WO2020091650A1

WO2020091650A1 - Determining transmit timings

Info

Publication number: WO2020091650A1
Application number: PCT/SE2019/051025
Authority: WO
Inventors: Boris Dortschy; Erik Dahlman; Per-Erik Eriksson; Robert Baldemair; Yezi HUANG
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2018-10-30
Filing date: 2019-10-18
Publication date: 2020-05-07

Abstract

In one aspect, a method, in one or more network nodes, for determining a transmit timing for a user equipment, UE, or mobile termination, MT, having a link to a first base station and having a link to a second base station. The network node or nodes determine (1302) a first parameter indicative of propagation delay from the UE or MT to the first base station and determine (1304) a second parameter indicative of propagation delay from the UE or MT to the second base station. Based on the first and second parameters, downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations are coordinated (1306) so as to align reception at the UE or MT of the downlink transmissions within a pre-determined limit.

Description

DETERMINING TRANSMIT TIMINGS

TECHNICAL FIELD

The present disclosure generally relates to the field of wireless network communications, and more particularly, to determining transmit timings for transmissions to or from a user equipment (UE) or mobile termination (MT) having a link to a first base station and having a link to a second base station.

BACKGROUND

Densification via the deployment of more and more base stations (whether they are macro or micro base stations) is one of the mechanisms that can be employed to satisfy the ever- increasing demand for more and more bandwidth/capacity in mobile networks. Due to the availability of more spectrum in the millimeter-wave band, deploying small cells that operate in this band is an attractive deployment option for these purposes. However, deploying fiber to small cells, which is the usual way in which small cells are deployed, can end up being very expensive and impractical. Thus, employing a wireless link for connecting small cells to an operator’s network is a cheaper and practical alternative. One such solution is an integrated access backhaul (LAB) network, where the operator can utilize part of the radio resources for the backhaul link.

Integrated access and backhaul has been studied earlier in 3GPP in the scope of Long Term Evolution (LTE) Rel-lO. In that work, an architecture was adopted where a Relay Node (RN) has the functionality of both an LTE eNB and a user equipment (UE) modem. The RN is connected to a donor eNB that has a S1/X2 proxy functionality hiding the RN from the rest of the network. This architecture enables the Donor eNB to also be aware of the UEs behind the RN and hide, from the core network (CN), any UE mobility between the Donor eNB and RN.

During the development of Rel-lO, other architectures were also considered, e.g., where the RNs are more transparent to the Donor gNB and where a separate stand-alone P/S-GW node was allocated.

For the 5^th-generation (5G) wireless radio access network commonly referred to as“NR,” or “New Radio,” a similar architecture option can also be considered. One potential difference compared to LTE (besides lower layer differences) is that a gNB-CU/DU (Centralized Unit/Distributed Unit) split is defined for NR, which allows a separation of time critical Radio Link Control/Medium Access Control/Physical layer (RLC/MAC/PHY) protocols from less time critical Radio Resource Control/Packet Data Convergence Protocol

(RRC/PDCP) protocols.

Figure 1 illustrates a high-level view of the 5G network architecture, consisting of a Next Generation RAN (NG-RAN) and a 5G Core (5GC). The NG-RAN can comprise a set of gNodeB’s (gNBs) connected to the 5GC via one or more NG interfaces, whereas the gNBs can be connected to each other via one or more Xn interfaces. Each of the gNBs can support frequency-division duplexing (FDD), time-division duplexing (TDD), or a combination thereof.

The NG RAN logical nodes shown in Figure 1 (and described in 3GPP TR 38.801 vl.2.0) include a Central Unit (CU or gNB-CU) and one or more Distributed Units (DU or gNB- DU). CU is a logical node that is a centralized unit that hosts high layer protocols and includes a number of gNB functions, including controlling the operation of DUs. A DU is a decentralized logical node that hosts lower layer protocols and can include, depending on the functional split option, various subsets of the gNB functions. (As used herein, the terms “central unit” and“centralized unit” are used interchangeably, and the terms“distributed unit” and“decentralized unit” are used interchangeability.)

The NG, Xn-C and Fl interfaces shown in Figure 1 are logical interfaces. For NG-RAN, the NG and Xn-C interfaces for a split gNB (e.g., consisting of a gNB-CU and gNB-DUs) terminate in the gNB-CU. Likewise, for a deployment providing dual connectivity to both NR and the LTE radio network, i.e., the Evolved UMTS Terrestrial Radio Access Network, referred to as E-UTRAN-NR Dual Connectivity (EN-DC), the Sl-U and X2-C interfaces for a split gNB terminate in the gNB-CU. The gNB-CU connects to gNB-DUs over respective Fl logical interfaces. The gNB-CU and connected gNB-DUs are only visible to other gNBs and the 5GC as a gNB, e.g., the Fl interface is not visible beyond gNB-CU. Furthermore, a CU can host protocols such as RRC and PDCP, while a DU can host protocols such as RLC, MAC and PHY. Other variants of protocol distributions between CU and DU exist, such as hosting the RRC, PDCP and part of the RLC protocol in CU (e.g., Automatic Retransmission Request (ARQ) function), while hosting the remaining parts of the RLC protocol in the DU, together with MAC and PHY. In some exemplary embodiments, the CU is assumed to host RRC and PDCP, where PDCP is assumed to handle both UP traffic and CP traffic. Nevertheless, other exemplary embodiments may utilize other protocol splits that by hosting certain protocols in CU and certain others in the DU. Exemplary embodiments can also locate centralized control plane protocols (e.g., PDCP-C and RRC) in a different CU with respect to the centralized user plane protocols (e.g., PDCP-U).

Such a split of the gNB functionality could also be applied for the integrated access and backhaul case. Other differences anticipated in NR as compared to LTE with regards to IAB is the support of multiple hops as well as the support of redundant paths.

Currently in 3 GPP, the following architectures for supporting user plane traffic over IAB node has been captured in 3GPP TS 38.874 (version 0.4.0):

Architecture la

Architecture la leverages CU/DU-split architecture. Figure 2 shows the reference diagram for a two-hop chain of IAB-nodes underneath an IAB-donor, for architecture la.

In this architecture, each IAB node holds a DU and a Mobile Termination (MT). Via the MT, the IAB-node connects to an upstream IAB-node or the IAB-donor. Via the DU, the IAB- node establishes RLC channels to UEs and to MTs of downstream IAB-nodes. For MTs, this RLC channel may refer to a modified RLC*.

The donor also holds a DU to support UEs and MTs of downstream IAB-nodes. The IAB- donor holds a CU for the DUs of all IAB-nodes and for its own DU. Each DU on an IAB- node connects to the CU in the IAB-donor using a modified form of Fl, which is referred to as Fl*. Fl*-U runs over RLC channels on the wireless backhaul between the MT on the serving IAB-node and the DU on the donor. F 1 *-U transport between MT and DU on the serving IAB-node as well as between DU and CU on the donor is to be further studied.

An adaptation layer is added, which holds routing information, enabling hop-by-hop forwarding. It replaces the IP functionality of the standard Fl -stack. Fl*-U may carry a GTP- U header for the end-to-end association between CU and DU. In a further enhancement, information carried inside the GTP-U header may be included into the adaption layer.

Further, optimizations to RLC may be considered such as applying automatic repeat request (ARQ) only on the end-to-end connection opposed to hop-by-hop. The right side of Figure 2 shows two examples of such Fl*-U protocol stacks. In this figure, enhancements of RLC are referred to as RLC*. The MT of each IAB-node further sustains NAS connectivity to the NGC, e.g., for authentication of the IAB-node. It further sustains a PDU-session via the NGC, e.g., to provide the IAB-node with connectivity to the OAM.

