Partitioning of frequency resources for transmission of control signals and data signals in SC-FDMA communication systems

(56) References cited:

EP-A2- 1 351 539 WO-A1-2008/048055 WO-A2-2008/137963

Note: Within nine months ofthe publication ofthe mention ofthe grant ofthe European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall nőt be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).

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EP 2 003 811 Β1 • SAMSUNG: Uplink ACK/NACK resource allocation, 3GPP DRAFT; R1-071574, 3RD GENERATION PARTNERSHIP PROJECT(3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCÉ, vol. RAN WG1, no. St. Julián; 20070403, 3 April 2007 (2007-04-03),

XP050105504, [retrieved on 2007-04-03] • NTT DOCOMO ETAL: ACK/NACK Signal Structure in E-UTRA Downlink, 3GPP DRAFT; R1-070867 DL ACK, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCÉ, vol. RAN WG1, no. St. Louis, USA; 20070206, 6 February 2007 (2007-02-06), XP050104879, [retrieved on 2007-02-06] • QUALCOMM EUROPE: Support of ACK Repetition fór E-UTRA Uplink, 3GPP DRAFT; R1-073261, 3RD GENERATION PARTNERSHIP PROJECT (3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCÉ, vol. RAN WG1, no. Athens, Greece; 20070815, 15 August 2007 (2007-08-15), XP050106896, [retrieved on 2007-08-15] • NEC GROUP: Downlink ACK/NACK signalling fór E-UTRA, 3GPP DRAFT; R1-072120, 3RD GENERATION PARTNERSHIP PROJECT(3GPP), MOBILE COMPETENCE CENTRE ; 650, ROUTE DES LUCIOLES ; F-06921 SOPHIA-ANTIPOLIS CEDEX ; FRANCÉ, vol. RAN WG1, no. Köbe, Japan; 20070502, 2 May 2007 (2007-05-02), XP050105869, [retrieved on 2007-05-02]

ΕΡ 2 003 811 Β1

Description

Field of the Invention [0001] The present invention isdirected, in generál, towirelesscommunication systems and, more specifically, although nőt exclusively, to a Single-Carrier Frequency Division Multiple Access (SC-FDMA) communication system and is further considered in the development ofthe 3^rd Generation Partnership Project (3GPP) Evolved Universal Terrestrial Rádió Access (E-UTRA) long term evolution (LTE).

Background to the Invention [0002] In particular, the present invention considers partitioning resources allocated to the transmissions of control signals and data signals in a SC-FDMA communication system. The invention assumes the UpLink (UL) communication corresponding to signal transmissions from mobile User Equipments (UEs) to a serving base station (or Node B). A UE, alsó commonly referred to as terminál or mobile station, may be fixed or mobile and may be a wireless device, a cellular phone, a personal computer device, a wireless modem card, etc. A Node B is generally a fixed station and may alsó be called a Base Transceiver System (BTS), an access point, or somé other terminology.

[0003] Several types of signals need to be supported fór the proper functionality of the communication system. In addition to data signals, which convey the Information content of the communication, control signals alsó need to be transmitted from the UEs to their serving Node B in the UL and from the serving Node B to the UEs in the DownLink (DL) in order to enable the proper transmission ofdata signals. The DL refers to the communication from the Node B to UEs. These control signals are subsequently described in detail with the focus being on the UL.

[0004] The UEs are assumed to transmit data signals (or data packets) through the Physical Uplink Shared CHannel (PUSCH). The PUSCH can be shared during the same time period by multiple UEs with each UE using a different part ofthe operating BandWidth (BW), as illustrated in FIG. 1, in order to avoid mutual interference (Frequency Domain Multiplexing (FDM)). UE1 110 transmits over BW 120 while UE2 130, UE3 150, and UE4 170, transmit over BW 140, BW 160, and BW 180, respectively. An exception is the use ofSpatial Division Multiple Access (SDMA) methods, where multiple UEs may share the same RBs over the same sub-frame fór their PUSCH data packet transmissions.

[0005] The Node B is assumed to transmitdata signals (ordata packets) to UEs through the Physical Downlink Shared CHannel (PDSCH). Similarly to the PUSCH, the PDSCH can be shared during the same time period by multiple UEs through FDM.

