as) United States
`a2) Patent Application Publication co) Pub. No.: US 2007/0097901 Al
`(43) Pub. Date: May3, 2007
`
`Tirkkonenet al.
`
`US 20070097901A1
`
`(54) APPARATUS, METHOD AND COMPUTER
`PROGRAM PRODUCT PROVIDING
`COMMON CHANNEL ARRANGEMENTS
`FOR SOFT FREQUENCY REUSE
`
`Related U.S. Application Data
`
`(60) Provisional application No. 60/731,552, filed on Oct.
`28, 2005.
`
`Publication Classification
`
`(75)
`
`Inventors: Olav Tirkkonen, Helsinki (FI); Preben
`Mogensen, Gistrup (DK); Mika P.
`Rinne, Espoo (FI)
`
`(51)
`
`Int. CL
`(2006.01)
`HO4B 7/185
`(52) U.S. C1.
`cecccsccssesssscsssseesterssensseeee 370/318; 455/522
`
`Correspondence Address:
`A device includes circuitry adapted to placeat least a portion
`HARRINGTON & SMITH, PC
`of at least one common channel onafraction of an available
`4 RESEARCH DRIVE
`
`(57)
`
`ABSTRACT
`
`SHELTON, CT 06484-6212 (US)
`
`(73) Assignee: Nokia Corporation
`
`(21) Appl. No.:
`
`11/588,519
`
`(22)
`
`Filed:
`
`Oct. 27, 2006
`
`bandwidth of a cell in a cellular communication system that
`uses soft reuse such that different orthogonal transmission
`resources are transmitted with different transmission powers
`and power usage is planned on a cell-by-cell basis; and a
`transmitter to transmit the common channelintothe cell for
`
`reception by a plurality of receivers. Also disclosed is a
`method and a computer program product operable with the
`device.
`
`NETwoRK 4
`
`| NETWORK. CONTROL
`
`
`
`APPLE 1023
`APPLE 1023
`
`

`

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`
`¢|LOvz
`
`Pr}
`
`Patent Application Publication May 3,2007 Sheet 1 of 5
`
`US 2007/0097901 Al
`
`YILNW
`WLANI:
`
`TLSYOMLIN-Bxool Cis
`|.da
`
`
`
`

`

`Patent Application Publication May 3,2007 Sheet 2 of 5
`
`US 2007/0097901 Al
`
`

`

`Patent Application Publication May 3, 2007 Sheet 3 of 5
`
`US 2007/0097901 Al
`
` () DRX optimized
`
`LEGEND
`Downlink Shared channel(DSCGH) (and possible dedicatedpilots)
`AA Control channlel (CCH), primary resources
`| AUVUUVEATATTATA Secondary resourcesforcontrol channels (used for CCHif required, else for DSCH)
`
`===III
`
`
`=
`(c) Allowing larger CCH.
`
`
`
`
`| ee Commonpilot subcarriers with othersubcarriers usedfor DSCH
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Commonpilot subcarriers with other eubeaniens used for CCH
`Commonpilot subcarriers with other subcarriers usedfor CCHif |
`required, else for DSCH
`
`Figure 3
`
`

`

`Patent Application Publication May 3,2007 Sheet 4 of 5
`
`US 2007/0097901 Al
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ZEEE
`
`— DRX optimized
`
`
`===MM
`
`FFIl
`=|||
`CUA
`II
`{iil
`
`
`|
`
`
`©) Allowing larger CCH
`a
`|
`LEGEND
`. Downlink Shared channel (DSGH) (and possible dedicat pilots)
`AAA Control channlel (CCH), primary resources
`ET Secondary resources for control channels (used forCCHif required, else for DSCH) -”
`
`== Commonpilot subcarriers with other subcarriers usedfor DSCH
`
`
`Common pilot subcarriers with other subcarriers used forCCH
`
`Commonpilot subcarriers with other subcarriers used for CCHif
`required, else for DSCH
`
`kL Commonpilotsubcarrierswith System-info Nansmiiee on othersubcarriers
`| Fieure A
`
`

