Cross-reference to Related Applications

[0001] The present application claims the benefit of the Singapore patent application 201109056-0 filed on 7 December 2011, the entire contents of which are incorporated herein by reference for all purposes.

Technical Field

[0002] Embodiments relate generally to spatial reuse in a communication system. Specifically, embodiments relate to an interference determination device and method for spatial reuse in a directional communication in a communication system.

Background

[0003] Numerous standardized technologies, including the IEEE 802.1 lad draft in progress, the standardized IEEE 802.15.3c and the standardized ECMA-387, are targeting at a Gigabit short range communication system. Recently, China Wireless Personal Area Network (CWPAN) working group under National Information Technology Standardization (NITS) has also worked on the technical solutions based on the recently released mm- Wave bands in China.

[0004] As the path loss can be very significant in this millimeter wave transmission, using directional antenna is critical for this type of communication system to get enough link budgets and achieve a suitable communication range. Furthermore, the directional transmission also leads to a possibility of achieving spatial sharing among devices in the network, and thereby increasing the network throughput significantly. For example, Fig. 1 shows a plurality of radio communication devices 102, 104, 106, 108 in a communication network 100. The first radio communication device 102 is in directional communication 1 10 with the second radio communication device 104, and the third radio communication device 106 is in directional communication 1 12 with the fourth radio communication device 108. It is needed to determine whether the directional transmission 110, 112 between the two pairs of radio communication devices interfere with each other in order to achieve spatial sharing among these devices.

[0005] There are many challenges for the medium access control (MAC) to deal with, for example, device discovery and beamforming training where the devices need to find the direction for communication among devices, contention based access scheme in the presence of directionality and how to exploit the spatial and frequency reuse in face of directional communication.

[0006] "Device" is widely used to describe a node in a network. In IEEE 802.1 1 ad network, "station (STA)" is usually used to describe a node in IEEE 802.11 network. In this context, "device" is used for a general description for a network and "STA" is used for IEEE 802.11 ad network.

[0007] In the draft specification of IEEE 802.1 lad, beamforming is a mechanism that is used by a pair of STAs to achieve the necessary directional transmission link budget. Beamforming training is a bidirectional sequence of beamforming training frame transmission that provides the necessary signalling to allow each STA to determine appropriate antenna system settings for both transmission and reception. After the successful completion of beamforming training, beamforming is said to be established.

[0008] There are two phases for the beamforming training described in IEEE 802.1 lad draft specification: Sector level sweep (SLS) and Beam Refinement Protocol (BRP).

[0009] Fig. 2 shows a diagram 200 illustrating an example of sector level sweep (SLS) beamforming training used in IEEE 802.1 lad. In particular, Fig. 2 shows an example of transmit sector sweeps (TXSS) and receive sector sweeps (RXSS) utilized for simple beamforming training. The purpose of the SLS is to enable communications between two participating STAs at a low rate transmission. Normally, the SLS phase provides only transmit beamforming training, as indicated as TX sector sweeps in Fig. 2. If one of the participating STAs chooses to use only one transmit antenna pattern, receive training may be performed as part of the SLS as indicated as RX sector sweeps in Fig. 2. The purpose of the BRP phase is to enable receiver training and enable iterative refinement of the antenna weight vector of both transmitter and receiver at both participating STAs.

[0010] In the TX sector sweep, the PBSS (Personal Basic Service Set) Control Point (PCP), which is the controller of the network, sends the beamforming training frame to STA in different directions and receives feedback from the receiving STA on the best direction for communicating with the STA. To make it concise in this context, sector ID is used to refer to the best transmission direction for the transmitting STA to receiving STA. [0011] Similarly, in the RX sector sweep, the transmitting STA transmits in an omnidirectional manner, and the receiving STA take turn to receive in different directions. The receiving STA knows the best direction, i.e., the best Sector ID, for communicating with the transmitting STA.

[0012] In accordance with the above, beamforming is said to be established with the beamforming training results of the best sector ID for pair of STAs.

[0013] In the draft specification of IEEE 802.1 lad, the strategy of spatial reuse is to perform and report the measurement to assess the possibility to perform spatial sharing and for interference mitigation. Furthermore, it has been proposed in IEEE 802.1 lad that only service period (SP) is considered to be used for spatial reuse.

[0014] In this context, a SP to be assessed for spatial sharing with other scheduled (or existing) SPs or considered to be reallocated in the beacon interval (BI) is hereby termed as a candidate SP. There might be multiple candidate and existing SPs at one time, and a SP may simultaneously assume the role of candidate and existing SP depending upon the context it is used for spatial sharing and interference assessment.

[0015] The assumption of STAs participating in an SP and supporting spatial sharing is that the STAs should perform beamforming training with each other before engaging in such strategy or performing any measurements.

