Hspa and wimax


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Hspa and wimax

  1. 1. white paper 284 23-3128 Uen Rev B | January 2009 Technical overview and performance of HSPA and Mobile WiMAX How the performance of HSPA and Mobile WiMAX compare, in theory and in practice.
  2. 2. Contents 1 Introduction 3 1.1 HSPA 4 1.2 Mobile WiMAX 5 2 Technical comparison 7 2.1 Similarities 7 2.2 Differences 11 2.3 Summary technical comparison 14 3 Performance characteristics 15 3.1 Peak data rates 15 3.2 Spectrum efficiency 16 3.3 Coverage 17 3.4 Real-life experience 19 4 Network architecture 21 4.1 WiMAX Forum and IEEE 22 4.2 Architecture comparison 23 4.3 System architecture evolution 24 4.4 Mobile WiMAX 24 5 Conclusion 25 6 Glossary 26 7 References 272 Technical overview and performance of HSPA and Mobile WiMAX Contents
  3. 3. 1 IntroductionIn a few short years, the internet has had a advanced antenna systems that rely ondramatic impact on our private and multiple antennas at both the transmitterprofessional lives. And it continues to grow in and receiver, effectively multiplying theimportance in our daily lives: To fully enjoy the peak ratebenefits of the internet, users need a ✒ for improved QoS and low latencybroadband connection. And in coming years, • dynamic scheduling, with end-usermillions of people will turn to wireless traffic streams prioritized according totechnology to deliver this experience. service agreements A host of technologies are competing to • short transmission time intervals (TTI),deliver commercial mobile broadband allowing for round-trip times approachingservices. By far the most successful of these wired equivalents (such as DSL)is HSPA, which has been commercially ✒ for higher capacitydeployed by more than 100 operators in more • shared-channel transmission to makethan 50 countries, with an additional 50 efficient use of available time/frequency/operators (and counting) committed to rolling codes and power resourcesout commercial services.1 HSPA is a state-of- • link adaptation to dynamically optimizethe art technology that can provide mobile transmission parameters, depending onand wireless broadband services with actual radio conditionsunsurpassed performance and economies of • channel-dependent scheduling to assignscale to the vast majority of the market. By radio resources to users with the most2010 we expect there to be more than 600 favorable radio conditionsmillion mobile broadband subscribers, rising • hybrid automatic repeat request (H-ARQ)to 900 million by 2012 and the vast majority, to enable rapid retransmission of missing70 percent, will be served by HSPA networks data, and soft combining to significantlyand 20 percent by CDMA EV-DO. improve performance and robustness A good mobile broadband system must ✒ for greater coveragefulfill certain criteria, including high data rate, • advanced antenna systems andhigh capacity, low cost per bit, low latency, advanced receivers to enhance the radiogood quality of service (QoS), and good link and improve cell range.coverage. Several techniques can be Both HSPA and Mobile WiMAX employused to meet these criteria in a wireless most of these techniques, and theirsystem, including: performance is broadly similar. However, they✒ for higher data rates (and capacity) differ in areas such as the duplex scheme • higher-order modulation schemes, such (FDD versus TDD), frequency bands, multiple as 16 quadrature amplitude modulation access technology, and control channel (16QAM) and 64QAM design, giving rise to differences mainly in • multiple-input, multiple-output (MIMO) uplink data rates and coverage.1 Source: Global mobile Suppliers Association (GSA), April 2007 Technical overview and performance of HSPA and Mobile WiMAX Introduction 3
  4. 4. 1.1 HSPA The 3rd Generation Partnership Project considerable increase in capacity, which (3GPP) is a collaboration that brings together translated into reduced production cost per a number of telecommunications standards bit. It also significantly reduced latency and bodies. The 3GPP was jointly formed by provided downlink data rates of up to telecommuncation associations from the US, 14Mbps. These enhancements, which Europe, Japan, South Korea and China. At commonly go under the denomination present, it has more than 400 member HSDPA (High Speed Downlink Packet companies and institutions. The 3GPP Access), were a first step in the evolution defines GSM and WCDMA specifications for of WCDMA. a complete mobile system, including terminal Although a great deal of traffic is downlink- aspects, radio access networks, core oriented, several applications also benefit networks, and parts of the service network. from an improved uplink. Examples include Standardization bodies in each world region the sending of large e-mail attachments, have a mandate to take the output from pictures, video clips and blogs. The key the 3GPP and publish it in their region as enhancement in WCDMA 3GPP Release 6 formal standards. was a new transport channel in the uplink, 3GPP specifications are structured in enhanced uplink (EUL) – also sometimes releases. Ordinarily, discussions of 3GPP referred to as HSUPA (High Speed Uplink technologies refer to the functionality in one Packet Access) – which improved throughput, release or another. It is worth noting that all reduced latency and increased capacity. EUL new releases are backward-compatible with provides data rates of up to 5.8Mbps. previous releases. The combination of HSDPA and EUL is The development of the 3GPP technology called as HSPA (High Speed Packet Access). track (GSM/WCDMA/HSPA) has been 3GPP Release 7 introduced HSPA spectacular. Within a ten-year span, for evolution (also called HSPA+), which supports example, there has been a 1000-fold increase MIMO, 64QAM in