(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2008/0119198 A1
`(43) Pub. Date:
`May 22, 2008
`HETTSTEDT et al.
`
`US 200801 19198A1
`
`(54) METHOD AND SYSTEM FOR WIRELESS
`CELLULARINDOOR COMMUNICATIONS
`
`(75) Inventors:
`
`Heinz-Dieter HETTSTEDT,
`Isernhagen (DE); Roland
`Munzner, Bissingen/Teck (DE);
`Ekkehard Schomburg, Burgwedel
`(DE)
`
`Correspondence Address:
`SUGHRUE MION, PLLC
`2100 PENNSYLVANIA AVENUE, N.W., SUITE
`8OO
`WASHINGTON, DC 20037
`
`(73) Assignee:
`
`Alcatel Lucent, Paris (FR)
`
`(21) Appl. No.:
`
`11/942,442
`
`(22) Filed:
`
`Nov. 19, 2007
`
`(30)
`
`Foreign Application Priority Data
`
`Nov. 20, 2006 (EP) .................................. O63O1157.1
`
`Publication Classification
`
`(51) Int. Cl.
`(2006.01)
`H04O 7/20
`(52) U.S. Cl. ........................................................ 45S/453
`(57)
`ABSTRACT
`The invention relates to a method for wireless cellular indoor
`communications, the method comprising at least one base
`station connected to a cell management unit through a first
`digital connection interface, the cell management unit con
`nected to at least one RF hub through a second digital con
`nection interface, and the at least one RF hub connected to at
`least one remote radiohead through a third digital connection
`interface, the at least one remote radiohead providing service
`in a certain cell area inside a confined environment, and the
`cell management unit comprising means for providing effi
`cient load balancing at and between base stations through
`adaptive cell reconfiguration; means for mapping carriers,
`time, frequency or time-frequency allocations to individual
`radio heads; means for alignment of individual delays accu
`mulated on the digital connections between the cell manage
`ment unit and each of the radio heads; means for synchroni
`Zation of the signals between the cell management unit and
`the individual remote radio heads; and means for failure
`detection of the individual digital links between the cell man
`agement unit and the remote radio heads.
`
`
`
`

`

`Patent Application Publication May 22, 2008 Sheet 1 of 4
`
`US 2008/O119198 A1
`
`Figure 1
`
`
`
`Patent Application Publication
`
`May 22,2008 Sheet 1 of 4
`
`US 2008/0119198 Al
`
`Figure 1
`
`Te \ Al
`
`
`
`B
`
`fol
`
`
`
`Ws
`wry A2
`
`vs
`
`]
`
`Am
`a
`
`
`
`A3
`
`Am
`
`
`
`
`
`
`
`
`A4
`
`Am
`
`y,
`
`Co2
`oO
`
`R
`
`
`
`Page 2
`
`CommScope Ex. 1005
`
`

`

`Patent Application Publication
`
`May 22, 2008 Sheet 2 of 4
`
`US 2008/O119198 A1
`
`
`
`Figure 2
`
`Figure 3
`
`Patent Application Publication
`
`May 22,2008 Sheet 2 of 4
`
`US 2008/0119198 Al
`
`Figure 2
`
`Figure 3
`
`
`
`OAR
`
`
`
`
`
`Bs
`BSI
`
`
`
`
`
`
`ES
`
`
`
`RH1
`
`RH2
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 3
`
`
`
`
`CommScope Ex. 1005
`
`

`

`Patent Application Publication May 22, 2008 Sheet 3 of 4
`
`US 2008/O119198 A1
`
`Figure 4
`
`
`
`
`
`
`
`RH-1
`(Ca 1 to 4,
`MA 1 to 4)
`
`RH-N
`(CaM-3 to M,
`MAM-3 to M)
`
`
`
`RH-2
`(Ca 5 to 8,
`MA 5 to 8)
`
`

