WO2016078524A1 - System and method for setting cyclic prefix length - Google Patents

System and method for setting cyclic prefix length Download PDF

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Publication number
WO2016078524A1
WO2016078524A1 PCT/CN2015/094304 CN2015094304W WO2016078524A1 WO 2016078524 A1 WO2016078524 A1 WO 2016078524A1 CN 2015094304 W CN2015094304 W CN 2015094304W WO 2016078524 A1 WO2016078524 A1 WO 2016078524A1
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Prior art keywords
cyclic prefix
length
station
scheduling information
multiple access
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PCT/CN2015/094304
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English (en)
French (fr)
Inventor
Zhigang Rong
Yunsong Yang
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Huawei Technologies Co Ltd
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Huawei Technologies Co Ltd
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Priority to KR1020207002299A priority Critical patent/KR102205775B1/ko
Priority to EP15860644.2A priority patent/EP3213576B1/en
Priority to KR1020177016861A priority patent/KR102071564B1/ko
Priority to JP2017527597A priority patent/JP6482666B2/ja
Priority to PL15860644T priority patent/PL3213576T3/pl
Priority to ES15860644T priority patent/ES2882171T3/es
Priority to CN201580063192.3A priority patent/CN107251629B/zh
Priority to EP21165237.5A priority patent/EP3860071B1/en
Publication of WO2016078524A1 publication Critical patent/WO2016078524A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2647—Arrangements specific to the receiver only
    • H04L27/2655—Synchronisation arrangements
    • H04L27/2666—Acquisition of further OFDM parameters, e.g. bandwidth, subcarrier spacing, or guard interval length
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0452—Multi-user MIMO systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2602—Signal structure
    • H04L27/2605—Symbol extensions, e.g. Zero Tail, Unique Word [UW]
    • H04L27/2607—Cyclic extensions
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H04L27/2626—Arrangements specific to the transmitter only
    • H04L27/2646—Arrangements specific to the transmitter only using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H04L5/0007—Time-frequency the frequencies being orthogonal, e.g. OFDM(A) or DMT
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H04W72/1263—Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows
    • H04W72/1268—Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows of uplink data flows
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/20—Control channels or signalling for resource management
    • H04W72/23—Control channels or signalling for resource management in the downlink direction of a wireless link, i.e. towards a terminal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W84/00—Network topologies
    • H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
    • H04W84/10—Small scale networks; Flat hierarchical networks
    • H04W84/12—WLAN [Wireless Local Area Networks]

Definitions

  • the present invention relates to digital communications, and, in particular embodiments, to setting cyclic prefix (CP) length.
  • CP cyclic prefix
  • WLANs Wireless Local Area Networks
  • APs access points
  • STA stations
  • APs access points
  • STA stations
  • High densities of APs and stations also commonly referred to as user, subscriber, terminal, and the like
  • EDCA enhanced distributed channel access
  • MAC media access control
  • a newly formed IEEE 802.11 Study Group named "High Efficiency WLAN (HEW)" has been formed to study, among other things, improving system performance in a high density environment.
  • HEW High Efficiency WLAN
  • a Task Group called TGax was formed.
  • Example embodiments of the present disclosure which provide a system and method for setting cyclic prefix length.
  • a method for communicating in a wireless communications system includes receiving, by a station, a trigger frame comprising scheduling information and a cyclic prefix indicator indicating a first length of a first cyclic prefix, wherein the trigger frame is received in accordance with the first cyclic prefix, determining, by the station, a second length of a second cyclic prefix for a transmission in accordance with the scheduling information and the cyclic prefix indicator, and transmitting, by the station, the transmission with the second cyclic prefix.
  • a method for communicating in a wireless communications system includes transmitting, by an access point, a trigger frame comprising scheduling information and a cyclic prefix indicator indicating a first length of a first cyclic prefix, wherein the trigger frame is transmitted in accordance with the first cyclic prefix, and wherein the scheduling information and the cyclic prefix indicator is configured to prompt an adjustment to a second length of a second cyclic prefix, and receiving, by the access point, a first transmission from a station, the first transmission with the second length of the second cyclic prefix determined in accordance with the scheduling information and the cyclic prefix indicator.
  • a station in accordance with another example embodiment of the present disclosure, includes a receiver, a processor operatively coupled to the receiver, and a transmitter operatively coupled to the processor.
