WO2013104119A1

WO2013104119A1 - Control channel design for low bandwidth users

Info

Publication number: WO2013104119A1
Application number: PCT/CN2012/070236
Authority: WO
Inventors: Chunyan Gao; Shuang TAN; Na WEI; Jing HAN; Wei Bai; Haiming Wang
Original assignee: Renesas Mobile Corp
Current assignee: Renesas Electronics Corp
Priority date: 2012-01-11
Filing date: 2012-01-11
Publication date: 2013-07-18
Anticipated expiration: 2014-07-11

Abstract

A hopping pattern is defined by L frequency hops among N candidate resources. L is determined from at least a total number M of frequency selective candidate resources. N is the number of candidate resources that are used for the frequency hopping. Control signaling such as an E-PDCCH is sent by a network to a UE according to this hopping pattern to achieve frequency diversity. In the examples the candidate resources are physical resource blocks PRBs. In one embodiment L=K when N=1 and L=1 otherwise (K is predefined by the network); in another embodiment ^L ⁼I^M /Nl. In the examples the E-PDCCH occupies different OFDM symbols in different candidate PRBs in each of the L frequency hops. Confining the hopping pattern to a maximum bandwidth of 1.4 MHz enables low cost machine type communication devices to obtain an E-PDCCH that gives their resource allocation.

Description

CONTROL CHANNEL DESIGN FOR LOW BANDWIDTH USERS

TECHNICAL FIELD:

[0001] The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs, and more specifically relate to arranging a control channel such that a user equipment's resource allocations lie only within a narrow bandwidth yet still have some frequency diversity for robustness. BACKGROUND:

[0002] Abbreviations used in this description and/or in the referenced drawings are defined below following the Detailed Description section.

[0003] Further development of the LTE system is expected to more specifically support MTC devices, which is a market expected to expand rapidly in the future. From the network operators perspective the need is to reduce the number of RATs their infrastructure supports so as to reduce overall network maintenance costs. Many MTC devices are targeting low-end (low cost, low data rate) applications that can be handled adequately by GSM/GPRS. Owing to the low cost of these devices and good coverage of GSM/GPRS, there is very little motivation for suppliers to MTC device manufacturers to use modules supporting the LTE radio interface. As more and more MTC devices are deployed in the field, this naturally increases the reliance on GSM/GPRS networks. This will cost network operators not only in terms of maintaining multiple RATs, but also prevent them from maximizing the use of their valuable spectrum since GSM/GPRS offer sub-optimal spectrum efficiency. Such inefficiencies would grow with an increasing number of deployed MTC devices that can only utilize GSM/GPRS.

[0004] Document RP-111112 entitled PROPOSED SID: PROVISION OF LOW-COST MTC UEs BASED ON LTE (by Vodafone; 3 GPP TSG RAN meeting #53; Fukuoka, Japan; 13-16 January 2011) suggest solutions for migrating low-end MTC devices from GSM/GPRS to LTE networks by investigating and evaluating LTE RAN specifications to clearly understand the feasibility of creating a type of terminal that would permit the cost of terminals tailored for the low-end of the MTC market to be competitive with that of GSM/GPRS terminals targeting the same low-end MTC market. In fact this has become a new study item in 3GPP RANI . [0005] Due to their low volume traffic needs narrow bandwidth is considered to be a property for low cost MTC UEs. But in the LTE system the PDCCH, which gives the UEs their resource allocations on which their data is sent and received, is spread across the entire bandwidth. In carrier aggregation systems that bandwidth may only span one component carrier but it is still wideband compared to the narrow bands low cost MTC devices operate, so this is one problem with adapting LTE for MTC purposes. A new channel E-PDCCH had been proposed in current 3 GPP discussion to enhance the PDCCH capacity, and it is assumed this new control channel will be sent in the PDSCH region of the bandwidth. While the E-PDCCH might be used to convey DL control information to MTC devices in a narrow band, but still there are additional considerations for the E-PDCCH and MTC devices.

[0006] A typical narrow bandwidth in which low cost MTC devices operate is about 1.4 MHz. With such a narrow bandwidth it is not desirable to assign too many PRBs else the control channel overhead becomes too high. For example, reserving 2 PRBs for E-PDCCH in a 1.4MHz bandwidth will count for one third of the overhead. But reserving only one PRB for E-PDCCH sacrifices frequency diversity gain.