`

`Patent Application Publication
`
`May 22, 2008 Sheet 4 of 4
`
`US 2008/O119198 A1
`
`
`
`Figure 6
`
`Patent Application Publication
`
`May 22, 2008 Sheet 4 of 4
`
`US 2008/0119198 Al
`
`
`
`
`
`— 77
`
`
`
`
`
`
`
`
`
`omtnmzx
`
`
`
`
`?
`Toesegss
`
`
`
`M
`
`
`
`
`
`
`
`
`
`
`BS1
`
`
`
`BS2
`
`
`
`BS3
`
`
`
`BS4
`
`BS5
`
`
`
`
`
`
`
`BS6
`
`
`
`BS7
`
`BS8
`
`
`
`
`
`Figure 6
`
`
`
`
`
`SW
`
`CN
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 5
`
`CommScope Ex. 1005
`
`

`

`US 2008/01 19198 A1
`
`May 22, 2008
`
`METHOD AND SYSTEM FOR WIRELESS
`CELLULARINDOOR COMMUNICATIONS
`
`BACKGROUND OF THE INVENTION
`0001. The invention is based on the priority application EP
`06301,157.1 which is hereby incorporated by reference.
`0002 The present invention relates to indoor communica
`tions systems, and particularly to wireless cellular communi
`cations systems in buildings and tunnels.
`0003 Wireless communications systems are becoming an
`increasingly widespread phenomenon of modern communi
`cations. Since many users place an increasing number of
`cellular calls or data transmissions within buildings or other
`confined structures, there is a need to achieve high quality
`indoor coverage at appropriate capacity.
`0004. A conventional configuration to extend a wireless
`communications service e.g. GSM or UMTS, from an out
`door environment to an indoor area is shown in FIG. 1 and is
`characterized by the utilization of a repeater R that is typically
`located within a building B to retransmit within the building
`a wireless signal WS received at an external antenna A1 or
`retransmit outside the building the wireless signals Ws of
`mobile stations Ms, e.g. mobile phones, handheld computers
`and the like, located inside the building B. In the downlink,
`that is when the wireless signals Ws from the external envi
`ronment are transmitted to the mobile stations Ms inside the
`building B, said outdoor wireless signals are passed along a
`first connection Col to the repeater R which forwards the
`signal along a second connection Co2 to a plurality of inter
`connected amplifiers Am, the amplifiers amplify the signals
`which are then transmitted over the in-building antennas A2
`to A4. In the uplink direction, that is, when the wireless
`signals Ws from the mobile stations Ms are transmitted to a
`wireless infrastructure outside the building B, the repeater R
`receives said signals along connection Co2 and transmits
`them along connection Co1 to the external antenna A1.
`0005. It is also possible that the repeater R of the indoor
`communications structure is replaced by a base station con
`nected to a communications core network along connection
`Co1. Typically, the information is distributed via analogue
`signals inside the buildings and confined areas.
`0006 Another known indoor communications system
`providing wireless cellular service is shown in FIG. 2. A core
`network CN is connected to a base station Bs. The radio
`frequency (RF) signals from the base station or an off-air
`repeater OAR are digitized into base band signals in a base
`station interface BSI (and vice versa in uplink transmission)
`and distributed in the form of data packets using data cables,
`e.g. category 5 (CAT5) or optical fiber, to at least one Ethernet
`switch ES. The Ethernet switch ES then distributes the infor
`mation to the corresponding remote radio heads RH1 to RH4
`serving a particular cell area C1 and C2. An example of Such
`system is disclosed in Patent Application US 2005/0157675
`A1. An advantage of Such systems is that they provide a
`cost-effective solution due to the use or re-use of low cost
