PATENT DOCUMENT

Publication Number: US-9031033-B2
Application Number: US-201113246810-A
Country: US
Kind Code: B2

Title: Wireless radio access network control channel capacity management

Abstract:
Transmission capacity for a control channel sent to multiple mobile wireless devices in a wireless network is increased by transmitting the control channel using multi user multiple input multiple output transmissions (MU MIMO). Received signal quality measured at mobile wireless devices in a radio sector are communicated to a radio node and used to determine one or more sets of mobile wireless devices to share transmission of control channel elements on the same time and frequency resource element. The radio node indicates the use of MU MIMO and the selection of precoding matrices to each of the mobile wireless devices in the each set of mobile wireless devices.

Claims:
What is claimed is: 
     
       1. A method to increase a transmission capacity for a control channel in a wireless network, the method comprising:
 at a radio node in a radio access network of the wireless network:
 estimating a received downlink signal quality for each mobile wireless device in a plurality of mobile wireless devices connected to the radio node; 
 categorizing the plurality of mobile wireless devices into a plurality of sets based on the estimated received downlink signal quality for each mobile device; 
 determining for each of the sets an available number of common control channel elements to assign for the control channel based on a number of mobile wireless devices in each set; 
 selecting a first set of mobile wireless devices in the plurality of mobile wireless devices, each selected mobile wireless device having an estimated downlink signal quality exceeding a first predetermined threshold; and 
 transmitting simultaneously to the first set of mobile wireless devices that share a first common control channel element on the control channel through a plurality of antennas using multi-user (MU) multiple-input multiple-output (MIMO) transmission. 
 
 
     
     
       2. The method as recited in  claim 1 , further comprising:
 at the radio node:
 assigning at least two mobile wireless devices in the first set of mobile wireless devices to the first common control channel element that occupies a first set of time and frequency resource elements in a transmission time interval; 
 wherein the transmission capacity of the control channel is limited by the number of control channel elements scheduled for each transmission time interval. 
 
 
     
     
       3. The method as recited in  claim 1 , further comprising:
 at the radio node:
 receiving downlink signal quality indicators from each of the plurality of mobile wireless devices; and 
 estimating the downlink signal quality to each mobile wireless device based on at least the received downlink signal quality indicator from the mobile wireless device. 
 
 
     
     
       4. The method as recited in  claim 1 , further comprising:
 at the radio node:
 assigning a unique rank one pre-coding matrix used for MU MIMO transmission on the control channel to each mobile wireless device in the first set of mobile wireless devices; and 
 notifying each mobile wireless device of the assigned rank one pre-coding matrix. 
 
 
     
     
       5. The method as recited in  claim 4 , further comprising:
 transmitting an indicator on a separate second control channel to each mobile wireless device when MU MIMO is used for transmission on the first control channel. 
 
     
     
       6. The method as recited in  claim 1 , wherein the wireless network uses a 3GPP LTE or LTE-Advanced communications protocol. 
     
     
       7. The method as recited in  claim 1 , wherein the number of mobile wireless devices in the first set of mobile wireless device depends on the estimated downlink signal quality for the mobile wireless devices in the first set of mobile wireless devices. 
     
     
       8. The method as recited in  claim 2 , further comprising:
 assigning at least two mobile wireless devices in the first set of mobile wireless devices to an second control channel element that occupies a second set of time and frequency resource elements in the transmission time interval. 
 
     
     
       9. The method as recited in  claim 8 , wherein the number of mobile wireless devices assigned to the first control channel element equals the number of mobile wireless devices assigned to the second control channel element. 
     
     
       10. The method as recited in  claim 9 , further comprising:
 at the radio node:
 selecting a second set of mobile wireless devices in the plurality of mobile wireless devices, each selected mobile wireless device having an estimated downlink signal quality that exceeds a second threshold and falls below the first threshold; 
 transmitting simultaneously to the second set of mobile wireless devices on the control channel through the plurality of antennas using MU MIMO transmission; and 
 assigning at least two mobile wireless devices in the second set of mobile wireless devices to a third control channel element that occupies a third set of time and frequency resource elements in the transmission time interval; 
 wherein the number of mobile wireless devices in the first set of mobile wireless devices assigned to the first control channel element exceeds the number of mobile wireless devices in the third set of mobile wireless devices assigned to the third control channel element. 
 
 
     
     
       11. A mobile wireless device comprising:
 a receiver configured to:
 receive and decode signals transmitted on a first control channel, wherein a transmission capacity on the first control channel is limited by a number of common control channel elements scheduled for each transmission time interval; 
 receive an indicator, transmitted on a separate second control channel, that indicates when transmissions on the first control channel are encoded using MU MIMO transmission; and 
 switch decoding of signals received on the first control channel between using and not using MU MIMO transmission based on the received indicator; and 
 
 a processor configured to:
 calculate a downlink signal quality for transmissions received from a radio node in a wireless network; 
 transmit the calculated downlink signal quality using channel quality indicators to the radio node in the wireless network; 
 wherein the wireless network categorizes the mobile wireless device into a first set of a plurality of sets based on the calculated downlink signal quality and determines to use MU MIMO transmission on the first control channel based at least in part on the communicated calculated downlink signal quality, and wherein the mobile wireless device shares a first common control channel element with at least a further mobile wireless device of the first set in the wireless network. 
 
 
     
     
       12. The mobile wireless device as recited in  claim 11 , wherein the wireless network uses a 3GPP LTE or LTE-Advanced communications protocol. 
     
     
       13. The mobile wireless device as recited in  claim 11 , wherein the receiver is further configured to:
 receive from the wireless network notification of an assigned unique rank one pre-coding matrix used for MU MIMO transmission on the first control channel, and 
 decode the signals received on the first control channel using the assigned rank one pre-coding matrix. 
 
