112) INTERN/\'I‘IONAI. .-\l’l’LICA'l"IUN PUBLISHED UNDER THE PA'l'l:'.NT COOPERATION TREATY {I-'CT)
`
`CORRECTED VERSION
`
`(19) World Intellectual Property
`Organization
`International Bureau
`
`(43) International Publication Date
`20 March 2003 (20.03.2003)
`
`
`
`(51) International Patent Classification’:
`12366, IIt}4B "H00, 10112, ll04Q "N24
`
`H04L 121123,
`
`(21) International Application Ntunber:
`PC'l'.-’Sl32002.-’00 1 S09
`
`(22) International Filing Date: 21 August 3002 (21.08.3002)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`[English
`
`English
`
`(30) Priority Data:
`0102978-4
`
`7 September 2001 (07.09.3001)
`
`SE
`
`(74)
`
`(81)
`
`(71) Applicant (for all designated States except US}: TELIA
`AB (puhl) |SlL’Sti|; Mzirbackagatan 1|. S-I23 so Farsla
`(Slit
`
`(84)
`
`(72) Inventors; and
`SCHUH, Ralf
`(T5)
`lnventorsmpplicants [for US rmty):
`ISEISEI; Slora Raby Byaviig 23, S-224 78 Lund (S13).
`SUNDBERG, Erland [Slit‘Sl£j', lloglunclaviigen 15, S-136
`
`(54) Title: AN lNTlERl"AC}€ FOR LOCAI. AREA N]:"l'W()[~‘.KS
`
`I||||||||||l|ll||||l|l||||||||||||||||||I||||||||l||||||||l||||||||l|J|||||ll|l|l||||||||||||
`
`(10) International Publication Number
`
`WO 2003/024027 A1
`
`54 llaninge (SE). VERRI, Berti] ISEISE]; Murslevsgtiind
`1, S-137 38 Viislcrhaningc (SE). ARKNER,
`'l'omm_v
`[SIi:’S1'i]; Mussemngfingcn 39, S I35 34 Tyrcsii (SE1.
`
`Agent: S\"ENSS()N, Peder; Telia Research AB. Vitsands-
`gatan 9, S-123 86 l-‘arsta (S15).
`
`1)cs.'tgnated States (mni.-mm‘): Ali, AG, A1,, AM, AT, AU,
`AZ, BA, BB, BG, BR. BY, BZ. CA, Cl 1, CN, CO, CR, CU,
`C37,, DE, DK, DM, DZ, EC. 1313, HS, 171, GB, GD, G13, (311,
`GM, ll'R, llU, ll), 11., IN. IS,Jl’, KE, KG, KP, KR, LC,
`LK, l.R, LS. LT, [.11.
`l.\-", MA, Ml), MG, MK, MN, MW,
`MX, M2, NO, NZ, OM, PH, PL, [’1‘, RO, RU, 81), S15, SG,
`SI, SK, SL, '1']. TM, TN, '['R._ ’l”[‘. '12, UA, UU, US, UZ,
`VN. YU. ZA, ZM, ZW.
`
`Designated States (regtotial): ARIPO patent (Gil. GM.
`KE, LS, MW, MZ, SD, SL, SZ,
`'12, UG, ZM, ZW},
`Eurasian patent (AM. AZ. BY. KG, KZ, MI), RU, TJ. TM}.
`liuropean patent {i'\’l‘, Bli, BC}, Cl-l, CY, (31, D15, DK. 1115,
`155, 1*], FR, GB, GR, 115, IT. LU, MC. NL, PT, Sli, SK,
`TR"), OAPI patent (BF. BJ. CF. CG, CI. CM. GA. GN. GQ,
`GW, ML, MR, Nli, SN, TD, TG).
`
`," Corttirtued on next page,’
`
`
`
`___________----..-_-.__---..-.-...-../
`
`
`
`
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`03/024027A1||||||||||||||||l||||||||||||||||||||||||||||||||||||||||||||||||||l||||||||||||||||||||l
`
`3 (57) Abstract: An integrated digital and analogue Radio Frequency (RF) interface (100) for transmitting combined digital and ana-
`logue RF signals over fibre based Local Area Networks (1../\NJ. The RF signals are ledfrcccivecl toflrom optical ltansceivcr(s} ( 102)
`0 over a separate electrical R1’ port (104). The digital and analogue R1’ signals are distributed over fibre cable (1 181. The architecture
`itself is transparent to the transmission of R17 signals. The interface is integrated within LAN equipment, e.g.
`lillliernel or l7|)l)I
`3
`switch, and allows the distribution of the signals to different buildings or locations within a building.