Architecture lb

Architecture lb also leverages CU/DU-split architecture. Figure 3 shows the reference diagram for a two-hop chain of IAB-nodes underneath an IAB-donor, for architecture lb. Note that the IAB-donor only holds one logical CU. Whether an IAB node can connect to more than one upstream IAB-node or IAB-donor is to be further studied. In this architecture, each IAB-node and the IAB-donor hold the same functions as in architecture la. Also, as in architecture la, every backhaul link establishes an RLC channel, and an adaptation layer is inserted to enable hop-by-hop forwarding of F 1 * .

As opposed to architecture la, the MT on each IAB-node establishes a protocol data unit (PDU)-session with a User Plane Function (UPF) residing on the donor. The MT’s PDU- session carries Fl* for the collocated DU. In this manner, the PDU session provides a point- to-point link between CU and DU. On intermediate hops, the PDCP-PDUs of Fl* are forwarded via adaptation layer in the same manner as described for architecture la. The right side of Figure 3 shows an example of the Fl*-U protocol stack.

Architecture 2a

Figure 4 depicts the reference diagram for a two-hop chain of IAB nodes for architecture 2a. In this architecture, the IAB-node holds an MT to establish an NR Uu link with a gNB on the parent IAB-node or IAB-donor. Via this NR-Uu link, the MT sustains a PDU session with a UPF that is collocated with the gNB. In this manner, an independent PDU session is created on every backhaul link. Each IAB-node further supports a routing function to forward data between PDU-sessions of adjacent links. This creates a forwarding plane across the wireless backhaul. Based on PDU-session type, this forwarding plane supports IP or Ethernet. In the event that the PDU session type is Ethernet an IP layer can be established on top. In this manner, each IAB-node obtains IP connectivity to the wireline backhaul network. An IAB node can connect to more than one upstream IAB-node or IAB-donor.

All IP -based interfaces such as NG, Xn, Fl, N4, etc., are carried over this forwarding plane. In the case of Fl, the UE-serving IAB-Node would contain a DU for access links in addition to the gNB and UPF for the backhaul links. The CU for access links would reside in or beyond the IAB Donor. The right side of Figure 4 shows an example of the NG-U protocol stack for IP -based and for Ethernet-based PDU-session type, for architecture 2a. For the case that the IAB-node holds a DU for UE-access, it may not be required to support PDCP -based protection on each hop since the end user data will already be protected using end to end PDCP between the UE and the CU. For Non- Standalone (NSA) operation with Evolve Packet Core (EPC), the MT is dual-connected with the network using E-UTRAN-NR Dual

Connectivity (EN-DC). In this case, the IAB-node’ s MT sustains a PDN-connection with a LIPA Gateway (LIPA - Local IP Access) (L-GW) residing on the parent IAB-node or the IAB-donor. All IP -based interfaces such as Sl, S5, X2, etc. are carried over this forwarding plane. There are other architectures that may have, in common, that data to an access UE serving gNB or DU in an IAB node is carried over a hop-by-hop or end-to-end PDU session. All of them have a MT as part of the IAB node that terminates the PDU session for its respective gNB or DU.

Wireless backhaul links are vulnerable to blockage, e.g., due to moving objects such as vehicles, due to seasonal changes (foliage), or due to infrastructure changes (new buildings). Such vulnerability also applies to physically stationary IAB-nodes. Also, traffic variations can create uneven load distribution on wireless backhaul links leading to local link or node congestion.

Topology adaptation refers to procedures that reconfigure the backhaul network under circumstances such as blockage or local congestion preferably without discontinuing services for UEs. It is required to support topology adaptation for physically fixed relays to enable robust operation, e.g., mitigate blockage and load variation on backhaul links.

The following IAB topologies, examples of which are illustrated in Figure 5, are considered in IAB:

1. Spanning tree (ST), illustrated on the left-hand side of Figure 5, and

2. Directed acyclic graph (DAG), shown on the right-hand side of Figure 5.

Note that in Figure 5, the arrows indicate the directionality of the corresponding graph edges. One way to provide robust operation for physically fixed relays is to provide redundant links to two or more parent nodes. For a directed acyclic graph (DAG) topology, the following options can be considered for redundant links and routes, as illustrated in Figure 6. First, the IAB-node may be multi- connected, i.e., with links to multiple parent nodes, as shown in part (a) of Figure 6. Second, the IAB-node may have multiple routes to another node, e.g. the IAB-donor. This is shown in part (b) of Figure 6. Alternatively, both options can be combined, i.e., the IAB-node may have redundant routes to another node via multiple parents, as shown in part (c) of Figure 6. Multi-connectivity or route redundancy may be used for back-up purposes. It is also possible that redundant routes are used concurrently, e.g., to achieve load balancing, reliability, etc. Examples of this are shown in Figure 7, for IAB architecture group 1, using either a single MT function or multiple MT functions.

A base station (eNB or gNB) requires a UE to align its transmission timing in the uplink direction according to timing alignment information provided by the base station, with the objective being that the reception of the EIE’s uplink signal is aligned with respect to uplink signals received from other EIEs. This timing alignment primarily depends on the propagation delay between the TIE and the base station and therefore depends on the distance between the two nodes or, more generally, the path length. The timing alignment also depends on all EIEs connected to a base station.

In the event that a MT of an IAB node or a TIE wants to maintain and/or use links to two or more base stations (or IAB parent nodes) in overlapping signal spectrum at the same time, as depicted in Figure 7, it can be unlikely that transmission timing in the uplink direction to one base stations complies with the timing requirements for a second base station, because at least the wireless path lengths will usually differ. If a TIE does not follow its requested uplink timing alignment, its signal reception at the base station is not likely to be aligned with the reception of signals from other EIEs. At the same time, a similar misalignment is likely in the downlink direction, when, due to different path lengths, downlink signals from different base stations arrive at the EIE with different downlink reception timing. Misalignment in reception timing between different signals, generated according to 3GPP TS 38.211 V15.2.0 (2018-06) or 3GPP TS 36.211 V15.3.0 (2018-09), can lead to losing orthogonality between different sub-carriers. This in turn can cause severe signal quality degradation.

The question then becomes how EIE uplink/downlink timings to/from different base stations and/or base station uplink/downlink timings from/to different EIEs can be harmonized. One possibility is that an IAB node supports multiple MTs. The multiple terminals could individually connect to one out of two or more base stations or parent nodes at the same time. However, this approach requires duplicating UE or MT transceiver arrangements.

SUMMARY

In Orthogonal Frequency-Division Multiplexing (OFDM), the concept of a cyclic-prefix, or more generally, a guard interval, which may include a cyclic prefix or a so-called unique word, in unique- word-based OFDM and Discrete Fourier Transform (DFT) Spread (DFTS)- OFDM, allows for low-complexity channel dispersion equalization. At the same time, having a cyclic-prefix of length X seconds can also be used, according to some of the embodiments described herein, to compensate for up to X seconds reception timing misalignment of signals from different sources.

According to embodiments described herein, a solution to managing the different timings for redundant radio links is to deviate from the ideal timing conventions within operational and required limits. In an example, the base stations can measure the propagation delay between each of them and the MT or UE. The base stations provide the propagation delay information to a timing-coordination network function (T-NF), which is a logical function that may reside in one of the base stations or in some other network node. The T-NF feeds back information and/or adjustment instructions, such that if a MT or UE receives from two or more base stations, the base stations are coordinated to individually adjust their downlink transmission timing such that the received signals at the MT or UE are received: with frame timing alignment at least better than the signals’ cyclic-prefix length (or a configurable percentage of the cyclic prefix length); with slot timing alignment at least better than the signals’ cyclic-prefix length (or a configurable percentage of the cyclic prefix length); and with OFDM symbol timing alignment at least better than the signals’ cyclic-prefix length (or a configurable percentage of the cyclic prefix length). In this example, the base station downlink timing adjustment should stay within a range so that requirements as in 3GPP TS 38.133 V15.1.0 (2018-03) are complied with.