[0006] PUSCH and PDSCH transmissions can be scheduled by the Node B through a UL or a DL scheduling assignment, respectively, using the Physical Downlink Control CHannel (PDCCH) or they can be preconfigured to occur periodically (persistent scheduling of PUSCH or PDSCH transmissions). Using the PDCCH, a data signal transmission in the PUSCH or the PDSCH may generally occur at any sub-frame decided by the Node B scheduler. Accordingly, the scheduling of such transmissions is referred to as dynamic.

[0007] To avoid excessive PDCCH overhead, somé PUSCH and PDSCH transmissions may be configured to occur periodically at predetermined parts of the operating bandwidth. Such scheduling is referred to as persistent FIG. 2 illustrates the concept of persistent scheduling where an initial packet transmission 210 occurs periodically every assignment interval 220. Persistent scheduling is typically used fór communication Services having relatively small bandwidth requirements per transmission period bút need to be provided fór many UEs making dynamic scheduling through the PDCCH inefficient due to the associated overhead introduced in the DL ofthe communication system. One typical example of such Services is Voice over Internet Protocol (VolP).

[0008] In response to the PUSCH and PDSCH transmissions, positive or negative acknowledgement signals, ACK or NAK respectively, are assumed to be transmitted to orfrom the UEs, respectively. As the invention considers the UL of the communication system, the focus will be on the ACK/NAK signals transmitted by UEs in response to a PDSCH transmission. ACK/NAK signaling is required fór use of Hybrid-Automatic Repeat reQuest (HARQ), where a data packet is retransmitted upon the reception of a NAK and a new data packet it transmitted upon the reception of an ACK. [0009] Because the PDSCH scheduling of a UE in the DL can be dynamic or persistent, the transmission of ACK/NAK signals from the UE is correspondingly dynamic or persistent. In the latter case, similarly to the PDSCH transmission, the ACK/NAK transmission from the UE is periodic.

[0010] In addition to periodic and dynamic transmission of ACK/NAK signals, other control signals may be periodically transmitted by UEs. One example of such a control signal is the Channel Quality Indication (CQI). The CQI is assumed to be sent periodically to inform the serving Node B of the channel conditions, which can be represented by the Signalto-Noise and Interference Ratio (SINR) the UE experiences in the DL. Additional periodic transmissions of control signals other than CQI or ACK/NAK may alsó exist.

[0011] Therefore, the UL ofthe communication system is assumed to support dynamic and persistent PUSCH transmissions, ACK/NAK transmissions due to dynamic and persistent PDSCH transmissions, CQI transmissions, and pos3

EP 2 003 811 Β1 sibly other control signaling. The transmissions of CQI, persistent PUSCH, and ACK/NAK due to persistent PDSCH are assumed to be periodic until deactivated by the serving Node B or until the corresponding configured transmission period expires. The ACK/NAK and CQI signals will be jointly referred to as the Physical Uplink Control CHannel (PUCCH). Other control signals may alsó be periodically transmitted in the PUCCH.

[0012] The PUSCH transmissions are assumed to occur over a Transmission Time Interval (TTI) corresponding to a sub-frame. FIG. 3 illustrates a block diagram ofthe sub-frame structure 310 assumed in the exemplary embodiment of the disclosed invention. The sub-frame includes of two slots. Each siót 320 further includes seven symbols and each Symbol 330 further includes a Cyclic Prefix (CP) fór mitigating interference due to channel propagation effects. The signal transmission in the two slots may or may nőt be in the same part of the operating bandwidth.

[0013] In an exemplary sub-frame structure of FIG. 3, the middle Symbol in each siót carries the transmission of Reference Signals (RS) 340, alsó known as pilot signals, which are used fór several purposes including fór providing channel estimation to allow coherent demodulation ofthe received signal. The number of symbols with RS transmission in the UL sub-frame may be different among the PUSCH, the PUCCH with ACK/NAK transmission, and the PUCCH with CQI transmission. Fór example, the middle three symbols in each siót may be used fór RS transmission in case of ACK/NAK PUCCH transmissions (the remaining symbols are used fór ACK/NAK transmission) while the second and sixth symbols in each siót may be used fór RS transmission in case of CQI PUCCH transmissions (the remaining symbols are used fór CQI transmission). This is alsó illustrated in FIG. 9, FIG. 10, and FIG. 11, which will be described later herein. [0014] The transmission bandwidth is assumed to comprise of frequency resource units, which will be referred to as Resource Blocks (RBs). The exemplary embodiment assumes that each RB includes 12 SC-FDMA sub-carriers and UEs are assumed to be allocated a multiple N of consecutive RBs 350 fór PUSCH transmission and 1 RB fór PUCCH transmission. Nevertheless, the above values are only illustrative and nőt restrictive to the invention.

