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Title:
APPARATUS AND METHOD FOR RECEIVING A PRIMARY AND A SECONDARY CARRIER
Document Type and Number:
WIPO Patent Application WO/2014/163545
Kind Code:
A1
Abstract:
The present disclosure concerns receivers for use in nodes or devices that participate in wireless communications. In one exemplary embodiment, a receiver 20 receives a first signal 22-1 attributable to a primary carrier and a second signal 22-2 attributable to a secondary carrier. Also, a first path searcher 24-1 detects taps in the first signal 22-1 attributable to the primary carrier. Furthermore, a channel tap selector 30 selects taps to be employed for the secondary carrier. The channel tap selector 30, which is connected to the first path searcher 24-1, can select the taps to be employed for the secondary carrier by supplementing initial taps detected by the first path searcher 24-1 (for the primary carrier) with additional taps.

Inventors:
TESSIER STÉPHANE (SE)
LYCKEGÅRD BO (SE)
Application Number:
PCT/SE2013/051017
Publication Date:
October 09, 2014
Filing Date:
August 30, 2013
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ERICSSON TELEFON AB L M (SE)
International Classes:
H04L25/02; H04B17/00
Domestic Patent References:
WO2011000947A12011-01-06
Foreign References:
US20110200075A12011-08-18
Other References:
None
Attorney, Agent or Firm:
BOU FAICAL, Roger (Patent Unit Kista RAN1, Stockholm, SE)
Download PDF:
Claims:
A receiver (20) for a device of a telecommunications network, wherein the receiver is configured to receive a first signal attributable to a primary carrier (22-1) and a second signal attributable to a secondary carrier (22-2); the receiver (20) comprising: a first path searcher (24-1) configured to detect taps in the first signal attributable to the primary carrier (22-1); and a channel tap selector (30) connected to the first path searcher (24-1), the channel tap selector (30) being configured to select a set of taps to be employed for the secondary carrier (22-2), wherein the channel tap selector (30) is configured to select said set of taps by supplementing an initial set of taps detected by the first path searcher (24-1) for the primary carrier with an additional set of taps.

The receiver (20) according to claim 1, wherein the channel tap selector (30) is configured to construct a grid of taps based on the initial set of taps and the additional taps.

The receiver (20) according to claim 1 or 2, wherein the channel tap selector (30) is configured to select the additional set of taps based on energy values for taps detected by the first path searcher (24-1).

The receiver (20) according to claim 3, wherein the channel tap selector (30) is configured to select those taps having energy values above an energy detection threshold to be included in the additional set of taps.

The receiver (20) according to any of the claims 1-4, wherein the channel tap selector (30) is configured to select the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers.

The receiver (20) according to any of the preceding claims, wherein first and second carriers are discontinuous and adjacent carriers.

7. The receiver according to any of the claims 1-6, wherein the receiver is comprised in a network node.

8. The receiver according to claim 7, wherein the network node is a base station (40-1).

9. The receiver according to any of the claims 1 -6, wherein the receiver is

comprised in a wireless terminal (40-2).

10. A method (500) performed by a receiver for a device of a telecommunications network, wherein the receiver comprises a first path searcher and a channel tap selector connected to the first path searcher, the method (500) comprising: receiving (510), by means of the receiver, a first signal attributable to a primary carrier and a second signal attributable to a secondary carrier; detecting (520), by means of the first path searcher, taps in the first signal attributable to the primary carrier; and selecting (530), by means of a channel tap selector, a set of taps to be employed for the secondary carrier, wherein the selecting comprises selecting said set of taps by supplementing (531) an initial set of taps detected by the first path searcher for the primary carrier with an additional set of taps.

11. The method (500) according to claim 10, comprising: constructing (530) a grid of taps based on the initial set of taps and the additional taps.

12. The method (500) according to claim 10 or 11, comprising: selecting (53 la) the additional set of taps based on energy values for taps detected by the first path searcher.

13. The method according to claim 12, wherein selecting (531a) the additional set of taps based on energy values for taps detected by the first path searcher comprises selecting those taps having energy values above an energy detection threshold to be included in the additional set of taps.

14. The method according to any of the claims 10-13, comprising: selecting (53 lb) the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers.

15. The method according to any of the claims 10-14, wherein first and second carriers are discontinuous and adjacent carriers.

Description:
APPARATUS AND METHOD FOR RECEIVING A PRIMARY AND A SECONDARY

CARRIER

TECHNICAL FIELD

[0001] The technology presented herein generally relates to receivers for use in nodes or devices that participate in wireless communications. More particularly, the technology presented herein relates to such receivers which are configured to receive signals over plural carriers. More specifically, some embodiments described herein relate to apparatuses and methods for receiving adjacent discontinuous carriers.

