WO2011039575A1

WO2011039575A1 - Dynamic allocation for control channel and data channel within a subframe

Info

Publication number: WO2011039575A1
Application number: PCT/IB2009/054330
Authority: WO
Inventors: Mieszko Chmiel; Lars Lindh; Jari J. Mattila
Original assignee: Nokia Siemens Networks Oy; Nokia Inc.
Priority date: 2009-10-02
Filing date: 2009-10-02
Publication date: 2011-04-07

Abstract

An apparatus, system and method for mapping an encoded data word into a subframe in a communication system. In one embodiment, the apparatus (620) includes a message controller (631) configured to allocate a first section of a subframe to a control channel and a complementary second section of the subframe to a data channel for an encoded data word. The apparatus (620) also includes a message formatter (633) configured to select one of: (1) map selected data bits of the encoded data word within the second section and repeat ones of the selected data bits within a part of the first section when the control channel is less than an upper limit, and (2) map selected data bits of the encoded data word within a part of the first section and the second section, and remove at least a portion of the selected data bits within the part of the first section when the control channel is more than a lower limit.

Description

DYNAMIC ALLOCATION FOR CONTROL CHANNEL AND DATA CHANNEL WITHIN A SUBFRAME

TECHNICAL FIELD

The present invention is directed, in general, to communication systems and, in particular, to an apparatus, system and method for mapping an encoded data word into a subframe in a communication system.

BACKGROUND

Long Term Evolution ("LTE") of the Third Generation Partnership Project ("3GPP"), also referred to as 3GPP LTE, refers to research and development involving 3GPP Release 8 and beyond, which is the name generally used to describe an ongoing effort across the industry aimed at identifying technologies and capabilities that can improve systems such as the universal mobile telecommunication system ("UMTS"). The goals of this broadly based project include improving communication efficiency, lowering costs, improving services, making use of new spectrum opportunities, and achieving better integration with other open standards. The 3GPP LTE project is not itself a standard-generating effort, but will result in new recommendations for standards for the UMTS. Further developments in these areas are also referred to as Long Term Evolution-Advanced ("LTE-A").

The evolved UMTS terrestrial radio access network ("E-UTRAN") in 3GPP includes base stations providing user plane (including packet data convergence protocol/radio link control/medium access control/physical ("PDCP/RLC/M AC/PHY") sublayers) and control plane (including radio resource control ("RRC") sublayer) protocol terminations towards wireless communication devices such as cellular telephones. A wireless communication device or terminal is generally known as user equipment ("UE") or a mobile station ("MS"). A base station is an entity of a communication network often referred to as a Node B or an NB.

Particularly in the E-UTRAN, an "evolved" base station is referred to as an eNodeB or an eNB. For details about the overall architecture of the E-UTRAN, see 3 GPP Technical Specification ("TS") 36.300, v8.5.0 (2008-05), which is incorporated herein by reference. The terms base station, NB, eNB, and cell refer generally to equipment providing the wireless-network interface in a cellular telephone system, and will be used interchangeably herein, and include cellular telephone systems other than those designed under 3GPP standards. Orthogonal frequency division multiplexing ("OFDM") is a multi-carrier data transmission technique that is advantageously used in radio frequency based transmitter-receiver systems such as 3GPP E-UTRAN/LTE/3.9G and others. The OFDM systems typically divide available frequency spectrum into a plurality of carriers or resource elements ("REs") that are transmitted in a sequence of time slots. Each of the plurality of carriers has a narrow bandwidth and is modulated with a low-rate signal stream. The carriers are closely spaced and orthogonal separation of the carriers controls inter-carrier interference ("ICI").

When generating an OFDM signal, each carrier is assigned a signal stream that is converted to samples from a constellation of admissible sample values based on a modulation scheme such as quadrature amplitude modulation ("QAM,") including binary phase shift keying ("BPSK"), quadrature phase shift keying ("QPSK"), and higher-order variants (16QAM, 64QAM, etc), and the like. Once phases and amplitudes are determined for the particular samples, they are converted to time-domain signals for transmission. A sequence of samples, such as a 128-sample sequence, is collectively assembled into a "symbol." Typically, OFDM systems use an inverse discrete Fourier transform ("iDFT") such as an inverse fast Fourier transform ("iFFT") to perform conversion of the symbols to a sequence of time-domain sample amplitudes that are employed to form a time domain transmitted waveform. The iFFT is an efficient process to map data onto orthogonal subcarriers. The time domain waveform is then up-converted to the radio frequency ("RF") of the appropriate carrier and transmitted.

Component carrier ("CC") aggregation is a technology included in LTE Release- 10

("Rel-10," also referred to as LTE-Advanced), as described in 3GPP Technical Report 36.814, entitled "Further Advancements for E-UTRA Physical Layer Aspects," VO.4.1, February 2009, which is incorporated herein by reference. Particularly in networks employing OFDM, a channel, which may have a bandwidth of 20 megahertz ("MHz"), typically includes subcarriers spaced 15 kilohertz ("kHz"). Each channel has a carrier frequency, and multiple channels may be semi-permanently allocated ("aggregated") to a user equipment to transmit a wide bandwidth signal such as a video signal, a large file, or a complex web page. With carrier aggregation, two or more component carriers are aggregated to support wider transmission bandwidths (e.g., an aggregation of five 20 MHz component carriers to provide a bandwidth of 100 MHz). The user equipment may simultaneously receive or transmit one or multiple component carriers depending on capabilities thereof.

