WO2018084756A1

WO2018084756A1 - Autonomous validation of stored connectivity information

Info

Publication number: WO2018084756A1
Application number: PCT/SE2016/051080
Authority: WO
Inventors: Yngve SELÉN; Jonas Kronander; Johan Nilsson
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2016-11-03
Filing date: 2016-11-03
Publication date: 2018-05-11

Abstract

Methods implemented in a radio device, e.g., a UE, for controlling access to a wireless communication network in which an access information table comprising multiple sets of possible access information is transmitted occasionally, and in which pointer information indicating a currently applicable portion of the access information table is transmitted more frequently than the access information table. An example method includes receiving (425) pointer information at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and initiating (430, 520, 620) access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. Various verification tests are disclosed for conditioning whether the previously stored version is used for initiating the access.

Description

AUTONOMOUS VALIDATION OF STORED CONNECTIVITY INFORMATION

TECHNICAL FIELD

The present disclosure is generally related to wireless communication networks and is more particularly related to techniques for managing information used to control access to such networks. BACKGROUND

When a user equipment (UE) initially accesses a wireless communication network based on the LTE (Long Term Evolution) radio access technology (RAT) specified by 3GPP (3rd Generation Partnership Project), the UE first needs to acquire what is called system information (SI). The SI is made available to UEs through the broadcast of certain information in each cell. This broadcasted information includes a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), which are used by the UE to obtain frequency and time synchronization. The PSS and SSS also encode the physical cell identity (PCI) for the broadcasting cell. After performing physical layer synchronization and PCI detection, using the PSS and SSS, the UE is capable of performing channel estimation using the constantly broadcasted cell-specific reference symbols (CRS) and, consequently, can finally decode the SI. The PSS and SSS are respectively transmitted in the first and sixth subframes within a radio frame. Accordingly, the PSS/SSS and CRS are always broadcasted by the network. These are used by the UE to synchronize to a given cell and enabling channel estimation.

In LTE systems, SI is broadcasted in each cell in System Information Blocks (SIBs), each of which contains a set of functionally related parameters. The SIB types that have been defined include a Master Information Block (M IB), which includes a limited number of the most frequently transmitted parameters which are essential for the UE's initial access to the network, a System Information Block Type 1 (SIB1), which contains parameters needed to determine if a cell is suitable for cell selection, as well as information about time-domain scheduling of the other SIBs, a System Information Block Type 2 (SIB2), which includes common and shared channel information, System Information Blocks of Type 3 to 8 (SIB3-SIB8), which include parameters used to control intra- frequency, inter-frequency and inter-RAT cell reselection, System Information Block Type 9, which is used to signal the name of a Home eNodeB (HeNB), System Information Blocks of Type 10 to 12 (SIB10-SIB12), which includes Earthquake and Tsunami Warning Service (ETWS) notifications and Commercial Mobile Alert System (CMAS) warning messages, System Information Block Type 13 (SIB13), which includes MBMS (Multimedia Broadcast Multicast Service) related control information, System Information Block Type 14 (SIB14), which is used to configure Extended Access Barring (EAB), System Information Block Type 15 (SIB15), which is used to convey M BMS mobility related information, and System Information Block Type 16 (SIB16), which is used to convey GPS (Global Positioning System) related information. This list of SIB types has been expanding over the years, and this expansion may be expected to continue as the 3GPP LTE RAT evolves.

Some of the SI is defined as "essential information," e.g., the information contained in the MIB, SIB1, and SIB2. For UEs that are EAB-capable, the information in SIB14 is also considered to be "essential information". Here, "essential information" is considered to be information that the UE needs to acquire before accessing the wireless communication network, e.g., via a random access procedure.

In the LTE RAT, the SI is constantly broadcasted. However, depending on the type of information, different periodicities are used for different parts of the SI. For example, the MIB and SIB1 may be broadcasted with periodicities of 40 milliseconds and 80 milliseconds. Furthermore, for the MIB the transmission is repeated four times during each broadcast period, i.e., every 10 milliseconds. The SIB1 is also repeated four times within each broadcast period, i.e. every 20 milliseconds, but with a different redundancy version for each transmission. For other SIB types, the time-domain scheduling may be dynamically adapted. In particular, each SIB may be transmitted in a periodically-occurring time-domain window, while physical layer control signaling indicates in which subframes within this window the SI is actually transmitted. The scheduling windows of the different SIBs, referred to as Sl-windows, are consecutive, i.e., without overlaps or gaps between them, and have a common length that is configurable. The Sl-windows can include subframes in which it is not possible to transmit SIBs, such as subframes used for the SIB1, and subframes used for the uplink in TDD (Time Division Duplex Mode).

As can be seen from the summary description above, the transmitting of SI in the LTE RAT results in a large amount of constantly broadcasted data. One objective in the currently ongoing development of a new fifth-generation (5G) radio access technology, which in 3GPP is referred to as "NR" ("New Radio"), is to minimize the total energy consumption. To do this, one design principle is to remove as much "always-on" signaling as possible, such as the cell-specific reference symbols

(CRS) in LTE. Accordingly, to increase the efficiency of fifth generation (5G) wireless communication networks, a concept based on a layered transmission of access information has been proposed. (See, e.g., "A Clean Slate Radio Network Designed for Maximum Energy Performance" by P. Frenger et al., presented on the IEEE 25th Annual International Symposium on Personal, Indoor, and Mobile Radio Communications (PIMRC), Washington, DC, September 2 - 5, 2014). According to this concept, user equipments (UEs) are provided with access information by using occasionally broadcasted tables of one or several sets of access information, referred to as access information tables (AITs), and more frequently broadcasted indices, which act as pointers to specific portions of the previously broadcasted tables. (It will be appreciated, of course that an AIT may in some cases include only one entry, in which case the "specific portion" referred to here will be the only portion.) These indices, or pointers, may be referred to as system signature sequences (SSSs) or, to avoid confusion with LTE's secondary synchronization signals, as system signature indices (SSIs).