`

`Patent Application Publication May 3,2007 Sheet 5 of 5
`
`US 2007/0097901 Al
`
`
`
`
`
`
`(SA) PLACING AT LEAST A PORTION OF AT
`LEAST ONE COMMON CHANNELON A
`FRACTIONOF AN AVAILABLE BANDWIDTH
`
`
`OF A CELL IN A CELLULAR
`COMMUNICATION SYSTEM THATUSES SOFT
`
`
`REUSE SUCH THAT DIFFERENT
`
`ORTHOGONAL TRANSMISSION RESOURCES
`
`
`ARE TRANSMITTED WITH DIFFERENT
`
`
`TRANSMISSION POWERS AND POWER USAGE
`IS PLANNED ON A CELL-BY-CELL BASIS
`
`
`(5B) TRANSMITTING THE COMMON
`CHANNEL INTO THE CELL FOR
`
`
`RECEPTION BY A PLURALITY OF
`
`
`RECEIVERS
`
`
`FIGURE 5
`
`
`
`(6A) RECEIVING AT LEAST A PORTION OF
`
`AT LEAST ONE COMMON CHANNEL FROM
`
`
`DIFFERENT ORTHOGONAL TRANSMISSION
`
`
`RESOURCESON A FRACTION OF AN
`
`
`
`AVAILABLE BANDWIDTH OF AT LEAST ONE
`OF HIGHER TRANSMISSION POWER ORA
`
`LOWER TRANSMISSION POWEROF SOFT
`REUSE
`
` (6B) USING INFORMATIONIN
`THE RECEIVED COMMON
`
`CHANNEL
`
`
`
`
`
`FIGURE 6
`
`