     
     
       14. A computer program product encoded in a non-transitory computer readable medium for increasing a transmission capacity for a control channel in a wireless network, the computer program product when executed by a processor causes the processor to perform operations, comprising:
 at a radio node in a radio access network of the wireless network:
 estimating a received downlink signal quality for each mobile wireless device in a plurality of mobile wireless devices connected to the radio node; 
 categorizing the plurality of mobile wireless devices into a plurality of sets based on the estimated received downlink signal quality for each mobile device; 
 determining for each of the sets an available number of common control channel elements to assign for the control channel based on a number of mobile wireless devices in each set; 
 selecting a first set of mobile wireless devices in the plurality of mobile wireless devices, each selected mobile wireless device having an estimated downlink signal quality exceeding a first predetermined threshold; and 
 transmitting simultaneously to the first set of mobile wireless devices on the control channel through a plurality of antennas using multi-user (MU) multiple-input multiple-output (MIMO) transmission. 
 
 
     
     
       15. The computer program product as recited in  claim 14 , wherein when executed by the processor causes the processor to perform operations further comprising:
 at the radio node:
 assigning at least two mobile wireless devices in the first set of mobile wireless devices to the first control channel element that occupies a first set of time and frequency resource elements in a transmission time interval; 
 wherein the transmission capacity of the control channel is limited by the number of control channel elements scheduled for each transmission time interval. 
 
 
     
     
       16. The computer program product as recited in  claim 14 , wherein when executed by the processor causes the processor to perform operations further comprising:
 at the radio node:
 receiving downlink signal quality indicators from each of the plurality of mobile wireless devices; and 
 estimating the downlink signal quality to each mobile wireless device based on at least the received downlink signal quality indicator from the mobile wireless device. 
 
 
     
     
       17. The computer program product as recited in  claim 14 , wherein when executed by the processor causes the processor to perform operations further comprising:
 at the radio node:
 assigning a unique rank one pre-coding matrix used for MU MIMO transmission on the control channel to each mobile wireless device in the first set of mobile wireless devices; and 
 notifying each mobile wireless device of the assigned rank one pre-coding matrix. 
 
 
     
     
       18. The computer program product as recited in  claim 17 , wherein when executed by the processor causes the processor to perform operations further comprising:
 transmitting an indicator on a separate second control channel to each mobile wireless device when MU MIMO is used for transmission on the first control channel. 
 
     
     
       19. The computer program product as recited in  claim 14 , wherein the wireless network uses a 3GPP LTE or LTE-Advanced communications protocol. 
     
     
       20. The computer program product as recited in  claim 14 , wherein the number of mobile wireless devices in the first set of mobile wireless device depends on the estimated downlink signal quality for the mobile wireless devices in the first set of mobile wireless devices. 
     
     
       21. The computer program product as recited in  claim 15 , wherein when executed by the processor causes the processor to perform operations further comprising:
 assigning at least two mobile wireless devices in the first set of mobile wireless devices to an second control channel element that occupies a second set of time and frequency resource elements in the transmission time interval; 
 wherein the number of mobile wireless devices assigned to the first control channel element equals the number of mobile wireless devices assigned to the second control channel element. 
 
     
     
       22. The computer program product as recited in  claim 21 , wherein when executed by the processor causes the processor to perform operations further comprising:
 selecting a second set of mobile wireless devices in the plurality of mobile wireless devices, each selected mobile wireless device having an estimated downlink signal quality that exceeds a second threshold and falls below the first threshold; 
 transmitting simultaneously to the second set of mobile wireless devices on the control channel through the plurality of antennas using MU MIMO transmission; and 
 assigning at least two mobile wireless devices in the second set of mobile wireless devices to a third control channel element that occupies a third set of time and frequency resource elements in the transmission time interval; 
 wherein the number of mobile wireless devices in the first set of mobile wireless devices assigned to the first control channel element exceeds the number of mobile wireless devices in the third set of mobile wireless devices assigned to the third control channel element.

