tailieunhanh - CDMA truy cập và chuyển mạch P4

Code Division Switching In this chapter we present and analyze the switching architecture of the exchange node for switched CDMA networks. As we have discussed in the previous chapter, in such a network CDMA traffic channels will be routed by the exchange node from any input to any output link. If we consider a traditional switching approach, the exchange node can be implemented as shown in Figure . | CDMA Access and Switching For Terrestrial and Satellite Networks Diakoumis Gerakoulis Evaggelos Geraniotis Copyright 2001 John Wiley Sons Ltd ISBNs 0-471-49184-5 Hardback 0-470-84169-9 Electronic 4 Code Division Switching Overview In this chapter we present and analyze the switching architecture of the exchange node for switched CDMA networks. As we have discussed in the previnus chapter in such a network CDMA traffic channels will be routed by the exchange node from any input to any output link. If we consider a traditional switchingapproach the exchaneg node can be implemented as shown in Figure . In this case we assume that Time Multiplexed Switching TMS is le l to provide tee switch fnnctions. As sliowu. after tee despreadingoperation all CDMA user channels are time multiplexed then routed to the destination output port by the TMS demultiplexed spread again and then combined for the output CDMA channel. The TMS approach however introduces additional complexities b ecause the switch input and output ports require time multiplexing while the incoming and outgoing signal is based on code multiplexing. In traditional switching methods such as time slot interchangers or space switching traffic channels are time multiplexed in each input or output port. Also the complexity for a strictly nonblocking TMS switch far ffi is isij r i. leant. This means that in applications such as SS CDMA where the available power and mass at the satellite are limited TMS may not be an efficient switching approach. Therefore we propose an alternative switchingmethod which is based on code division. That is the signals in the switch are distinguished and routed according to their spreadingcodes. This method is directly applicable in all switched CDMA networks such as SS CDMA BS CDMA or CS CDMA. In this chapter we provide illustrative Code Division Switch CDS architectures performance and complexity evaluation analysis and comparisons with traditional switchingmethods. As shown the