`distribution cabling which is usually already present, totally
`or partly, in buildings and used for other types of digital
`communications e.g. local area network LAN structures
`using Ethernet protocol.
`0007 Using standard Ethernet switches, cell configura
`tions can be achieved due to the sectorization of data flow.
`Normally, an Ethernet hub is needed in each Ethernet sector
`for data distribution in downlink and data packaging in
`uplink. The hub function is placed in at least one of the
`
`associated remote radio heads. In complex systems, series of
`Ethernet switches are necessary and bottlenecks of data flow
`are evident due to the 1 to n distribution characteristic of the
`Ethernet Switch resulting in limiting the capacity of the net
`work.
`
`SUMMARY OF THE INVENTION
`0008. The object of the present invention is to provide a
`method and a system for wireless cellular indoor communi
`cations with improved cell and load balancing management.
`0009. The object is achieved by a wireless cellular indoor
`communications system comprising at least one base station
`connected to a cell management unit through a first digital
`connection interface, the cell management unit connected to
`at least one RF hub through a second digital connection
`interface, and the at least one RF hub connected to at least one
`remote radio head through a third digital connection inter
`face, the at least one remote radio head providing service in a
`certain cell area inside a confined environment,
`0.010
`the cell management unit comprising
`00.11
`means for providing efficient load balancing at
`and between base stations through adaptive cell
`reconfiguration,
`0012 means for mapping carriers, time, frequency or
`time-frequency allocations to individual radio heads,
`00.13 means for alignment of individual delays accu
`mulated on the digital connections between the cell
`management unit and each of the radio heads,
`0014) means for synchronization of the signals
`between the cell management unit and the individual
`remote radio heads,
`0015 means for failure detection of the individual
`digital links between the cell management unit and
`the remote radio heads.
`0016. This object is further achieved by a method for wire
`less cellular indoor communications, the method comprising
`0017 a base station transmitting or receiving call or
`data information to/from a cell management unit
`through a first digital connection interface,
`0.018
`the cell management unit transmitting or receiv
`ing call or data information to/from at least one RF hub
`through a second digital connection interface, and
`0.019
`the at least one RF hub transmitting or receiving
`call or data information to/from at least one remote radio
`head through a third digital connection interface, the at
`least one remote radiohead providing service in a certain
`cell area inside a confined environment, and
`0020 the cell management unit
`0021 providing efficient load balancing at and
`between base stations through adaptive cell recon
`figuration,
`0022 mapping carriers, time, frequency or time-fre
`quency allocations to individual radio heads,
`0023 aligning individual delays accumulated on the
`digital connections between the cell management unit
`and each of the radio heads,
`0024 synchronizing signals between the cell man
`agement unit and the individual remote radio heads,
`0025 detecting failure of the individual digital links
`between the cell management unit and the remote
`radio heads.
`0026. The system for wireless cellular indoor communi
`cations of the invention uses a cell management unit with
`
`

