Abstract:
There is provided a communication method for a coordinator communication device, including generating a first scheduling element to be used by a first communication device and a second scheduling element to be used by a second communication device; and transmitting the first and second scheduling elements to the first and second communication devices. The second scheduling element includes a second allocation indicating a time-frequency resource allocated to the second communication device. The first scheduling element includes a first allocation indicating a time-frequency resource allocated to the first communication device and optionally includes a first virtual allocation that is a duplicate of the second allocation. The first communication device performs communication in accordance with a first communication system using a first frequency band, and the second communication device performs communication in accordance with the first communication system or a second communication system using a second frequency band that includes the first frequency band.

Description:
BACKGROUND 
     1. Technical Field 
       [0001]    The present disclosure relates to a communication method and a communication device and specifically relates to a communication method and a communication device for suppressing interference in a WLAN (wireless local area network). 
       2. Description of the Related Art 
       [0002]    A 60-GHz millimeter-wave network that requires no license is receiving increasing attention. The wireless HD technology is the first industry standard for the 60-GHz millimeter wave and enables multi-gigabit wireless streaming of high-definition sounds, videos, and data between home electrical appliances, personal computers, and portable devices. 
         [0003]    As another multi-gigabit wireless communication technology operating on the 60-GHz millimeter frequency band, the WiGig (Wireless Gigabit) technology is available. The WiGig technology is standardized by IEEE (Institute of Electrical and Electronics Engineers) as the IEEE 802.11ad standard (see IEEE 802.11ad-2012). The WiGig technology uses a wide channel bandwidth of 2.16 GHz to provide PHY (physical layer) data rates of up to 6.7 Gbps. 
         [0004]    The MAC (Medium Access Control) layer of WiGig supports a centralized network architecture, such as an infrastructure BSS (basic service set) or a PBSS (personal BSS). In this architecture, a central coordinator (for example, an AP (access point) or a PCP (personal BSS control point), hereinafter referred to as a PCP/AP) transmits DMG (directional multi-gigabit) beacons to synchronize all STAs (stations) on the network. 
         [0005]    On the MAC layer of WiGig, a mechanism called PCP/AP clustering is introduced in order to enable spatial sharing and interference mitigation with other BSSs using the same channel. In the PCP/AP clustering, transmission is scheduled so that a clustering-capable PCP/AP that is a member of a cluster performs transmission in a period that does not overlap those of other members in the same cluster. 
         [0006]    In the PCP/AP clustering, scheduling information regarding channel time allocation is included in an ESE (extended schedule element). A PCP/AP transmits a SMG beacon including one or more ESEs in accordance with a time-division system. 
         [0007]    As a technology for achieving a data rate higher than that of existing WiGig (hereinafter referred to as legacy WiGig) devices, a technology called NG60 (next-generation 60 GHz) WiGig (hereinafter referred to as NG60_WiGig) is being developed. In order for NG60_WiGig to achieve PHY data rates of up to several tens of Gbps, a technology for supporting MIMO (multiple input, multiple output) transmission and a variable channel bandwidth while maintaining downward compatibility with legacy WiGig devices is desirable. 
         [0008]    In an NG60_WiGig network, a PCP/AP based on NG60_WiGig that is a coordinator communication device (hereinafter referred to as an NG60_PCP/AP) can coexist with a neighboring PCP/AP based on legacy WiGig (hereinafter referred to as a legacy PCP/AP) in the same PCP/AP cluster or in a different PCP/AP cluster due to downward compatibility. 
         [0009]    Meanwhile, an ESE based on NG60_WiGig (hereinafter referred to as an NG60_ESE) has a format different from that of an ESE based on legacy WiGig (hereinafter referred to as a legacy ESE), and therefore, a legacy PCP/AP has difficulty in decoding an NG60_ESE transmitted by an NG60_PCP/AP. Because of the difficulty in decoding an NG60_ESE, a legacy PCP/AP has difficulty in obtaining scheduling information included in the NG60_ESE. Accordingly, the legacy PCP/AP has difficulty in rescheduling channel time allocation thereof or performing any other appropriate operations. 
       SUMMARY 
       [0010]    One non-limiting and exemplary embodiment provides a communication method and a communication device for generating an ESE (extended schedule element) for rescheduling channel time allocation or performing any other appropriate operations in an environment in which a communication device based on legacy WiGig and a communication device based on NG60_WiGig coexist. 
         [0011]    In one general aspect, the techniques disclosed here feature a communication method for a coordinator communication device, the communication method including: generating a first scheduling element to be used by at least one first communication device and a second scheduling element to be used by at least one second communication device; and transmitting the first scheduling element and the second scheduling element to the at least one first communication device and to the at least one second communication device. The second scheduling element includes at least one second allocation that indicates a time-frequency resource allocated to the at least one second communication device. The first scheduling element includes at least one first allocation that indicates a time-frequency resource allocated to the at least one first communication device and optionally includes at least one first virtual allocation that is a duplicate of the at least one second allocation. The at least one first communication device performs communication in accordance with a first communication system using a first frequency band. The at least one second communication device performs communication in accordance with the first communication system or a second communication system using a second frequency band that includes the first frequency band. 
         [0012]    According to one aspect of the present disclosure, scheduling information included in an NG60_ESE is duplicated and is included in a legacy ESE to thereby generate an ESE (extended schedule element) for rescheduling channel time allocation or performing any other appropriate operations in an environment in which a communication device based on legacy WiGig and a communication device based on NG60_WiGig coexist. 
         [0013]    It should be noted that general or specific embodiments may be implemented as a system, a method, an integrated circuit, a computer program, a storage medium, or any selective combination thereof. 