Similarly, if an MT or UE transmits to two or more base stations, the base stations may be coordinated to adjust the MT’s or UE’s uplink transmit timing, through the use of time advance commands, so that the UE transmit timing to both or all base stations is identical (or at least within the granularity of a timing advance step or a configured/pre-determined tolerance) and such that the base stations’ reception of the MT’s or UE’s uplink signal is aligned within a cyclic-prefix length of signals received from the other UEs that connect to the same BS. In the alternative, the base stations are coordinated to adjust the MT’s or UE’s uplink transmit timing advance command such that the UE transmit timing to both or all base stations is identical (or at least within the granularity of a timing advance step or configured/pre-determined tolerance). The resulting uplink reception timing at each base station is used as a reference to set the timing advance to all other ETEs connected to respective base station, such that the timing of uplink reception from each UE connected to respective base station is identical, or at least within a predetermined tolerance of another.

In some embodiments, the coordinating of the transmit timing advance commands sent to the UE or MT is performed so as to ensure that reception at each of the first and second base stations of the uplink transmissions from the UE or MT is aligned with reception of uplink signals by the respective base station from first one or more other UEs or MTs, within a pre-determined limit.

In some embodiments, after the coordinating, the method includes sending transmit timing advance commands to second one or more other UEs or MTs, by or via the first base station, so as to align reception at the first base station of uplink transmissions from the second one or more UEs or MTs with reception at the first base of uplink transmissions from the UE or MT, within a/the pre-determined limit.

According to some embodiments, a method, in one or more network nodes, for determining transmit timings for transmissions to a UE or MT having a link to a first base station and having a link to a second base station includes determining a first parameter indicative of propagation delay from the UE or MT to the first base station and determining a second parameter indicative of propagation delay from the UE or MT to the second base station. The method further includes, based on the first and second parameters, coordinating downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and base stations within a pre-determined limit.

According to some embodiments, a method, in one or more network nodes, for determining a transmit timing for a UE or MT having a link to a first base station and having a link to a second base station includes determining a first parameter indicative of propagation delay from the UE or MT to the first base station and determining a second parameter indicative of propagation delay from the UE or MT to the second base station. The method further includes, based on the first and second parameters, coordinating transmit timing advance commands sent to the UE or MT so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another. According to some embodiments, a method, in a first base station, for determining a transmit timing for a UE or MT having a link to the first base station and having a link to a second base station includes measuring a parameter indicative of propagation delay from the UE or MT to the first base station and sending the measured parameter or a parameter derived from the measured parameter to a coordinating network node. The method further includes receiving, from the coordinating network node, an indication of a timing advance adjustment for the UE or MT, and sending, to the UE or MT, one or more timing advance commands based on the indication of the timing advance adjustment.

Further aspects of the present invention are directed to an apparatus, network node, base station, wireless device, UE, computer program products or computer readable storage medium corresponding to the methods summarized above and functional implementations of the above-summarized apparatus and UE.

The embodiments allow an MT of an IAB node or a UE to maintain and use links to two or more base stations (or parent nodes) at the same time, where even the ideal operation of each individual link requires different timing requirements. Of course, the present invention is not limited to the above features and advantages. Those of ordinary skill in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates an example of 5G logical network architecture. Figure 2 is a reference diagram for integrated access backhaul (IAB) architecture la.

Figure 3 is a reference diagram for architecture lb.

Figure 4 is a reference diagram for architecture 2a.

Figure 5 illustrates example IAB topologies. Figure 6 illustrates redundant links and routes in a directed acyclic graph topology.

Figure 7 illustrates route redundancy in IAB architecture 1.

Figure 8 shows timing of uplink and downlink signals in an example network of three nodes.

Figure 9 is a schematic diagram illustrating coordination of timing adjustments with a Timing-Coordination Network Function (T-NF).

Figure 10 is a signal and information exchange diagram illustrating a timing adjustment procedure.

Figure 11 illustrates an example network node, according to some embodiments.

Figure 12 is a process flow diagram illustrating an example method for determining a transmit timing for a user equipment (UE) or MT.

Figure 13 is a process flow diagram illustrating an example method for determining transmit timings for transmissions to a UE or MT

Figure 14 is a process flow diagram illustrating another example method for determining a transmit timing for UE or MT. Figure 15 is a block diagram illustrating an example UE, according to some embodiments.

Figure 16 illustrates an example telecommunication network connected to a host via an intermediate network, in accordance with some embodiments.

Figure 17 illustrates a host computer communicating over a partially wireless connection with, in accordance with some embodiments. Figure 18 is a flowchart illustrating methods implemented in a communication system that includes a host computer, a base station, and a user equipment, in accordance with some embodiments.

Figure 19 is another flowchart illustrating methods implemented in a communication system that includes a host computer, a base station, and a user equipment, in accordance with some embodiments. Figure 20 shows another flowchart illustrating methods implemented in a communication system that includes a host computer, a base station, and a user equipment, in accordance with some embodiments.

Figure 21 shows still another flowchart illustrating methods implemented in a communication system that includes a host computer, a base station, and a user equipment, in accordance with some embodiments.

Figure 22 is a block diagram illustrating functional components of an example network node, according to some embodiments.

Figure 23 is another block diagram illustrating functional components of an example network node, according to some embodiments.

DETAILED DESCRIPTION

Exemplary embodiments of the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which examples of embodiments of inventive concepts are shown. Inventive concepts may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of present inventive concepts to those skilled in the art. It should also be noted that these embodiments are not mutually exclusive. Components from one embodiment can be tacitly assumed to be present/used in another embodiment. Any two or more embodiments described in this document may be combined with each other.

Embodiments described herein involve the situation where an MT or TIE transmits to two or more base stations. The base stations may be coordinated to adjust the MT’s or ETE’s uplink transmit timing advance command such that the TIE transmit timing to both or all base stations is identical, or at least within the granularity of a timing advance step or a

configured/pre-determined tolerance.

Figure 8 illustrates a network of three nodes, where nodes Nl and N2 are considered base stations and node N3 is considered a EGE or MT of an IAB node that is transmitting and receiving to/from Nl and N2 simultaneously. Without loss of generalization, it is assumed that Nl and N2 start transmitting their downlink signal simultaneously and the relative timing of the uplink signal received by Nl and N2 is identical to their downlink transmission timing. The propagation delay between Nl and N3 is denoted as TP2a, and between N2 and N3 as TP2b. It is further assumed that TP2a > TP2b.

Without any timing adjustments, the timing relations would look like those depicted in part (a) of Figure 8. Under the assumption of simultaneous downlink transmission and uplink reception at node Nl and N2, node N3 would receive its downlink signal from Nl shifted by A_DL = TP2a - TP2b relative to the received signal from N2. At the same time, if propagation delay from Nl and N2 to N3 is different, N3 would be instructed via timing advance command to transmit to Nl by A_UL earlier than to N2. For reasons of symmetry (same propagation delay in UL and DL) one can assume A_DL = A_UL In the following, it is assumed that a receiver R(k) can process two signals arriving with a maximum timing difference of A_max(k), whereas A_max(k) can depend on the receiver itself and/or all channels over which signals are received. A_max(k) may also depend on the signal-to-noise ratio (SNR) and used Modulation and Coding Scheme (MCS), since lower SNR and/or MCS can tolerate larger inter-symbol interference and thus larger timing misalignment.

