The TFS Story

1
The TFS Story

• Andy Klein
• BWRC
• 4/28/00

2
Once upon a time. . .

• Feb 1999
• BWRC opens for business, with the Universal Radio
  (UR) listed as one of 3 design drivers.
• An ambitious radio design that allows for
  uncoordinated co-existence with other radios.
• Adapts to provide requested service given type of
  service, location, and dynamic variations in
  environment (i.e. number of users).
• Allows for continuous upgrades to support new
  services as well as advances in communication
  engineering and implementation technologies.

3
The USS era

• June 1999
• Spectrum sharing is identified as the key
  challenge for the UR.
• UR driver evolves from a radio design into a
  spectrum management initiative, and is renamed
  "Universal Spectrum Sharing" (USS).
• USS study group is formed to investigate strategy
  for uncoordinated use of spectra without loss in
  capacity.
• Simultaneously exploit time, frequency, space.
• Main goal change the way spectrum is allocated.

4
USS Guidelines

• Fall, 1999
• Several guidelines proposed for spectrum sharing
• Use transmit power as a constraint which
  encourages good behavior
• Good behavior means
• localization in temporal-frequency-spatial
  signal space which allows other users to coexist
  without interference
• stationary or predictable behavior which
  facilitates adaptation by other users
• alignment to a time and frequency structure
  which facilitates co-existence

5
USS difficulties

• Jan, 2000
• We had no rigorous results for the difficult
  problem of spectrum sharing -- we only had
  guidelines.
• This may stem from lack of results in information
  theory. The interference channel has not yet
  been solved" by information theorists -- even
  for the seemingly simple Gaussian case
• Realized that we needed to refocus our efforts on
  what we do best designing radios.
• Then, as we were hastily preparing slides 10
  minutes before Retreat2k, the idea came to us. . .

6
Time
Space
Enter the TFS Radio. . .
Simulink
Frequency
is
our
friend!
7
So what is the TFS Radio?

• A general framework that describes a wide range
  of next-generation communications algorithms
• Incorporates three key features common to all
  next generation indoor systems
• multiple-access capability
• resistance to multi-path fading
• high bandwidth efficiency
• Leads to feasible designs while maintaining an
  appropriate level of generality

8
TFS transmitter
A
A
transpose
transpose
N
1
MEA
N
1
Coding and modulation
spreading, S/P
1
1
1
A
A
N
2
MEA
2
N
spreading, S/P
2
2
2
AN
bits
. . .
. . .
. . .
N
N
A
A
spreading, S/P
A
A
A
N
MEA
from Rx
N
A ? of antennae N ? of carriers ? of users
user 1
user 2
. . .
user k
9
TFS receiver
to Tx
A
A
transpose
transpose
N
1
MEA
N
1
Decoding, detection, decision making
despreading
1
1
FFT
remove cyclic prefix, pulse shape
S/P
1
1
A
A
N
2
MEA
N
2
despreading
2
2
FFT
S/P
2
2
remove cyclic prefix, pulse shape
bits
. . .
A/D, RF, timing recovery
. . .
. . .
N
N
A
A
despreading
A
A
A
FFT
S/P
A
remove cyclic prefix, pulse shape
N
MEA
N

• As it has been said, we can effectively assume
  infinite processing power on the digital
  backend.
• Still, theres a fundamental complexity problem
  the basestation could require as many as N2
  antenna processing units (with 64 carriers,
  thats 4096 MEA units!!).
• This arises because we are trying to employ
  narrowband MEA algorithms (e.g. BLAST, SVD-MEA)
  in a wideband environment.
• Can we build a radio today that exploits time,
  frequency, and space? Yes.

10
A downlink design Hornet

• Goals
• Design a practical system to support the BEE
  platform and the design flow
• Demonstrate proof-of-concept of MEA-SVD algorithm
• Gain an understanding of practical issues related
  to OFDM-like systems
• Parameters (for BEE version)
• 4 transmit and 4 receive antennas, using SVD-MEA
• Multi access scheme is OFDMA
• 16 carriers (? support for 16 synchronous users)
• 15 MHz sampling rate ? 1.5Mbps/user/chan w/QPSK

Thanks to G.Wright for the creative name and
theme
11
Hornet transmitter
user 1
transpose
16
16
1
1
1
IFFT
cyclic prefix
P/S
D/A, RF
pulse shape
Coding and modulation
1
user 2
16
16
2
P/S
2
IFFT
cyclic prefix
2
pulse shape
2
4
4
SVD-MEA
bits
. . .
. . .
. . .
. . .
. . .
16
16
user 16
4
4
IFFT
cyclic prefix
P/S
4
pulse shape
16
from Rx
TFS vs. Hornet
12
Conclusion

• Have presented a general framework that uses
  time, frequency, and space.
• Have proposed a specific implementable system
  Hornet.
• Currently investigating performance of Hornet
  with Simulink (see \\hitz\designs\hornet\simulink\
  floatingpoint)
• Design of synchronization / timing recovery in
  early stages (Jack)