         [0014]    Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a diagram illustrating an example of PCP/AP clustering based on legacy WiGig; 
           [0016]      FIG. 2A  is a diagram illustrating example operations in the PCP/AP clustering illustrated in  FIG. 1 ; 
           [0017]      FIG. 2B  is a diagram illustrating an example of a DMG beacon; 
           [0018]      FIG. 3  is a diagram illustrating the format of an ESE based on legacy WiGig; 
           [0019]      FIG. 4  is a diagram illustrating the format of an NG60_ESE described in US Patent Application No. 2014/0177543; 
           [0020]      FIG. 5  is a diagram illustrating an example of PCP/AP clustering according to an embodiment of the present disclosure; 
           [0021]      FIG. 6  is a diagram illustrating a first example of allocations in accordance with an NG60_ESE and a legacy ESE according to an embodiment of the present disclosure; 
           [0022]      FIG. 7A  is a diagram illustrating a second example of allocations in accordance with an NG60_ESE and a legacy ESE according to an embodiment of the present disclosure; 
           [0023]      FIG. 7B  is a diagram illustrating the second example illustrated in  FIG. 7A  in a different form; 
           [0024]      FIG. 8  is a diagram illustrating an example format of an NG60_ESE according to an embodiment of the present disclosure; 
           [0025]      FIG. 9  is a diagram illustrating a third example of allocations in accordance with an NG60_ESE and legacy ESEs according to an embodiment of the present disclosure; 
           [0026]      FIG. 10  is a flowchart illustrating a transmission process for transmitting ESEs by an NG60_PCP/AP according to an embodiment of the present disclosure; 
           [0027]      FIG. 11  is a flowchart illustrating a transmission process for transmitting an ESE by an NG60_STA according to an embodiment of the present disclosure; 
           [0028]      FIG. 12  is a block diagram illustrating an example configuration of an NG60_PCP/AP according to an embodiment of the present disclosure; and 
           [0029]      FIG. 13  is a block diagram illustrating an example configuration of an NG60_STA according to an embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0030]    The present disclosure relates to a communication device and a communication method for generating an ESE (extended schedule element) in an environment in which a communication device based on legacy WiGig and a communication device based on NG60_WiGig coexist. 
         [0031]      FIG. 1  is a diagram illustrating an example of PCP/AP clustering based on legacy WiGig. A PCP/AP cluster  100  includes clustering-capable PCP/APs  102 ,  104 , and  106  that operate on the same channel. In  FIG. 1 , the PCP/AP  102  is an S-PCP/S-AP (synchronization PCP/synchronization AP)  102 , and the PCP/APs  104  and  106  are member PCP/APs  104  and  106  respectively. The PCP/AP cluster  100  includes STAs (not illustrated) that are associated with the PCP/APs. 
         [0032]      FIG. 2A  is a diagram illustrating an example operation of each of the PCP/APs in the PCP/AP clustering illustrated in  FIG. 1 . The PCP/APs  102 ,  104 , and  106  transmit. DMG beacons in accordance with a time-division system.  FIG. 2B  is a diagram illustrating an example structure of a DMG beacon frame. A DMG beacon  1400  includes one MAC header  1410 , at least one non-IE (non-information element)  1411 , at least one IE (information element)  1412 , and an FCS (frame check sequence)  1413 . In the IEEE 802.11ad standard, a plurality of types of IEs are defined, and an IE of any type includes an element ID  1402 , a length  1404 , and a body  1406 . One of the IE types is an ESE (extended schedule element). A DMG beacon includes at least one ESE. The ESE includes scheduling information regarding channel time allocation. 
         [0033]    Note that, in  FIG. 2A , the S-PCP/S-AP  102  performs scheduling in a period from a beacon transmission interval (BTI)  202  to a BTI  204  in which transmission from the S-PCP/S-AP  104  is performed, and the member PCP/AP  104  performs scheduling in a period from the BTI  204  to a BTI  206  in which transmission from the member PCP/AP  106  is performed. 
         [0034]    The S-PCP/S-AP  102  transmits DMG beacons during the period of the BTI (beacon transmission interval)  202  within a beacon interval  220 . The member PCP/APs  104  and  106  receive, during the period of an Rx (reception interval)  212  (a standby state), the DMG beacons transmitted by the S-PCP/S-AP  102  during the period of the BTI  202 . 
         [0035]    The member PCP/AP  104  transmits DMG beacons during the period of the BTI  204 , which is a period a predetermined time interval (indicated by “Cluster Time Offset (n=2)”) after the Rx  212 . The PCP/AP  106  transmits DMG beacons during the period of the STI  206 , which is a period a predetermined time interval (indicated by “Cluster Time Offset (n=3)”) after the Rx  212 . 
         [0036]    As illustrated in  FIG. 2A , in the PCP/AP clustering, different offsets from the time point of the start of DMG beacon transmission from the PCP/AP  102  are allocated to the respective PCP/APs. Accordingly, the PCP/APs can start transmitting their DMG beacons on the basis of the allocated offsets respectively. 
         [0037]    The member PCP/APs  104  and  106  can directly receive a DMG beacon from the S-PCP/S-AP  102 , and therefore, can receive an ESE from the S-PCP/S-AP  102 . 
         [0038]    A member PCP/AP (for example, the member PCP/AP  106 ) has difficulty in directly receiving a DMG beacon transmitted from another member PCP/AP (for example, the PCP/AP  104 ) but can receive an ESE via an STA associated therewith. Specifically, an STA associated with the member PCP/AP  106  receives a DMG beacon including an ESE from the member PCP/AP  104  and transmits one or more frames that include the received ESE to the member PCP/AP  106 . 
         [0039]    Further, a PCP/AP that belongs to the PCP/AP cluster  100  directly receives an ESE from a clustering-capable PCP/AP that does not belong to the PCP/AP cluster  100  or receives such an ESE via an STA associated therewith. The PCP/AP, which receives an ESE from another clustering-capable PCP/AP, can reschedule allocation thereof in the beacon interval, change the BTI, change the cluster time offset, or perform other appropriate operations as an attempt to suppress interference with transmission indicated by the received ESE. 