Description:
TECHNICAL FIELD 
     The described embodiments generally relate to methods and apparatuses for control channel communication between mobile wireless devices and a wireless network. More particularly, the present embodiments describe increasing capacity of a control channel between a radio access portion of a wireless network a multiple mobile wireless devices using multi-user multiple-input multiple-output communication. 
     BACKGROUND 
     Wireless networks continue to evolve to support new services and increased transmission rates as new communication technologies develop and standardize. A representative wireless network for a wireless network service provider can include support for one or more releases of the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) wireless communication standard and LTE-Advanced wireless communication standard. This representative wireless network can support packet switched connections (voice or data) through an LTE or LTE-Advanced network. 
     An LTE (LTE-Advanced) wireless network can support high rate packet communication to multiple mobile wireless devices simultaneously within a geographic area. The radio frequency spectrum used for communication to the multiple mobile wireless devices can be shared among the multiple mobile wireless devices using an orthogonal frequency division multiplexing (OFDM) transmission method. A transceiver (transmitter/receiver) in a mobile wireless device can adapt to radio frequency spectral variation using the OFDM transmission method, which can divide the occupied radio frequency spectrum into a set of parallel narrower bandwidth and lower data rate communication sub-channels transmitted on parallel subcarriers, and each sub-channel can experience approximately flat frequency spectrum fading. An OFDM communication system can divide transmissions into a series of successive OFDM symbols in time, with each OFDM symbol providing multiple sub-channels centered at different frequencies simultaneously. A transmission “resource element” (RE) can be considered a unit of transmission capacity on a single sub-channel within a single OFDM symbol, and the wireless network can allocate multiple RE across multiple sub-channels among multiple wireless devices dynamically over time. The wireless network can regularly broadcast control information about the allocation of the RE to the multiple wireless devices within a geographic area served by a radio frequency access system of the wireless network. The control information itself can be transmitted using a subset of the total available RE, and the number of RE available to support communication of control information can limit the total number of mobile wireless devices that can be connected simultaneously to the wireless network. 
     Communication systems can be sensitive to errors that can occur in the control information received at the wireless devices, and the wireless network can use different rates of error correction coding to protect the control information during transmission and reception by the mobile wireless device in the presence of noise and interference. Received signal quality at a mobile wireless device can vary significantly based on the location of the mobile wireless device with respect to a transmitting radio frequency access system located in an access network portion of the wireless network and also based on the amount of noise and interference received by the mobile wireless device. Mobile wireless devices located at a greater distance, such as nearer the edge of a geographic coverage area of the access network transmitter, can receive weaker signals than mobile wireless devices located closer to the access network transmitter. As the control information can be broadcast simultaneously to all of the multiple wireless devices served by the access network transmitter, the transmit power used for control channel transmissions can be the same for the different multiple wireless devices, while the amount of error correction coding applied can be varied to better protect transmissions to the different mobile wireless devices. Specifically more RE can be allocated for communication of control information to mobile wireless devices with lower received signal quality, and fewer RE can be allocated to control channel messages sent to mobile wireless devices with higher received signal quality. The same RE can be allocated to multiple mobile wireless devices by sharing the same frequency band/time slot occupied by the RE using a form of spatial division multiplexing. Multi-user multiple input multiple output (MU-MIMO) transmission methods can be applied to transmissions of the control information to share selected RE among multiple mobile wireless devices and to increase the total number of mobile wireless devices that can be simultaneously supported by a radio sector of the wireless network. 
     SUMMARY OF THE DESCRIBED EMBODIMENTS 
     In one embodiment, a method of increasing transmission capacity for a control channel in a wireless network is described. The method includes at least the following steps. In a first step, a radio node in a radio access network of the wireless network estimates a received downlink signal quality for each mobile wireless device in a plurality of mobile wireless devices connected to the radio node. The radio node selects a first set of mobile wireless devices in the plurality of mobile wireless devices. Each selected mobile wireless device has an estimated downlink signal quality exceeding a first threshold. The radio node transmits simultaneously to the first set of mobile wireless devices on the control channel through a plurality of antennas using multi-user (MU) multiple-input multiple-output (MIMO) transmission. In a representative embodiment, the radio node assigns at least two mobile wireless devices in the first set of mobile wireless devices to a first control channel element that occupies a first set of time and frequency resource elements in a transmission time interval. The transmission capacity of the control channel is limited by the number of control channel elements scheduled for each transmission time interval. 
     In another embodiment, a mobile wireless device including a receiver and a configurable processor is described. The receiver is configured to receive and decode signals transmitted on a first control channel. The receiver is also configured to receive an indicator transmitted on a separate second control channel. The transmitted indicator indicates when transmissions on the first control channel are encoded using MU MIMO transmission. The receiver is further configured to switch decoding of signals received on the first control channel between using and not using MU MIMO transmission based on the indicator. The processor is configured to calculate a downlink signal quality for transmissions received from a radio node in a wireless network. The processor is also configured to transmit the calculated downlink signal quality using channel quality indicators to the radio node in the wireless network. The wireless network determines to use MU MIMO transmission on the first control channel based at least in part on the communicated calculated downlink signal quality. 
     In a further embodiment, non-transitory computer program product encoded in a non-transitory computer readable medium for increasing transmission capacity for a control channel in a wireless network is described. The non-transitory computer program product in a radio node in a radio access network of the wireless network includes the following non-transitory computer program code. Non-transitory computer program code for estimating a received downlink signal quality for each mobile wireless device in a plurality of mobile wireless devices connected to the radio node. Non-transitory computer program code for selecting a first set of mobile wireless devices in the plurality of mobile wireless devices, each selected mobile wireless device having an estimated downlink signal quality exceeding a first threshold. Non-transitory computer program code for transmitting simultaneously to the first set of mobile wireless devices on the control channel through a plurality of antennas using multi-user (MU) multiple-input multiple-output (MIMO) transmission. 
     Although described in terms of an LTE or LTE-Advanced network, the embodiments disclosed herein can be extended to other wireless networks that can support multi-user multiple-input multiple-output transmissions as well. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The described embodiments and the advantages thereof may best be understood by reference to the following description taken in conjunction with the accompanying drawings. 
         FIG. 1  illustrates components of a generic wireless communication network. 
         FIG. 2  illustrates components of a LTE wireless communication network. 
         FIG. 3  illustrates components of an OFDM transmission frame in an LTE wireless network. 
         FIG. 4  illustrates constituent components of a transmission time interval for OFDM transmissions in the LTE wireless network. 
         FIG. 5  illustrates several architectures for select components in a mobile wireless device that supports receive diversity. 
         FIG. 6  illustrates an organization of resource elements for transmission on multiple antennas within a transmission time interval across multiple subcarriers. 
         FIG. 7  illustrates transmission paths for a multiple input multiple output transmission. 
         FIG. 8  illustrates multiple mobile wireless devices arrayed in a radio sector for a radio access subsystem in the LTE wireless network. 
         FIG. 9  illustrates a representative method to increase transmission capacity for a control channel in a wireless network. 
         FIG. 10  illustrates another representative method to increase transmission capacity for a control channel in a wireless network. 
     
    
    
