Design and Performance Trade-offs in Parallelized RF SDR Architecture Ville Saari 1 arssinen 2 Sami Kiminki Aarno P¨ Antti Immonen 2 Vesa Hirvisalo Jussi Ryyn¨ anen Tommi Zetterman Aalto University Aalto University Nokia Research Center Computer Science and Eng. Micro- and Nanosciences 1 currently with EPCOS Nordic 2 currently with Renesas Mobile Europe
Outline ◮ Parallel RF SDR platform for LTE and WLAN (UE) ◮ Holistic RF platform design ◮ effect on RX and TX front-end filters ◮ Multi-radio opportunities ◮ we show system-level data throughput opportunities by RF resource sharing (simulation results) Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 9%
Parallel RF SDR Architecture Filter bank Option 2 A Duplexers D Band # A D A D D A ISM-band filtering D A Figure: Archetype of a parallel multi-standard RF transceiver. The number of RX and TX pipes may be varied. Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 18%
In-device RF Interference ◮ We analyse how the RX noise floor is accumulated from different sources ◮ receiver noise figure ◮ TX signal spilling to RX frequencies due to TX non-linearities ◮ TX signal transferred to RX noise due to RX non-linearities ◮ By setting the allowed desensitization threshold, we can determine RX and TX filter requirements ◮ Focus on a difficult case ◮ WLAN 2.4-GHz (2400–2483.5 MHz) ◮ LTE Band 7 (TX: 2500–2570 MHz, RX: 2620–2690 MHz) Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 27%
RX Filter Requirements 45 40 Attenuation Requirement [dB] WLAN 35 LTE 30 25 20 −10 −5 0 5 10 Receiver IIP3 [dBm] Figure: TX blocker attenuation requirement vs. IIP3 of the receiver to achieve 1 dB sensitivity loss Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 36%
TX Filter Requirements 0 −10 Attenuation Requirement [dB] WLAN LTE RX −20 −30 −40 −50 LTE TX −60 −70 2300 2400 2500 2600 2700 2800 Frequency [MHz] Figure: TX stopband attenuation requirement for LTE band 7 for sensitivity losses of 1 dB and 3 dB in 2.4-GHz WLAN receiver Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 45%
Multi-radio Opportunities ◮ Non-dedicated RF resources ◮ Two approaches for sharing ◮ more performance in the average case (high-end) ◮ less hardware for same functionality (low-end) ◮ Sharing requires favourable conditions, e.g. , discontinuous modes in use ◮ high-end approach is currently more feasible Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 55%
RF Resource Scheduling ◮ The fundamental idea ◮ when one radio does not need full HW capabilities, use spare resources to boost another radio ◮ all radios maxed out is not the common case ◮ Some techniques ◮ semi-static scheduling: SISO vs MIMO ◮ dynamic scheduling: fine-grain traffic shaping i.e. , “TDM of chip resources” Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 64%
LTE and WLAN on Shared Resources ◮ Assume discontinuous modes ◮ LTE: DRX ◮ WLAN: powersave ◮ The idea ◮ LTE reserves the resources first ◮ WLAN uses what is left ◮ PS-Poll enables fine-grained traffic shaping for RX ◮ In experiments, we assume ◮ bandwidths are 20 MHz ( ≈ 150 Mbps) ◮ device has control on SISO vs MIMO ◮ MCS & RI feedback Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 73%
LTE and WLAN: Performance Estimation (1/2) 160 Sharing overhead Opportunity area (co-op LTE) 140 Opportunity area (non-co-op LTE) Guaranteed area WLAN Throughput [Mbps] 120 100 80 60 40 20 0 0 20 40 60 80 100 120 140 160 LTE Throughput [Mbps] Figure: Performance estimation for 2 shared receivers Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 82%
LTE and WLAN: Performance Estimation (2/2) 160 Sharing overhead Opportunity area (co-op LTE) 140 Guaranteed area WLAN Throughput [Mbps] 120 100 80 60 40 20 0 0 20 40 60 80 100 120 140 160 LTE Throughput [Mbps] Figure: Performance estimation for 3 shared receivers Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 91%
Conclusions ◮ RF systems must be designed as a whole, not only per-protocol ◮ e.g. , additional filter requirements ◮ Parallel SDR approach brings new opportunities ◮ Resource sharing for better system-level throughputs ◮ Is there even a fundamental reason for dedicated RF pipes? ◮ Cognitive radio connection: Don’t share only the spectrum, share the resources too ◮ Resource sharing calls for further protocol work ◮ We want better flexibility and predictability ◮ ongoing in-device coexistence work helps in this ◮ Ultimately, we’d like to see general-purpose RF platforms ◮ think CPUs, GPGPUs, FPGAs, . . . Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 100%
Bonus Slides Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 109%
Resource Schedule Example Figure: A resource schedule for LTE and WLAN on 2 RX + 2 TX platform. LTE allocates resources with higher priority. Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 118%
Effect of Desensitization 100 80 Range (%) Range Range 60 loss loss 40 10% 30% 20 0 0 2 4 6 8 10 Desensitization (dB) Relation of desensitization and Visualization for 1 dB and 3 dB range loss desensitization Figure: Desensitization as range loss in free space Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 127%
WLAN Frame Scheduling Defer sending PS-Poll here because of allocation gap Resource allocation block Resource allocation block Wait until free to send Wait until free to send Wait until free to send DATA DATA DATA RX TX PS-Poll ACK PS-Poll ACK PS-Poll ACK time Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 136%
Multi-radio Resource Schedule Example ◮ External PNG slides Design and Performance Trade-offs in Parallelized RF SDR Architecture Sami Kiminki — 2011-06-02 145%
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