Search

EP-4102794-B1 - NR BROADCAST CHANNEL TRANSMISSION

EP4102794B1EP 4102794 B1EP4102794 B1EP 4102794B1EP-4102794-B1

Inventors

  • WANG, JIANFENG
  • SAHLIN, HENRIK
  • GRÖVLEN, Asbjörn

Dates

Publication Date
20260506
Application Date
20180321

Claims (12)

  1. A method performed by a wireless device, for determining how to perform an initial access procedure in a wireless communication system, the method comprising: receiving a first synchronization signal, SS, block from a network node, the first SS block comprising first information necessary for the wireless device to perform the initial access procedure and second information indicating which SS block of multiple SS blocks transmitted by the network node is the first SS block; characterized by determining, based on an error-detection code corresponding to the first information, whether the wireless device accurately received the second information; and choosing whether to initiate the initial access procedure based on the first information as received from the first SS block or to receive another SS block before initiating the initial access procedure, based on said determining.
  2. The method of claim 1, wherein the first SS block does not include an error-detection code corresponding to the second information.
  3. The method of any of the preceding claims, wherein choosing whether to initiate the initial access procedure based on the first information or to receive another SS block before initiating the initial access procedure comprises, in response to determining that the wireless device did not accurately receive the second information, receiving a second SS block before initiating the initial access procedure, the second SS block comprising information necessary for the wireless device to perform the initial access procedure and information indicating which SS block of the multiple SS blocks is the second SS block.
  4. The method of any of the preceding claims, wherein said receiving comprises: descrambling a first portion of the SS block, corresponding to the first information, using a scrambling sequence based on information received from a second portion of the SS block, corresponding to the second information; and performing a cyclic-redundancy code (CRC) check on the descrambled first portion, using the error-detection code.
  5. The method of claim 4, wherein the scrambling sequence is a pseudo-random sequence and is further based on an identity of a cell related to the SS block.
  6. The method of any of the preceding claims, further comprising determining where the boundary of the SS burst set is or where the SS burst set starts, using the second information.
  7. A wireless device configured to determine how to perform an initial access procedure in a wireless communication system, the wireless device being configured to: receive a first synchronization signal, SS, block from a network node, the first SS block comprising first information necessary for the wireless device to perform the initial access procedure and second information indicating which SS block of multiple SS blocks transmitted by the network node is the first SS block; characterized by the wireless device being further configured to: determine, based on an error-detection code corresponding to the first information, whether the wireless device accurately received the second information; and choose whether to initiate the initial access procedure based on the first information as received from the first SS block or to receive another SS block before initiating the initial access procedure, based on said determining.
  8. The wireless device of claim 7, wherein the first SS block does not include an error-detection code corresponding to the second information.
  9. The wireless device of any of claims 7-8, wherein the wireless device is configured to, in response to determining that the wireless device did not accurately receive the second information, receive a second SS block before initiating the initial access procedure, the second SS block comprising information necessary for the wireless device to perform the initial access procedure and information indicating which SS block of the multiple SS blocks is the second SS block.
  10. The wireless device of any of claims 7-9, wherein the wireless device is configured to: descramble a first portion of the SS block, corresponding to the first information, using a scrambling sequence based on information received from a second portion of the SS block, corresponding to the second information; and perform a cyclic-redundancy code (CRC) check on the descrambled first portion, using the error-detection code.
  11. The wireless device of claim 10, wherein the scrambling sequence is a pseudo-random sequence and is further based on an identity of a cell related to the SS block.
  12. The wireless device of any of claims 7-11, wherein the wireless device is further configured to determine where the boundary of the SS burst set is or where the SS burst set starts, using the second information.

Description

TECHNICAL FIELD The invention relates to methods for transmitting system information in a synchronization signal block, as well as to a wireless device, a network node, computer programs, and computer program devices. BACKGROUND The fifth generation (5G) of mobile telecommunications and wireless technology is not yet fully defined but in an advanced draft stage within 3rd Generation Partnership Project (3GPP). It includes work on 5G New Radio (NR) Access Technology. Long term evolution (LTE) terminology is used in this disclosure in a forward looking sense, to include equivalent 5G entities or functionalities although a different term is specified in 5G. A general description of the agreements on the physical layer aspects of 5G NR Access Technology so far is contained in 3GPP Technical Report 38.802 v1.2.0 (2017-02). Final specifications may be published inter alia in the future 3GPP TS 38.2** series. Figure 1 schematically illustrates a wireless communication network, where a User Equipment UE1 is wirelessly connectable to a Base Station BS 2. The BS 2 is connected to a core network CN 3. In an NR access network, the BS may be referred to as a gNB, and the corresponding terminology for an LTE access network is an eNB. The BS 2 serves the UE 1 located within the BS's geographical area of service, called a cell. Initial access and synchronization in cellular systems When a wireless device (or UE) first accesses a wireless communication system, it must synchronize to the system. The synchronization is required for the UE to know when the network will transmit various signals such as broadcast of system information (SI). The UE must also synchronize to the system to understand when it should transmit uplink signals, such as the random access signals transmitted during initial access. A wireless communication system uses different time units to keep track of time. In systems using orthogonal frequency division multiplexing (OFDM), the term OFDM symbol is used for the smallest time unit. A number of symbols may form slots, a number of slots may form subframes, and a number of subframes may form radio frames. System information and paging information are typically distributed on a time scale where a radio frame is a relevant time unit. In many cellular system standards, a radio frame is 10 ms. In LTE, there are two synchronization signals: Primary synchronization signal (PSS) and Secondary synchronization signal (SSS). To perform initial access, the UE must obtain at least symbol and frame synchronization. To obtain symbol synchronization, the UE searches for a special synchronization sequence, which corresponds to the PSS. The PSS is typically one symbol long. By finding that sequence, the UE can establish symbol timing. The UE may also use the received PSS to determine frame synchronization. For that to be possible, every PSS must be transmitted with a fixed timing relation to the frame start. When the UE has found the PSS, it can also read an identifier of the current cell, and very basic system information, called the master information block (MIB). The PSS and SSS are thus used to indicate the physical-layer cell identity (PCI) to a UE, besides the functionality to provide the synchronization. In NR, the concepts of PSS and SSS are re-used to provide the initial synchronization and are referred to as NR-PSS and NR-SSS. NR-PSS is defined for initial symbol boundary synchronization to the NR cell. NR-SSS is defined for detection of NR cell identity (cell ID) or at least part of NR cell ID. In NR, a broadcast channel referred to as NR Physical Broadcast Channel (NR-PBCH) is defined. NR-PBCH is a non-scheduled broadcast channel carrying a part of minimum system information with fixed payload size and a periodicity predefined in the specification depending on carrier frequency range. NR-PBCH contents shall include at least part of the system frame number (SFN), and a Cyclic Redundancy Check (CRC). The following is a list of options to what the NR-PBCH may carry in terms of system information: Option 1: NR-PBCH carries a part of essential system information for initial access including information necessary for UE to receive a channel carrying remaining essential system information;Option 2: NR-PBCH carries minimum information necessary for UE to perform initial UL transmission in addition to the information in Option 1 allowing for initial access; andOption 3: NR-PBCH carries all essential system information for initial access. In NR, it will be possible to transmit the NR-PSS using beamforming. The NR-PSS will be transmitted in different beams at different time instants. The beams over which the NR-PSS is transmitted are chosen so that a UE at any position in the cell can receive at least one NR-PSS transmission. Sometimes, the term beam sweep is used for this procedure. To support beam sweeping of the NR-PSS, more than one NR-PSS must be transmitted in each frame, otherwise, the synchronization delay will be t