WO2008038090A2

WO2008038090A2 - Flexible spectral sharing

Info

Publication number: WO2008038090A2
Application number: PCT/IB2007/002753
Authority: WO
Inventors: Zhi-Chun Honkasalo; Preben E. Mogensen; Asbjorn Grovlen
Original assignee: Nokia Corporation; Nokia, Inc.
Priority date: 2006-09-29
Filing date: 2007-09-21
Publication date: 2008-04-03
Also published as: WO2008038090A3

Abstract

A retained bandwidth N2 is determined from an available bandwidth N1 (N2<=N1). An offset Delta in the frequency domain between a first bandwidth N0 and the retained bandwidth N2 is determined, where the first bandwidth is for a first type physical channel and the retained bandwidth is for a second type physical channel, and N0≤N1. The first type physical channel may be mapped to the first bandwidth N0 and transmitted and the second type physical channel may be mapped to the retained bandwidth N2 and transmitted. The offset Delta and the retained bandwidth are transmitted in a cell such as in a broadcast system information message. Advantageously this is used to align center frequencies of corresponding first N0 or retained N2 bandwidths in adjacent cells by adaptively selecting the offset Delta in view of the retained bandwidth N2. Apparatus, method and computer programs are detailed.

Description

FLEXIBLE SPECTRAL SHARING

TECHNICAL FIELD:

[0001] The exemplary and non-limiting embodiments of this invention relate generally to wireless communications systems, devices, methods and computer program products, that operate to adapt the relative disposition of physical channels of a wireless communications network, and are particularly advantageous for Evolved UTRA (E-UTRA) networks.

BACKGROUND:

[0002] The third generation partnership project (3 GPP) is working on adapting current implementations of wideband code division multiple access (W-CDMA and multi-carrier MC-CDMA) to achieve potentially much higher data rates than the theoretical 14.4 Mbps under current adaptations of high speed packet access (HSPA). These efforts are commonly termed Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network Long Term Evolution (UTRAN LTE, or LTE for short), 3.9G, or Evolved UTRAN (E-UTRA or E-UTRAN). Particularly relevant to these teachings is the variable channel bandwidth characteristic under consideration for LTE.

[0003] LTE has been designed to operate over different channel bandwidths in the operator network. To enable all the mobile terminals/user equipment (UE) to function when entering the network (and also when it moves from one part of the network to another where the operating bandwidth maybe different), the general structure of LTE is described with reference to Figure 1. The available spectrum is divided into frequency blocks Ia, each with twelve sub-carriers Ib and spanning 180 kHz. The minimum operating bandwidth is designated NO, shown in Figure 1 by example as six frequency blocks Ia (N0=6*180 KHz), and the maximum operating bandwidth is designated Nl, shown in Figure 1 by example as 100 frequency blocks Ia (Nl=100*180 KHz). The minimum step between physical channels is one frequency block Ia, so that the operator may deploy the LTE radio network with any channel bandwidth that is between the minimum and maximum at the resolution of 18OkHz. [0004] Physical channels of the E-UTRA system are mapped for LTE purposes to one of two channel types: Type 1 or Type 2. Type 1 channels Ic span a fixed value NO in all LTE networks. Type 2 channels Id span a variable bandwidth N2, limited in that N2 is at leastNO and no greater than Nl (NO<=N2<=N1). Figure 1 shows the Type 2 channel Id as spanning the entire available bandwidth Nl= 100 frequency blocks. The bandwidth N2 of the Type 2 channel may differ between different networks, and can be changed within different cells of the same network in order to most efficiently use the available spectrum (see Figures 2A-2B). It is this dynamic adjustability of N2 that gives the network operator flexibility in LTE. Since N2 can never be less than NO, Type 1 channels are considered narrowband and Type 2 channels are considered wideband. Currently, the Type 1 channels are (roughly) aligned with the center of the Type 2 channel.

[0005] To enable this variable architecture, the UE must know at least the value of

N2. For example, the value of N2 may be broadcast on the broadcast channel (BCH or BCCH, generally the primary BCH/BCCH if more than one is in use), and given to the UE directly when the UE first gains access to a network via other methods. For example, the LTE network can utilize the binary sequence in the synchronization channel (SCH) or other physical layer methods to convey the N2 bandwidth information to the UE. These are the alternative proposals to convey this N2 bandwidth information by other than the BCH. As will be shown, knowing the N2 bandwidth under current proposals for LTE enables the UE to know both the Type 1 and Type 2 channels because there is a pre-determined relation that the center frequencies of both are roughly aligned, to within one half of a frequency block (detailed below). When entering a new cell, the UE needs to decode the BCH message of the new cell in order to obtain the value of N2 for that cell.

[0006] Key parameters related to the variable channel bandwidth property of the

E-UTRA physical layer are summarized in Tables 7.1.1-1 / 9.1.1-lof TR 25.814. Some of these parameters (e.g. "Transmission BW", "Number of occupied sub-carriers") are strongly related to E-UTRA deployment scenarios and their associated RF performance requirements (e.g. out-of-band OOB leakage requirements, regulatory emission limits, etc.). These parameters are therefore under discussion in current working groups related to E-UTRA and LTE. Ultimately, the appropriate relationship between the number of occupied sub-carriers for each E-UTRA radio-frequency (RF) channel bandwidth will be determined by RF related requirements such as:

• E-UTRA and adjacent system's frequency raster;

• OOB requirements, both from a regulatory and a RF co-existence point of view. [There is no agreement yet which concept will be used for defining OOB emission limits.]