Some embodiments provide a solution for the topology indicated in Figure 8. An extension of this approach for more than two base stations is straightforward for a skilled person.

With the assumption TP2a > TP2b, Nl can advance its downlink transmission by D TcI and/or delay (by means of uplink timing advance control signaling) its uplink reception by A_Rx 1 N2 can delay its downlink transmission by D_Tc2 and/or advance (by means of uplink timing advance control signaling) its uplink reception by A_Rx2. This is indicated in the upper part (timing adjustments for Nl and N2) of part (b) of Figure 8.

If Nl and N2 span overlapping cells, D_Tc1 and D_Tc2 are limited by constraints, such as the maximum downlink timing mis-alignment must not exceed thresholds (e.g., a maximum of 3us). For the example in part (b) of Figure 8, it is further required that abs(A _DL -

D_Tc1 - D_Tc2) < R(N3) , where D_Tc1 andA_Tx2 are assumed to be positive and where R(N3) is the alignment requirement for N3, e.g., a cyclic prefix length or a portion of a cyclic prefix length.

If A Rxl + A_Rx2 = A UL (uplink), then by definition, it is required that A Rxl < R(Nl) and A_Rx2 < R(N2), where R(Nl) and R(N2) are alignment requirements for N 1 and N2, respectively. An exception that would relax these last two requirements would be if Nl and N2 would harmonize, the uplink reception timing alignment for all UEs connect to Nl and N2, respectively, by delaying the uplink transmission timing for all UEs connected to Nl by A Rxl and advancing the uplink transmission timing for all UEs connected to N2 by A_Rx2. The determining of the timing adjustment terms D TcI, D_Tc2, A Rxl and A_Rx2 can be performed by a network function with which Nl and N2 can communicate, as indicated in Figure 9. This network function, illustrated in Figure 9 as a Timing-Coordination Network Function (T-NF), can be co-located with Nl or N2, in some embodiments, or in some other network node. In some embodiments, for example, this coordinating network function may reside in the same physical node as a CU, in a split-gNB architecture.

To determine the timing adjustment terms, as depicted in the signal and information exchange diagram in Figure 10, a UE or MT of an IAB node N3 sends a Random- Access Preamble to Nl, based on which Nl can determine the propagation delay between Nl and N3. Sending a Random- Access Preamble to N2 allows N2 to determine the propagation delay between N2 and N3 (the two random access preambles can be two different random access preambles, or it can be the same random access preamble received by both Nl and N2). N2 and N3 connect to the Timing-coordination Network-Function (T-NF) and provide their propagation delay measurements. T-NF determines individual adjustment terms for the DL Tx timing of Nl and N2 and the UL Rx timing for Nl and N2 and feeds back this information to Nl and N2. N 1 and N2 can use this information to adjust the timing advance command to N3. In another embodiment, Nl and N2 adjust the timing advance command to all their connected UEs. Nl and N2 can also use the information provided from T-NF to adjust the DL transmit timing. We note the T-NF could be in a separate node, it could be part of Nl or N2, or it could be a distributed function. Some embodiments may also be applicable to the case when there are MTs in an IAB node, as depicted in parts (c) and (d) of Figure 7.

Accordingly, Figure 11 shows a network node 30, which may be configured to carry out all or parts of one or more of these disclosed techniques. More particularly, network node 30, which in the illustrated example is a radio network node (because it includes a radio for communicating with one or more UEs or MTs), may perform those operations attributed in the above discussion to either Nl or N2, in various embodiments. In some embodiments, it may also carry out the operations attributed in the above discussion to the T-NF.

In other embodiments, the operations attributed to the T-NF in the above discussions may be performed in a network node separate from both Nl and N2, in which case this network node may not be a radio network node at all. Such a network node may have a structure like the network node 30 illustrated in Figure 11, but without the transceiver circuitry 36 and antennas 34, for example. In short, it should be understood that the functionality attributed to Nl, N2, and the T-NF in the discussion above may be distributed among several different network nodes, in various ways, especially given the various ways that base station functionality may be distributed, e.g., as in the split-gNB model (with CU and DU logical nodes) described above.

Network node 30 may be an evolved Node B (eNodeB), Node B or gNB. While a radio network node 30 is shown in Figure 11, the operations can be performed by other kinds of network nodes, including a radio network node such as base station, radio base station, base transceiver station, base station controller, network controller, NR base station (BS), Multi cell/multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH), or a multi- standard BS (MSR BS). Network node 30 may also, in some cases, be a core network node (e.g., MME, SON node, a coordinating node, positioning node, MDT node, etc.), or even an external node (e.g., 3rd party node, a node external to the current network), etc. Network node 30 may also comprise test equipment.

In the non-limiting embodiments described below, network node 30 will be described as being configured to operate as a cellular network access node in an LTE network or NR network. In some embodiments, the technique can be implemented in the RRC layer. The RRC layer could be implemented by one or more network nodes in a cloud environment and hence some embodiments can be implemented in a cloud environment.

Those skilled in the art will readily appreciate how each type of node may be adapted to carry out one or more of the methods and signaling processes described herein, e.g., through the modification of and/or addition of appropriate program instructions for execution by processing circuits 32. Network node 30 facilitates communication between wireless terminals (e.g., UEs), other network access nodes and/or the core network. Network node 30 may include communication interface circuitry 38 that includes circuitry for communicating with other nodes in the core network, radio nodes, and/or other types of nodes in the network for the purposes of providing data and/or cellular communication services. Network node 30 communicates with wireless devices using antennas 34 and transceiver circuitry 36. Transceiver circuitry 36 may include transmitter circuits, receiver circuits, and associated control circuits that are collectively configured to transmit and receive signals according to a radio access

technology, for the purposes of providing cellular communication services. Network node 30 also includes one or more processing circuits 32 that are operatively associated with the transceiver circuitry 36 and, in some cases, the communication interface circuitry 38. Processing circuitry 32 comprises one or more digital processors 42, e.g., one or more microprocessors, microcontrollers, Digital Signal Processors (DSPs), Field

Programmable Gate Arrays (FPGAs), Complex Programmable Logic Devices (CPLDs), Application Specific Integrated Circuits (ASICs), or any mix thereof. More generally, processing circuitry 32 may comprise fixed circuitry, or programmable circuitry that is specially configured via the execution of program instructions implementing the functionality taught herein, or some mix of fixed and programmed circuitry. Processor 42 may be multi- core, i.e., having two or more processor cores utilized for enhanced performance, reduced power consumption, and more efficient simultaneous processing of multiple tasks.

Processing circuitry 32 also includes a memory 44. Memory 44, in some embodiments, stores one or more computer programs 46 and, optionally, configuration data 48. Memory 44 provides non-transitory storage for the computer program 46 and it may comprise one or more types of computer-readable media, such as disk storage, solid-state memory storage, or any mix thereof. Here,“non-transitory” means permanent, semi-permanent, or at least temporarily persistent storage and encompasses both long-term storage in non-volatile memory and storage in working memory, e.g., for program execution. By way of non limiting example, memory 44 comprises any one or more of SRAM, DRAM, EEPROM, and FLASH memory, which may be in processing circuitry 32 and/or separate from processing circuitry 32. Memory 44 may also store any configuration data 48 used by the network access node 30. Processing circuitry 32 may be configured, e.g., through the use of appropriate program code stored in memory 44, to carry out one or more of the methods and/or signaling processes detailed herein.