The technique of component carrier aggregation as a bandwidth extension can provide significant communication gains in terms of peak data rate and cell throughput compared to non- aggregated operation in LTE Release-8. A control channel such as a physical downlink control channel ("PDCCH") in a component carrier can be employed to assign data resources on this component carrier or another component carrier with the use of a component carrier indicator ("CO"). Scenarios in which a component carrier indicator can be beneficial are heterogeneous networks or component carriers with non-balanced control channel coverage and load balancing of control channel resources in multiple component carriers. Heterogeneous networks may employ base stations of varying size, coverage, and power level, such as low-power "hot spot" access nodes in public and residential facilities in conjunction with wider area base stations employing high power transmitters with antennas on towers.

The 3 GPP community has agreed to support component carrier aggregation using a

PDCCH on a component carrier to assign physical downlink shared channel ("PDSCH") resources on the same component carrier and physical uplink shared channel ("PUSCH") resources on a single, linked uplink ("UL") component carrier. In this process, a carrier indicator field is not necessary (i.e., the 3GPP Rel-8 PDCCH frame structure may be used with the same coding and control channel element-based ("CCE-based") resource mapping and the same downlink control information ("DO") formats). The 3GPP community has also agreed to support component carrier aggregation using PDCCH on a component carrier to assign PDSCH or PUSCH resources in one of multiple component carriers using the carrier indicator field. To achieve this end, 3 GPP Rel-8 downlink control information formats are extended with a one to three bit carrier indicator field. The 3GPP Rel-8 frame structure is now planned to be reused in later 3GPP releases (i.e., the same coding and resource mapping are planned to be reused).

In view of the growing deployment and sensitivity of user equipment to communication performance in wireless communication networks, it is important that the user equipment accurately decode a PDCCH so that a PDSCH carrying payload data can be accurately decoded. However, solutions for the problem of physical control format indicator channel ("PCFICH") detection errors on a component carrier carrying PDSCH to the user equipment are unresolved in case of cross component carrier PDSCH scheduling or in case of semi-persistent PDSCH scheduling. Therefore, what is needed in the art is an apparatus, system and method that provides improved immunity for decoding errors on control channel such as a PCFICH so that a related data channel such as a PDSCH carrying payload data can be decoded, particularly a PDSCH in another component carrier, thereby overcoming deficiencies of conventional communication systems. SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, and technical advantages and effects are generally achieved, by embodiments of the present invention, which include an apparatus, system and method for mapping an encoded data word into a subframe in a communication system. In one embodiment, the apparatus (e.g., a processor) for use with a base station includes a message controller configured to allocate a first section of a subframe to a control channel and a complementary second section of the subframe to a data channel for an encoded data word. The apparatus also includes a message formatter configured to select one of: (1) map selected data bits of the encoded data word within the second section and repeat ones of the selected data bits within a part of the first section when the control channel is less than an upper limit, and (2) map selected data bits of the encoded data word within a part of the first section and the second section, and remove at least a portion of the selected data bits within the part of the first section when the control channel is more than a lower limit.

In another aspect, the present invention provides an apparatus (e.g. , a processor) for use with user equipment including a message controller configured to identify a first section of a subframe as a control channel and a complementary second section of the subframe as a data channel for an encoded data word. The apparatus also includes a message interpreter configured to select one of: (1) identify selected data bits of the encoded data word within the second section and repeated ones of the selected data bits within a part of the first section for decoding when the control channel is less than an upper limit, and (2) identify selected data bits of the encoded data word within the second section for decoding when the control channel is more than a lower limit.

The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features, advantages and technical effects of the invention will be described hereinafter, which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:

FIGURES 1 and 2 illustrate system level diagrams of embodiments of communication systems including a base station and wireless communication devices that provide an

environment for application of the principles of the present invention;

FIGURES 3 and 4 illustrate system level diagrams of embodiments of communication systems including a wireless communication systems that provide an environment for application of the principles of the present invention;

FIGURE 5, illustrated is a graphical representation demonstrating communication channel performance related to the present invention;

FIGURE 6 illustrates a system level diagram of an embodiment of a communication element of a communication system constructed in accordance with the principles of the present invention; and

FIGURES 7 to 9 illustrate block diagrams of embodiments of subframes demonstrating exemplary methods of operating a communication system according to the principles of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments are discussed in detail below. It should be appreciated, however, that the present invention provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention. In view of the foregoing, the present invention will be described with respect to exemplary embodiments in a specific context of an apparatus, system and method for rate matching data in a downlink to enable user equipment to decode a data channel such as a PDSCH despite decoding errors in a control channel such as a PCFICH in a communication system. Although systems and methods described herein are described with reference to a 3 GPP LTE cellular network, they can be applied to any communication system including a Global System for Mobile Communications ("GSM") system.

Turning now to FIGURE 1 , illustrated is a system level diagram of an embodiment of a communication system including a base station 115 and wireless communication devices (e.g., user equipment) 135, 140, 145 that provides an environment for application of the principles of the present invention. The base station 115 is coupled to a public switched telephone network or a packet switched network (not shown). The base station 115 is configured with a plurality of antennas to transmit and receive signals in a plurality of sectors including a first sector 120, a second sector 125, and a third sector 130, each of which typically spans 120 degrees. Although FIGURE 1 illustrates one wireless communication device (e.g., wireless communication device 140) in each sector (e.g., the first sector 120), a sector (e.g., the first sector 120) may generally contain a plurality of wireless communication devices. In an alternative embodiment, a base station 115 may be formed with only one sector (e.g., the first sector 120), and multiple base stations may be constructed to transmit according to collaborative/cooperative multiple-input multiple-output ("C-MIMO") operation, etc. The sectors (e.g., the first sector 120) are formed by focusing and phasing radiated signals from the base station antennas, and separate antennas may be employed per sector (e.g., the first sector 120). The plurality of sectors 120, 125, 130 increases the number of subscriber stations (e.g., the wireless communication devices 135, 140, 145) that can simultaneously communicate with the base station 115 without the need to increase the utilized bandwidth by reduction of interference that results from focusing and phasing base station antennas. Turning now to FIGURE 2, illustrated is a system level diagram of an embodiment of a communication system including a base station and wireless communication devices that provides an environment for application of the principles of the present invention. The communication system includes a base station 210 coupled by communication path or link 220 (e.g., by a fiber-optic communication path) to a core telecommunications network such as public switched telephone network ("PSTN") 230 (or a packet switched network). The base station 210 is coupled by wireless communication paths or links 240, 250 to wireless communication devices 260, 270, respectively, that lie within its cellular area 290.

