doc.: ieee802.15-06-0447-01-003c submission november 2006 slobodan nedic, nedics associatesslide 1...

November 2006

Slobodan Nedic, Nedics AssociatesSlide 1

doc.: IEEE802.15-06-0447-01-003c

Submission

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

Submission Title: [Bridging the gap between SC and OFDM as a basis for the 802.15.3c PHY]Date Submitted: [14 November, 2006]Source: [Slobodan Nedic, Nedics Associates]Address [336 Sonoma Aisle, Irvine, CA 92618]Voice: [949-748-7020], Cell: [732-421-2045], E-Mail:[[email protected]] Re: []

Abstract: [This document highlights a signaling/accessing format with potential to provide good basis for PHY implementation, with high flexibility in terms of trade-offs between power and spectral efficiency, and incremental future enhancements. It essentially conciliates the SC and OFDM signaling formats by filling the gap that currently exists between them. The basic element that enables orthogonal frequency division multiplexing of spectrally shaped (sub-)channels is staggering between in-phase and quadrature components. This feature is inherent to MSK modulation, and can be extended to more spectrally efficient O(ffset)QAM-MC, or OFDM/OQAM flavors. A rough estimation of achievable data rates is provided.]

Purpose: [For information only.]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.

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

Introduction• When considering PHY for the 802.15.3c, it is often

stated that power efficiency is primary importance, but very soon spectral efficiency will also be needed, no matter how wide bandwidths

• The first 60Gz range WPAN standard should not impede enhancements due to backward compatibility issues; should also serve as basis for some form of 60GHz 10Gbps WLAN ?!

• This contribution brings to the attention of the standardization group a signaling format that can meet the short-term and long-term objectives with best performance/complexity trade-off, by bridging the gap between SC and OFDM

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

Pros and Cons for Single-Carrier and OFDM

• SC– High complexity for good

spectral efficiency– Moderate PAPR in such case– Long equalizer and slow rate

(adaptation, and tracking)– Directly exploits multipath

diversity through DFE– Insensitivity to frequency

offset and phase jitter– Can be concatenated with CC

for better performance

• OFDM– Needs large number of subchannels for

reasonable spectral efficiency, due to CP– Reduced power efficiency– Simple equalization, but high loss due to

imperfect channel estimation– Reliance on coding overhead and

interleaving– High sensitivity to frequency offset and

phase jitter– Needs SDM/STC to be effective ?!

Conciliatory solution: To use a relatively small number of sub-channels for best trade-off between complexity and performance

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

MC-CDMA

TDMA; F-H

-band” “Multi -band” “Single

SC C

U W B

M - ary P M

M -ary

M F P

Multi-Carrier with OQAM in Sub-channels: The Missing Link

SF >>1

(SF A M

O 64+ sub

sub-ch

chnls

2K to

8K

F M =1)

D D

P

Visualization of broad-band signaling/accessing formats and the “technology gap”

Legend: OFDM – Orthogonal Frequency Division Multiplex; SC – Single Carrier, and CDMA – Code Division Multiple Access, SF – spreading factor in CDMA, (SF=1 for SC); TDMA – Time Division Multiple Access; F-H – Frequency Hopping; UWB – Ultra Wide-Band; PPM – Pulse Position Modulation and FPM – Frequency Position Modulation, as two forms of M-ary orthogonal signaling; OQAM – Offset, or Staggered Quadrature Amplitude Modulation; MC-CDMA – Combination of OFDM and CDMA

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

1/T

The key – alternating T/2 staggering of I and Q sub-channel components:

numerous systems dating back from early sixties (Chang, Saltzberg, Hirosaki …), known under different names (OFDM/OQAM, WDMT, TLO, IOTA …), essentially “differing” only in the type of the (filter-bank) referent base-band impulse response.

f

t

- I component

T

Sub-channel k

T – QAM signaling interval (AM at T/2 instants)

T/2

- Q component

0

1/T

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

w/ over-lapping

w/o over-lapping

Modulation Code Rate Comments

UnitedStates,

2.968** 0.742* QPSK 1/2 *Spectral Efficiency 0.5·0.5*Power Efficiency 100%

**SE (3/4) ·0.5; PE maintained ?

Canada,and

5.332† † 1.333 † QPSK 8/9 †Spectral Efficiency 0.5·(8/9)† Power Efficiency 100%

† † SE (3/4) ·8/9; PE maintained ?

