TITLE

PDU FORMATS WITH FIXED-SIZE SDUS FOR WIRELESS NETWORKS

TECHNICAL FIELD

[0001] This description relates to communications.

BACKGROUND

[0002] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is an architecture that is being standardized by the 3 ^rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile

Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments.

[0004] A global bandwidth shortage facing wireless carriers has motivated the consideration of the underutilized millimeter wave (mmWave) frequency spectrum for future broadband cellular communication networks, for example. mmWave (or extremely high frequency) may, for example, include the frequency range between 30 and 300 gigahertz (GHz). Radio waves in this band may, for example, have wavelengths from ten to one millimeters, giving it the name millimeter band or millimeter wave. The amount of wireless data will likely significantly increase in the coming years. Various techniques have been used in attempt to address this challenge including obtaining more spectrum, having smaller cell sizes, and using improved technologies enabling more bits/s/Hz. One element that may be used to obtain more spectrum is to move to higher frequencies, above 6 GHz. For fifth generation wireless systems (5G), an access architecture for deployment of cellular radio equipment employing mmWave radio spectrum has been proposed. Other example spectrums may also be used, such as cmWave radio spectrum (3-30 GHz).

SUMMARY

[0005] According to an example implementation, a method may include sending, by a first node to a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0006] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: send, by a first node to a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0007] According to an example implementation, an apparatus includes means for sending, by a first node to a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed- length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0008] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: sending, by a first node to a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed- length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0009] According to an example implementation, a method may include receiving, by a first node from a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed- length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0010] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: receive, by a first node from a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0011] According to an example implementation, an apparatus includes means for receiving, by a first node from a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0012] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: receiving, by a first node from a second node in a wireless network, a protocol data unit including: a plurality of sets of fixed- length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0013] According to an example implementation, a method may include sending, by a first node to a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0014] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: send, by a first node to a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed- length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable- length service data unit.

[0015] According to an example implementation, an apparatus includes means for sending, by a first node to a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0016] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: sending, by a first node to a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0017] According to an example implementation, a method may include receiving, by a first node from a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0018] According to an example implementation, an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to: receive, by a first node from a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed- length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable- length service data unit.

[0019] According to an example implementation, an apparatus includes means for receiving, by a first node from a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0020] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method including: receiving, by a first node from a second node in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0021] The details of one or more examples of implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a block diagram of a wireless network according to an example implementation.

[0023] FIG. 2 is a diagram illustrating a format of a protocol data unit according to an example implementation.

[0024] FIG. 3 is a diagram illustrating a format of another protocol data unit according to an example implementation.

[0025] FIG. 4 is a diagram illustrating a format of a protocol data unit according to another example implementation.

[0026] FIG. 5 is a diagram illustrating a format of a protocol data unit according to another example implementation.

[0027] FIG. 6 is a diagram illustrating a format of a protocol data unit according to another example implementation.

[0028] FIG. 7 is a diagram illustrating a format of a protocol data unit according to another example implementation.

[0029] FIG. 8 is a flow chart illustrating operation of a node in a wireless network according to an example implementation.

[0030] FIG. 9 is a flow chart illustrating operation of a node in a wireless network according to another example implementation.

[0031] FIG. 10 is a block diagram of a node or wireless station (e.g., base

station/access point or mobile station/user device) according to an example implementation. DETAILED DESCRIPTION

[0032] FIG. 1 is a block diagram of a wireless network 130 according to an example implementation. In the wireless network 130 of FIG. 1 , user devices 131 , 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB) or a network node. At least part of the functionalities of an access point (AP), base station (BS) or (e)Node B (eNB) may be also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices 131 , 132, 133 and 135. Although only four user devices are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via a S1 interface 151 . This is merely one simple example of a wireless network, and others may be used.

[0033] A user device (user terminal, user equipment (UE)) may refer to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, and a multimedia device, as examples. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network.

[0034] In LTE (as an example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility/handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks.

[0035] The various example implementations may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G, cmWave, and/or mmWave band networks, or any other wireless network. LTE, 5G, cmWave and mmWave band networks are provided only as illustrative examples, and the various example implementations may be applied to any wireless technology/wireless network.