In operation of the communication system illustrated in FIGURE 2, the base station 210 communicates with each wireless communication device 260, 270 through control and data communication resources allocated by the base station 210 over the communication paths 240, 250, respectively. The control and data communication resources may include frequency and time-slot communication resources in frequency division duplex ("FDD") and/or time division duplex ("TDD") communication modes. Turning now to FIGURE 3, illustrated is a system level diagram of an embodiment of a communication system including a wireless communication system that provides an environment for the application of the principles of the present invention. The wireless communication system may be configured to provide evolved UMTS terrestrial radio access network ("E- UTRAN") universal mobile telecommunications services. A mobile management entity/system architecture evolution gateway ("MME/SAE GW," one of which is designated 310) provides control functionality for an E-UTRAN node B (designated "eNB," an "evolved node B," also referred to as a "base station," one of which is designated 320) via an S I communication link (ones of which are designated "S I link"). The base stations 320 communicate via X2

communication links (designated "X2 link"). The various communication links are typically fiber, microwave, or other high-frequency metallic communication paths such as coaxial links, or combinations thereof.

The base stations 320 communicate with user equipment ("UE," ones of which are designated 330), which is typically a mobile transceiver carried by a user. Thus, communication links (designated "Uu" communication links, ones of which are designated "Uu link") coupling the base stations 320 to the user equipment 330 are air links employing a wireless

communication signal such as, for example, an orthogonal frequency division multiplex

("OFDM") signal (e.g., formed from OFDM symbols). Turning now to FIGURE 4, illustrated is a system level diagram of an embodiment of a communication system including a wireless communication system that provides an environment for the application of the principles of the present invention. The wireless communication system provides an E-UTRAN architecture including base stations (one of which is designated 410) providing E-UTRAN user plane (payload data, packet data convergence protocol/radio link control/media access control/physical sublayers) and control plane (radio resource control sublayer) protocol terminations towards user equipment (one of which is designated 420). The base stations 410 are interconnected with X2 interfaces or communication links (designated "X2"). The base stations 410 are also connected by SI interfaces or communication links (designated "SI") to an evolved packet core ("EPC") including a mobile management entity/system architecture evolution gateway ("MME/SAE GW," one of which is designated 430). The SI interface supports a multiple entity relationship between the mobile management entity/system architecture evolution gateway 430 and the base stations 410. For applications supporting inter-public land mobile handover, inter-eNB active mode mobility is supported by the mobile management entity/system architecture evolution gateway 430 relocation via the SI interface.

The base stations 410 may host functions such as radio resource management. For instance, the base stations 410 may perform functions such as internet protocol ("IP") header compression and encryption of user signal streams, ciphering of user signal streams, radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to user equipment in both the uplink and the downlink, selection of a mobility management entity at the user equipment attachment, routing of user plane (also referred to as "U-plane") data towards the user plane entity, scheduling and transmission of paging messages (originated from the mobility management entity), scheduling and transmission of broadcast information

(originated from the mobility management entity or operations and maintenance), and measurement and reporting configuration for mobility and scheduling. The mobile management entity/system architecture evolution gateway 430 may host functions such as distribution of paging messages to the base stations 410, security control, termination of user plane packets for paging reasons, switching of user plane for support of the user equipment mobility, idle state mobility control, and system architecture evolution bearer control. The user equipment 420 receives an allocation of a group of information blocks from the base stations 410.

According to 3GPP TS 36.211, entitled "Evolved Universal Terrestrial Radio Access (E- UTRA); Physical Channels and Modulation," V8.7.0, June 2009, which is incorporated herein by reference, the allocation of the control channel in each subframe can vary dynamically. For example, the control channel may be allocated within a first section of a subframe in three OFDM symbols for bandwidths greater than 1.4 MHz and four OFDM symbols for a bandwidth of 1.4 MHz. The allocation of the control channel is given by the control format indicator ("CFI") value transmitted on the PCFICH in each subframe. Then the data channel is mapped to a complementary second section of the subframe next to the control channel. For example. 13, 12 or 11 out of 14 OFDM symbols may be used for the PDSCH in the case of a subframe employing a normal cyclic prefix ("CP"). In other words, the starting position and the rate matching operation of the data channel such as the PDSCH depend on the allocation of the control channel within the first section of the subframe.

As an example, if the user equipment correctly receives the PCFICH on a component carrier, the user equipment knows the allocation of the PDCCH on the component carrier. The user equipment could then decode the PDCCH on the component carrier and find an allocation for the user equipment identifier ("UE ID," e.g., its cell radio network temporary identifier ("C- PvNTI")). The component carrier indicator in the correctly decoded PDCCH indicates that the payload data allocation is on another component carrier in the component carrier aggregation. The user equipment, however, may then incorrectly decode the PCFICH on the other component carrier and thus obtain a wrong allocation of the PDCCH on the other component carrier. The user equipment would then attempt to decode the assigned PDSCH on the other component carrier with a wrong assumption on the starting position of the PDSCH. As a result, the user equipment would fail to decode the PDSCH, and would store corrupted PDSCH bits in its soft buffer. Hybrid automatic retransmission request ("HARQ") retransmissions of this packet are likely to fail as well due to soft buffer corruption, and a higher layer automatic retransmission request ("ARQ") might be necessary. Thus, a communication delay would incur, and resources would be necessary on a higher layer to enable communications, resulting in inefficient utilization of scarce communication resources.

