Patent Publication Number: US-11652677-B2

Title: Control channel architecture with control information distributed over multiple subframes on different carriers

Description:
RELATED APPLICATIONS 
     The present application is a continuation of and claims priority to U.S. application Ser. No. 16/528,294, entitled “CONTROL CHANNEL ARCHITECTURE WITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES ON DIFFERENT CARRIERS” and filed on Jul. 31, 2019; which is a continuation of and claims priority to U.S. application Ser. No. 13/703,871, entitled “CONTROL CHANNEL ARCHITECTURE WITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES ON DIFFERENT CARRIERS” and filed on Dec. 12, 2012; which is a national stage application of PCT/US2010/039175, entitled “CONTROL CHANNEL ARCHITECTURE WITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES ON DIFFERENT CARRIERS” and filed on Jun. 18, 2010; which is related to International Patent Application Serial Number PCT/US2010/039185 entitled “CONTROL CHANNEL ARCHITECTURE WITH CONTROL INFORMATION DISTRIBUTED OVER MULTIPLE SUBFRAMES” and filed Jun. 18, 2010; all of which are assigned to the assignee hereof and hereby expressly incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     The invention relates in general to wireless communication systems and more specifically to control signals in a wireless communication system. 
     Base stations in cellular communication systems provide communications services to wireless communication devices within geographical cells where each base station exchanges signals with wireless communication devices within an associated cell. The size and shape of each cell and, therefore, the coverage area of the base station are determined by several factors and are at least partially based on design parameters of the base station. In addition to large macro cells that provide services to numerous devices within relatively large geographical areas, some cellular communication systems are increasingly employing smaller cells to increase efficiency, improve coverage, improve the quality of service, and provide additional services. The smaller cells may include a variety of sizes typically referred to as microcells, picocells and femtocells. Microcells and picocells are often implemented within office buildings, shopping centers and urban areas in order to provide additional security, higher user capacity for the area, additional service features, and/or improved quality of service. Femtocells have relatively smaller geographical areas and are typically implemented at residences or small office locations. Since typical cellular backhaul resources may not be available in these locations, femtocells are sometimes connected to the cellular infrastructure through DSL or cable modems. Femtocells are part of the cellular network and, therefore, communicate with the wireless devices using the same techniques as those used by macrocells. In addition to data information, control signals are exchanged between the base stations and mobile communication devices. In some circumstances, control information is transmitted within a downlink control channel from a base station to a mobile communication where the control information indicates how data communication can be received such as information on demodulation, decoding, etc. Communication resources may be divided into frames including subframes. In conventional systems, control information regarding the reception of data in a subframe is transmitted in the same subframe as the data. 
     SUMMARY 
     Control information related to the reception of data within a subframe is transmitted over multiple subframes over multiple carriers from communication system infrastructure. A controller in a mobile wireless communication device reconstructs the control information received over multiple subframes based on at least some control information in a first physical control channel in a first subframe transmitted over a first carrier and at least some other control information in a second physical control channel in a second subframe transmitted over a second carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is a block diagram of a communication system in accordance with an exemplary embodiment of the invention. 
         FIG.  1 B  is a block diagram of the communication system where the first frame and the second frame are transmitted from a single base station. 
         FIG.  1 C  is a block diagram of the communication system where the first frame is transmitted from a first base station and the second frame is transmitted from a second base station. 
         FIG.  2    is a graphical illustration of the first frame and the second frame with a plurality of resource elements. 
         FIG.  3    is an illustration of a sub-frame in accordance with a 3GPP Long Term Evolution (LTE) communication specification. 
         FIG.  4    is a flow chart of a method performed at the communication system infrastructure. 
         FIG.  5    is a flow chart of a method performed at a mobile wireless communication device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1 A  is a block diagram of a communication system  100  in accordance with an exemplary embodiment of the invention. The communication system  100  may be implemented in accordance with any of numerous technologies and communication standards. For the examples discussed below, the system  100  operates in accordance with an orthogonal frequency division multiplex (OFDM) standard. The various functions and operations of the blocks described with reference to the communication system  100  may be implemented in any number of devices, circuits, and/or elements as well as with various forms of executable code such as software and firmware. Further, the reference to “first” and “second” components is made for identification purposes and does not necessarily indicate any relative timing information. For example, a second signal may be transmitted before, after, or at the same time as a first signal. 