[0036] According to an example implementation, various example implementations provide a protocol data unit (PDU) encoding or PDU format for efficiently transferring/communicating one or more equal-size (or fixed-length) service data units (SDUs) in the PDU. According to an example implementation, equal-size, or fixed-length service data units (SDUs) include SDUs of the same size/length (e.g., same number of bits in each SDU of a set of fixed-length SDUs). One or more sets of fixed-length SDUs may be provided within a PDU, either with or without one or more variable-length SDUs.

[0037] A number of illustrative example PDUs will be briefly described, with reference to FIGs. 2 - 9, wherein like numerals indicates like or similar items/elements. Also, each successive PDU (in FIGs. 2-7) may describe any differences or new items or elements within a PDU (as compared to one or more previous PDU examples), since similar or same items in each PDU/FIG. will have been described in earlier FIGs./example PDUs, for example. All or some, or any combination, of features or elements illustrated in or described with reference to the example PDUs shown in FIGs. 2-7, and/or described in FIGs. 8-9, may be combined together, in any combination.

[0038] FIG. 2 is a diagram illustrating a format of a protocol data unit 200 according to an example implementation. In the illustrative example of protocol data unit (PDU) 200 shown in FIG. 2, the PDU 200 may include N octets (or bytes), including a header that includes one or more fields and data 216. The data may include one or more service data units (SDUs), for example.

[0039] Referring to FIG. 2, according to an example implementation, the PDU 200 may include a variable/fixed (V/F) field 210 that may be used to indicate if the PDU 200 contains one or more SDUs of equal size/equal length (fixed-length SDUs). According to an example implementation, V/F field 210 may be set to Fixed to indicate that the PDU 200 includes one or more fixed-length SDUs (e.g., one or more sets of fixed-length SDUs, with each set of fixed-length SDUs including one or more SDUs of an associated size, and may also include a segment SDU of a different size, as described below). Alternatively, the V/F field 210 may be set to Fixed to indicate the PDU 200 includes only fixed-length SDUs (PDU 200 would not include variable-length SDUs in such case, but only one or more sets of fixed- length SDUs, each set with an associated length/size, except for possibly a segment SDU, as noted below, in some cases). In another example implementation, the V/F field 210 may be set to Variable to indicate that the PDU 200 may include SDUs of any size (fixed-length SDUs and/or variable-length SDUs). In another example implementation, setting the V/F field 210 to Variable may indicate that the PDU 200 includes only variable-length SDUs, and PDU 200 does not include one or more sets of fixed-length SDUs. In another example

implementation, the V/F field 210 may not be present in the PDU header; in case of higher layer configuration a dedicated PDU format may be used, e.g., per logical channel/logical channel group or per radio bearer.

[0040] As shown in FIG. 2, PDU 200 also includes a sequence number (SN) field 212 that indicates a sequence number for PDU 200. PDU 200 may also include a fixed-length indicator field (LI _F ) 214 that identifies a length of each of one or more SDUs of a set of fixed- length data units. Data 216 is also provided within PDU 200, which may include one or more SDUs.

[0041] According to an example implementation, e.g., as shown in FIG. 2, when V/F field 210 is present and set to Fixed to indicate the presence of fixed-length SDUs within PDU 200, PDU 200 may include (at least according to one example implementation) only a single fixed-length indicator field 214 (LI _F ) associated with one set of fixed-length SDUs. When V/F field 210 is set to Fixed, a receiving protocol entity reads the LI _F field (identifying a length or size of one or more fixed-length SDUs in the set of fixed-length SDUs) and is able to calculate the number of SDUs in the PDU by using the knowledge of the PDU size (e.g., PDU size provided by a lower layer indication etc.). As an illustrative example, a receiving protocol entity may determine a number of fixed-length SDUs that are provided in a PDU by, e.g., subtracting the PDU header size (header size may be fixed size) from the PDU size (e.g., PDU size may be provided by a lower layer protocol entity), which provides the PDU payload size, and then dividing the PDU payload size by fixed-length indicator field 214 (LI _F ), for example. In this manner, the number of fixed length SDUs need not be indicated in the PDU header, but can be calculated.

[0042] FIG. 3 is a diagram illustrating a format of a protocol data unit 300 according to another example implementation. According to an example implementation, PDU 300 may include a fixed data field element (FDFE) 312 to identify a number of fixed-length SDUs in the PDU. For example, the FDFE field 312 may identify a number of fixed-length SDUs within a set of fixed-length SDUs, within the PDU 300. The one or more fixed-length SDUs (e.g., wherein the number of such fixed-length SDUs is indicated by FDFE field 312, and a length of each fixed-length SDU of the set of fixed-length SDUs is indicated by the LI _F field 214) are provided within the data 216 of PDU 300, for example.

