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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [ NICT PHY Pre-Proposal to Call for Contributions ] Date Submitted: [ February 27th , 2014] Source: [Marco Hernandez, Huan-Bang Li, Igor Dotlić, Ryu Miura ] Company: [ NICT]

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slide1

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

Submission Title:[ NICT PHY Pre-Proposal to Call for Contributions ]

Date Submitted: [ February 27th, 2014]

Source: [Marco Hernandez, Huan-Bang Li, Igor Dotlić, Ryu Miura]

Company: [NICT]

Address: [3-4 Hikarino-oka, Yokosuka, 239-0847, Japan]

Voice:[+81 46-847-5439] Fax:[+81 46-847-5431] E-Mail:[]

Re: [In response to call for technical contributions in TG8]

Abstract: [ ]

Purpose: [Material for discussion in 802.15.8 TG]

Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15.

Hernandez,Li,Dotlić,Miura (NICT)

outline
Outline
  • Physical Channels
  • PHY Frame Structure
  • Data Formatting
    • FEC coding, scrambling, interleaving, modulations
  • Multicarrier Modulation Parameters
  • Multiple Antenna Procedures
  • Discovery Signal
  • Random Access Procedure during Peering

Hernandez,Li,Dotlić,Miura (NICT)

physical channels
Physical Channels
  • Frequency bands of operation are:
    • Sub-GHz, 2.4 GHz and 5.7 GHz bands.
  • Those are selected because they do not require operation license. Hence, implementers only comply with local regulations. Moreover, those bands cover all PAC applications in terms of capacity, mobility and operational distance.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels1
Physical Channels
  • PAC applications require discovery and data communication links for many PAC users as possible at moderate data rate.
    • That is, sacrifice bandwidth against number of users.
  • This is a different requirement as compared to WiFi, which requires to sacrifice number of users against bandwidth, as it is well documented in the CSMA performance literature.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels2
Physical Channels
  • Hence, PAC applications require as many channel resources for multiplexing (and consequently multiple access) as possible.
    • That is, 15 channels of 10 MHz rather than 7 channels of 20 MHz to accommodate more users!
    • Multiplexing is how multiple users communicate simultaneously sharing a common wireless medium without interfering each other. Example: FDM, TDM, SDM or combinations like time-frequency division multiplexing.
    • Multiple access is how to allocate resources in time, frequency or both, to users, even if there are more users than available resources.
    • Example: TDMA, FDMA, OFDMA, SC-FDMA, CDMA, etc.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels3
Physical Channels
  • Using 10 MHz channels with high order modulations and possibly MIMO technologies, PAC applications can have high throughput.
  • We consider that support for high number of user rather than high data rate is a distinct requirement for PAC as compared to other standards, specially WiFi.
  • Coexistence with WiFi and other systems can be achieved with power control, low duty cycle, etc., rather than using the same bandwidth.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels4
Physical Channels
  • However, we propose another way to increase data rate.
  • We propose to use carrier aggregation, where 2 or more channels of 10 MHz can be added together to increase data rate for a given user, if the scenario allows it.

Hernandez,Li,Dotlić,Miura (NICT)

proposed frequency band allocations
Proposed frequency band allocations
  • Channelization of 5.7 GHz band
    • Such frequency band ranges from 5.725 GHz to 5.875 GHz, which is divided into 15 channels of 10 MHz. The central frequencies are given by

fc = 5730 MHz + 10 n for n = 0, 1, ..., 14

  • Channelization of 2.4 GHz band
    • Such frequency band ranges from 2.4 GHz to 2.4835 GHz, which is divided into 8 channels of 10 MHz. The central frequencies are given by

fc = 2405 MHz + 10 n for n = 0, 1, ..., 7

Hernandez,Li,Dotlić,Miura (NICT)

physical channels5
Physical Channels
  • Carrier aggregation
    • The aggregated channel can be considered by the PD as a single enlarged channel from the RF viewpoint.
    • Thus channels of 20 MHz or more can be considered for higher data rate transmission.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels6
Physical Channels
  • Channelization of 920 MHz band by regulations in Japan:
    • 1bandwidth rule tolerance: 200n kHz, where n=1,2,3,4,5.
    • 2bandwidth rule tolerance: 100n kHz, where n=1,2,3,4,5.