     The system  100  includes communication system infrastructure  102  and at least one wireless communication device  104 . The communication system infrastructure  102  includes at least one base station but may include several base stations and controllers connected through a backhaul. In most circumstances, several base stations are connected to a network controller through network infrastructure to provide wireless communication services to multiple wireless communication devices. 
     One or more wireless transceivers in the communication system infrastructure  102  exchange wireless signals  106  over at least two frequency carriers  107 ,  108  with a wireless transceiver  110  in the wireless communication device  104 . Accordingly, the communication system infrastructure  102  includes one or more transmitters for transmitting wireless signals to the wireless communication device  104  which includes a receiver for receiving the signals. Transmissions from the communication system infrastructure  102  and from the wireless communication device  104  are governed by a communication specification that defines communication signaling, protocols, and parameters of the transmission. The communication specification may provide strict specifications for communication and may also provide general requirements where specific implementations may vary while still adhering to the communication specification. Although the discussion below is directed to the 3GPP Long Term Evolution (LTE) communication specification, other communication specifications may be used in some circumstances. The communication specification defines at least a data channel and a control channel for uplink and downlink transmissions and specifies at least some timing and frequency parameters for a physical downlink control channel from base stations to wireless communication devices. The control channel includes a broadcast control channel as well as control channels scheduled to specific wireless communication devices. In an OFDM based system, a physical channel can be defined by allocating specific frequency-time resources. The granularity of these resources depends on the specification and design of the system. 
     As discussed in further detail below, the transmission of frequency-time resources, sometimes referred to as resource elements, is defined within frames  111 ,  112 . The frames  111 ,  112  are simultaneously transmitted over different frequency carriers  107 ,  108 . In  FIG.  1   , the second carrier  108  and the frame  112  are represented with an arrow and box having heavier lines than the arrow and box representing the first carrier  107  and frame  111  in order to convey that the first frame  111  is transmitted over the first carrier  107  and the second frame  112  is transmitted over the second carrier  108 . The first frame  111  transmitted over the first carrier  107  includes several subframes  113 ,  114  and the second subframe  112  includes several subframes  115 ,  116 . Each subframe  113 ,  114 ,  115 ,  116  includes a physical control channel  117 ,  118 ,  120 ,  123  and a physical data channel  119 ,  122 ,  124 ,  125 . The physical channels  117 - 125  of the two frames  111 ,  112  are different channels since the physical channels  117 - 125  of the two frames  111 ,  112  are transmitted at different frequencies. Although a particular implementation may further specify frequency, timing, and coding parameters for each base station and/or wireless communication device, conventional systems transmit control information and the related data for a wireless communication device  104  only within the same subframe. 
     In the examples discussed herein, however, the control information  126  related to data  128  in a subframe  116  is distributed over at least one other subframe  113  transmitted over a different frequency carrier  107 . In one example, at least a first portion  130  of the control information  126  is transmitted over a first physical control channel  118  of a first subframe  113  in the first frame  111  transmitted over the first carrier  107  and at least a second portion  132  of the control information  126  is transmitted over a second physical control channel  120  of a second subframe  116  of the second frame  112  transmitted over the second frequency carrier  108 , where the control information  126  facilitates reception of data  128  in the physical data channel  124  of the second subframe  116 . The transceiver  110  in the wireless communication device  104  receives the subframes  113 ,  116  and a controller  134  reconstructs the control information  126  from at least some of the control information  130  in the first subframe  113  and at least some of the control information  132  in the second subframe  116 . The control information  126  is used by the receiver of the transceiver  110  to receive the data  128  in the physical data channel  124  in the second subframe  116 . Although the example discusses distributing the control information  126  over only two subframes, the technique may also be applied to more than two subframes. In some circumstances, the control information  126  is transmitted over the physical control channels of one or more subframes other than the subframe  116  including the data to which the control information  126  corresponds. Also, the second portion  132  of the control information may not be transmitted within the same subframe  116  as the subframe used for transmitting the data  128 . For example, the control information  126  may provide information regarding the reception of data  135  in a subframe  114  other than the second subframe  116 . For the example of  FIG.  1   , the data  135  is transmitted in a physical data channel  125  in a subframe in the first frame  111  and is illustrated with a dashed line box to indicate that the transmission of this data  135  is an alternative to transmitting the data  128  in the second subcarrier  116 . Further, the first and second subframes may be transmitted simultaneously in some circumstances. Therefore, the control information is distributed over different subframes transmitted over different carriers and is received at the mobile communication device which uses the control information to receive the data. 