`

`US 2007/0097901 Al
`
`May3, 2007
`
`APPARATUS, METHOD AND COMPUTER
`PROGRAM PRODUCT PROVIDING COMMON
`CHANNEL ARRANGEMENTS FOR SOFT
`FREQUENCY REUSE
`
`CLAIM OF PRIORITY FROM COPENDING
`PROVISIONAL PATENT APPLICATION
`
`[0001] This patent application claims priority under 35
`US.C. §119(e) from Provisional Patent Application No.
`60/731,552, filed Oct. 28, 2005, the disclosure of which is
`incorporated by reference herein in its entirety.
`
`TECHNICAL FIELD
`
`[0002] The exemplary and non-limiting embodiments of
`this invention relate generally to wireless cellular commu-
`nications systems and devices and, more specifically, relate
`to those wireless cellular communications systems that
`employ soft frequency reuse with channels transmitted to a
`receiver.
`
`BACKGROUND
`
`[0003] The following abbreviations are herewith defined.
`
`[0004]
`
`3GPPthird generation partnership project
`
`[0005] UTRANuniversalterrestrial radio access network
`
`[0006]
`
`E-UTRANevolved UTRAN
`
`[0007]
`
`CDMcode division multiplex
`
`[0008] CCH common channel
`
`[0009] DL downlink (Node B to UE)
`
`[0010]
`
`[0011]
`
`[0012]
`
`[0013]
`
`UL uplink (UE to Node B)
`DSCH downlink shared channel
`
`DRX discontinuous reception
`DTX discontinuous transmission
`
`[0014]
`
`DSPdigital signal processor
`
`[0015]
`
`FDM frequency division multiplex
`
`[0016]
`
`[0017]
`
`[0018]
`
`[0019]
`
`FDMA frequency divisional multiple access
`Node B basestation
`
`OFDM orthogonal frequency division multiplex
`SR sub-band soft reuse sub-band
`
`[0020]
`
`TDM timedivision multiplex
`
`[0021]
`
`UE user equipment
`
`[0022]
`
`[0023]
`
`WCDMA wideband code division multiple access
`
`WCDMA LTE WCDMAlong term evolution
`
`interference is a serious problem that
`Inter-cell
`[0024]
`needs to be addressed during the design of a multi-cellular
`communication system. Some conventional systems reduce
`the amountof interference of geographically adjacent cells
`by allocating their carrier frequencies to different center
`frequencies, separated by the bandwidth ofthe carrier. Thus,
`there is a reuse factor, which determinestiers of geographi-
`cal cells such that base stations transmitting on the same
`center frequency are much further away than the geographi-
`cally closest neighbors. This approach is known to compli-
`
`cate network planning, since when introducing a new base
`station the operator may need to update the frequency plan
`of all the base stations in that area.
`
`Some modern systems, such as WCDMA, are
`[0025]
`designed so that frequency reuse planning is not needed at
`all, 1.e., full coverage network can be deployed by applying
`the same frequency in all the cells within a certain geo-
`graphical area. This is also preferred as the system band-
`width can be large, e.g., 5 MHz for WCDMA.Thus, it would
`not be efficient to deploy such a wideband system with
`frequency reuse. WCDMA,as any modem signal structure,
`is designed so that a frequency reuse 1 deployment
`is
`possible, practical and efficient.
`
`[0026] This same requirement has been set for E-UTRAN.
`The system bandwidth of E-UTRANis scalable from values
`ranging from 1.25 MHz up to 20 MHz, and possibly even
`higher (e.g., up to 100 MHz).
`
`[0027] E-UTRAN will be designed so that DL transmis-
`sion is a multi-carrier signal, where a mathematical trans-
`form is applied to form sub-carriers, each of which carry
`modulated symbols. Such a block of sub-carrier symbols is
`referred to as an OFDM symbol, if the transforms applied
`are DFT or FFT transforms. Other types of multi-carrier
`compositions exist by other mathematical transforms, such
`as sine or cosine transforms, lapped transforms, bi-orthogo-
`nal transforms,
`isotropic transforms, etc. In the UL, the
`E-UTRANmay be a similar multi-carrier signal as well, but
`is presently defined as a single carrier, FOMA (SC-FDMA)
`characterized by a frequency division multiplex of users. In
`any of the afore-mentioned techniques, the frequency reuse
`1 technique is feasible.
`
`[0028] One potential solutionto the inter-cell interference
`problem employs a so-called soft reuse method (in time/
`frequency). In a soft reuse method, different orthogonal
`transmission resources are given different transmission pow-
`ers, and the powerusageis plannedin the cellular system on
`a cell-by-cell basis. While time domain soft reuse may be
`applied to any multiplexing technology, frequency domain
`soft reuse requires the presence of a multi-carrier system in
`order to be applicable.
`[0029] While soft reuse has been considered in the time
`domain and in the frequency domain, a frequency domain
`arrangement is more advantageousin an asynchronous com-
`munication system. It has been stressed in the requirements
`for WCDMA LTEthat the E-UTRANshould be operable in
`an asynchronous fashion (see 3GPP TR 25.913, “3rd Gen-
`eration Partnership Project; Technical Specification Group
`Radio Access Network; Requirements for Evolved UTRA
`(E-UTRA) and Evolved UTRAN (E-UTRAN); (Release
`7)”. As such, a frequency domain soft reuse implementation
`is a strong candidate for a LTE system architecture. Such has
`been suggested in 3GPP by Huawei (“Soft frequency reuse
`scheme for UTRAN LTE”, R1-050404, Athens meeting,
`May 2005). Reference may also be madeto Alcatel, “Inter-
`ference coordination in new OFDM DLair interface’,
`R1-050407, Athens meeting, May 2005 (attached hereto as
`Exhibit B), and to Ericsson,“Inter-cell interference handling
`for E-UTRA”, R1-050764, August 2005. Note also the
`“Flarion FLEXband” concept (Signals Ahead, Vol 2, no 3,
`February 2005).
`[0030] Further, the concept of soft reuse is well described
`in the commonly assigned U.S. Pat. No. 6,259,685 B1,
`
`