         [0040]    In general, the WiGig technology is used to replace cables in a wired digital interface. For example, the WiGig technology is used to implement a wireless USB (universal serial bus) link for initial synchronization between smartphones or between tablets or a wireless HDMI (high-definition multimedia interface) (registered trademark) link for video streaming. State-of-the-art wired digital interfaces (for example, USB 3.5 and HDMI 1.3) can achieve data rates of up to several tens of Gbps, and therefore, the WiGig technology needs to be evolved so as to match these interfaces. 
         [0041]    As a technology for achieving PHY data rates of up to several tens of Gbps, a technology called NG60 (next-generation 60 GHz) WiGig (hereinafter referred to as NG60_WiGig) is being developed. 
         [0042]    Here, the format of an ESE based on legacy WiGig (that is, a legacy ESE) is different from the format of an NG60_ESE according to the related art. First, the format of a legacy ESE is described. 
         [0043]      FIG. 3  is a diagram illustrating the format of an ESE based on legacy WiGig (that is, a legacy ESE). The format of the legacy ESE includes an element. ID field  302 , a length field  304 , and a plurality of allocation fields  306 . 
         [0044]    The element ID field  302  is a field for uniquely identifying the legacy ESE. The length field  304  is a field for specifying the number of octets of the plurality of allocation fields  306 . 
         [0045]    Each of the allocation fields  306  is a field that indicates scheduling information regarding channel time allocation. The allocation field  306  includes an allocation control field  312 , a BF (beamforming) control field  314 , a source AID (association identifier) field  316 , a destination AID field  318 , an allocation start field  320 , an allocation block duration field  322 , a number-of-blocks field  326 , and an allocation block period field  328 . 
         [0046]    The allocation control field  312  includes an allocation ID field  332 , an allocation type field  334 , a semi-static field  336 , a truncatable field  338 , an extendable field  340 , and other fields. 
         [0047]    The allocation type field  334  indicates whether the channel access mechanism used upon allocation is based on a CBAP (contention-based access period) or an SP (service period). 
         [0048]    The source AID field  316  is a field for specifying an STA that starts channel access when the SP or the CBAP is allocated. Alternatively, the source AID field  316  is set to a broadcast AID in a case of CBAP allocation and if all STAs are allowed to perform transmission when the CBAP is allocated. 
         [0049]    The destination AID field  318  is a field for specifying an STA that is expected to communicate with the source STA upon allocation. Alternatively, the destination AID field  318  is set to a broadcast AID in a case where all STAs are expected to communicate with the source STA upon allocation. 
         [0050]    The allocation ID field  332  is a field for identifying airtime allocation for communication from the source STA specified by the source AID to the STA specified by the destination AID if the allocation ID field  332  is set to a value other than 0. The allocation ID field  332  is set to 0 in the case of CBAP allocation where the broadcast source AID and the broadcast destination AID are used. 
         [0051]    Except for the case of CBAP allocation where the broadcast source AID and the broadcast destination AID are used, a tuple (the source AID, the destination AID, and the allocation ID) is used to uniquely identify the allocation. 
         [0052]    The semi-static field  336  indicates whether the allocation is semi-static. The semi-static allocation is repeated in several beacon intervals for the same duration with the same time offset after an ESE including semi-static allocation has been received last. The truncatable field  338  indicates whether the source STA and the destination STA can request truncation of the SP (service period), and the extendable field  340  indicates whether the source STA and the destination STA can request extension of the SP. 
         [0053]    The allocation start field  320  indicates the timing at which the SP or the CBAP starts. The allocation block duration field  322  indicates the duration of a time block over which the SP or the CBAP is allocated and which does not extend beyond the boundary of the beacon interval. 
         [0054]    The number-of-blocks field  326  includes the number of time blocks that constitute the allocation. The allocation block period field  328  includes a time between the start of one of the two consecutive time blocks that belong to the same allocation and the start of the other. The allocation start field  320 , the allocation block duration field  322 , the number-of-blocks field  326 , and the allocation block period field  328  are used together to specify the position of the allocation in the time domain. 
         [0055]    Next, the format of an NG60_ESE according to the related art is described. 
         [0056]      FIG. 4  is a diagram illustrating the format of an NG60_ESE described in US Patent Application No. 2014/0177543. The format of the NG60_ESE includes an element ID field  402 , a length field  404 , and a plurality of allocation fields  406 . 
         [0057]    The element ID field  402  is a field for uniquely identifying the NG60_ESE. The length field  404  is a field for specifying the number of octets of the plurality of allocation fields  406 . That is, the element ID field  402  and the length field  404  are the same as the element ID field  302  and the length field  304  illustrated in  FIG. 3 . 
         [0058]    Each of the allocation fields  406  is a field that indicates scheduling information regarding channel time allocation. The allocation field  406  includes a bandwidth parameter field  412  and an information field  414 . The bandwidth parameter field  412  indicates the channel bandwidth of the corresponding allocation. The information field  414  includes information, data, or both information and data that are included in the allocation field  306  in the legacy ESE as specified in  FIG. 3 . 
         [0059]    That is, the format of the NG60_ESE illustrated in  FIG. 4  includes the bandwidth parameter field  412 , which is a difference from the format of the legacy ESE illustrated in  FIG. 3 . 
         [0060]    As illustrated in  FIG. 3  and  FIG. 4 , the format of the NG60_ESE is different from the format of the legacy ESE. Therefore, a legacy PCP/AP is unable to decode the NG60_ESE and has difficulty in recognizing allocations included in the NG60_ESE. Accordingly, the legacy PCP/AP has difficulty in rescheduling channel time allocation thereof or performing any other appropriate operations. 
         [0061]    In view of such circumstances, the present disclosure is made while focusing on the difference in format between the legacy ESE and the NG60_ESE. 
         [0062]    Hereinafter, an embodiment of the present disclosure is described with reference to the drawings. Note that an embodiment described below is an example, and the present disclosure is not limited by the embodiment. In the following description, detailed description of publicly known functions and structures included herein is omitted in order to provide clear and brief description. 
