What is Multiple Input Multiple Output (MIMO) ?

Multiple Input Multiple Output (MIMO) technologies that provide next-generation wireless communications products with the throughput, range and reliability to enable mobile wireless applications in the home, at the office and on the road.

MIMObility™ and 802.11n

Ralink patented MIMObility™ technology supports up to 300Mbps PHY and robust connections at extended range while mitigating dead spots. With MIMObility™, Wi-Fi applications can be extended from traditional PC networking to a wide range of digital multimedia and handheld devices including cell phones, PDAs, cameras, print servers, HDTV and video game players. On the path to draft 802.11n, Ralink chipsets will integrate multiple channels on a single die, with 2T3R mode for a very high level of RF integration on-chip. Customers can anticipate six times the coverage for the same throughput when compared to legacy 802.11a/b/g implementations.


MIMO XR™ (eXtended Range) employs multiple techniques – including frame aggregation, packet bursting and maximum ratio combining (MIMO-MRC) – to dramatically increase the throughput and range of wireless networking products. Our current maximum-ratio-combining (MRC) solutions deliver sustained high throughput to mitigate indoor multi-path, cost-effectively, while ensuring compatibility with legacy devices. Ralink partners are choosing MIMO XR™ for its field-proven range expansion, throughput performance, reliability and value for wireless networking applications. Ralink offers a draft 802.11n product utilizing MIMO technology, with plans for 802.11a and g enhancements.

Understanding MRC-OFDM

Understanding MRC-OFDM: a first step in MIMO technology
The market for wireless LANs, particularly in the consumer and small business segments, has grown significantly in recent years. By all accounts, annual growth in wireless LAN device shipments has increased from threefold to fivefold since 2001. With huge opportunities for wireless LANs looming in home entertainment, Voice over IP (VoIP), and public access, the biggest market growth may yet lie ahead. Next generation wireless LANs will include new technology to enable these exciting applications.
Market adoption of wireless LANs has been spurred by the growing popularity of the broadband access in the home. Twenty-nine percent of North American households connected to the Internet using broadband connections in 2004, up from 19 percent in 2003. Networks can be found in 8.8 percent of US households, and these tend to be dominated by homes with multiple PCs and broadband access to the Internet. Access to music, video and online gaming becomes possible when the network can interface seamlessly with entertainment centers, laptops, and handheld devices. The wireless medium is ideal for these applications, but today's wireless LANs need improved performance to meet the challenge.
The typical user experiences three basic qualities of a wireless connection: speed, range and reliability. Prior to the development of MIMO-OFDM, the three parameters were interrelated according to strict rules. Speed could be increased only by sacrificing range and reliability; while range could be extended only at the expense of speed and reliability. And reliability could be improved by reducing speed and range. MIMO OFDM has redefined the tradeoffs, clearly demonstrating that it can boost all three parameters simultaneously. While MIMO will ultimately benefit every major wireless industry including mobile telephone, the wireless LAN industry is leading the way in exploiting MIMO innovations.

Multiple Input/Multiple Output (MIMO) is an area of intense development in the wireless industry because it delivers profound gains in range, throughput and reliability. As a result, manufacturers of wireless local area network (WLAN), wireless metropolitan area network (WMAN), and mobile phone equipment are embracing MIMO technology.
This White Paper describes how MIMO-OFDM (Multiple Input Multiple Output-
Orthogonal Frequency Division Multiplexing) technology delivers significant performance improvements for wireless LANs, enabling them to serve existing applications more cost-effectively as well as making new, more demanding applications possible. It also explains how manufacturers and end-users can benefit by deploying MIMO-OFDM products today without sacrificing compatibility with the popular 802.11a and 802.11g standards.