User's Guide Part 1

PureWave Quantum 6600 User Guide v2.1
Page 23
2.3.2.3 Smart Antenna Capabilities
Beamforming is a technique that combines and focuses signals to and from multiple antennas to
improve both downlink and uplink performance. On the uplink, the Base Station combines signals
received on its multiple antennas, resulting in substantial link budget gains that improve range and
throughput. Maximum Ratio Combining (MRC) and Minimum Mean-Square Error (MMSE) are basic
techniques from which more sophisticated uplink processing techniques (such as interference
mitigation) are built.
On the downlink (Base Station to Subscriber Station), sophisticated digital signal processing algorithms
exploit information gathered during the uplink beamforming process to concentrate the transmitted RF
energy from the antenna array to the exact subscriber stations locations, improving gain, efficiency and
signal to noise ratio (SNR), resulting in greater range and throughput.
MIMO Matrix A utilizes a technique called space-time coding (STC), which exploits the spatial diversity
of the channel to improve downlink performance. By improving data reception, it can increase range
and maximize the utilization of available sector capacity.
MIMO Matrix B utilizes a technique called spatial multiplexing (SM), in which multiple streams of data
are simultaneously transmitted through multiple antennas and effectively separated by the receiving
device. This technique can actually increase the spectral efficiency and, hence, the capacity of a system.
The effectiveness of MIMO relies upon the spatial diversity inherent within the channel as well as other
factors, and therefore a given technique may be more appropriate for certain users or deployments.
Fortunately, PureWave Quantum Base Stations make these decisions automatically, maximizing the
efficiency of your valuable spectrum.
Cyclic Delay Diversity (CDD) is a technique employed by PureWave Quantum Base stations to allow the
power of multiple antennas to be combined in transmitting a single stream of data even when MIMO or
beamforming cannot be supported (e.g., when transmitting the MAP).