       Embodiment 
       [0063]      FIG. 5  is a diagram illustrating an example of PCP/AP clustering according to an embodiment of the present disclosure. A PCP/AP cluster  500  includes clustering-capable NG60_PCP/APs  502  and  504  and a clustering-capable legacy PCP/AP  506 . In  FIG. 5 , the NG60_PCP/AP  502  is an S-PCP/S-AP (synchronization PCP/synchronization AP), and the NG60_PCP/AP  504  and the legacy PCP/AP  506  are member PCP/APs. 
         [0064]    The PCP/AP cluster  500  includes STAs  512   a ,  512   b ,  514   a , and  514   b , which are associated with the NG60_PCP/AP  504 . Each of the STAs  512   a ,  512   b ,  514   a , and  514   b  is an STA based on NG60_WiGig (hereinafter referred to as an NG60_STA) or an STA based on legacy WiGig (hereinafter referred to as a legacy STA). 
         [0065]    The legacy PCP/AP  506  transmits a beacon including a legacy ESE. The NG60_PCP/APs  502  and  504  transmit a DMG beacon including both an NG60_ESE and a legacy ESE. 
         [0066]    The legacy ESE is used to specify allocations for transmission related to a legacy STA. That is, in a case of an allocation in the legacy ESE, at least one of the source AID and the destination AID indicates a legacy STA. In other words, at least the other of the source AID and the destination AID may indicate an NG60_STA. This is because an NG60_STA has downward compatibility. 
         [0067]    The NG60_ESE is used to define allocations for transmission related to an NG60_STA. That is, in a case of an allocation in the NG60_ESE, both the source AID and the destination AID respectively indicate NG60_STAs. 
         [0068]    In a case where no legacy STA is associated with the NG60_PCP/APs  502  and  504  that transmit DMG beacons, an allocation in which at least one of the source AID and the destination AID is a broadcast AID may be defined in the NG60_ESE. Otherwise, such an allocation may be specified in the legacy ESE. 
         [0069]    An allocation defined in the legacy ESE corresponds to transmission on a single channel bandwidth of 2.16 GHz. On the other hand, an allocation specified in the NG60_ESE corresponds to transmission on a variable channel bandwidth (for example, 2.16 GHz, 4.32 GHz, 6.48 GHz, or 8.64 GHz). 
         [0070]    As described above, an allocation for transmission related to an NG60_STA can be included in both a legacy ESE and an NG60_ESE. Therefore, after an NG60_STA associated with an NG60_PCP/AP has received a DMG beacon including an NG60_ESE and a legacy ESE from the NG60_PCP/AP, the NG60_STA usually needs to analyze both the NG60_ESE and the legacy ESE in order to recognize allocations for transmission related thereto. An NG60_PCP/AP according to the present disclosure transmits an NG60_ESE so as to allow an NG60_STA to recognize allocations for transmission related thereto by analyzing the NG60_ESE. 
         [0071]    Specifically, an NG60_PCP/AP generates a duplicate of some of the allocations in a legacy ESE for transmission related to both an NG60_STA and a legacy STA and includes the duplicate in an NG60_ESE. 
         [0072]    Now, allocations in an NG60_ESE and in a legacy ESE according to this embodiment are described with reference to the drawings.  FIG. 6  is a diagram illustrating a first example of allocations in an NG60_ESE  622  and in a legacy ESE  624  according to an embodiment of the present disclosure.  FIG. 6  illustrates scheduling information regarding channel time allocation indicated by the allocation fields included in the NG60_ESE (that is, time-frequency resources) and time-frequency resources indicated by the allocation fields included in the legacy ESE. In  FIG. 6 , the vertical axis related to the allocations in the NG60_ESE  622  and the vertical axis related to the allocations in the legacy ESE  624  represent a frequency on the same scale, and the horizontal axis related to the allocations in the NG60_ESE  622  and the horizontal axis related to the allocations in the legacy ESE  624  represent time on the same scale. 
         [0073]    The allocations in the legacy ESE  624  in  FIG. 6  include allocations  616  and  618 , which are real allocations. The allocation  616  includes information regarding a communication device based on legacy WiGig (for example, a legacy STA), and the allocation  618  includes information regarding a communication device based on NG60_WiGig (for example, an NG60_STA). 
         [0074]    The allocations in the NG60_ESE  622  in  FIG. 6  include allocations  602 ,  604 ,  606 , and  608 . The allocations  602 ,  604 , and  606  are real allocations, and the allocation  608  is a virtual allocation. Each of the real allocations indicates a time-frequency resource used in actual communication by one of the NG60_STAs that receive the NG60_ESE. The virtual allocation indicates a time-frequency resource that is not used in actual communication by any NG60_STA that receives the NG60_ESE but is being used by another device (for example, a legacy STA). 
         [0075]    NG60_WiGig supports communication using a variable channel bandwidth, and therefore, the allocation  602  in the NG60_ESE  622  has a channel bandwidth different from that of the allocations  604  and  606 . On the other hand, the allocation  616  and the allocation  618  in the legacy ESE  624  have a channel bandwidth of 2.16 GHz. 
         [0076]    The virtual allocation  608  is obtained by using and duplicating the allocation  618  among the allocations in the legacy ESE  624 . 
         [0077]    The NG60_ESE illustrated in  FIG. 6  includes all allocations for transmission related to an NG60_STA. As a result, after an NG60_STA associated with the NG60_PCP/AP  502  or  504  has received a DMG beacon including the NG60_ESE and the legacy ESE from the NG60_PCP/AP  502  or  504 , the NG60_STA need not analyze both the NG60_ESE and the legacy ESE and needs to analyze the NG60_ESE. Accordingly, the NG60_STA can reduce power consumption. 
         [0078]    Further, in the present disclosure, an SPSH (spatial sharing) mechanism can be employed in order to maximize the performance of a BSS. With the SPSH mechanism, two or more SP allocations that belong to different STAs in the same spatial vicinity can be simultaneously scheduled on the same channel. In this case, the two or more SP allocations under SPSH may partially or completely overlap in the time domain. 