BACKGROUND

[0002] In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks (CN). The radio access network (RAN) covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a "NodeB" (UMTS) or "eNodeB" (LTE). A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations. [0003] In some versions of the radio access network, several base stations are typically connected (e.g., by landlines or microwave) to a controller node (such as a radio network controller (RNC) or a base station controller (BSC)) which supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks. [0004] The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The Universal Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access (WCDMA) for user equipments (UEs), or user equipment units. In a forum known as the Third Generation Partnership Project (3 GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. Specifications for the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) are defined for the 3 r Generation Partnership Project (3 GPP).

[0005] The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) comprises the Long Term Evolution (LTE) and System Architecture Evolution (SAE). Long Term Evolution (LTE) is a variant of a 3 GPP radio access technology wherein the radio base station nodes are connected to a core network (via Access Gateways( AGWs)) rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are distributed between the radio base stations nodes (eNodeB's in LTE) and AGWs. As such, the radio access network (RAN) of an LTE system has an essentially "flat" architecture comprising radio base station nodes without reporting to radio network controller (RNC) nodes.

[0006] The International Telecommunications Union-Radio communications sector (ITU-R) has specified a set of requirements for 4G standards, named the International Mobile Telecommunications Advanced (EVIT-Advanced) specification. ITU-R has also stated that Mobile WiMAX and LTE, as well as other beyond-3G technologies that do not fulfill the IMT- Advanced requirements, could nevertheless be considered "4G", provided they represent forerunners to IMT-Advanced compliant versions and have a substantial level of improvement in performance and capabilities with respect to the initial third generation system.

[0007] The nodes and devices, such as base stations and wireless terminals, which participate in wireless communications generally employ a communication interface that typically includes a transmitter and a receiver, and one or more antenna(s) that may connect to both the transmitter and the receiver. In some technologies such as multiple input multiple output (MEVIO), one or both of the node(s) and device(s) participating in the wireless communications have plural antennas. [0008] A baseband receiver, which may be found in a wireless terminal or a network node such as a base station in WCDMA technology, may apply an equalizer to compensate for dispersivity of the channel. The dispersivity may be a result of receiving multiple reflections of the same transmitted signal, which may resemble several echoes of a same source. Those reflections are also known as channel "taps". [0009] The baseband receiver may employ a "path searcher" to find the channel taps. A reference signal sent by the source is generally correlated at the receiver to a known pattern to identify the delays of the different taps. More particularly, the 'path searcher' finds the channel taps by integrating energy (i.e., correlation of the known reference and signal and summation) of the continuously transmitted reference signal. The detection of the channel taps decides if the receiver is declared to be in synchronization, e.g., in "sync" state. The receiver, e.g., path searcher, generally detects some of the delays, may miss some of the delays, and may even add extra delays on its own even though it does not detect the reference signal. Since each tap generally fades during the transmission independently of the other taps, some taps will be too weak for the receiver to detect. The delays selected by the receiver are called "fingers". When the fingers have been selected, the data signal can be decoded at each finger and combined together by an equalizer such as MMSE (Minimum-Mean-Square-Error), Rake or GRake, for example. Generally, the data part of the channel is not processed until the sync-state is achieved.

[0010] The procedure of detecting the taps can take time, but the channel taps are generally required to process data transmitted over the channel. Ideally, the path searcher would track the channel continuously in order to catch all channel taps where the energy is present, but in reality this would take or consume more time and resources. Thus the path searcher might not be run continuously, which can lead to missing a channel tap. Furthermore, since the channel is generally changing during the detection procedure, the path searcher may have to estimate the time interval during which the integration is performed. This also can lead to missing some channel taps.

[0011] In some networks it is possible to transmit and receive over plural carriers or sub- carriers, e.g., over plural carrier frequencies. In such networks, information is typically transmitted over the air interface between base stations and wireless terminal in units, such as a frame, which is formatted in such a manner to be understood by both the base station and the wireless terminals. In some radio access technologies, a frame (or subframe) is conceptualized as comprising a two dimensional array or "resource grid" of resource elements (RE). The resource elements are generally arranged in symbol order along a first (horizontal) direction and according to frequency subcarrier along a second (vertical) direction.

