SFN timing for frequency hopping systems
According to an aspect, a wireless device identifies system frame numbers (SFNs) that are used for wireless transmissions that use a broadcast channel (BCH) transmission time interval (TTI), where frequency hopping cycles (FHCs) are not aligned with a cycle of the SFNs. The wireless device receives FH information indicating how the FHC used for wireless transmissions relates to the SFN cycle and identifies an SFN timing for the wireless transmissions based on the FH information.
1. A method, in a wireless device, for identifying system frame number (SFNs) that are used for wireless transmissions that use a broadcast channel (BCH) transmission time interval (TTI) wherein frequency hopping (FH) cycles (FHCs) are not aligned with a cycle of the SFNs (SFN cycle), the method comprising:
receiving FH information indicating how the FHC used for wireless transmissions relates to the SFN cycle; and
identifying an SFN timing for the wireless transmissions based on the FH information according to:
SFN=( t hop ·T dwell /10)mod SFN_cycle,
where t hop =(FHCN·N), FHCN is an FHC number, T dwell is a dwell time for each frequency, and N is the number of hops in the FHC.
2. The method of claim 1 , further comprising using the SFN timing to determine a specific frequency hop within the FHC.
3. The method of claim 1 , wherein identifying the SFN timing comprises identifying the SFN timing based on a number of frequency hops in the FHC, a dwell time for each hopping frequency, and a number of the SFNs in the SFN cycle.
4. The method of claim 1 , wherein receiving the FH information comprises receiving an FHCN identifying the FHC to be used, and wherein the SFN timing is based on the FHCN.
5. The method of claim 4 , wherein the FHCN is determined by pseudo-randomly deriving the FHC from a physical cell identity (PCID) and/or a network identifier (NetID) associated with a network node.
6. The method of claim 1 , wherein the wireless transmissions use a narrow band (NB) physical broadcast channel (NPBCH) TTI.
7. The method of claim 1 , wherein the TTI is divided into a plurality of blocks, each block comprising a plurality of radio frames and carrying a code subblock (CSB) version that is transmitted in one or more subframes in one or more radio frames, wherein different CSB versions are used in successive blocks within the TTIs, and wherein identifying the SFN timing comprises using the CSB version to help identify a block, the SFN timing, and/or the FHC for the TTI.
8. The method of claim 7 , further comprising, in response to using a CSB version to help identify the FHC, identifying the FHC with fewer bits than if the CSB version was not used, wherein the number of the fewer bits is based on a total number of CSB.
9. The method of claim 7 , wherein the one or more subframes are one or more specific subframes within a radio frame or multiple consecutive subframes.
10. The method of claim 4 , wherein the FHCN is received in a master information block (MIB).
11. The method of claim 10 , wherein the MIB is acquired in one dwell of the FHC.
12. A wireless device configured for identifying system frame numbers (SFNs) that are used for wireless transmissions that use a broadcast channel (BCH) transmission time interval (TTI) wherein frequency hopping cycles (FHCs) are not aligned with a cycle of the SFNs (SFN cycle), the wireless device comprising:
transceiver circuitry configured for communicating with network nodes in a wireless communication network; and
processing circuitry operatively associated with the transceiver circuitry and configured to:
receive frequency hopping (FH) information indicating how the FHC used for wireless transmissions relates to the SFN cycle; and
identify an SFN timing for the wireless transmissions based on the FH information according to:
SFN=( t hop ·T dwell /10)mod SFN_cycle,
where t hop =(FHCN·N), FHCN is an FHC number, T dwell is a dwell time for each frequency, and N is the number of hops in the FHC.
13. The wireless device of claim 12 , wherein the processing circuitry is configured to use the SFN timing to determine a specific frequency hop within the FHC.
14. The wireless device of claim 12 , wherein the processing circuitry—is configured to identify the SFN timing by identifying the SFN timing based on a number of frequency hops in the FHC, a dwell time for each hopping frequency and the number of SFNs in the SFN cycle.
15. The wireless device of claim 12 , wherein the processing circuitry is configured to receive the FH information by receiving an FHC number (FHCN) identifying the FHC to be used, and wherein the SFN timing is based on the FHCN.
16. The wireless device of claim 12 , wherein the wireless transmissions use a narrow band physical broadcast channel (NPBCH) TTI.
17. The wireless device of claim 12 , wherein the TTI is divided into a plurality of blocks, each block comprising a plurality of radio frames and carrying a code subblock (CSB) version that is transmitted in one or more subframes in one or more radio frames, wherein different CSB versions are used in successive blocks within the TTIs, and wherein the processing circuitry is configured to use the CSB version to help identify a block, the SFN timing, and/or the FHC for the TTI.
18. The wireless device of claim 17 , wherein the processing circuitry—is configured to, in response to using a CSB version to help identify the FHC, identify the FHC with fewer bits than if the CSB version was not used, wherein the number of fewer bits is based on a total number of CSB.
19. The wireless device of claim 17 , wherein the one or more subframes are one or more specific subframes within a radio frame or multiple subframes are consecutive subframes.
20. The wireless device of claim 12 , wherein the FHCN is received in a master information block (MIB).
21. The wireless device of claim 20 , wherein the MIB is acquired in one dwell of the FHC.
22. The wireless device of claim 15 , wherein the FHCN is determined by pseudo-randomly deriving the FHC from a physical cell identity (PCID) and/or a network identifier (NetID) associated with the network node.
23. A non-transitory, computer-readable medium storing a computer program for identifying system frame numbers (SFNs) that are used for wireless transmissions that use a broadcast channel (BCH) transmission time interval (TTI) wherein frequency hopping (FH) cycles (FHCs) are not aligned with a cycle of the SFNs, the computer program comprising instructions that, when executed by a processing circuit of a wireless device—operating in a wireless communication network, cause the wireless device to:
receive FH information indicating how the FHC used for wireless transmissions relates to the SFN cycle; and
identify an SFN timing for the wireless transmissions based on the FH information according to:
SFN=( t hop ·T dwell /10)mod SFN_cycle,
where t hop =(FHCN·N), FHCN is an FHC number, T dwell is a dwell time for each frequency, and N is the number of hops in the FHC.