Half Duplex Operation in Multimode/Multiband/MIMO-capable Handsets
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Half Duplex Operation in Multimode/Multiband/MIMO-capable Handsets Half Duplex Operation in Multimode/Multiband/MIMO-capable Handsets Presentation Transcript

  • Half Duplex Operation inMultimode/Multiband/MIMO-capable Handsets Francesc Boixadera and Cyril Valadon Cambridge, 6th December 2012 F-3697
  • Agenda • The RF Front End Multiband Problem • Terminology Summary • Comparison between full-duplex and half-duplex single-band operation • Related 3GPP TSG RAN1 conclusions • Case study for 3 multimode, multiband RF front end architectures • Half-duplex operation for LTE • Half-duplex operation for HSPA+ • Half-duplex operation for roaming-only • Conclusions2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 2
  • LTE Deployments – up to 40 frequency bands Source: RFMD - RF Front End Challenges for 3G/4G Wireless Handsets http://www.rfmd.com/cs/documents/CommJBaoSemiConChina12.pdf2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 3
  • The RF Front End Multiband Problem • Limited number of bands supported by handsets in the near future (~10) – Multiple reference designs needed to address different regions or operators – Poorer economies of scale – Difficult to address small markets and infrequent band combinations – Difficult to produce global roaming phones • Additional cost per band in the order of 1 USD on RFFE components – Power Amplifiers, Filters, Duplexers, Switches, PCB area • Additional performance loss per added band – Poorer Rx Noise Figure due to higher losses • Increased power consumption per additional band – Higher insertion losses lead to poorer power efficiency and ultimately reduced talk-time • Increased volume and PCB footprint • RFFE modules available but not for all band combinations • Poorer efficiency in wideband antennas. • Inter-band Carrier Aggregation adds further complication (12 combinations currently defined in 3GPP) • Baseband complexity mainly increases with # modes, not # bands2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 4
  • Quick Terminology Summary • Full-Duplex Frequency Division Duplexing – FD-FDD – Used in 3GPP WCDMA/HSPA, IS95, 3GPP2 CDMA2000, 3GPP LTE • Time Division Duplexing – (HD)-TDD – Used in 3GPP TD-SCDMA and 3GPP LTE – Same band for UL and DL and usually (but not always) Half-Duplex • Half-Duplex Frequency Division Duplexing – HD-FDD – Used in GSM/GPRS/EGPRS, officially supported in 3GPP LTE2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 5
  • Back to basics – Do we really need Full Duplex FDD? • The RFFE multiband problem can be resolved by technology improvements – This may take some time to reach mass market cost/performance/reliability • GSM/GPRS/EDGE handsets extremely successful because of economies of scale – Quad-band RF, a single reference design for world market • GSM/GPRS/EDGE quad band RF is much simpler – Partly because operates in Half Duplex – Frequency Division Duplex (HD- FDD) – Simple Architecture, lower cost, good size/performance/power efficiency balance • Is Full Duplex operation in multimode handsets strictly necessary?2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 6
  • Full-Duplex FDD Single-Band Architecture2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 7
  • Half-Duplex FDD Single Band Architecture2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 8
  • Single-Band HD-FDD Advantages • No simultaneous Rx/Tx – No self de-sense due to high-level Tx blocking and high-level Tx noise • Possible removal of Rx filter – Minimum coupling loss for external blocker should be at least 20-30 dB, relaxing Rx filter rejection significantly compared to duplexer for FD-FDD – Some re-design to increase Rx linearity may enable Rx filter removal • Possible removal of Tx filter – Reduction in loss/volume/PCB area/cost – Better power efficiency and sensitivity – Tx unwanted emissions may still be an issue in the short term for some scenarios • Some GSM transceiver designs can operate in 100% “SAWless” albeit with some power consumption penalty • Note: HD-FDD presents lower peak data rates – Not necessarily the case when cell capacity shared between multiple users2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 9