[0012] Two carrier frequencies are considered to be adjacent if they are quite close to each other, i.e., typically 20MHz from each other. As used herein, the criteria for adjacency is as follows: When a transmitter sends two signals simultaneously, one on each frequency (i.e., one on the primary frequency and one of the adjacent frequency), the channels that each signal will experience will have different fast fading tracks, but the channel taps will most likely be the same or at least belong to the same delay spread interval.

[0013] There are situations in the context of a multi-carriers scenario where one of the carriers is generally not transmitting its reference signal continuously. Such discontinuous reference signal transmission may occur in the case when Continuous Packet Connectivity (CPC) is activated on one of the carriers (e.g., shutting down the transmitter at pre-determined intervals of time to reduce interference) or in the case of a Lean carrier concept where the reference signal is only sent during data transmission on one carrier. The reason for not transmitting continuously on one carrier may be to allow a maximum utilization of the bandwidth by allowing other transmitters to have access to the full capacity without or with less (CPC) interference from other users, or UEs.

[0014] In operating a path searcher of a receiver, a delay generally has to be observed to enable the receiver to detect the strongest channel taps. The strongest taps on one carrier may in fact differ from the taps on the other carrier. As used herein, a "primary carrier" is said to be a carrier that is continuously transmitting its reference signal while a "secondary carrier" is a carrier that transmits its reference signal discontinuously.

[0015] A potential problem with a discontinuous carrier, i.e., a carrier that transmits its reference signal discontinuously, is that delay caused by omission of the reference signal may cripple utilization of the discontinuous carrier (i.e., secondary carrier), since conventionally no data is transmitted until the taps of the secondary carrier are detected.

[0016] Conventionally existing technology generally requires a period of path searching for channel taps with no processing of data. This may induce a Bandwidth-loss. The information from the 'path searcher' of the primary carrier is, alone, not sufficient because of the independence of the fast fading, e.g., the fading occurs independently in the different carriers.

SUMMARY

[0017] It is in view of the above considerations and others that the various embodiments disclosed herein have been made. [0018] In one of its aspects, the technology presented herein concerns a receiver for a device of a telecommunications network. The device may be a network node, such as a base station. Alternatively, the device may be a wireless terminal such as a UE.

[0019] The receiver is configured to receive a first signal attributable to a primary carrier and a second signal attributable to a secondary carrier. Also, the receiver comprises a first path searcher configured to detect taps in the first signal attributable to the primary carrier.

Furthermore, the receiver comprises a channel tap selector connected to the first path searcher. The channel tap selector is configured to select a set of taps to be employed for the secondary carrier. More particularly, the channel tap selector is configured to select said set of taps by supplementing an initial set of taps detected by the first path searcher for the primary carrier with an additional set of taps.

[0020] The above-mentioned first and second carriers may be discontinuous and adjacent carriers.

[0021] The channel tap selector may be configured to construct a grid of taps based on the initial set of taps and the additional taps.

[0022] In some embodiments, the channel tap selector may be configured to select the additional set of taps based on energy values for taps detected by the first path searcher. As one example, the channel tap selector may be configured to select those taps having energy values above an energy detection threshold to be included in the additional set of taps.

[0023] Additionally, or alternatively, the channel tap selector may be configured to select the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers. [0024] In one embodiment, the above-mentioned receiver is comprised in a network node, such as a base station.

[0025] In another embodiment, the above-mentioned receiver is comprised in a wireless terminal.

[0026] In another of its aspects, the technology presented herein concerns a method performed by a receiver for a device of a telecommunications network. The device may be network node, such as a base station. Alternatively, the device may be a wireless terminal such as a UE. The receiver comprises a first path searcher and a channel tap selector connected to the first path searcher.

[0027] The method comprises receiving, by means of the receiver, a first signal attributable to a primary carrier and a second signal attributable to a secondary carrier. The method also comprises detecting, by means of the first path searcher, taps in the first signal attributable to the primary carrier. Furthermore, the method comprises selecting, by means of a channel tap selector, a set of taps to be employed for the secondary carrier. The selecting of said set of taps to be employed for the secondary carrier comprises selecting said set of taps by supplementing an initial set of taps detected by the first path searcher for the primary carrier with an additional set of taps

[0028] The first and second carriers may be discontinuous and adjacent carriers.

[0029] The method may comprise constructing a grid of taps based on the initial set of taps and the additional taps.

[0030] The method may further comprise selecting the additional set of taps based on energy values for taps detected by the first path searcher.

[0031] Selecting the additional set of taps based on energy values for taps detected by the first path searcher may comprise selecting those taps having energy values above an energy detection threshold to be included in the additional set of taps.