`

`US 2007/0097901 Al
`
`May3, 2007
`
`“Method for Channel Allocation Utilizing Power Restric-
`tions”, Mika Rinne, Mikko Rinne and Oscar Salonaho,
`incorporated by reference herein.
`
`[0031] Also of interest is 3GPP TR 25.814, “3rd Genera-
`tion Partnership Project; Technical Specification Group
`Radio Access Network; Physical Layer Aspects for Evolved
`UTRA (Release 7)”.
`
`SUMMARY
`
`In an exemplary aspect of the invention a method
`[0032]
`is providedthat includes placing at least a portion of at least
`one common channel on a fraction of an available band-
`
`width of a cell in a cellular communication system that uses
`soft
`reuse such that different orthogonal
`transmission
`resources are transmitted with different transmission powers
`and power usage is planned on a cell-by-cell basis; and
`transmitting the common channelinto the cell for reception
`by a plurality of receivers.
`
`In another exemplary aspect of the invention there
`[0033]
`is provided a computer program product having program
`instructions embodied on a tangible computer-readable
`medium, where execution of the program instructions results
`in operations that comprise placing at least a portion ofat
`least one common channel on a fraction of an available
`
`bandwidth of a cell in a cellular communication system that
`uses soft reuse such that different orthogonal transmission
`resources are transmitted with different transmission powers
`and power usage is planned on a cell-by-cell basis; and
`transmitting the common channelinto the cell for reception
`by a plurality of receivers.
`
`Ina further exemplary aspect of the invention there
`[0034]
`is provided a device that includes circuitry adapted to place
`at least a portion of at least one common channel on a
`fraction of an available bandwidth of a cell in a cellular
`communication system that uses soft reuse such that differ-
`ent orthogonal transmission resources are transmitted with
`different transmission powers and powerusageis planned on
`a cell-by-cell basis; and a transmitter to transmit the com-
`mon channel into the cell for reception by a plurality of
`receivers.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0035] The foregoing and other aspects of embodiments of
`this invention are made more evident
`in the following
`Detailed Description, when read in conjunction with the
`attached Drawing Figures, where:
`
`DETAILED DESCRIPTION
`
`[0041] The exemplary embodimentsof this invention per-
`tain generally to multi-cellular, multi-carrier communication
`systems, such as one known as evolved UTRAN (E-UT-
`RAN)being standardized in the 3GPP. However, the exem-
`plary embodimentsof this invention should not be construed
`as being limited for use with only one particular type of
`wireless communications system, or with only oneparticular
`type of wireless communications system access technology.
`[0042] A problem that is addressed and solved by the
`exemplary embodiments of this invention is in the area of
`the design of common channels in a system where soft reuse
`may be applied at least partly in the frequency domain.
`Common channels (common to more than one user terminal
`device) are preferably designed so that they may be detected
`as reliably as is possible over the entire cell coverage area.
`Tt should be appreciated that for this to occurthe facilitation
`of soft reuse, often understood as being a technology that
`does not need specification, still has implications for stan-
`dards specifications.
`[0043] Reference is made to FIG. 1 for illustrating a
`simplified block diagram of various electronic devices that
`are suitable for use in practicing the exemplary embodi-
`ments of this invention. In FIG. 1 a wireless network 1 is
`
`adapted for communication with a UE 10 via at least one
`Node B (basestation) 12 (also referred to herein as an eNode
`B 12). The network 1 mayinclude a network control element
`14 coupled to the eNode B 12 via a data link 13. The UE 10
`includes a data processor (DP) 10A, a memory (MEM) 10B
`that stores a program (PROG) 10C, and a suitable radio
`frequency (RF) transceiver 10D for bidirectional wireless
`communications with the eNode B 12, which also includes
`a DP 12A, a MEM 12Bthat stores a PROG 12C, and a
`suitable RF transceiver 12D. The eNode B 12 is typically
`coupled via the data path 13 to the network control element
`14 that also includes at least one DP 14A and a MEM 14B
`
`storing an associated PROG 14C. Atleast one of the PROGs
`10C, 12C and 14C is assumed to include program instruc-
`tions that, when executed by the associated DP, enable the
`electronic device to operate in accordance with the exem-
`plary embodiments of this invention, as will be discussed
`below in greater detail.
`[0044]
`Shown for completeness in FIG. 1 is at least one
`second eNode B, referred to as 12'. Note that in practice the
`cells of adjacent eNodeBs mayatleast partially overlap one
`another.
`
`[0036] FIG. 1 shows a simplified block diagram of various
`electronic devices that are suitable for use in practicing the
`exemplary embodiments of this invention;
`
`[0045] Although the Node B 12 is shown having one
`antenna 13, in practice there may bea plurality of antennas
`at least for transmitting to the UE 10. Similarly, the UE 10
`is depicted with one antenna, but in practice there may be a
`[0037] FIG. 2 depicts an example of a power mask ofacell
`plurality of antennas.
`in a soft-reuse system;
`[0046]
`In general, the various embodiments of the UE 10
`can include, but are not limited to, cellular phones, personal
`digital assistants (PDAs) having wireless communication
`capabilities, portable computers having wireless communi-
`cation capabilities, image capture devices such as digital
`cameras having wireless communication capabilities, gam-
`ing devices having wireless communication capabilities,
`music storage and playback appliances having wireless
`communication capabilities, Internet appliances permitting
`wireless Internet access and browsing, as well as portable
`units or terminals that incorporate combinations of such
`functions.
`
`[0038] FIG.3 shows a non-limiting example of sub-frame
`formats for the cell depicted in FIG.2;
`
`[0039] FIG. 4 shows a non-limiting example of sub-frame
`formats forthe cell depicted in FIG. 2, with at least a portion
`of a Syslnfo field in a fixed resource for directly signaling
`CCH placement; and
`
`[0040] FIGS. 5 and 6 are logic flow diagrams descriptive
`of the operation of a transmitter and a receiver, respectively,
`in accordance with exemplary embodiments of this inven-
`tion.
`
`