  • the receiver receives a trigger frame comprising scheduling information and a cyclic prefix indicator indicating a first length of a first cyclic prefix, wherein the trigger frame is received in accordance with the first cyclic prefix.
  • the processor determines a second length of a second cyclic prefix for a transmission in accordance with the scheduling information and the cyclic prefix indicator.
  • the transmitter transmits the transmission with the second cyclic prefix.
  • an access point in accordance with another example embodiment of the present disclosure, includes a transmitter, and a receiver operatively coupled to the transmitter.
  • the transmitter transmits a trigger frame comprising scheduling information and a cyclic prefix indicator indicating a first length of a first cyclic prefix, wherein the trigger frame is transmitted in accordance with the first cyclic prefix, and wherein the scheduling information and the cyclic prefix indicator are configured to prompt an adjustment to a second length of a second cyclic prefix.
  • the receiver receives a first transmission from a station, the first transmission with the second length of the second cyclic prefix determined in accordance with the scheduling information and the cyclic prefix indicator.
  • One advantage of an embodiment is that the cyclic prefix length is set in accordance with implicit or explicit indicators without requiring timing advance commands, therefore, communications overhead is reduced.
  • a further advantage of an embodiment is that the uplink cyclic prefix length is adjustable through adjusting the downlink cyclic prefix length, therefore, the signaling overhead of indicating the uplink cyclic prefix length is reduced by taking advantage of the existing indication of downlink CP length.
  • FIG. 1 illustrates wireless communications system in accordance with an embodiment
  • Figure 2 illustrates a diagram of channel access timing in accordance with an embodiment
  • Figure 3a illustrates a flow diagram of operations occurring in an AP as the AP transmits uplink scheduling information to stations in accordance with an embodiment
  • Figure 3b illustrates a flow diagram of operations occurring in a station as the station transmits to its AP in accordance with an embodiment
  • FIG. 4 illustrates an example interaction between an AP and two stations (STA1 and STA2) in accordance with an embodiment
  • Figure 5 illustrates a message exchange diagram highlighting messages exchanged between a station and its AP, where an indicator of the use of OFDMA and/or UL MU-MIMO is included in uplink scheduling information in accordance with an embodiment
  • Figure 6 illustrates a message exchange diagram highlighting messages exchanged between a station and its AP, where the station determines if OFDMA and/or UL MU-MIMO is being used in accordance with an embodiment
  • Figures 7a and 7b illustrate flow diagrams of example operations occurring in an AP as the AP transmits uplink scheduling information to stations and a station as the station transmits to its AP in accordance with an embodiment
  • Figure 8 illustrates a computing platform that may be used for implementing, for example, the devices and methods described herein, in accordance with an embodiment.
  • the present disclosure will be described with respect to example embodiments in a specific context, namely communications systems that uses different length cyclic prefixes to help maintain signal orthogonality.
  • the disclosure may be applied to standards compliant communications systems, such as those that are compliant with Third Generation Partnership Project (3GPP) , IEEE 802.11, and the like, technical standards, and non-standards compliant communications systems, that uses different length cyclic prefixes to help maintain signal orthogonality.
  • 3GPP Third Generation Partnership Project
  • IEEE 802.11 IEEE 802.11
  • non-standards compliant communications systems that uses different length cyclic prefixes to help maintain signal orthogonality.
  • FIG. 1 illustrates an example wireless communications system 100.
  • Wireless communications system 100 includes an access point (AP) 105 that serves one or more stations, such as stations (STA) 110 -116, by receiving communications originating from the stations and then forwarding the communications to their intended destinations or receiving communications destined to the stations and then forwarding the communications to their intended stations.
  • AP 105 access point
  • stations stations
  • some stations may directly communicate with one another.
  • station 116 may transmit directly to station 118. While it is understood that communications systems may employ multiple APs capable of communicating with a number of stations, only one AP, and a number of stations are illustrated for simplicity.
  • WLANs make use of carrier sense multiple access with collision avoidance (CSMA/CA) , where a station desiring to transmit needs to contend for access to the wireless channel before it can transmit.
  • a station may contend for access to the wireless channel using a network allocation vector (NAV) .
  • the NAV may be set to a first value to represent that the wireless channel is busy and to a second value to represent that the wireless channel is idle.