[0032] Additionally, or alternatively, the method may comprise selecting the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers.

[0033] In yet another of its aspects, the technology disclosed herein concerns a network node or device comprising a receiver that selects channel taps to be used for correlation by fingers of the receiver for data processing of a secondary discontinuous carrier after a frame in which the secondary discontinuous carrier has no reference signal or data. The receiver is configured to use channel taps selected from a path searcher of an adjacent primary carrier as well as other channel taps chosen to form a grid. In an example embodiment, the grid is configured to cover delays wider than those selected by the path searcher for the primary carrier. The technology disclosed herein described herein also is directed to the receivers themselves, and to methods of operating such nodes/devices and receivers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The foregoing and other objects, features, and advantages of the technology disclosed herein will be apparent from the following more particular description of preferred embodiments as illustrated in the accompanying drawings in which reference characters refer to the same parts throughout the various views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the technology disclosed herein. [0035] Fig. 1 is a diagrammatic view of selected functionalities of a receiver according to an example embodiment;

[0036] Fig. 2 is a diagrammatic view showing a grid constructed by a finger selector (a.k.a. channel tap selector) which uses at least initial fingers, or initial taps, detected by a path searcher of a primary carrier and supplemental fingers, or taps;

[0037] Fig. 3 is a schematic view depicting various example embodiments of a telecommunications network wherein the receivers described herein may be employed;

[0038] Fig. 4 is a schematic view of a more detailed example embodiment of a receiver which implements a finger selector (a.k.a. channel tap selector) which merges delays from plural discontinuous adjacent carriers; and

[0039] Figs. 5 A-D are flowcharts of methods according to example embodiments.

DETAILED DESCRIPTION

[0040] In the following description, for purposes of explanation and not limitation, specific details are set forth such as particular architectures, interfaces, techniques, etc. in order to provide a thorough understanding of the technology disclosed herein. However, it will be apparent to those skilled in the art that the technology disclosed herein may be practiced in other embodiments that depart from these specific details. That is, those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the technology disclosed herein and are included within its scope. In some instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the technology disclosed herein with unnecessary detail. All statements herein reciting principles, aspects, and embodiments of the technology disclosed herein, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

[0041] Thus, for example, it will be appreciated by those skilled in the art that block diagrams herein can represent conceptual views of illustrative circuitry or other functional units embodying the principles of the technology. Similarly, it will be appreciated that any flow charts, state transition diagrams, pseudocode, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown. [0042] The functions of the various elements including functional blocks, including but not limited to those labeled or described as "computer", "processor" or "controller", may be provided through the use of hardware such as circuit hardware and/or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and/or computer-implemented, and thus machine-implemented.

[0043] In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) [ASIC], and/or field programmable gate array(s) (FPGA(s)), and (where appropriate) state machines capable of performing such functions.

[0044] In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer and processor and controller may be employed interchangeably herein. When provided by a computer or processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, use of the term "processor" or "controller" shall also be construed to refer to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

[0045] The following terminologies may be used in the disclosure for consistency and simplicity. The technology described herein may apply to a heterogeneous network.

[0046] As used herein, the term "node" may encompass nodes using any technology including, e.g., high speed packet access (HSPA), long term evolution (LTE), code division multiple access (CDMA)2000, GSM, etc. or a mixture of technologies such as with a multi- standard radio (MSR) node (e.g., LTE/HSPA, GSM/HS/LTE, CDMA2000/LTE etc).

Furthermore the technology described herein may apply to different types of nodes e.g., base station, eNode B, Node B, relay, base transceiver station (BTS), donor node serving a relay node (e.g., donor base station, donor Node B, donor eNB), supporting one or more radio access technologies.

[0047] Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory, magnetic disk, or optical disk containing an appropriate set of computer instructions that would cause a processor to carry out the techniques described herein.

[0048] Fig. 1 illustrates, in simplified form, a receiver 20 which is configured to receive a signal 22-1 attributable to a first or primary carrier. The receiver 20 is also configured to receive a signal 22-2 attributable to a second or secondary carrier. The secondary carrier is adjacent to the primary carrier. As used herein, the primary carrier and the secondary carrier can be said to be both adjacent and discontinuous, both terms having been explained above.

[0049] The receiver 20 illustrated in Fig. 1 comprises a first path searcher 24-1 configured to detect taps in the signal 22-1 attributable to the primary carrier. The receiver 20 further comprises a second path searcher 24-2 configured to detect taps in the signal 22-2 attributable to the secondary carrier. Each path searcher 24, to detect the taps, typically correlates the received signal, which is generally the sum of the reference signal and the data signal, with a known pattern transmitted by a reference signal. The correlation is performed for each delay belonging to a certain maximum range, where the granularity could be a fraction of the length of a chip or symbol. The path searcher will then pick the delays that have high correlation level.