The AIT may, for example, define settings concerning how a UE shall access the system, e.g., by a random access procedure, concerning how the UE can be reached by the system in a paging procedure, or concerning more advanced settings, such as related to beam forming or link adaptation. The AITs are typically transmitted at a relatively low rate, e.g., with a long periodicity, while the SSIs are typically transmitted more frequently. Typically, each access node, e.g., a base station, will transmit an SSI, which allows the UE to identify the information applicable to this access node from the AIT. The AITs, in contrast, need not be transmitted by every access node. For example, a base station serving a macro cell may transmit both an AIT and an SSI, while a base station serving a small cell within a coverage region of the macro cell may transmit only an SSI. Accordingly, the AIT will typically include entries defining multiple differing configurations, which apply to various access nodes. The AIT may therefore have considerable size, so that in view of resource efficiency it is generally desirable to broadcast the AIT at a relatively low update rate.

Figure 1 illustrates an example of several transmissions of access information table (AIT) 210 and system signature indices (SSIs) 220, according to the approach described above. Figure 2 illustrates an example scenario for AIT and SSI delivery, where the AIT is transmitted by an overlay node, e.g., a macro node having a relatively large area, and where individual (and possibly differing) SSIs are transmitted by each of several access nodes in within the overlay coverage area.

From Figure 1, it can be seen that the AIT 210 is transmitted relatively infrequently, e.g., with a periodicity of several seconds, while SSIs 220 are transmitted more often and are more lightweight in terms of their data content. Note that Figure 1 illustrates a scenario where an access node is transmitting both the AIT 210 and SSIs 220; this access node may be the access node shown at the center of Figure 2, for example. The SSIs 220 shown in Figure 1 are relevant to the access node that is broadcasting them, and are essentially pointers to the portion or portions of the AIT 210 that are applicable to the broadcasting access node. The AIT 210, on the other hand, may include detailed access information for both the broadcasting access node and other access nodes. As seen in Figure 2, some of those other access nodes, e.g., access nodes having coverage areas that fall within a macro node broadcasting both AIT 210 and SSIs 220, may broadcast only SSIs 220, at a rate similar to that shown in Figure 1, where the SSIs 220 point to portions of the AIT 210 that are relevant to the broadcasting access nodes.

A UE that wishes to access the 5G radio access network will thus typically receive both the AIT 210 and SSI 220, and then attempt access to the network based on the system information in the AIT 210 indicated by the SSI 220. As discussed above, the AIT 210 may be received from a different node than the SSI 220. Further, it should be noted that from the perspective of the UE, the order of receiving the AIT 210 and SSI 220 is not important. However, both are generally needed for the UE to attempt access to the system. Further, the AIT 210 should be stored by the UE so that it can be referred to again, e.g., in the event that the UE subsequently detects a new SSI 220.

SUMMARY

In system access procedure described above, a UE must receive both the AIT and the SSI to be able to initiate a random access procedure to gain access to the network. For a UE that is switched on and remains within coverage of the network, the AIT will be continuously updated, as necessary, and thus the most recently stored version of the AIT generally can be assumed to be valid. However, there are some situations in which a UE cannot be certain that it has correct AIT information and hence would need to wait to receive the AIT to ensure it has the correct AIT information. Example situations include when a UE comes back to coverage from an out-of- coverage situation, a UE is switched on or is awakened from a deep sleep (in which it does not read AIT), a UE is operated in an extreme power-saving mode to conserve energy, such as when the UE is almost out of battery power or when the UE is a device that requires extremely low power consumption (e.g., a sensor device).

To be certain that the UE is operating with a valid version of the AIT, i.e., to be certain that the AIT has not changed since the version stored in the UE was obtained, the UE must verify that its stored (previously read) AIT information is up to date before, e.g., doing a random access. This implies waiting until the AIT is broadcast again. However, because the AIT is transmitted relatively infrequently, e.g., at a periodicity on the order of 10 seconds, this can result in significant and undesirable delays before random access can be attempted. Accordingly, solutions for reducing the initial access times for some or all of these scenarios are needed.

Several embodiments of the presently disclosed techniques address these problems by using information that is already available to the UE, or easily and quickly retrievable by the UE, to validate the AIT information that is currently stored in the UE. This information, which may be referred to as "local" information, may comprise, example, the geographical position of the UE, the age of the stored AIT, UE motion data, or some combination thereof.

Example embodiments include methods implemented in a radio device, e.g., a UE, for controlling access to a wireless communication network in which an access information table (e.g., an AIT, as discussed above) comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating a currently applicable portion of the access information table (e.g., an SSI, as discussed above) is transmitted more frequently than the access information table. An example method includes receiving pointer information at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and initiating access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information.

It may be unknown to the radio device whether the previously stored version of the access information table matches the most recently transmitted access information table for any of several reasons, such as any one or more of the following: the radio device has recently been powered on; the radio device has begun to receive signals from the wireless communication network after being out of coverage of the wireless communication network for an interval; and the radio device has recently awakened from an energy-saving mode in which one or more transmissions of the access information table were not received. In some embodiments, the receiving of pointer information is triggered by one of these scenarios, e.g., by a powering on of the radio device, by the receiving of signals from the wireless communication network after being out of coverage of the wireless communication network for an interval of at least a predetermined length, or by an awakening of the radio device from an energy-saving mode.

The use of the previously stored version of the access information table, even though the pointer information is received at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, may be based on one or more of several tests, based on information known or readily accessible to the radio device. For example, in some embodiments, the method further comprises determining that the received pointer information indicates a portion of the previously stored version of the access information table that is known to the radio device, according to a predetermined setting, to be a static portion of the access information table, and the initiating access to the wireless communication network is then conditioned on this determination. In some embodiments, the method further comprises determining that an age of the previously stored version of the access information table is less than a predetermined age threshold, where initiating access to the wireless communication network is then conditioned on determining that the age is less than the predetermined age threshold. In some embodiments, the method further comprises estimating a change in location for the radio device, relative to a location associated with the stored version of the access information table, and initiating access to the wireless communication network is conditioned on determining that the estimated change in location is less than a predetermined location-change threshold. In some of these latter embodiments, estimating the change in location for the radio device may comprise dead- reckoning from the location associated with the stored version of the access information table. In others, estimating the change in location for the radio device may comprise determining a position of the radio device using a satellite-based navigation system and comparing the determined position to a stored position associated with the previously stored version of the access information table. In any of these and/or in other embodiments, the method further comprises determining whether or not data to be transmitted by the radio device is of a time- critical type, and initiating access to the wireless communication network is conditioned on determining that the data to be transmitted is of the time-critical type.