     DETAILED DESCRIPTION OF SELECTED EMBODIMENTS 
     In the following description, numerous specific details are set forth to provide a thorough understanding of the concepts underlying the described embodiments. It will be apparent, however, to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the underlying concepts. 
     The examples and embodiments provided below describe various methods and apparatuses for increasing control channel capacity in a wireless network for communication with multiple wireless mobile devices. More specifically, methods and apparatuses are described that use multi-user multiple-input multiple-output (MU MIMO) transmission in an LTE network. It should be understood, however, that other implementations of the same methods and apparatuses can apply to mobile wireless devices used in other types of wireless networks that support MU MIMO transmission. 
     Mobile wireless devices continue to evolve and offer more advanced features that can benefit from higher data throughput rates. The 3GPP LTE and LTE-Advanced communication protocols standardize packet communication to provide a broad variety of services varying from high speed data to basic voice communication. The LTE protocols use a flexible communication method known as orthogonal frequency division multiplexing (OFDM) that divides the occupied frequency spectrum into multiple parallel low rate sub-channels. A downlink transmitted OFDM symbol can contain information intended for multiple users by assigning different sub-channels to different users in the OFDM symbol. Assignments of individual sub-channels for one or a set of OFDM symbols can be communicated using a control channel broadcast to all wireless mobile devices connected to a particular radio sector of a radio access subsystem in a wireless network. As the performance of a mobile wireless device can be particularly sensitive to errors on a control channel, on which errant control message can affect multiple data packets, the control channel can be protected using various levels of error correction capability. Mobile wireless devices that are located in areas of weak signal quality can require greater levels of error protection for the control channel than those mobile wireless devices with strong signal quality. Higher levels of error protection can require more bandwidth to communication the same amount of information; and thus, mobile wireless devices having weaker signal quality can require greater allocations of control channel resources. The total number of control channel resources for allocation among all mobile wireless devices simultaneously served by the radio access subsystem within a geographical area covered by a radio sector can be limited in number. As such, the total number of mobile wireless devices that can be served simultaneously can be limited by the total amount of control channel resources available. 
     The LTE and LTE-Advanced communication protocols include provisions for transmission and reception of signals between the radio access subsystem and the mobile wireless device using multiple antennas. Transmission techniques known as multiple-input multiple-output (MIMO) can be used to increase the capacity and/or improve the reliability of transmission. One MIMO transmission technique known as spatial multiplexing can allow control channel communication to be shared among multiple users on the same sub-channels in the same OFDM symbol, i.e. to re-use the same frequency/time resources for multiple independent mobile wireless devices. Transmissions to one mobile wireless device can be separated by transmission to another mobile wireless device by sending the transmissions on multiple antennas at the same time and in the same frequency band. The different transmissions can be separated from one another by each receiver in the mobile wireless devices by using multiple receive antennas and sophisticated signal processing techniques. Transmissions to other mobile wireless devices can be considered “noise” with respect to the “signal” transmission intended for a particular mobile wireless device. The receiver in the mobile wireless device can separate the “signal” from the “noise” when the mobile wireless device receives sufficiently high quality signals. By using such techniques, the capacity of the control channel can also be increased, i.e. the number of mobile wireless devices that can served simultaneously can be increased. Determining with which mobile wireless device to use MIMO spatial multiplexing can be based on knowledge of the respective received signal quality at the multiple mobile wireless devices. Devices with higher receive signal quality can share the same frequency/time resources more readily than those mobile wireless devices that have lower receive signal quality. Control elements in the radio access subsystem of the wireless network that communicates with the mobile wireless devices can determine to which mobile wireless devices to use MIMO spatial multiplexing (and in which OFDM frequency subchannels and time symbols to use MIMO as well.) The use of MIMO spatial multiplexing on the control channel can be communicated in advance to the mobile wireless devices and can be adapted as receive signal quality changes over time. 
     These and other embodiments are discussed below with reference to  FIGS. 1-10 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  illustrates a representative generic wireless communication network  100  that can include multiple mobile wireless devices  102  connected by radio links  126  to radio sectors  104  provided by a radio access network  128 . Each radio sector  104  can represent a geographic area of radio coverage emanating from an associated radio node  108  using a radio frequency carrier at a selected frequency. Radio sectors  104  can have different geometric shapes depending on antenna configuration, such as radiating outward in an approximate circle or hexagon from a centrally placed radio node  108  or cone shaped for a directional antenna from a corner placed radio node  108 . Radio sectors  104  can overlap in geographic area coverage so that the mobile wireless device  102  can receive signals from more than one radio sector  104  simultaneously. Each radio node  108  can generate one or more radio sectors  104  to which the mobile wireless device  102  can connect by one or more radio links  126 . 
     In some wireless networks  100 , the mobile wireless device  102  can be connected to more than one radio sector  104  simultaneously. The multiple radio sectors  104  to which the mobile wireless device  102  is connected can come from a single radio node  108  or from separate radio nodes  108  that can share a common radio controller  110 . A group of radio nodes  108  together with the associated radio controller  110  can be referred to as a radio access subsystem  106 . Typically each radio node  108  in a radio access subsystem  106  can include a set of radio frequency transmitting and receiving equipment mounted on an antenna tower, and the radio controller  110  connected to the radio nodes  108  can include electronic equipment for controlling and processing transmitted and received radio frequency signals. The radio controller  110  can manage the establishment, maintenance and release of the radio links  126  that connect the mobile wireless device  102  to the radio access network  128 . Each mobile wireless device  102  connected to the radio access subsystem  106  can be located at a different distance from the radio node  108  from which it can receive radio frequency signals for the radio links  126 . The radio controller  110  and/or the radio node  108  can control monitor and control the strength of transmitted and received signals to each mobile wireless device  102  to manage performance of the radio link  126  connections. The radio access subsystem  106  can use a combination of signal strength, data rate encoding, error correction capability and multiple antenna transmission to improve the performance of signal reception at the mobile wireless device  102  in the presence of variable noise and interference in the wireless network  100 . 
