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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z [NUMBER ENTRIES]

MAN (Metropolitan Local Area Network)

Although some definitions of terms as LAN, MAN, and WAN, depend on the geographical area covered by the network, we prefer a definition that also takes into account the technology used.  In general, a MAN (Metropolitan Area Network) covers a geographical area between a city and a campus.  MAN technologies have some overlap with WAN technologies--specifically, some WAN technologies sometimes also function as MAN technologies.  One distinguishing feature is that MAN technologies typically provide access to many points within a city, whereas WAN technologies are more likely to be point-to-point.  In that respect, the defining characteristic of a MAN is in how it is used, more so than what technology it consists of.  802.16 and 802.20 are two potential MAN technologies, although ATM and SONET are also sometimes used to create a MAN.

Megahertz

"MHz" 1-million Hertz which is the same as 1-million cycles per second. The unit of signal frequency is the "Hertz", where 1 Hz = 1 frequency cycle per second. 1000 Hertz is referred to as a "kilohertz" (kHz) and commercial AM radio broadcast stations operate in the range of 550 to 1600 kHz. 1,000,000 Hertz is referred to as a "megahertz" (MHz) and FM broadcast radio stations operate in the range of 88 to 108 MHz. When you get to 1-billion Hertz you may hear it called "one thousand megahertz" or, more correctly, "one GigaHertz" (GHz). The generally accepted, correct way to write the three abbreviations is, "kHz", "MHz", and "GHz". There is no accepted reason why the Greek prefix receives a lower-case letter for "kHz", but is written with an upper-case letter for "MHz" and "GHz".

Mesh Router / Mesh Routing Implementation
A mesh router, in the context of Wi-Fi, is an 802.11 device that creates a series of connections between other mesh routers to form a "cloud" of connectivity. The individual mesh routers operate in a manner very similar to an 802.11 access point except they only connect to each other, and not to client computers directly. Some 802.11 access points support a "repeater mode" which is very similar to Wi-Fi mesh routing. An 802.11 repeater receives data on one channel and retransmits it on another channel. There is no intelligence in the forwarding process, much like a legacy Ethernet simple repeating hub in a wired network. The mesh router, on the other hand, uses a logical routing algorithm to determine where a particular data packet should be sent. This is similar to the way an Ethernet Layer 2 switch operates in a wired network. The purpose for using mesh routing (or 802.11 repeaters, for that matter) is to extend the size of an area of interconnected devices without having to physically run Ethernet cables. You may want to read the encyclopedia entry for Wireless Distribution System (WDS) to compare and contrast WDS with mesh routing. These two technologies are described in very similar terms and, although they are fundamentally different, they're sometimes confused with each other.
	Consider the wireless mesh routing diagram to the left. Entering the mesh from the left are a wired Ethernet client device and an 802.11 wireless client. Note that the wireless client is actually coming in to the mesh in exactly the same way as the wired client. The wired client is Ethernet-attached to Mesh Router A (perhaps through a switch) and the wireless client is coming through the Access Point which is also Ethernet-attached to Mesh Router A. Data is forwarded through the mesh (perhaps from A, to B, to C) and ultimately reaches the file server or other end-device (perhaps a router is the actual target; it doesn't matter). We'll assume that Mesh Router E is out of the RF range of Mesh Router B. Consequently, transmissions from B don't compete with transmissions from E.

MHz

"Megahertz" 1-million Hertz which is the same as 1-million cycles per second. The unit of signal frequency is the "Hertz", where 1 Hz = 1 frequency cycle per second. 1000 Hertz is referred to as a "kilohertz" (kHz) and commercial AM radio broadcast stations operate in the range of 550 to 1600 kHz. 1,000,000 Hertz is referred to as a "megahertz" (MHz) and FM broadcast radio stations operate in the range of 88 to 108 MHz. When you get to 1-billion Hertz you may hear it called "one thousand megahertz" or, more correctly, "one GigaHertz" (GHz). The generally accepted, correct way to write the three abbreviations is, "kHz", "MHz", and "GHz". There is no accepted reason why the Greek prefix receives a lower-case letter for "kHz", but is written with an upper-case letter for "MHz" and "GHz".

MIMO (Multiple Input / Multiple Output)

Basically, the definition of MIMO is that it's the method for transmitting wireless data at high bit rates and is the mechanism used to achieve 100 Mbps throughput rates in the 802.11n standard. MIMO technology divides a higher-rate data stream into multiple lower-rate data streams. In essence, the information is sent using two or more sets of antennas. Unlike conventional radio signaling where multipath transmissions cause degradation, MIMO is able to utilize multiple paths to carry more information, hence increasing the effective throughput. Using complex signal-processing techniques, each of the lower-rate streams is then transmitted on the same channel, but through a different transmit antenna. On the receiving end, MIMO can take advantage of something that is normally the enemy of wireless networks: multipath propagation. Multipath is basically the way in which RF (radio frequency) signals bounce off walls, ceilings, and other obstructions and then arrive with different amounts of delay at the receiver. MIMO technology is able to process and recombine these multiple RF signals using complex algorithms.

MOS (Mean Opinion Score)

The Mean Opinion Score (MOS), in voice communications, is a value that provides a numerical measure of the quality of human speech at the receiving end of a voice circuit. The MOS uses subjective tests that are then averaged to obtain a particular MOS value. This value was originally created as a way to evaluate the quality of analog telephone lines. A panel of listeners rates the quality of test sentences read over the circuit by both male and female speakers. The listener then rates the quality on a scale of 1-5 as follows:

MOS is a subjective measurement, as opposed to the ITU E-Model's "R value" which provides a quantitative measurement of circuit quality. See Converting MOS to R-Values for an explanation of how these two metrics relate to each other.