Also described in detail below are radio devices, e.g., UEs, adapted to carry out one or more of the methods summarized above, and variants thereof. An example radio device is adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table. The radio device is further adapted to receive pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and to initiate access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. The radio device may comprise a radio transceiver and a processing circuit operatively coupled to the radio transceiver and configured to carry out one or more of the methods summarized. In particular, the processing circuit may be configured to condition the radio device's use of the previously stored access information table based on any of the various tests summarized above, or variants thereof.

Other embodiments include computer program products for execution by a processor in a radio device adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table. An example computer program product comprises program instructions that, when executed by the processor, cause the radio device to receive pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and to initiate access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. Still other embodiments include a computer-readable medium, which may be a non-transitory computer-readable medium, that comprises the computer program product described above stored thereupon.

Embodiments of the presently disclosed techniques may be used to enable a UE to autonomously make an assessment of whether access information parameters previously obtained from the network still are applicable. This enables the UE to quickly connect to the network without the need to wait for receiving an updated access information transmission from the network. These techniques may reduce the network access latency for the UE, e.g., when it comes back from an out-of-coverage state, deep sleep or other state of extreme power saving, or being powered off.

Details of the embodiments summarized above and further embodiments will be apparent from the following detailed description of embodiments.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 illustrates an example of the transmissions of access information table (AIT) and system signature indices (SSIs).

Figure 2 illustrates an example scenario for AIT and SSI delivery, where the AIT is transmitted by an overlay node and where individual (and possibly differing) SSIs are transmitted by each of several access nodes in within the overlay coverage area.

Figure 3 is a system diagram illustrating an example system in which the presently disclosed techniques may be used.

Figure 4 is a process flow diagram illustrating a no-AIT-verification approach.

Figure 5 is a process flow diagram illustrating an age-verification approach.

Figure 6 is a process flow diagram illustrating a position/movement-based verification approach.

Figure 7 is a block diagram illustrating an example radio device.

Figure 8 is another block diagram illustrating an example radio device.

DETAILED DESCRIPTION

In the following, concepts in accordance with exemplary embodiments of the invention will be explained in more detail and with reference to the accompanying drawings. The illustrated embodiments relate to control of access to a wireless communication network by radio devices, in the following also referred to as UEs. The wireless communication network may for example be based on a 5G radio access technology, such as an evolution of the LTE RAT or the 3GPP New Radio (NR). However, it is to be understood that the illustrated concepts could also be applied to other RATs. In examples as further illustrated below, it is assumed that information which is utilized by the UEs for accessing the wireless communication network is provided in a layered manner to the UEs. Specifically, access information tables (AITs) are transmitted by some access nodes of the cellular network to the UEs. The AITs include one or more entries which are each identified by an identifier, and each of such entries includes one or more parameters of a configuration that may be selected by the UE to be applied when accessing the wireless communication network, in particular in a certain coverage area, e.g. cell, of the wireless communication network. The identifier may correspond to a system signature index (SSI) or other pointer information transmitted by an access node of the cellular network. The access nodes each transmit such pointer information, and the UEs may utilize this pointer information identifier to identify an entry of the AIT that is applicable for the specific access node or for a coverage area controlled by this access node. The entry of the AIT may define a configuration, or set of parameters, to be applied for a given coverage area and/or access node, such as a set of parameters to be used when initiating a random access procedure to the access node or in the coverage area.

The pointer information may encode an index that differs between different access nodes. In the following, this pointer information is alternately referred to as SSI (System Signature Index). The AITs do not need to be transmitted by every access node. That is to say, there may be access nodes which transmit the identifier, but no AIT. The UEs may then utilize the transmitted identifier to identify an AIT entry of an AIT transmitted by another access node. Further, the AITs may be transmitted less frequently than the identifiers. Accordingly, changes in the way of utilizing a certain access node for accessing the wireless communication network may be indicated by modifying the identifier transmitted by this access node. Having received the AIT, the UE will store the AIT and may then utilized the system information from this stored AIT until the AIT is updated.

Figure 3 schematically illustrates a wireless communication network architecture which may be used for implementing the concepts as outlined above. In particular, Figure 3 illustrates UEs 10 and various access nodes 110, 110' of the cellular network. In the illustrated example, the access nodes 110, 110' are assumed to be base stations 110 serving macro cells and base stations 110' serving small cells, e.g., pico cells or femto cells, within a coverage region of such macro cell.

However, it is noted that the illustrated concepts could also be applied in other scenarios, e.g., where the access nodes 110, 110' serve densely distributed small coverage areas.

As mentioned above, the UEs 10 utilize information from AITs received from the wireless communication network to control their respective access to the wireless communication network. Such control of the access may for example relate to a random access procedure performed by the UE 10 for gaining initial access to the wireless communication network or to a paging procedure performed by the wireless communication network to reach a certain UE 10. Further, the information from the AITs may be utilized by the UE 10 for setting a beam-forming configuration, a link adaptation configuration, and/or a HA Q configuration applied when accessing the wireless communication network. The AIT entry including the information which is applicable for a specific access node 110, 110' is identified by the UE 10 on the basis of the identifiers transmitted by each access node 110, 110'. In the following, it will be assumed that the identifiers correspond to an SSI transmitted by each access node 110, 110'. Here, it should be noted that the AIT transmitted by the access nodes 110 and the AIT transmitted by the access node 110', if transmitted, may be different from one another or may be identical.