[0015] Although nőt matéria! to the disclosed invention, an exemplary block diagram of the transmitter structure fór the PUSCH is illustrated in Figure 4. If a UE has both data and control (ACK/NAK, CQI, etc.) bits to transmit in the same PUSCH sub-frame, then, in order to transmit the ACK/NAK, certain data bits (such as, fór example, the parity bits in the case of turbó coding) may be punctured and replaced by the ACK/NAK bits. Simultaneous PUSCH and PUCCH transmission by a UE is thus avoided and the single-carrier property is preserved. Coded CQI bits 405 (if they exist) and coded data bits 410 are multiplexed 420. If ACK/NAK bits alsó need to be transmitted in the PUSCH, data bits (or possibly CQI bits) are punctured to accommodate ACK/NAK bits 430. The Discrete Fourier Transform (DFT) ofthe combined data bits and control bits is then obtained 440, the sub-carriers 450 corresponding to the assigned transmission bandwidth are selected 455, the Inverse Fást Fourier Transform (IFFT) is performed 460 and finally the Cyclic Prefix (CP) 470 and filtering 480 are applied to the transmitted signal 490.

[0016] Zero padding is assumed to be inserted by a reference UE in sub-carriers used by another UE and in guard sub-carriers (nőt shown). Moreover, fór brevity, additional transmitter circuitry such asdigital-to-analog converter, analóg filters, amplifiers, and transmitter antennas as they are known in the art, are nőt illustrated in FIG. 4. Similarly, the encoding process fór the data bits and the CQI bits as well as the modulation process fór all transmitted bits are well known in the art and are omitted fór brevity.

[0017] Atthe receiver, the inverse (complementary) transmitterfunctions are performed. This is conceptually illustrated in FIG. 5 where the reverse operations of those in FIG. 4 apply. As it is known in the art (nőt shown fór brevity), an antenna receives the Radio-Frequency (RF) analóg signal and after further Processing units (such as filters, amplifiers, frequency down-converters, and analog-to-digital converters) the digital received signal 510 passes through a time windowing unit 520 and the CP is removed 530. Subsequently, the receiver unit applies an FFT 540, selects 545 the sub-carriers 550 used by the transmitter, applies an Inverse DFT (IDFT) 560, extracts the ACK/NAK bits and places respective erasures fór the data bits 570, and de-multiplexes 580 the CQI. bits 590 and data bits 595. As fór the transmitter, well known in the art receiver functionalities such as channel estimation, demodulation, and decoding are nőt shown fór brevity and they are nőt matéria! to the invention.

[0018] Alsó without being matéria! to the disclosed invention, a block diagram ofthe PUCCH (ACK/NAK, CQI) transmission structure is illustrated in FIG. 6. The transmission is assumed to be through the modulation of Constant Amplitude Zero Autocorrelation (CAZAC)-based sequences 610. Similarly, the RS transmission is assumed to be through nonmodulated CAZAC-based sequences 610. The sub-carriers corresponding to the assigned transmission bandwidth are selected 620 and the sequence elements are mapped on the selected PUCCH sub-carriers 630. The Inverse Fást Fourier Transform (IFFT) is performed 640, the output is then cyclically shifted in the time domain 650, and finally the Cyclic Prefix (CP) 660 and filtering 670 are applied to the transmitted signal 680. With respect to the PUSCH transmitter structure in FIG. 4, the main difference is the absence of a DFT block (because, although nőt required, the CAZACbased sequence is assumed to be directly mapped in the frequency domain to avoid the DFT operation) and the application ofthe cyclic shift 650. In addition, Walsh covering may apply to the ACK/NAK, RS, and possibly the CQI signals across the corresponding symbols in the sub-frame (FIG. 3).