the downlink, and 16QAM in supported data rates. What is more, the in the uplink, to further boost the peak data 3GPP technologies continue to evolve. rate and capacity. HSPA evolution supports WCDMA 3GPP Release 99 provided data data rates of up to 42Mbps in the downlink rates of 384kbps for wide-area coverage. and 11.5Mbps in the uplink. However, greater speed (data rates) and LTE (Long Term Evolution), currently being capacity were soon required (at lower specified by 3GPP for Release 8 (scheduled production cost) as the use of packet for completion by the end of 2007), data services increased and new services introduces OFDM/OFDMA in the downlink were introduced. and single-carrier FDMA (SC-FDMA) in the Among other things, WCDMA 3GPP uplink. LTE supports very high data rates, Release 5 extended the specification with a exceeding 300Mbps in the downlink and new downlink transport channel, the high- 80Mbps in the uplink. LTE will support speed downlink shared channel, which operation in both paired and unpaired enhanced support for high-performance spectrum (FDD and TDD) using channel packet-data applications. Compared with bandwidths of approximately 1.25MHz up to Release 99, the enhanced downlink gave a at least 20MHz.4 Technical overview and performance of HSPA and Mobile WiMAX Introduction
  5. 5. Table 1: Progressive enhancements to 3GPP specifications Version Released Info Release 99 2000 Q1 Specified the first UMTS 3G networks, incorporating a WCDMA air interface Release 4 2001 Q2 Added features, including an all-IP core network Release 5 2002 Q1 Added IMS and HSPA Release 6 2007 Q4 Integrated operation with Wireless LAN networks, added enhanced uplink, MBMS and enhancements to IMS such as Push to Talk over Cellular (PoC) Release 7 2007 Q2 Added downlink MIMO, reduced latency, improved QoS and improvements to real-time applications like VoIP Release 8 In progress Includes E-UTRA (LTE) and the Evolved Packet Core (SAE) architecture and further enhancements of HSPA1.2 Mobile WiMAXThe IEEE 802.16 Working Group on The WiMAX Forum thus defines andbroadband wireless access standards, which conducts conformance and interoperabilitywas established by the IEEE Standards Board testing to ensure that different vendorin 1999, prepared the formal specifications systems work seamlessly with each other.for broadband wireless metropolitan area WiMAX certification profiles specifynetworks (WirelessMAN, the 802.16 family of characteristics including spectrum band,standards is the basis of Mobile WiMAX). duplexing and channelization. Several profiles IEEE 802.16-2004 (also called simply exist for fixed and Mobile WiMAX.802.16d) provides support for non-line of There are currently two waves ofsight (NLOS) and indoor end-user terminals certification planned for Mobilefor fixed wireless broadband. In 2005, WiMAX equipment:the standard was amended (IEEE 802. ✒ Wave 1: Mobile WiMAX system profile with16e-2005 or 802.16e) adding support single-input single-output (SISO) terminalsfor data mobility. for the 2.3GHz and 3.5GHz bands IEEE 802.16e, or Mobile WiMAX, improves ✒ Wave 2: Mobile WiMAX system profile withon the modulation schemes used in the multiple-input, multiple-output (MIMO)original (fixed) WiMAX standard by terminals and beamforming support for theintroducing SOFDMA (scalable orthogonal 2.6GHz band (sometimes referred to asfrequency division multiple access). the 2.5GHz band). The system profile in IEEE 802.16e-2005 is Because IEEE 802.16 standardization onlynot backward compatible with the fixed covers basic connectivity up to the mediaWiMAX system profile. access (MAC) level, the WiMAX Forum also The charter of the WiMAX Forum, which addresses network architecture issues forhas more than 400 members, is to promote Mobile WiMAX networks. The focus of theand certify the compatibility and first network architecture specificationinteroperability of broadband wireless access (Release 1.0) is on delivering a wirelessequipment that conforms to IEEE 802.16 and internet service with mobility.the ETSI HiperMAN standard. Release 1.5 will add support for telecom- Technical overview and performance of HSPA and Mobile WiMAX Introduction 5
  6. 6. grade mobile services, supporting full IMS offers the promise of high-speed wireless interworking, carrier-grade VoIP, broadcast broadband services, it is still very much in its applications, such as mobile TV, and over- infancy and real-life performance has yet to the-air provisioning. While Mobile WiMAX be proved. Table 2: Evolution of WirelessMAN (802.16 family of standards) Version Released Info IEEE 802.16d 2004 Q2 Replaced all previous 802.16 specifications. IEEE 802.16-2004 Support for non-line of sight operation IEEE 802.16e 2005 Q4 Enhanced 802.16-2004 with support for data mobility IEEE 802.16e-2005 WiMAX Forum Network 2007 Q1 Networking specifications for fixed, nomadic, portable Architecture Specification and mobile WiMAX systems. Release 1.0 covers Release 1.0 internet applications and data mobility WiMAX Forum Network In progress Enhancements to the Release 1.0 specification for Architecture Specification carrier-grade VoIP, location-based services, MBMS, Release 1.5 full IMS interworking and over-the-air client provisioning6 Technical overview and performance of HSPA and Mobile WiMAX Introduction