`

`US 2007/0097901 Al
`
`May3, 2007
`
`[0047] The MEMs10B, 12B and 14B maybeof any type
`suitable to the local
`technical environment and may be
`implemented using any suitable data storage technology,
`such as semiconductor-based memory devices, magnetic
`memory devices and systems, optical memory devices and
`systems, fixed memory and removable memory. The DPs
`10A, 12A and 14A maybe of any type suitable to the local
`technical environment, and may include one or more of
`general purpose computers, special purpose computers,
`microprocessors, digital signal processors (DSPs) and pro-
`cessors based on a multi-core processor architecture, as
`non-limiting examples.
`
`[0048] Note that some aspects of the exemplary aspects of
`this invention will be practiced by the eNode Bs 12, 12',
`while certain other aspects, such as those related to overall
`control and coordination between the eNode Bs 12, 12', such
`as for the use and re-use of resources, mayat least partly be
`performed at or by the network control element 14. It is
`pointed out that the network control element need not be an
`active element of the system/data architecture, but may be
`embodied as operator’s tools for tuning, controlling and
`optimizing the network.
`
`[0049] Turning now to a detailed discussion of the exem-
`plary embodimentsofthis invention,it is first noted that one
`of the advantages of frequency domain soft reuse is that it
`does not require standardization. When employing soft
`frequency reuse, the transmit power level used on different
`frequency bands(referred to as soft reuse bands below)is
`made different, and this different power usage may change
`from cell-to-cell. This has been previously discussed in
`3GPP, see, e.g., the above-cited: Ericsson, “Inter-cell inter-
`ference handling for E-UTRA”, R1-050764, August 2005.
`
`Soft reuse may be implemented by a wireless
`[0050]
`network provider as a slowly time varying network optimi-
`zation feature. When applying non-standardized soft reuse,
`the power of pilots transmitted within a soft reuse band
`reflect the power used for data transmission in the same soft
`reuse band. As an example, in soft frequency reuse OFDM,
`pilot subcarriers in a soft reuse band are transmitted with a
`powerthat depends on the power used on the data subcar-
`riers in the same band. In this case a possible change of
`transmission power level
`from one soft reuse band to
`another need not be signaled, since the UE 10 would
`automatically detect
`the changes in transmission power
`when receiving the pilot symbols. Note that this feature is
`not compromised by having a (standardized or signaled)
`pilot offset. Such an offset would imply that pilots are
`transmitted with a fixed power offset as compared to data
`symbols, e.g., 3 dB. This offset would be the sameforall soft
`reuse bands, and thus by knowing the pilot offset, and by
`estimating the pilots, the UE 10 would have knowledge of
`the received power on the data subcarriers, irrespective of
`possible soft reuse induced differences in transmission
`power.
`
`[0051] However, if the potential of soft reuse is to be fully
`exploited, the transmission resources that have higher power
`should be utilized for the transmission of information that
`requires especially high reliability. For example, common
`channels (CCH) should be reliably detected by all users in
`the cell (and potentially also by users in adjacent cells). In
`E-UTRA, for example, the common channels maybe used,
`for example, to allocate physical layer resources to users
`
`through the use of an Allocation Table), and for
`(e.g.,
`broadcasting system information (SysInfo) to the users.
`
`In general, the common channels may need to be
`[0052]
`received by all active UEs 10 in the cell, and often no
`user-specific SINR (signal-to-interference noise ratio) infor-
`mation may be used for selecting the transmission format.
`Thus, CCHs should be encoded robustly to ensure a high
`detection probability.
`
`Dueto these various characteristics, if soft reuse is
`[0053]
`employed the common channels should advantageously be
`transmitted on resources (e.g., on soft reuse frequency
`bands) that have a higher transmit powerin the cell. How-
`ever, this approach may be expected to require standardiza-
`tion, as the orthogonal resources in time-frequency (and
`possibly code) where most common channels are transmit-
`ted should be variable from cell to cell, and it should thus be
`possible to signal their placement to the UEs 10 by at least
`one of the common channels.
`
`In accordance with the exemplary embodiments of
`[0054]
`this invention, at least a portion of the common channels are
`primarily placed on a fraction of the available bandwidth.
`This fraction may be different
`in different cells in the
`network, and the placement of this bandwidth fraction in a
`cell (and possibly neighboring cells) is signaled to the users.
`
`[0055] The signaling of CCH placement maybedirect, so
`that there is, e.g., an indicator in a special system informa-
`tion field that indicates where to find other common chan-
`
`nels. Such a system information field is preferably transmit-
`ted in a specified time-frequency-code resource in a radio
`frame so that
`it can be located by the UE 10 without
`searching. Thus, at least that portion of the CCH that carries
`information about the Syslnfo field need not always be
`transmitted on a resource having higher transmission power.
`[0056]
`In accordance with the exemplary embodiments of
`this invention, the signaling of the CCH placement may be
`implicit. This may be arranged, for example, so that there is
`a set of possible pilot codes that may be used in a cell. As
`an example, the set may contain 128 different pilot codes.
`When synchronizing to the cell during an initial cell search
`procedure, the pilot code is acquired by measurements and
`sequence detection. For handover, the pilot code of neigh-
`boring cells may be indicated in one or more system
`information transmissions from each cell.
`
`In accordance with the exemplary embodiments of
`[0057]
`this invention that employ implicit signaling, the possible
`pilot codes are divided into sets so that the subband(s) where
`control channels are to be found depend on which pilot code
`set the pilot code of the cell belongs to. Thus, for a soft
`frequency reuse factor of three, the 128 (by example) pilot
`codes may be divided into three sets with, for example, 42
`pilot codes in one set and 43 in each of the other twosets.
`A more natural numerology, consistent with the soft reuse
`factor 3, would be to have, for example, 32 or 64 codes in
`a set, with 96 or 192 codes totally. One advantage ofthis
`approach is that when soft reuse is planned in the network
`the pilot code planning is automatically facilitated, and vice
`versa. Further, all system information may be placed on
`resources that enjoy better performance, as the UE 10
`performinga cell search would know hereto look for system
`information as soon as the UE 10 is able to synchronize to
`the cell, i.e., as soon as the UE 10 has identified the pilot
`code used in that cell.
`
`