     As discussed herein, therefore, control information  126  is the complete control information required to be received by the wireless communication device  104  in order to receive the data  128  to which the control information  126  corresponds. Before transmission, the control information  126  may be coded, or otherwise processed, to reduce errors. Consequently, some redundancy of information may occur between subframes and/or within a subframe. In some circumstances, the wireless communication device  104  may be capable of only accurately receiving some of the control information transmitted within each subframe but is capable of reconstructing all of the control information  126  required to receive the data  128 . The control information  126  may also be scrambled before or after being separated into the multiple portions. 
     A controller  136  in the communication system infrastructure  102  separates the control information  126  into a first portion  130  and a second portion  130  and assigns the portions to two or more subframes that may be transmitted over different carriers  107 ,  108 . The separation is typically performed as a mapping of error coded control information across the subframes after the control information is error coded. The mapping results in the first portion of the control information  130  mapped to the first physical control channel  118  of the first subframe  113  and the second portion of the control information  132  mapped to the second physical control channel  120  of the second subframe  116 . The second subframe  116  also includes the data  128  within the data channel  124 . The frame  112  having the control information distributed over the subframes  114 ,  116  is transmitted to the wireless communication device  104 . Based on at least some of the received information of the two or more portions of control information  130 ,  132 , the controller  134  in the wireless communication device  104  reconstructs the control information  126 . The received and decoded control information is used to receive the data  128 . 
     As discussed herein, the control information  126  is information or data related to communication between the base station  102  and the wireless communication device  104 . The control information  126  is transmitted within control channels. Accordingly, although a control channel may be defined across multiple subframes in conventional systems, the examples herein discuss transmitting information over multiple subframes using either multiple control channels or a single control channel defined over multiple subframes. 
     Transmission of the multiple portions of the control information  126  may be from a single base station or multiple base stations. As discussed below with reference to  FIG.  1 C , for example, the first portion  132  is transmitted from a first base station over the first carrier  107  and the second portion  132  is transmitted from the second base station over a second carrier  108 . 
       FIG.  1 B  is a block diagram of the communication system  100  where the control information  126  is transmitted from a single base station  138 . The base station  138  transmits the first portion of the control information  130  in the first frame  111  over the first carrier  107  and the second portion of the control information  132  in the second frame  112  over the second carrier  108 . The transmission of the first frame  111  and the second frame  112  is synchronized. The base station  138  may include multiple transmitters or may include a single transmitter capable of transmitting multiple carriers. The controller  136  that separates the control information  126  in the portions  130 ,  132  may be a network controller or a base station controller depending on the particular implementation. A receiver  140  in the transceiver  110  of the wireless communication device  104  receives the multiple carriers  107 ,  108 . After any required demodulation, descrambling, and decoding, the portions of the control information are combined to reconstruct the control information  126 . The control information  126  is used by the receiver  140  and controller  134  to receive the data  128 . As described above, the data  128  is transmitted over the same carrier  108  and subframe  116  as the second portion  132  of the control information. In some circumstances, however, the data  128  may be transmitted over a different carrier and/or different subframe. 