  7. 7. 2 Technical comparisonThe HSPA and Mobile WiMAX technologies mechanism, and operating frequency bands.have been designed for high-speed packet- This chapter provides a high-level descriptiondata services. They feature similar technology of the similarities and differences betweenenablers, including dynamic scheduling, link HSPA and Mobile WiMAX. Technical detailsadaptation, H-ARQ with soft combining, of HSPA can be found in the 3GPPmultiple-level QoS, and advanced antenna specifications. Likewise, details of Mobilesystems. Notwithstanding, their performance WiMAX can be found in the IEEE 802.16e-differs due to differences in the physical layer 2005 standard and the WiMAX Forum Mobilesignal format, duplex scheme, handover System Profile.2.1 Similarities2.1.1 Dynamic schedulingTraditional circuit-switched telephone systems When a mobile device is scheduled forset up connections as dedicated links during transmission, the quality of its radio link willthe entire session. This approach wastes vary in time. The modulation scheme andcommunication resources for packet data channel-coding rate used for a scheduled linkbecause the dedicated link is tied up even can be adapted to minimize errors under aduring idle periods. For high-speed packet- variety of radio conditions. Link adaptationdata systems with bursty traffic, it makes (Figure 2) enables full utilization of channelbetter sense to allocate radio resources only capacity for each communication link in theduring active periods. wireless environment and so maximizes the Given the volatile nature of wireless throughput of scheduling-based systems.channels, radio links often experience HSPA and Mobile WiMAX support dynamicfluctuations in signal strength. It is thus more selection between QPSK, 16QAM and 64QAMeffective to schedule the base station and modulation schemes, as well as of the channel-terminal to communicate only when radio coding rate, where the lowest coding rateconditions are good. HSPA and Mobile without repetition is 1/2 for Mobile WiMAX andWiMAX systems use channel-dependent 1/3 (additional coding gain) for HSPA. Overall,scheduling (Figure 1) for efficient and effective HSPA has finer granularity of modulation anduse of resources for packet data. coding formats than Mobile WiMAX.Figure 1. Channel-dependent scheduling Scheduling: determines which end user to transmit to, at a given moment Channel-dependent Scheduling: transmit at fading peaks Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison 7
  8. 8. 2.1.2 Link adaptation Adjust transmission parameters and match instantaneous channel conditions Figure 2. Link adaptation 2.1.3 H-ARQ with soft combining Because of delays in channel quality On the uplink, H-ARQ with soft combining feedback, link adaptation may suffer from also reduces transmission power and errors incurred between time instances of improves system capacity, thanks to lower reporting and scheduling. H-ARQ with soft interference and more stable power control. combining on the downlink and uplink quickly In HSPA, incremental redundancy is used for corrects these error packets without having to extra coding gain of the lower coding rate rely on higher-layer ARQ. that goes along with the retransmission. In H-ARQ with soft combining is an effective Mobile WiMAX, only Chase combining is remedy to link adaptation errors and reduces available for energy gain; the coding rate is retransmission delays that are vital for higher- not adjusted after retransmission. layer throughput. Figure 3. Hybrid acknowledgement request (H-ARQ) with soft combining8 Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison
  9. 9. 2.1.4 Multi-level quality of serviceHSPA and Mobile WiMAX support multiple mechanisms defined for different QoS levelsQoS levels. In HSPA, QoS levels are divided in the uplink: unsolicited grant service (UGS),into four categories: conversational, extended real-time polling service (ertPS),streaming, interactive, and background. real-time polling service (rtPS), non-real-time In Mobile WiMAX, there are five scheduling polling service (nrtPS), and best-effort.2.1.5 Advanced antenna technologiesAdvanced multiple antenna technologies downlink channel conditions. Therefore,improve the performance and capability of in addition to diversity, WCDMA closed-modern mobile communication systems. In loop transmit diversity allows forgeneral, they rely on the use of multiple beamforming gains.transmit and/or receiver antennas to achieve: WCDMA open-loop and closed-loop✒ diversity against fading on the transmit diversity are also available for HSPA. radio channel In addition, 2x2 spatial multiplexing (in HSPA✒ beamforming, to improve the radio link Release 7) effectively doubles downlink peak signal-to-noise/interference ratio data rates.✒ spatial multiplexing, often referred to as The Mobile WiMAX system profile MIMO (multiple-input, multiple-output) specifies two types of multi-antenna antenna processing, to increase the transmission schemes: peak data rates and utilize high radio- ✒ transmit diversity using the Alamouti link signal-to-noise/interference ratios space-time code (STC), which is more efficiently. similar to WCDMA/HSPA open-loopWCDMA supports two multi-antenna transmit diversitytransmission schemes: open-loop transmit ✒ spatial multiplexing (MIMO).diversity, and closed-loop transmit diversity. Mobile WiMAX also supports beamforming,WCDMA open-loop transmit diversity uses which is enabled by uplink sounding. Bymodified Alamouti coding and can be applied taking advantage of TDD channel reciprocity,to dedicated as well as common channels. the spatial characteristics measured at theOpen-loop transmit diversity provides base station can be used to form downlinkdiversity against radio-channel fading. beams. In practice, however, performance isWCDMA closed-loop transmit diversity limited by the asymmetry of interference andallows for adjustment of transmission phase different antenna settings at the terminal andand amplitude, based on instantaneous base station. Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison 9
  10. 10. Figure 4. Overview of different antenna transmission schemes10 Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison
