METHOD AND APPARATUS FOR COMMUNICATING WITH LTE TERMINALS HAVING RESTRICTED CAPABILITIES

• US 20150085689A1
• Filed: 09/25/2014
• Published: 03/26/2015
• Est. Priority Date: 09/26/2013
• Status: Active Grant

• Current Assignee: Semtech Corporation
• Original Assignee: Sierra Wireless Incorporated
• Inventors: Vos, Gustav Gerald
• Granted Patent: US 9,716,988 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04W 4/18 Information format or content conversion, e.g. adaptation by the network of the transmitted or received information for the purpose of wireless delivery to users or terminals
• CPC Class Codes: H04W 4/70 Services for machine-to-machine communication [M2M] or machine type communication [MTC]
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 74/0833 Random access procedures, e.g. with 4-step access

Abstract

A method and system for facilitating communication in an LTE network between an eNB and Limited Capability Terminal Equipments (LCTEs). A subset of PRACH preambles is defined for use by the LCTEs. PRACH preambles are selected by LCTEs only from said subset for inclusion in transmission of a PRACH preamble message to the eNB. Upon receipt of a PRACH preamble belonging to the subset, the eNB adjusts its operation to accommodate a limitation of the LCTE corresponding to the PRACH preamble. For example, the eNB may schedule transmission of the associated RAR on a restricted set of PRBs which is predictable and accessible to said LCTEs, to accommodate LCTE reception limitations. The subset of PRACH preambles can be adjusted in size in order to control system performance. The subset may include one or more preambles for exclusive use by LCTEs and/or preambles for non-exclusive use by LCTEs.

Claims

1. A Long Term Evolution (LTE) system comprising:

a) a Limited Capability Terminal Equipment (LCTE) configured, upon initiating a physical random access channel (PRACH) random access operation, to select a PRACH preamble from a predetermined subset of PRACH preambles, said subset being strictly smaller than a set of all PRACH preambles used in the LTE system, the selected PRACH preamble included in wireless transmission of a PRACH preamble message; and

b) an evolved Node B (eNB) configured, in response to receipt of the PRACH preamble belonging to said subset, to schedule transmission of an associated random access response (RAR) on a restricted set of physical resource blocks (PRBs) which is predictable and accessible to said LCTE.

2. The system of claim 1, wherein the predetermined subset of PRACH preambles is advertised, to terminal equipments (TEs) other than the LCTE, as belonging to a pool of contention-free preambles, and wherein the eNB is configured to avoid assigning the predetermined subset of PRACH preambles for contention-free usage by said TEs other than the LCTE.

3. The system of claim 1, wherein the predetermined subset of PRACH preambles is at least partially used by TEs other than the LCTE.

4. The system of claim 1, wherein the eNB is further configured to monitor one or more indicators of system performance and to adjust a size of the predetermined subset of PRACH preambles based on said one or more indicators of system performance.

5. The system of claim 4, wherein one of said one or more indicators of system performance is indicative of usage distribution of the set of all PRACH preambles, and wherein the eNB is configured to adjust the size of the predetermined subset of PRACH preambles to facilitate an increased evenness in said usage distribution.

6. The system of claim 1, wherein the system is configured to cause the restricted set of PRBs to vary over time.

7. The system of claim 1, wherein the restricted set of PRBs is identified by a function commonly known to both the eNB and the LCTE or the eNB is configured to communicate the restricted set of PRBs to the LCTE via a System Information Block (SIB).

8. The system of claim 1, wherein the eNB is further configured to transmit the RAR on the restricted set of PRBs with increased gain relative to Random Access Responses transmitted on PRBs other than the restricted set of PRBs.

9. The system of claim 1, wherein the set of all PRACH preambles available for use correspond to PRACH preambles used by the LTE system, wherein the LCTE is capable of receiving PRBs within a limited bandwidth, and wherein the restricted set of PRBs corresponds to said limited bandwidth.

10. The system of claim 1, wherein a size of the RAR, a Modulation and Coding Scheme corresponding to the RAR and a sub-frame time of the RAR are specified in advance, and wherein scheduling of the RAR on the Physical Downlink Control Channel (PDCCH) is omitted.

11. A method for facilitating random access communication in an LTE network between an eNB and a Limited Capability Terminal Equipment (LCTE), the method comprising:

a) defining a subset of Physical Random Access Channel (PRACH) preambles for use by the LCTE, said subset being strictly smaller than a set of all PRACH preambles available for use;

b) upon initiating a PRACH random access operation by the LCTE, selecting PRACH preambles from said subset for inclusion in transmission of a PRACH preamble message to the eNB;

c) in response to receipt of a PRACH preamble belonging to said subset by the eNB, scheduling transmission of an associated Random Access Response (RAR) on a restricted set of Physical Resource Blocks (PRBs) which is predictable and accessible to said LCTE.