Turning now to FIGURE 5, illustrated is a graphical representation demonstrating communication channel performance related to the present invention. More specifically, the graphical representation demonstrates PCFICH performance in an LTE employing a bandwidth of 1.4 MHz, with bit error rate ("BER") on the vertical axis and signal-to-interference noise ratio ("SINR") in decibels ("dB") on the horizontal axis. The graphical representation illustrates two receive ("RX") channels (an estimated receive channel 510 and an ideal receive channel 520), and 2x2 {i.e., two transmit and two receive antennas) space frequency block coding ("SFBC") channels (an estimated 2x2 SFBC channel 530 and an ideal 2x2 SFBC channel 540). It can be seen from FIGURE 5 that in cell-edge conditions, the bit error rate is in, for instance, the range of 1.5% to 4.5% (with realistic channel estimation), which is unacceptably high. Similar graphs can be constructed for higher bandwidths. It should be noted that in 3GPP Rel-8, a similar soft buffer corruption can occur in the case of false positive PDCCH detection (when the PDCCH is correctly decoded but no PDSCH transmission is received). The false positive detection has a much lower probability (e.g., 1.5 x 10^"5) than the PCFICH bit error rates shown in FIGURE 5.

In case of dynamic scheduling of a 3GPP Rel-8 PDSCH, correct decoding of the PDCCH is conditioned on correct decoding of the PCFICH. Therefore, the user equipment that attempts to decode the PDSCH typically have a correct value of the allocation of the PDCCH. Another case wherein soft buffer corruption can occur in Rel-8 is the following sequence of events in the downlink ("DL") scheduling, namely, a HARQ [NACK-to-ACK (i.e., negative

acknowledgment-to-positive acknowledgment) misdetection at the base station], a PDCCH error at the user equipment, and a DTX-to-ACK (i.e., discontinuous transmission-to-positive acknowledgment) misdetection at the base station, which is also very unlikely and less probable than the PCFICH errors. It should also be noted that a use case for cross-component carrier scheduling includes heterogeneous networks in which severe interference conditions are expected, further degrading PCFICH performance.

Several solutions have been proposed for the error situations described above. One solution is to include the control format indicator (i.e., the two bits indicating the control channel allocation) of the other component carrier in the PDCCH of the component carrier. However, this requires a greater number of transmitted bits by the base station, which is an expensive resource resulting in reduced cellular area coverage. Another solution is to assume that the allocation of the PDCCH on the other component carrier is the same as the one detected on the component carrier. However, component carriers are generally not coordinated in the control channel length or other aspects, which results in mismatching issues. A third solution is to change the PDSCH-to-RE mapping so that it starts outside of the maximum possible region for the PDCCH and continues in a reverse order within the OFDM symbols not allocated to the PDCCH. This solution is not operable in certain conditions, such as when multiple code blocks are required for payload data greater than around six kilobits and this solution would incur additional processing delay at the user equipment.

Based on the description above of control channel operation baselined in 3GPP LTE Rel-

8, an apparatus, system and method is introduced herein to alleviate decoding errors in a communication system. The apparatus, system and method enable data channel transmission and rate matching for component carrier aggregation with cross component carrier scheduling or for semi-persistent scheduling.

When the PDCCH on the present component carrier indicates a PDSCH allocation on another component carrier, the PDSCH is rate matched (i.e., the number of bits of an encoded data word is adjusted), assuming that OFDM symbols for the data channel (i.e., the PDSCH) are available outside of the region of the PDCCH. Stated another way, a circular buffer for the data channel (i.e., the PDSCH) is constructed assuming that OFDM symbols for the data channel are available outside of the region of the PDCCH. When the PDCCH allocation is smaller than a maximum or upper limit thereof, a subset of the rate-matched bits is repeated within the available region for the PDCCH so that the location of the repeated PDSCH bits does not depend on the actual PDCCH allocation.

The invariant PDSCH repetition in a region allocated to the control channel may be achieved in the following way: Ones of selected bits of an encoded data word allocated to the data channel (i.e., PDSCH) are repeated in a region that can be occupied by the control channel (i.e., PDCCH) assuming an allocation for the control channel is less than the upper limit therefor. As the allocation for the PDCCH is extended from the minimum (or lower limit) to an upper limit, then the ones of the selected bits corresponding to the encoded data word located in the region for the PDCCH are removed or punctured, and the selected bits from the encoded data word not occupied by the PDCCH are transmitted (i.e., the selected bits allocated to the data channel). The upper limit of the control channel region is defined as the first 3 OFDM symbols of a subframe for bandwidths greater than 1.4 MHz, and as the first 4 OFDM symbols of a subframe for a bandwidth of 1.4 MHz. Recall that puncturing bits only removes redundant information from the encoded data word, allowing the data word to be decoded at the receiver (e.g., of user equipment) under reasonable channel signal-to-interference noise ratio conditions. In the case of multiple code block transmission, the data bits that are repeated in the region for the PDCCH can correspond to a part of a first code block or alternatively can be constructed from parts of all code blocks then interlaced and mapped in a normal or reverse order. Also, a proposed rate matching/mapping modification is triggered based on the value of at least one of the coding rate, transport block size ("TBS"), number of code blocks, modulation and coding scheme ("MCS") signal-to-noise ratio ("SNR") and channel quality indication ("CQI"). For example, when the coding rate or transport block size are above a threshold the proposed rate matching modification may not by used by the user equipment and base station. Turning now to FIGURE 6, illustrated is a system level diagram of an embodiment of a communication element 610 of a communication system constructed in accordance with the principles of the present invention. The communication element or device 610 may represent, without limitation, a base station, user equipment (e.g., a subscriber station, a terminal, a mobile station, a wireless communication device), a network control element, a local area support node, or the like. The communication element 610 includes, at least, a processor 620 and memory 650 that stores programs and data of a temporary or more permanent nature. The communication element 610 may also include a radio frequency transceiver 670 coupled to the processor 620 and a plurality of antennas (one of which is designated 660). The communication element 610 may provide point-to-point and/or point-to-multipoint communication services.