`

`US 2008/01 19198 A1
`
`May 22, 2008
`
`complex matrix function, instead of distributed standard Eth
`ernet switches, for flexible cell management of multi-service
`and multi-operator functions.
`0027. The cell management unit is the interface between a
`number of base stations and the Ethernet connection. It pro
`vides multi-functions for a broad scope of complex scenarios
`of operation, with multi-carrier, multi-service and multi-op
`erator functions, and efficient data management. In this way,
`the remote radio heads can be used in parallel for different
`services and at different functions, such as for frequency
`division duplex (FDD) and time division duplex (TDD). The
`remote radio heads are serviced by RF-Hubs similar to the
`original Ethernet hub functionality. Due to a compact
`arrangement of the cell management unit, data concentrations
`can be avoided and high data transfer can be achieved in
`complex networks.
`0028. The cell management unit provides data manage
`ment in terms of packaging and addressing to the radio heads
`in downlink and un-packaging and addressing to the base
`stations in uplink. Since the cell management unit performs
`the frequency allocation of the remote radio heads, cell man
`agement for different services and operators can be achieved.
`Cell management can be performed manually, by Software
`control or even automatically adaptive to current cell sce
`narios.
`0029. Due to a traffic activity control, un-used carriers in
`remote radio heads can be de-activated at locations of low
`traffic and can be shifted and activated in remote radio heads
`at locations of high traffic. The load-balancing in base stations
`can be performed independently of the cell management
`function. In this way, capacity can follow moving users in
`complex buildings, such as airports, stations, etc., with
`dynamic distribution of hot-spots.
`0030 Cost optimization can be achieved when cell archi
`tectures must no longer be designed for peak traffic with
`moving users all over the whole building. Further cost opti
`mization is achieved using base stations with digital interface
`and remote radioheads at dedicated locations, where capacity
`and coverage is needed. Additionally, since information is
`distributed in digital base-band, cost-effective transport can
`be used or eventually re-used, such as CAT5 cabling and
`optical fiber. Due to the LAN characteristic of the digital
`distribution infrastructure, the remote radio heads can advan
`tageously be easily relocated.
`0031
`Radio heads can be designed using low-cost tech
`nology of mobile stations avoiding high RF transmission
`levels.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`0032. An embodiment example of the invention is now
`explained with the aid of FIGS. 1 to 6.
`0033 FIG. 1 shows a first typical indoor communications
`system structure, for analogue systems, according to the prior
`art.
`0034 FIG. 2 shows a wireless cellular indoor communi
`cations system, with digital distribution of signals over Eth
`ernet, according to the prior art.
`0035 FIG. 3 shows a first example of a wireless cellular
`indoor communications system, with separated cell configu
`ration, according to the invention.
`0036 FIG. 4 shows a second example of a wireless cellular
`indoor communications system, with overlapping cell con
`figuration, according to the invention.
`
`0037 FIG. 5 shows an example of carrier distribution
`according to the wireless cellular indoor communications
`method of the invention.
`0038 FIG. 6 shows an example block schematic of a wire
`less cellular indoor communications system according to the
`invention.
`0039. A first example of a wireless cellular indoor com
`munications system structure according to the invention is
`shown in FIG. 3, comprising a core network CN, a base
`station Bs, a cell management unit CMU, an off-air repeater
`(OAR), digital interfaces i1 to i3, RF hubs RFH1 and RFH2,
`and remote radio heads RH1 to RHS.
`0040. In the downlink direction, communications core
`network signals intended for the mobile station inside the
`indoor environment, e.g. a building or a tunnel, are received
`by the base station BS. Said signals are then passed in digital
`form through a first connection interface i1, e.g. an electrical
`or optical connection using Ethernet protocol or of other
`standards (e.g. OBSAI or CPRI), to the cell management unit
`CMU. The cell management unit CMU performs data pack
`aging in downlink and forwards said digital packets through
`a second digital connection interface i2, e.g. an electrical or
`optical connection using Ethernet protocol, to the RF Hubs
`RFH1 and RFH2, which in turn pass the packets through a
`third connection interface i3, e.g. an electrical or optical con
`nection using Ethernet protocol, to the remote radio heads
`RH1 to RHS.
`0041. Similarly, in the uplink direction, radio signals Ws
`transmitted by the mobile stations located in the indoor envi
`ronment are received by the remote radio heads RH1 to RH5
`and sent to the core network CN with data packaging in the
`RF HubS.
`0042. The base station is a conventional base station with
`out radio equipment. The cell management unit CMU pro
`vides transparent operation of the radio heads RH1 to RH5
`from the base station and comprises standard digital inter
`faces to the base station Bs and to the off-air repeater OAR, at
`least one Ethernet interface to connect the RF Hubs RFH1 and
`RFH2, an intelligent switching unit for data distribution and
`cell organization configurable in size and functionality
`according to system dimensions, a complex matrix function
`to combine different base stations with a number of RF hubs,
`multi-service and multi-operator functionality for full trans
`parency, flexible cell management for static cell configura
`tions, automatic cell management for adaptive cell configu
`rations.
`0043. The CMU preferably comprises the following func
`tionality (in a form independent of the used air interface
`standard):
`0044 means for Supporting efficient load balancing at
`and between base stations through adaptive cell recon
`figuration, especially through the shifting of un-used
`carriers from radio heads inside areas of low traffic load
`to radioheads inside areas of high traffic load, e.g. means
`for individual load identification for each carrier on each
`of the radio heads by air interface activity detection and
`interference sensing. Air interface activity detection
`thereby is realized on the basis of the individually sup
`ported air interface protocols; means for de-activation of
`un-used carriers per radio head on an individual basis;
`means for shifting carriers from radioheads, where these
`carriers are not used for radio heads with high load on
`their active carriers, means for activation of the shifted
`carriers at locations (radio heads) of high loading. The
`
`