  • the NAV may be set by station in accordance with physical carrier sensing and/or reception of transmissions from other stations and/or APs. Therefore, contending for access to the wireless channel may require the station to expend a significant amount of time, thereby decreasing wireless channel utilization and overall efficiency. Furthermore, contending for access to the wireless channel may become difficult if not impossible as the number of stations contending for access increases.
  • FIG. 2 illustrates a diagram 200 of example channel access timing.
  • a first trace 205 represents channel access for a first station (STA 1)
  • a second trace 207 represents channel access for a second station (STA 2)
  • a third trace 209 represents channel access for a third station (STA 3) .
  • a short inter-frame space (SIFS) has a duration of 16 microseconds
  • a point coordination function (PCF) inter-frame space (PIFS) has a duration of 25 microseconds
  • a distributed inter-frame space (DIFS) may last longer than either the SIFS or the PIFS.
  • a backoff period may be a random duration. Therefore, active scanning may not provide the best solution when there are large numbers of stations attempting to perform AP/network discovery.
  • OFDMA orthogonal frequency division multiple access
  • OFDMA has the ability to support multiple users simultaneously by carrying traffic from different users on different portions of the communications system bandwidth.
  • OFDMA can support a large number of users more efficiently, especially when data traffic from individual users is low.
  • OFDMA can avoid wasting frequency resources if traffic from one user cannot fill the entirety of the communications system bandwidth by utilizing the unused bandwidth to carry transmissions from other user (s) .
  • the ability to utilize unused bandwidth may become crucial as the communications system bandwidth continues to become wider.
  • uplink multi-user multiple input multiple output (UL MU-MIMO) techniques have also been used in cellular communications systems, e.g., 3GPP LTE, to enhance communications system performance.
  • UL MU-MIMO allows multiple users to simultaneously transmit on the same time-frequency resource (s) with the transmissions being separated in space (i.e., on different spatial streams) .
  • uplink synchronization is achieved through an evolved NodeB (eNB) sending timing advance commands to user equipments (UE) .
  • eNBs are also commonly referred to as NodeBs, APs, base stations, controllers, communications controllers, and the like.
  • UEs are also commonly referred to as stations, users, subscribers, mobile stations, mobiles, terminals, and the like.
  • the timing advance value controls the timing offset of a UE's transmission on the uplink. For UEs that are closer to the eNB (hence with shorter propagation delay) , a smaller timing advance value may be used. For UEs that are farther away from the eNB (hence with greater propagation delay) , a larger timing advance value may be used. By controlling the uplink transmission timing for different UEs, the eNB can make sure that the arrival time of signals originating from multiple UEs are aligned.
  • timing advance commands to a large number of stations may not be feasible.
  • IEEE 802.11 compliant communications systems are asynchronous in nature, it is difficult for an AP to estimate the required timing offset for each station due to factors such as the existence of a random backoff interval.
  • sending timing advance commands to a large number of stations may consume a considerable amount of resources in the communications system, leading to a large communications system overhead.
  • an indicator of the use of OFDMA and/or UL MU-MIMO in the uplink is used to inform stations that OFDMA and/or UL MU-MIMO is being used for uplink transmissions and to adjust their cyclic prefix (CP) .
  • the length of the cyclic prefix may be based on a value derived from a length of a cyclic prefix used in the transmission of the trigger frame.
  • the length of the cyclic prefix used in the transmission of the trigger frame may be indicated in the trigger frame.
  • a station receives uplink scheduling information from its AP.
  • the uplink scheduling information may be carried in a trigger frame.
  • the trigger frame is a stand-alone downlink frame comprising control information such as the uplink scheduling information.
  • Another example of the trigger frame is a downlink frame where the control information such as the uplink scheduling information is sent together with other downlink data.
  • the trigger frame can be in the form of a MAC frame.
  • the trigger frame can also be in the form of a null data packet (NDP) frame.
  • the uplink scheduling information may include an indicator of the use of OFDMA and/or UL MU-MIMO.
  • the indicator may be set to a first value (e.g., TRUE or ON) to indicate that OFDMA and/or UL MU-MIMO is being used for this uplink transmission, and the indicator may be set to a second value (e.g., FALSE or OFF) to indicate that OFDMA and/or UL MU-MIMO is not being used for this uplink transmission.
