How MIMO Changed Signal Transmission
Wireless communications has been around for a century, and for much of that time, engineers have labored to
overcome the nastiness of multipath interference. If you count yourself among the pre-cable generation, you've
experienced multipath video interference, manifested in ghosted images on your TV screen. If you're younger,
your multipath experience might include dropped cell-phone calls or dropped data packets on your company's
Wi-Fi network.
Multipath occurs when signals reflect off solid objects, resulting in multiple instances of a transmitted radio wave
arriving at a receiver at slightly different times. These signals can cancel each other out, but more often the
effects are more subtle. A number of technologies have been developed to mitigate multipath, but none
represented a breakthrough--until MIMO.
In the mid-1990s, Greg Raleigh and, V.K. Jones were exploring the vagaries of wireless communications at
Stanford University when they discovered a way to turn multipath on its head. As if in some parallel world where
up is down and strikes are balls, they discovered that multipath isn't bad. In fact, if your goal is to transmit lots of
data over a wireless network at maximum distance, multipath is good. In a discipline defined by Shannon's Law,
the mathematical rule governing channel capacity, the rules suddenly changed.
The discovery came to be known as MIMO, short for multiple-input, multiple-output. Rather than using a single
radio, MIMO uses multiple transmitters and receivers on the same channel, thereby increasing channel capacity
proportionally. Spatial multiplexing was born, aided by advances in digital signal processing.
Raleigh and Jones commercialized MIMO at Airgo Networks and began selling their chipsets to home wireless
router manufacturers, which had grown wary of product returns from customers who couldn't get a good signal.
Airgo's technology solved those problems and boosted performance.
REFERENCES
Research article 1
Studies the pixelated wireless optical channel, which transmits data at high rates using a series of coded
time-varying images.
Research article 2
Investigates MIMO technology on high data density barcodes that can be easily
photographed and decoded by mobile phones.
Wireless communications has been around for a century, and for much of that time, engineers have labored to
overcome the nastiness of multipath interference. If you count yourself among the pre-cable generation, you've
experienced multipath video interference, manifested in ghosted images on your TV screen. If you're younger,
your multipath experience might include dropped cell-phone calls or dropped data packets on your company's
Wi-Fi network.
Multipath occurs when signals reflect off solid objects, resulting in multiple instances of a transmitted radio wave
arriving at a receiver at slightly different times. These signals can cancel each other out, but more often the
effects are more subtle. A number of technologies have been developed to mitigate multipath, but none
represented a breakthrough--until MIMO.
In the mid-1990s, Greg Raleigh and, V.K. Jones were exploring the vagaries of wireless communications at
Stanford University when they discovered a way to turn multipath on its head. As if in some parallel world where
up is down and strikes are balls, they discovered that multipath isn't bad. In fact, if your goal is to transmit lots of
data over a wireless network at maximum distance, multipath is good. In a discipline defined by Shannon's Law,
the mathematical rule governing channel capacity, the rules suddenly changed.
The discovery came to be known as MIMO, short for multiple-input, multiple-output. Rather than using a single
radio, MIMO uses multiple transmitters and receivers on the same channel, thereby increasing channel capacity
proportionally. Spatial multiplexing was born, aided by advances in digital signal processing.
Raleigh and Jones commercialized MIMO at Airgo Networks and began selling their chipsets to home wireless
router manufacturers, which had grown wary of product returns from customers who couldn't get a good signal.
Airgo's technology solved those problems and boosted performance.
REFERENCES
Research article 1
Studies the pixelated wireless optical channel, which transmits data at high rates using a series of coded
time-varying images.
Research article 2
Investigates MIMO technology on high data density barcodes that can be easily
photographed and decoded by mobile phones.
| MIMO (Multiple In, Multiple Out) What is MIMO? MIMO is a technique using multiple receivers and transmitters on wireless devices to improve performance. By using 2 transmitters and 2 receivers two data streams are produced simultaneously which doubles the data rate and increase the distance allowed between devices. |