[0016] Fig. 3 shows a diagram 300 illustrating an example of spatial sharing assessment used in IEEE 802.1 lad. In this example, SP1 is the existing SP between STAs A and B and SP2 is the candidate SP between STAs C and D. The PCP/AP (Access Point) transmits a request to STAs C and D to perform measurements for the purpose of spatial sharing in the existing SP1 after the STAs C and D have a beamforming trained with each other. STAs C and D perform measurement during the duration of the existing SP1 which is used for the transmission between STAs A and B. The measurement report is feedback to PCP/AP. Subsequently, PCP/AP requests STAs A and B to perform measurement during the candidate SP (SP2) where STAs C and D is communicating with each other. The corresponding measurement result will be feedback to PCP/AP as well. PCP/AP then decides if there is any interference occurred. If there is no interference or the received SNR is higher than a threshold, PCP/AP may agree to convert the candidate SP (SP2) into existing SP to achieve the spatial sharing with the existing SP (SP 1).

[0017J The above example indicates that the basic idea of the current strategy of spatial reuse used in IEEE 802.1 lad is "try and use", i.e., perform the measurement first and decide if the candidate SP can be converted into existing SP to achieve the spatial reuse. However, from the PCP/AP perspective, it is a sort of blind selection process. When STAs C and D request the resources, there is no priori information for PCP/AP to allocate a suitable SP which can be concurrently used by the pair of STAs for spatial sharing. If PCP/AP blindly selects an existing SP and requests performing measurement and feedback report, then such operation may become intensive when there are many existing SPs and candidate SPs in a network. This may make the PCP/AP inefficient to allocate resources for spatial reuse.

Summary

[0018] Various embodiments provide an interference determination device including a directional communication properties receiver configured to receive directional communication properties of communications between each two of a first radio communication device, a second radio communication device, a third radio communication device, and a fourth radio communication device. The interference determination device may further include an interference determination circuit configured to determine interference between a communication of the first radio communication device with the second radio communication device and a communication of the third radio communication device with the fourth radio communication device based on the received directional communication properties.

[0019] Various embodiments provide an interference determination method. The method may include receiving directional communication properties of communications between each two of a first radio communication device, a second radio communication device, a third radio communication device, and a fourth radio communication device; and determining interference between a communication of the first radio communication device with the second radio communication device and a communication of the third radio communication device with the fourth radio communication device based on the received directional communication properties.

Brief Description of the Drawings

[0020] In the drawings, like reference characters generally refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments are described with reference to the following drawings, in which:

Fig. 1 shows a plurality of radio communication devices in a network. Fig. 2 shows a diagram illustrating an example of sector level sweep (SLS) beamforming training used in IEEE 802.1 1 ad.

Fig. 3 shows a diagram illustrating an example of spatial sharing assessment used in IEEE 802.11 ad..

Fig. 4 shows an interference determination device according to an embodiment.

Fig. 5 shows a flowchart illustrating an interference determination method according to an embodiment.

Fig. 6 shows an example of a network with directional transmission.

Fig. 7 shows a flowchart illustrating a method of initial assessment for spatial sharing according to an embodiment.

Fig. 8 shows a flowchart illustrating a method of initial assessment for spatial sharing for IEEE 802.11 ad network according to an embodiment.

Fig. 9 shows a network according to an embodiment, wherein a pair of radio communication devices requests allocating of a timing schedule for communication.

Fig. 10 shows a network with directional transmission according to another embodiment.

Description

[0021) Various embodiments provide a solution to achieve spatial reuse in a directional transmission in a communication system, such as short range indoor high data rate communication networks, e.g., 60GHz millimeter wave Gigabit communication systems. [0022] Various embodiments are directed to a method providing initial assessment that enables the intended transmission pair between source and destination devices to concurrently transmit directionally with another existing directional transmission among a pair of devices for spatial sharing. Various embodiments are also applicable to scenario where the existing pair of devices use scheduled slots or contention based slots for its directional transmission. Various embodiments can avoid performing unnecessary measurement and feedback report for those STAs that may cause interference with each other, thereby, improving the allocation efficiency of PCP/AP for spatial sharing with the existing SPs.

[0023] It is important to assess if two concurrent directional transmissions are interfering with each other based on the information of beamforming training results. According to various embodiment, a method and a device provide an initial assessment that enables the two concurrent directional transmissions for spatial sharing..

[0024] In this context, an interference determination device as described in this description may include a memory which is for example used in the processing carried out by the interference determination device. A memory used in the embodiments may be a volatile memory, for example a DRAM (Dynamic Random Access Memory) or a non-volatile memory, for example a PROM (Programmable Read Only Memory), an EPROM (Erasable PROM), EEPROM (Electrically Erasable PROM), or a flash memory, e.g., a floating gate memory, a charge trapping memory, an MRAM (Magnetoresistive Random Access Memory) or a PCRAM (Phase Change Random Access Memory). [0025] In this context, an interference determination device as described in this description may be or may include one or more circuits for carrying out the respective determination.

[0026] In an embodiment, a "circuit" may be understood as any kind of a logic implementing entity, which may be special purpose circuitry or a processor executing software stored in a memory, firmware, or any combination thereof. Thus, in an embodiment, a "circuit" may be a hard-wired logic circuit or a programmable logic circuit such as a programmable processor, e.g. a microprocessor (e.g. a Complex Instruction Set Computer (CISC) processor or a Reduced Instruction Set Computer (RISC) processor). A "circuit" may also be a processor executing software, e.g. any kind of computer program, e.g. a computer program using a virtual machine code such as e.g. Java. Any other kind of implementation of the respective functions which will be described in more detail below may also be understood as a "circuit" in accordance with an alternative embodiment.