[0007] Another consideration relates to the OFDM symbols. Since the E-PDCCH is located in the PDSCH region, the position and region size of the E-PDCCH depends on the number of OFDM symbols used for normal PDCCH in the same subframe. The number of PDCCH symbols is indicated by the PCFICH, but that channel also spreads over the whole system bandwidth and is so not detectable to low cost MTC UEs which can operate only within a narrow bandwidth such as 1.4 MHz. So even if the frequency diversity issue could be solved with effective E-PDCCH PRB patterns, the normal PCFICH cannot be used to indicate to the low cost MTC devices the E-PDCCH region and the PRB pattern.

[0008] During various discussions in LTE Release 10 concerning relay nodes there were proposals concerning the R-PDCCH. See for example document Rl -091783 by Research in Motion (UK Limited) entitled RELAY LINK CONTROL SIGNALLING; and document Rl -091689 by NEC Group entitled MBS FN SUBFRAME AND CONTROL STRUCTURE FOR RELAY TYPE 1 NODES (both from 3 GPP TSG RAN WG1 meeting #57; San Francisco, USA; 4-8 May 2009). This is relevant because in Release 1 1 discussions the R-PDCCH is being considered as a reference for E-PDCCH design to get an enhanced downlink control channel, and to solve the downlink control capacity issue in MU-MIMO and CoMP scenarios. The E-PDCCH study is ongoing and now the discussion is focused on the motivations and scenarios for E-PDCCH. See for example document Rl-113321 by Alcatel-Lucent Shanghai Bell and Alcatel- Lucent entitled PDCCH CAPACITY ANALYSIS AND DESIGN PRINCIPLES FOR ENHANCED PDCCH and document Rl-113179 by Renesas Mobile Europe Ltd entitled VIEWS ON MOTIVATIONS

AND TARGETS FOR CONTROL SIGNALING ENHANCEMENTS (both from 3 GPP TSG RAN

WG1 meeting #66bis; Zhuhai, China; 10-14 October 2011). These designs under discussion have not taken into account how to achieve frequency diversity when only limited resources are available to the E-PDCCH for low cost MTC UEs that have capacity for operating only within a narrow bandwidth. Neither do any of the current discussions propose details for indicating a E-PDCCH pattern to the UEs so they can map indication bits to the resource allocated for E-PDCCH.

SUMMARY:

[0009] In a first exemplary embodiment of the invention there is a method comprising: determining a number/, of frequency hops from at least a total number M of frequency selective candidate resources and a number N of the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers; and one of sending or receiving control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping. [0010] In a second exemplary embodiment of the invention there is an apparatus comprising at least one processor and at least one memory storing a computer program. In this embodiment the at least one memory with the computer program is configured with the at least one processor to cause the apparatus to at least: determine a number L of frequency hops from at least a total number M of frequency selective candidate resources and a number N of the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers; and one of send or receive control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping.

[0011] In a third exemplary embodiment of the invention there is a computer readable memory tangibly storing a computer program executable by at least one processor, the computer program comprising: code for determining a number L of frequency hops from at least a total number M of frequency selective candidate resources and a number Nof the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers; and code for one of sending or receiving control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping.

[0012] These and other embodiments and aspects are detailed below with particularity. BRIEF DESCRIPTION OF THE DRAWINGS:

[0013] Figure 1 is a schematic diagram of OFDM symbol/time (horizontal axis) versus PRB/frequency (vertical axis) illustrating by outlining the E-PDCCH for each of four examples according to a first implementation of these teachings.

[0014] Figure 2 is similar to Figure 1 but outlining the E-PDCCH for each of two examples according to a second implementation of these teachings.

[0015] Figure 3 is similar to Figure 1 but outlining the E-PDCCH for each of two examples according to a third implementation of these teachings.

[0016] Figure 4 is a logic flow diagram that illustrates from the perspective of the network eNB and of the UE/MTC device the operation of a method, and a result of execution of computer program instructions embodied on a computer readable memory, in accordance with an exemplary embodiment of this invention. [0017] Figure 5 is a simplified block diagram of a UE and an eNB which are exemplary electronic devices suitable for use in practicing the exemplary embodiments of the invention.

DETAILED DESCRIPTION:

[0018] The following examples are in the specific context of the LTE/LTE- Advanced systems (for example, Release 1 1 and later) but these teachings are more broadly applicable to any wireless radio system which employs radio resource grants from the network to the UEs. These examples consider only a single UE but it will be understood the description applies for all such UEs being scheduled for radio resources according to the teachings described for one UE. Additionally, these teachings are particularly advantageous for machine-to-machine (M2M) type devices which use machine-type communications (MTC) for generally small volume and infrequent data transmissions. Such a machine-to-machine type device is included under the more generic term UE or user device to distinguish it from any network node.