  • a first value e.g., TRUE or ON
  • FALSE or OFF e.g., FALSE or OFF
  • the indicator may be an explicit indicator, meaning that it is present in the uplink scheduling information and the station receiving the uplink scheduling information may readily determine the value of the indicator included in the uplink scheduling information.
  • the indicator may be an implicit indicator, meaning that the station receiving the scheduling information may infer the value of the indicator by examining the uplink scheduling information intended for the station and/or uplink scheduling information intended for other stations.
  • the station may decide on the CP length value for the uplink (CP UL ) that it will use in its uplink transmission as informed by the uplink scheduling information. If the uplink scheduling information includes the indicator set to the second value (i.e., OFDMA and/or UL MU-MIMO is not being used) the station may set its CP UL to a first CP length value (CP1) , while if the indicator is set to the first value (i.e., OFDMA and/or UL MU-MIMO is being used) the station may set its CP UL to a second CP length value (CP2) , which is derived from CP DL .
  • CP1 first CP length value
  • CP2 second CP length value
  • CP1 may be the same value as CP DL and CP2 is larger than CP DL (and hence CP1) to help accommodate the different propagation delay between different stations and the AP when OFDMA and/or UL MU-MIMO is being used.
  • CP2 may be a default value specified by a technical standard, an operator of the communications system, and the like, and may not need to be signaled to the station. It is noted that other values for CP1 and CP2 are possible and that the described relationship of CP1 ⁇ CP2 may not hold in all situations.
  • CP2 is derived from a set of possible CP length values.
  • a set of possible CP length values is defined (e.g., by a technical standard, an operator of the communications system, and the like) and CP2 is selected from the set of possible CP length values as long as CP2 is larger than or equal to CP DL .
  • the set of possible CP length values includes 4 values: 0.4 us, 0.8 us, 1.6 us, and 3.2 us.
  • the set of possible CP length values is indexed by a two-bit index: "00" , "01” , "10” , and "11” , respectively.
  • the station may derive an index for CP2 by incrementing an index for CP DL by value K.
  • K may be a fixed value defined by a technical standard, an operator of the communications system, and the like.
  • the value of K may be signaled by an AP in a system information message, e.g., in a Beacon frame. If the resulting index for CP2 is greater than a maximum index value (e.g., the total number of indices) , the station sets the index for CP2 to the maximum index value.
  • the value of CP2 may be determined from the index of CP2.
  • index of CP2 min (index of CP DL + K, maximum index value)
  • K 3
  • value of CP DL 0.8 us
  • index of CP DL 1
  • the station may be able to derive the index for CP2 by
  • index of CP2 min (index of CP DL + K, maximum index value)
  • Figure 3a illustrates a flow diagram of example operations 300 occurring in an AP as the AP transmits uplink scheduling information to stations.
  • the AP may perform a check to determine if it is using OFDMA and/or UL MU-MIMO for the uplink being scheduled (block 305) . If it is, the AP may transmit the uplink scheduling information along with the indicator set to indicate that OFDMA and/or UL MU-MIMO is to be used for the scheduled uplink (block 310) . If it is not, the AP may transmit the uplink scheduling information along with the indicator set to indicate that OFDMA and/or UL MU-MIMO is not to be used for the scheduled uplink (block 315) .
  • the uplink scheduling information may be carried in a trigger frame. In addition to the uplink scheduling information, the trigger frame may also comprise an indicator indicating the cyclic prefix length value for the downlink (e.g., CP DL ) .
  • Figure 3b illustrates a flow diagram of example operations 350 occurring in a station as the station transmits to its AP.
  • the station may receive uplink scheduling information from its AP (block 355) .
  • the station may also receive the indicator of CP DL from the trigger frame.
  • the station may perform a check to determine if OFDMA and/or UL MU-MIMO is going to be used in the uplink (block 360) .
  • the station sets the value of the UL cyclic prefix to CP2, which may be derived from CP DL (block 365) and transmits to the AP (block 370) . If OFDMA and/or UL MU-MIMO is not going to be used in the uplink, i.e., the indicator is set to the second value (FALSE or OFF) , the station sets its cyclic prefix length to CP1 or CP DL (block 375) and transmits to the AP (block 370) .
  • the station may start its uplink transmission with cyclic prefix length of CP UL on a resource as indicated in the uplink scheduling information.