12. The method of claim 11, wherein the predetermined subset of PRACH preambles is advertised, to terminal equipments (TEs) other than the LCTE, as belonging to a pool of contention-free preambles, and wherein the eNB is configured to avoid assigning the predetermined subset of PRACH preambles to said TEs other than the LCTE for contention-free usage.

13. The method of claim 11, wherein the predetermined subset of PRACH preambles is at least partially used by TEs other than the LCTE.

14. The method of claim 11, further comprising monitoring, by the eNB, one or more indicators of system performance and to adjust a size of the predetermined subset of PRACH preambles based on said one or more indicators of system performance.

15. The method of claim 14, wherein one of said one or more indicators of system performance is indicative of usage distribution of the set of all PRACH preambles, and wherein adjusting the size of the predetermined subset of PRACH preambles is performed to facilitate an increased evenness in said usage distribution.

16. The method of claim 11, further comprising varying the restricted set of PRBs over time.

17. The method of claim 11, wherein the restricted set of PRBs is identified by a function commonly known to both the eNB and the LCTE or the restricted set of PRBs is communicated from the eNB to the LCTE via a System Information Block (SIB).

18. The method of claim 11, further comprising transmitting the RAR on the restricted set of PRBs with increased gain relative to Random Access Responses transmitted on PRBs other than the restricted set of PRBs.

19. The method of claim 11, wherein a size of the RAR, a Modulation and Coding Scheme corresponding to the RAR and a sub-frame time of the RAR are specified in advance, and wherein scheduling of the RAR on the Physical Downlink Control Channel (PDCCH) is omitted.

20. A set of computer program products for facilitating random access communication in an LTE network between an eNB and an LCTE, the computer program products comprising code stored on non-transitory computer readable media which, when loaded into memory and executed on microprocessors of respective computing devices corresponding to the eNB and the LCTE, is adapted to perform the method of claim 11.

21. An evolved Node B (eNB) servicing a Long Term Evolution (LTE) communication system, the eNB configured to:

a) receive Physical Random Access Channel (PRACH) preamble messages from a plurality of Terminal Equipments (TEs) of the LTE system, said TEs including a Limited Capability Terminal Equipment (LCTE), at least one PRACH preamble from a predetermined subset of PRACH preambles, said subset being strictly smaller than a set of all PRACH preambles used by the plurality of TEs, the at least one PRACH preamble included in a corresponding PRACH preamble message; and

b) upon receipt of the at least one PRACH preamble belonging to said subset, schedule transmission of an associated random access response (RAR) on a restricted set of physical resource blocks (PRBs) which is predictable and accessible to said LCTE, the restricted set of PRBs being strictly smaller than a set of all PRBs used in the LTE communication system.

22. A Limited Capability terminal equipment (LCTE) for use in a Long Term Evolution (LTE) communication system, the LCTE configured, upon initiation of a physical random access channel (PRACH) random access operation, to:

a) select a PRACH preamble from a predetermined subset of PRACH preambles, said subset being strictly smaller than a set of all PRACH preambles used in the LTE communication system;

b) wirelessly transmit a PRACH preamble message including the selected PRACH preamble;

c) predict and monitor a restricted set of physical resource blocks (PRBs) for a Random Access Response (RAR) to the PRACH preamble message, the restricted set of PRBs being strictly smaller than a set of all PRBs used in the LTE communication system, the RAR transmitted by an evolved Node B (eNB), wherein the eNB is configured, upon receipt of the PRACH preamble message containing the PRACH preamble belonging to said subset, to transmit the RAR on the restricted set of PRBs.

23. A Long Term Evolution (LTE) system comprising:

a) a Limited Capability Terminal Equipment (LCTE) configured, upon initiating a physical random access channel (PRACH) random access operation, to select a PRACH preamble from a predetermined subset of PRACH preambles, said subset being strictly smaller than a set of all PRACH preambles used in the LTE system, the selected PRACH preamble included in wireless transmission of a PRACH preamble message; and

b) an evolved Node B (eNB) configured, in response to receipt of the PRACH preamble belonging to said subset, to adjust one or more operations pertaining to interaction with the LCTE in a manner which accommodates a limitation of the LCTE, said limitation indicated by membership of the PRACH preamble in the subset of PRACH preambles.

24. A method for facilitating communication in an LTE network between an eNB and a Limited Capability Terminal Equipment (LCTE), the method comprising:

a) defining a subset of Physical Random Access Channel (PRACH) preambles for use by the LCTE, said subset being strictly smaller than a set of all PRACH preambles available for use;

b) upon initiating a PRACH random access operation by the LCTE, selecting PRACH preambles from said subset for inclusion in transmission of a PRACH preamble message to the eNB;

in response to receipt of a PRACH preamble belonging to said subset by the eNB, adjusting one or more operations pertaining to interaction with the LCTE in a manner which accommodates a limitation of the LCTE, said limitation indicated by membership of the PRACH preamble in the subset of PRACH preambles.