  11. 11. 2.2 Differences2.2.1 Physical signal formatThe main differences between Mobile WiMAX accesses, Mobile WiMAX base stationsand HSPA in the physical layer lie in the signal must fine tune the frequency errors offormat. Mobile WiMAX is based on each terminal within tolerable ranges, andorthogonal frequency domain multiplexing minimize the total interference level by(OFDM), whereas HSPA is a direct-sequence means of power control.spread-spectrum system. One of the most OFDM signals also have a relatively largeimportant features of OFDM is its robustness peak-to-average power ratio (PAPR), whichto multi-path propagation. The key enabler of means that for a given average power, thethis feature is the use of narrowband tones in power amplifier must be able to handlecombination with a cyclic prefix. The cyclic significantly higher power peaks, whileprefix serves two purposes: It provides a avoiding distortion of the transmitted signal.guard time against inter-symbol interference, HSPA uses CDM code (orthogonal Walshand it ensures that the multipath channel only code) aggregation to offer a high-speedimposes a scalar distortion on each tone, downlink channel, and direct-sequence codemaking equalization simple and effective. division multiple access (CDMA) for theWhen properly synchronized and protected uplink. While this method is less sensitive toby cyclic prefix, tones of an OFDM signal Doppler spread, the loss of orthogonality inremain mutually orthogonal even after going time-dispersive channels creates intra-cellthrough multipath channels. The interference that limits the use of highorderdisadvantage of using cyclic prefix is modulation. Generalized RAKE receiversincreased overhead, which effectively can alleviate interference through advancedreduces bandwidth efficiency. signal processing on the receiver side The ability of an OFDM signal to maintain at the moderate cost of additionalorthogonality under multipath conditions receiver complexity.gives an intra-cell interference-free system When compared with OFDM signals,that is well suited to high-speed data the HSPA uplink signals have lower PAPR –transmission. However, inter-tone interference which implies a less complex power amplifier.arises (degrading performance) when there Alternatively, for a given complexity, aare large Doppler spreads in OFDM. When higher average power can be used, givingOFDM signals are used for uplink multiple greater coverage.2.2.2 Duplex schemeOne other difference between HSPA and separate frequency channels (usually denotedMobile WiMAX is the duplex scheme. HSPA as 2x5MHz to indicate two separate 5MHzis an FDD technology, with uplink and channels, one for the uplink and one fordownlink transmission taking place in the downlink). Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison 11
  12. 12. The Mobile WiMAX system profile, as between FDD and TDD systems (Figure 6). currently defined in the WiMAX Forum, is a FDD systems use a frequency duplex gap TDD technology with just one frequency between the uplink and the downlink to channel (10MHz for example) that is shared in prevent interference between transmissions. the time domain between the uplink and TDD systems use a guard time between the downlink. The ratio between the uplink and uplink and downlink. downlink defines how the frequency channel When building a TDD network, one must is shared. A 2:1 ratio means the channel deal with a variety of interference scenarios: is used two-thirds of the time for the ✒ Interference within a network – interference downlink and one-third of the time for the between base stations and between uplink (Figure 5). terminals. All the base stations must be The IEEE 802.16 specification allows for FDD fully time-synchronized with each other (for operation, but to date, the Mobile WiMAX example, using a GPS receiver at each system profile solely stipulates TDD. TDD has base station). the flexibility of changing the downlink-to- ✒ Between a network and an adjacent TDD uplink ratio to accommodate a variety of network – two or more TDD networks traffic asymmetries, although in practice the using the same frequency band in the ratio needs to be fixed system-wide (unless same geographical area. To avoid guard bands are used to limit interference interference, synchronization must be effects). In addition, TDD systems with a large coordinated between neighboring downlink-to-uplink ratio, will have a link networks, or guard bands must be used. budget penalty as the uplink average power This scenario might occur at national or is reduced for a given peak power. state borders, especially where only local The interference scenarios are different licenses have been issued. Figure 5. Overview of FDD and TDD12 Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison
  13. 13. ✒ Between a network and a spectrum- TDD network in relation to adjacent adjacent TDD network – one TDD network networks – in addition to synchronization uses adjacent frequencies, giving rise to in time, when setting the uplink/downlink base station-to-base station interference if ratio in a TDD network, the ratio within the the base stations from the different network and with neighboring networks networks are in close proximity. The uplink must be coordinated, to avoid all the to one base station can suffer interference interference cases mentioned above. from the out-of-band leakage (ACLR) from Alternatively, guard bands can be used. another base station. This interference can Stringent requirements from existing satellite be reduced by synchronizing the services in specific bands make it difficult to networks, or by using guard bands. deploy TDD technologies in these✒ FDD and TDD spectrum borders – an FDD frequencies. The tougher coexistence network uses frequencies adjacent to the environment for TDD puts heavy TDD network, giving