       FIG.  1 C  is a block diagram of the communication system  100  where the control information  126  is transmitted from two base stations  138 ,  142 . The controller  136  that separates the control information  126  in the portions  130 ,  132  is a network controller in the example discussed with reference to  FIG.  1 C . The controller  136 , however, may be a base station controller in one of the base stations  138 ,  142  or may be distributed over multiple controllers. In such implementations, communication channels are established between the controllers and base stations to provide adequate transfer of information. The receiver  140  in the transceiver  110  of the wireless communication device  104  receives the multiple carriers  107 ,  108  from the two base stations  138 ,  142 . After any required demodulation, descrambling, and decoding, the portions of the control information are combined to reconstruct the control information  126 . The control information  126  is used by the receiver  140  and controller  134  to receive the data  128 . As described above, the data  128  is transmitted over the same carrier  108  and subframe  116  as the second portion  132  of the control information. In some circumstances, however, the data  128  may be transmitted over a different carrier and/or different subframe or may be transmitted from a third base station (not shown). 
       FIG.  2    is a block diagram of the frames  111 ,  112  in a frequency-time graph  200  showing frequency-time resource elements  201 ,  202 . The graph  200  in not necessarily drawn to scale and only provides an exemplary visual representation. Numerous other combinations of resource elements may be used to transmit the control information  126  and the data  132 . 
     The first frame  111  includes a plurality of subframes including at least a first subframe (K)  113  and a first frame second subframe (K+1)  114 . The second frame  112  includes a plurality of subframes including at least a second frame first subframe (K)  115  and a second subframe (K+1)  114 . The frequency carriers  107 ,  108  used for transmission are each divided into a plurality of subcarriers. Transmissions is also divided in time to define a plurality of times slots where the time slots are further divided into symbol times. For LTE communication specifications, each time slot includes seven symbol times. The combination of symbol times and subcarriers defines resource elements  201 ,  202  of the first frame  111  and second frame  112 , respectively. Accordingly, a symbol transmitted over a subcarrier is a resource element. Each portion of control information  130 ,  132  transmitted in a subframe is transmitted using one or more resource elements. The resource elements used for transmission of related information may or may not be contiguous. For the example of  FIG.  2   , the first portion of control information  130  is transmitted using first symbols  204  over a first subcarrier  206  and second symbols  208  over a second subcarrier  210  in the first subframe  113 . The second portion of the control information  132  is transmitted using third symbols  212  over the second subcarrier  210  and a third subcarrier  214  in the second subframe  116  of the second frame  112 . The data  128  is transmitted using fourth symbols  216  over the second subcarrier  210  in the second subframe  116 . As explained above, at least some of the control information in the first portion  130  and at least some of the control information of the second portion  132  are required to reconstruct the control information  126 . For example, the controller  134  in the wireless communication device  104  may be able to reconstruct the control information  126  from successful reception of only the information transmitted in the second subcarrier and third subcarrier. For such a situation, corruption of the first symbols  204  transmitted over the first subcarrier  206  would not hinder the wireless communication device from receiving the control information  126  and consequently accurately receiving the data  132 . 
       FIG.  3    is an illustration of a subframe  300  in accordance with a 3GPP LTE communication specification. The subframe  300  includes two slots  302 ,  304 , where each slot includes seven symbol times  306 . The symbol times 0, 1 and 2 in the first slot  302  form the physical control channel  117 ,  118 ,  120 ,  123  which is a Physical Downlink Control Channel (PDCCH)  308 . Pilot signals (or Reference Signals)  310  are injected at symbol times 0 and 4. The subframe  300  includes a broadcast channel that is a Physical Broadcast Channel (PBCH)  312  and spans portions of symbol times 3 and 4 of the first slot  302  and portions of symbol times 0 and 1 of the second slot  304 . The data channel  119 ,  122 ,  124 ,  125  is a Physical Downlink Shared Channel (PDSCH)  314  and is covered by the remainder of symbol times 3-6 of the first slot  302  and symbol times 1-6 of the second slot  304 . The sub-frame  300  also includes a primary synchronization channel (P-SCH)  316  and a secondary synchronization channel (S-SCH)  318 . 
     In an example where the control information  126  is transmitted in accordance with the 3GPP LTE communication specification, therefore, a first portion of the control information  130  is transmitted within symbol time 1 and/or symbol time 2 within the first and second subframes. As described above, the resource elements may be contiguous or noncontiguous within a subframe. The data  128  transmitted in the second subframe is transmitted over symbol times 3, 4, 5, and/or 6 of the first slot  302  and/or symbol times 1, 2, 3, 5, and/or 6 of the second slot  304 . 