  • 3GPP RAN1 Low-Cost MTC LTE Devices • “Half duplex operation will result in no loss of coverage” • “Compared to the reference category 1 LTE modem, power consumption is likely to be reduced. The insertion loss of the switch in the HD-FDD UE is less than in the duplexer of an FD-FDD UE: reducing the electrical power required to produce a certain amount of radiated RF power. Half duplex operation means some components can be put in a reduced power state until required” • “Since there are insignificant cell spectrum efficiency impacts from the support of LTE HD-FDD UEs, the spectral efficiency of an LTE cell is unlikely to be degraded through supporting LTE HD-FDD UEs.” • “if it is assumed that some cost saving could be achievable with RF components optimized for HD-FDD operation that take advantage of relaxation in performance and/or functional requirements (the absence of self-transmitter blocking and interference easing filtering rejection requirements) then this results in an overall cost saving of 12-19%” • ‘Conclusion and recommendation’ of the study item: – “Half duplex FDD is expected to be supported at least as an optional feature for UE category specified for low-cost MTC devices” Source: 3GPP TR36.888 http://www.3gpp.org/ftp/Specs/html-info/36888.htm2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 10
  • Multiband Reference Case Study • 12 bands supported in all reference configurations – 4 ‘Low bands’ (700-900 MHz), bands L1 L2 L5 L6. – 4 ‘Mid Bands’ (1700-2100 MHz) bands M3 M4 M7 M8. – 4 ‘High Bands’ (2300 MHz – 2600 MHz) H9 H10 H11 H12. – On each group, 2 bands are FDD and two bands are TDD • Two Power Amplifiers required (Mid+Low bands, High Bands) – PA sharing through switches • FD-FDD requires one duplexer for each supported frequency band – And also one Rx filter for each FD-FDD diversity branch • FD-FDD requires one LNA for each FDD band • HD-FDD and TDD do not require Rx/Tx filters (options 2 and 3) – Single Rx port and wideband LNA covers one whole band group • 3 multimode configurations – Option 1: FD-FDD+TDD, Rx/Tx filters/duplexers for all bands – Option 2: FD-FDD+TDD, duplexer for FDD, no Rx/Tx filter for TDD – Option 3: HD-FDD+TDD, no Rx/Tx filters2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 11
  • FD-FDD + TDD Multiband Architecture Option 1Rx/Tx filters orDuplexers for all bands2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 12
  • FD-FDD + TDD Multiband Architecture Option 2 Duplexers and Rx filters for FDD bands only2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 13
  • Option 3 - HD FDD + TDD Multiband RF Architecture2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 14
  • Component Comparison Component FD-FDD+TDD FD-FDD+TDD FD-FDD+TDD (Option 1) (Option 2) (Option 3) Duplexers 6 6 0 Rx Filters 18 6 0 Power Amplifiers 2 2 2 and Tx ports Switches 4 4 2 (throw count) (3, 5, 12, 14) (3, 5, 9, 11) (5, 3) LNAs and Rx ports 24 18 6 Multiband Antennas 2 2 2 Frequency 2 2 2 synthesisers (maybe 1) • Loss increases with # components crossed between transceiver and antenna • Each component adds approx 0.5 dB loss (0.2 – 1 dB) • Losses in switches increase with # throws2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 15
  • HD-FDD Architecture – Some caveats • Tx filters may be required by HD-FDD to meet some co-existence requirements with services operating in other frequency bands – Not all frequency bands should require a Tx filter – Over time transceiver/PA technology will improve and more filters could be removed • Rx filters for strong out-of-band blockers may be required in some bands – A wideband LNA without a band filter receives a larger number of higher-level blockers – There are already 100% “SAW-less” receiver designs for GSM, see e.g. [1] • LNA linearity can be improved by increasing transceiver front end bias current at the expense of some increase in power consumption • Filters may be required to address in-device co-existence – Example: Simultaneous Bluetooth/WiFi and TDD LTE in band 41 [1] Chi-Yao Yu et al. , "A SAW-Less GSM/GPRS/EDGE Receiver Embedded in 65-nm SoC," Solid-State Circuits, IEEE Journal of , vol.46, no.12, pp.3047-3060, Dec. 20112012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 16
  • Is Half Duplex possible for LTE? • Half-duplex FDD LTE operation mode is officially supported since the first release – Support for half-duplex operation mode is signalled by the UE – A small set of minor changes to the specifications is required (see next slide) • Conflict avoidance at the UE between Rx and Tx activity is handled by the scheduler in the eNode-B in a flexible manner – There is no fixed allocation between UL and DL subframes and the UE can monitor DL activity in every slot where transmission has not been scheduled • There are also some 3GPP standard changes which would require duplexers even for TDD bands with Carrier Aggregation (CA). TDD-LTE isn’t necessarily operating in half-duplex mode anymore when different UL/DL configurations are supported for different carriers. – Support for half-duplex operation is currently signalled for both FDD and TDD bands with CA such that UEs can still operate in half-duplex mode to take advantage of the half-duplex benefits2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 17