Hernandez,Li,Dotlić,Miura (NICT)

physical channels7
Physical Channels
  • Proposed channelization for sub-GHz band (Japan):

Hernandez,Li,Dotlić,Miura (NICT)

phy frame structure
PHY Frame Structure
  • There are 4 distinct data formatting functionalities:
    • Network synchronization, discovery, peering and data transmission
  • These constitute the PHY frame structure, or signals on the air:
    • In burst mode, consecutive ultra frames may be transmitted without discovery and peering.

Hernandez,Li,Dotlić,Miura (NICT)

phy frame structure psdu
PHY Frame Structure: PSDU

Hernandez,Li,Dotlić,Miura (NICT)

tdd switching s
TDD switching (S)
  • S consists of a guard interval, preamble for fine synchronization and channel sounding, and control channel

Asymmetric traffic

Hernandez,Li,Dotlić,Miura (NICT)

tdd switching s1
TDD switching (S)
  • Propagation time:
    • Tp=1 Km/3x108m/s = 3.3 µsec (worst case).
    • Tp=10 m/3x108m/s = 0.033 µsec (typical case).
  • Last symbol of PD1 arrives to PD2 after Tp, the symbol is detected, PD2 switches from Rx to Tx. Then, the first transmitted symbol of PD2 arrives to PD1 after Tp.
  • Tp+Tdec+Tsw+Tcomp+Tp=GI
    • Tdec=time to detect the last symbol
    • Tsw=time to switch from Rx to Tx or vice-versa
    • Tcomp=compensation time to align GI to FFT sampling

Hernandez,Li,Dotlić,Miura (NICT)

common mode phy for psdu
Common mode PHY for PSDU

Hernandez,Li,Dotlić,Miura (NICT)

psdu construction
PSDU construction
  • The MAC protocol data unit (MPDU) is passed to the PHY
  • Such Data is encoded by QC-LDPC codes.
  • QC-LDPC codes allows performance close to turbo codes, besides that encoder/decoder enable high throughput and low implementation complexity (efficient implementation in parallel architectures).
  • Quasi-cyclic LDPC codes are systematic, linear codes satisfying

Hernandez,Li,Dotlić,Miura (NICT)

fec coding
FEC coding
  • QC-LDPC parameters
  • k= number of information bits, n=number of coded bits,
  • n-k=number of parity bits.

Hernandez,Li,Dotlić,Miura (NICT)

interleaver
Interleaver
  • Maximum contention-free quadratic permutation polynomial interleaver:
  • Proposed short length interleaver:
  • Proposed long length interleaver:

Hernandez,Li,Dotlić,Miura (NICT)

interleaver1
Interleaver
  • Total number of coded bits in a packet is NTc=Ncwn
    • Ncwis the number of codewords in a package.
    • nis the codeword length.
    • cnk+i for i=0,1,…,n−1 and k=0,1,…,Ncw−1
  • NTccoded bits are interleaved in blocks of NI bits as
    • for j=0,1,…,NTc−1.

Hernandez,Li,Dotlić,Miura (NICT)

scrambler
Scrambler
  • A scrambler is used to shape the data spectrum and to randomize data across users in order to reduce interference.
  • Gold code generator of length 63 is proposed as scrambler
    • PN sequence with period L=263 (truly random for long packets)
    • Different initialization seeds, enables a different Gold code per user with low correlation respect to other user using a different seed.
  • 63 shift register initialization
    • User ID and group ID (already known during discovery phase)
    • Fast forward 100 times to reduce PAPR (OFDM)

Hernandez,Li,Dotlić,Miura (NICT)

scrambler1
Scrambler
  • The Gold code generator with polynomials x6+x+1 and x6+x5+x2+x+1 outputs si, which is used to scramble the interleaved coded-bits as
    • where i=0,1,…,Ncwn−1