`

`US 2008/01 19198 A1
`
`May 22, 2008
`
`cell management unit mechanism of adaptive cell re
`configuration thereby will neither require any changes to
`the load balancing mechanisms at or between the access
`nodes (e.g. BTS, Node-B, WiMAX base station) nor any
`dedicated messaging between access nodes and CMU
`for Supporting load balancing.
`004.5 mapping means from carriers or time, frequency
`or time-frequency allocations to individual radio heads,
`as identified e.g. through their MAC addresses or the
`connectors of the respective digital lines to which the
`radio heads are connected,
`0046 delay management means for alignment of the
`individual delays accumulated on the digital connec
`tions between the cell management unit and each of the
`radio heads,
`0047 means for synchronization of the signals between
`the cell management unit and the individual radioheads,
`0048 failure detection means for the individual digital
`links between the cell management unit and the radio
`heads.
`0049. The RF hubs provide data distribution to the remote
`radio heads in downlink and data packaging in uplink
`0050. The remote radio heads RH1 to RH5 are RF air
`interfaces to users providing a digital interface to the network.
`They are part of the BTS according to standards, such as
`OBSAI or CPRI. The remote radio heads are equipped to
`transmit four carriers over the full RF bandwidth of each
`service but channel-selective at least in uplink. In this way, a
`remote radio head can operate individually for dedicated
`operators only. Since frequency allocation of each carrier can
`be tuned remotely by the cell management unit CMU, the
`remote radio heads RH1 to RH5 can represent an individual
`cell and/or can be part of a greater cell. Thus, in both cases,
`extension of capacity and/or coverage, can be achieved. Dif
`ferent types of remote radio heads can be planned either for
`FDD or for TDD operation.
`0051. In FIG. 3, the wireless cellular indoor communica
`tions system, according to the invention, is illustrated with
`separated cell configuration, that is, a first RF Hub RFH1 is
`connected to two remote radio heads RH1 and RH2 which
`provide service in a first cell area C1 inside a certain first
`indoor location area A1, and a second RF Hub RFH2 is
`connected to three remote radio heads RH3 to RH5 which
`provide service in a second cell area C2 inside a certain
`second indoor location area A2, and the first and second
`indoor location areas A1 and A2 being isolated or separated.
`On the other hand, FIG. 4 illustrates a wireless cellular indoor
`communications system, according to the invention, which
`presents overlapping cell configuration, that is, now the first
`RF Hub RFH1 is connected to two remote radio heads RH1
`and RH2, RH1 providing service in cell C1, and RH2 provid
`ing service in cell C2, and cells C1 and C2 overlapping in the
`same indoor location area A1, and the second RF Hub RFH2
`is connected to three remote radio heads RH3, RH4 and RH5
`which also provide service in different overlapping cells C1,
`C2 at the same indoor location area A2.
`0052 For the sake of generalization, other cell configura
`tions, as the ones illustrated in the examples of FIGS. 3 and 4,
`are possible according to the invention. Each remote radio
`head can service a different cell area, or two, or more, remote
`radio heads can belong the same cell area, said cell areas
`overlapping inside a certain indoor location area or being in
`
`different location areas. The RF hubs can be connected to
`remote radio heads which serve the same cell or serve differ
`ent cells.
`0053 FIG. 5 shows an example of carrier distribution
`according to the wireless cellular indoor communications
`method of the invention considering four carriers per remote
`radiohead RH-1 to RH-N. The base station Bs provides the M
`carriers Ca1 to CaM to the cell management unit CMU which
`in turn distributes it between the at least one RF Hub RFH 1
`to X of the next stage. The one or more RF Hubs distribute
`carriers 1 to 4 to a first remote radio head RH-1 according to
`medium access control (MAC) addresses MA1 to MA4 in the
`Ethernet packets, carriers 5 to 8 to a second remote radiohead
`RH-2 according to MAC addresses 5 to 8, and carriers M-3 to
`M to an N remote radio head RH-N according to MAC
`addresses M-3 to M, where M=NX4.
`0054 FIG. 6 shows an example block schematic of a wire
`less cellular indoor communications system according to the
`invention. In the example of the figure the cell management
`unit CMU operates on eight base stations BS1 to BS8 and on
`eight RF Hubs RFH1 to RFH8 (but, of course, more or less
`base stations Bs and RF Hubs could also be connected to the
`CMU). Each base station can provide four carriers at indi
`vidual services. The eight BS can cover different services of
`different operators. The network between interfaces 11 and
`13 is fully transparent, while the remote radio heads RH1 to
`RH32 are dedicated for individual services.
`
`1. A wireless cellular indoor communications system com
`prising at least one base station connected to a cell manage
`ment unit through a first digital connection interface, the cell
`management unit connected to at least one RF hub through a
`second digital connection interface, and the at least one RF
`hub connected to at least one remote radio head through a
`third digital connection interface, the at least one remote radio
`head providing service in a certain cell area inside a confined
`environment,
`the cell management unit comprising
`means for providing efficient load balancing at and
`between base stations through adaptive cell recon
`figuration,
`means for mapping carriers, time, frequency or time
`frequency allocations to individual radio heads,
`means for alignment of individual delays accumulated
`on the digital connections between the cell manage
`ment unit and each of the radio heads,
`means for synchronization of the signals between the
`cell management unit and the individual remote radio
`heads,
`means for failure detection of the individual digital links
`between the cell management unit and the remote
`radio heads.
`2. The wireless cellular indoor communications system of
`claim 1, wherein the means for Supporting efficient loadbal
`ancing comprise means for shifting un-used carriers from
`remote radio heads inside areas of low traffic load to remote
`radio heads inside areas of high traffic load.
`3. The wireless cellular indoor communications system of
`claim 2, wherein the means for shifting un-used carriers from
`remote radio heads inside areas of low traffic load to remote
`radio heads inside areas of high traffic load comprise
`means for individual load identification for each carrier on
`each of the radio heads by air interface activity detection
`and interference sensing,
`
`