rise to base station- requirements on the RF filters, which are just to-base station interference if the base as complex as the duplex filter requirements stations from the different networks are in for FDD. close proximity. This interference can only The 3GPP specification covers FDD and be resolved using suitable guard bands. TDD, but there have not been any major✒ Duty cycle uplink/downlink settings in the deployments of TDD-based cellular systems.Figure 6. Overview of interference scenarios for FDD and TDD systems2.2.3 Handover mechanismHSPA supports soft handover in the uplink, Hard handover is used for intrafrequencywhich yields macro combining gain and handover and inter-system handover to GSM.improves the link budget (by 1.5dB on The Mobile WiMAX system profile includesaverage). It also helps increase network only hard handover.capacity by reducing intra-cell interference. Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison 13
  14. 14. 2.2.4 Operating frequency bands HSPA currently supports frequency bands discussion for Mobile WiMAX, but current ranging from 800MHz to 2600MHz, including Mobile WiMAX certification profiles only cover most current 2G operating bands in Europe, the 2.3GHz, 2.6GHz and 3.3–3.8GHz Africa, the Americas and Asia-Pacific. The frequency bands. At present, there are only a most common bands for HSPA are 2.1GHz, few deployments of Mobile WiMAX, mainly in deployed worldwide, and the 850MHz band the 2.3GHz band. deployed in the Americas, Australia, New Approximately 90 percent of all spectrum Zealand, and parts of Asia. allocations worldwide are FDD. Several frequency bands are under 2.3 Summary technical comparison Table 3 summarizes the technical similarities and differences between HSPA and Mobile WiMAX. Table 3.Technical comparison of HSPA and Mobile WiMAX HSPA Mobile WiMAX Physical signal format DL code aggregation, OFDMA for both DL and UL UL DS-CDMA Hybrid ARQ with soft Adaptive IR + Chase Chase combining combining combining Multi-level QoS √ √ Link adaptation QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM Lowest code rate: 1/3 Lowest code rate: 1/2 Duplex scheme FDD TDD Frequency bands 850MHz to 2,600MHz 2.3GHz, 2.6GHz and 3.4–3.8GHz Handover Hard handover, Hard handover Soft handover Frequency reuse one √ √ Advance antenna • Closed- and open-loop • Open-loop transmit diversity technologies transmit diversity • Spatial multiplexing • Spatial multiplexing • Beam forming • Beam forming14 Technical overview and performance of HSPA and Mobile WiMAX Technical Comparison
  15. 15. 3 Performance characteristicsVital characteristics of system performance which might give a misleading picture – theare data rates, delay, spectrum efficiency and discussion covers a set of HSPA and Mobilecoverage. For end users, these WiMAX releases, to enable a fair comparison.characteristics determine which services can Because many features are common to bothbe offered. For operators, they define number system families, including antenna (MIMO)of users and base station coverage area, concepts, modulation and channel coding,which directly influences the cost of operating the performance is similar in many respects.the system. There are some differences, however, such as This chapter presents the performance the duplex scheme, frequency bands,characteristics of HSPA and Mobile WiMAX in multiple access technology and controlterms of peak data rates, spectrum efficiency channel design, which give rise toand coverage. Rather than cover just one differences, for example, in uplink bit ratesversion (or release) of each system family – and coverage.3.1 Peak data ratesThe peak data rate indicates the bit rate a data rates, measured above the MAC layer,user in good radio conditions can reach when for a set of system concepts. Early releasesthe channel is not shared with other users. of HSPA (Release 6) and Mobile WiMAXFigure 7 shows the downlink and uplink peak Wave 1 achieve comparable peak rates.Figure 7. Peak data rates for a set of HSPA releases and WiMAX waves. For WiMAX, the TDD symmetry is expressed interms of number of downlink and uplink slots for data (that is, 28:15). The use of multi-stream MIMO is indicated by a factorin front of the modulation scheme. The HSPA Release 8 results are based on preliminary features. Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics 15
  16. 16. Mobile WiMAX uses higher-level modulation case, the same modulation formats (64QAM (64QAM in the downlink and 16QAM in uplink) and 16QAM) and comparable MIMO than HSPA, which uses 16QAM in the schemes (two streams in the downlink) are downlink and QPSK in the uplink. HSPA used, but HSPA has less overhead. Further Release 7 introduces 64QAM and two-stream enhancements for HSPA Release 8 are MIMO in the downlink (but not for under evaluation. simultaneous use) and offers comparable Mobile WiMAX may use TDD asymmetries performance to Mobile WiMAX Wave 2. to increase downlink peak data rates at the The peak data rate of HSPA Release 8 expense of reduced uplink peak data rates. betters that of Mobile WiMAX Wave 2. In this 3.2 Spectrum efficiency Spectrum efficiency measures the maximum traffic load per user, spectral efficiency can total amount of data that can be carried by a be used to determine the number of users a cell per unit of time, normalized with the cell can support. occupied system bandwidth. For any given Figure 8. Spectrum efficiency comparisons (Note that absolute spectrum efficiency values vary with models and assumptions. The above values should be used for relative comparisons. The HSPA Release 8 results are based on preliminary features.)16 Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics
  17. 17. The spectrum efficiency figures have been receivers, such as GRAKE with receiveevaluated using models, assumptions and diversity, give substantially higher spectrummethodology aligned with 3GPP standards efficiency. A comparison of HSPA Release[1] (in this case, a system with 19 three-sector 6 with advanced receivers (which issites, placed on a regular grid with 500m available earlier than Mobile WiMAXinter-site distance). “Full buffer” type users Wave 1 devices) shows that HSPA hasare uniformly distributed. The selected greater spectrum efficiency.propagation models (which model spatial HSPA Release 7 is modeled with two-correlation between antennas to enable stream MIMO in the downlink and 16QAM inaccurate MIMO evaluations) simulate an the uplink. Mobile WiMAX Wave 2urban environment. performance (which has approximately the System models, such as antenna solutions same availability as HSPA Release 7) isand output powers, have been aligned with comparable to HSPA Release 7.the capabilities of the studied systems. HSPA Release 8 is modeled withSimilar assumptions have been made for all preliminary features and shows bettersystems, with the aim of achieving fair spectrum efficiency than Mobile WiMAXcomparisons. The figures should be used Wave 2. These results are similar to thosefor comparative purposes and not as presented by 3G Americas. [2] The figures forabsolute values. Mobile WiMAX are somewhat lower than The spectrum efficiency achieved by HSPA those presented by WiMAX Forum [4],Release 6 is dependent on receiver type. probably because of differences in modeling.Mobile WiMAX Wave 1 has better spectrum The WiMAX Forum does not present resultsefficiency than HSPA Release 6 with basic for HSPA Release 7 or 8. Its HSPA Release 6RAKE receivers (indicated by the dotted line results are similar to those presented here,in Figure 8). However, more advanced assuming simple receivers.3.3 CoverageCoverage is a crucial metric of performance, specific case. Relative comparisons of linkbecause it determines the number of sites budgets for different system concepts areneeded to deploy a complete network, and easy to make and informative. HSPA andthe data rate available at a given distance in a Mobile WiMAX have distinctivegiven deployment. A common way of characteristics that affect the link budget,measuring coverage is to use link budgets, including output power, duplex method andwhich provide an estimate of the maximum frequency band – especially on the uplink,path loss the system can sustain between the which is typically the limiting link. Figure 9base station and terminal. summarizes the impact of these Accurate absolute link budgets depend on characteristics.several factors and are best simulated for a Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics 17
  18. 18. Figure 9. HSPA typically has 6-10dB greater coverage than Mobile WiMAX. Using typical terminal power classes, the operating at about 2.0GHz, the path loss maximum output power of Mobile WiMAX increases by a factor of (2.6/2.0)2 = 1.7, terminals (23dBm) is 1dB lower for than for or 2.3dB. At 3.5GHz the corresponding HSPA (24dBm), which is a difference of 1dB figure is 4.9dB. in the link budget. One reason for this Apart from these differences, soft handover difference is the difference in uplink in HSPA improves coverage, and lower modulation and multiple access methods. overhead improves sensitivity. With TDD, if the link is only used half the In summary, although Mobile WiMAX and time for a given average data rate, the data HSPA are based on similar techniques, the rate when transmitting must be twice as high. link budget of Mobile WiMAX can be up to If the link is used one-quarter of the time, the 6dB worse than that of HSPA. In a coverage- data rate when transmitting must be four limited network, this would translate into the times higher. Radio links to terminals at the need for 2.2 times as many sites. This figure cell border are typically power-limited, so that is derived on the basis of d3.5 propagation the bit rate achieved is proportional to the (which is typical in urban and suburban transmitted power but insensitive to channel areas). In this case, a path loss increase of bandwidth. To compensate for this loss, the 6dB, or a factor of four, corresponds to a terminal must thus have a factor 2 (3dB) or 4 distance coverage loss of a factor of 41/3.5 = (6dB) better path loss for activity factors of 50 1.5, or an area coverage loss of a factor 1.52 percent and 25 percent, respectively. = 2.2. In rural areas with lower path loss Deploying Mobile WiMAX in higher exponents, the differences are larger. frequency bands than are typically used for For a coverage-driven deployment, Mobile HSPA will lead to an additional loss in link WiMAX at 2.6GHz would need approximately budget. Path loss is proportional to the 2.3 to 3.4 times more sites than HSPA at square of the frequency. With Mobile WiMAX 2.1GHz. Even compared with HSPA at 2.6 operating in the 2.6GHz band and HSPA GHz, Mobile WiMAX increases the site count operating in the 2.1GHz band, and the uplink by approximately 1.7 to 2.5 times.18 Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics
  19. 19. 3.4 Real-life experienceHSDPA has been commercially available 7.2Mbps. Tests using these terminals onsince 2005, and has been rolled out for commercial systems have proved thecommercial operation in networks around the simulated results (Figure 11).world. Initially, user terminals were limited to HSPA is a mature technology that offersfive codes and 16-QAM modulation, giving a mobile broadband services to rival thetheoretical maximum data rate of 3.6Mbps. performance of fixed broadband networksFeedback from live networks shows that the (such as ADSL and cable). Load calculationsactual rates are close to the theoretical in an HSPA network show that operators cansimulations (Figure 10). User terminals are deliver a commercially viable flat rate mobilenow available that support ten codes and broadband service, with a 10GB monthly “bithave a theoretical maximum data rate of bucket,” to every subscriber in the network.Figure 10. HSPA performance measured in a live commercial network Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics 19