[0027] Fig. 4 shows an interference determination device according to an embodiment.

[0028] The interference determination device 400 may include a directional communication properties receiver 402 configured to receive directional communication properties of communications between each two of a first radio communication device, a second radio communication device, a third radio communication device, and a fourth radio communication device. The interference determination device 400 may further include an interference determination circuit 404 configured to determine interference between a communication of the first radio communication device with the second radio communication device and a communication of the third radio communication device with the fourth radio communication device based on the received directional communication properties.

[0029] The directional communication properties receiver 402 and the interference determination circuit 404 may be connected through line or cable 406 for communication therebetween.

[0030] In an embodiment, the first radio communication device and the second radio communication device may be configured to communicate during a first pre-determined timing schedule. In the context of various embodiment, the timing schedule may also be referred to a service period (SP).

[0031] In an embodiment, the third radio communication device and the fourth radio communication device may be configured to communicate during a second predetermined timing schedule, and seek to communicate with each other during the first pre-determined timing schedule. Accordingly, the interference determination device 400 may be configured to determine whether the communication of the third radio communication and the fourth radio communication device during the first predetermined timing schedule would interfere with the communication of the first radio communication and the second radio communication device.

[0032] According to an embodiment, the directional communication properties of communications between each two of the radio communication devices may include at least one property selected from a list of properties consisting of: a direction of signal transmission from one of said each two radio communication devices to the other of said each two radio communication devices, and vice versa; and a direction of signal reception of one of said each two radio communication devices from the other of said each two radio communication devices, and vice versa. The direction may be represented by an angle or a range of angles, for example.

[0033] According to another embodiment, the directional communication properties of communications between each two of the radio communication devices may include at least one property selected from a list of properties consisting of: an indication of a sector of a circle for a direction of signal transmission from one of said each two radio communication devices to the other of said each two radio communication devices, and vice versa; and an indication of a sector of a circle for a direction of signal reception of one of said each two radio communication devices from the other of said each two radio communication devices, and vice versa. For example, the circle may be divided into a plurality of sectors, and the indication of a sector may be represented by a number or an ID of the sector.

[0034] According to an embodiment, the directional communication properties of communications between each two of the radio communication devices may be achieved by beamforming. In an embodiment, the directional communication properties may be received as beamforming training results.

[0035] In an embodiment, the first radio communication device and the second radio communication device may be included in a first group, and the third radio communication device and the fourth radio communication device may be included in a second group. The interference determination circuit 404 may be configured to determine the interference based on whether a first directional communication property of communications between the radio communication devices of the first group matches a second directional communication property of communications between a radio communication device of the first group and a radio communication device of the second group.

[0036] According to an embodiment, the interference determination circuit 404 may be configured to determine whether the first directional communication property matches the second directional communication property based on a computation of a difference between an angle represented by the first directional communication property and an angle represented by the second directional communication property.

[0037] In a further embodiment, the difference between an indication of a sector of a circle represented by the first directional communication property and an indication of a sector of a circle represented by the second directional communication property may be used to determine whether the first directional communication property matches the second directional communication property.

[0038] In various embodiments, the matching of the first directional communication property and the second directional communication property may indicate overlapping or superposition between a communication within the first group and a communication between the first group and the second group, and may be used to determine an interference between the two groups.

[0039] In an illustrative embodiment, the first directional communication property may be received for the communication from the first radio communication device to the second communication device in the first group. The second directional communication property may be received for the communication from the first radio communication device of the first group to the third communication device of the second group. In a further embodiment, the second directional communication property may also be received for the communication from the first radio communication device of the first group to the fourth communication device of the second group. In a similar manner, the similar directional communication properties may be received for the communications from the second radio communication device to the radio communication devices of the first group and the second group, and may be used to determine the interference.

[0040] In an illustrative embodiment, a degree of match between the first directional communication property and the second directional communication property may be represented by the minimum difference between the angle/sector of a circle represented by the first directional communication property and the angle/sector of a circle represented by the second directional communication property. In an illustrative example, the angle/sector of a circle represented by the second directional communication property may include more than one angles/sectors of a circle, for example, one being the angle/sector of a circle for the communication from the first radio communication device to the third communication device and the other being the angle/sector of a circle for the communication from the first radio communication device to the fourth communication device. The minimum difference of these two angles/sector of a circle to the angle/sector of a circle represented by the first directional communication property is determined to be the corresponding degree of match.