  • Any further work for HD-FDD LTE? • Some further work may be required to complete the standardization effort – Transition gap needs to be created at the UE to enable Rx-to-Tx switching. This can be achieved by allowing the UE to drop some symbols at the end of a DL subframe preceding an UL subframe – Transition from UL to DL is enabled through the use of timing advance. It may be beneficial to specify mechanisms allowing the eNode-B to decide on the amount of timing advance which is required – The UE needs to be guaranteed reception periods of a sufficient duration in order to perform intra-frequency and inter-frequency mobility measurements – Additional conflict resolution rules need to be specified to address some cases where it isn’t possible to avoid conflicts between the DL and the UL through scheduler,. An example is the unscheduled transmission of contention-based PRACH.2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 18
  • Is HD-FDD possible for WCDMA/HSPA? • In the 3GPP Rel.99 WCDMA standard, concurrent transmission and reception is necessary when data is being transmitted and received in connected state • 3GPP Release 7 introduced Continuous Packet Connectivity (CPC) features which reduce UE transmit and receive activity – UE DTX removes the need for continuous transmission of the dedicated physical control channel (DPCCH) in the absence of data to transmit – UE DRX allows reception to be disabled in the absence of data to be received • 3GPP Release 7 also introduced support of HSDPA in CELL_FACH state – Makes it possible to receive data on the HSDPA channels without any dedicated uplink transmissionSource: Understanding HSPA+ Cellular Technology, Jodi Zellmer,http://electronicdesign.com/article/communications/understanding-hspa-cellular-technology-74012 2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 19
  • Is HD-FDD possible for WCDMA/HSPA? • While potentially feasible, further modifications to the standards for half-duplex support need to investigated – Fractional DPCH (F-DPCH) still needs to be received for HS-PDCCH power control – Scheduling rules would need to be introduced to avoid conflicts between HS-DSCH/HS- SCCH monitoring and transmissions on the HS-PDCCH and/or E-DCH – HD-FDD HSPA+ UEs cannot be backwards compatible with existing releases2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 20
  • FD-FDD at Home Network, HD-FDD for Roaming • This seems an attractive combination to produce multiband User Equipment capable of global roaming • FD-FDD (and TDD) operation in frequently-used bands – e.g. 4 bands, home network and frequent roaming bands – Option to support Carrier Aggregation operation on these bands • HD-FDD and TDD operation for roaming – Increase band coverage for roaming with more limited RF complexity increase – Lower theoretical peak data rates – Similar data rates in practice when cell capacity shared among multiple users – Non-contiguous Carrier Aggregation not possible for roaming bands2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 21
  • Conclusion on Half-Duplex FDD • HD-FDD is an approach to enable simpler, smaller, cost-effective multimode/multiband RF Front End • Economies of scale – fewer reference designs to address a global market • HD-FDD seems feasible as 3GPP Releases are moving away from continuous Rx/Tx and support DRX/DTX operation – Limited standardisation effort for LTE – CPC HSPA+ from Release 7 onwards, LTE Connected DRX – HSPA+ seems feasible, more detailed assessment required • HD-FDD improves cost/complexity/performance for FDD terminals and brings them to a similar level as TDD-only terminals – Probably a significant consideration for M2M market • There appears to be no loss in terms of overall network capacity • Combining FD-FDD for home network and HD-FDD for roaming seems attractive • There are indeed other options available, mostly based around technology PA/Filter/switch evolution or integration – Integration alone will not fully address market fragmentation as UE supply to smaller markets and less frequent bands will remain an issue – Technology evolution may require a longer period to mature2012/12/7 F-3697 Copyright © 2012 MStar Semiconductor, Inc. All rights reserved. 22