         [0079]    For example, as illustrated in  FIG. 5  and  FIG. 6 , the allocation  604  in the NG60_ESE  622  is an allocation for communication between the STA  512   a  and the STA  512   b , and the allocation  606  in the NG60_ESE  622  is an allocation for communication between the STA  514   a  and the STA  514   b . Regarding the allocations under SPSH, the allocations  604  and  606  partially overlap in the time domain. 
         [0080]    In the above description, the configuration in which an NG60_PCP/AP creates a duplicate allocation (virtual allocation) also in an NG60_ESE from a real allocation in a legacy ESE is described. Now, a configuration in which an NG60_PCP/AP creates a duplicate allocation (virtual allocation) also in a legacy ESE from a real allocation in an NG60_ESE is described. 
         [0081]      FIG. 7A  is a diagram illustrating a second example of allocations in accordance with an NG60_ESE and a legacy ESE according to an embodiment of the present disclosure.  FIG. 7B  is a diagram illustrating the second example illustrated in  FIG. 7A  in a different form. In  FIG. 7A  and  FIG. 7B , the vertical axis related to the allocations in an NG60_ESE  722  and the vertical axis related to the allocations in a legacy ESE  724  represent a frequency on the same scale, and the horizontal axis related to the allocations in the NG60_ESE  722  and the horizontal axis related to the allocations in the legacy ESE  724  represent time on the same scale. Further, the allocations in the NG60_ESE  722  are the same as the allocations in the NG60_ESE  622  illustrated in  FIG. 6 . 
         [0082]    A virtual allocation  712  in the legacy ESE  724  is a virtual allocation corresponding to a single real allocation  702  in the NG60_ESE  722 , and a virtual allocation  714  is a virtual allocation corresponding to two real allocations  704  and  706  under SPSH. 
         [0083]    Note that the virtual allocation  712  indicates a frequency bandwidth different from that of the real allocation  702 . This is because an NG60_ESE has the bandwidth parameter field while a legacy ESE does not have the bandwidth parameter field. However, a legacy STA or a legacy PCP/AP can reschedule channel time allocation for suppressing interference or perform any other appropriate operations as long as the legacy STA or the legacy PCP/AP can recognize the time width of the real allocation  702  in the NG60_ESE. Therefore, the virtual allocation  712  in the legacy ESE indicates the time width of the allocation  702  without using the bandwidth parameter field so that the time width of the real allocation  702  can be recognized upon decoding the legacy ESE. 
         [0084]    According to the structure of the legacy ESE illustrated in  FIG. 7A  and  FIG. 7B , a legacy STA or a legacy PCP/AP that has difficulty in decoding an NG60_ESE decodes a legacy ESE to thereby recognize a virtual allocation corresponding to a real allocation in the NG60_ESE. Accordingly, the legacy STA or the legacy PCP/AP can reschedule channel time allocation or perform any other appropriate operations. 
         [0085]    According to the structure of the legacy ESE illustrated in  FIG. 7A  and  FIG. 7B , a single virtual allocation (for example, the virtual allocation  714 ) is created from a plurality of real allocations (for example, the allocation  704  and the allocation  706 ). Accordingly, unlike in the case of creating a virtual allocation from a single real allocation, system overhead involved can be decreased. 
         [0086]    A virtual allocation (for example, the virtual allocation  714 ) in the legacy ESE completely overlaps corresponding real allocations (for example, the allocation  704  and the allocation  706 ) in the NG60_ESE in the time domain. That is, the virtual allocation  714  in the legacy ESE and the corresponding real allocations  704  and  706  in the NG60_ESE have the same allocation start timing and at least have the same overall allocation duration. 
         [0087]    A method for creating a virtual allocation (for example, the virtual allocation  712 ) in the legacy ESE from a single real allocation (for example, the allocation  702 ) in the NG60_ESE is performed such that information fields in the allocation field of the virtual allocation  712  that are related to the timing of allocation (that is, the allocation start field, the allocation block duration field, the number-of-blocks field, and the allocation block period field) are the same as those of the corresponding real allocation  702 . Accordingly, the virtual allocation  712  completely overlaps the corresponding real allocation  702  in the time domain. 
         [0088]    In the case of creating a virtual allocation (for example, the virtual allocation  714 ) in the legacy ESE from a plurality of real allocations (for example, the allocations  704  and  706 ) in the NG60_ESE, information fields of the virtual allocation  714  that are related to the timing of allocation (that is, the allocation start field, the allocation block duration field, the number-of-blocks field, and the allocation block period field) are appropriately adapted on the basis of the information fields of the corresponding real allocations  704  and  706  by performing any of the first to third methods, for example, described below. The allocation start field of the virtual allocation  714  is set to the same value as that of an allocation that starts earliest (for example, the allocation  704 ) among the plurality of corresponding real allocations. 
         [0089]    In the first method, two fields among the allocation block duration field, the number-of-blocks field, and the allocation block period field of the virtual allocation  714  are respectively set to the same values as those of the real allocation  704 . The remaining field is appropriately set so that the overall allocation duration of the corresponding real allocations  704  and  706  is completely covered. 
         [0090]    In the second method, any one of the allocation block duration field, the number-of-blocks field, and the allocation block period field of the virtual allocation  714  is set to the same value as that of the real allocation  704 . The remaining two fields are appropriately set so that the overall allocation duration of the corresponding real allocations  704  and  706  is completely covered. 
         [0091]    In the third method, all of the allocation block duration field, the number-of-blocks field, and the allocation block period field of the virtual allocation  714  are appropriately set so that the overall allocation duration of the corresponding real allocations  704  and  706  is completely covered. 
         [0092]    In the case of creating a virtual allocation in a legacy ESE from one or more real allocations in an NG60_ESE, one of or both the information fields (that is, the source AID and the destination AID) of the virtual allocation that are related to identification information regarding the allocation may be set to specific values that uniquely indicate the virtual allocation. In this case, an NG60_STA or an NG60_PCP/AP can easily identify the virtual allocation in the received legacy ESE. 