[0019] In the LTE physical layer specification [3 GPP TS 36.211 vl0.3.0 (201 1-09) E-UTRA; PHYSICAL CHANNELS AND MODULATION (RELEASE 10)], frequency hopping is allowed for PUSCH and SRS transmission. The hopping pattern is slot based and preconfigured via higher layer signaling. According to exemplary embodiments of these teachings, similar frequency hopping is also used to design the E-PDCCH. But the E-PDCCH hopping disclosed in the examples below is not a direct substitution from the current hopping method used by the PUSCH/SRS. Namely, the E-PDCCH frequency hopping examples below differ from the TS 36.211 procedures for hopping PUSCH/SRS transmissions in at least the following ways:

• How to determine the number of hopping;

• How to determine the resource to be used for each hop;

• How to get diversity for E-PDCCH with one CCE; and

• How to indicate the E-PDCCH pattern.

[0020] Below are presented three distinct implementations for symbol-level frequency hopping patterns which enable frequency diversity for the E-PDCCH. These hopping patterns obtain frequency diversity even if only one PRB pair is configured for the E-PDCCH.

[0021 ] In a first implementation first we define a few terms. The PRBs allowed for frequency hopping are predefined and denoted as ( i, P_2;..., P_M). So in total there are PRBs allowed for frequency hopping, M being an integer greater than one. Note that these predefined hopping PRBs i, P₂, and PM are not necessarily frequency continuous, so for example

The number of PRBs used for E-PDCCH in each hop is denoted as N and this number is signalled to the UE in the narrow band. The number of frequency hopping, denoted as L, can be determined implicitly or explicitly. Following are some examples of this. In a first example the value for L is implicitly determined based on number of PRBs for hopping, for example

L = \^M/

I 1 or L=2 for N=l and no hopping otherwise. In a second example L is explicitly indicated via higher layer signalling, or is explicit in that its value is predefined such as published in a RAT standard. In a third example the value for L is implicitly determined by the number of RS per antenna port, denoted as P, and configured to use for E-PDCCH. So for example one implicit determination might relate these as L = P.

[0022] In each hop, N PRBs in ^{5 ~} L OFDM symbols are used for the E-PDCCH, where Y is configured by higher layers or is predefined (such as for example Y^~l 2). For any given z^'th hop, the resource for E-PDCCH is determined as follows:

• in the time domain, OFDM symbols = 2 -if- ί I S -f- ft are _used

(where k = 0, 1 , ..., S-\);

• in the frequency domain, PRBs P_M, P_m+i, ..., and P_ffl+;v-i ar used

(where wt = 1 + i i JV ).

[0023] For this first implementation there are different ways to determine the number of hops. In one particular embodiment the manner in which the number of hops is determined is configurable by the eNB. Figure 1 illustrates some exemplary different methods for this, denoted as examples A through D. Figure 1 assumes the PRBs are indexed sequentially from the top (PRBs 1 through 6 are illustrated at the Figure 1 examples) so the shaded rows are those PRBs that are predefined for hopping in the various examples there. Each example of Figure 1 spans one subframe so each horizontal block represents one OFDM symbol indexed left to right as 0 through 13.

[0024] In each of examples A and B of Figure 1, it is assumed that the number of hopping L is determined by the number of PRBs 7Y in the way that L=2 for N= 1 and L= 1 (no hopping) otherwise. In both example A and B, there are M=3 PRBs for hopping and those PRBs are predefined as PRBs 1 , 5 and 3 as shown by shading. The order 1 ,5,3 is a PRB priority order which is relevant so long as there are more PRBs than hops (M>L). Also for examples A and B, the OFDM symbols for hopping are indexed from 2 to 13 (meaning 7=12). The predefined PRBs are noncontiguous to get more frequency diversity gain and the PRBs are listed with decreasing priority order. So if the E-PDCCH will not occupy all the M PRBs which are predefined, the PRBs will be selected to be used according to the defined priority order. [0025] In example A of Figure 1, there is signaling to indicate 7V=1 PRB in each hop, and so there is an L=2 hopping pattern which is triggered implicitly. Specifically for example A, PRB #1 will be used in the first hop and PRB #5 will be used in the second hop, with 6 symbols occupied per hop as shown by the outlining. Specifically, OFDM symbols 2 through 7 in PRB 1 and OFDM symbols 8 through 13 for PRB 5 as shown in Example A.

[0026] For example B, N=2 is signaled and so hopping is disabled implicitly according to the rule that is assumed for these examples (L=2 for N=l , else L^~\ and thus no hopping otherwise). Since N=2, according to the 1 ,5,3 priority order only PRBs 1 and 5 are selected to be used. With no hopping and OFDM symbols 2 through 13 used for E-PDCCH, then as shown by outlining at example B OFDM symbols 2 through 13 in each of PRBs 1 and 5 are used for the E-PDCCH.