[0050] Fig. 2 illustrates an example scenario of operation of the receiver 20 for both the signal 22-1 attributable to the primary carrier and the signal 22-2 attributable to the secondary carrier. It comprises the tap detection for two path searchers, e.g., for path searcher 24-1 and path searcher 24-2 of Fig. 1. For sake of simplicity, Fig. 2 shows a possibility of thirteen taps or delays for both path searchers 24-1 and 24-2, respectively. It will be appreciated that the number of such taps or delays is not critical, and that in an actual embodiment the number of taps or delays may preferably be on the order of from about one to about sixteen, but could also range from about one to about one hundred or more, for example. It is preferable, but not required, to choose the same taps or delays for both the first carrier and the second carrier.

Each tap or delay in Fig. 2 is represented by a dashed vertical line. Superimposed on some of the vertical "tap" lines of Fig. 2 are rectangles which represent energy values detected by path searchers 24-1 with respect to the signal 22-1 attributable to the primary carrier. The rectangles representing the energy values for the respective taps detected by the first path searcher 24-1 are shown with dotted or stippled interiors. The length of each of the rectangles is proportional to the received energy value, and a relative number depicting the received energy value is displayed in the interior of each rectangle. For the primary carrier, the first path searcher 24-1 detects taps 5, 7, and 9, those taps having respective energy values of 8, 5, and 5. For the example shown, the respective energy levels for selected taps 5, 7, and 9 are 8, 5, and 5. The energy levels are measured in dBm, e.g. integrated coherent and non-coherent energy per delay. In this example, the path searcher 24-1 failed to detect the energy at tap 3, the energy level of tap 3 being below a detection threshold (the detection threshold being depicted by a dashed double-dotted line). The detection threshold may be referred to as an energy detection threshold. In the period of time shown in Fig. 2 there is no reference signal borne by and/or detectable for the secondary carrier, for which reason no rectangles, e.g., no received energy, is shown for the secondary carrier in Fig. 2.

[0051] In one of its aspects, the receiver 20 disclosed in Fig. 1 is configured to receive a first signal 22-1 attributable to the primary carrier and the second signal 22-2 attributable to the secondary carrier. The first path searcher 24-1 is configured to detect taps in the first signal 22- 1 attributable to the primary carrier. Furthermore, a channel tap selector 30 (a.k.a. finger selector 30) is connected to the first path searcher 24-1. The channel tap selector 30 is configured to select a set of taps to be employed for the secondary carrier. More particularly, the channel tap selector 30 is configured to select the set of taps by supplementing an initial set of taps detected by the first path searcher 24-1 for the primary carrier with an additional set of taps. As will be further described hereinbelow, the channel tap selector 30 may be configured to construct a grid of taps based on the initial set of taps and the additional taps. In some embodiments, the channel tap selector 30 may be configured to select the additional set of taps based on energy values for taps detected by the first path searcher. As one example, the channel tap selector 30 may be configured to select those taps having energy values above an energy detection threshold to be included in the additional set of taps. Additionally, or alternatively, the channel tap selector 30 may be configured to select the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers.

[0052] Thus, the technology disclosed herein enables selection of fingers, or taps, to use for detecting data on the secondary carrier by using taps selected (or, detected) by the path searcher 24-1 for the primary carrier as well as other or additional taps selected to form a grid.

In an example embodiment, illustrated by the scenario of Fig. 2, the finger selector 30 uses the taps or fingers selected by the path searcher 24-1 for the primary carrier as an initial state (e.g., initial fingers or taps, or initial set of fingers or taps) for the secondary carrier and additionally uses other taps or fingers (i.e. an additional set of fingers or taps) to form a grid to cover a wider area. As will be appreciated, the finger selector 30 may also be known as the channel tap selector, or even as a grid builder or grid controller. Fig. 2 shows the grid G as being framed by a broken line.