`

`US 2007/0097901 Al
`
`May3, 2007
`
`[0058] One non-limiting approach to implement this tech-
`nique, and to gain the benefits for synchronization channels
`as well, is to design secondary synchronization channels in
`a FDM manner. Secondary synchronization channels
`(S-SCH)are such that not all cells in a system transmit the
`same S-SCH,andnotall cells transmit different S-SCHs. By
`synchronizing to the S-SCH the UE 10 may gain knowledge
`of the pilot (or scrambling) code group usedin the cell. That
`is, after successful reception of the S-SCH the UE 10 knows
`that the pilot (scrambling) code is one out of a group of
`several codes. The S-SCHs may be arranged so that part of
`the S-SCHidentity is the set of subcarriers that the S-SCH
`is transmitted on. According to exemplary embodiments of
`the invention, the S-SCHidentity further indicates in which
`resources at least a portion of the one common channelis
`transmitted.
`
`In accordance with the exemplary embodiments of
`[0059]
`this invention the S-SCH maybetransmitted in a portion of
`the spectrum having higher transmission power so as to
`improveat least the synchronization performance of the UE
`10. This may be exemplified in the example of 128 pilot
`codes, discussed above, with 42, 43 and 43 pilot codes in the
`sets indicating that common channels are to be found on
`frequency resources 1, 2 and 3, respectively. In such an
`arrangementthe possible S-SCHs may be divided into three
`sets. As a non-limiting example, in thefirst set the possible
`S-SCHsindicate a group of possible pilot codes in thefirst
`set of 42 codes, and directly indicate that common channels
`are to be found on frequency resource 1. In the secondset
`the possible S-SCHsindicate a group ofpossible pilot codes
`in the second set of 43 codes, and directly indicate that
`common channels are to be found on frequency resource 2.
`In the third set the possible S-SCHs indicate a group of
`possible pilot codes in the third set of 43 codes, and directly
`indicate that common channels are to be found on frequency
`resource 3.
`
`[0060] To obtain the benefits of soft reuse to improve
`synchronization performancethe three sets of S-SCH codes
`maybe frequency division multiplexed,i.e., transmitted on
`the same frequency resource as the S-SCH identity that
`indicates where the CCHsare transmitted.
`
`It should be appreciated that control channels may
`[0061]
`primarily be transmitted on resources with higher power.
`However, this is not meant to imply that control channels
`should never be transmitted on resources with lower power.
`For example, if a multistage approach is used for control
`channel encoding, where there is a first part of the control
`channel
`that has higher protection against errors than a
`second part, the first part could be transmitted on resources
`with higher transmit power. This first part may be used to
`allocate users in degraded channel conditions.
`
`Asis shown with regard to the FIGS. 2, 3 and 4,
`[0062]
`primary and secondary placements for CCHsare indicated.
`The primary placements of CCHs may be used for SysInfo
`(to the degree possible). The primary placements of CCHs
`are preferably used for allocating UEs 10 in weak channel
`conditions. The secondary placements, if needed, may be
`used to allocate UEs 10 in better channel conditions.
`
`In FIG. 2 an exemplary power mask is depicted for
`[0063]
`an exemplary cell
`in a system applying soft reuse. The