`
`
`
`I
`
`Apple 1019
`Apple 1019
`U.S. Pat. 7,535,890
`U.S. Pat. 7,535,890
`
`

`
`WO 2003/024027 A1
`
`||||||||||||||||I|||||||||lllll||||l||||Ill|||||||||||||l||||||||||||||||l|||||l|||||||||I||
`
`Published:
`— with irirentariorml ward: repon
`
`(48) Date of publication of this corrected version:
`22 /\pn'I 2004
`
`(15) Information about Corrlaclion:
`See PCT Gaifltillrd Nu.
`|7fl[304 (W33 April 3004, Seclion ll
`
`Pbr two-Ietrer ::ade.\‘ and other abbrew'm‘.l'am‘. refer {G the "Guid-
`once Notex on Cod1:.s' andzibbrexwiariorts"appearing at the begin-
`nfng ofeach regm'ar issue ofthe PCT Gmlzerre.
`
`II
`II
`
`

`
`W0 2003;"024027
`
`PCTlSE 2002![II] 1509
`
`AN INTERFACE FOR LOCAL AREA NETWORKS
`
`1
`
`FIELD OF THE INVENTION
`
`The present invention relates in general
`
`to distribution of
`
`radio signals between terminals and Base Stations, Bss, via
`
`Local Area Networks, LAN, more particular to an interface
`
`that can handle combined digital and analogue Radio
`
`RF,
`
`signals for transmission over fibre based
`
`Frequency,
`LANS .
`
`10
`
`BACKGROUND
`
`Passive and active Distributed Antenna Systems
`
`(DAS) using
`
`coax or optical fibre are currently often used for Global
`
`I
`indoor coverage.
`System for Mobile communications (GSM)
`These DASs are using a separate fibre — coax architecture
`
`15
`
`to the e.g. digital Local Area Network (LAN) architecture.
`
`Multiple infrastructures are adding up in the price and
`
`increase the operation and maintenance cost.
`
`20
`
`GSM~on«the~Net uses the existing LAN architecture by
`
`connecting pico base stations to the LAN. The radio signal
`
`is distributed digitally in such a radio LAN architecture.
`
`For GSM—on—the—Net a special gateway is needed in order to
`
`ensure security from the intranet to the public network-
`
`25
`
`The number of transceiver units in a pico base station is
`
`currently limited to a maximum of two transceivers.
`
`Moreover, GSM—on—the—Net cannot make use of trunking
`
`efficiency.
`
`30
`
`35
`
`In buildings there are often many different cabling systems
`
`deployed,
`
`for supporting different applications:
`
`I
`
`For LANs, Ethernet and Fibre Distributed DATA Interface
`
`(FDDI)
`
`the dominant digital transmission standards are
`
`IEEE 803.3 Gigabit-Ethernet Standard and ANSI XBT12
`
`FDDI Standard which are defined for Category 5 cable.
`
`copper twisted pair,
`
`CAT5 ;
`
`fibre and coax cabling.
`
`
`
`

`
`W0 20lJ3ffl2-I027
`
`PCT.-"S E2ll02;"0fI 1 509
`
`antennas.
`
`In the European patent application EP 792 048, “Point-
`
`routeur multiprotocoles poure réseaux indudtriels”,
`
`inventor J Alexandre,
`
`is described a system for
`
`transmitting signals having different protocols on the same
`
`optical fibre. One embodiment can distribute analogue and
`
`digital signals, modulated on different bearer waves on the
`
`same optical fibre.
`
`10
`
`SUMMARY OF_ THE INVENTION
`
`The present invention relates to a common digital and radio
`
`signals distribution architecture using standard Local Area
`
`Network (LAN) architecture and equipment for distributing
`
`15
`
`the radio signals to remote antennas.
`
`The present invention is using a common interface for the
`
`digital and radio signal distribution. This interface can
`
`solve multiple infrastructure problems by distributing
`
`radio signals {e.g. GSM, UMTS} between a Base Transceiver
`station (BTS) and its remote antennas over the fibre based
`
`LAN infrastructure. The interface is integrated in the LAN
`
`equipments (e.g. Ethernet switch or Ethernet coax to fibre
`
`media converter). Fibre in general offers a huge bandwidth
`
`and can accommodate both the digital and radio signal
`
`20
`
`25
`
`transmission.
`
`The present invention uses an integrated digital and
`
`analogue Radio Frequency (RF)
`
`interface for transmitting
`
`30
`
`combined digital and analogue RF signals over fibre based
`
`LANS.
`
`The RF signals are fed/received to/from optical
`
`transceiveris) over a separate electrical RF port. The
`
`digital and analogue RF signals are distributed over the
`
`fibre—cable LAN architecture.
`
`Radio cell architecture can
`
`35
`
`be built—up by connecting antennas to the electrical RF
`
`ports at the LAN equipment. The architecture itself is
`
`
`
`

`
`W0 20|]3.I'l]2-I|]2'."