  20. 20. Figure 11. HSPA performance measured on a commercial system using a terminal that supports up to 7.2Mbps20 Technical overview and performance of HSPA and Mobile WiMAX Performance characteristics
  21. 21. 4 Network architectureThe 3rd Generation Partnership Project is a specification, as is the network. In step withcollaboration agreement that brings together HSPA, the 3GPP Release 7 referencea number of telecommunications standards architecture has been enhanced with a 3Gbodies. 3GPP handles GSM and WCDMA Direct Tunnel that optimizes the delivery ofstandardization for the complete mobile mobile and wireless broadband services. Thesystem, including terminal aspects, radio Direct Tunnel architecture provides a directaccess networks, core networks and parts of data-path from the RNC to the GGSN,the service network. increasing topological flexibility and The radio interface is progressively being improving latency compared with 3GPPimproved with every advance in the 3GPP Release 6 and earlier architectures.Figure 12. Overview of the 3GPP reference architecture Technical overview and performance of HSPA and Mobile WiMAX Network architecture 21
  22. 22. 4.1 WiMAX Forum and IEEE Figure 13. Mobile WiMAX network architecture The IEEE 802.16 standard covers the air • split radio resource management, with interface (IEEE 802.16e) and basic the radio resource agent in the base connectivity up to the media access (MAC) station and the radio resource controller level. The WiMAX Forum defined the network in the ASN-GW architecture specifications for WiMAX • open interfaces for Profile A: R1, R6, R4, networks. The first specification (Release 1.0) and R3 focuses on delivering internet services with ✒ Profile B: mobility. At present, the network architecture • ASN solution where the base station and defines three RAN profiles, each with a ASN-GW functions are implemented on different functional allocation: a single platform ✒ Profile A: • open interfaces Profile B: R4 and R3 • centralized ASN model with base station ✒ Profile C: and ASN gateway (ASN-GW) • Similar to Profile A except that radio implemented on separate platforms, resource management is not split and is interacting through the R6 interface located entirely in the base station.22 Technical overview and performance of HSPA and Mobile WiMAX Network architecture
  23. 23. 4.2 Architecture comparisonFigure 14 shows a comparison of the However, using IP tunneling protocols tosuggested Mobile WiMAX architecture and meet the need for wireless mobility requires athe 3GPP Release 7 architecture for mobile lot of functionality in areas such as bearerbroadband services. management, QoS, charging, radio access The target requirements are broadly similar type information and others. From the verywith similar functional allocations and outset GTP has been tailor made to supportarchitecture. However, the selection of this functionality. This differs from theprotocols in each standards organization has approach of the WiMAX Forum, which hasbeen influenced by the chosen technology. instead extended the baseline IETF protocols3GPP builds on GTP and Diameter, which to include wireless-specific functionality andprovides optimized interworking with legacy to deploy multiple protocols in parallel overGSM terminals and common anchoring in the the same interface.GGSN for dual-mode GSM/WCDMA/HSPA At a high level, Radius and Diameter lookterminals. GTP also provides an efficient way quite similar. Both were developed by IETF,of handling QoS and of creating binding to and Diameter is an evolved version of Radius.radio bearers. The WiMAX Forum, by Diameter is widely used within IMScontrast, has gone with Mobile IP and specifications and provides functionalityRadius; it also supports PMIP and CMIP for beyond Radius, mainly in the area of carrier-both IPV4 and IPV6. grade performance. This translates into A comparison of Mobile IP and GTP reveals functionality, such as standardizedseveral similarities in terms of functionality. For application packages (instead of vendor-instance, the protocols solve the same types of specific attributes), reliable transportproblems in areas such as session layer, bidirectional communication, andmanagement, user plane tunnel set-up for IPv4 heartbeat mechanisms.and IPv6 payload, and multiple packet sessions.Figure 14. HSPA and Mobile WiMAX network architectures Technical overview and performance of HSPA and Mobile WiMAX Network architecture 23
  24. 24. 4.3 System Architecture Evolution The System Architecture Evolution (SAE), The mobility management entity (MME), an specified together with LTE, is the next step in evolution of the SGSN server, has been the 3GPP architecture evolution. It will deliver specified for 3G Direct Tunnel functionality in flattened network architecture with simplified 3GPP Release 7. In all likelihood, many QoS, for the delivery of IP services (Figure 15). implementations, will co-locate the MME with Scheduled for completion in 2007, SAE is the SGSN. an evolution of 3GPP Release 7, with support The SAE-GW node will include evolved for 3GPP LTE and non-3GPP access GGSN functionalities including IP networking technologies, as well as current 2G and 3G interfaces and end-user IP point of presence, access technologies. shallow and deep packet inspection, as well The architecture splits packet core control as real-time charging, policy control, and and user plane functionality into separate mobility to non-3GPP accesses using mobile nodes. Moreover, it further optimizes the IP. What is more, operators who evolve their HSPA architecture for mobile broadband networks to LTE/SAE from GSM/WCDMA/ services with two nodes (eNodeB and SAE HSPA will enjoy full backward compatibility gateway, SAE-GW) in the user plane for the with legacy networks. main use cases. Figure 15. Overview of the SAE architecture 4.4 Mobile WiMAX The details of the network architecture to include enhanced functionality, such as evolution for Mobile WiMAX beyond the policy management and IMS support, prepaid Release 1.0, approved in March 2007, have support, emergency services, and roaming. yet to be determined. However, it is expected24 Technical overview and performance of HSPA and Mobile WiMAX Network architecture