[0053] In an example, non-limiting embodiment, a grid comprises a set of candidate delays (or, taps) chosen for providing a sufficient delay range and for including potential delay positions for detecting taps of the secondary carrier. The set of candidate delays of the grid may include at least some delays detected by the path search of the primary carrier and additional delays. In an example implementation, some of the additional delays may comprise a delay pattern which may be based on or related to the delays detected by the path search of the primary carrier. [0054] In Fig. 2, the grid G thus includes the taps 5, 7, and 9 selected, or detected, for the primary carrier by path searcher 24-1, as well as supplemental taps or fingers corresponding to finger/delay/tap positions 1, 3, 1 1, and 13. The finger/delay/tap positions 1, 3, 1 1, and 13 which fill out the grid G are depicted as circles having in their interior the letter "G". The grid G of Fig. 2 can thus form a pattern that is chosen to try to correspond to possible energy reception positions for data borne by the secondary carrier. The grid G is beneficial to avoid (or reduce the risk of) missing a tap that could be weak in the primary carrier but strong in the secondary carrier. In this example, one such possible weak tap in the primary carrier is tap 3, which although not selected, or detected, by path searcher 24-1 for the primary carrier is nevertheless fortunately covered by the grid G. [0055] It was noted above that fingers, or taps, detected by path searcher 24-1 are used for initial finger (or, tap) positions for the grid. But the initial fingers (or, taps) provided by the path searcher 24-1 may not be sufficient. In this regard, in general an adjacent carrier will have the same tap delays as its counterpart but the same tap in each of the carriers will experience uncorrected fading. Depending on the Doppler of the channel, some of the taps might have faded away and are not be selected by the respective path searcher 24. So using the path searcher from the primary carrier into the secondary carrier may not be entirely sufficient. A grid can thus be understood as a structure to try not to miss strong taps that could be weak in the primary carrier. By using a grid, as described herein, the probability of missing one tap is reduced, since most of the taps will likely be close, or relatively close, to each other. [0056] Criteria for selecting the supplemental taps or fingers to form the grid (beyond the initial fingers or taps borrowed from path searcher 24-1) may vary from embodiment to embodiment. One criterion is to try to maximize the energy received on the primary carrier. Another or additional criterion may be historical experience of previous grids for the primary carrier and the secondary carrier. [0057] The technology disclosed herein involving the finger selector 30 can thus avoid the need for a synchronization procedure where the receiver has to track the channel. This way, the transmitter is allowed to transmit data right away on the second carrier even though it was silent on the second carrier prior to transmission. [0058] Returning again to Fig. 1, the shown receiver 20 further comprises the

aforementioned finger selector 30 which essentially selects or configures the delays or taps for the fingers to be employed for the secondary carrier by constructing a finger grid as above described. The finger selector 30 is shown as being connected to the path searcher 24-1 so that the finger selector 30 may know the taps or delays selected, or detected, by path searcher 24-1 for the primary carrier. The path searcher 24-1 receives the first signal 22-1 for the primary carrier and detects the fingers on the primary carrier. The finger selector 30 receives the delays or taps for the primary carrier and uses the primary carriers as a starting point in configuring the grid G. [0059] Fig. 1 overlays, on the functional operations, a broken line demarcation which depicts data processing relative to frame numbers. The right-hand side of the broken line of Fig. 1 depicts data processing at frame n based on paths detected in frame n-1. Fig. 1 thus illustrates that it typically takes 1 frame to do the path detection. Inner Loop Power Control generally requires one TPC command (+1 or -1 dB in transmission power) every slot (there are 15 slots in one WCDMA frame). Therefore, the DPCCH symbols need to be decoded and thus finger allocation is generally needed. However, one slot is quite a short time period to perform a good path detection.

[0060] At time T(n-l) of Fig. 1 there is neither data nor the reference signal for the secondary carrier. However, at time T(n) both data and the reference signal for the secondary carrier are generally present, but path searching has not yet been performed for the secondary carrier. Thus, in order to process the data at T(n), path searcher information that is not yet computed by the path searcher 24-2 for the secondary carrier is generally needed. So for processing the data at T(n) the taps or delays selected by finger selector 30 for T(n-l) are used by the data process DP. As described herein, the taps or delays selected by finger selector 30 are based on results of the path searcher from T(n-l) of the primary carrier and the additional taps of the grid. In this way the data can indeed be processed at T(n), rather than having to waiting for an extra frame to detect the paths. At the beginning of T(n) the path searcher 24-2 is starting to track the secondary channel and at T(n+1) some data detected by path searcher 24-2 can be used. [0061] The technology disclosed herein which includes the finger selector 30 thus advantageously enables starting of despreading data essentially at once with channel tap delays of the primary carrier by using a grid based on the position of channel tap delays of the primary carrier. When enough energy is received on the reference channel, the new channel taps based on the secondary channel (maybe also the primary carriers channel tap delays) may be used to despread the data stream. It is important to able to start despreading both the reference signal as well as data to be able to, for instance, start inner loop power control (ILPC) of the secondary carrier and despread data (using available data-bandwidth).