`
`PCTJ'SE2l|02:'0fl1509
`
`3
`
`transparent to the transmission of RF signals.
`
`The present invention uses existing LAN architecture
`
`{cabling and devices), which enables low cost radio signal
`
`distribution e.g. for Distributed Antenna Systems
`
`(DASS)
`
`in
`
`buildings. The digital and radio signals are separated in
`
`the frequency domain or can be separated in the space
`
`domain by using different transceiver units in the LAN
`
`equipment or fibres in the cable. The present invention is
`
`a Distribution of Radio Signals using Local Area Network
`
`Infrastructure {DoRSuLANI) here called the interface.
`
`One advantage by using this interface is that no gateways
`
`to the public network is needed, e.g. if compared with GSM—
`
`on—the—Net, because the radio and digital signals can be
`
`separated in the frequency domain or in the space domain by
`
`using different transceiver units in the LAN equipment. The
`
`interface can also make use of trunking efficiency as the
`
`Base Station (BS) can be centralized.
`
`Multiple infrastructures with separate cabling and access
`
`points, e.g. fibre based LAN and passive coax DAS, are not
`
`needed. The invention allows a single cabling
`
`infrastructure with common access points.
`
`The invention allows reduced installation, deployment and
`
`operation and maintenance (DAM) costs. The LAN can be
`
`public or private.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`A more complete appreciation of the present invention and
`
`many of the attendant advantages thereof will be readily
`
`obtained as the same becomes better understood by reference
`
`to the following detailed description when considered in
`
`35
`
`connection with the accompanying drawings, wherein:
`
`Figure l shows an overview of the interface,
`
`
`
`

`
`W0 2003;"024027
`
`PC T;"SE2{|02;'00 I 509
`
`4
`
`Figure 2 shows a FDDI backbone network with interfaces,
`
`that allow distribution of the digital and radio signal to
`
`different buildings,
`
`Figure 3 shows a typical Ethernet LAN architecture within a
`
`building,
`
`Figure 4 shows measurement set—up for the combined
`
`simultaneous digital—radio transmission using standard
`
`Gigabit Ethernet components,
`
`Figure 5 shows intermodulation attenuation for GSM and
`
`10
`
`interfering CW signal transmission over the fibre link,
`
`Figure 6 shows BER versus received RF power for the GSM
`
`1800 signal, measured with TEMS,
`
`Figure.7 shows BER versus received optical power for 1
`
`Gbit/sec data transmission (PRES = 23-1), for back—to—back
`
`15
`
`and 600 meter M fibre,
`
`Figure 8 shows a link budget calculation for typical GSM
`
`in—building,
`
`Figure 9 shows a set—up using the interface with 4
`
`antennas ,
`
`20
`
`Figure 10 shows path loss versus distance,
`
`Figure 11 shows second setwup for figure 9,
`
`Figure 12 shows third set—up for figure 9, and
`
`Figure 13 shows fourth set—up for figure 9.
`
`25
`
`DETAILED DESCRIPTION
`
`The following abbreviations are used:
`
`BER
`
`BS
`
`BTS
`
`Bit Error Rate
`
`Base Station
`
`Base Transceiver station.
`
`30
`
`CATS
`
`Category 5 cable, copper twisted pair
`
`CPU
`
`DAS
`
`DR
`
`Central Processing Unit
`
`Distributed Antenna System
`
`Dynamic Range
`
`DWDM
`
`Dense Wavelength Division Multiplexing
`
`35
`
`FDDI
`
`Fibre Distributed DATA Interface
`
`FTTS
`
`Fibre—to~the~Subscriber
`
`
`
`

`
`W0 2{}03;’02-I027
`
`PCT!SE2lllJ2!'001509
`
`5
`
`GSM
`
`IM
`
`LAN
`
`MAN
`
`o1o1oa1 system for Mobile communications
`
`Intermodulation Distortion
`
`Local Area Network
`
`Metropolitan Area Networks
`
`5 M
`
`Mu1ti—mode fibre
`
`OAM
`
`PRBS
`
`RF
`
`TEMS
`
`Operation and Maintenance
`
`Pseudorandom Bit Sequence
`
`Radio Frequency
`
`Test Mobile Station
`
`10
`
`TEX
`
`Transceiver
`
`VCSEL
`
`Vertical Cavity Surface Emitting Laser
`
`WAN
`
`WDM
`
`Wide Area Network
`
`Wavelength Division Multiplexing
`
`15 Referring now to the drawings, wherein like reference
`
`numerical designate identical or corresponding parts
`
`throughout the several views.
`
`Fig.
