MIMO OFDM

MIMO-OFDM

OVERVIEW OF MIMO AND USE OF DIFFERENT TECHNIQUES TO IMPROVE WIRELESS COMMUNICATION

USING MIMO

By:

Darshan Patil, B.E Electronics and Telecommunications, LTCOE

Significance & Introduction of MIMO-OFDM

Ever-increasing demands in communication industry towards wireless

Challenges: - to improve spectral efficiency

- efficient bandwidth utilization

- economical Signal Processing algorithms - high speed processing h/w

Solution: MIMO-OFDMLaptop mimo antenna prototype

Problem statement:

To build a prototype of Next genx wireless WAN’s with MIMO-OFDM system using set of algorithms and techniques to analyze the performance and replicate it as a practical implementation through simulations.

Scope of the project

Coupling MIMO and OFDM concepts to improve data rates in downlink of wireless communication networks.

Analyzing the performance and building a prototype of Wireless WAN’S using MIMO-OFDM

Use of adaptive loading algorithms such as Chows and Compello’s.

Employing SVD (singular value decomposition) method to increase the performance incase of MIMO

Literature survey and R&D

1)MIMO concept overview

- Multiple i/p multiple o/p antenna array

- Used to increase data rates,

improve capacity and BER (bit error rate) of the system

- Typically used with ofdm so as to suit best needs in next genx comm. i.e. “4G”

Diagram of a MIMO wireless transmissionsystem.

2) OFDM concept overview

- Converts a frequency selective channel into a parallel collection of frequency flat sub channels

- Orthogonal frequency division multiplexing uses bandwidth efficiently

- Improves multipath fading issues

- Reduces the effect of ISI (inter-sub carrier interference)

OFDM System block Diagram

3) Adaptive algorithms and SVD method

good sub carriers with high channel power gain are made to carry more bits and/or be allocated with less transmission power, and vice versa for the weak sub carriers.

Two algorithms :-

1. Chows :

2. Campellos optimum discrete loading algorithm :

SVD: method used to overcome sub channel interference, to allocate transmitted Bit/Power through sub channels in an optimum manner.

Technologies needed

STTD (space time transmit diversity)

SM (spatial multiplexing)

AMC (adaptive modulation & coding) with modulation techniques such as QPSK, 16-QAM, 64-QAM

H-ARQ (Hybrid automatic repeat request)

Shared access and MAC (medium access control) used for scheduling packet access with Qos

Comparison of technologies

Antenna & types

Multibeam MIMO antenna with 3 beams/ sector and 3 sectors/cell

Full frequency Reuse concept across cells

Equipments

Modem TMS 320c6x digital signal processor

Power PCTM processor

MAC and controller kit

High end D/A converters

RF and power amplifiers

Turbo decoder IC

Implementation and simulation

Architectures1. Node B prototype hardware

architecture

2. UE prototype hardware architecture

Simulation results

Prototype is helpful in Indoor/indoor application rather than outdoor/indoor

RF channel replicators are used to create the correlation between outdoor/indoor and indoor/indoor

Project Activities

Survey, Implementation and performance analysis of existing MIMO

Learning s/w and h/w

Developing efficient algorithms

Software synchronization development

Various candidate coding and receiver strategies

Identification of Equipment

Implementation of prototype

Project Schedule

Conclusion

The results obtained from these tests indicate very good performance for the MIMO-OFDM prototype.

Concept is proving to be very robust in highly dispersive channels

Cost reduction is being investigated through various methods

Simulation results show that at any given BER the adaptive SISO system will be outperformed by the adaptive MIMO system

Other future work areas involve the improvement of MIMO processing complexity and practical implementation issues.

THANK YOU!!