[0007] An example for the involved complexities in matching the number of occupied sub-carriers with the E-UTRA RF channel bandwidth was presented in two co-owned papers attached to the priority document respectively as Appendices B and C: R4-060747, CONSIDERATIONS REGARDING DL CO-EXISTENCE OF 1.25 MHz E-UTRA WITH GSM IN 900 MHz; and Rl-062360 / R4-060742, ANALYSIS OF 1.25 MHz E-UTRA BS SPECTRUM SHAPING REQUIREMENTS. In the former paper it was shown that a RF bandwidth of 1.25 MHz is not necessarily meaningful from the perspective of uncoordinated deployment adjacent to global system for mobile communications (GSM) networks and that another RF bandwidth (e.g. 1.4 MHz) may be more appropriate for the definition of the RF requirements. Identifying suitable pairings (number of radio blocks, RF bandwidth) for GSM co-existence / re-farming scenarios will require further effort.

[0008] During the continuous development of E-UTRA specifications it is also anticipated that a number of different frequency bands and related RF deployment scenarios need to be supported. In order to be able to advance the work efficiently within the various radio access network (RAN) working groups (WG) (e.g., RAN WGl and WG4), it is therefore highly desirable to develop the E-UTRA physical specifications generically and independently from RF deployment scenario related parameters such as the number of occupied sub-carriers (frequency blocks). These teachings detail embodiments for how that might be achieved.

SUMMARY:

[0009] According to an exemplary embodiment of the invention is a method that includes determining a retained bandwidth, and determining an offset Delta in the frequency domain between a first bandwidth and the retained bandwidth, where the first bandwidth is for a first type physical channel and the retained bandwidth is for a second type physical channel, and where the retained bandwidth encompasses the first bandwidth. Further in the method, in a cell is transmitted the offset Delta and the retained bandwidth.

[0010] According to another exemplary embodiment of the invention is a memory embodying computer readable instructions, the execution of which results in actions that include determining a retained bandwidth, and determining an offset Delta in the frequency domain between a first bandwidth and the retained bandwidth, where the first bandwidth is for a first type physical channel and the retained bandwidth is for a second type physical channel and wherein the retained bandwidth encompasses the first bandwidth. The actions further include transmitting in a cell the offset Delta and the retained bandwidth.

[0011] According to another exemplary embodiment of the invention is an apparatus that includes a processor coupled to a memory. The processor is configured to determine a retained bandwidth and an offset Delta in the frequency domain between a first bandwidth and the retained bandwidth, where the first bandwidth is for a first type physical channel and the retained bandwidth is for a second type physical channel that encompasses the first bandwidth. The apparatus further includes a transmitter configured to transmit in a cell the offset Delta and the retained bandwidth.

[0012] According to another exemplary embodiment of the invention is an apparatus that includes processing means for determining a retained bandwidth and an offset Delta in the frequency domain between a first bandwidth for a first type physical channel and the retained bandwidth for a second type physical channel that encompasses the first bandwidth. The apparatus further includes transmit means for transmitting in a cell the offset Delta and the retained bandwidth. In a particular embodiment, the processing means is embodied as a processor coupled to a memory, and the transmit means is embodied as a transmitter.

[0013] According to yet another embodiment of the invention is a method that includes receiving in a cell an offset Delta and a retained bandwidth, determining from the received offset Delta and the retained bandwidth a first bandwidth within the retained bandwidth, and tuning a receiver to the first bandwidth to receive at least one of a broadcast channel or a synchronization channel.

[0014] According to another embodiment of the invention is an apparatus that includes a receiver that is configured to receive in a cell an offset Delta and a retained bandwidth, and a processor coupled to a memory. The processor is configured to determine from the received offset Delta and the . retained bandwidth a first bandwidth within the retained bandwidth, and thereafter to tune the receiver to the first bandwidth to receive at least one of a broadcast channel or a synchronization channel.

BRIEF DESCRIPTION OF THE DRAWINGS:

[0015] Exemplary embodiments of the present invention are detailed below with reference to the following drawing figures.

[0016] Figure 1 is a prior art diagram showing physical channel mapping of a Type

1 channel at a center frequency of available Type 2 channel bandwidth.

[0017] Figure 2 shows geographic disposition of two adjacent areas of a network, or adjacent areas of different networks.

[0018] Figure 3 shows a side-by-side view of prior art mapping of Type I/Type 2 channels for different but overlapping areas such as those of Figure 2 that use a different N2 bandwidth.

[0019] Figure 4 shows two embodiments of the prior art mapping of Figure 3, showing the individual frequency blocks of a Type 1 channel mapped against even or odd numbers of available frequency blocks.

[0020] Figure 5 shows an embodiment of the invention with the Type 1 channels offset zero from the available variable spectrum. [0021 ] Figure 6 shows a side-by-side view of physical channel mapping for different but overlapping areas such as those of Figure 2 using the zero offset of Figure 5.

[0022] Figure 7 is similar to Figure 5, but with the offset greater than zero.

[0023] Figure 8 is similar to Figure 6, using the offset of Figure 7.

[0024] Figure 9 is a schematic block diagram of hardware used in implementing embodiments of the invention, including a controlling network element, a base station, and a user equipment.

