04-0626r3

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Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
DSSS UWB Radio System Date Submitted January
2005 Source Saeid Safavi and Ismail Lakkis
Company Wideband Access, Inc. Address 10225
Barnes Canyon Road, Suite A209, San Diego,
CA Voice858-642-9114, FAX [phone],
E-Mailssafavi_at_widebandaccess.com Re
Response to Call for Proposals Abstract
This document describes Wideband Access Inc.s
approach for the TG4a alternate
PHY Purpose Preliminary Proposal for the
IEEE802.15.4a Standard 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.
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Wideband Access, Inc.Preliminary Proposal for
IEEE 802.15.4a Alternate PHY

• DSSS UWB Radio System
• Saeid Safavi
• Ismail Lakkis

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Proposal Summary

• A robust direct sequence spread spectrum radio
  with large processing gains is proposed.
• Despite its robustness the radio has a very
  simple and implementable architecture which is
  anticipated to support the size, cost and power
  consumption requirements of the altPHY.
• Using DSSS, channel coding and a low receiver
  sensitivity, the system provides extended
  coverage beyond 30 m.
• The radio design supports all of the technical
  requirements of TG4a.

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Advantages

• Simple Architecture
• Facilitates manufacturability and time to market
• Low Power Consumption
• Low rate ADC
• CMOS technology
• Low Cost
• Single chip implementation
• Small Size
• Compact architecture
• Minimal usage of external components
• Extended Range
• Large processing gain
• Improved receiver sensitivity
• FEC
• Resistant to Interference, Multipath and
  Frequency Offsets
• Proven Location Awareness Methodology

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System Block Diagram
(Transmitter)
Information Bits
Radio Channel
4 Mcps
BPSK Mod Channel Coding
BPF
Short Code Spreading
A
125 kbps 2 Mbps
4 GHz (50 ppm)
Modulated Long Code Generator
Integrator (Short Code Despreader) Channel Decod
ing Data Detection
Recovered Bits
Integrator (Long Code Despreader)
BPF
LNA
ADC
Tb
Differential Detector
(Receiver)
Modulated Long Code Generator
4 GHz (50 ppm)
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Band Plan
Future Development
3 dB BW 1GHz
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Distinctive Radio Features

• Data Rates Raw (125 kbps to 2 Mbps), Coded (250
  kbps to 4 Mbps)
• BW 1.0 GHz (3.5 4.5 GHz)
• Chip Rate 1 Gcps
• Local Oscillator Offset 50 ppm
• High Processing Gain 24dB _at_ 4 Mb/s to 36 dB _at_
  250 kb/s
• Link Margin 6 dB gain over OOK
• Extended Range due to large processing gain, low
  sensitivity and FEC the range is larger than 30 m
• Robust robustness against noise and phase
  reversal errors, and high interference resistance
  due to large processing gain
• Low Levels of Interference to other systems due
  to the usage of DSSS with large processing gains
• Single low-power CMOS chip
• ADC operation at low rate (rather than chip rate)
  and Small Size ADC (1- 2 bit)
• Simple and Cheap Implementation (no expensive
  components such as SAW filters, etc.)
• Wide Dynamic Range
• High Frequency Efficiency due to efficient use
  of frequency within the band
• Precise Ranging Procedure based on TDOA
• Simple, all digital Signal Acquisition and
  Synchronization
• Support of large LO offsets due to the
  differential detection Scheme
• Support of Intra-cell mobility
• Low Interchip Interference an excellent code
  cross-correlation through usage of a subset of
  Kasami codes

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Properties of Kasami Sequences

• The small set of Kasami sequences is an optimal
  set of binary sequences with respect to the Welch
  Bound.
• Long Code Spreading
• Sequence length 255
• Number of possible sequences 16
• Max. Autocorrelation SLL 17
• Max. Cross-correlation level 17
• For lower data rates, a 2nd level of spreading
  (short code spreading) is introduced using the
  same set of Kasami sequences (further increasing
  the processing gain).
• If more codes are needed, the large set of Kasami
  codes can be used