     The radio access network  128 , which provides radio frequency air link connections to the mobile wireless device  102 , connects also to a core network  112  that can include a circuit switched domain  122 , usually used for voice traffic, and a packet switched domain  124 , usually used for data traffic. Radio controllers  110  in the radio access subsystems  106  of the radio access network  128  can connect to both a circuit switching center  118  in the circuit switched domain  122  and a packet switching node  120  in the packet switched domain of the core network  112 . The circuit switching center  118  can route circuit switched traffic, such as a voice call, to a public switched telephone network (PSTN)  114 . The packet switching node  120  can route packet switched traffic, such as a “connectionless” set of data packets, to a public data network (PDN)  116 . 
       FIG. 2  illustrates a representative Long Term Evolution (LTE) wireless network  200  architecture designed as a packet switched network exclusively. A mobile terminal  202  can connect to an evolved radio access network  222  through radio links  226  associated with radio sectors  204  that emanate from evolved Node B&#39;s (eNodeB)  210 . The eNodeB  210  includes the functions of both the transmitting and receiving base stations (such as the radio node  108  in the generic wireless network  100 ) as well as the radio access network subsystem radio controllers (such as the radio controller  110  in the generic wireless network  100 ). The equivalent core network of the LTE wireless network  200  is an evolved packet core network  220  including serving gateways  212  that interconnect the evolved radio access network  222  to public data network (PDN) gateways  216  that connect to external internet protocol (IP) networks  218 . Multiple eNodeB  210  can be grouped together to form an evolved UTRAN (eUTRAN)  206 . The eNodeB  210  can also be connected to a mobility management entity (MME)  214  that can provide control over connections for the mobile terminal  202 . 
     The radio links  226  between the eNodeB  210  in the eUTRAN  206  of the evolved radio access network  222  can include transmissions that use multiple antennas at the transmitting end, at the receiving end and/or at both ends. Transmission and reception using multiple antennas can improve signal reception in the presence of variable noise and interference between the mobile terminal  202  and the eNodeB  210  with the radio sector  204 . Multiple antenna transmission can occur in several different forms, including transmit diversity, single user spatial diversity and multiple user spatial diversity. With transmit diversity, the same information can be sent through two different paths, which can provide redundancy for recovering the information at the receiver of the mobile terminal  202 . With single user spatial diversity, different information can be sent through two different paths, which provides for increased throughput to an individual mobile terminal  202 . With multiple user spatial diversity, different information can be sent to different mobile terminals  202 , thereby increasing the aggregate amount of information that can be transmitted to a set of mobile terminals  202 . The number of mobile terminals  202  that can served simultaneously by the eUTRAN  206  in the evolved radio access network  222  can depend on the available transmission capacity to send control information to the set of mobile terminals  202 . As will be described further herein, the transmission capacity for control information can be increased through spatial diversity by using multiple user multiple input multiple output transmissions with multiple antennas in the LTE network  200 . 
     Transmission on the LTE network  200  can use a form of orthogonal frequency division multiple access (OFDMA) in the downlink direction, i.e. from the eNodeB  210  to the mobile terminal  202 , and single carrier frequency division multiple access (SC-FDMA) in the uplink direction. With OFDMA, data can be transmitted on multiple parallel sub-channels, each sub-channel centered at a different sub-carrier frequency, to multiple mobile terminals  202  at the same time. The allocation of sub-channels to the multiple mobile terminals  202  can vary for different OFDM symbols, and control information can be transmitted to the mobile terminals  202  to indicate the allocation of radio frequency resources over time. Each mobile terminal  202  can be allocated a number of sub-channels for a specified period of time, i.e. a set of frequencies across a number of successive OFDM symbols. Allocation of the radio frequency resources can be scheduled by the eNodeB  210  in the eUTRAN  206  of the evolved radio access network  222 . 
     LTE transmissions can be organized into a succession of OFDM symbols  308  as illustrated in  FIG. 3 . An LTE frame  302  can span a period of 10 ms and can include 10 transmission timer intervals (TTI)  304  that each span a time period of 1 ms. Each TTI  304  can include two time slots  306  that each span 0.5 ms, and each time slot  306  can include seven OFDM symbols  308 . The OFDM symbol  308  as shown in  FIG. 3  can include a cyclic prefix  310  that can provide a time domain guard interval to minimize inter-symbol interference between successive OFDM symbols  308 . 
     Each OFDM symbol  308  can include data transmitted on multiple sub-channels, each sub-channel on a separate frequency. An aggregate of a set of sub-channels (sub-carriers) for a set of successive OFDM symbols can be considered a resource block  406  as shown in  FIG. 4 . In a representative embodiment, the resource block  406  can include a set of twelve adjacent frequency subcarriers during a time slot  306  of seven OFDM symbols  308 . Two successive resource blocks can span a transmission time interval (TTI)  306  and can include fourteen OFDM symbols  308  divided into a set of control  402  OFDM symbols and a set of data  404  OFDM symbols. The total number of frequency sub-carriers used for an OFDM symbol can depend on the bandwidth allocated. With a sub-carrier spacing of 15 kHz, each resource block  406  can span 180 kHz of bandwidth, and the total bandwidth occupied can depend on the number of available resource blocks  406 . For example, an LTE transmission system that uses fifty resource blocks  406  can span a bandwidth of 9 MHz (lowest to highest sub-carrier center frequency) and can fit within a 10 Mhz radio frequency total bandwidth (including side lobes). 
