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A method to interconnect UTRA Basestations by using TDD systems as terrestrial link replacement Disclosure Number: IPCOM000018542D
Original Publication Date: 2002-Sep-01
Included in the Prior Art Database: 2003-Jul-23
Document File: 2 page(s) / 196K

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Michael Färber: AUTHOR


The deployment of Universal Mobile Telecommuni- cations System (UMTS) node B based on UMTS Terrestrial Radio Access (UTRA) technology re- quires the connection of node B to the RNC that serves a multitude of node B (figure 1). The physical connection is made by landlines or microwave con- nections. On top of this physical layer, a protocol is used to transmit user and control data (ATM or IP).

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A method to interconnect UTRABasestations by using TDD systemsas terrestrial link replacement

Idee: Michael Färber, München

The deployment of Universal Mobile Telecommuni-cations  System  (UMTS)  node  B  based  on UMTSTerrestrial Radio Access  (UTRA)  technology  re-quires  the  connection  of  node  B  to  the RNC thatserves a multitude of node B (figure 1). The physicalconnection is made by landlines or microwave con-nections. On top of this physical layer, a protocol isused to transmit user and control data (ATM or IP).

Fig. 1: Block diagram of an UTRAN

A problem of the UTRA deployment is, that a highnode B density (referred to densities known of sys-tems today, e.g. GSM) is needed for a high qualitycoverage. Typical cell radius for UMTS range be-tween  200m  and  5km,  where  for  a GSM systemranges up to 35km are possible. Therefore the de-ployment of UTRA systems requires more node Bsites, which have to be connected to a RNC. How-ever, the  physical  layer  properties,  especially  theneeded bandwidth is usually not provided by twistedpair telephone lines. The installation of new lines orthe use of microwave equipment is cost intensive andrequires  a  lot  of  administrative work.  It  requiresmicrowave spectrum, permissions for the set up ofantennas or for new wiring in third parties real es-tates.

The operator can use transmission capacities he isalready licensed for in order to circumvent the costand  complexity  of  such solutions. UTRA containstwo parts of spectrum, suitable for the multiple ac-cess schemes Frequency Division Duplex (FDD) andTime division Duplex (TDD). The limited spectrumavailable  for  TDD  (usually  TDD  spectrum  is  lessthan FDD spectrum), the TDD terminal availabilityand the fact, that in multi mode FDD/TDD terminalequipment the TX peak power capability is ruled bythe FDD needs are reasons for the intention to useTDD in later deployment phases.

The  above  mentioned  problems  can be solved byusing  the  licensed  UTRA  spectrum  for connectingnode B to RNC. To establish this connection a TDD

system at the location of the FDD BTS is used as aremote station (figure  2).  This  allows  a  capacityhandling via the remote TDD Base Transceiver Sys-tem (BTS) higher than for a usual TDD MS. The twoTDD elements can be connected by using directionalantennas. The TX power is very low also for con-necting  far  distant  TDD  elements.  Interference toother TDD connections is limited by the use of highgain antennas. Further the use of directional antennasand the reduced power limits the impact on adjacentFDD spectrum. In case of line of sight connections,preferably without obstructing the first Freznelzone,multipath effects are significantly re...