MIMO technology (Multiple Input Multiple Output) is not new, but it hits the market that at the end of the first decade of the 2000s due to a very complex implementation. MIMO aims to carry multiple streams in parallel on different antennas but using the same frequency. [Read more…] about What is MIMO (Multiple Input Multiple Output)?

Random Access, which is to issue a completely random time, relies on the Aloha method. The latter takes its name from an experiment performed on a network connecting the various islands of the Hawaiian Archipelago early 1970. In this method, when a coupler has information to transmit, it sends it without worry about other users. If there is a collision, that is to say superposition of two signals or more users, the signals become indecipherable and are lost. They are subsequently transmitted, as shown in Figure, in which the couplers 1, 2 and 3 collide. The coupler 1 transmits its field first because he shot the smallest timer. Then, the module 2 emits, and its signals collide with the coupler 1. Both derive a random time of retransmission. The coupler 3 is listening while the couplers 1 and 2 are silent, so that the frame of the coupler 3 passes successfully. Technical aloha is the origin of all the random access methods. [Read more…] about Random Access Methods in Computer Networks

SONET/SDH standard was carry telephone speech, and it took many adaptations for the transport of frames and type of IP packets, ATM, or others. The successor of SONET/SDH has been launched in early 2002 and standardized by ITU-T as the OTN (Optical Transport Network). Its role is to channel packages on routes to 2,5, 10 and 40 Gbit/s. The corresponding recommendation G.709 carries the number. [Read more…] about What is OTN (Optical Transport Network) ?

SDH recommendation was standardized by ITU-T (G.707 and G.708): [Read more…] about What is Synchronous Digital Hierarchy (SDH)?

To achieve simultaneous multiplexing multiple telephone lyrics on the same circuit, Americans have adopted a standard for multiplexing 24 channels of 64 kbit/s on a support at 1544 Kbit / s. This channel is called DS-1. Europeans have responded to this technique by the E-1 channel multiplexing 30 voice channels on a support 2048 Mbit/s. From this basic multiplexing, a hierarchy has been defined, it is a multiple of the base channel, as in the case of Europe, or a little more complex, as in the US case, because an area of supervision rate-dependent. [Read more…] about What is Plesiochronous media?

In the 1970s, the Department of Defense, or DOD (Department Of Defense), decided before the proliferation of machines using different, incompatible communication protocols, to define its own architecture. This architecture, called TCP / IP, is the source of the Internet. It is also adopted by many private networks, called intranets. [Read more…] about TCP/IP Architecture

CRC (cyclical redundancy checking) is a rather sophisticated error checking routine used to assure that two communicating computers are really getting the correct data. There are a whole bunch of these error correction and checking methods out there, but they all have pretty much the same objective: making sure that no data is lost or misinterpreted when two computers are exchanging information over the phone lines (through a modem, of course).