[0041] In other embodiments, the degree of match may be represented by the average or aggregated difference between the angle/sector of a circle represented by the first directional communication property and the angle/sector of a circle represented by the second directional communication property. [0042] In a further embodiment, in a similar manner to the above embodiments, the interference determination circuit 404 may be further configured to determine the interference based on whether a directional communication property of communications between the radio communication devices of the second group matches a directional communication property of communications between a radio communication device of the first group and a radio communication device of the second group. In an illustrative embodiment, the directional communication property may be received for the communication from the third radio communication device to the fourth communication device in the second group. Another directional communication property may be received for the communication from the third radio communication device of the second group to the first communication device of the first group. In a further embodiment, the another directional communication property may also be received for the communication from the third radio communication device of the second group to the second communication device of the first group. In a similar manner, the similar directional communication properties may be received for the communications from the fourth radio communication device to the radio communication devices of the first group and the second group, and may be used to determine the interference.

[0043] According to a further embodiment, the interference determination circuit 404 may be configured to determine interference between the communication of the third radio communication device with the fourth radio communication device and a communication of a fifth radio communication device with a sixth radio communication device, based on received directional communication properties of communications between each two of the third radio communication device, the fourth radio communication device, the fifth radio communication device, and the sixth radio communication device.

[0044] In this embodiment, the fifth radio communication device and the sixth radio communication device may be configured to communicate during a third pre-determined timing schedule. The third radio communication device and the fourth radio communication device may seek to communicate with each other during the third predetermined timing schedule. Accordingly, the interference determination device 400 may be configured to determine whether the communication of the third radio communication and the fourth radio communication device during the third pre-determined timing schedule would interfere with the communication of the fifth radio communication and the sixth radio communication device.

[0045] According to an embodiment, the fifth radio communication device and the sixth radio communication device may be included in a third group. The interference determination circuit 404 may be configured to determine the interference based on whether a third directional communication property of communications between the radio communication devices of the third group matches a fourth directional communication property of communications between a radio communication device of the second group and a radio communication device of the third group.

[0046] In an illustrative embodiment, the third directional communication property may be received for the communication from the fifth radio communication device to the sixth communication device in the third group. The fourth directional communication property may be received for the communication from the fifth radio communication device of the third group to the third communication device of the second group, and may in a further embodiment be received for the communication from the fifth radio communication device of the third group to the fourth communication device of the second group. In a similar manner, the similar directional communication properties may be received for the communications from the sixth radio communication device of the third group to the radio communication devices of the third group and the second group, and may be used to determine the interference.

[0047] In a further embodiment, in a similar manner to the above embodiments, the interference determination circuit 404 may further be configured to determine the interference based on whether a directional communication property of communications between the radio communication devices of the second group matches a directional communication property of communications between a radio communication device of the third group and a radio communication device of the second group. In an illustrative embodiment, the directional communication property may be received for the communication from the third radio communication device to the fourth communication device in the second group. Another directional communication property may be received for the communication from the third radio communication device of the second group to the fifth communication device of the third group, and may in a further embodiment also be received for the communication from the third radio communication device of the second group to the sixth communication device of the third group. In a similar manner, the similar directional communication properties may be received for the communications from the fourth radio communication device to the radio communication devices of the third group and the second group, and may be used to determine the interference. [0048] According to an embodiment, the interference determination circuit 404 may be configured to determine whether the third directional communication property matches the fourth directional communication property based on a computation of a difference between an angle represented by the third directional communication property and an angle represented by the fourth directional communication property.

[0049) In a further embodiment, the difference between an indication of a sector of a circle represented by the third directional communication property and an indication of a sector of a circle represented by the fourth directional communication property may be used to determine whether the third directional communication property matches the fourth directional communication property.

[0050] In various embodiments, the matching of the third directional communication property and the fourth directional communication property may indicate overlapping or superposition between a communication within the third group and a communication between the third group and the second group, and may be used to determine an interference between the two groups.

[0051] In an embodiment, the interference determination circuit 404 may determine that the communication of the third radio communication device and the fourth radio communication does not interfere with the communication of the first radio communication device and the second radio communication. In other words, the third radio communication device and the fourth radio communication may be configured to communicate during first pre-determined timing schedule configured for the communication between the first radio communication device and the second radio communication. [0052] In another embodiment, the interference determination circuit 404 may determine that the communication of the third radio communication device and the fourth radio communication does not interfere with the communication of the fifth radio communication device and the sixth radio communication. In other words, the third radio communication device and the fourth radio communication may be configured to communicate during third pre-determined timing schedule configured for the communication between the fifth radio communication device and the sixth radio communication.

[0053] In a further embodiment, the interference determination circuit 404 may be further configured to determine whether the third radio communication device and the fourth radio communication device communicate with each other during the third predetermined timing schedule or during a first pre-determined timing schedule configured for communication between the first radio communication device and the second radio communication, based on a comparison of a degree of match between the first directional communication property and the second directional communication property with a degree of match between the third directional communication property and the fourth directional communication property. This may, for example, correspond to a situation that the interference determination circuit 404 determines that the communication of the third radio communication device and the fourth radio communication neither interferes with the communication of the first radio communication device and the second radio communication, nor interferes with the communication of the fifth radio communication device and the sixth radio communication. [0054] In an embodiment, the interference determination circuit 404 may be configured to determine that the third radio communication device and the fourth radio communication device communicate with each other during one of the first and the third timing schedules which corresponds to the lower degree of match between the respective directional communication property.