       FIG.  4    is a flow chart of a method performed at the communication system infrastructure  102 . Although the method may be performed using any combination of code and/or hardware, the method is facilitated by executing code on the controller  136  in the exemplary embodiment. 
     At step  400 , the control information is separated into portions and assigned to a plurality of subframes. The separation may include processing, scrambling, coding and mapping in accordance with known techniques of downlink physical channel processing. For the example of  FIG.  4   , step  400  includes processing the control information at step  402  and mapping the control information to multiple subframes at step  404 . Mapping may include, antenna ports processing (related to MIMO/SDMA), and resource element mapping within Frequency-Time space as well as other processing. The processing and mapping results in error coding of the control information and distribution of the control information  126  over multiple subframes in subframes that are transmitted over different carriers. As discussed above, for example, a first portion  130  is mapped to a first physical control channel  118  of a first subframe  113  of the first frame  111  and a second portion  132  is mapped to a second physical control channel  120  of a second subframe  116  of a second frame, where the data  128  to which the control information  126  corresponds is within a physical data channel  124  of the second subframe  116 . The processing may also include scrambling of the control information  126  before and/or after the control information  126  is divided into portions. 
     At step  406 , the control information is transmitted over multiple subframes over multiple carriers. Based on the mapping and processing, downlink OFDM signals  107 ,  108  are generated and transmitted from the communication system infrastructure  102  to the wireless communication device  104 . As discussed above, a frame  111  is transmitted within the signal on the first carrier  107  and another frame  112  is transmitted within the signal on the second carrier  108 , where each of the two frames has a plurality of time-frequency resource elements arranged in a plurality of subframes. The subframes include at least the first subframe  113  and the second subframe  116 . Accordingly, a first portion of the control information  130  is transmitted in a physical control channel in a first subframe  113  in a first frame  111  over a first carrier  107  and a second portion of the control information  132  is transmitted in a physical control channel in a second subframe  116  in a second frame  112  over a second carrier  108 . 
     At step  408 , the data  128  is transmitted within the second subframe  116 . Since the second portion  132  and the data  128  are transmitted within the same subframe, step  406  and step  408  are performed simultaneously. In some situations, the data  128  is transmitted over third carrier and/or a third subframe. 
       FIG.  5    is a flow chart of a method performed at the wireless communication device  104 . Although the method may be performed using any combination of code and/or hardware, the method is facilitated by executing code on the controller  134  within the wireless communication device  104  in the exemplary embodiment. 
     At step  502 , the first portion of the control information  130  is received within the first subframe  113 . The receiver within the wireless communication device  110  receives the OFDM signal over the first carrier  107  where the signals includes the first frame  111 , the first subframe  113  and the first portion of the control information  130 . 
     At step  504 , the second portion of the control information  132  is received within the second subframe  116 . The receiver  140  receives OFDM signal over the second carrier  108  where the signal includes the second frame  112 , the second subframe  116  and the second portion of the control information  132 . The signal is demodulated, decoded and otherwise processed, to receive the first and second portions  130 ,  132  of the control information  126 . The first frame  111  and the second frame  112  are synchronized and are simultaneously received. 
     At step  506 , the control information  126  is reconstructed from at least some of the first portion  130  and at least some of the second portion  132 . The portions may require additional processing in some circumstances in order to reconstruct the control information. Where the control information has been error coded or scrambled across the subframes, descrambling and error decoding is applied to the received portions to retrieve the control information. As discussed above, in some circumstances, the control information  126  is retrieved with only some of the information of the first portion  130  and some information of the second portion  132 . If the control information  126  is scrambled, it is also descrambled by the receiver and/or the controller. 
     At step  508 , the data  128  is received using the control information  126 . The receiver and controller  134  apply the control information  126  to accurately decode, demodulate, and otherwise process the data  128  in the second subframe  116 . 
     Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. The above description is illustrative and not restrictive. This invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings. The scope of the invention should, therefore, be determined not with reference to the above description, but instead should be determined with reference to the appended claims along with their full scope of equivalents.