  • the technique as presented herein affords greater flexibility in setting UL cyclic prefix length when OFDMA and/or MU-MIMO is used in the UL since the station can derive the UL cyclic prefix length from the DL cyclic prefix length. Therefore, the orthogonality between signals from the different stations is maintained at the receiver (e.g., the AP) .
  • the maximum round-trip propagation delay is about 0.67 us.
  • the guard interval i.e., CP length
  • a longer CP length value for example, 1.6 us, for the UL when UL OFDMA and/or UL MU-MIMO is used, after deducting the maximum round-trip delay of 0.67 us, there still is about 0.93 us left for mitigating channel delay spread and STA timing inaccuracy, which most likely will be sufficient for most of the scenarios.
  • low overhead associated with the use of shorter CPs is maintained when longer CPs are not needed.
  • OFDMA and/or UL MU-MIMO when OFDMA and/or UL MU-MIMO is not used, the longer CP is not necessary and a shorter CP may be employed, thus reducing the overhead arising from the CP.
  • OFDMA and/or UL MU-MIMO although a longer CP is employed, the additional overhead from longer CP will be compensated for due to the use of OFDMA and/or UL MU-MIMO. In fact, additional gain may be achieved due to the use of OFDMA and/or UL MU-MIMO (e.g., supporting transmissions from multiple stations) .
  • FIG. 4 illustrates an example interaction 400 between an AP and two stations (STA1 and STA2) . It is noted that for simplicity reasons, on both the uplink and the downlink, only one OFDM symbol is shown. In reality, actual downlink and uplink transmissions may occur over a plurality of OFDM symbols.
  • the AP transmits uplink scheduling information 405 to STA1 and STA2 on the downlink, with a CP length of CP DL 407.
  • the uplink scheduling information includes the indicator that OFDMA is to be used on the scheduled uplink transmissions. Due to propagation delay, after T Delay1 , STA1 receives the uplink scheduling information (shown as uplink scheduling information 409) .
  • STA2 receives the uplink scheduling information (shown as uplink scheduling information 411) .
  • uplink scheduling information 4111 shows uplink scheduling information.
  • the distance between STA2 and AP is larger than the distance between STA1 and AP, therefore, T Delay2 > T Delay1 .
  • STA1 and STA2 check their uplink scheduling information, find their resource allocation information, and also find that OFDMA and/or UL MU-MIMO is to be used in the scheduled uplink transmission, so the stations set the CP length of UL transmission CP UL to CP2, which is larger than CP DL .
  • the use of OFDMA and/or UL MU-MIMO may be determined from an implicit indicator or an explicit indicator.
  • STA1 and STA2’s uplink transmissions arrive at the AP after a delay of T Delay1 and T Delay2 , respectively.
  • the AP receives the uplink transmissions from STA1 and STA2 and performs additional operations accordingly.
  • Figure 5 illustrates a message exchange diagram 500 highlighting messages exchanged between a station and its AP, where an indicator of the use of OFDMA and/or UL MU-MIMO is included in uplink scheduling information.
  • the AP may determine resource allocations for stations, as well as determine if OFDMA and/or UL MU-MIMO is to be used by the stations in transmissions in the resource allocations (block 505) .
  • the AP may send UL scheduling information in a trigger frame (shown as event 510) .
  • the UL scheduling information is sent with a CP length of CP DL .
  • the indication of CP DL may also be sent in the trigger frame.
  • the station receives the UL scheduling information.
  • the station may also receive the indicator of CP DL from the trigger frame. From the UL scheduling information, the station may be able to determine resource allocation information, as well as an indicator if OFDMA and/or UL MU-MIMO are being used in the UL transmission (block 515) .
  • the station may send an UL transmission in a resource (s) allocated for it (shown as event 520) .
  • the UL transmission is sent with a CP length of CP UL .
  • the station may determine whether the UL scheduling information includes scheduling information for more than one station. If the scheduling information is for more than one station, the station may determine that OFDM and/or MU-MIMO is to be used in the scheduled UL transmission. The station may set its CP UL to CP2, which is derived from CP DL . If the scheduling information is not for more than one station, the station may set its CP UL to CP1. In general, CP2 is larger than CP1.
  • Figure 6 illustrates a message exchange diagram 500 highlighting messages exchanged between a station and its AP, where the station determines if OFDMA and/or UL MU-MIMO is being used from the scheduling information.