10055] It is understood that the interference determination circuit 404 may be configured to determine interference for a plurality of combinations of radio communication devices (e.g. more than six radio communication devices) and timing schedules (e.g. more than three timing schedules) in other embodiments.

[0056] In one embodiment, the interface determination device 400 may be configured to be provided in at least one of a personal basis service set control point (PCP) or an access point (AP). In another embodiment, the interference determination device 400 may be or may include a PCP or an AP. In various embodiments described with reference to the figures below, the interference determination device 400 may be referred to as a PCP/AP.

[0057] In an embodiment, at least one of the first radio communication device, the second radio communication device, the third radio communication device, the fourth radio communication device, the fifth radio communication device, and the sixth radio communication device may be configured to be provided in or may include at least one of a personal basis service set control point (PCP) or an access point (AP) or a mobile station (MS) or a station (STA). In various embodiments described with reference to the figures below, the first/second/third/fourth/fifth/sixth radio communication device may be referred to as a device or a STA. [0058] Fig. 5 shows a flowchart 500 illustrating an interference determination method according to an embodiment. The method may include receiving directional communication properties of communications between each two of a first radio communication device, a second radio communication device, a third radio communication device, and a fourth radio communication device at 502; and determining interference between a communication of the first radio communication device with the second radio communication device and a communication of the third radio communication device with the fourth radio communication device based on the received directional communication properties at 504.

[0059] Various embodiments described above in the context of the interference determination device 400 above are analogously valid for the corresponding interference determination method.

[0060] In an embodiment, the first radio communication device and the second radio communication device are configured to communicate during a first pre-determined timing schedule.

[0061] In an embodiment, the third radio communication device and fourth radio communication device are configured to communicate during a second pre-determined timing schedule and seek to communicate with each other during the first pre-determined timing schedule.

[0062] In an embodiment, the directional communication properties of communications between each two of the radio communication devices may include at least one property selected from a list of properties consisting of: a direction of signal transmission from one of said each two radio communication devices to the other of said each two radio communication devices, and vice versa; a direction of signal reception of one of said each two radio communication devices from the other of said each two radio communication devices, and vice versa.

[0063] In another embodiment, the directional communication properties of communications between each two of the radio communication devices may include at least one property selected from a list of properties consisting of: an indication of a sector of a circle for a direction of signal transmission from one of said each two radio communication devices to the other of said each two radio communication devices, and vice versa; an indication of a sector of a circle for a direction of signal reception of one of said each two radio communication devices from the other of said each two radio communication devices, and vice versa.

[0064] According to an embodiment, the first radio communication device and the second radio communication device may be included in a first group, and the third radio communication device and the fourth radio communication device may be included in a second group. The method may further include determining the interference based on whether a first directional communication property of communications between the radio communication devices of the first group matches a second directional communication property of communications between a radio communication device of the first group and a radio communication device of the second group.

[0065] In an embodiment, the method may further include determining whether the first directional communication property matches the second directional communication property based on a computation of a difference between an angle represented by the first directional communication property and an angle represented by the second directional communication property.

[0066] In a further embodiment, the method may include determining interference between the communication of the third radio communication device with the fourth radio communication device and a communication of a fifth radio communication device with a sixth radio communication device based on received directional communication properties of communications between each two of the third radio communication device, the fourth radio communication device, the fifth radio communication device, and the sixth radio communication device. The fifth radio communication device and the sixth radio communication device are configured to communicate during a third predetermined timing schedule, and the third radio communication device and the fourth radio communication device seek to communicate with each other during the third predetermined timing schedule.

[0067] According to an embodiment, the fifth radio communication device and the sixth radio communication device may be included in a third group. The method further includes determining the interference based on whether a third directional communication property of communications between the radio communication devices of the third group matches a fourth directional communication property of communications between a radio communication device of the second group and a radio communication device of the third group.

[0068] The interference determination device and method according to various embodiments may be illustrated in more detail below in illustrative examples. [0069] In the current draft of IEEE 802.1 lad, all STAs are required to perform beamforming training with PCP/AP when they join the network and the trained beamforming results are kept and updated within PCP/AP. However, the beamforming training among non-PCP/AP STAs is only performed prior to their actual transmission. The information related to the trained beamforming results among non-PCP/AP is not be informed or updated to PCP/AP.

[0070) It is in this context assumed that non-PCP/AP STAs will keep PCP/AP be informed and updated of the results of the beamforming training among non-PCP/AP STAs. It can be achieved through the ScS-Feedback or ScS-ACK frames which contain the ScS Feedback fields indicating the beamforming related information, such as Sector Select, DBand Antenna Select and SNR Report, etc., as defined in IEEE 802.1 lad. Therefore, PCP/AP is able to establish a table that includes the beamforming results among any two STAs in the network including PCP/AP and non-PCP/AP STAs, and, non-PCP/AP STA and non-PCP/AP STA.

[0071] Fig. 6 shows a typical example of a network with directional transmission. In Fig. 6, the network 600 includes six devices A, B, C, D, E, and F. In an embodiment, each device may have 12 sectors with each sector having 30 degree transmission angel for directional transmission. The sector numbers, also referred to as sector IDs, are arranged in a clockwise or counter-clockwise from 1 to 12.