[0043] According to an example implementation, a receiving entity may determine or calculate a number of full SDUs in the PDU: if the "SDU sizes+header" is smaller than the PDU size, the receiving entity may assume that the rest of the octets in the PDU to be padding.

[0044] As an illustrative example calculation of padding size for a PDU: PDU size 1500 octets, SDU size 40 bytes, FDFE=37, header of 3 octets 1500bytes - ( 3bytes + 40bytes ^* 37) = 17bytes padding.

[0045] FIG. 4 is a diagram illustrating a format of a protocol data unit 400 according to another example implementation. In the example PDU 400 illustrated in FIG. 4, a segment (S) field 410 may indicate whether a different-sized SDU (e.g., not the same size as a set of fixed-length SDUs) is padding or a segment SDU. Padding bits may be added to extend the length of a PDU, but such padding bits do not convey information and, thus, may be discarded by a receiving entity (e.g., base station or user device/UE). A segment SDU may be a part/portion of a segment and/or a segment that is provided within the PDU that is not the same size as other fixed-length SDUs. Thus, a segment SDU may have been added to the PDU 400, if there was room for the segment SDU, and such segment SDU may not be the same length/size as fixed-length SDUs within the PDU 400, for example. According to an example implementation, the Segment (S) field 410 may be set to padding to indicate that any extra bits are padding, and may be set to Segment to indicate that any extra bits in a PDU 400 are a segment SDU (e.g., SDU that is added to a PDU, but such segment SDU is not the same size as any of the fixed-length SDUs in the current PDU (however the total size of the segmented SDU may be the same as other SDUs in the PDU, as this is a segment (only a portion of the SDU)), and there may be more than one set of fixed-length SDUs). For example, a segment SDU may be a portion or segment of a SDU, and thus, the segment SDU may be provided at the end of a PDU, and may be a different size (e.g., smaller) than other fixed-length SDUs in the PDU 400, for example. As an example, e.g., the fixed SDU size may be 3 bytes and the segment size is 2 bytes but the total size of the segmented SDU is 3 bytes (next segment, or 1 byte, is provided in next transmitted PDU).

[0046] Thus, according to the example implementation of PDU 400 shown in FIG. 4, a transmitting entity (BS or user device/UE) may include a different size SDU at the end (for example, or other location) of the PDU 400. For example, the receiving entity may

calculate/determine a length of the fixed-length (fixed-size) SDUs in the PDU 400 as follows, for example: if the "SDU size ^* FDFE+header" is smaller than the PDU size, the receiving entity may assume rest of the octets in the PDU belonging to different size/length of SDU. The PDU header may further indicate whether the last SDU is full or segmented. For example, the segment (S) field 410 may, in an example implementation, indicate whether any last SDU is a segment SDU or a full SDU. With respect to the segment (S) field 410, this segment/full SDU information may be provided/conveyed (by segment field 410) instead of, or in addition to, the padding/segment SDU information. Thus, the segment (S) field 410 may be 1 bit, or 2 bits, as examples, depending on the information conveyed by the segment (S) field 410, for example.

[0047] For example, if the segment (S) field 410 is only one bit, it may only indicate that there is padding or a segment of a SDU ( but not full SDU) present within PDU, with a remainder of the segmented SDU being provided in a next PDU, for example. Or in another example implementation, with a 2 bit segment (S) field 410, the segment field 410 is able to indicate whether: the remainder of data is padding, a segment (but not last segment), or a full SDU, or whether this is a last segment.

[0048] This way it is possible to, e.g., fit one variable length SDU into a PDU without explicitly indicating its size

[0049] E.g., PDU size 1503 octets, SDU size 40 bytes, FDFE=25, header 3 octets

[0050] 1503B - (3B + 40B ^* 25) = 500B is size of last SDU (or SDU segment).

[0051 ] In yet another implementation example the transmitting entity may optimize the LI _F field (214) size when transmitting the fixed size SDUs. A receiving entity may

determine/calculate the length of the LI _F field by utilizing the information of FDFE field 312 and the PDU size, e.g., as follows (by way of example):

[0052] LI _F = ROUNDUP(Log2((PDUsize-header)/FDFE)).