[0027] In example C of Figure 1, there are M-6 predefined PRBs for hopping use and they are PRBs #1 to #6 in that priority order, and like examples A and B the OFDM symbols for hopping are indexed from 2 to 13 (Y-12). For example C assume the number of hopping L is determined by , and that N=2 is signalled from the eNB to the UE. Therefore the number of hopping can be derived implicitly by L=6/2=3, with PRBs #1 and #2 in the first hop, PRBs #3 and #4 in the second hop, and PRBs #5 and #6 used for the third hop. The 7=12 OFDM symbols are divided among the M-3 hops so there are four OFDM symbols occupied in each hop as shown by outlining in example C. That outlining gives the E-PDCCH resources in the narrow band which may be received by the MTC devices.

[0028] In example D of Figure 1, PRB #1, #3 and #5 are predefined for hopping use in that priority order and the OFDM symbols for hopping are again indexed from 2 to 13 since still 7=12. For example D assume that the number of hopping is determined by the number of RS per antenna port in the last 12 OFDM symbols. So for example D if we assume CRS port 0 is the only one configured then 1=3. If the network indicates N=l, then PRBs #1, #3 and #5 are determined to be used in the 3 hops respectively. And with 7 =12 OFDM symbols configured for hopping, the UEs can assume that the normal PDCCH will always occupy 2 OFDM symbols, or the number of OFDM symbols used in the first hop can be adjusted based on the number of OFDM symbols for normal PDCCH if signaled by the eNB (in any of various ways).

[0029] In the second implementation new signalling to the UE is introduced in the narrow band for indicating the start position of the first hop. This indication can be used to carry information of OFDM symbol and PRB index used for the E-PDCCH. The radio resources which are allowed to be a start position are predefined. As an example, PRBs 1 and 2 in the first four OFDM symbols are the allowed candidates for the start position. [0030] In this second implementation the selected hopping pattern and the E-PDCCH region can be implicitly derived from the indication of start position. So if the start position is indicated as the i^'-th OFDM symbol and the y^'-th PRB, then the below equations shows how the UE might determine the 2-hop hopping pattern the E-PDCCH is to follow.

· for the 1^st hop, E-PDCCH is in the region of OFDM symbols /, i+l , and 6, and PRB j if ( mod 2) = 1 or PRBs j and +1 otherwise;

• for the 2^nd hop, E-PDCCH is in the region of OFDM symbols 7, 8, and 13, and PRB j+4 if (J mod 2)=1 or PRBs j+4 and j+5 otherwise. [0031] Figure 2 illustrates two non-limiting examples for how the hopping pattern is determined according to this second implementation. The Figure 2 examples assume that 2 hops are predefined; and that it is also predefined that if the E-PDCCH starts in an odd-indexed PRB then 1 PRB is used for the hop, else if the E-PDCCH starts in an even-indexed PRB then 2 PRBs are used for the hop. Similar to Figure 1 , for the Figure 2 diagrams the PRBs are indexed sequentially from the top and these examples show PRBs 1 through 6, and each diagram of Figure 2 spans one subframe so each horizontal block represents one OFDM symbol indexed left to right as 0 through 13.

[0032] In example A of Figure 2, the start position is OFDM symbol #2 and PRB #1. This is an odd-numbered PRB index so from the above predefined rules only 1 PRB is used per hop. So for the first hop, PRB #1 in OFDM symbols 2-6 is used for the E-PDCCH, while in the second hop PRB #5 in OFDM symbols 7-13 is used for the E-PDCCH. The specific OFDM symbols are determined from the example equations above. This example also assumes that a hopping step of 4 PRBs is preconfigured. The E-PDCCH is shown specifically by outlining in the example A of Figure 2.

[0033] In example B of Figure 2, the start position is OFDM symbol #0 and PRB #2. Since this start position is an even-numbered PRB index the above rule tells that 2 PRBs are occupied for each hop. Therefore the first hop uses PRBs #2 and #3 in OFDM symbols 0-6 for the E-PDCCH, and the second hop uses PRBs #6 and #1 in OFDM symbols 7-13 for the E-PDCCH. As with example A of Figure 2, the specific OFDM symbols for each hop is determined from the equations above. The E-PDCCH is also shown specifically by outlining in the example B of Figure 2.