[0025] Figure 10 is similar to Figure 6 but showing an embodiment where the center frequencies of the Type 2 channels align across neighboring cells but the center frequencies of the respective Type 1 channels do not.

[0026] Figure 11 is a process flow diagram summarizing exemplary aspects of the invention.

DETAILED DESCRIPTION:

[0027] The below examples of embodiments of this invention relate to the design of the variable channel bandwidth property of LTE, and how the LTE concept can be utilized in the network deployment of the spectral domain to co-exist in a flexible way with the existing cellular systems (for example, re-farming of GSM spectrum to LTE system). Of course, these teachings are not limited only to re-farming spectrum among LTE and GSM systems, but such examples are enlightening of the invention's broader aspects.

[0028] Currently there appears to be an implication among the various LTE working groups that the number of occupied sub-carriers used for each E-UTRA RF channel bandwidth must be explicitly specified as part of the physical layer attributes. However, the inventors do not believe that this is necessary, and that it does not represent the best way of developing E-UTRA specifications jointly in the above-referenced radio access network RAN working groups. Therefore this disclosure presents implementations to better define the variable channel bandwidth property of E-UTRA from the physical layer perspective, independently of potential E-UTRA deployment scenarios that may occur in the future, in order to obtain flexible specifications adaptable to future refinements of E-UTRA and to enable the different working groups to move forward independently.

[0029] As noted in the background section above, the variable channel bandwidth property of LTE enables the network operator to deploy the LTE network using the same frequency band, even partially over-lapping channel spectrum, with existing cellular network(s) such as GSM. As presently contemplated, the position of the Channel Type 1 (narrowband) is defined to be roughly around the middle part of the Channel Type 2 (wideband). The inventors have determined that this leads to an adverse result, as illustrated with reference to Figures 2-3. Assume for example that the network operator is using 5MHz LTE in one part of the network (area A) and using 10MHz LTE in another part (area B). At the border 2a between cells of areas A and B of Figure 2, the SCH/BCH physical channels (or other narrowband Type 1 channels) are not lined up in the frequency domain as seen in Figure 3 by the respective channels 3b, 3d. These teachings contemplate that the common control physical channels BCH and SCH are always and in every network mapped to a Type 1 channel, and in the discussion below of the prior art mapping of Type 1 and Type 2 channels it is assumed that the BCH and SCH are mapped to a Type 1 channel (though it is noted that the prior art is not seen to make such a mapping mandatory). In some embodiments of this invention, all common control physical channels are always and everywhere mapped to a Type 1 channel, and further all other physical channels (such as shared control and shared data physical channels) are mapped to a Type 2 channel.

[0030] Returning to the example shown in Figure 3, the area A cell chooses N2=25 frequency blocks for the wideband channels 3 a (which are mapped to a Type 2 channel) and disposes the BCH/SCH 3b (which is mapped to a Type 1 channel spanning NO frequency blocks) at the center of those N2=25 FBs. The center of the BCH/SCH 3b in area A is then the center of the twelfth frequency block. The RF channel carrier number of a cellular system is defined by its center frequency (e.g., center frequency F_N of channel carrier number N is F_N=F_O+1-*N; where F₀ represents the center frequency of the first available LTE channel in an cellular frequency band, k is the channel raster, and N=O, 1, 2, ...), so knowing N2 enables the UE to know both the Type 1 and Type 2 channels since their center frequencies are aligned as in each area of Figure 3. In the equation, F₀ represents the edge of the whole LTE band, not necessarily the edge of a Type 2 channel (wideband). For example, if an LTE cell operates in the 900MHz band of GSM, then F₀ represents the first available LTE channels' center frequency.

[0031] Now consider the spectrum in area B, where the network or cell chooses

N2=50 frequency blocks for the wideband channels 3c. The BCH/SCH 3d in area B is also mapped to a Type 1 channel spanning NO frequency blocks, but the BCH/SCH 3d for area B is located at the center of N2=50 frequency blocks. The BCH/SCH 3b, 3d of the different areas A and B are not aligned. This results in the UEs having to perform neighboring cell measurements, such as they do in the case of an inter-frequency handover. While this result may be functional since all UEs must be capable of supporting inter-frequency mobility anyway, the inventors have determined that channel re-use 1 can be facilitated by aligning the narrowband channels (e.g., SCH and BCH) whenever possible. Under current views of LTE, since the Type 1 channels are disposed at roughly the center of the N2 spectrum and each network or cell can operate with a different N2 bandwidth, any alignment of the Type 1 channels between neighboring cells is happenstance: it occurs only when both neighboring cells use the same N2 value. For the specific example of 5MHz and 10MHz in an LTE network as above, re-use of the Type 1 channels could be made possible by aligning the SCH/BCH in both areas A and B, since both Areas A and B over-lap their LTE-used spectrum by 5MHz. These teachings describe how that alignment may be made purposeful.

[0032] As further background into the assumptions currently underlying development of LTE, Figure 4 illustrates two different mappings of a Type 1 channel spanning six frequency blocks into the center of the Type 2 available spectrum. In one example (top of Figure 4), there is an even number of frequency blocks in the entire N2 spectrum. At either side of the center frequency 4a are then N2/2 frequency blocks, of which one side carries three (half) of the Type 1 channel frequency blocks (4c, 4d, 4e) and half of the remaining Type 2 channel frequency blocks (4j), and the other side of the center frequency carries the other three of the Type 1 channel frequency blocks (4f, 4g, 4h) and the other half of the remaining Type 2 channel frequency blocks (4j). The center frequency lies between frequency blocks when N2 is an even number (and NO is also an even number, as assumed for the upper portion of Figure 4), and the center frequency 4a of the Type 1 and Type 2 channels coincide.