Processing circuitry 32 of the network node 30 is configured, according to some

embodiments, to perform all or part of the techniques described herein for one or more network nodes of a wireless communication system, including determining a transmit timing for a UE or MT having a link to a first base station and having a link to a second base station. Thus, processing circuitry 32 may be configured to determine a first parameter indicative of propagation delay from the UE or MT to the first base station and to determine a second parameter indicative of propagation delay from the UE or MT to the second base station. Processing circuitry 32 may also be configured to, based on the first and second parameters, coordinate transmit timing advance commands sent to the UE or MT so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another.

The processing circuitry 32 of network node 30 is, in some embodiments, configured to perform all or parts of a method 1200, shown by the flowchart of Figure 12. More generally, it will be appreciated that a single node, acting as a T-NF, for example, may carry out the method shown in Figure 12. Likewise, two or more network nodes may operate together to carry out the method shown in Figure 12.

Method 1200 includes determining a first parameter indicative of propagation delay from the UE or MT to the first base station (block 1202) and determining a second parameter indicative of propagation delay from the UE or MT to the second base station (block 1204). In some embodiments, e.g., where the method is carried out by a single network node separate from either of the first and second base stations, this determining of the first and second parameters may comprise receiving the parameters from the first and second base stations, respectively, e.g., as shown in Figure 10. In other embodiments, e.g., where the method of Figure 12 is carried out by the first base station, the first base station may determine the first parameter by measuring it, while determining the second parameter by receiving it from the second base station.

Method 1200 also includes the step of coordinating transmit timing advance commands sent to the UE or MT, based on the first and second parameters, so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another (block 1206). Here, as elsewhere herein, “coordinating transmit timing advance commands” refers to actions taken to cause appropriate transmit timing advance commands to be sent to the UE or MT. In some embodiments, this may include the sending of the feedback information to the first and second base stations, based on the first and second propagation delay parameters, as shown in Figure 10. In some embodiments, e.g., where the coordinating is carried out by one of the base stations, this may include the actual sending of all or part of the transmit timing advance commands to the UE or MT. It will be appreciated that the base stations and T-NF may together be regarded as“one or more network nodes” that carry out the coordinating step, such that it includes both determining the appropriate timing differences and/or adjustments and communicating corresponding timing advance commands to the UE or MT.

In some embodiments, the coordinating of the transmit timing advance commands sent to the UE or MT is performed so as to ensure that reception at each of the first and second base stations of the uplink transmissions from the UE or MT is aligned with reception of uplink signals by the respective base station from first one or more other UEs or MTs, within a pre- determined limit, e.g., the length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions. This inter-symbol guard interval may include a cyclic prefix or a unique word, in a unique-word OFDM signal, for example. Method 1200 may include, after the coordinating, sending transmit timing advance commands to second one or more other UEs or MTs, by or via the first base station, so as to align reception at the first base station of uplink transmissions from the second one or more UEs or MTs with reception at the first base of uplink transmissions from the UE or MT, within a/the pre-determined limit. Again, the pre-determined limit may be a length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions. The inter-symbol guard interval may include a cyclic prefix or a unique word, in a unique-word OFDM signal.

The predetermined tolerance mentioned above may be a granularity of a timing advance step. As noted, the coordinating may be performed by either the first or second base station, or by a separate network node. The coordinating of the transmit timing advance commands sent to the UE or MT may include determining a first uplink timing adjustment parameter, based on the first and second parameters, and sending the first uplink timing adjustment parameter to the first base station.

In some embodiments, determining the first parameter indicative of propagation delay from the UE or MT to the first base station includes receiving the first parameter from the first base station. In some cases, the node performing the coordinating could receive both parameters from the respective base station, in the event that it is a separate node, or just one, in the event that it is co-located with the second base station.

In some embodiments, determining the second parameter indicative of propagation delay from the UE or MT to the second base station includes measuring the second parameter, based on a random access preamble transmitted by the UE or MT. This is compatible with the coordinating function being located in one of the base stations. In such embodiments, the base station performing the coordinating can receive the parameter from the other base station.

One or more network nodes like network node 30 may be configured, according to other embodiments, to perform other techniques described herein for one or more network nodes.

In particular, these one or more network nodes may be configured to coordinate downlink transmit timings for the first and second base stations. In some such embodiments, the one or more network nodes are configured to determine a first parameter indicative of propagation delay from the UE or MT to the first base station and to determine a second parameter indicative of propagation delay from the UE or MT to the second base station. The one or more network nodes are further configured to, based on the first and second parameters, coordinate downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and base stations within a pre-determined limit. Figure 13 shows a method 1300 consistent with these embodiments. Again, the operations shown in Figure 13 may be performed by a single network node, in some embodiments, or may be split among two or more network nodes, in others.

Method 1300 includes determining a first parameter indicative of propagation delay from the UE or MT to the first base station (block 1302) and determining a second parameter indicative of propagation delay from the UE or MT to the second base station (block 1304). Again, this determining may be done by receiving one or each parameter from the corresponding base station. The determining may include measuring one or each parameter, in other embodiments.

Method 1300 also includes, based on the first and second parameters, coordinating downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and base stations within a pre-determined limit (block 1306).

Once again, the pre-determined limit may be a length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions. The inter-symbol guard interval may include a cyclic prefix or a unique word, in a unique-word OFDM signal.

In some embodiments, the coordinating is performed so as to align received slot timings and/or frame timings of the downlink transmissions sent to the UE or MT by the first and second base stations, within the pre-determined limit.

According to some embodiments, processing circuitry 32 of the network node 30 is configured, according to other embodiments, to perform techniques described herein for a first base station, including determining a transmit timing for a UE or MT having a link to the first base station and having a link to a second base station. Processing circuitry 32 is configured to measure a parameter indicative of propagation delay from the UE or MT to the first base station and send the measured parameter or a parameter derived from the measured parameter to a coordinating network node. Processing circuitry 32 is also configured to receive, from the coordinating network node, an indication of a timing advance adjustment for the UE or MT, and send, to the UE or MT, one or more timing advance commands based on the indication of the timing advance adjustment.

The processing circuitry 32 in these embodiments may thus be configured to perform a corresponding method 1400, shown by the flowchart of Figure 14.

Method 1400 includes measuring a parameter indicative of propagation delay from the UE or MT to the first base station (block 1402) and sending the measured parameter or a parameter derived from the measured parameter to a coordinating network node (block 1404). Method 1400 also includes receiving, from the coordinating network node, an indication of a timing advance adjustment for the UE or MT (block 1406), and sending, to the UE or MT, one or more timing advance commands based on the indication of the timing advance adjustment (block 1408).

Figure 15 illustrates a diagram of a UE 50 configured to carry out one or more of the disclosed techniques, according to some embodiments. UE 50 may be considered to represent any wireless devices or mobile terminals that may operate in a network, such as a UE in a cellular network. Other examples may include a communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), a sensor equipped with UE, PDA (personal digital assistant), tablet, IPAD tablet, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), etc.

UE 50 is configured to communicate with a network node or base station in a wide-area cellular network via antennas 54 and transceiver circuitry 56. Transceiver circuitry 56 may include transmitter circuits, receiver circuits, and associated control circuits that are collectively configured to transmit and receive signals according to a radio access

technology, for the purposes of using cellular communication services. This radio access technologies can be NR and LTE for the purposes of this discussion.