[0019] The reverse functions are performed fór the reception of the CAZAC-based sequence as illustrated in FIG. 7. The received signal 710 passes through a time windowing unit 720 and the CP is removed 730. Subsequently, the cyclic

ΕΡ 2 003 811 Β1 shift is restored 740, an FFT 750 is applied, the sub-carriers 760 used by the transmitter are selected 765, correlation with the replica 770 ofthe CAZAC-based sequence is applied 780 and the output 790 is obtained. The output can be passed to a channel estimation unit, such as a time-frequency interpolator, in case of an RS, orcán be used fór detecting the transmitted information, in case the CAZAC-based sequence is modulated by ACK/NAK orCQI information bits. [0020] An example of CAZAC-based sequences is given by the following Equation (1):

c_k(n) = exp j2?rk

<img file="HUE032111T2_D0001.tif" />

(0 [0021] In Equation (1), L is the length ofthe CAZAC sequence, n is the index of a particular element ofthe sequence n = {0,1,2 ..., L -1}, and finally, k is the index ofthe sequence itself Fór a given length L, there are L -1 distinct sequences, provided that L is prímé. Therefore, the entire family of sequences is defined as k ranges in {1,2 ..., L - 1}. However, the CAZAC sequences used fór PUCCH signaling need nőt be generated using the exact above expression as it is further discussed below.

[0022] Fór CAZAC sequences of prímé length L, the number of sequences is L-1. As the RBs are assumed to include an even number of sub-carriers, with 1 RB includes 12 sub-carriers, the sequences used to transmit the ACK/NAK and RS can be generated, in the frequency or time domain, by either truncating a longer prímé length (such as length 13) CAZAC sequence or by extending a shorter prímé length (such as length 11) CAZAC sequence by repeating its first element(s) atthe end (cyclicextension), although the resulting sequences do notfulfill thedefinition ofa CAZAC sequence. Alternatively, CAZAC sequences can be generated through a computer search fór sequences satisfying the CAZAC properties.

[0023] Different cyclic shifts ofthe same CAZAC sequence provide orthogonal CAZAC sequences. Therefore, different cyclic shifts ofthe same CAZAC sequence can be allocated to different UEs in the same RB fór their RS, ACK/NAK, or CQI transmission and achieve orthogonal UE multiplexing. This principle is illustrated in FIG. 8.

[0024] In orderforthe multiple CAZAC sequences 810, 830, 850, 870 generated correspondingly from multiple cyclic shifts 820, 840, 860, 880 ofthe same root CAZAC sequence to be orthogonal, the cyclic shift value □ 890 should exceed the channel propagation delay spread D (including a time uncertainty error and filter spillover effects). IfTs is the duration of one Symbol, the number of cyclic shifts is equal to the mathematical floor ofthe ratio T_s/D. The cyclic shift granularity equals an element of the CAZAC sequence. Fór a CAZAC sequence of length 12, the number of possible cyclic shifts is 12 and fór Symbol duration of about 66 microseconds (14 symbols inai millisecond sub-frame), the time separation of consecutive cyclic shifts is about 5.5 microseconds.

[0025] The CQI transmission parameters, such as the transmission RB and the transmission sub-frame, are configured fór each UE through higher layer signaling and remain valid over time periods much longer than a sub-frame. Símilarly, the ACK/NAK transmission parameters due to persistent PDSCH scheduling and the persistent PUSCH transmission parameters (such as the RB and sub-frame) alsó remain the same over comparable time periods.

[0026] A consequence of SC-FDMA signaling is that the transmission bandwidth of a signal needs to be contiguous. In order to avoid bandwidth fragmentation fór PUSCH transmissions, the PUCCH transmissions need to be placed towards the two ends of the operating bandwidth. Otherwise, if there are RBs available on each side of the PUCCH transmission bandwidth, they cannot be used fór PUSCH transmission by the same UE while preserving the single carrier property of the transmission.

[0027] Moreover, as PUCCH transmission includes periodic CQI transmissions, periodic ACK/NAK transmissions, and dynamic ACK/NAK transmissions, an appropriate ordering fór the corresponding RBs atthe two ends ofthe operating bandwidth needs to be determined.

[0028] In addition to PUCCH transmission, persistent scheduling of PUSCH transmissions alsó results in similar bandwidth occupancy characteristics as the PUSCH.