[0034] Figure 3 illustrates two non-limiting examples for how the hopping pattern is determined according to the third implementation of these teachings. The Figure 3 examples achieves frequency diversity of the E-PDCCH by distributing the CCEs which make up the E-PDCCH in different PRBs, and in the Figure 3 examples each CCE of the E-PDCCH is distributed in a different PRB. The resource element distribution of one CCE is implicitly determined by the CCE index and the hopping pattern (for example, the number of hops, the start position, etc.). As background, in the LTE system each CCE corresponds to 9 resource element groups, and there are 4 resource elements per group, (so each CCE consists of 36 resource elements); , and the regular PDCCH can be 1, 2, 4 or 8 CCEs depending on the PDCCH format and the channel status. In the Figure 3 examples one CCE is distributed in multiple PRBs, and the distribution pattern is determined by the hopping pattern and CCE index,

[0035] Specifically, for example A of Figure 3 there is a 2-hop pattern, and there is a predetermined rule that CCEs with an odd index will occupy 2 OFDM symbols in the first hop and occupy 1 OFDM symbol in the second hop, while CCEs with an even index will occupy 1 OFDM symbol in the first hop and 2 OFDM symbols in the second hop, so long as there are available OFDM symbols to do so. So assuming the E-PDCCH is four CCEs, CCE#1 in the first hop occupies OFDM symbols 2-3 designated as 301 A and in the second hop occupies OFDM symbol 7 designated as 301B. CCE#3 is also odd and so will hop similarly as shown by reference numbers 303A and 303B. CCE#2 is an even index so in the first hop it will occupy only one OFDM symbol (index 4) designated as 302 A and in the second hop will occupy two OFDM symbols (indices 8-9) designated as 302B. There are no further OFDM symbols available in the first hop to use for CCE#4 since example A of Figure 3 assumes slot-based hopping and the next symbol at position #7 (when indexed as 0...13 ) lies in the next slot of the subframe. The first two symbol positions 0-1 of the 7 total OFDM symbols that make up the first slot are reserved for legacy PDCCHs in this example. The end result of these considerations is that CCE#4 will have no frequency hopping in Example A of Figure 3 and will instead occupy three OFDM symbols (indices 11-13) designated as 304B in the second hop/second slot. For this example, the E-PDCCH is CCE #s 1-4 and only CCE #s 1 -3 have frequency diversity, which is maximized by using PRBs 1 and 6 for those CCEs.

[0036] For example B of Figure 3 there is a 3-hop pattern, where each CCE occupies 1 OFDM symbol in each hop. Specifically, the available OFDM symbols 2-13 are divided into the number of hops (3) leaving 4 OFDM symbols per PRB. There are 4 CCEs so each will occupy one OFDM symbol per used PRB. The PRBs used for the E-PDCCH are every other one to maximize frequency diversity across the multiple hops. CCE#1 occupies OFDM symbol 2 in PRB1 designated as 305A in the first hop, OFDM symbol 6 in PRB3 designated as 305B in the second hop, and OFDM symbol 10 in PRBS designated as 305C in the third hop. Similarly, CCE#2 occupies OFDM symbols 3, 7 and 1 1 in respective PRBs 1 , 3 and 5 for the respective first, second and third hops, designated respectively as 306A, 306B and 306C. CCE #s 3 and 4 follow this same pattern but are not given reference numbers for example B of Figure 3. For this example frequency diversity is achieved in each CCE.

[0037] For each of the second and third implementations, the number of hops L for each example is also

(with or without the qualifier that L—2 for N-l) as was detailed above for the first implementation. Specifically, at example A of Figure 2 there were M=2 PRBs for hopping and N=l since the PRB index (even or odd) gave the value for N and so the number of hops L=2. At example B of Figure 2 there were there =4 PRBs for hopping and N=2 due to the even numbered PRB index so L=2 for that example also. At example A of Figure 3 there were M=2 PRBs for hopping and JV=1 since only one PRB is used per hop in both Figure 3 examples, so the number of hops was again L=2. At example B of Figure 3 there were M=3 PRBs for hopping and N=l for Figure 3 so the number of hops was the X=3.

[0038] Embodiments of the invention detailed above provide certain technical effects, such as for example these hopping pattern implementations provide frequency diversity even if only one PRB is allocated for control signaling, and the control channel for that signaling (the E-PDCCH region in the examples) and pattern indication can be indicated via minimum signaling. [0039] Further technical effects of the above implementations is that the hopping patterns and the related signaling allows dynamic adjustment of the PRBs for the E-PDCCH (such as in the second implementation via the starting position indication) which helps to reduce/randomize the interference from adjacent cells. Additionally for the third implementation, the CCE distribution into multiple PRBs enables frequency diversity per CCE of the E-PDCCH, and the corresponding distribution pattern can be known implicitly based on the E-PDCCH hopping pattern and the CCE index. [0040] Now are detailed with reference to Figure 4 further particular exemplary embodiments from the perspective of either the network/eNB or of the UE/MTC device. Figure 4 may be performed by the whole eNB, or by one or several components thereof such as a modem, a processor in combination with a program stored on a memory, etc. At block 402 a number L of frequency hops is determined from at least a total number M of frequency selective candidate resources and a number N of the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers. And at block 404, depending on whether it is from the perspective of the eNB or the UE, control signaling is sent or received according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping.