Hernandez,Li,Dotlić,Miura (NICT)

modulation mapper
Modulation mapper
  • The scrambled-interleaved-coded-bits, bi , are modulated with either BSPK, QPSK, 16QAM or 64QAM.
  • Pad bits shall be appended to align on a symbol boundary:
    • M is the cardinality of the modulation scheme.
    • , NPSDU=NMPDU+Nbs, where Nbs=Ncwk−NMPDU
  • The total number of bits on the air is given by

Hernandez,Li,Dotlić,Miura (NICT)

modulation mapper1
Modulation mapper
  • The complex modulation symbols, dl, are given by
    • BPSK: dl(bi)=I+jQ
    • QPSK: dl(bi, bi+1)=I+jQ
    • 16QAM: dl(bi,bi+1,bi+2,bi+3)=I+jQ
    • 64QAM: dl(bi,bi+1,bi+2,bi+3 ,bi+4,bi+5)=I+jQ
    • Fori=0,…,NT−1; l=0,…,Nsym−1 and Nsym=NT /M an integer.
  • BPSK mapping QPSK mapping

Hernandez,Li,Dotlić,Miura (NICT)

modulation mapper2
Modulation mapper
  • 16 QAM mapping

Hernandez,Li,Dotlić,Miura (NICT)

slide26

64 QAM

Hernandez,Li,Dotlić,Miura (NICT)

layer mapping
Layer mapping
  • Two MIMO technologies are supported: open loop spatial multiplexing and transmit diversity (SFBC) for 2 and 4 antennas.
  • The [complex] modulation symbols per codeword di for i=0,1,…,Nsym-1 are mapped into several layers
    • Layer=independent stream of symbols in a MIMO configuration.
    • Rank=number of layers transmitted.
  • As for
    • where is the number of layers and is the number of symbols per layer for the qth codeword.

Hernandez,Li,Dotlić,Miura (NICT)

precoding
Precoding
  • Precoding allows to increase system performance and robustness by feeding back to the transmitter CSI.
  • Schematic diagram of MIMO support with precoding

Hernandez,Li,Dotlić,Miura (NICT)

multicarrier modulation dft s ofdm or ofdm parameters
Multicarrier ModulationDFT-S OFDM or OFDM Parameters
  • ∆f is constant and equal to 15 KHz.
  • Maximum FFT size:
    • M=1024 (if BW=10 MHz), M=2048 (if BW=20 MHz)
  • Sampling time:
    • Ts=65.10 nsec (if BW=10 MHz), Ts=32.6 nsec(if BW=20 MHz)
  • Timing based on a common clock at
    • Rc=15.36 MHz (if BW=10 MHz), Rc=30.72 MHz (if BW=20 MHz)

Hernandez,Li,Dotlić,Miura (NICT)

multicarrier modulation
Multicarrier Modulation
  • Cyclic prefix
  • 73Ts=4.75 µsec for BW=10 MHz
  • 146Ts=4.75 µsec for BW=20 MHz

Hernandez,Li,Dotlić,Miura (NICT)

multicarrier modulation1
Multicarrier Modulation
  • Resource block (RB) is a set of time-frequency slots enabling multiple access

Hernandez,Li,Dotlić,Miura (NICT)

multicarrier modulation2
Multicarrier Modulation
  • BW is obtained by concatenating RBs

DFT-S OFDM or OFDM symbols

(2 upper and lower subcarriers are empty)

Hernandez,Li,Dotlić,Miura (NICT)

multicarrier modulation3
Multicarrier Modulation
  • Proposed bandwidths (considering max FFT size=1024)

Hernandez,Li,Dotlić,Miura (NICT)

optional fsk phy
Optional FSK PHY
  • An optional and very low power PHY based on FSK modulation is contemplated for the sub-1 GHz band.
  • No support for MIMO technologies, i.e., layer mapper and precoding are not necessary.
  • The proposed channel encoder, bit interleaver and scrambler are used as well.
    • The modulation mapper is CP-GFSK.