`
`1 shows an overview of interface 100, an optical
`
`20
`
`interface, for the integrated digital and radio signal
`
`transmission. There can be one or more interfaces 100
`
`within the LAN equipment, each interface connected to at
`
`least one standard optical unit 106, e.g. standard optical
`
`connectors to an optical fibre cable 118. There can be more
`
`25
`
`than one cable 118. The cable 118 is containing optical
`
`fibrets), which distributes signals to LAN equipment at
`
`different locations or the same location, e.g. within a
`
`building or a campus area, see Fig.
`
`2 and Fig. 3. Each
`
`interface 100 has at least one common/integrated — standard
`
`30
`
`optical transceiver unit
`
`(TRXJ
`
`102.
`
`The radio signals can
`
`be fed/received to/from the optical units 106 over an
`
`external electrical RF port 104.
`
`In order to combine and or
`
`split the radio signals to more than one antenna or feed
`
`into more than one optical TRx 102 {star architecture)
`
`35
`
`external radio signal splitterts)/combiner{s} can be used.
`
`The RF port 104 is connected to a radio unit 112 over
`
`
`
`

`
`W0 2|]03;'()2402'?
`
`PCT.*'SE2002{0l|l5lI9
`
`6
`
`signal path 120, e.g. with coax cable. The radio signal
`
`path could be a direct connection to the optical
`
`transceiver unit 102 but could also contain some radio
`
`frequency specific processing like: filters, amplifiers,
`
`splitters and combiners, duplexer, etc. In general
`
`the
`
`interface 100 is transparent if no radio mode specific
`
`filters, amplifiers, etc, are used in radio unit 112. If
`
`simultaneous digital and radio signal transmission is used
`
`over a single transceiver unit 102, a splitter 108 and
`
`10
`
`signal combiners 110 are needed in order to separate the
`
`digital and radio signal. The splitter and combiner may
`
`need filters in order to prevent signal distortion from the
`
`digital into the radio band and vice versa.
`
`15
`
`The base stationls} (BS5)
`
`(e.g. for GSM/UMTS) or the remote
`
`antenna unit(s) are connected over coax cables to the
`
`electrical RF In/Output port(s) 104. The interface 100 is
`
`in general transparent to the digital and radio signal
`
`transmission within the bandwidth of the optical link.
`
`20
`
`Low bit rate data transmission for alarm and controlling
`
`function between the base station and the connected LAN
`
`equipment may be utilised over:
`
`I The 104 interfaceis}
`
`0 Separate digital interface which could connect directly
`
`25
`
`to the motherboard of the LAN equipment
`
`A digital interface 116 connects the LAN cards {Gigabit
`
`Ethernet card or the interface card 100)
`
`to the
`
`motherboard, back plane, of the LAN Central Processing Unit
`
`30
`
`(CPU), e.g.
`
`switch, hub, router,
`
`etc. The motherboard is
`
`normally fulfilling tasks like: controlling of the LAN
`
`cards, encryption, addressing, digital signal processing,
`
`etc. For the radio signal the alarming and controlling
`
`function in case of failure could be implemented processed
`
`35
`
`in the motherboard-
`
`
`
`

`
`W0 2003.-"02-|02';‘
`
`PC T!S E2 002;’00 1509
`
`Fig. 2 shows a FDDI backbone network 200 with interface 100
`
`that allows distribution of the digital and radio signal to
`
`different buildings A, B, and C that are connected via an
`
`FDDI ring 222. The interface 100 is integrated in the FDDI
`
`equipment 202 and 218. Unit 202 can be a FDDI switch or
`
`router. In the Fig.2 the switch 202 is a router that is
`
`connected to a public Wide Area Network (WAN) 212 over a
`
`firewall 206. The unit 218 could be an FDDI switch, router
`
`or concentrator.
`
`In building A radio base station 204 RF
`
`output signal is fed into the interface card 100 located in
`
`the FDD router 202. After the electrical to optical
`
`conversion in the interface{s) 100 the radio signal is,
`
`together with the digital signal,
`
`transmitted to the
`
`different buildings A, B, and C in the campus area. For
`
`clarity only one interface 100 is shown at each FDDI
`
`device, however,
`
`for each point—to—point connection of two
`
`FDDI devices a separate interface 100 is needed.
`
`10
`
`15
`
`20
`
`Within the buildings A, B, and C the radio signal can be in
`
`general further distributed, as shown in Fig. 3, using e.g.
`
`an Ethernet fibre architecture. The Ethernet switch/router
`
`208 in building A is connected to the radio base station
`
`over an interface 100 in the FDDI equipment 202.
`
`25
`
`In building B the FDDI concentrator 218 is connected to
`
`application servers 210 and to remote antennas 220 over the
`
`interface(s) 100. More than one antenna can be connected to
`
`one interface 100 by using either external or internal
`
`30
`
`splitter/combiner.