[0053] e.g., PDU size 1500 octets, FDFE = 37, header 3 octets

[0054] ROUNDUP(Log2((1500B - 3B)/37)) = 6 bit LI _F field used

[0055] In one example implementation, a transmitting entity may indicate the use of padding/segmentation in the header part with the presence of the segmentation (S) field/bit 410, shown in FIG. 4. Alternatively it may be configured that segmentation/padding is never/always used and segmentation (S) field 410 bit may be omitted.

[0056] In another example implementation, if the "SDU size ^* FDFE + header" does not match the received PDU size, the receiving entity assumes that a (e.g., last) SDU has been segmented, with a segment of the SDU being sent in this PDU (as a segment SDU) and the rest of the segmented SDU is transmitted in the subsequent PDU, for example.

[0057] In yet another implementation example, the segment (S) field 410 may be used to indicate if the first SDU carried in the PDU is a SDU segment. For example, the segment (S) field 410 may be present in the PDU header if the V/F field 210 indicates that fixed-length (or fixed size) SDUs are present in the PDU. The length of the segment may be determined by including a LI for the total size of the SDU in the previous PDU (which contains the first segment of the said SDU. By reading the LI field and subtracting the SDU segment size transmitted in the previous PDU the receiver can calculate the remaining segment size in the current PDU without inclusion of an LI since it was already provided. The remainder of the data in the PDU can be calculated as previously indicated by using the LI _F .

[0058] Therefore, according to an example implementation, if the segment (S) field 410 indicates a presence of an SDU which is a segment the length of the segment may be determined from the LI (which is not present in this PDU but was present, e.g., in the previous PDU). For example PDU 1 contains the LI for an SDU1 which has to be a segment as it cannot fit within PDU1 . Then in the PDU2 (next PDU in sequence) the receiver knows the total SDU1 size by having read it in the LI in the PDU1 and, thus, the LI need not be present in PDU2but the indication of a segment means that the rest of the SDU 1 is present in the PDU2. Then rest of the PDU2 may contain the fixed size SDUs indicated by the LI F,

[0059] FIG. 5 is a diagram illustrating a format of a protocol data unit 500 according to another example implementation. In one example embodiment a mixed PDU format may be provided. According to an example implementation, a mixed PDU format may include both variable-length SDU(s) and one or more sets of fixed-length SDUs. Thus, in an example implementation, the V/F field 210 may indicate if the PDU includes only fixed-length SDUs, only variable-length SDUs, or a mixed format that includes both fixed-length SDUs and variable-length SDUs. In the mixed format PDU 500 (as an example), the FDFE field 312 identifies the number of fixed-length SDUs, and a fixed-length indicator (LIF) field 214 indicates the length of the fixed-length SDUs in the PDU, and the rest of the length indicator (LI) fields (Lli , .. . LI _n -2, Ll _n -i ) in the PDU 500 correspond to the (identify a length of a corresponding) variable sized SDUs.

[0060] Thus, for example, with reference to the example shown in FIG. 5, a fixed- length indicator field LIF 214 identifies a length of one or more fixed-length SDUs, including fixed-length SDU1 522; variable-length indicator field Lh 510 identifies a length of variable- length SDU1 524; variable-length indicator field Ll _n - ₂ 514 identifies a length of variable-length SDUn-2 (not shown in FIG. 5); and, variable-length indicator field Ll _n -i 518 identifies a length of variable-length SDUn-1 526.

[0061 ] According to an example implementation of PDU 500 (FIG. 5), a extension (or extend) bit or field (E) may indicate the presence of a further/additional variable-length indicator field, or not. For example, extension field (E) 512 may be set to Extend to indicate a presence of another variable length indicator field (e.g., LI _n - ₂ ) after the LI1 length indicator field. And, extension field (E) 516 may be set to Extend to indicate a presence of an additional variable-length indicator field Ll _n -i . While, extension field 520 may be set to No- Extend to indicate that there are no further variable-length indicator fields in PDU 500 after [0062] Thus, the presence and size indications (numbers) for the various length indicator fields, e.g., fixed-length indicator field LI _F and the variable length indicator fields Lli , .. . LI _n -2, Lln-i , may be used by a receiving entity to decode the received PDU, since these length indicators may indicate a presence of such SDUs and a length/size of such SDUs. Also, the receiving entity may determine a number of fixed-length SDUs in the PDU based on the FDFE field 312. Information used by a receiving entity to decode variable-length SDUs in the PDU are provided in variable length indicator fields L\ i - Ll _n -i - Also, setting the variable/fixed (V/F) field 210 to different values may impact the way or manner in which a receiving entity decodes or interprets specific bits or fields in the header of the PDU. For example, if the V/F field 210 is set to fixed (or mixed format), then this indicates the presence of fixed-length SDUs, and the FDFE will indicate a number of fixed-length SDUs in the PDU. Otherwise, if the V/F field 210 is set to variable (meaning only variable-length SDUs are present, for example), then the FDFE field 21 0 may typically not be present since there are no fixed-length SDUs present in the PDU.