`

`US 2008/01 19198 A1
`
`May 22, 2008
`
`means for de-activation of un-used carriers per remote
`radio head on an individual basis;
`means for shifting carriers from radio heads, where these
`carriers are not used for radio heads with high load on
`their active carriers,
`means for activation of the shifted carriers at locations
`where the remote radio heads are loaded over a prede
`termined value.
`4. The wireless cellular indoor communications system of
`claim 1, wherein the carriers, time, frequency or time-fre
`quency allocations are identified through their MAC
`addresses or the connectors of the respective digital lines to
`which the radio heads are connected.
`5. The wireless cellular indoor communications system of
`claim 1, wherein the first, second and third digital interface is
`an electrical or optical connection using Ethernet protocol.
`6. A method for wireless cellular indoor communications,
`the method comprising
`a base station transmitting or receiving call or data infor
`mation to/from a cell management unit through a first
`digital connection interface,
`
`the cell management unit transmitting or receiving call or
`data information to/from at least one RF hub through a
`second digital connection interface, and
`the at least one RF hub transmitting or receiving call or data
`information to/from at least one remote radio head
`through a third digital connection interface, the at least
`one remote radio head providing service in a certain cell
`area inside a confined environment, and
`the cell management unit
`providing efficient load balancing at and between base
`stations through adaptive cell reconfiguration,
`mapping carriers, time, frequency or time-frequency
`allocations to individual radio heads,
`aligning individual delays accumulated on the digital
`connections between the cell management unit and
`each of the radio heads,
`synchronizing signals between the cell management
`unit and the individual remote radio heads,
`detecting failure of the individual digital links between
`the cell management unit and the remote radio heads.
`
`c
`
`c
`
`c
`
`c
`
`c
`
`