`
`In Building C computers 216 and remote antennas are
`
`connected to the FDDI equipment, where similar to building
`
`B the interfacefs) 100 RF port(s) 104 is used to connect to
`
`35
`
`the antennas.
`
`
`
`

`
`WO 2003302402?
`
`PCTlSE20l]2!I]{}1509
`
`8
`
`The interface 100 in general is applicable to any LAN
`
`architecture, e.g. a mixture of Ethernet, Token Ring and
`
`FDDI, when deploying fibre for the data transmission.
`
`Fig.
`
`3 shows an example of the interface 100 within an
`
`Ethernet infrastructure, see also Fig. 2 building A.
`
`We assume full duplex mode for the fibre Ethernet
`
`architecture, one fibre for transmit and one fibre for
`
`receive.
`
`10
`
`The Ethernet switch 208 in location A.l is connected
`
`over the FDDI router 202 to the radio base station but
`
`could be in general directly connected to the radio
`
`base station 204 over coax cable. If the Ethernet
`
`15
`
`devices are equipped with interfaceis} 100 the radio
`
`signal can be distributed within the building to
`
`different locations A.1 and A.2. The digital and radio
`
`signals may use:
`
`0
`
`I
`
`20
`
`the same fibre and optical transceiver unit 102,
`
`the same fibre and different optical transceiver
`
`units 102, e.g. use Wavelength Division Multiplexing
`
`{WDM} with optical filters, or
`
`I
`
`separate fibres and separate transceiver units.
`
`25
`
`Location A.l comprising a firewall 206, which is
`
`connected to Internet
`
`(WWW) 312,
`
`the base station {BS}
`
`204, e.g. GSM/UMTS, connected to the GSM network 214
`
`another Ethernet switch 208, another application
`
`server 210, and computers 216.
`
`In location A.l one of
`
`the computers 216 is connected to the interface 100 in
`
`the Ethernet switch 208. The interface 100 at the
`
`stationary terminal could be,
`
`e.g-
`
`an external fibre-
`
`to~coax media converter box. Different mobiles 308,
`
`which are connected to the base station over the
`
`remote antennas, are indicated in the figure.
`
`30
`
`35
`
`
`
`

`
`W0 20|]3.I'l]2-I|]2'."
`
`PCTfSE2tI02;‘0fl1509
`
`9
`
`If the computers 216 intend to send radio signals they
`are connected to the interface 100 in the Ethernet
`
`switches 208 otherwise the computers 216 are connected
`
`direct to the Ethernet switches 208. A portable laptop
`
`304 is physically connected to a mobile terminal 308.
`
`such as GSM/UMTS terminal, which in its turn is in
`
`contact with the base station 204 via the concentrator
`
`202.
`
`10
`
`The Ethernet equipment 208 in location A.2 is
`
`connected to the Ethernet equipment 208 in location
`
`A.l over the interface 100. The Ethernet switch in
`
`location A.2 connects further to a
`
`repeater/router/switch 314 in location A.3 over
`
`15
`
`interfaces 100 at both locations. The
`
`repeater/router/switch 314 in location A.3 connects to
`
`a stationary IP telephone 302, and a stationary
`
`computer 216 (in radio mobiles are often called
`
`terminals!). Remote antennas are connected to the
`
`20
`
`interfaces 100 in location A.2 and A.3
`
`The interface 100 could in general support multiple
`
`radio systems over a single interface 100 if the radio
`
`systems work at different frequencies, e.g. GSM
`
`operating at 1.8 GHZ and UMTS operating at 2 GHz.
`
`25
`
`Depending on the radio system,
`
`remote antenna network
`
`system,
`
`number of antennas, cell size,
`
`environment,
`
`etc the radio signal may need external amplifiers,
`
`filters and combiners for the radio uplink and
`
`30
`
`downlink between the interface 100 and the remote
`
`antennas.
`
`The interface I00 can be built in different ways:
`
`I The interface 100 has more than one optical transceiver
`
`35
`
`unit 102. One TRx unit 102 could be used for the digital
`
`transmission and one for the radio transmission. Two
`
`
`
`

`
`W0 2{}03;’02-1027
`
`PC1YSE2u02flNH509
`
`10
`
`optical TRx units may be built in for redundancy
`
`purposes.
`
`- Each optical TRX unit 102 has its own Rx and Tx optical
`
`output for the transmit and receive paths although only
`
`one optical fibre may be used as the signal can be split
`
`and combined in the optical domain using wavelength
`
`division multiplexing technology.