Broadcast transmissions may be utilized for providing the AITs and the SSIs to the UEs 10. As used herein, a broadcast transmission is considered to be a transmission addressed to all UEs 10 in a certain coverage region of the wireless communication network. The broadcast transmission may be a single frequency network transmission by multiple access nodes 110, 110'. However, other transmission modes could be utilized as well, e.g., unicast transmissions or multicast transmissions. Here, a unicast transmission is considered to be a transmission addressed to one specific UE 10 and a multicast transmission is considered as a transmission which is addressed to a certain group of UEs 10. Also the multicast transmission may be single frequency network transmission by multiple access nodes 110.

The AITs do not need to be transmitted by each access node 110, 110'. In the illustrated example, the AITs are assumed to be transmitted only by the access nodes 110 serving the macro cells, thereby ensuring that the AITs can be received throughout the coverage area of the wireless communication network. Further, each of the base stations 110 serving the macro cells and the base stations 110' serving the small cells broadcasts a corresponding SSI. Here, it is to be understood that the broadcasted SSIs may vary between the access nodes 110, 110'. However, it is also possible that certain access nodes 110, 110' broadcast the same SSI, e.g., when similar access parameters apply for these access nodes 110, 110'. By way of example, in the scenario of Fig. 1 the base stations 110 serving the macro cells could broadcast a first SSI, and the base stations 110' serving the small cells could broadcast a second SSI which is different from the first SSI.

Each SSI may for example define a 10-bit data value, which allows for distinguishing between 1024 different SSIs. The received SSI is utilized by the UE 10 to identify an applicable entry of the received AIT, which defines a configuration to be used by the UE 10 when accessing the wireless communication network.

In the system access procedure described above, a UE must receive both the AIT and the SSI to be able to initiate a random access procedure to gain access to the network. For a UE that is switched on and remains within coverage of the network, the AIT will be continuously updated, as necessary, and thus the most recently stored version of the AIT generally can be assumed to be valid. However, there are some situations in which a UE cannot be certain that it has correct AIT information and hence would need to wait to receive the AIT to ensure it has the correct AIT information. Example situations include when a UE comes back to coverage from an out-of-coverage situation, a UE is switched on or is awakened from a deep sleep (in which it does not read AIT), a UE is operated in an extreme power-saving mode to conserve energy, such as when the UE is almost out of battery power or when the UE is a device that requires extremely low power consumption (e.g., a sensor device).

As discussed above, to be certain that the UE is operating with a valid version of the AIT, i.e., to be certain that the AIT has not changed since the version stored in the UE was obtained, the UE must verify that its stored (previously read) AIT information is up to date before, e.g., doing a random access. This implies waiting until the AIT is broadcast again. However, because the AIT is transmitted relatively infrequently, e.g., at a periodicity on the order of 10 seconds, this can result in significant and undesirable delays before random access can be attempted. Accordingly, solutions for reducing the initial access times for some or all of these scenarios are needed.

Other solutions to this problem have been proposed where the UE stores AIT and the SSI contains one or several cyclic redundancy code (C C) checksums that can be used by the UE to verify that at least critical parts of the AIT information are valid and may be used for random access. A drawback with this solution, however, is that the data payload in the SSI transmissions becomes larger and the SSI hence requires more resources. As these are transmitted often, the added overhead may become quite large.

Several embodiments of the presently disclosed techniques address these problems by instead using information that is already available to the UE, or easily and quickly retrievable by the UE, to validate the AIT information that is currently stored in the UE. This information, which may be referred to as "local" information, may comprise, for example, the geographical position of the UE, the age of the stored AIT, UE motion data, or some combination thereof. The presently disclosed techniques will be exemplified below by the explicit example of AIT/SSI, but can be generalized to other similar approaches where multi-layer system information is provided. The techniques described herein can be done entirely in the UE, which reduces the latency to connect to the network.

Note that the stored AIT information may be stored in local memory or "cached" in the device. The stored AIT will typically be the latest read AIT from network signaling, but could also be known to the UE by other means, for instance, inband-signaled, sent over the top, read in another radio access technology, stored on SIM-card, etc.

Scenarios where the presently disclosed techniques may be employed to speed up the system access time (reduce the system access latency), from the UE perspective, include, but are not limited to:

• when the UE moves into coverage from an out-of-coverage state, and does not have the time to wait for AIT to be received;

• when the UE wakes up from a "deep sleep," and does not have time to wait for reception of AIT;

• when, in an extreme power-save mode, allowing very low power consumption or if the UE is almost out of battery, the UE skips reading the AIT (sometimes or often); and

• when the UE is first powered up and cannot wait to read for AIT.

Consider a UE that becomes active after having been disconnected from the network (hereafter denoted as the "disconnected state"), e.g., where the UE has been in a deep sleep mode for a period of time. The UE in this example has a stored AIT, which is associated with a timestamp that indicates when the AIT data was last validated, received or updated. Before the UE attempts a system access using the stored AIT, one or more of the following techniques might be performed, in any order.

No AIT verification

With this approach, the stored AIT is used directly. This is the most direct method, and may be used in standard UE operation, where the UE monitors the AIT transmissions and constantly keeps it up to date. This approach is opportunistic and may, e.g., result in failure in a system access (such as a random access) if the UE just returned from a disconnected state, wherein it did not monitor the AIT.

Figure 4 is a process flow diagram illustrating this approach. As seen at blocks 410 and 420, the method begins with the UE in an out-of-coverage state - as shown at block 420, the UE occasionally checks whether the UE is in coverage. When it returns to coverage, the UE obtains an SSI, as shown at block 425, and attempts a system access to the network using the stored AIT, as shown at block 430, using the SSI as the pointer to access parameters in the AIT. This system access may be a random access, for example.