     Each transmission on a single frequency subcarrier within a single OFDM symbol  308  can be considered an individual resource element (RE)  408  of a physical layer transmission. In general, the RE  408  can be referred to as a frequency/time resource. The resource elements  408  in the data portion  404  of a TTI  304  can be allocated among multiple mobile terminals  202 , and the allocation of the RE  408  can be communicated to the mobile terminals  202  using resource elements  408  in the control portion  402  of the TTI  304 . Four different resource elements  408  within a single OFDM symbol  308  can form a resource element group (REG)  410 , and nine different REGs  410  can form a control channel element (CCE). A physical downlink control channel (PDCCH) message in the LTE transmission system to one of the mobile terminals  202  can use one, two, four or eight CCEs depending on a format selected for the PDCCH message. The PDCCH message format can be based on received downlink signal quality conditions measured at the mobile terminal  202  and reported to the eNodeB  210  of the LTE wireless network  200 . With a high receive signal quality at the mobile terminal  202 , one CCE can suffice for the PDCCH message, while with a low receive signal quality, up to eight CCE can be required to minimize decoding errors of the PDCCH message at the mobile terminal  202 . 
     The total number of mobile terminals  202  that can be supported simultaneously in a given TTI  304  can depend on the available signal quality at each of the mobile terminals  202  and on the number of OFDM symbols  308  available for control channel transmission. For each TTI  304 , a total of fourteen OFDM symbols  308  can be available and can be divided between control transmission and data transmission. One, two or three OFDM symbols  308  of the fourteen total OFDM symbols  308  in the TTI  304  can be used for control  402 , while the remaining OFDM symbols  308  in the TTI  304  can be used for data  404 . Some of the resource elements  408  in each resource block  406  can be reserved to carry reference signals  412 , as indicated by select RE  408  labeled with the letter “R” in the resource block  408  of  FIG. 4 . The reference signal  412  resource elements  408  can provide a pre-determined known signal to which the mobile terminal  202  can locate and synchronize as well as characterize the downlink communication channel to the mobile terminal  202  from the eNodeB  210  in the evolved radio access network  222  of the wireless network  200 . Within a resource block  406 , which can have three OFDM symbols available for control  402  channel transmissions, two of the thirty six resource elements  408  can be used for reference signals  412 . As a minimum allocation of one CCE (36 RE) can be required for control channel communication for each mobile terminal  202  for a given TTI  304 , even with three OFDM symbols  308  assigned for transmission of control  402  information, a maximum of less than fifty independent mobile terminals  202  can be accommodated in an LTE transmission system that occupies 10 MHz of frequency bandwidth. Each mobile terminal  202  that requires more than one CCE for control channel transmissions, i.e. when a mobile terminal  202  can have poor receive radio frequency signal quality and can require 2, 4 or 8 CCE, can reduce the total number of mobile terminals  202  that can be supported simultaneously per TTI  304 . As LTE systems can be expected to transport both high speed data and numerous lower rate voice connections, increasing the number of mobile terminals  202  that can be simultaneously supported in each TTI  304  can prove beneficial. 
       FIG. 5  illustrates select elements for several different architectures that can be used in a mobile wireless device  102  (or mobile terminal  202 ). A mobile terminal  202  can include multiple antennas to improve downlink received signal performance, such as increased robustness in the presence of noise and interference as well as higher data rates. The architecture for a mobile terminal  202  can include an application processor (AP)  502 , one or more transceivers and multiple antennas. In a first architecture  500 , the mobile terminal  202  can include one transceiver  504  connected to the AP  502  and also connected to two antennas. The AP  502  of the mobile terminal  202  can initiate and terminate connections with the wireless network  200  in response to application level services active in the mobile terminal  202 . The AP  502  can provide “higher layer” processing that can establish packet level connections through the wireless network  200 , while the transceiver  504  can provide “lower layer” signal processing that can translate the higher layer packet messages into a format suitable for transmission over the radio links  226  in the radio sector  204  supported by the eNodeB  210  of the eUTRAN  206  in the evolved radio access network  222 . The transceiver  504  can receive downlink transmissions from the eNodeB  210  through one of the two antennas, e.g. by selecting among the antennas having a stronger signal strength or a higher signal quality, or through both antennas simultaneously and combine the received signals to improve signal reception. 
     In a basic form of diversity, the mobile terminal  202  with configuration  500  can receive signals transmitted by a single antenna at the eNodeB  210  through one of the antennas, either antenna  0  or antenna  1 , where the antenna used is switched into service by the mobile terminal  202  (switch not shown). This form of diversity can be considered “antenna diversity” in which one of the antennas can provide better performance, e.g. based on signal strength and/or signal quality, and the antenna used can be chosen dynamically for a connection. Alternatively, when the transceiver  504  in the mobile terminal  202  can process signals from both antennas simultaneously, the transceiver  504  can combine signals transmitted on each of the different frequency sub-channels in an OFDM symbol to improve signal strength and/or signal quality throughout a received frequency spectrum. This combining of signals received through multiple antennas simultaneously can be considered “receiver diversity”. With these basic forms of diversity, the receive signal quality reported to the eNodeB  210  in the wireless network  200  can be higher than without diversity, and the number of CCE assigned for PDCCH transmissions can be lower, thereby freeing up some CCE to be used for other mobile terminals  202 . 
     A more advanced form of diversity can use simultaneous transmission through multiple antennas at the eNodeB  210  and simultaneous reception through multiple antennas at the mobile terminal  202 . This form of diversity can be referred to as multiple input multiple output (MIMO) transmission and can be used to increase transmission data rates to a single mobile terminal  202 , i.e. single user (SU) MIMO or to transmit data simultaneously to multiple mobile terminals  202 , i.e. multiple user (MU) MIMO. Sharing the same frequency/time resources using MU MIMO across multiple mobile terminals  202  can increase the number of mobile terminals  202  that can be served simultaneously by the limited number of CCE available per TTI  304 , thereby increasing the capacity of control channel communication in the LTE system. The number of transmit and receive antennas used for MIMO can be two, as shown for the architecture  500 , as well as four as shown for architecture  520  or even more (not shown). The LTE and LTE-Advanced communication protocols include options for one, two, four and eight antenna configurations. The mobile terminal  202  can determine the number of transmit antennas used by the eNodeB  210  in the wireless network  200  by using the transmitted reference signals  412 . 