  • the AP may determine resource allocations for stations, as well as determine if OFDMA and/or UL MU-MIMO is to be used by the stations in transmissions in the resource allocations (block 605) .
  • the AP may send UL scheduling information in a trigger frame (shown as event 610) .
  • the UL scheduling information is sent with a CP length of CP DL .
  • the indication of CP DL may also be sent in the trigger frame.
  • the station receives the UL scheduling information. From the UL scheduling information, the station may be able to determine resource allocation information, as well if OFDMA and/or UL MU-MIMO is being used in the UL transmission (block 615) .
  • the station may send an UL transmission in a resource (s) allocated for it (shown as event 620) .
  • the UL transmission is sent with a CP length of CP UL .
  • Figure 7a illustrates a flow diagram of example operations 700 occurring in an AP as the AP transmits UL scheduling information.
  • Operations 700 may begin with the AP determining resource allocations for stations.
  • the AP may transmit UL scheduling information in a trigger frame (block 705) .
  • the trigger frame may also comprise an indicator indicating the cyclic prefix length value for the downlink (e.g., CP DL ) .
  • Figure 7b illustrates a flow diagram of example operations 750 occurring in a station as the station transmits on an uplink.
  • Operations 750 may begin with the station receiving UL scheduling information (block 755) .
  • the station may also receive the indicator of CP DL from the trigger frame.
  • the UL scheduling information may include information about a resource (s) scheduled for the station.
  • the station may perform a test to determine if the UL scheduling information is intended for more than one station (block 760) . If the UL scheduling information is intended for more than one station, the station may adjust its CP UL in accordance with CP2, which is derived from CP DL (block 765) . While if the UL scheduling information is not intended for more than one station, the station adjust its CP UL in accordance with CP1 (block 770) . The station may make the UL transmission with CP value as indicated (block 775) .
  • a table is used to derive CP2 from CP DL .
  • a table (which may be stored in memory of the station) may provide a mapping between DL cyclic prefix length values and UL cyclic prefix length values for UL transmissions.
  • the station may select the value of CP2 from CP DL , which is indicated in the trigger message.
  • An example table is shown below:
  • CP DL is 0.8 us. From the table shown above, the station may be able to determine that CP2 should be 1.6 us. As another illustrative example, assume that CP DL is 0.4 us. From the table shown above, the station may be able to determine that CP2 should be 1.6 us.
  • the table may be defined by a technical standard, an operator of the communications system, and the like. The table may also be signaled to the station in system information, e.g., in a Beacon frame.
  • the value of CP2 may be derived from CP DL using a mathematical expression.
  • a station receives a trigger frame including a CP DL indicator.
  • the station may add a value (CP delta ) to CP DL to obtain CP2, where CP delta represents a difference between UL CP length value for UL transmission and DL CP length value.
  • An example mathematical expression may be
  • CP2 CP DL + CP delta .
  • CP delta may be defined in a technical standard, an operator of the communications system, and the like. CP delta may be signaled to the station as system information, e.g., in a Beacon frame.
  • the value of CP2 may be derived from CP DL using a mathematical expression.
  • a station receives a trigger frame including a CP DL indicator.
  • the station may multiply a scaling factor (CP scale ) to CP DL to obtain CP2, where CP scale represents the ratio of UL CP length value for UL transmission to DL CP length value.
  • CP scale may be an integer value or a non-integer (i.e., a real number) value.
  • CP scale is generally larger than 1.
  • An example mathematical expression may be
  • CP2 min (CP DL *CP scale , CP max ) ,
  • CP scale may be defined in a technical standard, an operator of the communications system, and the like. CP scale may be signaled to the station as system information, e.g., in a Beacon frame.
  • a cyclic prefix for the uplink (CP UL ) is longer than the cyclic prefix for the downlink (CP DL ) , which may help to accommodate different propagation delays between different stations and the AP, thereby maintaining the orthogonality among signals from the different stations at the AP.
  • Adaptive cyclic prefix length also helps to maintain low overhead.
  • OFDMA and/or UL MU-MIMO When OFDMA and/or UL MU-MIMO is used, longer cyclic prefixes are used, but the increased overhead may be compensated for by the additional gain achieved through the use of OFDMA and/or UL MU-MIMO.