The communication element 610, such as a base station in a cellular network, may be coupled to a communication network element, such as a network control element 680 coupled to a public switched telecommunication network 690 ("PSTN" or a packet switched network). The network control element 680 may, in turn, be formed with a processor, memory, and other electronic elements (not shown). The network control element 680 generally provides access to a telecommunication network such as a PSTN (or a packet switched network). Access may be provided using fiber optic, coaxial, twisted pair, microwave communication, or similar link coupled to an appropriate link-terminating element. A communication element 610 formed as user equipment is generally a self-contained device intended to be carried by an end user.

The processor 620 in the communication element 610, which may be implemented with one or a plurality of processing devices, performs functions associated with its operation including, without limitation, encoding and decoding (encoder/decoder 623) of individual bits forming a communication message, formatting of information, and overall control (controller 625) of the communication element, including processes related to management of resources represented by resource manager 628. Exemplary functions related to management of resources include, without limitation, hardware installation, traffic management, performance data analysis, tracking of end users and equipment, configuration management, end user

administration, management of user equipment, management of tariffs, subscriptions, and billing, accumulation and management of characteristics of a local area network, and the like. When the communication element 610 is formed as user equipment, the resource manager 628 includes a message controller 631 configured to identify a first section of a subframe as a control channel (e.g. , a PDCCH) and a complementary second section of the subframe as a data channel (e.g., PDSCH) for an encoded data word. The resource manager 628 also includes a message interpreter 932 configured to select one of: (1) identify selected data bits of the encoded data word within the second section and repeated ones of the selected data bits within a part of the first section for decoding when the control channel is less than an upper limit, and (2) identify selected data bits of the encoded data word within the second section for decoding when the control channel is more than a lower limit. The encoder/decoder 623 may then decode the selected data bits (and/or the repeated ones of the selected data bits) to enable the user equipment to decode the encoded data word. Also, the first and second sections of the sub frame include OFDM symbols.

When the communication element 610 is formed as a base station associated with an LTE cellular network or the like, the resource manager 628 includes a message controller 631 configured to allocate a first section of a subframe to a control channel (e.g., a PDCCH) and a complementary second section of the subframe to a data channel (e.g., PDSCH) for an encoded data word. The resource manager 628 also includes a message formatter 633 configured to select one of: (1) map selected data bits of the encoded data word within the second section and repeat ones of the selected data bits within a part of the first section when the control channel is less than an upper limit, and (2) map selected data bits of the encoded data word within a part of the first section and the second section, and remove at least a portion of the selected data bits within the part of the first section when the control channel is more than a lower limit. While the allocation of the resources to the first section may be limited, the message controller 631 in conjunction with the message formatter 633 may move the boundary within the subframe to accommodate the control channel and the data channel. Also, the message formatter 633 is configured to puncture the encoded data word to map the selected data bits thereof within the second section when the control channel is less than the upper limit. As another example, when the selected data bits of the encoded data word include systematic bits and parity bits, the message formatter 633 is configured to remove ones of the systematic bits and the parity bits within the part of the first section when the control channel is more than a lower limit. Also, the first and second sections of the subframe include OFDM symbols.

The execution of all or portions of particular functions or processes related to

management of resources may be performed in equipment separate from and/or coupled to the communication element 610, with the results of such functions or processes communicated for execution to the communication element 610. The processor 620 of the communication element 610 may be of any type suitable to the local application environment, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors ("DSPs"), and processors based on a multi-core processor architecture, as non- limiting examples.

The transceiver 670 of the communication element 610 modulates information onto a carrier waveform for transmission by the communication element 610 via the antenna 660 to another communication element. The transceiver 670 demodulates information received via the antenna 660 for further processing by other communication elements. The transceiver 670 is capable of supporting duplex operation for the communication element 610.

The memory 650 of the communication element 610, as introduced above, may be of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and removable memory. The programs stored in the memory 650 may include program instructions that, when executed by an associated processor, enable the communication element 610 to perform tasks as described herein. Of course, the memory 650 may form a data buffer for data (e.g., payload data) transmitted to and from the communication element 610. Exemplary embodiments of the system, subsystems, and modules as described herein may be implemented, at least in part, by computer software executable by processors of, for instance, the user equipment and the local area support node, or by hardware, or by combinations thereof. As will become more apparent, systems, subsystems and modules may be embodied in the

communication element 610 as illustrated and described herein.

