Paper Keywords: Intel, NR, Bandwidth Part, SCS, Channel Bandwidth, UE, RF Capability
Papers link: https: //arxiv.org/ftp/arxiv/papers/1712/1712.09724.pdf
Part of notes:
III. RF limited capability terminal
Problem Scenario:
NR defined CBW (Channel Bandwidth, the channel bandwidth) wide, and therefore, it is necessary to consider that the limited capacity of radio frequency terminals should be how to deal with? These terminals may not cover the wide band carrier (a wideband carrier) defined by the network side. Especially in the early stages of NR, RF capabilities of the UE is not too high, in other words with the advance of the deployment of the UE will constantly enhance the ability of NR.
Further illustrate the problem scenario:
Shown in Figure -1, as shown in Case-A, which can cover the entire width of the terminal on a radio link CBW; As shown in Case-B, the plurality of terminals of a radio frequency link to be able to cover the entire width of the CBW .
In other words, NR system needs to support radio terminals having different capabilities capabilities coexist in the same network.
[TODO guess: LTE is a 20M if the carrier is not a system message informs UE, configuration information when it is bound configured bandwidth of 20M? --- coarse reading other 3GPP specifications, when the answer is affirmative, a corresponding RRC message IE capable of carrying the information. Write a follow-up study notes related signaling interaction for BW. ]
Alternative solutions:
- Alternatively -1: network side configures Case-A and Case-B with a wideband CC (Component Carrier), and the terminal under the Case-B scene using a plurality of wideband radio frequency link to cover the CC;
- Alternative-2: Case-A network side configures the CC with a wide band, while the network-side configuration using Case-B CA (Carrier Aggregate) dispensing a continuous technique (intra-band contiguous) CC within a band set.
Decision alternatives to consider:
When a plurality of RF link signaling transmission, amplitude and phase signaling can problem of discontinuity occurs between radio frequency link. Thus, the channel estimation needs to be performed and the signaling transmission on the respective radio frequency link. Based on this consideration, alternatively -2 is NR adopted.
Since the radio network side to adapt to different capabilities of each terminal to do so flexible operation, such as, at the same time as some of the terminals for broadband CC, both as intra-band CA for some other terminal. This flexibility in the operation of the LTE system is not. Accordingly, the CC is not the same meaning as in the NR and LTE representation. On the UE is NR CC level; CC Cell level is on LTE.
IV. Bandwidth Parts (fractional bandwidth, BWP)
A. Background
NR wide bandwidth data provided directly affect the user peak rate. However, because the terminal is not at all times, high data rate, high bandwidth configuration and increases RF and baseband signal processing idle power consumption (idling power consumption). For these reasons, a new concept is introduced in NR bandwidth, BWP (Bandwidth Parts), BWP terminal may be configured such that a smaller bandwidth than the CBW. BWP provides NR enhance power efficiency program. Alternatively, we need to consider scheduling a terminal, while it is possible to send or receive signals within a given frequency range. Compared to this method, the use of BWP, the terminal does not need to send or receive a signal which Oh arranged outside the frequency range.
B. Configuration
Shown in Figure -2, a BWP contains a set of consecutive physical resource blocks (PRBs). [Upper limit value] of claim BWP BWP bandwidth can not exceed a given configuration of the terminal CC BW (Component Carrier Bandwidth). [Required] BWP lower limit value must be at least a bandwidth of a BWP SS block (SS block BW); [claim] BWP BWP with the SS block may contain or may not contain SS Block. BWP each associated with a specific notation, such as SCS and the CP type. Thus, BWP is a method for reconfiguration to the UE notation. FIG -2 illustrated on the right side can give a network terminal configured by RRC signaling plurality BWPs, [each BWP may overlap together in frequency]. BW size is configured PRB.
BWP assigned for each service cell constraint Description:
- ON THE
- It supports up to four UL BWP
- UL / DL spectrum symmetry
- BWP configuration support DL and UL: independent and non-independent configuration Configuration
- DL or UL respectively supports up to four BWPs
- UL / DL spectrum asymmetrical
- DL and UL BWP configuration support: non-independent configuration (joint configuration)
- DL or UL respectively supports up to four BWPs
Constraints associated with the set of control resources (Control Resource Set, CORESET):
Each DL BWP configuration comprises at least one set of control resources, comprising the CORESET specified terminal for controlling the search space (UE-specific Search Space, USS). USS search space is likely to accept and control information for a terminal. For the primary carrier, the at least one configuration of the DL BWP comprising CORESET common search space (Common Search Space, CSS) comprising a. CSS is used in a search space of all terminal or the destination terminal. [Note that the terminal wishes to activate only the BWP reception signal. ] However, the system still want: a terminal may perform RRM (Radio Resource Management) measurements or transmitting reference signals (Sounding Reference Signal, SRS) by a frequency point outside the measurement gap BWP activated. BWP is a tool that can be used to switch operation notation (SCS CP, and the like) of a terminal. For notation DL BWP configured for at least PDCCH, PDSCH demodulation reference signal and the corresponding (Demodulation RS, DMRS). UL BWP notation arranged for at least PUCCH, PUSHCH and the corresponding DMRS. Early versions for bound [NR notation requirements: in the same PUCCH needs to contain the same set notation. ]
C. activation / deactivation BWP
Activation and deactivation BWPs have several options. In addition to the complete activation through dedicated RRC signaling / deactivation, downlink control information (Downlink Control Information, DCI) can complete the activation / deactivation of operation BWP. Further, although the method is more rapid than the DCI MAC CE, but requires additional consideration DCI Error Error handling [Example: When a terminal decodes DCI BWP comprising activation / deactivation command fails]. To recover from this loss DCI scene introduced timer (Timer) process to activate the DL BWP / deactivation. In this mechanism, if the terminal is in a given time is not scheduled (switching BWP), such timer expires, the terminal will try to its activation DL BWP (or DL / UL BWP for Pair Specrum) is switched to the default BWP.
Initialization activation BWP: During initialization the access terminal, a terminal to initialize the activation process BWP. BWP is the default initialization activate BWP, unless otherwise explicitly configured. In Release 15-version, at most a predetermined activation DL BWP and at most a UL BWP. When activated BWP switching terminal, HARQ at the different BWPs retransmission.
D. RF retune time
When the UE performs handover BWP, the UE RF adapter required this switching, therefore, the time required to make clear reconstituted radio during a predetermined physical. Preliminary RAN4 given RF retune time specified as follows:
- For intra-band operation, at least for the Sub-6 GHz, the time required if conversion does not need to change the center frequency in 20us;
- For intra-band operation, at least for the Sub-6 GHz, if required switching time required change in the center frequency point within 50 ~ 200us;
- For inter-band operation, at least for the Sub-6 GHz, the conversion time required 900us
For BWPs NR is disposed within a carrier, therefore, inter-band RF retune time of the last bullet point BWP independent handover. Studies on millimeter wave radio frequency needs to be re-adjusted. For unpaired spectrum, the UE is not expected to retune the center frequency of the CBW between DL and UL. Considering the RF retuning time for BWP switching, if a PDCCH and the corresponding PDSCH scheduled by the PDCCH are transmitted in different BWPs, a UE does not expect the PDSCH to start earlier than K symbols after the end of the corresponding PDCCH. The active BWP switching time is up to RAN4 including whether the transition time (s) of active BWP switching is reported to the network as UE capability or not .