Figure 4 also shows an optional sub-procedure in which the UE checks whether the system access was successful, as shown at block 440. If so, the UE continues with normal communication, as shown at block 450. If not, the UE waits for the AIT to be read, as shown at block 442, and then performs system access using parameters obtained from the newly read AIT, as shown at block 444. Upon a successful access, normal communication takes place, as shown at block 450. Note that in some embodiments, the UE may attempt to access the system more than once, using the stored AIT, before waiting for a new AIT and using the AIT for performing system access. Thus, the check shown at block 440 may comprise a check of whether system access has failed a predetermined number of times, where the predetermined number may be one or some number larger than one. Further note that during the normal communication (450) the UE would typically receive (and in the future use) updated AITs, which could lead to an update of some parameters in the UE which were not critical for the successful system access (440).

Partial AIT verification

In some embodiments, some parts of the AIT are pre-defined as static (e.g., by the operator), meaning that these parts do not need any additional verification at all. In short, if the SSI points to these parts of the AIT table the UE will know that those parts of the AIT are valid and may proceed with system access.

Age verification

In some embodiments, the UE checks the age of the AIT, i.e., to determine whether a longer time has passed than a certain threshold. This threshold may be determined by an external stakeholder like the operator, the device manufacturer, or similar. It may be pre-determined statically and be stored in the memory of the device, the SIM-card or similar, or it may possible to update. The threshold may alternatively be based on the UE's own experience from monitoring AIT validity durations (i.e., the time the AIT remains valid until critical information therein is changed or updated). The threshold may be based on the UE location (in which case this needs to be known; see below), i.e., the AIT update frequency may be different in different locations. In some embodiments, the threshold can be varying for different parts of the AIT, in that the AIT may contain some parts that are static over a long duration of time and valid for large spatial regions, while other parts of the data vary more frequently in time and/or space. In still other embodiments, only the part(s) of AIT that are critical to the system access procedure are verified according to these techniques. In other embodiments, the UE can read the AIT at a longer periodicity than the transmission periodicity of the network. In such a case the UE will know (at least if the AIT was correctly received) that the stored AIT is not older than the AIT reading periodicity, in which case the AIT age check is implicit.

Figure 5 is a process flow diagram illustrating an example age-verification approach. The illustrated method begins in the same way as the method shown in Figure 4, i.e., with the UE returning to an in-coverage state from being out of coverage and receiving an SSI, as shown at blocks 410, 420, and 425. As shown at block 510, the method continues with a test of whether the stored AIT is too old. This may be done, as discussed above, by evaluating the difference between the current time and a stored timestamp associated with the stored AIT, with respect to a

predetermined threshold. Alternatively, a timer may be started when the AIT is stored (or revalidated), and the timer value compared to a threshold when the UE is ready to initiate a system access.

If the stored AIT is not too old, according to the evaluation shown at block 510, a system access is attempted, using the stored AIT, as shown at block 520. Again, this may be a random access attempt, for example. If this system access is successful, then normal communication may commence, as shown at block 540. Otherwise, the UE waits for the AIT to be read again, as shown at block 512, and performs a system access with the new AIT, as shown at block 514. Note that the illustrated method may include an optional step, as shown at block 530, of verifying whether the system access attempt based on the stored AIT was successful - if not, the fallback procedure of waiting for a new AIT is used.

Position/Movement-based verification

In some embodiments, the UE checks whether its geographical position (UE location) has changed since the AIT was stored and/or last verified. An estimate of the UE location can possibly be made available to the UE without turning on the GPS, by using low power motion sensor(s) to estimate whether the UE has moved or not during the disconnected state and detect a change from a UE location detected e.g., via GPS or other means, before going to the disconnected state. If there has not been any significant change in the UE location (e.g., as compared to a threshold value) and, optionally, if the AIT age also passes the threshold discussed above, for the concerned part of the AIT, the UE considers the AIT to be valid and uses the information, in combination with the most recently received SSI information, to do a system access. For this to work properly, the UE in some embodiments will need to store location information together with the storage of the latest received AIT.

Figure 6 is a process flow diagram illustrating an example method using a

position/movement-based verification test. Once again, the illustrated method begins in the same way as the method shown in Figure 4, i.e., with the UE returning to an in-coverage state from being out of coverage and receiving an SSI, as shown at blocks 410, 420, and 425. As shown at block 610, the method continues with an evaluation of whether the geographic position has changed by at least a predetermined amount. This may be based on a comparison of the UE's absolute position (e.g., as determined by a GPS measurement) with the UE's position as of the time the stored AIT was stored and/or re-stored. Alternatively, this may be based on an estimate of whether the UE has moved a sufficient difference relative to its position when the AIT was stored or re-validated, e.g., using a dead-reckoning process based on motion-detector inputs and elapsed time.

As with the other procedures, if the test indicates that the position has not changed more than a threshold value, a system access attempt with the stored AIT can be initiated, as shown at block 620. If this is successful, then normal communication may commence, as shown at block 640. Otherwise, the UE waits for the AIT to be read again, as shown at block 612, and performs a system access with the new AIT, as shown at block 614. Note that the illustrated method may include an optional step, as shown at block 630, of verifying whether the system access attempt based on the stored AIT was successful - if not, the fallback procedure of waiting for a new AIT is used.

Any or all of the procedures described above remove the need to wait for an updated AIT to be received, at least in certain circumstances, and hence may be used to reduce the system access latency of the UE.

Below a few embodiments/aspects of the invention are further detailed.

Detection of estimate of UE movement through use of low power motion detectors

Turning on a Global Positioning Service (GPS) receiver or other satellite-based positioning receiver in a UE and waiting to obtain an accurate position for the UE is time and energy consuming, and will not, in all situations, provide a viable and energy efficient solution for estimating UE location in particular in relation to the location in which it received the last AIT. In some embodiments, then, the UE uses a motion detection processor (as e.g., available in present day smartphones to track movement by using low energy consuming processes) combined with a timer, to track rough UE movement without relying on GPS. In short, the UE may use dead-reckoning techniques, given a starting position associated with the latest storing or verification of the AIT, to estimate the movement of the UE from that starting point, based on input from low-energy motion detectors.

This approach provides information on whether the UE has moved only a reasonably short distance, such that the access information parameters are still valid. This approach may be suitable for UEs in deep sleep, since this approach uses power efficient motion sensors and clock functions, but does not rely on GPS or similar technology.