[0033] For the situation where there are an odd number of N2 frequency blocks, the lower portion of Figure 4 shows that the center frequency 4a splits one of the frequency blocks 4k of the Type 1 channel, so that (N2-l)/2 of the Type 2 channel frequency blocks lie on one side and the remaining (N2+l)/2 of the Type 2 channel frequency blocks lie on the other side. As can be seen, the entire Type 1 channel is not always mapped to the exact center of the N2 available bandwidth due to the possibility of an odd number of N2 frequency blocks, but roughly mapped to within one half frequency block of that center frequency. The indicated center frequency 4a is the center frequency of the Type 2 channel in both instances, and as seen in the lower diagram of Figure 4, the center frequency 4b of the Type 1 channel can deviate from the center frequency 4a of the Type 2 channel by no more than one half of a frequency block, and only when N2 is an odd number.

[0034] Therefore, the UE is still able to know both Type 1 and Type 2 channels once it knows N2, such as by BCH signaling noted above. It is noted that because the Type 1 channel need not occupy every OFDM symbol in its band (NO), the remaining symbols may be used by the Type 2 channels for traffic/data (or any other Type 2 signals), so the Type 2 channels are shown as spanning the entire N2 bandwidth, including that used by the Type 1 channel. The N2 bandwidth is termed a retained bandwidth since it is retained from the available Nl spectrum, and the NO bandwidth is termed simply a first bandwidth which as above is encompassed by the retained bandwidth N2 due to the Type 2 channels' use of the remaining symbols within the NO/first bandwidth as noted above. [0035] In accordance with these teachings, the position of the Type 1 channels

(narrowband) relative to the Type 2 channels (wideband) is fixed to an offset variable, termed herein as Delta. The offset Delta may indicate a difference between center frequencies of the Type 1 and Type 2 channels, or between start frequencies, end frequencies, or any other border or interim frequencies, so long as the UE knows a priori how to apply the offset Delta. The description below is in the context of Delta indicating an offset from a start frequency of the bandwidth N2 to the start frequency of the Type 1 channel, though the same results may be obtained using any of the other implementations for Delta noted above. As a default condition in the absence of the network specifying a value to its UEs, the value of Delta can be set to zero for all LTE networks, resulting in Type 1 and Type 2 channels being lined up on the left side of the N2 channel spectrum. A different default may be selected, but the above zero-offset condition is shown at Figures 5 and 6. The illustration of Figure 5 follows the convention of Figure 4, with individual frequency blocks shown. The six frequency blocks of the Type 1 channel 5a in Figure 5 are aligned with the leftmost (lowest frequency) portion 5c of the available N2 spectrum 5b, and channels mapped to a Type 2 channel 5b will be at a higher frequency than the Type 1 channels in this zero-offset condition (excepting the OFDM symbols not used by the Type 1 channel signalling and used by the Type 2 channel signalling). The center frequency 5d of the Type 1 channel is not aligned with the center frequency 5e of the Type 2 channels and the difference is greater than one half frequency block (which is the maximum possible in the prior art approach). As above, Delta may instead be measured as the center frequency offset rather than an offset from the lowermost edge 5c of the Type 2 channel 5b as in this example.

[0036] Figure 6 shows a side-by-side comparison of this zero-offset mapping done in two adjacent network areas such as the areas A and B of Figure 2. Note again that it does not matter if these areas A and B are under control of the same network operator or different network operators. Assume the network node for Areas A and B each have 5 MHz of available bandwidth for use as that node/network sees fit. Figure 6 shows the network node for Area A selecting N2 at twelve frequency blocks, spanning roughly 2.5 MHz where each frequency block spans 180 kHz (the total span is rounded up to avoid interference among adjacent cells). This choice of N2 enables Area A to 'give' its excess bandwidth 6a (the remaining 2.5 MHz) to another network system, such as a GSM system operating in the same physical area A. With a zero offset (Delta=0), the Type 1 channel 6b is aligned with the left side of the available bandwidth (lowermost frequency), so the spectrum released 6a to the different GSM system in the same cell comes from the right side of the overall Nl frequency band as shown. Due to the Type 2 channel 6c using some symbol positions in the Type 1 frequency blocks, the bandwidth available for Type 2 channel mapping spans the entire N2 spectrum including that set aside for the Type 1 channel 6b for area A.

[0037] In adjacent area B, the network node chooses the entire 5MHz for LTE use, so N2=5 MHz is the bandwidth of the Type 2 channel 6e. There is no need for the GSM system in area B to use some of the LTE bandwidth so the LTE system retains all of the available Nl=5MHz bandwidth as the Type 2 channel rather than giving some 6a as seen for Area A. Recall that with mis-matched N2 spectrum, the prior art was incapable of aligning the adjacent area Type 1 channel center frequencies as seen at Figure 3. But since both areas A and B operate with a zero offset in Figure 6, the Type 1 channel 6d for area B aligns with the Type 1 channel 6b of area A. Assuming the SCH and/or BCH are mapped to this Type 1 channel, the channel is reused despite the fact that the nodes for areas A and B make different selections for N2. The bandwidth available for Type 2 mapping spans the N2=5MHz bandwidth 6e at area B. Note that while the center frequencies of the Type 1 channels align across areas A and B, the center frequencies of the Type 2 channels do not.