         [0093]    Note that an NG60_PCP/AP need not create, for each real allocation in an NG60_ESE, a corresponding virtual allocation in a legacy ESE. For example, an NG60_PCP/AP may disable, for a real allocation, in an NG60_ESE, that is not semi-static, creation of a corresponding virtual allocation in a legacy ESE. Determination as to whether a real allocation is semi-static is performed on the basis of the semi-static field included in the allocation field. With such a method, extra system overhead involved can be reduced. 
         [0094]    Further, in a case where an NG60_PCP/AP recognizes that a neighboring BSS includes no legacy PCP/AP or legacy STA, the NG60_PCP/AP may disable creation of a virtual allocation in a legacy ESE. With such a method, extra system overhead involved can be reduced. 
         [0095]    Further, the allocations in the NG60_ESE  722  illustrated in  FIG. 7A  and  FIG. 7B  include a virtual allocation  708 , which corresponds to an allocation  718  in the legacy ESE  724 . However, the allocations in an NG60_ESE according to the present disclosure need not include a virtual allocation that corresponds to an allocation in a legacy ESE. 
         [0096]    Now, the format of an NG60_ESE according to this embodiment is described. 
         [0097]      FIG. 8  is a diagram illustrating an example format of an NG60_ESE according to an embodiment of the present disclosure. The format of the NG60_ESE illustrated in  FIG. 8  includes an element ID field  802 , a length field  804 , and a plurality of allocation fields  806 . Each of the allocation fields  806  includes a bandwidth parameter field  812 , a virtual allocation indication field  814 , and an information field  816 . The element ID field  802  and the length field  804  are the same as the element ID field  402  and the length field  404  illustrated in  FIG. 4 . 
         [0098]    The bandwidth parameter field  812  indicates the channel bandwidth of the corresponding allocation. The virtual allocation indication field  814  indicates whether a virtual allocation corresponding to the allocation is present in a legacy ESE. The information field  816  includes any information, data, or both information and data that are included in the allocation field in the legacy ESE as specified in  FIG. 3 . 
         [0099]    The virtual allocation indication field  814  is used to identify the channel bandwidth of the allocation in a case where an NG60_STA needs to analyze both an NG60_ESE and a legacy ESE. For example, an NG60_STA checks whether the allocation ID of an allocation included in the legacy ESE matches the allocation ID of an allocation included in the NG60_ESE and checks a flag (the presence or absence of a virtual allocation) of the virtual allocation indication field  814  to thereby identify the channel bandwidth. Accordingly, the NG60_STA need not analyze the other fields of the NG60_ESE. 
         [0100]    In this embodiment, as a method for including (encapsulating) in a legacy ESE a virtual allocation corresponding to a real allocation in an NG60_ESE, the following methods can be employed. 
         [0101]    In a first method, a virtual allocation created from a real allocation in an NG60_ESE as well as a real allocation is encapsulated in a legacy ESE. For example, as illustrated in  FIG. 7A  and  FIG. 7B , the legacy ESE includes the virtual allocations  712  and  714  as well as a real allocation  716  and the real allocation  718 . 
         [0102]    In a second method, a virtual allocation created from a real allocation in an NG60_ESE is encapsulated in a virtual-allocation-only legacy ESE. The second method is described with reference to the drawings. 
         [0103]      FIG. 9  is a diagram illustrating a third example of allocations in accordance with an NG60_ESE and legacy ESEs according to an embodiment of the present disclosure. In  FIG. 9 , the allocations in an NG60_ESE  922  are the same as the allocations in the NG60_ESE  622  illustrated in  FIG. 6 . 
         [0104]    In  FIG. 9 , allocations  916  and  918  are real allocations. A virtual allocation  912  is a virtual allocation corresponding to a single real allocation  902  in the NG60_ESE  922 , and a virtual allocation  914  is a virtual allocation corresponding to two real allocations  904  and  906 . 
         [0105]    As illustrated in  FIG. 9 , a legacy ESE  924  includes the real allocations  916  and  918 . On the other hand, a legacy ESE  926  serves as a virtual-allocation-only legacy ESE and includes the virtual allocations  912  and  914 . 
         [0106]    The number of legacy ESEs is smaller in the first method when compared with that in the second method. However, in the second method, processing by a receiver in an NG60_STA is simplified, which is described below. 
         [0107]    Now, description is given of operations of a legacy PCP/AP, those of a legacy STA, those of an NG60_PCP/AP, and those of an NG60_STA according to this embodiment described above. 
         [0108]    When a legacy PCP/AP ( 506 , for example) receives a DMG beacon including an NG60_ESE and a legacy ESE directly from an NG60_PCP/AP ( 504 , for example), the legacy PCP/AP  506  analyzes the received legacy ESE. Virtual allocations in the received legacy ESE completely overlap real allocations in the received NG60_ESE respectively corresponding to the virtual allocations in the time domain. Therefore, the legacy PCP/AP  506  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the received NG60_ESE and legacy ESE. 
         [0109]    When a legacy STA receives a DMG beacon including an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ) associated therewith, the legacy STA analyzes the received legacy ESE and checks a tuple (the allocation ID, the source AID, and the destination AID) to thereby identify real allocations. The format of the NG60_ESE is different from the format of the legacy ESE, and therefore, the legacy STA does not decode the received NG60_ESE. 
         [0110]    When a legacy STA associated with a legacy PCP/AP (for example, the legacy PCP/AP  506 ) receives a DMG beacon including an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), the legacy STA simply transmits one or more frames that include the received legacy ESE to the legacy PCP/AP  506 . Virtual allocations in the received legacy ESE completely overlap respective corresponding real allocations in the NG60_ESE in the time domain, and therefore, the legacy PCP/AP  506  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the NG60_ESE and the legacy ESE. 
