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Overview on PreTrial

 

To me, 5G is a new interesting topics that I've been chasing for about 3 years now (as of Dec 2016), but 3GPP is still at too early stage as opposed to the expectations of industry (at least some major players in the industry). There might be some reasonable reasons with seeminly slow progress in 3GPP, but the demand in the industry (at least some part of the industry) got too high to wait until 3GPP is fully ready with the specification.

As a result, some major players in industry decided to deploy a small scale 5G system with their own specification that some people call 'Pre Trial'. As of now, there are two pretrial specifiction out there, one from Verizon (a US Carrier) and the other one from KT (a South Korea Carrier). You can get these specification in the following link :

I haven't compared these two specification line by line , word by word.. but at least to me they seem to be almost same (at least at physical layer). This is good since I study only one of them and can understand both of them :)

 

The main purpose of this section ('PreTrial') is to give you brief introductions on these specification. I will start with physical layer and keep adding things towards higher layers later.

 

I cannot guarantee that all of these specification will be adopted by 3GPP official specification, but my guess that large portions of these specification will be absorbed by 3GPP specification (at least, early eMBB specification). So I would recommend you to look into these specifications and it will definitely help you understand the 3GPP specification when it is out.

 

 

Summary of Key Parameters

 

Followings are some of the key parameters specified in Pre Trial specification (Based 211 in both Verizon and KT specification)

 

< Overall Specification >

Parameter

Description

Frequency

In 28 Ghz range

System Bandwidth

100 Mhz for Single Carrier. Open to Multi Carrier Operation

Maximum number of Carriers

8 Carriers (1 PCC + 7 SCC)

Waveform

DL : OFDMA, UL : OFDMA

Subcarrier Spacing

75 Khz (5 times larger than current LTE spacing)

Subframe Length

0.2 ms (5 times shorter than current LTE)

Synchronization Signal

PSS, SSS, ESS

Max Number of Layers

8 ( Max 2 layers for one UE)

Modulation Schemes supported

QPSK, 16QAM, 64QAM in DL/UL

Diverse Reference Signals

 

 

Downlink

Beam measurement Reference Signal (BRS)

Beam Refinement Reference Signal (BRRS)

Reference Signal (DM-RS) associated with ePBCH

CSI Reference Signal (CSI-RS)

Phase noise reference signal, associated with transmission of xPDSCH

UE-specific Reference Signal (DM-RS) associated with xPDSCH

UE-specific Reference Signal (DM-RS) associated with xPDCCH

Uplink

Phase noise reference signal, associated with transmission of xPUSCH

Sounding reference signal, not associated with transmission of xPUSCH or xPUCCH

Demodulation reference signal, associated with transmission of xPUCCH

Demodulation reference signal, associated with transmission of xPUSCH

 

< Numerology >

Parameter

5G Pre Trial

LTE

Subcarrier Spacing

75 Khz

15 Khz

Sampling Time (Ts)

6.5 ns

32.5 ns

Sampling Rate

153.6 M sps

30.72 M sps

Subframe Length

0.2 ms

1 ms

Number of OFDM Symbols per subframe

14

14

Number of Subcarrier per RB

12

12

Max RB per Carrier

100 (per 100 Mhz)

100 (per 20 Mhz)

Length of Radio Frame

10 ms

10 ms

Number of subframes per Radio Frame

50

10

 

 

< Squence Template >

Sequence Type

Application

Zadoff Chu Sequence

6.8.1 Primary Synchronization Signal

6.8.3 Extended Synchronization Signal

5.5.4 Sounding reference signal

5.7.2 Preamble sequence generation (PRACH)

 

Psuedo Random Sequence :

Gold Code (Gold Sequence)

6.5.1 Scrambling (xPDSCH)

6.5A.1 Scrambling (ePBCH)

5.5.2 Demodulation reference signal associated with xPUCCH

5.5.3 Demodulation reference signal associated with xPUSCH

5.5.5 Phase noise compensation reference signal

6.6.2 xPDCCH multiplexing and scrambling

6.7.1 UE-specific reference signals associated with xPDSCH

6.7.2 UE-specific reference signals associated with xPDCCH

6.7.3 CSI reference signals

6.7.4 Beam reference signal (BRS)

6.7.5 Beam refinement reference signals

6.7.6 DL Phase noise compensation reference signal

6.7.7 Demodulation reference signals associated with ePBCH

6.8.2 Secondary Synchronization Signal

6.8.3 Extended Synchronization Signal (Scrambling a ZadOff-Chu Seq)