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Status of WP2.3 “Radio Interface and Baseband signal

Processing”Progress from Milestone 0072 to Deliverable D15

5th CAPANINA Meeting

BARCELONA – March 3rd/4th, 2005

– Marina Mondin –

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WP2.3 in the Annex 1

“Radio Interface and Baseband Signal Processing”

Participants:JSI, Polito, Eucon, UPC, UOY

Objectives:to propose the most suitable adaptive modulation schemes and coding techniques to be used with the selected communication standards in targeting fixed and mobile operating scenariosto develop advanced signal processing algorithms for HAP using software radio architectureto implement and assess the performance of selected signal processing algorithms on a DSP platform.

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Focus of WP2.3

From Annex 1…From Annex 1…

Proposal of possible modifications of radio interface of the selected broadband communication standards, for the implementation in identified operating scenarios:

wireless access to broadband applications via HAPs for fixed terminals wireless access to broadband applications via HAPs and for collective terminals in high speed moving vehicles

Two different standards are likely to be selected on lower layers for fixed and for mobile operating scenarios

Possible contribution to international standardisation and regulatory bodies

Addressed baseband signal processing techniques:joint modulation and coding schemesMIMO/diversity techniques channel estimation and equalizationcarrier and clock synchronizationadvanced software radio signal processing techniques

Implementation on DSP platform of selected signal processing algorithms

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Progress at March 2005

Milestone M0072 “Specification of adaptive modulation schemes and coding techniques to guarantee required QoS and performance evaluation in the HAP propagation channel”

Due by the end of January 05Released on time

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M0072: QoS for Broadband Wireless Services

In BWA (Broadband Wireless Access) systems, the wireless link will likely be the bottleneck

QoS provides a mean for effectively partitioning the limited resources of the wireless medium

Users can be provided different levels of service, and service providers can use this to derive revenues

The improvements in wireless link performance directly translate to the overall improvement of the end-to-end QoS

The IEEE 802.16 MAC provides QoS differentiation for different types of applications. The standard defines four types of scheduling services

Unsolicited Grant Services (UGS), Real-Time Polling Services (rtPS), Non-Real-Time Polling Services (nrtPS), Best Effort (BE) Services

Several QoS metrics are associated with each scheduling servicesmaximum sustained rate (MSR), minimum reserved rate (MRR), maximum latency, maximum jitter, and priority

At PHY layer, the 802.16 standard employs dynamic control of modulation and coding to mitigate the environmental effects and maintain a constant BER.

Dynamic modulation and coding parameters are defined by the carrier to interference and noise ratio (CINR).

Packet retransmission is employed for data services, which can accommodate high latency

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M0072: Operating Scenarios & System Architecture

HAP communication systems can be used in different configurations:

stand-alone platformsmulti-platform constellation

A HAP system can be deployed as a stand-alone network, or it can be connected to external networks via gateways

There is a potential gain in exploiting space and platform diversity

space diversity: the same signal is received through independent channels, by using multiple antennas suitably separated in space (ok for ground terminals)platform diversity: the same signal is transmitted from multiple platforms, which determine independent channels

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M0072: Adaptive Coding and Modulation

Performance comparison between Fixed Coding Modulations (FCM) and Adaptive Coding Modulations (ACM)

Bandwidth efficient coding modulation schemes for LOS conditions in ACMPower efficient coding modulation schemes for FCM and for shadowed channel in ACM

Considered modulation schemes:16-QAM for LOS conditionsUncoded and encoded QPSK for the shadowed HAP mobile radio channel

Considered coding rates of convolutional encoder for QPSK signal:

r = 1/2 and r = 1/4.

Simulation results:the FCM modulation scheme has lower BER and much lower system throughput in comparison to the ACM modulation scheme for any simulated environment.

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M0072: Performance of ACM Combined with Spatial Diversity

Applying space diversity to adaptive coding and modulation significantly increases the system throughput and bandwidth efficiency

increase in average bandwidth efficiency using different combining methods:

Selective Combining: +20%Equal Gain Combining: +30%Maximum Ratio Combining: +250%

Platform diversity: when the signal from one platform is blocked due to high obstacles, the platform diversity can generally provide an alternative propagation channel with LOS conditions

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M0072: Advanced Coding Techniques

Investigations on variable-rate, variable-length Serially Concatenated Convolutional Codes (SCCCs)

coupled with the IEEE 802.16a-OFDM physical layer

The interleaver length N can be selected in order to guarantee the required QoS, given possible constraints on the amount of delay introduced by the serial concatenation.

The interleaver has been optimized according to a design method for variable-length, prunable interleavers that guarantees optimal BER/FER performance for any interleaver size between 1 and the target maximal length N.