[0038] Alternatively, any non-zero value of Delta may be sent to the individual UEs on the BCH, together with the value of N2, as system parameters. A non-zero Delta value enables greater freedom for the network operator when implementing spectral re-farming to deploy LTE across his own network, while still enabling re-use of Type 1 channels in SCH/BCH across his network. The position of the Type 1 channel relative to the Type 2 channels may be stipulated in the Physical layer specification (e.g., either in the middle, or aligned with one side or another of the Type 2 channel, or a fixed offset Delta defined by any of the options noted above or other variations) as a default condition. The network operator can then adjust the value of Delta as need be to ensure alignment of the Type 1 channels whenever feasible. Where adjacent cells are from different LTE networks, they or their controlling nodes may communicate directly to coordinate alignment. Where they are from the same LTE operator, they may coordinate directly or be directed by a common higher network node. The values of N2 may also be standardized to support the radio profile, so that the network signals N2 and the offset Delta in the same message with minimal signalling.

[0039] An example of a non-zero Delta is shown in Figures 7 and 8. At Figure 7, the non-zero Delta 7a is shown as offsetting the Type 1 channel 7b from the start frequency 7c of the retained N2 spectrum (Type 2 channel 7d), though Delta might alternatively be an offset from the N2 center frequency 7e, a start or center or end frequency 7f of the Nl bandwidth, or some other starting point. The distinction over Figures 5 and 6 will be detailed with respect to Figure 8.

[0040] As with Figure 6, Figure 8 assumes that each network node (area A and area

B) has 5 MHz available, area A selects for the Type 2 channel 8b N2=12 frequency blocks and (temporarily at least) gives 2.5 MHz 8d of its available Nl spectrum 8c to another system. Figure 8 further assumes that the area B cell selects as its Type 2 channel 8f N2=25 frequency blocks, retaining its entire 5 MHz N12 spectrum (also 8f) for use in the E-UTRA LTE system. The node B for Area A broadcasts, for example, that N2=12 and Delta=3, which the UEs under its control recognize as mapping the Type 1 channel 8a to begin after the third frequency block of the retained N2 spectrum 8b. This leaves three frequency blocks available for Type 2 channel mapping on either side of the Type 1 channel 8a (in addition to those portions/symbol positions of the Type 1 channel 8a bandwidth not being used by the Type 1 channel and used by the Type 2 channel 8b instead). Since area A releases 2.5 MHz (total of the 8d portions) of its spectrum to another system and is using a non-zero offset (Delta), that released spectrum may be lower in frequency or higher in frequency than the retained N2 spectrum 8b. As seen in Figure 8 for area A, the released spectrum is at frequencies both below and above that of the retained spectrum 8b. In the particular case of area A for Figure 8, the center frequencies (dashed line) of both the Type 1 and Type 2 channels 8a and 8b align with one another. [0041] Area B in Figure 8 also uses an offset (Delta'), but the value is not identical to that of area A, since only Area A releases spectrum lower in frequency that of the retained spectrum Type 2 channel 8b and Area B does not. Area B offsets to align in frequency its Type 1 channel 8e with that 8a of area A, and the N2 bandwidth for mapping of Type 2 channels 8f spans the entire available 5MHz bandwidth. Note that for area B, the center frequency 8g of the Type 2 channel 8f is not aligned with the center frequency 8h of the Type 1 channel 8e, even though both those center frequencies are aligned with one another in area A and the center frequencies of the Type 1 channels 8a, 8e for both areas align. In both Figures 6 and 8, the center frequencies of the Type 1 channels align across areas A and B despite the different area Node B's selecting a different value for N2, which is not seen to be possible in the prior art. It should be noted that the main motivation of the prior-art approach was to enable the center frequencies of Type 1 and Type 2 channels in one cell to align, so that when a UE moves from receiving a Type 1 channel to a Type 2 channel, it does not need to re-tune the RF frequency in the receiver. However, due to the fact that NO is fixed at 6 blocks, while N2 is a variable of odd or even number, its not always possible to align the center frequencies of the two channel types anyway (as can be seen from Figure 4). With this invention, the frequency position of Channel Type 1 can vary relative to the Channel Type 2 within one cell. This means the prior-art case (i.e. having the Type 1 spectrum approximately to be in the middle of the Type 2 spectrum) can still be realized, as well as other network configurations which enable the Type 1 channels of neighboring cells to align. The latter simplifies the UE processing of Type 1 channels, to support neighboring cell monitoring.