[0041 ] Blocks 402 and 404 recite using more general terms than the above non-limiting examples which were in the context of an LTE system. In the above examples the control signaling of block 404 is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system; the candidate resources of block 402 are physical resource blocks; and the number L of block 402 is determined by the above non-limiting

i ^= \^M!

examples as I ' Ί 1. In another example above the number L of block 402 is determined as L=K when 7V=1, and as L=l otherwise; where K is a predefined value determined by the eNB. In each of the above non-limiting examples the E-PDCCH occupies different OFDM symbols in different candidate physical resource blocks in each of the L frequency hops. To solve the specific problem with low cost MTC devices detailed in the background section, the hopping pattern is confined to a maximum bandwidth of 1.4 MHz.

[0042] Further portions of Figure 4 represent several of the specific but non-limiting embodiments detailed above. Block 406 summarizes an aspect of the first implementation, where a value for N is signaled between a network access node that sends the control signaling of block 304 and a user equipment which receives the control signaling of block 404. Block 408 gives further detail for the Figure 1 implementation in that M is predefined for frequency hopping of the control signaling/E-PDCCH; and in each of the L hops the N candidate physical resource blocks in L > L\ OFDM symbols are used for the control signaling/E-PDCCH, where Ύ is configured by higher layers or is predefined. The control signaling/E-PDCCH occupies, for any fth hop of the L hops, OFDM symbols t. ^: = 2 + ί I S + k in the time domain (where k - 0, 1 , S-l); and physical resource blocks P_m, P_m+\, and P_m+N-\ in the frequency domain (where rn = l + i I JV )

[0043] Figure 4 summarizes aspects of the second implementation at blocks 410 and 412. Namely, at block 410 a value for N is determined from an index of the candidate resource indicated in signaling between a network access node and a user equipment, in which that same signaling further indicates a start osition for a first of the L frequency hops. Block 412 gives further detail in specifying that the start position indicates an i^th OFDM symbol and a ^h candidate resource; and for L^~2: or a 1^st hop of the hopping pattern, the E-PDCCH occupies OFDM symbols i, i+l, and 6, and N=l candidate resource j if (J mod 2) - 1 or N=2 candidate resources j and j+\ otherwise; and for a 2^nd hop of the hopping pattern, the E-PDCCH occupies OFDM symbols 7, 8, ..., and 13, and N=l candidate resource j+4 if (j mod 2)=1 or N=2 candidate resources j+4 and j+5 otherwise.

[0044] Figure 4 further summarizes aspects of the third implementation at block 414 which provides that the control signaling comprises multiple control channel elements of which at least all but one are distributed among the N candidate resources in each hop of the hopping pattern. In the Figure 3 examples was detailed that the distribution of the control channel elements among the JV candidate resources is implicitly determined from an index of the respective control channel element, and from the hopping pattern.

[0045] The logic flow diagram of Figure 4 may be considered to illustrate the operation of a method, and a result of execution of a computer program stored in a computer readable memory, and a specific manner in which components of an electronic device are configured to cause that electronic device to operate. The various blocks shown in Figure 4 may also be considered as a plurality of coupled logic circuit elements constructed to carry out the associated function(s), or specific result of strings of computer program code stored in a memory.

[0046] Such blocks and the functions they represent are non-limiting examples, and may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention.

[0047] Reference is now made to Figure 5 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 5 an eNB 22 is adapted for communication over a wireless link 21 with an apparatus, such as a UE 20 embodied as a low cost MTC device as one non-limiting example. The eNB 22 may be any access node (including frequency selective repeaters) of any wideband wireless network such as LTE, LTE-A, WCDMA, and the like. The operator network of which the eNB 22 is a part may also include a network control element such as a mobility management entity MME and/or serving gateway SGW 24 which provides connectivity with further networks (e.g., a publicly switched telephone network and/or a data communications network/Internet).