`transmission resources on the y-axis can include, at least in
`part, frequency division multiplexed (FDM) resources. For
`
`a non-limiting example that pertains to E-UTRA,the fre-
`quency resource may be oneofthe bandwidth alternatives of
`1.25 MHz, 2.5 MHz, 5 MHz, 10 MHz, 15 MHz, 20 MHz. In
`FIG. 2 the resources (e.g., bandwidth) are divided into six
`parts, and in the cell two of the resources are used with a
`higher allowed transmission power than the remaining four
`resources. Thus, there is frequency diversity in each of the
`soft reuse patterns, and higher power transmission may be
`concentrated in more than one part of the spectrum. In the
`exemplary allocation shown in FIG.2 the diversity degree is
`2.
`
`FIG. 3 shows a non-limiting example of sub-frame
`[0064]
`formats for the cell depicted in FIG. 2, and FIG. 4 shows a
`non-limiting example of sub-frame formats for the cell
`depicted in FIG. 2 with a portion of the SysInfo placed into
`a fixed resource (in this non-limiting example in the fixed
`resource labeled as #1 in FIG.2).
`
`[0065] Morespecifically, in FIG. 3 exemplary EUTRAN
`downlink sub-frame formats in the cell applying the power
`mask according to FIG. 2 are depicted. The sub-frame
`consists of seven OFDM symbols, and the subcarriers in
`each of these symbols are divided into six parts, on which
`the power mask of FIG. 2 is used.
`
`In FIG. 3 (a) the common channel placement is
`[0066]
`optimized to minimize the power usage of a DRX/DTXuser.
`For this purpose the common pilots and common channels
`are placed in the same OFDM symbol, and in this case
`simply by receiving this symbol the UE 10 mayestimate the
`channel and obtain information related to future allocations.
`The CCHsare primarily transmitted on the resources allow-
`ing higher transmission power. If these resources are not
`sufficient, the lower power resources in the same symbol
`maybe used.
`
`In FIG. 3 (6) the common channel placement is
`[0067]
`optimized so that the performance of the CCHsis made as
`efficient as possible. In this case the common channels are
`always transmitted on the resources that allow the highest
`transmit power, primarily in the same OFDM-symbolas the
`commonpilots.
`
`In FIG. 3 (c) the common channelsare placed in an
`[0068]
`OFDM symbol adjacent to a symbol with commonpilots.
`This schemeprovides an advantage that larger CCHs may be
`accommodated. Also,
`since processing may potentially
`execute in a serial fashion,
`the channel estimation that
`begins after receiving the symbol with commonpilots would
`be ready when the second symbol with the CCHs would be
`available for processing.
`
`FIG. 4 shows exemplary EUTRAN down-link sub-
`[0069]
`frame formats in the cell having the power mask according
`to FIG. 2,
`for a case of direct signaling of the CCH
`placements. Thus, the cell search procedure may follow the
`pattern of primary resources, even without an implicit sig-
`naling of the primary resources. Direct signaling, or explicit
`signaling, implies that there is a field (e.g. a SysInfo field)
`where a VE 10 performinga cell search can find information
`that indicates (explicitly) the placement of any oneorall of
`the CCHs. This field is preferably indicated in a subsetofall
`sub-frames, according to the pertinent frame format where
`synchronization channels are placed in an appropriate man-
`ner. In FIGS. 4 (a), (6) and (c) it can be seen that a fixed
`location for at least a part of the Syslnfo has been added to
`
`