Hernandez,Li,Dotlić,Miura (NICT)

optional fsk phy1
Optional FSK PHY
  • CP-GFSK modulation
    • V is amplitude, S(t)=sin(2πfct)is the modulating-carrier signal, fcis the carrier frequency, is the peak frequency deviation, β=1 is the modulation index, Tsym is the symbol time and φ0 is the initial phase of the modulating-carrier signal
  • The information bearing signal is
    • gm is information bit, p(t) is a Gaussian pulse shape of bandwidth-symbol duration product of 0.8

Hernandez,Li,Dotlić,Miura (NICT)

reference signals
Reference Signals
  • Reference signals are required for network synchronization as well as for fine synchronization and channel estimation for coherent detection and equalization in either Synchronization, Discovery, Peering and PSDU of the PHY frame structure.
  • Zadoff-Chu (ZC) sequences have good correlation properties and easy implementation for devices with multicarrier modulation.

Hernandez,Li,Dotlić,Miura (NICT)

zc sequences
ZC sequences
  • ZC sequences have constant amplitude and so its N-point DFT.
    • This limits the PAPR and simplifies implementation as only phases have to be generated and stored, besides of bypassing the FFT at transmitter for DFT-S OFDM.
  • ZC sequences have ideal cyclic autocorrelation, i.e., the correlation with its shifted version is a delta function
    • Thus, a [large] set of orthogonal preambles or reference signals is possible to generate.

Hernandez,Li,Dotlić,Miura (NICT)

zc sequences1
ZC sequences
  • Zadoff-Chu (ZC) sequences of length N:
    • Constant-amplitude zero-correlation (CAZAC) sequences
  • where WN is a primitive nth root of unity, r is a relative prime to N, sequence index k = 0, 1, ...,N-1and q is any integer.

Hernandez,Li,Dotlić,Miura (NICT)

phy frame structure discovery
PHY Frame Structure: Discovery
  • We propose to use a discoveryresource block (DRB) from a modified (DTF-S) OFDM or OFDM signal.
    • The DRB formed the Discovery Signal (DS).
  • Moreover, we propose to use one channel (from the proposed channelization for sub-GHz, 2.4 GHz and 5.7 GHz bands) for only discovery of devices.
    • PAC devices can either transmit or receive the DS in this unique channel asynchronously.
  • Such unique channel for discovery is named Shared Discovery Channel (SDCH).

Hernandez,Li,Dotlić,Miura (NICT)

phy frame structure discovery1
PHY Frame Structure: Discovery
  • The discovery signal (DS) sent over a discovery shared channel (DSCH) after the synchronization preamble:
    • The DRB is formed by Nfsfrequency slots and Ntstime slots.
  • Once synchronized, a receiver knows the location of the discovery resource block (DRS) to scan for possible peers or to pick time-frequency slots to transmit its DS.

Hernandez,Li,Dotlić,Miura (NICT)

slide41
DRB
  • The proposed PHY for data transmission can be reused with some simplifications for discovery.
  • The discovery process is energy intensive.
  • In order to minimize power consumption, in case of DTF-Spread OFDM, the M-point FFT is bypassed (this is not required for OFDM) and only one subcarrier of the N-point IFFT is used per user.
    • The PAPR is set to the minimum.
    • Across the frequency domain, users are orthogonal (OFDMA)

Hernandez,Li,Dotlić,Miura (NICT)

slide42
DRB
  • For discovery, the nth symbol transmitted over the kth subcarrier is given by
    • for l=−L+1,,…,0,1,…,N-1 and L the CP length.

Hernandez,Li,Dotlić,Miura (NICT)

drb structure
DRB structure

Contiguous subcarriers are orthogonal.

The DS is transmitted with a predefined duty-cycle (see NICT MAC pre-proposal).

Hernandez,Li,Dotlić,Miura (NICT)

drb structure1
DRB structure
  • From upper layers, terminals pick time-frequency slots in the DRB to transmit the DS.
  • A set of 126 symbols are transmitted per time slot:
    • such frame contains information about a given peer (peer ID, service ID, application ID, etc.) and which channel is used for association (different from the SDCH).
  • The number of frequency slots Nfs=1024 (IFFT size) and the number of time slots Ntsis chosen as 20.
  • Consequently, the DRB can support up to NfsxNts=20,480 users for discovery per PD.

