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MIMAX is a European Union funded project in the 7th Framework Programme. It deals with the extension of 802.11a with multiple-inputs multiple-outputs (MIMO) features using an innovative signal combining approach in the RF front-end. This transceiver is able to exploit full spatial diversity at lower system sizes, power consumption and complexity compared to state-of-the-art approaches.
Contents
1 Overview
2 Methodology
3 Technical developments
4 Wireless and mobile services
5 Internal links
6 External links
//
Overview
MIMAX is a European Union funded project within the 7th Framework Programme that develops smart radio access susing smart antenna systems in wireless short-range communication networks. Because mobile wireless communication represents a rapidly growing market segment, existing network infrastructures are not able to tackle the increased amount of data and users in the near future. Therefore, innovative and novel concepts to overcome these limits are needed. In this context, MIMAX develops a smart MIMO transceiver in state-of-the-art silicon technologies that allows a significant improvement concerning the relation between performance at the one hand and power consumption and costs at the other hand.
Methodology
MIMAX uses a coherent signal combining concept of smart antennas in the RF front-end. This means that significant parts of the spatial code is already applied at the analogue front-end and that synergies of subsystems in the upconversion and downconversion paths of the transmitter and receiver can be used.
Bexcause spatial and temporal en- and decoder are now operating separately from each other, the base band signal processing has to adapt the properties of the analogue spatial processing. RF impairments and lower quantization demands for new algorithms in the MIMO communication scheme.
This concept applies to several wireless technologies and the benefits are mainly determined by economic factors rather than technical limitations. The current focus of MIMAX lies on enhancing WLAN 802.11a with MIMO schemes but still guaranteeing backward compatibility to existing devices. Using MIMAX in this WiFi standard, better quality of services in the links can be expected.
Technical developments
RF front-end
Single-input single-output (SISO) transceiver use a single transmit and receive antenna for communication. For example, in a SISO receiver the incoming signal are received and demodulated by a single antenna and one receive paths. Several concepts can be used in this receuve paths, e.g. super-heterodyne or homodyne techniques. After demodulation, the received symbols are further processed by the digita? base band. Because only a single antenna is available, no spatial processing can be performed and, therefore, no spatial diversity or spatial multiplexing can be obtained.
The conventional MIMO approach for full-diversity and full-multiplexing gain uses multiple antennas at the transmitter and the receiver, respectively. Hence, MIMO systems consist of as many parallel operating SISO radios as antennas are available at the transmitter or the receiver. Each air interfaces receives incoming signals and demodulates the RF signal. The digital base band performs a spatial and temporal processing of all parallel operating SISO air interfaces.
MIMAX trades off both concepts by shifting spatial processing to the analogue RF front-end. This means that multiple antennas are used at the transmitter and the receiver but only a single upconversion or downconversion path is implemented in the wireless radio. The spatial signal processing is performed in the air interface by means of analogue weighting circuitry that weights each antenna signal with a complex number. This allows adjusting signal strength and phase delay of each antenna idependently and exploting the spatial diversity of the antenna array. However, the digital base band has to determined the spatial code applied in the analogue front-end.
Base band signal processing
The MIMO RF front-end needs new algorithms to exploit the available spatial diversity of the 802.11a communication schemes. Several challenges occur due to the analogue spatial processing. First the impairments of the RF front-end impact the maximum quantization of the spatial code and therefore, the MIMO algorithms must operate reliably and robustly with respect to this limited resolution. Moreover, these algorithms must determine and select the weights for each antenna under different communication situations and channel conditions. Different optimisation goals are used when determining the weights for the transmission.
As a result of the WLAN...(and so on)

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