Turning now to FIGURES 7 to 9, illustrated are block diagrams of embodiments of subframes demonstrating exemplary methods of operating a communication system according to the principles of the present invention. Beginning with FIGURE 7, illustrated are three representative subframes 705, 730, 760 including OFDM symbols employable with a bandwidth greater than 1.4 MHz. For simplicity, the resource elements occupied by reference signals (e.g. , pilot signals) are not illustrated herein. Each subframe is formed of OFDM symbols in the horizontal direction with resource elements (one of which is designated "RE") spanning subcarriers in the vertical direction. An exemplary resource block includes 12 OFDM subcarriers. The exemplary subframes illustrated in FIGURE 7 span 14 OFDM symbols to produce subframes each spanning one milliseconds ("ms"). The OFDM symbols allocated to a control channel (e.g., PDCCH) are dynamically allocated according to traffic and coverage needs, and also the limit of the number of OFDM symbols allocatable to the control channel. The first subframe 705 has a control format indicator of one and includes a first section formed by OFDM symbol 1 (generally designated 710) allocated to the control channel. The complementary second section of the first subframe 705 (consistent with the OFDM symbols 2 to 14) is allocated to a data channel (e.g., PDSCH) for an encoded data word. Also, selected data bits of the encoded data word (or words in case of multiple codeword transmission) are rate matched to the OFDM symbols 4 to 14 within the data channel of the first subframe 705.

Repeated ones of the selected data bits are allocated to OFDM symbol 3 and/or OFDM symbols 2 and 3 (for bandwidths greater than 1.4) and to OFDM symbol 4 and/or OFDM symbols 2 and 3 (for the bandwidths of 1.4 MHz), which alternatively can be allocated to the control channel. While the upper limit for the control channel is demonstrated as three OFDM symbols, the upper limit for the control channel may be more OFDM symbols (e.g. , 4 OFDM symbols) or less OFDM symbols depending on the bandwidth.

The second subframe 730 has a control format indicator of two and includes a first section formed by OFDM symbols 1 and 2 (generally designated 735) allocated to the control channel. The complementary second section of the second subframe 730 (consistent with

OFDM symbols 3 to 14) is allocated to a data channel (e.g., PDSCH) for an encoded data word. Also, selected data bits of the encoded data word (or words in case of multiple codeword transmission) are rate matched to the OFDM symbols 4 to 14 within the data channel of the second subframe 730. Repeated ones of the selected data bits are allocated to OFDM symbol 3 (for bandwidths greater than 1.4) and to OFDM symbol 4 and/or OFDM symbol 3 (for the bandwidths of 1.4 MHz), which alternatively can be allocated to the control channel. While the upper limit for the control channel is demonstrated as three OFDM symbols, the upper limit for the control channel may be more OFDM symbols (e.g., 4 OFDM symbols) or less OFDM symbols depending on the bandwidth. The third subframe 760 has a control format indicator of three and includes a first section formed by OFDM symbols 1 to 3 (generally designated 765) allocated to the control channel. The complementary second section of the third subframe 760 (consistent with the OFDM symbols 4 to 14) is allocated to a data channel (e.g., PDSCH) for an encoded data word. Also, selected data bits of the encoded word (or words in case of multiple codeword transmission) are rate matched to the OFDM symbols 4 to 14 of the third subframe 760. As the length of the third subframe 760 is fixed and the allocation to the control channel is at a maximum or upper limit of three OFDM symbols representing a bandwidth greater than 1.4 MHz (or four OFDM symbols representing a bandwidth of 1.4 MHz), the data channel does not include any repeated data bits beyond the rate matched section of the data channel. Thus, selected data bits of the encoded data word are allocated to OFDM symbols 4 to 14 of the data channel. While the upper limit for the control channel is demonstrated as three OFDM symbols, the upper limit for the control channel may be more OFDM symbols (e.g. , 4 OFDM symbols) or less OFDM symbols depending on the bandwidth.

To maintain a fixed length of a subframe, a complementary second section of the subframe is dynamically allocated to the data channel. Accordingly, selected data bits of the encoded data word are rate matched to the data channel. For reliable decoding, it is necessary that the user equipment receiving the subframe knows the allocation of the subframe to the data channel. If only one OFDM symbol is allocated to the control channel, as illustrated by the first subframe 705, then the selected data bits assigned to the dynamically allocated OFDM symbols of the PDSCH must be rate matched to this resource allocation. Additionally, repeated ones of the selected data bits are allocated to OFDM symbols 2 and 3. If two OFDM symbols are allocated to the control channel, as illustrated by the second subframe 730, then repeated ones of the selected data bits are allocated to the OFDM symbol 3. Similarly, if three OFDM symbols corresponding are allocated to the control channel, as illustrated by the third subframe 760, there is no repetition. As introduced herein, the selected data bits of the encoded data word are allocated to the data channel to enable the user equipment to decode the data word even if the user equipment is unable to accurately determine the allocation to the control channel. If the user equipment is able to make an accurate determination of allocation to the control channel or in even in some error cases, the redundantly transmitted data bits in variably allocated data channel can be advantageously employed by the user equipment to improve decoding reliability.

Turning now to FIGURE 8, illustrated are three representative subframes 805, 830, 860 including OFDM symbols employable with a bandwidth greater than 1.4 MHz. For simplicity, the resource elements occupied by reference signals (e.g., pilot signals) are not illustrated herein. In this embodiment, the rate matching operation begins with an assumption that the available section for the control channel (e.g., PDCCH) corresponds to the minimum or lower limit allocation. For an explanation of similar features of the subframes of FIGURE 8 to the subframes of FIGURE 7, see the description above. The first subframe 805 has a control format indicator of three and includes a first section formed by OFDM symbols 1 to 3 (generally designated 810) allocated to the control channel. The second subframe 830 has a control format indicator of two and includes a first section formed by OFDM symbols 2 and 3 (generally designated 835) allocated to the control channel. The third subframe 860 has a control format indicator of one and includes a first section formed by OFDM symbol 1 (generally designated 865) allocated to the control channel. The complementary second section of the subframes 805, 830, 860 (consistent with the remaining OFDM symbols) are allocated to a data channel (e.g., PDSCH) for an encoded data word 815 (e.g., a turbo encoded data word). Accordingly, the encoded data word 815 includes systematic bits, parity bits 1 and parity bits 2.