[0072] Table 1 shows the beamforming training results among any two devices in a network, in this example, the network 600 of Fig. 6. The first two columns indicate the source and destination devices (a, b). The third column defines the best sector ID among the source and destination devices, referred to as S(a, b). Table 1: Beamforming training results among STAs in a network

[0073] According to various embodiments, a method is provided to assess whether two pair of devices with directional transmission can be used concurrently for spatial reuse, based on the priori information of beamforming training results among devices in a network, e.g. the beamforming training results of Table 1.

[0074] Fig. 7 shows a flowchart 700 illustrating a method of initial assessment for spatial sharing according to an embodiment. [0075] After starting at 702, a table is established at 704 using beamforming training results among any two available devices (source device a and destination device b) within a network, showing the best sector S(a,b) selected by the source device a. In the following illustrative embodiments, Table 1 is established showing the beamforming training results among any two available devices in a network 600 depicted in Fig. 6.

[0076] At 706, the two pairs of devices (A, B) and (C, D) are selected to assess whether they can be used concurrently for spatial reuse.

[0077] Given two pair of devices (A, B) and (C, D) shown in Fig. 6, a temporary Table 2 showing beamforming training results for devices A, B, C and D is established at 708.

Table 2: Beamforming training results among the given device set {A, B, C, D}

[0078] At 710, a parameter δ = min[ |S(a, b) - S(a, c)|, 12 - |S(a, b) - S(a, c)| ] is defined to indicate the sector number difference between the two best sectors S(a, b) and S(a, c) chosen by one source device a to two different destination devices b and c. The typical value of δ varies from 0 to 6. The selection of δ is a factor to determine the level of accuracy of the assessment for the spatial reuse. [0079] At 712, a source device is chosen from the (A, B, C, D), and it is checked for any two destination devices whether the sector number difference δ is equal to zero or not. If it is determined that a value of δ for any two destination devices is equal to zero, the two pair of devices (A, B) and (C, D) are not recommended for spatial sharing at 714.

[0080] For example, for the source device A, the values of δ for {(A, B), (A, C)} and {(A, B), (A, D)} are determined as { 1, 2} . The values of δ for the source device A are not equal to zero, and then it is determined whether all the source devices from the device set (A, B, C, D) have been checked at 716. If not, the process goes back to 712 to perform the similar process of source device A for the situation of selecting the device B, C and D as the source device, respectively.

[0081] In the example based on the beamforming training results of Table, 2, it is determined that the values of δ for {(B, A), (B, C)} and {(B, A), (B, D)} are {2, 1} ; the values of δ for {(C, D), (C, A)} and {(C, D), (C, B)} are {1, 2} ; and the values of δ for {(D, C), (D, A)} and {(D, C), (D, B)} are { 1, 2}, respectively. It is thus determined that all the values of δ are greater than 0, i.e., devices (A, B) and (C, D) may not interfere with each other. Thus it is concluded that devices (A, B) and (C, D) are recommended for spatial sharing in the same SP at 718.

[0082] The above process can also be intuitively understood as the following: as long as any two pair of devices do not fall in the coverage region of the selected sectors at both the source and destination devices of each other, then the pair of devices can be concurrently used for spatial reuse.

[0083] In another situation wherein any two pair of devices satisfies the above concurrent transmission condition (δ≠0) and meanwhile all the values of δ are greater than 1, more space is allowed to avoid the interference among the concurrent directional transmission. Accordingly, the parameter δ may be used as the criteria of the selection for scheduled slots or contention based slots according to an embodiment.

[0084] In another embodiment, the method may be applied for IEEE 802.11 ad network. The PCP/AP, as the network controller, may have the beamforming training results and may use such information as priori information to provide initial recommendation of a suitable SP for the intended transmission pair of STAs to perform measurement and feedback report. This will significantly reduce the operation of measurement and feedback report.

[0085] In this embodiment, a dimension, service period (SP), is introduced into the process. Fig. 8 shows a flowchart 800 illustrating a method of initial assessment for spatial sharing for IEEE 802.1 lad network according to an embodiment. As the PCP/AP receives the reservation request of SP from the intended transmission pair of STAs, it will allocate a candidate SP to this pair of STAs. In the current draft specification of 802.1 lad, it randomly selects an existing SP to perform measurement and feedback report as described above, which may cause inefficient resource allocation and lead to many unnecessary operations of measuring and report. In accordance with various embodiments, a method is provided for PCP/AP to provide an initial recommendation of the suitable existing SP based on priori information of beamforming training results. When the PCP/AP uses the method of various embodiments to search the suitable existing SP for spatial sharing with the candidate SP, it will significantly reduce the operation of performing measurement and feedback report among the existing SP and the candidate SP. The method according to various embodiments eliminates possible collisions among the owner of the candidate SP and the owner of the recommended existing SP.