UE 50 also includes one or more processing circuits 52 that are operatively associated with the radio transceiver circuitry 56. Processing circuitry 52 comprises one or more digital processing circuits, e.g., one or more microprocessors, microcontrollers, DSPs, FPGAs, CPLDs, ASICs, or any mix thereof. More generally, processing circuitry 52 may comprise fixed circuitry, or programmable circuitry that is specially adapted via the execution of program instructions implementing the functionality taught herein or may comprise some mix of fixed and programmed circuitry. Processing circuitry 52 may be multi-core. Processing circuitry 52 also includes a memory 64. Memory 64, in some embodiments, stores one or more computer programs 66 and, optionally, configuration data 68. Memory 64 provides non-transitory storage for computer program 66 and it may comprise one or more types of computer-readable media, such as disk storage, solid-state memory storage, or any mix thereof. By way of non-limiting example, memory 64 comprises any one or more of SRAM, DRAM, EEPROM, and FLASH memory, which may be in processing circuitry 52 and/or separate from processing circuitry 52. Memory 64 may also store any configuration data 68 used by UE 50. Processing circuitry 52 may be configured, e.g., through the use of appropriate program code stored in memory 64, to carry out one or more of the methods and/or signaling processes detailed hereinafter.

Processing circuitry 52 of the UE 50 is configured, according to some embodiments, to perform any methods that support or correspond with the techniques described herein for the network nodes or first base station.

Figure 16, according to some embodiments, illustrates a communication system that includes a telecommunication network 1610, such as a 3GPP-type cellular network, which comprises an access network 1611, such as a radio access network, and a core network 1614. The access network 1611 comprises a plurality of base stations l6l2a, l6l2b, l6l2c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area l6l3a, l6l3b, l6l3c. Each base station l6l2a, l6l2b, l6l2c is connectable to the core network 1614 over a wired or wireless connection 1615. A first UE 1691 located in coverage area l6l3c is configured to wirelessly connect to, or be paged by, the corresponding base station l6l2c. A second UE 1692 in coverage area l6l3a is wirelessly connectable to the corresponding base station l6l2a. While a plurality of UEs 1691, 1692 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 1612.

The telecommunication network 1610 is itself connected to a host computer 1630, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 1630 may be under the ownership or control of a service provider or may be operated by the service provider or on behalf of the service provider. The connections 1621, 1622 between the telecommunication network 1610 and the host computer 1630 may extend directly from the core network 1614 to the host computer 1630 or may go via an optional intermediate network 1620. The intermediate network 1620 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 1620, if any, may be a backbone network or the Internet; in particular, the intermediate network 1620 may comprise two or more sub-networks (not shown). The communication system of Figure 16 enables connectivity between one of the connected UEs 1691, 1692 and the host computer 1630. The connectivity may be described as an over- the-top (OTT) connection 1650. The host computer 1630 and the connected UEs 1691, 1692 are configured to communicate data and/or signaling via the OTT connection 1650, using the access network 1611, the core network 1614, any intermediate network 1620 and possible further infrastructure (not shown) as intermediaries. The OTT connection 1650 may be transparent in the sense that the participating communication devices through which the OTT connection 1650 passes are unaware of routing of uplink and downlink communications. For example, a base station 1612 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 1630 to be forwarded (e.g., handed over) to a connected UE 1691. Similarly, the base station 1612 need not be aware of the future routing of an outgoing uplink communication originating from the UE 1691 towards the host computer 1630.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 17. In a communication system 1700, a host computer 1710 comprises hardware 1715 including a communication interface 1716 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 1700. The host computer 1710 further comprises processing circuitry 1718, which may have storage and/or processing capabilities. In particular, the processing circuitry 1718 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 1710 further comprises software 1711, which is stored in or accessible by the host computer 1710 and executable by the processing circuitry 1718. The software 1711 includes a host application 1712. The host application 1712 may be operable to provide a service to a remote user, such as a UE 1730 connecting via an OTT connection 1750 terminating at the UE 1730 and the host computer 1710. In providing the service to the remote user, the host application 1712 may provide user data which is transmitted using the OTT connection 1750.

The communication system 1700 further includes a base station 1720 provided in a telecommunication system and comprising hardware 1725 enabling it to communicate with the host computer 1710 and with the UE 1730. The hardware 1725 may include a

communication interface 1726 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 1700, as well as a radio interface 1727 for setting up and maintaining at least a wireless connection 1770 with a UE 1730 located in a coverage area (not shown in Figure 17) served by the base station 1720. The communication interface 1726 may be configured to facilitate a connection 1760 to the host computer 1710. The connection 1760 may be direct or it may pass through a core network (not shown in Figure 17) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 1725 of the base station 1720 further includes processing circuitry 1728, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 1720 further has software 1721 stored internally or accessible via an external connection.

The communication system 1700 further includes the UE 1730 already referred to. Its hardware 1735 may include a radio interface 1737 configured to set up and maintain a wireless connection 1770 with a base station serving a coverage area in which the UE 1730 is currently located. The hardware 1735 of the UE 1730 further includes processing circuitry 1738, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 1730 further comprises software 1731, which is stored in or accessible by the UE 1730 and executable by the processing circuitry 1738. The software 1731 includes a client application 1732. The client application 1732 may be operable to provide a service to a human or non-human user via the UE 1730, with the support of the host computer 1710. In the host computer 1710, an executing host application 1712 may communicate with the executing client application 1732 via the OTT connection 1750 terminating at the UE 1730 and the host computer 1717. In providing the service to the user, the client application 1732 may receive request data from the host application 1712 and provide user data in response to the request data. The OTT connection 1750 may transfer both the request data and the user data. The client application 1732 may interact with the user to generate the user data that it provides. It is noted that the host computer 1710, base station 1720 and UE 1730 illustrated in Figure 17 may be identical to the host computer 1630, one of the base stations l6l2a, l6l2b, l6l2c and one of the UEs 1691, 1692 of Figure 16, respectively. This is to say, the inner workings of these entities may be as shown in Figure 17 and independently, the surrounding network topology may be that of Figure 16.

In Figure 17, the OTT connection 1750 has been drawn abstractly to illustrate the

communication between the host computer 1710 and the use equipment 1730 via the base station 1720, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 1730 or from the service provider operating the host computer 1710, or both. While the OTT connection 1750 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 1770 between the UE 1730 and the base station 1720 is in accordance with the teachings of the embodiments described throughout this disclosure, such as provided by nodes such as UE 50 and network node 30, along with the corresponding methods 1200, 1300, 1400. The embodiments described herein allow an MT of an IAB node or a UE to maintain and use links to two or more base stations (or parent nodes) at the same time, where even the ideal operation of each individual link requires different timing requirements. The teachings of these embodiments may improve the data rate, capacity, latency and/or power consumption for the network and UE 1730 using the OTT connection 1750 for emergency warning systems and thereby provide benefits such as more efficient and targeted emergency messaging that saves on network and UE resources while improving the ability of users to take safe action.

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1750 between the host computer 1710 and UE 1730, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 1750 may be implemented in the software 1711 of the host computer 1710 or in the software 1731 of the UE 1730, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 1750 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 1711, 1731 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1750 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 1720, and it may be unknown or imperceptible to the base station 1720. Such procedures and functionalities may be known and practiced in the art. In certain

embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 1710 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 1711, 1731 causes messages to be transmitted, in particular, empty or‘dummy’ messages, using the OTT connection 1750 while it monitors propagation times, errors etc. Figure 18 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.

The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 16 and 17. For simplicity of the present disclosure, only drawing references to Figure 18 will be included in this section. In a first step 1810 of the method, the host computer provides user data. In an optional substep 1811 of the first step 1810, the host computer provides the user data by executing a host application. In a second step 1820, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 1830, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 1840, the UE executes a client application associated with the host application executed by the host computer.

Figure 19 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 16 and 17. For simplicity of the present disclosure, only drawing references to Figure 19 will be included in this section. In a first step 1910 of the method, the host computer provides user data. In an optional substep (not shown), the host computer provides the user data by executing a host application. In a second step 1920, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 1930, the UE receives the user data carried in the transmission.

