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MIMO OFDM Testbed

The combination of MIMO systems with OFDM has emerged as a dominant physical layer technology in recent years. It has been adopted by different wireless standards all over the world including IEEE 802.11n (WLANs), IEEE 802.16e-2005 (WiMAX) and 3rd Generation Partnership Project’s (3GGP) Long Term Evolution (LTE). Renzym has been actively involved not only in developing communication related products but also it is also offering communication system design services and trainings. We have taken this initiative to pursue research in MIMO-OFDM technology in collaboration with different universities.

SCOPE OF RESEARCH
The aim of research is to develop a flexible, real-time MIMO-OFDM testbed for research and rapid prototyping of wireless systems. Key research areas of focus are
  • MIMO-OFDM physical layer research with main emphasis on developing efficient and robust MIMO detection, channel estimation and synchronization algorithms.
  • Development of a GNU radio based integrated SDR framework, for both PHY and MAC, to enable rapid prototyping of MIMO-OFDM systems and network experimentations in real-time.
  • Cross-layer designs for co-operative MIMO communication and link adaptation etc.
Highlights
  • A 2×2 MIMO-OFDM Testbed implemented using USRP N210
  • Software Defined Radio (SDR) based design approach
  • GNU Radio based software framework and Ettus USRP1 and N210 platform
  • GNU Radio based software framework and Ettus USRP1 and N210 platform
  • Modified N210’s RTL to incorporate compute-intensive part of MIMO receiver on FPGA
  • MIMO synchronization and channel estimation algorithms
  • MIMO Detection
1
A 2x2 MIMO-OFDM Testbed implemented using USRP N210
2
Software Defined Radio (SDR) based design approach
3
GNU Radio based software framework and Ettus USRP1 and N210 platform
4
Modified N210’s RTL to incorporate compute-intensive part of MIMO receiver on FPGA
5
MIMO synchronization and channel estimation algorithms
6
MIMO Detection

Applications

MIMO-OFDM has been selected for supporting various wireless systems like IEEE 802.11n (WLANs), IEEE 802.16e-2005 (WiMAX) and 3rd Generation Partnership Project’s (3GGP) Long Term Evolution (LTE). Using our reference implementation of integrated PHY and MAC frameworks and prototyping capabilities of MIMO testbed, researchers can rapidly develop prototypes for these wireless networks. Specifically some of its applications are
  • Prototyping of Customer Premises Equipment (CPE) for WiMAX, User Equipment (UE) for LTE and WLAN cards for IEEE 802.11a/g/n etc after the addition of other components as per respective standard requirements.
  • Network analyzers and scanners for WiMAX and LTE Networks for optimization and fine tuning to ensure efficient network performance.
  • Furthermore it can be also used for integrated experimentation and performance evaluation of PHY and MAC layer protocols for future industry standards.
Software defined radio based approach makes MIMO testbed an ideal candidate for undergraduate and graduate labs to enable real-time communication system design.
  • Students can readily build real-time communication systems by directly applying the concepts learnt in the theory classes without requiring any hardware expertise. In addition, they can compare the theoretical performance of various techniques studied in the class with their performance in a practical environment. Such blending of theory and related practical issues is generally missing from most of the communication courses.
  • It also allows researchers working on MIMO systems to quickly experiment and test their algorithms in real-time environment with a minimum of programming effort. Most of the academic research is based on a set of assumptions that might not hold in practical sceneries. MIMO testbed provides a unique opportunity to the researchers working on algorithm development to verify their design in various practical scenarios.
  • Multi-antenna capability is also very useful in cognitive radio research where different antennas can be used to perform certain tasks simultaneously. For example one antenna can perform spectrum sensing/scanning while others can be used for communication. Furthermore wide range of spectrum can be covered for using different RF transceiver cards for different antennas.

Development Phase

The overall development of MIMO-OFDM testbed will be completed in two phases. In the first phase a low-scale 2×2 MIMO-OFDM prototype for the indoor environment will be developed. Prototype hardware will consist of USRP boards with XCVR2450 dual band, 2.4 GHz and 5 GHz, RF-transceiver cards. Furthermore a MIMO-OFDM software framework with integrated MAC and PHY support will also be will be a key outcome of this phase. This phase is expected to be completed in August 2010.

In the 2nd phase a full-scale real-time 4×4 MIMO-OFDM testbed that can process bandwidth up to 20 MHz will be developed. Currently Renzym is developing a custom 4×4 MIMO testbed hardware that will be used as target platform for this final phase. This fully functional 4×4 MIMO testbed will provide an ideal platform for research and rapid prototyping of wireless networks like WiMAX, WLAN, LTE etc.

The main idea behind this two phased approach is to concentrate on the development of robust and efficient algorithms in the first phase which is near completion now. In the 2nd phase the main emphasis will be on the efficient software/hardware partitioning and optimization of the implementation related issues so that 20 MHz bandwidth can be processed and without compromising the ease of implementation.

MIMO-OFDM SDR Framework

The overall development of MIMO-OFDM testbed will be completed in two phases. In the first phase a low-scale 2×2 MIMO-OFDM prototype for the indoor environment will be developed. Prototype hardware will consist of USRP boards with XCVR2450 dual band, 2.4 GHz and 5 GHz, RF-transceiver cards. Furthermore a MIMO-OFDM software framework with integrated MAC and PHY support will also be will be a key outcome of this phase. This phase is expected to be completed in August 2010.

In the 2nd phase a full-scale real-time 4×4 MIMO-OFDM testbed that can process bandwidth up to 20 MHz will be developed. Currently Renzym is developing a custom 4×4 MIMO testbed hardware that will be used as target platform for this final phase. This fully functional 4×4 MIMO testbed will provide an ideal platform for research and rapid prototyping of wireless networks like WiMAX, WLAN, LTE etc.

The main idea behind this two phased approach is to concentrate on the development of robust and efficient algorithms in the first phase which is near completion now. In the 2nd phase the main emphasis will be on the efficient software/hardware partitioning and optimization of the implementation related issues so that 20 MHz bandwidth can be processed and without compromising the ease of implementation.

Testbed Specifications

Specifications
Antenna Configurations (Tx × Rx)
PHY Design
MAC Protocol
Transmission Bandwidth
Processing Platform
RF Frequency Band
Operating Environment
Data Interfaces
Applications
Values
2 × 2, 2 x 1, 1 x 2
MIMO-OFDM
CSMA (CA)
Up to 2 MHz
FPGA + GPP
Dual ISM Band (2.4 and 5.8 GHz)
Indoor
Ethernet, USB 2.0
WLAN, WiMAX, LTE etc (Scale down versions)

MIMO Implementation’s Block Diagram

Testbed HW & GNU Radio SW

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