[0062] Thus, the foregoing description of Fig. 1 and Fig. 1 itself primarily concentrates on the starting phase, just when the primary carrier is transmitting again after a silent period. The arrows from path searcher 24-1 to the data process DP and from path searcher 24-2 to the data process DP are pertinent to times after T(n) when outputs from the two path searchers 24 may be combined, e.g., when path searcher 24-2 obtains some knowledge of the secondary carrier.

[0063] The technology disclosed herein with its finger selector 30 thus avoids the need for a synchronization procedure where the receiver has to track the channel. In this way the transmitter is allowed to transmit data right away on the second carrier even though it was silent on the second carrier prior to transmission.

[0064] The grid of possible channel taps on the secondary carrier, based on primary path searcher results, is sufficient to start processing data on the secondary carrier, in parallel with a 'path searcher' on the secondary carrier. This way, the transmitter is allowed to transmit data right away on the second carrier even though it was silent on the second carrier prior to transmission.

[0065] Fig. 3 illustrates a first node 40-1 and a second node or device 40-2. Each node/device 40 comprises communications interface 42 and various node/device functionalities 44. Each communications interface 42 cooperates with one or more antenna(s) 46, and typically comprises both transmitter 48 and receiver 20. The first node 40-1 and the second node/device 40-2 communicate over an air or radio interface 50. Such communication may occur using "frames" 52 of information which are transmitted using plural carriers, such as the aforementioned primary carrier and the adjacent secondary carrier. [0066] It should be understood, particularly with reference to Fig. 3, that the receiver 20 which selects fingers for adjacent carriers in the manner described herein or otherwise encompassed hereby may be in a network node or in another device such as a wireless terminal. For example, in one example scenario of Fig. 1 the first node 40-1 may be a base station and the second node/device 40-2 may be a wireless terminal. In another example scenario the first node 40-1 may be a relay base station and the second node/device 40-2 may be another base station. [0067] Fig. 4 illustrates an example receiver 20 in more detail according to one example, non-limiting embodiment. The receiver 20 of Fig. 4 comprises a RF processing unit RF which forwards the signals 22-1 attributable to the first carrier and the signals 22-2 attributable to the second carrier to respective analog to digital conversion units ADC. The digitally converted signals for each carrier are both applied to respective path searchers 24 and to correlators COR associated with each finger F, an integer number n of such fingers being illustrated in Fig. 4. The fingers F may be rake fingers. The path searcher 24 may comprise matched filters which receive the digitally converted signals and an impulse response measurement unit IMR. The impulse response measurement unit of the path searchers 24 perform a channel impulse response measurement using correlators that correlate the received signal with a known reference code sequence (e.g., scrambling code) such as a pilot channel code. The path searchers 24 may perform the correlation piece-wise during intervals where the channel does not vary much, since the channel may change during a full sequence of the reference code. The path searchers 24 generate the tap lists as a result of the correlation for taps which have energy values which exceed a given threshold. The path-searchers 24 create a power-delay- profile (pdf), where power level per delay is placed (a vector with power values per carrier). Channel taps (fingers/delays) are selected if fingers are local maximum as well as over a threshold. The threshold is generally a level which is above noise level. Channel taps generally needs to be separated by a predetermined amount of time, e.g., 3/4 chip between each other (for one carrier), to ensure an independence between taps.

[0068] The example embodiment of Fig. 4 shows structure capable of processing the carriers at the time T(n-l), T(n), and T(n+1), etc. At time T(n-l), however, there is no signal on the secondary carrier, so the output of the secondary path searcher 24-2 should be zero. If a zero finger is received, the finger selector 30 uses the result of the path searcher 24-1 for the primary carrier to form the grid with delays to be used by the fingers F for the secondary carrier during time T(n), as explained above. When the reference signal (and the data) is received so that enough energy is integrated will (hopefully) the path searcher produce channel taps' delays to be used in the finger selector.