`
`In general
`
`the interface 100 is similar to a standard
`
`10
`
`digital LAN equipment card (e.g. Gigabit Ethernet card),
`
`which can be plugged in to the motherboard of the LAN
`
`switch/router (e.g. Gigabit Ethernet switch). It is also
`
`possible to integrate the interface 100 in external LAN
`
`media converters (optical—to—electrical converter).
`
`In Fig.
`
`15-
`
`3 like in Fig.
`
`2 only one interface 100 is shown at each
`
`Ethernet equipment, for clarity, although for every point-
`
`to—point connection between Ethernet devices a separate
`
`interface card 100 is needed.
`
`20
`
`Some processing of the radio signal can be implemented in
`
`the-radio unit 112 {e.g. filtering, amplification, etc}.
`
`This radio signal processing could be done at RF or at an
`
`intermediate frequency. If it is done at an intermediate
`
`frequency up— and down converters are needed. The radio
`
`25
`
`signal could be sent at an intermediate frequency over the
`
`fibre network, using e.g.
`
`frequency down converter at the
`
`LAN interface 100 connected to the base station and
`
`frequency up converters at the interfaces 100 connecting to
`
`the remote antenna units. At intermediate frequencies the
`
`30
`
`radio signal experiences less loss in the optical link. In
`
`the US patent 6,157,810, J. B. Georges and D. M. Cutrer,
`
`“Distribution of radio—frequency signals through low
`
`bandwidth infrastructures”, an intermediate frequency is
`
`used to distribute radio signals between the base station
`
`35
`
`and remote antennas.
`
`
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`

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`The RF signal uses an input and output radio frequency port
`
`104.
`
`It could also be just a single RF connector and the
`
`transmit/receive signal could be split in the radio signal
`
`path 120 using radio duplexers.
`
`Another example where the interface 100 may be of future
`
`interest are Ethernet based Metropolitan Area Networks
`
`(MANS). Ethernet based MANS show a growing popularity.
`
`Similar to Fig.
`
`2 an Ethernet based Fibre—to~the~Subscriber
`
`10
`
`(FTTS} architecture can be used to distribute radio
`
`signals, e.g.
`
`to individual houses/buildings A, B, and C,
`
`using the interface 100.
`
`A set—up according to Fig. 4 has been used for showing
`
`15
`
`.how the interface works.
`
`The interface has been made
`
`using standard Gigabit Ethernet LAN equipment. Penalty
`
`free simultaneous GSM—l80D and l Gbit/s digital data
`
`transmission are established over the same optical
`
`link in the set—up in Fig. 4.
`
`In the Gigabit Ethernet,
`
`when using multi—mode fibres,
`
`fiibre lengths up to 550
`
`meters may be used. This is the minimum operational
`
`range requirement for operation at short wavelengths
`
`of 850 nm. Multi—mode fibre, although having higher
`
`losses and dispersion compared to single—mode fibre,
`
`allows the use of potential cheap optical transceiver
`
`units. The interface in general can be used for any
`
`type of fibre,
`
`laser and radio system. However,
`
`the
`
`multi—mode fibre in combination with Vertical Cavity
`
`Surface Emitting Laser {VCSEL) and the simultaneous
`
`digital — radio transmission puts the highest
`
`constraints on the interface link budget. For all the
`
`other types of lasers and fibres, as recommended in
`
`the LAN standards,
`
`the link performance can be
`
`expected to be better for such fibre lengths.
`
`20
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`25
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`30
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`35
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`A transmission from GSM—l80O and 1 Gigabit/s digital data
`
`over a single optical link using 600 meters MM fibre has
`
`been used. From the maximum input power,
`
`loss and noise,
`
`Fig. 7, of the fibre radio system a link budget calculation
`
`has been done for a typical GSM in—building system
`
`considering cell—size per antenna and radio path loss for
`
`different indoor environments. The fibre radio system like
`
`used in the set—up showed to have sufficient dynamic range
`
`for typical GSM in—building distributed antenna systems
`
`10
`
`even in the case if more than one carrier is send over the
`
`link.
`
`In the set—up, Fig. 4, a low—cost commercially available
`
`un—cooled 850 nm VCSEL and PIN photodiode with preamplifier
`
`15
`
`‘are used, e.g. Mitel 1A4.48 SC—2A, acme SC—2A. These-
`
`components are designed for Gigabit Ethernet applications.
`
`The MT length is 600 m in order to comply with the minimum
`
`range requirements in the lOO0Base—SX Gigabit Ethernet
`
`recommendations. The MF is Corning’s Infinicor 600 multi-
`
`mode 50/125 Um fibre designed for Gigabit Ethernet
`
`transmission, 600 m at 850 nm using laser sources. The 1
`
`Gigabit/S non—return—to—zero pseudorandom bit sequence
`
`signal, PRES = 2” H 1, Anritsu MP 1604B, and the GSM radio
`
`signal operating at 1800 MHZ,
`
`Ericsson RES 2202, are
`
`combined using a 5 dB power combiner operating from DC — 2
`
`GHZ. The bias current of 10 mA and the combined digital,
`
`‘Km = 0.3 V, and radio signal,'fim =
`
`0.4 V, are fed to the
`
`VCSEL using a bias tee.