[0063] FIG. 6 is a diagram illustrating a format of a protocol data unit 600 according to another example implementation. In FIG. 6, an example PDU 600 is shown with mixed format SDUs (e.g., including both fixed-length SDUs and variable-length SDUs). A FDFE field 312 may identify a number of fixed-length service data units within the PDU. In addition, as a further optimization of a PDU format, PDU 600 may also include data field element (DFE) field 610 that identifies a number of variable-length SDUs in the PDU. Thus, in an example implementation, with one variable-length indicator LI provided for each variable- length SDU, the DFE field 61 0 may identify both a number of variable-length SDUs and a number of variable-length indicator fields in the PDU, for example.

[0064] In one example implementation, a receiving entity (e.g., a protocol entity of either BS or user device/UE) may employ queue management actions to select same size (same-length) SDUs when encoding a PDU to optimize control/header overhead. Thus, for example, the more fixed-length SDUs, and the fewer variable-length SDUs that are provided in a PDU, this may reduce the number of variable-length indicator fields in the PDU, thus reducing overhead, for example.

[0065] FIG. 7 is a diagram illustrating a format of a protocol data unit 700 according to another example implementation. In the example PDU format 700 shown in FIG. 7, multiple FD FE fields may be provided, e.g., with an extension field provided after each FDFE field. For example, a FDFEi field 710 identifies a number of fixed-length SDUs provided for a first set of fixed-length SDUs, where a length/size of each SDU within such first set of fixed-length SDUs is indicated by LI _F i - An extension field (E) 712, set to Extend, indicates that there is another FDFE field after FDFEi field. A FDFE ₂ field 714 identifies a number of fixed-length SDUs provided for a second set of fixed-length SDUs, where a length/size of each SDU within such second set of fixed-length SDUs is indicated by L\ _F2 . An extension field (E) 71 6, set to No-Extend, indicates that there are no additional FDFE fields after FDFE ₂ field 714. Of course, more than two FDFE fields may be provided in the PDU , with one FDFE field being provided for each set of fixed-length SDUs that are included in the PDU, with each set possibly having different size/length SDUs (a size of the SDUs of each set being indicated by the corresponding fixed length indicator, e.g., LI _F i , LI _F 2, ...). Thus, according to an example implementation, a PDU may include several FDFE fields to indicate multiple fixed sized SDU sets/groups (where a number of SDUs in the set/group is indicated by

corresponding/associated length indicator/LI) in the PDU. One LI may be provided for each FDFE.

[0066] In one additional example, depending on the size of the LI fields, the receiver may implicitly determine the presence of padding, e.g. if LI length = 1 octet and the PDU size is one octet larger than the total size of PDU header+SDUs, the remaining octet may include only LI field but no data (same logic applies for LI length= 2 octets etc.). However,

alternatively the LI may indicate an SDU size in the next PDU (thus a single LI may be omitted as it is already provided in the current PDU). Yet in another alternative, if PDU size is multiple octets larger (more than LI length) than PDU header+SDUs, then a single LI may be used to indicate the presence of padding, e.g., by setting LI to a special value such as zero (LI = 0x00). Thus the remaining octets in the PDU are interpreted as padding in such example.

[0067] In an example implementation, the above example PDUs may be provided in a format of 3GPP RLC (radio link control) PDUs, by way of example. However, the use of aforementioned PDUs formats are not restricted to any specific protocol layer. The PDU encoding/decoding methods can be used, for example, in any protocol layer, such as, for example, MAC (media access control) layer or PDCP layer, or for example, any protocol layer may be used, as well as protocol layers of different RATs/radio access technologies, such as 2G,3G,4G, IEEE 802.1 1 /Wireless LAN, etc.