The convolutional encoders, along with the Puncturing Patterns applied, have been chosen in order to maximize the interleaver gain produced by the serial concatenation

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M0072: Advanced Coding Techniques (II)

Evaluation of BER performance:

Different coding schemes (combination of coding rates and puncturing patterns) Ricean fading channel with Rice factor equal to 10 dB and 20 dB

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M0072: Coded Polarization Diversity Aspects

Dual-polarized data transmission: two signals sharing the same bandwidth and carrier frequency are transmitted simultaneously on the two orthogonal polarizations of the antenna

Performance analysis of 4-D trellis coded polarization multiplexing under varying channel conditions

comparison with spatial multiplexing

Computationally feasible optimal decoding strategy for 4-D TCM

Considered systems:rate-4/5 16-state 4-D trellis code chosen as channel code. uncoded 16-QAM chosen as a reference system (it has the same information bit rate as the trellis code)

Considered channel conditions:NLOS and LOS

Simulation results:In a Ricean environment, the performance of Polarization Multiplexed system is significantly superior to that of Spatial MultiplexingIn Rayleigh channel, the coding gain of 4-D TCM in PM system is still larger than that in SM system

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M0072: Coded Polarization Diversity Aspects (II)

Application of dual-polarized antennas in conjunction with spatial multiplexing and space-time coding

Investigation on the performance of an hybrid transmission system:

two dual-polarized transmit antennas one dual-polarized receive antenna at both ends of the system

In a high LOS environment, the performance of Spatial Multiplexing-Space Time Block Coding with dual-polarized antennas is greatly superior to that with uni-polarized ones.

Indeed, the cochannel interference from other terminals is extremely high when uni-polarized antennas are deployed

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M0072: Channel Estimation & Synchronization

Kalman filter based algorithms have been investigated as one of the most serious candidate for channel estimation and synchronization.

The performance of the Kalman equaliser algorithms through DSP have been assessed by reproducing real working conditions

Channel equaliser with adaptive capability. Two solutions are possible: LMS for channel estimation and Kalman filter working like equaliser, or Kalman filter used for channel parameter estimation and transversal filter for channel equalisation with tap coefficients obtained from Kalman filter outputsOther possibilities: requirement of training sequences to estimate channel parameters, or use of blind equalisers.

Detailed analysis of the programming issues and computational requirements, for different Kalman filtering alternatives

Analysis of the implementation aspects related to the IF and RF subsystems in the laboratory prototype

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Experimentation setup

Experimentation setup used to test the baseband signal processing algorithms

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Conclusions of Milestone 0072…

The report analyzed various aspects of possible advanced signal processing solutions able to either significantly increase the throughput of the wireless access system, or to improve bit error rate performance with respect to more common solutions

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… toward Deliverable D15

“Report on required adaptations of radio interface and on baseband signal processing”

Due by M18 (end of April 2005)Based on the material collected in Milestone 0072

WHICH WAY TOWARD D15?WHICH WAY TOWARD D15?

Do we want to suggest modifications to the IEEE 802.16-SC radio interface?

proposals must be supported by the demonstration of their effectiveness with respect to the standard specifications

We have to provide consistent comparisons with different transmission systems (i.e. modulations and coding schemes, algorithms for the adaptability of the transmission schemes, bit rates, channelizations, synchronization and channel estimation algorithms etc...)

we need to select one, or more, “reference operating scenarios”

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D15: Common Parameters (I)

QoS values for different service requirements: can we refer to the document IEEE 802.16.1- Functional Requirements, issued in 1999?

BER = 10e-6, for most applications

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D15: Common Parameters (II)

It may be preferable to show BER performance as a function of the Eb/No ratio

Eb is the energy per uncoded bit

unless SNR is an essential parameter.

Other common parameters are selected for each “reference scenario”

NOTE: Milestone 0081-“Determination of Signal Processing Techniques for MIMO Communications” due at the same time of D15. Can we include M0081 within D15?

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First Reference Scenario

Fixed Users' Antenna & Very High Bit Rates

Slow Doppler effect (just the HAP is in movement)

LOS propagation (Rice factors: 20 dB and 15 dB)

Services: Trunking and Non Time CriticalBER=10e-6 and BER=10e-8

Bit Rate = 120 Mbit/s (with channel coding)

Maximum Delay: 5 ms or N/A

High gain ground antenna

Channel bandwidths = 20, 25, 28 MHz

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Second Reference Scenario

Fixed Users' Antenna & Medium Bit Rates

Slow Doppler effect (just the HAP is in movement)

LOS propagation (Rice factors: 15 dB and 10 dB)

Services: Time Critical Packet Services and MPEG video

BER=10e-6 and BER=10e-11

Bit Rate = 32 Mbit/s and 8 Mbit/s (with channel coding)

Maximum Delay: 10 ms

High gain ground antenna

Channel bandwidths = 20, 25, 28 MHz

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Third Reference Scenario

Train Users' Antenna & High Bit Rates

High Doppler effect

LOS propagation (Rice factors: 20 dB and 15 dB)

Services: Trunking and Non Time Critical BER=10e-6 and BER=10e-8

Bit Rate = 120 Mbit/s (with channel coding)

Maximum Delay: 5 ms or N/A

Medium gain train antenna

Channel bandwidths = 20, 25, 28 MHz

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Fourth Reference Scenario

Train Users' Antenna & Medium Bit Rates

High Doppler effect

LOS propagation (Rice factors: 15 dB and 10 dB)

Services: Time Critical Packet Services and MPEG video

BER=10e-6 and BER=10e-11

Bit Rate = 32 Mbit/s and 8 Mbit/s (with channel coding)

Maximum Delay: 10 ms

Medium gain train antenna

Channel bandwidths = 20, 25, 28 MHz

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Document Properties

Document Title Status of WP2.3 “Radio Interface and Baseband signal Processing” Progress from Milestone 0072 to Deliverable D15

Document Number

Author (s) Emanuela Falletti, Marina Mondin

Date February 28, 2005

Participant (s) (short names) Polito

Workpackage(s) WP2.3

Total number of slides (including title and this slide)

Security level (PUB, RES, CON)

CON

Description / Abstract