1.0 Introduction
Without any doubt MIMO techniques count to the few emerging key technologies for wireless communications. The number of yearly publications in this area is tremendous and meanwhile it is almost impossible to keep an overview about the numerous proposed algorithms. Moreover, the number of research teams worldwide is astonishingly high. For example, only in Europe more than 100 scientific and industrial organizations are performing serious research in multiple antenna techniques.
Interestingly, although multiple antenna techniques are so auspicious,no relevant breakthrough in terms of highly successful MIMO products has been observed yet. Intuitive simple reasons are high MIMO complexity as well as critical cost issues When trying to push the promising MIMO theory towards practice. Taking both reasons into account requires that algorithm testing has to be performed on a very flexible and modular MIMO hardware platform where significant insights with the respect to cost issues can be obtained in parallel.
This goal can be briefly denoted by rapid MIMO prototyping and is the aim of this contribution to shed some light on this topic and related challenges In section 2 general considerations about MIMO platforms will be given in a Consecutive way. Section 3 highlights a universal rapid prototyping methodology, Needed to achieve quick and meaningful results and required to avoid common pitfalls. The final section covers a typical design example and discusses the essential Hardware components from a more fundamental point of view.
1.1 General Consideration About Mimo Plate
IMO platforms for current and future wireless communication can be characterized by a large number of different properties like:
- Environment (indoor/ outdoor)
- Wireless standard
- Carrier frequency
- Bandwidth
- Sapling frequency
- Measurement device, demonstrator, prototype
- Real time, off-line
- Number of antennas
- With or without feedback
- Single or multiple users
- Type of modulation
- Basic algorithms
- Achievable data rates
Modularity, not all of the listed items can be served satisfactory. Hence, in order to Figure out the relevant properties of such flexible scalable and modular platform, some A-priori thoughts are given in the following. An easy decision can be made regarding the wireless environment of the Experiments: while indoor systems can be even for a small organization or University Tested in reality: significant investigations in outdoor scenarios require a more expensive Mobile equipment. in the following we will primarily focus on indoor scenarios.
1.2 Types of Mimo
1) Mimo
involves Space Time Transmit Diversity (STTD), Spatial Multiplexing (SM) and Uplink Collaborative MIMO.
2) Space Time Transmit Diversity (STTD)
The same data is coded and transmitted through different antennas, which effectively doubles the power in the channel. This improves Signal Noise Ratio (SNR) for cell edge performance.
3) Spatial Multiplexing (SM)
The “Secret Sauce” of MIMO. SM delivers parallel streams of data to CPE by exploiting multi-path. It can double (2×2 MIMO) or quadruple (4×4) capacity and throughput. SM gives higher capacity when RF conditions are favorable and users are closer to the BTS.
4) Uplink Collaborative Mimo Link
Leverages conventional single Power Amplifier (PA) at device. Two devices can collaboratively ransmit on the same sub-channel which can also double uplink
1.3 How Mimo Work
- MIMO takes advantage of multi-path.
- MIMO uses multiple antennas to send multiple parallel signals (from transmitter).
- In an urban environment, these signals will bounce off trees, buildings, etc. And continue on their way to their destination (the receiver) but in different directions.
- “Multi-path” occurs when the different signals arrive at the receiver at various times.
- With MIMO, the receiving end uses an algorithm or special signal processing to sort out the multiple signals to produce one signal that has the originally transmitted data. Multiple data streams transmitted in a single channel at the same time Multiple radios collect multipath signals Delivers simultaneous speed, coverage, and reliability improvements
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