An example procedure according to this approach is as follows. When the UE receives an AIT or validates an already stored AIT (e.g., by receiving an identical AIT or system information indicating that the stored AIT matches the current version), it stores the time at which the AIT was received or validated, and then starts the motion tracking. The UE may then go into a disconnected state, e.g., into a deep sleep state. Upon waking up, the UE uses the collected motion data to make a rough assessment of whether it has moved a significant distance or not, e.g., by comparing an estimated movement distance to a threshold. In some embodiments, it may also assess whether the (relevant parts of the) stored AIT is too old, e.g., by comparing the difference between the current time and the stored time to another time threshold. If the UE has not moved far and the (relevant parts of the) stored AIT is not considered to be too old (optional in this embodiment), the UE uses the current SSI (which may have been read while the UE is carrying out the assessment of whether the UE has moved too far and/or whether too much time has elapsed since the relevant parts of the AIT were stored) to retrieve access information from the stored AIT. The UE assumes, under these conditions, that the retrieved access information is valid, and uses it to access to the network

If the stored AIT does not pass the one or more checks described above, the UE falls back to the standard behavior, i.e., it waits until a new AIT is received, and thereby get valid access information, and uses this to access the network.

Time stamping the AIT

In some embodiments, it is sufficient to only perform age verification of the AIT, e.g., based on time-stamping the AIT upon reception. Upon reception and storage of AIT the UE records the time. Alternatively, the UE can start a timer that keeps track of the age of the stored AIT. This timestamp/timer value is used when the UE wants to subsequently use the access information, after returning from a disconnected state. If the timestamp approach is used, the current time is compared to the AIT timestamp to calculate the age of the AIT. Otherwise, the value of the timer started when the AIT was stored may be used as an indicator of the AIT age. The AIT age is compared to a time threshold - if it is below the threshold the UE uses the AIT to get access information and access the network. If not, the UE falls back to the standard procedure of waiting to receive a new AIT.

In some embodiments, the threshold may be dynamically decided in the UE while operating in a connected mode, by monitoring the changes in different parts of the AIT information over time and location. By receiving several AITs over a long period of time in a connected state the UE may infer that some parts of the AIT do not change, or that changes are occurring seldom - this may (or may not) be treated in a location-specific way, so that the AIT update frequency is only valid for nearby locations. In this case, the time/age threshold may be set to a rather high value (i.e., the stored AIT is allowed to be quite old and still be valid). If, on the other hand, the UE detects that the AIT, or some parts of the AIT critical for, e.g., random access, changes frequently the UE sets the threshold to a lower value. Geographically stamping the AIT

A monitoring of the AIT similar to that described above may also be applied to dynamically decide the distance threshold described above. In some embodiments, this requires explicit location to be stored together with the AIT; in some other embodiments only a change in location is relevant - this is the geographical correspondence to starting a timer in the above described age verification techniques.

Priority traffic as trigger

In some embodiments, the techniques of autonomously estimating the validity of the AIT are limited to situations in which there is time-critical traffic to be transmitted. For example, only certain types of critical machine communication, e.g., U LLC (ultra-reliable low latency

communication) or alarm/alert type of traffic may trigger the UE to use the techniques described, while Facebook or web browsing might not, since the user experience would not be significantly degraded by the latency imposed by waiting to receive an updated AIT. In practice, services could be divided by, e.g., an operator, into different classes based on their criticality - in the simplest case in two classes: time-critical services and non-time-critical services (the latter class may be implicitly defined only - e.g., services which are not in the time-critical class). In some embodiments, then, only if a time-critical service is requesting system access the present techniques would be used and in all other cases the standard method of waiting for an AIT update would be used. In more complex embodiments, certain data or categories of data to be transmitted may be associated with a particular time limit specifying a time before which the data should have been transmitted - in some of these embodiments, if the "normal" way of accessing the network (i.e., by waiting for a new AIT, etc.) is estimated to require a time that would go past this deadline, then one or several of the techniques described herein for using the previously stored AIT information are used.

Roaming handling

In some configurations it may not be fully clear to the UE what operator is sending out the

SSIs, and in principle the AIT stored in the UE could be from another operator than the received SSIs. Assuming that operator identifiers are not included in the AITs or SSIs, this would increase the risk for using erroneous parameters. To address this possibility, the UE in some embodiments may adapt its behavior based on what caused the UE to not have access to the most recent AIT. For example, if the UE is recovering from being completely switched off, e.g., manually (by the user of the UE) or if it is recovering from flight mode, the chances of being in a roaming situation are higher. In some embodiments, detecting these scenarios may trigger the UE to (be more likely to) fall back to the standard way of connecting to the network, i.e., wait until it has received an AIT update and proceed from there.

In some embodiments, if it becomes clear to the UE by reading the SSI that the stored AIT is not from the correct operator, then the UE would most likely have to wait until it receives a new AIT. Safety fallback solution in UE

As the connection procedure is based on stored AIT information, which sometimes will have changed, additional precautions may be used, in some embodiments. For instance, if system access fails with the stored system information, the system information could be re-read before another system access is tried. When doing a random access attempt, for example, according to the above procedures, the UE receives the random access response from the network and may use it to assess the validity of the used random access parameters (SSI+AIT). If the response is as expected, the procedure has succeeded, if not the UE falls back to the default mechanisms of waiting to receive the AIT transmission and updating the random access information accordingly, and then retries to access the network.

By employing this technique, the system access latency is always at the most the standard system access latency (when the UE falls back to the safety procedure or when the UE deems that the AIT is not valid), but in many cases (where the assessment is successful) the system access latency can be significantly decreased compared to the latency of the fall back procedure.

Critical system access parameters

In some embodiments, an operator of a network may define parts of the AIT as "static," such that any UE reading an SSI pointing at a "static" portion of the AIT can assume that a previous AIT reading is correct (at least assuming that the AIT is from the same network). Other parts of the AIT can be given other validity times, which will in turn affect the behavior of the UE. The operator may in some cases define which parameters in the AIT are critical for system access, i.e., worse to estimate incorrectly than others.