[0068] The various example PDU formats may have a number of advantages, such as, for example: Saves overhead when encoding multiple SDUs with same size (or fixed- length) SDUs, and may especially optimize or reduce size of the PDU header for small packets, e.g., by reducing the number of fields in header where one or more sets of fixed- length SDUs are provided, either with or without variable-length SDUs. Minor signaling overhead to indicate whether the PDU format includes fixed size SDUs, variable size SDUs or both, e.g., by use of a V/F field, for example.

[0069] FIG. 8 is a flow chart illustrating operation of a node in a wireless network according to an example implementation. Operation 810 includes sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, comprising the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0070] According to an example implementation of the method of FIG. 8, the header further includes: a variable/fixed field that is set to fixed to indicate a presence of the fixed- length service data units in the protocol data unit.

[0071] According to an example implementation of the method of FIG. 8, the protocol data unit further includes: one or more variable-length service data units; and wherein the header further comprises, for each of the variable-length service data units, a variable-length indicator field that identifies a length of an associated variable-length service data unit.

[0072] According to an example implementation of the method of FIG. 8, wherein the number field includes a first number field (e.g., FDFE) that identifies a number of fixed-length service data units of the set of fixed-length service data units, wherein the protocol data unit further includes: a second number field (e.g., DFE) that identifies a number of variable-length service data units in the protocol data unit, the second number field also identifying a number of variable-length indicator fields in the protocol data unit with one variable-length indicator field being provided for each variable-length service data unit in the protocol data unit.

[0073] According to an example implementation of the method of FIG. 8, wherein the header further includes: an extension field associated with each number field, the extension field indicating whether or not there are additional number fields in the protocol data unit after the associated number field.

[0074] According to an example implementation of the method of FIG. 8, wherein the number field includes: a fixed data field element (FDFE) that identifies a number of fixed- length service data units of the set of fixed-length service data units.

[0075] According to an example implementation of the method of FIG. 8, wherein the header further includes: a segment field that indicates whether or not a last service data unit in the protocol data unit is padding or a segment of a service data unit that is a different size than any of the fixed-length service data units in the protocol data unit.

[0076] According to an example implementation an apparatus includes at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform the method of: sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0077] According to an example implementation of the apparatus, the header further includes: a variable/fixed field that is set to fixed to indicate a presence of the fixed-length service data units in the protocol data unit.

[0078] According to an example implementation of the apparatus, the protocol data unit further includes: one or more variable-length service data units; and wherein the header further comprises, for each of the variable-length service data units, a variable-length indicator field that identifies a length of an associated variable-length service data unit.

[0079] According to an example implementation of the apparatus, wherein the number field includes a first number field (e.g., FDFE) that identifies a number of fixed-length service data units of the set of fixed-length service data units, wherein the protocol data unit further includes: a second number field (e.g., DFE) that identifies a number of variable-length service data units in the protocol data unit, the second number field also identifying a number of variable-length indicator fields in the protocol data unit with one variable-length indicator field being provided for each variable-length service data unit in the protocol data unit.

[0080] According to an example implementation of the apparatus, wherein the header further includes: an extension field associated with each number field, the extension field indicating whether or not there are additional number fields in the protocol data unit after the associated number field. [0081] According to an example implementation of the apparatus, wherein the number field includes: a fixed data field element (FDFE) that identifies a number of fixed- length service data units of the set of fixed-length service data units.

[0082] According to an example implementation of the apparatus, wherein the header further includes: a segment field that indicates whether or not a last service data unit in the protocol data unit is padding or a segment of a service data unit that is a different size than any of the fixed-length service data units in the protocol data unit.

[0083] According to an example implementation, a computer program product includes a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0084] According to an example implementation, an apparatus includes means (e.g., 1002A/1002B, and/or 1004, FIG. 10) for sending, by a first node to a second node (or means (e.g., 1002A/1002B, and/or 1004, FIG. 10) for receiving, by a first node from a second node) in a wireless network, a protocol data unit including: a plurality of sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units.

[0085] FIG. 9 is a flow chart illustrating operation of a node in a wireless network according to another example implementation. Operation 910 includes sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0086] According to an example implementation of the method of FIG. 9, the number field includes a first number field, and wherein the header also includes the following for each of the one or more variable-length service data units: a second number field that identifies a number of variable-length service data units in the protocol data unit, the second number field also identifying a number of variable-length indicator fields in the protocol data unit with one variable-length indicator field being provided for each variable-length service data unit in the protocol data unit.