Figure 20 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 16 and 17. For simplicity of the present disclosure, only drawing references to Figure 20 will be included in this section. In an optional first step 2010 of the method, the UE receives input data provided by the host computer. Additionally, or alternatively, in an optional second step 2020, the UE provides user data. In an optional substep 2021 of the second step 2020, the UE provides the user data by executing a client application. In a further optional substep 2011 of the first step 2010, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 2030, transmission of the user data to the host computer. In a fourth step 2040 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Figure 21 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment.

The communication system includes a host computer, a base station and a UE which may be those described with reference to Figures 16 and 17. For simplicity of the present disclosure, only drawing references to Figure 21 will be included in this section. In an optional first step 2110 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 2120, the base station initiates transmission of the received user data to the host computer. In a third step 2130, the host computer receives the user data carried in the transmission initiated by the base station.

As discussed in detail above, the techniques described herein, e.g., as illustrated in the process flow diagrams of Figures 12-14, may be implemented, in whole or in part, using computer program instructions executed by one or more processors. It will be appreciated that a functional implementation of these techniques may be represented in terms of functional modules, where each functional module corresponds to a functional unit of software executing in an appropriate processor or to a functional digital hardware circuit, or some combination of both. Figure 22 illustrates an example functional module or circuit architecture for a network node, such as network node 30.

The functional implementation includes a parameter determining module 2202 for determining a first parameter indicative of propagation delay from the UE or MT to the first base station and determining a second parameter indicative of propagation delay from the UE or MT to the second base station. The implementation also includes a coordinating module 2204 for, based on the first and second parameters, coordinating transmit timing advance commands sent to the UE or MT so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another. In another functional implementation, the coordinating module 2204 is for, based on the first and second parameters, coordinating downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and base stations within a pre- determined limit.

Figure 23 illustrates an example functional module or circuit architecture for a network node 30 that is a first base station.

The functional implementation includes a measuring module 2302 for measuring a parameter indicative of propagation delay from the UE or MT to the first base station and a sending module 2304 for sending the measured parameter or a parameter derived from the measured parameter to a coordinating network node. The implementation also includes a receiving module 2306 for receiving, from the coordinating network node, an indication of a timing advance adjustment for the UE or MT. The sending module 2304 is also for sending, to the UE or MT, one or more timing advance commands based on the indication of the timing advance adjustment. Example embodiments can include, but are not limited to, the following enumerated examples:

1. A method, in one or more network nodes, for determining a transmit timing for a user equipment (UE) or mobile termination (MT) having a link to a first base station and having a link to a second base station, the method comprising:

determining a first parameter indicative of propagation delay from the EGE or MT to the first base station;

determining a second parameter indicative of propagation delay from the EGE or MT to the second base station; and,

based on the first and second parameters, coordinating transmit timing advance

commands sent to the TIE or MT so as to provide the TIE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another. 2. The method of example embodiment 1, wherein said coordinating of the transmit timing advance commands sent to the TIE or MT is performed so as to ensure that reception at each of the first and second base stations of the uplink transmissions from the TIE or MT is aligned with reception of uplink signals by the respective base station from first one or more other EIEs or MTs, within a pre-determined limit.

3. The method of example embodiment 1 or 2, wherein the method further comprises, after said coordinating, sending transmit timing advance commands to second one or more other EIEs or MTs, by or via the first base station, so as to align reception at the first base station of uplink transmissions from the second one or more EIEs or MTs with reception at the first base of uplink transmissions from the EIE or MT, within a/the pre-determined limit.

4. The method of example embodiment 2 or 3, wherein the pre-determined limit is a length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions.

5. The method of example embodiment 4, wherein the inter-symbol guard interval comprises a cyclic prefix. 6. The method of example embodiment 4, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal. 7. The method of any of example embodiments 1-6, wherein the predetermined tolerance is a granularity of a timing advance step.

8. The method of any of example embodiments 1-7, wherein said coordinating is performed by either the first or second base station.

9. The method of any of example embodiments 1-7, wherein said coordinating of the transmit timing advance commands sent to the UE or MT comprises determining a first uplink timing adjustment parameter, based on the first and second parameters, and sending the first uplink timing adjustment parameter to the first base station.

10. The method of any of example embodiments 1-9, wherein determining the first parameter indicative of propagation delay from the UE or MT to the first base station comprises receiving the first parameter from the first base station.

11. The method of any of example embodiments 1-10, wherein determining the second parameter indicative of propagation delay from the UE or MT to the second base station comprises measuring the second parameter, based on a random access preamble transmitted by the UE or MT.

12. A method, in one or more network nodes, for determining transmit timings for transmissions to a user equipment (UE) or mobile termination (MT) having a link to a first base station and having a link to a second base station, the method comprising:

determining a first parameter indicative of propagation delay from the UE or MT to the first base station;

determining a second parameter indicative of propagation delay from the UE or MT to the first base station; and,

based on the first and second parameters, coordinating downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and base stations within a pre-determined limit.

13. The method of example embodiment 12, wherein the pre-determined limit is a length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions.

14. The method of example embodiment 13, wherein the inter-symbol guard interval comprises a cyclic prefix.

15. The method of example embodiment 13, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal. 16. The method of any of example embodiments 12-15, wherein said coordinating is performed so as to align received slot timings and/or frame timings of the downlink transmissions sent to the UE or MT by the first and second base stations, within the pre determined limit. 17. A method, in a first base station, for determining a transmit timing for a user equipment

(UE) or mobile termination (MT) having a link to the first base station and having a link to a second base station, the method comprising:

measuring a parameter indicative of propagation delay from the UE or MT to the first base station;

sending the measured parameter or a parameter derived from the measured parameter to a coordinating network node;

receiving, from the coordinating network node, an indication of a timing advance adjustment for the UE or MT; and

sending, to the UE or MT, one or more timing advance commands based on the

indication of the timing advance adjustment.

18. One or more network nodes or base stations adapted to perform the methods of any of example embodiments 1-17. 19. A network node or base station comprising transceiver circuitry and processing circuitry operatively associated with the transceiver circuitry and configured to perform the methods of any of example embodiments 1-17.

20. A computer program comprising instructions that, when executed on at least one processing circuit, cause the at least one processing circuit to carry out the method according to any one of example embodiments 1-19.

21. A carrier containing the computer program of example embodiment 20, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

22. A communication system including a host computer comprising:

processing circuitry configured to provide user data; and

a communication interface configured to forward the user data to a cellular network for transmission to a user equipment (UE), wherein the cellular network comprises a base station having a radio interface and processing circuitry, the base station’s processing circuitry configured to perform any of the operations comprising embodiments 1-17.

23. The communication system of the previous embodiment further including the base station.

24. The communication system of the previous two embodiments, further including the UE.

25. The communication system of the previous three embodiments, wherein:

the processing circuitry of the host computer is configured to execute a host application, thereby providing the user data; and

the UE’s processing circuitry is further configured to execute a client application associated with the host application. 26. A communication system including a host computer comprising a communication interface configured to receive user data originating from a transmission from a User equipment (UE) to a base station, the base station comprising a radio interface and processing circuitry configured to communicate with the base station and cooperatively perform operations of any of embodiments 1-17.

27. The communication system of the previous embodiment further including the base station.

28. The communication system of the previous two embodiments, further including the UE. 29. The communication system of the previous three embodiments, wherein:

the processing circuitry of the host computer is configured to execute a host

application; and

the UE is further configured to execute a client application associated with the host application, thereby providing the user data to be received by the host computer.