[0048] The UE 20 includes processing means such as at least one data processor (DP) 20A, storing means such as at least one computer-readable memory (MEM) 20B which tangibly stores at least one computer program (PROG) 20C or other set of executable instructions, and communicating means such as a transmitter TX 20D and a receiver RX 20E for bidirectional wireless communications with the eNB 22 via one or more antennas 20F, Also stored in the MEM 20B at reference number 20G are the rules or algorithm for determining the frequency hopping pattern for the E-PDCCH (or other control channel) as detailed above in the various exemplary but non-limiting embodiments. [0049] The eNB 22 also includes processing means such as at least one data processor (DP) 22A, storing means such as at least one computer-readable memory (MEM) 22B that tangibly stores at least one computer program (PROG) 22C or other set of executable instructions, and communicating means such as a transmitter TX 22D and a receiver RX 22E for bidirectional wireless communications with the UE 20 via one or more antennas 22F. The eNB 22 stores at block 22G similar rules or algorithm for determining the frequency hopping pattern for the E-PDCCH or other control channel as detailed above. [0050] For completeness, the MME 24 is also shown to have a processor DP 24A, a memory 24B storing a program 24C and a modem 24H for digitally modulating and demodulating data it communicates over the data and control link 25 with the eNB 22.

[0051] While not particularly illustrated for the UE 20 or eNB 22, those devices are also assumed to include as part of their wireless communicating means a modem and/or a chipset which may or may not be inbuilt onto an RF front end chip within those devices 20, 22 and which also operates utilizing the new DCI format according to these teachings. [0052] At least one of the PROGs 20C in the UE 20 is assumed to include a set of program instructions that, when executed by the associated DP 20A, enable the device to operate in accordance with the exemplary embodiments of this invention, as detailed above. The eNB 22 also has software stored in its MEM 22B to implement aspects of these teachings relevant to it as detailed above for Figure 4. In these regards the exemplary embodiments of this invention may be implemented at least in part by computer software stored on the MEM 20B, 22B which is executable by the DP 20A of the UE 20 and/or by the DP 22A of the eNB 22, or by hardware, or by a combination of tangibly stored software and hardware (and tangibly stored firmware). Electronic devices implementing these aspects of the invention need not be the entire devices as depicted at Figure 5 or may be one or more components of same such as the above described tangibly stored software, hardware, firmware and DP, or a system on a chip SOC or an application specific integrated circuit ASIC. [0053] In general, the various embodiments of the UE 20 can include, but are not limited to personal portable digital devices having wireless communication capabilities, including but not limited to cellular telephones, navigation devices, laptop/palmtop/tablet computers, digital cameras and music devices, and Internet appliances, as well as the machine-to -machine type devices mentioned above.

[0054] Various embodiments of the computer readable MEMs 20B, 22B include any data storage technology type which is suitable to the local technical environment, including but not limited to semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory, removable memory, disc memory, flash memory, DRAM, SRAM, EEPROM and the like. Various embodiments of the DPs 20A, 22A include but are not limited to general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and multi-core processors.

[0055] Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description. While the exemplary embodiments have been described above in the context of the LTE and LTE-A system, as noted above the exemplary embodiments of this invention may be used with various other wideband wireless communication systems so as to constrain a control channel to a narrow bandwidth.

[0056] Further, some of the various features of the above non-limiting embodiments may be used to advantage without the corresponding use of other described features. The foregoing description should therefore be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof. [0057] The following abbreviations used in the above description and/or in the drawing figures are defined as follows:

3 GPP third generation partnership project

CCE control channel element

CoMP coordinated multipoint transmission DL downlink

eNB node B/base station in an E-UTRAN system

E-PDCCH enhanced PDCCH

E-UTRAN evolved UTRAN (LTE)

GRPS general packet radio service

GSM global system for mobile communications

LTE long term evolution (of UTRAN)

MIMO multiple-input multiple-output

MTC machine type communications

MU multi user

OFDM orthogonal frequency division multiplexing

PCFICH physical control format indicator channel

PDCCH physical downlink control channel

PDSCH physical downlink shared channel

PRB physical resource block

PUSCH physical uplink shared channel

RAN radio access network

RAT radio access technology

RS reference signal

R-PDCCH relay PDCCH

SRS sounding reference signal

UE user equipment

UL uplink

UTRAN universal terrestrial radio access network

Claims

What is Claimed is:

1. A method comprising:

determining a number L of frequency hops from at least a total number M of frequency selective candidate resources and a number Nof the candidate resources that are used for the frequency hopping, where L, and N are each positive integers; and one of sending or receiving control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping .

2. The method according to claim 1 , in which the control signaling is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as L=K when N=l , and as L=\ otherwise; in which K is a predefined value determined by a network access node which sends the control signaling according to the hopping pattern.