If the control channel spans one OFDM symbol, as represented by the third subframe 860, selected data bits of the encoded data word 815 are inserted without puncturing into the data channel. If the control channel spans two OFDM symbols, as represented by the second subframe 830, selected data bits of the encoded data word 815 are inserted with puncturing into the data channel to accommodate rate matching. Thus, leading systematic bits (or alternatively other bits depending on the redundancy version) 822 of the encoded data word 815 are removed or punctured according to the bits present in the one OFDM symbol. If the control channel spans three OFDM symbols corresponding, as represented by first subframe 805, selected data bits of the encoded data word 815 are inserted with puncturing into the data channel to accommodate rate matching. Thus, leading systematic bits (or alternatively other bits depending on the redundancy version) 827 of the encoded data word 815 are removed or punctured according to the bits present in the two OFDM symbols. With respect to first and second subframes 805, 830, the data channel is populated with selected bits of the respective punctured encoded data word so that the same predictably ends at the end of the data channel, enabling a receiver (e.g., user equipment) to decode the encoded data word without knowing the length of the data channel.

Turning now to FIGURE 9, illustrated is a representative subframe 905 having a control format indicator of two and including a first section formed by OFDM symbols 1 and 2

(generally designated 910) allocated to the control channel employable with a bandwidth greater than 1.4 MHz. The complementary second section of the subframe 905 (consistent with remaining OFDM symbols 3 to 14) is allocated to a data channel (e.g., PDSCH) for an encoded data word. Also, selected data bits of the encoded word (or words in case of multiple codeword transmission) are rate matched to OFDM symbols 4 to 14 within the data channel of the subframe. Also, repeated ones of the selected data bits are allocated to OFDM symbol 3 (copied from the data bits in OFDM symbol 4) of the data channel, which alternatively can be allocated to the control channel. Again, while the upper limit for the control channel is demonstrated as three OFDM symbols, the upper limit for the control channel may be more OFDM symbols (e.g. , 4 OFDM symbols) or less OFDM symbols depending on the bandwidth. For an explanation of similar features of the subframe 905 of FIGURE 9 to the subframes of FIGURE 7, see the description above.

Implementation of the embodiments introduced herein provides minor modifications to 3GPP Rel-8 circular buffer rate matching for data channel. In one embodiment, the data channel is constructed for selected data bits of an encoded data word and a subset thereof is available for repeated ones of the selected data bits. In accordance therewith, an implementation- specific metric may be employed at the user equipment to indicate the probability of a decoded control format indicator value being correct. If the metric indicates that it is likely that a decoded control format indicator is erroneous, the user equipment can decide not to use the repeated ones of the selected bits (bits in the region that can be allocated to the control channel), but base decoding on the selected data bits outside of the control channel to reduce partial soft buffer corruption, with the cost of an increased code rate. In another embodiment, the data channel is constructed assuming a minimum control channel allocation, and selected data bits of the encoded data word are transmitted corresponding to the actual size of the control region (i.e., a subset of the selected data bits is accordingly punctured).

Thus, a data channel can be correctly decoded even though the user equipment assumes an incorrect allocation therefor within a subframe. If the user equipment assumes an incorrect allocation for the control channel, this erroneous assumption may result in a data channel decoding error and soft buffer corruption, compromising communication performance. No additional overhead is required on the control channel. There is no need for coordination of the control channel resources between cross-component carrier scheduled component carriers. Also, modifications to PDSCH-to-RE mapping are not required, resulting in no added user equipment processing delay and more robustness for high coding rates for multiple code blocks per transport block. In embodiments introduced herein, allocating the data channel without the control channel in the same subframe enables optimization of downlink ("DL") semi-persistent data channel scheduling.

Program or code segments making up the various embodiments of the present invention may be stored in a computer readable medium or transmitted by a computer data signal embodied in a carrier wave, or a signal modulated by a carrier, over a transmission medium. The "computer readable medium" may include any medium that can store or transfer information. Examples of the computer readable medium include an electronic circuit, a semiconductor memory device, a read only memory ("ROM"), a flash memory, an erasable ROM ("EROM"), a floppy diskette, a compact disk ("CD")-ROM, an optical disk, a hard disk, a fiber optic medium, a radio frequency ("RF") link, and the like. The computer data signal may include any signal that can propagate over a transmission medium such as electronic communication network channels, optical fibers, air, electromagnetic links, RF links, and the like. The code segments may be downloaded via computer networks such as the Internet, Intranet, and the like.

As described above, the exemplary embodiment provides both a method and

corresponding apparatus consisting of various modules providing functionality for performing the steps of the method. The modules may be implemented as hardware (embodied in one or more chips including an integrated circuit such as an application specific integrated circuit), or may be implemented as software or firmware for execution by a computer processor. In particular, in the case of firmware or software, the exemplary embodiment can be provided as a computer program product including a computer readable storage structure embodying computer program code (i.e., software or firmware) thereon for execution by the computer processor.

Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the features and functions discussed above can be implemented in software, hardware, or firmware, or a combination thereof. Also, many of the features, functions and steps of operating the same may be reordered, omitted, added, etc., and still fall within the broad scope of the present invention.

Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims

WHAT IS CLAIMED IS:

1. An apparatus, comprising:

a message controller configured to allocate a first section of a subframe to a control channel and a complementary second section of said subframe to a data channel for an encoded data word; and

a message formatter configured to select one of:

map selected data bits of said encoded data word within said second section and repeat ones of said selected data bits within a part of said first section when said control channel is less than an upper limit, and

map selected data bits of said encoded data word within a part of said first section and said second section, and remove at least a portion of said selected data bits within said part of said first section when said control channel is more than a lower limit.

