What is WIFI MIMO technology and how does it benefit us?

In 1996, Greg Raleigh and Gerard J. Foschini further refined new approaches to MIMO technology, specifically exploring configurations where multiple antennas are placed on a single transmitter to enhance link throughput. However, Bell Labs pioneered the application of Spatial Multiplexing in a laboratory setting in 1998, demonstrating that Spatial Multiplexing is the primary technique for enhancing MIMO technology performance.

Basic configurations of MIMO technology:

- 2x2 MIMO (two transmitting antennas, two receiving antennas).

- 3x3 MIMO (three transmitting antennas, three receiving antennas).

- 4x4 MIMO (four transmitting antennas, four receiving antennas).

- 8x8 MIMO (eight transmitting antennas, eight receiving antennas).

2. How MIMO Technology Works

Previous Wifi technologies like SISO on a router only utilized a single antenna on the router to connect to a single antenna on the receiving device. Wi-Fi waves transmit and receive data packets through antennas.

In a MIMO technology system, signals are transmitted through multiple antennas on the same path and bandwidth. Therefore, each signal received by the receiving antenna will pass through a different path, making the data more reliable. The signal speed also increases due to the number of transmitting and receiving antennas. MIMO technology allows the use of more antennas on both devices to increase signal stability and transmission speed, overcoming the limitations of previous wifi technologies encountered with obstacles.

MIMO relies on three fundamental methods: Beamforming, Spatial Multiplexing, and Space-time coding. These methods are used individually or in combination to achieve efficiency such as lower transmit power, greater range, better noise immunity, or higher bandwidth.

• Spatial Multiplexing

In this method, high-speed signals are split into lower-speed signals (streams), and each stream is transmitted from a different antenna operating at the same center frequency. The number of receiving antennas must be equal to or greater than the number of transmitting antennas to decode each transmitted stream accurately.

• Space-time coding

This is a mechanism that allows multiple copies of data to be transmitted across multiple antennas. Furthermore, this method helps improve the reliability of data transmission with similar benefits achievable when using multiple antenna diversity reception. In Space-time coding, signals (data) are transformed into different versions of the same information and transmitted through multiple antennas.

Subsequently, the receiver combines all copies of the received signal (data) from different antennas in an optimal way to extract as much information as possible from each antenna. Space-time coding also enhances the receiver's ability to prevent signal interference. This method utilizes both spatial and temporal diversity to achieve significant improvement. Moreover, using multiple copies of signals compensates for channel issues such as fading and white noise.

• Beamforming

It is a method of creating a specific required antenna pattern at the transmitter with appropriate phase and gain weights so that the signal power at the receiver is maximized. Beamforming is achieved through intelligent antennas that can be organized into phased-array or adaptive systems.

3. Benefits and Limitations of MIMO Technology

• Benefits

The waiting time for data reception on each device is minimized. Additionally, MIMO WiFi allows continuous data transmission, sending data to multiple connected devices simultaneously. Enhancing user experience to a new level such as watching movies on a laptop while browsing the web on a phone.

MIMO technology helps mitigate fading effects, reducing bit error rate (BER). MIMO algorithms transmit signals outward through two or more antennas, and information is also received through multiple antennas. Additionally, MIMO provides precise power levels compared to conventional single-antenna RF systems, along with enhanced reliability in transmission.

• Limitations:

The main drawback of this technology lies in its complexity. Resource requirements and hardware complexity are higher compared to single-antenna systems. Each antenna requires separate RF units to handle wireless signals. Moreover, advanced DSP chips are necessary to run advanced mathematical signal processing algorithms.

Furthermore, hardware resources increase power demands. Specifically, batteries will deplete faster due to processing complex and deep signal algorithms. This reduces the battery life of MIMO-based devices. On the other hand, MIMO-based systems are more expensive than single-antenna systems due to the increased hardware and advanced software requirements.

4. Comparing SU-MIMO and MU-MIMO

MIMO technology comprises two main types: SU-MIMO and MU-MIMO. In SU-MIMO systems, data streams can only interact with one device on the network at a time. Therefore, MU-MIMO systems outperform SU-MIMO. SU stands for Single User, referring to one user, introduced in 2007 with the Wifi 802.11.n standard to enhance Wifi speed by allowing two wireless devices to transmit and receive data simultaneously. This technology enables a router to send and receive data to one device at the same time.

MU stands for Multiple User, this is the next generation of SU-MIMO introduced in 2015 to address the shortcomings of SU-MIMO. With the Wifi 802.11ac standard, it allows Wifi routers to interact with multiple devices simultaneously, minimizing the waiting time for each device, reducing signal wait time, and increasing network speed.

Issues arise with SU-MIMO when multiple users attempt to use the network simultaneously. If one person is uploading a video and another is attending a conference, the data stream will get congested, causing latency or skyrocketing delays. And MU-MIMO is developed to overcome the shortcomings of SU-MIMO as MU-MIMO has the advantage of streaming multiple data sets to multiple devices simultaneously.

5. Future and Applications of MIMO Technology

MIMO technology is used for Wi-Fi networks and long-term development technologies (LTE), specifically fourth-generation (4G) and fifth-generation (5G) wireless communication technologies, including in many markets such as politics, society, and entertainment. This technology is also used in wireless local area networks (WLANs) and supported by all wireless products with 802.11n.

This technology is utilized in various forms within most wireless communication devices and is increasingly spreading its influence with practical applications such as digital television (DTV), wireless local area networks (WLANs), mobile communications, and home networks...

Conclusion

MIMO technology is gradually becoming a key tool to improve all aspects of wireless communication. This technology plays a crucial role in 5G technology and is influencing how users interact with these technologies on a daily basis. What do you think about MIMO Wi-Fi technology? Will MIMO lead wireless technology in the future? Feel free to share your thoughts below!

Source: SSLA, TechTarget, ElectronicsNotes, and RFwireless.

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