[0087] According to an example implementation of the method of FIG. 9, the header further includes: a variable/fixed field that is set to fixed to indicate a presence of the fixed- length service data units in the protocol data unit.

[0088] According to an example implementation of the method of FIG. 9, wherein the header further includes: an extension field associated with each number field, the extension field indicating whether or not there are additional number fields in the protocol data unit after the associated number field.

[0089] According to an example implementation of the method of FIG. 9, wherein the number field includes: a fixed data field element (FDFE) that identifies a number of fixed- length service data units of the set of fixed-length service data units.

[0090] According to an example implementation of the method of FIG. 9, the header further includes: a segment field that indicates whether or not a last service data unit in the protocol data unit is padding or a segment of a service data unit that is a different size than any of the fixed-length service data units in the protocol data unit.

[0091] An apparatus including at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform the method of sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed-length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable-length service data unit.

[0092] A computer program product including a computer-readable storage medium and storing executable code that, when executed by at least one data processing apparatus, is configured to cause the at least one data processing apparatus to perform a method of sending, by a first node to a second node (or receiving, by a first node from a second node) in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed- length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable- length service data unit.

[0093] According to an example implementation, an apparatus includes means (e.g., 1002A/1002B, and/or 1004, FIG. 10) for sending, by a first node to a second node (or means (e.g., 1002A/1002B, and/or 1004, FIG. 10) for receiving, by a first node from a second node) in a wireless network, a protocol data unit including: one or more variable-length service data units; one or more sets of fixed-length service data units, wherein each of the sets of fixed- length service data units including one or more service data units of an associated length; and a header, including the following fields provided for each set of the plurality of sets of fixed-length service data units: a number field that identifies a number of fixed-length service data units of the set of fixed-length service data units; and a fixed-length indicator field that identifies a length of each of the one or more service data units of the set of fixed-length data units; and the header also including the following for each of the one or more variable-length service data units: a variable-length indicator field that identifies a length of the variable- length service data unit.

[0094] FIG. 10 is a block diagram of a wireless station (e.g., AP or user device) 1000 according to an example implementation. The wireless station 1000 may include, for example, one or two RF (radio frequency) or wireless transceivers 1002A, 1002B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 1004 to execute instructions or software and control transmission and receptions of signals, and a memory 1006 to store data and/or instructions.

[0095] Processor 1004 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1004, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1002 (1002A or 1002B). Processor 1004 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down- converted by wireless transceiver 1002, for example). Processor 1004 may be

programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1004 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 1004 and transceiver 1002 together may be considered as a wireless

transmitter/receiver system, for example.

[0096] In addition, referring to FIG. 10, a controller (or processor) 1008 may execute software and instructions, and may provide overall control for the station 1000, and may provide control for other systems not shown in FIG. 10, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 1000, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software.

[0097] In addition, a storage medium may be provided that includes stored

instructions, which when executed by a controller or processor may result in the processor 1004, or other controller or processor, performing one or more of the functions or tasks described above. [0098] According to another example implementation, RF or wireless transceiver(s) 1002A/1002B may receive signals or data and/or transmit or send signals or data. Processor 1004 (and possibly transceivers 1002A/1002B) may control the RF or wireless transceiver 1002A or 1002B to receive, send, broadcast or transmit signals or data.

[0099] The embodiments are not, however, restricted to the system that is given as an example, but a person skilled in the art may apply the solution to other communication systems. Another example of a suitable communications system is the 5G concept. It is assumed that network architecture in 5G will be quite similar to that of the LTE-advanced. 5G is likely to use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in cooperation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates.

[00100] It should be appreciated that future networks will most probably utilise network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into "building blocks" or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations may be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be nonexistent.

[00101] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Implementations may implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a

machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Implementations may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium.

Implementations of the various techniques may also include implementations provided via transitory signals or media, and/or programs and/or software implementations that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, implementations may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[00102] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

[00103] Furthermore, implementations of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers,...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems. Therefore, various implementations of techniques described herein may be provided via one or more of these technologies.

[00104] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a

communication network.

[00105] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application-specific integrated circuit).

[00106] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto-optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[00107] To provide for interaction with a user, implementations may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[00108] Implementations may be implemented in a computing system that includes a back-end component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a front-end component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an implementation, or any combination of such back-end, middleware, or front-end components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[00109] While certain features of the described implementations have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the various embodiments.