1 / 13

DESIGN OF A SPECIFIC CDMA SYSTEM FOR AIR TRAFFIC CONTROL APPLICATIONS

UNIVERSIDAD POLITÉCNICA DE MADRID. UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA. DESIGN OF A SPECIFIC CDMA SYSTEM FOR AIR TRAFFIC CONTROL APPLICATIONS. Outline. 1.- Motivation and objectives 2.- Operational aspects 2.1.- Proposal for the TMA / taxiing scenarios: C band Duplex options

zlata
Download Presentation

DESIGN OF A SPECIFIC CDMA SYSTEM FOR AIR TRAFFIC CONTROL APPLICATIONS

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. UNIVERSIDAD POLITÉCNICA DE MADRID UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA DESIGN OF A SPECIFIC CDMA SYSTEM FOR AIR TRAFFIC CONTROL APPLICATIONS

  2. Outline • 1.- Motivation and objectives • 2.- Operational aspects • 2.1.- Proposal for the TMA / taxiing scenarios: C band • Duplex options • Topics covered • 2.2.- Proposal for the en route scenario: VHF band • Coexistence with legacy systems • Transmit Beamforming • Codes with arbitrary spectral nulls • 3.- Deployment in two steps

  3. Communication strategies Eurocontrol 8,33 kHz + VDL2SATCOM Communication capacities POTENTIAL NEW SYSTEMS Communication needs 2010 2020 1.- Motivation and objectives • New needs require new systems • CDMA technologies might complement current narrowband VHF transmissions. Main advantage: very mature and available technology • Two available bands: VHF and ‘C’ band. Global solution • Provide a flexible simulation tool to test different alternatives in realistic aeronautical environments • Contribute to EUROCONTROL initiatives, ad-hoc working groups …

  4. 1.- Main goal of the project: flexible simulation tool CDMA Standard Tx Aeronautical channel + interferences CDMA Advanced receivers • CDMA standard transmitters to obtain representative results • Aeronautical channel simulator: en route, TMA, Taxiing • Advanced CDMA receivers • MultiUser Detection covering also ISI increase • Doppler Correction. Adaptive implementation • Multiple antennas at the ground station: beamforming and spatial diversity

  5. 2.- Operational aspects. Proposal for the ‘C’ band • Very high attenuation: link budget analysis recommends coverage around 25 Km. Limited to TMA / Parking • Available bandwidth: 60 MHz, from 5.090 to 5.150 GHz. • WCDMA (5 MHz Bw) is the most suitable option. Larger bandwidth, larger gain. • Two duplex options: FDD vs TDD

  6. TDD. Time Division Duplex. • Extra time guard interval is required for time alignment of different users in uplink. Maximum time guard depends on the cell size. • To cover 25 Km, time guard should be 688 chips instead of the UMTS 96 chips. • 96 chips means 3.7 % efficiency loss per slot • 688 chips means 26.9 % efficiency loss per slot Data transmission Guard Key disadvantage • FDD. Frequency Division Duplex • No such limitation. • Pay attention to the assigned bands of both links

  7. Further considerations regarding the spreading factor in TDD /FDD and aeronautical channel delay spread. Typical delay spread • En route: 33 msec. • Arrival, parking: 7 msec. • Taxi: 0.7 msec CDMA symbol length • TDD (16 chips/Symbol)=4.16 msec (indoor applications) • FDD (256 chips/Symbol)=66.6 msec (outdoor applications) • Conclusions • TDD suffers strong ISI (performance degradation). This point may be compensated by the use of advanced MultiUser Detectors • FDD is more suitable for these scenarios. MultiUser Detectors are not realistic. The interference limitation behaviour may be reduced by using beamforming • We have simulated both systems. Evaluated pros & cons.

  8. Our proposal for the ‘C’ band. UMTS-FDD. Topics covered in our research • MRC detector. SingleUser detector • Adaptive implementation to follow channel variations • Adaptive beamforming • Several antennas at the ground stations • Tx beamforming (Downlink) • Rx beamforming (Uplink) • Increase SNR (or coverage) • Reduce intra and inter-cell interferences

  9. 2.- Operational aspects. Proposal for the VHF band • Large coverage (around 300 Km). Ideal for en route scenario. • FDD is mandatory with both links separated around 12 MHz (current technology provides enough isolation). • Main problem: mutual interference with existing narrowband systems. • Narrower band CDMA is recommendable: type IS-95 (or its Multicarrier version CDMA-2000).

  10. 2.- VHF band: coexistence with legacy narrowband systems: voice, VDLx • Interference of NB over CDMA is not a big deal • Interference of CDMA over VDL is easy to solve VDL’s use the same channels for all the sectors CDMA has to avoid these channels • Interference of CDMA over voice channels is the key issue • Voice channels use different frequencies per sector • The use of these channels is dynamic depending on the activity factor • It is mandatory to guarantee null degradation of these voice channels to allow the deployment of the new system

  11. Demonstration: Interference on Voice Channels Analog Communications Envelope Detector Received Samples as Recorded (without Interference) Original Received Samples with Interference (Ratio is given at the output) SIR=0 dB Received Samples with Interference (Ratio is given at the output) SIR=10 dB Received Samples with Interference (Ratio is given at the output) SIR=20 dB

  12. 2.- VHF band: coexistence with legacy narrowband systems: Our proposal • Minimize interference by the combination of two techniques • CDMA transmit beamforming to eliminate interference of no co-located victim • Transmit a CDMA modified spectrum with spectral nulls in some specific channels New codes design Victim 2 CDMA 2 CDMA 2 Freq. Victim 1 no suffering interference by spatial filtering Victim 2 Suffering interference by spatial filtering Interference eliminated by frequency filtering CDMA 1 CDMA 2

  13. C band CDMA C band CDMA VHF AM, VDL VHF AM, VDL VHF AM, VDL CDMA Current state First step Second step 3.- Deployment in two steps ‘C’ Band: WCDMA- FDD VHF: IS-95 like FDD (new codes) Exploit: spatial dimension !!

More Related