Many variations and modifications can be made to the embodiments without substantially departing from the principles of the present inventive concepts. All such variations and modifications are intended to be included herein within the scope of present inventive concepts. Accordingly, the above disclosed subject matter is to be considered illustrative, and not restrictive, and the examples of embodiments are intended to cover all such modifications, enhancements, and other embodiments, which fall within the spirit and scope of present inventive concepts. Thus, to the maximum extent allowed by law, the scope of present inventive concepts is to be determined by the broadest permissible interpretation of the present disclosure including the examples of embodiments and their equivalents and shall not be restricted or limited by the foregoing detailed description.

Claims

CLAIMS What is claimed is:

1. A method, in one or more network nodes, for determining transmit timings for transmissions to a user equipment, UE, or mobile termination, MT, having a link to a first base station and having a link to a second base station, the method comprising:

determining (1302) a first parameter indicative of propagation delay from the UE or MT to the first base station;

determining (1304) a second parameter indicative of propagation delay from the UE or MT to the second base station; and,

based on the first and second parameters, coordinating (1306) downlink transmit timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and second base stations within a pre- determined limit.

2. The method of claim 1, wherein the pre-determined limit is a length of an inter-symbol guard interval in uplink transmissions or a pre-determined fraction of the length of the inter symbol guard interval in uplink transmissions.

3. The method of claim 2, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal.

4. The method of any of claims 1-3, wherein said coordinating (1306) is performed so as to align received slot timings and/or frame timings of the downlink transmissions sent to the UE or MT by the first and second base stations, within the pre-determined limit.

5. The method of claim 4, wherein the pre-determined limit is a cyclic prefix length of the downlink transmissions or a configurable percentage of the cyclic prefix length.

6. A method, in one or more network nodes, for determining a transmit timing for a user equipment, UE, or mobile termination, MT, having a link to a first base station and having a link to a second base station, the method comprising:

determining (1202) a first parameter indicative of propagation delay from the UE or MT to the first base station; determining (1204) a second parameter indicative of propagation delay from the UE or MT to the second base station; and,

based on the first and second parameters, coordinating (1206) transmit timing advance commands sent to the UE or MT so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another.

7. The method of claim 6, wherein said coordinating (1206) of the transmit timing advance commands sent to the UE or MT is performed so as to ensure that reception at each of the first and second base stations of the uplink transmissions from the UE or MT is aligned with reception of uplink signals by the respective base station from first one or more other UEs or MTs, within a pre-determined limit.

8. The method of claim 6 or 7, wherein the method further comprises, after said coordinating (1206), sending transmit timing advance commands to second one or more other UEs or MTs, by or via the first base station, so as to align reception at the first base station of uplink transmissions from the second one or more UEs or MTs with reception at the first base of uplink transmissions from the UE or MT, within a/the pre-determined limit.

9. The method of claim 7 or 8, wherein the pre-determined limit is a length of an inter symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions.

10. The method of claim 9, wherein the inter-symbol guard interval comprises a cyclic prefix.

11. The method of claim 9, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal.

12. The method of any of claims 6-11, wherein the predetermined tolerance is a granularity of a timing advance step.

13. The method of any of claims 6-12, wherein said coordinating (1206) is performed by either the first or second base station.

14. The method of any of claims 6-12, wherein said coordinating (1206) of the transmit timing advance commands sent to the UE or MT comprises determining a first uplink timing adjustment parameter, based on the first and second parameters, and sending the first uplink timing adjustment parameter to the first base station.

15. The method of any of claims 6-14, wherein determining (1202) the first parameter indicative of propagation delay from the UE or MT to the first base station comprises receiving the first parameter from the first base station.

16. The method of any of claims 6-15, wherein determining (1204) the second parameter indicative of propagation delay from the UE or MT to the second base station comprises measuring the second parameter, based on a random access preamble transmitted by the UE or MT.

17. A network node adapted to perform a method according to any one of claims 1-16.

18. A network node (30), comprising:

transceiver circuitry (36); and

processing circuitry (32) operatively associated with the transceiver circuitry (36) and configured to:

determine a first parameter indicative of propagation delay from a user

equipment, UE, or mobile termination, MT, to a first base station; determine a second parameter indicative of propagation delay from the UE or MT to a second base station; and,

based on the first and second parameters, coordinate downlink transmit

timings for downlink transmissions sent to the UE or MT by the first and second base stations, so as to align reception at the UE or MT of the downlink transmissions sent by the first and second base stations within a pre-determined limit.

19. The network node (30) of claim 18, wherein the pre-determined limit is a length of an inter-symbol guard interval in uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in uplink transmissions.

20. The network node (30) of claim 19, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal.

21. The network node (30) of any of claims 18-20, wherein the processing circuitry (32) is configured to perform the coordinating so as to align received slot timings and/or frame timings of the downlink transmissions sent to the UE or MT by the first and second base stations, within the pre-determined limit.

22. The network node (30) of claim 21, wherein the pre-determined limit is a cyclic prefix length of the downlink transmissions or a configurable percentage of the cyclic prefix length.

23. The network node (30) of any of claims 18-23, wherein the network node is the first base station or the second base station.

24. A network node (30), comprising:

transceiver circuitry (36); and

determine a first parameter indicative of propagation delay from a user

based on the first and second parameters, coordinate transmit timing advance commands sent to the UE or MT so as to provide the UE or MT with uplink transmit timings to the first and second base stations that are within a predetermined tolerance of one another.

25. The network node (30) of claim 24, wherein said coordinating of the transmit timing advance commands sent to the UE or MT is performed so as to ensure that reception at each of the first and second base stations of the uplink transmissions from the UE or MT is aligned with reception of uplink signals by the respective base station from first one or more other UEs or MTs, within a pre-determined limit.

26. The network node (30) of claim 24 or 25, wherein the processing circuitry (32) is configured to, after said coordinating, send transmit timing advance commands to second one or more other UEs or MTs, by or via the first base station, so as to align reception at the first base station of uplink transmissions from the second one or more UEs or MTs with reception at the first base of uplink transmissions from the UE or MT, within a/the pre-determined limit.

27. The network node (30) of claim 25 or 26, wherein the pre-determined limit is a length of an inter-symbol guard interval in the uplink transmissions or a pre-determined fraction of the length of the inter-symbol guard interval in the uplink transmissions.

28. The network node (30) of claim 27, wherein the inter-symbol guard interval comprises a cyclic prefix.

29. The network node (30) of claim 27, wherein the inter-symbol guard interval comprises a unique word, in a unique-word Orthogonal Frequency-Division Multiplexed, OFDM, signal.

30. The network node (30) of any of claims 24-29, wherein the predetermined tolerance is a granularity of a timing advance step.

31. The network node (30) of any of claims 24-30, wherein the processing circuitry (32) is configured to coordinate the transmit timing advance commands sent to the UE or MT by determining a first uplink timing adjustment parameter, based on the first and second parameters, and sending the first uplink timing adjustment parameter to the first base station.

32. The network node (30) of any of claims 24-31, wherein the processing circuitry (32) is configured to determine the first parameter indicative of propagation delay from the UE or MT to the first base station by receiving the first parameter from the first base station.

33. The network node (30) of any of claims 24-32, wherein the processing circuitry (32) is configured to determine the second parameter indicative of propagation delay from the UE or MT to the second base station by measuring the second parameter, based on a random access preamble transmitted by the UE or MT.

34. The network node (30) of any of claims 24-33, wherein the network node (30) is the second base station.

35. A computer program (46) comprising instructions that, when executed on at least one processing circuit, cause the at least one processing circuit to carry out the method according to any one of claims 1-16.

36. A carrier (44) containing the computer program (46) of claim 35, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.