         [0111]    When a legacy STA associated with an NG60_PCP/AP (for example, the NG60_PCP/AP  502 ) receives a DMG beacon including an NG60_ESE and a legacy ESE from another NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), the legacy STA simply transmits one or more frames that include the received legacy ESE to the NG60_PCP/AP  502 . Virtual allocations in the received legacy ESE completely overlap respective corresponding real allocations in the NG60_ESE in the time domain, and therefore, the NG60_PCP/AP  502  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the NG60_ESE and the legacy ESE. 
         [0112]    When an NG60_PCP/AP (for example, the NG60_PCP/AP  502 ) receives a DMG beacon including an NG60_ESE and a legacy ESE directly from another NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), the NG60_PCP/AP  502  analyzes the received NG60_ESE and legacy ESE. The NG60_PCP/AP  502  needs to identify and ignore virtual allocations in the received legacy ESE. Then, the NG60_PCP/AP  502  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the received NG60_ESE and legacy ESE. 
         [0113]    When an NG60_STA receives a DMG beacon including an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ) associated therewith, the NG60_STA analyzes the received NG60_ESE and identifies real allocations. The NG60_STA needs to identify real allocations by analyzing the received legacy ESE and discard virtual allocations. In a case where virtual allocations are encapsulated in a virtual-allocation-only legacy ESE, the NG60_STA can stop analyzing the virtual-allocation-only legacy ESE upon identifying the virtual allocations in the virtual-allocation-only legacy ESE. 
         [0114]    When an NG60_STA associated with a legacy PCP/AP (for example, the legacy PCP/AP  506 ) receives a DMG beacon including an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), the NG60_STA can transmit one or more frames that include the received legacy ESE to the legacy PCP/AP  506 . Alternatively, the NG60_STA can analyze the received NG60_ESE. Then, the NG60_STA can create, in the received legacy ESE, virtual allocations that correspond to real allocations for which virtual allocations are not present at the discretion thereof and transmit one or more frames that include the received legacy ESE to the legacy PCP/AP  506 . The virtual allocations in the received legacy ESE completely overlap the respective corresponding real allocations in the NG60_ESE in the time domain, and therefore, the legacy PCP/AP  506  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the NG60_ESE and the legacy ESE. 
         [0115]    When an NG60_STA associated with an NG60_PCP/AP (for example, the NG60_PCP/AP  502 ) receives a DMG beacon including an NG60_ESE and a legacy ESE from another NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), the NG60_STA transmits one or more frames that include the received NG60_ESE and legacy ESE to the NG60_PCP/AP  502 . The NG60_PCP/AP  502  needs to identify and ignore virtual allocations in the received legacy ESE. Then, the NG60_PCP/AP  502  can reschedule allocations thereof or perform any other appropriate operations in an attempt to suppress interference with transmission indicated by the NG60_ESE and the legacy ESE. 
         [0116]    In a case of generating a virtual allocation (for example, the virtual allocation  712 ) in a legacy ESE from a single real allocation (for example, the allocation  702 ) in an NG60_ESE, information fields of the virtual allocation  712  other than information fields related to the timing of allocation (that is, the allocation start field, the allocation block duration field, the number-of-blocks field, and the allocation block period field) and identification information regarding the allocation (that is, the source AID and the destination AID) can be set to the same values as those of the corresponding real allocation  702 . As a result, a legacy PCP/AP or an NG60_PCP/AP can use such information to perform determination regarding a method for rescheduling allocations thereof or regarding a method for performing any other appropriate operations in an attempt to mitigate interference with transmission indicated by the NG60_ESE on the basis of the received legacy ESE. 
         [0117]    In a case of generating a virtual allocation (for example, the virtual allocation  714 ) in a legacy ESE from a plurality of real allocations (for example, the allocations  704  and  706 ) in an NG60_ESE, information fields of the virtual allocation  714  other than information fields related to the timing of allocation (that is, the allocation start field, the allocation block duration field, the number-of-blocks field, and the allocation block period field) and identification information regarding the allocation (that is, the source AID and the destination AID) can be set to the same values as those of an allocation (for example, the allocation  704 ) that starts earliest among the plurality of corresponding real allocations. As a result, a legacy PCP/AP or an NG60_PCP/AP can use such information to perform determination regarding a method for rescheduling allocations thereof or regarding a method for performing any other appropriate operations in an attempt to suppress interference with transmission indicated by the NG60_ESE on the basis of the received legacy ESE. 
         [0118]    Now, the configuration and process of an NG60_PCP/AP and those of an NG60_STA according to this embodiment are described with reference to the drawings. 
         [0119]      FIG. 10  is a flowchart illustrating a transmission process  1000  for transmitting ESEs by an NG60_PCP/AP according to an embodiment of the present disclosure. 
         [0120]    The transmission process  1000  performed by an NG60_PCP/AP starts at step S 1002 . In step S 1004 , an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ) defines real allocations in an NG60_ESE and in a legacy ESE. Specifically, the NG60_PCP/AP determines time-frequency resources to be allocated to an STA that is associated therewith and generates an NG60_ESE or a legacy ESE by using the determined resources as real allocations. 
         [0121]    In step S 1006 , the NG60_PCP/AP  504  creates, in the legacy ESE, virtual allocations that correspond to the real allocations in the NG60_ESE at the discretion thereof by performing any of the first to third methods, for example, described above. In step S 1008 , the NG60_PCP/AP  504  transmits a DMG beacon that includes the legacy ESE and the NG60_ESE. At step S 1010 , the process  1000  ends. 
         [0122]      FIG. 11  is a flowchart illustrating a transmission process  1100  for transmitting an ESE by an NG60_STA according to an embodiment of the present disclosure. 
         [0123]    The transmission process  1100  for transmitting scheduling information by an NG60_STA starts at step S 1102 . In step S 1104 , an NG60_STA associated with a legacy PCP/AP (for example, the legacy PCP/AP  506 ) receives a DMG beacon that includes an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ). 