     While the description herein covers several different architectures for mobile terminals  202  that can use multiple antennas with one or more transceivers, some mobile wireless devices  102  can include multiple receivers to support connections to wireless networks that offer different wireless communication protocols. The evolution of wireless network deployment can result in periods of overlapping technologies that use different wireless communication protocols that can require different transceivers. The architecture  540  for a mobile wireless terminal  102  shown in  FIG. 4  includes a first transceiver  504  that can support multiple antenna communication and a second transceiver  542  that can support single antenna communication. The description provided herein outlined in terms of a mobile wireless terminal  102  having multiple antennas and a single transceiver block  504  can apply equally to dual transceiver mobile wireless terminals  102 . In some embodiments, the single transceiver block  504  can also include multiple parallel transceivers or configurable blocks that can support reception through multiple antennas in parallel. No loss of generality is intended by the depiction of a “single” transceiver block  504  as shown for architecture  504  of the mobile wireless terminal  102  in  FIG. 5 . 
     With MIMO transmission, the eNodeB  210  in the wireless network  200  can send signals through multiple antennas.  FIG. 6  illustrates how reference signals  412  can be divided between two different antennas of the eNodeB  210 . The resource blocks  610  for one TTI  304  output by a first antenna  0  can include reference signals  412  in select frequency/time resource elements  408  and can exclude sending signals in other resource elements  408  (labeled as “unused” RE  602 ). Similarly the resource blocks  620  for one TTI  304  output by a second antenna  1  can include reference signals  412  in the same frequency/time resource elements  408  that were “unused” by the first antenna  0 . Thus, distinct reference signals  412  can be transmitted by each antenna, and the mobile terminal  202  can measure transmission channel characteristics for each antenna separately using the distinct reference signals  412 . 
       FIG. 7  illustrates four distinct transmission paths that can be characterized by the mobile terminal  202  using reference signals  412  sent from transmit (TX) processing  702  at the eNodeB  210 . Receive (RX) processing  704  in the mobile terminal  202  can be used to receive reference signals  412  transmitted by TX antenna  0  at the eNodeB  210  through each of the receive antennas separately. The TX 0 /RX 0  transmission path can be characterized separately from the TX 0 /RX 1  transmission path by the RX processing  704  of the mobile terminal  202  using reference signals  412  transmitted in specific time/frequency resource elements  408  by the TX antenna  0 . Similarly the TX 1 /RX 1  and TX 1 /RX 0  transmission paths can be characterized separately using reference signals  412  transmitted in a different set of frequency/time resource elements  408  by the TX antenna  1  to RX antenna  0  and RX antenna  1 . As the reference signals from TX antenna  0  and TX antenna  1  can be sent in separate time/frequency resource elements  408  as shown in  FIG. 6 , the separate transmission paths can be characterized independently. Once the transmission paths are characterized, constituent component transmissions for each of two different transmitting antennas can be determined from the linear combinations of the transmitted signals received at each antenna. MIMO transmission as shown in  FIG. 7  can be used to increase the amount of information transmitted to an individual mobile terminal  202  by sending twice the amount of data using the two transmitting antennas simultaneously for the same frequency/time resource element. MIMO transmission can also be used to transmit to two different mobile terminals  202 , e.g. by increasing the data throughput rate, with half of the data used for one mobile terminal  202  and the other half of the data used for another mobile terminal  202  simultaneously. 
     The LTE and LTE-Advanced communication protocols specify several different MIMO transmission methods that can be applied to downlink data channels; however, for downlink control channels only a transmit diversity method is specified. Transmit diversity can improve signal integrity but does not directly share the same frequency/time radio frequency resource element between multiple users. By applying MU MIMO for control channel communication from the eNodeB  210 , the wireless network  200  can increase the capacity of the control channel and thereby serve more mobile terminals  202  simultaneously. Using MU MIMO and two spatially separated transmitting antennas, the eNodeB  210  can transmit two parallel control channel data streams simultaneously to two different mobile terminals  202  sharing the same frequency/time resource elements. Each of the parallel control channel data streams can be separately encoded so that control channel data intended for one mobile terminal  202  can be separated from control channel data intended for another mobile terminal  202 . This encoding at the eNodeB  210  can be referred to as “precoding” and can map control channel data streams into suitable control channel data symbols for transmission by the multiple antennas. 
     In a representative embodiment, the control channel data stream for one mobile terminal  202  can be precoded using one “rank 1” vector, while the control channel data stream for a second mobile terminal  202  can be precoded using a separate “rank 1” vector. A representative set of four different “rank 1” vectors from which to select precoding vectors for each mobile terminal  202  can include the following complex valued vectors: 
               {         1     2       ⁡     [         1           1         ]       ,       1     2       ⁡     [         1             -   1           ]       ,       1     2       ⁡     [         1           j         ]       ,       1     2       ⁡     [         1             -   j           ]         }     ,         
where the upper entry in each vector can signify the precoding applied for data transmitted on a first antenna and the lower entry in each vector can signify the precoding applied for data transmitted on a second antenna. Each mobile terminal  202  in a set of mobile terminals that can share frequency/time resources through MU MIMO can be assigned a different one of the precoding vectors and can use that knowledge to correctly decode signals received through its two antennas and to reconstruct its own intended original data stream. When using four transmit antennas, the set of precoding vectors can include vectors of length four instead of length two as shown above for two transmit antennas.
 
