SELEX Elsag. 5/18/2012 R. Pucci SDR 12 WinnComm 1

Transcription

1 SELEX Elsag 5/18/01 R. Pucci SDR 1 WiComm 1

2 Military BU - SELEX Elsag

3 Possible update of SDR Platforms to COGNITIVE architectures COGNITIVE MANAGER INTERFACE Geolocatio, Voice, Video, etc Applicatio Policy Database (Security, QoS, Power, etc) CR TRANSPORT PROTOCOL Trasport NETWORKING Network Kowledge Database (Awareess, routig, past experiece, etc) RADIO CR MAC PROTOCOL SENSING Lik Physical SDR Platform

4 SELEX Elsag SDR Waveform Platforms ad HANDHELD Vehicular Moo-Chael SELFNET Soldier Broadbad Waveform WIDEBAND QoS MANET MULTIHOP VOICE/DATA SERVICES

5 PERFORMANCE EVALUATION OF A SPECTRUM-SENSING TECHNIQUE FOR LDACS AND JTIDS COEXISTENCE IN L-BAND Bartoli G., R. Fatacci, D. Marabissi, L. Micciullo Uiversity of Florece C. Armai, R. Merlo SELEX Elsag

6 Outlie LDACS overview JTIDS overview Prelimiary iterferece aalysis Proposed sesig ad mitigatio method Numerical Results Coclusios

7 LDACS overview 1/ Icreasig demad for advaced commuicatio services i civil aviatio leads to the eed for a ew commuicatio system able to support the capacity ad security requiremets of the air trasportatio system. SESAR project (Sigle Europea Sky ATM Research) aims to develop a ew commuicatio ifrastructure to support the air traffic maagemet L-Bad Digital Commuicatio System (LDACS) will provide support for air/groud data lik Due to high cogestio of the VHF frequecies, LDACS will work o the L- bad ([ ] MHz) Spectral compatibility with other legacy systems operatig i L-bad eeds to be addressed JTIDS

8 LDACS overview / Two optios are curretly uder cosideratio: LDACS1 FDD: flexible frequecy allocatio Orthogoal Frequecy Divisio Multiplex (OFDM): allows to cotrast multipath effects B= khz N sub =64 f s =65 khz T symb =10.0 µs QPSK, 16QAM, 64QAM Reed Salomo Code (outer) Covolutioal Code (ier) LDACS TDD: flexible resource divisio Cotiuos Phase Frequecy Shift Keyig (CPFSK): miimizes out-of-bad emissios

9 JTIDS oveview Joit Tactical Iformatio Distributio System (JTIDS) is a military system used for several purposes. High trasmitted power (up to 1000W) Impulsive trasmissio (6.4 μs) Spreaded sigal (3MHz) Frequecy hoppig (N hp =51) JTIDS operates i a large rage of frequecy bad [ ] MHz, hece iterferece with LDACS becomes uavoidable JTIDS iterfrece affects all the LDACS badwidth JTIDS iterferece affects oly few samples of the LDACS symbol

10 Prelimiary Iterferece Aalysis Prelimiary aalysis permits to idetify the coditios (distace, d ad frequecy offset Df) that allow to LDACS to operate i presece of JTIDS iterferece. The iterferece power level is compared with the maximum tolerable iterferece power level (i.e. mi C/I): I( d, Df ) EIRP PL( d) G rx L rx OCR( Df ) DC - EIRP is the JTIDS Equivalet Isotropically Radiated Power; - PL(d) is the free space path loss; - G rx e L rx are the LDACS receiver atea gai ad cable loss, respectively; - OCR(Δf) (Off Chael Rejectio) takes ito accout the ability of the victim receiver to reject the iterferer sigal. - DC is a term that takes ito accout the iterferer duty cycle.