2. The apparatus as recited in Claim 1 wherein said message formatter is configured to puncture said encoded data word to map said selected data bits thereof within said second section when said control channel is less than said upper limit.

3. The apparatus as recited in Claim 1 wherein said selected data bits of said encoded data word comprise systematic bits and parity bits and said message formatter is configured to remove ones of said systematic bits and said parity bits within said part of said first section when said control channel is more than a lower limit.

4. The apparatus as recited in Claim 1 wherein said control channel is a physical downlink control channel (PDCCH).

5. The apparatus as recited in Claim 1 wherein said data channel is a physical downlink shared channel (PDSCH).

6. The apparatus as recited in Claim 1 wherein said first and second sections of said subframe comprise orthogonal frequency division multiplexed (OFDM) symbols.

7. An apparatus, comprising:

means for allocating a first section of a subframe to a control channel and a

complementary second section of said subframe to a data channel for an encoded data word; and means for selecting one of: mapping selected data bits of said encoded data word within said second section and repeat ones of said selected data bits within a part of said first section when said control channel is less than an upper limit, and

mapping selected data bits of said encoded data word within a part of said first section and said second section, and removing at least a portion of said selected data bits within said part of said first section when said control channel is more than a lower limit.

8. The apparatus as recited in Claim 7 wherein said means for selecting one of punctures said encoded data word to map said selected data bits thereof within said second section when said control channel is less than said upper limit.

9. A computer program product comprising a program code stored in a computer readable medium configured to:

allocate a first section of a subframe to a control channel and a complementary second section of said subframe to a data channel for an encoded data word; and

select one of:

10. The computer program product as recited in Claim 9 wherein said program code stored in said computer readable medium is configured to puncture said encoded data word to map said selected data bits thereof within said second section when said control channel is less than said upper limit.

11. A method, comprising:

allocating a first section of a subframe to a control channel and a complementary second section of said subframe to a data channel for an encoded data word; and

selecting one of:

mapping selected data bits of said encoded data word within said second section and repeat ones of said selected data bits within a part of said first section when said control channel is less than an upper limit, and mapping selected data bits of said encoded data word within a part of said first section and said second section, and removing at least a portion of said selected data bits within said part of said first section when said control channel is more than a lower limit.

12. The method as recited in Claim 11 wherein said selecting comprises puncturing said encoded data word to map said selected data bits thereof within said second section when said control channel is less than said upper limit.

13. The method as recited in Claim 11 wherein said selected data bits of said encoded data word comprise systematic bits and parity bits and said method further comprises removing ones of said systematic bits and said parity bits within said part of said first section when said control channel is more than a lower limit.

14. The method as recited in Claim 11 wherein said control channel is a physical downlink control channel (PDCCH) and said data channel is a physical downlink shared channel (PDSCH).

15. The method as recited in Claim 11 wherein said first and second sections of said subframe comprise orthogonal frequency division multiplexed (OFDM) symbols.

16. An apparatus, comprising:

a message controller configured to identify a first section of a subframe as a control channel and a complementary second section of said subframe as a data channel for an encoded data word; and

a message interpreter configured to select one of:

identify selected data bits of said encoded data word within said second section and repeated ones of said selected data bits within a part of said first section for decoding when said control channel is less than an upper limit, and

identify selected data bits of said encoded data word within said second section for decoding when said control channel is more than a lower limit.

17. The apparatus as recited in Claim 16 wherein said selected data bits comprise ones of systematic bits and parity bits of said encoded data word.

18. The apparatus as recited in Claim 16 further comprising an encoder/decoder configured to decode said selected data bits of said encoded data word.

19. The apparatus as recited in Claim 16 wherein said control channel is a physical downlink control channel (PDCCH).

20. The apparatus as recited in Claim 16 wherein said data channel is a physical downlink shared channel (PDSCH).

21. The apparatus as recited in Claim 16 wherein said first and second sections of said subframe comprise orthogonal frequency division multiplexed (OFDM) symbols.

22. An apparatus, comprising:

means for identifying a first section of a subframe as a control channel and a

complementary second section of said subframe as a data channel for an encoded data word; and means for selecting one of:

identifying selected data bits of said encoded data word within said second section and repeated ones of said selected data bits within a part of said first section for decoding when said control channel is less than an upper limit, and

identifying selected data bits of said encoded data word within said second section for decoding when said control channel is more than a lower limit.

23. The apparatus as recited in Claim 22 wherein said selected data bits comprise ones of systematic bits and parity bits of said encoded data word.

24. A computer program product comprising a program code stored in a computer readable medium configured to:

identify a first section of a subframe as a control channel and a complementary second section of said subframe as a data channel for an encoded data word; and

select one of:

25. The computer program product as recited in Claim 24 wherein said selected data bits comprise ones of systematic bits and parity bits of said encoded data word.

26. A method, comprising:

identifying a first section of a subframe as a control channel and a complementary second section of said subframe as a data channel for an encoded data word; and

selecting one of:

27. The method as recited in Claim 26 wherein said selected data bits comprise ones of systematic bits and parity bits of said encoded data word.

28. The method as recited in Claim 26 further comprising decoding said selected data bits of said encoded data word.

29. The method as recited in Claim 26 wherein said control channel is a physical downlink control channel (PDCCH) and said data channel is a physical downlink shared channel (PDSCH).

30. The method as recited in Claim 26 wherein said first and second sections of said subframe comprise orthogonal frequency division multiplexed (OFDM) symbols.