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Deliverable R4.1.3

Deliverable R4.1.3. CEFRIEL – Politecnico di Milano. Milano – 17 novembre 2004. Performance evaluation of the adaptive modulation and channel coding techniques. Table of Contents. Goals Implemented simulator Adaptive modem architecture The Supervisor algorithm Future work. Goals.

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Deliverable R4.1.3

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  1. Deliverable R4.1.3 CEFRIEL – Politecnico di Milano Milano – 17 novembre 2004 Performance evaluation of the adaptive modulation and channel coding techniques

  2. Table of Contents • Goals • Implemented simulator • Adaptive modem architecture • The Supervisor algorithm • Future work

  3. Goals • Define an adaptive modem architecture • Define suitable optimization logics • Develop a simulator to test the model

  4. Simulator: general features • IEEE 802.16-2004 OFDM baseband transceiver developed and tested with Matlab 6.5 • Full standard compliant • Flexible and reconfigurable

  5. Simulator: TX/RX chain • OFDM 256 subcarriers • RS + convolutional • access technique: TDM / TDMA • bit-rate: up to 74 Mbit/s • adaptive burst profile channel model

  6. IEEE fixed/nomadic channel models • SUI (Stanford University Interim) Models • Various environment scenarios: • desert • rural ambient • Manhattan–like urban agglomerates • Characteristics • Ricean distribution tap value generation • 28 Scenarios characterized by different antenna types, delay spread and K-factor • Three Taps Delay Line • For each Tap a delay and a relative magnitude are defined

  7. ETSI mobile channel • ETSI mobile channels developed for UMTS • Characteristics • Rayleigh channel model • six taps delay line model • for each Tap a delay and a relative magnitude are defined • Doppler effects caused by mobile terminals speed • Two delay spread Channel A / Channel B • Three user scenarios: indoor, mixed-pedestrian and vehicular use Mobile Simulation Scenarios Mixed-Pedestrian Vehicular 1 m/s 75 km/h 150 km/h

  8. Simulation Results

  9. Adaptive modem architecture • Approach: introduction in 802.16-2004 baseband standard of a new architectural element (supervisor, SPV) performing optimization procedures • minimization of the consumed power (both transmitted and used by the electronic components) for a negotiated level of Quality of Service (appropriately translated at PHY layer) • SPV input • from MAC: Target BER and Target Bit-Rate (QoS parameters at PHY layer) • from PHY: channel state information (the set of the channel power gains |Hi|2). • access to an internal look-up table containing the error correction code gains for every RateID in AWGN channel • SPV output • to PHY: RateID, the number and the position of the ON SCs • to MAC: actual bit-rate and BER achieved

  10. The Supervisor algorithm (1) The aim of the SPV algorithm is to switch off the OFDM subcarriers that are heavily attenuated by the channel, meeting at the same time (if possible) the Target Bit-Rate and Target BER requirements current channel response

  11. The Supervisor algorithm (2) 1 SPV calculates the maximum bit-rate achievable by every RateID with all data SCs turned on SPV does not consider the RateIDs for which the maximum achievable bit-rate is less than the target one If there is not a single RateID that meets the requested Target Bit-Rate, the SPV informs the MAC layer that it is not able to fulfill the requirements. The MAC layer will then decide the next steps. 2 SPV orders the gains of the measured channel (by the receiver)

  12. The Supervisor algorithm (3) For each useful RateID the SPV 3 3.a calculates the minimum number of SCs, required to achieve the Target Bit-Rate 3.b reads form a pre-stored look-up table the Eb/N0 needed at the receiver by any subcarriers in order to achieve the desired Target BER 3.c For each subcarrier from the Nas selected, calculates the Eb/N0 to be transmitted in order to have the desired Eb/N0 at the receiver (after the OFDM signal passed through the channel) that allows each subcarrier to respect the Target BER calculates the mean required transmitted Eb/N0, [Eb/N0], for the considered RateID 3.d

  13. The Supervisor algorithm (4) 4 Among all the useful RateID, the SPV choose the one that requires the lower mean transmitted Eb/N0 5 SPV switches off the subcarriers that are not required to get the Target Bit-Rate for the chosen RateID Obviously the switching-off operation starts from the weakest subcarriers SPV reorders the subcarriers so that the OFDM signal is now ready to be transmitted 6

  14. Future work • Simulations and performance testing • Synchronization algorithms • Adaptive modem architecture optimization analysis

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