Japan ld(L)·2.968

ld(L)· 0.742

L-QAM 1/2 Spectral efficiency increased,Power efficiency decreased

B=2.225 MHz ld(L)· 5.332

ld(L)· 1.333


Europe -

in proportion

with reduced

Bandwidth

‘Aggregate’ data rates (Gbps) per single, and four overlapped channels

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

w/ over-lappin↓

w/o over-lapping ↓

Modulation Code Rate Comments

UnitedStates,

3.3375** 1.1125* QPSK 1/2 *Spectral Efficiency 0.5·0.5*Power Efficiency 100%

**SE (3/4) ·0.5; PE maintained ?

Canada,and

6.000† † 2.000 † QPSK 8/9 †Spectral Efficiency 0.5·(8/9)† Power Efficiency 100%

† † SE (3/4) ·8/9; PE maintained ?

Japan ld(L)·3.3375

ld(L)· 1.1125


B=2.225 MHz ld(L)· 6.000

ld(L)· 2.000


Europe -

in proportion

with reduced

Bandwidth

‘Aggregate’ data rates (Gbps) per single, and three overlapped channels

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

• Some equalization will quite likely be needed– Available for staggered QAM, both in SC and MC

• Even w/ directional antennas, MSK may need more than T/2 fractional equalizer (same complexity as in T-spaced QAM)

• With omni-directional antennas, Nyquist shaping is preferable

• With synchronized TDD MAC, fully overlapped sub-channels of different users may be possible

• Equalization overhead low for longer packets• At early development stages, multiple channels for the

same user through transceiver replication– In future enhancements to be used for SDM-diversity

• Relatively small number of sub-channels may allow for relatively simple PAPR reduction

System-level and networking aspects

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

• Starting with the conventional (“bookish”) MSK, in its spectrally maximally efficient QPSK form, and one plausible basic partition of the available bandwidths s, incremental modifications have been suggested to meet the current and future PARs

• The basis is the use of OFDM of sub-channels with staggered QAM, enabling relatively small number of sub-carriers for bridging the gap between SC and traditional OFDM for an optimal trade-off between performance and complexity

• This signaling format has been around for quite some time, and virtually all aspects of its implementation have been well researched and elaborated in numerous publications

Conclusions

November 2006


doc.: IEEE802.15-06-0447-01-003c

Submission

[1] 15-06-0306-01-003c-msk-system-multi-gbs-wireless-communications-60ghz[2] 15-06-0325-00-003c-chennelization-requirements-802-15-3c[3] 15-05-0299-00-003c-preliminary-channel-proposal[4] 15-06-0387-02-003c-phy-layer-modulation-802-15-3c-system-level-issues[5] R.W. Chang, “Synthesis of band-limited orthogonal signals for multicarrier data transmission,” The

BSTJ, Vol. 45, pp. 1775-1796, December 1966.[6] B.R. Saltzberg, “Performance of an efficient parallel data transmission system,” IEEE Tr. On

Communications Technology, December 1996. [7] B. Hirosaki, “An orthogonally multiplexed QAM system using discrete Fourier transform,” IEEE Tr.

On Communications, July 1981. [8] R. Lee and G. Stette, “Time-limited orthogonal multi-carrier modulation schemes,” IEEE Tr. On

Communications, February/March/April 1995. [9] A. Valin and N. Holte, “Optimal finite duration pulses for OFDM,” IEEE Tr. On Communications,

January 1996.[10] B. Hirosaki, “An Analysis of Automatic Equalizers for Orthogonally Multiplexed QAM Systems”,

IEEE Trans. on Communications, Jan 1980.[11] P.A. Bello and K. Pahlavan, “Adaptive equalization for SQPSK and SQPR over frequency

selective microwave channels,” IEEE Tr. On Comm., May1984 [12] S. Nedic, “An unified approach to equalization and echo cancellation in OQAM-based multi-carrier

data transmission”, Globecom’97.[13] H. Bölcskei, “Blind estimation of symbol timing and carrier frequency offset in pulse shaping OFDM systems,” in Proc. Int. Conference on Acoustics, Speech, and Signal Process., vol. 5, Phoenix, AZ, 1999, pp. 2749–2752.[14] P. Ciblat and E. Serpedin, “A Fine Blind Frequency Offset Estimator for OFDM/OQAM Systems,”

IEEE Tr. On Signal Processing, January 2004.

References

doc.: ieee802.15-06-0447-01-003c submission november 2006 slobodan nedic, nedics associatesslide 1...

Documents