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Synchronous multiple access procedure for use with an ultra wideband system Disclosure Number: IPCOM000017925D
Original Publication Date: 2001-Oct-01
Included in the Prior Art Database: 2003-Jul-23
Document File: 5 page(s) / 220K

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Karl-Heinz Moehrmann: AUTHOR


Channelising can be done by applying a relatively large time offset (many nanoseconds) to each impulse and using “pseudo-random noise” codes (PN codes) for distinguishing between channels. The system could then have virtually an unlimited number of channels.

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Synchronous multiple access pro-cedure for use with an ultra wide-band system

Idee: Karl-Heinz Moehrmann, München

Channelising can be done  by  applying  a  relativelylarge time offset (many nanoseconds) to each impulseand using “pseudo-random noise” codes (PN codes)for distinguishing  between  channels.  The  systemcould  then  have  virtually  an unlimited number ofchannels.

This virtually  unlimited  number  of  channels  may,however, not be of high practical importance sincethe  reach  of  an  ultra  wideband  (UWB)  system  isseverely limited by the necessary limitation of trans-mit power, in order not to unduly interfere with otherradio systems. This will very probably be a stringentregulatory  requirement.  Such  a limitation in reachand, therefore, of the area of the radio cell means, onthe other hand, that the number of users that is to beinterconnected within the cell is also limited.

Since UWB can only become a success if it can com-pete in cost  with  other  existing  radio  systems  likeWireless local are networks (WLAN), an UWB sys-tem should be as simple as possible.

Basically, a baseband UWB system according to theknown state-of-the-art can only  be  realised  in  anasynchronous manner, i.e. the phases of the transmitframes in the two directions are not correlated. Thereason is that in WLANs it is normally not feasible touse directional antennas because the location of theterminals  is  not  known  beforehand  and  may fre-quently, or even dynamically, change. Use of omnidi-rectional antennas causes, however, that (within cer-tain  limits)  any  station  can  hear  any  other  station.Any  transmission  from  a  terminal transceiver (TT)will interfere with transmissions from other TTs inany receiver in an undefined manner because of thelimited propagation  speed  of  the  electromagneticwave  (30  cm/ns,  which  means  that  a difference indistance of 30 m leads to a delay difference of 100ns!). Only the use of user specific codes (de facto avariant of Code Division Multiple Access [CDMA])according to the known state-of-the-art would allowseparation of the signals if omnidirectional antennaswere used.

It might, on the other hand, be interesting to imple-ment a   synchronised system  . Obviously this is notpossible with Time Division Multiplexing (TDM), asdescribed above. It could be done, however, if it werepossible  to  somehow  separate the upstream anddownstream channels in a point-to-multipoint systemwhere a base station (BS) is used to which all termi-nal transceivers TT of  the  users  are  connected  byUWB, and where all communication is running over

Siemens  Technik Report      Jahrgang 4  Nr.13      Oktober 2001

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the base station, even also that between topologicallyneighboured terminal transceivers. Then only the BScould hear the transmissions from the TTs, but notthe TTs themselves.

For separation of upstream and downstream signals,code  division®..