Research activity on IMT- Advanced systems · 19. November 2010

Research activity on IMT- Advanced  systems

1. VTT Technical Research Centre of Finland

In IMT-Advanced research, VTT participated in the ITU-R spectrum demand calculation for IMT-Advanced in preparation for WRC-07. VTT participated in the development of several ITU-R Recommendations and Reports and authored five book chapters on the topic. VTT also participated in the definition of minimum requirements for IMT-Advanced at the ITU-R and the evaluation of the candidate IMT-Advanced technologies.

2. Center for TeleInfrastruktur (CTIF) at Aalborg University, Aalborg, Denmark

CTIF is strongly contributing to advancing state of the art and standardisation of LTE-Advanced and IMT-Advanced systems with research projects in the area of Flexible Spectrum Usage in Self-Organizing Networks; Cooperative Spectrum Sensing, Cognitive radio, Spectrum and Carrier Aggregation. Among others, CTIF has a secure cognitive network test bed (S-COGITO) able to showcase flexible spectrum usage on cellular networks towards the improvement of user experience and spectral efficiency.

In particular, for the area of spectrum and carrier aggregation, work is focused on the modeling and simulation aspects of these two enabling techniques for IMT-A and their integration with proposed frameworks for upper layers radio resource management strategies. Current work has proposed an integration of spectrum aggregation strategies with common radio resource management as specified for LTE and LTE-A for a scenario of non-contiguous bands for a single and multiple operators, with the objective of increasing the overall system throughput by a better user allocation in the shared band in consideration of the quality of service requirements of the user and the available system resources. In this context a novel multi-band scheduling strategy has been proposed that manages the balance between the data pipe and the obtained extra source of spectrum, and performs an optimized user scheduling. The radio allocation mechanism allocates the user packets to the available radio resources in order to satisfy the user requirements, and to ensure efficient packet transport to maximize spectral efficiency and is part of the overall set of radio resource management mechanisms. This enables the pooling of the resources together; while the integration allows for mapping of the service requirements onto an available spectrum amount and translates the latter into network load. The approach uses the widely separated frequency bands for achieving lower delays and jitters and higher user throughput by exploiting the channel diversity. These show independent Channel Quality Indicators (CQIs) over time and space, which becomes a source of diversity at the Physical (PHY) layer, allowing for opportunities for higher spectrum efficiency. Information from the network about the system state (e.g., received signal strength, transmitted power, user terminal velocity, etc) and used in RRM procedures such as load, admission and congestion control can successfully be combined with dynamic spectrum use and reduce the need of spectrum aggregation in some cases. Related current work is targeting novel spectrum-aware network discovery and mobility management strategies for IMT-A systems.

3.  Center for Wireless Systems (Copenhagen University College of Engineering,  Copenhagen, Denmark)

Quality of Service Estimation

4G communication uses LTE and Advanced LTE with foundation of OFDM to avoid ISI and achieve high spectral efficiency.  Security is main issue in these comprehensive wireless communication systems, which are subjected hostile environments. To avoid jamming, interference or interception and efficient spectrum usage, it is fundamental requirment to use cognitive approach. Actually, the backbone in this approach is to notch out  those channel/subchannels with low QoS parameters and hopping between the available good quality channels.

QoS in OFDM/ OFDMA where the subchannel have the same center frequency but different users use these subchannels. By using this technique, high data transmission rate is achieved among multiuser simultaneously. The basic modulation scheme such as BPSK, QPSK, etc., can be used. While using Phase Modulation schemes, EVM is the best parameter to measurement quality of service from which BER can be calculately easily. Depending on BER of the subchannel, it can decided to notch out for a specific time period to avoid antijamming attacks such as DoS.

Encryption at Physical Layer

Future 4G/5G wireless links are expected to move beyond Giga bit bandwidth making it difficult to encrypt/decrypt data in real-time at application layer or link layer of devices using their general purpose processing unit. Dedicated hardware for encryption/decryption is required.

Most wireless devices in 5-10 years will be based on cognitive radio technology for intelligent spectrum management. The central part of such radio is a high performance FPGA which is able to carry out the needed signal processing for, e.g., OFDM.

In this research we combine encryption/decryption with the radio physical layer signal processing and in this way use same FPGA for both at same time. This will save hardware and reduce the price and the approach is expected to save power as well. Standard FPGAs year 2010 are able to encrypt or decrypt 10 Giga bit per sec. or more with AES using 128 bit key.

4. Aalborg University (Radio Access Technology Section (RATE))

Aalborg University is performing research related to spectrum management and radio resource management for LTE –Advanced: two main topics are Carriers Aggregation (CA - and RRM for CA), and Autonomous Component Carrier Selection (ACCS):

 Under the CA topic, several challenges and techniques related to the utilization of multiple Component Carriers (CCs), are researched. This includes aspects of CC in different frequency bands and also paired and unpaired carriers.

ACCS is meant for unplanned deployment of Home eNB in Local Areas, where one or several operators can optimally assign and share spectrum among the autonomous Home eNB’s according to time varying interference and load conditions. 

 

Go to news list