[0029] WO 2008/048055 (A1) relates to a method fór transmitting a control signal. A rádió frame is comprised of subframes, a subframe may include two slots. A subframe can be divided info two parts of a control region and a data region. The control region is a region in which only a control signal is transmitted and is allocated to a control channel. The data region is a region in which data is transmitted and is allocated to a data channel. A plurality of user equipments uses control channels allocated to different frequency bands on the control region. The control region is divided info a plurality of frequency bands and a frequency bánd is allocated to the control channel fór each user equipment. 2N control channels are allocated to 2N user equipments.

[0030] It is the object to provide a more efficient frequency allocation.

[0031] This object is solved by the subject matter of the independent claims.

[0032] Preferred embodiments are defined by the dependent claims.

EP 2 003 811 Β1

SUMMARY [0033] Accordingly, the present invention has been designed to solve the above-mentioned problems occurring in the prior art, and the present invention provides an apparátus and method fór allocating frequency resources fór the transmission of control signals and data signals from user equipments to their serving Node B, as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS [0034] The above and other aspects, features, and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a partitioning of an operating bandwidth fór an orthogonal transmission of signals from multiple UEs through frequency division multiplexing;

FIG. 2 is a diagram illustrating the concept of persistent (periodic) data signal transmission from a UE;

FIG. 3 is a block diagram illustrating an exemplary sub-frame structure fór the SC-FDMA communication system; FIG. 4 is a block diagram illustrative of a first exemplary SC-FDMA transmitter fór multiplexing data bits, CQI bits, and ACK/NAK bits in a transmission sub-frame;

FIG. 5 is a block diagram illustrative of an exemplary SC-FDMA receiver fór demultiplexing data bits, CQI bits, and ACK/NAK bits in a reception sub-frame;

FIG. 6 is a block diagram illustrating an exemplary transmitterfor a CAZAC-based sequence in a frequency domain; FIG. 7 is a block diagram illustrating an exemplary receiver fór a CAZAC-based sequence in a frequency domain; FIG. 8 is a block diagram illustrating an exemplary construction of orthogonal CAZAC-based sequences through the application of different cyclic shifts on a root CAZAC-based sequence;

FIG. 9 is a diagram illustrating an exemplary partitioning of resource blocks fór CQI, ACK/NAK, and data signal transmissions;

FIG. 10 is a diagram illustrating a first exemplary partitioning of resource blocks fór CQI, persistent and dynamic ACK/NAK, and persistent and dynamic data signal transmissions; and

FIG. 11 is a diagram illustrating a second exemplary partitioning of resource blocks fór CQI, persistent and dynamic ACK/NAK, and persistent and dynamic data signal transmissions.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS [0035] The present invention now will be described more fully hereinafterwith reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should nőt be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope ofthe invention to those skilled in the art.

[0036] Additionally, although the present invention assumes a Single-Carrier Frequency Division Multiple Access (SCFDMA) communication system, it alsó applies to all FDM systems in generál and to OFDMA, OFDM, FDMA, DFT-spread OFDM, DFT-spread OFDMA, Single-Carrier OFDMA (SC-OFDMA), and single-carrier OFDM in particular.

[0037] System and methods ofthe embodiments ofthe invention solve problems related to the need fór maximizing the utilization of the available bandwidth fór the transmission of signals from user equipments to a serving Node B, fór facilitating the achievement of desired transmission reliability targets, and fór informing the UEs with transmission of acknowledgement signals ofthe first frequency unit (or resource block (RB)) available fór the transmission of these signals. [0038] As discussed in the foregoing background, several signals in the UL have a periodic natúré and the corresponding allocation of resource blocks (RBs), or frequency units, per sub-frame can be predetermined over relatively long time periods compared to the sub-frame duration. These signals include the CQI, the ACK/NAK associated with persistent PDSCH transmissions, and the persistent PUSCH. As it will be subsequently explained in detail, fór several reasons, including avoiding bandwidth fragmentation while supporting single carrier transmission, it is desirable to piacé these signals towards the two edges (ends) ofthe operating bandwidth.

[0039] In addition to dynamically scheduled PUSCH transmissions, other signals that may require a variable number of RBs per sub-frame include the ACK/NAK fór dynamic PDSCH transmissions (dynamic ACK/NAK). The RBs fór dynamic ACK/NAK transmissions should therefore be placed next to the ones fór dynamic PUSCH transmissions, start after the last RB allocated to periodic PUCCH and PUSCH transmissions, and be placed towards the interior of the operating BandWidth (BW).