[0086] After starting at 802, the PCT/AP is configured to process a candidate SP _k and set δ to zero at 804. <5* _k is defined as the smallest value of δ if a SP is chosen for an intended transmission pair of STAs (i, j). In other embodiments, 5* _k may also be defined as the average value or the aggregated value of δ if a SP is chosen for an intended transmission pair of STAs (i, j).

[0087] At 806, for each scheduled transmission pair (x, y) in the candidate SP _k , it is determined whether the best section ID overlaps between the intended transmission pair (i, j) and the scheduled transmission pair (x, y). In particular, it is checked whether S(x, i) == S(x, y) II S(x, j) == S(x, y) \\ S(y, i) == S (y, x) \\ S(y, j) == S(y, x) || S(i, x) = S(i, j) || S(i, y) == S(i, j) II S(j, x) == S j, i) || S(j, y) == S(j, i) is true. If yes, the current candidate SPk cannot be shared by the intended transmission pair of STAs (i, j) and the scheduled transmission pair (x, y), and the process goes back to 804 to process the next candidate SPk-

[0088] If it is determined that there is no interference between the intended transmission pair of STAs (i, j) and the scheduled transmission pair (x, y), the value of the sector number difference δ is calculated at 810.

[0089] At 812, it is checked whether the traverse of the transmission set (x, y) _k in the SP _k is finished. If not, the process goes back to 806 until all the scheduled transmission pairs in SP _k have been processed.

[0090] At 814, SP _k is added into the initial SP candidate set {SP _k } with its corresponding value of <5* _k . [0091] At 816, it is checked whether the traverse of the existing SP set {SP _k } has finished. If not, the process goes back to 804 to process the next candidate SP _k until all the existing SPs have been processed.

[0092] At 818, the best initial SP is searched from {SP _k } based on a selection criteria to select the largest δ , and the process ends at 820.

[0093] The above process is described in more detail below, in an example of a pair of STAs (E, F) requesting for allocation of SP as in Fig. 9.

[0094] Fig. 9 shows a network 600 similar to the network 600 of Fig. 6, wherein the pair of STAs (E, F) requests the PCP/AP to allocate SP. In this exemplary embodiment, the PCP/AP has scheduled SP1 and SP2 for the respective transmission pair (A, B) and (C, D), and has established a table of the beamforming training results between any two of STAs A, B, C, D, E, and F as shown in Table 1 above.

[0095] The procedures of choosing the best initial SP candidate from the allocated SP set {SP1, SP2} for the intended transmission pair (E, F) in accordance with the flowchart of Fig. 8 are illustrated as follows:

[0096] (1) PCP/AP establishes a temporary Table 3 for the STAs (A, B, E, F) to check whether SP1 is available for (E, F), i.e., whether (A, B) and (E, F) can transmit concurrently. From Table 3, it is observed that SP1 has already been occupied by (A, B), where A uses its Sector 1 and B uses its Sector 7, respectively. Now, E intends to use Sector 3 and F intends to use Sector 7, respectively, to communicate with each other.

[0097] Suppose that A is transmitting to B with its best sector 1 after beamforming. The resulted interference to E and F is then evaluated. Neither E nor F would be affected by A, because the beamforming results listed in Table 3 show that the Sector 4 and 2 would be the best sector for A to transmit to E and F, respectively, which are not the same as Sector 1 for A to transmit to B. Moreover, the values of δ for {(A, B), (A, E)} and {(A, B), (A, F)} are calculated as {3, 1 } . Thus, A's transmission has no interference to E and F.

[0098] However, if B is transmitting to A with Sector 7, E would be affected by B because the same Sector 7 is selected for B to transmit to A and E. In this case, δ for {(B, A), (B, E)} is equal to 0.

[0099] Thus, (E, F) does not satisfy with the conditions of spatial sharing with the scheduled SP1.

Table 3: Beamforming training results among the given device set {A, B, E, F}

[00100] (2) Then, PCP/AP checks the SP2.

[00101] In a similar way, PCP/AP establishes another temporary Table 4 for the STAs (C, D, E, F) to check whether SP2 is available for (E, F).

[00102] In this example, for the STA C, S(C, D) = 10 is different from S(C, E) = 8 and S(C, F) = 12. The sector number difference δ for {(C, D), (C, E)} and {(C, D), (C, F)} is given by {2, 2} . For the STA D, S(D, C) = 4 is different from S(D, E) = 5 and S(D, F) = 3. The sector number difference δ for {(D, C), (D, E)} and {(D, C), (D, F)} is given by { 1, 1 } . Moreover, for the STA E, S(E, F) = 3 is different from S(E, C) = 4 and S(E, D) = 1, and 6 for {(E, F), (E, C)} and {(E, F), (E, D)} is given by { 1, 2}. For the STA F, S(F, E) = 7 is different from S(F, C) = 6 and S(F, D) = 9, and 6 for {(F, E), (F, C)} and {(F, E), (F, D)} is given by {1, 2} .

[00103] Therefore, SP2 can be recommended as an initial SP candidate for (E, F).

Table 4: Beamforming training results among the given device set {C, D, E, F}

[00104] (3) Finally, PCP/AP responds to E and F with the best initial SP being the existing SP2.