         [0124]    In step S 1106 , the NG60_STA creates, in the received legacy ESE, virtual allocations that correspond to real allocations in the received NG60_ESE at the discretion thereof by performing any of the first to third methods, for example, described above. In step S 1108 , the NG60_STA transmits one or more frames that include the received legacy ESE to the legacy PCP/AP  506 . At step S 1110 , the process  1100  ends. 
         [0125]      FIG. 12  is a block diagram illustrating an example configuration of an NG60_PCP/AP according to an embodiment of the present disclosure. 
         [0126]    The NG60_PCP/AP illustrated in  FIG. 12  includes a controller  1202 , a scheduler  1204 , a message processor  1206 , a message generator  1208 , a PHY processor  1210 , and a plurality of antennas  1212 . 
         [0127]    The controller  1202  is a MAC protocol controller and controls general MAC protocol operations. 
         [0128]    The scheduler  1204  schedules channel time allocation in accordance with control by the controller  1202 . 
         [0129]    The message generator  1208  receives scheduling information from the scheduler  1204  and generates a corresponding control message, such as a DMG beacon, a data message, or a management message. 
         [0130]    The PHY processor  1210  performs a PHY process, such as modulation, on transmission data, namely, the corresponding control message, such as a DMG beacon that includes a legacy ESE and an NG60_ESE, the data message, the management message, or other messages. The plurality of antennas  1212  transmit the transmission data, which has been subjected to the PHY process. 
         [0131]    The antennas  1212  receive reception data, and the PHY processor  1210  performs a PHY process, such as demodulation, on the reception data. 
         [0132]    The message processor  1206  analyzes and provides, to the controller  1202 , received messages. The received messages include a DMG beacon. The DMG beacon includes an NG60_ESE and a legacy ESE, and the legacy ESE includes virtual allocations that correspond to real allocations in the NG60_ESE. 
         [0133]    The NG60_PCP/AP illustrated in  FIG. 12  performs the transmission process  1000  illustrated in  FIG. 10  as follows. 
         [0134]    The scheduler  1204  defines real allocations in an NG60_ESE and in a legacy ESE as scheduling. Specifically, the scheduler  1204  determines time-frequency resources to be allocated to an STA that is associated therewith and generates an NG60_ESE or a legacy ESE by using the determined resources as real allocations. 
         [0135]    The message generator  1208  receives information regarding the real allocations (that is, information regarding the determined resources) from the scheduler  1204  and creates, in the legacy ESE, virtual allocations that correspond to the real allocations in the NG60_ESE. The legacy ESE, which includes the virtual allocations, as well as the NG60_ESE is included in a DMG beacon. 
         [0136]    The PHY processor  1210  performs a PHY process, such as modulation, on the DMG beacon, which includes the legacy ESE and the NG60_ESE. The plurality of antennas  1212  transmit transmission data that has been subjected to a PHY process. 
         [0137]      FIG. 13  is a diagram illustrating an example configuration of an NG60_STA according to an embodiment of the present disclosure. The NG60_STA illustrated in  FIG. 13  includes a controller  1302 , a message generator  1304 , a message processor  1306 , a PHY processor  1308 , and a plurality of antennas  1310 . 
         [0138]    The controller  1302  is a MAC protocol controller and controls general MAC protocol operations. 
         [0139]    The message generator  1304  generates a control message, a data message or a management message in accordance with control by the controller  1302 . 
         [0140]    A message generated by the message generator  1304  includes frames that include an NG60_ESE and a legacy ESE received from an NG60_PCP/AP. The NG60_STA generates, in the legacy ESE, virtual allocations that correspond to real allocations in the received NG60_ESE. 
         [0141]    The PHY processor  1308  performs a PHY process, such as modulation, on the message generated by the message generator  1304 . The antennas  1310  transmit transmission data that has been subjected to a PHY process. 
         [0142]    The antennas  1310  receive reception data, and the PHY processor  1308  performs a PHY process, such as demodulation, on the reception data. 
         [0143]    The message processor  1306  analyzes and provides, to the controller  1302 , a received control message, data message, or management message in accordance with control by the controller  1302 . 
         [0144]    The NG60_STA illustrated in  FIG. 13  performs the process  1100  illustrated in  FIG. 11  as follows. 
         [0145]    The antennas  1310  receive a DMG beacon that includes an NG60_ESE and a legacy ESE from an NG60_PCP/AP (for example, the NG60_PCP/AP  504 ), and the PHY processor  1308  performs a PHY process, such as demodulation, on the received beacon. The message processor  1306  analyzes and provides, to the controller  1302 , the NG60_ESE and the legacy ESE. 
         [0146]    The message generator  1304  generates, in the received legacy ESE, virtual allocations that correspond to real allocations in the received NG60_ESE. The generated legacy ESE and the received NG60_ESE are subjected to a PHY process, such as modulation, by the PHY processor  1308 , and thereafter, are transmitted via the antennas  1310 . 
         [0147]    Note that the configurations illustrated in  FIG. 12  and  FIG. 13  can be implemented by using hardware, such as an LSI circuit. The method for circuit integration is not limited to LSI, and a dedicated circuit or a general-purpose processor may be used for circuit integration. An FPGA (field-programmable gate array), which is programmable after LSI manufacture, or a reconfigurable processor, which allows reconfiguration of connections or settings of circuit cells inside the LSI circuit, may be used. 
         [0148]    In the above-described embodiment, the example case of configuring the present disclosure by using hardware is described; however, the present disclosure can be implemented by using software. 
         [0149]    According to this embodiment described above, a legacy STA or a legacy PCP/AP that has difficulty in decoding an NG60_ESE decodes a legacy ESE to thereby recognize virtual allocations that correspond to real allocations in the NG60_ESE. Accordingly, the legacy STA or the legacy PCP/AP can reschedule channel time allocation or perform any other appropriate operations. 
         [0150]    The communication method and the communication device according to the present disclosure are desirably used in communication over a millimeter-wave network.