[0040] The partitioning of periodic PUCCH transmissions, such as the CQI signaling, and dynamic PUCCH ACK/NAK transmissions is first considered in the exemplary setup illustrated in FIG. 9. The CQI transmission from a UE is assumed to take piacé at the opposite ends ofthe operating BW in the first siót 910A and the second siót 910B. According to the invention, the RBs used fór dynamic ACK/NAK transmission from another, different, UE in the first siót 920A and the

ΕΡ 2 003 811 Β1 second siót 920Β are placed to the interior of the ones used fór the CQI transmission and are adjacent to and to the exteriőr of the RBs used fór dynamic PUSCH transmission in the first siót 930A and second siót 930B of the sub-frame. [0041] As the number of UEs having dynamic PDSCH transmissions in a sub-frame may vary, the number of RBs used by the corresponding dynamic ACK/NAK transmissions in the PUCCH may alsó vary per sub-frame (although only one RB is illustrated in FIG. 9 fór dynamic ACK/NAK transmissions). Such variations cannot be expected in advance as the Node B scheduler is assumed to operate without constraints on the number of assigned dynamic PDSCH transmissions per sub-frame.

[0042] As each UE with dynamic ACK/NAK transmission is assumed to know the multiplexing capacity in one RB (this paraméter can be broadcasted by the serving Node B) and its relatíve position with respect to ACK/NAK transmissions from other UEs (either through explicit signaling by the serving Node B or implicitly, such as fór example through the index ofthe PDCCH used fór the scheduling assignment), it can know which RB and which resource within the RB (such as which cyclic shift of a CAZAC-based sequence) to use. Fór example, if the ACK/NAK multiplexing capacity is 18 and the relatíve order of a UE fór ACK/NAK transmission is 20, that UE uses fór its ACK/NAK transmission the second resource in the second RB used fór dynamic ACK/NAK transmissions. In generál, if the ACK/NAK multiplexing capacity in an RB is M and the relatíve order of a UE with dynamic ACK/NAK transmission is P, the UE may use the resource:

mod(P, M), within the RB number of

Q = ceil(P/M), where mod(x, y) is x minus (n times y) where n equals to floor(x divided by y). The floor operation rounds a number to its immediately smaller integer while the ceil operation rounds a number to its immediately larger integer.

[0043] Piacing the RBs fór dynamic ACK/NAK transmissions towards the interior ofthe operating bandwidth after the ones used fór periodic PUCCH transmissions (such as the CQI ones) fór which the number of RBs per sub-frame are fixed over long time periods, and adjacent and to the exteriőr ofthe RBs used fór dynamic PUSCH transmissions, avoids bandwidth fragmentation .or bandwidth waste due to unused RBs. Otherwise, if the RBs fór dynamic ACK/NAK transmissions were placed before the ones fór periodic PUCCH transmissions and towards the exteriőr of the operating bandwidth, bandwidth fragmentation would occur when the number of RBs fór dynamic ACK/NAK transmissions varied between sub-frames.

[0044] Instead, with the RB partitioning between periodic and dynamic PUCCH transmissions as illustrated in FIG. 9, any variation in the number of RBs used fór dynamic ACK/NAK transmissions can be seamlessly absorbed in the scheduling of dynamic PUSCH transmissions in the remaining RBs without resulting to any wasted RBs or causing bandwidth fragmentation as the former RBs can simply be viewed as an extension ofthe latter and the reverse. The serving Node B knows how many RBs will be required in every sub-frame fór dynamic ACK/NAK transmissions and can therefore accordingly allocate the RBs fór PUSCH transmissions without incurring bandwidth fragmentation.

[0045] Another reason fór having the RBs fór the dynamic ACK/NAK transmissions in the interior ofthe ones allocated to periodic PUCCH transmissions is that the former RBs can become available fór PUSCH transmission after a certain number of UL sub-frames. This happens when the DL sub-frames carry multicast-broadcast traffic because there is no ACK/NAK transmission in corresponding subsequent UL sub-frames (no unicast PDSCH transmissions requiring ACK/NAK feedback are assumed to occur during multicast-broadcast DL sub-frames). This may nőt be possible, due to the single carrier property, if the RBs fór ACK/NAK transmission are nőt adjacent to the ones fór PUSCH transmission. [0046] Yet another reason fór having the dynamic ACK/NAK RBs in the interior part of the operating bandwidth used fór dynamic ACK/NAK and periodic PUCCH transmissions is that the former typically need to be more reliable than the latter. Transmissions in interior RBs largely avoid out-of-band interference created by transmissions in adjacent bandwidths, which may be at a substantially larger power, and therefore ACK/NAK signals are better protected against such interference if they are placed in interior RBs.