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Scalability
RRaw 2 Mbps 1 Mbps 500 kbps 250 kbps 125 kbps
RCoded 4 Mbps 2 Mbps 1 Mbps 500 kbps 250 kbps
Spreading Factors 256 256 2 256 4 256 8 256 16
Total Processing Gain 24 dB 27 dB 30 dB 33 dB 36 dB
Total Gain (FER Spreading) 27 dB 30 dB 33 dB 36 dB 39 dB
Required Eb/No for PER of 1 5.8 dB 5.8 dB 5.8 dB 5.8 dB 5.8 dB
Max. Range 23.49 m 33.22 m 46.98 m 66.43 m 93.95 m
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Link Budget
Parameter Data Rates Data Rates
Peak payload bit rate (Rb) 250 kbps 4 Mbps
Average Tx power (Pt) -10.00 dBm -10.00 dBm
Tx antenna gain (Gt) 0 dBi 0 dBi
Geometric center frequency of waveform (fc) 3.944 GHz 3.944 GHz
Path loss at 1 meter (L1) 44.36 dB 44.36 dB
Path loss at d m (Ld) 29.54 dB at d 30 m 20.00 dB at d 10 m
Rx antenna gain (Gr) 0 dBi 0 dBi
Rx power (Pr) -83.91 dBm -74.36 dBm
Average noise power per bit ( ) -119.82 dBm -107.78 dBm
Rx Noise Figure ( ) 7 dB 7 dB
Average noise power per bit ( ) -112.82 dBm -100.78 dBm
Minimum Eb/N0 (S) 8 dB 8 dB
Implementation Loss ( I ) 3 dB 3 dB
Link Margin 17.92 dB 15.42 dB
Proposed Min. Rx Sensitivity Level -101.82 dBm -89.78 dBm
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Simultaneously Operating Piconets

• More channel can be identified with
  quasi-orthogonal spreading codes.
• There are two levels of spreading which provide
  an extra degree of flexibility when defining
  system parameters for co-located piconets.
• Kasami codes provide excellent cross-correlation
  properties which allows coexistence with other
  devices.

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Coexistence and Interference Susceptibility

• Due to the usage of a simple DSSS scheme with no
  frequency or time hopping, the interference to
  the neighboring systems is minimal (resulting in
  low levels of both instantaneous as well as
  average interference), satisfying the TG4as
  coexistence requirements
• DSSS with large processing gain would also
  ensures robustness against interfering devices,
  hence a high interference susceptibility.

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Location Strategy

• The location strategy is based on Time Difference
  of Arrival (TDOA) using one-way ranging (OWR).
  This method involves measuring the time of
  arrival of a known signal from the mobile device
  at three or more reference (fixed) nodes. The
  location estimate is derived from the value of
  the Geometric Time Difference (GTD) between the
  time of arrivals at each node and a known time
  reference.
• The server or controller node periodically
  broadcasts synchronization packets to the
  reference nodes. Each reference node captures the
  message packet it has received to a specific time
  resolution. The signals received at each fixed
  node is transmitted back to the controller node
  to give the time difference of arrival. Each of
  the time differences represent a location
  hyperbola that the mobile node can reside on
  (based on its TDOA). The intersection of two such
  hyperbolas are used to locate the position of the
  mobile in a 2D space.
• Therefore, the position is calculated at the
  controller node location (based on hyperbolic
  trilateration).

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Location Strategy
Fixed Node
A
C
Fixed Node
(TDOA)
B
Fixed Node
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Conclusions

• The DSSS system proposed herein is a simple and
  implementable radio that through its counter
  measures against fading, noise and interference
  can provide the robustness and extended range
  (well above 30 m) required by TG4a.
• The location awareness methodology based on TDOA
  provides a precision ranging capability.
• This system can be integrated in a compact CMOS
  chip with minimal external components and hence
  is a small-size, low-cost device. This combined
  with the radio robustness and location accuracy
  can support various 802.15.4a applications.
• The simplicity and the proven modulation
  techniques used ensures feasibility and
  scalability of the radio.
• FFDs and RFDs for different applications can
  be supported due to the scalability provided by a
  large set of spreading codes.