[00105] Fig. 10 shows a network 1000 having a plurality of STAs. Based on Fig. 10, it is described in the following how to choose the best initial SP candidate for an intended transmission pair if both SPl and SP2 are appropriate candidate SPs according to another embodiment.

[00106] In the embodiment of Fig. 10, each STA may have 24 sectors with each sector having 15 degree transmission angel for directional transmission. Table 5 below shows the beamforming training results for devices {A, B, E, F} in SPl and {C, D, E, F} in SP2. The procedures of choosing the best initial SP candidate for the intended transmission pair (E, F) are described as follows.

Table 5: Beamforming training results for device sets {A, B, E, F} in SPi and

{C, D, E, F} in SP ₂

[00107] (l)Firstly, PCP/AP checks SPI . In accordance with Table 5, (A, B) has no interference with (E, F), as there is no overlap of their best section numbers. In this embodiment, since each STA has 24 sectors, the parameter δ is determined by min[ |S(a, b) - S(a, c)|, 24 - |S(a, b) - S(a, c)| ], to indicate the sector number difference between the two best sectors S(a, b) and S(a, c) chosen by one source device a to two different destination devices b and c. Generally, in other embodiments, if the STA has N sectors, the parameter δ is determined by min[ |S(a, b) - S(a, c)|, N -|S(a, b) - S(a,c)| ] to indicate the sector number difference between the two best sectors S(a, b) and S(a, c).

[00108] According to Table 5, all the values of δ for this device set {A, B, E, F} are greater than 2. In particular, all the values of δ for {(A, B), (A, E)} and {(A, B), (A, F)} ; {(B, A), (B, E)} and {(B, A), (B, F)} ; {(E, F), (E, A)} and {(E, F), (E, B)}; {(F, E), (F, A)} and {(F, E), (F, B)} are 3. Thus, SP1 will be added into the initial SP candidate set for (E, F).

[00109] Define δ* as the smallest value of δ if a SP is chosen for (E, F). Then δ* for SPl is 3.

[00110] Although δ* is illustrated as the smallest value of δ in this embodiment, it is understood that in other embodiments, δ* may also be defined as the average value or the aggregated value of δ if a SP is chosen for the intended transmission pair (E, F). δ* may represent a degree of match among the best section numbers for the device set {A, B, E, F} . A higher value of δ* may represent a lower degree of match among the best section numbers (which may correspond to the directional communication properties described in the above embodiments), and may indicate a lower possibility of interference among the device set {A, B, E, F} .

[00111] (2) Secondly, PCP/AP checks SP2. In accordance with Table 5, SP2 is also competent for spatial reuse with (E, F), since there is no overlap of best section numbers among the device set {C, D, E, F}. All the values of δ for the device set {C, D, E, F}are equal to or greater than 1. In particular, all the values of δ for {(C, D), (C, E)} and {(C, D), (C, F)}; {(D, C), (D, E)} and {(D, C), (D, F)}; {(E, F), (E, C)} and {(E, F), (E, D)} ; and {(F, E), (F, C)} and {(F, E), (F, D)} are either 1 or 5. 5* for SP2 is 1, being the smallest value between 1 and 5.

[00112] Thus, SP2 will also be added into the initial SP candidate set for (E, F).

[00113] (3)Thirdly, PCP/AP chooses the best one from SP candidate set {SPl, SP2}. In an embodiment, the selection criteria is that the SP with the largest value of δ* is the best SP. From (1) and (2), δ* for SP l and SP2 are given by 3 and 1, respectively. Thus, SPl is selected as the best initial SP candidate for (E, F).

[00114] (4) Finally, PCP/AP responds to E and F with the result of the best initial SP being SPl.

[00115] The method described in various embodiments above searches the best existing pair of devices in directional transmission that can share spatially with intended transmission pair of devices in directional transmission with minimum co-channel interference, based on the priori information of trained beamforming results among devices. The following advantageous are achieved by the various embodiments:

[00116] - Accurate allocation of spatial reuse among pairs of devices;

[00117] - Fast allocation of spatial reuse among pairs of devices;

[00118] - Avoids unnecessary operation of measuring and report feedback among those pairs of devices which may cause interference with each other if they transmit concurrently; and

[00119] - Power saving of the resource allocation for the spatial reuse as it can significantly reduce the number of pairs of devices that can be used for measuring and report feedback. [00120] Embodiments provides a method of identifying the best existing pair of devices with directional transmission that can share the transmission channel spatially, in an timeslot, with an intended transmission pair of devices with directional transmission. In an embodiment, the method may include

[00121] a) Determining if an intended transmission pair of devices fall into the same transmission regions of the best selected sectors of an existing pair of devices;

[00122] b) Calculating the minimum number of sectors between the best selected sector ID among the existing pair of devices and the intended transmission pair of devices;

[00123] c) identifying the best existing pair of devices with directional transmission, with the maximum value in the minimum number of sectors, that can share the transmission channel spatially, in an timeslot, with the intended transmission pair of devices with directional transmission; and

[00124] d) The best existing pair of devices and the intended transmission pair may use the schedule slots or the contention based slots.

[00125] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.