[0042] Figure 10 shows another aspect of the invention. Both cells A and B

(neighboring as seen in the inset) select N2=50 frequency blocks. The Type 1 channels 10a, 10b are not aligned across the neighboring cells, but the center frequency 1Oe of the Type 2 channels 10b, 1Od is aligned across those same neighboring cells. In this example, cell A and the neighboring cell B select the same Type 2 channel bandwidths, but the Type 1 channels 10a, 10c on the two cells are configured to be different by their relative placement within their respective Type 2 channel 10b, 1Od. [The same center-frequency result may also be obtained even if the N2 bandwidths across the cells were different; the N2 center frequencies 1Oe could still be made to align even if the N2 bandwidths were not equal across the cells.] In the case where the Type 2 channel center frequencies 1Oe align across cells but not the Type 1 center frequencies, the position of the Type 1 channel 10c of Cell B relative to that of Cell A should be informed to the UE who are connected to Cell A. This may be done for example in the neighboring cell information. A UE in cell A can then use this information to find the SCH (mapped to 10c) of Cell B and include it in the neighboring cell measurement and reporting, as needed. An advantage of aligning Type 2 channels 10b, 1Od across neighboring cells but not Type 1 channels 10a, 10c is to avoid interference on SCH/BCH, which is desirable in some radio environments.

[0043] Now consider how the above results can be obtained under a current LTE signalling regimen. When searching for a neighboring cell (e.g., for handover candidates), the UE looks for the SCH in the Type 1 channel frequency blocks (which is an advantage of re-use=l on the SCH). The UE finds the SCH for a candidate cell, and from that determines frame timing which informs the UE where it can find the candidate cell's reference signal sequence, which the UE then tries to decode. This is part of the normal UE inter-cell mobility procedure, hi the prior art, the SCH position (e.g., channel number) was also signalled to the UE since alignment was unlikely, as seen in Figure 3. Where the new cell's SCH (Type 1 channel) aligns with that of the old cell as with embodiments of these teachings, the UE already has the new cell's SCH. Knowing N2 and Delta enables the UE to know both the Type 1 and Type 2 channels and their relative frequency relation.

[0044] An advantage of the above teachings gives a greater freedom for the network operator to maintain re-use=l on the Type 1 channel carrying SCH/BCH, where-ever possible across his network, at the same time LTE data channels, those mapped to Channel Type 2 (wideband), can be deployed to share spectrum with an existing network (e.g., GSM) differently in different parts of the overall network. [For two adjacent areas, the re-use is one but it is contemplated that several areas might align their Type 1 channels when conditions are favorable to obtain a re-use greater than one.] This is in contradistinction to the current assumption under LTE development working groups that SCH/BCH is to be always allocated roughly at the center of the data channels (Type 2). Adaptively disposing the Type 1 channels in the Type 2 channels enables the network operators to re-farm spectrum (N1-N2) to another system, such as a narrowband GSM system which is based on 200 kHz spacing. If Delta is to become a system parameter of the LTE system (sent in BCH and in neighboring cell information), the complexity for the UEs may rise slightly so as to monitor the adaptively disposed SCH/BCH.

[0045] Channel Type 2 operates at a variable system bandwidth N2, where N0<= N2

<= N1. As a further teaching, the FFT size (see Table 7.1.1-1 of 3GPP TR 25.814, attached as Appendix A to the priority document) is defined at the transmit end of the wireless system for each possible value of N2 for inclusion in the physical layer specification. This could be done either by defining a mapping from N2 to FFT size, or by an explicit table stored in the memory of each of the UE and network nodes exploiting these teachings for LTE. An example for a possible mapping would be to set the FFT size as the smallest power of 2 >= (N2*12 +l)/0.9. Thus, for example, for N2=7 (to enable the smallest number of subcarriers 76 in Table 7.1.1-1), the equation yields 94.4 and the FFT size would then be 128 (2^Λ7=128, and 7 is the smallest power of 2 that is greater than 94.4), as seen in the table. For an explicit table stored in a memory, the discrete values of N2 would be mapped to explicit FFT sizes.

[0046] The sampling frequency and cyclic prefix CP duration (in samples) can be then derived from the FFT size together with other fixed parameters such as the 15 kHz subcarrier spacing, 0.5 ms subframe duration and number of symbols/subframe seen in Table 7.1.1-1.

[0047] As is shown in the paper referenced above as R4-060747 (Appendix B of the priority document), there is no need to standardize the E-UTRA spectrum shaping, because in OFDM/FDE based systems there is no need to match the receive filtering to the detailed characteristics of the transmit filters (or time domain windowing). Naturally, it is important that the spectrum shaping meets a number of OOB emission requirements to ensure RF compatibility with adjacent systems and compliance with regulatory requirements. However, the details of the spectrum shaping method would not need to be directly specified, but could be indirectly captured by OOB and related RF requirements to be defined for the selected values of N2. This also aids in decoupling the work of disparate E-UTRAN LTE working groups to enable them to move forward independently toward a full set of LTE specifications. These teachings describe the variable channel bandwidth property of E-UTRA in such a way that the exact number of occupied sub-carriers at each RF operating bandwidth does not need to be explicitly defined in the physical layer specification.