[0069] In an example embodiment and as depicted by way of example in Fig. 4, the finger selector 30 may be realized by a machine platform. To this end Fig. 4 employs a broken line to represent machine platform P which comprises finger selector 30 and other functional units of receiver 20 as well. The terminology "machine platform" is a way of describing how the functional units of receiver 20 can be implemented or realized by machine. The machine platform P can take any of several forms, such as for example electronic circuitry in the form of a computer implementation platform or a hardware circuit platform. A computer implementation of the machine platform may be realized by or implemented as one or more computer processors or controllers as those terms are herein expansively defined, and which may execute instructions stored on non-transient computer-readable storage media. In such a computer implementation the machine platform P may comprise, in addition to a processor(s), a memory section (which in turn can comprise random access memory; read only memory; an application memory (a non-transitory computer readable medium which stores, e.g., coded non instructions which can be executed by the processor to perform acts described herein); and any other memory such as cache memory, for example). Another example platform suitable for transmission mode selector 40 is that of a hardware circuit, e.g., an application specific integrated circuit (ASIC) wherein circuit elements are structured and operated to perform the various acts described herein.

[0070] Fig. 5A is a flowchart illustrating a method according to an example embodiment. The method may be performed by a receiver, such as the receiver 20 illustrated in Fig. 1. The receiver 20 comprises a first path searcher 24-1 and a channel tap selector 30 connected to the first path searcher 24-1 (see Fig. 1). [0071] The receiver receives 510 a first signal attributable to a primary carrier and a second signal attributable to a secondary carrier. Also, the first path searcher 24-1 detects 520 taps in the first signal attributable to the primary carrier. Furthermore, the channel tap selector 30 (or, finger selector) selects 530 a set of taps to be employed for the secondary carrier.

Turning now to Fig. 5B, as can be seen the selecting 530 of said set of taps to be employed for the secondary carrier may comprise selecting said set of taps by supplementing 531 an initial set of taps detected by the first path searcher for the primary carrier with an additional set of tap. Again, it should be appreciated that the first and second carriers may be discontinuous and adjacent carriers.

[0072] The method may also comprise constructing a grid of taps based on the initial set of taps and the additional taps. This may, for example, be part of the step or act 531.

[0073] The method may further comprise selecting the additional set of taps based on energy values for taps detected by the first path searcher. Turning to Fig. 5C, one example embodiment is illustrated. In this embodiment, the act or step 531 includes selecting 53 la the additional set of taps based on energy values for taps detected by the first path searcher.

Selecting 53 la the additional set of taps based on energy values for taps detected by the first path searcher may comprise selecting those taps having energy values above a energy detection threshold to be included in the additional set of taps. [0074] Additionally, or alternatively, the method may comprise selecting the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers. Turning to Fig. 5D, one example embodiment is illustrated. In this embodiment, the act or step 531 includes selecting 531b the additional set of taps based on historical values of previous grids of taps for the primary and the secondary carriers.

[0075] The various embodiments described herein may provide several advantages. For example, by utilizing a channel tap selector or finger selector 30 it is made possible to avoid, or at least reduce, the need for a synchronization procedure where the receiver first has to track the channel. In this way, the transmitter can be allowed to transmit data right away on the second carrier even though it was silent on the second carrier prior to transmission. A grid of possible channel taps on the secondary carrier, based on primary path searcher results, is generally sufficient to start processing data on the secondary carrier. In some embodiments, this can be done in parallel with a 'path searcher' on the secondary carrier. This way, the transmitter can be allowed to transmit data right away on the second carrier even though it was silent on the second carrier prior to transmission.

[0076] As used herein, "terminal" or "wireless terminal" or "user equipment (UE)" may be a mobile station such as a mobile telephone or "cellular" telephone or a laptop with wireless capability and thus may be, for example, a portable, pocket, hand-held, computer-included, or car-mounted mobile device which communicates voice and/or data via a radio access network. Moreover, a terminal or wireless terminal or UE may be a fixed terminal which communicates voice and/or data via a radio access network.

[0077] Furthermore, while two adjacent carriers have been illustrated in the example embodiments and description, it should be understood that the technology disclosed herein encompasses merging or combining of more than two adjacent carriers (provided that the carriers are truly adjacent, e.g., the frequencies are sufficiently close to each other).

[0078] Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of the invention. It will be appreciated that the scope of the present invention fully encompasses other embodiments which may come to mind to those skilled in the art having benefit of the teachings presented herein, and that the scope of the present invention is accordingly not to be limited. In other words, although the present invention has been described with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein and, accordingly, the invention is only limited by the appended claims. To this end, it should be borne in mind that although individual features may be included in different claims, these may possibly be advantageously be combined, and the inclusion of different claims does not imply that a combination of features is not feasible and/or advantageous. Reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more. " Also, the terms

"comprise/comprises" or "include/includes" do not exclude the presence of other elements or steps. All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for a device or method to address each and every problem sought to be solved by the present invention, for it to be encompassed hereby.