`
`After transmission through the fibre the signals are split
`
`into a digital and radio path. The bit error rate (BER) of
`
`the digital signal was measured after low pass filtering
`
`and amplification using a bit error test set, Anritsu MP
`
`1605B. The data transmission speed of 1 Gbit/s was chosen
`
`as the available low pass filters had a cut—off frequency
`
`of about 1 GHZ. At the transmitter site it was necessary to
`
`20
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`25
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`30
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`35
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`limit the output spectrum of the digital signal entering
`
`the GSM band, and at the receiver site to limit the GSM
`
`signal to enter the broadband receiver of the bit error
`
`test set.
`
`5
`
`0
`
`The BER of the radio signal was measured with an
`
`Ericsson test mobile station {TEMSJ for GSM. The
`
`circulator separated the radio downlink and uplink path.
`
`The remote antenna would be normally connected to the
`
`circulator output as indicated in the figure.
`
`10
`
`The following characteristics have been measured in order
`
`to quantify the optical link for the combined analogue —
`
`digital transmission:
`
`0 Fibre link parameters
`
`15
`
`I
`
`Intermodulation attenuation
`
`0 Blocking characteristics
`
`0 BER for the digital and analogue transmission
`
`From these parameters the dynamic range of the optical link
`
`20
`
`is calculated. The dynamic range is then compared with
`
`dynamic range requirements measured at typical indoor GSM
`
`Distributed Antenna System (DAS)
`
`installations.
`
`For the used fibre link the following RF parameters have
`
`25 been measured:
`
`0
`
`0
`
`The 1 dB compression point is at ~5dBm RF input power to
`
`the laser
`
`RF loss of ~ 25dB at 1.8GHz, e.g. for GSM, and 29dB at
`
`~2 GHZ, e.g. for UMTS, for 600 metre MM fibre
`
`30
`
`0 Output noise power at optical receiver ~ —14ldBm/Hz (for
`
`200 kHz BW this corresponds to ~ —88dBm)
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`The laser was biased at 10 mA which corresponded to a laser
`
`output power of ~—lD dBm. The optical attenuation is < 2.5
`
`dB at X = 850 nm.
`
`The intermodulation attenuation of the link is measured by
`
`applying a GSM signal and an interfering CW signal at 30dB
`
`below the power level of the wanted signal
`
`(GSM 05.05
`
`paragraph 4.7.2. reference [GSM specification GSM 05.051}.
`
`This measurement is relevant for the downlink as the non-
`
`10
`
`linear elements in the transmitter path cause distortion if
`
`more than one RF channel is transmitted. The standard -
`
`requires the IMD product not to exceed —70dBc or —36dBm
`
`whichever is the higher.
`
`15
`
`For indoor DAS—GSM installations the input power at the
`
`antenna connector is typically about 10 dBm/carrier. Fig.
`
`5
`
`shows the measured IMD power versus the input power of the
`
`wanted GSM signal. A post—amplifier with a gain of ~34 dB
`
`after the receiver has been used to boost the output power.
`
`It can be seen that the maximum RF input power to the laser
`
`should be <1 dBm in order not to exceed the —36dBm maximum
`
`allowed IM.
`
`The blocking characteristic is a measure of the uplink
`
`ability to receive a wanted signal at its channel frequency
`
`in the presence of a strong unwanted signal, below a
`
`specified limit, on other frequencies without degradation
`
`of the performance.
`
`20
`
`25
`
`30
`
`Since the fibre link in the uplink can be considered as the
`
`input “amplifier” to the base station receiver, and because
`
`a GSM—l800 BS is used in this set—up,
`
`the blocking
`
`characteristics are measured according to the GSM 05.05
`
`specification, section 5.1. The signal level of a wanted
`
`35
`
`GSM signal is set 3 dB above the BS receiver sensitivity
`
`limit
`
`(including the interface link with 600—meter MM
`
`
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`fibre) and the unwanted sine wave (800 kHz away from the
`
`GSM signal} signal level is increased until the BER shows
`
`impairments. The power of the unwanted sine wave could be
`
`increased up to ~5 dBm, at the input of the laser, without
`
`impairing the BER in the wanted GSM signal.
`
`The BER penalty of the fibre link for the digital and radio
`
`transmission has been measured,
`
`in order to understand if
`
`the link caused distortions degrade the radio and optical
`
`10
`
`receiver sensitivity levels.