[0048] Reference is now made to Figure 9 for illustrating a simplified block diagram of an exemplary apparatus for practicing the invention. An electronic mobile device such as a UE 10, or any entity operating with similar functions as those described herein for a UE, includes a data processor (DP) 12A, a memory 14A that stores a program 16A, and a suitable radio frequency (RF) transceiver 18A and antenna 2OA for bidirectional communications over a wireless link 22 with an antenna 23 of a base station BS 24. The BS/Node B 24 includes similar functional blocks as shown in Figure 1 for the UE, denoted there with the suffix B. The BS 24 is under control of a network control element 28 such as a radio network controller RNC (alternatively referred to as a mobility management entity MME, a gateway GW, or the like), also with similar functional blocks numbered with the suffix C, and an Iu interface or other hardwire link 26 couples a modem (not shown) or other data input/output device of the BS 24 to a similar one in the network control element 28 for communications therebetween. Alternatively or additionally, the link 26 between the network control element 28 and BS 24 maybe wireless without departing from the teachings herein. Generally, all nodes disposed upstream of the UE 10 are considered the network (except another destination UE not shown). While only one is shown, it is assumed that the UE 10 include more than one receiver, so as to monitor the BCH of a neighboring cell other than its serving cell, as detailed above. Alternatively, the UE 10 may use a single receiver and change frequencies at predetermined and time-limited periods, as known in the art, to monitor the neighboring cell.

[0049] At least one of the programs 16A, 16B, 16C stored in the memory 14 A, 14B,

14C is assumed to include program instructions that, when executed by the associated processor 12A, 12B, 12C, enable the UE 10/BS 24/network controller 28 to operate in accordance with the exemplary embodiments of this invention, as detailed above.

[0050] In general, the various embodiments of the UE 10 can include, but are not limited to, mobile stations, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming 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.

[0051] The embodiments of this invention may be implemented by computer software executable by the processor 12A of the UE 10, the processor 12B of the BS 24, and/or the processor 12C of the network controller 28, or by hardware, or by a combination of software and hardware. In some embodiments, signaling specific to the invention, such as an information element indicative of an offset Delta sent over a BCH, is sent from the BS 24 or the network controller 28 (e.g., through the BS 24) to the UE 10. For those embodiments, the appropriate software program 16B, 16C to effect that signaling is embodied in the respective memory 14B, 14C and executable by the digital processor 12B, 12C. In other embodiments, adjacent Node Bs may communicate with one another to coordinate alignment of their respective Type 1 or Type 2 channels with one another. Alternatively, one Node B (such as one choosing to give some of its available Nl spectrum to another system) may monitor the Type 1 channel of an adjacent Node B and choose the N2 spectrum that it retains so as to provide a Delta within its cell that will align its Type 1 or Type 2 channel with that of its neighbor.

[0052] The memory 14A, 14B, 14C may be of 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 processor 12A, 12B, 12C may be 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 processors based on a multi-core processor architecture, as non-limiting examples.

[0053] Figure 11 illustrates process steps according to an exemplary embodiment showing both Node B and UE actions. At block 1101 the Node B determines a retained bandwidth N2. At block 1102 it determines an offset Delta, in the frequency domain, between NO (a first bandwidth) and the retained bandwidth N2. N2 encompasses NO in the frequency domain. At block 1103 the Node B maps the first type physical channels (all common control channels) to the NO bandwidth and maps the second type physical channels (all others in the cell) to the N2 bandwidth. Then at block 1104 the Node B transmits in the cell the offset Delta, N2, and the mapped channels from block 1103. At block 1105 the UE receives the Node B's transmission from block 1104, uses the received offset Delta and N2 to determine the location of NO within the N2 spectrum, and tunes its receiver to receive the physical channels mapped to the NO bandwidth.

[0054] In this disclosure is described a method, apparatus and computer program embodied on a storage medium to dynamically dispose a Type 1 channel relative to the Type 2 channels by offsetting the Type 1 channel in the frequency domain by an amount Delta. The value of Delta may be signalled to the UE (for example, but not limited to, by means of Cell system information messages) over a BCH, and the value may be zero. All E-UTRA physical channels are mapped to either a Type 1 or a Type 2 channel. In an embodiment, the value of Delta is set to a default value (e.g., zero) in the absence of specific signalling. In an embodiment, the BCH and SCH are always and everywhere mapped to a Type 1 channel and all other channels are mapped to a Type 2 channel, but the specific disposition of the Type 1 channel relative to the Type 2 channels may vary among network cells. In an embodiment, the value of Delta is sent to the UE in the same broadcast message as the value N2, where N2 is the spectrum in use in the broadcasting network area, both Delta and N2 dynamically configurable by the network. Preferably, the values for N2 are limited to a discrete and pre-defined set. Embodiments of this invention may be realized in the UE, which receives the value Delta and adjusts its receiver accordingly to monitor the Type 2 channel at a frequency determined by that offset value Delta, and at least also in a Node B/base station that determines the value Delta and/or that sends the value Delta to the UE in a wireless message, and possibly also in a network control element or other network node that determines the value Delta and sends it to the node B/BS 24.

[0055] hi general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic 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 exemplary embodiments of this invention may be illustrated and described as block diagrams, or as signaling formats, or by using some other pictorial representation, it is well understood that 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 computing devices, or some combination thereof.

[0056] 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 automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. Figure 11 gives functional steps that may be executed by an integrated circuit according to an embodiment of the invention.

[0057] Programs, such as those provided by Synopsys, hie. of Mountain View,

California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well-established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication. [0058] Various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications of the exemplary embodiments of this invention will still fall within the scope of the non-limiting embodiments of this invention.

[0059] Furthermore, some of the features of the various non-limiting embodiments of this invention maybe used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not limitations thereof.

Claims

CLAIMS: We claim:

1. A method comprising: determining a retained bandwidth; determining an offset Delta in the frequency domain between a first bandwidth for a first type physical channel and the retained bandwidth for a second type physical channel that encompasses the first bandwidth; and transmitting in a cell the offset Delta and the retained bandwidth.