3. The method according to claim 1, in which the control signaling is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as

'⁼ [ !

4. The method according to claim 3, in which the E-PDCCH occupies different OFDM symbols in different candidate physical resource blocks in each of the L frequency hops.

5. The method according to claim 1, in which the hopping pattern is confined to a maximum bandwidth of 1.4 MHz.

6. The method according to any one of claims 1 through 5, in which a value for N is signaled between a network access node that sends the control signaling and a user equipment which receives the control signaling.

7. The method according to claim 6, in which;

M is predefined for frequency hopping of the control signaling; in each of the L hops, the N candidate resources in 5 = 1 L*7 >^" \ I OFDM symbols are used for the control signaling, where Y is configured by higher layers or is predefined; and

for any ith hop of the L hops, the control signaling occupies:

• OFDM symbols ^l i = ² + ^{i 1 5} + ^k in the time domain, where k = 0, 1, 5-1 ; and

• physical resource blocks P_M, P_M+\, · · · , an P,„+N-_\ in the frequency domain, where w = 1 + ϊ I iV .

8. The method according to any one of claims 1 through 5, in which a value for N is determined from an index of the candidate resource indicated in signaling between a network access node and a user equipment, in which the said signaling further indicates a start position for a first of the L frequency hops.

9. The method according to claim 8, in which the start position indicates an ^th OFDM symbol and a ^h candidate resource, and for L=2;

• for a l^sl hop of the hopping pattern, the control signaling occupies OFDM symbols i, z+1, ..., and 6, and N=l candidate resource j if (J mod 2) = 1 or N=2 candidate resources j and +1 otherwise; and

• for a 2^nd hop of the hopping pattern, the control signaling occupies OFDM symbols 7, 8, and 13, and N=l candidate resourcey^'+4 if (/^" mod 2)= 1 or N=2 candidate resources j+4 and j+5 otherwise.

10. The method according to any one of claims 1 through 4, in which the control signaling comprises multiple control channel elements of which at least all but one are distributed among the N candidate resources in each hop of the hopping pattern.

1 1. The method according to claim 10, in which the distribution of the control channel elements among the N candidate resources is implicitly determined from an index of the respective control channel element and the hopping pattern.

12. An apparatus comprising:

at least one processor and at least one memory storing a computer program; in which the at least one memory with the computer program is configured with the at least one processor to cause the apparatus to at least:

determine a number L of frequency hops from at least a total number M of frequency selective candidate resources and a number N of the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers; and one of send or receive control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping.

13. The apparatus according to claim 12, in which the control signaling is an E-PDCCH sent or received in one radio subframe of an B-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as L=K when N=l, and as L=\ otherwise; in which K is a predefined value determined by a network access node which sends the control signaling according to the hopping pattern.

14. The apparatus according to claim 12, in which the control signaling is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as H%1

15. The apparatus according to claim 14, in which the E-PDCCH occupies different OFDM symbols in different candidate physical resource blocks in each of the L frequency hops.

16. The apparatus according to claim 12, in which the hopping pattern is confined to a maximum bandwidth of 1.4 MHz.

17. The apparatus according to any one of claims 12 through 16, in which a value for N is signaled between a network access node that sends the control signaling and a user equipment which receives the control signaling.

18. The apparatus according to any one of claims 12 through 16, in which a value for N is determined from an index of the candidate resource indicated in signaling between a network access node and a user equipment, in which the said signaling further indicates a start position for a first of the L frequency hops.

19. The apparatus according to any one of claims 12 through 16, in which the control signaling comprises multiple control channel elements of which at least all but one are distributed among the N candidate resources in each hop of the hopping pattern,

20. A computer readable memory tangibly storing a computer program executable by at least one processor, the computer program comprising:

code for determining a number L of frequency hops from at least a total number M of frequency selective candidate resources and a number N of the candidate resources that are used for the frequency hopping, where L, M and N are each positive integers; and

code for one of sending or receiving control signaling according to a hopping pattern defined by the L frequency hops among the N candidate resources that are used for the frequency hopping.

21. The computer readable memory according to claim 20, in which the control signaling is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as L=K when N=l, and as L=\ otherwise; in which K is a predefined value determined by a network access node which sends the control signaling according to the hopping pattern.

22. The computer readable memory according to claim 20, in which the control signaling is an E-PDCCH sent or received in one radio subframe of an E-UTRAN system, the candidate resources are physical resource blocks, and the number L is determined as

23. The computer readable memory according to claim 22, in which the E-PDCCH occupies different OFDM symbols in different candidate physical resource blocks in each of the L frequency hops.