[0047] A generalization of the RB allocation of FIG. 9 is presented in FIG. 10 where in addition to the RBs fór CQI, dynamic ACK/NAK, and dynamic PUSCH transmissions, the RBs fór persistent ACK/NAK and persistent PUSCH transmissions are alsó included. The order of the periodic transmissions can be interchanged or mixed. Such an alternative order fór the periodic transmissions is illustrated in FIG. 11.

[0048] The RBs fór persistent ACK/NAK transmissions 1010A and 1010B orthe RBs fór persistent PUSCH transmissions 1020A and 1020B are located to the exteriőr of RBs fór dynamic ACK/NAK transmissions 1030A and 1030B which are again placed adjacent and to the exteriőr ofthe RBs fór dynamic PUSCH transmissions 1040A and 1040B because they are the only ones that may vary between sub-frames in a way that cannot be predetermined. While the RBs fór the periodic PUCCH and persistent PUSCH transmissions may alsó vary between sub-frames, this happens in a predeter7

ΕΡ 2 003 811 Β1 mined manner.

[0049] Moreover, although in FIG. 10 the RBs tor ACK/NAK transmission due to persistent PDSCH scheduling are located in both slots to the interior of the RBs fór CQI transmission, this is nőt necessary and the latter can be located to the interior of theformer in one ofthe two slots. Additionally, the transmission fór any of these signals may be confined in only one siót or extend pást one sub-frame.

[0050] FIG. 11 illustrates the same principle as FIG. 10 with the only difference being the relatíve piacement of persistent PUSCH 1110A and 1110B and CQI transmissions 1120A and 1120B. As CQI transmissions typically require better reception reliability than persistent PUSCH transmissions as the latter benefitfrom the use of HARQ, avoiding the CQI piacement in RBs at the edge ofthe operating bandwidth protects the CQI signal from potential out-of-band interference and can therefore improve its reception reliability.

[0051] In both FIG. 10 and FIG. 11, the RBs fór persistent ACK/NAK transmissions are located to the exteriőr of the RBs tor dynamic ACK/NAK transmissions and to the interior of the RBs tor CQI transmissions or persistent PUSCH transmissions. In this manner, if there is no PDSCH scheduling in a previous DL sub-frame, such as when that subframe conveys multicast-broadcast communication traffic, no ACK/NAK transmission occurs in a corresponding subsequent UL sub-frame and the RBs that would otherwise be used tor ACK/NAK transmissions by UEs can be used tor PUSCH transmissions.

[0052] Having a fixed number of RBs per sub-frame tor all periodic transmissions (CQI, ACK/NAK due to persistent PDSCH scheduling, persistent PUSCH scheduling), and piacing the ACK/NAK RBs due to dynamic PDSCH scheduling between the ones tor periodic transmissions and the ones tor dynamic PUSCH transmissions, the RBs available tor dynamic PUSCH transmissions are contiguous and well defined. This fixed numberof RBs per sub-frame tor the periodic transmissions can be communicated to the UEs through a broadcast channel. This information is used as an index by the UEs to determine the RBs tor dynamic ACK/NAK transmissions (first RB) if these RBs do nőt start from the edges ofthe operating bandwidth. Knowing the fixed number of RBs per sub-frame used tor periodic transmissions, a UE can apply an offset equal to the number of these RBs (equal to the index) in order to determine the first available RB tor ACK/NAK transmission due to dynamic PDSCH scheduling.

[0053] Using FIG. 10 as an example, the serving Node B broadcasts the totál number of RBs used tor all periodic transmissions (such as CQI, persistent PUSCH scheduling, ACK/NAK due to persistent PDSCH scheduling) and this value serves as an index tor a UE to determine the first RB available tor ACK/NAK transmission due to dynamic PDSCH scheduling by applying a respective offset, equal to that index, relatíve to the first RB at either end of the operating bandwidth.

[0054] While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from scope ofthe present invention as defined by the appended claims.