       FIG. 8  illustrates a partition  800  of a radio sector  104  for a wireless network  100  into three distinct regions nominally based on distance from a radio access subsystem  106  of the wireless network  100 . A set of mobile wireless devices  102  in a far region  806  can be located at a farthest distance from the radio access subsystem  106 , and signals transmitted by the radio access subsystem  106  to a mobile wireless device  102  in the far region  806  can incur significant amounts of attenuation. As such, mobile wireless devices  102  in the far region can have the weakest receive signal strength and/or the weakest signal quality of mobile wireless devices  102  served by the radio access subsystem  106  in the radio sector  104  of the wireless network  100 . As mobile wireless devices  102  can report periodically a channel quality indicator (CQI) to the radio access subsystem  106 , and the radio access subsystem  106  can categorize the mobile wireless devices  102  based on the CQI (or other performance information) to determine the number of CCE to assign for a downlink control channel (e.g. the physical downlink control channel PDCCH) to each mobile wireless device  102  served by the radio access subsystem  106 . 
     For mobile wireless devices with a relatively high signal strength and/or high signal quality, e.g. located in a near region  802  relatively close to the radio access subsystem  106 , a minimum of only one CCE can be used for the control channel information. As the number of mobile wireless devices  102  in the radio sector that can be served simultaneously can be limited by the total number of CCE available, the radio access subsystem  106  can group together one or more sets of mobile wireless devices  102  located in the near region  802  of the radio sector  104 . Each mobile wireless device  102  in the set can have comparable signal strength and/or signal quality and can share one CCE among of the set of mobile wireless devices  102  in the near region  802  using MU MIMO transmission for the control channel information. When transmitting from the radio access system  106  with two antennas to mobile wireless devices  102  having two antennas, the radio access subsystem  106  can pair up mobile wireless devices  102  in the near region  802  in sets of two mobile wireless devices  102  with comparable signal strength/quality. When transmitting with four antennas to mobile wireless devices  102  that can receive MU MIMO transmissions with four antennas, the radio access subsystem  106  can group the mobile wireless devices  102  in the near region  802  into sets of up to four mobile wireless devices  102  to share a single CCE. 
     The radio access subsystem  106  can use different strategies to add control channel capacity with MU MIMO transmission depending on one or more factors such as the number of mobile wireless devices  102  associated with the radio access subsystem  106 , the number of mobile wireless devices  102  actively connected to the radio access subsystem  106 , the number of transmit antennas at the radio access subsystem  106 , the number of receive antennas at each of the mobile wireless devices  102 , measured receive signal strength and/or signal quality communicated from each mobile wireless device  102  to the radio access subsystem  106 , and selection and use of MU MIMO on data channels for a particular mobile wireless device  102 . 
       FIG. 9  illustrates a representative method  900  to increase transmission capacity for a control channel in a wireless network  100 . The method can be executed at a radio node  108  in a radio access network  128  of the wireless network  100 . In step  902 , the radio node  108  can estimate downlink signal quality for a plurality of mobile wireless devices  102 . In a representative embodiment, the downlink signal quality can be reported by one or more of the plurality of mobile wireless devices  102  to the radio node  108  using channel quality feedback indicators. In step  904 , the radio node  108  can select a set of mobile wireless devices  102  each having an estimated downlink signal quality that exceeds a first pre-determined threshold. In a representative embodiment, the first pre-determined threshold can be set the wireless network  100  and can be communicated to the mobile wireless device  102 . In step  906 , the radio node  108  can transmit simultaneously to the set of mobile wireless devices  102  on the control channel using MU MIMO transmission. In a representative embodiment, at least two of the mobile wireless devices  102  in the set of mobile wireless devices  102  can be assigned to a common control channel element (CCE) that occupies a set of time and frequency resource elements during a transmission time interval for the control channel. The transmission capacity of the control channel can be limited by the number of control channel elements that can be scheduled for each transmission time interval. In a representative embodiment, the radio node can transmit an indication to the mobile wireless device  102  when MU MIMO transmission is used for transmission of the control channel. The number of mobile wireless devices  102  that share a common CCE using MU MIMO transmission can depend on the estimated receive downlink signal quality. Higher receive downlink signal quality can support sharing of the common CCE among more mobile wireless devices  102  simultaneously than lower receive downlink signal quality. 
       FIG. 10  illustrates another representative method  1000  to increase transmission capacity for a control channel in a wireless network  100 . The method can be executed at a mobile wireless device  102  in the wireless network  100 . In step  1002 , the mobile wireless device  102  can calculate a received downlink signal quality. In step  1004 , the mobile wireless device  102  can transmit the calculated downlink signal quality using channel quality indicators to a radio node  108  in the wireless network  100 . In step  1006 , the mobile wireless device  102  can receive and decode signals on a first control channel. In step  1008 , the mobile wireless device  102  can receive an indicator on a second control channel that can indicate when transmissions on the first control channel can use MU MIMO. In step  1010 , the mobile wireless device can switch decoding of signals received on the first control channel between using and not using MU MIMO based on the received indicator from the wireless network  100 . In a representative embodiment, the mobile wireless device  102  can receive from the wireless network  100  notification of an assigned rank one pre-coding matrix used for MU MIMO transmission on the first control channel. The mobile wireless device  102  can decode the signals received on the first control channel using the assigned rank one pre-coding matrix. 
     In a representative embodiment, the first control channel, on which the mobile wireless device  102  can receive MU MIMO transmissions, and the second control channel, on which the mobile wireless device  102  can receive indications when transmissions on the first control channel use MU MIMO transmissions, can be the same physical control channel. An exemplary physical control channel can be the PDCCH control channel. The mobile wireless device  102  can receive the physical control channel initially without using MU MIMO and can switch to using MU MIMO based on a message transmitted in the physical control channel. The message can indicate a switch to MU MIMO transmission at a particular frame. Messages in the physical control channel can use MU MIMO transmission from that particular indicated frame onward until a subsequent message can indicate a switch to not use MU MIMO transmission. In another embodiment, the mobile wireless device  102  can detect when MU MIMO transmission is used and can appropriately decode the received transmissions on the PDCCH control channel based on the detection. In another embodiment, the mobile wireless device  102  can decode transmissions on the PDCCH control channel trying different transmission modes, such as with MU MIMO and without MU MIMO, to achieve a best decoding of the PDCCH control channel. 
     In another representative embodiment, the first control channel and the second control channel can be separate physical control channels. Separate physical control channels can be, for example, a first PDCCH and a second PDCCH. Messages on the first control channel can switch between using and not using MU MIMO based on messages transmitted on the second control channel. The second control channel can use a fixed transmission method with high reliability, such as with transmission diversity. 
     In another representative embodiment, the first control channel and the second control channel can be separate logical channels on the same physical control channel. Separate logical channels can be two different logical channels that share the same PDCCH. A PDCCH can use multiple control channel elements (CCEs) that span multiple time/frequency resource elements, a two different blocks of time/frequency resource elements that are used by the PDCCH can be grouped into separate control channels (effectively separate control sub-channels within the PDCCH control channel). 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings. 
     The advantages of the embodiments described are numerous. Different aspects, embodiments or implementations can yield one or more of the following advantages. Many features and advantages of the present embodiments are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the embodiments should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents can be resorted to as falling within the scope of the invention.

Metadata:
Filing Date: 20110927
Publication Date: 20150512
Grant Date: 20150512
Priority Date: 20110927
Inventors: NUKALA GAURAV R.
RAMASAMY VENKATASUBRAMANIAN
DEIVASIGAMANI GIRI PRASSAD
Assignee: APPLE INC
CPC Classifications: [{"code": "H04W72/23", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W72/542", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L1/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0452", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L5/0053", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0023", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0417", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04L1/0072", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/0072", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0023", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0053", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W4/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W72/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0417", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04L1/007", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0023", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/001", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0452", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0417", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04W24/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L5/0053", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04L1/0072", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04B7/0452", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 47178280