Hernandez,Li,Dotlić,Miura (NICT)

drb structure2
DRB structure
  • The discovery data is formatted as illustrated
  • Append 57 bits for user ID, device ID, Group ID, etc.
  • Append 6 bits from CRC-6-ITU error detection code
  • Append 63 parity bits from shorten BCH(126,63) code

Hernandez,Li,Dotlić,Miura (NICT)

d iscovery algorithm parameters
Discovery algorithm parameters
  • Devices are in three possible states:
    • RDM –receiving discovery mode,
    • TDM –transmitting discovery mode,
    • Sleep -idle.
    • Also, devices are equipped with clear channel assessment (CCA).
    • The proposed discovery algorithm delineates the interplay between the PHY and MAC.

Hernandez,Li,Dotlić,Miura (NICT)

discovery algorithm
Discovery Algorithm
  • 1) At start up or after idle or after command, a device enters into receiving discovery mode (RDM) and listens for a DS.
    • Synchronization subsystem detects the preamble (and hence the position of the DRB in time) and detection subsystem scans the DRB for DRB usage and detection of peer ID, service ID, etc. Go to Sleep mode.
  • 2) After command, a device enters into transmitting discovery mode (TDM)
    • Device chooses a free time-frequency slot to transmit its DS over the next DRB transmission. Go to Sleepmode.

Of course, there are intermediate steps like time-out for DRB scanning, miss detection, etc. Here, we present the core algorithm only.

Hernandez,Li,Dotlić,Miura (NICT)

discovery range
Discovery range
  • An estimate of the distance range of peers is obtained from the link budget as
    • Receiver’s sensitivity:
  • Once the value of path loss is known, an estimate of the transmission distance is obtained depending on a desired path loss law.

Hernandez,Li,Dotlić,Miura (NICT)

discovery range1
Discovery range
  • Path loss parameters
    • 920 MHz band, option C.
    • The maximum transmit power at the input antenna: Pt = 250 mW.
    • Antenna gains are assumed as Gt = Gr = 0 dBi.
    • The fade margin: Fm = 6 dB.
    • Receiver’s implementation losses: Il = 3 dB.
    • Receiver’s noise figure: NF = 6 dB.
    • Through simulations: Eb/N0= 8 dB for BER= 10-7 (BPSK).
    • Data rate: 1 Mbps, 250 kbps.
  • The maximum allowed path losses are:
    • L1= 114:97 dB for 1 Mbps
    • L2= 120:98 dB for 250 kbps

Hernandez,Li,Dotlić,Miura (NICT)

discovery range2
Discovery range
  • Using the ITU outdoor path loss model with hb=hm=1.5 m, distances are:
    • 900 m for 1 Mbps
    • 1200 mfor 250 kbps.
  • Using the indoor path loss model with n = 3.27 and 2 block walls, distances are:
    • 60 m for 1 Mbps
    • 80 mfor 250 kbps.

Hernandez,Li,Dotlić,Miura (NICT)

discovery peering
Discovery-Peering
  • Notice that discovery is performed after network synchronization update. There is not central control.
  • For association or peering, intended devices that want to establish a communication link, request that through a random access preamble transmitted during the peering period.

Hernandez,Li,Dotlić,Miura (NICT)

association preambles
Association Preambles
  • The random access association preambles are named Random Access Preambles (RAPs).
  • Such RAPs are formed with ZC sequences as well.
  • Hence, a pool of orthogonal RAPs is formed
    • in order to reduce interference from competing terminals for random access.
  • A unique RAP is assigned to every device in a Group.
  • Such unique RAP is used for fine synchronization and control messages (how a communication link is granted).

Hernandez,Li,Dotlić,Miura (NICT)

rap structure
RAP structure
  • The RAP signal is illustrated as
    • GI is guard interval
    • In MAC lingo, it is known as beacon.

Hernandez,Li,Dotlić,Miura (NICT)

random access procedure
Random access procedure
  • Once initial synchronization and decoding of discovery RB are achieved by Terminal 2 over Terminal 1:
    • Terminal 2 requests association by a random access procedure based on an orthogonal RAP.

Hernandez,Li,Dotlić,Miura (NICT)

slide55
End
  • Thanks for your attention

Hernandez,Li,Dotlić,Miura (NICT)