2. The method of claim 1, wherein determining the retained bandwidth and determining the offset Delta are adaptively determined within a cell of a wireless communication system.

3. The method of claim 1 , wherein the first bandwidth is fixed.

4. The method of claim 1 , wherein the first type physical channel comprises at least one of a broadcast common control channel and a common synchronization channel.

5. The method of claim 4, wherein transmitting in the cell the offset Delta and the retained bandwidth comprises sending the offset Delta and the retained bandwidth in a system information message over the broadcast common control channel.

6. The method of claim 1 , further comprising mapping the first type physical channel to the first bandwidth and mapping the second type physical channel to the retained bandwidth; and wherein transmitting further comprises transmitting the mapped first type physical channel and the mapped second type physical channel.

7. The method of claim 1, wherein the offset Delta is transmitted anytime it is determined to be non-zero and is not transmitted when it is determined to be zero.

8. The method of claim 1 , wherein all physical channels in the cell are either of the first type physical channel or of the second type physical channel.

9. The method of claim 1, wherein all possible values for the retained bandwidth are limited to a discrete and pre-defined set.

10. The method of claim 1, wherein determining the offset Delta comprises aligning a center frequency of either of the first bandwidth or the retained bandwidth with a corresponding center frequency of an adjacent cell.

11. The method of claim 1 executed by a Node B.

12. A memory embodying computer readable instructions, the execution of which results in actions comprising: determining a retained bandwidth; determining an offset Delta in the frequency domain between a first bandwidth for a first type physical channel and the retained bandwidth for a second type physical channel that encompasses the first bandwidth; and transmitting in a cell the offset Delta and the retained bandwidth.

13. The memory of claim 12, wherein determining the retained bandwidth and determining the offset Delta are adaptively determined within a cell of a wireless communication system, and wherein the first bandwidth is fixed.

14. The memory of claim 12, wherein the first type physical channel comprises a broadcast common control channel and wherein transmitting in the cell the offset Delta and the retained bandwidth comprises sending the offset Delta and the retained bandwidth in a system information message over a broadcast common control channel.

15. The memory of claim 12, wherein determining the offset Delta comprises aligning a center frequency of either of the first bandwidth or the retained bandwidth with a corresponding center frequency of an adjacent cell.

16. An apparatus comprising: a processor coupled to a memory configured to determine a retained bandwidth and an offset Delta in the frequency domain between a first bandwidth for a first type physical channel and the retained bandwidth for a second type physical channel that encompasses the first bandwidth; and a transmitter configured to transmit in a cell the offset Delta and the retained bandwidth.

17. The apparatus of claim 16, wherein the processor is configured to determine the retained bandwidth and to determine the offset Delta adaptively within a cell of a wireless communication system.

18. The apparatus of claim 16, wherein the first bandwidth is fixed.

19. The apparatus of claim 16, wherein the first type physical channel comprises at least one of a broadcast common control channel and a common synchronization channel.

20. The apparatus of claim 19, wherein the transmitter is configured to transmit in the cell the offset Delta and the retained bandwidth in a system information message over the broadcast common control channel.

21. The apparatus of claim 16, wherein the processor is further configured to map the first type physical channel to the first bandwidth and to map the second type physical channel to the retained bandwidth; and wherein the transmitter is further configured to transmit the mapped first type physical channel and the mapped second type physical channel

22. The apparatus of claim 16, wherein the transmitter is configured to transmit the offset Delta anytime it is determined to be non-zero and is configured to not transmit the offset Delta when it is determined to be zero.

23. The apparatus of claim 16, wherein all physical channels in the cell are either of the first type physical channel or of the second type physical channel.

24. The apparatus of claim 16, wherein all possible values for the retained bandwidth are limited to a discrete and pre-defined set stored in the memory.

25. The apparatus of claim 16, wherein determining the offset Delta comprises aligning a center frequency of either of the first bandwidth or the retained bandwidth with a corresponding center frequency of an adjacent cell.

26. The apparatus of claim 16, comprising a Node B.

27. An apparatus comprising: processing means for determining a retained bandwidth and an offset Delta in the frequency domain between a first bandwidth for a first type physical channel and the retained bandwidth for a second type physical channel that encompasses the first bandwidth; and transmit means for transmitting in a cell the offset Delta and the retained bandwidth.

28. The apparatus of claim 27, wherein: the processing means comprises a processor coupled to a memory; and the transmit means comprises a transmitter.

29. A method comprising: receiving in a cell an offset Delta and a retained bandwidth; determining from the received offset Delta and the retained bandwidth a first bandwidth within the retained bandwidth; tuning a receiver to the first bandwidth to receive at least one of a broadcast channel or a synchronization channel.

30. The method of claim 29, wherein the offset Delta and the retained bandwidth are received in a system information message on a common broadcast channel.

31. The method of claim 29 executed by a user equipment in a wireless communication system.

32. An apparatus comprising: a receiver configured to receive in a cell an offset Delta and a retained bandwidth; a processor coupled to a memory and configured to determine from the received offset Delta and the retained bandwidth a first bandwidth within the retained bandwidth, and thereafter to tune the receiver to the first bandwidth to receive at least one of a broadcast channel or a synchronization channel.

33. The apparatus of claim 32 comprising a wireless user equipment.