Safe mode

Another option is that the operator (or other entity) specifies a 'safe mode' which is stored in the UE and which is always safe to use as settings when attempting to connect to the network. This safe mode could consist of a subset of a larger set of connectivity parameters, e.g., ACH power, etc.

The 'safe mode' parameters may be transmitted in a static (non-changing) part of the AIT or may be stored in the SIM-card or elsewhere in the UE. Hence, a UE returning from a disconnected state can always first try to do a random access using the safe mode. This is a potential fallback solution if other techniques described herein cannot be used or are unsuccessful, e.g., because the various checks (e.g., AIT age or similar) do not pass.

With the detailed example approaches described above in mind, it will be appreciated that generalized embodiments of the presently disclosed techniques include methods implemented in a radio device, e.g., a UE, for controlling access to a wireless communication network in which an access information table (e.g., an AIT, as discussed above) comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating a currently applicable portion of the access information table (e.g., an SSI, as discussed above) is transmitted more frequently than the access information table. Example methods, including several of those illustrated in Figures 4-6 and described above, include the steps of receiving pointer information at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and initiating access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information.

As was discussed above, it may be unknown to the radio device whether the previously stored version of the access information table matches the most recently transmitted access information table for any of several reasons, such as any one or more of the following: the radio device has recently been powered on; the radio device has begun to receive signals from the wireless communication network after being out of coverage of the wireless communication network for an interval; and the radio device has recently awakened from an energy-saving mode in which one or more transmissions of the access information table were not received. In some embodiments, the receiving of pointer information is triggered by one of these scenarios, e.g., by a powering on of the radio device, by the receiving of signals from the wireless communication network after being out of coverage of the wireless communication network for an interval of at least a pre-determined length, or by an awakening of the radio device from an energy-saving mode.

The techniques described herein may be embodied in radio devices, e.g., UEs, adapted to carry out one or more of the methods summarized above, and variants thereof. Figure 7 illustrates an example radio device 50, which may be a UE, for example. Radio device 50 is adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table. Radio device 50 is further adapted to receive pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and to initiate access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. Radio device 50 may comprise a radio transceiver, illustrated in Figure 7 as transceiver circuit 56, and a processing circuit 52 operatively coupled to the radio transceiver and configured to carry out one or more of the methods summarized. In particular, the processing circuit 52 may be configured to condition the radio device's use of the previously stored access information table based on any of the various tests summarized above, or variants thereof.

The UE 50 communicates with one or more radio nodes or base stations, such as one or more network nodes 30, via antennas 54 and a transceiver circuit 56. The transceiver circuit 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 providing wireless communication services.

As shown in Figure 7, radio device 50 includes one or more processing circuits 52 that are operatively associated with and control the radio transceiver circuit 56. The processing circuit 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, the processing circuit 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.

The processing circuit 52 also includes a memory 64. The memory 64, in some

embodiments, stores one or more computer programs 66 and, optionally, configuration data 68. The memory 64 provides non-transitory storage for the 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, the memory 64 comprises any one or more of SRAM, DRAM, EEPROM, and FLASH memory, which may be in the processing circuit 52 and/or separate from processing circuit 52. In general, the memory 64 comprises one or more types of computer-readable storage media providing non-transitory storage of the computer program 66 and any configuration data 68 used by the radio device 50.

Accordingly, embodiments of the presently disclosed techniques include computer program products for execution by a processor in a radio device adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table. An example computer program product comprises program instructions that, when executed by the processor, cause the radio device to receive pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table, and to initiate access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. Still other embodiments include a computer-readable medium, which may be a non-transitory computer-readable medium, that comprises the computer program product described above stored thereupon.

As discussed in detail above, the techniques described herein, e.g., as illustrated in the process flow diagrams 4-6, 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 8 illustrates an example functional module or circuit architecture as may be implemented in a radio device 50 adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table. The

implementation includes a receiving module 82 for receiving pointer information, e.g., at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table. The

implementation also includes a system access initiation module 86 for initiating access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information. The illustrated embodiment further includes an access information table verification module 84, in some embodiments, for determining whether or not to use the stored access information table for initiating the random access, using one or several of the verification techniques described above. Thus, for example, access information table verification module 84 may be configured to determine that an age of the previously stored version of the access information table is less than a predetermined age threshold, such that initiating access to the wireless communication network by system access initiation module 86 is conditioned on determining that the age is less than the predetermined age threshold. Similarly, access information table verification module 84 may be configured to estimate a change in location for the radio device, relative to a location associated with the stored version of the access information table, such that initiating access to the wireless communication network by system access initiation module 86 is conditioned on determining, by the access information table verification module 84, that the estimated change in location is less than a predetermined location-change threshold. In some embodiments, access information table verification module 84 may instead or additionally be configured to determine whether or not data to be transmitted by the radio device is of a time-critical type, such that the initiating access to the wireless communication network by system access initiation module 86 is conditioned on a determination that the data to be transmitted is of the time-critical type.

Notably, modifications and other embodiments of the disclosed invention(s) will come to mind to one skilled in the art having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention(s) is/are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of this disclosure. Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

1. A method, in a radio device, of controlling access to a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating a currently applicable portion of the access information table is transmitted more frequently than the access information table, the method comprising:

receiving (425) pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table; and

initiating (430, 520, 620) access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information.

2. The method of claim 1, wherein it is unknown to the radio device whether the previously stored version of the access information table matches the most recently transmitted access information table because of at least one of the following:

the radio device has recently been powered on;

the radio device has begun to receive signals from the wireless communication network after being out of coverage of the wireless communication network for an interval; and

the radio device has recently awakened from an energy-saving mode in which one or more transmissions of the access information table were not received.

3. The method of claim 1 or 2, wherein said receiving of pointer information is triggered by at least one of the following:

a powering on of the radio device;

receiving signals from the wireless communication network after being out of coverage of the wireless communication network for an interval of at least a pre-determined length; and

an awakening of the radio device from an energy-saving mode.