  • the example embodiments presented herein also afford greater flexibility in setting UL cyclic prefix length when OFDMA and/or MU-MIMO is used in the UL since the station can derive the UL cyclic prefix length from the DL cyclic prefix length.
  • FIG. 8 is a block diagram of a processing system 800 that may be used for implementing the devices and methods disclosed herein.
  • the processing system 800 comprises a UE.
  • Specific devices may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device.
  • a device may contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc.
  • the processing system may comprise a processing unit 805 equipped with one or more input/output devices, such as a human interface 815 (including speaker, microphone, mouse, touchscreen, keypad, keyboard, printer, and the like) , display 810, and so on.
  • the processing unit may include a central processing unit (CPU) 820, memory 825, a mass storage device 830, a video adapter 835, and an I/O interface 840 connected to a bus 845.
  • CPU central processing unit
  • the bus 845 may be one or more of any type of several bus architectures including a memory bus or memory controller, a peripheral bus, video bus, or the like.
  • the CPU 820 may comprise any type of electronic data processor.
  • the memory 825 may comprise any type of system memory such as static random access memory (SRAM) , dynamic random access memory (DRAM) , synchronous DRAM (SDRAM) , read-only memory (ROM) , a combination thereof, or the like.
  • the memory 825 may include ROM for use at boot-up, and DRAM for program and data storage for use while executing programs.
  • the mass storage device 830 may comprise any type of storage device configured to store data, programs, and other information and to make the data, programs, and other information accessible via the bus 845.
  • the mass storage device 830 may comprise, for example, one or more of a solid state drive, hard disk drive, a magnetic disk drive, an optical disk drive, or the like.
  • the video adapter 835 and the I/O interface 840 provide interfaces to couple external input and output devices to the processing unit 800.
  • input and output devices include the display 810 coupled to the video adapter 835 and the mouse/keyboard/printer 815 coupled to the I/O interface 840.
  • Other devices may be coupled to the processing unit 800, and additional or fewer interface devices may be utilized.
  • a serial interface such as Universal Serial Bus (USB) (not shown) may be used to provide an interface for a printer.
  • USB Universal Serial Bus
  • the processing unit 800 also includes one or more network interfaces 850, which may comprise wired links, such as an Ethernet cable or the like, and/or wireless links to access nodes or different networks 855.
  • the network interface 850 allows the processing unit 800 to communicate with remote units via the networks 855.
  • the network interface 850 may provide wireless communication via one or more transmitters/transmit antennas and one or more receivers/receive antennas.
  • the processing unit 800 is coupled to a local-area network or a wide-area network 855 for data processing and communications with remote devices, such as other processing units, the Internet, remote storage facilities, or the like.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)
PCT/CN2015/094304 2014-11-20 2015-11-11 System and method for setting cyclic prefix length Ceased WO2016078524A1 (en)

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KR1020207002299A KR102205775B1 (ko) 2014-11-20 2015-11-11 순환 전치 길이를 설정하는 시스템 및 방법
EP15860644.2A EP3213576B1 (en) 2014-11-20 2015-11-11 System and method for setting cyclic prefix length
KR1020177016861A KR102071564B1 (ko) 2014-11-20 2015-11-11 순환 전치 길이를 설정하는 시스템 및 방법
JP2017527597A JP6482666B2 (ja) 2014-11-20 2015-11-11 サイクリック・プレフィックスの長さを設定するためのシステムおよび方法
PL15860644T PL3213576T3 (pl) 2014-11-20 2015-11-11 Układ i sposób ustawiania długości prefiksu cyklicznego
ES15860644T ES2882171T3 (es) 2014-11-20 2015-11-11 Sistema y método para ajustar la longitud de prefijo cíclico
CN201580063192.3A CN107251629B (zh) 2014-11-20 2015-11-11 用于设置循环前缀长度的系统和方法
EP21165237.5A EP3860071B1 (en) 2014-11-20 2015-11-11 System and method for setting cyclic prefix length

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US10749724B2 (en) 2020-08-18
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US20200213175A1 (en) 2020-07-02
EP3860071A1 (en) 2021-08-04
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JP6482666B2 (ja) 2019-03-13
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JP6884805B2 (ja) 2021-06-09
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EP3860071B1 (en) 2022-11-02
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ES2936646T3 (es) 2023-03-21
KR102071564B1 (ko) 2020-01-30

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