was develop new receivers specially designed for demonstrated to improve network performance receiving OSC transmission. These new receivers in typical deployment cases. Further evolution are aware of the constellation structure of Fig. 2 steps are still desirable for taking full advantage and can properly cancel the interference of the of OSC. Standardization in 3GPP is working other subchannel sharing the same radio toward that direction, and looking for potential resource. This improvement may significantly research and development areas related to RRM increase OSC performance, since it would make and OSC concept improvements. receivers more robust to interference. Addition- ally, it would also allow non-SAIC receivers to REFERENCES be multiplexed into OSC channels, when large [1] Global Mobile Awards 2012, http://www.globalmo- _____________ SCPI ratios can be used improve the legacy ________________________ visited on bileawards.com/awards-2013/winners-2012/, receiver performance. 27 Sept. 2012. It is also important to develop network-level [2] A.N. Barreto, L.G.U. Garcia, and E. Souza, “GERAN Evo- interference management features optimized lution for Increased Speech Capacity,” IEEE VTC ’07- Spring, Apr. 2007, pp. 1287–91. especially for OSC when the challenging inter- [3] GP-070214, Voice Capacity Evolution with Orthogonal ference conditions are limiting OSC gains in Sub Channel; 3GPP TSG GERAN#33, Seoul, Korea, Feb. high traffic density networks. One example is the 2007. dynamic frequency and channel allocation [4] R. D. Vieira et al., “GSM Evolution Importance in Re- farming 900MHz Band,” IEEE VTC ’10-Fall, Sept. 2010. (DFCA) [2] feature, which dynamically opti- [5] H. Holma et al., “High-Speed Packet Access Evolution in mizes network performance by adapting to the 3GPP Release 7 [Topics in Radio Communications],” network load and interference conditions, and by IEEE Commun. Mag., vol. 45, no. 12, Dec. 2007, pp. allocation of the best available radio resource in 29–35. [6] D. Astely et al., “LTE: The Evolution of Mobile Broad- time and frequency. band,” IEEE Commun. Mag., vol. 47, no. 4, April 2009, pp. 44–51. [7] GP-072027, WID on MUROS; 3GPP TSG GERAN#36, CONCLUDING REMARKS Vancouver, Canada, Nov. 2007. [8] M. Säily et al., “Orthogonal Subchannel with AMR/SAIC GSM networks, after two decades of operation, Chapter,” M. Säily, G. Sebire, and E. P. Riddington, still have an important role in the telecommuni- Eds., GSM/EDGE: Evolution and Performance, Wiley, cations market even though new wireless tech- 2010. nologies, like 3G and LTE/4G, are emerging; [9] GP-081309, New WID on Voice Services over Adaptive Multiuser Orthogonal Subchannels (VAMOS); 3GPP TSG therefore, further enhancements are still neces- GERAN#39, Florence, Italy, Aug. 2008. sary. In this context, OSC has proven to be an [10] GP-110991, Study on VAMOS Enhancements (ENHVA- important feature to optimize the resources MOS); 3GPP TSG GERAN#50, Dallas, TX, May 2011. IEEE Communications Magazine • December 2012 85C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®
    • C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND® [11] TR 45.914 V10.1.0, Circuit Switched Voice Capacity RENATO FARIA IIDA received his Telecom Engineer and M.Sc. Evolution for GSM/EDGE Radio Access Network (GERAN) degrees from the University of Brasília (UnB), Brazil, in (Release 10): 3GPP, Nov. 2011. 2002 and 2006, respectively. He is a researcher at INdT, [12] P. Ojala et al., “The Adaptive Multi-rate Wideband Brazil, since 2008. He worked in GSM/EDGE research and Speech Codec: System Characteristics, Quality Advances, radio resource management using the OSC technology, and Deployment Strategies,” IEEE Commun. Mag., vol. TCP/IP networking and Location based services. Current 44, no. 5, May 2006, pp. 59–65. research topic is development of drivers and applications [13] R. C. D. Paiva et al., “Improving the Speech Quality for Windows phone 7 and 8. with OSC: Double full-rate Performance Assessment,” IEEE VTC ’10-Fall, 2010. FERNANDO M. L. TAVARES received his Electrical Engineer and [14] TS 45.008 V10.4.0, Radio Subsystem Link Control M.Sc. degrees from UnB) in 2005 and 2009, respectively. (GERAN) (Release 10): 3GPP, Mar. 2011. 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 current BIOGRAPHIES research interests are mostly related to interference man- RAFAEL CAUDURO DIAS DE PAIVA (rafael.paiva@indt.org.br) is a _____________ agement concepts for beyond 4G networks. researcher at Nokia Institute of Technology (INdT), Manaus, Brazil, since 2008 and is a doctoral student at the Aalto JARI HULKKONEN graduated in 1999 (M.Sc.EE) from Oulu Uni- University School of Electrical Engineering, Espoo, Finland. versity, Finland. Since 1996 he has worked with Nokia and He obtained his Bachelor’s degree in electrical engineering later with NSN. During 1996–2007 he was working in from UFSM in 2005, and his Master’s degree in signal pro- GSM/EDGE research and standardization projects, and his cessing from UFRJ in 2008. Among his research interests are studies focused on radio resource management methods real-time models of nonlinear analog audio systems, new and system performance evaluation. In 2006 he started to technologies, and standardization of wireless networks. lead a radio research team in Oulu with focus on LTE and beyond radio research and standardization. He has pub- ROBSON DOMINGOS VIEIRA received M.Sc. and Ph.D. degrees lished several conference papers on wireless communica- in electrical engineering from the Catholic University of Rio tions and holds multiple patents. de Janeiro, Brazil, in 2001 and 2005, respectively. During 2005 to 2010, he was working with white space concepts, RAULI JÄRVELÄ graduated in 1998 with an M.Sc. in applied and supporting some GERAN and 802.16m standardization mathematics from Oulu University, Finland. He has been activities focused on system performance evaluation at working with Nokia and NSN since 1998. He has been INdT. Since 2010, he is an R&D technical manager at INdT. involved in various GSM research and standardization pro- His research interests include Wi-Fi Evolution, B4G, and jects during his research career as a senior specialist and cognitive radio networks. project manager. Currently he works as a senior specialist in DSP SW integration. MIKKO SÄILY graduated from Raahe School of Engineering and Business with a Bachelor’s degree in embedded sys- KARI NIEMELÄ received his B.Sc degree in electrical engineer- tems and computer engineering. He joined Nokia in 1994 ing from Helsinki Polytechnic in 1986. Currently he is a and worked as a senior specialist in the areas of algo- product manager in NSN in Oulu, Finland, and has worked rithms, digital signal processing, and radio performance. with radio communication since 1988. He holds 29 U.S. He has been involved in 3GPP standards and radio perfor- patents and has pioneered several enhancements, includ- mance evolution. Currently he works as a research manag- ing OSC, and contributed in 3GPP. He still aims for further er at Nokia Siemens Networks (NSN). He holds multiple enhancements. He co-received a best paper award at patents and has published several conference papers. ICWMC 2010. 86 IEEE Communications Magazine • December 2012C qM IEEE M ommunications q qM Previous Page | Contents | Zoom in | Zoom out | Front Cover | Search Issue | Next Page MqM q Qmags THE WORLD’S NEWSSTAND®