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Banyan Switches are complex Crossover Switch es used in electrical or Optical Switch es. Like a Banyan tree's roots they crossover in complex patterns. Logical banyan switches are used in logic or signal pathways to crossover switching of signals onto new pathways. They can be mechanical MEMS , electrical or optical NLO . A Banyan Switch is one type of crossover switch. Their complexity depends on the topology of the individual switches in a switch matrix (how wide it is by how many 'plies' or layers of switches it takes), to implement your desired crossover logic. Typical crossover matrices follow the formula: an N×N Banyan switch uses (N/2) log2 N elements. Other formulas are used for differing number of crossover layers and scaling is possible, but becomes very large and complex with large NxN arrays. CAD and AI can be used to take the drudgery out of creating these designs. The switches are measured by how many stages, and how many up/down sorters and crosspoints. Switches often have buffers built-in to speed up switching speeds. A typical switch may have: # A 2x2 and 4x4 down sorter # Followed by an 8x8 up sorter # Followed by a 2x2 crosspoint Banyan Switch network This results in 3 level sorting for a 3 stage banyan network switch. A SIMPLE EXAMPLE Consider a 2x2 Banyan switch, which requires (2/2) log2 2 = 1 switching element. This switch takes two inputs, numbered 0 and 1, and two outputs, numbered 0 and 1. Every packet that comes in has a header that contains one bit letting you know what its destination is (either 0 or 1). If the switch reads the bit and it has value 0, it sends the packet to its higher output (which is 0 in this case), and to its lower output if the routing bit is one. By connecting these switching elements in series and parallel it is possible therefore, to route packets in more complicated ways depending on the routes you want to establish. FUTURE DIRECTIONS AND FURTHER INFORMATION The future is moving to larger arrays of inputs and outputs needed in a very small space. See Wafer Fabrication and VLA 's. See Optical Computer s, Crossover Switch es, Crossbar Switch es, Nonblocking Minimal Spanning Switch and signal switching. |
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