`
`The BER of the 1 Gbit/s digital signal versus optical
`
`received power is shown in Fig. 6.
`
`The optical attenuator
`
`after the laser was used to reduce and balance the received
`
`15
`
`power. The results are shown for the fibre back—to—back
`
`case, ~7 m MM fibre, with the GSM signal switched off and
`
`switched on, and for the 600 m M fibre with the GSM signal
`
`switched on. No penalty could be observed for the
`
`simultaneous digital and radio signal transmission. Indeed
`
`20
`
`the measured BER for.the 600 m M fibre with simultaneous
`
`radio transmission showed slightly better receiver
`
`sensitivity than the back—to—back cases; This difference
`
`could also be observed by repeating the measurements. One
`
`reason for this observation may be the restricted laser
`
`launch condition used in the setwup, as equilibrium mode
`
`distribution may be not reached over such a short fibre
`
`length. The achieved receiver sensitivity is ~ -15.5 dBm
`
`for a BER of 10“.
`
`For the BER measurement on the GSM 1800 signal the optical
`
`attenuator was set to zero as the electrical attenuator in
`
`front of the TEMS receiver was used to reduce and balance
`
`the received signal level {RXLev).
`
`The raw BER in the
`
`radio downlink was measured on the radio broadcast channel.
`
`Fig. 7 shows the BER as a function of received power for
`
`25
`
`30
`
`35
`
`
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`PC T.-‘S E2002/0l| 1 509
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`
`back—to—back case using coaxial cable, coax cable ~6 m, 600
`
`m MM fibre with the digital signal switched off and with
`
`the radio and digital signal running simultaneously. No BER
`
`penalty is observed for the simultaneous radio and digital
`
`transmission over the 600 m MT. The fibre back—to—back
`
`transmission showed similar BER values to the 600 m M
`
`fibre transmission and the measurement points have been
`
`omitted in the figure for clarity. For input powers > -102
`
`dBm no BER could be measured within the resolution given by
`
`10
`
`the TEMS equipment. The reference sensitivity level for GSM
`
`1800 terminals and base stations is ~l02 and ~104 dBm
`
`respectively, with the maximum BER depending on the type of
`
`channel, e.g. data channel BER S 0.1%,
`
`/3/. The back~to—
`
`back case using coax cable showed slightly larger BERs than
`
`15
`
`the radio over fibre transmission. This difference is
`
`within the resolution of the used TEMS equipment.
`
`For the parallel digital ~ GSM signal transmission,
`
`the 1dB
`
`compression point limits the maximum input power to the
`
`20
`
`laser. From the maximum input power,
`
`loss and noise figure
`
`of the fibre radio system we could do a link budget
`
`calculation for a typical GSM in—building system, as shown
`
`in Fig. 8.
`
`In the link budget calculation is made for the
`
`loss and noise of the signal from one optical feeder
`
`25
`
`(interface 100) when considering 4 remote antennas, see
`
`Fig. 9.
`
`The radio uplink limits the maximum path loss for the fibre
`
`radio system (Fig. 4)
`
`to about 82 dB. The link budget as
`
`given in Fig. 8 is just an indication and could be
`optimised,
`for example by carefully placing of the remote
`
`antenna units in order to prevent high signal levels at the
`
`radio uplink in order to increase the gain in the first
`
`amplifier.
`
`30
`
`35
`
`For indoor environments the path loss can be estimated
`
`
`
`

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`WO 2003102402?
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`PC1TSE2002flm1509
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`17
`
`using the Multiple Wall Model as described in the COST
`
`Action 231 [COST Action 231, "Digital mobile radio towards
`
`future generation systems,” final report 1999.]. By taking
`
`a room size of 4 metres and allowing for a surface outage
`
`of 5% the path loss a shown in Fig. 10 could be computed.
`
`The maximum cell radius for 82 dB path loss is about 20 m.
`
`In current indoor distributed antenna installations cell
`
`radii between ~15 to ~25 m are quite common.
`
`10
`
`The system link budget can be increased by about 6 dB if
`
`using separate optical transceiver units for the digital
`
`and radio transmission. If transmitting more than one GSM
`
`carrier and if using just one laser the RF input power has
`
`to be decreased by ~20xlog(#carriers),
`
`in order to prevent
`
`15
`
`signal clipping.
`
`The interface architecture is in general scalable to any
`
`future LAN standard, as the radio and digital signal may be
`
`fed to separate optical transceiver units within the LAN
`
`20
`
`equipment, e.g. one interface 100 with multiple 102
`
`interfaces. For future LAN standards the optical
`
`transceivers and fibres will be able to support higher
`
`digital data rates. This in turn will be beneficial to
`
`interface, as e.g.
`
`the link budget for the radio
`
`2