4. The method of any of claims 1-3, wherein the method further comprises determining that the received pointer information indicates a portion of the previously stored version of the access information table that is known to the radio device, according to a predetermined setting, to be a static portion of the access information table, and wherein said initiating access to the wireless communication network is conditioned on said determining.

5. The method of any of claims 1-4, wherein the method further comprises determining (510) that an age of the previously stored version of the access information table is less than a predetermined age threshold, and wherein said initiating access to the wireless communication network is conditioned on said determining that the age is less than the predetermined age threshold.

6. The method of any of claims 1-5, wherein the method further comprises estimating a change in location for the radio device, relative to a location associated with the stored version of the access information table, and wherein said initiating access to the wireless communication network is conditioned on determining (610) that the estimated change in location is less than a predetermined location-change threshold.

7. The method of claim 6, wherein estimating the change in location for the radio device comprises dead-reckoning from the location associated with the stored version of the access information table.

8. The method of claim 6, wherein estimating the change in location for the radio device comprises determining a position of the radio device using a satellite-based navigation system and comparing the determined position to a stored position associated with the previously stored version of the access information table.

9. The method of any of claims 1-8, wherein the method further comprises determining whether or not data to be transmitted by the radio device is of a time-critical type, and wherein the said initiating access to the wireless communication network is conditioned on determining that the data to be transmitted is of the time-critical type.

10. The method of any of claims 1-9, wherein said initiating (430, 520, 620) access to the wireless communication network using a portion of the previously stored version of the access information table fails, and wherein the method further comprises, responsive to determining (440, 530, 630) that access attempts using the previously stored version of the access information table have failed a predetermined number of times, waiting (442, 512, 612) for reception of a new version of the access information table and initiating (444, 514, 614) access to the wireless communication network using the new version of the access information table.

11. The method of any of claims 1-10, wherein the radio device is a user equipment, UE.

12. A radio device (50) adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table, wherein the radio device (50) is adapted to:

receive pointer information, at a time at which it is unknown to the radio device (50)

whether a previously stored version of the access information table matches a most recently transmitted access information table; and

initiate access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information.

13. The radio device (50) of claim 12, wherein it is unknown to the radio device (50) whether the previously stored version of the access information table matches the most recently transmitted access information table because of at least one of the following:

the radio device (50) has recently been powered on;

the radio device (50) has begun to receive signals from the wireless communication network after being out of coverage of the wireless communication network for an interval; and

the radio device (50) has recently awakened from an energy-saving mode in which one or more transmissions of the access information table were not received.

14. The radio device (50) of claim 12 or 13, wherein the radio device (50) is adapted to trigger the receiving of pointer information in response to at least one of the following:

a powering on of the radio device (50);

an awakening of the radio device (50) from an energy-saving mode.

15. The radio device (50) of any of claims 12-14, wherein the radio device (50) is further adapted to determine that the received pointer information indicates a portion of the previously stored version of the access information table that is known to the radio device (50), according to a predetermined setting, to be a static portion of the access information table, and wherein the radio device (50) is adapted to condition the initiating of access to the wireless communication network on said determining.

16. The radio device of any of claims 12-15, wherein the radio device (50) is further adapted to determine that an age of the previously stored version of the access information table is less than a predetermined age threshold, and wherein the radio device (50) is adapted to condition the initiating of access to the wireless communication network on said determining that the age is less than the predetermined age threshold.

17. The radio device of any of claims 12-16, wherein the radio device (50) is further adapted to estimate a change in location for the radio device (50), relative to a location associated with the stored version of the access information table, and wherein the radio device (50) is adapted to condition the initiating of access to the wireless communication network on determining that the estimated change in location is less than a predetermined location-change threshold.

18. The radio device of claim 17, wherein the radio device (50) is adapted to estimate the change in location for the radio device (50) using dead-reckoning from the location associated with the stored version of the access information table.

19. The radio device of claim 17, wherein the radio device (50) is adapted to estimate the change in location for the radio device (50) by determining a position of the radio device (50) using a satellite- based navigation system and comparing the determined position to a stored position associated with the previously stored version of the access information table.

20. The radio device of any of claims 12-19, wherein the radio device (50) is further adapted to determine whether or not data to be transmitted by the radio device (50) is of a time-critical type, and wherein the radio device (50) is adapted to condition the initiating of access to the wireless communication network on determining that the data to be transmitted is of the time-critical type.

21. The radio device of any of claims 12-20, wherein the radio device (50) is further adapted to, responsive to determining that access attempts using the previously stored version of the access information table have failed a predetermined number of times, wait for reception of a new version of the access information table and initiate access to the wireless communication network using the new version of the access information table.

22. The radio device of any of claims 12-21, wherein the radio device (50) is a user equipment, UE.

23. A radio device (50) configured for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table, wherein the radio device (50) comprises:

a radio transceiver (56); and

a processing circuit (52) operatively coupled to the radio transceiver (56) and configured to: receive pointer information, via the radio transceiver (56), at a time at which it is unknown to the processing circuit (52) whether a previously stored version of the access information table matches a most recently transmitted access information table; and

use the radio transceiver (56) to initiate access to the wireless communication

network, using a portion of the previously stored version of the access information table, based on the received pointer information.

24. A radio device (50) adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table, wherein the radio device (50) comprises:

a receiving module (82) for receiving pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table; and a system access initiation module (86) for initiating access to the wireless communication network using a portion of the previously stored version of the access information table, based on the received pointer information.

25. A computer program product for execution by a processor in a radio device adapted for operation in a wireless communication network in which an access information table comprising multiple sets of possible information is transmitted occasionally, and in which pointer information indicating an applicable portion of the access information table is transmitted more frequently than the access information table, the computer program product comprising program instructions that, when executed by the processor, cause the radio device to:

receive pointer information, at a time at which it is unknown to the radio device whether a previously stored version of the access information table matches a most recently transmitted access information table; and

26. A computer-readable medium, which may be a non-transitory computer-readable medium, comprising the computer program product of claim 25 stored thereupon.