`

`US 2007/0097901 Al
`
`May3, 2007
`
`the sub-frames according to FIGS. 3 (a), (6) and (c). This (at
`least) part of the SysInfo field indicates where CCHs may be
`found, or at least where allocation tables and possibly the
`remaining part of the SysInfo may be found.
`
`[0070] Based on the foregoing it should be appreciated
`that at least one advantage that can be realized by the use of
`the exemplary embodiments of this invention is that com-
`mon channel performance may be optimized in a situation
`where soft reuse is used.
`
`[0071] Referring to FIG. 5, it should be appreciated that a
`method in accordance with the exemplary embodiments of
`this invention, and the operation of a computer program
`product, includes (Block 5A) placing at least a portion of at
`least one common channel on a fraction of an available
`bandwidth ofa cell in a cellular communication system that
`uses soft reuse such that different orthogonal transmission
`resources are transmitted with different transmission powers
`and power usage is planned on a cell-by-cell basis; and
`(Block 5B) transmitting the common channel into the cell
`for reception by a plurality of receivers.
`
`[0072] Referring to FIG.6, it should be appreciated that a
`further method in accordance with the exemplary embodi-
`ments of this invention, and the operation of a computer
`program product, includes (Block 6A) receiving at least a
`portion of at
`least one common channel from different
`orthogonal transmission resources on a fraction of an avail-
`able bandwidth of at least one of higher transmission power
`or a lowertransmission powerof soft reuse; and (Block 6B)
`using information in the received common channel.
`
`[0073] The various blocks shown in FIGS. 5 and 6 may be
`viewed as methodsteps, and/or as operations that result from
`operation of computer program code, and/oras a plurality of
`coupled logic circuit elements constructed to carry out the
`associated function(s).
`
`In general, the various embodiments may be imple-
`[0074]
`mented in hardware or special purpose circuits, software,
`logic, Application Specific Integrated Circuits (ASICs) or
`any combination thereof. For example, some aspects may be
`implemented in hardware, while other aspects may be
`implemented in firmware or software which may be
`executed by a controller, microprocessor or other computing
`device, although the invention is not limited thereto. While
`various aspects of the invention may be illustrated and
`described as block diagrams, flow charts, or using some
`other pictorial representation,it is well understoodthat these
`blocks, apparatus, systems, techniques or methods described
`herein may be implemented in, as non-limiting examples,
`hardware, software, firmware, special purpose circuits or
`logic, general purpose hardware or controller or other com-
`puting devices, or some combination thereof.
`
`[0075] Embodiments of the inventions may be practiced in
`various components such as integrated circuit modules. The
`design of integrated circuits is by and large a highly auto-
`mated process. Complex and powerful software tools are
`available for conv