  25. 25. 5 ConclusionGiven that HSPA and Mobile WiMAX employ factors help ensures nationwide coveragemany of the same techniques, their for voice (GSM/WCDMA) and dataperformance is comparable in many areas. (HSPA/EDGE).However, key differences in areas such as Thanks to its heritage, HSPA givesduplex mode (FDD versus TDD), frequency operators a single network for multiplebands, multiple access technology, and services with a sound business case built oncontrol channel design give rise to differences revenues from voice, SMS, MMS, roaming,in uplink bit rates and coverage. and mobile broadband. While the peak data rates, spectral HSPA offers an ecosystem of unrivalledefficiency and network architecture of HSPA breadth and depth as well as unmatchedEvolution and Mobile WiMAX are similar, economies of scale that benefit all players inHSPA offers better coverage. In short, Mobile the ecosystem, which currently serves moreWiMAX does not offer any technology than two billion subscribers.advantage over HSPA. Operator choices of technology today will What is more, HSPA is a proven mobile influence operations for many years to come.broadband technology deployed in more than The good news in this context is that 3GSM100 commercial networks. It is built on the technologies are future-proof in terms of initialfirm foundations of the 3GPP family, offering investment, economies of scale, and theusers the broadband speeds they want and ability to extend and continuously enhancethe carrier-grade voice services they expect. the solution. HSPA can be built out using existing GSM Compared with other alternatives, HSPA isradio network sites and is a software upgrade the clear and undisputed choice for mobileof installed WCDMA networks. When used broadband services.together with dual-mode terminals, these Technical overview and performance of HSPA and Mobile WiMAX Conclusion 25
  26. 26. 6 Glossary AAA authentication, authorization and accounting 3G (third generation) Radio technology for mobile networks, telephones and other devices. Narrowband digital radio is the second generation of technology. 3GPP 3rd Generation Partnership Project – a collaboration agreement that brings together a number of telecommunications standards bodies 3G LTE/SAE 3G Long Term Evolution/System Architecture Evolution DSL digital subscriber line EDGE Enhanced Data rates for Global Evolution FDD frequency division duplexing GSM Global System for Mobile communications GPRS General Packet Radio Service HSPA High Speed Packet Access – an extension of WCDMA to provide high bandwidth and enhanced support for interactive, background, and streaming services IEEE Institute of Electrical and Electronics Engineers IMS IP Multimedia Subsystem IPR intellectual property rights ITU International Telecommunication Union MAC Media Access Control MIMO multiple input, multiple output OFDM orthogonal frequency division multiplexing – a digital encoding and modulation technology used by 802.16-based systems (including WiMAX) as the air interface PC personal computer TDD time division duplexing WCDMA Wideband Code Division Multiple Access – a wideband spread-spectrum 3G mobile telecommunication air interface WiMAX Worldwide Interoperability for Microwave Access – a standards-based technology that enables the delivery of last mile wireless broadband access as an alternative to cable and DSL VoIP Voice over IP technology enables users to transmit voice calls via the internet using packet-linked routes; also known as IP telephony.26 Technical overview and performance of HSPA and Mobile WiMAX Glossary
  27. 27. 7 References1. 3GPP. October 2006. TR 25.814, Physical layer aspect for evolved Universal Terrestrial Radio Access (UTRA). Available at: http://www.3gpp.org/ftp/Specs/html-info/25814.htm <http://www.3gpp.org/ftp/Specs/html-info/25814.htm> [Accessed 8 December 2008].2. 3G Americas. September 2006. Mobile Broadband: EDGE, HSPA and LTE. Available at: www.3gamericas.org/English/Technology_Center/WhitePapers/ <http://www.3gamericas. org/English/Technology_Center/WhitePapers/> [Accessed 8 December 2008].3. 3rd Generation Partnership Project (3GPP). http://www.3gpp.org/ [Accessed 8 December 2008].4. WiMAX Forum, http://www.wimaxforum.org/ <http://www.wimaxforum.org/> [Accessed 8 December 2008].5. IEEE-SA. June 2004. IEEE 802.16-2004 Air Interface for Fixed Broadband Wireless Access Systems. Part 3: Radio Conformance Tests (RCT)for 10–66 GHz WirelessMAN-SC™ Air Interface. Available at: http://standards.ieee.org/ getieee802/802.16.html [ <http://standards.ieee.org/getieee802/802.16.html> Accessed 8 December 2008].6. IEEE-SA. February 2006. IEEE 802.16e-2005 Air Interface for Fixed and Mobile Broadband Wireless Access Systems. Part 16: Air Interface for Fixed and Mobile Broadband Wireless Access Systems. Available at: http://standards.ieee.org/ getieee802/802.16.html [Accessed 8 December 2008]. Technical overview and performance of HSPA and Mobile WiMAX References 27