11 Prelimiary Iterferece Aalysis Results Assumptios: The ratio C/I is fixed to 10 db ad C=receiver sesitivity (worst case) The JTIDS trasmissio power is fixed to 1000 W. TSDF is set to 50% ad 5% that represet the maximum ad miimum values. 1 Sceario Groud Statio to Airbore Aircraft No Iterferig Distace TSDF=50% TSDF=5% d > 500km d > 157km 3 4 Airbore Aircraft to Airbore Aircraft to Airbore Aircraft to Groud Statio Groud Statio to Groud Statio d > 500km d > 500km d > 500km d > 500km d > 60km d > 500km Operatioal distace: miimum vertical separatio of the aircrafts: 300mt 5 Aircraft o the Groud to Aircraft o the Groud d > 6.6km d > 18.5km 6 Groud Statio to Aircraft o the Groud d > 500km d > 16km 7 Aircraft o the Groud to Groud Statio d > 46.5km d > 5.5km

12 Proposed Sesig ad Mitigatio method The basic idea is the retrasmissio of the Packet Data Uit (PDU) whe the presece of JTIDS system is detected. The first copy of the packet is stored ad combied with its retrasmissio Packet combiig is used either to improve iterferece detectio ad sigal decodig. JTIDS ad LDACS trasmissios are idepedet processes: eve if both the copies of the PDU are affected by JTIDS iterferece with high probability differet portios of the PDU are corrupted

13 Sesig method 1/ Spectrum sesig is a well-kow topic i Cogitive Radio eergy detector: computes the eergy of the received samples durig a time iterval called sesig period ad Accuracy of eergy detector is proportioal to the duratio of the sesig period I the cosidered sceario: There is ot a dedicated sesig iterval The goal is to detect which samples are corrupted ad ot oly if the iterferece is preset Modified eergy detector sesig period must be limited at W samples defied accordig to the JTIDS sigal duratio (W=T p /f s +1 where f s is the samplig frequecy ad T p the pulse duratio) exploits a slidig widow which collects the eergy of a part of the received sigal

14 Sesig method / Sesig is performed o the differece betwee the two packet s replicas Dr[ i] r1 [ i] r[ i] This permits to reduce the false alarm probability due to by the a high peak to average ratio (PAPR) that characterizes the LDACS (i.e. OFDM) sigal T W W i a i Dr[ i] M cosecutive test statistics (T ) are observed: if at least M=L-1 cosecutive samples are over the threshold we assume the iterferece is preset.

15 Iterferece mitigatio i i i ad r r if r ad r r if r i if r r r ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ ] [ Observig the retrasmissios differece is possible to kow which samples are affected by iterferece it is ot kow if the iterferece is itroduced by the first, r 1 [], or the secod r [] copy of the received sigal Idicatig i as the samples affected by the iterferece: 1) for each i the values of r 1 [ i ]ad r [ i ] are compared: the maximum is blaked while the miimum is doubled. ) the resultig sigals are summed together 3) r [] is used for data detectio

16 Workig Hypotesis LDACS modulatio scheme: QPSK LDACS codig scheme: RSC Iterleaver CC 1/ JTIDS TSDF = 50% Oly oe JTIDS hoppig frequecy iterfers with LDACS system SIR values: 0, 5, 10 db Ricea fadig chaels with K factor equal to 4 db

17 Numerical results D mea square distortio of the sigal D 1 P P 1 p0 r'[ p] s[ p]

18 Numerical results Bit Error Rate without chael codig: The mitigatio techique permits to reduce the BER eve if compared with traditioal blackig techique A floor effect is preset for high SRN due to the residual iterefece For low SNR a 3dB gai due to soft comibiig is itroduced

19 Numerical results Bit Error Rate with chael codig: The mitigatio techique permits to activate the codig gai Floor effect is completely removed Iterferece is completely removed A 3dB gai due to soft comibiig is itroduced respect the No-iterferece case Additioal 1 db gai i itroduced respect traditioal blakig techique

20 Coclusios Future LDACS systems for air/groud commuicatios will work o L-Bads Coexistece with JTIDS system has bee cosidered ad evaluated A Iterferece Sesig ad Mitigatio techique has bee proposed: It is based o sigal retrasmissio ad packet combiig Sesig capabilities of the modified eergy detector are improved The mitigatio scheme is able to reject the iterferece ad a 3dB gai is itroduced due to the packet combiig A additioal 1dB gai is itroduced respect the blakig techique.